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description | The present invention relates to a charged particle beam irradiation apparatus employing a ridge filter and being included in a particle beam cancer treatment system or the like. A conventional charged particle beam irradiation apparatus described in patent document 1 uses a ridge filter, which has ridge portions and valley portions, to create a desired distribution in particle-beam energy so that a point at a depth in a subject to be irradiated which a particle beam reaches can have a desired width, and thus creates a dose distribution in a depth direction. Patent document 1: JP-A-10-314324 The charged particle beam irradiation apparatus included in a particle beam cancer treatment system or the like includes a beam radiation-field expansion unit that forms a desired radiation field in a direction orthogonal to a beam axis of a particle beam, and a ridge filter that exhibits a cyclic depth distribution for causing the particle beam to exhibit a desired energy distribution. The kinetic energy of the particle beam having passed through the ridge filter varies depending on a position in the ridge filter which the particle beam has passed. Therefore, once the depth distribution of the ridge filter and the size of an area exhibiting the depth distribution are set to desired ones, the energy of the particle beam having passed through the ridge filter exhibits the desired distribution as a whole. When the particle beam passes through the ridge filter, the particle beam has the advancing direction thereof changed by the beam radiation-field expansion unit. A majority of particles passes in a direction oblique to the beam axis. When the particle beam passes through the ridge filter, a difference from a designed value is produced in a mean value of thicknesses through which the particle beam passes. Accordingly, an energy loss in the particle beam occurring in the ridge filter varies. An obtained energy distribution has a difference from the distribution envisaged in a design. An object of the present invention is to highly precisely create a desired depth dose distribution in a charged particle beam irradiation apparatus employed in a particle beam cancer treatment system or the like. According to the present invention, in a charged particle beam irradiation apparatus that expands a radiation field of a particle beam radiated from a particle beam generation unit, and irradiates the particle beam to a subject to be irradiated via a ridge filter exhibiting a cyclic depth distribution for causing the particle beam to exhibit a desired energy distribution, the ridge filter has plural ridges thereof arranged to be perpendicular to an entering direction of the particle beam whose radiation field has been expanded. In a charged particle beam irradiation apparatus in accordance with the present invention, a ridge filter has plural ridges arranged to be perpendicular to an entering direction of a particle beam whose radiation field has been expanded. Therefore, the precision in an energy distribution in the particle beam having passed through the ridge filter can be upgraded, and a desired depth dose distribution can be highly precisely created. 1: particle beam, 2: X-direction transmission source point, 3: second expansion means, 4: first expansion means, 5: ridge filter, 6: ridge filter attachment base, 7: Y-direction transmission source point, 8: wheel, 9: through hole, 10: beam path. FIG. 1 is a schematic configuration diagram (X-Z section) of a charged particle beam irradiation apparatus in accordance with an embodiment 1 of the present invention. In FIG. 1, a particle beam 1 radiated from a particle beam generation unit (not shown) is irradiated to a subject to be irradiated (not shown) through an X-direction transmission source point 2. The particle beam 1 is expanded by a first expansion means 4, and further expanded by a second expansion means 3. The expanded particle beam 1 passes through a ridge filter 5 including plural ridges 5a such as bar ridges and being attached to a ridge filter attachment base 6. The particle beam 1 having passed through the ridge filter 5 is reshaped in a desired form by a collimator (not shown), and then irradiated to the subject to be irradiated (not shown). As shown in FIG. 1, the ridge filter 5 is, as described later, tilted in a particle-beam entering direction at a disposed position on a circle concentric to a circle having the X-direction transmission source point 2 as a center. Now, the X direction refers to a direction perpendicular to a long-side direction of the ridges 5a included in the ridge filter 5. Next, an operation of the charged particle beam irradiation apparatus in accordance with the embodiment 1 will be described below. First, a particle beam (for example, a proton beam) is generated by the particle beam generation unit (for example, an ion source that generates hydrogen ions). After the proton beam is accelerated by a particle beam acceleration means (not shown), which is realized by a charged particle accelerator or the like, until the proton beam exerts kinetic energy equivalent to an underwater range ranging from about 20 cm to about 30 cm, the proton beam is routed to a particle beam irradiation means by a particle beam transport means (not shown) including a beam optical system composed of an electromagnet and others. The particle beam 1 routed to the particle beam irradiation means is a proton beam whose kinetic energy is, for example, approximately several hundreds of mega electron volts as mentioned above. The sectional size of the particle beam 1 routed to the particle beam irradiation means normally falls below 1 cm. In order to irradiate such a particle beam to a tumor or the like, the tumor has to be scanned by shifting the position of the particle beam. Otherwise, the beam size has to be expanded. The particle beam 1 is routed to the first expansion means 4 realized with a scattering body made of lead or tungsten, and scattered by electrons and atoms contained in the scattering body. After passing through the first expansion means 4, the particle beam 1 has the advancing direction thereof dispersed though the particle beam 1 has been concentrated nearly on a forward direction. The particle beam 1 comes to exhibit a predetermined angle distribution. Therefore, the sectional size of the particle beam 1 is expanded to be several centimeters or more when seen at the position of the subject to be irradiated (not shown). A sufficiently large beam size may not be obtained using only the first expansion means 4 realized with the scattering body. Therefore, the second expansion means 3 realized with a deflection electromagnet is used to further expand the particle beam. The second expansion means 3 may be realized with two deflection electromagnets whose magnetic-field directions are orthogonal to each other. The two deflection electromagnets are excited by alternating-current power supplies for sin ωt and cos ωt and exciting current patterns to be synchronized with each other. Therefore, the particle beam 1 having passed through the second expansion means 3 is deflected as if to draw a circle. The expansion means is an existing conventional technique and referred to as a wobbling electromagnet. The radius of the circle is referred to as a wobbling radius. Once the ratio of a scattering radius of a particle-beam section provided by the first expansion means 4 to the wobbling radius provided by the second expansion means 3 is adjusted to be equal to a predetermined ratio, a particle-beam distribution that is substantially flat in a transverse direction can be created near the center of a radiation domain. A domain in which the particle-beam distribution is not uniform and which is separated by a predetermined distance from the center of the radiation domain is removed by the collimator (not shown). The collimator is realized with plural foliated plates that has a thickness not permitting the particle beam 1 to pass through and that is made of iron or the like. The arrangement of the foliated plates is controlled so that an opening of the collimator takes on an arbitrary two-dimensional shape. If the two-dimensional shape is matched with the shape of a tumor, a radiation field is created in line with the existing range of the tumor. By the way, a depth (range) in a human body to which a particle beam propagates is generally determined with the energy of the particle beam. The particle beam rapidly releases its energy near the terminal of the range and comes to a halt. This phenomenon is called a Bragg peak. The phenomenon is utilized in order to kill a tumorous cell existent at a considerable depth from the body surface. The tumor has a thickness in a depth direction. Therefore, for uniformly irradiating a particle beam to the tumor (lesion), it is necessary to perform manipulations for uniformly spreading the Bragg peak in the depth direction of the tumor. The uniformly spread dose is referred to as a spread-out Bragg peak (SOBP). In order to create a distribution in the depth direction of a radiation field as mentioned above, an energy distribution in the particle beam 1 has to be adjusted. A method that has been adopted in the past and is also employed in the present invention is to pass the particle beam 1 through the ridge filter 5 exhibiting a predetermined depth distribution. The ridge filter 5 can spread the energy distribution in the particle beam within a predetermined range according to the predetermined depth distribution. Specifically, the energy of the particle beam having passed through the ridge filter varies depending on an incident position of the particle beam 1 on the ridge filter 5. For example, the first passing particle beam is a particle beam having passed through the thickest region of one bar ridge out of plural bar ridges of the ridge filter 5. The second passing particle beam or third passing particle beam is a particle beam having passed through a region equivalent to a valley between two bar ridges out of the plural bar ridges of the ride filter 5. The particle-beam energy of the first passing particle beam 1 is lower than that of the second or third passing particle beam, and the depth in a subject to be irradiated which the particle beam reaches is shallower. In contrast, the second or third passing particle beam may reach the deepest position in the subject to be irradiated. As mentioned above, a radiation field having a predetermined width is formed in the depth direction of the subject to be irradiated. The predetermined width is generally determined with a difference between the thickness of the thickest part of the ridge filter 5 and the thickness of the thinnest part thereof. In other words, the individual ridge filter 5 exhibits an inherent SOBP. Incidentally, a width of the Bragg peak spread by the ridge filter in the depth direction of a tumor (namely, the width of the SOBP) normally ranges from 1 cm to 20 cm. After a predetermined setting parameter is given to each of the first expansion means 4 and second expansion means 3, when the ridge filters 5 exhibiting predetermined SOBPs are combined, a desired three-dimensional dose area is formed in a subject to be irradiated. For exposing a tumor, it is necessary to highly precisely create a dome distribution in the three-dimensional dose area. In order to make the dose distribution uniform in the three-dimensional does area, the particle beam passing through the ridge filter 5 should preferably enter the ridge filter in parallel with the ridge filter, and a certain percentage of the particle beam defined in a design should pass through the ridge filter material having a thickness defined in the design so as to lose its energy. However, the orientation of a particle beam entering the ridge filter is deflected during expansion of a beam radiation field by the first expansion means 4 and second expansion means 3. When the particle beam passes through the ridge filter 5, the components of the particle beam are oriented in the most diverse directions in the center of the radiation field. On the edge of the radiation field, the advancing directions of many components of the particle beam are the most external directions. Therefore, on the edge of the radiation field, particles entering the ridge filter in oblique directions become most influential. As mentioned above, in a place where many components enter obliquely, that is, on the edge of the radiation field, particles do not advance through the ridge filter as they are designed to do. A distribution of energy losses becomes different from a designed distribution thereof. In efforts to resolve the influence of oblique entry of a particle beam on the edge of the radiation field, in the embodiment 1 of the present invention, the plural ridges 5a included in the ridge filter 5 are, as shown in FIG. 1, tilted at arranged positions on a circle concentric to a circle, which has the X-direction transmission source point 2 as a center thereof, so that the ridges can be perpendicular to particle-beam entering directions. Accordingly, the precision in a distribution of values energy, which charged particles lose in the ridge filter 5, can be upgraded. The precision in an energy distribution of particles having passed through the ridge filter can also be upgraded. Therefore, a desired depth dose distribution can be highly precisely created, and the precision in treatment can be upgraded. As mentioned above, in the embodiment 1 of the present invention, in the charged particle beam irradiation apparatus that expands the radiation field of the particle beam 1 radiated from the particle beam generation unit, and irradiates the particle beam to a subject to be irradiated via the ridge filter 5 exhibiting a cyclic thickness distribution for causing the particle beam to exhibit a desired energy distribution, the plural ridges 5a included in the ridge filter 5 are arranged to be perpendicular to particle-beam entering directions. Therefore, the precision in the distribution of values of energy which charged particles lose can be upgraded. Eventually, the precision in the energy distribution among particles having passed through the ridge filter can also be upgraded. Since a desired depth dose distribution can be created, the precision in treatment can be upgraded. Further, an expanded Bragg peak exhibiting a large flatness domain can be attained over a wide radiation field. In addition, since the distance from the radiation field expansion means to the subject to be irradiated can be shortened, even a compact apparatus can form the wide radiation field. FIG. 2 is a schematic configuration diagram (X-Z section) of a charged particle beam irradiation apparatus in accordance with the embodiment 2 of the present invention. In FIG. 2, the plural ridges 5a included in the ridge filter 5 are arranged to be most exactly perpendicular to mean incident particle beam directions on a plane of arrangement (X-Y plane in FIG. 2). In order to compensate an adverse effect on the cyclic thickness distribution of a ridge filter material through which the particle beam passes, the arrangement spacing between ridges may be modulated in a direction in which the ridge filter 5 exhibits the cyclic thickness distribution. According to the embodiment 2, the precision in creating a depth dose distribution, that is, the precision in treatment can be upgraded. Compared with the embodiment 1, a width (Z direction) necessary to dispose the ridge filter 5 can be decreased. In the charged particle irradiation apparatus in accordance with the embodiment 1 or 2, a ridge filter including bar ridges is adopted as the ridge filter 5. The present invention is not limited to this type of ridge filter. For example, an existing conical ridge filter may be employed as long as the ridge filter exhibits a cyclic depth distribution permitting obtaining of an SOBP. FIG. 3 is a schematic configuration diagram (Y-Z section) of a charged particle beam irradiation apparatus in accordance with the embodiment 3 of the present invention. In FIG. 3, as described later, the ridge filter 5 is deformed in such a manner that the plural ridges 5a (bar ridges) included in the ridge filter 5 are perpendicular to particle-beam entering directions. As mentioned previously, in a place where many components of a particle beam enter obliquely, that is, on the edge of a radiation field, particles do not advance through the ridge filter as designed. A distribution of energy losses has a difference from a designed one. In order to resolve an adverse effect of oblique entry of the particle beam on the edge of the radiation field, according to the embodiment 3 of the present invention, as shown in FIG. 3, the ridge shape (Y-axis direction in FIG. 3) of the ridge filter 5 that is normally a linear shape parallel to the Y axis in FIG. 3 is varied depending on a distance from the center of the radiation field in the long-side direction of the ridge filter. The example shown in FIG. 4 has a roof tile shape. A vaulted shape like the one shown in FIG. 4 will do. According to the embodiment 3, the precision in creating a depth dose distribution, that is, the precision in treatment can be upgraded in a direction (Y-axis direction in FIG. 3) obtained by turning 90° the direction in the embodiment 1. In the aforesaid embodiments 1 to 3, a desired depth expanded radiation domain (SOBP) is obtained under a predetermined radiation-field condition. For cancer treatment, the size of the radiation field and the SOBP have to be varied depending on the size of a tumor. A conventional particle beam treatment system uses different ridge filters for different SOBPs, but uses the same ridge filter under different conditions for radiation-field formation. In the present embodiment 4, plural ridge filters are prepared for different conditions for radiation-field formation. Any of the ridge filters is selected and disposed on a beam path along which a particle beam passes under a predetermined condition for radiation-field formation. FIG. 5 is a schematic plan view showing a ridge filter replacement unit included in a charged particle beam irradiation apparatus in accordance with the embodiment 4. As shown in FIG. 5, plural ridge filters 5 associated with different conditions for radiation-field formation are attached to ridge filter attachment bases 6, and the plural ridge filter attachment bases 6 are mounted on a wheel 8. The wheel 8 is rotated in order to selectively dispose an arbitrary ridge filter attachment base 6 on a beam path 10. The wheel has a through hole 9 for fear the wheel may hinder inspection such as calibration of a beam axis. In the present embodiment 4, when a condition for radiation-field formation is a different one, an optimal ridge filter associated with the condition can be selected. Therefore, irradiation can be achieved with a radiation field and SOBP highly precisely determined. The present invention uses a large number of types of ridge filters. By applying the present embodiment, the ridge filters can be readily managed and selected. In the charged particle irradiation apparatus in accordance with any of the aforesaid embodiments, a wobbler type including the first expansion means and second expansion means is adopted as the expanded radiation field formation unit. The present invention is not limited to the type. A double scattering body type capable of forming an expanded radiation field or a two-dimensional scanning type will do. In addition, the disposed positions of the first expansion means 4 and second expansion means 3 may be switched. |
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043671934 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates an embodiment of a module 1 of a fusion generating device in accordance with the principles of the invention. A fusion power core 2 is shown housed within two clamshaped regions 4a and 4b of a blanket 4. The blanket 4 absorbs radiation emanating from the fusion power core as a result of the fusion reaction. It is the function of the blanket 4 to absorb such radiated energy which appears mostly as neutrons generated in the fusion reaction. These neutrons could be used to generate fission in fission plates incorporated as neutron multipliers in the blanket assembly or simply for the production of heat by neutron slowing and neutron capture reactions. Such heat energy is extracted by means of a coolant passing through conduits 8 which are shown diagrammatically as penetrating the blanket region 4a. The conduit 8 may in fact be a plurality of cavities or conduits passing through both regions 4a and 4b of blanket 4 and may be of the multiple artery type so as to cover a large region of the blanket to absorb maximum amount of heat energy. The fluid conduit 8 passes to heat exchange means and pump means indicated at 10. The blanket material may, for example, be composed of graphite, fluoride salts, beryllium or other materials as well known in the art. The coolant material may be water or oil or any other suitable fluid serving a cooling/heat extracting function. Heat exchange means 10 may be connected to thermal/electrical or thermal/mechanical power generating equipment. Also shown in FIG. 1 is a heat exchange means and pump means 12 associated with a conduit 14 which passes through the blanket 4 and into the fusion power core 2. The coolant flowing through conduit 14 serves to cool the field coils utilized to provide the magnetic confinement within the fusion power core 2. Only one such conduit 14 is illustrated although it is understood that a plurality of conduits may be provided (and a single or an associated plurality of heat exchange means and pump means as required) for cooling various sections of the magnetic field coils. The coolant stream may provide heat energy to heat exchange means 12 for utilization in thermal/electrical conversion equipment in order to produce electrical power therefrom and/or thermal/mechanical equipment for generation of mechanical (shaft) energy. The coolant/thermal extraction system provided by conduits 14 and heat exchange means 12 may be separate and independent from the coolant/thermal extraction system employed for the blanket 4 or alternately the two systems may utilize common components. The temperatures within the coils of the fusion core must be kept below the melting or structurally limiting temperatures of the coil materials (copper or aluminum coils, for example). The heat developed within the blanket 4, however, has no such restriction and the coolant within the blanket may thus be heated to considerably higher temperatures than the coolant passing through the fusion power core (conduits 14). The thermal/electrical conversion equipment, for example, associated with the higher temperature coolant will thus be able to operate at higher thermal/electrical conversion efficiencies than possible for the lower temperature coolant. For a fusion power core of the toroidal type, coolant is typically provided in the toroidal field coils but may also be provided for other field coils if desired (ohmic heating, vertical field or auxiliary heating coils). Additionally, coolant means similar to that shown by conduits 14 and heat exchange and pump means 12 may be provided for other regions of the fusion power core, such as a region between the toroidal shell and the toroidal coil as more fully set forth below. An alternate or additional means for cooling and obtaining thermal energy from the fusion power core 2 and blanket 4 is provided by heat exchange means and pump means 15 together with conduits 16. In this embodiment, the fluid inflow to module 1 passes between the blanket regions 4a and 4b and is heated by the fusion power core 2 which effectively serves to preheat the coolant which is subsequently heated to higher temperatures by energy from the blanket region 4. In this manner, a single coolant may be utilized with a single thermal/electrical conversion unit. Blanket 4 may also contain a tritium breeding section 17 which may contain for example lithium utilized to capture neutrons for the breeding of tritium for subsequent use in the D,T fusion reaction. Heat exchange and pump means 18 together with conduits 20 may be utilized to cool the lithium breeding section 16, or alternately, a molten fluoride salt of lithium (or lithium plus beryllium, for example) may be used to provide for tritium breeding as well as self-cooling. Appropriate tritium extraction apparatus 22 is connected to the conduits 20 to extract the tritium for subsequent utilization. An electrical control means 24 is utilized to provide the current to drive the various field coils within the fusion power core via a plurality of power conductors 26. Thus, in the case of a toroidal or tokamak-type device, conductors 26 serve to provide the necessary current for the toroidal field as well as for the ohmic heating transformer, auxiliary heating coils, vertical coils and the like. The fusion power core 2 is provided with a containment region 28 for housing the plasma. In the embodiment in which the toroidal-type fusion power core is utilized, the containment region 28 is simply the toroidal shell or vacuum cavity containing the plasma gas. Means are provided for evacuating the containment region 28 such as by utilizing a vacuum pump 30. Gas feeding means 32 are also shown for supplying the fusible fuel or gas to the containment region 28. The gas feeding means 32 may comprise for example a supply of D,T gas and remotely operable valve means for controlling flow of gas into the containment region 28. Each fusion power core 2 also may be provided with diagnostic ports 33 for measuring plasma position, density and temperature as is well known in the art. As stated below, the fusion power core 2 may be of the tokamak type and include the required toroidal magnetic field coils and ohmic heating coils. However, it is envisioned that other fusion power cores may be utilized wherein other types of magnetic confinement are obtained, e.g., stellarator confinement principles, for example. The description herein is presented in terms of specific embodiment of the tokamak-type fusion reactor and specifically utilizing a D, T fusion reaction process. However, it is clear that other fusion reaction processes, for example, the D,D or D,He.sup.3 may be utilized separately, or simultaneously with D,T. A prime consideration of the present invention is the fact that the fusion power core 2 is removable from the blanket 4 and, in fact, is disposable, or recyclable. The high temperatures and high fields attained in the fusion power core result in an extremely high radiation flux significantly higher than the first well loading heretofore assumed acceptable for practical large scale fusion reactor designs. As a result of such a high radiation flux on the first wall of the fusion power core, the fusion power core may deteriorate over a relatively short time. In this circumstance, the present invention allows for and provides a means for replacing the entire fusion power core. Depending upon specific operating parameters replacement could be required at time intervals on the order of weeks to months. However, the relatively small size of the fusion power core 2 will allow economical means of removal and subsequent disposal and/or reprocessing/recycling thereof and replacement by a new fusion power core utilizing the same blanket 4. Consequently, the blanket regions 4a and 4b are made separable, and the fusion power core 2 may be removed therefrom. For tokamak-type fusion power cores, it is possible to reprocess the fusion power core 2 such that the copper and other materials within the core may be utilized again. As an exemplary conventional frame of reference, assuming a D,T reaction, the fusion power core may have a radius on the order of 1 meter and height of approximately 1 meter. Each blanket region may typically be on the order of 1 meter thick. In practice the exact thickness and shape of the blanket is somewhat arbitrary and may be designed to provide adequate thickness for capture of neutrons generated in the fusion power core. Additionally, the first wall of the blanket shell may be made of high Z or other materials which allow n,2n reactions to enhance blanket neutron yield thus assuring a simple T-breeding design. As shown in FIG. 2A, a plurality of modules 1.sub.1 . . . 1.sub.n, each having a corresponding blanket 4.sub.1 . . . 4.sub.n and cores 2.sub.1 . . . 2.sub.n may be arranged together to form a power generating system wherein corresponding coolant conduits 8'.sub.1 . . . 8.sub.n are separately connected to one or more heat exchange and pump means (not shown). An alternate arrangement is shown in FIG. 2B wherein a plurality of modules 1'.sub.1, 1'.sub.2 . . . 1'.sub.n is shown with series connected coolant conduits 8".sub.1, 8".sub.2 . . . 8".sub.n. In any such series arrangement, a system bypass means 9 may be provided so that upon replacement of any individual fusion power core, the remaining assembly of modules 1' may be left operational. In FIGS. 2A and 2B, the arrows labeled 8'.sub.1, 8'.sub.2 etc. and 8".sub.1, 8".sub.2 etc. are used to represent both the blanket coolant/thermal extraction system and corresponding fusion power core coolant/thermal extraction system whether they be separate or integral systems as taught in FIG. 1. Obviously, in FIG. 2B, the fusion power core (blanket) coolant/thermal extraction system could be connected in series with a separate plurality of blanket (fusion power core) coolant/thermal extraction system for the modules. It is advantageous in these configurations to closely pack the modules 1 together so that neutrons escaping one module may be trapped in an adjacent module thereby increasing overall efficiency. FIG. 2C shows yet another embodiment of the invention wherein a plurality of fusion power cores are surrounded by a single blanket 34. FIG. 3 illustrates an electrical power generating system comprising a fusion reaction room containing an array of modules 1" such as those illustrated in FIG. 2A. Each module in the array is connected to an electrical supply, gas feeding and vacuum unit in accordance with FIG. 1 to supply both the electrical power to each individual fusion power core and the necessary gas feeding and vacuum pumping means. Also interconnected to each of the modules 1" are heat exchange means and conduits which are connected in accordance with elements 8, 10, 12 and 14 of FIG. 1 to extract heat from the blanket units as well as to provide cooling means and heat extraction means for the fusion power cores. A low temperature heat exchange means 42a forms part of the fusion power core coolant/thermal extraction system and is connected to conduit means feeding each fusion power core. For simplicity of illustration, only one such connecting line is shown. A low temperature condenser 44a is connected to the low temperature heat exchange and pump means 42a and to one state of turbine 46. A high temperature heat exchange and pump means 42b forms part of the blanket coolant/thermal extraction system for the modules 1" and is connected to conduit means for feeding each blanket. Again, for simplicity of illustration, only one such conduit means is illustrated. The high temperature heat exchange and pump means 42b is connected to a high temperature condenser 44b and to a second stage of turbine 46. The turbine 46 drives a generator 48 which supplies electrical energy to an electrical gridwork which may in turn be fed by a plurality of units similar to those shown in FIG. 3. Alternatively, instead of or in addition to the electrical conversion one may utilize the turbine 46 to provide mechanical energy such as shaft rotational energy. A remotely operable means is also provided for removing any given fusion power core from its corresponding blanket so that the fusion power core may be handled, moved, disposed of, or reprocessed to recycle valuable metals, dispose of radioactive contaminants, and/or to remanufacture and refabricate an additional (replacement) fusion power core. The remotely operable means may comprise remote handling means 51 and a recycle and disposal means 52. Remote handling means 51 may comprise an overhead crane and means for connecting and disconnecting the various conduits and cables feeding the fusion power core 2. A control room 54 is also shown for providing a monitor and control means 56 and to provide office space for personnel. Monitor and control means 56 monitors and controls the operation of the entire power generating plant and, in particular, monitors and controls each of the various elements in FIG. 1 shown associated with module 1. Additionally, plasma position, temperature and density may be monitored via diagnostic ports (33 of FIG. 1) in each module 1". An enlarged top view of a single module 1 is illustrated in FIG. 4. The fusion power core 2 is shown in cross section. The blanket is shown to be composed of two regions 4a and 4b which surround the fusion power core 2. The blanket regions 4a and 4b are also shown in cross section but may not necessarily be taken along the same horizontal plane with respect to each other. The blanket region 4a is shown permeated with an artery array of conduits 8 which serve to remove thermal energy generated by neutrons emanating from the fusion power core 2 and absorbed in the surrounding blanket 4. Although not specifically illustrated in FIG. 4, the blanket region 4b may similarly contain an array of conduits for carrying a cooling/thermal energy extraction fluid. The blanket may be comprised of a fluid material instead of the more commonly utilized solid blanket material. If desired, the fluid material may be circulated to serve both as a neutron absorbing medium and as its own coolant/thermal extraction means, i.e., the fluid may be fed via conduits to heat exchange means. The fusion power core 2 is illustrated in the preferred embodiment as comprising a tokamak-type reactor wherein plasma is contained in cavity region 101 of a toroidal shell 100 which may, for example, be composed of aluminum, stainless steel, niobium, molybdenum or the like. The shell may be in the range of approximately one to a few millimeters thick, and may be coated internally with beryllium, carbides, graphite or aluminum oxide for protection. The shell may likewise be coated with an aluminum oxide or other insulating layer on the outside thereof for insulation of the shell from the surrounding conductors. A series of current carrying conductors or disk coils 102 are disposed around the toroidal shell 100 for establishing the toroidal magnetic field. A plurality of spiral grooves 103 may be provided in the disk coil 102 for passage of a cooling fluid therethrough. The grooves 103 communicate with peripheral channels 103a in the disk coils 102. The coolant fluid passing adjacent the disk coils 102 may be connected to heat exchange means as shown in FIG. 1 to remove thermal energy therefrom for utilizing same for the generation of electric power. Between the disk coil 102 and the shell 100 there may be disposed a cooling channel 104 for passage of the cooling fluid around and along the length of the shell 100. The cooling channel 104 is thus in fluid communication with the spiral grooves 103 and peripheral channels 103a. Supporting the shell 100 in the cooling channel 104 are a plurality of supports 105 which may take the form of small button-like elements or rib members surrounding the toroidal shell. The cooling channel 104 around the shell 100 (first wall) is utilized to maintain the shell at controlled temperatures. The channel may typically be on the order of one to a few millimeters wide. If necessary for stress and strength considerations, surrounding the disk coils 102 may be a support means 106 which holds the coils 102 in tension against an outer rib 108 and top and bottom support members 110. The support means 106 thus supports the disk coils 102 and shell 100 from the strong forces produced by the generated magnetic fields. Support means 106 may be fabricated, for example, from steel and may be an integral toroidal unit or a plurality of supports, one for each disk 102. If the support means is integral over two or more disk coils, then insulation means are provided between the disk coils 102 and support means 106 to prevent shorting out of the disk coils. The support member 110 as well as the outer rib 108 may be made of aluminum or other material and are typically insulated from the support means 106 by insulation means 112 (made, for example, of aluminum oxide). Support members 110 are held together by means of a central load carrying member 114 (made of ceramic, for example) as well as by sealed joints 116 at the periphery of the support means 106. The fusion power core 2 is provided with ohmic heating coils 120 which may take the form of an air core or saturated iron core transformer. All of the coils illustrated in FIG. 4 are utilized for ohmic heating. Additional auxiliary heating and vertical field coils may also be provided as more clearly illustrated in reference to FIG. 5 discussed below. Various coolant conduits are provided in the module 1 of FIG. 4 such as fluid conduits 124, 125, 126 and 127. Fluid conduits 124 and 125 are inflow and outflow conduits respectively which are associated with shell 100 and disk coil 102. The fluid is passed into the fusion power core 2 and circulates in grooves 103 and channels 103a of the disk coils 102 and within the cooling channel 104 adjacent and exterior to the shell 100. Fluid conduits 126 and 127 are inflow and outflow conduits respectively and associated with the ohmic heating coils (as well as vertical and auxiliary heating coils if desired). Thus, conduits 124, 125, 126 and 127 form part of the fusion power core coolant/thermal extraction system as disclosed in reference to FIGS. 1 and 3. In order to facilitate removal of the fusion power core 2 from the blanket 4 for replacement of the fusion power core, the conduits 124-127 are passed through coupling means 128 before interconnecting to the fusion power core 2. Coupling means 128 permits easy separation of the fluid conduit sections contained within the fusion power core from the external conduits leading to the heat exchange and pump means. Consequently, when the fusion power core is separated from the blanket 4, it is only necessary to disconnect the sections of the fluid conduit at the coupling means 128. Functionally similar coupling means 128' are provided for electrical connections 129 to ohmic heating (OH) coils 120 of the fusion power core 2. The fusible gas, for example, an equal mixture of deuterium and tritium is fed into the cavity region 101 of shell 100 via a fuel inlet conduit 134. Valve means (32 of FIG. 1) are connected to the fuel conduit 134 to regulate the flow of fusible fuel into the plasma cavity region 101. An extraction fuel conduit 136 is connected to pump means (30 of FIG. 1) and is provided to extract the plasma during the gas purge cycle of operation. Both conduits 134 and 136 may be provided with small nozzle means to couple to the cavity region 101. Coupling means 128 may also be provided for the conduits 134 and 136 as shown. FIG. 4 also illustrates in region 4b of the blanket 4 special fluid passages 130 for cooling regions 132 containing lithium used for breeding tritium. The tritium may later be used in the fusion power core for the D,T fusion reaction. Region 132 may contain, for example, canned lithium alloys. A neutron monitor 133 is shown positioned between the fusion power core 2 and blanket 4 to provide a means for measuring the reaction rates within the plasma. The fusion reaction rate may, of course, be indicative of the plasma temperature or density. The plasma temperatures may be determined in a conventional manner as, for example, by utilizing laser interferometer techniques via the diagnostic port 33 (FIG. 1). The overall size of the fusion power core 2 in FIG. 4 is quite small in comparison with conventional tokamak designs. In particular, the fusion power core 2 may have a major radius of approximately 50 centimeters and a minor radius of approximately 20 centimeters. The radial thickness of the disk coils 102 is approximately 10 centimeters and each coil may extend a few centimeters in thickness. One particular coil is illustrated in FIGS. 5, 5A and 5B and employs cooling grooves 103' in the form of radial grooves which may alternately be used instead of the spiral grooves shown in FIGS. 4 and 6. One portion of the disk coil is bent outwardly for alignment with the adjacent disk coil around the toroidal shell 100. The disk coils 102 are arranged around the plasma shell 100 and are placed adjacent to each other to form a complete coil producing the toroidal field. It is contemplated that 176 such disk coils may be utilized either series connected or connected in modular groups such that there are 8 separate coils per each coil group with a total of 22 coil groups. In such an arrangement each coil group would comprise one complete turn and would be electrically connected to the next coil group to form a series current path through the entire plurality of coils. FIG. 6 illustrates an enlarged sectional view of part of the fusion power core as shown in FIG. 4. Fluid conduits 124 and 126 and fuel conduit 134 have already been discussed in relation to FIG. 4. Various field coils are shown in FIG. 6 in addition to the OH coils 120. For example, field coils 142 may be used to provide a vertical field (VF) for positioning the plasma, and coils 144 may be used, if desired, as auxiliary heating coils. Auxiliary heating of the plasma may, of course, be provided by other means such as ripple currents on the VF coils 142, microwave techniques etc. FIG. 7 illustrates a cross-sectional view of the fusion power core showing the disk coils 102 and support means 106 as taken along line 7--7 of FIG. 6. Ohmic heating coils and conduits are now shown for simplicity of illustration. FIG. 7 shows the disk coils 102 with an integral support means 106'. Support means 106' is shown broken away so that the disk coils 102 may be more clearly seen. Each disk coil 102 is wedged-shaped and separated by an insulation means 152 which may take the form of a thin ceramic disk. The insulation means 152 may alternately be provided by an insulating coating on the disk coils 102. FIG. 7A illustrates the disk coils 102 with separate support means 106, one such support means associated with each disk coil 102. FIG. 8 is a side plan view of a module 1 wherein the fusion power core 2 is being removed from the blanket regions 4a and 4b by an overhead crane 160 forming part of the remote handling means 51. The blanket regions 4a and 4b are carried on support means such as a remotely operable trolley 168 for separating the blanket regions to allow removal of the fusion power core 2. For ease of illustration, various fluid conduits, gas and vacuum feed lines and electrical connection lines are not shown. The crane 160 lifts the fusion power core 2 from a support means 170 and moves it to the recycle and disposal means 52 (FIG. 3) for processing. A new or recycled fusion power core 2 is then placed on the support means 170 via the overhead crane 160 and the fluid conduit, gas feed and vacuum lines as well as electrical connections are connected via the remote handling means 51 to the new fusion power core 2. The fusion power core may be driven to ignition and thence to power producing levels in cycles utilizing gas staging techniques as described in copending application Ser. No. 755,794 filed Dec. 30, 1976 and/or utilizing e-beam techniques as described, for example in U.S. Pat. No. 3,831,101 incorporated herein by reference. In practice, each fusion power core 2 of FIG. 3 is cycled through an initial start-up stage, ignition stage and burn stage so that the residual gas in the plasma cavity 101 may be pumped out and a new gas mixture introduced at the beginning of stage 1. Power is switched into each fusion power core 2 in a sequential manner by means of the electrical supply units 40 and monitor and control means 56 of FIG. 3. For example, assume that there are 20 fusible power core units operating at a "burn time" of 25 seconds with a 30-second total cycle time. The control means for the power system activates unit 1 associated with the first fusion power core. Approximately 1.5 seconds later (30/20) power is supplied to unit 2 while continuing power to unit 1. Three seconds later, unit 3 is switched on while continuing power to units 1 and 2, etc., until all units are being driven at the 30-second cycle time. In this manner, an average power output may be supplied by the generator 48. It is expected, of course, that not all of the fusion power cores will need replacement at the same time. The replacement of any given fusion power core is thus made as required, but because of the small size and simplicity of the replacement procedure such replacement takes a relatively short time and does not require shutdown of other fusion power cores. Consequently, such replacement will not appreciably affect the overall power output of the generating plant. While the invention has been described in reference to the preferred embodiments set forth above, it is evident that modifications and improvements may be made by one of ordinary skill in the art, and it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically set forth herein. |
description | This application claims the priority, under 35 U.S.C. §119, of German application DE 10 2010 024 501.1-12, filed Jun. 21, 2010; the prior application is herewith incorporated by reference in its entirety. The invention relates to a system for the fastening of sealing elements for a pressure vessel, which has at least one opening and a sealing part provided for the opening. In this case, this can be both a mobile pressure vessel, for example a transport container or a hydraulic reservoir, and a stationary pressure vessel, for example a process control pressure vessel or a reactor pressure vessel. In the case of such pressure vessels, in each case at least one sealing element is introduced in the operating state between the contact surfaces of the pressure vessel in the region of the respective opening and the contact surfaces of the corresponding sealing parts. In some cases, the sealing elements are fastened with the aid of a sealing element fastening system either to the pressure vessel or to the sealing part in order to simplify, among other things, the opening and sealing of the pressure vessel. Published, Korean patent application No. 1020010038819 A makes known a sealing element fastening system, by way of which O-ring seals are fastened to a pressure vessel sealing part in the operating state of the pressure vessel. To this end, the O-ring seals are inserted at least partially in an accommodating groove in the pressure vessel sealing part. Cap screws, which are screw-connected to the pressure vessel sealing part, are arranged in a countersunk manner in a plurality of indentations that connect directly in each case to the accommodating groove. The cap screws fix, in each case, a holding element that is shaped in the manner of an angle bracket, the portion of which remote from the respective cap screw abutting against the corresponding O-ring seal in such a manner that, on the one hand, the O-ring seal is held in the accommodating groove and, on the other hand, the holding element is positioned in a countersunk manner in the pressure vessel sealing part. In the case of the sealing element fastening system, in each case a free space remains in the region of the respective indentation and the accommodating groove adjacent thereto. These free spaces result in free contact surfaces at the corresponding O-ring seals. In the operating state of the pressure vessel, a substance kept in the pressure vessel spreads out into those free spaces as far as the contact surfaces. The contact between the substance and the O-ring seal can then lead to unwanted reaction processes, where the O-ring seal is damaged and the substance contaminated. It is accordingly an object of the invention to provide a sealing element fastening system for a pressure vessel which overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which the spreading out of the substance into the free spaces is prevented. With the foregoing and other objects in view there is provided, in accordance with the invention a sealing element fastening system for sealing elements of a pressure vessel. The sealing element fastening system contains a sealing part having an accommodating groove and an indentation. The sealing part is provided for covering an opening of the pressure vessel. In an operating state of the pressure vessel each sealing element is at least partially inserted in the accommodating groove in the sealing part. Corresponding sealing element fastening devices are disposed in each case in one of the indentations in the sealing part. Filling elements are provided, the indentations in each case sealed by one of the fill elements in the operating state of the pressure vessel. A sealing element fastening system is provided for at least one sealing element of a pressure vessel, which has at least one opening and a complementary sealing part. Corresponding to the teaching of the invention, in the operating state of the pressure vessel, each sealing element is inserted at least partially in an accommodating groove in the sealing part and corresponding sealing element fastening devices are positioned, in each case, in an indentation, sealed by a fill element, in the sealing part. Through the sealing of the indentations, the spreading of the substance into the free spaces, and as a consequence the interaction between sealing elements and the substance kept in the pressure vessel, is prohibited as extensively as possible. Although in particular in the case of process control pressure vessels, high priority is given to the avoiding of contamination of the substances kept in the pressure vessel, in the case of this invention, proceeding from the fact that the substances can also be hazardous substances, the most important objective is deemed, above all, to be the protection of the sealing elements and consequently the assurance of the tightness of the pressure vessel. According to a preferred embodiment, each sealing element fastening device includes a ring-shaped holding element with an integrally molded holding arm, which is fixed to the sealing part in the operating state of the pressure vessel. A screw, for example, can be provided for the fixing process. A fastening variant that is technically very simple is realized in this manner. In this conjunction, it is deemed to be advantageous when, in the operating state of the pressure vessel, each holding arm engages into a recess on the respective sealing element and consequently holds the sealing element on the sealing part. In this case, the engagement of each holding arm in a corresponding recess can be realized in both a detachable and non-detachable manner. Detachable versions, such as, for example, plug-in connections, are to be preferred in particular when simple exchangeability of the sealing elements is desired. A particularly expedient variant of the sealing element fastening system is characterized in that threaded bolts with two separate threaded portions are used. Whereas the first threaded portion of each threaded bolt passes through a holding element in the operating state of the pressure vessel and is screw-connected into a complementary counter thread in the sealing part, the second threaded portion of each threaded bolt passes through a fill element together with a bolt nut, which serves for fastening the fill element to each second threaded portion. In this case this is a variant with an upgrade character and is conceived, in particular, for already available sealing element fastening systems without a fill element, where the sealing elements are fixed by cap screws. In an advantageous further development of this variant, a ring-shaped projection is integrally molded in each case between the two threaded portions, as a stop member for the fill element, on the one hand, and for the holding element, on the other. This means that it is possible to perform the fastening of the respective holding element to the sealing part and the fixing of the respective fill element to the threaded bolt by two operating steps that are separate from each other. Such a separation of this type can be helpful, for example, when one individual fill element has to be exchanged on account of damage. In this context, an embodiment with a number of recesses on each ring-shaped projection as a point of application for a tool is preferred. The tool provided for this is, on the one hand, to simplify the handling of the threaded bolts and, on the other hand, to open up the possibility of predetermining an exact torque at which the threaded bolts are screw-connected into the respective counter thread in the sealing part. Over and above this, it is particularly advantageous to provide recesses also on each bolt nut, the recesses matching those on the ring-shaped projection in form and relative position to each other. This means that the complete assembly of each unit of the sealing element fastening system is able to be performed with the aid of only one tool. The corresponding tool is preferably provided with a variable torque preset. Different torque values can be predetermined in this way for the tightening of each bolt nut when fastening the corresponding fill element and for the screw-connecting of each threaded bolt into the respective counter thread. In an alternative variant with an upgrade character, a clamping bush is provided for each unit of the sealing element fastening system, the clamping bush in each case fastening a holding element in a rotatable manner on the corresponding fill element. During the pre-assembly of the respective unit, the clamping bush, passing through the holding element, is pressed for this purpose into a central opening in the fill element. Finally, in the operating state of the pressure vessel, each system module of the sealing element fastening devices is preassembled in such a manner and is preferably fixed on the sealing part by way of a cap screw that passes through the fill element, the holding element and the clamping bush. The rotatability of the holding elements, implemented in this manner, in relation to the fill elements allows, for example, greater tolerance ranges when aligning the sealing elements in the assembly process of the sealing element fastening system. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a sealing element fastening system for a pressure vessel, in particular a reactor pressure vessel, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. In all the figures parts that correspond to each other are provided with the identical references. Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a sealing element fastening system for ring-shaped sealing elements 1 of a reactor pressure vessel of a nuclear power station. FIG. 1 shows a top view of an O-ring seal of this type. A plurality of accommodating openings 2 are positioned circumferentially on the inside of the seal as a type of equipartitioning, recesses connecting to the accommodating openings radially outward. A cross section of the O-ring seal represented in FIG. 2 discloses that the sealing element 1 used is a hollow body. Accordingly, each recess also serves as an access channel to a hollow space 3 of the tubular sealing element 1. The base area 4 of such an access channel is shown in FIG. 3. It is realized in the shape of a slot in a circumferential direction 5 of the O-ring seal and can essentially be reduced to a basic rectangular shape, where the two opposite shorter sides have been replaced in each case by an outwardly curved segment. The reactor pressure vessel looked at in this exemplary embodiment can be regarded in a first approximation as having two parts. In this case the first part, designated below as a reactor pressure vessel or simply only as pressure vessel 6, functions as a container that is open at one end. The container can be supplemented by the second part, a sealing part 7, for which the term cover is also used below, to form a serviceable pressure vessel 6 (see FIG. 16). Two ring-shaped sealing elements 1, which are fastened to the cover of the pressure vessel 6, are provided for the reactor pressure vessel. To this end, the two O-ring seals, in the operating state of the pressure vessel 6, are inserted at least partially in two concentric and equally ring-shaped accommodating grooves 8 in the cover of the pressure vessel 6. A top view of the accommodating grooves 8 is shown in detail in FIG. 4. The concentric arrangement of the two sealing elements 1 creates a double seal-barrier in a radial direction 9. The accommodating groove 8, partially visible on the right-hand side in the figure, is a component of the inner seal and the adjacent left-hand accommodating groove 8 is part of the outer seal. A number of indentations 10 corresponding to the number of accommodating openings 2 are provided on the inside of the respective ring-shaped seal in the sealing part 7 with a U-shaped base surface, into which indentations in each case a unit 11 of the sealing element fastening system can be inserted. A bore 12, placed approximately centrally, connects to the bottom of each indentation 10 in the direction of the cover of the pressure vessel 6. The bore 12 is provided with a counter thread 13 for accommodating a screw or a threaded bolt 14. The profile of each indentation 10, just as the profile of the two accommodating grooves 8, is rectangular. This is illustrated by a cross section of the sealing part 7, represented in FIG. 5, centrally through an indentation 10, selected as an example, and through the accommodating groove 8 connected thereto. FIG. 6 shows a unit 11 of a variant of the sealing element fastening system. A ring-shaped body 16, on which a cuboidal-shaped holding arm 17 is integrally molded, serves as a holding element 15. In the operating state of the pressure container 6, each holding arm 17 engages in a correspondingly positioned access channel on the sealing element 1. The corresponding state is documented in FIG. 7. The ring-shaped periphery of the holding element 15 and the two side faces of the holding arm 17 connected thereto have been provided at the edge with chamfers 18, which are to make an assembly or insertion easier. On a threaded bolt 14 with two separate threaded portions 20, 21, a thread-free region with a reduced outside diameter is provided between the threaded portions 20, 21, the thread-free region bearing a ring-shaped projection 19 in the center. In the operating state of the pressure vessel 6, the first threaded portion passes through the holding element 15 associated therewith and is screw-connected into a counter thread 13 in the cover of the pressure vessel 6. The top side of the ring-shaped projection 19 facing the first threaded portion 20 serves, in this case, as a stop member for the ring-shaped body 16 of the holding element 15, such that this latter is clamped quasi between the ring-shaped projection 19 and the bottom of the indentation 10 in the sealing part 7. The underside of the ring-shaped projection 19 facing the second threaded portion 21 functions, in contrast, as a stop member for a fill element 22, which, in its turn, in the operating state of the pressure vessel 6, is clamped between the underside of the ring-shaped projection 19 and a cylindrical bolt nut 23 screw-connected onto the second threaded portion 21. The fill element 22, which is to seal the corresponding indentation 10 in the operating state of the pressure vessel 6, has a basic shape similar to a U supplementing the indentation 10. A cylindrical opening 24 that is positioned approximately centrally in the fill element 22 is subdivided into three regions which differ with regard to the diameter of the opening and the measurement in the direction of the order of assembly 25. The first opening portion facing the threaded bolt 14 is provided with an inside diameter that is slightly greater than the outside diameter of the ring-shaped projection 19 on the threaded bolt 14. For the second opening portion an inside diameter has been selected that, on the one hand, is smaller than the outside diameter of the ring-shaped projection 19 and of the bolt nut 23 and, on the other hand, is greater than the outside diameter of the threaded bolt 14. The third opening portion finally has an inside diameter that is somewhat greater than the outside diameter of the bolt nut 23. The measurements of the opening portions in the order of assembly 25 are selected such that the ring-shaped projection 19, on the one hand, and the bolt nut 23, on the other hand, in the operating state of the pressure vessel 6, are arranged countersunk in the fill element 22 closed off in a flush manner. The wording used in this context, such as, for example, “somewhat greater”, is to be understood in this description to the effect that no precisely complementary shapes are provided for the components placed opposite each other in each case. Instead of which, the assembling of the components is to be made easier with a little play. In particular in the case of the reactor pressure vessel, the important point is the fit as the assembly of the units 11 can only be performed in protective clothing including appropriate gloves. Accordingly, a deviation in this regard is implemented even for the shapes of fill element 22 and indentation 10 that in principle complement each other. Three cylinder-like recesses 26, admitted on the periphery of the ring-shaped projection 19 and being a type of equipartitioning, serve as a point of application for a tool 27, by which the threaded bolt 14 is screw-connected into the counter thread 13 in the sealing part 7. On the cylindrical bolt nut 23 associated therewith are also situated three recesses 26, which in form and relative position to each other match those on the ring-shaped projection 19 to such an extent that the identical tool 27 is able to be used for both elements. By using a threaded bolt 14 with a ring-shaped projection 19 in place of a simple screw, it is possible to perform the assembly of the units 11 of the sealing element fastening system, as shown in the diagrams in FIGS. 8 to 10, in two part steps. In the first step, the holding element 15 is positioned in the corresponding indentation 10 and the holding arm 17 is introduced into the access channel. To pre-fix the holding element 15, the first threaded portion 20, passing through the holding element 15, is screw-connected into a counter thread 13 on the cover of the pressure vessel 6 until the holding element 15 is fastened to the cover, but is still able to be rotated about a central longitudinal axis 28 of the threaded bolt 14. The degree of freedom of movement consequently remaining serves for compensating inaccuracies in the production of the access channels and for creating a large tolerance range when inserting the O-ring seal into the accommodating groove 8 provided for this purpose. Once the arm positions of all the holding elements 15 used have been adjusted, the threaded bolt 14 is screwed down. In the second assembly step, the fill element 22 is inverted over the second threaded portion 21 and fixed with the bolt nut 23. The achievement by separating holding element fastening and fill element fastening is that the fill element 22 does not obstruct the view when the holding arm 17 is being aligned. FIGS. 11 to 13 show a tool 27 constructed for a two-stage assembly. In this case this is a rigid body with a tool grip 29, a tool shaft 30 and a tool head 31. Three pin-like grip elements 33, which can engage in the complementary recesses 26 on the bolt nuts 23 or on the threaded bolt projections 19, are integrally molded on the end face 32 of the hollow-cylindrical tool head 31. The pin length, in this case, is matched precisely to the recesses 26 on the bolt nuts 23. The inside diameter of the tool head 31, formed in the manner of a hollow cylinder, is greater than the outside diameter of the threaded bolt 14 and smaller than the outside diameter of the ring-shaped projection 19. This means that the tool head 31 can be inverted so far over the second threaded portion 21 until its pin-like gripping elements 33 engage in the recesses 26 on the ring-shaped projection 19. A unit 11 of the sealing element fastening system of an alternative variant can be seen in FIG. 14. The holding element 15 is also ring-shaped in this version and has a cuboidal integral molding as holding arm 17. However, contrary to the previous version, the edge-face edges are not chamfered. In a pre-assembly, the holding element 15 is fastened so as to be rotatable on the fill element 22 by a clamping bush 34, which is pressable into a central opening on the fill element 22 by way of the opening 24 that connects thereto. The rotatability of the holding arms 17 makes it possible, even in the case of the alternative variant of the sealing element fastening system, to undertake adaptations with regard to the relative position of the access channels. It is accepted here that during the final assembly vision is at least partially restricted by the fill element 22. On the other hand, the ability to pre-assemble the individual components of a unit 11 of the sealing element fastening system device that the time spent at the final assembly is reduced. This is of great importance, above all in the case of reactor pressure vessels, as the time a fitter is allowed to remain in the near range of the pressure vessel 6 has to be restricted on account of increased radioactive radiation. Within the pre-assembly process, the hollow-cylindrical part of the clamping bush 34, passing through the holding element 15, is pushed into the opening 24 in the fill element 22. To realize a frictional connection, the outside diameter of the cylindrical part of the clamping bush 34 is slightly greater than the inside diameter of the equally cylindrical opening 24 on the fill element 22. As the outside diameter of the cylindrical part of the clamping bush 34 is smaller than the inside diameter of the ring-shaped holding element 15 and as a conical part with an increasing outside diameter connects to the cylindrical part of the clamping bush 34, it is ensured, on the one hand, that the holding element 15 is fastened to the fill element 22 and, on the other hand, the holding arm 17 is rotatably mounted. In the final assembly, the pre-assembled unit 11 shown in FIG. 15 is inserted into the indentation 10 in the sealing part 7 and fastened to the cover of the pressure vessel 6 by way of a cap screw 35 that passes through the pre-assembled unit. In the operating state of the pressure vessel 6, the cap 35 or fastening screw is then screw-connected far enough into the counter thread 13 in the sealing part 7 so that the head of the screw is positioned countersunk in the fill element 22. |
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abstract | A lower pole piece of an electromagnetic superposition type objective lens is divided into an upper magnetic path and a lower magnetic path. A voltage nearly equal to a retarding voltage is applied to the lower magnetic path. An objective lens capable of acquiring an image with a higher resolution and a higher contrast than a conventional image is provided. An electromagnetic superposition type objective lens includes a magnetic path that encloses a coil, a cylindrical or conical booster magnetic path that surrounds an electron beam, a control magnetic path that is interposed between the coil and sample, an accelerating electric field control unit that accelerates the electron beam using a booster power supply, a decelerating electric field control unit that decelerates the electron beam using a stage power supply, and a suppression unit that suppresses electric discharge of the sample using a control magnetic path power supply. |
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049888838 | description | DETAILED DESCRIPTION The fingernail light system has a housing 1, in the center of which a telescoping arm 2 having a vertically aligned axis 3 is located. A support body 4 is secured to the upper end of the telescoping arm, and on it a hand, indicated by dot-dash lines, is placed in such a way that it grasps the support body 4 from above. A support frame 6 is also secured to the upper end of the telescoping arm 2, and two spiral springs 8 engaging the bottom plate 7 of the housing 1 are located on the underside of the support frame 6, with their axes 9 extending parallel to the axis 3 of telescoping arm 2. The spring 8 on the left in FIG. 1 is shown in a position in which the support body 4 is retracted from the housing 1 via an upper housing opening 10 via the telescoping arm 2, while the spiral spring 8 on the right is shown compressed, in a position in which the support body 4 has been thrust into the housing 1. Located beneath the upper housing cover 11 is an annular irradiation lamp 12 surrounded by a reflector 13. The axis 14 of the irradiation lamp 12 extends horizontally, that is, at a right angle to the axis 3 of telescoping arm 2. As FIG. 2 also shows, the irradiation lamp 12 and the reflector 10 both extend concentrically to the axis 3 of the telescoping arm 2, which simultaneously forms the axis of the support body 4 as well. In its upper position, the support body 4 is readily accessible; the lower position, represented by the dot-dash line, is selected so that the fingernails 15 are positioned in the irradiation zone of the irradiation lamp 12, which is limited by the reflectors 13 to a narrow annular sector. In the lower position, the forearm 16 rests on a support 17 that merges with the edge of the housing opening 10, which assures a relaxed hand posture during irradiation of the fingernails 15 in the housing 1. The support body 4, has a generally convex surface and, in FIGS. 1-3 has an approximately cylindrical outer contour, has a plurality of channels 18, which extend axially and have a depth in the vicinity of the groove bottom of approximately 2 to 5 mm. There is a total of seven channels, as shown clearly in FIG. 2, distributed about the outer circumference of support body 4; the middle channel, which coincides with the first plane 19, serves to position the middle finger 20 of either a left or a right hand 5. This channel 18 for the middle finger 20 is exactly opposite the seated position of the person whose fingernails are to be irradiated. Two further channels 18 are offset by approximately 45.degree. with respect to the channel 18 for the middle finger 20, and they serve to receive the ring finger 21 and index finger 22, for instance of a right hand as in FIG. 2; when the fingernails of a left hand are irradiated, the channel 18 for the ring finger 21 is then used for the index finger instead, while the channel 18 for the index finger now serves to receive the ring finger. Two further channels 18 are located offset to the channel for the index finger or ring finger 21, 22 by 90.degree.; they serve to receive the little finger 23 of a hand to be irradiated. Of the channels 18, one channel 18 each is definitively associated with the little finger of a right hand and the little finger of a left hand. Finally, two channels 18 for the thumbs 24 of a left and a right hand are provided, which are offset by an angle of approximately 135.degree. to both sides with respect to the channel 18 for index finger 22. To avoid blinding the person being treated, the housing opening 10 is surrounded by a continuous glare protection rim 25. In the lower position of the support body 4, its underside actuates an end switch 26 (see FIG. 1), in order to put the irradiation lamp 12, as well as further systems, such as a fan 27 located laterally in the housing 1, into operation. In the lower portion of the housing 1, next to the fan 27, there is also sufficient room for power supply parts 28 and chokes 29. By comparison with the version of FIG. 1, in the FIG. 3 embodiment of the light system, the axis 3 of the telescoping arm 2 and support body 4 extends at an angle 30 of about 45.degree. to the orthogonal axis 31, represented by the broken line, of the bottom plate 7. The entire light system, formed by the irradiation lamp 12, the reflector 13 surrounding irradiation lamp 12, and the spiral springs 8, is correspondingly tilted. The axis 14 of the irradiation lamp 12 is again aligned at an angle of 90.degree. with respect to the axis 3 of telescoping arm 2 and support body 4, as in the version of FIG. 1. The housing opening 10 is located in a front housing panel 32, so that the hand 5 rests from the front on the support body 4, and the fingers can be positioned in the channels 18. The support 17 for the forearm 16 is an extension of the lower rim of the housing opening 10, which simultaneously forms the glare protection rim 25. A hinged glare protection hood 33 is also secured to the upper part of the glare protection rim 25. The glare protection hood 33 can be folded over the back of the hand, once the hand 5 along with the support body 4 has been moved into the housing 1. In FIGS. 1-3, a support body 4 of approximately cylindrical outer contour is used. FIG. 4 shows a support body 4 formed as a truncated cone. This support body 4 is again rounded on top, to form a rest for the palm of the hand 5. The fingernails 15 of the fingers placed in the channels 18 protrude past the lower rim of the support body 4, so that they do not touch any part of the light system, and can be freely irradiated from all sides. Besides the channels 18 as positioning means for the various fingers, an additional positioning means can be used in the form of stops or an encompassing bead 34, against which the fingertips of the hand 5 placed on the support body 4 come to rest. FIG. 5 illustrates an embodiment similar to that of FIGS. 1 and 2, with the axis 3 of the support body 4 again oriented vertically with respect to the bottom plate 7. However, the support body 4 is surrounded by four separate irradiation lamps 12, each having a straight lamp axis 14. These straight irradiation lamps 12 are lined up with one another in such a way that they form an approximate circle about the support body 4, at least over the circumference over which the various channels 18 for the fingers are distributed. This circle need not be closed, because the irradiation zone begins at the channel 18 for one thumb 24 and ends with the channel 18 for the other thumb 24, so that an irradiation zone of only 300.degree. to approximately 320.degree. is required. The irradiation lamps 12 shown in FIG. 5 are again surrounded by reflectors 13, which aim the light at the support body 4, and in particular at the lower region thereof. Various changes and modifications may be made, and features described in connection with any one of the embodiments may be used with any of the others, within the scope of the inventive concept. |
summary | ||
description | 1. Field of the Invention The present invention generally relates to forming patterns on electronic wafers, and more specifically to a new mask technology called SUPREMA (Surface Potential Reflection Electron MAsk) which allows manipulation of reflection characteristics of areas on a mask wafer surface that may be thought of as pixels in a matrix. As a beam illuminates the mask wafer, individual pixels are effectively turned on and off so that the beam will subsequently write the pattern of interest with deep submicron resolution onto a target wafer. In a preferred embodiment providing a programmable mask, writing a new pattern on the mask surface does not require a change of the mask surface itself, but instead changes in software which then controls a voltage of individual pixel-areas on the mask surface. 2. Description of the Related Art Modern microelectronic manufacturing requires high resolution lithography. As 0.1 μm feature sizes are approached, optical lithography methods are rapidly becoming obsolete. Several large efforts are under way to develop so-called Next Generation Lithography (NGL) methods. These include Extreme Ultra-Violet (EUV), ion beam projection, and electron beam projection lithographies. The principal efforts in electron beam lithography are “Scalpel”® and “Prevail”®, in which a high energy electron beam passes through a mask. As shown in FIG. 1, in “Scalpel”®, a thin film mask 11 with a metallic scattering layer is used to disperse the electron beam 10 in areas that are not to be exposed on the wafer 12. Wafer 12 has a photoresist layer on its upper surface (not shown in the figure). A contrast aperture 13 in the objective lens backfocal plane removes these scattered electrons from the beam. The thin film mask is supported by an array of struts that periodically interrupt the pattern to be printed. “Prevail”® uses a stencil mask. Since a stencil mask cannot support free-floating elements, two consecutive masks are required to expose the wafer to a given pattern. In both schemes, mask and wafer must be scanned together in lockstep, at a fixed demagnification, with the mask stage periodically jumping ahead over the struts. The electron beam sweeps across the mask, exposing the wafer in a manner much like an electron beam sweeping across a CRT monitor. For both “Scalpel” and “Prevail”, the mask technology is complex and expensive, and the resulting masks are extremely fragile. Like all current lithography methods other than direct e-beam write, a new pattern requires a new mask to be manufactured and introduced into the e-beam projection column. With mask costs easily exceeding $50K, this constitutes a significant cost in the microelectronic manufacturing process. What is needed in the art is a technology that allows mask costs to be reduced while maintaining or even improving resolution and throughput. Prior to the present invention, no such technology has been known. In view of the foregoing problems, drawbacks, and disadvantages of the conventional systems, it is an object of the present invention to provide a structure (and method) for electronic wafer preparation in which a mask for generating an image of the wafer is a programmable mask. It is another object of the present invention to provide for an electronic wafer mask having reduced cost compared to current technologies. It is another object of the present invention to teach a variety of forms for the electronic mask in this new technology. To accomplish these goals and objectives, as a first aspect of the present invention, described herein is a method and apparatus of controlling a beam used to generate a pattern on a target surface, including generating a beam of charged particles and directing the beam to a mask surface and causing the beam to be one of absorbed by and reflected from the mask surface, thereby either precluding or allowing the beam to continue on to strike the target surface based on a reflection characteristic of the mask surface. As a second aspect of the present invention, described herein is a mask used to control a beam for generating a pattern on a target wafer surface, the beam including charged particles directed onto a surface of the mask, the mask including an essentially planar surface in which the surface contains a plurality of areas, each area having a surface characteristic such that the beam is one of essentially absorbed by the surface and essentially reflected from the surface. Referring now to the drawings, a new electron beam lithography method based on a new mask technology called SUPREMA is now described in detail. SUPREMA technology allows the writing of patterns on a wafer by a projection method utilizing a large number of individually addressable parallel electron beams generated by a universal mask. These beams may be thought of as pixels in a matrix. This beam pixel matrix is scanned across the wafer, turning individual pixels on and off to write the pattern of interest with deep submicron resolution. Writing a new pattern does not require a change of mask, but rather a change of software addressing the mask. Unlike the conventional projection electron beam lithography methods (e.g., “Scalpel”, “Prevail”) the mask is stationary, and is not traversed by a high energy electron beam. Instead, the mask is fabricated on a standard Si wafer, using standard fabrication methods. Thus, mask motion, exposure and fabrication methods common to “Scalpel” and “prevail” are eliminated by this invention. Wafer throughput numbers are estimated to be somewhat better than “Scalpel”/“Prevail”. Optimally, an electronic wafer mask would be universal in the same sense that a computer display is universal. To present a new image on a computer screen the display screen is not exchanged. Rather, the pattern used to address the pixels on the display screen is generated for each image. Similarly, mask fabrication costs could be reduced significantly if it relied on standard semiconductor manufacturing schemes that can be applied in bulk, if the mask is easily programmable for new patterns, and if the mask would be assembled on a bulk wafer, rather than a thin membrane. This invention describes such a mask technology. FIG. 2 shows an exemplary layout of the present invention. Basically, an electron beam 20 is deflected to mask wafer 21. The surface of this mask wafer 21 has a pattern to be transferred to the resist layer on target wafer 22. The pattern is represented on the surface of mask wafer 21 by differences in reflectivity of individual points or regions on the mask wafer surface. Based on this surface reflectivity, the beam 20 will be allowed either to continue on to the target wafer 22 because it was reflected by a mask wafer surface point or would be precluded from striking the target wafer because a point on the mask wafer absorbed the beam rather than reflecting it. Additional details of a preferred implementation of a SUPREMA projection system can be seen with reference to FIG. 2. An electron source creates an electron beam. Using suitable condenser optics 23, this beam is steered into a magnetic prism array 24 that deflects the beam over an angle θ, here conveniently chosen at 90 degrees although other deflection angles are possible. The prism array 24 acts like a series of round lenses with well-defined optical properties. The prism array can be designed to be achromatic over its full range of working distances. Such prism arrays have recently been employed successfully in several Low Energy Electron Microscopy (LEEM) designs. The electron beam is focused in the backfocal plane of the reflector lens 25. The mask wafer 21 is held at a potential 28 close to that of the gun electron emitter, so that the incident electron beam is decelerated to near zero energy. The mask is in fact an integral part of the reflector lens 25 imaging system, as it is in LEEM. Electrostatic potentials applied to the individual pixel elements on the mask turn individual beam elements on and off as desired. The reflected beam pixel array is accelerated back into the reflector lens 25, forming a crossover in the backfocal plane. A contrast aperture 26 placed in this backfocal plane, or in a conjugated plane further down the beam path (as is shown in FIG. 2), selects only specularly scattered electrons to optimize on/off contrast. The prism array 24 now deflects the beam pixel array downward, again over an angle θ. Suitable projection optics 27 can now demagnify the beam pixel array for target wafer 22 exposure. For instance, if the pixel elements on the mask have a lateral extent of 250 nm, a 10× demagnification would give rise to 25 nm beam pixels on the wafer. With a reasonable beam size of 50×50 μm impinging on the mask, divided in 200×200 250×250 nm pixels, the wafer is exposed to a 40,000 PBA, with an individual pixel beam size of 25×25 nm. Since the exposure dose in μC/cm2 is fixed for a given combination of electron beam resist and electron energy, the time required to expose a square centimeter of wafer area depends on the available beam current only, not on the beam demagnification. Thus, a demagnification can be chosen that is optimal for the feature sizes to be written. To write a pattern on the wafer it is desirable to rapidly scan the beam pixel array back and forth along one direction (using scan coils 29 in the projector column), while the wafer stage moves incrementally along the orthogonal direction, effectively moving the pixel array in a raster-like fashion across the wafer surface. Such raster scanning is preferable over a stationary beam with all motions carried out by the wafer stage, because it strongly reduces stage velocity and acceleration. The programmable SUPREMA mask does not move, nor does the electron beam at that point in the column. From a simple analysis of realistically available electron beam sources, electron beam resist sensitivities, required wafer throughputs (equal or better than “Scalpel”), and resulting beam scanning speeds, beam pixel ‘live’ times of 0.1-1μ seconds can be arrived at, i.e., switching frequencies of 1-10 MHz. Such switching frequencies are well within the range of available transistor technologies. Turning now to FIG. 3, the principle behind SUPREMA is explained as based on an observation commonly made in Low Energy Electron Microscopy (LEEM). In LEEM, the sample under study forms a cathode in an electrostatic immersion objective lens. That is, there is a strong electrostatic field between the objective lens and the sample. An electron beam (typical energy 5-20 keV) is focused in the backfocal plane of the objective lens, and decelerated by the immersion field to near zero energy on its way to the sample. The exact electron energy at the sample is determined by the voltage difference between the electron gun emitter (field emitter or filament) and the sample. After sample interaction, electrons are accelerated back into the objective lens, forming a cross-over in the backfocal plane of the objective lens, and a Gaussian image of the sample at some greater distance. The electron reflectivity from the sample depends strongly on the electron energy at the sample surface. When the electrons strike the sample prior to reflection (i.e., a sample potential smaller than gun potential), reflectivity is on the order of 1-5 percent, and reflected electrons are scattered over a wide range of angles, as shown in the right side of FIG. 3. When the electrons reflect in front of the sample (often referred to as ‘mirror’ mode, with the sample potential greater than the gun potential), reflectivity is 100 percent and specular, as shown in the left side of FIG. 3. When a contrast aperture is placed in the backfocal plane, accepting only electrons in the specular direction, the contrast difference between mirror and non-mirror electrons is accentuated even further, with resulting contrast ratios of about 100:1. The sample voltage swing between mirror and non-mirror is small, around one to two volts. The mask wafer 21 shown in FIG. 2 takes advantage of this reflection phenomenon. As shown in FIG. 4, this mask wafer 21 could have various entire regions 40 whose reflectivities comprise a pattern. Alternatively, the mask wafer 21 could be considered as a matrix of pixels 41, each pixel being a point or area whose reflectivity is individually controlled. There are several ways to affect the electrostatic potential on the surface, as embodied by the target mask 21 of the present invention. The first method relies on variations of electron workfunction for different elements. Elements such as Barium (Ba) and Niobium (Nb) have very low electron workfunctions of about 2.5 V. Platinum (Pt) on the other hand has a high workfunction of about 5.5 V. If a pattern of Pt areas (i.e., dots) is printed on top of a Nb thin film, the Pt dots will have an electrostatic potential that is higher than the Nb film by about 3 eV. Thus, as shown in FIG. 3, an electron beam with a potential between the Pt and Nb workfuntions will be reflected specularly with 100% efficiency by the Pt dots, but scattered diffusely with 1-5% efficiency by the Nb film. The reflected electron beam includes an array of bright spots corresponding to the Pt dots, against a much darker uniform background, as shown in FIG. 5. Such a static workfunction-based SUPREMA mask has both advantages and disadvantages. For example, such a mask is easy to make on a bulk substrate and relies on conventional lithographic methods. However, since the mask is too large to be printed all at once, the electron beam must image the entire mask onto the wafer in a scanning fashion, as is the case in “Scalpel” and “Prevail” discussed above. To do this effectively, both the mask and the wafer need to move under the electron beam. In addition, the workfunction may not be an entirely robust property. For instance, if the mask were to get covered with a 1 nm contaminating carbon film, the workfunction contrast would be largely lost. Fortunately, a simple alternative scheme can be devised to switch a reflected electron beam ON and OFF by controlling the voltage of the surface of the mask wafer. In this scheme, the voltage is dropped below mirror mode voltage to turn the beam OFF and raised above mirror mode to turn it ON. If the sample surface is not a single plane held at a single potential, but a pixelated plane containing n×m metallic electrodes and the potential of each electrode is controlled individually, then the mask becomes a pixelated plane with points individually controlled for reflectivity. Such could be performed in several ways. One way would be to attach a control conductor to each pixel and separately control the voltage of each electrode. As shown by exemplary array 60, 61, 62 in FIG. 6, various configurations of arrays could be used, with each configuration having advantages and disadvantages. As examples, the n×n array 60 has a disadvantage that it would be hard to wire all pixels in the array. The advantage is that the throughput does not depend on layout, only total beam current. The n×1 vector array 61 has the advantage that it would be much easier to wire the pixels but has the disadvantages of having an extreme aspect ratio and large field size. The n×m skinny array 62 has a middle ground in that it has a modest aspect ratio and is not too hard to wire all the pixels. Alternatively, as shown in FIG. 7, a matrix of photodiodes 70, each photodiode corresponding to a pixel, could be fabricated into the mask wafer 71. Each pixel is individually controlled by shining light 72 on the corresponding photodiode from a source such as a light emitting array 73. An illuminated pixel would have a voltage different from a pixel that has no illumination, and this difference in potential is used to control the pixel reflectivity for electron beam 74. This latter scheme significantly reduces concerns due to pixel density and associated multilayer wiring. The incident electron beam is now reflected in an n×m pixel array, and the electron beam in each pixel can be turned on and off independently of all other pixel elements. Effectively, the reflected beam now includes n×m independent electron beams, each with a high-contrast on/off ratio. This programmable electron beam array can be scanned across a wafer to write arbitrary patterns at high resolution and high speed. This method solves the disadvantages of the workfunction-based SUPREMA mask since the programmable mask is stationary. If the mask gets covered by a contaminating carbon film, it may be necessary to adjust the overall potential of the mask by a volt or so, but the contrast between on and off pixels is completely unaffected by this overall voltage shift. In addition, the mask is universal. That is, printing a new pattern does not require a new mask wafer but only a new pattern generated by the software addressing the mask surface pixels. Of course, the programmable mask is significantly more complex than the workfunction mask, but given the high costs of present high resolution masks, and the escalation of that cost to be expected for membrane and stencil masks, SUPREMA mask costs should not present an unsurmountable barrier, in particular because one mask can serve many different products. The total electron current in the beam is of the same order as that used in the “Scalpel” and “Prevail” projection methods, resulting in comparable wafer throughput. In fact, the wafer throughput in “Scalpel” is limited by the deleterious effects of space charge in the electron beam crossover just below the objective lens, which carries the full electron beam current. In the inventive scheme presented here, preferably only active pixels carry current, reducing the projected beam current by a factor of two to ten, and mitigating space charge effects. Thus, it is anticipated that the inventive SUPREMA based e-beam writing systems will be capable of wafer throughputs that exceed “Scalpel” throughputs by up to a factor of two. Having read the above description, one of ordinary skill in the art would readily recognize that software control of any of the various reprogrammable masks is straightforward since it merely includes identifying (and, optionally, retaining in storage on a digital medium) which individual components of an array or matrix are considered “ON” and which are considered “OFF”. FIG. 8 illustrates a typical hardware configuration of an information handling/computer system in accordance with the invention and which preferably has at least one processor or central processing unit (CPU) 811. The CPUs 811 are interconnected via a system bus 812 to a random access memory (RAM) 814, read-only memory (ROM) 816, input/output (I/O) adapter 818 (for connecting peripheral devices such as disk units 821 and tape drives 840 to the bus 812), user interface adapter 822 (for connecting a keyboard 824, mouse 826, speaker 828, microphone 832, and/or other user interface device to the bus 812), a communication adapter 834 for connecting an information handling system to a data processing network, the Internet, an Intranet, a personal area network (PAN), etc., and a display adapter 836 for connecting the bus 812 to a display device 838 and/or printer 839 (e.g., a digital printer or the like). In addition to the hardware/software environment described above, a different aspect of the invention includes a computer-implemented method for performing the above method. As an example, this method may be implemented in the particular environment discussed above. Such a method may be implemented, for example, by operating a computer, as embodied by a digital data processing apparatus, to execute a sequence of machine-readable instructions. These instructions may reside in various types of signal-bearing media. Thus, this aspect of the present invention is directed to a programmed product, comprising signal-bearing media tangibly embodying a program of machine-readable instructions executable by a digital data processor incorporating the CPU 811 and hardware above, to perform the method of the invention. This signal-bearing media may include, for example, a RAM contained within the CPU 811, as represented by the fast-access storage for example. Alternatively, the instructions may be contained in another signal-bearing media, such as a magnetic data storage diskette 900 (FIG. 9), directly or indirectly accessible by the CPU 811. Whether contained in the diskette 900, the computer/CPU 811, or elsewhere, the instructions may be stored on a variety of machine-readable data storage media, such as DASD storage (e.g., a conventional “hard drive” or a RAID array), magnetic tape, electronic read-only memory (e.g., ROM, EPROM, or EEPROM), an optical storage device (e.g. CD-ROM, WORM, DVD, digital optical tape, etc.), paper “punch” cards, or other suitable signal-bearing media including transmission media such as digital and analog and communication links and wireless. In an illustrative embodiment of the invention, the machine-readable instructions may comprise software object code. While the invention has been described in terms of a single preferred embodiment, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. |
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claims | 1. A nuclear reactor power monitor, comprising:a first calculation unit configured to calculate a first stability index of the reactor core based on time series data which indicate a power oscillation in nuclear instrumentation signals outputted from a plurality of nuclear instrumentation detectors which detect neutrons in a reactor core;a first determination unit configured to compare the first stability index and a first reference value and determine whether nuclear thermal hydraulic stability of the reactor core is stable or deteriorated;a second calculation unit configured to calculate a second stability index of the reactor core based on the time series data when the nuclear thermal hydraulic stability is determined to be deteriorated in the first determination unit; anda second determination unit configured to compare the second stability index and a second reference value and determine whether to perform suppressing operation of the power oscillation,wherein in response to determination in the first determination unit and the second determination unit, any of an alarm, oscillation information and an automatic start signal of an oscillation suppression device is issued in stages as a suppression operation of the power oscillation. 2. The nuclear reactor power monitor according to claim 1, comprisinga grouping unit configured to divide the nuclear instrumentation detectors into groups, whereinthe grouping unit performs grouping of the nuclear instrumentation detectors based on information including any of an estimated power distribution of the reactor core, a higher order space mode distribution of neutron fluxes, and a specified fuel assembly position. 3. The nuclear reactor power monitor according to claim 2, whereinthe nuclear instrumentation signals processed in the first calculation unit and are individual signals of the nuclear instrumentation detectors selected from the groups or an average signal of a plurality of nuclear instrumentation detectors in units of the groups. 4. The nuclear reactor power monitor according to claim 2, whereinthe power distribution or the higher order space mode distribution of neutron fluxes is estimated based on a physical model or a data base. 5. The nuclear reactor power monitor according to claim 1, whereinan index indicating variations in oscillation period of a plurality of the time series data is used as the first stability index. 6. The nuclear reactor power monitor according to claim 1, whereinan amplitude or a decay ratio of a plurality of the time series data is used as the second stability index. 7. The nuclear reactor power monitor according to claim 5, whereinthe oscillation period is obtained by applying a statistical method including an autoregression analysis method, an autocorrelation function method, and a spectrum analysis method, to the time series data. 8. The nuclear reactor power monitor according to claim 6, whereinthe amplitude or the decay ratio is obtained by a peak detection method including fitting the time series data set on intervals by a polynomial and searching for a point where a differential value of the polynomial is equal to zero, andthe point where the differential value is equal to zero is first searched within a period of time, composed of half of the oscillation period and a margin, with a switchover point from the first determination unit as an origin, and then the point is searched within a period of time, composed of a half of the oscillation period and a margin, with searched point as an origin in a repeated manner. 9. The nuclear reactor power monitor according to claim 5, whereina sampling period of the time series data converted into digital data or the sampling period multiplied by a coefficient set in consideration of a decay ratio is used as the first reference value, andthe first determination unit executes the determination based on duration time during which the nuclear thermal hydraulic stability is indicated to be in a deteriorated state in comparison between the first stability index and the first reference value. 10. The nuclear reactor power monitor according to claim 8, whereina spline function is used as the polynomial, andout of intervals which are interposed in between data points that constitute the time series data, an interval in which a product of derivatives of the data points placed on both sides of the interval is a minus-sign product is obtained, the obtained interval is further divided, and out of these dividing points, a point where an absolute value of a derivative is minimum is searched as the point where the differential value is equal to zero. 11. The nuclear reactor power monitor according to claim 1, whereinwhile the second calculation unit is in operation, the first calculation unit is concurrently operated, andwhen a determination to execute power control of the reactor core is not made in the second determination unit in predetermined time, operation of the second calculation unit is stopped and operation of the first calculation unit is continued. 12. The nuclear reactor power monitor according to claim 1, whereina spatial distribution of phase difference in the power oscillation is obtained based on phase difference in the time series data from the nuclear instrumentation detectors positioned at a local instability central region and peripheral regions of the local instability central region so as to estimate a power oscillation mode including any of a local oscillation, a regional oscillation and a core-wide oscillation. 13. The nuclear reactor power monitor according to claim 2, whereina power oscillation mode is estimated by calculating phase difference between average signals in units of the groups, and the first reference value and the second reference value are changed into optimum values corresponding to the estimated power oscillation mode. 14. A nuclear reactor power monitor, comprising:a first calculation unit configured to calculate a first stability index of the reactor core based on time series data which indicate a power oscillation in nuclear instrumentation signals outputted from a plurality of nuclear instrumentation detectors which detect neutrons in a reactor core;a first determination unit configured to compare the first stability index and a first reference value and determine whether nuclear thermal hydraulic stability of the reactor core is stable or deteriorated;a second calculation unit configured to calculate a second stability index of the reactor core based on the time series data when the nuclear thermal hydraulic stability is determined to be deteriorated in the first determination unit; anda second determination unit configured to compare the second stability index and a second reference value and determine whether to perform suppressing operation of the power oscillation, further comprisinga third determination unit configured to execute the power oscillation suppression operation if it is determined that the first stability index satisfies a third reference value which is set more severely than the first reference value even when the power oscillation suppression operation has been determined to be unnecessary based on the second stability index. 15. The nuclear reactor power monitor according to claim 1, whereinthe first calculation unit calculates a decay ratio as the first stability index, andthe second calculation unit calculates the second stability index by counting the time series data determined to indicate the deterioration in the first determination unit. 16. The nuclear reactor power monitor according to claim 15, whereinthe nuclear instrumentation detectors are divided into groups, andthe second calculation unit calculates the second stability index in units of the group. 17. The nuclear reactor power monitor according to claim 15, further comprisinga reference value updating unit configured to update the first reference value once the second stability index exceeds the second reference value, whereinwhenever the updating is performed, a plurality of power suppression devices different in suppression level are activated in stages. 18. The nuclear reactor power monitor according to claim 17, whereinthe power suppression devices include those implementing at least three kinds of different effects: alarm issuance; suppression preparation; and suppression. 19. The nuclear reactor power monitor according to claim 15, whereina decay ratio which exceeds the first reference value and a decay ratio which does not exceed the first reference value are distinguishably displayed on a map which displays placement configuration of the nuclear instrumentation detectors. 20. The nuclear reactor power monitor according to claim 19, whereinthe map is automatically displayed in synchronization with instruction to activate the power suppression device. 21. The nuclear reactor power monitor according to claim 16, whereinan activation instruction unit instructs activation of the power suppression device when the second stability index exceeds the second reference value at least in two or more groups. 22. The nuclear reactor power monitor according to claim 21, comprisinga reference value correction unit configured to obtain an average value of the decay ratios in units of the group and to correct the first reference value based on a deviation between the average values. 23. The nuclear reactor power monitor according to claim 15, comprisinga weighting factor setting unit configured to set a weighting factor, whereinthe second calculation unit calculates a plurality of second stability indexes based on the first reference values each having a different value, multiplies the calculated index values by the weighting factors corresponding to respective indexes, adds up the multiplied values, and then outputs the resulting value. 24. The nuclear reactor power monitor according to claim 23, whereinthe weighting factor is normalized to provide a value of 1 when respective values corresponding to the second stability indexes are added up. 25. The nuclear reactor power monitor according to claim 23, further comprisinga reference value updating unit configured to update the second reference value once the second stability index exceeds the second reference value. |
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050646044 | abstract | A sensor assembly comprising a rod-shaped thermally conductive element oriented radially with respect to a flow pipe and two or more thermocouples installed on the thermally conductive element. A first end of the thermally conductive element is arranged in contact with or in thermal communication with the outer periphery of the pipe, while a second end of the thermally conductive element is spaced from the pipe. As a result of heat conduction through the pipe to the first end, a temperature gradient is provided across the thermally conductive element. The temperature gradient exhibits a relatively high temperature near the first end and a relatively low temperature near the second end. The thermocouples are installed along the length of the thermally conductive element. One thermocouple is arranged nearer to the pipe than the other thermocouple. Temperature dependent signals obtained from the thermocouples are transmitted to suitable evaluation electronics. The evaluational electronics determines a temperature difference between the two thermocouples based on the thermocouple signals. The temperature difference is then compared with known or preset values to determine the flow status of the pipe. |
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claims | 1. An isotope production target, comprising:an outer diameter wall;an inner diameter wall located within the outer diameter wall, wherein a top of both the inner diameter wall and the outer diameter are sealed together and a bottom of both the inner diameter wall and the outer diameter are sealed together to form a sealed chamber;an isotope source comprising particles of fissile material loosely placed between the inner diameter wall and the outer diameter wall to facilitate removal of the loosely placed particles of fissile material after irradiation of the isotope production target, wherein the loosely placed particles of fissile material are in contact with each other and interspersed with a plurality of voided regions around each of the loosely placed particles of fissile material in the sealed chamber to capture fission gases released from the loosely placed particles of fissile material due to the irradiation of the isotope production target; anda central region located within the inner diameter wall, wherein the central region houses a neutron thermalization volume. 2. The isotope production target of claim 1, wherein the plurality of voided regions located in the sealed chamber capture the fission gases produced from irradiation of the loosely placed particles of fissile material, and wherein the plurality of voided regions remain in place during operation of the isotope production target. 3. The isotope production target of claim 2, wherein the one or more voided regions are sealed between the outer diameter wall and the inner diameter wall to prevent the fission gases from exiting the isotope production target. 4. The isotope production target of claim 1, wherein the loosely placed particles of fissile material are substantially ball-shaped, and wherein the plurality of voided regions are formed around contact points of adjacent ball-shaped particles. 5. The isotope production target of claim 1, wherein the loosely placed particles of fissile material comprise powder, and wherein the plurality of voided regions are formed around contact points of adjacent particles of the powder. 6. The isotope production target of claim 1, wherein the neutron thermalization volume comprises water. 7. The isotope production target of claim 6, wherein the isotope production target is configured to be installed in a reactor core, and wherein the water comprises a primary coolant associated with the reactor core. 8. The isotope production target of claim 7, wherein the reactor core is associated with a reactor of less than twenty megawatts thermal, and wherein the isotope source comprises low-enriched uranium (LEU). 9. The isotope production target of claim 1, wherein the central region is configured to cause neutrons that are generated in the loosely placed particles of fissile material to be thermalized by the neutron thermalization volume before re-entering the loosely placed particles of fissile material. 10. The isotope production target of claim 1, wherein the loosely placed particles of fissile material comprise substantially round balls of fissile material. 11. The isotope production target of claim 1, wherein the loosely placed particles of fissile material comprise fissile powder. 12. The isotope production target of claim 1, wherein the sealed chamber comprises an annular-shaped isotope production chamber located between the outer diameter wall and the inner diameter wall, and wherein one or more of the loosely placed particles of fissile material are in contact with at least one other particle located along a circumference of the annular-shaped isotope production chamber. 13. An isotope production target, comprising:an isotope source comprising particles of fissile material;means for housing the particles of fissile material, wherein the particles of fissile material are loosely placed within the means for housing to facilitate removal of the loosely placed particles of fissile material after irradiation of the isotope production target, and wherein the loosely placed particles of fissile material are interspersed with a plurality of voided regions around contact points of laterally adjacent particles located in a circumference of the means for housing to capture fission gases released from the loosely placed particles of fissile material due to the irradiation of the isotope production target; andmeans for thermalizing neutrons located within a central region of the isotope production target. 14. The isotope production target, of claim 13, wherein the means for thermalizing comprises primary coolant associated with a reactor core. 15. The isotope production target, of claim 14, further comprising means for directing the primary coolant through the isotope production target. 16. The isotope production target, of claim 13, wherein the loosely placed particles of fissile material comprise substantially round balls of fissile material. 17. The isotope production target, of claim 13, wherein the loosely placed particles of fissile material are stored in a powder form in the means for housing. 18. The isotope production target, of claim 13, wherein the means for housing comprises an enclosed annular-shaped isotope production chamber, and wherein each of the loosely placed particles of fissile material are in contact with at least one other particle located along a circumference of the annular-shaped isotope production chamber. 19. The isotope production target, of claim 13, wherein the plurality of voided regions are configured to capture the fission gases generated from irradiating the loosely placed particles of fissile material located in the means for housing. 20. The isotope production target, of claim 13, wherein the loosely placed particles of fissile material are substantially ball-shaped, and wherein the plurality of voided regions are formed between contact points of adjacent ball-shaped particles. 21. The isotope production target, of claim 13, further comprising:means for directing primary coolant associated with a reactor core to pass through the central region. 22. The isotope production target of claim 21, wherein the primary coolant is directed through the central region of the isotope production target to thermalize neutrons generated by the isotope production target before the neutrons re-enter the loosely placed particles of fissile material and generate further neutrons that are thermalized by the primary coolant in the central region. |
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abstract | In order to control a collimator so that an X-ray impingement position on an X-ray detector is kept constant, an error of the impingement position of a fan-shaped beam (400) in the direction of side-by-side arrangement of a plurality of detector element rows in a detector element array (24) is detected (101), and the collimator is controlled (103) based on the detected error so that the impingement position of the fan-shaped beam is kept at a constant position. |
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abstract | An electromagnetic wave-absorbing composition is obtained by dispersing in a base polymer a magnetic powder coated with electrically insulating inorganic fines and optionally, a heat conductive powder. The composition has a high breakdown voltage, and can be applied to any adequate site within electronic equipment without a need to pay substantial attention to short-circuits. |
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abstract | Attenuating, while in or on a body of water, one's own emanated electromagnetic field by wearing apparel that includes an electromagnetically shielding fabric. The shielding fabric comprises a substantially continuous system of conductive fibers combined with non-conductive fabric. Or attenuating, while a person is in or on a body of water, the electromagnetic field emanated by the person, by (i) providing to the person apparel that includes the electromagnetically shielding fabric, and (ii) instructing the person to wear it while in or on the water. The attenuation of the emanated electromagnetic field decreases the likelihood of a person being located in the body of water by a water-borne predator detecting that person's emanated electromagnetic field. |
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claims | 1. A fluid element device comprising: a plurality of fluid elements arranged in a matrix configuration having rows and columns, the level of fluid in each of said fluid elements being controllable by means of an electric force, said fluid elements comprising capillary tubes, each of said capillary tubes comprising a plurality of electrode segments electrically insulated from one another such that each of said segments is receivable of a different electric voltage; first means for applying an electric force to a number of selected fluid elements in one or more of said rows of fluid elements; and second means for applying an electric force to a number of selected fluid elements in one or more of said columns of fluid elements such that the fluid level rises in the selected fluid elements to which an electric force is applied by both said first means and said second means. 2. The device according to claim 1 , wherein said electrode segments of each of said capillary tubes are arranged inside said capillary tubes. claim 1 3. The device according to claim 1 , wherein said electrode segments each comprise a coating layer of an electrically conducting material. claim 1 4. The device according to claim 1 , wherein said electrode segments of at least one of said capillary tubes extend in a longitudinal direction of said capillary tube. claim 1 5. The device according to claim 1 , wherein said electrode segments of at least one of said capillary tubes extend in a transverse direction of said capillary tube. claim 1 6. The device according to claim 1 , wherein at least one of said electrode segments is coupled to said first means. claim 1 7. The device according to claim 1 , wherein at least one of said electrode segments is coupled to said second means. claim 1 8. The device according to claim 1 , further comprising third means for applying an electric force to at least one of said electrode segments such that when the level of fluid in said capillary tube reaches said electrode segment, application of a voltage of a predetermined value to said electrode segment by said third means will maintain the level of fluid in said capillary tube independent of the application of an electric force by said first and second means to thereby provide said capillary tube with a memory effect with said electrode segment constituting a memory electrode. claim 1 9. An X-ray filter comprising a device according to claim 1 , wherein said capillary tubes are at least partially filled with an X-ray absorbing fluid. claim 1 10. The device according to claim 1 , wherein said plurality of electrode segments in at least one of said capillary tubes comprises sequentially arranged first, second and third electrode segments. claim 1 11. The device according to claim 10 , wherein said first electrode segment is coupled to said first means and said second electrode segment is coupled to said second means, said first and second means being controllable such that upon application of voltages of predetermined values to both said first and second electrode segments by said first and second means, the fluid in said capillary tube will rise above said first and second electrode segments. claim 10 12. The device according to claim 11 , further comprising third means for applying an electric force to said third electrode segment such that when the level of fluid in said capillary tube reaches said third electrode segment, application of a voltage of a predetermined value to said third electrode segment will maintain the level of fluid in said capillary tube independent of an electric force applied by said first and second means to thereby provide said capillary tube with a memory effect with said third electrode segment constituting a memory electrode. claim 11 13. The device according to claim 10 , wherein said second electrode segment is coupled to said first or second means, whereby upon application of a voltage to the fluid in said capillary tube above a threshold relative to the voltage applied to said second electrode segment, the fluid will rise above a gap between said first and second electrode segments. claim 10 14. The device according to claim 13 , further comprising third means for applying an electric force to said third electrode segment such that when the level of fluid in said capillary tube reaches said third electrode segment, application of a voltage of a predetermined value to said third electrode segment will maintain the level of fluid in said capillary tube independent of the application of an electric force by said first and second means to thereby provide said capillary tube with a memory effect with said third electrode segment constituting a memory electrode. claim 13 15. The device according to claim 1 , wherein said electrode segments are spaced from one another to define a gap between each adjacent pair of electrode segments. claim 1 16. The device according to claim 1 , wherein said plurality of electrode segments comprises at least first and second electrode segments, said first electrode segment being coupled to said first means and said second electrode segment being coupled to said second means. claim 1 17. An X-ray examination device comprising: an X-ray source; an X-ray detector spaced from said X-ray source; and an X-ray filter arranged between said X-ray source and said X-ray detector, said X-ray filter comprising a reservoir for storing X-ray absorbing fluid; a plurality of fluid elements arranged in a matrix configuration having rows and columns, said fluid elements being in fluid communication with said reservoir, the level of fluid in each of said fluid elements being controllable by means of an electric force, said fluid elements comprising capillary tubes, each of said capillary tubes comprising a plurality of electrode segments electrically insulated from one another such that each of said segments is receivable of a different electric voltage; first means for applying an electric force to a number of selected fluid elements in one or more of said rows of fluid elements; and second means for applying an electric force to a number of selected fluid elements in one or more of said columns of fluid elements such that the fluid level rises in the selected fluid elements to which an electric force is applied by both said first means and said second means. 18. A fluid element device, comprising: a plurality of fluid elements arranged in a matrix configuration having rows and columns, the level of fluid in each of said fluid elements being controllable by means of an electric force; first means for applying an electric force to a number of selected fluid elements in one or more of said rows of fluid elements; second means for applying an electric force to a number of selected fluid elements in one or more of said columns of fluid elements such that the fluid level rises in the selected fluid elements to which an electric force is applied by both said first means and said second means; and fluid level retention means for maintaining the level of fluid in the selected elements, after the fluid has risen by the application of an electric force applied by both said first means and said second means, at the elevated level independent of the application of an electric force by said first means and said second means. 19. The device according to claim 18 , wherein said fluid elements comprise capillary tubes, each of said capillary tubes comprising a plurality of electrode segments electrically insulated from one another such that each of said segments is receivable of a different electric voltage. claim 18 20. The device according to claim 19 , wherein said fluid level retention means comprise one of said electrode segments and third means for applying an electric force to said one of said electrode segments. claim 19 |
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051749505 | abstract | A grid for use on a PWR fuel element comprises a belt of hexagonal shape and three sets of plates secured to the belt. The plates in each set are mutually parallel and are at an angle of 120.degree. with the plates of the two other sets. All plates have the same length and have a 120.degree. bend in their middle. Each plate is parallel to two successive faces of the belt. |
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description | 1. Field of the Invention The present invention relates to an X-ray microscope apparatus and, more particularly, to an X-ray microscope apparatus capable of forming an enlarged X-ray image of a specimen held in contact condition. 2. Description of the Related Art Some of X-ray microscopes that form a high-resolution transmission image of an object by using X-rays of short wavelengths having high penetrating power use an X-ray imaging device and the others do not. X-ray imaging devices include Fresnel zone plates, grazing incidence mirrors, etc. Since the X-ray imaging device has low converging power, the focal length of an X-ray magnification optical system is inevitably long and hence the X-ray microscope has a big overall length. Although the resolution of the most advanced zone plate system is 50 nm, the zone plate system needs a light source capable of emitting intense light, such as synchrotron radiation, because the condensing efficiency of the X-ray imaging device is low. Since it is difficult to provide an X-ray imaging device with a zooming function that enables magnification adjustment, another image enlarging device, such as an optical microscope, must be used in combination with the X-ray imaging device to specify the observation position of the object, which requires troublesome operations. Some of the X-ray microscopes not using the X-ray imaging device use a projection enlargement method of observing a projected image formed by diverging X-rays emitted by a point light source and transmitted trough a specimen placed near the point light source, while the others use a contact imaging method of observing an enlarged X-ray image obtained by magnifying an image formed by irradiating a specimen held in contact with a photoresist plate with X-rays, and developing a latent image and enlarging by a proper optical system. The projection enlargement method inevitably involves penumbral blurring due to the size of the X-ray source and diffraction blurring due to the specimen. Therefore, the practical resolution of the projection enlargement method is in the range of about 0.1 to 0.2 μm. The contact imaging method does not use any X-ray enlarging optical system and hence does not cause any aberration and the image of the specimen is blurred scarcely because the specimen is held in contact with the photoresist plate. Thus, in principle, the contact imaging method is able to form easily an image of a high resolution. The resolution achievable by the contact imaging method is dependent on the particle size of the photoresist. The contact imaging method is able to form images of a high resolution of 10 nm or below when an X-ray resist of a high resolution. However, since the photoresist plate in the present state has a very low sensitivity, an X-ray source capable of emitting intense X-rays is necessary. The observation of an enlarged X-ray image needs troublesome operations for taking the photoresist plate out of a vacuum vessel, forming an X-ray image by a developing process, and enlarging the developed X-ray image by an optical microscope or the like for observation. Since the vacuum of the vacuum vessel needs to be broken in taking the photoresist plate out of the vacuum vessel, many X-ray images cannot continuously be obtained. X-ray microscope apparatuses disclosed in JP-A Nos. 117252/1989 and 29600/1996 enlarge an X-ray image obtained by irradiating a specimen with X-rays by an X-ray imaging device to obtain an enlarged X-ray image, project the enlarged X-ray image on a photocathode to convert the X-ray image into an electron image, enlarge the electron image by the agency of magnetic lenses to obtain an enlarged electron image, project the enlarged electron image on a fluorescent screen to form an optical image on the fluorescent screen, and photograph the optical image by a camera to obtain a picture for observation. These previously disclosed X-ray microscope apparatuses using X-ray enlargement, electronic enlargement and optical enlargement do not need any developing process and any other microscope for the observation of enlarged images, and are capable of forming a large image obtained by magnifying an original image at a very high magnification in a real-time mode. However, those known X-ray microscope apparatuses using the X-ray enlarging optical system are large and cannot be installed in a narrow place. Accordingly, it is an object of the present invention to provide an X-ray microscope apparatus using a contact imaging method capable of forming sharp X-ray images, having a small size and easy to use. According to the present invention, an X-ray microscope apparatus comprises; an X-ray generator; a photocathode disposed on a path of X-rays generated by the X-ray generator, the photocathode being configured to produce electrons when irradiated with X-rays generated by the X-ray generator so that an electron image of a specimen held on the photocathode is formed; an electron image enlarging device configured to enlarge the electron image of the specimen, the electron image enlarging device including an acceleration anode configured to accelerate electrons produced by the photocathode and a magnetic lens configured to enlarge and focus an electron beam of electrons emitted by the photocathode; an electron beam detecting device configured to detect an electron beam focused thereon by the electron image enlarging device; and an image processing device configured to process an electron image formed by the electron beam detecting device so as to provide a visible image. The X-ray microscope apparatus holds a specimen on a photocathode in close contact condition, and irradiates the specimen from behind with X-rays generated by the X-ray generator to form an electron image of the specimen by X-rays penetrated the specimen on the photocathode. Then, the electron image enlarging device pulls electrons emitted by the electron image to accelerate the electrons for travel in a direction opposite a direction toward the X-ray generator, and forms an enlarged electron image on the surface of the electron beam detecting device. The image processing device processes the electron image formed on the surface of the electron beam detecting device to display a visible image. The X-ray microscope apparatus does not use any X-ray optical system that enlarges an X-ray image formed by X-rays projected on and penetrated a specimen. Therefore, the X-ray microscope apparatus is small in construction. Since the specimen is held in close contact with the photocathode, a sharp X-ray transmission image can be formed. The photocathode provided with a two-layer thin film consisting of a gold thin film and a film of cesium iodide or cesiumantimonide converts this X-ray image into an electron image, the electron image enlarging device provided with the magnetic lenses enhance electron currents emitted from the back surface of the photocathode and projects the same on the surface of an electron beam detecting device, such as a CCD to form a visible image. Thus, the high-resolution X-ray transmission image can be formed in a real-time mode without using troublesome processes, such as a developing process and such. The magnification of the electron image enlarging device can continuously be varied by adjusting currents supplied to the magnetic lenses. Therefore, a minute object can precisely be located and observed by determining the position of the object using the electron image enlarging device at a low magnification and displaying a desired object at a high magnification. The X-ray generator may be a synchrotron radiation source capable of generating synchrotron radiation. Since the synchrotron radiation source is capable of generating intense X-rays of wavelengths in a narrow wavelength range, a sufficiently sharp X-ray transmission image can be formed even if the photocathode has a low sensitivity. The X-ray generator may be a conventional electron-beam-pumped X-ray generator that generates X-rays by accelerating electrons and makes accelerated electrons collide with a metal target or an electric-discharge-pumped X-ray generator that uses an electric discharge produced by a large-capacity capacitor. The X-ray generator maybe a laser-plasma X-ray generator that produces a plasma by irradiating a solid or gaseous target with a fine laser beam, and uses X-rays generated by the plasma. The X-ray microscope apparatus can be built in small construction when a laser-plasma X-ray generator is used because laser-plasma X-ray generator uses a comparatively small laser. X-rays generated by the laser-plasma X-ray generator may be condensed by an X-ray optical device to irradiate the specimen with the condensed X-rays, which enables forming an image of satisfactory contrast even if the X-rays generated by the laser-plasma X-ray generator are weak. Naturally, intense X-rays generated by an X-ray generator having a sufficient power may be used without being condensed. Preferably, the target is covered with a target cover made of a thin film capable of transmitting X-rays to prevent particles emitted by the target from scattering in the vacuum vessel. Preferably, a proper target is used selectively according to purposes because different images of the same specimen can be formed by using X-rays of different properties. The contamination of the vacuum vessel can be prevented by changing the metal target together with the target cover. Preferably, the target cover is provided with an opening in its part corresponding to the passage of the laser beam to avoid attenuating the laser beam. Preferably, a target cover formed of a material that transmits X-rays of wavelengths in the range of 2.3 to 4.4 nm generally called water window, such as silicon nitride or carbon, is used for the observation of a biological specimen. Preferably, the X-ray microscope apparatus according to the present invention is small in construction so that it is not subject to restrictions on places for installation, is capable of being installed in a comparatively narrow place, and is utilizable in various fields. Floor space necessary for installing the X-ray microscope apparatus can be reduced by adjacently disposing the laser and the electron image enlarging device such that the laser beam emitted by the laser and the electron beam used by the electron image enlarging device are parallel. When the X-ray microscope apparatus is formed such that the axis of the laser beam emitted by the laser and the axis of the electron beam used by the electron image enlarging device are included in a common horizontal plane, the positional adjustment of the X-ray microscope apparatus is easy in installing or reusing the X-ray microscope apparatus. When the X-ray microscope apparatus is formed such that the axis of the laser beam emitted by the laser and the axis of the electron beam used by the electron image enlarging device are included in a common vertical plane, the X-ray microscope apparatus needs less floor space for installation. The X-ray microscope apparatus can be formed in compact construction by disposing the laser below the electron image enlarging device, and disposing a power supply unit for supplying power to the laser and a vacuum pump below the laser, and the X-ray microscope apparatus can be installed in a small space. The installation of the X-ray microscope apparatus with the axis of the electron beam used by the electron image enlarging device vertically extended prevents the change of the optical axis of the X-ray microscope apparatus due to the displacement of the magnetic lenses by gravity and the resultant formation of a blurred image attributable to unsatisfactory focusing due to the displacement of the focal point, and is effective in forming an image of a good image quality. The X-ray generator may be disposed either above the electron image enlarging device to make the electron beam travel downward or below the electron image enlarging device to make the electron beam travel upward. Referring to FIG. 1, an X-ray microscope apparatus in a first embodiment according to the present invention includes an X-ray generator 1, a photocathode 2, an electron image enlarging device 3, an electron beam detecting device 4 and an image processing device 5. The X-ray generator 1 includes a vacuum vessel 12 defining a vacuum chamber for holding a target 11 of a metal therein, a laser 13, and a condenser lens 14. The condenser lens condenses a laser beam 15 emitted by the laser 13. The condensed laser beam 15 travels through an inlet nozzle 16 attached to the vacuum vessel 12 onto the vacuum chamber and falls on a surface of the target 11. The metal forming the target 11 is heated rapidly into a plasma and thereby X-rays 17 are generated. The target 11 may be surrounded by a target cover 19 to prevent metal particles from scattering and adhering to the inner surface of the vacuum vessel 12. The target cover 19 must be formed of a material transparent to X-rays, such as a beryllium film or a plastic film. Preferably, the target cover 19 is provided with an opening in a part corresponding to the passage of the laser beam 15 to avoid intercepting the laser beam 15. The X-rays 17 emitted by the target 11 are radiated outside through a radiation nozzle 18 and falls on a receiving surface of the photocathode 2. A specimen 6 is attached to the photocathode 2 in close contact with the receiving surface thereof. An image having shades corresponding to the specimen 6 is formed on the photocathode 2. The receiving surface of the photocathode 2 is formed of a photoelectric film capable of photoelectric conversion, such as a two-layer thin film consisting of a metal thin film and a film of cesium iodide or cesium antimonide. The photocathode 2 is attached to the inner surface of an entrance window 31, which is covered with an X-ray transmitting film, of the electron image enlarging device 3. Parts of the photocathode 2 irradiated with incident X-rays emit amounts of photoelectrons according to the intensities of the incident X-rays fallen thereon, respectively, to form an electron image corresponding to the X-ray image. The electron image enlarging device 3 has an X-ray entrance window 31, an acceleration anode 32, and magnetic lenses 33, 34 and 35. The acceleration anode 32 accelerates the photoelectrons emitted from the inner surface of the photocathode 2 toward the electron image enlarging device 3. The first magnetic lens 33 and the second magnetic lens 34 enlarge and focus a photoelectron image to form am enlarged photoelectron image on the entrance surface of the electron beam detecting device 4 disposed at a predetermined position. The first magnetic lens 33 serves as an objective lens for magnifying an electron image formed by the photocathode 2, and the second magnetic lens 34 serves as a projection lens for the further enlargement of a real electron image formed by the objective lens and forming the enlarged electron image on the entrance surface of the electron beam detecting device 4. The magnification of the first magnetic lens 33 and the second magnetic lens 34 can be adjusted by adjusting the respective intensities of currents supplied to the first magnetic lens 33 and the second magnetic lens 34 without changing focal length corresponding to the distance between the photocathode 2 and the electron beam detecting device 4. X-rays fallen on the electron beam detecting device 4 produce noise in the electron image formed by the electron beam detecting device 4. Since X-rays travel rectilinearly and are difficult to deflect, the electron beam detecting device 4 is disposed at a position apart from the axis of the electron image enlarging device 3, and the third magnetic lens 35 interposed between the second magnetic lens 34 and the electron beam detecting device 4 deflects the electron beam to focus the electron beam on the entrance surface of the electron beam detecting device 4. Since X-rays are not deflected by magnetic lenses, X-rays do not fall on the electron beam detecting device 4 and thereby noise in the electron image can effectively be reduced. The electron image enlarging device 34 is provided with a vacuum vessel 38, through which the electron beam 36 travels. The electron beam detecting device 4 is a functional device for visualizing the electron beam. For example, the electron beam detecting device 4 may comprise a microchannel plate, and a fluorescent screen disposed behind the microchannel plate to display a visible image for observation and may further comprise an optical system including a relay lens and disposed behind the fluorescent screen, and a CCD camera to produce electric signals. Electric image signals produced by the electron beam detecting device 4 are sent to the image processing device 5. The image processing device 5 processes the electric image signals properly to display a proper image meeting the object of measurement on the screen of a monitor. The conventional X-ray microscope apparatus needs to use an optical microscope to locate a specimen in determining a part, to be observed, of the specimen, which is troublesome and takes much time for adjustment. The present X-ray microscope apparatus is easily able to determine a part, to be observed, of a specimen and to display the part in an enlarged image by the agency of the zooming function of the magnetic lenses. The conventional X-ray microscope apparatus attaches a specimen to a film in close contact with the film, prints an X-ray transmission image of the specimen on the film, forms a visible image by subjecting the film to developing and fixing processes, and enlarges the visible image by an optical microscope for observation. Therefore, the X-ray transmission image can be formed without aberration, and the visible image can be formed in a high resolution. However, the conventional X-ray microscope apparatus thus takes much time for observation. The X-ray microscope apparatus of the present invention is able to achieve observation without requiring much time and is easily able to achieve the observation of an enlarged, high-resolution image. It goes without saying that the X-ray microscope apparatus may employ a synchrotron radiation source, an electron-beam-pumped X-ray generator or an electric-discharge-pumped X-ray generator as the X-ray generator. FIG. 2 is an enlarged diagrammatic sectional view of an X-ray generator included in an X-ray microscope apparatus in a second embodiment according to the present invention. FIG. 3 is a perspective view of the X-ray microscope apparatus in the second embodiment. FIG. 4 is a perspective view of an X-ray microscope apparatus in a first modification of the X-ray microscope apparatus in the second embodiment. FIG. 5 is a perspective view of an X-ray microscope apparatus in a second modification of the X-ray microscope apparatus in the second embodiment. The X-ray microscope apparatus in the second embodiment differs from the X-ray microscope apparatus in the first embodiment only in that a laser and an electron image enlarging device are disposed such that the axis of a laser beam emitted by the laser and the axis of an electron beam in the electron image enlarging device 3 are parallel, and hence parts of the second embodiment like or corresponding to those of the first embodiment are denoted by the same reference characters and the description thereof will be omitted to avoid duplication. As shown in FIG. 2, in the X-ray microscope apparatus according to the second embodiment, the laser 13 and the electron image enlarging device 3 are disposed such that the axis of a laser beam 15 emitted by the laser 13 and the axis 37 of an electron beam 36 in the electron image enlarging device 3 are parallel. An incident angle adjusting mirror 20 is disposed between the laser 13 and an entrance nozzle 16 formed on the vacuum vessel 12. The incident angle adjusting mirror 20 reflects the laser beam 15 emitted by the laser 13 toward the metal target 11. Even though the laser 13 and the electron image enlarging device 3 are disposed such that the axis of the laser beam 15 emitted by the laser 13 and the axis 37 of the electron beam 36 in the electron image enlarging device 3 are parallel, a sharp X-ray image can be formed by adjusting the position of the incident angle adjusting mirror so that the laser beam 15 falls at a predetermined incident angle on the metal target 11, because a specimen 6 attached to a photocathode 2 in close contact with the entrance surface of the photocathode 2 can be irradiated with X-rays of an intensity sufficient for observation. An electron image formed on a surface, on the side of the electron image enlarging device 3, of the photocathode 2 is pulled and accelerated by an acceleration anode 32 and is enlarged by the agency of an electron lens, thereby, an image is formed on an imaging surface of an electron beam detecting device 4. Since the laser 13 and the electron image enlarging device 3, which are long components of the X-ray microscope apparatus, are disposed side by side, the X-ray microscope apparatus can be formed in small construction having a comparatively short length, so that the X-ray microscope apparatus requires a comparatively small area for installation. Thus, restrictions on a place for the installation of the X-ray microscope apparatus are reduced, and the X-ray microscope apparatus can simply be installed in a small laboratory. Thus, the present invention succeeded in further facilitating using an X-ray microscope apparatus of a contact imaging system. In the X-ray microscope apparatus in the second embodiment, the specimen can be disposed at a distance of 100 mm or below from the X-ray generator 13. In the X-ray microscope apparatus shown in FIG. 3, the laser 13 and the electron image enlarging device 3 are disposed such that the axis of the laser beam 15 emitted by the laser 13 and the axis of the electron beam 36 in the electron image enlarging device 3 are parallel and are included in a common horizontal plane. A first frame 7 containing an evacuating unit 71, and a second frame 8 containing a power supply unit 81 for supplying power to the laser 13 are arranged side by side. The vacuum vessel 12 holding the metal target 11, the electron image enlarging device 3 including the electron beam detecting device 4, and the image processing device 5 are mounted on the first frame 7. The laser 13, and an optical box 22 containing an optical system including the incident angle adjusting mirror 20 are mounted on the second frame 8. Thus, the components of the X-ray microscope apparatus are assembled in compact, three-dimensional construction and hence the X-ray microscope apparatus can easily be installed in a narrow place. The arrangement of the laser 13 and the electron image enlarging device 3 such that the axis of the laser beam 15 and the axis 37 of the electron beam 36 are parallel and are included in a common horizontal plane facilitates the alignment of the components of the X-ray microscope apparatus. FIG. 4 shows an X-ray microscope apparatus in a first modification of the X-ray microscope apparatus in the second embodiment. In the X-ray microscope apparatus shown in FIG. 4, a laser 13 and an electron image enlarging device 3 are disposed such that the axis of a laser beam emitted by the laser 13 and the axis of an electron beam in the electron image enlarging device 3 are parallel and are included in a common vertical plane. A first frame 7 containing an evacuating unit 71, and a second frame 8 containing a power supply unit 81 for supplying power to the laser 13 are arranged longitudinally. The laser 3 and an incident angle adjusting mirror 20 are placed on the frames 7 and 8. A vacuum vessel 12 included in an X-ray generator 1, the electron image enlarging device 3 and an image processing device 5 are mounted on the laser 13. Since the components of the X-ray microscope apparatus are thus stacked, the X-ray microscope apparatus occupies a small floor space and leaves a wide floor space unoccupied for other uses. FIG. 5 shows an X-ray microscope apparatus in a second modification of the X-ray microscope apparatus in the second embodiment. In the X-ray microscope apparatus shown in FIG. 5, an electron image enlarging device 3 is set in a vertical position. A laser 13 and an optical box 22 containing an optical system are stacked. A vacuum vessel 12 holding a metal target, an electron image enlarging device 3 and an electron beam detecting device 4 are stacked in front of the laser 13 and the optical box 22. Image signals provided by the electron beam detecting device 4 are transmitted through a cable to an image processing device 5, and images are displayed on the screen of a monitor. If the electron image enlarging device 3 is set in a horizontal position, the magnetic lenses disposed at the most effective positions with respect to the axis of the electron beam may be displaced perpendicularly to the axis of the electron beam due to gravity and, consequently, the axis of the electron beam may be deviated from the optical axis of the electron image enlarging device 3. As a result, when the magnetic lenses are energized for electron image enlargement, the electron beam may not accurately be focused. Even if the magnetic lenses of the electron image enlarging device 3, which is set in a vertical position, of the X-ray microscope apparatus shown in FIG. 5 are displaced vertically by gravity, the effect of the vertical displacement of the magnetic lenses on the position of the axis of the electron beam is insignificant and does not affect significantly to the enlargement and focusing of the electron beam. Thus, the setting of the electron image enlarging device 3 in a vertical position is effective in preventing the deterioration of the performance of the X-ray microscope apparatus. Needless to say, the vacuum vessel 12 may be disposed below the electron image enlarging device 3 to emit the electron beam upward, and the electron beam may be focused on the detecting surface of the electron beam detecting device 4 disposed above the electron image enlarging device 3. As apparent from the foregoing description, the X-ray microscope apparatus according to the present invention forms an X-ray image of a specimen held in close contact with the photocathode, enlarges an electron image directly by the electron image enlarging device and displays an enlarged electron image. Thus, the X-ray microscope apparatus enables the simple observation of an X-ray image in a real time mode without requiring troublesome operations. Since the X-ray microscope apparatus of the present invention does not include a long X-ray optical system, the X-ray microscope apparatus is small and compact in construction and is not particular about places for installation. The arrangement of the laser and the electron image enlarging device in which the axis of the laser beam and the axis of the electron beam are parallel enables the X-ray microscope apparatus to be formed in further compact construction and to be utilized in various fields. Although the invention has been described in its preferred embodiments with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced otherwise than as specifically described herein without departing from the scope and spirit thereof. |
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description | The present invention relates to a particle therapy system. A particle beam irradiation apparatus making an actual dose distribution consistent to a planned dose distribution to provide the inside of a target volume with a uniform dose distribution is disclosed in JP-A-2009-66106 (PTL 1) which is characterized by including: a beam generation unit for generating particle beams; a beam extraction control unit for controlling extraction of the particle beams; abeam scan command unit sequentially and two-dimensionally commanding positions of the particle beams to scan slices, which are formed by dividing the target volume to be irradiated along an axial direction of the particle beams, along predetermined trace patterns set in the slices; and a beam scan unit for two-directionally scanning the slices with the particle beams based on the command signal from the beam scan command unit, wherein, after scanning the trace pattern along a forward direction, the beam scan command unit commands the scan positions for scanning the trace patterns along an inverse direction. PTL 1: JP-A-2009-66106 There is known a therapy method of irradiating a patient's target volume such as cancer with any particle beams (an ion beam; hereinafter referred to as an ion beam) such as protons or carbon ions. A particle beam irradiation system used in such a therapy includes an ion beam generator, a beam transport system, and an irradiation apparatus. As an irradiation method of the irradiation apparatus, a scatterer method of cutting a beam shape with a collimator in conformity with a target shape after spreading a beam with a scatterer or a beam scanning method of scanning a thin beam in a target volume region is known. In the particle beam irradiation system using the beam scanning method, an ion beam accelerated by an accelerator of the ion beam generator reaches to the irradiation apparatus via the beam transport system, is scanned onto a plane vertical to a beam traveling direction by a scanning magnet provided in the irradiation apparatus, and is irradiated onto the target volume of the patient from the irradiation apparatus. As a method of forming a uniform radiation field distribution in the beam scanning method, a wobbler method is known in which the thin beam is appropriately scattered and then scanned in a circular shape, a spiral shape, or a zigzag shape. In this case, it is necessary to cut out the formed uniform distribution with the collimator in conformity with the target shape. On the other hand, a spot scanning method is known as a method of making the dose distribution applied with the thin beam conformal to the target shape or forming an arbitrary dose distribution rather than uniform. This is to divide the target shape into minute small regions (irradiation spots) and to set and irradiate a desired irradiation dose for each section in advance. The spot scanning method includes two irradiation methods that are generally classified into a discrete spot scanning method and a raster scanning method, and the flow of processing with respect to the respective methods is disclosed in PTL 1. As defined in PTL 1, the discrete spot scanning method is a method in which extraction of the beam is stopped while moving a position of the particle beam to the next irradiation spot from any irradiation spot and the extraction of the beam is restarted after completion of the movement, and the raster scanning method is a method in which the extraction of the beam is continued without interruption while scanning the same slice. In the two particle therapy systems each implementing these two spot scanning method, performance and control contents of the instrument are different depending on instrument specifications of the accelerator, extraction control of the accelerator, and beam monitoring which are required. In addition, these two spot scanning methods can be substituted for each other, and there is no suggestion of the need to use properly. However, as a general need of the particle therapy system, there is a demand to aim at a further highly accurate irradiation and there is also a demand for a high dose rate to increase the number of treatable patients. In response to such a problem, the present inventors have found the following viewpoints. The discrete spot scanning method and the raster scanning method cause benefits in different cases. In particular, the discrete spot scanning method enables highly accurate irradiation in moving object tracking. Since the X-ray irradiation for tracking the target volume necessary for movement of the target volume is performed between spots where the particle beam is not irradiated, it is advantageous in terms of dose management accuracy and target volume identification accuracy. On the other hand, the raster scanning method is advantageous in throughput because the irradiation period of continuous irradiation is relatively long, and is advantageous in the case of organs with less movement and keeping on periodically for a fixed time. However, in a system which adopts a plurality of nozzles implementing different spot scanning methods or a system having a plurality of treatment rooms implementing different irradiation methods, there is a problem of handling the nozzles in the treatment room and space. Particularly, in hospitals located in urban areas with many patients, it is not desirable to easily increase the footprint size and the number of treatment rooms of the particle therapy system. The present invention has been made in view of such circumstances, and an object thereof is to provide a small particle therapy system capable of achieving both higher accuracy irradiation and high dose rate improvement. In order to solve the above problems, for example, the configuration described in claims is adopted. The present invention includes a plurality of units for solving the above problems, but as an example is characterized by a particle therapy system that divides an irradiation object into a plurality of small regions and sequentially irradiates the plurality of small regions with a particle beam, the particle therapy system including: an accelerator that accelerates the particle beam; an irradiation apparatus that irradiates a target with the particle beam accelerated by the accelerator; and a control system that controls the accelerator and the irradiation apparatus, wherein the accelerator, the irradiation apparatus, and the control system are capable of performing, with the irradiation apparatus, both irradiation methods of an irradiation method in which irradiation of the particle beam is not stopped when moving to the next small region and an irradiation method in which irradiation of the particle beam is stopped. According to the present invention, both higher accuracy irradiation and high dose rate improvement of the particle beam irradiation can be achieved. Embodiments of particle therapy systems according to the present invention will be described below with reference to the drawings. A particle therapy system according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. First, an overall configuration will be described with reference to FIG. 1. FIG. 1 is a schematic diagram illustrating the overall configuration of the particle therapy system according to the first embodiment. A particle therapy system 100 includes an ion beam generator 200, a beam transport system 300 that guides a generated ion beam to a treatment room 400, an irradiation apparatus 500 that irradiates a target volume 41 (illustrated in FIG. 2) of a patient 4 in conformity with the shape thereof with the ion beam in the treatment room 400, and a control system 600. The ion beam generator 200 includes a preaccelerator 21 and a synchrotron 20 that accelerates a charged particle pre-accelerated by the preaccelerator 21 up to a predetermined energy level and then extracts the charged particle. Instead of the synchrotron 20, an accelerator such as a cyclotron or a linear accelerator not having a preaccelerator may be used. The synchrotron 20 is an apparatus for accelerating ion beams (protons, heavy particle ions such as carbon, neutrons, or the like) accelerated by the preaccelerator 21 to a predetermined energy level, and includes a plurality of bending magnets 22 and a plurality of quadrupole magnets (not illustrated) that circulate the ion beam, a radiofrequency acceleration system 23 that accelerates the circulating ion beam, and an extraction apparatus 24 that extracts the ion beam accelerated to the predetermined energy level. The extraction apparatus 24 includes an extraction radiofrequency electrode (not illustrated) for extraction, the extraction radiofrequency electrode is connected to a radiofrequency power supply 26 via an extraction switch 25, and ON/OFF of extraction of the ion beam is performed by opening/closing of the extraction switch 25. The beam transport system 300 includes a plurality of bending magnets 31 and a plurality of quadrupole magnets (not illustrated), and is configured to transport the ion beam extracted from the synchrotron 20 to the irradiation apparatus 500. Here, a configuration of the irradiation apparatus 500 used in the particle therapy system. 100 according to the present embodiment will be described with reference to FIG. 2. FIG. 2 is a diagram illustrating the configuration of the irradiation apparatus 500. The irradiation apparatus 500 includes an X-direction scanning magnet 51A that scans the ion beam accelerated by the synchrotron 20 and guided by the beam transport system 300 in a horizontal direction (an X-direction in the drawing) and makes it conformal to the shape of the target volume 41 of the patient 4 and a Y-direction scanning magnet 51B that scans the ion beam in a vertical direction (a Y-direction in the drawing, which is a direction perpendicular to the page). These scanning magnets 51A and 51B are connected to a scanning magnet power supply 61. The scanning magnet power supply 61 is controlled by a power supply control system 62. The ion beam deflected scanning magnets 51A and 51B passes through a beam position monitor 52A and a dose monitor 53A, and is irradiated to the target volume 41 as an irradiation object. The beam position monitor 52A is connected to a beam position detector 52B, and the beam position detector 52B detects position and width (spread) of the ion beam. The dose monitor 53A is connected to an irradiation dose detector 53B, and the irradiation dose detector 53B detects the amount of the ion beam to be irradiated. Here, a spot scanning method will be described with reference to FIGS. 2 and 3. FIG. 3 is an explanatory view of the target volume 41 viewed from an upstream side of the ion beam. As illustrated in FIG. 2, the target shape of the target volume 41 of the patient 4 is three-dimensionally divided into a plurality of layers in a depth direction (a Z-direction in the drawing). As illustrated in FIG. 3, each of the layers is further two-dimensionally divided into in the horizontal direction (the X-Y direction in the drawing) which is a direction crossing the traveling direction of the ion beam to set a plurality of dose sections (small regions, which are described bellow as irradiation spots 42). The depth direction corresponds to an arrival degree of the ion beam, and is changed by an energy change of the ion beam extracted from the synchrotron 20 or an energy change of the ion beam due to the insertion of an energy absorber upstream from the irradiation apparatus 500, whereby each of the layers is selectively irradiated. In each of the layers, the ion beam is two-dimensionally scanned by the scanning magnets 51A and 51B, for example, along a path 43 illustrated in FIG. 3, and thus a predetermined dose is given to each of the irradiation spots 42. The amount of the ion beam irradiated to each of the irradiation spots 42 is detected by the dose monitor 53A and the irradiation dose detector 53B, and the position or the spread (width) of the ion beam is detected by the beam position monitor 52A and the beam position detector 52B. The irradiation control using the spot scanning method is performed by an irradiation control system 64 for controlling the beam extraction from the ion beam generator 200. Here, the spot scanning method is generally classified into a discrete spot scanning method which is an irradiation method in which irradiation of the ion beam is stopped when moving to the next irradiation spot 42 and a raster scanning method in which irradiation of the ion beam is not stopped even when moving to the next irradiation spot 42 after the ion beam is irradiated to each of the irradiation spots 42 with a target dose. In the discrete spot scanning method, since the beam extraction is stopped while the irradiation point of the ion beam is moved from a certain lattice point to the next lattice point and the beam extraction is restarted after the movement is completed, the beam extraction is intermittent while the same slice is scanned. Therefore, the irradiation control system 64 controls an excitation current of the scanning magnets 51A and 51B to scan the ion beam and changes the irradiation point to the next irradiation spot 42 when the irradiation dose of the ion beam irradiated to one spot 42 of the plurality of irradiation spots 42 reaches to the target dose. Then, the irradiation control system 64 stops the extraction of the ion beam from the ion beam generator 200 when the irradiation does of the ion beam irradiated to one spot reaches the target dose. In the stop state of the beam extraction, the irradiation control system controls the excitation current of the scanning magnets 51A and 51B to scan the ion beam, changes the irradiation point to the next irradiation spot 42, and controls to start the extraction of the ion beam from ion beam generator 200 after the change. The operation of the discrete spot scanning method will be described in more detail below with reference to FIG. 4. A time chart illustrated in FIG. 4 shows the operation while a certain layer in the target volume 41 illustrated in FIG. 3 is irradiated. In FIG. 4, a horizontal axis indicates a time t. A vertical axis in FIG. 4(a) represents an opening/closing signal output from the irradiation control system 64 to the extraction switch 25 via a central control system 65 and an accelerator control system 66, that is, a beam ON/OFF signal for controlling the extraction of the ion beam. Since there are four ON states, that is, four irradiation spots 42 in FIG. 4(a), these spots are defined as S1, S2, S3, and S4, respectively. Here, the initial beam ON signal is generated at a time when preparation for operation of the whole system including the ion beam generator 200 is completed through processes such as beam injection, acceleration of the synchrotron 20 and the ion beam becomes ready for irradiation after a doctor or a therapist instructs the start of irradiation. A vertical axis of FIG. 4 (b) represents an irradiation dose of the irradiate ion beam detected by the dose monitor 53A and the irradiation dose detector 53B, the irradiation dose is integrated at the same time as the beam ON, and the detection signal is taken into the irradiation control system 64. When the integrated dose reaches a predetermined amount, the irradiation control system 64 executes the beam OFF and stores the detected amount in a memory of the irradiation control system 64, and then the irradiation dose detector 53B is reset. Although the irradiation dose detected by the dose monitor 53A and the irradiation dose detector 53B is illustrated herein to be reset for each irradiation spot 42, the irradiation dose may be determined by the difference between values obtained through integration. FIG. 4(c) illustrates an actual irradiation current of the ion beam, and illustrates a case where a minute amount of ion beam is irradiated because there is an OFF reaction time even after the beam reaches a predetermined dose and is turned OFF as illustrated in FIG. 4(b). In the discrete spot scanning method, since a leakage current is generated for each irradiation spot due to a transient response after the beam OFF, unless the extraction control of the accelerator and extraction ON/OFF response performance determined by the accelerator are high, a large influence is exerted on uniform dose application. A vertical axis in FIG. 4(d) represents a detection state of the beam position monitor 52A and the beam position detector 52B for detecting position and width of the irradiation beam illustrated in FIG. 4(c), and for example, the detection of an irradiation spot S1, that is, a signal collection at a section of M1 is performed by the irradiation control system 64. After completion of the signal collection of the beam position detector illustrated in FIG. 4(d), the irradiation control system 64 calculates the beam position a width (standard deviation) based on the collected signal and compares with a tolerance set previously in the memory of irradiation control system 64, thereby determining whether the beam position/width value is within a desired error range. When the calculation result of the beam position/width deviates from the tolerance, the irradiation control system 64 generates an interlock signal, and stops the progression to the next irradiation spot 42. For example, when the calculation result of the beam position/width of the section S1 at the irradiation spot 42 deviates from the tolerance, the progression stops at an arbitrary timing before a predetermined time in the next section S2. In the discrete spot scanning method, the irradiation beam current flows only during the irradiation period on the irradiation spot and the subsequent response period, the period of monitor detection is also performed therebetween, and the irradiation beam current can be stopped with a delay in a period during which irradiation is not performed between the irradiation spots. A vertical axis in FIG. 4(e) represents a current pattern of the scanning magnet power supply 61 in the case of two-dimensionally scanning the charged particles as illustrated in FIG. 3. Such a pattern is a pattern prescribed in the irradiation control system 64, and indicates an operation of successively changing an excitation amount after the irradiation dose at each irradiation spot 42 reaches the prescribed value and then the irradiation beam stops and changing an irradiation point. A vertical axis in FIG. 4(f) represents a state of the scanning magnet power supply 61, the scanning magnet power supply 61 is turned ON (hereinafter, referred to as a scanning state being ON) while a current deviation deviates from a desired range by a change of the excitation current, and the scanning magnet power supply 61 is turned OFF (hereinafter, referred to as a scanning state being OFF) after the change of the excitation current is completed and it is determined that the current deviation has fallen within the desired range. That is, after the ion beam is irradiated at the section S1 in the irradiation spot 42, the irradiation point is changed to the next irradiation spot 42 in the section B1. In FIG. 4, the irradiation start at the section S2 in the irradiation spot 42 is the timing at which the irradiation point is changed after the irradiation at the section S1 in the irradiation spot 42, that is, the scanning state being ON in FIG. 4(f) is completed. The flow after the completion at the section S1 in the irradiation spot 42 is also repeated after the irradiation at the section S2 in the irradiation spot 42, and two-dimensional scanning as illustrated in FIG. 3 proceeds. The series of operations illustrated in FIGS. 4(a) to (f) are repeated, and the layer in the depth direction of the target volume 41 illustrated in FIG. 3 is irradiated with the ion beam. The irradiation dose and the irradiation point of each irradiation spot 42 and the excitation amount of the scanning magnet power supply 61 corresponding thereto are in accordance with the prescribed treatment planning, and contents thereof are transmitted from the treatment planning system. 67 to the central control system 65 before the treatment is started and are stored in the memory in the irradiation control system 64. According to the contents thereof, the irradiation control system 64 defines the excitation pattern of the scanning magnet power supply 61, and the central control system 65 transmits the energy corresponding to the depth, which is obtained by dividing the target volume 41 into layers in the depth direction, to the accelerator control system 66 or a transport control system 68 and performs the operation with the corresponding energy. When the irradiation of one layer of the target volume 41 is completed, an energy switching instruction is transmitted so as to perform the operation with energy corresponding to another layer. By repetition of these operations, the irradiation of the entire target volume 41 is completed. On the other hand, in the raster scanning method, the beam extraction is continued without stopping even when the irradiation point of the ion beam is moved from a certain lattice point to the next lattice point. That is, while the same slice is being scanned, the beam extraction is continued without interruption. Therefore, when the irradiation dose of the ion beam irradiated to one spot 42 of the plurality of irradiation spots 42 reaches the target dose, the irradiation control system 64 controls the excitation current of the scanning magnets 51A and 51B to scan the ion beam, and changes the irradiation point to the next irradiation spot 42. In the meantime, the irradiation control system 64 does not stop the extraction of the ion beam from the ion beam generator 200, but controls the excitation current of the scanning magnets 51A and 51B in a state where the beam is extracted to scan the ion beam and controls so as to change the irradiation point to the next irradiation spot 42. Details of the raster scanning method will be described in more detail below with reference to FIG. 5. A time chart illustrated in FIG. 5 shows the operation while a certain layer in the target volume 41 illustrated in FIG. 3 according to the present embodiment is irradiated. In FIG. 5, a horizontal axis indicates a time t. FIG. 5(a) indicates the progression of the irradiation spot 42, and each of sections S1, S2, S3, and S4 indicates an irradiation section to each of the irradiation spots 42. A vertical axis in FIG. 5 (b) represents an ion beam current that is extracted from the ion beam generator 200 and is injected to the irradiation apparatus 500 through the beam transport system 300. In the raster scanning method, since the transient response accompanying the beam OFF occurs only at the end of the slice, the influence due to the beam-off response delay is limited as compared with the discrete spot scanning method. A vertical axis in FIG. 5(c) represents an integrated value of the measured dose of the dose monitor 53A and the irradiation dose detector 53B in the irradiation apparatus 500. A vertical axis in FIG. 5(d) represents an excitation current of the scanning magnet power supply 61. At the same time that the integrated amount of irradiation illustrated in FIG. 5(c) reaches the planned dose prescribed in advance for each spot, it is determined that the irradiation of the irradiation spot 42 is completed, and the movement to the next irradiation spot is started. Therefore, the irradiation to the next irradiation spot 42 is first performed during the change of the excitation amount of the scanning magnet, and the change of the excitation amount of the scanning magnets 51A and 51B is stopped until the integrated amount of irradiation reaches the planned value after the change of the excitation amount is finished, and an operation of changing the excitation current of the scanning magnets 51A and 51B for shifting to the next spot at the same time that the dose reaches the planned value is repeated. Then, the ion beam continues to be irradiated during the operation. A vertical axis in FIG. 5(e) represents a measurement state of the beam position monitor 52A and the beam position detector 52B at each irradiation spot 42, and a beam position at each irradiation spot 42 is measured by the beam position monitor 52A and the beam position detector 52B in the section M1 until the dose during the scanning and the scanning stop reaches the prescribed value, as described above. After completion of the signal collection of the beam position detector illustrated in FIG. 5(e), the irradiation control system 64 calculates the beam position and a width (standard deviation) based on the collected signal and compares with a tolerance set previously in the memory of irradiation control system 64, thereby determining whether the beam position/width value is within a desired error range. In FIG. 5, the start of the irradiation at the section S2 in the irradiation spot 42 is the timing after the end of the irradiation at the section S1 in the irradiation spot 42. The flow after the completion at the section S1 in the irradiation spot 42 is also repeated after the irradiation at the section S2 in the irradiation spot 42, and two-dimensional scanning as illustrated in FIG. 3 proceeds. As in the repetition of the series of operations illustrated in FIGS. 4(a) to (f), even when the series of operations illustrated in FIGS. 5(a) to (e) are repeated, the layer in the depth direction of the target volume 41 illustrated in FIG. 3 is irradiated with the ion beam according to the treatment planning. In such a raster scanning method, the irradiation of the beam is stopped in a case where a space between the irradiation spots 42 becomes large while irradiating one layer of the target volume 41 illustrated in FIG. 3 and the dose to be irradiated therebetween cannot be ignored, in a case of irradiating a certain layer illustrated in FIG. 3 to change it to another depth layer, that is, to change the energy of the ion beam to be injected into the irradiation apparatus 500, or in a case where an unacceptable beam stop factor occurs. Regardless of the irradiation control method, the irradiation control system. 64 reads the signal obtained from the beam position monitor 52A and the beam position detector 52B from the inside of the irradiation control system 64, and then the irradiation control system 64 calculates the beam position and width and determines whether the calculation value of the ion beam position/width deviates from the tolerance. Then, when the calculation value of the ion beam position/width deviates from the tolerance, the irradiation control system outputs an interlock signal to the accelerator control system 66 via the central control system 65, and stops the extraction of the ion beam from the ion beam generator 200. In the particle therapy system according to the present embodiment, whether to perform any one irradiation method of the raster scanning method and the discrete spot scanning method can be previously selected depending on the target volume 41 of the patient 4 to be irradiated, and both the irradiation methods of the raster scanning method and the discrete spot scanning method are configured to be performed by one common ion beam generator 200, one common beam transport system 300, one common irradiation apparatus 500, and the control system 600 in which many units are united. The configuration for that will be described below. The control system 600 is a system for controlling respective apparatuses included in the synchrotron 20, the beam transport system 300 and the irradiation apparatus 500, and includes the accelerator control system 66, the irradiation control system 64, the central control system 65, the transport control system 68, and the treatment planning system 67. The treatment planning system 67 is a system for preparing a plan to irradiate an ion beam, and prepares a treatment planning by treating and selecting with any one of a raster scanning method and a discrete spot scanning method, based on information on the target volume 41 of the patient 4 to be irradiated. The treatment planning system 67 outputs the prepared treatment planning to the central control system 65. The central control system 65 outputs a control signal to each of the control systems, which are the accelerator control system 66, the irradiation control system 64, and the transport control system 68, such that irradiation control on the target volume 41 of the patient 4 is performed with the irradiation method of any one of the raster scanning method and the discrete spot scanning method based on the input treatment planning. The central control system 65 further includes a display unit 65a displaying which irradiation method of either the raster scanning method or the discrete spot scanning method is selected. The accelerator control system 66 includes a common control unit 66a used in any of the irradiation methods, a non-stop control unit 66b used only in the raster scanning method, and a stop control unit 66c used only in the discrete spot scanning method, and each apparatus in the ion beam generator 200 such as the synchrotron 20 is controlled by the accelerator control system 66. In the accelerator control system 66, based on the control signal from the central control system 65, control is performed by the common control unit 66a and the non-stop control unit 66b in a case where irradiation is performed with the raster scanning method, and control is performed by the common control unit 66a and the stop control unit 66c in a case where irradiation is performed with the discrete spot scanning method. For example, the common control unit 66a is a common control parameter set between the discrete spot scanning method and the raster scanning method, and is used to control the preaccelerator 21, the bending magnet 22, and the radiofrequency acceleration system 23 which are common in both methods for control when particles are injected from the preaccelerator 21 and the particles are accelerated in the synchrotron 20. The non-stop control unit 66b is a control parameter set used only in the raster scanning method, and is used for controlling the extraction apparatus 24 and the extraction switch 25. The stop control unit 66c is a control parameter set used only in the discrete spot scanning method, and is used for controlling the extraction apparatus 24 and the extraction switch 25. Apparatuses such as extraction electromagnets and beam extraction control that are common in both methods need to achieve beam current response speed that satisfies the requirements of the discrete spot scanning method. In addition, in the accelerator control system 66, the stop control unit 66c corresponding to the discrete spot scanning method is used for irradiation with the raster scanning method, and it is possible to perform the control with both methods by one common control unit. In this case, at the time of irradiation with the raster scanning method, normally the stop control unit 66c transmits a beam OFF signal when the irradiation dose reaches a specified value, and it is controlled to maintain the beam in ON state until finishing the slice. The irradiation control system 64 includes a common control unit 64a used in any of the irradiation methods, a non-stop control unit 64b used only in the raster scanning method, and a stop control unit 64c used only in the discrete spot scanning method, and controls each apparatus in the irradiation apparatus 500. In the irradiation control system 64, based on the control signal from the central control system 65, control is performed by the common control unit 64a and the non-stop control unit 64b in a case where irradiation is performed with the raster scanning method, and control is performed by the common control unit 64a and the stop control unit 64c in a case where irradiation is performed with the discrete spot scanning method. For example, the common control unit 64a is a common control parameter set between the discrete spot scanning method and the raster scanning method, and controls power supply of the scanning magnet power supply 61 common to both methods. The non-stop control unit 64b is a control parameter set used only in the raster scanning method, and the stop control unit 64c is a control parameter set used only in the discrete spot scanning method and controls the beam position detector 52B or the irradiation dose detector 53B which are different in timing or control method in the both methods, for example. The transport control system 68 controls each apparatus such as the bending magnet 31 in the beam transport system 300. Effects of the present embodiment will be described below. The particle therapy system according to the present embodiment can obtain various advantages that irradiation can be realized using both types of the raster scanning method and the discrete spot scanning method having the same basic configuration with one irradiation apparatus 500, an appropriate method depending on the irradiation object can be selected, both improvement of irradiation accuracy and high dose rate can be achieved, and irradiation can be performed at a short time. For example, in a case of irradiating in synchronization with movement while confirming the movement of the target volume such as childhood cancer with X-rays, the irradiation is performed by the discrete spot scanning method with high accuracy. In a case of prostate cancer in which movement of the target volume is small, an irradiation time can be shortened by continuously striking with the raster scanning method for a long period. Since both irradiation methods can be realized with a single system, there are also advantages that the system becomes inexpensive and the size of the treatment system can be reduced. It is to be noted that although the case of using the extraction apparatus 24 including the extraction radiofrequency electrode for extraction as the beam extraction apparatus has been described by way of example, the beam extraction apparatus is not limited to the extraction apparatus 24, and may use a quadrupole magnet for extraction, a betatron core, or the like. A particle therapy system according to a second embodiment of the present invention will be described with reference to FIG. 6. The same reference numerals are given to the same configurations as those in FIGS. 1 to 5, and a description thereof will not be presented. This is also applied to the following embodiments. FIG. 6 is a schematic diagram illustrating an overall configuration of the particle therapy system according to the second embodiment. In a particle therapy system 101 according to the present embodiment, whether to perform any one irradiation method of the raster scanning method and the discrete spot scanning method can also be selected based on the previous selection depending on the target volume 41 of the patient 4 to be irradiated, and either of the irradiation methods of the raster scanning method and the discrete spot scanning method is configured to be capable of being performed by one irradiation apparatus 500. As illustrated in FIG. 6, a treatment planning system 67A according to the present embodiment includes a selection unit 67a1 that allows an operator to select any irradiation method of the raster scanning method and the discrete spot scanning method for treatment at the time of preparing the treatment planning, and prepares a treatment planning with the irradiation method selected by the selection unit 67a1. The treatment planning system 67A outputs the prepared treatment planning to the central control system 65. The configuration and operation of components other than the treatment planning system 67A are substantially the same as those of the particle therapy system according to the first embodiment described above, and the details are not be presented. In the particle therapy system according to the second embodiment of the present invention, it is possible to prepare the treatment planning with excellent balance between the dose distribution accuracy and the irradiation time by allowing the operator to select from two spot scanning methods at the time of treatment planning or to change the method. Particularly, in the raster scanning method, since the dose is also applied between the irradiation spots, the overall dose distribution largely depends not on the position of the irradiation spot but also on the scanning path and the present or absence of moving object tracking control. It is therefore desirable for the treatment planning system 67A to compare and confirm the dose distribution when each spot scanning method is selected at the treatment planning stage for the purpose of improvement of the dose distribution accuracy and from the calculation capability, and the treatment planning system 67A has a large effect of providing a function capable of selecting two spot scanning methods. Furthermore, a case is also considered which combines the treatment planning system capable of selecting two spot scanning methods with the particle therapy system capable of performing two spot scanning methods with a single common irradiation apparatus. This is because it becomes unnecessary to successively correct the differences in characteristics and performances due to the state of the nozzle, the transport system, and the accelerator which are necessary for another apparatus or the individual difference at the time of changing two spot scanning methods, whereby dose distribution calculation efficiency is improved, the dose distribution is improved, or the time loss required for switching is reduced. A particle therapy system according to a third embodiment of the present invention will be described with reference to FIG. 7. FIG. 7 is a schematic diagram illustrating an overall configuration of the particle therapy system according to the third embodiment. In a particle therapy system 102 according to the present embodiment, whether to perform any one irradiation method of the raster scanning method and the discrete spot scanning method can also be selected based on the previous selection depending on the target volume 41 of the patient 4 to be irradiated, and either of the irradiation methods of the raster scanning method and the discrete spot scanning method is configured to be capable of being performed by one irradiation apparatus 500. As illustrated in FIG. 7, a central control system 65B of the particle therapy system 102 according to the present embodiment includes an input unit 65b1 that receives input of information on the target volume 41 of the patient 4 to be irradiated from a treatment planning system 67B outside the system 102. The central control system 65B analyzes the information on the target volume 41 of the patient 4 input to the input unit 65b1, determines whether the irradiation control is performed on the target volume 41 of the patient 4 by any irradiation method of the raster scanning method and the discrete spot scanning method, and outputs the control signal to the respective control system of the accelerator control system 66, the irradiation control system 64, and the transport control system 68. The configuration and operation of components other than the central control system 65B and the treatment planning system 67B are substantially the same as those of the particle therapy system according to the first embodiment described above, and the details are not be presented. The particle therapy system according to the third embodiment of the present invention can be obtained substantially the same effect as that of the particle therapy system according to the first embodiment described above. It should be noted that the input unit 65b1 of the central control system 65B is not limited to the aspect in which the input of the information on the target volume 41 of the patient 4 to be irradiated is received from the treatment planning system 67B outside the system 102, and may include an aspect of inputting information on selection by the operator at the time of preparing the treatment planning or an aspect of inputting information on selection by the operator other than the preparation timing of the treatment planning. In addition, when the particle therapy system 102, the central control system 65, or the treatment planning system 67 selects either the raster scanning method or the discrete spot scanning method, the dose distribution accuracy, the obtained dose rate, the treatment time is calculated, the irradiation method close to numerical values based on parameters described in the table stored in advance is selected in addition thereto, and these items may be displayed on a display unit 65a. In that case, either the raster scanning method or the discrete spot scanning method is then selected based on the display by the input of the operator to the central control system 65B. A particle therapy system according to a fourth embodiment of the present invention will be described with reference to FIGS. 8 and 9. FIG. 8 is a schematic diagram illustrating an overall configuration of the particle therapy system according to the fourth embodiment. In the particle therapy system, the confirmation of the position of the target volume is important for forming the dose distribution conformal to target shape. Particularly, in order to improve the dose distribution accuracy on the target volume moving with the movement of the body such as respiration, there is a method of irradiating the ion beam in synchronization with the movement of the target volume accompanying the movement or the respiration of the patient by measuring the movement of the chest according to the movement of the body surface or measuring the target volume, a marker in the vicinity of the target volume, or a region having a high density with an MRI, an X-ray, or other radioactive rays. In the raster scanning method, since the ion beam is continuously irradiated, there is one aspect in which the response to respiration synchronization irradiation, which needs to turn on/off of the ion beam irregularly, is not easy. In addition, when the X-ray is exposed for tracking a moving object during the particle beam irradiation in the raster scanning method, there is a problem that timing suitable for exposure to the X-ray in which the particle beam irradiation is stopped does not exist. Further, if X-ray exposure for tracking the moving object is performed regardless of the particle beam irradiation, problems may arise in measurement accuracy of irradiation dose and accuracy of identification of the target volume. The present embodiment is to provide the particle therapy system for achieving both improvement of dose distribution accuracy and high dose rate by appropriately using the irradiation method with the same apparatus even when irradiating the target volume moving with the movement of the body such as respiration. As illustrated in FIG. 8, the particle therapy system 103 according to the present embodiment includes a fluoroscopic X-ray imaging apparatus 510. The fluoroscopic X-ray imaging apparatus 510 includes two X-ray generators for generating an imaging X-ray capable of pulse irradiation and two X-ray image receivers for detecting the generated X-ray. The irradiation timing of the X-ray generator is controlled, and each apparatus is installed in the treatment room 400 so that the imaging can be performed in biaxial directions. That is, the X-ray generator and the X-ray image receiver are disposed so as to face each other with a region where the patient is placed, and the X-ray image receiver is installed on the beam delivery system. Two line segments connecting the X-ray generator and the X-ray image receiver facing each other are installed so as to intersect with each other in the region where the target volume 41 of the patient 4 is placed. A relation between movement detection of the target volume 41 and beam irradiation will be described with reference to FIG. 9. FIG. 9(a) indicates a signal that detects the movement of the target volume 41, and sets a threshold for guaranteeing that the target volume 41 is at a desired position or within a certain range from the desired position with respect to the signal. The beam is irradiated only when there is a position detection signal of the target volume 41 within the threshold. In this case, the timing at which the irradiation apparatus 500 according to the present embodiment can irradiate is as illustrated in FIG. 9(b), and since the signal is movement accompanying the movement of the patient, the timing can be irregular. As described above, when the method of detecting the movement of the target volume 41 and irradiating in only the case where the movement amount is within the desired range is adopted, the particle beam irradiation is difficult with the raster scanning method, but can easily be performed with the discrete spot scanning method. Therefore, the information on the target volume 41 of the patient 4 to be irradiated includes information on whether the movement of the target volume 41 is detected, and the treatment planning system 67C selects, based on the information, any one of irradiation methods of the raster scanning method and the discrete spot scanning method used for treatment of the target volume 41 of the patient 4 to be irradiated, and prepares treatment planning. For example, the discrete spot scanning method is basically selected when the movement of the target volume 41 is detected, and the raster scanning method is selected in other cases. The treatment planning system 67C outputs the prepared treatment planning to the central control system 65, and the central control system 65 outputs control signals to control systems of the accelerator control system 66, the irradiation control system 64, and the transport control system 68 such that the irradiation control is performed on the target volume 41 of the patient 4 by any one of irradiation methods of the raster scanning method and the discrete spot scanning method, based on the information on the target volume 41 of the patient 4 input from the treatment planning system 67C. In the present embodiment, a fluoroscopic X-ray image is acquired by the fluoroscopic X-ray imaging apparatus 510 when the ion beam is irradiated onto the target volume 41 in the irradiation control system 64, and irradiation control of the particle beam is performed based on the acquired fluoroscopic X-ray image. It should be noted that configurations other than those described above are substantially the same as those of the particle therapy system according to the first embodiment described above, and their operations are basically the same, so the details are not be presented. The particle therapy system according to the fourth embodiment of the present invention can be obtained substantially the same effect as that of the particle therapy system according to the first embodiment described above. Particularly, according to the particle therapy system of the present embodiment, even when the particle beam is irradiated onto the target volume moving accompanying the movement of the body such as respiration, the irradiation apparatus of both types of spot scanning is not necessary to be realized by a separate treatment room, a separate irradiation apparatus, or a plurality of switching nozzles, and it is possible to improve both the dose distribution accuracy and the high dose rate without increasing costs and enlarging the installation area. Although the fluoroscopic X-ray imaging apparatus 510 is used as a unit for detecting the movement of the target volume 41 of the patient 4, it is considered that the movement detection unit includes, for example, a method of monitoring the movement of the body surface for detecting respiratory movement and a method of monitoring the flow of expiration and inspiration accompanying the respiration of the patient at the mouth of the patient without being limited to the fluoroscopic X-ray imaging apparatus 510. In addition, the fluoroscopic X-ray imaging apparatus 510 may be disposed to perform imaging from one axis direction, and the X-ray generator and the X-ray image receiver may be disposed in a reverse manner. <Others> The present invention is not intended to be limited to the embodiments described above, and includes various modifications. For example, the embodiments are described in detail in order to better illustrate the present invention and are not intended to limit the present invention always to those inclusive of full configuration as described above. In addition, the configuration of a certain embodiment can partially be replaced by the configuration of another embodiment, or the configuration of a certain embodiment can be added with the configuration of another embodiment. Also, the configuration of respective embodiments can partially be removed, or added with or replaced by another configuration. For example, a unit for selecting either of the raster scanning method and the discrete spot scanning method depending on the irradiation object may be provided in the process from the reception of the patient 4 to the treatment, and the ion beam may be irradiated onto the target volume 41 with one irradiation apparatus 500 using the irradiation method selected by such a selection unit. 4: patient 20: synchrotron 21: preaccelerator 22: bending magnet 23: radiofrequency acceleration system 24: extraction apparatus 25: extraction switch 26: radiofrequency power supply 31: bending magnet 41: target volume 42: irradiation spot 43: path 51A: X-direction scanning magnet 51B: Y-direction scanning magnet 52A: beam position monitor 52B: beam position detector 53A: dose monitor 53B: irradiation dose detector 61: scanning magnet power supply 62: power supply control system 64: irradiation control system 64a: common control unit 64b: non-stop control unit 64c: stop control unit 65, 65B: central control system 65a: display unit 65b1: input unit 66: accelerator control system 66a: common control unit 66b: non-stop control unit 66c: stop control unit 67, 67A, 67B, 67C: treatment planning system 67a1: selection unit 68: transport control system 100, 101, 102, 103: particle therapy system 200: ion beam generator 300: beam transport system 400: treatment room 500: irradiation apparatus 510: fluoroscopic X-ray imaging apparatus 600: control system |
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059303131 | description | DETAILED DESCRIPTION With reference to the drawing figures, wherein like numbers indicate like parts throughout the several views, FIG. 1 shows an apparatus according to the invention. A laser 12 produces an output 14 which traverses members 16 and 18 to reach chamber 20 containing target 28. Chamber 20 contains a gas 22 which laser output 14 ionizes to form a plasma channel 24. Member 16 is a particle accelerator, which generates a pulse of positive ions 26 directed through drift passage 18 into chamber 20 and plasma channel 24. Member 18 is optional, and could be any conventional means for maintaining an ion beam focused, for example a magnetic lens. FIG. 1 shows ion beam 26 inside chamber 20, where it has propagated since ejection by accelerator 16, heading in the direction of target 28. Target 28 could be any of a number of materials, ranging from a tool or structural metal which beam 26 will harden by impact, to a fuel pellet for nuclear fusion. In general, it is necessary to maintain a vacuum in accelerator 16, and also in the drift region 18. To accomplish this, chamber 20 may be separated from the drift region 18 by a thin foil through which the beam passes. Alternatively, there may be an aperture between 18 and 20, in which case the vacuum could be maintained by differential pumping in region 18. For certain applications, notably heavy ion fusion, it is necessary to strip the beam into a high charge state at the entrance to chamber 20. This will occur if the beam passes through a foil or gas puff. FIG. 2 illustrates the pinching of ion beam 26. Beam 26 travels through plasma channel 24 at a mildly-relativistic velocity indicated by arrow 30. Because velocity 30 is well below the speed of light, the electric field generated by the ions in beam 26 propagates ahead of beam 26. Being ahead of the beam, this electric field pulls free electrons 36 from the plasma axially towards head 37 of beam 26. This establishes a flow of electrons along the same axis (30) along which beam 26 propagates, but in the opposite direction. Since the electron charge is opposite to the ion charge, this electron current flows in the same direction as the ion beam current. Because of Lenz's law, the current which is initially established by the electron flow is maintained during the passage of the ion beam. As beam 26 traverses plasma channel 24, it also pulls in free electrons 32 from the channel. This tends to establish charge equilibrium within beam 26, which is necessary to eliminate strong electrostatic self-repulsion of the beam ions. The net current I.sub.n, i.e. the sum of the ion beam current and the current carried by plasma electrons, remains essentially frozen at the magnitude initially set by the precursor electron flow. The conditions under which a charged particle beam will be pinched are generally known to workers in this field, and are given by the pinch equation: EQU I.sub.n >(17kA)(.epsilon./a).sup.2 .beta..gamma.(m.sub.i /m.sub.e)(1/Q.sub.i) where: a is the beam radius. PA1 .epsilon. is the emittance of the particle beam, a standard measure of the quality of such a beam (i.e. of how well the velocities of the beam particles are aligned, and hence how much the beam will tend to diverge during propagation). p1 .beta.=v/c, where v is the mean velocity of the beam, and c is the speed of light. Thus .beta. is the speed at which the beam travels, expressed as a fraction of the speed of light. PA1 .gamma.=(1-.beta..sup.2).sup.-1/2 PA1 m.sub.i is the mass of the particles which constitute the beam. PA1 m.sub.e is the mass of an electron. PA1 Q.sub.i is the charge of the particles which constitute the beam, expressed in multiples of electron charge. (For example, for heavy ion fusion it may be appropriate to use ions such as bismuth, which are stripped to an average ionization state Q.sub.i =50.) PA1 Ion beam energy of 10 GeV, roughly corresponding to .beta.=0.3 for bismuth. PA1 I.sub.b Q.sub.b =5 kAmp upon entry into the channel. PA1 m.sub.i =209 times the proton mass (i.e. bismuth). PA1 .epsilon.=10.sup.-3 rad-cm. PA1 Beam pulse duration of 10 nsec. PA1 Radius of ion beam: 1.0 cm. PA1 Radius of the plasma channel: 1.5 cm. PA1 The channel electron charge, per unit length, was five times the beam charge. To ensure pinching, the charge density .rho..sub.p of plasma channel 24 must be larger than the charge density .rho..sub.b of beam 26. A minimum condition for this would be that the density .rho..sub.g of atoms in gas 22 exceed .rho..sub.b /Q.sub.p, where Q.sub.p is the average number of electrons removed from atoms in gas 22. (Beam 26 may itself contribute to the ionization of channel 24 by collisions, thus relaxing the demands on laser 12 to fully ionize the channel.) One skilled in the art will know how to create these conditions, after having been instructed by this application in the desirability of so doing. Nominally, a gas pressure in chamber 20 of between 10.sup.-3 to 1 Torr should suffice. The term .beta. must not be so close to the speed of light that the electric field from beam 26 cannot significantly outrun the beam itself. Numerical simulations indicate that useful pinching will occur at least within the range .beta.=0.3 to 0.8, corresponding to an energy of 0.05 to 0.66 A measured in GeV, where A is the atomic weight of an ion in the beam. The channel radius should be one to a few times the beam radius in order to supply electrons outside the beam for charge neutralization, and a well-collimated precursor electron current for pinching. Gas 22 and the constituents of ion beam 26 can be any molecular or atomic species. Member 12 can be any type of laser which effectively ionizes the gas 22. This will occur if the laser frequency is well matched to the quantum states of gas 22, for example a KrF laser used to create a plasma channel in an organic gas such as benzine, or a device such as a free electron laser which can be tuned to the optimal frequency for the gas 22 in chamber 20. Alternatively, a laser or microwaves source can be used to trigger an avalanche breakdown in the gas in order to create a plasma channel. A third technique is to use a low-energy (about a few hundred volts), low current (about a few amps) electron beam, guided by a weak magnetic field (about 50 G) to create the plasma channel. A numerical simulation was done to investigate the working of the invention. The simulation used the FRIEZR beam simulation code, which was developed by workers at the Naval Research Laboratory in Washington, D.C., in support of their research. It is one of a number of numerical codes available for simulating charged particle beams. The parameters of the simulated beam were: FIGS. 3 and 4 show the results of that simulation. In FIG. 3, the solid line indicates beam current, and the dashed line net current, at a time 6 nsec after the tail of the ion pulse had passed point z=0. As seen in the figure, the two are of the same order. The net current is well in excess of the requirement from the pinch equation (for I.sub.n, above), which should indicate good pinching. FIG. 4 plots the "half radius" of the beam, i.e. the radius which contains half the beam current, at the time when the beam tail had passed z=0 (solid curve), and 6 nsec thereafter (dashed curve). As seen from these curves, the half radius stayed roughly the same during this time, and in fact the half radius contracted, indicating good pinching. Referring again to FIG. 1, the laser could be positioned differently, for example at the opposite end of chamber 20 as illustrated in FIG. 1 as laser 12'. Here, laser output 14' goes directly into chamber 20, where it creates plasma channel 24 in the manner discussed above concerning laser 12. Although laser 12' is advantageously positioned closer to chamber 20, it suffers the disadvantage that target 28 obscures its output 14'. This would be unacceptable if target 28 is sensitive to light at the frequency of laser 12', or if it is desired that the diameter of plasma channel 24 be close to that of the target. The invention has been described in what is considered to be the most practical and preferred embodiments. It is recognized, however, that obvious modifications may occur to those with skill in this art. Accordingly, the scope of the invention is to be discerned solely by reference to the appended claims, wherein: |
051732505 | claims | 1. A method of demolishing a biological shield wall of a nuclear reactor using a demolishing apparatus comprising a concrete cutter device, consisting of a driving part for a wire saw and a concrete cutting part attached to an engaging receiver of the driving part, a core boring machine and a carrier truck to carry the wire saw driving part of said cutter device, said method comprising the steps of: setting a carrier truck on a operating floor of a reactor building, with a core boring machine attached on the engaging receiver of the driving part; boring holes downwardly from atop the shield wall a predetermined distance; substituting the concrete cutting part for the boring machine on the engaging receiver; inserting a pair of vertical rods in corresponding bored holes and circulating the wire saw between the lower ends of the vertical rods, the vertical rods being controlled and adjusted to the distance between bored holes to enable the cutting action of the wire saw to cut a concrete block from the shield wall; cutting a concrete block from the shield wall with the wire saw; and removing the cut concrete block from the shield wall. a pair of vertical rods; means for moving said vertical rods vertically down and up, into and out of spaced downwardly directed holes in said wall; means for adjusting the spacing between said vertical rods; and a wire saw member strung between the lower ends of said pair of vertical rods and along at least a portion of the length of each said rod. a pulley adjacent the lower end of each of said vertical rods around which said wire saw member is strung; and guide rollers at the lower ends of said vertical rods positioned to engage the inner surfaces of the holes bored in the biological shield wall, thereby preventing said pulleys and said wire saw member from contacting and binding against such inner surfaces, and for maintaining said wire saw member on said pulley in case of stack in said wire saw member. positioning said pair of vertical rods in corresponding holes bored in the shield wall, the holes being aligned circumferentially along the top of the shield wall; sawing vertically downward between the holes to form a first cut; raising the vertical rods to above the upper surface of the shield wall, and rotating the pair of vertical rods until one vertical rod lies above a first one of said holes and the other vertical rod is aligned horizontally spaced from the shield wall, and sawing vertically downward between the first hole and the periphery of the shield wall to form a second cut; raising the vertical rods to above the upper surface of the shield wall, and moving the pair of vertical rods until one vertical rod lies above a second one of said holes and the other vertical rod is aligned horizontally spaced from the shield wall, and sawing vertically downward between the second hole and the periphery of the shield wall to form a third cut; raising the vertical rods to above the upper surface of the shield wall, and rotating the pair of vertical rods until said rods are aligned with the first and second holes, stringing the wire saw in the first and second cuts and adjacent the periphery of the shield wall while lowering said vertical rods into the first and second holes; and sawing horizontally inward between the holes to form a fourth cut meeting with said first cut, thereby freeing the concrete block for removal. 2. An apparatus for demolishing a biological shield wall of a nuclear reactor, including a movable support body and a wire saw mechanism mountable on said movable support body, said wire saw mechanism comprising: 3. The apparatus as claimed in claim 2, comprising: 4. The apparatus as claimed in claim 2, wherein said movable support body comprises a receiver member, and said wire saw mechanism comprises an attachment means for releasable connection with said receiver member, thereby permitting said wire saw mechanism to be selectively mounted on said support body. 5. The apparatus as claimed in claim 4, including a concrete core boring machine for boring downwardly directed holes in the biological shield wall, said core boring machine comprising an attachment means for releasable connection with said receiver member on said body, thereby permitting said core boring machine to be selectively mounted on said support body. 6. The apparatus as claimed in claim 2, wherein said support body comprises a driving mechanism for operating said wire saw mechanism. 7. The apparatus as claimed in claim 2, wherein said support body comprises a carrier truck with wheels. 8. The apparatus as claimed in claim 2, comprising a table pivotally mounted on said receiver of said body, said wire saw mechanism mounted on said table. 9. The apparatus as claimed in claim 8, wherein said table is pivotable about a vertical axis to permit said wire saw mechanism to swing horizontally and adjustably on said receiver. 10. The apparatus as claimed in claim 9, comprising a hydraulic cylinder coupled between said support body and said table for effecting horizontal swinging and angular adjustment of said table relative to said support body. 11. The method as claimed in claim 1, wherein said cutting step includes: |
claims | 1. A method for inspecting equipment, the method comprising,storing in a portable instrument (a) application instructions for receiving, storing and analyzing focal plane array imaging sensor data to derive at least one imagery indication of equipment health, (b) application instructions for receiving, storing, and analyzing dynamic sensor data to derive at least one dynamic indication of equipment health wherein the analyzing dynamic sensor data includes one or more analyzing techniques selected from the following group: Fast Fourier Transform (FFT) vibration analysis, waveform vibration analysis, spectral vibration analysis, stress wave analysis, transient analysis, sonic analysis, ultrasonic analysis, FFT flux analysis, and FFT current analysis, and (c) application instructions for correlating at least one imagery indication of equipment health with at least one dynamic indication of equipment health;while on a route or survey, receiving and storing focal plane array imaging sensor data and dynamic sensor data at approximately the same time in the portable instrument using at least a portion of the application instructions;deriving at least one imagery indication of equipment health comprising thermographic image data from the imaging sensor data using at least a portion of the application instructions;deriving at least one dynamic indication of equipment health comprising an ultrasonic dB value from the dynamic sensor data using at least the dynamic signal analysis portion of the application instructions, wherein the at least one imagery indication of equipment health and the at least one dynamic indication of equipment health are derived from the imaging sensor data and the dynamic sensor data that were acquired at approximately the same time; andcorrelating the thermographic image data with the ultrasonic dB value to assess performance of a valve. 2. The method of claim 1 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing focal plane array imaging sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing focal plane array infrared imaging sensor data, and the step of receiving and storing focal plane array imaging sensor data in the instrument comprises receiving and storing focal plane array infrared imaging sensor data in the instrument. 3. The method of claim 1 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data using FFT analysis, and the step of deriving at least one dynamic indication of equipment health comprises deriving at least one dynamic indication of equipment health using FFT analysis. 4. A method for inspecting equipment, the method comprising,storing in a portable instrument (a) application instructions for receiving, storing and analyzing focal plane array imaging sensor data to derive at least one imagery indication of equipment health, and (b) application instructions for receiving, storing, and analyzing dynamic sensor data to derive at least one dynamic indication of equipment health wherein the analyzing dynamic sensor data includes one or more analyzing techniques selected from the following group: Fast Fourier Transform (FFT) vibration analysis, waveform vibration analysis, spectral vibration analysis, stress wave analysis, transient analysis, sonic analysis, ultrasonic analysis, FFT flux analysis, and FFT current analysis, and (c) application instructions for correlating at least one imagery indication of equipment health with at least one dynamic indication of equipment health;while on a route or survey, receiving and storing focal plane array imaging sensor data and dynamic sensor data in the portable instrument using at least a portion of the application instructions;deriving at least one imagery indication of equipment health comprising a thermal indication from the imaging sensor data using at least a portion of the application instructions;deriving at least one dynamic indication of equipment health from the dynamic sensor data using at least the dynamic signal analysis portion of the application instructions; andwhile on the route or survey, isolating a fault from a normal condition using both the imagery indication and the dynamic sensor indication to conclude whether the thermal indication likely indicates a normal condition or an abnormal condition. 5. A method for inspecting equipment, the method comprising,storing in a portable instrument (a) application instructions for receiving, storing and analyzing focal plane array imaging sensor data to derive at least one imagery indication of equipment health, (b) application instructions for receiving, storing, and analyzing dynamic sensor data to derive at least one dynamic indication of equipment health wherein the analyzing dynamic sensor data includes one or more analyzing techniques selected from the following group: Fast Fourier Transform (FFT) vibration analysis, waveform vibration analysis, spectral vibration analysis, stress wave analysis, transient analysis, sonic analysis, ultrasonic analysis, FFT flux analysis, and FFT current analysis, and (c) application instructions for correlating at least one imagery indication of equipment health with at least one dynamic indication of equipment health;while on a route or survey, receiving and storing focal plane array imaging sensor data and dynamic sensor data at approximately the same time in the portable instrument using at least a portion of the application instructions;deriving at least one imagery indication of equipment health comprising an infrared image showing relatively hot coupling from the imaging sensor data using at least a portion of the application instructions;deriving at least one dynamic indication of equipment health comprising vibration analysis from the dynamic sensor data using at least the dynamic signal analysis portion of the application instructions, wherein the at least one imagery indication of equipment health and the at least one dynamic indication of equipment health are derived from the imaging sensor data and the dynamic sensor data that were acquired at approximately the same time; andcorrelating the infrared image showing relatively hot coupling with vibration analysis results to assess hardware misalignment. 6. The method of claim 5 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing focal plane array imaging sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing focal plane array infrared imaging sensor data, and the step of receiving and storing focal plane array imaging sensor data in the instrument comprises receiving and storing focal plane array infrared imaging sensor data in the instrument. 7. The method of claim 5 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data using FFT analysis, and the step of deriving at least one dynamic indication of equipment health comprises deriving at least one dynamic indication of equipment health using FFT analysis. 8. A method for inspecting equipment, the method comprising,storing in a portable instrument (a) application instructions for receiving, storing and analyzing focal plane array imaging sensor data to derive at least one imagery indication of equipment health, (b) application instructions for receiving, storing, and analyzing dynamic sensor data to derive at least one dynamic indication of equipment health wherein the analyzing dynamic sensor data includes one or more analyzing techniques selected from the following group: Fast Fourier Transform (FFT) vibration analysis, waveform vibration analysis, spectral vibration analysis, stress wave analysis, transient analysis, sonic analysis, ultrasonic analysis, FFT flux analysis, and FFT current analysis, and (c) application instructions for correlating at least one imagery indication of equipment health with at least one dynamic indication of equipment health;while on a route or survey, receiving and storing focal plane array imaging sensor data and dynamic sensor data at approximately the same time in the portable instrument using at least a portion of the application instructions;deriving at least one imagery indication of equipment health comprising delta-temperature data from the imaging sensor data using at least a portion of the application instructions;deriving at least one dynamic indication of equipment health comprising heterodyned ultrasonic sounds from the dynamic sensor data using at least the dynamic signal analysis portion of the application instructions, wherein the at least one imagery indication of equipment health and the at least one dynamic indication of equipment health are derived from the imaging sensor data and the dynamic sensor data that were acquired at approximately the same time; andcorrelating the delta-temperature data with the heterodyned ultrasonic sounds to assess a power line insulator connection. 9. The method of claim 8 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing focal plane array imaging sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing focal plane array infrared imaging sensor data, and the step of receiving and storing focal plane array imaging sensor data in the instrument comprises receiving and storing focal plane array infrared imaging sensor data in the instrument. 10. The method of claim 8 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data using FFT analysis, and the step of deriving at least one dynamic indication of equipment health comprises deriving at least one dynamic indication of equipment health using FFT analysis. 11. A method for inspecting equipment, the method comprising,storing in a portable instrument (a) application instructions for receiving, storing and analyzing focal plane array imaging sensor data to derive at least one imagery indication of equipment health, (b) application instructions for receiving, storing, and analyzing dynamic sensor data to derive at least one dynamic indication of equipment health wherein the analyzing dynamic sensor data includes one or more analyzing techniques selected from the following group: Fast Fourier Transform (FFT) vibration analysis, waveform vibration analysis, spectral vibration analysis, stress wave analysis, transient analysis, sonic analysis, ultrasonic analysis, FFT flux analysis, and FFT current analysis, and (c) application instructions for correlating at least one imagery indication of equipment health with at least one dynamic indication of equipment health;while on a route or survey, receiving and storing focal plane array imaging sensor data and dynamic sensor data at approximately the same time in the portable instrument using at least a portion of the application instructions;deriving at least one imagery indication of equipment health comprising a bore scope image from the imaging sensor data using at least a portion of the application instructions;deriving at least one dynamic indication of equipment health comprising a vibration spectrum from the dynamic sensor data using at least the dynamic signal analysis portion of the application instructions, wherein the at least one imagery indication of equipment health and the at least one dynamic indication of equipment health are derived from the imaging sensor data and the dynamic sensor data that were acquired at approximately the same time; andcorrelating the bore scope image with the vibration spectrum to characterize gear or bearing components. 12. The method of claim 11 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing focal plane array imaging sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing focal plane array infrared imaging sensor data, and the step of receiving and storing focal plane array imaging sensor data in the instrument comprises receiving and storing focal plane array infrared imaging sensor data in the instrument. 13. The method of claim 11 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data using FFT analysis, and the step of deriving at least one dynamic indication of equipment health comprises deriving at least one dynamic indication of equipment health using FFT analysis. 14. A method for inspecting equipment, the method comprising,storing in a portable instrument (a) application instructions for receiving, storing and analyzing focal plane array imaging sensor data to derive at least one imagery indication of equipment health, (b) application instructions for receiving, storing, and analyzing dynamic sensor data to derive at least one dynamic indication of equipment health wherein the analyzing dynamic sensor data includes one or more analyzing techniques selected from the following group: Fast Fourier Transform (FFT) vibration analysis, waveform vibration analysis, spectral vibration analysis, stress wave analysis, transient analysis, sonic analysis, ultrasonic analysis, FFT flux analysis, and FFT current analysis, and (c) application instructions for correlating at least one imagery indication of equipment health with at least one dynamic indication of equipment health;while on a route or survey, receiving and storing focal plane array imaging sensor data and dynamic sensor data at approximately the same time in the portable instrument using at least a portion of the application instructions;deriving at least one imagery indication of equipment health comprising image data from the imaging sensor data using at least a portion of the application instructions;deriving at least one dynamic indication of equipment health comprising vibration data from the dynamic sensor data using at least the dynamic signal analysis portion of the application instructions, wherein the at least one imagery indication of equipment health and the at least one dynamic indication of equipment health are derived from the imaging sensor data and the dynamic sensor data that were acquired at approximately the same time; andcorrelating image and vibration data before and after thermal growth to evaluate misalignment. 15. The method of claim 14 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing focal plane array imaging sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing focal plane array infrared imaging sensor data, and the step of receiving and storing focal plane array imaging sensor data in the instrument comprises receiving and storing focal plane array infrared imaging sensor data in the instrument. 16. The method of claim 14 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data using FFT analysis, and the step of deriving at least one dynamic indication of equipment health comprises deriving at least one dynamic indication of equipment health using FFT analysis. 17. A method for inspecting equipment, the method comprising,storing in a portable instrument (a) application instructions for receiving, storing and analyzing focal plane array imaging sensor data to derive at least one imagery indication of equipment health, (b) application instructions for receiving, storing, and analyzing dynamic sensor data to derive at least one dynamic indication of equipment health wherein the analyzing dynamic sensor data includes one or more analyzing techniques selected from the following group: Fast Fourier Transform (FFT) vibration analysis, waveform vibration analysis, spectral vibration analysis, stress wave analysis, transient analysis, sonic analysis, ultrasonic analysis, FFT flux analysis, and FFT current analysis, and (c) application instructions for correlating at least one imagery indication of equipment health with at least one dynamic indication of equipment health;while on a route or survey, receiving and storing focal plane array imaging sensor data and dynamic sensor data at approximately the same time in the portable instrument using at least a portion of the application instructions;deriving at least one imagery indication of equipment health comprising a thermographic image from the imaging sensor data using at least a portion of the application instructions;deriving at least one dynamic indication of equipment health comprising ultrasonic leak detection from the dynamic sensor data using at least the dynamic signal analysis portion of the application instructions, wherein the at least one imagery indication of equipment health and the at least one dynamic indication of equipment health are derived from the imaging sensor data and the dynamic sensor data that were acquired at approximately the same time; andcorrelating the ultrasonic leak detection with the thermographic image to assess a system containing compressed or heated gas. 18. The method of claim 17 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing focal plane array imaging sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing focal plane array infrared imaging sensor data, and the step of receiving and storing focal plane array imaging sensor data in the instrument comprises receiving and storing focal plane array infrared imaging sensor data in the instrument. 19. The method of claim 17 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data using FFT analysis, and the step of deriving at least one dynamic indication of equipment health comprises deriving at least one dynamic indication of equipment health using FFT analysis. 20. A method for inspecting equipment, the method comprising,storing in a portable instrument (a) application instructions for receiving, storing and analyzing focal plane array imaging sensor data to derive at least one imagery indication of equipment health, (b) application instructions for receiving, storing, and analyzing dynamic sensor data to derive at least one dynamic indication of equipment health wherein the analyzing dynamic sensor data includes one or more analyzing techniques selected from the following group: Fast Fourier Transform (FFT) vibration analysis, waveform vibration analysis, spectral vibration analysis, stress wave analysis, transient analysis, sonic analysis, ultrasonic analysis, FFT flux analysis, and FFT current analysis, and (c) application instructions for correlating at least one imagery indication of equipment health with at least one dynamic indication of equipment health;while on a route or survey, receiving and storing focal plane array imaging sensor data and dynamic sensor data at approximately the same time in the portable instrument using at least a portion of the application instructions;deriving at least one imagery indication of equipment health comprising a relatively hot location on a thermogram from the imaging sensor data using at least a portion of the application instructions;deriving at least one dynamic indication of equipment health comprising an ultrasonic signature from the dynamic sensor data using at least the dynamic signal analysis portion of the application instructions, wherein the at least one imagery indication of equipment health and the at least one dynamic indication of equipment health are derived from the imaging sensor data and the dynamic sensor data that were acquired at approximately the same time; andcorrelating the imagery indication of equipment health with the dynamic indication of equipment health to verify that the infrared indication of equipment health indicates heating caused by friction. 21. The method of claim 20 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing focal plane array imaging sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing focal plane array infrared imaging sensor data, and the step of receiving and storing focal plane array imaging sensor data in the instrument comprises receiving and storing focal plane array infrared imaging sensor data in the instrument. 22. The method of claim 20 wherein the step of storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data comprises storing in an instrument application instructions for receiving, storing and analyzing dynamic sensor data using FFT analysis, and the step of deriving at least one dynamic indication of equipment health comprises deriving at least one dynamic indication of equipment health using FFT analysis. |
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claims | 1. A method to analyze fatigue damage values of wheels each to be installed at a number of axle positions on a vehicle, comprising:(a) simulating installations by randomly determining the axle positions of each wheel on the vehicle;(b) determining at each of the axle positions for each wheel a fatigue damage value for each of a plurality of critical locations at the wheel during an installation;(c) storing the fatigue damage values of the critical locations for each installation;(d) summing the respective retained fatigue damage value for each critical location to determine a respective total fatigue damage value;(e) repeating (a), (b), (c) and (d) a number of times to obtain at each of the critical locations a distribution of total fatigue damage values; and(f) determining whether or not at least a subset of the total fatigue damage values at each of the critical locations exceeds a respective threshold total fatigue damage value. 2. A method as defined in claim 1, wherein the simulated installations of the wheel substantially equals an expected number of installations of the wheel. 3. A method as defined in claim 1, further including determining the number of installations of the wheel on the vehicle. 4. A method as defined in claim 3, wherein the number of installations is determined by approximately the number of tires that may be used by the wheel during a service life of the wheel. 5. A method as defined in claim 4, wherein a tire life of a tire may be one of a constant value or a value selected from a normal distribution of tire lives. 6. A method as defined in claim 1, wherein the critical locations are provided by determining locations subject to critical fatigue stress at the wheel. 7. A method as defined in claim 6, wherein repeating (a), (b), (c) and (d) continues until the fatigue damage value at each of the critical locations for a current installation is substantially the same as the fatigue damage value of the corresponding critical location for an immediately prior installation. 8. A method as defined in claim 1, further comprising determining, at each of the critical locations at the wheel, the fatigue damage value corresponding to a preload value of fasteners of the wheel. 9. A method as defined in claim 8, wherein the fasteners of the wheel are presumed to have the same preload value. 10. A method as defined in claim 9, wherein the preload value is determined for each of the simulated installations. 11. A method as defined in claim 8, wherein determining a preload value comprises randomly selecting one of a plurality of preload values to obtain a corresponding fatigue damage value, wherein the random selection of the preload value uses one of a uniform probability of selection or a highest probability of selection. 12. A method as defined in claim 1, wherein the subset comprises at least 95% of the total fatigue damage values. 13. An apparatus to analyze fatigue damage values of wheels each to be installed at a number of axle positions on a vehicle, comprising:(a) an axle position generator to simulate random determinations of the installed axle positions of each wheel on the vehicle;(b) a fatigue damage value generator to obtain the positions of each wheel from the axle position generator to determine at each of the axle positions for each wheel a fatigue damage value for each of a plurality of critical locations at the wheel during an installation, to store the fatigue damage values of the critical locations for each installation, to sum the respective retained corresponding fatigue damage value for each critical location to determine and store a respective total fatigue damage value, and to store total fatigue damage values of a distribution of respective total fatigue damage values obtained from repeating the summing of the fatigue damage values, and(c) a comparator to determine whether or not at least a subset of the respective total fatigue damage values at a critical location exceeds a respective threshold total fatigue damage value for the wheel. 14. The apparatus as defined in claim 13, further comprising an installation quantity value generator to determine a number of installations of the wheel to be simulated on the vehicle. 15. The apparatus as defined in claim 14, further comprising a tire life value generator to determine a life of a tire to be used on the wheel. 16. The apparatus as defined in claim 13, further comprising a wheel life value generator to determine a life of a wheel to be used on the vehicle. 17. The apparatus as defined in claim 13, further comprising a torque preload value generator to determine a preload value of fasteners of the wheel. 18. The apparatus as defined in claim 17, wherein a preload value is determined for each of the simulated installations. 19. The apparatus as defined in claim 17, wherein the fatigue damage value determined for each of the plurality of critical locations at the wheel during an installation is a function of the preload value. 20. A computer-readable medium storing computer readable instructions which, when executed by a computer, causes the computer to:(a) simulate installations by randomly determining the axle positions of each wheel on the vehicle;(b) determine at each of the axle positions for each wheel a fatigue damage value for each of a plurality of critical locations at the wheel during an installation;(c) store the fatigue damage values of the critical locations for each installation;(d) sum the respective retained fatigue damage value for each critical location to determine a respective total fatigue damage value;(e) repeat (a), (b), (c) and (d) a number of times to obtain at each of the critical locations a distribution of total fatigue damage values; and(f) determine whether or not at least a subset of the total fatigue damage values at each of the critical locations exceeds a respective threshold total fatigue damage value. |
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055704085 | summary | FIELD OF THE INVENTION This invention relates broadly to the field of x-rays. More particularly this invention relates to the field of x-ray optics. This invention provides a device and a method for improvement in the capability of capillary x-ray optic/x-ray source systems to produce high intensity, small diameter x-ray beams. BACKGROUND OF THE ART When samples are analyzed by various x-ray techniques, such as x-ray diffraction, it is desirable that the dimensions of the x-ray beam hitting the sample be on the order of the sample size, or of the order of the spot on the sample to be examined. This criteria on beam size is important because it maximizes spacial resolution, while minimizing background noise produced by unwanted photons. In many cases, for example in the case of x-ray diffraction of protein crystals, sample sizes are very small, and conventional x-ray diffraction equipment does not function efficiently. When traditional laboratory x-ray sources are used to analyze such small samples, beams of appropriate size are typically obtained by collimation methods. This includes such things as passing the x-ray beam through pin holes cut into x-ray absorbing materials such as lead. Because low beam divergence is also desirable, these pin holes must be placed a significant distance away from the source. This means that the solid angle of collection from the source is quite small. This in turn results in a very low intensity beam reaching the sample. One significant disadvantage of a low intensity beam is that measurement times can be extremely long. For some samples this is merely an inconvenience. However, for samples like protein crystals which have relatively short life times, this extended period of analysis can render the analysis technique useless. In all cases, extended measurement times lead to a decrease in the signal-to-noise ratio. Also, it is important for commercial analysis operations to maximize the sample through-put by minimizing analysis time. Shorter analysis times can thus lead to substantial financial rewards. It is known in the art that to obtain more x-rays from a source, a larger spot size on the anode is required. Thus, conventional wisdom dictates that in order to decrease power transmitted to a sample, either with or without an optic, a more powerful source with a larger spot size should be used. A general rule that is followed is that the source spot size should be the size of the sample being analyzed. It is known to the art that single hollow glass capillaries can form x-ray beams of very small dimensions see for example P. B. Hirsch and J. N. Keller, Proc. Phys. Soc. 64 369 (1951). Tapering these single capillaries to further limit output spot size is also known to the art see E. A. Stern et. al.Appl. Opt. 27 5135 (1988). However, both these devices only capture x rays from a very small portion of the source. Thus, their use also leads to x-ray beams of less intensity than is desired. Yet another disadvantage of the tapered devices is that the minimum x-ray spot size is located right at the tip of the device. This places strict limitations on the positioning of a sample. In addition, these single tapered capillaries can only form a small spot with considerable divergence. Often times for diffraction experiments, a parallel beam is desirable. Also known to the art are multi-fiber polycapillary x-ray optics. These devices form a particular class of a more general type of x-ray and neutron optics known as Kumakhov optics. See for example U.S. Pat. No. 5,192,869 to Kumakhov. Disclosed in this patent are optics with multiple fibers which are designed to produce high flux quasi-parallel beams. Although these optics can capture a large solid angle of x-rays from diverging sources, their potential for capturing from a small spot source or for forming small dimension output beams is limited by the relatively large outer diameter of the individual polycapillary fibers. The outer diameter of the fibers is on the order of 0.5 millimeters. Because of the fiber outer diameter these multi-fiber optics have a minimum input focal length roughly 150 millimeters. The critical angle for total external reflection at 8 keV for glass is four milliradians. Effective transmission after many reflections is obtained only if the photons are approximately one-half the critical angle. So using 0.5 mm diameter fibers, geometry shows that with a source as small as 100 .mu.m, the source-optic distance should be at least 150 mm for the outer channels to transmit effectively. Because of this relatively long input focal distance to capture a large angular range of x-rays from the source the input diameter needs to be relatively large which in turn constrains the minimum diameter and maximum intensity (photons/unit area) of the output beam. The minimum beam diameter for a multi-fiber polycapillary optic with a 0.15 radian capture angle which forms a quasi-parallel beam is on the order of 30 millimeters. These optics are thus not appropriate to produce the intense small diameter x-ray beams needed for small sample diffraction experiments such as protein crystallography. For focusing optics, because of the fiber diameter, the minimum focused spot sized has a diameter on the order of 0.5 millimeters. OBJECT OF THE INVENTION Thus it is the object of the subject invention to provide a solution to the long felt need in the art for laboratory based, small dimension, high intensity x-ray beams. It is another object of this invention to allow the analysis sample to be placed at a position removed from the output end of the device. It is yet another object of this invention to provide a small, intense x-ray beam which is highly collimated with a minimum of divergence. Yet another object of this invention is to produce small, high intensity, focused x-ray spots. Another object of this invention is to provide these benefits in a relatively compact, and cost effective system. BRIEF SUMMARY OF THE INVENTION The subject invention accomplishes these objects with a carefully engineered x-ray source/capillary optic system comprising: 1) A monolithic multiple-channel capillary optic with scaled down input and output diameters minimized with respect to photon energy, source diameter, and channel diameter; and, PA1 2) an x-ray source with a spot size designed to maximize optic output intensity for a desired output beam diameter. The specially designed optic is positioned within 60 mm or less relative to the x-ray source. Monolithic optics are an essentially integral one-piece structure in which fiber channels are closely packed and self-aligning along their entire length. At the input end of the optic the channels are oriented to aim substantially at the x-ray source. The output end of the optic can be shaped to form either a converging, or a quasi-parallel beam, depending on the intended use of the invention. The smaller source, although less powerful, provides an increase in the areal density of x-rays. The monolithic optic enables the efficient capture of the small spot x rays, because each individual channel can be aligned more efficiently with the source spot. Surprisingly, it has been discovered that a small spot, lower power source, when combined with a monolithic capillary optic's superior x-ray collection abilities, can lead to a higher intensity of x-rays at the output of the optic when compared with the use of a large spot, higher power source with or without an optic. The basic idea behind the invention then, is to continue to capture the x-rays from the source, and to squeeze these photons into a smaller output space in order to produce the desired high intensity, small diameter beam. This requires significant reengineering of existing optic designs, and modification of the x-ray source used. The first modification is that the input diameter of the optic must be decreased from what is currently known. A critical point to the invention is that in order to keep the same amount of photons entering the input end of the optic, the optic must be moved closer to the x-ray source to maintain the same capture solid angle. Characteristic input focal lengths of the subject invention are less than half of the roughly 150 millimeters required for the best multi-fiber polycapillary optics. Moving closer and using smaller input diameters all aimed at a common point, means the optic will "see" a smaller portion of the source. Thus, another key element of the subject invention is to decrease the source spot size in order to increase the power density and therefor the x-ray production from the area of the source from the which the optic captures photons. This is done in spite of the fact that the total number of x-rays emerging from the source is decreased. This invention provides for more efficient use of existing x-ray power. |
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039492281 | description | Referring to the drawings and particularly FIG. 1, there is shown an electron gun 10 for producing a beam 11 of charged particles in the well-known manner. The electron beam 11 is passed through an aperture 12 in a plate 14 to shape the beam 11. The beam 11 is preferably square shaped and has a size equal to the minimum line width of the pattern that is to be formed. The beam 11 passes between a pair of blanking plates 16, which determine when the beam is applied to the material and when the beam is blanked. The blanking plates 16 are controlled by an analog unit 17 from circuits, which form part of a digital control unit 18. The digital control unit 18 is connected to a computer 19, which is preferably an IBM 370 computer. The beam 11 then passes through a circular aperture 21 in a plate 22. This controls the beam 11 so that only the charged particles passing through the centers of the lenses (not shown) are used so that a square-shaped spot without any distortion is produced. The beam 11 is next directed through magnetic deflection coils 23, 24, 25, and 26. The magnetic deflection coils 23 and 24 control the deflection of the beam 11 in a horizontal or X direction while the magnetic deflection coils 25 and 26 control the deflection of the beam 11 in a vertical or Y direction. Accordingly, the coils 23-26 cooperate to move the beam 11 in a horizontal scan by appropriately deflecting the beam. While the beam 11 could be moved in a substantially raster fashion as shown and described in the aforesaid Kruppa et al patent, it is preferably moved in a back and forth scan so that the beam 11 moves in opposite directions along adjacent lines. The beam 11 then passes between electrostatic deflection plates 27, 28, 29, and 30. The plates 27 and 28 cooperate to deflect the beam in a horizontal or X direction while the electrostatic deflection plates 29 and 30 cooperate to move the beam 11 in the vertical or Y direction. The plates 27-30 are employed to provide any desired offset of the beam 11 at each of the predetermined positions or spots to which it is moved. The beam 11 is then applied to a target such as a semiconductor chip having resist that is exposed by the beam 11. The target is supported on a table 31. The table 31 is movable in X and Y directions as more particularly shown and described in the aforesaid Kruppa et al patent. The beam 11 is moved through A, B and C cycles as shown and described in the aforesaid Kruppa et al patent. The system of the present invention is concerned with controlling the beam 11 during the B cycle when pattern writing of the chip occurs by exposing the resist. As shown in FIG. 2A, the digital control unit 18 includes a pattern memory 40, which has the number of words of data therein equal to or greater than the number of predetermined positions or spots to which the beam 11 is moved during its horizontal scan along a single line. That is, each of the predetermined positions or spots to which the beam 11 is moved during its movement in the X direction along a single line is correlated to one word of the pattern memory 40. The pattern memory 40 is connected directly to a channel 41 (see FIG. 2B) of the computer 19 when a gate 42 is activated by an internal control latch identified as "ENABLE INITIAL LOAD." With activation of the gate 42, initial information can be supplied directly to the pattern memory 40 from the channel 41 of the computer 19. However, the initial writing of information into the pattern memory 40 normally occurs during an initial scan by the beam 11. That is, as the beam 11 scans in one direction, information is written in the pattern memory 40 for the scan in the opposite direction as no pattern writing of the chip occurs during the scan in the one direction. When the gate 42 is activated, information is supplied from the channel 41 of the computer 19 to a subroutine memory 43 (see FIG. 2B). All of the information to be stored in the subroutine memory 43 for pattern writing of the entire chip is supplied at this time to the subroutine memory 43. Upon completion of transmittal of information to the pattern memory 40 and the subroutine memory 43, a signal from the channel 41 of the computer 19 causes the internal control latch to close the gate 42. Except for when the gate 42 is enabled, the pattern memory 40 receives its information from either the channel 41 of the computer 19 through a pattern input surge buffer 44 or from the subroutine memory 43. The subroutine memory 43 supplies data only when the need for updating the information in the memory 40 would exhaust the data in the pattern input buffer 44. The pattern input buffer 44 transmits the information through a pattern input decoder 45 to a selector 46. The information from the pattern input buffer 44 is transmitted from the selector 46 to the pattern memory 40 through an exposure update register 47 and/or an offset update register 48 only when an update counter 49 is at zero and a subroutine latch 50 is not activated to allow information to be supplied from the subroutine memory 43. The subroutine latch 50 is connected to a decoder and gate 51 to receive the necessary signal therefrom when the subroutine latch 50 is to be activated to allow the information to be supplied from the subroutine memory 43. When information is to be supplied to the pattern memory 40, information is transmitted from the selector 46 through the exposure data register 47 to an exposure select gate 52 (see FIG. 2A) and through the offset update register 48 to an offset select gate 53. The gates 52 and 53 are connected through a pattern input register 54 to the pattern memory 40. The new information need only update either the exposure of the beam 11 or the offset of the beam 11. Of course, it can supply information for both. However, the update counter 49 (see FIG. 2B) goes to zero whenever updating of either exposure or offset is required and activates a zero detector 55, which then enables the selector 46 to transmit information to at least one of the registers 47 and 48. The exposure update register 47, the offset update register 48, the update counter 49, the exposure select gate 52, the offset select gate 53, and the zero detector 55 are all inactivated through the decoder and gate 51 when an internal control latch identified as "ENABLE PATTERN UPDATES" is inactivated to prevent updating of information in the pattern memory 40 at desired times. Thus, when the gate 42 is activated, updating is prevented by the inactivation of the internal control latch through the decoder and gate 51, and this updating is prevented throughout the initial scan by the beam 11 after the gate 42 has been inactivated. The exposure signal determines whether the beam 11 is maintained in an off condition for the entire time period at which the beam 11 is disposed at a predetermined position, an on condition for the entire time period at which the beam 11 is disposed at the predetermined position, or an on condition for a portion of the time period at which the beam 11 is disposed at the predetermined position. The time period from the time that the beam 11 reaches a predetermined position until the time that the beam 11 is at the next of the predetermined positions is divided into sixteen portions or ticks with the first fourteen portions or ticks being when exposure of the beam 11 can occur while the last two portions or ticks is when the beam 11 is stepped to the next predetermined position or spot. When the beam 11 is to be exposed for less than the total of the fourteen positions, exposure occurs so that the beam 11 completes its exposure at the time that the beam 11 is to be stepped to the next predetermined position. For example, if the beam 11 is to be exposed for only six portions or ticks, the beam 11 would be blanked for the first eight portions or ticks and then turned on for the next six portions or ticks. The timing for these sixteen portions or ticks is obtained from an X' counter. Thus, the X' counter provides sixteen portions or ticks during each time period or spot interval. The offset signal determines whether the beam 11 is offset and the amount of offset. It should be understood that the beam 11 is offset during the stepping of the beam 11 from one predetermined position to the next. This is during the last two ticks. The data includes information for offset in both X and Y directions. The offset in the X direction is in a direction along which the beam 11 is moving while the Y direction is perpendicular thereto in the plane of the material to which the beam 11 is being applied. The beam 11 can be offset in increments that either advance or retard the beam 11 in the direction in which it is moving with respect to the predetermined position to which it is moved and in increments that move the beam 11 to either side of the X direction in which it is moving. When the beam 11 is moving forwardly, a positive offset in the X direction is an advance of the beam 11 in the direction in which the beam 11 is moving while a negative offset retards the beam 11 in the direction in which it is moving. When the beam 11 is moving rearwardly, a positive offset in the X direction retards the beam 11 while a negative offset in the X direction advances the beam 11. Thus, the positive offset and negative offset are always in the same direction irrespective of which direction the beam 11 is moving. A positive offset in the Y direction always offsets the beam 11 above its line of movement while a negative offset in the Y direction always offsets the beam 11 below its line of movement. The update counter 49 receives a clock signal from the X' counter each time that the beam 11 is moved to the next of the predetermined positions or spots. When the update counter 49 is not inactivated through the decoder and gate 51 being inactivated, the update counter 49 is decremented one count during each stepping of the beam 11. When the update counter 49 goes to zero due to being decremented, the zero detector 55 enables update information to be supplied from the selector 46. The selector 46 transmits the information from the pattern input buffer 44 unless the subroutine latch 50 is activated. The subroutine latch 50 is activated initially from the decoder and gate 51 with this occurring when the zero detector 55 produces its signal to indicate that the update counter 49 is at zero. The information from the pattern input buffer 44 through the selector 46 to the decoder and gate 51 includes an address for transmittal to a subroutine address register 57 as well as the data to cause the subroutine latch 50 to be activated when the update counter 49 goes to zero. This data selects a particular address in the subroutine memory 43 from which information is to be supplied through a subroutine output register 58 to the selector 46 for updating the exposure update register 47 and/or the offset update register 48 and the update counter 49. The information transmitted from the subroutine memory 43 upon the initial activation of the subroutine latch 50 includes data to determine whether the subroutine latch 50 remains activated. If it does, then the next time that the zero detector 55 is activated due to the update counter 49 going to zero, the data again is transmitted from the subroutine memory 43 to the selector 46 rather than from the pattern input buffer 44. When the zero detector 55 again produces a signal due to the update counter 49 going to zero with the subroutine latch 50 activated, a gate 59 is activated because of the subroutine latch 50 already being activated and the zero detector 55 producing a signal. The activation of the gate 59 causes incrementing of the subroutine address register 57. The incrementing of the subroutine address register 57 addresses the next address in the subroutine memory 43 to cause the information at this address in the subroutine memory 43 to be supplied through the subroutine output register 58 to the selector 46 from which the data is transmitted to the exposure update register 47 and/or the offset update register 48 and the update counter 49. The subroutine memory 43 is continuously addressed to receive information therefrom with each activation of the zero detector 55 by incrementing the addresss through the gate 59 being opened until the data from the subroutine memory 43 does not include activation of the subroutine latch 50. When this does not occur, the next activation of the zero detector 55 results in information being supplied from the pattern input buffer 44 to the selector 46 with this information either supplying data from the pattern input buffer 44 to the exposure update register 47 and/or the offset update register 48 and the update counter 49 or activating the subroutine latch 50 through the decoder and gate 51 and selecting another address in the subroutine address register 57 to cause data to be supplied from the subroutine memory 43. The activation of the subroutine latch 50 with a completely different address in the subroutine memory 43 being accessed is done when it is not desired to obtain the data from the next address in the subroutine memory 43 from the prior one as would occur through incrementing the address by the gate 59 being opened. As previously mentioned, the information can be supplied to the pattern memory 40 through the pattern input register 54 (see FIG. 2A) only when the select gates 52 and 53 are opened. Even though the select gates 52 and 53 receive information from the exposure update register 47 and/or the offset update register 48 for transmittal to the pattern input register 54, they open to transmit this information only after there is also a signal from a pattern output register 62. This insures that the line in the pattern memory 40 receiving the new information has already transmitted its stored information to the pattern output register 62. If the information in the exposure update register 47 and/or the offset update register 48 is zero, then the information for exposure and/or offset is transmitted from the pattern output register 62 through the exposure select gate 52 and/or the offset select gate 53 to the pattern input register 54. This zero in the register 47 or 48 when there is no change for the same spot in the next line. At the time of reading out the information from the pattern memory 40, a parity check is performed. If there should be an error, the beam 11 is turned off by an error detector 63 (see FIG. 2B) to which a signal is transmitted due to the parity check error. Similarly, a validity check is made to determine if the new information from the pattern input register 54 is correct. If not, a signal is transmitted to the error detector 63 so as to turn off the beam 11 and to the computer 19 so that the computer 19 can initiate an error recovery sequence. The exposure information from the pattern output register 62 is transmitted through an exposure detector 64 (see FIG. 2A) and an exposure gate 65 to the analog unit 17. At the same time, the offset information is supplied from the pattern output register 62 to the analog unit 17 through an offset gate 66. If either the exposure decoder 64 or the exposure gate 65 is inactivated, no signal can be transmitted to turn on the beam 11. If the offset gate 66 is turned off, then no information concerning offset can be transmitted to the analog unit 17. The exposure decoder 64 is turned off by an internal control latch, identified as "ENABLE BEAM OFF DURING SAWTOOTH RESET," when the beam 11 is being stepped to the next predetermined position. Thus, this forces the beam 11 to be off during stepping of the beam 11. It should be understood that the state of this latch is constant during any given line. While the exposure detector 64 can transmit a signal to turn the beam 11 on when the internal control latch does not have the exposure decoder 64 turned off, the data from the pattern output register 62 determines whether the exposure decoder 64 is turned on or remains off when the appropriate clock signal from the X' counter is receved at the exposure decoder 64. If the beam 11 is to be turned on for the entire period of time, the data from the pattern output register 62 indicates this so that the exposure decoder 64 is turned on as soon as stepping of the beam 11 is completed. If the beam 11 is to be turned on for only a portion of the period of time when the beam 11 is at a particular predetermined position, a gray register 67 is activated by the data from the pattern output register 62 so that the exposure decoder 64 is turned on for only the portion of the time that the beam 11 is to be applied through cooperation with the clock signal from the X' counter. Each of the gates 65 and 66 is connected to an internal control latch identified as "ENABLE BEAM CONTROL." When this latch is turned on, the output of the exposure decoder 64 and the offset information from the pattern output register 62 is transmitted to the analog unit 17. When this latch is turned off, no exposure or offset information is transmitted to the analog unit 17. The ENABLE PATTERN UPDATES latch and ENABLE BEAM CONTROL latch are independent. This permits beam control information to be sent to the analog unit 17 without requiring updates to be made in the pattern memory 40. This also permits the pattern memory 40 to be updated without simultaneously causing beam control information to be sent to the analog unit 17. Normally, the ENABLE BEAM CONTROL latch is off to inactivate the gates 65 and 66 in the first scan of the B cycle when the pattern memory 40 is being updated through the pattern input buffer 44. The gates 65 and 66 are inactivated by the ENABLE BEAM CONTROL latch prior to the gate 42 being opened by its internal control latch and remain in this condition until activated after the first scan of the B cycle. As the beam 11 is moved in its forward and backward scans, the pattern memory 40 is addressed from a pattern address register 68. As the beam 11 moves in one direction, preferably forward, the address in the pattern address register 68 is incremented each time that the beam 11 is moved to the next predetermined position. When the beam 11 moves in the opposite direction, the address in the pattern address 68 is decremented each time that the beam 11 is moved to the next predetermined position. A gate 69, which receives a clock signal from the X' counter, causes incrementing of the pattern address register 68 during each stepping of the beam 11 in the forward scan with the scan direction being indicated by a signal from a Y counter. Thus, this arrangement insures that the pattern address register 68 causes each of the words in the pattern memory 40 be to addressed in sequence in an ascending order during scan in one direction, preferably from left to right of a chip of a semiconductor wafer on the table 31, for example. When the beam 11 has completed its forward scan and retrace has ended so that backward scan is to start, the Y counter supplies a signal to the gate 69 and a gate 70 to inactivate the gate 69 and enable activation of the gate 70 whenever a clock signal from the X' counter is received at the gate 70. The opening of the gate 70 causes the pattern address register 68 to be decremented each time that the beam 11 steps in the backward (right to left) scan from one predetermined position to the next. This causes the pattern memory 40 to be addressed in the opposite direction to that in which it was addressed during the movement of the beam 11 in the forward scan. Accordingly, the information written in the pattern memory 40 always corresponds to the spot on the next line to be scanned. Of course, if the beam 11 were to be moved in a substantially raster fashion so as to move only in the forward scan, for example, then the pattern memory 40 would always be addressed in the same direction whereby only one of the gates 69 or 70 would be employed to cause only incrementing or decrementing, depending on which direction access to the pattern memory 40 was had, during each clock signal from the X' counter. During retrace, a gate 72 is opened by a clock signal from an R counter to enable either 0 (zero), which represents the first count in the forward scan and the top address in the pattern address register 68, or X.sub.w, which represents the last count in the forward scan and the bottom address in the pattern address register 68, to be supplied to the pattern address register 68. The Y counter also is connected to a selector 73 to supply the scan direction to cause selection of either 0 (zero) or X.sub.w prior to the gate 72 being opened during retrace. At this time, the signal from the Y counter is opposite to that which will be supplied to the gates 69 and 70 at the end of retrace. Thus, when a forward scan has been completed, the signal from the Y counter results in 0 being selected during retrace after a forward scan for gating through the gate 72 to the pattern address register 68 and results in X.sub.w being selected for transmitting through the gate 72 to the pattern address register 68 when backward scan has been completed and retrace is occurring. Thus, this enables the pattern memory 40 to be addressed at successively higher addresses during forward scan and at successively lower addresses during backward scan. There also is an X counter employed to count each spot to which the beam 11 moves. The X counter can count from 0 to 4095 as can the Y counter, which counts each line along which the beam 11 moves. The X counter actually counts only to X.sub.w and the Y counter actually counts only to Y.sub.w, which represents the number of lines in the B cycle. The X counter, the Y counter, the X' counter, the R counter, and other counters can be driven from an oscillator in the manner more particularly shown and described in the aforesaid Kruppa et al patent. These counters are the clock for the entire system. At the beginning of each line, a longitudinal redundancy check (LRC) register 74 (see FIG. 2B) is set at all ones. As each byte of data is taken from the pattern input buffer 44 to be decoded by the pattern decoder 45, it is exclusive-OR'd with the contents of the longitudinal redundancy check register 74 with the result inverted and then written into the register 74. When the end-of-line code from the pattern input buffer 44 is encountered, the bits therefrom, when exclusive-OR'd into the register 74 with the result inverted, should produce a zero result. The error detector 63 determines whether the output from the longitudinal redundancy check register 74 is a zero at this time due to also receiving a signal from the pattern decoder 45 at the time when the bits from the end-of-line code are exclusive-OR'd into the longitudinal redundancy check register 74. If the output from the longitudinal redundancy check register 74 is zero, then the next line can be scanned by the beam 11 at the end of retrace. If the output from the longitudinal redundancy check register 74 is not zero, the error detector 63 causes the beam 11 to be turned off by turning off the ENABLE BEAM CONTROL latch. It is not necessary to again turn on the beam 11 for the line that has been scanned although all of the update information must again be passed through the selector 46. If the longitudinal redundancy check register 74 has an output of zero, then the ENABLE BEAM CONTROL latch is allowed to remain on. The error detector 63 also receives the output of the pattern decoder 45 for each update of the pattern memory 40. If the output of the pattern decoder 45 is invalid, the error detector 63 causes turning off of the beam 11 by turning off the ENABLE BEAM CONTROL latch. A zero detector 75, which is connected to the error detector 63 and is disabled by the same internal control latch as controls the zero detector 55, senses the data supplied from the selector 46 to the update counter 49. If this data has a zero therein as determined by the zero detector 75, the error detector 63 disables the beam 11 by turning off the ENABLE BEAM CONTROL latch. The error detector 63 also receives a signal when there is a parity error during transmittal of data from the pattern memory 40 or an error during writing of new data in the pattern memory 40. The error detector 63 disables the beam 11 whenever it detects an error during read of or write into the pattern memory 40. Accordingly, the error detector 63 senses a plurality of different errors. These include the error due to a 0 being supplied to the update counter 49, an error at the end of any line being scanned, an error during read of the information in any line of the pattern memory 40, an error during write of any line in the pattern memory 40, and an error in the information from the pattern decoder 45 for updating the pattern memory 40. Any of these errors results in the error detector 63 causing the beam 11 to be disabled by turning off the ENABLE BEAM CONTROL latch. Considering the operation of the present invention, the gate 42 is opened by the ENABLE INITIAL LOAD latch to enable data to be supplied to the subroutine memory 43. In some instances, initial information also may be supplied to the pattern memory 40 from the channel 41 of the computer 19, but the initial information is normally supplied to the memory 40 from the pattern input buffer 44 during a scan by the beam 11 across the chip prior to pattern writing. When the information supplied to the subroutine memory 43 and the pattern memory 40 has been completed, the internal control latch is reset from the channel 41 of the computer 19 to close the gate 42. After this, the internal control latch, which has been inactivated to disable the exposure update rgister 47, the offset data register 48, the update counter 49, the select gates 52 and 53, and the zero detectors 55 and 75 through the decoder and gate 51, is activated to enable data to be transmitted to the pattern memory 40 from the selector 46. The gates 65 and 66 normally remain closed by their internal control latch until the first scan of the B cycle has been completed. The first scan by the beam 11 during the B cycle occurs after the internal control latch enables information to be supplied from the selector 46 through the decoder and gate 51. During this scanning, the pattern memory 40 is receiving information for the next line to be scanned by the beam 11. After the pattern memory 40 has the data for the line to be scanned, the information from the pattern memory 40 is obtained for each spot to which the beam 11 is stepped. When backward scan is occurring, the pattern address register 68 is decremented by the gate 70 being opened. After reading out the information from the pattern memory 40 for transmittal to the analog unit 17 through the pattern output register 62 for a particular predetermined position or spot, the gates 52 and 53 enable the information in the exposure update register 47 and the offset update register 48 to be transmitted through the pattern input register 54 to the pattern memory 40 if there is to be updating due to a change for the same spot in the next line. Whenever the update counter 49 goes to zero as detected by the zero detector 55, new data is supplied to the exposure update register 47 and/or the offset update register 48 and the update counter 49 from either the pattern input buffer 44 or the subroutine memory 43. This is determined by whether the subroutine latch 50 is activated or not. If the subroutine latch 50 is activated, then the information comes from the subroutine memory 43 through the subroutine output register 58. Otherwise, the information comes from the pattern input buffer 44. At the completion of beam scan in each direction, access is had to the pattern address register 68 during retrace through the gate 72 to select the correct address for the start of the next scan, and the gate 69 or 70 is opened at the end of the retrace. Then, the pattern memory 40 is addressed in the opposite direction from that to which it was addressed in the prior scan. As the beam 11 is stepped to each of the predetermined positions, the amount of exposure, if any, of the beam 11 is obtained from the pattern memory 40 as is any offset of the beam 11. In this manner, the resist is exposed by the beam 11 to produce the desired pattern in the chip. It should be understood that the form of the update commands, which comprise the information transmitted from the computer 19 to the pattern input decoder 45, must be chosen both to enhance the speed of decode by the pattern input decoder 45 and to minimize the volume of data necesssary to produce all sequences of updates. At the same time, the update commands must conform to the width of the data path through the channel 41 of the computer 19. Any suitable form of update commands may be employed as long as the foregoing requirements for transmitting the information from the computer 19 to the pattern input decoder 45 are met. However, the preferred update commands are one byte (eight bits) of data, two bytes (sixteen bits) of data, or three bytes (twenty-four bits) of data depending on the amount of information required to be transmitted with there being three different groups of two bytes of data and one group of each of the one byte and three bytes of data. When using the preferred update commands, the update counter 49 is twelve bits wide and has a range of 1 to 4080. However, the update counter 49 is normally restricted to a value no greater than X.sub.w. The update counter 49 is divided into four low-order bits and eight high-order bits with the four low-order bits giving a range of 1 to 15 spots or predetermined positions of the beam 11 and the eight high-order bits giving a range of 16 to 4080 spots or predetermined positions of the beam 11 in steps of sixteen. Thus, the update counter 49 receives either four bits or eight bits depending on the number of predetermined positions or spots of the beam 11 to which the update counter 49 is to be updated by the update command. It should be understood that intermediate update counts between 17 and 4095, not in steps of sixteen, must be obtained with two update commands. With the group of update commands having a width of one byte of data, there are four possible states, represented by the first four bits of the byte of data, to which the exposure update register 47 is set. These consist of no change in exposure of the beam 11, change exposure of the beam 11 to off, change exposure of the beam 11 to on, or change exposure of the beam 11 to a portion of the time period at which the beam 11 is disposed at the predetermined position. The last four bits of this update command of one byte width is a four-bit count for the four low-order bits of the update counter 49. It should be understood that the offset update register 48 is set to zero so that there is no change. Thus, the form of each of these update commands is aaaa nnnn where aaaa specifies the bit configuration to be inserted in the exposure update register 47 and nnnn is the four-bit count to be inserted in the update counter 49. A second group of update commands has a width of two bytes of data. This group of update commands sets the exposure update register 47 at one of its four possible states, places a four bit count in the four low-order bits of the update counter 49, and sets the offset update register 48 with the second byte (last eight bits) of the update command. The data supplied to the offset update register 48 can cause offset of the beam 11 in the X direction, the Y direction, or both. Thus, the form of these update commands is aaaa nnnnn bbbbbbbb where aaaa specifies the bit configuration to be inserted in the exposure update register 47, nnnn is the four-bit count to be placed in the update counter 49, and bbbbbbbb are the data to be placed in the offset update register 48. Another group of update commands also has a width of two bytes of data. However, these update commands do not supply any information to the offset update register 48 as the register 48 is set to zero. Instead, the first four bits of these update commands indicate that the update count is to be placed in the update counter 49 in the eight high-order bits. The next 4 bits set the exposure update register 47 to one of its four possible states, and the last 8 bits are supplied to the update counter 49. The form of these update commands in cccc aaaa nnnnnnnn where cccc is the signal that the update counter 49 is to receive an 8-bit count, aaaa specifies the bit configuration to be inserted in the exposure update register 47, and nnnnnnnn is the eight-bit count to be inserted in the eight high-order bits of the update counter 49. Another group of update commands has a width of three bytes of data. These update commands have the first 4 bits to indicate that the update counter 49 is to have eight bits inserted in its eight high-order bits with the next four bits setting the exposure update register 47 to one of its four possible states. The next eight bits (second byte) are placed in the update counter 49 to indicate the period of time that the offset update register 48, which is set by the last 8 bits, provides the same offset information. Thus, the form of each of the update commands of this group is cccc aaaa nnnnnnnn bbbbbbbb where cccc is the signal that the update counter 49 is to receive an eight-bit count, aaaa specifies the bit configuration to be inserted in the exposure update register 47, nnnnnnnn is the eight-bit count to be inserted in the eight high-order bits of the update counter 49, and bbbbbbbb are the date to be placed in the offset update register 48. Another group of update commands also is employed with each of these having a width of two bytes. One of these update commands uses the first four bits to specify that the subroutine latch 50 is to be set and the last twelve bits to be inserted into the subroutine address register 57 to select a word of the subroutine memory 43. The form of this update command is dddd eeee eeeeeeee where dddd specifies that the subroutine latch 50 is to be set and eeee eeeeeeee is the address selected in the subroutine address register 57. The other of the update commands of this group uses the first four bits to specify that end-of-line check is to be performed with the next four bits being compared to the four low-order bits of the Y counter during retrace and indicating an error if there is a mismatch through the error detector 63 while the last eight bits are exclusive-OR'd with the contents of the longitudinal redundancy check register 74 and the result inverted. The form of this update command is ffff gggg hhhhhhhh where ffff specifies the end-of-line check is to be performed, gggg is to be compared to the four low-order bits of the Y counter during retrace, and hhhhhhhh is the 8 bit data word to be exclusive-OR'd with the contents of the longitudinal redundancy check register 74. While the present invention has described the beam 11 as being utilized to expose resist on a semiconductor chip, it should be understood that control of the charged particles could be employed for other than exposing the resist on the chip of the semiconductor. In addition to the other examples set forth in the aforesaid Kruppa et al patent, the beam also could be used for ion implantation, for example. Thus, the control of the beam 11 could determine where the ions were implanted without requiring a mask, for example. While the beam 11 has been shown and described as a movable means controlled by the method and apparatus of the present invention, it should be understood that the method and apparatus of the present invention may be employed to control any other means movable in a line by line pattern to each of a plurality of predetermined positions along each of the lines. Thus, the present invention has utility whenever it is desired to take advantage of the correlation of at least one function of a movable means between corresponding positions of adjacent lines. An advantage of this invention is that faster pattern writing by an electron beam is obtained. Another advantage of this inventon is that there is an error check during both read and write for each line and an error check at the end of each line. A further advantage of this invention is that it enables data to be transferred to the memory at times at a faster rate than the data is received by a surge buffer from which the information is transmitted. Still another advantage of this invention is that faster processing of chip patterns is produced. A still further advantage of this invention is that it reduces the data rate volume by at least one order of magnitude from that required without encoding. Yet another advantage of this invention is that it eliminates the peak data rate problem. While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. |
summary | ||
042971691 | claims | 1. For use in a nuclear reactor, an oxide composition nuclear fuel material in compacted pellet form containing at least one fissionable isotope and an amount of a chemical displacement compound selected from the group consisting of CuFe.sub.2 O.sub.4 and CuTiO.sub.3 and mixtures thereof effective to immobilize cadmium resulting from nuclear fission chain reactions of the nuclear fuel material through a reaction between the said cadmium and the said chemical displacement compound and thereby prevent cadmium embrittlement of nuclear fuel cladding at reactor operating temperatures. 2. The composition of claim 1 in which the nuclear fuel material comprises compounds selected from the group consisting of uranium oxide compounds, plutonium oxide compounds, thorium oxide compounds and mixtures thereof. 3. The composition of claim 1 in which the nuclear material comprises uranium oxide compounds. 4. The composition of claim 1 in which the immobilizing additive is CuFe.sub.2 O.sub.4. 5. The composition of claim 1 in which the immobilizing additive is CuTiO.sub.3. 6. The composition of claim 1 in which the chemical displacement compound additive is CuTiO.sub.3 in an amount between about 0.0025 and 0.025 weight percent on the basis of the nuclear fuel material. 7. The composition of claim 1 in which the chemical displacement compound is CuFe.sub.2 O.sub.4 in an amount between about 0.0033 weight percent and 0.033 weight percent on the basis of the nuclear fuel material. 8. The composition of claim 1 in which the chemical displacement compound additive is present in an amount approximately 0.01 weight percent on the basis of the nuclear fuel material. 9. The method of immobilizing fission product cadmium generated in nuclear fuel material of oxide composition in pellet form containing at least one fissionable isotope which comprises the step of providing in contact with the nuclear fuel material an amount of a chemical displacement compound selected from the group consisting of CuFe.sub.2 O.sub.4 and CuTiO.sub.3 and mixtures thereof effective to immobilize the cadmium generated in the nuclear fission chain reaction of the nuclear fuel material through a reaction between the said cadmium and the said chemical displacement compound and thereby prevent cadmium embrittlement of nuclear fuel cladding at reactor operating temperatures. 10. The method of claim 9 in which the chemical displacement compound additive is mixed with and distributed through the nuclear fuel material. 11. The method of claim 9 in which the chemical displacement compound additive is disposed in contact with the pellet of nuclear fuel material. |
044709528 | claims | 1. A floating nuclear reactor decontamination apparatus for use in a cylindrical nuclear reactor vessel containing water at a level which decreases during shutdown periods, said apparatus for decontaminating an interior cylindrical wall of such vessel as it is exposed by the decreasing water level comprising (a) a buoyant annular frame floatable on the water and hence capable of descending with the decreasing water level, (b) a plurality of trolleys movable cylically in a reciprocating manner back and forth around the circumference of the annular frame, (c) a plurality of water nozzle means on the respective trolleys for directing high-pressure water sprays outwardly against the vessel wall as the annular frame descends, (d) said nozzle means being disposed radially outwardly around said annular frame and their respective trolleys being movable with respect to one another in a manner such that reaction forces on said frame from water sprayed from the nozzles are substantially cancelled. 2. Apparatus according to claim 1 wherein said trolleys move around said frame in opposed pairs such that each of said nozzle means is paired with another facing radially outwardly in the opposite direction on the opposite side of the frame so as to substantially cancel the reaction forces of the sprays on the frame. 3. Apparatus according to claim 1 which includes guide means for preventing the annular frame from rotating within the cylindrical vessel. 4. Apparatus according to claim 1 which includes means connected to the frame for retrieving the apparatus from within the vessel. 5. Apparatus according to claim 1 which includes reversible air motor means mounted on the frame and coupled to said trolleys for automatically moving the trolleys cyclically back and forth around the circumference of the frame. |
abstract | The process of the present application facilitates the production of electric energy by the excitation and capture of electrons from atoms, molecules and ions from ground or water sources, or any other form of matter that can be passed along the surface or through the electron extraction assembly. The electrons are captured, collected, isolated and controlled for distribution as electric energy. It is an energy efficient process for the capture of electrons and for the production of electric energy. These results are accomplished by the excitation and capture of electrons from the object particles by electrically charged components in an electric field. It can operate continuously without interruption. Through the subject process, electric energy can be supplied individually to each structure, community or demand location allowing independence from any other energy source. It can be scaled to accommodate the electric energy requirements of many implementations and utilizations that extend from the national power grid to portable units and units fitted to stationary or portable appliances, devices, apparatus and vehicles. |
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description | This application claims the benefit of U.S. Provisional Application No. 61/041,344, filed Apr. 1, 2008 and entitled METHOD AND APPARATUS FOR OBTAINING IMAGES BY RASTER SCANNING E-BEAM OVER PATTERNED WAFER ON A CONTINUE MODE STAGE, the entire contents of which are incorporated herein by reference. 1. Field of the Invention The present invention relates generally to an apparatus and method to obtain an image of a patterned substrate, and more particularly to an apparatus and method to raster scan a charged-particle beam over a patterned substrate on a continuously moving stage. 2. Description of Related Art The traditional charged-particle beam imaging system, such as a Scanning Electron Microscope (SEM), generates images by raster scanning a primary charged-particle beam such as an electron beam (e-beam) over a sample held on a stationary stage. Referring to the drawings, FIG. 1 illustrates a charged-particle beam microscope 100 according to the prior art. A primary charged-particle beam is generated from a charged-particle beam source 110 which may be, such as an electron beam gun. The primary charged-particle beam is condensed by a condenser lens module 120 and focused by an objective lens module 130 to form a charged-particle beam probe 140. A deflection unit 150 scans the charged-particle beam probe 140 in lines across the surface of a sample 195 on a sample stage 190. It is noted that the one dimensional line scan call be converted to a two dimensional raster by offsetting the beam center, or by moving the stage 190 properly in an orientation perpendicular to the line-scan direction. After the bombardment of the charged-particle beam probe 140 on the sample 195, secondary charged particles 160, such as secondary electrons, are emitted from the sample 195 and, along with the backscattered charged particles, such as backscattered electrons, are collected by a charged-particle detector 170. Since the amount of secondary charged particles is modulated by surface topography or voltage of the scanned area, a two dimensional image representing the topography contrast or voltage contrast is obtained. The sample 195 may be a patterned substrate such as a wafer, a lithography mask or a semiconductor device and so on, or any combination thereof. FIG. 2(a) illustrates a raster-scan operation in accordance with traditional prior-art principles. As shown, the raster scanning is performed by repeating line scans N times with each line advancing in a direction perpendicular to the line-scan direction. FIG. 2(b) illustrates the formation of an image of a raster-scanned substrate in accordance with the traditional art. Secondary and/or backscattered electrons are collected by a detector or detectors. Detector output signal is sampled at even timing intervals during the line scan, yielding a line matrix 201 of M pixels. Combining line pixel matrixes for all line scans forms a 2-dimensional pixel matrix 202, called a frame, wherein a frame represents the image of the raster-scanned area of the substrate being imaged. It is noted that the size of an image is referenced as a Field of View, or FOV, hereinafter. In an actual raster scan, after reaching the last pixel of a line, the primary charged-particle beam traverses back to the starting point of the next line. The extra time required/spent for this fly-back is called line overhead. For simplicity of explanation, a line scan is represented only by the effective line scan in the following figures, but the line scan time or line scan repetition period actually (e.g., preferably) will be measured from the beginning of one line scan to the beginning of the next line scan within one frame, which by default includes the fly-back time or overhead time. Fly back time also exists in repeating frames. Frame time or raster-scan repetition period is measured from the beginning of one frame to the beginning of a next repeating frame, which by default includes the fly-back time or overhead time. In order to improve the quality of the image, two types of image averaging methods, Line Averaging and Frame Averaging, are often employed. Line Averaging is performed by repeating the line scan multiple times at the same position before advancing to the next line, thereby acquiring P matrixes of pixels for each image line. Averaging the line matrixes, pixel by pixel, yields an averaged line matrix. Combining all averaged line matrixes forms a line-averaged image of 2-dimensional pixel arrays. Frame Averaging is performed by repeating the identical raster scan a designated number of times, S, with the stage held at a stationary position. This process generates S sets of 2-dimensional pixel matrixes. Averaging these matrixes, pixel by pixel, forms a single image of 2-dimensional pixel matrix, which is a frame-averaged image. Frame averaging can be applied to line-averaged frames. A charged-particle beam inspection system based on scanning electron microscope (EB Inspector) typically acquires inspection images in either of two image acquisition modes, one known as “Step-and-Repeat” mode and the other known as “Continuous-Scan” mode. For an inspection to be performed, a user specifies the certain areas on the pattern of the substrate (i.e., wafer or mask) to be scan-imaged. These areas are called Areas of Interest (AOI). The EB inspector acquires electron beam images covering an AOI and processes the images to identify abnormalities of the patterns or alien objects on the pattern. In Step-and-Repeat mode, a series of images is acquired in a sequential manner. FIG. 3 illustrates Step-and-Repeat mode imaging covering an AOI on a substrate in accordance with the traditional art. Taking each image 301, the stage whereupon the substrate is secured for imaging is moved along a stage stepping direction so that the center of the imaging area of the pattern is brought to the center of electron optical axis (a small error or offset is usually tolerable and managed by the system). As a result, the imaging action of interested areas is stepped as required, for example, as illustrated by arrow 302. When the movement is settled, such that, for example, the stage is at/in a stationary position, the charged-particle beam is raster-scanned over the imaging area. A 2-dimensional array of pixel data representing the image of the scanned area thus can be obtained. The stage then steps forward to the next stationary position. This type of process is repeated until a desired AOI 303 is covered. The image averaging methods, Line Averaging and Frame averaging, are often employed to improve the image quality to achieve the required inspection sensitivity. Throughput of the inspection available for the system operating in Step-and-Repeat mode is largely limited by the image FOV and stage stepping time. Image FOV determines the total number of stage steps required for covering a given AOI, while stage stepping time depends mainly on the stepping distance and tolerable position error. Stage stepping time is purely an overhead time and generally falls into the range between 0.1 to 0.5 seconds. It is important to reduce the number of steps and stage stepping time. A relatively recent EB Inspector, which operates in Step-and-Repeat as the default image acquisition mode, addressed this throughput issue by introducing an electron optics design to achieve Large Field of View (LFOV). FIG. 4(a) illustrates a Step-and-Repeat mode using LFOV to improve the throughput in accordance with the traditional art. If the LFOV is L times larger than a normal FOV, the number of stage steps required to cover the given AOI will be reduced by a factor of L2. As shown, with other settings kept the same as in FIG. 3, image 401 is acquired using an FOV three times larger in size than that used for image 301. That is, if image 301 is of a size of single FOV, then image 401 is of a size of 3 FOV. The imaging action again steps as required, as illustrated by arrow 402. As a result, it can be seen in FIG. 4(a) that, by using LFOV image 401, only three stage steps are required to cover the same AOI 303. As compared to the greater number of stage steps needed in FIG. 3 using LOV image 301, the throughput of the embodiment of FIG. 4(a) would appear to offer improvement. In practice, a LFOV is divided into multiple sub-FOV fields for beneficial low noise and high speed raster scanning. While each sub-field is imaged with traditional raster scanning, a relatively low frequency step signal, which is synchronized with sub-field frame rate, is superimposed onto the raster-scan signal for positioning or stitching each sub-field sequentially. FIG. 4(b) illustrates a Step-and-Repeat mode raster-scan imaging operation using a LFOV with multiple sub-fields in accordance with the traditional art. As shown, LFOV image 403 includes four sub-FOV fields 404 captured with one stage move. The imaging action steps again as illustrated by arrow 402. It is noted that usually the fly-back time of the charged-particle beam, such as an electron beam, between each sub-field raster scan is negligible. It is also noted that the number of sub-fields does not change the number of stage steps. The number of stage moves depends mainly on the size of LFOV. For the implementation of a LFOV 12 times larger than a normal FOV, the number of stage steps in optimal cases can be reduced by a factor of 144. However, as endless demand for higher throughput in EB inspector applications pushes toward higher pixel rates, with image raster time getting shorter and shorter, stage stepping time still remains as the top throughput-limiting factor in Step-and-Repeat mode imaging. It may be noted that in FIG. 4(b) the width of the sub-FOV 404 is much smaller than its height. Line Scan is required to be driven by high speed (i.e., high bandwidth) electronic/electric circuitry, where enlarging the dynamic to extend the line length is limited by the requirement to maintain noise level to a required specification. Also, the beam scan optical scheme needs to be constructed in a simpler fashion, where the scan range is limited to keep the beam under tolerable blur. Moving the line scan to the next line can require much slower electronics, which may allow a designer to construct much larger dynamic ranges, staying in the noise tolerance. The slower operation may also allow a designer to choose a more sophisticated beam deflection scheme(s), which can allow the nominal beam path to be minimally impacted relative to the beam property when the line scan is moved gradually from the top to the bottom of the sub-FOV by a large distance. FIG. 5 illustrates Continuous-Scan mode imaging in accordance with the traditional art. Unlike Step-and-Repeat mode, which relies on raster scanning to achieve both line scan and line-to-line stepping to cover a full frame of image, as shown, in Continuous-Scan mode the stage moves at a constant speed. More particularly, the stage moves at a constant speed along a stage-moving direction 502 while an e-beam repeatedly line scans at a fixed offset from optical axis in a line-scan direction 501 usually perpendicular to the stage-moving direction 502. The stage continuously moves for the imaging action to be continuously performed, as illustrated by arrow 503, until a desired quantity (e.g., length) of image is acquired. This can form a relatively long image/frame. It is noted that in Continuous-Scan mode the sample is scanned at an equal pitch of the stage speed multiplied by the line scan period. FIG. 6(a) illustrates an AOI being imaged in Continuous-Scan mode in accordance with the traditional art. As shown, a large AOI 601 can be covered by multiple long images formed by raster scanning in Continuous-Scan mode. It may be noted that the stage-moving direction alternates though the neighboring images, as shown by the curved arrows 602, known as a serpentine stage scan, to minimize stage-moving time between each image scan. The time period of such alternating stage movement is known as the stage turnaround time. Continuous-Scan mode provides much higher throughput compared with Step-and-Repeat mode for a large AOI, because stage stepping times required in Step-and-Repeat mode can be significantly reduced. The number of stage turnarounds is only a function of the AOI height divided by the line scan width, thus the stage-scan direction is generally chosen to be parallel to the long side of the AOI rectangles. The line scan width, that is, the height of the inspection image in Continuous-Scan mode, is limited by two factors: (1) image FOV of electron optic design; (2) high speed scan requirement and tolerable scan/detection noise. For inspection of a small AOI which is relatively narrow in width, for example along the stage-moving direction, the inspector has to stack up a number of inspection images to cover the height of the AOI, accumulating stage turnaround actions while the actual imaging time per image is small due to the limited width of the small AOI. Stage turnaround time is usually larger than the stage stepping time by approximately a factor of 0.7 to 2.0. FIG. 6(b) illustrates imaging of a small AOI in Continuous-Scan mode and in Step-and-Repeat mode using LFOV in accordance with the traditional art. As shown, assuming AOI 603 has a height of 24K, if the height of the Continuous-Scan mode image is 2K pixels, 8 stage turnaround actions are required to cover AOI 603. On the other hand, with the use of LFOV and a size of 12K pixels, only 3 stage steps are required for the Step-and-Repeat mode operation. Therefore, the Step-and-Repeat mode with LFOV benefits the imaging of small AOI, as the number of stage steps can be less than the number of stage turnarounds in Continuous-Scan mode. For scattered smaller AOIs or arrays of small AOIs within a die, Continuous-Scan mode wastes more time either on the non-AOI region with the stage moving at the constant speed of imaging, or with the stage frequently skipping the non-AOI region at a higher speed but then taking extra time to settle back to the constant speed of imaging before entering an AOI. In such cases, the original throughput advantage of Continuous-Scan mode over Step-and-Repeat mode often diminishes steeply and may even become worse than Step-and-Repeat mode. FIG. 7(a) and FIG. 7(b) respectively illustrate the imaging of scattered small AOIs 701 in Continuous-Scan mode and in Step-and-Repeat mode using LFOV in accordance with the traditional art. As shown, again with the use of LFOV, Step-and-Repeat mode benefits the imaging of small AOIs 701, as the number of stage steps (3×3=9) can be less than the number of stage turnarounds in Continuous-Scan mode (6+6+3=15). Accordingly, what is needed is a system and method that overcomes the above identified issues. The present invention addresses such a need. The present invention provides EB inspectors with a method to acquire images of pixel arrays by moving the wafer stage at a constant speed and scanning the electron beam in a raster-scan fashion (e.g., 2-dimensional scan). The proposed method removes stage-stepping overhead time between frames of images required in traditional raster-scan operation in Step-and-Repeat mode. In addition, the number of stage turnarounds can be reduced due to the enlarged FOV. In some embodiments of the present invention, the proposed method also provides flexible ways to efficiently acquire images over small AOIs (e.g., relatively narrow in width along the stage-moving direction) evenly or randomly distributed along the stage-moving direction, where the conventional Continuous-Scan mode imaging suffers throughput lost. In other embodiments of the present invention, the proposed method also allows line-scan to be performed in the stage-moving direction which is not possible in conventional continuous-scan imaging. The present invention relates generally to an apparatus and method to obtain an image of a sample. The sample can be a patterned substrate such as a wafer or lithography mask, but will be referred to as “sample” hereinafter for simplicity. The following description is presented in the form of exemplary embodiments to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment(s) and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and features described herein. A tradition raster-scan signal is generally configured to image a frame of square area, that is, where line scan width equals frame height. All of the embodiments herein and related figures are not intended to be restricted to such, and can be extended, for example, to other rectangles or parallelograms with one side shorter or longer than the adjacent ones. As mentioned earlier, the present invention generally discloses a method and apparatus for raster scanning over a sample secured on a continuously moving stage. The stage may be moved at a constant speed, that is, at a fixed speed and direction, or simply along a fixed direction. The raster scans form scan lines on the surface of the sample. A number of adjacent scan lines produced by raster scanning forms a 2-dimensional line array which may be used to form a frame (of image data of the sample(s)). For convenience of explanation, formation of one such line array will be considered completion of one raster scan hereinafter. In one embodiment of the present invention, a method for raster scanning a sample on a stage continuously moving along the line-scan direction is disclosed. FIG. 8 illustrates operation of a raster-scanning method in accordance with an embodiment of the present invention. In FIG. 8(a), the charged-particle beam is raster scanned over a sample which is held at/in a stationary position. In such case, a square or rectangle image area is scan-imaged, and an image 801 is acquired accordingly as from the view of a stationary coordinate system which will be referred to as the “system coordinate” hereinafter. The system coordinate is always a stationary coordinate. On the other hand, a corresponding “moving coordinate” which will also be used frequently in this specification is the sample coordinate when the stage is moving. The coordinate being sampled thus is a moving coordinate when the stage is moving and is a stationary (system) coordinate when the stage is stopped. In FIG. 8(b), the sample on the stage is moving along a direction 803 pointing to the left, opposite to the line-scan direction 802. In such a case, as shown, the beam will scan over a skewed parallelogram (e.g., rectangle) area on the sample and an image 804 will be acquired accordingly again as viewed in the moving sample coordinate. It is noted that the “positions” of the formed first scan lines in respective images 801 and 804 are the same. Therefore, for convenience of explanation for the following examples, the origin of the stationary coordinate system is set to be at the starting point of the first scan line as a reference. In FIG. 8(c), to correct the skewed scan area resulting from the moving stage, a compensation offset is employed. It is noted that FIG. 8(c) corresponds to operation of a raster scan with compensation offset viewed in the system (stationary) coordinate. As shown, each time the line scan advances to the next line, the scanning beam (thus the starting point of the next scan line to be formed) is shifted by an accumulative fixed distance ofd=StageSpeed×LineScanPeriod In short, the distance d is substantially equal to the stage travel/motion during one line scan, as shown in FIG. 8(b). In other words, to compensate the skewed angle that would result in the formed frame of image due to the stage motion, raster scan can be performed in a skewed manner by offsetting the starting point of each line scan electrically to trace the stage movement, as shown in FIG. 8(c). It is noted that the line scan period refers to the time period of formation of a physical scan line. This scan line has a width which will be referred to as the line scan width hereinafter. The physical scan line does not necessarily need to be the effective scan line from which the image signals are collected and used to form the image. The effective scan line width may be shorter than the physical scan line width. Having said this, as will be understood by those skilled in the art, the frame of image can be formed from the effective scan line rather than the physical scan line. Therefore, the length of a formed frame, which will be referred to as the frame length or the length of frame hereinafter, can be longer or shorter than the (physical) scan line width. Furthermore, in the embodiment(s), as the line scan is performed along a direction parallel to the stage-moving direction, the scan line width, effective scan line width and length of frame all are measured along the stage-moving direction. In FIG. 8(d), a corrected image viewed in the moving sample coordinate is illustrated. As shown, if the offset exactly matches stage movement, an image 805 with corrected vertical edge can be obtained. It is noted that since the stage is continuously moving during line scanning, the effective line scan width will expand if the stage moves in the opposite direction to the line scan, or shrink if the stage moves in the same direction as the line scan, on the sample by an amount dL as shown in FIG. 8(b):dL=StageSpeed×EffectiveLineScanTime, in which EffectiveLineScanTime is the effective line scan time or, in other words, the time period of formation of the effective scan line. The effective line scan time is generally a specified portion of the entire line scan repetition period. The line scan width is dependent upon the strength of the line scan signal. Therefore, the line scan width, that is, the line scan signal strength, is adjusted to compensate dL so that scan width on the sample is matched to the intended line scan width, as shown in FIGS. 8(e) and 8(f). As a result, an image 806 with corrected scan-area width can be obtained. In one embodiment, a method for performing Line Averaging in the proposed raster-scan operation is disclosed. FIG. 9 illustrates a method of performing Line Averaging in accordance with an embodiment of the present invention. Line Averaging can be performed by applying an accumulative offset, d, as that shown in FIGS. 8(b) and 8(c), at every single line scan in the sequence order at a fixed position in a line-to-line offset direction 902 of the raster scans. It is noted that the offset d can be accumulative with reference to, for example, the beginning of the first line scan of the current image whether it is being frame-averaged or not. In other words, the accumulative offset can be seen as a distance that the stage traveled since the beginning of the first line scan through the beginning of the current line scan (to be performed) of the image being formed. It is also noted that at the same time Frame Averaging may be performed to this concerned image as well, which case will be described in further detail later in conjunction with FIG. 10. It is also noted that the line-to-line offset direction 902 is typically perpendicular to the line-scan direction 901. For convenience of explanation, this fact will be kept true in all the embodiments of the present invention. For example, taking x as the line-scan direction and y as the line-to-line offset direction, the Line Averaging can be carried out by repeating line scans along the x direction at a fixed y position. Next, the line matrixes obtained from the repeated line scans are averaged, pixel by pixel, in the same way as described with reference to the prior art. An averaged line pixel matrix is thereby obtained. In FIG. 9(a), an image 910 without being Line Averaged is illustrated. In FIGS. 9(b) and 9(c), images 920 and 930 which are 2-fold and 3-fold Line Averaged, respectively, are illustrated. It is noted that in FIG. 9 the solid lines and arrows represent the original scan line formed first, while the gray broken lines and arrows represent the repeat scan lines formed later for delivering the effect of Line Averaging. It is also noted that the left-hand side portion of FIG. 9 is viewed from the system (stationary) coordinate, while the right-hand side portion of FIG. 9 is viewed from the sample (moving) coordinate. In one embodiment, a method for performing Frame Averaging in the proposed raster-scan operation is disclosed. FIG. 10 illustrates a method of performing Frame Averaging in accordance with an embodiment of the present invention. As shown, Frame Averaging can be performed by repeating the same raster-scan frame at the same position on the moving sample, which is realized by applying an accumulative offset of dF to the successive raster scans. It is noted that the offset dF can be accumulative with reference to, for example, the beginning of the first line scan of the first raster scan of this image being Frame Averaged. The offset dF thus can be represented as:dF=StageSpeed×RasterScanRepetitionPeriod. It is noted that, as mentioned earlier, the accumulative offset is a distance that the stage has traveled since the beginning of the first line scan of the first raster scan of the image being Frame Averaged, through the beginning of the current line scan to be performed of the current raster scan of the image being Frame Averaged. Next, the obtained frame images are averaged pixel by pixel to form an averaged frame image. In detail, with reference to FIG. 10(a), the sample is at/in a stationary position. Raster scan is simply repeated at the same position on the sample for Frame 1 (solid lines and arrows) and Frame 2 (gray broken lines and arrows), and corresponding pixels are averaged to represent the pixels in the averaged image 1001 on the right. In FIG. 10(b), the sample is moving at a constant velocity along a direction 1100 pointing to the left. Raster scan for Frame 2 (gray broken lines and arrows) is performed following raster scan for Frame 1 (solid lines and arrows), with (accumulative) position offset dF to compensate the stage movement. As a result, corresponding line scans between Frame 1 and Frame 2 overlay in the sample (moving) coordinate. Corresponding pixels are averaged to represent the pixels on the averaged image 1002 on the right. In one embodiment, a method for acquiring multiple successive frames on the moving sample is disclosed. Repeating the raster scans with accumulative line scan offset produces a series of rectangular images of the sample surface being equally spaced. It is noted that the line scan offset is reset between frames of images. Each time when a frame image is completed, the charged-particle beam is directed to the beginning position of the first line scan of the next frame image to be formed, and the line scan offset starts to accumulate again for the line scans within this next image to be formed, starting from the beginning of the first line scan thereof. FIG. 11 illustrates an image acquisition method in different modes in accordance with an embodiment of the present invention. Before going into the details of FIG. 11, a physical quantity, referred to as the image width, is defined. When raster scanning a sample, a frame image having a shape of a parallelogram is typically formed in the form of a 2-dimensional line array composed of a plurality of scan lines lying adjacent to each other. This parallelogram, which includes square and rectangle shapes as the most common cases, has two parallel-edge pairs. At least one of the two parallel-edge pairs, or its extension lines, would intersect with the axis of the stage movement. The image width in the embodiments of the present invention refers to the distance, along the axis of stage movement, between the two intersection points of the parallel edges (or their extension lines) with the axis of stage movement. This definition holds true for all embodiments of the present invention, regardless of the shape of the formed frame image. With the image width defined, a series of images can be acquired in different ways using the image width as an operational factor. As shown, depending on the stage speed, the series of the images acquired is/are: (a) Partially overlapped if StageSpeed<ImageWidth/RasterScanRepetitionPeriod, (b) Stitched if StageSpeed=ImageWidth/RasterScanRepetitionPeriod, and (c) Gapped by a space if StageSpeed>ImageWidth/RasterScanRepetitionPeriod. It is noted that in this embodiment, the image width is substantially the length of the effective scan lines, as shown in FIG. 11. This embodiment can also provide a way to evenly sample fractions of image areas (e.g., evenly sampling imaging fraction of areas) inside a large area of interest (AOI). For instance, if the separation is equivalent to the width of a frame image, a sampling ratio of 50% can be employed. In FIG. 11(a), a series of partially overlapped frame images 1110 along the stage-moving direction 1101 is acquired. In this case, the stage speed is set to be smaller than ImageWidth/RasterScanRepetitionPeriod. In practice, a certain amount of overlap is necessary when capturing a series of frame images to compensate for possible position error, or to get more marginal areas which may later be sacrificed in image processing, such as image alignment. If the overlap ratio is not less than ½ and can be expressed as (2N−1)/2N, (N=1, 2, 3, . . . successive images of N frame average will be produced. For instance, an overlap ratio of ½ corresponds to 2-frame averaging; an overlap ratio of ¾ corresponds to a 4-frame averaged image being obtained. It is noted that a certain fraction of 1st and last frames in one successive acquisition are not fully overlapped with the same amount of frames and should be sacrificed. It is also noted that the embodiment of frame averaging here is different from the embodiment shown in FIG. 10, as in FIG. 10 the image is averaged by frames of a full size image, while in FIG. 11 the image is averaged by fractional images. In FIG. 11(b), a series of frame images 1120 connected (with each other) along the stage-moving direction is acquired. This is also illustrated in FIG. 12 in more detail. In this case, the stage speed is set to be substantially equal to ImageWidth/RasterScanRepetitionPeriod. FIG. 12 illustrates acquisition of stitched images in accordance with an embodiment of the present invention, wherein the acquired image 1120 viewed in the system (stationary) coordinate is illustrated on the left and the same image viewed in the sample (moving) coordinate is illustrated on the right as 1201. As shown in FIG. 12, this case is similar to the FIG. 4 traditional Step-and-Repeat mode, with a difference being that no stage-stepping overhead is incurred during imaging along the stage-moving direction, whereby the throughput is improved. On the other hand, when compared with traditional Continuous-Scan mode imaging as shown in FIG. 5, the advantage of the embodiment in FIG. 12 is its flexible frame length control whereby, first, the height of the frame image can be made larger than that in the traditional Continuous-Scan mode, which is substantially equal to the line-scan width. As a result, an imaging task of AOIs of a height greater than the line-scan width will benefit from this embodiment, as a smaller number/amount of stage turnaround action(s) is needed to cover a given AOI. Moreover, the height of frame image can also be made shorter than the line-scan width as in the traditional Continuous-Scan mode. An imaging task of AOIs with a height smaller than line-scan width will benefit from this case as the number of line-scans in a frame image is reduced and/when the stage can be moved at a faster speed. In FIG. 11(c), a series of frame images 1130 equally spaced along the stage-moving direction 1101 is acquired. This is also illustrated in FIG. 13 in more detail. In this case, the stage speed is set to be greater than ImageWidth/RasterScanRepetitionPeriod. FIG. 13 illustrates acquisition of spaced images in accordance with an embodiment of the present invention, wherein the acquired image 1130 viewed in the system (stationary) coordinate is illustrated on the left and the same image viewed in the sample (moving) coordinate is illustrated on the right as 1301. Every frame of image 1301 is evenly spaced with this embodiment. One particular application for this embodiment is the imaging of narrowly and equally spaced arrays of AOIs 1310. In such case, the narrow side of AOI 1310 can be covered by one line-scan and the space between adjacent AOIs 1310 is less than the maximum length of a frame 1301. The length of each frame 1301 and the space between successive frames 1301 are controlled by stage speed, number of line scans per frame and step size of line scan. It is noted that in FIG. 13, the individual AOI 1310 in the AOI arrays do not need to be equally spaced if the charged-particle beam inspection system based on scanning electron microscope (EB inspector) is configured such that (1) raster frame can be triggered, (2) raster-frame trigger timing is programmed in a sequencer, referencing the stage position in the sequencer, and (3) each raster scan in the sequence accepts scan offset, which is programmed in the sequencer. So far the embodiments of the present invention have been disclosed in the context of providing a raster-scan method where the line-scan direction is parallel to the stage-moving direction. In other embodiment, alternative relationships of the line-scan direction with the stage-moving direction are also possible. FIG. 14 illustrates a raster scan over a sample on a stage moving at constant speed, and whose direction is perpendicular to the line-scan direction, in accordance with an embodiment of the present invention. In FIG. 14, the stage-moving direction is horizontal as illustrated by the left-pointing arrow 1402, and the line-scan direction is vertical as illustrated by upwardly-directed arrow 1401. The upper portion of FIG. 14 illustrates the traditional Continuous-Scan mode. The arrow 1403 on the left represents the repeating line scanning action. The right-hand side drawing 1405 illustrates the acquired image viewed in the sample (moving) coordinate. As shown, in the traditional Continuous-Scan imaging mode the line scan is repeated at an equal pitch of the stage speed multiplied by the line scan period. The lower portion of FIG. 14 illustrates the proposed raster-scan operation according to the current embodiment. The arrow array 1404 on the left represents the raster-scanning action. The right-hand side drawing 1406 illustrates the acquired image viewed in the sample (moving) coordinate. With continuing reference to the embodiment of FIG. 14, raster scan is applied in such a way that the line-scan direction 1401 is kept perpendicular to the stage-moving direction 1402, while the line-to-line advancement is a combined effect of the mechanical movement of the stage and the electrical offset within the raster scans. This embodiment will be identical to the conventional Continuous-Scan imaging of FIG. 5 when the line scan is kept at a fixed position during raster scanning. According to this embodiment, again depending on the stage speed, the series of the images obtained by the proposed raster-scan method can be: (a) Partially overlapped if StageSpeed<RasterScanRepetitionPeriod, wherein if the overlap ratio can be expressed as (2N−1)/2N, (N=1, 2, 3, . . . ), successive images of N frame-averaging will be produced, with, for instance, an overlap ratio of ½ corresponding to a 2-frame averaged image and an overlap ratio of ¾ corresponding to a 4-frame averaged image, (b) Stitched if StageSpeed=ImageWidth/RasterScanRepetitionPeriod, and (c) Gapped by a space if StageSpeed>ImageWidth/RasterScanRepetitionPeriod. In this embodiment, as the scan lines are perpendicular to the stage moving direction, a rectangular image (frame-averaged or not) is formed from the raster scans with two of its edges intersecting the axis of stage movement at a right angle. The image width therefore can be selected to be the distance 1411 between the first and last formed scan lines 1415 and 1416 within one line array formed by the raster scans, as shown in the lower portion of FIG. 14. Again this embodiment can also be a way to evenly sample fractions of areas within a large AOI; for instance, a separation equivalent to the width of a frame image can correspond to a sampling ratio of 50%. One particular application for the embodiment illustrated in FIG. 14 is the raster scanning of narrow AOIs. FIG. 15 illustrates raster-scanning spaced narrow AOIs in accordance with an embodiment of the present invention. As shown in FIG. 15, again as in FIG. 14, the line-scan direction 1401 of the raster scans 1404 is set to be perpendicular to the stage-moving direction 1402. For reference, the bottom region of the FIG. 15 drawing (cf. FIG. 15(b)) illustrates a traditional Continuous-Scan mode in which arrow 1403 on the left represents the repeating line scanning action. In the upper right-hand part of the drawing, reference number designator 1512 elucidates the acquired image viewed in the sample (moving) coordinate, which is intended to cover the narrow AOIs 1501 spaced by non-interest or blank regions (i.e., where no patterns are formed) 1502. As shown, in the traditional Continuous-Scan imaging mode the line scan is repeated at an equal pitch of the stage speed multiplied by the line scan period. As a result, AOI 1501 and non-interest/blank region 1502 are equally scanned and imaged. In such case, part of the tool time is wasted on scanning non-interest/blank regions 1502. FIG. 15(a) illustrates the proposed raster-scan operation of this embodiment. The arrow array 1404 on the left represents the raster-scanning action. The right-hand side drawing 1511 illustrates the acquired image viewed in the sample (moving) coordinate, which is intended to cover the spaced narrow AOIs 1501. As shown, an advantage of this embodiment is that the width of the frame (here, it is the number of line-scans in the concerned frame along the stage-moving direction) on the sample can be made small to fit the narrow AOI 1501. This task is similar to the case shown in FIG. 13 in which a fixed line-scan width is kept during the raster scanning. This may lead to some tool time wasted on each line-scan outside the narrow AOI 1501. In the embodiment of FIG. 15, however, as its line-scan direction is along the longer edge of narrow AOI 1501, a majority of a line scan can be utilized to cover the AOI 1501, resulting in a more efficient use of each line scan action. Therefore, the embodiment of FIG. 15 is suitable for an array of narrow AOIs, such as 1501, which are distributed and/or aligned along the stage-moving direction 1402 and equally spaced at relatively short pitch. The throughput of the inspection, accordingly, can be enhanced. Because of the AOI 1501 relatively narrow dimension along the stage-moving direction 1401, raster scanning for imaging AOI 1501 may easily miss the target due to the real-time stage position error, wafer charging effect, etc. However, the drift of the target position is expected to be slow. Therefore, the system can be configured to monitor the position of the AOIs 1501 within the recent image frames 1511 and apply the scan offset in a real-time fashion to keep the AOI 1501 inside of coming image frames 1511. In this embodiment, again the AOIs 1501 do not need to be equally or narrowly spaced if the EB inspector is configured such that (1) raster frame can be triggered, (2) raster-frame trigger timing is programmed in the sequencer, referencing to the stage position in the sequencer, and (3) each raster scan in the sequence accept scan offset, which is programmed in the sequencer. In another embodiment, the line-scan direction is designed to be oriented at an angle with the stage-moving direction. In other words, the line scan is kept off-angle from the major orientation of the moving stage. FIG. 16 illustrates a raster scan of a moving sample with the line-scan direction off-angle from the stage-moving direction in accordance with an embodiment of the present invention. The left-hand side portion of FIG. 16 illustrates a raster scan performed on the system (stationary) coordinate. The right-hand side portion of FIG. 16 illustrates a raster scan performed on the sample (moving) coordinate. The stage-moving direction is horizontal and pointing to the left, as illustrated by arrow 1602, and the line-scan direction is illustrated by arrow 1601. As shown, the line-scan direction 1601 extends along a direction which intersects the stage-moving direction 1602 at an angle between 0 and 180 degrees but is off from the major system directions, the x and y directions. In other words, the angle between the line-scan direction 1602 and the stage-moving direction 1601 is not 0, 90 or 180 degrees, which means that the formed scan lines are “tilted” from the view point of the axis of stage movement. In this embodiment, again depending on the stage speed, the series of images obtained by the proposed raster-scan method can be (a) Partially overlapped if StageSpeed<ImageWidth/RasterScanRepetitionPeriod, (b) Stitched if StageSpeed=ImageWidth/RasterScanRepetitionPeriod, and (c) Gapped by a space if StageSpeed>ImageWidth/RasterScanRepetitionPeriod. According to the depiction of FIG. 16 for this embodiment, the frame, or, say the line arrays formed from the raster scans, is an inclined parallelogram, with two vertical edges (or, say their extension lines) intersecting the axis of stage movement. The preferable image width for this embodiment can therefore be selected to be a distance along the axis of stage movement and between the intersection points of these two vertical edges and the axis of stage movement. As will be understood by those skilled in the art, although the series of frames acquired are stitched, overlapped and/or spaced successive frames of images are also obtainable by way of, inter alia, selecting the stage-moving speed in accordance with the principles set forth herein. The raster-scan method described above in conjunction with reference to the accompanying figures can be implemented in a variety of ways for charged-particle beam imaging of a sample. For example, the method can be implemented in the form of a controller which is coupled to a traditional charged-particle beam microscope capable of operating in the Continuous-Scan mode, such as the microscope 100 in FIG. 1. This configuration is illustrated in FIG. 17, which shows a charged-particle beam imaging system 1700 which comprises a controller 1710 coupled to a traditional charged-particle beam microscope 100 (cf. FIG. 1). To simply the description, the charged-particle beam microscope will be referred to as comprising a charged-particle beam provider that may include a charged-particle beam source 110, a condenser lens module 120, and an objective lens module 130 for providing the focused charged-particle beam 140, a deflection module equivalent to deflection unit 150 for deflecting charged-particle beam 140 to scan across the surface of sample 195, and a moving stage equivalent to stage 190 whereupon sample 195 is secured for imaging. The stage 190 should be able to move along a fixed direction. The controller 1710 can be implemented as a purely hardwared circuit such as an independent integrated circuit (IC), a firmware and/or a pure computing program. For example, the controller 1710 can be implemented to comprise a computer readable medium encoded with a computer program, wherein the program is able to instruct and coordinate relevant components in the charged-particle beam imaging system so as to carry out the details of the proposed method as described in the previous embodiments. Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there can be variations to the embodiments and those variations would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the present invention as defined by the appended claims. |
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039403114 | description | DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings, particularly to FIG. 1, the reactor shown therein comprises a pressure vessel 10, having a removable closure head 11 attached to the vessel by a plurality of bolts (not shown). The vessel 10 may be of a type well known in the art suitable for containing a fluid coolant at a relatively high pressure. In the present case the coolant utilized is light water. However, other suitable fluids may be utilized as a coolant if desired. The vessel 10 has an inlet nozzle 12 and an outlet nozzle 13. The coolant is circulated through the reactor vessel in a manner well known in the art by means of a pump (not shown). Fuel assemblies 14 are mounted within the vessel between a lower core plate 15 and an upper core plate 16. The fuel assemblies constitute the reactor core. The lower core plate 15 is attached by welding to a core barrel 17 having an upper flange 18 which rests on a ledge 19 of the pressure vessel 10. The core periphery is bordered by a form fitting baffle structure 21 which limits the core by-pass flow of the coolant. The upper core plate 16 is supported from a deep-beamed upper support plate 22 by means of a plurality of support tubes 23 which are attached to the two plates by bolting, as described hereinafter. A flange 24 on the upper support plate is held between the flange 25 of the closure head and the core barrel flange 18. A top plate 26 covers the upper side of the upper support plate, to which it is attached by bolting (not shown). The heavy beam construction 27, shown for the upper support plate, is required to resist the load exerted on it by the upper core plate if a major break in one of the outlet coolant pipes 28 should occur. The reactor is provided with fluid pressure operated control rod drive mechanisms 31 which may be of a type described in U.S. Pat. No. 3,607,629, issued Sept. 21, 1971 to Erling Frisch and Harry Andrews and assigned to the Westinghouse Electric Corporation. As described in the aforesaid patent, the pressure of the fluid coolant within the vessel 10 is utilized to operate the control rods. In the present case eight individual control rod units are associated with one mechanism. The valves for individually controlling the operation of the control rod units are located in a lower flange 32 of each mechanism 31 and are controlled by magnet coils 33. The control rods are raised by the fluid pressure and are retained in their raised position by means of electromagnets 34 mounted on the mechanism. The mechanisms are attached by bolting (not shown) to upper flanges 35 on adapter tubes 36 which penetrate the pressure vessel closure head 11 to which they are attached by welding. As shown more clearly in FIGS. 2, 3, 4 and 6, control rod drive shafts 37 enter the reactor interior through the adapter tubes 36 and, in the present case, each drive shaft 37 is attached to a pair of control rods 38 by a spider 39. Between the adapter tubes 36 and the fuel assemblies 14 the control rods and the drive shafts operate with a rectilinear movement in completely enclosed guide tubes 41. The support tubes 23 serve a second, but important, function; namely that of aligning and supporting the control rod guide tubes 41. Heretofore, the guide tube assemblies have been located between the support tubes and have been provided with their own support structures. This clutters up the space above the core and acts as an obstruction to cross flow of coolant to the outlet nozzles besides increasing to a considerable extent the cost of producing the upper internals of the reactor. As shown more clearly in FIGS. 2 and 3, the guide tubes 41 extend uninterrupted from the top plate 26 of the upper support plate 22 to a few inches above the fuel assemblies 14. As shown in FIG. 4, part of the guide tubes are generally triangular in cross section and part are generally oblong in cross section. The support tubes 23 are generally cylindrical and the drive shafts 37 which are attached to the control rods 38 for a preselected fuel assembly are arranged in a circle about the center line of the support tube containing the drive shafts and control rods for that fuel assembly. The guide tubes 41 are also arranged in a circle with the oblong guide tubes disposed between the triangular guide tubes. Each guide tube has generally circular portions formed integrally therewith for receiving and guiding the drive shaft and the two control rods attached to each drive shaft. The guide tubes may be produced from round tubing by roll forming over internal mandrils. The relative lateral position of the eight guide tubes 41, associated with one control rod mechanism is maintained by a number of generally ring-shaped support plates 42 which are spaced at distances of approximately two feet along the length of the tubes. As shown in FIG. 4, the support plates 42 are cut in the form of an odd-shaped ring to offer minimum resistance to the vertical flow of coolant from the fuel assemblies. The guide tubes are attached to the plates by spot welds 43 on both sides of the plate. The plate 42 may be produced at a relatively reasonable cost by electro-chemical machining techniques followed by more accurate spot machining in the vicinity of the welds and also of four locating slots 44 angularly spaced in the outer periphery of each plate. At their upper end the guide tubes for each support tube are attached to a generally square end plate 45 (see also FIG. 7) which is solid except for contoured holes provided for tube penetration. The attachment to the end plate 45 is obtained by welding at 46 along the entire periphery of the tubes to provide a leak-proof joint as shown in FIG. 6. The guide tube assembly is aligned in the support tube 23 by a series of keys 47 which are attached by bolts 48 to the outside of the support tube. Accurate location of the keys with relation to the support tube flanges is obtained by fitting the keys into oblong holes 49 machined in the tube walls. Local flat spots 51 on the outside tube surface provide proper seating of the keys. Actual alignment between the keys and the guide tube plates 42 is obtained by inserts 52 attached to the keys by bolts 53. Firm contact between the insert and plate slot 44 is insured by a cantilever spring 54 provided with the insert. The spring must be sufficiently stiff to maintain contact and prevent fretting for any condition of vibratory forces developed by the coolant flow. If special, hard machining material is not required for the spring, the key and the spring may be made in one integral piece. In the fuel assemblies, the control rods operate in cylindrical guide tubes 55 which also serve as the main, structure members for the assembly. Because of the relatively close clearances available for the control rods in these tubes and also in the guide tubes 41, it is of great importance that the fuel assemblies and the associated support tubes are accurately aligned. Alignment of a fuel assembly in relation to the upper core plate 16 is achieved by means of two dowel pins 56, with tapered ends, secured to the core plate. The tapered ends of the dowel pins 56 enter holes in the fuel assembly top nozzle 57 when the upper internals are lowered into the reactor vessel. The individual fuel rods 50-1 are supported laterally in the fuel assembly by several axially spaced egg-crate support grids 50 of a type as described in U.S. Pat. No. 3,379,617 by Andrews and Keller and assigned to Westinghouse Electric Corporation. The grids are, in turn, supported by the guide tubes 55 in which they are attached by welding. Alignment of the support tube 23 with the core plate 16 is achieved by two close fitting shoulder bolts 58 which in addition to two regular bolts 59 serve to secure the lower end of the support tube to the core plate 16. At its upper end, the support tube 23 is attached to the upper support plate 22 by four regular bolts 60, while center line positioning only is provided by a spigot fit between a projecting rim 61 on the upper end and a large circular hole in the support plate. Coolant water exits from the support tube through a number of large windows 62 cut in the tube wall. The windows 62 also serve as passage for some of the cross flow from other fuel assemblies. After all the support tubes are secured to the upper core plate and to the upper support plate, the guide tube assemblies are inserted from above. In order to simplify this task, the assembly is rotated approximately 20.degree. from its real position so that the relative position of the alignment keys 47 and the support plates 42 will be as indicated by the dot-dash lines and the arrow 63 in FIG. 4. This permits almost complete insertion without any interference. A short distance before reaching the fully inserted position, the assembly is rotated back and lowered further to permit the two alignment pins 64 in top plate 26 to enter associated holes 65 in the assembly end plate 45 as shown in FIG. 9. The free downward movement is finally checked when the slots 44 in the ring-shaped plates 42 come in contact with the alignment keys 47. To bring the assembly into its final position now requires a considerable downward force since the key springs for all support plates must be compressed simultaneously. This force may be produced conveniently by temporary utilization of special long fixture bolts 67 in the end plate mounting holes as shown in FIG. 9. By sequential tightening of these bolts, the end plate 45 is finally brought into contact with plate 26 after which regular bolts 66 are inserted, tightened and locked. The unique construction of the guide tube assembly and its method of mounting make it possible to replace an assembly if this becomes necessary due to excessive wear during operation of a guide tube or for other reasons. Without this feature, damage to a guide tube assembly might require replacement of the entire upper internal structure. As shown in FIG. 6, a support column 68 extends upwardly into the adapter tube 36. Several guide plates 69 attached to the column 68 by welding serve to guide the control rod drive shaft 37 in the space between the upper support plate and the externally mounted control rod drive mechanisms. The lower end of the support column 68 is secured to a base plate 70 by welding. As shown in FIG. 7, the base plate 70 has holes 71 therein for control rod penetration. The base plate 70 is mounted on top of the guide tube end plate 45 and secured by four bolts 72. This is normally done at the reactor site to simplify the shipment of the upper internals. In order to utilize the control rod mechanism fluid pressure operating system for failed fuel rod detection, it is imperative that coolant samples, received from a fuel assembly through guide tubes 41, are not permitted to mix with the coolant above the upper support plates. To achieve this, it is necessary to provide a seal assembly 73 between the lower end of each control rod mechanism adapter 36 and the top surface of the support column base plate 70. As shown in FIG. 6, the seal assembly 73 comprises a generally conical cup 74 supported by a bushing 75 which is threaded on the lower end of the adapter tube 36 and secured by a pin 76. The seal cup has a flat lower rim 77 which contacts the upper surface of the base plate 70. The necessary contact pressure for sealing is provided by several coil springs 78 compressed by a ring 79 attached to the bushing 75 by screws 81. A tubular thermal shield 80 inside the adapter 36 has a flange clamped between the lower end of the adapter and the bushing 75. Considerable relative motion between the seal cup and its support bushing is possible to compensate for variations in the distance between adapters 36 and base plates 70 and to insure even contact pressure along the entire seal periphery in the event of slight angular variations. Sealing between the seal cup and the support bushing is achieved by means of a piston ring 82 disposed in a groove 90 in the bushing. The piston ring is held in contact with the seal cup and with the lower surface of the piston ring groove by two wave springs 83 disposed in the groove 90. In the modified structure shown in FIG. 10, the piston ring 82 is held in contact with the cup 74 by means of a Belleville spring 84 and with the bushing 75 by means of a garter spring 85. The structures shown do not provide complete leakproofness, but this is not necessary because the amount of leakage is limited by the low differential pressure (less than 5 psi) to insignificant amounts. Sealing may be accomplished also with a structure utilizing bellows to obtain the necessary flexibility and spring action. The method utilized for obtaining coolant samples directly from the outlet of a fuel assembly to an external radiation monitor is best understood by referring to FIG. 1. The 300-400 psi pressure drop, required for operation of the fluid pressure operated control rod mechanisms, is produced by a canned motor pump 86. The suction side of the pump is connected to a header line 87, to which the individual mechanisms are connected through feeder lines 88. The pump outlet is connected directly to the primary system through which the coolant is circulated. An orificed by-pass line 89 is provided around the pump to insure sufficient flow through the pump to present overheating when the mechanisms are not being operated. A radiation monitor 91 is mounted on the common header line. Assuming now that it is desired to check fuel assembly "A" for a possible fuel rod failure. This is accomplished by energizing one of the valve operating coils "B" of the control rod mechanism located directly above the fuel assembly. It should be noted that the control rods are in their raised position during normal operation of the reactor and that they are retained in this position by the electromagnets 34, thereby permitting the valve operating coils to be deenergized during normal operation of the reactor. Opening of the valve causes coolant to flow directly to the mechanism through the previously described totally isolated system consisting of guide tubes 41, seal assembly 73 and mechanism adapter tube 36. As shown by the arrows, the coolant passes through the mechanism and eventually reaches the radiation monitor 91 through the low pressure header line 87. Since only one valve in the entire system is permitted to open during the test period, the coolant reaching the monitor is a true sample of the coolant passing through the fuel assembly being tested. Since the flow through the mechanism structure is limited to a relatively small quantity, a few seconds elapse from the time of a valve opening until the coolant samples arrives at the monitor. However, this does not affect the radiation measurement since the half-like of any of the fission products is not less than several hours. To obtain the desired information, the monitor reading is compared to a simultaneous reading of the general radiation level of the reactor coolant system. Defects in other fuel assemblies can be located by indirect methods. By suppressing the power output of a tested, nondefective fuel assembly by temporarily inserting all control rods of that assembly, coolant from the adjoining assemblies is caused to mix with coolant from the tested assembly in sufficient quantities to determine if any of these has developed a defect. The fuel assemblies are not enclosed and mixing takes place along the entire length of adjacent assemblies. This is accomplished by opening one of the mechanism valves, thereby causing a sample of the coolant mixture to flow to the mechanism as hereinbefore described. Pinpointing of a defective assembly is now possible by testing in the immediate neighborhood. From the foregoing description it is apparent that the invention provides a failed fuel rod detection system which greatly reduces the time heretofore required to locate a fuel assembly with defective fuel rods. The system is suitable for utilization with reactors having fluid pressure operated control rod drive mechanisms. The structure of the upper internals of a reactor is simplified to facilitate testing for a defective fuel assembly. The cost of producing the upper internals is reduced and the replacement of an individual guide tube assembly is made possible without requiring replacement of the entire upper internal structure. |
044217161 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION The present invention is embodied in a Boiling Water Reactor (BWR) nuclear power plant. The reactor is basically a water boiler, and therefore process systems are required a water boiler, and therefore process systems are required which clean and control the chemistry of the water in the reactor vessel as well as to provide protection for the reactor core. These systems may be divided into two general categories: those systems necessary for normal nuclear boiler operations, including startup and shutdown; and those systems which accommodate or provide backup in case of an abnormal or accident condition. Systems used during normal plant operation include the reactor water cleanup system, the fuel and containment pools cooling and filtering system, the closed cooling water system for reactor services, and the shutdown cooling function of the residual heat removal system. The reactor water cleanup system provides continuous purification of the reactor coolant to control the concentration level of long half-life fission products and activation products. The shutdown function of the residual heat-removal system removes heat during reactor shutdown and prior to refueling. Backup systems used during abnormal or accident plant operation include the reactor core isolation cooling system, the standby liquid control system, the steam condensing function of the residual heat removal (RHR) system and the suppression pool cooling function of the RHR system. Further process systems, referred to as emergency core cooling systems, are safety systems which are brought into action during emergency situations that could otherwise lead to core damage and release of fission products to the environment. These systems consist of the low pressure coolant injection function of the RHR system, the high pressure and low pressure core spray systems, and automatic depressurization. A more detailed description of a boiling water reactor can be found in the following publication: "The Thermal-Hydraulics of a Boiling Water Nuclear Reactor," American Nuclear Society, 1977, by R. T. Lahey, Jr. and F. J. Moody. The purpose of the safety monitor of the present invention is to provide summary information which informs a nuclear power plant operator of the status of the cooling water inventory of each of the above-described systems needed to keep the reactor core cool. In this regard, the monitor performs two basic functions: it tells the operator if the core is covered and if it is likely to remain covered; and it informs the operator in simple terms of the status of each of the systems needed to cool the core and maintain core integrity. The monitor performs the above functions by taking raw data from the plant instrumentation, such as flowmeters, and valve position indicators, and processing this information through an interpreter logic. The function of the interpreter logic is to integrate and analyze the information available and to inform the operator of the status of critical systems by means of a visual display so that the operator can take the best action to protect the core in the event of an emergency. The monitor is operational at all times; however it is not intended for use during normal operation of the plant, nor does it replace the instrumentation on the operator control panel. It is most effective when the number of signals or alarms on the main control panel are so great as to potentially confuse the operator. In such a situation, the operator can refer to the monitor for essential safety information to use in determining the proper action to take in an emergency. Once the operator has consulted the monitor for guidance needed to interpret the signals on the main control panel, the monitor's interpretation can be verified by the operator by checking the appropriate instruments on the main control panel. Referring now to FIG. 2, the operator receives information from the monitor by means of cathode ray tube (CRT) displays (9, 10) which has a pushbutton keyboard (16) which is used to call up the desired display on the CRT screen. The pushbutton keyboard is shown in more detail in FIG. 3. The CRT and selector are located in the main control room near the plant operator control panel (12). A primary output display (POD) is generated by means of the POD generator (14) and is continuously displayed on one of the CRT screens (9). The operator can select a number of secondary output displays (SOD) by depressing a selector pushbutton (16). The secondary output displays include system status statements and graphical trend displays which are generated by generators 18 and 20, respectively. A secondary output display remains displayed on the second CRT screen (10) as long as the operator desires. Table 1 shows the POD data which is displayed normally on one CRT screen. Items in the trend column are displayed only when a rate change is in progress. Table 2 shows a listing of all the statements available for display as generated by the system status statement's generator (18). The SOD data is displayed when the operator depresses one of the pushbuttons shown in FIG. 3. Pushbuttons 1 through 6 call up system status displays and pushbuttons 7 through 11 call up graphical trend displays. The system status displays show abnormal or accident conditions that may exist in critical systems related to core cooling. The graphical displays show the trend of selected parameters, during a given time period, graphically on a timebase display. The POD on the CRT screen shows which of the pushbuttons to depress when an abnormal or accident condition occurs by means of a prompt message (such as "Press pushbuttons 1 and 4"). The interpreter logic (22) receives data from plant instrumentation and processes the data to make available the displayed output information. Specified limits on selected variables are determined by the logic, and a flashing display or a change of color in the display is initiated for certain out-of-limit parameters. Other parameters are only made available for display when an out-of-limit condition exists and are suppressed when conditions are normal. Plant-system valve lineups and pump arrangements are checked for correctness under the prevailing plant conditions and a display message is generated when an abnormal condition exists. When such a condition occurs, the interpreter hardware logic energizes one of the lines (24) to thereby instruct the primary output display generator logic (14) to display on the screen, along with the normally-displayed information, the prompt message "press pushbutton XX". This message informs the operator that further information can be obtained by depressing one of the pushbuttons (16) as called out on the POD. When one of the pushbuttons on the keyboard (16) is depressed, an inhibit line (17) from the keyboard (16) is energized to deselect the primary output display which normally passes through the POD selector (26). If one of the pushbuttons in the group of pushbuttons 1-6 is depressed, then one of the output lines (28) from keyboard (16) is energized. The appropriate output (19) for one of the group of statements from generator (18) is then selected by means of the system status displays selector (34). The output (35) of the selector passes to the CRT control logic (11) where it is processed and brought up on the CRT screen. Similarly, if one of the pushbuttons in the group of pushbuttons 7-11 is depressed, then one of the output lines (30) from the keyboard (16) is energized. The appropriate output (33) for one of the graphical displays from generator (20) is then selected by means of the graphical displays selector (32). The output of the selector (33) passes to the CRT control logic (11) where it is processed and brought up on the CRT screen. The following paragraphs describe how the interpreter monitors ten reactor systems in order to obtain essential information and how the interpretor analyzes this information. One of the systems, the low pressure core spray system (LPCS), is then described in detail to illustrate how the hardware logic within the interpreter logic (22) of FIG. 2 is implemented in accordance with the teachings of the present invention. The remaining nine systems are not described in detail. REACTOR VESSEL INFLOW SOURCES The interpreter logic must continually monitor outflow from the reactor vessel (100) and inflow to the vessel to calculate the net water inventory. The flow of coolant into the reactor is determined as described below for each of the systems that contribute to inflow: Feedwater The feedwater system has a flowmeter designed for use during normal operation. The flow signal from this flowmeter is combined with on/off signals from the pumps in the feedwater string to provide extra assurance that the indicated flow is correct. As a backup flow measurement, the pump suction flowmeters are combined to determine flow rate. Control Rod Drive (CRD) Cooling Water This source of water is estimated from the cooling water flow element, backed up by secondary flow element plus pump motor current and valve position. HPCS and RCIC The high pressure core spray system (HPCS) and the reactor core isolation cooling system (RCIC) flow rate are determined by a flow element, backed up by flow estimated from startup test data, correlated with reactor vessel pressure, pump status, and the position of valves in the system. RHR and LPCS The residual heat removal system (RHR) has two modes for pumping water into the reactor pressure vessel at low pressure: the shutdown cooling mode and the low pressure coolant injection (LPCI) mode. In the shutdown cooling mode, the water is injected into the feedwater line. In the LPCI mode, the coolant is injected directly into the core region through special penetrations. Low pressure core spray (LPCS) is injected into the vessel through one of the core spray spargers. The RHR and LPCS flow rates are measured with a flowmeter. The signal from the flowmeter is combined with valve position signals to determine the flow rate into the vessel. This flow rate is checked by estimating the RHR and LPCS flow rate based on reactor vessel pressure, the number of pumps, operating and the position of the valves. Any significant deviation between the measured and estimated RHR and LPCS flow rate is brought to the operator's attention on the CRT screen. Reactor Water Cleanup (RWCU) The reactor water cleanup (RWCU) system is a continuously-operating system which takes suction from the reactor vessel; cools, filters, and demineralizes the water; then heats it and returns it to the feedwater loop. Under normal circumstances, the outflow and inflow are exactly equal, and the net inflow is therefore zero. However, because there are alternate paths for makeup, letdown, backflushing, etc., it is possible for the RWCU system to have a net inflow or outflow to the reactor vessel, depending on valve alignment. The interpreter estimates the net inflow or outflow based on valve position, and includes this in its inventory. Standby Liquid Control (SLC) The standby liquid control (SLC) system is a standby system which would normally never be operated during the lifetime of a plant. It may be actuated manually or by signals that indicate that an abnormal event has occurred. The flow rate may be accurately estimated by valve position and pump power signals. The flow rate is backed up by the water level instrumentation in the SLC storage tank. REACTOR OUTFLOW SOURCES The interpreter logic must also monitor water outflow from the reactor pressure vessel, in order to determine the net change in water inventory as a function of time. The sources of water outflow are: main steamlines (to turbine and bypass to condenser); safety relief valves; reactor water cleanup system; steam line to RCIC turbine; leakage through pump seals, flanges, and valve bonnets; broken pipes, leaking or broken instrument lines; RHR steam line; and RHR shutdown cooling line. The flow of coolant from the reactor is described below for the indicated outflow sources: Main Steam Lines The main steamlines have flowmeters designed for use during normal operation. The flow signal from these flowmeters is processed directly into the interpreter logic, which compares the flow signal to the main steam isolation valve (MSIV) position signals for verification of appropriateness of information. This flow rate is backed up by flow rate estimated from turbine first stage pressure and by generator output. Safety Relief Valve The flow rate from safety relief valves is determined in the manufacturer's facility prior to installation in the nuclear power station. Because the safety relief valve (SRV) flow rate is limited by critical flow in the throat of the valve, it can be calculated from the reactor pressure. Thus, by monitoring valve position and reactor pressure, the total outflow through the SRVs can be readily determined. For plants without valve position indicators, a discharge line pressure may be used instead. Note that there is no satisfactory way of determining leakage rate from a simmering valve, so SRV flow rate is assumed to be either several hundred thousand pounds per hour, or zero. Determination of valve position is from a position indicator, not from thermocouples, since thermocouples cannot differentiate from a simmering valve or a wide open valve. Reactor Water Cleanup System See the discussion in the Inflow Section above. RCIC Steam Line The steam line to the RCIC turbine carries the steam which provides the motive power for the RCIC turbine pump. The flow rate of steam is estimated from startup test data, valve lineup, and reactor pressure. Leakage The normal sources of leakage from the reactor vessel (such as pump seals and valve stems) are monitored through the flow from equipment drains and floor sumps. This flow, which is normally intermittent at a fixed flow rate is integrated into the interpreter logic to monitor leakage as a source of vessel outflow. Abnormal leakage, such as through a broken pipe or instrument line, may or may not be capable of being monitored, depending on location and size of the leak. A large leak in the primary system could overwhelm the equipment drain monitoring system. RHR The residual heat removal system (RHR) has two potential sources of coolant outflow: the condensing heat exchanger steam line and the shutdown heat removal line. At normal operating pressure, only the condensing heat exchanger steam line is a potential coolant outflow source since the shutdown cooling mode is a low-pressure system and is automatically isolated above intermediate vessel pressure. The shutdown cooling line outflow is normally routed into the RHR heat exchanger and back into the reactor vessel. However, it is possible for the valves to be arranged such that water flows out, and not back in. The interpreter logic monitors the many RHR valve positions to determine if there is a net outflow of RHR in the shutdown cooling mode. INTEGRATION OF OUTFLOW AND INFLOW The mass flow rate of all the above sources of inflow and outflow are continuously monitored by the interpreter logic and displayed on the cathode ray tube (CRT) output screen (10) in a form which is immediately useful to the operator. First, the interpreter logic integrates the outflow and inflow of mass to the reactor system. Then, based upon temperature measurements and a thermal hydraulic core flow model, it converts this into a distribution of liquid in the vessel. The final step is to relate the liquid volume to the distance from the top of the active fuel. The output is then displayed on the CRT screen as illustrated by the following example: The reactor scrammed at 07:15:37 Two-phase water level is 10 feet above the top of the active fuel Water level is dropping at a rate of 2 feet per minute Net outflow from reactor is 100,000 lb/hr At the present rate, it will take 13 minutes before the top of the core is uncovered Primary source of outflow is through the relief valves Primary source of inflow is from the feedwater system Core flow is in natural circulation at 1 million pounds per hour 20% of rated core flow. The above output is typical of the primary output of the interpreter logic, which is the normal output to which the screen reverts when there are no requests for secondary information. In addition to the primary output, there is also a secondary output which can be displayed upon request. ______________________________________ Examples of Secondary Output Forms ______________________________________ Reactor Vessel Inflow and Pushbutton #1. Outflow in Ranked Order. Parameter Value Units ______________________________________ OUTFLOW: a. Main Steam Lines XX lb/sec b. Safety Relief Valve No. XX XX lb/sec c. RHR XX lb/sec d. RCIC Turbine Exhaust XX lb/sec e. RWCU XX lb/sec f. Leak Detection XX lb/sec ______________________________________ Parameter Value Units ______________________________________ INFLOW: a. Feedwater XX lb/sec b. HPCS XX lb/sec c. LPCS XX lb/sec d. RHR XX lb/sec e. RCIC XX lb/sec f. Standby Liquid Control XX lb/sec g. CRD Return XX lb/sec ______________________________________ Pushbutton #2. Status of Reactor Core Parameter Value Units ______________________________________ Reactor Scrammed at XX:XX:XX Hrs/Min/Sec Current Decay Heat Level XX Mwt *Current Power Level XXX Mwt Reactor Coolant Level above Core XX Inches above Active Core Reactor Pressure XXXX Psig ______________________________________ Pushbutton #2. System Status Statements Display ______________________________________ Averaged wide range water level is R .times. WLW inches using the following transmitter signals: B22-N026A, xxx inches B22-N026B, xxx inches B22-N026C, xxx inches Reactor water level is below the range of narrow range instruments. ______________________________________ Pushbutton #3. Status of Containment Parameter Value Units ______________________________________ Containment Pressure XX lb/sec Suppression Pool Water Level XXX feet Suppression Pool Water Average XXX .degree.F. Temperature Suppression Pool Water Peak Temperature XXX .degree.F. *Suppression Pool Water Peak XXX .degree.F./min Temperature Rate Coolant Flow into Suppression Pool XXX lb/sec Coolant Flow out of Suppression Pool XXX lb/sec *Suppression Pool Water Cooling Rate XX .degree.F./min Containment Region Hydrogen Concentration XX % Containment Region Oxygen Concentration XX % Drywell Environmental Temperature XXX .degree.F. ______________________________________ Pushbutton #4. Status of Makeup Sources* WATER MAKEUP SYSTEMS - DISABLED: Feedwater HPCS LPCS RHR RCIC Standby Liquid Control Control Rod Drive Cooling WATER MAKEUP SYSTEMS - NORMAL: Feedwater HPCS LPCS RHR RCIC Standby Liquid Control Control Rod Drive Cooling SYSTEM STATUS STATEMENTS (Examples) Displays ______________________________________ Valve 5-4V22 is open and feedwater is being bypassed to the condenser. SLC Pump A motor breaker disconnected. SLC Pump B motor breaker disconnected. RHR Pump A motor breaker disconnected. RHR Pump B motor breaker disconnected. RHR Pump C motor breaker disconnected. RHR Loop A: Incorrect valve lineup; pump discharge is lined up for LPCI; suction is lined up for shutdown cooling. RHR Loop B: Incorrect valve lineup; pump discharge is lined up for LPCI; suction is lined up for shutdown cooling. RHR Seawater to RHR Loop B connection valves are open, and the Loop B is lined up for flooding the reactor with seawater. ______________________________________ Pushbutton #5. Status of Instrumentation System Status Statements (Examples) Displays ______________________________________ The three methods of calculating main steam flow do not agree within xxx psi. Main steam flow is being calculated by averaging the following methods: Measured steam flow, xxx lb/sec Turbine first stage pressure, xxx lb/sec Generator output, xxx lb/sec Feedwater measured by nozzles in reactor feedwater line and flow measured at reactor feed pump suction lines disagree by xxx lb/sec. -Both wide range level transmitter signals B22-N026A and B22-N026C do not indicate within xxx to xxx inches. A power failure may exist. Wide range level transmitter B22-N026B is being used. Narrow range and wide range water level indication differs by xxx inches. Narrow range value is being used. Reactor Water Level is below the range of narrow range instruments. Narrow range reactor water level instruments do not agree with xxx psi. ______________________________________ Pushbutton #6. Status of Auxiliary Support System System Status Statements (Examples) Displays ______________________________________ Loss of Instrument Air, A Loss of Instrument Air, B Loss of Essential Bus #1 Loss of Essential Bus #2 Loss of Essential Bus #3 Loss of DC Bus A Loss of DC Bus B Loss of Auxiliary Power Bus A Loss of Auxiliary Power Bus B RHR Seawater pump A motor breaker disconnected RHR Seawater pump B motor breaker disconnected RHR Seawater pump C motor breaker disconnected RHR Seawater pump D motor breaker disconnected ______________________________________ GRAPHICAL DISPLAYS Pushbuttons 7-11 are for the graphical trend displays. The following graphical displays are available for selection by the operator): Pushbutton #7. Reactor Coolant Level PA0 Pushbutton #8. Reactor Pressure PA0 Pushbutton #9. Reactor Power PA0 Pushbutton #10. Containment Pressure Range: 2 feet below active core to 2 feet above level 8. PA2 Time Range: 15 min., 1 hr., 2 hr., 4 hr. PA2 Different color in level trace above and below the top of active core. PA2 Range: 0 to 1400 psia PA2 Time Scale: 15 min., 1 hr., 2 hr., 4 hr. PA2 Different color on level trace above 1150 psia. PA2 Range: 0 to 110% power. PA2 Time scale: 1 min., 10 min., 1 hr., 2 hr. PA2 Range: 0 to 70 psia PA2 Time Range: 15 min., 2 hr., 4 hr., 12 hr. PA2 Different color for pressure above 60 psia. PA2 (a) either the condensate storage tank suction valve or the suppression pool suction valve is open, and PA2 (b) either test valves are closed, and PA2 (c) there is a control room panel red light indicating the pump is operating? PA2 (d) the discharge line valve is open and check valve is not closed. The primary output indicated above is displayed on the CRT (9), unless the operator selects one of the eleven secondary outputs for display by pushing the button asociated with that display. The secondary output is displayed as long as the operator presses the button, then the CRT screen reverts to the primary display automatically when he releases the button. Alternatively, the graphical displays or all the secondary displays may be displayed on a second CRT (10). During normal operation, when the interpreter logic is in a standby mode, it is calculating the water level based on the integration of the inflow and outflow, while the level is being measured directly by process instrumentation level meters. Because the inflow and outflow cannot be measured perfectly, the calculated water level will tend to drift gradually away from the actual level, and must be reset periodically to be consistent with the actual indicated level. The resulting process is done periodically and selectively so that it does not introduce a mechanism which could thwart the primary function of the interpreter logic during a severe transient or accident, when it is expected to provide an alternate means of determining whether the core is covered. In other words, if the backup level indication is parroting the normal level instrumentation, it's not a backup at all. For that reason, resetting of water level is only done when the interpreter logic verifies that the plant is in a normal mode of operation. A preferred embodiment of the invention will now be described in detail with respect to FIG. 1 which shows in detail one of the ten systems, the low pressure core spray systems (LPCS), and how its interconnections are made with the interpreter logic of FIG. 2, in accordance with the teachings of the present invention. The operation of the LPCS hardware logic within the interpreter logic (22) shown in FIG. 2 will be described in detail with reference to the logic flowcharts of FIGS. 4, 5, 6, and 7. Referring now to FIG. 1, the core spray nozzles (102) are shown within the reactor vessel (100). A manually-operated gate valve (V1), having an indicator light which appears on the main control panel, is connected to the spray nozzles (102). Other valves and flowmeters in the loop are as follows: air-operated testable check valve with an indicator light (V2); motor-operated gate valve, normally closed (V3); flowmeter (114) with flow element (FE) and transmitter (F1); pressure transmitter (112) with output (P1); LPCS pump (104) without output (C1); motor-operated gate valve, normally open (V6), which is connected to provide for pumping water from the suppression pool (106). A motor-operated globe valve (V4), normally open, is provided in a test line (109) and a motor-operated globe valve (V5), normally open, is provided in a minimum bypass line (110). The line (110) provides for injecting water into the suppression pool as indicated by the arrowhead. Valve V4 is open when the elements in the loop (V6), pump (104), pressure transmitter (112), and flowmeter (114) are to be tested by routing water through the test valve (V4). The function of the low pressure core spray system (LPCS) is to provide reactor pressure vessel water makeup during a break of a large primary coolant pipe within the primary containment system. The LPCS will spray cooling water into the active core region within the reactor vessel (100) to prevent overheating of the reactor fuel elements and to preclude failure of the clad. Refer now to the logic flowcharts of FIGS. 4 through 7. The system flow rate is measured using the flowmeter (114) at logic block 150 in FIG. 4. The control panel indicating light which indicates that the pump is operating or the pump discharge pressure (P1) from pressure transmitter (112) is checked to see if it is within the high pressure set point, logic block 152, or the low pressure set point, logic block 154. If both of the outputs from blocks 152 and 154 are no, a yes signal (Y4) is generated from logic block 156. A pump-operating indication (C1) from logic block 158 provides a confirming signal (160) to assure that flow rate is present, i.e., that the pump is running. If the pump is running, decision block 162 provides a yes output (Y2) to the logic block 164. In logic block 164, the inputs Y2 and Y4 are checked to see if either input is yes. If either one is yes, then the value (G2) at logic block 168 is assigned the flow rate value (S1) from the flowmeter logic block 150. The value of G2 provided at 168 in FIG. 4 is used at FIG. 7 to ultimately calculate the LPCS flow rate into the reactor in pounds per second. Returning again to decision block 162, if the pump is not running, a no output is transferred to decision block 170. If th pump is not in standby, a no output from decision 170 causes the system status statements generator (FIG. 2, 118) to generate Message 3 in the secondary output display (4). The plant operator assistance messages for the low pressure core spray system are as follows: Message 1: LPCS minimum flow bypass valve is open. Message 2: LPCS valve lineup is incorrect for injection. Message 3: LPCS pump motor breaker is disconnected. Message 4: LPCS injection line valves are incorrect for injection. Check valves V1, V2, and V3. Message 5: LPCS test valve is open. In addition to generating Message 3 in secondary output display (SOD) 4 at logic block 172, the logic block 174 energizes one of the lines (24) of FIG. 2, to cause the primary output display selector (26) to generate the message "press pushbutton 1 and pushbutton 4" in the primary output display. The operator, when viewing the primary output display, sees the message "press pushbutton 1 and pushbutton 4." The operator can then press these pushbuttons shown in FIG. 3. When pushbutton 4 is pressed, the status of makeup sources will be displayed. Along with this display is the Message 3 "LPCS pump motor breaker is disconnected" (as an example). The valve lineups are checked by the interpreter logic (22) to assure that the coolant is being injected into the reactor pressure vessel (100). This is done by means of the logic shown in FIG. 5. The manual isolation valve (V1) output from logic block 180 is checked in decision block 182 to see if the valve is open. The testable check valve (V2) output from logic block 184 is checked in decision block 186 to see if the valve is not closed. The injection valve (V3) at logic block 188 is checked in decision block 190 to see if the valve is open. If all of these inputs are yes, as indicated at logic block 192, then an output (Y1) at block 194 is provided. This output is passed on to the logic shown in FIG. 7. If one or more of the inputs of block 192 is not yes, Message 4 is generated in SOD4 at logic block 196. Message 4 states that "LPCS injection line valves are incorrect for injection; Check valves V1, V2, and V3." Furthermore, the interpreter logic (22, FIG. 2) raises appropriate lines (24) to cause the primary output display selector (26) to generate the message "press pushbutton 1 and pushbutton 4" in the primary output display as illustrated by the logic block 198. In FIG. 6, the interpreter logic checks the bypass valve (V5) position at logic block 200. At decision block 202, if the valve is open, a yes output is generated which causes Message 1 to be generated in SOD4, at logic block 204, and the message "press pushbutton 1 and pushbutton 4" to be generated in the POD at logic block 206. In FIG. 7, at block 208, the position of the LPCS pump suction line valve (V6) is checked. If the valve is open, an output from decision block 210 is provided to logic 212. Furthermore, the test valve position (214) of valve V4 is checked at decision block 216. If the valve is closed, a yes output is provided to block 212. If the valve is not closed, a no output is provided to block 216 which causes Message 5 to be generated in SOD4. Message 5 states that "LPCS test valve is open." Additionally, the message "press pushbutton 1 and pushbutton 4" is generated in the SOD as shown at logic block 218. If both of the inputs to logic block 212 are yes, an output (Y3) is provided to the logic block (220). If the input (Y1) from FIG. 5, (which indicates that the valve lineups for V1, V2, and V3 are correct), and the input Y3 (which indicates that the valve lineups for V4 and V6 are correct), are present, then the LPCS flow rate (WLPCS) to the reactor is set equal to G2. G2 is the value from FIG. 4 calculated by the flowmeter (F1). If either Y1 or Y3 is not yes, indicating that the valve lineups are incorrect, then the flow rate (WLPCS) is set to zero. At logic block 222, the value for the flow rate is inserted into the secondary output displays, SOD1 and SOD2. Referring now to logic block 224, if all of the inputs are not yes, that is if any of the valve lineups are incorrect, then a no output is provided to logic block 226. This causes Message 2 to be generated in SOD4. Message 2 states that "LPCS valve lineup is incorrect for injection." Furthermore, the interpreter logic raises appropriate ones of the lines (24) in FIG. 2 to cause the message "press pushbutton 1 and pushbutton 4" to be generated in the primary output display. As has been illustrated, plant operator assistance messages are displayed when the flowmeter indication does not agree with the pump operating indication. Furthermore, improper valve position messages are displayed. These incorrect valve alignments would impair or impede coolant flow into the reactor pressure vessel. The messages alert the operator so that the operator can confirm the incorrect alignment and take proper corrective action. What follows is a detailed description of each of the remaining nine systems which provide information as to the net water inventory. NUCLEAR BOILER SYSTEM Reactor Pressure The reactor pressure is an important parameter to determine the reactor status. Its measurement must be known as precisely as possible. There are only two power supplies available for two pairs of pressure transmitters. A loss of one power supply can affect two pressure transmitters simultaneously. In the event of one power supply failure, two pressure transmitters would likely indicate different output pressures from the remaining two nonfailed pressure transmitters. This would lead to the indeterminant state of each pair confirming their validity. To avoid the dilemma of the indeterminant state, only three of the four available pressure transmitters are used. The interpreter logic compares the pressure transmitter output signals against an upper (U1) and lower (L1) expected operating range pressure limit. If the two signals (S1 and S2) of a pair of pressure transmitters having a common power supply are both outside the upper and lower range, the interpreter logic assumes that they are both incorrect due to a failure of their common power supply. The logic then uses the remaining pressure transmitter signal (S3). In the event that either S1 or S2 fall within the range of U1 to L1, the interpreter logic compares three pressure signals using pressure transmitter signals S1, S2, and S3. If any two of these signals agree within a first level of accuracy (A1), the average of all signals agreeing within A1 is calculated and used in the priority selection process. If there is no agreement within A1 of any of the signals, a comparison is made at the second level of accuracy (A2). If there is agreement within at least one pair at this level of accuracy, the logic selects a signal using the average of all signals within A2 and displays a message regarding the fact of the poor accuracy of the pressure measurement. If there is no agreement at the second level of accuracy, an average of all three signals that are within expected reactor operating range, U1 to L1, is used, and a similar caveat regarding accuracy of pressure is dislayed. Safety/Relief Valve Flow Rate The safety/relief valve (S/RV) employs an external actuator when the valve is operated in the relief mode or in the automatic depressurization system (ADS) mode. A position switch indicating the actuator position of valve open or valve closed is displayed on the control room panel. The actuator position indicator will indicate correctly when the more likely relief function occurs. It will not indicate when the valve open in its safety function or fails to close. A direct step position indicator device is also installed. The interpreter logic accepts a digital actuator position signal and one analog signal from a valve stem position signal. The S/RV steam flow (per valve) as a function of reactor pressure is provided by an empirical equation supplied by the valve manufacturer. The interpreter logic uses the pressure vs. flow curve to establish the steamflow rate. Main Steamline Flow Rate The main steamline flow contributes significantly to the changes in reactor water inventory. Three methods are used to calculate the value of main steamflow. They are: (1) flow nozzles, (2) turbine first stage pressure, and (3) generator output. The turbine bypass flow in the second and third methods are accounted for in the determination. Flow Nozzle Method This method uses the total steamflow signal from a process computer. This process computer signal is generated from the flow meter and transmitter, F1 and T1, respectively. The main steamflow transmitter is calibrated to measure steamflow rate at rated reactor pressure of 1020 psia. The actual flow for a transmitter at 1020 psia will vary directly with reactor pressure. The interpreter logic provides this calculation. Turbine First Stage Pressure Method This method uses the turbine first stage pressure signal. The flow rate as a function of first stage pressure is provided by the vendor. A typical equation is in the form of: EQU W.sub.istg =C1.times.P.sub.istg +C2 where W.sub.istg =turbine first stage flow rate PA1 P.sub.istg =turbine first stage pressure PA1 C1 and C2=empirical constants determined by tests or plant operation PA1 W.sub.istg =turbine first stage flow rate PA1 P.sub.istg =turbine first stage pressure PA1 P.sub.cond =condenser vacuum pressure PA1 C3, C4, and C5=constants of determination. These are determined from the milliamp scale of the pressure output signal and the range of condenser vacuum. PA1 Q=heat energy PA1 W=cooling flow PA1 C.sub.p =specific heat capacity PA1 T.sub.o =heat exchanger outlet temperature PA1 T.sub.i =heat exchanger inlet temperature. PA1 K=a constant determined by the properties of the steam for the operating conditions. The above equation can be converted to an equation in terms of milliamp output of a pressure transmitter signal. The signal needs to be corrected for the condenser vacuum compensation. The expression takes on a form of: EQU W.sub.istg =C3.times.P.sub.istg +C4.times.P.sub.cond +C5 where Generator Output Method The generator output vs. calculated main steamflow rate is provided by the vendor. This relationship between the two parameters is used for the comparison of steamflow rates. The turbine bypass flow as a function of accumulated open position of the five bypass valves are provided by the vendor. The flow is usually based upon rated turbine inlet pressure. The interpreter logic compares the three flow signals discussed above. If any two of these signals agree within a first level of accuracy (A4), the average of the two flow signals within A4 is calculated and used in the priority selection process. If there is no agreement within A4 lb/sec of any of the signals, a comparison will be made at a second level (A5) of accuracy, the average of the two signals within A5 is calculated and used in the priority selection process. If there is no agreement within A5, an average of all three flow signals is used in the priority selection process. Reactor Water Level There are three sets of reactor water level instrumentation. They are: (1) narrow range, (2) wide range, and (3) fuel zone reactor level instruments. The three sets overlap over a limited range. The narrow range instrumentation is completely overlapped by the wide range monitor, because the narrow range instrumentation range is less than the wide range. Thus, there is a region covered only by the wide range instrumentation. The interpreter logic uses the narrow range instrument signals as the primary signal which is checked by the wide range measurement. If the two signals disagree by greater than a preset amount, a display is shown on the CRT display. The wide range instrumentation is overlapped over its lower range by the fuel zone reactor water level instrumentation. The wide range instrument signal is solely used in the span between the bottom of the narrow range instrument signal and the top of the fuel zone reactor water level signal. The wide range monitors are also used in the interpreter logic in the zone where both the wide range and the fuel zone reactor water level instruments are available. The wide range instrument signal is checked by the fuel zone signal. If the water level indication differs by a predetermined amount, a CRT display is announced. The primary signal for the algorithm is the wide range water level indication over this zone. The fuel zone reactor water level instrument is the only available source below the lower limit of the wide range instrument signal. Therefore, it is used for indications of water level in that region. The wide range water level instrumentation consists of four instruments, four vessel pressure taps at four azimuth locations at one elevation. However, there are two power supplies each powering two instruments. Failure mode of the power supply would result in affecting two instruments identically. Including four instruments in the algorithm to determine the correctness of the signal would lead only to an indeterminate state. The interpreter logic uses only three of the four wide range instruments and calculates the average value of the signals that agree within a predetermined amount of inches as the processed value of reactor wide range water level. Control Rod Drive (CRD) System Cooling water can be added to the reactor pressure vessel by the control rod drive cooling water. The interpreter logic uses the output of a flow element as the coolant rate added to the reactor vessel. The flow element output is used as long as the value exceeds a minimum established flow element uncertainty value. In addition to the flow element output signal, the valve alignment is checked to assure that the flowpath is correct for flow to the vessel. The interpreter logic checks this, then establishes that the flow is directed to the vessel. Feedwater Control System The primary flow measurement used in the interpreter logic is the total feedwater flow analog signal to the plant control process computer. The secondary flow signal is developed using the output of the four flowmeters located in the feedwater pump suction lines. These flowmeters are provided for controlling the minimum flow bypass valves. If the valves are open, the interpreter logic calculates the bypass flows. The interpreter logic will always use the primary flow signal in the coolant inventory calculation, but will cause an alarm if there is disagreement by an error value amount between the primary and secondary signals and if the valve in the line from the reactor feedwater line to the main condenser is open. Standby Liquid Control System (SLCS) The principal function of the standby liquid control system is to provide a diverse and redundant reactor protection system. Upon demand, the manually-initiated SLCS injects a borated solution into the reactor vessel. The borated solution is a neutron-absorbing substance that is capable of shutting down the reactor. The borated solution contains a significant amount of water that can be credited to providing reactor vessel makeup water. The valve alignments are checked for positioning to inject into the reactor vessel. The pump suction valves are checked for opening. One or both valves open would permit flow to the pumps. Either Squib valves on the discharge line are checked for opening. One is sufficient for SLC flowpath success. The pump status is established by the operating indicator lights on the control room panel. If both the red and green indicator lights are not on, then an error message indicating the circuit breaker being disconnected is displayed. If the pump green light is on, then the pump has indicated that it is in standby state. If the red light is on, then the pump is running. The interpreter logic performs an integration of the pump output with time to derive the flow going to the reactor vessel. This calculation is compared to the SLC storage tank liquid level indication to confirm the solution is being delivered to the reactor vessel. If the quantity of water being depleted from the storage tank does not agree with the integrated flow calculational quantity by an acceptable amount, an error message is displayed. Containment System The purpose of the containment system algorithm is to provide the logic and input necessary to produce a status display and determine the enthalpy of the water being drawn from the suppression pool. There are typically four suppression pool temperature sensors on Boiling Water Reactors. The interpreter logic uses the average and the maximum temperatures for its input. For the drywell temperature, two of the five drywell cooler supply air temperature detectors are used to obtain maximum and average drywell air temperatures. Water can be added to the suppression pool from the following sources: 1. Condensed steam from the safety/relief valve discharge. 2. Residual heat removal system steam condensing, sea water or service water flooding, and reactor to pool path. 3. High pressure core spray system from the condensate storage tank in the test mode. 4. Reactor core isolation cooling system turbine exhaust. Water can be removed by pumping through the RHR loop A to the radwaste system. The net change in the suppression pool inventory is calculated by the net inflow and outflows integrated over time. Energy changes to the suppression pool are calculated by integrating the flow times the enthalpy product for each flow source. Residual Heat Removal The residual heat removal (RHR) system is designed to remove decay and sensible heat from a nuclear boiling water reactor under normal and accident conditions as well as during refueling operations. The system also cools the suppression pool. The RHR system forms a closed loop with the reactor vessel or the containment. It consists essentially of piping, water pumps, and heat exchangers. The system is made up of four subsystems used under normal and emergency conditions: 1. Low pressure coolant injection (LPCI) 2. Suppression pool cooling 3. Reactor steam condensing 4. Shutdown cooling. The LPCI subsystem operates in conjunction with the high pressure core spray (HPCS) system or the automatic depressurization system (ADS) and the low pressure core spray (LPCS) system to restore and maintain the desired water level in the reactor vessel for cooling after a loss-of-coolant accident caused by a line break large enough to deplete the coolant inventory to below the top of the core. The suppression pool cooling subsystem cools the suppression pool by using the RHR pumps and heat exchangers. During reactor core isolation cooling system operation, the RHR heat exchangers may operate as reactor steam condensing units thereby making it possible to maintain the reactor at hot standby. This mode is the reactor steam condensing subsystem. The shutdown cooling subsystem removes enough of the residual heat (decay and sensible heat) from the reactor primary system to cool it for refueling and servicing. The RHR system is made up of Loop A, Loop B, and Loop C. Loops A and B have heat exchangers incorporated in their loops. These loops are used for the suppression pool cooling, shutdown cooling, and the reactor steam condensing subsystems. Loop C does not have a heat exchanger in its loop. It operates as a low pressure coolant injection mode only, adding water to the reactor vessel for cooling following a loss-of-coolant accident. Loops A and B are almost identically designed loops operating in parallel. In the decay heat removal modes of operation, they are redundant systems for better reliability (i.e., if one loop is out of service, the other loop is capable of performing its intended design function). All three loops (A, B, and C) function in the LPCI mode. This function is to supply a large quantity of water to the reactor pressure vessel following a loss-of-coolant accident. These loops operate in parallel and sufficient redundancy to make the system reliability acceptable. The RHR system consists of many potential flowpaths and combinations of flowpaths or valve lineups. The pump discharge, pump suction, and other RHR flowpaths are described in Table 3. The valve lineups described in Table 3 can be combined in many ways to allow normal and abnormal modes of operation of the RHR system. These combinations are described in Table 4. Residual Heat Removal (RHR) Pump Flow RHR pump flow is measured by flowmeters in each RHR loop. Two methods of confirming that the measured flow is correct are: 1. pump is running as indicated by the panel light 2. the pump discharge pressure high/low switch. In some cases, calculation of flow in valve lineup combination is not simply based on metered flow, but is based on a heat balance, fluid friction in the RHR system and/or two-phase flow. Valve Lineup Combination 8 and 12 These flowpath combinations provide a path from the reactor to the containment. The flow is measured by a flow element. These path combinations can result in loss of reactor coolant inventory, reactor depressurization and two-phase flow at the flow element. The flow transmitters are calibrated for water at 68.degree. F. In event there is two-phase flow in the flow element, the flow transmitter output must be adjusted to account for the difference in density of the two-phase mixture. As flashing to two-phase flow occurs in the flow meter, the actual flow versus that indicated by the flow transmitter will reduce as the square root of the density change. The density change will be a function of reactor pressure and temperature, the hydraulic losses between the return line and the flow element, and the Moody two-phase flow correlation. Valve Lineup Combination 10--Minimum Bypass Flow Normally the minimum flow bypass orifice is sized for 10% of rated pump flow with a pump total density head (TDH) corresponding to 20% flow. Losses in the return line are usually negligible compared to the orifice. The orifice controls the hydraulic characteristics of the reactor--through minimum bypass line--to suppression pool flowpath. During the initial phase of the transient of bypass valve open/shutdown suction line open, flow through the orifice will be cold water. If the condition continues for awhile, the piping down to the orifice will fill with hot water and two-phase flow will occur. The interpreter logic conservatively assumes that the higher, single-phase flow rate of cold water is used as long as the condition of the valve lineup combination 10 exists. Valve Lineup Combination 18--Steam Flow to Heat Exchanger There are no analog signals of steam flow to the RHR heat exchangers during steam condensing mode of operation. The elbow taps on the RHR steamline are used only as a high steam flow isolation signal. A method of calculating steam flow is to determine heat transferred (cooling water flow times the temperature rise in the cooling water) and equate it to the steam condensed and the amount of subcooling. The total heat transfer is calculated by EQU Q=WC.sub.p (T.sub.o -T.sub.i) where There is no heat exchanger inlet temperature measurement. However, the service water source, ocean water, will change temperature very slowly with the seasons. The interpreter logic makes adjustments to compensate for these temperature changes. Isenthalpy expansion of steam to condensing pressure of 200 psig in the RHR heat exchanger and subsequent subcooling to the design value of 140.degree. F. results in a steam condensing flow rate, W.sub.sc of: ##EQU1## Where W, C.sub.p, T.sub.o and T.sub.i have previously been defined. The amount of subcooling of the condensate can be lower than 140.degree. F. It can be as low as 60.degree. F. at low flow rates and cold sea water. The enthalpy at 60.degree. F. is 28 Btu/lb, a difference of approximately 80 Btu/lb. An error in the flow calculation as high as 7% will result if a constant denominator value of K is used. Therefore, the equations are modified to improve the accuracy. Valve Lineup Combination 20--Reactor Outflow This reactor coolant outflow path will exist if the RHR Loop A shutdown line from the reactor (Lineup 9) is open and the valves from Loop A to the radwaste collector tank (Lineup 13) are open. The flow in the line to the collector tank will be limited primarily by the flow capacity of the valves in the B line to the collector tank. Initially, cold water from the RHR piping will flow to the tank as the piping fills with hotter reactor coolant. There will be two-phase flow if the coolant is above 212.degree. F., and the flow rate will vary depending on the reactor pressure and if RHR pump A is operating. The interpreter logic accounts only for cold water flow. Valve Lineup Combination 22--Reactor Outflow This reactor coolant outflow path will exist if the shutdown line from the reactor (Lineup 9) is open and the heat exchanger vent line is open. The flow in the line will be limited primarily by the flow capacity of the valves in the one-inch line. Initially, cold water from the RHR piping will flow to the suppression pool as the piping fills with hotter reactor coolant. There will be flashing of liquid to two-phase flow if the reactor is above 212.degree. F., and the flow rate will vary depending on reactor pressure and if RHR pump A is operating. The interpreter logic accounts only for cold water flow. Valve Lineup Combination 16 The line from the RHR heat exchanger delivering condensate from the RHR heat exchanger to the suppression pool and RCIC pump suction is four inches in size. At design flow rate, the velocity in this line is approximately seven feet per second. This is a low velocity for water flow. As a result, the pressure drop in the line will be low. The control valve must, therefore, provide a high pressure drop even in its wide open position for the design case of 200 psig in the RHR heat exchanger, and 0 psig in the suppression pool. The interpreter logic assumes that the hydraulic characteristic of this valve lineup combination is controlled only by the position of the valve and its hydraulic loss coefficient versus position. Lineup of Valves In the event that both Loop A or suction line is open at the same time that the shutdown line is open, there will be a high blowdown rate if the reactor is above atmospheric pressure. The interpreter logic calculates the flow by using the frictional characteristic of the flow path and the Moody two-phase flow correlation for saturated liquid. Heat Removal Rate The interpreter logic calculates the RHR heat transfer rate by EQU Q.sub.cc =WC.sub.p (T.sub.o -T.sub.i) This value is assigned to the containment cooling rate if valve lineup combination 1, 4, or 11 exists. It is assigned to the shutdown cooling rate if valve lineup combination 2 or 5 exists. Energy Dump to Suppression Pool In the event that valve lineup combinations 8, 10, 16, or 22 exists, energy will be transferred from the reactor to the suppression pool. Assuming that the reactor coolant blowing to the suppression pool is nearly saturated, the enthalpy of saturated water vs. pressure is calculated and used. RHR Service Water Flow to the Suppression Pool This flow is set equal to the output of the flow transmitter, if either valve lineup combination 9, 13, or 17 exists and RHR pump B is not operating with suction from the suppression pool. If RHR pump B is operating with suction from the suppression pool, service water flow to the suppression pool is set equal to the output of the flowmeter if a key valve is closed. For all other conditions, this flow is set at zero. High Pressure Core Spray System The high pressure core spray (HPCS) system is one of the systems comprising the emergency core cooling system. The operation of the HPCS system in the injection mode will result in an increase in reactor coolant inventory. The interpreter logic accounts for the coolant inventory increase by: 1. measuring the flow rate using a flowmeter and transmitter 2. flow is calculated by comparing measured pump total head (TDH) versus flow 3.if the pump motor is energized, a maximum flow rate based upon preoperational tests, is calculated 4. if the minimum flow bypass valve is open, the above calculated flow rates are reduced by a calculated minimum flow rate 5. the flow rates determined by items 1 and 2 above are compared. If there is agreement within a predetermined value, the flow measured using the flowmeter is used to calculate the reactor coolant inventory 6. if there is no agreement between flowmeter flow rate and flow rate determined by the total density head (TDH) method within another predetermined value, the metered flow rate will be used by the interpreter logic if it is both less than the maximum flow rate discussed in item 3 above and less than the flow rate calculated by pump TDH. If the meter flow rate does not pass this test, the interpreter logic will next use the flow rate determined by calculated pump TDH, if it is both less than the maximum flow rate and less than flow measured by the meter. If this flow rate does not pass the test, the interpreter logic will use the maximum flow rate discussed in item 3. 7. The interpreter logic will permit the flowmeter signal or the flow rate signal that is based on measured pump TDH to be used in the reactor coolant inventory calculation if: Leak Detection System The leak detection system measures four flows that can affect reactor coolant inventory. The interpreter logic processes these four flows as follows: 1. RWCU blowdown to the main condenser is obtained from a flow transmitter and made available to the RWCU part of the interpreter logic. 2. Drywell high conductivity (floor drain sump) flow is obtained from a flow transmitter. 3. Drywell low conductivity (equipment drain sump) flow is obtained from a flow transmitter. 4. Drywell air cooler condensate flow is obtained from a flow transmitter. The total leakage flow in the drywell is calculated by adding the low and high conductivity flows. After the initiation of reactor isolation signal, the total leakage is calculated to be total leakage at the time of isolation plus variation in drywell air cooler flow after isolation. The total flow in the low and high conductivity sump drain lines will not exceed 25 liters/min and 125 liters/min, respectively. Since the flow rates are low, the status of the isolation and bypass valves for the flowmeters are not monitored nor used in the interpreter logic. It is assumed that these valves are correctly operated and isolated if an isolation signal exists. It is also assumed that the low and high conductivity sump drain flows are all reactor coolant leakage. Also, time lag from leak to drain line is ignored. Reactor Core Isolation System The reactor core isolation cooling (RCIC) system is a steam turbine driven pump to provide water makeup during reactor core isolation transients. RCIC injection results in an increase in reactor coolant inventory. The interpreter logic calculates flow into the reactor as the output of the flowmeter if: 1. either of the test line valves is closed, and 2. the pump operation is confirmed by the turbine speed at pressures greater than 135 psig. In addition, the interpreter logic displays are generated for RCIC initiation and isolation, system inoperable due to valve alignment, and mechanical overspeed trip. A steamline isolation valve is assumed to be closed if the turbine inlet pressure is a predetermined pressure less than reactor pressure. A mechanical overspeed trip is assumed if there is an initiation signal, but there is no remote manual trip, and turbine speed is less than the minimum operating range of 40%. Reactor Water Cleanup System The RWCU system under normal conditions is a closed loop system (flow out is equal to the flow in). However, there can be some valves open to blow down the reactor water to the main condenser, waste collector, or the surge tank. The interpreter logic accounts for this flow stream in the coolant inventory calculation. The RWCU also has a flowmeter to measure flow from the reactor and return to the reactor vessel. These are used in the leak detection system. The interpreter logic uses the output of the flowmeters as the measure of net flow out of the RWCU, since any other flow stream out of the RWCU would have to be by a pipe break or an open, unindicated drain valve. PROGRAMMING DESCRIPTION Introduction There are two main categories of interpreter logic, the thermal-hydraulics subroutine (the thermal-hydraulics core model) and the hardware logic associated with conditioning the incoming signals for the interpreter logic (22) of FIG. 2. A general flowchart illustrating the basic elements of the interpreter logic and its interrelationship with the software is shown in FIG. 8. The following sections describe the features of the master program and the thermal-hydraulics subroutine. The purpose of the master program in conjunction with the interpretor hardware logic is to: 1. Collect and calculate data for display (blocks 250-254). 2. Monitor trends and limits that initiate changes of display (block 256). 3. Monitor and alert the operator that a system status statement exists by generating a prompt message to instruct the operator to push a SOD button for additional information (blocks 258 and 262). The thermal-hydraulics subroutine (block 260) defines a thermal-hydraulics core model and calculates the reactor water level. It serves as a backup to the reactor water level instrumentation. The thermal-hydraulics subroutine is a separate software unit and is employed as a subroutine to the master program. Master Program The master program calculates an average value for the following parameters using a one-minute average of the input signals: Reactor Power Reactor Coolant Level Reactor Pressure Reactor Coolant Inventory Net Change Containment Pressure The master program calculates the rate of change of the parameters shown in Table 1, by taking the updated average value of the parameters identified in the previous one-minute value. The master program is provided with algorithms that detect and display the information stated in the previous description of the primary output display (POD). The Primary Output Display parameter of Reactor Coolant Level above Core shall be equal to R.times.ML minus 369.75 inches, since interpreter logic calculates R.times.ML as distance above the reactor pressure vessel bottom head invert. Sources of Parameter Input The master program is programmed to employ the variables noted in Table 5 for display in the Primary Output Display (POD) shown in Table 1. Variables denoting rates of change on the POD are calculated by averaging five derivatives taken over one-minute intervals using the appropriate variables noted in Table 5. TABLE 5 ______________________________________ POD Parameter Set Variable Name Units Source ______________________________________ Reactor Power Pwr % Rated Power Nuclear boiler system Reactor Coolant R .times. ML Inches Nuclear boiler Level system Reactor Pressure Pr psig Nuclear boiler system Containment Pc psig Containment Pressure system Reactor Coolant In- W.sub.NET lbm/sec See below ventory Net Change Electrical Loss of -- -- See below Power Loss of Instrument -- -- See below Air ______________________________________ Reactor Coolant Inventory Net Change Table 2 shows the reactor coolant outflows and inflows. The master program sums the inflows and outflows to obtain the net change in inventory. EQU W.sub.NET =WFW+WHPCS+WLPCS+WRCICI+WCRD+WSLC-C*WMSM-WSRV-WRCICO-WRWCU-WLDS FNT Note: See FIG. 11, block 308, for definition of "C." Electrical Loss of Power The master program is provided with signals that indicate loss of AC or DC power and identifies what bus the loss of power has occurred on. Loss of Instrument Air The master program is provided with signals that indicate loss of instrument air pressure. Determination of Time to Limits Time to Top of Core The time interval projected for the core to uncover is an important parameter because of the dependence of fuel integrity on reactor water level. Estimating this time interval by extrapolating the instrument water level to the level corresponding to core uncovery is not acceptable because changes in the vessel interval geometry with elevation and changes in the reactor power, pressure, and external flow rates can cause the water level to drop at varying rates. Employing the thermal-hydraulics subroutine with some interpolation logic and some assumptions regarding the reactor conditions at the time of core becoming uncovered significantly improves the estimation of time to core uncovery. This procedure is illustrated in FIG. 9. The subscript "u" in FIG. 9 denotes quantities associated with core uncovery. The resultant delta t.sub.u (block 286) is displayed on the POD as the time to core uncovery. Time to Maximum Vessel Pressure The time required to reach the vessel pressure limit is determined by extrapolating the vessel pressure time history to the limiting pressure. The time interval is determined by subtracting the current time from the time associated with the limiting pressure and is displayed on the POD. The extrapolation is based on the first derivative of the pressure history only, but the pressure history is exponentially weighted so that the most recent data contributes more to the projection than older data. No value will be calculated if the extrapolated pressure slope is less than or equal to zero, i.e., the pressure is decreasing. Time to Maximum Containment Pressure The time required to reach the containment design limit is calculated in a similar manner as the time required to reach the vessel pressure limit (see previous paragraph), except the containment pressure is used rather than the vessel pressure in the extrapolation. Interfaces with the thermal-hydraulics subroutine The thermal-hydraulics subroutine's primary function is to serve as a backup to instrument water level measurements. The thermal-hydraulics subroutine calculated water level, SWL (block 300, FIG. 10), is the last choice in the selection process for the reactor water level, R.times.ML. The thermal-hydraulics subroutine provides the variable SWL continuously (i.e., once a minute) using the current reactor state for the calculation. The thermal-hydraulics subroutine also is used in the calculation of time to core uncovery (FIG. 9). The thermal-hydraulics subroutine is also employed in the water level calculation mode (FIG. 10). This process is performed once a minute as well. The final thermal-hydraulics subroutine usage does not result in output to the POD but serves to correct the mass balance which may drift off due to instrument inaccuracy; hence, the term vessel mass update mode (FIG. 10). This calculation is initiated whenever the calculated water level differs from the instrument water level by more than 5%. The calculation employs current reactor states. The Thermal-Hydraulic Subroutine--A Steady Thermal-Hydraulic Model for the Boiling Water Reactor System The Physical Model The Boiling Water Reactor (BWR) nuclear steam supply system, in its simplest form, consists of a nuclear reactor core and a recirculation coolant loop. FIG. 12 depicts the system layout for a BWR. The core is made up of an array of fuel bundles (350) and a core bypass region which provides a many parallel-path flow circuit to the passage of the coolant (shown schematically in FIG. 13). The recirculation loop consists of a flow path to return the nonvaporized coolant to the reactor vessel lower plenum (352), mixing the returning feedwater with it enroute. In a BWR, the return coolant circuit is partially within the reactor vessel and partially dual-path outside the vessel, with the dual-path external circuit (354) containing motor-driven pumps (356). The coolant entering the bottom of the core, flows upwards through the fuel bundle, achieving partial vaporization. Consequently, two-phase flow exists in the fuel bundles (350), the upper plenum (358), the standpipes (360), and the steam separators (362). There may also be a very small amount of steam carryunder in the coolant in the path from the steam separators to the feedwater sparger ring. The hydraulics model of the BWR primary system, which is in the thermal-hydraulics subroutine, performs a steady-state analysis of the system recirculation flow. In its natural circulation mode, the model requires as input either the downcomer level and core power, from which it calculates the recirculation flow and system inventory (FIG. 14), or the system inventory and core power from which it calculates the recirculation flow and level in the downcomer (FIG. 15). Thus, it can be used to confirm either the downcomer level measurement from the calculated system inventory or the system inventory using the downcomer level measurement. For all cases, the model assumes that inside the core shroud the system is always full, i.e., the level is at the top of the steam separators (362). This allows the interpreter logic to track inventory up to the point where a two-phase level appears in the upper plenum (358). At this point, operator action to avoid core uncovery will be obvious. The Analytical Model--Core Cooling (The thermal-hydraulics subroutine) Core steady-state, thermal-hydraulic analyses are performed using a model of the reactor core, which includes hydraulic descriptions of orifices, lower tie plates, fuel rods, fuel rod spacers, upper tie plates, the fuel channel, and core bypass flow paths. The orifice, lower tie plate, fuel rod spacers, upper tie plate, and, where applicable, holes in the lower tie plate are hydraulically represented as being separate, distinct local losses of zero thickness. The fuel channel cross-section is represented by a square section with enclosed area equal to the unrodded cross-sectional area of the actual fuel channel. The recirculation loop (flow paths 1 through 6 in FIG. 12) steady-state, thermal-hydraulic analyses are performed using a model which includes the steam separators (362), the internal jet pumps (366), and all measured coolant inflows and outflows. The cross-section of each flow path is a volume average of the variable geometry within the flow path. The total pressure drop in a flow path (core path or recirculation loop path) is the summation of pressure drops due to friction, local losses, elevation, and acceleration. Each of these pressure drop components is modeled for two-phase and single-phase flow conditions. Thermal Hydraulics Core Model Inputs There are three general types of inputs to the thermal-hydraulic model. The first type consists of fixed parameters such as core and recirculation path geometry, pressure-drop factors and core power distribution factors. The pressure-drop factors are chosen such that calculated flows in the forced-flow mode agree with measured flows in startup tests or separate component tests. The second type consists of numerical convergence parameters. These parameters are chosen on the basis of off-line model calculations on a wide variety of system conditions. The third type consists of time varying conditions such as core power, system pressure, reactor vessel inflow and outflow rates, reactor vessel inflow enthalpies, and measured downcomer level. These inputs are determined by the interpreter logic from system measurements and are updated each time the thermal-hydraulic model performs a calculation. The locations at which the model considers inflows or outflows are shown in FIG. 12. The seven possible system inflow locations are: 1. Feedwater sparger (feedwater and/or HPCI); 2. Bottom of bypass, 372, (CRD cooling flow); 3. Upper plenum, 358, (core spray); 4. Bypass, 370, (LPCI in BWR/5 or BWR/6); 5. Lower plenum, 352, (standby liquid control); 6. Recircultion line, 354, (LPCI in BWR/3 or BWR/4); 7. Top head, 376, (RCIC in BWR/6). The two possible system outflow locations are: 1. Steam line, 374, (main steam and/or safety/relief valves); 2. Recirculation line, 354, (leakage). Flow Calculation Process The flow calculation process must be iteractive since pressure drop is not a linear function of coolant flow rate. The recirculation loop analysis iteration scheme for the case in which downcomer level and core power are known is shown in FIG. 14 (blocks 400-412). The process is one of trial and error. First a total coolant flow is assumed (block 402), and the resultant pressure drops are calculated around the recirculation loop (block 404). This calculated pressure drop or rise is then applied across the reactor core and individual fuel and bypass coolant flow rates are calculated (block 406). The individual fuel channel and bypass leakage flow rate are determined such that the core plenum-to-plenum pressure drop through all parallel paths is equal to the recirculation loop pressure rise, within an allowable convergence limit. Following convergence, the total core flow (fuel channels plus bypass) is calculated by summing the component flows (block 406). This flow is then compared to the loop flow that was used to calculate the recirculation loop pressure rise (block 408). If these flows agree within an allowable convergence limit, the calculation is complete. If not, the assumed total coolant flow is incremented (block 412) and the steps 402-408 are repeated until convergence is obtained (block 408). The recirculation loop analysis iteration for the case in which total fluid mass and core power are known is shown in FIG. 15 (blocks 422-448). The iteration schemes for the two calculation models are very similar, the only difference being the outer iteration on downcomer level (block 444 of FIG. 15) for the case in which the total mass is known and the level must be calculated. The calculation of the recirculation loop pressure drop is straightforward since there are no parallel paths in the analytical model. In a natural circulation mode, the flow in the recirculation pump loop (356, FIG. 12) is assumed to the zero. In a forced flow mode, the pressure rise at the jet pump throat must be input. The calculation of the core flow (blocks 406 and 428 in FIGS. 14 and 15) is more complicated since there are many parallel paths. The individual fuel channel and bypass flow rates result in core plenum-to-plenum pressure drops through all parallel paths equal to the calculated recirculation pressure drop (within an allowable convergence limit). Fluid properties are calculated from the average flow enthalpy at the node of interest and are based on 1967 International Standard Steam-Water Properties. A void-quality relationship based on a drift flux model is used to account for vapor slip in the core, upper plenum, and steam separators. The iteration scheme used by the hydraulic model in its natural circulation mode assumes co-current up-flow in both the fuel bundles and bypass. Once the level outside the core shroud can no longer support up-flow in the bypass, the bypass flow is set to zero. This assumption should not greatly affect the calculation of core flow or downcomer level as long as the bypass remains full and without voids. The hydraulic model will continue to calculate natural circulation flow until the downcomer level can no longer support co-current up-flow in the fuel bundles and upper plenum. Beyond this point a two-phase level will exist inside the shroud and the level outside the shroud will probably be somewhere below the top of the active fuel. System natural circulation operation beyond this condition cannot be calculated by the interpreter logic hydraulic model, but once this point is reached in the transient, partial uncovery of the core is imminent and some form of operator action is required to restore system inventory. In terms of the intended use of the interpreter logic, the calculation of the level and inventory up to this point satisfies the requirements of the safety monitor, which is to assist the operator in avoiding system conditions which could yield core damage. Table 1 ______________________________________ PRIMARY OUTPUT DISPLAY Reactor Scrammed at XX:XX:XX Time to Reach Parameter Trend Value Units Limit ______________________________________ Reactor (Increasing)* XXX % rated Power Reactor XXX Inches Coolant above Level active above Core core Reactor (Increasing)* XXX Inches/ XXX min.*** Coolant min. to top of Level core Reactor XXXX Psig Pressure Reactor (Increasing)* XXX Psi*/min XXX min.*** Pressure to 1350 psia** Reactor (Increasing)* XXX, lb/hour Coolant XXX Inventory Net Change Containment (Increasing)* XX Psig/min XXX min.*** Pressure to 60 psia ##STR1## Loss of pneumatic Air For further information depress buttons X, X, X, X. ______________________________________ *Alternate display (decreasing). **1550 psia. ***Flashing signal when time is less than 20 minutes. ****Fixed point numbers (not in engineering notation). NOTE: Asterisks are for explanation and clarification and not to be displayed o the CRT. TABLE 2 ______________________________________ SECONDARY OUTPUT DISPLAY System Status Displays (Pushbuttons 1-6): Pushbutton #1. Reactor Vessel Inflow and Outflow in Ranked Order. Parameter Value Units ______________________________________ OUTFLOW: a. Main Steam Lines XX lb/sec b. Safety Relief Valve No. XX XX lb/sec c. RHR XX lb/sec d. RCIC Turbine Exhaust XX lb/sec e. RWCU XX lb/sec f. Leak Detection XX lb/sec INFLOW: a. Feedwater XX lb/sec b. HPCS XX lb/sec c. LPCS XX lb/sec d. RHR XX lb/sec e. RCIC XX lb/sec f. Standby Liquid Control XX lb/sec g. CRD Return XX lb/sec ______________________________________ Pushbutton #2. Status of Reactor Core Parameter Value Units ______________________________________ Reactor Scrammed at XX:XX:XX Hrs/Min/Sec Current Decay Heat Level XX Mwt *Current Power Level XXX Mwt Reactor Coolant Level above Core XX Inches above Active Core Reactor Pressure XXXX Psig ______________________________________ *Displayed only if reactor did not scram. This statement will replace the Decay Heat Level statement. - Pushbutton #2. System Status Statements Display ______________________________________ Averaged wide range water level is R .times. WLW inches using the following transmitter signals: B22-N026A, G25 inches (print if G30 not equal 0 and G31 not equal 0) B22-N026B, G26 inches (print if G30 not equal 0 and G32 not equal 0) B22-N026C, G27 inches (print if G31 not equal 0 and G32 not equal 0) Reactor water level is below the range of narrow range instruments. ______________________________________ Pushbutton #3. Status of Containment Parameter Value Units ______________________________________ Containment Pressure XX lb/sec Suppression Pool Water Level XXX feet Suppression Pool Water Average Temper- XXX .degree.F. ature Suppression Pool Water Peak Temperature XXX .degree.F. *Suppression Pool Water Peak Temperature XXX .degree.F./min Rate Coolant Flow into Suppression Pool XXX lb/sec Coolant Flow out of Suppression Pool XXX lb/sec *Suppression Pool Water Coolant Rate XX .degree.F./min Containment Region Hydrogen Concentration XX % Containment Region Oxygen Concentration XX % Drywell Environmental Temperature XXX .degree.F. ______________________________________ *To be displayed only when rate of change is measured. Pushbutton #3. System Status Statements Display ______________________________________ A Main Steam Line isolation signal is present. SRV A open indication by valve stem position. SRV B open indication by valve stem position. SRV C open indication by valve stem position. SRV D open indication by valve stem position. SRV E open indication by valve stem position. SRV F open indication by valve stem position. SRV G open indication by valve stem position. SRV H open indication by valve stem position. SRV J open indication by valve stem position. SRV K open indication by valve stem position. SRV L open indication by valve stem position. SRV M open indication by valve stem position. SRV N open indication by valve stem position. SRV P open indication by valve stem position. SRV R open indication by valve stem position. SRV S open indication by valve stem position. SRV U open indication by valve stem position. SRV V open indication by valve stem position. SRV A open indication by valve operator position. SRV B open indication by valve operator position. SRV C open indication by valve operator position. SRV D open indication by valve operator position. SRV E open indication by valve operator position. SRV F open indication by valve operator position. SRV G open indication by valve operator position. SRV H open indication by valve operator position. SRV J open indication by valve operator position. SRV K open indication by valve operator position. SRV L open indication by valve operator position. SRV M open indication by valve operator position. SRN N open indication by valve operator position. SRV P open indication by valve operator position. SRV R open indication by valve operator position. SRV S open indication by valve operator position. SRV U open indication by valve operator position. SRV V open indication by valve operator position. ______________________________________ Pushbutton #4. Status of Makeup Sources* WATER MAKEUP SYSTEMS-DISABLED: Feedwater HPCS LPCS RHR RCIC Standby Liquid Control Control Rod Drive Cooling WATER MAKEUP SYSTEMS-NORMAL: Feedwater HPCS LPCS RHR RCIC Standby Liquid Control Control Rod Drive Cooling SYSTEM STATUS STATEMENTS Displays ______________________________________ Valve 5-4V22 is open and feedwater is being bypassed to the condenser. SLC Pump A motor breaker disconnected. SLC Pump B motor breaker disconnected. RHR Pump A motor breaker disconnected. RHR Pump B motor breaker disconnected. RHR Pump C motor breaker disconnected. RHR Loop A: Incorrect valve lineup; pump discharge is lined up for LPCI; suction is lined up for shutdown cooling. RHR Loop B: Incorrect valve lineup; pump discharge is lined up for LPCI; suction is lined up for shutdown cooling. RHR Seawater to RHR Loop B connection valves are open, and the Loop B is lined up for flooding the reactor with seawater. Seawater injection into the reactor is (WVLC3) lb/sec. Combined seawater and suppression pool water into the reactor is (WVLC1B) lb/sec. Seawater injection rate into the reactor cannot be determined because RHR Pump B is operating and valve E12-F068B is not closed. RHR Loop A: Incorrect valve lineup; pump discharged lined up for shutdown cooling; pump suction lined up for LPCI. RHR Loop B: Incorrect valve lineup; pump discharge lined up for shutdown cooling; pump suction lined up for LPCI. RHR Loop A: Reactor water is draining to the pool through the minimum flow bypass line. RHR Loop B: Reactor water is draining to the pool through the minimum flow bypass line. RHR Loop A: Incorrect valve lineup; pump discharge lined up for head spray; pump suction lined up for LPCI. RHR Loop A: Incorrect lineup; pump discharge in lineup to the suppression pool through the heat exchanger condensing mode condensate line; pump suction is lined up for shutdown cooling; reactor coolant is flowing into the suppression pool. RHR Loop B: Incorrect lineup; pump discharge in lineup to the suppression pool through the heat exchanger condensing mode condensate line; pump suction is lined up for shutdown cooling; reactor coolant is flowing into the suppression pool. Reactor coolant is flowing to the radwaste collector tank through valves E12-F040 and E12-F049. Reactor coolant is flowing to the suppression pool through the RHR A heat exchanger vent valves. Reactor coolant is flowing to the suppression pool through the RHR B heat exchanger vent valves. RHR Loop A: Incorrect lineup; pump suction is from the reactor shutdown line; discharge is through the test line or the containment/suppression pool spray line; reactor coolant is flowing into the drywell or suppression pool. RHR Loop B: Incorrect lineup; pump suction is from the reactor shutdown line; discharge is through the test line or the containment/suppression pool spray line; reactor coolant is flowing into the drywell or suppression pool. Incorrect valve lineup; the RHR shutdown line is open and Loop A or B suction line from the suppression pool is open; reactor coolant flowing into the suppression pool. LPCS minimum flow bypass valve is open. LPCS valve lineup incorrect for injection. LPCS pump motor breaker disconnected. HPCS minimum flow bypass valve open HPCS valve lineup for injection is incorrect. HPCS pump motor breaker disconnected. There is an RCIC isolation signal. The RCIC is inoperable; check the position of valves E51-F012, E51-F022, E51-F059, E51-F068, E51-F063, and E51-F064. The RCIC turbine has been tripped by the mechanical overspeed mechanism; it must be reset locally. RWCU blowdown to main condenser, waste collector or waste surge tank is occurring. ______________________________________ *Systems will be displayed only under one heading (i.e., either Disabled or Normal), at a given point in time. Pushbutton #5. Status of Instrumentation System Status Statements Displays ______________________________________ The three methods of calculating main steam flow do not agree within K20 psi. Main steam flow is being calculated by averaging the following methods: Measured steam flow, G13 lb/sec (print if G20 not equal 0 and G22 not equal 0) Turbine first stage pressure, G15 lb/sec (print if G20 not equal 0 and G21 not equal 0) Generator output, G18 lb/sec (print if G21 not equal 0 and G22 not equal 0) Feedwater measured by nozzles in reactor feedwater line and flow measured at reactor feed pump suction lines disagree by G6 lb/sec. Both wide range level transmitter signals B22-N026A and B22-N026C do not indicate within K26 to K25 inches. A power failure may exist. Wide range level transmitter B22-N026B is being used. Narrow range and wide range water level indication differs by G54 inches. Narrow range value is being used. Reactor Water Level is below the range of narrow range instruments. Narrow range reactor water level instruments do not agree with K6 psi. Wide range and fuel zone water level indication differs by G46 inches. Wide range value is being used. Both Turbine first stage pressure and condenser pressure current input signals are less than K30 mA or greater than K31 mA. A common mode power supply failure may exist. The total steam flow signal is being used. The reactor pressure indicators do not agree within K3 psi. The reactor pressure indicators do not agree within K4 psi. Reactor pressure is being calculated by averaging the following pressure transmitter signals: B22N051A (G5 not equal 0 and G7 not equal 0) B22N051B (G5 not equal 0 and G6 not equal 0) C34N005 (G6 not equal 0 and G7 not equal 0) Both reactor pressure transmitter signals B22-N051B and C34-N005 do not indicate within K14 to K15 psig. A common power supply failure may exist. Reactor pressure transmitter B22-N051A is being used. SRV A valve stem and operator position indication disagree. SRV B valve stem and operator position indication disagree. SRV C valve stem and operator position indication disagree. SRV D valve stem and operator position indication disagree. SRV E valve stem and operator position indication disagree. SRV F valve stem and operator position indication disagree. SRV G valve stem and operator position indication disagree. SRV H valve stem and operator position indication disagree. SRV J valve stem and operator position indication disagree. SRV K valve stem and operator position indication disagree. SRV L valve stem and operator position indication disagree. SRV M valve stem and operator position indication disagree. SRV N valve stem and operator position indication disagree. SRV P valve stem and operator position indication disagree. SRV R valve stem and operator position indication disagree. SRV S valve stem and operator position indication disagree. SRV U valve stem and operator position indication disagree. SRV V valve stem and operator position indication disagree. There is a scram signal, but the APRMs selected for input to the process computer do not indicate less than 1% power. The CRD cooling flowmeter indicates flow, but the pressure control valve C12-F003 is closed. SLC measured and calculated flows disagree. HPCS measured flow and calculated flows disagree by G8 lb/sec. RHR B flowmeter does not indicate flow, but the panel indi- cating light shows RHR pump B is running. Also, pressure switch E12-N022B is indicating low dis- charge pressure. The interpreter logic is assuming the flowmeter is correct. RHR C flowmeter does not indicate flow, but the panel indi- cating light shows RHR pump C is running, Also, pressure switch E12-N022C is indicating low dis- charge pressure. The interpreter logic is assuming the flowmeter is correct. RHR A flowmeter does not indicate flow, but the panel indi- cating light shows RHR pump A is running. Also, pressure switch E12-N022A is indicating that pump discharge pressure is in the normal operating range. The interpreter logic is assuming the flow is equal to pump minimum flow of (K9) lb/sec. RHR B flowmeter does not indicate flow, but the panel indi- cating light shows RHR pump B is running. Also, pressure switch E12-N022B is indicating that pump discharge pressure is in the normal operating range. The interpreter logic is assuming the flow is equal to pump minimum flow of (K9) lb/sec. RHR C flowmeter does not indicate flow, but the panel indi- cating light shows RHR pump C is running. Also, pressure switch E12-N022C is indicating that pump discharge pressure is in the normal operating range. The interpreter logic is assuming the flow is equal to pump minimum flow of (K9) lb/sec. RHR A flowmeter indicates flow, and RHR pump A is running. However, a high or low pump discharge pressure signal from E12-N022A exists. RHR B flowmeter indicates flow, and RHR pump B is running. However, a high or low pump discharge pressure signal from E12-N022B exists. RHR C flowmeter indicates flow, and RHR pump C is running. However, a high or low pump discharge pressure signal from E12-N022C exists. RHR A flowmeter indicates flow, and E12-N022A shows pump discharge pressure to be within operating range. However, the panel indicating light does not show that RHR pump A is running. RHR B flowmeter indicates flow, and E12-N022B shows pump discharge pressure to be within operating range. However, the panel indicating light does not show that RHR pump B is running. RHR C flowmeter indicates flow, and E12-N022C shows pump discharge pressure to be within operating range. However, the panel indicating light does not show that RHR pump C is running. RHR A flowmeter indicates flow. However, pump discharge pressure is low, and the panel indicating light does not show that RHR pump A is running. The interpreter logic assumes flow is zero. RHR B flowmeter indicates flow. However, pump discharge pressure is low, and the panel indicating light does not show that RHR pump B is running. The interpreter logic assumes flow is zero. RHR C flowmeter indicates flow. However, pump discharge pressure is low, and the panel indicating light does not show that RHR pump C is running. The interpreter logic assumes flow is zero. RHR A flowmeter does not indicate flow, but the panel indi- cating light shows RHR pump A is running. Also, pressure switch E12-N022A is indicating low dis- charge pressure. the interpreter logic is assuming the flowmeter is correct. ______________________________________ Pushbutton #6. Status of Auxiliary Support System System Status Statements Displays ______________________________________ Loss of Instrument Air, A Loss of Instrument Air, B Loss of Essential Bus #1 Loss of Essential Bus #2 Loss of Essential Bus #3 Loss of DC Bus A Loss of DC Bus B Loss of Auxiliary Power Bus A Loss of Auxiliary Power Bus B RHR Seawater pump A motor breaker disconnected RHR Seawater pump B motor breaker disconnected RHR Seawater pump C motor breaker disconnected RHR Seawater pump D motor breaker disconnected ______________________________________ GRAPHICAL DISPLAYS Pushbuttons 7-11 are for the graphical trend displays. The following graphical displays are available for selection by the operator): Pushbutton #7. Reactor Coolant Level Range: 2 feet below active core to 2 feet above level 8. Time Range: 15 min., 1 hr., 2 hr., 4 hr, Different color on level trace above and below the top of active core. ______________________________________ Pushbutton #8. Reactor Pressure Range: 0 to 1400 psia Time Scale: 15 min., 1 hr., 2 hr., 4 hr. Different color on level trace above 1150 psia. Pushbutton #9. Reactor Power Range: 0 to 110% power. Time scale: 1 min., 10 min., 1 hr., 2 hr. Pushbutton #10. Containment Pressure Range: 0 to 70 psia Time Range: 15 min., 2 hr., 4 hr., 12 hr. Different color for pressure above 60 psia. Pushbutton #11. Reactor Coolant Inventory Net Flow Range: 10,000 (out)-0-10,000 (in) gpm Time Range: 15 min., 1 hr., 2 hr., 4 hr. Different colors are to be used for (in) and (out) flows. ______________________________________ TABLE 3 ______________________________________ RHR SYSTEM FLOW PATHS (VALVE LINEUPS) ______________________________________ Pump Discharge Valve Lineups Lineup 1 Around or through heat exchanger (P1) Open if valves (E12-F003 and E12-F047) are open or valve E12-F048 is not closed. Separate calculations for Loop A and Loop B. Lineup 2 LPCI (P2) Open if valves (E12-F042 and E12-092) are open and valve E12-F041 is not closed. Separate calculations for Loop A, Loop B and Loop C. Lineup 3 Shutdown Cooling (P3) Open if valve E12-F090 is open. Separate calcula- tions for Loop A and Loop B. Lineup 4 Test Line (P4) Open if valve E12-F024 is open. Calculate separately for Loop A and Loop B. Loop C - open if valve E12-F021 is open. Lineup 5 Pump Minimum Flow (P5) Open if valve E12-F064 is open. Calculate for Loop A, Loop B, and Loop C. Lineup 6 Drywell/Suppression Pool Spray (P6) Open if valves (E12-F016 and E12-F017) or valve E12-F027 are open. Calculations for Loops A and B are required. Lineup 7 Vessel Head Spray Line (Pump A Only) (P7) Open if valves E12-F023 and E51-F066 are open. Pump Suction Valve Lineups Lineup 8 From Suppression Pool (P8) Open if valve E12-F004 is open. Calculate for Loop A and Loop B. Open if valve E12-F004C is open for Loop C. Lineup 9 From Reactor (P9) Open if valves E12-F009 and E12-F091 are open. In addition, valve E12-F006A for Loop A or E12-F006B for Loop B must be open. Other Valve Lineups Lineup 10 Heat Exchanger to Suppression Pool (P10) Open if pneumatic valve F12-F065 is not closed and valve E12-F011 is open. Calculate for Loop A and Loop B. Lineup 11 Service Water Injection (P11) Open if valves E12-F093 and E12-F094 are open. (Loop B only). Lineup 12 Reactor Steam to Heat Exchanger (P12) Open if both valve E51-F063 and E51-F064 and either valves E12-F051 and E12-F052 or valve E12-F087 are not closed. Calculate for both Loop A and Loop B. Lineup 13 Loop A to Radwaste Collector Tank (P13) Open if valve E12-F039 is open and valve E12-F040 is not closed. Lineup 14 RHR Heat Exchanger Vent (P14) Open if valve E12-F073 and E12-F074 are not closed. Calculate for Loop A and Loop B. ______________________________________ NOTE: The valve designations shown in this table are for a specific plant. They are used here as an example. TABLE 4 ______________________________________ VALVE LINEUP COMBINATIONS Valve Lineup Combination Loops Description Notes ______________________________________ 1 P1 + P2 + P8 A,B,C LPCI injection Flow Measurement: FT Flow Direction: in 2 P2 + P3 + P9 A,B LPCI valving in Alarm, discharge, incorrect suction from valve reactor lineup 3 P2 + P11 B Reactor fill with Alarm water Flow Measurement: FT Flow Direction: in 4 P1 + P3 + P8 A,B LPCI injection to Alarm recirc lines Flow Measurement: FT Flow Direction: in 5 P1 + P3 + P9 A,B Shutdown cooling Flow Measurement: 0 6 P3 + P11 B Reactor fill with Alarm service water Flow Measurement: Same as Combination 3 Flow Direction: in 7 P1 + P4 + P8 A,B,C Pump test Flow Measurement: 0 8 P1 + P4 + P9 Reactor blowdown Alarm to pool Flow Measurement: FT Flow Direction: out 9 P1 + P4 + P11 B Postaccident con- Change tainment flood suppres- with service sion pool water inventory Flow Measurement: 0 10 P5 + P9 A Pump bypass open, Alarm or draining down B reactor Flow Measurement: W = f (orifice, P, T) Flow Direction: out 11 P1 + P6 + P8 A,B Containment spray Flow Measurement: FT 12 P1 + P6 + P9 A Reactor blowdown Alarm or Flow Measurement: FT B with 2 phase flow correction Flow Direction: out 13 P1 + P6 + P11 B Containment flooding Flow Measurement: Same as Combination 3 14 P1 + P7 + P8 A Reactor fill from pool Flow Measurement: FT Flow Direction: in ______________________________________ NOTE: FT = Flow transmitter. Flow Direction: In into reactor pressure vessel; Out out of reactor pressure vessel. While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. |
abstract | Disclosed herein is an articulated manipulator capable of moving a tool such as an inspection device, a processing device, or a welding device to a desired position for inspection or repair of a defect portion in a limited place. The articulated manipulator includes a base plate, a movable unit slidably coupled on the base plate, a rotatable unit rotatably coupled on the movable unit, and a rotation unit rotatably coupled to one side of the rotatable unit. |
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claims | 1. A radiation imaging apparatus comprising:a radiation detection panel configured to detect radiation irradiated by a radiation generation unit;a first member and second member arranged on a radiation-incident direction side;a third member and fourth member arranged on a side opposite to the radiation-incident direction side; anda housing containing the radiation detection panel and at least the fourth member,wherein the fourth member is configured as a base which supports the radiation detection panel, andwherein the second member is arranged between the first member and the radiation detection panel,the third member is arranged between the radiation detection panel and the fourth member and in contact with the radiation detection panel,the second member and the third member are lower in elastic modulus than the first member and the fourth member, andthe elastic modulus of the second member is lower than the elastic modulus of the third member. 2. The radiation imaging apparatus according to claim 1, wherein a plate thickness of the second member is not smaller than a plate thickness of the third member. 3. The radiation imaging apparatus according to claim 1, wherein a rigidity of the second member is lower than a rigidity of the third member. 4. The radiation imaging apparatus according to claim 1, wherein the fourth member has a rigidity higher than the rigidity of the first member. 5. The radiation imaging apparatus according to claim 1, wherein a rigidity of the radiation detection panel is lower than the rigidity of the first member and the rigidity of the fourth member. 6. The radiation imaging apparatus according to claim 1, wherein an area of each of the first member and the fourth member is not smaller than an area of the radiation detection panel when viewed from the radiation-incident direction. 7. The radiation imaging apparatus according to claim 1, wherein the radiation detection panel is constituted by integrating at least the first member, the second member, the third member, and the fourth member with the radiation detection panel. 8. The radiation imaging apparatus according to claim 1, wherein a rigidity of an integrated structure of the first member and second member arranged in the incident direction of the radiation is lower than a rigidity of an integrated structure of the third member and fourth member arranged on the side opposite to the incident direction of the radiation. 9. The radiation imaging apparatus according to claim 1, wherein the first member is part of the housing. 10. The radiation imaging apparatus according to claim 1, wherein the fourth member is a member supporting a control unit configured to process data detected by the radiation detection panel. 11. The radiation imaging apparatus according to claim 1, wherein a radiation shielding member is arranged between the fourth member and the third member. 12. The radiation imaging apparatus according to claim 11, wherein the radiation shielding member is constituted using a material containing at least one heavy metal selected from the group consisting of lead (Pb), barium (Ba), tantalum (Ta), molybdenum (Mo), and tungsten (W), or stainless steel. 13. The radiation imaging apparatus according to claim 1, wherein the second member and the third member are constituted by buffer materials. 14. The radiation imaging apparatus according to claim 1, wherein the fourth member is fastened to the housing. |
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051805456 | claims | 1. A lower end nozzle of a nuclear fuel assembly, comprising an adaptor plate (2, 2', 2") having water passage holes and a bottom face, supporting feet (3, 12, 15) and a device for the retention of particles contained in the coolant flow of the reactor, in which the retention device (6, 11, 16, 30, 46) consists of a filter plate pierced with filtration holes having a smaller size than said water passage holes and being fastened against the bottom face of the adaptor plate over a substantial part of its surface. 2. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is attached to the adaptor plate (2, 2', 2") by welding. 3. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is attached to the adaptor plate (2, 2', 2") by brazing. 4. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is attached to the adaptor plate (2, 2', 2") by riveting. 5. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is attached to the adaptor plate (2, 2', 2") by means for attaching the guide tubes of the assembly to lower end nozzle. 6. The lower end nozzle as claimed in claim 1, in which the holes of the filter plate (6, 11, 16, 30, 46) are made by cutting out from the plate. 7. The lower end nozzle as claimed in any one of claims 1 to 5, in which the holes of the filter plate (6, 11, 16, 30, 46) are made by stamping. 8. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) has apertures (36) opposite zones of connection of guide tubes of the assembly to the adaptor plate (2, 2', 2") of the lower end nozzle (1). 9. The lower end nozzle as claimed in claim 1, in which the filter plate (30) has apertures of square form (40). 10. The end nozzle as claimed in claim 1, in which the lower filter plate (46) has apertures delimited by parallel lamellae (45). 11. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) has a recessed central part (35) coming in contact with a central part of the adaptor plate (2, 2', 2"), and in which the adaptor plate (2, 2', 2") has, in this zone, holes of a dimension smaller than the size of the particles to be retained, instead of water passages of larger dimension passing through the adaptor plate (2, 2', 2") in its other parts. 12. The lower end nozzle as claimed in claim 1, in which the filter plate (11) consists of a thin plate of elastic material capable of being introduced in a deformed state between the feet (12) of the lower end nozzle (10) and then placed flat against the bottom face of the adaptor plate. 13. The lower end nozzle as claimed in claim 1, in which the filter plate (16) comprises at least two parts (16a, 16b) which are introduced separately between the feet (15) of the lower end nozzle and which are placed in abutment with one another along a connecting edge (17). 14. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is produced from a nickel alloy with structural hardening. 15. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is produced from a martensitic steel. 16. A nuclear fuel assembly having a lower filtering end nozzle as claimed in any one of claims 1 to 6. 17. a nuclear fuel assembly having guide tubes (8) with lower ends attached to a lower end nozzle (1) having openings therethrough (41) for a coolant flow and a debris filter, said filter comprising a plate (6, 11, 16, 30, 46) attached to the bottom of the adaptor plate (2, 2', 2"), said adaptor plate comprising coolant flow apertures disposed in a square array. 18. A fuel assembly comprising a lower end nozzle (1), a first set of guide tubes (8) attached to the lower end nozzle (1) and ensuring structural rigidity of the fuel assembly, a plurality of spacer grids (9) and a second set of guide tubes (8') not attached to the lower end nozzle (1), said fuel assembly having a lower filtering end nozzle as claimed in any one of claims 1 to 6. 19. The fuel assembly according to claim 18, in which the adaptor plate (2") of the lower end nozzle (1) has passing through it an aperture (18-23) aligned with each of the guide tubes (8') of the second set, in which fuel assembly the filter plate (30) id attached to the adaptor plate (2") by means of rivets (32), each engaged in an aperture (18-33) of the adaptor plate (24) and in a corresponding aperture (37) of the filter plate. |
062193996 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS A maintenance method in a nuclear power plant according to the present invention will be described hereunder by way of one preferred embodiment with reference to FIGS. 1 through 9, and it is to be noted that FIGS. 10 through 12 are referred to for a reactor primary containment vessel and the like applied in the following embodiment. FIG. 1 is a flowchart schematically showing a maintenance method in a nuclear power plant in this embodiment. As shown in FIG. 1, substances or matters floating in the water of a suppression pool 6, which are typically referred to in this art field as chalk river unclassified deposit or substance, are collected together with surrounding water so as to purify the water of the pool 6 and improve water clearness (in a step S1). When the water of the pool 6 is purified and clear enough, a diver or divers (workers) start an underwater operation or working. The underwater maintenance conducted by the divers is to collect the substances deposited on the inner bottom surface of a suppression pool wall as sludge, to decontaminate the inner surface of the suppression pool wall in the water and to clean the inner surface of the suppression pool wall (in a step S2). Further, it is to be noted that, in the disclosure of the present specification, floating substance such as chalk river unclassified deposit or substance and substance deposited on the inner bottom surface of the suppression pool are treated to be collected and removed, but in this specification, hereunder, these floating substances and deposited sludges may be handled as substances inclusively. Both the substances, i.e. floating substance and sludgesubstance, and contaminants are collected (recovered or removed) together with the surrounding water. The substances together with the surrounding water which have been collected and recovered in the operations of the steps S1 and S2 are separated into solid part and liquid part (solid-liquid separation) by means of water treatments (steps S1' and S2'), respectively. In a case where the inner surface of the suppression pool wall 6a is cleaned, a coating film applied on the inner surface of the suppression pool wall 6a is inspected underwater (in a step S3), and in this step, when a portion at which the coated film is discovered to become defective, it is repaired and coated through the underwater operation or working (in a step S4). The maintenance method in a nuclear power plant according to this embodiment will be described in detail hereunder. FIG. 2 is a schematic view for explaining the operation for collecting the floating substances in the water of the suppression pool 6 (the step S1) and the water treatment for the collecting operation (step S1'). As shown in FIG. 2, the floating substances are collected by using a suction pump 11 disposed above the suppression pool 6 and a suction member 13 connected to the suction pump 11 through a flexible hose 12 and movable in the water of the suppression pool 6. The suction member 13 is hung from the upper place into the water by using, for example, a crane, and sucks up the floating foreign matters together with the surrounding water. A water treatment apparatus 14 and a substance collecting tank 15 provided outside the pool are connected to the suction pump 11 through a collecting piping 11a. The water treatment apparatus 14 carries out the solid-liquid separation to the foreign matters and surrounding water. The substances are collected in the substance collecting tank 15 through a discharge piping 15a, whereas purified water is returned to the suppression pool 6 through a return piping 11b. Through such operation, the water of the pool can be purified and the clearness thereof can be improved. FIG. 3 is an explanatory view showing various maintenance apparatus used for the underwater maintenance in the steps S2 to S4. In case of collecting the substances deposited as sludge on the inner bottom surface of the suppression pool 6 and decontaminating the inner surface of the suppression pool wall 6a (in step S2), a rotating brush 16 is used. As will be described later in detail, the rotating brush 16 is designed so as to suck up surrounding water and is connected to the suction pump 17 disposed outside the pool. By means of the sucking action of the suction pump 17, the sludges on the inner bottom surface of the suppression pool 6, deposits and deteriorated matters on the inner surface of the suction pool wall 6a are sucked up together with the surrounding water therein. In the case of the underwater inspection of a coated film applied on the inner surface of the suppression pool wall 6a (in a step S3), an underwater light 18, a fixed camera 19, the first movable camera 20 and the second movable camera 21 are used. The underwater light 18 is attached to a helmet 23 of a diver 22 and can be switched on and off by an underwater light switch 24. By switching on the underwater light 18, light can be shed on inspection target portions. The fixed camera 19 is swingably disposed in a suppression chamber 3 and used to determine general inspection positions within the suppression pool 6. The fixed camera 19 is connected to a TV monitor 26 provided in an air part 25 (which is filled up with an air). The TV monitor 26 allows for operators to observe images from the fixed camera 19 in the air part 25. The first movable camera 20, for determining fine positions close to the inspection portions, is installed on the helmet 23 of the diver 22. The first movable camera 20 is connected to a TV monitor 27 in the air part 25 so as to observe the coated film in the air part 25. The second movable camera 21 is manually operated and carried underwater by the diver 22. The second movable camera 21 is used to observe the state of the coating film while approaching the inspection positions more closely than the first movable camera 20. The second movable camera 21 is connected to a TV monitor 28 to allow the operators to observe the state of the coated film in the air part 25. Underwater repair coating operation is conducted to the position which is discovered to be necessary to repair as a result of the underwater inspection (in a step S4). In the underwater repair coating operation, the substrate treatment for coating a portion to be repaired is first performed. In the substrate treatment, deteriorated coated film or coating or the like is ground by using either a disc sander 29 or a grinder 30 or using both of them. The disc sander 29 and the grinder 30 are designed to suck up surrounding water (as will be described later typically for the grinder 30 with reference to FIG. 6) and connected to the suction pump 17 mentioned above. With this arrangement, the substrate treatment is conducted while sucking up the deteriorated coated or coating pieces or the like together with the surrounding water out of the pool. After the substrate treatment for the repair position has been completed, the underwater coating is applied on the repair surface as underwater coating repair operation. In the coating operation, a brush 31 is used, for example. The brush 31 is designed to be capable of sucking up the surrounding water and connected to the suction pump 17. If the underwater coating is applied by means of the suction pump 17, the coating splashing in the water is sucked together with the surrounding water to thereby prevent the contamination of the water of the pool. The above-mentioned rotating brush 16, disc sander 29 and grinder 30 used in the underwater decontamination and underwater repair coating are driven by an air motor and rotated by means of air pressure supplied from a predetermined air system 32a. The diver 22 is supplied with air from an air feeding unit 34, an air storage tank 35 and a predetermined air system 32b through, for example, an air hose 33. A backup air cylinder 36 is connected to the air feeding unit 34 for use in emergency. An underwater portable cylinder may be used. In addition, the diver 22 can communicate with an operator in the air part 25 by a communication system 37. The operating steps S2 to S4 will be described hereunder in more detail. FIG. 4 concretely shows a state in which the diver 22 removes and collects the sludges deposited on the inner bottom surface of the suppression pool 6. As shown in FIG. 4, the diver 22 dives into the suppression pool 6 with the rotating brush 16 being rotated. Since the rotating brush 16 is connected to the suction pump 17 provided above the water of the suppression pool 6 through a flexible vacuum hose 38, the brush 16 is freely movable in the water. The suction pump 17, which is connected to a water treatment apparatus 40 provided on a platform 39, sucks up the sludges on the inner bottom surface of the suppression pool 6 together with the surrounding water. The collected substances and the surrounding water are subjected to the solid-liquid separation in the water treatment apparatus 40. The purified water is returned to the suppression pool 6, and the substances are collected in a substance collecting tank which is not shown. FIG. 5 is a cross-sectional view showing the rotating brush 16 in an enlarged scale. The rotating brush 16 includes a rotating brush main body 16a driven by an air motor 41. The rotating brush main body 16a is surrounded by a shield cover 43 and a shield brush 44. The air motor 41 is connected to the predetermined air system 32a through an air hose 42 as shown in FIG. 3. If the air motor 41 is driven by air supplied from the predetermined air system 32a, the rotating brush main body 16a rotates. According to the rotation of the rotating brush main body 16a, the sludges on the inner bottom surface of the suppression pool 6 can be peeled off. Further, the shield cover 43, which is connected to the suction pump 17 shown in FIG. 3 through the vacuum hose 38, sucks up the water surrounding the rotating brush main body 16a from the suction port 45 of the vacuum hose 38. That is, the shield cover 43, the shield brush 44, the vacuum hose 38 and the suction pump 17 serve as suction means 46 as a whole. The sludges peeled off by the rotation of the rotating brush main body 16a are diffused into the water once. However, the suction means 46 sucks up the floating substances and/or sludges together with the surrounding water, and accordingly, it becomes possible to remove and collect the sludges and to decontaminate the inner surface of the suppression pool wall 6a without diffusing the substances or sludges and deteriorated or affected substances into the water of the suppression pool 6. It is noted that the rotating brush 16 shown in FIG. 5 is merely one example. As long as a suction port is provided around the rotating brush main body 16a, the arrangement of the remaining constituent elements can be modified in a various manner. The underwater inspection of the coating (coated) film on the inner surface of the suppression pool wall 6a (in the step S3) will be described hereunder. In the underwater inspection, as stated above, the underwater light 18, the fixed camera 19, the first movable camera 20 and the second movable camera 21 shown in FIG. 3 are used. The underwater light is provided on the front surface of the helmet 23 which the diver 22 wears, so that the light can lights the inspection portions (portions to be inspected). The fixed camera 19 is swung by the remote control operation from the air part 25 side to catch the movement of the diver 22 in the suppression pool 6. An image (video) signal obtained by the fixed camera 19 is outputted to a TV monitor 26 provided in the air part 25, thereby allowing the operator to observe the inspection positions on the TV monitor 26 in the air part 25. The first movable camera 20, which is provided on the front surface of the helmet 23 which the diver 22 wears, can display an image of a position approaching the inspection position at a certain distance. Since the first movable camera 20 is also connected to the TV monitor 27 provided in the air part 25, it is possible to obtain detailed positional information on the moving position of the diver 22 in the air part 25 and to observe the overall images of the coating film portion at the same moving position. Moreover, the diver 22 operates the second movable camera 21 manually. The second movable camera 21 is used to observe the state of the coating film while approaching the inspection position more closely than the first movable camera 20. Since the second movable camera 21 is also connected to the TV monitor 28 provided in the air part 25, it is possible to observe the state of the coating film in the air part 25 in an extremely detailed manner. As a result, the coated film can be accurately inspected in the unit of 0.5 mm according to the present embodiment. The deterioration of the coated film can be determined from the fact that rust or blister appears on the deteriorated part. The diver 22 applies a mark on the deteriorated part of the coated film. Thus, the diver 22 can specify the repair position to be repaired and easily confirm the position in a later repair coating step. After specifying the repair position of the coated film on the inner surface of the suppression pool wall 6a in the above-stated inspection operation, the substrate treatment for the repair position is performed as the pre-treatment of underwater repair coating operation (step S4) for repairing that position. The substrate treatment in the repair coating region is performed by using the disc sander 29 or grinder 30 shown in FIG. 3. The disc sander 29 or the grinder 30 uses a steel plate which is the base material of the coated surface of the suppression chamber 3 designed to be dedicated for a coated film removal purposes, and which is not cut, and only the coated film deteriorated or deformed at the repair coating position is peeled off by using the disc sander 29 or the grinder 30. The suction pump 17 is connected to the disc sander 29 and the grinder 30, and the floating substances and/or sludges and the surrounding water are sucked up by this suction pump 17, so that substrate treatment can be performed without diffusing the substances and sludges into the water. FIG. 6 is a cross-sectional view typically showing the grinder 30 in an enlarged scale. The grinder 30 includes a grinder main body 30a driven by an air motor 41. The grinder main body 30a is surrounded by a shield cover 48 and a shield brush 49. The air motor 41 is connected to the predetermined air system 32a shown in FIG. 3 through the air hose 42. If the air motor 41 is driven by air supplied from the predetermined air system 32a, the grinder main body 30a rotates. The rotation of the grinder main body 30a allows the deteriorated or deformed coated film degenerated to be peeled off. The shield cover 48 is connected to the suction pump 17 shown in FIG. 3 through the vacuum hose 50 to suck up the water surrounding the grinder main body 30a from the suction port 51. That is, the shield cover 48, the shield brush 48, the vacuum hose 50 and the suction pump 17 serve as suction means 52 as a whole. Therefore, the deteriorated or deformed coated film which is peeled off through the rotation of the grinder main body 30a is diffused into the water once. However, the deteriorated or deformed coated film together with the surrounding water is sucked by the suction means 52. According to such manner, the substrate treatment for the repair position can be performed without diffusing the substances into the water of the suppression pool 6. It is noted that the grinder 30 shown in FIG. 6 is merely one example. As long as a suction port is provided around the grinder main body 30a, the arrangement of the remaining constituent elements may be modified. After the substrate treatment for the repair position is completed, the underwater coating operation which is the main operation for the repair coating is carried out. Although a coating material used for the underwater coating is prepared by mixing a main agent and a curing agent, an underwater coating cannot be used in general in one or two hours after mixing, so that only the quantity which can be used up in one or two hours is mixed. The resultant coating material is applied onto the repair surface by using the brush 31 shown in FIG. 3. The brush 31 which is provided with a suction unit, though not shown, having a suction port similar to the grinder and the like mentioned above for sucking the surrounding water. The suction port is connected to the suction pump 17 which sucks up the coating material diffused around the repair surface together with surrounding water, so that the repair coating operation can be carried out without diffusing the coating material into the water. If the repair coating region is small, a finger portion of a glove of the diver 22, a knife or the like may be used for such coating operation. On the contrary, if the repair coating region is wide, a coating roller which is not shown may be used for this purpose. FIG. 7 is a view for explaining the operation state of the diver 22. As shown in FIG. 7, a vent pipe 7 communicating with the dry well 2 is inserted into the suppression chamber 3. The vent pipe 7 is connected to the downcomer 8 which is opened to the water of the suppression pool 6 at the tip end portion thereof. A strainer 53 is disposed in the suppression pool 6. Further, a platform 54, a ladder 55 and a diving stage 55a are provided to the suppression chamber 3. The diver 22 dives into the suppression pool 6 from the diving stage 55a. In the example of FIG. 7, a plurality of divers 22a, 22b, 22c and 22d dive into the suppression pool 6, in which, for example, the diver 22a engages decontamination of the inner surface of the suppression pool wall 6a and the diver 22b engages the repair coating for the coating film on the inner surface of the suppression wall 6a. The diver 22c engages the closing of the strainer 53. The strainer closing operation is carried out for the inspection of the valve of a piping communicating with the outside of the pool 6 through the strainer 53 (so called, a valve in water). That is, the inspection of the valve, which is not shown, communicating with the strainer 53 can be carried out in a state in which the inflow of the water of the pool into the valve is stopped by, for example, putting a closing cover on the strainer 53 or providing a closing flange which is not shown. If the inspection of the valve is over, the closing flange is promptly detached to return the strainer 53 in operation. Thus, the inspection of the valve provided in the suppression pool 6 can be performed while the pool 6 is filled up with water. Furthermore, the diver 22d engages the inspection of the thickness of the coating film on the inner surface of the suppression pool wall 6a or that of the steel plate of the suppression pool wall 6a. The thickness of the coated film can be measured in the water using a wet film thickness measuring device which is not shown. Likewise, the thickness of the steel plate of the suppression pool wall 6a can be measured in the water using an underwater plate thickness measuring device which is not shown. The inspection of the coating thickness or steel plate thickness facilitates the checking validity or the like. Furthermore, the diver(s) 22 may perform a pad welding as repairing working to a portion of a steel plate extremely damaged in its soundness and weldings to inner structure of the suppression pool, ducts, equipments, duct supports and the like as repairing operation to defective portions or portions to be repaired. These workings are performed, after the inspection of the steel plate thickness of the suppression pool wall 6a, by using an underwater welding machine, not shown, in the underwater condition. The diver 22 may also perform the repairing working or operation for inspecting the quality of the welded portions mentioned above by using a non-destructive test apparatus in the underwater condition. Still furthermore, the diver 22 may perform a cutting working to the portions mentioned above in the underwater condition by using an underwater welding machine, not shown, as a repairing working. A series of maintenance operations stated above, as shown in FIG. 8, are desirably performed in cooperation with a plurality of divers 22 within the suppression pool 6, a diving operation supervisor 56 positioned in the air part 25, a control operator 57, an air feeding operator 58, a tender 59 and a stand-by diver 60. The diving operation supervisor 56, for instance, is a general representative for the diving operations and working and he plans and controls the diving schedule and diving operation. The control operator 57 engages the communication with the divers 22 through a communication system 37 and the recording of time. The air feeding operator 58 engages the management of the air feeding unit 34. The tender 59 supports the air hose 33 and observes the divers 22 in the suppression pool 6. The stand-by diver 60 rescues the diver(s) 22 in the suppression pool 6 in the event that any accident occurs to the diver(s) 22. In this way, the respective operators take their shares of responsibility and safe maintenance operations can be ensured. After a series of maintenance operations are over, the divers 22 are desirably decontaminated in a shower equipment 61 provided in the suppression chamber as shown in FIG. 9 for preventing the divers 22 from being exposed to radioactivity in addition to the advantageous operations in the decontaminated water of the pool. As stated above, according to this embodiment, it is possible to dispense with lots of workload, time, cost and the like which have been required for the conventional maintenance due to the need to drain off the pool and chamber, by carrying out the coating and other maintenance operations in the water of the suppression pool 6. In this embodiment, although the method of the present invention is applied to the maintenance of the suppression pool 6, the maintenance method is also applicable to the spent fuel storage pool 10. Although the above embodiment represents a case where a diver or divers carry out the operations, a diving robot equipped with the above-stated movable cameras, a mechanism hung from the upper portion of the pool or the like may perform the operations instead of the diver or divers. As mentioned hereinbefore, the present invention has excellent advantage such that much workload, time, cost and the like which have been required for the conventional method due to the need to drain off the pool and chamber can be dispensed with and maintenance can be conducted with relatively simple operation for a short time and at low cost in a state in which the suppression pool and the spent fuel storage pool are filled up with water. It is to be noted that the present invention is not limited to the described embodiment and many other changes or modifications may be made without departing from the scopes of the appended claims. |
description | This application is related to and claims priority from provisional application Ser. No. 61/227,899, filed Jul. 23, 2009, entitled “Method of Processing Steam Generator Tube Eddy Current Data”. 1. Field The invention relates generally to nuclear power plants and, more particularly, to a method of evaluating the tubes of a steam generator of a nuclear power plant. 2. Description of the Related Art Nuclear power plants are generally well known. Nuclear power plants can generally be stated as comprising a reactor that includes one or more fuel cells, a primary loop that cools the reactor, and a secondary loop that drives a steam turbine which operates an electrical generator. Such nuclear power plants typically additionally include a heat exchanger between the primary and secondary loops. The heat exchanger typically is in the form of a steam generator which comprises tubes that carry the primary coolant and a plenum that carries the secondary coolant in heat-exchange relationship with the tubes and thus with the primary coolant. As is also generally known, the tubes of a steam generator are subject to wear from mechanical vibration, corrosion, and other mechanisms. It thus is necessary to periodically inspect the tubes of a steam generator for wear in order to avoid failure of a tube which might result in nuclear contamination of the secondary loop, by way of example. While numerous methodologies have been employed for performing such inspection, such methodologies have not been without limitation. One method of inspecting the tubes of a steam generator involves the insertion of an eddy current sensor into one or more of the tubes and to receive from the eddy current sensor a signal which typically is in the form of a voltage and a phase angle. An analyst reviewing the signal data typically must possess a high degree of expertise in order to accurately ascertain from the signal data the current condition of the tubes of the steam generator. A typical steam generator might possess between three thousand and twelve thousand tubes, by way of example, with each tube being several hundred inches in length. Thus, the review of eddy current data can require the expenditure of large amounts of time by an analyst. While certain testing protocols may require the testing of fewer than all of the tubes of a steam generator, depending upon the particular protocol, the time in service, and other factors, the analysis of such data still requires significant time and expense. Among the difficulties involved in the analysis of eddy current data is the determination of whether a signal is indicative of a possible failure of a portion of a tube or whether the signal is not indicative of such a failure. Each tube of a steam generator typically has a number of bends and a number of mechanical supports. In passing an eddy current sensor through such a tube, the signal from the eddy current sensor will vary with each mechanical support and with each bend, and the signal also will vary in the presence of a flaw such as a crack or a dent in the tube. As such, the difficulty in analysis involves the ability to determine whether a change in a signal from an eddy current is indicative of a known geometric aspect of a tube such as a bend or support, in which case further analysis of the signal typically is unnecessary, or whether the change in signal from the eddy current sensor is indicative of a crack or a dent, in which case further analysis of the signal typically is necessary. Existing methodologies for analyzing tube signals have involved the use of one or more pre-established signal thresholds. However, due to the great variability of tube geometries within a given steam generator and the differing actual condition of each such tube, the use of a limited number of fixed signal thresholds to interpret eddy current signal data from the tubes still results in many portions of many tube signals exceeding the limited number of fixed signal thresholds and therefore requiring further manual examination by an analyst. It thus would be desirable to provide an improved system for assessing a current condition of the tubes of a steam generator. Accordingly, an aspect of the invention can include providing an improved system for modeling a steam generator that includes both baseline parameters of one or more regions of interest (ROIs) and that further includes exception data for individual ROIs of individual tubes based upon historic analysis of the tubes. The historic analysis of the tubes may have been conducted at the time of manufacture of the steam generator or during a prior in-service inspection. During the collection of such historic data, eddy current data for each tube of a steam generator can be collected and evaluated for quality assurance. Data for a particular ROI of a particular tube that exceeds what otherwise would be the baseline performance of the ROI can be stored as exception data. Such exception data relates to particular ROIs that have been determined to generate signal data that would exceed what would be the corresponding baseline signal parameters but that is still acceptable because it is indicative of a historic aspect of the ROI rather than being indicative of a flaw in the ROI. Once the tube data has been collected, a model of the steam generator can be created that includes both baseline performance parameters for a large variety of ROIs and that can further include the aforementioned exception data. During testing of a steam generator, a signal from an eddy current sensor is input into a location algorithm to identify an actual physical ROI of the tube under analysis and to also identify an exemplary ROI in the model of the steam generator. If the signal from the eddy current sensor with respect to the physical ROI exceeds the baseline parameters of the corresponding exemplary ROI, the need for additional analysis is triggered. Initially, the additional analysis involves accessing the exception data to determine whether exception data exists for the particular physical ROI of the particular tube that is under analysis with the eddy current sensor. If such exception data exists, the historic exception data is compared with the current signal of the physical ROI from the eddy current sensor, and the need for still further analysis is triggered only if the current signal exceeds the historic exception data by a predetermined threshold. Also, if no corresponding exception data exists for the current physical ROI, the need for further analysis is likewise triggered. However, if the eddy current sensor data for a given ROI does not exceed the baseline parameters of the corresponding exemplary ROI from the model, or if the signal from the given physical ROI fails to exceed the exception data for that ROI by a predetermined threshold, no action is taken as to that particular ROI, meaning that the ROI is considered to PASS, and no further evaluation by an analyst is required. The collection of data can additionally involve the collection and storage of data for each tube at its transition with a tube sheet, both at the hot leg and the cold leg of the tube. Due to the thickness of the tube sheet in relation to the thicknesses of the tubes themselves and the other support structures, baseline signals cannot be reliably established for all tube sheet transitions. As such, tube sheet transition eddy current data is collected and stored for each leg of each tube of a steam generator at the time of manufacture or at an in-service inspection. During subsequent testing of the steam generator tubes, the historic signal from any given tube sheet transition can be compared with and effectively subtracted from the current signal from the same tube sheet transition in order to generate a new signal that is indicative of a change in the tube sheet transition and that is generally free of historic signal artifacts. The resultant signal can then be amplified in order to magnify the change in condition of the tube for simplified evaluation by an analyst or otherwise. Accordingly, an aspect of the invention is to provide one or more improved methodologies that reduce the effort required to analyze the tubes of a steam generator of a nuclear power plant. Another aspect of the invention is to provide a system that improves the accuracy of evaluating the current condition of the tubes of a steam generator of a nuclear power plant by requiring less manual evaluation by an analyst, thereby avoiding fatigue of the analyst and improved overall results with respect to ROIs that are in genuine need of evaluation by an analyst. These and other aspects of the invention can be generally described as relating to an improved method of non-destructively assessing a current condition of a number of tubes of a steam generator of a nuclear power plant, the general nature of which can be stated as comprising collecting at a first time a historic data set for each of at least some of the number of tubes, collecting at a second time a current data set for each of at least some of the number of tubes, and employing at least a portion of the historic data set together with a corresponding at least portion of the current data set to generate another data set representative of a change in condition of a tube of the number of tubes between the first time and the second time. Similar numerals refer to similar parts throughout the specification. Improved methods in accordance with the invention are depicted in general terms in FIGS. 1-3. The methods generally all relate to nuclear power plants and, more particularly, the inspection of tubes of a steam generator of a nuclear power plant. The various methodologies discussed herein can be employed in whole or in part in any combination without departing from the present concept. Certain aspects of the methodologies employed herein involve the collection of data with the use of an eddy current sensor that is received within the interior of an elongated tube of a steam generator and that is passed through the interior of the tube along the longitudinal extent thereof. Longitudinal movement of the sensor can be performed manually, although it can also advantageously be performed by a robotically-controlled advancement mechanism that advances the eddy current sensor at a controlled rate and that is capable of providing a data stream component representative of the longitudinal distance of the eddy current sensor along the tube at any given time. Other data streams from the eddy current sensor typically comprise a voltage component that characterizes an amplitude and another component that characterizes a phase angle. Although many methodologies can be employed for the storage and analysis of such data streams, one methodology involves the storage of voltage and phase data at given points along the longitudinal length of a tube. Typically, thirty data points per inch are collected and stored, but other data distributions and densities can be employed without departing from the present concept. As is generally understood, a typical steam generator includes a plenum that encloses perhaps four thousand to twelve thousand individual tubes that each comprise a hot leg and a cold leg that pass through a tube sheet, which is itself a slab of metal that is typically twenty or more inches thick. Each tube may be several hundred inches long and have either a single U-bend or a pair of elbow bends, although other geometries can be employed without departing from the present concept. Each such tube typically additionally includes twenty to thirty physical supports of differing geometries. During initial manufacture, the hot and cold legs of each tube are assembled to the tube sheet by receiving the two ends of the tube in a pair of holes drilled through the tube sheet and by hydraulically bulging the ends of the tube into engagement with the cylindrical walls of the drilled holes. While the geometry of each tube of a steam generator typically is different from nearly every other tube of the steam generator, the overall construction of the steam generator enables generalizations to be made with regard to the geometry of the tubes as a whole. That is, each tube can be said to include a pair of tube sheet transitions at the ends thereof which typically are characterized by an eddy current sensor voltage on the order of thirty (30.0) volts. Between the two tube sheet transitions are various straight runs, supports, and bends. The typical eddy current voltage for a straight section of tube is 0.05 volts, and the typical voltage for a bend of a tube is 0.1 volts. A typical voltage for a support may be 0.2 volts, but various types of supports can exist within a given steam generator, all of which may produce different characteristic voltages. Advantageously, however, the various arrangements of straight sections, supports, and bends as a function of distance along a tube are of a limited number of permutations within any given steam generator. As such, a location algorithm is advantageously developed from the known geometry of the steam generator and the historic data that can be collected from the steam generator, wherein an input to the algorithm of a series of voltage and distance values can identify a particular region of interest (ROI) of a tube that is under analysis. That is, the wear that is experienced by a tube often can occur at a tube sheet transition, at a location of attachment of a tube to a mechanical support, at a transition between a straight section and a bend in a tube, or at other well understood locations. The various segments of a given tube can be divided into various regions of interest (ROIs) which can be identified during data collection with a high degree of accuracy based upon the details of the steam generator geometry that are incorporated into the location algorithm. As such, by inputting voltage, phase, and distance data into the location algorithm, the location algorithm can identify a specific segment and thus physical ROI of the tube being analyzed. The invention can also be said to include the development of a model for the steam generator that includes baseline parameters such as voltage and phase for each of a plurality of exemplary ROIs that exist in the particular steam generator. Advantageously, and as will be set forth in greater detail below, the model additionally includes exception data for particular ROIs of particular tubes that have voltage and/or phase angle parameters that would exceed the baseline parameters of the corresponding ROI of the model but that are nevertheless acceptable, i.e., the signals from such ROIs are not themselves indicative of flaws that require further evaluation by an analyst. The baseline parameters for the various exemplary ROIs of the model can be established in any of a variety of ways. In the exemplary embodiment described herein, the various baseline parameters for the various exemplary ROIs of the model are established based upon theoretical evaluation of tubes and their ROIs, as well as experimental data based upon eddy current analysis of actual tubes and their physical ROIs. The direct physical analysis of tubes such as through the collection of eddy current data of individual tubes of a steam generator advantageously enables the collection of data with respect to typical ROIs that can be employed in establishing baseline parameters for exemplary ROIs of the model. Such direct physical analysis of tubes can additionally be employed to collect data that is later stored as exception data for particular ROIs of particular tubes. Additionally and advantageously, such direct collection of eddy current data during the initial manufacture of a steam generator can enable an initial evaluation of each tube to assess whether the tube should be rejected or whether the data appears to be unreliable and should be recollected. A tube may be rejected if the data suggests that it is defective in manufacture. On the other hand, the data may need to be recollected if it appears that the eddy current sensor was functioning improperly or if other data collection aspects appear to be erroneous or unreliable. FIG. 1 generally depicts an exemplary methodology for the collection of tube data which enables the development of a model of a steam generator and the development of a location algorithm that is based upon the geometry of the steam generator. Processing begins, as at 104, where eddy current data is collected for a given tube of the steam generator. As mentioned elsewhere herein, the data stream typically will include components of voltage, phase, and distance, all of which can be detected as a continuous signal or as a discrete set of data points along the length of the tube. The insertion of the eddy current sensor into the tube and the longitudinal progression of the eddy current sensor along its longitudinal length can be performed manually or can advantageously be performed by a specially configured robot. Processing continues, as at 108, where it is determined whether the data derived from the eddy current sensor signal is potentially unreliable. For instance, if the data suggests a possible data collection error, processing continues as at 112, where the tube data is rejected, and the tube is retested. Processing thereafter would continue, as at 104. However, if at 108 the data is not determined to be unreliable, processing continues, as at 116, where it is determined whether the tube data derived from the eddy current signal exceeds an acceptance threshold, such as would indicate that the tube itself is mechanically or otherwise defective. In the event that the data exceeds an acceptance threshold, the tube is rejected, as at 120. If the tube data does not exceed the acceptance threshold at 116, processing continues, as at 124, where it is determined whether any portions of the tube data exceed what should theoretically be the baseline parameters of that portion of the tube, i.e., the baseline parameters for the corresponding exemplary ROI of the model of the steam generator. By way of example, it may be determined that the physical ROI of the tube that is under analysis includes a physical support and the eddy current sensor is indicating a voltage of 0.4 volts. While an analyst may determine that the voltage that would typically be expected for such an ROI is 0.2 volts, the analyst may nevertheless determine that the particular physical ROI is acceptable and that the voltage of 0.4 volts is an acceptable anomaly. In such a circumstance, the data for the particular ROI for this particular tube will be saved, as at 132, as a portion of an exception data set. In this regard, it is reiterated that the tube or its data would already have been rejected, as at 112 or 120 respectively, if the data for the aforementioned ROI suggested that the ROI would be unacceptable. Processing continues from both 124 and 132 onward to 128 where the tube data is stored in a data set. It is then determined, as at 136, whether further tubes require eddy current analysis as set forth above. If further tubes await testing, processing continues, as at 104, with a new tube. Otherwise, processing continues, as at 140, where the model of the steam generator is developed with a set of baseline parameters for each of a plurality of exemplary ROIs. The model further includes the aforementioned exception data for one or more particular ROIs of one or more particular tubes. It is understood that the inclusion as at 140 of the development of the steam generator model at this particular location within the exemplary methodology is intended to be merely an example of a point at which a model of the steam generator can be developed. It is understood that with analytical methods, at least an initial model of the steam generator can be developed, with the experimental collection of tube data from 104 through 132 being supplied to the model to provide refinement of the model and to provide exception data. It thus is understood that the model of the steam generator can be developed in whole or in part at any time depending upon the data and the analysis that are available. Processing continues to 144 where the location algorithm which identifies various ROIs can be developed based upon the geometry of the steam generator and other factors. As was mentioned elsewhere herein with respect to the development of the model of the steam generator, the location algorithm can likewise be developed in whole or in part at any time depending upon the analytical and experimental data that is available in the development process depicted generally in FIG. 1. When completed, the location algorithm advantageously can receive a data stream from an eddy current sensor within the tube of the steam generator and can employ the voltage, phase, and distance data components to identify any of a variety of exemplary ROIs that are stored within the model of the steam generator. That is, the location algorithm can employ the eddy current signal within a tube of the steam generator to identify a particular segment of the tube and thus a physical ROI of the tube, and the location algorithm can additionally identify from the model that was developed of the steam generator a corresponding exemplary ROI and its baseline parameters for comparison with the eddy current signal that is being collected from the physical ROI. The testing of the tubes of a steam generator is depicted in an exemplary fashion in FIG. 2. It is understood that the operations depicted generally in FIG. 1 typically will occur at a first time and will be in the nature of a historic data set. The operations occurring in FIG. 2 typically occur at a second, subsequent time and may more likely be directed toward current or present testing of a steam generator. Processing begins, as at 204, where a signal is extracted from a tube of the steam generator. The signal from the eddy current sensor is processed with the aforementioned location algorithm, as at 208, to determine the physical ROI that is the source of the signal that is being collected from the tube under analysis. The location algorithm then employs, as at 212, the signal from the eddy current sensor to retrieve from the model an exemplary ROI that is determined to correspond with the physical ROI that has been located by the location algorithm. It is then determined, as at 216, whether the signal data for the physical ROI exceeds the baseline parameters of the exemplary ROI from the model that was identified and retrieved at 212. If it is determined at 216 that the eddy current signal for the physical ROI does not exceed the baseline parameters of the exemplary ROI, processing will continue, as at 220, where no further action will be taken with respect to this particular physical ROI. That is, no additional analysis will be triggered for this particular physical ROI, thereby avoiding the need for an analyst to perform any evaluation with respect to this physical ROI. It is then determined, as at 224, whether the end of the tube under analysis has been reached. If so, the analysis of the current tube ends, as at 228. Another tube can then be analyzed. However, if the end of the tube is determined at 224 to not be reached, processing continues, as at 204, where the eddy current signal is continued to be extracted from the tube under analysis. The aforementioned baseline parameters of the various exemplary ROIs of the model can be developed in any of a variety of fashions. Most typically, the baseline parameters will be developed with the use of theoretical data and experimental data, as suggested above. For instance, the typical eddy current voltage that one might expect to detect from a straight section of a tube is 0.05 volts, and the data collection effort depicted generally in FIG. 1 might demonstrate, by way of example, that the tested voltage values for each straight segment of each tube is 0.08 volts or less. As such, the baseline voltage for an exemplary ROI that corresponds with a straight section of a tube might be established 0.1 volts. This would enable all physical ROIs that are straight sections of tubes to, in their original condition, not exceed the baseline parameter of 0.1 volts and thus not trigger the need for further analysis, as at 220. Similarly, the typical eddy current sensor voltage that one might expect from a curved section of a tube is 0.1 volts, and the baseline parameter for experimental ROIs of bend segments of each tube might be established at 0.2 volts. Physical supports typically generate an eddy current voltage of 0.2 volts, so the baseline parameter for a physical support ROI might be established at 0.3 volts. Such baseline parameters typically will be based upon the various specifications of the steam generator and the nuclear power plant, along with theoretical and experimental data regarding the steam generator. It is understood, however, that the baseline parameters typically will be selected such that an eddy current sensor signal that exceeds a baseline parameter is worthy of further evaluation by an analyst, assuming that applicable exception data for the particular physical ROI does not already exist in the model. That is, the baseline parameters desirably will be selected such that no further action is triggered when the eddy current sensor signals are below that which should reasonably trigger further analysis of the particular physical ROI. It is understood, however, that various methodologies may be employed for establishing the baseline parameters of the exemplary ROIs without departing from the present concept. It is also noted that the baseline parameters can include voltages, phase angles, pattern data, and any other type of characterization of an exemplary ROI that may be appropriate. The degree of sophistication of the baseline parameters is limited only by the ability to collect and analyze data regarding the tubes. As such, the baseline parameters of an exemplary ROI can be determined to be exceeded if any one or more of the various parameters in any combination are exceeded by a signal without limitation. Additionally or alternatively, the baseline parameters could have an even greater degree of sophistication wherein certain combinations of parameters need to be exceeded in a certain fashion for the system to trigger the need for further analysis, by way of example. On the other hand, if it is determined, as at 216, that the signal for the physical ROI exceeds in some fashion the baseline parameters of the identified corresponding exemplary ROI, processing continues, as at 230, where it is determined whether exception data exists for the physical ROI that is under analysis. As mentioned elsewhere herein, the exception data advantageously will be a part of the model of the steam generator. If such exception data is determined at 230 to exist, processing continues, as at 234, where it is determined whether the signal from the physical ROI exceeds the exception data by a predetermined threshold. That is, it is not expected that the physical ROI that is the subject of the exception data will remain unchanged during the life of the steam generator, and rather it is expected that the physical ROI might degrade over time due to wear, corrosion, etc. Since the physical ROI has already been determined at the time of taking the historic data set to have a signal which exceeds the baseline parameters that would otherwise be expected from a similar ROI, the threshold that is already built into the baseline parameters is unlikely to be useful in evaluating the particular physical ROI that is the subject of the retrieved exception data. As such, a separate threshold is established based upon various factors which, if exceeded by the present signal from the physical ROI, will trigger further analysis as at 238, of this particular physical ROI. Such further analysis likely will be manual evaluation by an analyst. On the other hand, if it is determined at 234 that the signal from the physical ROI fails to exceed the retrieved exception data by the predetermined threshold, processing continues, as at 220, where no further action is taken for this particular physical ROI. Further evaluation by an analyst is also triggered, as at 238, if it is determined, as at 230, that no exception data exists for this particular physical ROI. It is noted that an additional notification can be triggered if the baseline parameters of the exemplary ROI are exceeded by a significant amount, or if the predetermined threshold for the exception data is exceeded by a significant amount, in order to alert an analyst that an increased level of attention should be directed to a particular physical ROI, for example. In the exemplary embodiment depicted herein, for instance, further analysis is triggered if either the baseline parameters of the exemplary ROI or the predetermined threshold of the exception data is exceeded in any fashion. However, an additional notification can be generated if the signal exceeds the baseline parameters or the predetermined threshold of the exception data by 25%, by way of example. It is understood that any type of criteria can be employed to trigger such heightened further analysis. It therefore can be seen that the eddy current data that is collected from a tube under analysis is evaluated using the model that includes exemplary ROIs with baseline performance parameters and further includes exception data for ROIs of particular tubes, with the result being the triggering of further analysis such as evaluation by an analyst only in specific predefined circumstances such as would occur at 238. As such, the manual evaluation effort that is required of an analyst using the exemplary methods set forth herein is greatly reduced compared with known methodologies. It is noted that the exemplary method depicted generally in FIG. 2 envisions a real-time automated analysis system wherein a signal that is collected from a tube is input directly into the location algorithm and is evaluated as it is collected. It is understood, however, that different methodologies may be employed. For instance, the data from one or more tubes can be collected and stored and then evaluated as a whole rather than being analyzed on a real-time basis. Other variations can be envisioned that are within the scope of the present concept. Due to the thickness of the tube sheet, as mentioned elsewhere herein, the eddy current data that is collected from a tube in the tube sheet transition region typically is of a voltage far in excess of any of the baseline parameters of any of the exemplary ROIs. Moreover, the variation in eddy current voltage from one tube sheet transition to another is also far in excess of any baseline parameter of an exemplary ROI. For instance, and has been mentioned elsewhere herein, the eddy current voltage for a tube sheet transition might be on the order of thirty (30.0) volts. The eddy current voltage of another tube sheet transition might be 25.0 volts, and that of another tube might be 35.0 volts. Since the eddy current voltages at tube sheet transitions are one or more orders of magnitude greater than any voltage that would be generated in other portions of the tube, i.e., portions other than the tube sheet transition, an improved method is depicted in FIG. 3 and is described herein for facilitating the analysis of signals collected from tube sheet transitions of a steam generator that is undergoing analysis. In general terms, it is understood that the eddy current signals from tubes in the tube sheet transition area of a steam generator are of a voltage that is sufficiently high that the portion of the eddy current signal which might indicate a possible flaw, i.e., the signal of interest, which might be on the order of 0.1 volts, is far too small in comparison with the overall eddy current signal to be easily detected or evaluated. As such, another aspect of the invention is to collect historic tube sheet transition signal data for each tube of a steam generator, as at 304, and employ the historic tube sheet transition data for use at a later time in comparison with tubes of a steam generator that is under analysis after a period of use. Advantageously, the historic data shares certain aspects with currently collected data, and the method advantageously suppresses from the current signal any aspects that were also present in the historic tube sheet transition data in order to generate an improved simpler signal that is indicative of a change in condition of the tube sheet transition area of a tube under analysis. The historic tube sheet transition signal data can be taken at the time of manufacture of the steam generator or can be taken at a later time, such as during an in-service inspection of a steam generator. The historic tube sheet transition signal data that is collected at 304 during manufacture or in-service inspection of a steam generator is then stored for future retrieval and comparison with subsequently collected data during a current testing operation. That is, current tube sheet transition signal data is collected, as at 308, for a given tube of a steam generator. The historic tube sheet transition data for the same tube is retrieved. It is typically the case that some type of scaling with respect to either the current data or the historic data will occur, as at 312, to permit comparison. By way of example, it may be necessary to reduce or increase or otherwise manipulate all of the values of either the current or historic data sets since different eddy current sensors or other instrumentation were employed to take both sets of data or because of other differing operating parameters between the eddy current sensors employed to take the historic and the current tube sheet transition data. Other types of scaling may be necessary if the data points of the historic tube sheet transition data do not match perfectly with the data points of the current tube sheet transition data. As mentioned elsewhere herein, data may be taken at thirty locations per inch, although forty-five locations per inch may likewise be employed, as can other data signal densities. Still other scaling may be required if the direction of movement of the eddy current sensor is different between the historic data and the current data. For example, the historic data may have been based upon longitudinal movement of an eddy current sensor in a direction from the tube sheet toward the tube sheet transition, whereas the current data may involve an eddy current sensor that is moving in a direction from the tube sheet transition toward the tube sheet. In such a situation, the relevant portion of the historic data or the current data must be reversed, as at 314. Regardless of the nature of the historic and current tube sheet transition data, scaling or other mathematical manipulations may be performed at 312 and 314 to permit comparison between the two. The current tube sheet transition data and the historic tube sheet transition data, as may be scaled at 312, are then employed to generate a new signal, as at 316. The new signal is simpler than either the historic or the current tube sheet transition data signals since the historic aspects of the data, as are indicated with the historic tube sheet transition data, are suppressed from the currently collected data signal. The new signal is representative of the change in condition of the tube sheet transition that is under analysis between the time at which the historic tube sheet data transition was collected, such as at the time of manufacture or during an in-service inspection, and the time at which the current tube sheet transition data has been collected. Moreover, it may be desirable to amplify, as at 320, one or more portions of the new signal that is generated, as at 316. Such an amplified signal would emphasize those aspects of the new signal that would be even more indicative of a change in the condition of the tube sheet transition between the time the historic data was collected and the time that the current data is collected. The amplified signal is then submitted, as at 324, for analysis. Such analysis might be performed automatically or may be performed manually by an analyst. It is then determined, as at 328, whether any additional tubes of the steam generator require analysis with respect to their tube sheet transition region. If further tubes require analysis, processing continues, as at 308. Otherwise, processing ends, as at 330. In this regard, it is understood that the aforementioned tube sheet transition analysis can be performed as a part of the analysis depicted generally in FIG. 2 or can be performed separately. In this regard, the historic tube sheet transition data that was collected at 304 potentially can be saved as part of the model of the steam generator, particularly as a special part of the exception data set. As such, it may be possible to completely analyze a tube from one tube sheet transition through its longitudinal extent and to its opposite tube sheet transition using the teachings herein. As mentioned elsewhere herein, however, it is possible to analyze the tube sheet transitions separately from the other portions of the tubes, as may be desired. It is also noted that the teachings employed herein can be applied in a cumulative fashion to permit multiple sets of historic data to be compared with current data. That is, historic data can be taken at a first time, such as at the time of manufacture of a steam generator or at an in-service inspection, and such historic data can be employed during a subsequent evaluation of the steam generator tubes. The data that is developed during such a subsequent evaluation may then be stored as a second historic data set. Both historic data sets can then be compared with data that is collected during a further inspection of the steam generator to enable the change in the condition of various tubes to be charted as a function of time over the course of several inspections that occur at several different times. Other uses of the data can be envisioned. It is understood that the analysis described herein can be performed on a digital computer or other processor of a type that is generally known. For instance, such a computer might include a processor and a memory, with the memory having stored therein one or more routines which can be executed on the processor. The memory can be any of a wide variety of machine readable storage media such as RAM, ROM, EPROM, EEPROM, FLASH, and the like without limitation. The signal from the eddy current sensor might be received by an analog-to-digital converter which provides a digital input to the computer for processing and storage of the signals. The historic and current data can be stored on any such storage media and can potentially be transported or transmitted for use on other computers or processors as needed. The present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope. |
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abstract | The present invention relates to a fuel rod for a nuclear plant and a plenum spring arranged to be provided in a fuel rod. The fuel rod (1) comprises a cladding tube (2) sealed at its ends by end plugs (3, 4), a plurality of fuel pellets (5) stacked on each other inside the cladding tube (2) such that they form a column of pellets and said plenum spring (6) arranged to hold with a spring force the column of pellets against the lower second end of the cladding tube (2) during operation. The plenum spring (6) comprises a first length variable part (8) which abuts the uppermost located fuel pellet (5) in the column of pellets with an end portion (9), a second part (10) which allows engagement of the plenum spring (6) against an inner surface of the cladding tube (2) by a radially outwardly directed pressure and a third part (11) which allows releasing of the second part (10) of the plenum spring (6) in the cladding tube (2) during operation of the nuclear plant. |
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046577335 | claims | 1. A nuclear fuel assembly for use in upright position, comprising: (a) a bundle of vertical fuel rods distributed in a regular array and each having a closure plug at the lower end thereof; (b) a structure having (c) an attachment plate secured against an upper surface of said lower end plate, formed with individual flow openings in alignment with said fuel rods, having a circular cross-section corresponding to that of said fuel rods and formed with a plurality of parallel downwardly facing grooves each corresponding to a row of said rods in said bundle and each communicating with a plurality of said openings; (d) wherein each of said closure plugs is formed with axially extending recesses defining at least three branches distributed angularly at equal intervals, and each of said branches has a lower radially outwardly projecting extension having a height corresponding to the depth of said grooves and projecting from the cross section of said plug by an amount proportioned to the width of said grooves for preventing rotation of said plugs in said grooves. 2. The fuel assembly as claimed in claim 1, wherein the attachment plate (14) is fixed on the end plate (6) through the intermediary of threaded hollow bushes (16) which are positioned inside openings (17) penetrating the end plate (6), are screwed into tapped holes in the plate (14) and which comprise a deformable skirt (16c) for its locking in rotation by deformation of the skirt in grooves provided in the end plate (6). 3. The fuel assembly as claimed in either of claims 1 or 2, wherein the fuel rods (1) comprise, above the lower plug (2) and below the upper plug (3), respectively, fertile material in two zones (1a) and (1b) of a small thickness relative to the length of the rod. 4. The fuel assembly as claimed in any one of claims 1 or 2, wherein the spacer grids (5) comprise only lateral protuberances or small bosses for the transversal holding of the rods (1). 5. A nuclear fuel assembly as claimed in claim 1, wherein each of said plugs has three branches and each of said grooves is laterally offset with respect to the associated row of said fuel rods. 6. A nuclear fuel assembly as claimed in claim 1, wherein the depth of each of said recesses, increases downwardly and each of said recesses extends above said attachment plate. |
description | The disclosure herein relates to X-ray detectors, particularly relates to semiconductor X-ray detectors. X-ray detectors may be devices used to measure the flux, spatial distribution, spectrum or other properties of X-rays. X-ray detectors may be used for many applications. One important application is imaging. X-ray imaging is a radiography technique and can be used to reveal the internal structure of a non-uniformly composed and opaque object such as the human body. Early X-ray detectors for imaging include photographic plates and photographic films. A photographic plate may be a glass plate with a coating of light-sensitive emulsion. Although photographic plates were replaced by photographic films, they may still be used in special situations due to the superior quality they offer and their extreme stability. A photographic film may be a plastic film (e.g., a strip or sheet) with a coating of light-sensitive emulsion. In the 1980s, photostimulable phosphor plates (PSP plates) became available. A PSP plate may contain a phosphor material with color centers in its lattice. When the PSP plate is exposed to X-ray, electrons excited by X-ray are trapped in the color centers until they are stimulated by a laser beam scanning over the plate surface. As the plate is scanned by laser, trapped excited electrons give off light, which is collected by a photomultiplier tube. The collected light is converted into a digital image. In contrast to photographic plates and photographic films, PSP plates can be reused. Another kind of X-ray detectors are X-ray image intensifiers. Components of an X-ray image intensifier are usually sealed in a vacuum. In contrast to photographic plates, photographic films, and PSP plates, X-ray image intensifiers may produce real-time images, i.e., do not require post-exposure processing to produce images. X-ray first hits an input phosphor (e.g., cesium iodide) and is converted to visible light. The visible light then hits a photocathode (e.g., a thin metal layer containing cesium and antimony compounds) and causes emission of electrons. The number of emitted electrons is proportional to the intensity of the incident X-ray. The emitted electrons are projected, through electron optics, onto an output phosphor and cause the output phosphor to produce a visible-light image. Scintillators operate somewhat similarly to X-ray image intensifiers in that scintillators (e.g., sodium iodide) absorb X-ray and emit visible light, which can then be detected by a suitable image sensor for visible light. In scintillators, the visible light spreads and scatters in all directions and thus reduces spatial resolution. Reducing the scintillator thickness helps to improve the spatial resolution but also reduces absorption of X-ray. A scintillator thus has to strike a compromise between absorption efficiency and resolution. Semiconductor X-ray detectors largely overcome this problem by direct conversion of X-ray into electric signals. A semiconductor X-ray detector may include a semiconductor layer that absorbs X-ray in wavelengths of interest. When an X-ray photon is absorbed in the semiconductor layer, multiple charge carriers (e.g., electrons and holes) are generated and swept under an electric field towards electrical contacts on the semiconductor layer. Cumbersome heat management required in currently available semiconductor X-ray detectors (e.g., Medipix) can make a detector with a large area and a large number of pixels difficult or impossible to produce. Disclosed herein is an apparatus suitable for detecting x-ray, comprising: an X-ray absorption layer comprising an electrode; a first voltage comparator configured to compare a voltage of the electrode to a first threshold; a second voltage comparator configured to compare the voltage to a second threshold; a counter configured to register a number of X-ray photons absorbed by the X-ray absorption layer; a controller; wherein the controller is configured to start a time delay from a time at which the first voltage comparator determines that an absolute value of the voltage equals or exceeds an absolute value of the first threshold; wherein the controller is configured to activate the second voltage comparator during (including the beginning and the expiration) the time delay; wherein the controller is configured to cause the number registered by the counter to increase by one, if the second voltage comparator determines that an absolute value of the voltage equals or exceeds an absolute value of the second threshold. The first voltage comparator and the second voltage comparator may be the same component. When a voltage comparator determines whether an absolute value of a voltage equals or exceeds an absolute value of a threshold, the voltage comparator does not necessarily compare the absolute values. Instead, when the voltage and the threshold are both negative, the voltage comparator may compare the actual values of the voltage and the threshold; when the voltage is equally or more negative than the threshold, the absolute value of voltage equals or exceeds the absolute value of the threshold. According to an embodiment, the apparatus further comprises a capacitor module electrically connected to the electrode, wherein the capacitor module is configured to collect charge carriers from the electrode. According to an embodiment, the controller is configured to activate the second voltage comparator at a beginning or expiration of the time delay. According to an embodiment, the controller is configured to deactivate the first voltage comparator at the beginning of, or during the time delay. According to an embodiment, the controller is configured to deactivate the second voltage comparator at the expiration of the time delay or at the time when the second voltage comparator determines that the absolute value of the voltage equals or exceeds the absolute value of the second threshold. According to an embodiment, the apparatus further comprises a voltmeter and the controller is configured to cause the voltmeter to measure the voltage upon expiration of the time delay. According to an embodiment, the controller is configured to determine an X-ray photon energy based on a value of the voltage measured upon expiration of the time delay. According to an embodiment, the controller is configured to connect the electrode to an electrical ground. The electrical ground may be a virtual ground. A virtual ground (also known as a “virtual earth”) is a node of a circuit that is maintained at a steady reference potential, without being connected directly to the reference potential. According to an embodiment, a rate of change of the voltage is substantially zero at expiration of the time delay. According to an embodiment, a rate of change of the voltage is substantially non-zero at expiration of the time delay. According to an embodiment, the X-ray absorption layer comprises a diode. According to an embodiment, the X-ray absorption layer comprises silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. According to an embodiment, the apparatus does not comprise a scintillator. According to an embodiment, the apparatus comprises an array of pixels. Disclosed herein is a system comprising the apparatus described above and an X-ray source, wherein the system is configured to perform X-ray radiography on human chest or abdomen. According to an embodiment, the system comprises the apparatus described above and an X-ray source, wherein the system is configured to perform X-ray radiography on human mouth. Disclosed herein is a cargo scanning or non-intrusive inspection (NII) system, comprising the apparatus described above and an X-ray source, wherein the cargo scanning or non-intrusive inspection (NII) system is configured to form an image using backscattered X-ray. Disclosed herein is a cargo scanning or non-intrusive inspection (NII) system, comprising the apparatus described above and an X-ray source, wherein the cargo scanning or non-intrusive inspection (NII) system is configured to form an image using X-ray transmitted through an object inspected. Disclosed herein is a full-body scanner system comprising the apparatus described above and an X-ray source. Disclosed herein is an X-ray computed tomography (X-ray CT) system comprising the apparatus described above and an X-ray source. Disclosed herein is an electron microscope comprising the apparatus described above, an electron source and an electronic optical system. Disclosed herein is a system comprising the apparatus described above, wherein the system is an X-ray telescope, or an X-ray microscopy, or wherein the system is configured to perform mammography, industrial defect detection, microradiography, casting inspection, weld inspection, or digital subtraction angiography. Disclosed herein is a method comprising: starting a time delay from a time at which an absolute value of a voltage of an electrode of an X-ray absorption layer equals or exceeds an absolute value of a first threshold; activating a second circuit during (including the beginning and expiration of) the time delay; if an absolute value of the voltage equals or exceeds an absolute value of a second threshold, increasing a count of X-ray photon incident on the X-ray absorption layer by one. According to an embodiment, the method further comprises connecting the electrode to an electrical ground. According to an embodiment, the method further comprises measuring the voltage upon expiration of the time delay. According to an embodiment, the method further comprises determining an X-ray photon energy based on a value of the voltage at expiration of the time delay. According to an embodiment, a rate of change of the voltage is substantially zero at expiration of the time delay. According to an embodiment, a rate of change of the voltage is substantially non-zero at expiration of the time delay. According to an embodiment, activating the second circuit is at a beginning or expiration of the time delay. According to an embodiment, the second circuit is configured to compare the absolute value of the voltage to the absolute value of the second threshold. According to an embodiment, the method further comprises deactivating a first circuit at a beginning the time delay. According to an embodiment, the first circuit is configured to compare the absolute value of the voltage to the absolute value of the first threshold. The first circuit and the second circuit may be the same circuit. Disclosed herein is a system suitable for phase-contrast X-ray imaging (PCI), the system comprising: the apparatus described above, a second X-ray detector, a spacer, wherein the apparatus and the second X-ray detector are spaced apart by the spacer. According to an embodiment, the apparatus and the second X-ray detector are configured to respectively capture an image of an object simultaneously. According to an embodiment, the second X-ray detector is identical to the apparatus. Disclosed herein is a system suitable for phase-contrast X-ray imaging (PCI), the system comprising: the apparatus described above, wherein the apparatus is configured to move to and capture images of an object exposed to incident X-ray at different distances from the object. FIG. 1A schematically shows a semiconductor X-ray detector 100, according to an embodiment. The semiconductor X-ray detector 100 may include an X-ray absorption layer 110 and an electronics layer 120 (e.g., an ASIC) for processing or analyzing electrical signals incident X-ray generates in the X-ray absorption layer 110. In an embodiment, the semiconductor X-ray detector 100 does not comprise a scintillator. The X-ray absorption layer 110 may include a semiconductor material such as, silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. The semiconductor may have a high mass attenuation coefficient for the X-ray energy of interest. The X-ray absorption layer 110 may include one or more diodes (e.g., p-i-n or p-n) formed by a first doped region 111, one or more discrete regions 114 of a second doped region 113. The second doped region 113 may be separated from the first doped region 111 by an optional the intrinsic region 112. The discrete portions 114 are separated from one another by the first doped region 111 or the intrinsic region 112. The first doped region 111 and the second doped region 113 have opposite types of doping (e.g., region 111 is p-type and region 113 is n-type, or region 111 is n-type and region 113 is p-type). In the example in FIG. 1A, each of the discrete regions 114 of the second doped region 113 forms a diode with the first doped region 111 and the optional intrinsic region 112. Namely, in the example in FIG. 1A, the X-ray absorption layer 110 has a plurality of diodes having the first doped region 111 as a shared electrode. The first doped region 111 may also have discrete portions. FIG. 1B shows a semiconductor X-ray detector 100, according to an embodiment. The semiconductor X-ray detector 100 may include an X-ray absorption layer 110 and an electronics layer 120 (e.g., an ASIC) for processing or analyzing electrical signals incident X-ray generates in the X-ray absorption layer 110. In an embodiment, the semiconductor X-ray detector 100 does not comprise a scintillator. The X-ray absorption layer 110 may include a semiconductor material such as, silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. The semiconductor may have a high mass attenuation coefficient for the X-ray energy of interest. The X-ray absorption layer 110 may not include a diode but includes a resistor. When an X-ray photon hits the X-ray absorption layer 110 including diodes, it may be absorbed and generate one or more charge carriers by a number of mechanisms. An X-ray photon may generate 10 to 100000 charge carriers. The charge carriers may drift to the electrodes of one of the diodes under an electric field. The field may be an external electric field. The electrical contact 119B may include discrete portions each of which is in electrical contact with the discrete regions 114. In an embodiment, the charge carriers may drift in directions such that the charge carriers generated by a single X-ray photon are not substantially shared by two different discrete regions 114 (“not substantially shared” here means less than 5%, less than 2% or less than 1% of these charge carriers flow to a different one of the discrete regions 114 than the rest of the charge carriers). In an embodiment, the charge carriers generated by a single X-ray photon can be shared by two different discrete regions 114. FIG. 2 shows an exemplary top view of a portion of the device 100 with a 4-by-4 array of discrete regions 114. Charge carriers generated by an X-ray photon incident around the footprint of one of these discrete regions 114 are not substantially shared with another of these discrete regions 114. The area around a discrete region 114 in which substantially all (more than 95%, more than 98% or more than 99% of) charge carriers generated by an X-ray photon incident therein flow to the discrete region 114 is called a pixel associated with that discrete region 114. Namely, less than 5%, less than 2% or less than 1% of these charge carriers flow beyond the pixel. By measuring the drift current flowing into each of the discrete regions 114, or the rate of change of the voltage of each of the discrete regions 114, the number of X-ray photons absorbed (which relates to the incident X-ray intensity) and/or the energies thereof in the pixels associated with the discrete regions 114 may be determined. Thus, the spatial distribution (e.g., an image) of incident X-ray intensity may be determined by individually measuring the drift current into each one of an array of discrete regions 114 or measuring the rate of change of the voltage of each one of an array of discrete regions 114. The pixels may be organized in any suitable array, such as, a square array, a triangular array and a honeycomb array. The pixels may have any suitable shape, such as, circular, triangular, square, rectangular, and hexangular. The pixels may be individually addressable. When an X-ray photon hits the X-ray absorption layer 110 including a resistor but not diodes, it may be absorbed and generate one or more charge carriers by a number of mechanisms. An X-ray photon may generate 10 to 100000 charge carriers. The charge carriers may drift to the electrical contacts 119A and 119B under an electric field. The field may be an external electric field. The electrical contact 119B includes discrete portions. In an embodiment, the charge carriers may drift in directions such that the charge carriers generated by a single X-ray photon are not substantially shared by two different discrete portions of the electrical contact 119B (“not substantially shared” here means less than 5%, less than 2% or less than 1% of these charge carriers flow to a different one of the discrete portions than the rest of the charge carriers). In an embodiment, the charge carriers generated by a single X-ray photon can be shared by two different discrete portions of the electrical contact 119B. Charge carriers generated by an X-ray photon incident around the footprint of one of these discrete portions of the electrical contact 119B are not substantially shared with another of these discrete portions of the electrical contact 119B. The area around a discrete portion of the electrical contact 119B in which substantially all (more than 95%, more than 98% or more than 99% of) charge carriers generated by an X-ray photon incident therein flow to the discrete portion of the electrical contact 119B is called a pixel associated with the discrete portion of the electrical contact 119B. Namely, less than 5%, less than 2% or less than 1% of these charge carriers flow beyond the pixel associated with the one discrete portion of the electrical contact 119B. By measuring the drift current flowing into each of the discrete portion of the electrical contact 119B, or the rate of change of the voltage of each of the discrete portions of the electrical contact 119B, the number of X-ray photons absorbed (which relates to the incident X-ray intensity) and/or the energies thereof in the pixels associated with the discrete portions of the electrical contact 119B may be determined. Thus, the spatial distribution (e.g., an image) of incident X-ray intensity may be determined by individually measuring the drift current into each one of an array of discrete portions of the electrical contact 119B or measuring the rate of change of the voltage of each one of an array of discrete portions of the electrical contact 119B. The pixels may be organized in any suitable array, such as, a square array, a triangular array and a honeycomb array. The pixels may have any suitable shape, such as, circular, triangular, square, rectangular, and hexangular. The pixels may be individually addressable. The electronics layer 120 may include an electronic system 121 suitable for processing or interpreting signals generated by X-ray photons incident on the X-ray absorption layer 110. The electronic system 121 may include an analog circuitry such as a filter network, amplifiers, integrators, and comparators, or a digital circuitry such as a microprocessors, and memory. The electronic system 121 may include components shared by the pixels or components dedicated to a single pixel. For example, the electronic system 121 may include an amplifier dedicated to each pixel and a microprocessor shared among all the pixels. The electronic system 121 may be electrically connected to the pixels by vias 131. Space among the vias may be filled with a filler material 130, which may increase the mechanical stability of the connection of the electronics layer 120 to the X-ray absorption layer 110. Other bonding techniques are possible to connect the electronic system 121 to the pixels without using vias. FIG. 3A and FIG. 3B each show a component diagram of the electronic system 121, according to an embodiment. The electronic system 121 may include a first voltage comparator 301, a second voltage comparator 302, a counter 320, a switch 305, a voltmeter 306 and a controller 310. The first voltage comparator 301 is configured to compare the voltage of an electrode of a diode 300 to a first threshold. The diode may be a diode formed by the first doped region 111, one of the discrete regions 114 of the second doped region 113, and the optional intrinsic region 112. Alternatively, the first voltage comparator 301 is configured to compare the voltage of an electrical contact (e.g., a discrete portion of electrical contact 119B) to a first threshold. The first voltage comparator 301 may be configured to monitor the voltage directly, or calculate the voltage by integrating an electric current flowing through the diode or electrical contact over a period of time. The first voltage comparator 301 may be controllably activated or deactivated by the controller 310. The first voltage comparator 301 may be a continuous comparator. Namely, the first voltage comparator 301 may be configured to be activated continuously, and monitor the voltage continuously. The first voltage comparator 301 configured as a continuous comparator reduces the chance that the system 121 misses signals generated by an incident X-ray photon. The first voltage comparator 301 configured as a continuous comparator is especially suitable when the incident X-ray intensity is relatively high. The first voltage comparator 301 may be a clocked comparator, which has the benefit of lower power consumption. The first voltage comparator 301 configured as a clocked comparator may cause the system 121 to miss signals generated by some incident X-ray photons. When the incident X-ray intensity is low, the chance of missing an incident X-ray photon is low because the time interval between two successive photons is relatively long. Therefore, the first voltage comparator 301 configured as a clocked comparator is especially suitable when the incident X-ray intensity is relatively low. The first threshold may be 5-10%, 10%-20%, 20-30%, 30-40% or 40-50% of the maximum voltage one incident X-ray photon may generate in the diode or the resistor. The maximum voltage may depend on the energy of the incident X-ray photon (i.e., the wavelength of the incident X-ray), the material of the X-ray absorption layer 110, and other factors. For example, the first threshold may be 50 mV, 100 mV, 150 mV, or 200 mV. The second voltage comparator 302 is configured to compare the voltage to a second threshold. The second voltage comparator 302 may be configured to monitor the voltage directly, or calculate the voltage by integrating an electric current flowing through the diode or the electrical contact over a period of time. The second voltage comparator 302 may be a continuous comparator. The second voltage comparator 302 may be controllably activate or deactivated by the controller 310. When the second voltage comparator 302 is deactivated, the power consumption of the second voltage comparator 302 may be less than 1%, less than 5%, less than 10% or less than 20% of the power consumption when the second voltage comparator 302 is activated. The absolute value of the second threshold is greater than the absolute value of the first threshold. As used herein, the term “absolute value” or “modulus” |x| of a real number x is the non-negative value of x without regard to its sign. Namely, x = { x , if x ≥ 0 - x , if x ≤ 0 . The second threshold may be 200%-300% of the first threshold. The second threshold may be at least 50% of the maximum voltage one incident X-ray photon may generate in the diode or resistor. For example, the second threshold may be 100 mV, 150 mV, 200 mV, 250 mV or 300 mV. The second voltage comparator 302 and the first voltage comparator 310 may be the same component. Namely, the system 121 may have one voltage comparator that can compare a voltage with two different thresholds at different times. The first voltage comparator 301 or the second voltage comparator 302 may include one or more op-amps or any other suitable circuitry. The first voltage comparator 301 or the second voltage comparator 302 may have a high speed to allow the system 121 to operate under a high flux of incident X-ray. However, having a high speed is often at the cost of power consumption. The counter 320 is configured to register a number of X-ray photons reaching the diode or resistor. The counter 320 may be a software component (e.g., a number stored in a computer memory) or a hardware component (e.g., a 4017 IC and a 7490 IC). The controller 310 may be a hardware component such as a microcontroller and a microprocessor. The controller 310 is configured to start a time delay from a time at which the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold (e.g., the absolute value of the voltage increases from below the absolute value of the first threshold to a value equal to or above the absolute value of the first threshold). The absolute value is used here because the voltage may be negative or positive, depending on whether the voltage of the cathode or the anode of the diode or which electrical contact is used. The controller 310 may be configured to keep deactivated the second voltage comparator 302, the counter 320 and any other circuits the operation of the first voltage comparator 301 does not require, before the time at which the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold. The time delay may expire before or after the voltage becomes stable, i.e., the rate of change of the voltage is substantially zero. The phase “the rate of change of the voltage is substantially zero” means that temporal change of the voltage is less than 0.1%/ns. The phase “the rate of change of the voltage is substantially non-zero” means that temporal change of the voltage is at least 0.1%/ns. The controller 310 may be configured to activate the second voltage comparator during (including the beginning and the expiration) the time delay. In an embodiment, the controller 310 is configured to activate the second voltage comparator at the beginning of the time delay. The term “activate” means causing the component to enter an operational state (e.g., by sending a signal such as a voltage pulse or a logic level, by providing power, etc.). The term “deactivate” means causing the component to enter a non-operational state (e.g., by sending a signal such as a voltage pulse or a logic level, by cut off power, etc.). The operational state may have higher power consumption (e.g., 10 times higher, 100 times higher, 1000 times higher) than the non-operational state. The controller 310 itself may be deactivated until the output of the first voltage comparator 301 activates the controller 310 when the absolute value of the voltage equals or exceeds the absolute value of the first threshold. The controller 310 may be configured to cause the number registered by the counter 320 to increase by one, if, during the time delay, the second voltage comparator 302 determines that the absolute value of the voltage equals or exceeds the absolute value of the second threshold. The controller 310 may be configured to cause the voltmeter 306 to measure the voltage upon expiration of the time delay. The controller 310 may be configured to connect the electrode to an electrical ground, so as to reset the voltage and discharge any charge carriers accumulated on the electrode. In an embodiment, the electrode is connected to an electrical ground after the expiration of the time delay. In an embodiment, the electrode is connected to an electrical ground for a finite reset time period. The controller 310 may connect the electrode to the electrical ground by controlling the switch 305. The switch may be a transistor such as a field-effect transistor (FET). In an embodiment, the system 121 has no analog filter network (e.g., a RC network). In an embodiment, the system 121 has no analog circuitry. The voltmeter 306 may feed the voltage it measures to the controller 310 as an analog or digital signal. The system 121 may include a capacitor module 309 electrically connected to the electrode of the diode 300 or the electrical contact, wherein the capacitor module is configured to collect charge carriers from the electrode. The capacitor module can include a capacitor in the feedback path of an amplifier. The amplifier configured as such is called a capacitive transimpedance amplifier (CTIA). CTIA has high dynamic range by keeping the amplifier from saturating and improves the signal-to-noise ratio by limiting the bandwidth in the signal path. Charge carriers from the electrode accumulate on the capacitor over a period of time (“integration period”) (e.g., as shown in FIG. 4, between t0 to t1, or t1-t2). After the integration period has expired, the capacitor voltage is sampled and then reset by a reset switch. The capacitor module can include a capacitor directly connected to the electrode. FIG. 4 schematically shows a temporal change of the electric current flowing through the electrode (upper curve) caused by charge carriers generated by an X-ray photon incident on the diode or the resistor, and a corresponding temporal change of the voltage of the electrode (lower curve). The voltage may be an integral of the electric current with respect to time. At time t0, the X-ray photon hits the diode or the resistor, charge carriers start being generated in the diode or the resistor, electric current starts to flow through the electrode of the diode or the resistor, and the absolute value of the voltage of the electrode or electrical contact starts to increase. At time t1, the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold V1, and the controller 310 starts the time delay TD1 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD1. If the controller 310 is deactivated before t1, the controller 310 is activated at t1. During TD1, the controller 310 activates the second voltage comparator 302. The term “during” a time delay as used here means the beginning and the expiration (i.e., the end) and any time in between. For example, the controller 310 may activate the second voltage comparator 302 at the expiration of TD1. If during TD1, the second voltage comparator 302 determines that the absolute value of the voltage equals or exceeds the absolute value of the second threshold at time t2, the controller 310 causes the number registered by the counter 320 to increase by one. At time te, all charge carriers generated by the X-ray photon drift out of the X-ray absorption layer 110. At time ts, the time delay TD1 expires. In the example of FIG. 4, time ts is after time te; namely TD1 expires after all charge carriers generated by the X-ray photon drift out of the X-ray absorption layer 110. The rate of change of the voltage is thus substantially zero at ts. The controller 310 may be configured to deactivate the second voltage comparator 302 at expiration of TD1 or at t2, or any time in between. The controller 310 may be configured to cause the voltmeter 306 to measure the voltage upon expiration of the time delay TD1. In an embodiment, the controller 310 causes the voltmeter 306 to measure the voltage after the rate of change of the voltage becomes substantially zero after the expiration of the time delay TD1. The voltage at this moment is proportional to the amount of charge carriers generated by an X-ray photon, which relates to the energy of the X-ray photon. The controller 310 may be configured to determine the energy of the X-ray photon based on voltage the voltmeter 306 measures. One way to determine the energy is by binning the voltage. The counter 320 may have a sub-counter for each bin. When the controller 310 determines that the energy of the X-ray photon falls in a bin, the controller 310 may cause the number registered in the sub-counter for that bin to increase by one. Therefore, the system 121 may be able to detect an X-ray image and may be able to resolve X-ray photon energies of each X-ray photon. After TD1 expires, the controller 310 connects the electrode to an electric ground for a reset period RST to allow charge carriers accumulated on the electrode to flow to the ground and reset the voltage. After RST, the system 121 is ready to detect another incident X-ray photon. Implicitly, the rate of incident X-ray photons the system 121 can handle in the example of FIG. 4 is limited by 1/(TD1+RST). If the first voltage comparator 301 has been deactivated, the controller 310 can activate it at any time before RST expires. If the controller 310 has been deactivated, it may be activated before RST expires. FIG. 5 schematically shows a temporal change of the electric current flowing through the electrode (upper curve) caused by noise (e.g., dark current, background radiation, scattered X-rays, fluorescent X-rays, shared charges from adjacent pixels), and a corresponding temporal change of the voltage of the electrode (lower curve), in the system 121 operating in the way shown in FIG. 4. At time t0, the noise begins. If the noise is not large enough to cause the absolute value of the voltage to exceed the absolute value of V1, the controller 310 does not activate the second voltage comparator 302. If the noise is large enough to cause the absolute value of the voltage to exceed the absolute value of V1 at time t1 as determined by the first voltage comparator 301, the controller 310 starts the time delay TD1 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD1. During TD1 (e.g., at expiration of TD1), the controller 310 activates the second voltage comparator 302. The noise is very unlikely large enough to cause the absolute value of the voltage to exceed the absolute value of V2 during TD1. Therefore, the controller 310 does not cause the number registered by the counter 320 to increase. At time te, the noise ends. At time ts, the time delay TD1 expires. The controller 310 may be configured to deactivate the second voltage comparator 302 at expiration of TD1. The controller 310 may be configured not to cause the voltmeter 306 to measure the voltage if the absolute value of the voltage does not exceed the absolute value of V2 during TD1. After TD1 expires, the controller 310 connects the electrode to an electric ground for a reset period RST to allow charge carriers accumulated on the electrode as a result of the noise to flow to the ground and reset the voltage. Therefore, the system 121 may be very effective in noise rejection. FIG. 6 schematically shows a temporal change of the electric current flowing through the electrode (upper curve) caused by charge carriers generated by an X-ray photon incident on the diode or the resistor, and a corresponding temporal change of the voltage of the electrode (lower curve), when the system 121 operates to detect incident X-ray photons at a rate higher than 1/(TD1+RST). The voltage may be an integral of the electric current with respect to time. At time t0, the X-ray photon hits the diode or the resistor, charge carriers start being generated in the diode or the resistor, electric current starts to flow through the electrode of the diode or the electrical contact of resistor, and the absolute value of the voltage of the electrode or the electrical contact starts to increase. At time t1, the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold V1, and the controller 310 starts a time delay TD2 shorter than TD1, and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD2. If the controller 310 is deactivated before t1, the controller 310 is activated at t1. During TD2 (e.g., at expiration of TD2), the controller 310 activates the second voltage comparator 302. If during TD2, the second voltage comparator 302 determines that the absolute value of the voltage equals or exceeds the absolute value of the second threshold at time t2, the controller 310 causes the number registered by the counter 320 to increase by one. At time te, all charge carriers generated by the X-ray photon drift out of the X-ray absorption layer 110. At time th, the time delay TD2 expires. In the example of FIG. 6, time th is before time te; namely TD2 expires before all charge carriers generated by the X-ray photon drift out of the X-ray absorption layer 110. The rate of change of the voltage is thus substantially non-zero at th. The controller 310 may be configured to deactivate the second voltage comparator 302 at expiration of TD2 or at t2, or any time in between. The controller 310 may be configured to extrapolate the voltage at te from the voltage as a function of time during TD2 and use the extrapolated voltage to determine the energy of the X-ray photon. After TD2 expires, the controller 310 connects the electrode to an electric ground for a reset period RST to allow charge carriers accumulated on the electrode to flow to the ground and reset the voltage. In an embodiment, RST expires before te. The rate of change of the voltage after RST may be substantially non-zero because all charge carriers generated by the X-ray photon have not drifted out of the X-ray absorption layer 110 upon expiration of RST before te. The rate of change of the voltage becomes substantially zero after te and the voltage stabilized to a residue voltage VR after te. In an embodiment, RST expires at or after te, and the rate of change of the voltage after RST may be substantially zero because all charge carriers generated by the X-ray photon drift out of the X-ray absorption layer 110 at te. After RST, the system 121 is ready to detect another incident X-ray photon. If the first voltage comparator 301 has been deactivated, the controller 310 can activate it at any time before RST expires. If the controller 310 has been deactivated, it may be activated before RST expires. FIG. 7 schematically shows a temporal change of the electric current flowing through the electrode (upper curve) caused by noise (e.g., dark current, background radiation, scattered X-rays, fluorescent X-rays, shared charges from adjacent pixels), and a corresponding temporal change of the voltage of the electrode (lower curve), in the system 121 operating in the way shown in FIG. 6. At time t0, the noise begins. If the noise is not large enough to cause the absolute value of the voltage to exceed the absolute value of V1, the controller 310 does not activate the second voltage comparator 302. If the noise is large enough to cause the absolute value of the voltage to exceed the absolute value of V1 at time t1 as determined by the first voltage comparator 301, the controller 310 starts the time delay TD2 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD2. During TD2 (e.g., at expiration of TD2), the controller 310 activates the second voltage comparator 302. The noise is very unlikely large enough to cause the absolute value of the voltage to exceed the absolute value of V2 during TD2. Therefore, the controller 310 does not cause the number registered by the counter 320 to increase. At time te, the noise ends. At time th, the time delay TD2 expires. The controller 310 may be configured to deactivate the second voltage comparator 302 at expiration of TD2. After TD2 expires, the controller 310 connects the electrode to an electric ground for a reset period RST to allow charge carriers accumulated on the electrode as a result of the noise to flow to the ground and reset the voltage. Therefore, the system 121 may be very effective in noise rejection. FIG. 8 schematically shows a temporal change of the electric current flowing through the electrode (upper curve) caused by charge carriers generated by a series of X-ray photons incident on the diode or the resistor, and a corresponding temporal change of the voltage of the electrode (lower curve), in the system 121 operating in the way shown in FIG. 6 with RST expires before te. The voltage curve caused by charge carriers generated by each incident X-ray photon is offset by the residue voltage before that photon. The absolute value of the residue voltage successively increases with each incident photon. When the absolute value of the residue voltage exceeds V1 (see the dotted rectangle in FIG. 8), the controller starts the time delay TD2 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD2. If no other X-ray photon incidence on the diode or the resistor during TD2, the controller connects the electrode to the electrical ground during the reset time period RST at the end of TD2, thereby resetting the residue voltage. The residue voltage thus does not cause an increase of the number registered by the counter 320. FIG. 9A shows a flow chart for a method suitable for detecting X-ray using a system such as the system 121 operating as shown in FIG. 4. In step 901, compare, e.g., using the first voltage comparator 301, a voltage of an electrode of a diode or an electrical contact of a resistor exposed to X-ray, to the first threshold. In step 902, determine, e.g., with the controller 310, whether the absolute value of the voltage equals or exceeds the absolute value of the first threshold V1. If the absolute value of the voltage does not equal or exceed the absolute value of the first threshold, the method goes back to step 901. If the absolute value of the voltage equals or exceeds the absolute value of the first threshold, continue to step 903. In step 903, start, e.g., using the controller 310, the time delay TD1. In step 904, activate, e.g., using the controller 310, a circuit (e.g., the second voltage comparator 302 or the counter 320) during the time delay TD1 (e.g., at the expiration of TD1). In step 905, compare, e.g., using the second voltage comparator 302, the voltage to the second threshold. In step 906, determine, e.g., using the controller 310, whether the absolute value of the voltage equals or exceeds the absolute value of the second threshold V2. If the absolute value of the voltage does not equal or exceed the absolute value of the second threshold, the method goes to step 910. If the absolute value of the voltage equals or exceeds the absolute value of the second threshold, continue to step 907. In step 907, cause, e.g., using the controller 310, the number registered in the counter 320 to increase by one. In optional step 908, measure, e.g., using the voltmeter 306, the voltage upon expiration of the time delay TD1. In optional step 909, determine, e.g., using the controller 310, the X-ray photon energy based the voltage measured in step 908. There may be a counter for each of the energy bins. After measuring the X-ray photon energy, the counter for the bin to which the photon energy belongs can be increased by one. The method goes to step 910 after step 909. In step 910, reset the voltage to an electrical ground, e.g., by connecting the electrode of the diode or an electrical contact of a resistor to an electrical ground. Steps 908 and 909 may be omitted, for example, when neighboring pixels share a large portion (e.g., >30%) of charge carriers generated from a single photon. FIG. 9B shows a flow chart for a method suitable for detecting X-ray using the system such as the system 121 operating as shown in FIG. 6. In step 1001, compare, e.g., using the first voltage comparator 301, a voltage of an electrode of a diode or an electrical contact of a resistor exposed to X-ray, to the first threshold. In step 1002, determine, e.g., with the controller 310, whether the absolute value of the voltage equals or exceeds the absolute value of the first threshold V1. If the absolute value of the voltage does not equal or exceed the absolute value of the first threshold, the method goes back to step 1001. If the absolute value of the voltage equals or exceeds the absolute value of the first threshold, continue to step 1003. In step 1003, start, e.g., using the controller 310, the time delay TD2. In step 1004, activate, e.g., using the controller 310, a circuit (e.g., the second voltage comparator 302 or the counter 320) during the time delay TD2 (e.g., at the expiration of TD2). In step 1005, compare, e.g., using the second voltage comparator 302, the voltage to the second threshold. In step 1006, determine, e.g., using the controller 310, whether the absolute value of the voltage equals or exceeds the absolute value of the second threshold V2. If the absolute value of the voltage does not equal or exceed the absolute value of the second threshold, the method goes to step 1010. If the absolute value of the voltage equals or exceeds the absolute value of the second threshold, continue to step 1007. In step 1007, cause, e.g., using the controller 310, the number registered in the counter 320 to increase by one. The method goes to step 1010 after step 1007. In step 1010, reset the voltage to an electrical ground, e.g., by connecting the electrode of the diode or an electrical contact of a resistor to an electrical ground. The semiconductor X-ray detector 100 may be used for phase-contrast X-ray imaging (PCI) (also known as phase-sensitive X-ray imaging). PCI encompasses techniques that form an image of an object at least partially using the phase shift (including the spatial distribution of the phase shift) of an X-ray beam caused by that object. One way to obtain the phase shift is transforming the phase into variations in intensity. PCI can be combined with tomographic techniques to obtain the 3D-distribution of the real part of the refractive index of the object. PCI is more sensitive to density variations in the object than conventional intensity-based X-ray imaging (e.g., radiography). PCI is especially useful for imaging soft tissues. According to an embodiment, FIG. 10 schematically shows a system 1900 suitable for PCI. The system 1900 may include at least two X-ray detectors 1910 and 1920. One or both of the two X-ray detectors 1910 is the semiconductor X-ray detector 100 described herein. The X-ray detectors 1910 and 1920 may be spaced apart by a spacer 1930. The spacer 1930 may have very little absorption of the X-ray. For example, the spacer 1930 may have a very small mass attenuation coefficient (e.g., <10 cm2g−1, <1 cm2g−1, <0.1 cm2g−1, or <0.01 cm2g−1). The mass attenuation coefficient of the spacer 1930 may be uniform (e.g., variation between every two points in the spacer 1930 less than 5%, less than 1% or less than 0.1%). The spacer 1930 may cause the same amount of changes to the phase of X-ray passing through the spacer 1930. For example, the spacer 1930 may be a gas (e.g., air), a vacuum chamber, may comprise aluminum, beryllium, silicon, or a combination thereof. The system 1900 can be used to obtain the phase shift of incident X-ray 1950 caused by an object 1960 being imaged. The X-ray detectors 1910 and 1920 can capture two images (i.e., intensity distributions) simultaneously. Because of the X-ray detectors 1910 and 1920 are separated by the spacer 1930, the two images are different distances from the object 1960. The phase may be determined from the two images, for example, using algorithms based on the linearization of the Fresnel diffraction integral. According to an embodiment, FIG. 11 schematically shows a system 1800 suitable for PCI. The system 1800 comprises the semiconductor X-ray detector 100 described herein. The semiconductor X-ray detector 100 is configured to move to and capture images of an object 1860 exposed to incident X-ray 1850 at different distances from the object 1860. The images may not necessarily be captured simultaneously. The phase may be determined from the images, for example, using algorithms based on the linearization of the Fresnel diffraction integral. FIG. 12 schematically shows a system comprising the semiconductor X-ray detector 100 described herein. The system may be used for medical imaging such as chest X-ray radiography, abdominal X-ray radiography, etc. The system comprises an X-ray source 1201. X-ray emitted from the X-ray source 1201 penetrates an object 1202 (e.g., a human body part such as chest, limb, abdomen), is attenuated by different degrees by the internal structures of the object 1202 (e.g., bones, muscle, fat and organs, etc.), and is projected to the semiconductor X-ray detector 100. The semiconductor X-ray detector 100 forms an image by detecting the intensity distribution of the X-ray. FIG. 13 schematically shows a system comprising the semiconductor X-ray detector 100 described herein. The system may be used for medical imaging such as dental X-ray radiography. The system comprises an X-ray source 1301. X-ray emitted from the X-ray source 1301 penetrates an object 1302 that is part of a mammal (e.g., human) mouth. The object 1302 may include a maxilla bone, a palate bone, a tooth, the mandible, or the tongue. The X-ray is attenuated by different degrees by the different structures of the object 1302 and is projected to the semiconductor X-ray detector 100. The semiconductor X-ray detector 100 forms an image by detecting the intensity distribution of the X-ray. Teeth absorb X-ray more than dental caries, infections, periodontal ligament. The dosage of X-ray radiation received by a dental patient is typically small (around 0.150 mSv for a full mouth series). FIG. 14 schematically shows a cargo scanning or non-intrusive inspection (NII) system comprising the semiconductor X-ray detector 100 described herein. The system may be used for inspecting and identifying goods in transportation systems such as shipping containers, vehicles, ships, luggage, etc. The system comprises an X-ray source 1401. X-ray emitted from the X-ray source 1401 may backscatter from an object 1402 (e.g., shipping containers, vehicles, ships, etc.) and be projected to the semiconductor X-ray detector 100. Different internal structures of the object 1402 may backscatter X-ray differently. The semiconductor X-ray detector 100 forms an image by detecting the intensity distribution of the backscattered X-ray and/or energies of the backscattered X-ray photons. FIG. 15 schematically shows another cargo scanning or non-intrusive inspection (NII) system comprising the semiconductor X-ray detector 100 described herein. The system may be used for luggage screening at public transportation stations and airports. The system comprises an X-ray source 1501. X-ray emitted from the X-ray source 1501 may penetrate a piece of luggage 1502, be differently attenuated by the contents of the luggage, and projected to the semiconductor X-ray detector 100. The semiconductor X-ray detector 100 forms an image by detecting the intensity distribution of the transmitted X-ray. The system may reveal contents of luggage and identify items forbidden on public transportation, such as firearms, narcotics, edged weapons, flammables. FIG. 16 schematically shows a full-body scanner system comprising the semiconductor X-ray detector 100 described herein. The full-body scanner system may detect objects on a person's body for security screening purposes, without physically removing clothes or making physical contact. The full-body scanner system may be able to detect non-metal objects. The full-body scanner system comprises an X-ray source 1601. X-ray emitted from the X-ray source 1601 may backscatter from a human 1602 being screened and objects thereon, and be projected to the semiconductor X-ray detector 100. The objects and the human body may backscatter X-ray differently. The semiconductor X-ray detector 100 forms an image by detecting the intensity distribution of the backscattered X-ray. The semiconductor X-ray detector 100 and the X-ray source 1601 may be configured to scan the human in a linear or rotational direction. FIG. 17 schematically shows an X-ray computed tomography (X-ray CT) system. The X-ray CT system uses computer-processed X-rays to produce tomographic images (virtual “slices”) of specific areas of a scanned object. The tomographic images may be used for diagnostic and therapeutic purposes in various medical disciplines, or for flaw detection, failure analysis, metrology, assembly analysis and reverse engineering. The X-ray CT system comprises the semiconductor X-ray detector 100 described herein and an X-ray source 1701. The semiconductor X-ray detector 100 and the X-ray source 1701 may be configured to rotate synchronously along one or more circular or spiral paths. FIG. 18 schematically shows an electron microscope. The electron microscope comprises an electron source 1801 (also called an electron gun) that is configured to emit electrons. The electron source 1801 may have various emission mechanisms such as thermionic, photocathode, cold emission, or plasmas source. The emitted electrons pass through an electronic optical system 1803, which may be configured to shape, accelerate, or focus the electrons. The electrons then reach a sample 1802 and an image detector may form an image therefrom. The electron microscope may comprise the semiconductor X-ray detector 100 described herein, for performing energy-dispersive X-ray spectroscopy (EDS). EDS is an analytical technique used for the elemental analysis or chemical characterization of a sample. When the electrons incident on a sample, they cause emission of characteristic X-rays from the sample. The incident electrons may excite an electron in an inner shell of an atom in the sample, ejecting it from the shell while creating an electron hole where the electron was. An electron from an outer, higher-energy shell then fills the hole, and the difference in energy between the higher-energy shell and the lower energy shell may be released in the form of an X-ray. The number and energy of the X-rays emitted from the sample can be measured by the semiconductor X-ray detector 100. The semiconductor X-ray detector 100 described here may have other applications such as in an X-ray telescope, X-ray mammography, industrial X-ray defect detection, X-ray microscopy or microradiography, X-ray casting inspection, X-ray non-destructive testing, X-ray weld inspection, X-ray digital subtraction angiography, etc. It may be suitable to use this semiconductor X-ray detector 100 in place of a photographic plate, a photographic film, a PSP plate, an X-ray image intensifier, a scintillator, or another semiconductor X-ray detector. While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. |
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044118619 | abstract | Method of protecting a zirconium-alloy cladding tube of a nuclear-reactor fuel rod against attack by radioactive fission products, such as iodine especially, which includes applying an internal pressure to the cladding tube at a temperature of from 300.degree. to 500.degree. C. so as to deform the cladding tube, depending upon the geometric dimensioning thereof, in the elastic range and up to nearly the yield point thereof and, while this condition exists, reacting a medium previously introduced into the interior of the cladding tube, with the inner surface of the cladding tube to form a protective layer. |
052271277 | claims | 1. A filtered venting system located in association with a reactor containment vessel installed in a reactor building comprising: a filter device disposed in the reactor building and including filter means; a first venting line disposed on an upstream side of the filter device and having one end connected to the reactor containment vessel and another end connected to the filter device; a stand-by gas treatment system connected to the first venting line, said stand-by gas treatment system including outlet drive means having a downstream side connected to the first venting line, inlet valve means, isolation valve means and check valve means; and a second venting line disposed at a downstream side of the filter device and having an end connected to discharge means; wherein said filter device is utilized as filtering means for the stand-by gas treatment system for treating and removing a radioactive substance in an atmosphere delivered from the reactor containment vessel. 2. A filtered venting system according to claim 1, wherein said outlet drive means is an outlet fan means. 3. A filtered venting system according to claim 1, wherein said filter means includes a water filter and a stainless fiber filter. 4. A filtered venting system according to claim 1, wherein an inert gas feed line is connected to the filter device. 5. A filtered venting system according to claim 4, wherein the inert gas is an N.sub.2 gas. 6. A filtered venting system according to claim 1, wherein isolation valve means, check valve means and rapture disk means are incorporated to the first venting line, and outlet valve means, rupture disk means and check valve means are incorporated to the second venting line. 7. A filtered venting system according to claim 1, wherein said outlet drive means is an outlet pump means. |
description | In FIGS. 1 and 2, preferred arrangements of the five-mirror projection objectives according to the invention are shown. Each has an optical free working distance that corresponds at least to the used diameter of the mirror closest to the wafer or object to be illuminated. In all embodiments below, the same reference numbers are used for the same components with the following nomenclature employed: first mirror (S1), second mirror (S2), third mirror (S3), fourth mirror (S4), and fifth mirror (S5). In particular, FIG. 1 shows a five-mirror projection objective with a beam path from the reticle plane 2 to the wafer plane 4. The embodiment can be considered as a series circuit with (1) a three-mirror system consisting of S1, S2 and S3, that produces a real, reduced image of the object, as the intermediate-image Z and (2) a two-mirror system S4, S5, which images the intermediate image Z in the wafer plane 4 while maintaining the telecentricity requirements. The aberrations of the subsystems are balanced against one another in such a way that the total system has sufficient quality for the application. A physical aperture stop B is arranged on the first mirror S1. To block light from passing above the aperture stop B, a narrow ring is used to block the light reflected toward S2 from S1. In the embodiment shown in FIG. 1, the aperture is realized as an opening at the S1 mirror. The aperture stop can also be positioned between the mirror S1 and the mirror S2. In the system according to FIG. 1, the optical free working distance D between the mirror next to the wafer plane 4, the fourth mirror S4 in the present embodiment, and the wafer plane 4 is greater than the used diameter of mirror S4, that is, the following condition is fulfilled: optical distance from S4 to the wafer plane 4 greater than used diameter S4. Other distance conditions are possible, for example, that the optical free working distance is greater than the sum of one-third of the used diameter of the mirror S4 nearest to the wafer plane 4 plus 20 mm or that the optical free working distance can be greater than 50 mm. In the embodiment of FIG. 1, the free optical working distance is 60 mm. Such an optical working distance guarantees sufficient free mechanical working distance, which is greater than 0, as well as the use of optical components with sufficient strength properties to be used at wavelengths less than 100 nm and preferably of 11 or 13 nm. The optical components for a wavelength of xcex=13 nm and xcex=11 nm include, for example, Mo/Si and Mo/Be multilayer coating systems, respectively, where the typical multilayer coating systems for xcex=13 nm are 40 Mo/Si layer pairs, while the Mo/Be systems that are suitable for xcex11 nm have approximately 70 layer pairs. Reflectivities of such systems lie in the range of approximately 70%. In the multilayer coating systems, layer stresses of above 350 MPa and more may occur. Stresses of such values may induce surface deformation, especially in the edge regions of the mirror. The systems according to the invention, as shown as an example in FIG. 1, have: RES=k1xcex/NA. This results in a nominal resolution of at least 50 nm and 35 nm at a minimum numerical aperture of NA=0.15 for k1=0.57 and xcex=13 nm, and k1=0.47 and xcex=11 nm, respectively, where k1 is a parameter specific for the lithographic process. Furthermore, the beam path of the objective shown in FIG. 1 is obscuration-free. For example, in order to produce image formats of 26xc3x9734 mm2 or 26xc3x9752 mm2, the projection objectives according to the invention are preferably used in an arc-shaped field scan projection exposure apparatus, where the secant length of the scan slit is at least 26 mm. Numerous types of mask can be used in the projection exposure apparatus, including transmission masks, stencil masks, and reflection masks, and the system, which is telecentric on the image-side can be telecentric or not telecentric on the object-side. For example, to form a telecentric beam path on the object-side, when using a reflection mask, a transmission-reducing beam splitter must be employed. With a beam path not telecentric on the object-side, unevenness of the mask will not lead to scaling errors in the image. The main beam angles at the reticle plane 2 are therefore preferably less than 10xc2x0, so that the requirements for reticle evenness lie in technologically realizable range. Moreover, the system according to FIG. 1 has an image-side telecentering error on the wafer plane 4 of 3xc2x10.1 mrad at a numerical aperture of 0.15. In the embodiment shown, all mirrors S1-S5 are aspherical, and the maximum asphericity in the used area lies at 14 xcexcm. The maximum asphericity occurs on mirror S3. The low asphericity of the arrangement is advantageous from a manufacturing point of view, since the technological difficulties in producing of the surfaces of the multilayer mirror increase with the aspherical deviation and increasing gradient of the asphere. The highest angle of incidence in the arrangement according to FIG. 1 occurs at S2 and is 18.9xc2x0. The wavefront error of the arrangement is better than 0.023 xcex in the 2 mm wide arc-shaped field at xcex=13 nm. With the embodiments shown in FIGS. 1 and 2, the disadvantage of a mirror system with an odd number of mirrors, namely that a stretched structure reticle-projection optics-wafer can no longer be realized, is overcome. This disadvantage results from the fact that the reticle plane and the wafer plane were illuminated from the same direction especially in the case of systems with near normal incidence. This condition led to the reticle plane and the wafer plane lying on the same side of the objective. According to FIG. 1 or 2, the reticle plane 2 is placed within the projection system. The mirror arrangement is chosen so that, in the direction of the optical axis, the structural space provided for the reticle stage, within the projection system, is as large as possible, preferably 400 mm. In addition, the plane of the object, i.e., the reticle, has a sufficiently large distance to the light bundles traveling in the objective. This ensures that a sufficiently large object, i.e., reticle, can be scanned in an annular field scanning operation. In a preferred example, approximately 200 mm can be scanned on the reticle, corresponding to 50 mm on the wafer. In the embodiment shown in FIG. 1, the two mirrors of the two-mirror subsystem (S4, S5) have approximately the same radii R, within a few percent, and the distance between the two of the two oblate ellipsoidal mirrors is approximately R/{square root over (2)}. The three-mirror subsystem near the reticle plane 2 consists of three almost concentric mirrors (S1, S2, S3) of which the primary (S1) and the tertiary mirror (S3) have similar radii. The subsystem near the reticle plane 2 differs from a disturbed Offner system mainly by the position of the aperture stop B on the primary mirror and the non-telecentric beam path on the reticle. A real intermediate image Z is produced between the two subsystems. The chief-ray angle inclination on the reticle plane 2 permits a vignetting-free illumination of a reflection mask. Furthermore, in the embodiments according to FIGS. 1 and 2, the distances between the mirrors are chosen to have a value such that the mirrors can be sufficiently thick so that the required strength properties are still obtained at the high layer stresses that occur. The parameters of the systems shown in FIG. 1 are given in Table 1 in Code V ((trademark)) nomenclature. The objective is a 4xc3x97 system with a 26xc3x972 mm2 arc-shaped field and a numerical aperture NA of 0.15. The mean image-side radius of the system is approximately 26 mm. FIG. 2 shows an alternative embodiment of the invention of a five-mirror system in which the aperture stop B is between the first mirror and the second mirror. The same components as in FIG. 1 are assigned the same reference numbers. The optical free working distance at the wafer plane 4 is approximately 60 mm in this embodiment, and thus it is larger than the used diameter of the mirror S4, which is closest to the wafer plane 4. In contrast to the embodiment according to FIG. 1, in FIG. 2 the aperture stop B is placed physically between the first and second mirrors so that it is freely accessible. The wavefront error is 0.024 xcex, within the 1.7 mm wide arc-shaped field at xcex=13 nm. Table 2 shows the constructional data of the 4xc3x97 objective according to FIG. 2 in Code V ((trademark)) nomenclature. The mean radius of the 26xc3x971.7 mm2 is again 26 mm and the aperture NA=0.15. FIGS. 3A and 3B illustrate the meaning of the used diameter D in the present application. As an example, let the illuminated field 100 on a mirror in FIG. 3A be a rectangular field. The used diameter D is then the diameter of the envelope circle 102, which encompasses the rectangle 100, where the corners 104 of the rectangle 100 lie on the envelope circle 102. FIG. 3B shows a second example. The illuminated field 100 has a kidney shape, as expected for the useful range when using the objective according to the invention in a microlithography projection exposure apparatus. The envelope circle 102 encompasses the kidney shape fully and coincides with the edge 110 of the kidney shape at two points 106, 108. The used diameter D is then the diameter of the envelope circle 102. Thus, with the invention, a five-mirror projection objective is given for the first time, with an imaging scale of preferably 4xc3x97, 5xc3x97 as well as 6xc3x97 for preferred use in an EUV arc-shaped projection system. The projection objection has the necessary resolution for the required image field and provides conditions that make functional structural design possible, since the aspheres are sufficiently mild, the angles are sufficiently small for the layers and the structural spaces for the mirror carriers are sufficiently large. |
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description | This application claims the benefit of U.S. Provisional Patent Application No. 61/476,624, filed Apr. 18, 2011, the entirety of which is incorporated herein by reference. The present invention relates generally to systems and methods of removing thermal energy from pools of liquid, and specifically to systems and methods of removing thermal energy from spent nuclear fuel pools that are self-powered and autonomous. The spent fuel pool (SFP) in a nuclear power plant serves to store used spent nuclear fuel discharged from the reactor in a deep pool (approximately 40 feet deep) of water. In existing systems, the decay heat produced by the spent nuclear fuel is removed from the SFP by circulating the pool water through a heat exchanger (referred to as the Fuel Pool Cooler) using a hydraulic pump. In the Fuel Pool Cooler, the pool water rejects heat to a cooling medium which is circulated using another set of pumps. Subsequent to ifs cooling in the Fuel Pool cooler, the pool water is also purified by passing it through a bed of demineralizers before returning it to the pool. In existing systems, the satisfactory performance of the spent fuel cooling and clean up system described above is critically dependent on pumps which require electric energy to operate. As the events at the Fukushima Dai-ichi showed, even a redundant source of power such as Diesel generators cannot preclude the paralysis of the classical fuel pool cooling system. In order to insure that the decay heat produced by the fuel stored in the SFP is unconditionally rejected to the environment, the present invention introduces a heat removal system and method that does not require an external source of electric energy or equipment that can be rendered ineffective by an extreme environmental phenomenon such as a tsunami, hurricane, earthquake and the like. These, and other drawbacks, are remedied by the present invention. An autonomous and self-powered system of cooling a pool of liquid in which radioactive materials are immersed is presented. The inventive system utilizes a closed-loop fluid circuit through which a low boiling point working fluid flows. The closed-loop fluid circuit of the inventive system, in accordance with the Rankine Cycle: (1) extracts thermal energy from the liquid of the pool into the working fluid; (2) converts a first portion of the extracted thermal energy into electrical energy that is used to power one or more forced flow units that induce flow of the working fluid through the closed-loop fluid circuit; and (3) transfers a second portion of the extracted thermal energy to a secondary fluid, such as air. In this way, the inventive system operates without the need for any electrical energy other than that which is generates internally in accordance with the Rankine Cycle. In one embodiment, the invention can be an autonomous self-powered system for cooling radioactive materials, the system comprising: a pool of liquid, the radioactive materials immersed in the pool of liquid; a closed-loop fluid circuit comprising a working fluid having a boiling temperature that is less than a boiling temperature of the liquid of the pool, the closed-loop fluid circuit comprising, in operable fluid coupling, an evaporative heat exchanger at least partially immersed in the liquid of the pool, a turbogenerator, and a condenser; one or more forced flow units operably coupled to the closed-loop fluid circuit to induce flow of the working fluid through the closed-loop fluid circuit; and the closed-loop fluid circuit converting thermal energy extracted from the liquid of the pool into electrical energy in accordance with the Rankine Cycle, the electrical energy powering the one or more forced flow units. In another embodiment, the invention can be an autonomous self-powered system for cooling a pool of liquid comprising: a closed-loop fluid circuit comprising a working fluid having a boiling temperature that is less than a boiling temperature of the liquid of the pool, the closed-loop fluid circuit comprising, in operable fluid coupling, an evaporative heat exchanger at least partially immersed in the liquid of the pool, a turbogenerator, and a condenser; one or more forced flow units operably coupled to the closed-loop fluid circuit to induce flow of the working fluid through the closed-loop fluid circuit; and the closed-loop fluid circuit converting thermal energy extracted from the liquid of the pool into electrical energy in accordance with the Rankine Cycle, the electrical energy powering the one or more forced flow units. In yet another embodiment, the invention can be a method of cooling a pool of liquid comprising: flowing the working fluid having a boiling temperature that is less than a boiling temperature of the liquid of the pool through a closed-loop fluid circuit that, in accordance with a Rankine Cycle: (1) extracts thermal energy from the liquid of the pool into the working fluid; (2) converts a first portion of the extracted thermal energy into electrical energy that is used to power one or more forced flow units that induce flow of the working fluid through the closed-loop fluid circuit; and (3) transfers a second portion of the extracted thermal energy to a secondary fluid. In a yet further aspect, the invention can be a vertical evaporative heat exchanger for immersion in a heated fluid comprising: a tubeside fluid circuit comprising: a top header; a bottom header; a core tube forming a downcomer passageway between the top header and the bottom header, the core tube having a first effective coefficient of thermal conductivity; a plurality of heat exchange tubes forming passageways between the bottom header and the top header, the plurality of the heat exchange tubes having a second effective coefficient of thermal conductivity that is greater than the first effective coefficient of thermal conductivity; a working fluid in the tubeside fluid circuit; an inlet for introducing a liquid phase of the working fluid into the tubeside fluid circuit; an outlet for allowing a vapor phase of the working fluid to exit the top header; and wherein transfer of heat from the heated fluid to the working fluid induces a thermosiphon flow of the liquid phase of the working fluid within the tubeside fluid circuit. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. While the invention is exemplified in FIGS. 1-6 as being used to cool pools of liquid in which radioactive materials are immersed (such as spent nuclear fuel, high level radioactive waste or low level radioactive waste), the invention is not so limited and can be used to cool any body of liquid in need of cooling. Referring first to FIG. 1, an autonomous self-powered cooling system 1000 according to an embodiment of the present invention is schematically illustrated. The autonomous self-powered cooling system 1000 generally comprises a closed-loop fluid circuit 100, an electrical circuit 200, and a pool of liquid 50. Radioactive materials 20 are immersed in the pool of liquid 50, which in the exemplified embodiment is a spent fuel pool. Radioactive materials 20, such as spent nuclear fuel, generate a substantial amount of heat for a considerable amount of time after completion of a useful cycle in a nuclear reactor. Thus, the radioactive materials 20 are immersed in the pool of liquid 50 to cool the radioactive materials 20 to temperatures suitable for dry storage. In embodiments where the radioactive materials 20 are spent nuclear fuel rods, said spent nuclear fuel rods will be supported in the pool of liquid 50 in fuel racks located at the bottom of the pool of liquid 50 and resting on the floor. Examples of suitable fuel racks are disclosed in United States Patent Application Publication No. 2008/0260088, entitled Apparatus and Method for Supporting Fuel Assemblies in an Underwater Environment Having Lateral Access Loading, published on Oct. 23, 2008, and United States Patent Application Publication No. 2009/0175404, entitled Apparatus or Supporting Radioactive Fuel Assemblies and Methods of Manufacturing the Same, published on Jul. 9, 2009, the entireties of which are hereby incorporated by reference. As a result of being immersed in the pool of liquid 50, thermal energy from the radioactive materials 20 is transferred to the pool of liquid 50, thereby heating the pool of liquid 50 and cooling the radioactive materials. However, as the pool of liquid 50 heats up over time, thermal energy must be removed from the pool of liquid 50 to maintain the temperature of the pool of liquid 50 within an acceptable range so that adequate cooling of the radioactive materials 20 can be continued. As discussed in greater detail below, the closed-loop fluid circuit 100 extends through the pool of liquid 50. A working fluid 75 is flowed through the closed-loop fluid circuit 100. The closed-loop fluid circuit 100 extracts thermal energy from the pool of liquid 50 (into the working fluid 75) and converts the extracted thermal energy into electrical energy. The electrical energy generated by said conversion powers the electrical circuit 200, which in turn powers forced flow units 190, 151 (described below) that induce flow of the working fluid 75 (FIG. 2) through the closed-loop circuit 100. The aforementioned extraction and conversion of thermal energy into electrical energy is accomplished by the closed-loop fluid circuit 100 in accordance with the Rankine Cycle. In certain specific embodiments, and depending on the identity of the liquid 50 to be cooled and the working fluid 75 being used, the closed-loop fluid circuit 100 can accomplish the extraction and conversion of thermal energy into electrical energy in accordance with the Organic Rankine Cycle. In order to cool the pool of liquid 50 prior to the liquid 50 of the pool evaporating/boiling, the working fluid 75 is preferably a low boiling-point fluid (relative to the liquid 50 of the pool). More specifically, the working fluid 75 is selected so that it has a boiling temperature that is less than the boiling temperature of the liquid 50 of the pool. It is appreciated that the temperature at which a liquid boils/evaporates is dependent on pressure and that the liquid 50 of the pool and the working fluid 75 may be subject to different pressures in certain embodiments of the invention. Furthermore, as discussed in greater detail below, the working fluid 75 is evaporated/boiled in an evaporative heat exchanger 110 that is immersed in the pool of liquid 50. In certain such embodiments, the liquid 50 of the pool will be under a first pressure and the working fluid 75 in the evaporative heat exchanger 110 will be under a second pressure that is greater than first pressure. Thus, in such an embodiment, the working fluid 75 is selected so that the boiling temperature of the working fluid 75 at the second pressure is less than the boiling temperature of the liquid 50 of the pool at the first pressure. In one specific embodiment, the first pressure will be atmospheric pressure and the second pressure will be in a range of 250 psia to 400 psia. In one embodiment, the liquid 50 of the pool is water. As used herein, the term “water” includes borated water, demineralized water and other forms of treated water or water with additives. Suitable working fluids 75 include, without limitation, refrigerants. Suitable refrigerants may include, without limitation, ammonia, sulfur dioxide, chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, haloalkanes, and hydrocarbons. One particularly suitable refrigerant that can be used as the working fluid 75 is tetraflouroethane, commonly known as HFC-134a. The exemplified embodiment of the closed-loop fluid circuit 100 generally comprise an evaporative heat exchanger 110, a turbogenerator 130, a condenser 150, a working fluid reservoir 170, and a hydraulic pump 190. The aforementioned components 110, 130, 150, 170, 190 of the closed-loop fluid circuit 100 are operably and fluidly coupled together using appropriate piping, joints and fittings as is well-known in the art to form a fluid-tight closed-loop through which the working fluid 75 can flow through in both a liquid phase 75A and a vapor phase 75B. The working fluid 75 is in the liquid phase 75A between a working fluid outlet 153 of the condenser 150 and a working fluid inlet 111 of the evaporative heat exchanger 110. The working fluid 75 is in the vapor phase 75B between a working fluid outlet 112 of the evaporative heal exchanger 110 and a working fluid inlet 152 of the condenser 150. As discussed in greater detail below, the evaporative heat exchanger 110, which is immersed in the liquid 50 of the pool, converts the working fluid 75 from the liquid phase 75A to the vapor phase 75B by transferring thermal energy from the liquid 50 of the pool into the working fluid 75. Conversely, the condenser 150 converts the working fluid 75 from the vapor phase 75B to the liquid phase 75A by transferring thermal energy from the working fluid 75 into a secondary fluid (which can be air that is rejected to the environment in certain embodiments). In the exemplified embodiment, the autonomous self-powered system 1000 further comprises two forced flow units that induce flow of the working fluid 75 through the closed-loop fluid circuit 100, namely the hydraulic pump 190 (which is considered part of the closed-loop fluid circuit 100) and a blower 151 which, when operated, forces cooling air to flow over heat exchange tubes 154 (as shown in FIG. 6) of the condenser 150. The hydraulic pump 190 directly induces flow of the working fluid 75 through the closed-loop fluid circuit 100 by drawing the liquid-phase 75A of the working fluid 75 from the working fluid reservoir 170 and forcing the liquid-phase 75A of the working fluid 75 into the evaporative heat exchanger 110. The blower 151 indirectly induces flow of the working fluid 75 through the closed-loop fluid circuit 100 by increasing air flow over the heat exchange tubes 154 of the condenser 150 (the working fluid 75 being the tubeside fluid in the condenser 150), thereby increasing the extraction of thermal energy from the working fluid 75 in the condenser 150 and promoting increased condensation and a thermo-siphon flow effect of the working fluid 75. In certain embodiments of the invention, more or less forced flow units can be incorporated into the autonomous self-powered system 1000 as desired. For example, in certain embodiments, the blower 151 may be omitted while, in certain other embodiments, the hydraulic pump 90 may be omitted. For example, if the condenser 150 were a natural draft air-cooled condenser (see FIGS. 4-5B), the blower 151 may be omitted. Furthermore, in certain embodiments where the condenser 150 is not an air cooled condenser, but is for example a shell and tube beat exchanger, a hydraulic pump that is used to force flow of the secondary fluid through the condenser 150 can be a forced flow unit. Irrespective of the exact number and identity of the forced flow units that are used to induce flow of the of the working fluid 75 through the closed-loop fluid circuit 100, all of said forced flow units are powered only by electrical energy generated through the conversion of the thermal energy that is extracted from the liquid 50 of the pool. More specifically, in the exemplified embodiment, both the hydraulic pump 190 and the blower 151 are operably and electrically coupled to the electrical circuit 200, which is powered solely by the electrical energy generated by the turbogenerator 130 (discussed in greater detail below). Thus, the autonomous self-powered system 1000 can operate to cool the liquid 50 of the pool for an indefinite period of time and completely independent of any outside sources of electrical energy, other than that electrical energy that is generated through the conversion of the thermal energy extracted from the liquid 50 of the pool. Stated simply, the thermal energy of the liquid 50 of the pool is the sole source of energy required to drive the cooling system 1000. Referring still to FIG. 1, the general operation cycle of the autonomous self-powered system 1000 will be described. The working fluid reservoir 170 stores an amount of the liquid phase 75a of the working fluid 75 to charge and control the quantity of the working fluid 75 in the thermal cycle at start up. The working fluid reservoir 170 also provides the means to evacuate the closed-loop fluid circuit 100 of air and to fill the closed-loop fluid circuit 100 with the required amount of the working fluid 75. In certain embodiments, the working fluid reservoir 170 is needed only at the beginning of the system operation (start up) to insure that the proper quantity of the working fluid 75 is injected into the thermal cycle. The hydraulic pump 190 is located downstream of the working fluid reservoir 170 in the exemplified embodiment. However, in alternate embodiments, the hydraulic pump 190 can be located upstream of the working fluid reservoir 170. Once started, the hydraulic pump 190 draws the liquid phase 75A of the working fluid 75 from the working fluid reservoir 170, thereby drawing the liquid phase 75A of the working fluid 75 into the working fluid inlet 191 of the hydraulic pump 190. As the hydraulic pump 190 operates, the liquid phase 75A of the working fluid 75 is expelled from the working fluid outlet 192 of the hydraulic pump under pressure. The expelled liquid phase 75A of the working fluid 75 is forced into the evaporative heat exchanger 110 via the working fluid inlet 111 of the evaporative heat exchanger 110. The evaporative heat exchanger 110 is at least partially immersed in the liquid 50 of the pool so that thermal energy from liquid 50 can be transferred to the working fluid 70 while in the evaporative heat exchanger 110. In the exemplified embodiment, the evaporative heat exchanger 110 is full immersed in the liquid 50 of the pool. Furthermore, the evaporative heat exchanger 110 is located at a top of the pool of liquid 50, which tends to be hotter than the bottom of the pool, of liquid 50 due to temperature differentials in the liquid 50 (hot fluids rise). In one embodiment, the evaporative heat exchanger 110 is mounted to one of the sidewalls 55 of the pool of liquid 50 so that the evaporative heat exchanger 110 does not interfere with loading and unloading operations that take place within the pool of liquid 50 for the radioactive materials 20. The details of one embodiment of the evaporative heat exchanger 110, including the operation thereof, will now be described with reference to FIGS. 1 and 2 concurrently. Of course, the invention is not so limited, and the evaporative heat exchanger 110 can take on other structural embodiments in other embodiments of the invention. The evaporative heat exchanger 110 generally comprises a core tube 113 (which acts as a downcomer tube in the exemplified embodiment), a plurality of heat exchange tubes 114, a working fluid bottom header 115, and a working fluid top header 116, which collectively define a tubeside fluid circuit. The working fluid bottom header 115 comprises a bottom tube sheet 117 while the working fluid top header 116 comprises a top tube sheet 118. In one embodiment, the bottom and top headers 115, 116 and the core pipe 113 are constructed of a corrosion resistant alloy, such as stainless steel. The bottom and top tube sheets are constructed of an aluminum clad stainless steel. The heat exchange tubes 114 are constructed of aluminum (as used herein the term “aluminum” includes aluminum alloys) and are welded to the aluminum cladding of the bottom and top tube sheets 117, 118 to make leak tight joints. The core pipe 113 will be welded to the stainless steel base metal of the bottom and top tube sheets 117, 118. Of course, other materials and construction methodologies can be used as would be known to those of skill in the art. The core tube 113 extends from the working fluid outlet header 116 to the working fluid inlet header 115, thereby forming a fluid-tight path between the two through which the liquid phase 75A of the working fluid 75 will flow. More specifically, the core tube 113 is connected to the lower and upper tube sheets 117, 118 of the working fluid headers 115, 116. The working fluid inlet 111 extends into the core tube 113 and introduces cool liquid phase 75A of the working fluid 75 into a top portion of the core tube 113. The core tube 113 is formed of a material that has a low coefficient of thermal conductivity (as compared to the material of which the heat exchange tubes 114 are constructed), such as steel. The core tube 113 may also comprise a thermal insulating layer, which can be an insulating shroud tube, to minimize heating of the liquid phase 75A of the working fluid 75 in the core tube 113 by the liquid 50 of the pool. Irrespective of the materials and/or construction of the core tube 113, the core tube 113 has an effective coefficient of thermal conductivity (measured from an inner surface that is contact with the working fluid 75 to an outer surface that is in contact with the liquid 50 of the pool) that is less than the effective coefficient of thermal conductivity of the heat exchange tubes 114 (measured from an inner surface that is contact with the working fluid 75 to an outer surface that is in contact with the liquid 50 of the pool) in certain embodiments of the invention. As discussed in detail below, this helps achieve an internal thermosiphon recirculation flow of the liquid phase 75A of the working fluid 75 within the evaporative heat exchanger 110 itself (indicated by the flow arrows in FIG. 2). The plurality of heat exchange tubes 114 form a tube bundle that circumferentially surrounds the core tube 113. The plurality of heat exchange tubes 114 are arranged in a substantially vertical orientation. The heat exchange tubes 114 are constructed of a material having a high coefficient of thermal conductivity to effectively transfer thermal energy from the liquid 50 of the pool to the working fluid 75. Suitable materials include, without limitation, aluminum, copper, or materials of similar thermal conductivity. In one embodiment, the heat exchange tubes 114 are fumed tubes comprising a tube portion 119 and a plurality of fins 120 extending from an outer surface of the tube portion 119 (shown in FIG. 6). In the exemplified embodiment, each heat exchange tube 114 comprises four fins 120 extending from the tube portion 119 at points of 90 degree circumferential separation. During operation of the autonomous self-powered system 1000, cool liquid phase 75A of the working fluid 75 enters the evaporative heat exchanger 110 via the working fluid inlet 111 as discussed above. The liquid phase 75A of the working fluid 75 is considered “cool” at this time because it had been previously cooled in the condenser 50. As the cool liquid phase 75A of the working fluid 75 enters the evaporative heat exchanger 110, it is introduced into the core tube 113. The cool liquid phase 75A of the working fluid 75 flows downward through the core tube and into the bottom header 115, thereby filling the bottom header 115 and flowing upward into the plurality of heat exchange tubes 114. As the liquid phase 75A of the working fluid 75 flows upward in the plurality of heat exchange tubes 114, thermal energy from the liquid 50 of the pool that surrounds the plurality of heat exchange tubes 114 is conducted through the plurality of heat exchange tubes 114 and into the liquid phase 75A of the working fluid 75, thereby heating the liquid phase 75A of the working fluid 75. The warmed liquid phase 75A of the working fluid 75 then enters the top header 116 where it is drawn back into the core tube 113 by a thermosiphon effect. As a result, the liquid phase 75A of the working fluid 75 is recirculated back through the aforementioned cycle until the liquid phase 75A of the working fluid 75 achieves the boiling temperature of the working fluid 75, thereby being converted into the vapor phase 75B of the working fluid 75. The vapor phase 75B of the working fluid 75 rises within the evaporative heat exchanger 110 and gather within a top portion of the top header 116 where it then exits the evaporative heat exchanger 110 via the working fluid outlet(s) 112. The internal design of the evaporative heat exchanger 110 promotes recirculation of the working fluid 117 and separation of the vapor phase 75B from the liquid phase 75A in the top header 116 (as shown in FIG. 2). As mentioned above, the evaporative heat exchanger 110 is pressurized to a supra-atmospheric pressure. In one embodiment, the pressure within the evaporative heat exchanger 110 is between 250 psia to 400 psia, with a more preferred range being between 280 psia and 320 psia, with approximately 300 psia being most preferred. Pressurization of the evaporative heat exchanger 110 is achieved through properly positioned valves as would be known to those of skill in the art. In one embodiment, the working fluid 75 and the pressure within the evaporative heat exchanger 110 are selected so that the working fluid evaporates at a temperature between 145° F. and 175° F., and more preferably between 155° F. and 165° F. Referring solely now to FIG. 1, the pressurized vapor phase 75B of the working fluid 75 exits the working fluid outlet 112 of the evaporative heat exchanger 110 and enters the working fluid inlet 131 of the turbogenerator 130. The pressurized vapor phase 75B of the working fluid 75 produced in the evaporative heat exchanger 110 then serves to energize a suitably sized turbogenerator 130. In other words, the turbogenerator 130 converts a first portion of the thermal energy extracted from the liquid 50 of the pool (which is now in the form of kinetic energy (velocity head) and/or potential energy (pressure head) of the vapor flow) to electrical power, as would be understood by those of skill in the art. As used herein, the term “turbogenerator” includes a device and/or subsystem that includes a turbine and electrical generator either in directed or indirect connection. The term “turbogenerator” is intended to include any device and/or subsystem that can convert the pressurized vapor phase 75B of the working fluid 75 into electrical energy. As the vapor phase 75B of the working fluid 75 passes through the turbogenerator 130 it is partially depressurized as it exits the working fluid outlet 132 of the turbogenerator still in the vapor phase 75B. At this point, the vapor phase 75B of the working fluid 75 may be at a pressure between 200 psia and 270 psia. As mentioned above, the forced flow units (which in the exemplified embodiment are the hydraulic pump 190 and the blower 151) are operably and electrically coupled to the turbogenerator 130 by the electrical circuit 130 via electrical lines 201. All of the forced flow units are powered solely by the electrical energy generated by the turbogenerator 130 as discussed above. Moreover, in many instances, the turbogenerator 130 will generate surplus electrical energy. Thus, the autonomous self-powered system 1000 may further comprise a rechargeable electrical energy source 202, such as a battery, operably and electrically coupled to the turbogenerator 130 by the electrical circuit 200. In certain embodiments, the rechargeable electrical energy source 202 will be operably coupled to a controller so that certain valves, sensors, and other electrical components can be operated even when the turbogenerator 130 is not running. Referring still to FIG. 1, the partially depressurized vapor phase 75B of the working fluid 75 that exits the turbogenerator 130 enters the working fluid inlet 152 of the condenser 150. The condenser 150 transfers a sufficient amount of thermal energy from the partially depressurized vapor phase 75B of the working fluid 75 to a secondary fluid so that the depressurized vapor phase 75B of the working fluid 75 is converted back into the liquid phase 75A of the working fluid 75. The condensed liquid phase 75A of the working fluid 75 exits the condenser 150 via the working fluid outlet 153 of the condenser where it flows back into the working fluid reservoir 170 for recirculation through the closed-loop fluid circuit 100. In one embodiment, the condenser 150 is an air-cooled condenser and, thus, the secondary fluid is air that is expelled to the environment. In other embodiments, the condenser 150 can be any type of heat exchanger than can remove thermal energy from the partially depressurized vapor phase 75B of the working fluid 75, including without limitation, a shell and tube heat exchanger, a plate heat exchanger, a plate and shell heat exchanger, an adiabatic heat exchanger, a plate fin heat exchanger, and a pillow plate heat exchanger. Referring to FIGS. 1 and 3 concurrently, an example of induced flow air cooled-condenser 150 that can be used in the system 1000 is exemplified. The induced flow air cooled-condenser 150 comprises a plurality of heat exchange tubes 154 (FIG. 6) positioned within an internal cavity formed by a housing 159. The working fluid 75 is the tubeside fluid and flows through the plurality of heat exchange tubes 154. The plurality of heat exchange tubes 154 are arranged in a substantially vertical orientation and are finned as discussed above with respect to the heat exchange tubes 114 of the evaporative heat exchanger 110, and as shown in FIG. 6. The induced flow air cooled-condenser 150 comprises a cool air inlet 155 and a warmed air outlet 156. The warmed air outlet 156 is at a higher elevation than the cool air inlet 155. The plurality of heat exchange tubes 154 are located in the cavity of the housing at an elevation between the elevation of the cool air inlet 155 and an elevation of the warmed air outlet 156. As such, in addition to the air flow within the housing 159 being forced by operation of the blower 151, which is located within the warmed air outlet 156, additional air flow will be achieved by the natural convective flow of the air as it is heated (i.e., the chimney effect). As warmed air exists the condenser 150 via the warmed air outlet 156, additional cool air is drawn into the cool air inlet 155. The induced flow air cooled-condenser 150, in certain embodiments, is located outside of the containment building in which the pool of liquid 50 is located. Referring now to FIGS. 4-5B concurrently, an example of natural draft air cooled-condenser 250 that can be used in the system 1000 is exemplified. Of note, the flow of air over the heat exchanger tubes 154 (which are also vertically oriented) is accomplished solely by natural convection (i.e., the chimney effect) and, thus, the blower 151 is not required. However, in certain embodiments, the blower 151 can be incorporated into the natural draft air cooled-condenser 250 as desired to accommodate for situations where the ambient air may reach elevated temperatures that could negatively affect adequate heat removal from the working fluid 75. Of further note, the natural draft air cooled-condenser 250 comprises a working fluid inlet header 260 comprising a plurality concentrically arranged toroidal tubes. Similarly, the natural draft air cooled-condenser 250 also comprises a working fluid outlet header 261 comprising a plurality concentrically arranged toroidal tubes. The plurality of heat exchange tubes 154 form a tube bundle that extends from the toroidal tubes of the working fluid inlet header 260 to the toroidal tubes of the working fluid outlet header 261. As with the air-cooled condenser 150, the natural draft air cooled-condenser 250 comprises a cool air inlet 255 and a warmed air outlet 256. The warmed air outlet 256 is at a higher elevation than the cool air inlet 255. The plurality of heat exchange tubes 254 are located in the cavity of the housing 259 at an elevation between the elevation of the cool air inlet 255 and an elevation of the warmed air outlet 256. The system 1000 of the present invention can be used to remove heat from any pool of water. In particular, it can be used to reject the decay heat from a spent fuel pool. Because the inventive system 1000 does not require any external active components such as pumps, motors, or electric actuators/controllers, it can engineered as an autonomous system that is not reliant on an external energy source to function. Thus, the inventive system 1000 is safe from an extreme environmental event such as a tsunami. It is evident that several of the systems 1000 can be deployed in a single pool of liquid if desired. The inventive system 1000 can be retrofit to existing plants for use both as an emergency cooling system under station blackout scenarios and as an auxiliary system to provide operational flexibility during corrective and elective maintenance (particularly during outages). The inventive system 1000 can also be incorporated into the plant design for new build projects to operate as the primary cooling system, thereby removing station blackout as a possible threat to spent fuel pool safety. As used throughout, ranges are used as shorthand for describing each and every value that is within the range. Any value within the range can be selected as the terminus of the range. In addition, all references cited herein are hereby incorporated by referenced in their entireties. In the event of a conflict in a definition in the present disclosure and that of a cited reference, the present disclosure controls. While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention. Thus, the spirit and scope of the invention should be construed broadly as set forth in the appended claims. |
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claims | 1. A multilayer grid containing alternate layers of an opaque or absorptive material and a transparent material for a neutron, hard X-ray, gamma-ray, imaging instrument containing a grid tray having openings to receive multilayer grids, the multilayer grid being a regular polyhedron having faces transparent to photons of interest, the polyhedron having two larger faces in the form of congruent polygons forming front and back surfaces of the polyhedron, remaining faces being smaller polygons separating the front and back surfaces a predetermined distance equal to the width of the two materials contained therein, the larger faces being shaped to form a multilayer grid fitting slidably within the grid opening in the grid tray, and the polyhedron containing a piston formed of a material transparent to photons of interest, which, through a drive shaft, compresses and retains the multilayers in place within the polyhedron, and which is allowed to remain in the polyhedron when, as a grid, the polyhedron is placed in the grid tray. 2. The multilayer grid of claim 1 wherein the parallelogram is an octagon. claim 1 3. The multilayer grid of claim 1 wherein the imaging instrument is a telescope, and the smaller polygons are parallelograms with perpendicular sides. claim 1 4. The multilayer grid of claim 2 wherein the piston drive shaft is coupled to a micrometer through a straight gear. claim 2 5. The multilayer grid of claim 2 wherein the piston drive shaft is coupled to a micrometer through a reciprocating double rack. claim 2 6. The multilayer grid of claim 2 wherein the polyhedron and the piston therein are made of glass. claim 2 7. The multilayer grid of claim 2 wherein the polyhedron and the piston therein are made of aluminum. claim 2 8. A method for improving a telescope used for neutron, hard X-ray and gamma-ray imaging, the telescope being one containing a grid tray having openings to receive multilayer grids, the improvement including assembling a regular polyhedron utilizing faces transparent to photons of interest, with two larger faces in the form of congruent polygons which form front and back surfaces of the polyhedron, and with smaller polygonal faces separating the front and back surfaces, the two larger faces being shaped to fit slidably within the grid opening in the grid tray, sizing a plurality of strips of absorptive and transparent materials so that their widths are equal to the width of the faces of the smaller polygons, inserting in the polyhedron, through an open face, alternate strips of the sized materials to form a multilayer, and compressing the multilayer to form a multilayer grid for insertion in the telescope grid tray. 9. The method of claim 8 wherein the uniform compressing of the inserted layers is accomplished by a piston sized to be inserted in the polyhedron through its open face, and contoured to fit slidably within the polyhedron. claim 8 10. The method of claim 9 wherein the piston is driven by a straight gear. claim 9 11. The method of claim 9 wherein the piston is driven by a reciprocating double rack. claim 9 12. The method of claim 9 wherein the piston is formed of a material transparent to photons of interest, and wherein it is allowed to remain in place within the polyhedron during use. claim 9 |
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048030406 | summary | BACKGROUND OF THE INVENTION This invention pertains to a system for diagnosing the status of a nuclear reactor operating with breached fuel elements and more particularly to a system which diagnoses the status of a nuclear reactor operating with breached fuel elements which utilizes an "expert system". The fuel in a fission type reactor is typically an isotope of uranium, such as uranium-235. The reactor fuel may take the form of a fluid, such as an aqueous solution of enriched uranium; but typically the fuel is solid, either metallic uranium or a ceramic such as uranium oxide or uranium-plutonium oxide. The solid fuel material is fabricated into various small plates, pellets, pins, etc.; which are usually clustered together and in an assemblage called a fuel element. Almost all solid fuel elements are clad with a protective coating or sheath that prevents direct contact between the fuel material and the reactor coolant. The cladding also serves as part of the structure of the fuel elements. The operation of fuel elements generates heat, which heat is typically dissipated by means of a coolant passed through the reactor. The coolant can be water, operating as either liquid or steam, or the coolant can be a liquid metal, such as sodium or a sodium-potassium mixture. The coolant passes in proximate contact over the cladded fuel elements; and sound cladding isolates or separates the coolant from the radioactive fuel material. However, in the event of a breach in the cladding, the coolant directly contacts the fuel. The radioactive discharge may then, in turn, be conveyed via the coolant throughout the entire coolant system, thereby contaminating the entire system. Also given off, as part of the radioactive discharge are isotopes, that not only give off typical gamma rays of radioactivity, but also give off what are known as delayed neutrons. The delayed neutron emitters are soluble in liquid sodium (the coolant) so that they readily blend in with the coolant, should a fuel element cladding breach occur, and flow from the coolant throughout the system. Therefore, it becomes readily apparent that the event of a fuel cladding breach must be taken into account when designing and operating a nuclear reactor. Not every occurance of a breached fuel element should trigger the automatic or manual shut-down of a nuclear reactor. In some instances, a reactor may be safely operated with breached fuel elements. Presently, liquid-metal cooled nuclear reactors (LMR's) exist which are licensed to operate with failed fuel. This mode of operation is typically referred to in the art as run-beyond-clad-breach (RBCB) operation. The current practice in most countries that have LMR programs is to set conservative shutdown limits on the magnitude of delayed-neutron (DN) signals coming from breached fuel. It would be advantageous in RBCB operation to significantly relax the conservatism in DN shutdown limits without compromising plant-safety assurance. Significant advantage could be derived from a system which could discriminate between cladding breach events which lead to plant operational degradation which might challenge safety or radiological performance guidelines and those events which do not. Such a system would allow the continued operation of the reactor under a stable breached pin condition, which would significantly improve reactor availability. A device called an equivalent recoil area (ERA) meter, which is a multiple detector DN monitoring station was previously developed for monitoring DN signals coming from breached fuel in LMR's. This device is disclosed in U.S. Pat. No. 4,415,524 entitled "Apparatus and Method of Monitoring for Breached Fuel Elements", issued to Kenny C. Gross et al., which patent is incorporated herein by reference. During breached-fuel operation, the ERA meter makes available to the reactor operator quantitative diagnostic information relating to the condition and dynamic evolution of a fuel breach. The diagnostic parameters include a continuous reading of the ERA value for the breach (which is a measure of the relative size of the breach). The ERA meter also provides continuous readings of the sodium transit time, T.sub.tr, to the detector station and the isotopic hold-up time, T.sub.h, a measure of the effective aging of DN precursors between birth in the fuel and their release to the coolant. Since the time that the ERA meter was originally conceived, it has been discovered that, contrary to earlier beliefs, the age of a DN signal is not constant with time. It has been learned from two recent experiments performed in the EBR-II reactor that the age of the signal can change spontaneously and frequently, even when all other reactor variables are at steady-state. The physical mechanism that initiates the changes in the isotopic hold-up time are still not fully understood. But the implications of a dynamically changing isotopic age are quite unsettling. It makes it virtually impossible for a human reactor operator to interpret and assess the safety significance of a changing DN signal. The reason for this is that the magnitude of a DN signal is a sensitive function of the age of the signal. Although, the ERA meter will help mitigate confusion and ambiquity by providing the operator with a separate reading of the DN age, the age is only one of several system variables that can cause a DN signal to change. If a signal is increasing, for example, table 1 lists nine possible physical variations that could have caused the signal to increase. Of course, any two or more of these physical variations could be occuring simultaneously. A similar matrix of physical causes also exists which may explain a decreasing DN signal. TABLE I ______________________________________ Possible Interpretations of an Increasing Delayed-Neutron Signal ______________________________________ 1. Increasing local fission rate 2. Increasing breach area 3. Increasing flow past source Depends on combination of age* and DN concen- 4. Decreasing flow past source tration in Na 5. Decreasing T.sub.h 6. Increasing flow rate in sample line to DND 7. New defect starting elsewhere (different pin or new location in same pin) 8. Change in dilation characteristics (e.g. at inlet scoop of bypass loop, or leakage component at assembly-facility interface) 9. Drifting DND characteristics (malfunction) ______________________________________ *Total age is a combination of holdup time, T.sub.h, and transit time, T.sub.tr It would, therefore, not be possible for a human operator to combine readings from the ERA meter with readings from flow, power, temperature, and various electrical sensors and then mentally step through the complex conditional branching hierarchy that is needed to arrive at an unambiguous interpretation of a change in a DN reading. Currently, full interpretation of these variables requires several days to weeks of detailed analysis by teams of specialists. The time needed for such interpretations is exemplified in well known cases that required several man-weeks of analysis for full interpretation, such as the TOPI-2 experiment, conducted by EBR-II, MST, and the PNC of Japan; breached assembly DE-9 that scrammed the FFTF in August 1984; the P4 experiment conducted by RAS; and the MOL-7C test by the French and Germans. Since a reactor operator must make an immediate decision whether to scram the reactor, continue reactor operation, or manually shutdown the reactor, the lengthy time periods required for the above referenced experiments are unacceptable. Therefore, in view of the above, it is an object of the present invention to make available a system that provides the reactor operator with a very rapid identification of off-normal RBCB conditions. It is another object of the present invention to provide an apparatus and method which will allow significant relaxation of the present conservatism in DN shut-down limits without compromising plant-safety assurance. It is still a further object of the present invention to provide a system which makes available, to a reactor operator, on-line diagnosis and interpretation of a variety of interacting physical variables during exposed fuel operation. It is yet another object of the present invention to provide a system which makes available, to a reactor operator, information needed to make proper decisions about technical-specification conformance of the reactor during RBCB operation. Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations, particularly pointed out in the appended claims. SUMMARY OF THE INVENTION To achieve the foregoing and other objects and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention provides a method and apparatus for surveillance and diagnosis of breached fuel elements in a nuclear reactor. A delayed neutron monitoring system generates output signals indicating the delayed neutron activity and delayed neutron age from a breached fuel element, and the equivalent recoil area of the breached fuel element. Sensors are used to detect the operability of each of the components of the delayed neutron monitoring system and to generate an output signal indicating the status of each component. Detectors also generate an output signal indicating the reactor power level and the reactor primary flow rate. The output from the detectors and sensors are interfaced with a knowledge system. The knowledge system includes a factual knowledge base and a judgmental knowledge base. The judgmental knowledge base uses predetermined logic, which accounts for the changing delayed neutron age. The knowledge system generates output signals indicating whether the reactor should continue to operate, be manually shutdown, be scrammed, or whether an alarm status should be set. |
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abstract | An example particle therapy system includes: a synchrocyclotron to output a particle beam; a magnet to affect a direction of the particle beam to scan the particle beam across at least part of an irradiation target; scattering material that is configurable to change a spot size of the particle beam, where the scattering material is down-beam of the magnet relative to the synchrocyclotron; and a degrader to change an energy of the beam prior to output of the particle beam to the irradiation target, where the degrader is down-beam of the scattering material relative to the synchrocyclotron. |
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description | The present application is a 35 U.S.C. §371 National Phase conversion of International (PCT) Patent Application No. PCT/CN2011/078063, filed on Aug. 5, 2011, the disclosure of which is incorporated by reference herein. The PCT International Patent Application was filed and published in Chinese. 1. Field of the Invention The present invention relates to solar cell manufacturing, and more particularly, to a plasma processing apparatus for fabricating thin film solar cells. 2. Background of the Invention Recently, large-area plasma processing apparatus have been widely used in the semiconductor field, such as thin film deposition or etching, for manufacturing such as flat panels and thin film solar cells. Radio-frequency (RF) power and frequency required for plasma processing are becoming higher and higher with the increase of processing size. In the current large-area plasma processing apparatus, the technique of double vacuum chambers is widely applied and the plasma reactor is placed inside a vacuum outer chamber, which protects the relatively fragile plasma reactor. However, as the RF power source is independently placed outside the vacuum outer chamber, it is needed to use RF power transmission line to transmit RF signals to an RF electrode inside the plasma reactor. As the vacuum chamber is not completely vacuumed but contains such gases as nitrogen, argon, silane and hydrogen, the condition for discharge can be easily satisfied when high power RF signals pass through the RF power transmission line. The discharge generated in the vacuum chamber may cause problems as follows: RF signals can not be effectively transmitted to the plasma reactor due to power losses, which may affect the plasma processing. High power discharge may destroy the transmission line, RF power source and other electronic circuits of the apparatus, and even bring about safety accidents. Therefore, how to transmit RF signals effectively and safely has become an urgent problem to be solved for the plasma processing apparatus. Theoretically, increasing vacuum degree can reduce the probability of discharge, but it is hardly possible to create an environment with absolute vacuum. Moreover, the increase of vacuum degree also correspondingly increases the use cost of apparatus. An objective of the present invention is to provide a plasma processing apparatus in which discharging is avoided when RF signals are transmitted in a vacuum chamber. The plasma processing apparatus of this present invention comprises: a vacuum chamber, a plasma reactor arranged in the vacuum chamber for plasma processing, a radio-frequency (RF) power source for providing RF signals for the plasma reactor and an RF power transmission unit for transmitting RF signals from the RF power source to the plasma reactor inside the vacuum chamber. The RF power transmission unit comprises a transmission line for transmitting RF signals and an outer conductor for shielding the electromagnetic field around the transmission line. The outer conductor may be a conduit, a conductive foil or a metal cover. The vacuum chamber is provided with an inner wall. The plasma reactor is provided with an outer wall. One end of the outer conductor is connected to the inner wall of the vacuum chamber, while the other end is connected to the outer wall of the plasma reactor. Materials for both the outer wall of the plasma reactor and the inner wall of the vacuum chamber are conductive. The outer wall of the plasma reactor, the inner wall of the vacuum chamber and the outer conductor together provide a closed electromagnetic shielding body. The transmission line may be tubular, columnar, metal netlike or wirelike. In one embodiment, the transmission line is a cylinder, and the outer conductor has a cylindrical inner surface. The diameter of the transmission line is larger than or equal to 10 mm. There is a gap of less than or equal to 10 mm between the outer conductor and the transmission line. The pressure of vacuum chamber may be 0.03-3 mbar, and the voltage of RF power source may be 100-500V. In one embodiment, the gap distance is greater than or equal to 1 mm. The inner diameter of outer conductor is greater than 12 mm but smaller than or equal to 60 mm. The material of outer conductor may comprise one or more selected from the group consisting of Cu, Au, Ag, Fe, Zn, Cr, Pb, Ti and their alloys. The material of transmission line may comprise one or more selected from the group consisting of Cu, Al, Au, Ag, Fe, Zn, Cr, Pb, Ti and their alloys. In one embodiment, a space between the transmission line and outer conductor is filled with an insulating medium. The transmission line is coaxial with the outer conductor. The vacuum chamber is provided with a vacuum chamber pressure adjustment unit which comprises a first gas outlet. The plasma reactor is provided with a plasma reactor pressure adjustment unit which comprises a second gas outlet. The first gas outlet and the second gas outlet are connected to a same exhaust pump, or, connected to different exhaust pumps, respectively. The plasma reactor further comprises an RF electrode and a first gas inlet communicated with the RF electrode. One end of the transmission line is connected to the RF power source, and the other end of the transmission line is connected to the RF electrode. The RF power source is placed outside the vacuum chamber and comprises an RF generator unit and a match box connected to the RF generator unit. The match box serves as a conditioner for regulating the coupling power of the RF signals. Compared with the prior art, the present invention may have following advantages: The RF power transmission unit has an outer conductor to shield the electromagnetic field around the transmission line, and thus RF signals can be effectively prevented from discharging in the vacuum chamber. The closed electromagnetic shielding body provided by the outer conductor, the outer wall of the plasma reactor, the inner wall of the vacuum chamber can further enhance the shielding effect from the electromagnetic field around the transmission line. The transmission line as a cylinder and the outer conductor with a cylindrical inner surface are coaxial and capable of maintaining a constant gap distance therebetween. Particularly, the diameter of transmission line is greater than or equal to 10 mm, while the gap distance is equal to or less than 10 mm. On the one hand, such a design can guarantee low impedance of transmission line and low equivalent inductance of the RF power transmission unit, which helps to reduce power losses of the RF power transmission unit and reduce glowing power of the plasma processing apparatus; On the other hand, it can also enhance the minimum discharge voltage of RF signals within the gap between the transmission line and the outer conductor so as to avoid the occurrence of discharge phenomenon. Furthermore, the gap larger than 1 mm between the outer conductor and the transmission line can guarantee effective insulation. The features of this invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention. In current plasma processing apparatus, when high-power radio-frequency (RF) signals pass through a transmission line located in a vacuum chamber, electric discharge may easily occur even if the gas in the vacuum chamber is extremely tenuous. It is not an effective way to solve discharge problem only by increasing the vacuum degree of vacuum chamber. An RF power transmission unit of the present invention has an outer conductor for shielding electromagnetic field around the transmission line, which can effectively avoid the electric discharge caused by the RF signals passing through the vacuum chamber. FIG. 1 is schematic illustration of an RF power transmission unit of the present invention. FIG. 2 is the cross sectional view of the RF power transmission unit taken along the line A-A′ in FIG. 1. As shown in FIG. 1 and FIG. 2, the RF power transmission unit of the present invention comprises a transmission line 101 for transmitting RF signals, and an outer conductor 102 for shielding the electromagnetic field of the transmission line 101. When the RF power transmission unit is applied to a plasma processing apparatus, since the transmission line 101 is arranged inside the outer conductor 102, the electromagnetic field of the transmission line 101 is shielded by the outer conductor 102. Therefore RF signals transmitted by the transmission line 101 can be effectively prevented from discharging in the vacuum chamber. In a preferred embodiment, two ends of the outer conductor 102 may be connected with an outer wall of the plasma reactor and an inner wall of the vacuum chamber, respectively. Moreover, both materials of the plasma reactor outer wall and vacuum chamber inner wall are conductive. The plasma reactor outer wall, the vacuum chamber inner wall and the outer conductor provide a closed electromagnetic shielding body, which can further enhance the shielding effect from the electromagnetic field around the transmission line 101. The transmission line 101 may be tubular, columnar, metal netlike or wirelike, and its material may comprise one or more selected from the group consisting of Cu, Al, Au, Ag, Fe, Zn, Cr, Pb, Ti and their alloys. The outer conductor 102 may be a conduit, a conductive foil or a metal cover, and its material may comprise one or more selected from the group consisting of Cu, Al, Au, Ag, Fe, Zn, Cr, Pb, Ti and their alloys. In some embodiments of the present invention, the transmission line 101 is a cylinder, and the outer conductor 102 has a cylindrical inner surface. Both the transmission line and the outer conductor are made from aluminum, and there is a gap between them. The gap may be filled with an insulating medium. In the best embodiment of the present invention, the gap is vacuumed so as to avoid negative effect of comparatively high impedance. The transmission line 101 and the outer conductor 102 may be coaxial so that a distance between them is substantially the same throughout the whole transmission line 101. However, in other embodiments of the present invention, the transmission line 101 may be not coaxial with the outer conductor 102. By using the RF power transmission unit as described above, the discharging problem of the vacuum chamber in a plasma processing apparatus can be solved. As illustrated in FIG. 3, the plasma processing apparatus of the present invention comprises: a vacuum chamber 30, a plasma reactor 20 arranged in the vacuum chamber 30 for plasma processing, an RF power source 40 for providing RF signals to the plasma reactor, an RF power transmission unit 10 for transmitting the RF signals from the RF power source 40 to the plasma reactor 20. The RF power transmission unit 10 comprises a transmission line 101 with one end thereof connected to the RF power source 40, and the other end thereof connected to the plasma reactor 20. The vacuum chamber 30 is provided with a vacuum chamber pressure adjustment unit which comprises a first gas outlet 501 connected with the vacuum chamber 30. The pressure adjustment unit can regulate the pressure in the vacuum chamber 30 by using the first gas outlet 501 to pump gases from the vacuum chamber 30. The plasma reactor 20 is provided with a plasma reactor pressure adjustment unit which comprises a second gas outlet 502 used for pumping gases from the plasma reactor 20 and thereby regulating the pressure of plasma reactor 20. Furthermore, each of the two opposite ends of the plasma reactor 20 may be provided with a said second gas outlet 502 respectively. The first gas outlet 501 and the second gas outlet 502 may be communicated with different exhaust pumps respectively so as to increase pumping speed and improve productivity efficiency. In other embodiments of the present invention, the first gas outlet 501 and the second gas outlet 502 may be communicated with a same exhaust pump in order to simplify apparatus and reduce cost. The plasma reactor 20 comprises a susceptor 201 arranged at the bottom of the reactor, an RF electrode 202 arranged at the top of the reactor, and a first gas inlet 503 communicated with the RF electrode 202. The susceptor is used to support a piece 203 to be processed. The RF electrode 202 may be a metal plate or a metal coil made of conductive material such as copper or aluminum and electrically connected with the RF power transmission unit 10 to act as a load of the RF power transmission unit 10. The first gas inlet 503 is used for injecting a reactant gas or pressure regulating gas to the plasma reactor. Said gas may be distributed uniformly through the RF electrode 202. Once being loaded to the RF electrode 202, RF signals may discharge in the plasma reactor 20 and generate plasma between the RF electrode 202 and the susceptor 201. The plasma comprises the ionized reaction gases injected from the first gas inlet 503, and is able to treat the piece 203 on the susceptor with plasma processing, for example, to deposit a thin film on a glass substrate. The RF power source 40 comprises an RF generator unit 401, and a match box 402 connected to the RF generator unit 401. The RF generator unit 401 can generate the necessary RF signals by means of frequency synthesis or oscillator. The match box 402 matches the impedance of RF signals to regulate its coupling power. The transmission line of RF power transmission unit 10 has one end thereof connected to the output of match box 402, and the other end thereof connected to the RF electrode 202, and thereby transmit the RF signals after regulation from the match box 402 to the RF electrode 202. FIG. 4 is a schematic illustration of a transmission circuit of aforesaid RF signals. As illustrated in FIG. 3 and FIG. 4, the RF generator unit 401 may be replaced with a power circuit 401a of the transmission circuit. The power circuit 401a includes a voltage source V0, and an internal resistance R0 in series with the voltage source V0. The match box 402 may be equivalent to a power control circuit 402a. The power control circuit 402a includes an equivalent capacitor (CM2) and an equivalent inductor (LM) which are in series with the output of power circuit 401a, and also includes a parasitic capacitor (CM1) between the power control circuit 402a and the ground. The RF power transmission unit 10 may be replaced with an RF transmission circuit 10a. The RF transmission circuit 10a includes an internal resistance Rt of the transmission line and an equivalent inductor Lt which are in series with the output of the power control circuit 402a, and also includes a parasitic capacitor Ct between the transmission circuit 10a and the ground. The RF electrode 202 may be equivalent to a circuit load 202a, which includes an equivalent inductor Lr and a discharge capacitor Cr which are connected with the output end of the RF transmission circuit 10a. When the RF signals pass through the transmission line 101, power loss always exist even without electric discharge due to existence of the internal resistance of transmission line 101 and the equivalent capacitor. It may be needed to decrease the power loss of transmission line 101 in order to reduce glowing power of the plasma processing apparatus. As used herein, the “glowing power” refers to the minimum power to make the RF electrode 202 discharge. According to the voltage partition principle, in FIG. 4, the voltage between the electrode plates of discharging capacitor Cr, i.e. the voltage between the RF electrode 202 and the susceptor 201, will increase with the decrease of the internal resistance Rt of the transmission line or the equivalent inductance Lt in the RF transmission circuit 10a. Therefore, decrease of both the internal resistance Rt of the transmission line and the equivalent inductance Lt can help to reduce the glowing power of the plasma processing apparatus. Referring back to FIG. 1, to simplify the illustration, in the RF power transmission unit 10 of the present invention, it is assumed that the transmission line 101 is coaxial with the outer conductor 102, the cross section of the transmission line 101 is circular, and the cross section of the inner surface of the outer conductor is circular as well. Based on this assumption, the dependence of the equivalent inductance Lt on the radius r of the transmission line 101 and the inner radius R of the outer conductor 102 can be calculated by the following formula: L t = μ 0 · l 2 π ( ln R r + 1 4 ) ;where l refers to the length of the transmission line 101, depending on the arrangement of transmission line 101 in the vacuum chamber 30, and μ 0 2 π is a constant. Accordingly, the only way to reduce the equivalent inductance Lt is to reduce the value of ln R r ,i.e. to make the radius r of the transmission line 101 and the inner radius R of outer conductor 102 as close to each other as possible. The internal resistance Rt of the transmission line can be reduced by increasing the diameter of the It should be noted that, when there is a gap between the transmission line 101 and the outer conductor 102, there may be gases in the gap, and thus the requirement for discharge may be satisfied. When the transmission line 101 discharges in the gap, there are still problems about apparatus security and transmission power loss. According to Paschen's law, in a gaseous environment with fixed components, the minimum discharge voltage between two conductors depends on their pressure and gap distance. As shown in FIG. 5, the Paschen curve of RF discharge reflects the relation among the minimum discharge voltage, with the pressure and gap distance. In FIG. 5, the horizontal axis represents the product P·d of the pressure P and gap distance d, and the vertical axis represents the corresponding minimum discharge voltage V. The aforesaid Paschen curve is of a shape of “L”, and the minimum discharge voltage V shows different trends within the interval between two ends of P·d. The reasons will be described as follows. When discharge occurs through the mechanism represented by the right half part of the Paschen curve, the ambient pressure is relatively higher, and there are too many gas molecules between adjacent conductors. The electrons moving between the adjacent conductors have relatively more elastic collisions with gas molecules and relatively heavier energy losses, which goes against the generation of impact ionization. With the increase of the value of P·d, the minimum discharge voltage becomes larger. When discharge occurs through the mechanism represented by the left half part of the Paschen curve, the ambient pressure is relatively lower and is almost vacuumed, and there are very few gas molecules between adjacent conductors. The electrons moving between the adjacent conductors have barely collisions, which also goes against the generation of impact ionization. With the decrease of the value of P·d, the minimum discharge voltage also becomes larger. Returning to FIG. 2, according to the aforesaid theories, in a plasma processing apparatus with an approximate vacuum environment, the discharge mechanism of transmission line 101 of the RF power transmission unit 10 and the outer conductor 102 should be represented by the left half part of the Paschen curve. Therefore, in order to reduce the discharge probability of RF signals within the gap between the transmission line 101 and the outer conductor 102, besides increasing vacuum degree of the gap and reducing gas pressure, it's still needed to decrease the corresponding gap distance d, namely the value of R-r. Moreover, with the premise of a fixed diameter of the transmission line 101, the value of the gap d also can be reduced by making the radius of transmission line 101 closer to the radius of outer conductor 102, and thereby reducing the equivalent inductance Lt of the RF power transmission unit 10. In addition, in order to guarantee insulating reliability between the transmission line 101 and the outer conductor 102, the gap distance d is inappropriate to be excessively small. Based on the reasons above, for an plasma processing apparatus of the present invention embodiments, in the RF power transmission unit 10, the diameter of transmission line 101 is larger than or equal to 10 mm, and the gap distance d between the transmission line 101 and the outer conductor 102 is equal to or smaller than 10 mm. Such a design can guarantee low impedance of the transmission line and low equivalent inductance of the RF power transmission unit, which contributes to reduction of the power loss of RF power transmission unit and the glowing power of plasma processing apparatus. On the other hand, the minimum discharge voltage of RF signals in the gap between the transmission line and the outer conductor is increased so as to avoid discharge. The pressure in the vacuum chamber 30 may be 0.03-3 mbar. The voltage of the RF power source may be 100-500V. The gap distance between the transmission line 101 and the outer conductor 102 is larger than or equal to 1 mm to guarantee effective insulation. The inner diameter of the outer conductor 102 may be larger than 12 mm and smaller than or equal to 60 mm. In a specific embodiment, the gas pressure in the vacuum chamber 30 is 0.03 mbar, and the voltage of the RF power is 100V. The transmission line 101 is a copper rod with a diameter of 10 mm, and the outer conductor 102 is an aluminum tube with an inner diameter of 30 mm and a tube thickness of 2 mm. The transmission line 101 and the outer conductor 102 are coaxial and have a 10 mm gap therebetween. In a specific embodiment, the gas pressure in the vacuum chamber 30 is 0.1 mbar, and the voltage of the RF power source 40 is 300V. The transmission line 101 is a copper rod with a diameter of 34 mm, and the outer conductor 102 is an aluminum tube with an inner diameter of 40 mm and a tube thickness of 2 mm. The transmission line 101 and the outer conductor 102 are coaxial and have a 3 mm gap therebetween. In a specific embodiment, the gas pressure in the vacuum chamber 30 is 3 mbar, and the voltage of the RF power is 500 V. The transmission line 101 is a copper rod with a diameter of 10 mm, and the outer conductor 102 is an aluminum tube with an inner diameter of 12 mm and a tube thickness of 1 mm. The transmission line 101 and the outer conductor 102 are coaxial and have a 1 mm gap therebetween. The use of the plasma processing apparatus disclosed by the present invention will be further explained hereinafter by taking a thin film deposition process for fabricating a thin-film solar cell as an example. Firstly, a large-area glass substrate to be treated is placed on the susceptor 201 in plasma reactor 20, and then the plasma reactor 20 and the vacuum chamber 30 are closed. Secondly, the pressure adjustment unit is used to pump gases from the vacuum chamber 30 via the first gas outlet 501, until the desired pressure is reached and an approximate vacuum environment in the vacuum chamber 30 is obtained. Thirdly, a reactant gas or pressure regulating gas is injected to the plasma reactor via the first gas inlet 503, and then the pressure adjustment unit is use to pump gases from the plasma reactor 20 via the second gas outlet 502. Therefore the gas pressure in the plasma reactor 20 is adjusted to meet process requirement for thin film deposition. Finally, the RF power source 40 is turned on to generate RF signals of desired power, and RF signals are transmitted to the RF electrode 202 of plasma reactor 20 via the RF power transmission unit 10. At this moment, relatively large voltage difference between the RF electrode 202 and the susceptor 201 is formed. When the voltage difference exceeds the minimum discharge voltage of the plasma reactor 20, i.e. the power of RF signals is larger than the glowing power, the RF electrode 202 will discharge in the plasma reactor 20 and ionize the reactant gases therein. The ionized reactant gases will react with the surface of the glass substrate to form a desired thin film. In the aforesaid plasma processing process, since the RF transmission unit can effectively avoid the discharge of the transmission line in the vacuum chamber, and also have relatively low impedance and low equivalent inductance, it is suitable to transmit high-power RF signals. The RF signals can be more effectively transmitted to the RF electrode of plasma reactor with lower power loss, which is beneficial to large-area plasma processing. It is to be understood, however, that even though numerous characteristics and advantages of preferred and exemplary embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only; and that changes may be made in detail within the principles of present disclosure to the full extent indicated by the broadest general meaning of the terms in which the appended claims are expressed. |
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description | The present invention relates to a device for reconstructing axial measurement values in a nuclear fuel, which is a device that reconstructs values measured by detectors provided in the core of a nuclear reactor. As a method of evaluating nuclear properties in the core of a nuclear reactor, there has been a method of comparing design values and actual values (measurement values) about items, such as the output peaking and the axial output deviation of the core. A neutron flux detector is provided in the core of the nuclear reactor and a distribution of reaction rates along the axial direction of the core is calculated on the basis of values measured by the neutron flux detector. By using a plurality of types of data, such as the distribution of reaction rates and the temperature along the axial direction of the core, reactor output distribution processing is regularly performed in order to monitor the core, and the output peaking and the axial output deviation of the core, etc. are calculated. Such methods are described in, for example, the following patent documents. Patent Literature 1: Japanese Laid-open Patent Publication No. 56-138291 Patent Literature 2: Japanese Laid-open Patent Publication No. 58-035492 As neutron flux detectors used in pressurized water reactors, there are mainly movable neutron flux detectors and fixed neutron flux detectors. As for movable neutron flux detector, because a movable neutron flux detector is inserted into an in-core nuclear instrumentation guide thimble and performs measurement while being moved in the longitudinal direction (in the direction along the height of a fuel assembly), it is possible to obtain continuous axial measurement distribution information on the nuclear fuel. On the other hand, as for fixed neutron flux detector, a plurality of fixed neutron flux detectors are disposed at predetermined intervals along the longitudinal direction in an in-core nuclear instrumentation guide thimble in a fuel assembly, it is possible to obtain a plurality of values of measurements at different levels in the fuel assembly by using the fixed neutron flux detectors, and it is thus possible to obtain an axial measurement distribution in the nuclear fuel by using the measurement values; however, the number of neutron flux detectors that can be disposed in an in-core nuclear instrumentation guide thimble in a fuel assembly is limited, which makes it difficult to obtain a detailed axial measurement distribution in the nuclear fuel. Because the neutron flux detectors are fixed in the in-core nuclear instrumentation guide thimble, it is not possible to replace a failed nuclear flux detector, which leads to a problem in that the number of measurement values decreases and this further lowers the accuracy of the axial measurement distribution in the nuclear fuel. The present invention is for solving the above-described problem and an objective of the present invention is to provide a device for and a method of reconstructing axial measurement values in a nuclear fuel, which are a device and a method enabling obtaining of an accurate axial measurement distribution in a nuclear fuel by reconstructing a plurality of measurement values. According to a device for reconstructing axial measurement values in a nuclear fuel of this invention, the device calculating an axial measurement distribution by reconstructing a plurality of measurement values measured by a plurality of detectors that are disposed at predetermined intervals in the nuclear fuel along the axial direction of the nuclear fuel. The device comprising a reconstruction parameter generator that generates a reconstruction parameter on the basis of core design data, or core analysis data, and a data adjustment factor; and an axial measurement distribution generator that calculates an axial measurement distribution in the nuclear fuel on the basis of the measurement values that are measured by the detectors and the reconstruction parameter that is generated by the reconstruction parameter generator. Accordingly, the reconstruction parameter is generated on the basis of the core design data, or the core analysis data, and the data adjustment factor and the axial measurement distribution in the nuclear fuel is calculated on the basis of the measurement values measured by the detectors and the reconstruction parameter. For this reason, it is possible to specify the shape of the distribution of measurements along the axial direction by using the core design data, or the core analysis data, and the data adjustment factor and it is possible to align the reconstruction parameter with each measurement value by using the measurement values. As a result, it is possible to obtain an accurate axial measurement distribution in the nuclear fuel by reconstructing the measurement values. According to the device for reconstructing axial measurement values in a nuclear fuel on this invention, the axial measurement distribution generator calculates the axial measurement distribution in the nuclear fuel by correcting the reconstruction parameter in accordance with the measurement values such that the deviation between the measurement values and the reconstruction parameter is at minimum. Accordingly, because the reconstruction parameter is corrected in accordance with each measurement value, it is possible to calculate an accurate axial measurement distribution. According to the device for reconstructing axial measurement values in a nuclear fuel on this invention, the reconstruction parameter generator generates the reconstruction parameter on the basis of an inclination adjustment factor, an axial distribution adjustment factor, and an integral value adjustment factor that serve as the data adjustment factor. Accordingly, by using the inclination adjustment factor, the axial distribution adjustment factor, and the integral value adjustment factor as the data adjustment factor, it is possible to correct the core design data or the core analysis data to the distribution along its inclination direction and axial direction and the magnitude in along the direction of the absolute value and it is possible to generate a reconstruction parameter with accuracy. According to the device for reconstructing axial measurement values in a nuclear fuel on this invention, the axial distribution adjustment factor is comprised of a plurality of adjustment factors that make adjustment with different periods. Accordingly, it is possible to generate the reconstruction parameter with accuracy by using the adjustment factors that make adjustment with different periods as the axial distribution adjustment factor. According to a method of reconstructing axial measurement values in a nuclear fuel on this invention, the method being a method of calculating an axial measurement distribution by reconstructing a plurality of measurement values measured by a plurality of detectors that are disposed at predetermined intervals in the nuclear fuel along the axial direction of the nuclear fuel. The method comprising: a step of generating a reconstruction parameter on the basis of core design data, or core analysis data, and a data adjustment factor; and a step of calculating an axial measurement distribution in the nuclear fuel on the basis of the measurement values that are measured by the detectors and the generated reconstruction parameter. Accordingly, it is possible to specify the shape of the distribution of measurements along the axial direction by using the core design data, or the core analysis data, and the data adjustment factor and it is possible to align the reconstruction parameter with each measurement value by using the measurement values. As a result, it is possible to obtain an accurate axial measurement distribution in the nuclear fuel by reconstructing the measurement values. According to the device for and method of reconstructing axial measurement values in a nuclear fuel, because the reconstruction parameter is generated on the basis of the core design data, or the core analysis data and the data adjustment factor and the axial measurement distribution in the nuclear fuel is calculated on the basis of the measurement values measured by the detectors and the reconstruction parameter that is generated by the reconstruction parameter generator, it is possible to obtain the accurate axial measurement distribution in the nuclear fuel. With reference to the accompanying drawings, a preferred embodiment of the device for and method of reconstructing axial measurement values in a nuclear fuel according to the present invention will be described in detail below. The embodiment does not limit the invention. If there are multiple embodiments, a configuration obtained by combining each embodiment may be covered. FIG. 1 is a schematic diagram illustrating a configuration of a nuclear reactor employing a device for reconstructing axial measurement value in a nuclear fuel according to the embodiment. FIG. 2 is a schematic diagram illustrating disposition of neutron flux detectors in a fuel assembly. Although not illustrated, a nuclear power plant includes, a nuclear reactor, a steam generator, and a steam turbine generation facilities that are disposed in a reactor vessel. The nuclear reactor according to the embodiment is a pressurized water reactor (PWR) that uses light water as a reactor cooling material and a neutron moderator, uses the light water as high-temperature and high-pressure water that does not boil in the entire core, generates vapor by heat exchange by transmitting the high-temperature and high-pressure water to the vapor generator, and generates power by transmitting the vapor to the turbine. The nuclear reactor heats primary cooling water by nuclear fission of the fuel and the vapor generator performs heat exchange between the high-temperature and high-pressure primary cooling water and secondary cooling water to generate vapor. The vapor turbine power facility generates power by driving the vapor turbine with the vapor. On the other hand, the vapor that has driven the vapor turbine is cooled by the condenser to be condensed water and the condensed water is returned to the vapor generator. As shown in FIG. 1, in a pressurized water reactor 10, a reactor vessel 11 is comprised of a reactor vessel body 12 and a reactor vessel lid (top mirror) 13 that is mounted on the top of the reactor vessel body 12 and the reactor vessel lid 13 is fixed to the reactor vessel body 12 with a plurality of stud bolts and nuts such that the reactor vessel lid 13 is openable and closable. The reactor vessel body 12 has a shape of a cylinder having a closed bottom and an upper part in which an inlet nozzle (inlet tube table) 14 for supplying light water (cooling material) serving as primary cooling water and an outlet nozzle (outlet tube table) 15 for discharging the light water are formed. In the reactor vessel body 12, a core barrel 16 is disposed and the upper part of the core barrel 16 is supported by the inner wall surface of the reactor vessel body 12. A core 17 is configured by disposing a large number of fuel assemblies 20 serving as a nuclear fuel in an area sectioned by an upper core plate 18 and a lower core plate 19 in the core barrel 16. The fuel assembly 20 is configured by bundling a plurality of fuel rods (not shown) along the vertical direction to form a grid. In the core 17, a large number of control rods (not shown) are disposed in the fuel assembly 20 and a control rod drive device 21 inserts/extracts the control rods into/from the core 17 to control the reactor output. In the fuel assembly 20, a plurality of neutron flux detectors 22 are disposed. As shown in FIGS. 1 and 2, the fuel assemblies 20 are disposed along the vertical direction and an in-core nuclear instrumentation guide thimble 23 is inserted from the top (or the bottom) between the fuel rods, and a plurality of (six according to the embodiment) neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f) are disposed in the in-core nuclear instrumentation guide thimble 23. The neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f) are disposed in the in-core nuclear instrumentation guide thimble 23 at predetermined intervals (preferably at constant intervals) in the axial direction of the fuel assembly 20 (fuel rods) (vertical direction). The neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f) detect the neutron flux of the core and outputs a signal proportional to the value of the output of the core 17. Accordingly, it is possible to calculate an axial output distribution (axial reaction rate distribution) serving as an axial measurement distribution in the core 17 on the basis of the output signals from the respective neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f). It is however difficult to obtain an accurate axial output distribution in the fuel assembly 20 because only the six neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f) are disposed in the fuel assembly 20 along its axial direction. Furthermore, when any one of the six neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f) fails, the number of measurement values decreases, which further lowers the accuracy of the axial output distribution. According to the embodiment, an accurate axial output distribution (axial response rate distribution) is calculated by reconstructing the measurement values (output signals) measured by the neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f). As shown in FIG. 1, the device for reconstructing axial measurement values in a nuclear fuel according to the embodiment is a device for reconstructing axial measurement values in a nuclear fuel that calculates an axial measurement distribution (hereinafter, axial reaction rate distribution) by reconstructing a plurality of measurement values measured by the neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f) that are disposed in the fuel assembly 20 at predetermined intervals in the fuel assembly 20 in its axial direction, and the device is comprised of a data processor 31, a data storage unit 32, and a data output unit 33. The data storage unit 32 is comprised of a core design/analysis data storage unit 41 that stores core design data and core analysis data and a data adjustment factor storage unit 42 that stores various data adjustment factors to be described below. The data processor 31 is comprised of a reconstruction parameter generator 51 that generates a reconstruction parameter on the basis of the core design data, or the core analysis data, and the data adjustment factors and an axial reaction rate distribution generator (an axial measurement distribution generator) 52 that calculates an axial reaction rate distribution in the fuel assembly 20 on the basis of the measurement values measured by the neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f) and the reconstruction parameter generated by the reconstruction parameter generator 51. The data output unit 33 is a display, a printer, or the like that outputs the axial reaction rate distribution that is generated by the axial reaction rate distribution generator 52. The axial reaction rate distribution generator 52 calculates an axial reaction rate distribution in the fuel assembly 20 by correcting the reconstruction parameter in accordance with the measurement values such that the deviation between the measurement values and the reconstruction parameter is at minimum. The reconstruction parameter generator 51 generates a reconstruction parameter on the basis of an inclination adjustment factor, an axial distribution adjustment factor, and an integral value adjustment factor serving as the data adjustment factors. The axial distribution adjustment factors are comprised of a plurality of adjustment factors that make adjustments with different periods. The method of reconstructing axial measurement values, which is a method performed by the device for reconstructing axial measurement values in a nuclear fuel will be described in detail here. FIG. 3 is a graph representing an axial inclination adjustment factor α, FIG. 4 is a graph representing a first axial distribution adjustment factor β1, FIG. 5 is a graph representing a second axial distribution adjustment factor β2, FIG. 6 is a graph representing an integral value adjustment factor γ, and FIG. 7 is a schematic diagram illustrating the method of reconstructing axial measurement values in a nuclear fuel. In the data storage unit 32, the core design/analysis data storage unit 41 stores the core design data and the core analysis data. As shown in FIG. 7, the core design data is data on design values of reaction rates (horizontal axis) with respect to the height of the core (vertical axis) at the time when the core is designed. The core analysis data is data on analysis values of reaction rates (horizontal axis) with respect to the height of the core (vertical axis) after a predetermined period from when the core is designed. In other words, the core design data is an axial distribution of reaction rates at the time when the core is designed and the analysis data is the axial distribution of reaction rates obtained by analyzing the core after the predetermined period from when the core is designed. In the data storage unit 32, the data adjustment factor storage unit 42 stores data adjustment factors. The axial inclination adjustment factor α, the axial distribution adjustment factors β (the first axial distribution adjustment factors β1 and the second axial distribution adjustment factor β2), and the integral value adjustment factor γ are set as the data adjustment factors. As shown in FIG. 3, the axial inclination adjustment factor α represented by the dashed line is an accommodation coefficient with respect to the height of the core (horizontal axis), which is an accommodation coefficient to correct an inclination of the design values (analysis values) represented by the solid line with respect to the axial direction. As shown in FIG. 4, the first axial distribution adjustment factor β1 represented by the dashed line is an accommodation coefficient with respect to the height of the core (horizontal axis), which is an accommodation coefficient to correct a primary period of the design values (analysis values) represented by the solid line with respect to the axial direction. As shown in FIG. 5, the second axial distribution adjustment factor β2 represented by the dashed line is an accommodation coefficient with respect to the height of the core (horizontal axis), which is an accommodation coefficient to correct a secondary period of the design values (analysis values) represented by the solid line with respect to the axial direction. As shown in FIG. 6, the integral value adjustment factor γ represented by the dashed line is an accommodation coefficient with respect to the height of the core (horizontal axis), which is an accommodation coefficient to correct the magnitude (absolute value) of the design values (analysis values) represented by the solid line. In the data processor 31, as shown in FIGS. 1 and 7, the reconstruction parameter generator 51 generates a reconstruction parameter on the basis of the core design data (core analysis data) and the four data adjustment factors. In other words, supposing that the reconstruction parameter is RRa(z), the core design data (core analysis data) is RRc(z), the axial inclination adjustment factor is α(z), the axial distribution adjustment factor is β(z), and the integral value adjustment factor is γ(z), a reconstruction parameter RRa(z) can be calculated according to the following Equation (1). RR ( z ) a = RR ( z ) c × ( 1 + α ( z ) 100 ) × ( 1 + β ( z ) 100 ) × γ ( z ) ( 1 ) The axial inclination adjustment factor α(z) and the axial distribution adjustment factor β(z) can be calculated according to the following Equation (2) and Equation (3), where H is the height of the core (effective height), z is the level at which measurement is performed by the neutron flux detector 22a, 22b, 22c, 22d, 22e, or 22f, and a is a variable for determining the axial inclination adjustment factor α, b1 and b2 are variables for determining each of the axial distribution adjustment factors β1 and β2, and n is a period. α ( z ) = a × ( z - H 2 H 2 ) ( 2 ) β ( z ) = b 1 · cos ( π z - H 2 H 2 ) + b 2 ( 2 π z - H 2 H 2 ) ( 3 ) When the reconstruction parameter generator 51 generates a reconstruction parameter, the axial reaction rate distribution generator 52 calculates an axial reaction rate distribution in the fuel assembly 20 on the basis of the measurement values measured by the neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f) and the reconstruction parameter. In other words, the reconstruction parameter only represents a variation in the reaction rate with respect to the axial direction (direction along the height) of the fuel assembly 20 and its magnitude is not enough. For this reason, by superimposing the reconstruction parameter onto the measurement values measured by the respective neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e, and 22f) and correcting the reconstruction parameter in accordance with each measurement value to minimize the deviation between each measurement value and the reconstruction parameter, it is possible to calculate an axial reaction rate distribution (reconstructed values) in the fuel assembly 20. FIGS. 8 and 9 are graphs representing results of reconstructing axial measurement values in the nuclear fuel and FIGS. 10 and 11 are graphs representing results of reconstructing axial measurement values in the nuclear fuel obtained when part of the neutron fuel detectors fails. In FIGS. 8 and 9, “-” represents values measured by the neutron flux detectors 22a, 22b, 22c, 22d, 22e, and 22f and “∘” represents reconstructed values. FIG. 8 represents data at the time when the core is designed and FIG. 9 is data after the predetermined period from when the core is designed. As understood from FIGS. 8 and 9, it is understood that values “-” measured by the neutron flux detectors 22a, 22b, 22c, 22d, 22e, and 22f and the reconstructed values “∘” generated according to the embodiment approximately coincide. Furthermore, as shown in FIGS. 10 and 11, even when the neutron flux detectors 22b and 22e that are part of the neutron flux detectors fail, it is understood that values “-” measured by the neutron flux detectors 22a, 22c, 22d, and 22f and the reconstructed values “∘” generated according to the embodiment approximately coincide. As for the device for reconstructing axial measurement values in a nuclear fuel according to the embodiment, a device for reconstructing axial measurement values in a nuclear fuel, which is a device that calculates an axial reaction rate distribution by reconstructing a plurality of measurement values measured by a plurality of neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e and 22f) that are disposed at predetermined intervals in a fuel assembly 20 along the axial direction of the fuel assembly 20, is provided with: a reconstruction parameter generator 51 that generates a reconstruction parameter on the basis of core design data, or core analysis data, and a data adjustment factor; and an axial reaction rate distribution generator 52 that calculates an axial reaction rate distribution on the basis of the measurement values that are measured by the neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e and 22f) and the reconstruction parameter that is generated by the reconstruction parameter generator 51. Accordingly, the reconstruction parameter is generated on the basis of the core design data, or the core analysis data, and the data adjustment factor and the axial reaction rate distribution is calculated on the basis of the measurement values measured by the neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e and 22f) and the reconstruction parameter. Accordingly, it is possible to specify the shape of the distribution of reaction rates along the axial direction by using the core design data, or the core analysis data, and the data adjustment factor, and it is possible to align the reconstruction parameter with each measurement value by using the measurement values. As a result, it is possible to obtain an axial reaction rate distribution in the fuel assembly 20 by reconstructing the measurement values. According to the device for reconstructing axial measurement values in a nuclear fuel according to the embodiment, the axial reaction rate distribution is calculated by correcting the reconstruction parameter in accordance with the measurement values such that the deviation between the measurement values and the reconstruction parameter is at minimum. Accordingly, because the reconstruction parameter is corrected in accordance with each measurement value, it is possible to calculate an accurate axial measurement distribution. According to the device for reconstructing axial measurement values in a nuclear fuel according to the embodiment, the reconstruction parameter generator 51 generates the reconstruction parameter on the basis of an inclination adjustment factor, an axial distribution adjustment factor, and an integral value adjustment factor that serve as the data adjustment factor. Furthermore, the multiple adjustment factors that make adjustment with different periods are used as the axial distribution adjustment factor. Accordingly, it is possible to correct the core design data or the core analysis data to the distribution along its inclination direction and axial direction and the magnitude in along the direction of the absolute value and it is possible to generate a reconstruction parameter with accuracy. Furthermore, the method of reconstructing axial measurement values in a nuclear fuel according to the embodiment includes: a step of generating a reconstruction parameter on the basis of e core design data, or core analysis data, and a data adjustment factor, and a step of calculating an axial reaction rate distribution on the basis of measurement values measured by the neutron flux detectors 22 (22a, 22b, 22c, 22d, 22e and 22f) and the generated reconstruction parameter. Accordingly, it is possible to specify the shape of the distribution of reaction rates along the axial direction by using the core design data, or the core analysis data, and the data adjustment factor, and it is possible to align the reconstruction parameter with each measurement value by using the measurement values. As a result, it is possible to obtain an accurate axial reaction rate distribution in the fuel assembly 20. According to the above-described embodiment, the axial reaction rate distribution is calculated as the axial measurement distribution; however, an axial output distribution may be calculated. Furthermore, replacing the neutron flux detectors with temperature detectors enables the detectors to calculate an axial temperature distribution. 10 PRESSURIZED WATER RECTOR 17 CORE 22, 22a, 22b, 22c, 22d, 22e, 22f NEUTRON FLUX DETECTOR 23 IN-CORE NUCLEAR DESIGN GUIDE THIMBLE 31 DATA PROCESSOR 32 DATA STORAGE UNIT 33 DATA OUTPUT UNIT 41 CORE DESIGN ANALYSIS DATA STORAGE UNIT 42 DATA ADJUSTMENT FACTOR STORAGE UNIT 51 RECONSTRUCTION PARAMETER GENERATOR 52 AXIAL RESPONSE RATE DISTRIBUTION GENERATOR (AXIAL MEASUREMENT DISTRIBUTION GENERATOR) |
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claims | 1. A method of removing a radioactive deposit from a nuclear fuel assembly in a nuclear plant, the method comprising: providing a container ( 2 ) arranged to accommodate the nuclear fuel assembly, and arranging said container ( 2 ) in a xcex3-radiation-dampening medium, wherein said xcex3-radiation-dampening medium comprises water, providing a first pumping means ( 3 , 4 , 5 ) for feeding by pumping a fluid through the container in order to release the deposit from the nuclear fuel assembly by abrasion and to transport radioactive deposit out of the container, said first means ( 3 , 4 , 5 ) also being provided for the feeding of a gas or steam or both to a fluid comprising a mixture of water and ice that is fed into and through the container in order to create a turbulence in the fluid; and further comprising feeding with said first means, a gas or steam or both to said fluid that is fed into and through the container ( 2 ) such that a turbulence is created in the fluid; providing a second receiving means ( 6 , 7 ) arranged to receive the radioactive deposit transported out of the container ( 2 ) by the fluid, and wherein said second receiving means comprises a filter ( 6 ) arranged to separate released radioactive material from said fluid; arranging at least said second means ( 6 , 7 ) in said xcex3-radiation-dampening medium, arranging a nuclear fuel assembly ( 1 ) in said container ( 2 ), feeding by pumping with said first pumping means ( 3 , 4 , 5 ) said fluid comprising a mixture of water and ice and said gas or steam or both through said container ( 2 ), thereby releasing, by abrasion, a radioactive deposit from said nuclear fuel assembly ( 1 ) and transporting the radioactive deposit out of the container ( 2 ), receiving the transported radioactive deposit in said second means ( 6 , 7 ), and further comprising filtering with said filter to separate from said fluid the radioactive material that is released. 2. The method, according to claim 1 , which comprises feeding a gas to said fluid that is fed into and through the container such that a turbulence is created in the fluid. claim 1 3. The method, according to claim 1 , which comprises feeding air to said fluid that is fed into and through the container such that a turbulence is created in the fluid. claim 1 4. The method according, to claim 1 , which comprises feeding steam to said fluid that is fed into and through the container such that a turbulence is created in the fluid. claim 1 5. The method of claim 4 wherein said steam comprises water steam. claim 4 6. The method according to claim 1 , which further comprises arranging said container ( 2 ) and said receiving means in a basin filled with said xcex3-radiation-dampening medium. claim 1 7. The method according to claim 1 , further comprising irradiating said fuel assembly with infrasound. claim 1 8. The method according to claim 1 , further comprising rotating said fuel assembly. claim 1 9. The method according to claim 1 , further comprising heating at least a portion of said fluid that is fed into said container. claim 1 10. The method according to claim 1 wherein said deposit comprises loose crud. claim 1 11. The method according to claim 1 wherein the nuclear fuel assembly is a boiling water nuclear fuel assembly and the flow rate of said fluid is about 10-50 kg/s. claim 1 12. The method according to claim 11 wherein the ice flow is about 30-70% of the water flow. claim 11 13. The method according to claim 11 wherein said flow rate is 15-35 kg/s. claim 11 14. The method according to claim 11 wherein said flow rate is 20-25 kg/s. claim 11 15. The method according to claim 1 wherein the nuclear fuel assembly is a pressure water nuclear fuel assembly and the flow rate of said fluid 50-200 kg/s. claim 1 16. The method according to claim 15 wherein the flow rate of said ice is about 30-70% of the flow rate of said fluid. claim 15 17. The method according to claim 15 wherein said flow rate is 75-150 kg/s. claim 15 18. The method according to claim 15 wherein said flow rate is 100-125 kg/s. claim 15 19. The method of claim 1 which comprises recycling fluid after the filtering back to said first pumping means. claim 1 |
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046631151 | abstract | An apparatus for protecting personnel and the environment from harmful emissions of radiation from a source thereof includes a plurality of shielding parts so located as to be in the path of the radioactive emissions and to absorb them (one such part being located farther away from the source of emissions than the other) so that an electrical potential difference between the shielding parts is established, due to different absorptions of radiation by them, means for consuming electrical power at a location remote from the radioactive source, and electrical conductors communicating the consuming means (or load) with such shielding parts. Although the invention is primarily intended for protecting personnel and the environment against emissions from radiation sources, such as radioactive wastes, it is also useful for shielding other sources of harmful radiated emissions. Also within the invention are processes for protecting personnel and the environment against radiation hazards. |
description | The present application claims priority from Japanese Patent application serial no. 2010-117915, filed on May 24, 2010, the content of which is hereby incorporated by reference into this application. 1. Technical Field The present invention relates to a boiling water nuclear plant and a method of reducing dose in a turbine system, and more particularly, to a boiling water nuclear plant and a method of reducing dose in a turbine system which accepts, as power energy, steam generated in a boiling water reactor. 2. Background Art In a boiling water nuclear plant, radioactive nitrogen (N-16) is generated from the reaction of oxygen (O-16) in reactor water with neutrons. This N-16 has a half-life of 7.1 seconds, emitting high-energy gamma rays (6.129 MeV). Among the generated N-16, the N-16 in chemical form of high-volatile ammonia (NH3) or nitrogen monoxide (NO) does not remain in the reactor water but is volatilized into steam introduced to a turbine, causing an increase in dose of a turbine system. Recently, in the boiling water nuclear plants, hydrogen injection is executed in order to prevent stress corrosion cracking in structural material of a reactor pressure vessel and reactor internals by decreasing the amount of dissolved oxygen in the reactor water in the reactor pressure vessel. However, when the amount of injection of the hydrogen is increased, a radiation dose rate in the turbine system tends to rapidly increase after reaching a certain amount of the injection of hydrogen. This is because some N-16 dissolved in the reactor water in a low-volatile chemical form such as nitrate ions during a normal operation are reduced by the hydrogen injection, turn mainly into NH3 which is a high-volatile chemical form, and move with the main steam. Because of the increase in the radiation dose rate, an upper limit is set for the amount of hydrogen to be injected. As a conventional technology of reducing the amount of N-16 introduced into the turbine system, moving with the main steam, a method has been proposed where the amount of N-16 volatilized into the steam is decreased by adding an agent for reacting with nitrogen compounds to form nonvolatile nitrogen compounds to the reactor water (see Japanese Patent Laid-open No. 2009-109318 for an example). In addition, a method has been proposed in which N-16 in a high-volatile ammonia form is oxidize into a low-volatile nitrogen oxide by function of a photocatalyst layer containing an ammonia-adsorbing layer provided to a location that Cherenkov light generated in a core reaches (see Japanese Patent Laid-open No. 2009-281893 for an example). Patent literature 1: Japanese Patent Laid-open No. 2009-109318 Patent literature 2: Japanese Patent Laid-open No. 2009-281893 Non-patent literature 1: Tanabe, Kozo, Catalyst, 17(3), 72-81 (1975) Unfortunately, as in the technology disclosed in Japanese Patent Laid-open No. 2009-109318, when an agent is added to reactor water, the amount of the agent to be added will be limited to a certain value to meet the water quality standard of the reactor water, so that degree of the effect may also be limited. Furthermore, the addition of the agent may increase a burden on a reactor water clean-up system. In the technology disclosed in Japanese Patent Laid-open No. 2009-281893, the photocatalyst is placed in a certain location to oxide ammonia, and the location is limited to one that is reached by the Cherenkov light required for the photocatalyst to act, thus the degree of the effect may also be limited. The present invention has been made in view of the above situations, and it is an object of the present invention to provide a boiling water nuclear plant in which a radiation dose rate in a turbine system of the boiling water nuclear power plant can be reduced by decreasing amount of N-16 entering into the turbine system. A feature of the present invention for attaining the above object is a boiling water nuclear plant in which a solid substance having an acid center in its molecular frame is disposed in a steam passage. Furthermore, in a the method of reducing dose in a turbine system of a boiling water nuclear plant according to the present invention, it is a feature that N-16 in the form of ammonia contained in the steam is adsorbed on a adsorbing body including a solid substance having an acid center in its molecular frame by disposing the adsorbing body in a steam passage and decayed. According to the present invention, the amount of N-16 in steam can be reduced and the dose in the turbine system can be reduced because a solid substance having an acid center in its molecular frame adsorbs ammonia in the acid center. Various embodiments of the present invention will be described below with reference to drawings. The present invention is not limited to these embodiments. [Embodiment 1] A boiling water nuclear plant of the present embodiment will be described with reference to FIG. 1, FIG. 2 and FIG. 3. FIG. 1 is a longitudinal sectional view showing the boiling water nuclear plant according to embodiment 1 of the present invention. The boiling water nuclear plant shown in FIG. 1 has a reactor pressure vessel 1 in which, a core 2, a steam separator 3, and a stream dryer 4 are installed. In the core 2, cooling water circulating in the reactor pressure vessel 1 and passing through the core 2 is heated by using heat generated by nuclear fission of the nuclear fuel substance included in a plurality of fuel assemblies loaded in the core 2 and a part the heated cooling water turns into steam. The steam generated in the core 2 moves upward in the reactor pressure vessel 1 along with the cooling water until it reaches the steam separator 3 disposed above the core 2. The steam generated in the core 2 is separated from the cooling water in the steam separator 3. The steam which has passed through the steam separator 3 reaches the steam dryer 4, where it is dried by removing droplets from the steam so that the amount of the droplets contained in the steam does not exceed a certain value. The steam containing N-16 nitrogen compounds, dried in the steam dryer 4 is supplied from a main steam nozzle 5 to a steam turbine through a main steam pipe. Structure of the steam dryer 4 and steam flow within the steam dryer 4 is described with reference to FIG. 2 and FIG. 3. The steam dryer 4 has a plurality of steam dryer units 14 shown in FIG. 2. The steam dryer unit 14 is provided with a hood plate 7, perforated plates 8 and 11, and a plurality of corrugated panels 9. The perforated plate 8 is disposed at an upstream side (inlet side) of the corrugated panels 9, and the perforated plate 11 is disposed at a downstream side (outlet side) of the corrugated panels 9. The perforated plate 8 faces the hood plate 7. The perforated plate 8 has a plurality of through holes 10 being fine pore and the perforated plate 8 also has a plurality of through holes 12 being fine pore. The corrugated panels 9 are disposed between the perforated plate 8 and the perforated plate 11. The hood plate 7 is placed in such a way that the hood plate 7 covers the perforated plate 8 of the steam dryer unit 14, and has an aperture (an inlet) on the lower side. In FIG. 2, only a part of the structure of the hood plate 7 is shown. In FIG. 3, the steam flow is shown by dashed arrows. The steam containing droplets that have passed through the steam separator 3 flows into between the hood plate 7 and the perforated plate 8 from the aperture formed on the lower side of the hood plate 7, and passes through the steam dryer unit 14. To be more specific, the flow direction of the steam is turned from the upward to the horizontal direction in the hood plate 7, and the steam is dispersed by the perforated plate 8 having the plurality of through holes 10, and passes between the corrugated plates 9. The droplets contained in the steam are removed by the corrugated panels 9 while the steam passes between the corrugated plates 9. The steam from which the droplets were removed goes through the plurality of through holes 12 formed in the perforated plate 11, and is discharged into an upper region in the reactor pressure vessel 1 from outlets of the steam dryer 4. In the steam dryer 4, each of the outlets is formed between the perforated plate 11 of one steam dryer unit 14 and the hood plate 7 of another steam dryer unit 14 that adjoins the one steam dryer unit 14. Adsorption member 13 (see FIG. 3) is disposed in each of the outlets of the steam dryer 4 and attached to the hood plate 7. The steam discharged from the plurality of through holes 12 formed in the perforated plate 11 passes through the adsorption member 13 and is introduced into the upper region in the reactor pressure vessel 1. Additionally, in the core 2, oxygen atoms (O-16) in the cooling water induce a nuclear reaction with neutrons (n) emitted from the nuclear fuel substance, and generate radioactive nitrogen (N-16) and hydrogen atoms (p), for example, as shown in equation (1).O-16 (n, p) N-16 (1) The generated N-16 reacts with water molecules in the cooling water and radicals generated by the radiation decomposition of water molecules, and turns into the chemical forms of ammonia and nitrogen oxides (NO, NO2, NO3, etc.) Among the nitrogen compounds containing N-16, those in a high-volatile ammonia form or a NO form move along with the steam in the core 2 as gas. In the conventional boiling water nuclear power plant executing hydrogen injection, ammonia is the main chemical form of N-16. The nitrogen compounds containing N-16, contained in the steam as gas, pass through the steam separator 3 and the steam dryer 4 along with the steam, and are supplied from the main steam nozzle 5 to the steam turbine through the main steam pipe. Because of this, a radiation dose rate in the turbine system is increased by high-energy gamma rays emitted from the N-16. N-16 has a half-life of 7.1 seconds. This means that the amount of N-16 supplied to the steam turbine can reduce to one half or less by holding the N-16 in the reactor pressure vessel 1 for 7.1 seconds or longer. In the boiling water nuclear plant according to the present embodiment, the adsorption member 13 is disposed in the reactor pressure vessel 1 as above-mentioned. The adsorption member 13 has a complex oxide, which is a solid substance having an acid center in its molecular frame, made up of two or more kinds of metal oxides so that N-16 is held in the reactor pressure vessel 1 for its half-life period or longer. As the complex oxide, the following may be used: that is, a mixed oxide of at least one of titanium oxide (TiO2), zirconium oxide (ZrO2), zinc oxide (ZnO), aluminum oxide (Al2O3), and silicon oxide (SiO2) and an oxide of at least one kind of metal other than the above; for example, those shown in Table 1 of Tanabe, Kozo, Catalyst, 17(3), 72-81 (1975), such as TiO2—ZrO2, TiO2—Fe2O3, ZnO—MgO, Al2O3—SiO2, Al2O3—MgO, and SiO2—Y2O3 may be used. These complex oxides have a Lewis acid or a Brønsted acid in their molecular frames. FIG. 4 shows representative models of the acid center structure of SiO2—Al2O3 as an example of the complex oxide. The Lewis acid is an unoccupied orbital 6 of the aluminum atom, and the Brønsted acid is an O+ portion of a water molecule (H2O) bonded to the aluminum. Ammonia, which is a main form of N-16, is a base; an ammonia molecule can be bonded to the Lewis acid of the complex oxide by supplying the lone pair of the nitrogen atom of the ammonia molecule or to the Brønsted acid through a hydrogen atom of a water molecule. When the bond of the ammonia to the acid center is held for the half-life period of N-16 or longer, a half or more of the N-16 decay into O-16 to become water (H2O), dissociating the bond. This renews the acid center so that ammonia can be newly bonded again. FIG. 5 shows a result of a test for checking ammonia adsorption behavior using ZrO2—TiO2 as an example of the complex oxide. In this test, a reactor vessel simulating the inside temperature condition of the reactor pressure vessel 1 was filled with ZrO2—TiO2, steam containing ammonia was supplied in pulses into the reactor vessel, and a concentration of ammonia contained in the steam was measured at an outlet of the reactor vessel. In FIG. 5, a horizontal axis shows the time passed since the beginning of the ammonia supply in pulses, and a vertical axis shows the concentration of ammonia contained in the steam at the outlet of the reactor vessel where measured values are normalized in a way that the highest concentration of ammonia is set to 1. FIG. 5 shows that the peak of a curve for the case when the reactor vessel was filled with the complex oxide occurred later than that for the case without the complex oxide, indicating that ammonia is adsorbed and held to ZrO2—TiO2. The complex oxide of the adsorption member 13 adsorbs a nitrogen compound containing N-16 contained in the steam discharged from the plurality of through holes 12 formed in the perforated plate 11. The adsorption member 13 may be disposed in any location in which the complex oxide of the adsorption member 13 is come in contact with steam passing in the reactor pressure vessel 1. Preferably, it is disposed in a location after steam has been dried, that is, anywhere between the steam dryer and an inlet of the main steam pipe. Even more preferably, it is disposed in the area where linear velocity of steam is small, for example, an area from the steam dryer to the vicinity of the upper portion of the steam dryer. The adsorption member 13 has a structure body made of metal and the like, and the complex oxide applied and attached to the structure body. The structure body may be a structure body which can minimize a pressure drop by as much as possible to prevent a decrease in power generation efficiency; for example, a honeycomb structure, a narrow tube, a foam structure, or a net-like structure may be chosen. The adsorption member 13 may be composed by filling a casing made of gauze with the complex oxide. The complex oxide to be installed may be one kind of complex oxide or a mixture of multiple kinds of complex oxides. A noble metal such as platinum and the like may be supported by the complex oxide. This may improve the performance of ammonia adsorption or produce an effect of adsorbing N-16 in the form of nitrogen monoxide as well. As above, according to the present embodiment, since the adsorption member 13 is installed in the location (for example, the outlets of the steam dryer 4) in which the complex oxide is come in contact with steam in the reactor pressure vessel 1, and ammonia containing N-16 is adsorbed and held by the complex oxide, the N-16 can be decayed into O-16 and the N-16 supplied to the turbine system can be decreased. Therefore, a radiation dose rate in the turbine system can be reduced by the complex oxide of the adsorption member 13. [Embodiment 2] An embodiment 2 of the present invention will be described. Since the flow of steam in the reactor pressure vessel 1 is the same as in the embodiment 1, it will not be described. In a boiling water nuclear plant according to the present embodiment, an adsorption member 13 having a metal oxide which is a solid substance having an acid center in its molecular frame, is installed in the outlet of the steam dryer 4 to hold N-16 for the half-life period of N-16 or longer as with the embodiment 1. As the metal oxide, at least one of titanium oxide (TiO2), zirconium oxide (ZrO2), aluminum oxide (Al2O3), zinc oxide (ZnO), silicon oxide (SiO2), molybdenum oxide (MoO3), and tin oxide (SnO2) may be used. Each of these oxides is acidic by itself and can bond with ammonia, which is a base. In addition, the oxides of alkaline earths, for example, magnesium oxide (MgO) and calcium oxide (CaO), and the oxides of lanthanoid and actinoid, for example, lanthanum oxide (La2O3), yttrium oxide (Y2O3), and thorium oxide (Th2O3), are mainly a basic solid substance. However, since they have an acid center in their molecular frames, these oxides can also bond with ammonia and hold it. As the metal oxide used in the present embodiment, one kind of metal oxide or a mixture of multiple oxides may be used. In the present embodiment, the adsorption member 13 having the metal oxide may be disposed in any location that is exposed to steam passing in the reactor pressure vessel 1; for example, any place between the steam separator and the inlet of the main steam pipe may be chosen. The adsorption member 13 has a structure body made of metal and the like, and the metal oxide applied and attached to the structure body. ZrO2 or Al2O3 can be shaped into a form by itself to produce a structure having the strength of metal, thus part of a reactor internal in the reactor pressure vessel 1 may be produced with the metal oxide. The adsorption member 13 may be composed by filling a casing made of gauze with the metal oxide. As above, according to the present embodiment, since the adsorption member 13 being a structure body made of the metal oxide or the adsorption member 13 having a structure body made of metal and the like, on which the metal oxide is attached, can be installed in a location (for example, the outlet of the steam dryer 4) in which the metal oxide is come in contact with steam in the reactor pressure vessel 1 to adsorb and hold N-16, the N-16 supplied to the turbine system can be decreased and a radiation dose rate in the turbine system can be reduced. [Embodiment 3] An embodiment 3 of the present invention will be described. Since the flow of steam in the reactor pressure vessel 1 is the same as in the embodiment 1, it will not be described. In a boiling water nuclear power plant according to the present embodiment, an adsorption member 13 having either zeolite, which is a solid acid, or a clay mineral such as montmorillonite is installed the outlet of the steam dryer 4 in the reactor pressure vessel 1 to hold N-16 for the half-life period of N-16 or longer as with the embodiment 1. These minerals have an acid center in their molecular frames and can adsorb and hold ammonia. Furthermore, they can hold ammonia by the substitution reaction of cations included in them. It is possible to synthesize zeolite including various metal ions and a clay mineral including various cations between layers of a layered structure, and selecting the metal ions or the cations can be adjusted the acid strength of the zeolite or the clay mineral, and the time period for holding N-16. As the minerals used in the present embodiment such as zeolite and clay minerals, those artificially synthesized or obtained by cation substitution, or those naturally produced may be used. One kind of mineral or a mixture of multiple minerals may be used. In the present embodiment, the adsorption member 13 having either the zeolite or the clay mineral may be installed in any location in which it is come in contact with steam in the reactor pressure vessel 1; for example, any place between the steam separator and the inlet of the main steam pipe may be chosen. The adsorption member 13 has a structure body made of metal and the like, and either the zeolite or the clay mineral applied and attached to the structure body. The adsorption member 13 may be composed by filling a casing made of gauze with either the zeolite or the clay mineral. As above, according to the present embodiment, since the adsorption member 13 having either the zeolite or the clay mineral can be installed in the location (for example, the outlet of the steam dryer 4) in which it is come in contact with steam in the reactor pressure vessel 1 to adsorb and hold ammonia containing N-16, the N-16 decays into O-16 and the N-16 supplied to the turbine system can be decreased. Therefore, a radiation dose rate in the turbine system can be reduced. In addition, the zeolite and the clay minerals to be installed can be those naturally produced, which are adaptable in the environment upon the final disposal by burial as radioactive waste. [Embodiment 4] A boiling water nuclear plant of embodiment 4 will be described with reference to FIG. 6. The boiling water nuclear plant of the present embodiment has an adsorption member 13A disposed in each of the inlet formed between the hood plate 7 and the perforated plate 8 in the steam dryer 4. The adsorption member 13A is attached to the hood plate 7, and has a structure body made of metal and the like, and the complex oxide applied and attached to the structure body as with the embodiment 1. The steam discharged from the steam separator 3 passes through the adsorption member 13A and is introduced a space formed between the hood plate 7 and the perforated plate 8 in the steam dryer 4. The complex oxide of the adsorption member 13A adsorbs a nitrogen compound containing N-16 contained in the steam supplied to the steam dryer 4. The steam from which the nitrogen compound was removed is supplied to the turbine through the main steam pipe. The present embodiment can obtain each effect generated in the embodiment 1. The adsorption member 13 used in the embodiment 2 or the adsorption member 13 used in the embodiment 3 may be used in the present embodiment as the adsorption member 13A. [Embodiment 5] A boiling water nuclear plant of embodiment 5 will be described with reference to FIG. 7. The boiling water nuclear plant of the present embodiment has an adsorption member 13B disposed in front of the steam inlet side of the perforated plate 8 in the steam dryer 4. The adsorption member 13B is attached to the perforated plate 8, and has a structure body made of metal and the like, and the complex oxide applied and attached to the structure body as with the embodiment 1. The steam discharged from the steam separator 3 is supplied to the steam dryer 4, passes through the adsorption member 13B and is introduced between the corrugated plates 9 through the plurality of through holes 10 formed in the perforated plate 8. The complex oxide of the adsorption member 13B adsorbs a nitrogen compound containing N-16 contained in the steam introduced between the corrugated plates 9 of the steam dryer 4. The steam from which the nitrogen compound was removed is supplied to the turbine through the main steam pipe. The present embodiment can obtain each effect generated in the embodiment 1. The adsorption member 13 used in the embodiment 2 or the adsorption member 13 used in the embodiment 3 may be used in the present embodiment as the adsorption member 13B. [Embodiment 6] A boiling water nuclear plant of embodiment 6 will be described with reference to FIG. 8. The boiling water nuclear plant of the present embodiment has an adsorption member 13C disposed in back of the steam outlet side of the perforated plate 11 in the steam dryer 4. The adsorption member 13C is attached to the perforated plate 11, and has a structure body made of metal and the like, and the complex oxide applied and attached to the structure body as with the embodiment 1. The steam discharged from the steam separator 3 is supplied to the steam dryer 4, is introduced between the corrugated plates 9 through the plurality of through holes 10 formed in the perforated plate 8, and is discharged from the plurality of through holes 12 formed in the perforated plate 11. The steam discharged from the through holes 12 passes through the adsorption member 13C and is introduced into the upper region in the reactor pressure vessel 1 through the outlet of the steam dryer 4. The complex oxide of the adsorption member 13C adsorbs a nitrogen compound containing N-16 contained in the steam discharged from the through holes 12. The steam from which the nitrogen compound was removed is supplied to the turbine through the main steam pipe. The present embodiment can obtain each effect generated in the embodiment 1. The adsorption member 13 used in the embodiment 2 or the adsorption member 13 used in the embodiment 3 may be used in the present embodiment as the adsorption member 13C. [Embodiment 7] A boiling water nuclear plant of embodiment 7 will be described with reference to FIG. 9. The boiling water nuclear plant of the present embodiment has an annular adsorption member 13D surrounding the steam dryer 4 and disposed between the steam dryer 4 and an inlet of the main steam nozzle 5 in the reactor pressure vessel 1. The adsorption member 13D is attached to an inner surface of the reactor pressure vessel 1, and has a structure body made of metal and the like, and the complex oxide applied and attached to the structure body as with the embodiment 1. The steam discharged from the steam dryer 4 passes through the adsorption member 13D, and is introduced into the main steam nozzle 5 and the main steam pipe. The complex oxide of the adsorption member 13D adsorbs a nitrogen compound containing N-16 contained in the steam discharged from the steam dryer 4. The steam from which the nitrogen compound was removed is supplied to the turbine through the main steam pipe. The present embodiment can obtain each effect generated in the embodiment 1. The adsorption member 13 used in the embodiment 2 or the adsorption member 13 used in the embodiment 3 may be used in the present embodiment as the adsorption member 13D. [Embodiment 8] A boiling water nuclear plant of embodiment 8 will be described with reference to FIG. 10. The boiling water nuclear plant of the present embodiment has an adsorption member 13E. The adsorption member 13E is disposed between the steam separator 3 and the steam dryer 4. That is, the adsorption member 13E is disposed above the steam separator 3 and below the steam dryer 4. The steam separator 3 is covered with the adsorption member 13E and the adsorption member 13E is attached to a support member of the steam dryer 4. The steam discharged from the steam separator 3 passes through the adsorption member 13E, and is introduced into the steam dryer 4. The complex oxide of the adsorption member 13E adsorbs a nitrogen compound containing N-16 contained in the steam discharged from the steam separator 3. The steam from which the nitrogen compound was removed is supplied to the turbine through the steam dryer 4 and the main steam pipe. The present embodiment can obtain each effect generated in the embodiment 1. The adsorption member 13 used in the embodiment 2 or the adsorption member 13 used in the embodiment 3 may be used in the present embodiment as the adsorption member 13E. 1: reactor pressure vessel, 2: core, 3: steam separator, 4: steam dryer, 5: main steam nozzle, 6: unoccupied orbital, 7: hood plate, 8, 11: perforated plate, 9: corrugated plate, 13, 13A, 13B, 13C, 13D, 13E: adsorption member. |
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abstract | A heavy radial neutron reflector for a pressurized water reactor that employs elongated lengths of round bar stock closely packed in either a triangular or rectangular array extending between former plates of a core shroud between the core barrel and the baffle plates which outline the periphery of the reactor core and are formed in axial and circumferential modules. Flow channels are formed in the long gaps between the adjacent round bar stock that communicates cooling water that enters through the core barrel at the top of the shroud and flows down through openings in the former plates to the bottom of the neutron reflector where it exits through a lower baffle orifice to join other cooling water flowing up through the lower core support plate. |
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053316746 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is concerned with nuclear reactor damage prevention, more particularly with preventing occurrence of a coolant void at the top of the nuclear fuel assembly from sudden loss of reactor coolant system (RCS) inventory level caused by nozzle dam removal at the completion of a maintenance cycle. 2. Description of the Prior Art There exists the possibility of a sudden, uncontrolled, substantial drop in reactor coolant system inventory level when a nozzle dam is removed, more specifically at the moment when the seal between the nozzle dam and the nozzle is broken, after the nozzle dam has been in place for sufficient time to perform an average maintenance cycle of several weeks or longer. If the drop is severe enough, the water will fall below the level of the reactor hot side opening to the residual heat removal system (RHR), starving the system and stalling the RHR pump. This can result in overheating and water not reaching the exposed top of the core. This is a potentially hazardous condition which must be prevented. A phenomena that is likely to be associated with this potential condition is an uncontrolled upward bounding of the nozzle dam, which can be hazardous to personnel unbolting the dam from the nozzle. This also must be prevented. Indications of the phenomena and lowered RCS inventory level were observed for example at the following instances, when nozzle dams were being removed after the usual industry procedure of lowering the water level to mid loop from being at the refueling level for some extended period. The following data is based on recollections by the technicians and on-site management personnel. No coordinated data collection, however, was made at the time to specifically record changes in RCS inventory levels during nozzle dam removal. In the summer of 1990, and spring of 1991, at the Catawba plant, Unit 2, 4-loop system with common drain on steam generator. The cold leg dam bounded. Although one of the incidents was recorded on video tape, the RCS inventory levels were not recorded. In the Spring of 1992, at the Callaway plant, 4-loop system, common drain on steam generator. The dams bounded in the 4th and 8th cold legs. The control room reported a substantial drop in the Reactor coolant system inventory level after removal of the 4th and 8th cold legs. In the Fall of 1992, at Diablo Canyon plant 4-loop, individual drain on steam generator system, a cold leg dam bounded. In present industry practice, after primary water is drained below the steam generator bowl, down to mid loop, and before it is restored to refueling level above the steam generator bowl, every precaution is taken to hermetically seal off the steam generator bowl from the hot and cold leg nozzles by a nozzle dam for each nozzle, and by a drain plug for each individual drain conduit between the bowl, also termed "channel head", and nozzle which bypasses the dam. Once the water is restored to the refueling level, leakage may occur around the seal of some nozzle dams. The typical procedure, as described in U.S. Pat. No. 4,959,192, Trundle et al, patented Sep. 25, 1990, is to monitor for leakage into the bowl, the leakage being acceptable provided a bowl drain pump can keep up with the leakage. Many nozzle dams, especially including ones with inflated seals such as the BUSI Nozzle Dam, available from Brand Utility Services Inc., and generally described in U.S. Pat. No. 4,957,215, Evans et al., patented Sep. 18, 1990, are designed to have no leakage across the seal barrier between the nozzle and the bowl interior once the dam is bolted in place. Having a combination of passive and inflated seals, the BUSI Nozzle Dam usually seals against cross leakage even without the inflatable seals being inflated. Inflatable seals are also described, for example, in U.S. Pat. No. 4,482,076, Wentzell, patented Nov. 13, 1984, and in U.S. Pat. No. 4,690,172, Everett, patented Sep. 1, 1987. In removing a nozzle dam, it is standard in the industry, as described in U.S. Pat. No. 4,959,192, Trundle, to remove the nozzle dam after the reactor coolant system has been drained to mid loop. Trundle suggests that it is preferable to remove the hot leg dam prior to the cold leg dam. He also suggests that in a system having an individual drain conduit to remove the drain plug after draining down below the nozzle dam in order to confirm that the loop is adequately drained, that is, drained below the level of the nozzle as indicated by an absence of water leaking up from the drain conduit, before removing the nozzle. He also suggests to allow several minutes to elapse between removal of the drain plug after the water level is drained below the nozzle dam and attempting removal of the nozzle dam when working in the cold leg, in order to allow any low pressure caused by draining the loop to dissipate. Although the above steps and precautions which are characteristic in the field are useful and continue to be advisable in installing and removing a nozzle dam and drain plug, they do not prevent chance of the aforedescribed bounding or of an uncontrolled drop in reactor coolant system, and may bring on the conditions leading to the occurrences. The present invention is designed to prevent the above described phenomena of nozzle dam bounding and sudden excessive drop in reactor coolant system inventory level when a nozzle dam is removed from the nozzle. SUMMARY OF THE INVENTION A nozzle dam has a passage comprising a hole through a wall of the dam which hermetically seals the nozzle of a water cooled nuclear reactor primary coolant system steam generator bowl nozzle. The passage is provided for releasing gas from the nozzle in the region below the nozzle dam, through the dam, to the bowl when the nozzle dam is mounted sealingly in the nozzle. A valve, connected by pipe means such as hose or connected by direct attachment means to the hole, provides for control of fluids through the passage. Pipe means such as a hose attached to the valve is positioned for directing the fluids out of the bowl. After the reactor coolant system water general level is raised to a level that is higher than the nozzle dam, and before completion of a later step of lowering the water level to a level that is below the nozzle dam, before the water is taken below the nozzle dam, a passage is opened exiting the nozzle for release of trapped gas through the passage from the nozzle from the region immediately below the nozzle dam. Preferably the passage is through the nozzle dam wall. It may, however, be through a wall of the bowl. |
description | This patent claims the benefit of priority to U.S. patent application Ser. No. 14/348,690, filed on Mar. 31, 2014, entitled “Method Of Operating An Automated Radiopharmaceutical Synthesizer,” which claims the benefit of priority to PCT Patent Application No. PCT/US2012/056868, filed on Sep. 24, 2012, entitled “Method Of Operating An Automated Radiopharmaceutical Synthesizer,”, which claims the benefit of priority to U.S. Provisional Patent Application No. 61/541,296, filed on Sep. 30, 2011, entitled “Calibration and Normalization Systems and Methods for Radiopharmaceutical Synthesizers”, each of which is incorporated herein by reference in its entirety for all purposes. The present invention relates to calibration and normalization systems and methods for ensuring the quality of radiopharmaceuticals during the synthesis thereof, such as radiopharmaceuticals used in Positron Emission Tomography (PET) and Single-Photon Emission Computed Tomography (SPECT). PET and SPECT imaging systems are increasingly used for detection of diseases and are useful in providing early detection and a definite diagnosis for such diseases (e.g., disease states within oncology and neurology). For example, currently, a large percentage of PET and SPECT tests are related to cancer detection and early Alzheimer detection. These diseases require early diagnosis to allow a timely and effective treatment. PET and SPECT imaging systems create images based on the distribution of positron-emitting isotopes and gamma emitting isotopes, respectively, in the tissue of a patient. The isotopes are typically administered to a patient by injection of radiopharmaceuticals including a probe molecule having a positron-emitting isotope, e.g., carbon-11, nitrogen-13, oxygen-15, or fluorine-18, or a gamma radiation emitting isotope, e.g. technetium-99. The radiopharmaceutical is readily metabolized, localized in the body or chemically binds to receptor sites within the body. Once the radiopharmaceutical localizes at the desired site (e.g., chemically binds to receptor sites), a PET or SPECT image is generated. Examples of known radiopharmaceuticals include 18F-FLT ([18F]fluorothymidine), 18F-FDDNP (2-(1-{6-[(2-[18F]fluoroethyl)(methyl)amino]2-naphthyl}ethylidene)malonitrile), 18F-FHBG (9-[4-[18F]fluoro-3-(hydroxymethyl)butyl]guanine or [18F]-penciclovir), 18F-FESP ([18F]-fluoroethylspiperone), 18F-p-MPPF (4-(2-methoxyphenyl)-1-[2-(N-2-pyridinyl)-p-[18p]fluorobenzamido]ethylpiperazine) and 18F-FDG ([18F]-2-deoxy-2-fluoro-D-glucose). Radioactive isotopes in radiopharmaceuticals are isotopes exhibiting radioactive decay, for example, emitting positrons. Such isotopes are typically referred to as radioisotopes or radionuclides. Exemplary radioisotopes include 18F, 124I, 11C, 13N and 15O, which have half-lives of 110 minutes, 4.2 days, 20 minutes, 10 minutes, and 2 minutes, respectively. Because radioisotopes have such short half-lives, the synthesis and purification of the corresponding radiopharmaceutical must be rapid and efficient. Any quality control (QC) assessments on the radiopharmaceutical must also take place in a short period of time. Preferably, these processes (i.e., synthesis, purification, and QC assessment) should be completed in a time well under the half-life of the radioisotope in the radiopharmaceutical. Presently, QC assessments (e.g., chemical yield and chemical purity) may be relatively slow mainly due to the fact that they are conducted manually. Accordingly, there is a need for systems, components, and methods for capturing, analyzing, and interpreting data obtained during the synthesis and purification processes of a radiopharmaceutical to ensure that those synthesis and purification are proceeding efficiently to produce quality radiopharmaceuticals in a desired quantity. From this analysis, changes can be implemented before, during or after the synthesis and/or purification of the radiopharmaceutical to correct any deficiencies, as they occur during the radiopharmaceutical's synthesis. The embodiments of the present invention provide such systems, components, and methods, which allow for capture and analysis of real data, as well as the correction of deficiencies, during the synthesis of the radiopharmaceutical. A site to site comparison can also be performed to enable comparison across geographically diverse sites conducting radiopharmaceutical synthesis. An exemplary embodiment includes a method of monitoring a radiopharmaceutical synthesis process. Data relating to the radiopharmaceutical synthesis process is received from a radiopharmaceutical synthesizer. The data is analyzed. One or more characteristics of the data is identified wherein the one or more characteristics pertain to quality control factors relating to the radiopharmaceutical synthesis process. The one or more characteristics of the data are extracted. The extracted data is analyzed. Another exemplary embodiment includes a method of normalizing a radiopharmaceutical process. A first set of data relating to a first radiopharmaceutical process is received from a first radiopharmaceutical synthesizer, wherein the first set of data is based on results using a known input sample and includes data pertaining to the output of the first radiopharmaceutical process. A first correlation factor to be applied the first set of data to normalize the first set to a first baseline is calculated. A second set of data relating to a second radiopharmaceutical process is received from a second radiopharmaceutical synthesizer, wherein the second set of data is based on results using the known input sample and includes data pertaining to the output of the second radiopharmaceutical process. A second correlation factor to be applied to the second set of data to normalize the second set to a second baseline is calculated. A comparison of the first set and second set of data is performed. A third correlation factor that normalizes the first and second set of data to a third baseline based upon the comparison is calculated. These and other embodiments and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the various exemplary embodiments of the invention. It will be readily understood by those persons skilled in the art that the embodiments of the inventions described herein are capable of broad utility and application. Accordingly, while the invention is described herein in detail in relation to the exemplary embodiments, it is to be understood that this disclosure is illustrative and exemplary of embodiments and is made to provide an enabling disclosure of the exemplary embodiments. The disclosure is not intended to be construed to limit the embodiments of the invention or otherwise to exclude any other such embodiments, adaptations, variations, modifications and equivalent arrangements. The following descriptions are provided of different configurations and features according to exemplary embodiments of the invention. These configurations and features may relate to providing systems and methods for quality control of radiopharmaceuticals and other compounds or formulations containing radioisotopes. While certain nomenclature and types of applications or hardware are described, other names and application or hardware usage is possible and the nomenclature provided is done so by way of non-limiting examples only. Further, while particular embodiments are described, these particular embodiments are meant to be exemplary and non-limiting and it further should be appreciated that the features and functions of each embodiment may be combined in any combination as is within the capability of one of ordinary skill in the art. The figures depict various functionality and features associated with exemplary embodiments. While a single illustrative block, sub-system, device, or component is shown, these illustrative blocks, sub-systems, devices, or components may be multiplied for various applications or different application environments. In addition, the blocks, sub-systems, devices, or components may be further combined into a consolidated unit. Further, while a particular structure or type of block, sub-system, device, or component is shown, this structure is meant to be exemplary and non-limiting, as other structure may be able to be substituted to perform the functions described. Exemplary embodiments of the invention relate to synthesis systems for radiopharmaceuticals. The synthesis system may produce radiopharmaceuticals for use with either PET or SPECT scanners. For example, the synthesis system may be the FASTlab® system from GE Healthcare. The use of the FASTlab system in examples described herein is meant to be exemplary and non-limiting. It should be appreciated that the embodiments described herein may be used with a variety of synthesis systems manufactured by companies other than GE Healthcare. It should further be appreciated that the use of the term “radiopharmaceutical”, “radiotracer”, “PET tracer”, or “SPECT tracer” herein is meant to be exemplary and non-limiting and the mention of one term does not exclude substitution of the other terms in the described embodiment. During the automated synthesis of radiopharmaceutical, a data collection file for the synthesis run is generally produced. For example, for every radiopharmaceutical synthesis run on a FASTlab system, a unique log file for the run is produced. This file consists of data collected at various points in the synthesis using various sensors and activity detectors that are a part of the process, such as radioactivity detectors. The data in the data collection file may be collected at certain time intervals. For example, in a FASTlab system, a log file consists of data collected at one second intervals throughout the entire synthesis with the data being measured by up to six different radioactivity detectors, as well as set values and measured values for the programmable process parameters in the FASTlab sequence file (e.g., reactor temperature, pressure, and syringe positions). It should be understood that the data collection intervals may be adjusted and may be measured at different intervals other than every second (e.g., every five seconds or every ten seconds). Data may be collected from different sensors or radioactivity detectors at different intervals for each (e.g., every second at one detector and every five seconds at another). The data in the data collection file file, such as a log file, when presented graphically, represents a diagnostic “fingerprint” for any given FASTlab synthesis run. The fingerprint of a successful synthesis run can be established based on established data. Subsequent synthesis runs may be then compared to the fingerprint of the successful synthesis run in order to compare the performance of the synthesis system. Deficiencies or problem areas in the synthesis process can then be identified and appropriate action taken. For example, deviations from the “good” or “acceptable” fingerprint can be determined and potential problem areas in the synthesis process can be identified, such as a which step of the process is experiencing a problem or not performing up to expected standards. Using this technique, synthesizer processes across multiple sites may also be compared. As part of such comparison, it may be necessary to calculate a correlation or normalization factor, as described below, to enable the data from each run to be moved to a common baseline to ensure an accurate comparison between different synthesizers at different locations. Accordingly, the data collection file can provide valuable information about each synthesis run and may be used, for example, to monitor variations between identical runs; to see the effect of modifications to the synthesis runs; for trouble shooting; and as a tool during PET center set-up. Useful information may therefore be obtained through analysis and correlation of the data collection file data. For example, quality control information, such as, for example, yield and purity, may be extracted from the data collection file data and analyzed. Through such analysis, the radiopharmaceutical synthesis process may be adjusted based on this quality control information. This analysis process may simplify quality control procedures through the potential elimination of post-production quality control tests since the results can be determined from the synthesis process itself. In addition to the information from sensors and activity detectors, such as the radioactivity detectors, the data collection file may contain set values and real, or measured, values for the programmable process parameters in the synthesizer's sequence file. For example, a FASTlab log file contains measurements of data from the following programmable process parameters: reactor heater temperature, nitrogen pressure, vacuum, and syringe position. Accordingly, the use of information from the activity detectors in combination with process parameters in the data collection file adds valuable information regarding given steps and actions in the process. According to other exemplary embodiments, using activity detector readings obtained from data collection files, the synthesizer reaction performance may be monitored. However, radioactivity detector measurements need to be corrected and correlated in order to account for variation in readings amongst different synthesizers located at different locations or sites. In order to perform such a correction, a calibration or normalization process is used to standardize the process data to enable comparison on an equivalent baseline. According to an exemplary embodiment, a basic sequence for the synthesizer is used where a sample with a known amount of radioactivity is passed through the synthesizer in the vicinity of the different radioactivity detectors. A correlation factor for each detector is then calculated based on the results compared to the known radioactivity amount and used during the data analysis to monitor the synthesizer process performance. Once instruments at different locations are calibrated or normalized, the resulting data can be collected and further normalized to account for variations at the different locations. In doing so, data collected from the different locations can be meaningfully compared. This collected data can be centrally analyzed and stored in order to provide various support functions to the different locations such as troubleshooting and customer service. During the above process, the sample is passed throughout the synthesizer hardware and the activity is read at each radioactivity detector. During the process, when comparing two sites, say, sites A and B, each having a synthesizer, the data collection file may show that all detectors in A read as expected, but one detector, for example, detector 5 at B reads 10% below what is expected. If it is known that the detector is functioning properly and is aligned properly, then the presumption is that there is a systematic error associated with that detector that causes it to read low. The data is collected from sites A and B at a central data collection site. The central collection site would use the data to normalize the data from the detectors at site B upwards by 10% so that the data for the same detector at site A can be compared to the data from site B. Once calibrated, sites A and B proceed with synthesis. Each synthesizer typically generates a data collection file during production of a radiopharmaceutical. The contents of the data collection file are transmitted to the same central data collection site either in real time or at some point after the synthesis run is complete. Provided the same radiopharmaceutical is being synthesized at each site, the data generated from sites A and B could be compared. The data for site B, of course, would have to be normalized up to account for the fact that its detector 5, is known to read low. The data may show production trends or issues with each site. For example, the data collection file data could show that there was a good solid phase extraction (SPE) recovery, but a low reported yield in the synthesizer at site A. These data may then form the basis for troubleshooting the synthesizer at site A. Upon analysis of the data, a conclusion may be drawn with regard to the problem at site A. For example, the conclusion could be that there was a low yield for the a radiolabelling step or some other synthesizer step. The data collection file data may serve a number of uses. Exemplary, non-limiting uses may include: Process development, including tuning of purification processes in a synthesizer, including the SPE process(es); Robustness testing: a robust process would show little deviation from run to run since the graphical representation of the data for each of the radioactivity detectors are like “fingerprints” of the process; Troubleshooting: problems can be spotted and pinpointed in the radiosynthesis from the trends of the radioactivity detectors deviating from a successful production based on established data; Support PET center set-up; Ensuring production quantity matches the patient need (e.g., ensuring that the proper number of patient doses is produced); Identification of trends of the radioactivity detectors at various sites to determine performance of different synthesizers; Identification of synthesizer hardware problems; Identification of synthesizer sequence file programming issue(s); Simplified post-synthesis quality control; Providing remote customer support; and Normalization of data collection files, e.g., log files. FIG. 1 depicts a flow chart of a method of synthesizing and using a PET or SPECT imaging agent and extracting data collection file data according to an exemplary embodiment of the invention. The method 100 as shown in FIG. 1, may be executed or otherwise performed by one or a combination of various systems, components, and sub-systems, including a computer implemented system. Each block shown in FIG. 1 represents one or more processes, methods, and/or subroutines carried out in the exemplary method 100. At block 102, a radioisotope is produced. The radioisotope (e.g., 18F or 11C) is typically produced using a cyclotron (e.g., GE PETtrace 700 cyclotron) for PET radioisotopes or using a generator for SPECT radioisotopes (e.g., to produce the 99Tc). The cyclotron or generator may be located at a manufacturing site or it may be located in proximity to the scanner. Locating the cyclotron or generator on-site with the PET or SPECT scanner minimizes transportation time for the radioisotope. It should be appreciated that while “PET” and “SPECT” are referred to herein such examples are exemplary and the mention of one does not preclude application to the other. At block 104, a radiopharmaceutical is synthesized using the radioisotope. A synthesizer is used to combine the radioisotope with a radioligand. The result is a radiopharnmaceutical. The synthesizer may be manually operated, semi-automated in operation, or fully automated. For example, the GE Healthcare FASTlab system is a fully automated synthesizer. The synthesizer is generally operated in a “hot cell” to shield the operator from the radioactivity of the radioisotope. During the synthesis of the radiopharmaceutical, data can be collected during the process. The data corresponds to radiodetector or sensor measurements at various points in the synthesis process. The data are collected at various time intervals and may be electronically stored. The data may be output or saved in the form a data collection file. The synthesizer may employ a cassette which is mated thereto and contains the various reagents and other equipment, such as syringe pumps and vials, required for the synthesis of the radiopharmaceutical. The cassette may be removable and disposable. Cassettes may be configured to support the synthesis of one or more radiopharmaceuticals. At block 106, the synthesized radiopharmaceutical is dispensed. The doses of the radiopharmaceutical are dispensed into collecting vials for patient administration and for QC. A sample of the bulk synthesized radiopharmaceutical may be dispensed directly into a QC system and/or cassette for QC testing. Systems and methods of QC testing are shown in PCT Appl. No. US 11/2011/048564 filed on Aug. 22, 2011, the contents of which are incorporated herein by reference in their entirety. At block 108, quality control checks on a radiopharmaceutical sample are performed. There may be one or more QC checks performed. These QC checks may be automated. The QC system may include a cassette having a plurality of components for performing the tests. The cassette may be configured for insertion into a QC system to carry out the QC checks. The QC system may be a stand-alone system or it may be integrated with the synthesizer described above. Radiopharmaceutical doses are dispensed from the synthesizer. Sample(s) from one or more dispensed vials may be selected for QC checks. These samples may be input to the QC system. Alternatively, the QC system may be connected or coupled to the synthesizer such that an appropriate sample may be directly output from the synthesizer to the QC system. At block 110, a dose from the same production batch as the sample on which the QC tests were conducted is administered to a patient. At block 112, a PET or SPECT scan is performed on the patient who received the dose. At block 114, a data collection file is produced from the synthesizer. This file, which contains data collected during the radiopharmaceutical synthesis, is produced. The data collection file may be formatted and contain data as described herein. Alternatively, other formats for the file may be used. For example, the file may be a log file such as produced by the GE Healthcare FASTlab system as described above. The use of the term “data collection file” or “log file” herein is mean to be exemplary and non-limiting, as there are other terms that may be used for such a data collection file with data collected during a radiopharmaceutical process. It should be appreciated that the data collection file may be produced at any point during the synthesis process. The data collection file may be produced in hard copy format and/or may be stored electronically. For example, the data collection file may be printed by an output device communicatively coupled to the synthesizer, such as a printer. Alternatively, the data collection file may be output or stored in an electronic format. For example, the synthesizer may have an electronic display or be coupled to a computer system for displaying the data collection file in an electronic format. The data collection file may be electronically saved using electronic storage, either internal to the synthesizer or external thereto. For example, the synthesizer may have solid state storage, both temporary, such as random access memory and/or more permanent such as flash memory or hard disk type storage. It should also be appreciated that the synthesizer may have input devices to allow for user interaction with the system. These input devices may be communicatively coupled to the system. For example, the synthesizer may have a QWERTY type keyboard, an alpha-numeric pad, and/or a pointing input device. Combinations of input devices are possible. The synthesizer may be communicatively coupled to a computer network. For example, the synthesizer may be communicatively coupled to a local area network or similar network. Through such a network connection, the synthesizer may be communicatively coupled to one or more external computers, computer systems, and/or servers. In some embodiments, the synthesizer may be communicatively coupled to the Internet. The synthesizer may be wirelessly connected to the computer network or may be connected by a wired interface. The synthesizer may transmit and receive data over the computer network. For example, the data collection file may be transmitted over the computer network to another computer system or server. This other computer system or server may be remotely located at a geographically separate location from the synthesizer. Furthermore, the synthesizer may be computer implemented such that synthesizer includes one or more computer processors, power sources, computer memory, and software. As stated above, the synthesizer may be communicatively coupled to one or more external computing systems. For example, the synthesizer may be communicatively coupled through a computer network, either wired or wireless or a combination of both, to an external computer system. The external computer system may provide commands to cause the synthesizer to operate as well as collect and analyze data from the data collection file. This combination of computer hardware and software may enable to the synthesizer to automatically operate and to perform certain collection of data, analysis of the data, and implementation of corrections or factors derived from the data. At block 116, the data collection is analyzed. In accordance with exemplary embodiments, the data collection file is analyzed as described herein. As part of the analysis, certain factors and information may be gleaned from the data collection file. Using these factors and information, the radiopharmaceutical process may be altered, modified, and/or tuned. For example, the data analysis may determine that the process is not operating efficiently because a low yield is indicated. By way of non-limiting example, this may be indicative of a problem in the reaction vessel. A fix or modification may be implemented. Such a fix or modification may be manually applied by an operator or may be implemented automatically by the synthesizer based on command issued through a computer system. In some embodiments, the system may be completely automatic and no outside intervention is needed to perform an analysis and implement a correction or modification to the process. FIGS. 2A and 2B depict a data collection file according to an exemplary embodiment. For example, FIGS. 2A and 2B may depict a log file from a FASTlab system. FIG. 2A depicts a first portion 200A of the data collection file and FIG. 2B depicts a second portion 200B of the data collection file. The first and second portions are parts of the data collection file: that is, FIGS. 2A and 2B may be put together side by side to form an exemplary data collection file. Alternatively, the data collection file may be apportioned as depicted, such as being split into multiple sections. It should be appreciated that the data collection file may be divided into different sections than shown. This data collection file may represent the data collection file containing data produced as shown in the method 100, for example. The data collection file has a header row 202 with labels on each of the data columns therebelow, as shown in FIGS. 2A and 2B. Exemplary column labels in the header row 202 are depicted in FIGS. 2A and 2B. It should be appreciated that additional or less column labels may be contained in the data collection file. Furthermore, the data and the formatting of the data depicted in each of the columns is meant to be exemplary and non-limiting. These data are meant to depict data collected during an exemplary radiopharmaceutical synthesis process for FACBC, which is used as a non-limiting example. As shown in FIG. 2A, the data points are shown at one second intervals. Each of the data columns (labeled by header row 202) represents a point or state in the radiopharmaceutical process. Data collected from different radioactivity detectors is shown (labeled as “Activity Detector No. N,” where “N” is the detector number). These radioactivity detectors measure radioactivity in their vicinity. It should be appreciated that the Activity Detectors described herein are positioned in exemplary positioned. More or less Activity Detectors may be used and the positioning of the Activity Detectors may be customizable with respect to the synthesizer and the cassette. FIG. 3 depicts a plot of data collection file data according to an exemplary embodiment. The plot 300 represents a plot of data collection file data, such as the data depicted in the exemplary data collection file of FIGS. 2A and 2B. The plot 300 has a legend 302. As can be seen, the plot 300 is a plot of the Activity Detector data for Activity Detectors Nos. 1, 2, 4, and 5. The plot 300 may plot Activity Measured 304 versus Elapsed Time 306. A detailed explanation of a data collection file plot is provided in FIG. 4 below. The details are equally application to other data collection file plots, such as the plot 300. FIG. 4 depicts a plot 400 with an overlay of the components of the radiopharmaceutical synthesis process. As shown by the legend 402, the plot 400 is a plot of the activity at three different detectors. The plot 400 represents the same data as plotted in the plot 300 described above. The plots 300 and 400 depict the activity during the radiopharmaceutical synthesis process. Specifically, by way of non-limiting example, the plots 300 and 400 depict a data collection file obtained during the synthesis of Fluciclatide. An exemplary radiopharmaceutical synthesis process is superimposed on the plot 400 as shown in FIG. 4. It should be appreciated that although this exemplary process is described in terms of production of Fluciclatide using 18F, the basics of the process and the components may be used in the production of other radiopharmaceuticals with appropriate modifications as understood in the art. The process begins with the purification of [18F] obtained through, e.g., the nuclear reaction 18O(p,n)18F by irradiation of a 95% 18-enriched water target with a 16.5 MeV proton beam in a cyclotron. The radioactivity is collected on a QMA cartridge 404 where 18F is trapped; impurities are removed; and the 18F is subsequently eluted at path 406 into a reaction vessel 408. In the reaction vessel 408, the 18F is first conditioned through a drying step to remove solvents including residual water, thus making the 18F more reactive. Next, at 408a, also in the reaction vessel 408, the 4-trimethylammnonium benzaldehyde is labeled using the 18F, thereby replacing the 4-trimethylammonium moiety with a 18F. The resulting 4-[18F]benzaldehyde (FBA) is transferred at path 410 to an MCX cartridge 412 for purification of FBA as shown at 412a. The FBA is transferred at path 414 back to the reaction vessel 408 and is conjugated at 408b with a Fluciclatide precursor AH111695 to form Fluciclatide as shown at 408c. This reaction is shown in detail in Scheme I, below. Next, using path 416, the Fluciclatide is transferred to and passed through the first of two SPE cartridges 418. The Fluciclatide obtained from the first SPE cartridge 418 subsequently migrates to a second SPE cartridge 420 for further purification (the SPE cartridges 418 and 420 may also be referred to as tC2 SPE cartridges). The Fluciclatide is transferred at 422 to a syringe 424 through which it is transferred at 426 into a production collection vial (PCV) 428. Although two SPE cartridges are shown in FIG. 4, the synthesizer may have one or more than two SPE cartridges and the SPE cartridges may be of different types and configurations. According to exemplary embodiments, Activity Detector No. 1 is positioned in the vicinity of the QMA cartridge, Activity Detector No. 2 is positioned in the vicinity of the Reactor Vessel, and Activity Detector No. 5 is positioned in the vicinity of the outlet of the process that leads to a syringe or a production collection vial. The elution of 18F off the QMA cartridge and into the reactor is illustrated by the sudden drop of the Activity Detector No. 1 trace and the rapid increase of the Activity Detector No. 2 trace at section 450 of the plot. The “jump” in the Activity Detector No. 2 trace after approximately 1000 sec (at section 452 of the plot) is caused by increased volume in the reactor when precursor is transferred into the reactor after evaporation of solvent. This jump occurs because activity is moved closer to the detector as the volume rises inside the reactor. The only difference in height is caused by the decay of 18F. During the labeling process, the volume remains constant and the slope of this plateau (at section 454 of the plot) illustrates the decay of the fluoride [18F—]. The activity detector is sensitive enough to even detect “splatter” inside the reactor when precursor is added. The purification of the FBA by the MCX cartridge is illustrated by the drop in the Activity Detector No. 2 trace followed by a lower plateau during the period the FBA is trapped inside the MCX cartridge, at section 456 of the plot. In other words, there is no detector located in proximity to the MCX cartridge. The trace increases again when activity is transferred back to the reactor. It should be appreciated that the elapsed time depicted refers to the start of the sequence, not the start of the overall synthesis. After starting a sequence, a synthesizer can be left idle for a period of time at a given step waiting for eventual delayed fluoride. A dialog box on the synthesizer may be need to be checked before proceeding. The start of sequence time is when this box is checked. After the second synthetic step the Activity Detector No. 2 trace drops when product was transferred out to two SPE cartridges for final purification as shown in section 458 of the plot. When product is eluted off the SPE cartridge, and transferred to the production collection vial, it passes by Activity Detector No. 5. FIG. 5 depicts a plot showing how certain information, specifically yield information, can be gleaned from the data collection file data according to an exemplary embodiment. Plot 500 depicts a plot similar to that of FIG. 4. The overall yield 502 is the sum of the first yield step 504 and the second yield step 506. These yield values can be used to assess the performance of the overall process, as well as identify problem areas of the process. According to exemplary embodiments, an exemplary or “standard” process with an exemplary yield may be determined for the system. The resulting data collected during the exemplary process, e.g., the measurements of the Activity Detectors, is plotted. The yield can be determined as shown in FIG. 5. This resulting plot may form an exemplary “fingerprint” for the system. Subsequent runs made using the system can then be compared to this exemplary process. Deviations from the fingerprint can be noted through plots of the data collection file data as described above. From analysis of the plots in this comparison, problems with the system and its process may be readily identified and subsequently corrected. According to exemplary embodiments, if the trace shown in FIG. 3 is taken to be the fingerprint of a process that is optimal, a subsequent trace (e.g., from a subsequent synthesis run or from an instrument at a different site) can be compared to it. If the fingerprint of the subsequent trace varies significantly (e.g., more than 2%; more than 5%; more than 10% or more than 15%) in any region (e.g., the region that is covered by detectors 1, 2, 3, 4 or 5), the operator (or the synthesizer automatically) can diagnose the step of the synthesis that is not proceeding properly. According to exemplary embodiments, variations in the first yield step 504 and the second yield step 506 can be used to identify where in the process a problem may be occurring, either at the labeling step that forms [18F]FBA; the conjugation step that forms [18F]fluciclatide; or with any purification step involved in the synthesis process. FIG. 6 depicts a set of yield predictions according to an exemplary embodiment. A table 600 represents data and yield predictions. The data is exemplary and non-limiting. According to exemplary embodiments, data is gathered from several synthesis runs on the same machine, as shown in column 602. Alternatively, or concurrently, these data can also be gathered from several locations or sites. These sites may be geographically separated and each site operates a radiopharmaceutical process on its synthesizer. The predicted yields, in this case from several runs on the same machine, are in column 604. The reported yields are in column 606. The predicted yields are calculated based upon the yields obtained from a plot, such as the plot 500. It can be recognized that the yield data gleaned from the data collection file data agrees with the reported yield for the radiopharmaceutical. The reported yield is determined by a comparison of the first and second yields to the overall yield as shown in FIG. 5 above. The difference between these quantities is the percentage yield. It should be appreciated that the process can have several steps and actions and this is an exemplary comparison, as additional steps and actions may need to be taken into account for determining the overall yield. It is advantageous to be able to glean overall yield data from the data collection file of the synthesizer because such a determination may mean one less QC assessment that has to be performed on the sample, post-production prior to administering any of the produced radiopharmaceutical to a patient, thus saving time and resources. In addition to yield data one can also glean purity data from the data collection file. One of the detectors not shown in FIGS. 4 and 5 is Activity Detector No. 4. This detector is located in the vicinity of the two SPE cartridges, as SPE cartridges 418 and 420 depicted in FIG. 4. While, the data from this detector is not shown in FIGS. 4 and 5, it is nevertheless collected during the synthesis run. When this data is plotted the traces shown in FIGS. 7A and 7B may be obtained. It should be understood that these traces are exemplary only. FIGS. 7A and 7B depict traces 700 and 702 of activity from Activity Detector No. 4 for a portion of the synthesis reaction. Both figures contain plots of multiple traces from different runs. For example, FIG. 7A depicts traces from multiple runs at a particular site as indicated by the legend 702. FIG. 7B shows three different traces obtained while the SPE cartridges were kept at three different temperatures, as shown by the legend 704. From these traces, it can be observed that the changes in activity measured from the highest, or maximum, activity read by Activity Detector No. 4 and the minimum activity read by the detector can be correlated to the level of impurities present in the radiopharmaceutical produced in any given synthesis run (referring to the right hand portion of the traces, shown by section 706 of the traces). For example, in FIG. 7A, the smaller the change in activity between the maximum value of any given trace, such as section 710, and the minimum value for any given trace, such as section 712, is correlated to high levels of impurities. In contrast, the larger the change in activity between the maximum value of any given trace, such as section 714, and the minimum value for any given trace, such as section 716, is correlated with lower levels of impurities. FIG. 7B also depicts this behavior, in this case of the synthesis of the radiopharmaceutical anti-1-amino-3-[18F]fluorocyclobutane-1-carboxylic acid, otherwise known as FACBC. The trace 720, which depicts activity at 27° C., has total impurities of 106 μg/mL. The trace 722, which depicts activity at 30° C., has total impurities of 56 μg/mL, while the trace 724, which depicts activity at 28° C., has total impurities of 79 μg/mL. The trace behavior depicts these impurity levels. From FIG. 7B, it can be seen that the distance from the point 730 of the trace 720 to its lowest value 732, it much less than either of the similar points of the traces 722 and 724 (such as, for example, the distance from the point 734 on the trace 722 and the lowest value 736 is greater than that of trace 720. A similar analysis may be performed for the trace 724 (with the highest point and lowest point being labeled as 738 and 740, respectively). A specific portion of the trace at a specific time may be designated for the measurement of the high and low points to ensure consistency among readings for different traces. From the data collection file one can also glean data regarding how effective certain processes are during the synthesis run. FIG. 8 depicts a plot 800 of a series of traces depicting a portion of runs shown activity at Activity Detector No. 5 during the final SPE purification step at a particular site. The plot 800 is exemplary and non-limiting. A legend 802 is provided. A table 804 provides a summary of the run number vs. SPE recovery % vs. reported yield percentage. The behavior of the traces shown in the plot 800 can be analyzed and conclusions drawn therefrom. For example, focusing on the trace and data corresponding to run J181 (labeled by 806 in the legend 802 and the table 804), certain behavior can be seen. For example, the large delta between the SPE Recovery % and the Reported Yield % is usually indicative of a problem in the synthesis process, specifically the labeling step (e.g., the step yielding [18F]FBA, when the radiopharmaceutical in question is [18F]fluciclatide). In the case of run J181, in the synthesis of [18F]fluciclatide, such a large delta is indicative of a problem in the labeling step yielding [18F]FBA. It should be appreciated that in practice every step and action are monitored and abnormal indications can be detected. For example, untypical syringe movement can be detected through the data collection files. The activity detectors are capable of catching the consequence or result of a particular step or action during the synthesis process. Hence, it can be see if the action, e.g., an atypical syringe movement, affected the outcome the production. Data corresponding to this run can be seen in FIG. 6 at 610 also. The data 610 shows that the run has a low fluorination in the step of 45% (depicted in the Yield Labeling column of table 600). Based on this, the trace 808 corresponding to this run in FIG. 8 behaves in a certain manner. For example, the trace 808 has a higher activity than the other runs in the latter part of FIG. 800. By noting behavior of this sort, insightful observations can be made into a particular synthesis process and what is happening at each step. This and other observations can be made from an analysis of the data and the traces therefrom. FIGS. 9A-C each depict an activity plots or traces from three different production sites based on data collection file data. By way of non-limiting example, FIG. 9A represent a production run at a site in Norway, FIG. 9B represents a production run at a site in Sweden, and FIG. 9C represents a production run at a site in the UK. Each run is a Fluciclatide production run using a synthesizer, which by way of non-limiting example are FASTlab systems here. As can be seen in each Figure, data corresponding to Activity Detectors Nos. 1, 2, 4, and 5 are plotted for each. Legends 902, 904, and 906 on each FIG. 9A-C, respectively, provide reference to the traces for each Activity Detector. As can be seen, each plot is similar in structure and shape to that shown in FIGS. 3 and 4 described above, as these plots were obtained using the same equipment and process as depicted in those Figures. When comparing FIGS. 9A-C, it can be seen that there are differences in the relative peak heights; e.g., between the readings of Activity Detector No. 1 (QMA) and Activity Detector No. 2 (reactor) between the different production sites and their specific synthesizers. In an ideal case, the readings of Activity Detectors Nos. 1 and 2 should be almost equal since the amount of activity entering reactor after elution of the QMA is supposed to be almost the same since the recovery activity from the QMA is >99%. The same variations are also seen between Activity Detectors Nos. 2 and 5. The differences between Activity Detectors Nos. 2 and 5 are used for the overall yield predictions (as described above). Hence, inaccuracy of these two detectors effects the accuracy of yield prediction. In data given in FIG. 6 (which represents data corresponding to FIG. 9A), correlation between estimated and reported yields is observed. However, when the same estimations are done on other synthesizers, e.g., FIGS. 9B and 9C, the effect of variations between Activity Detectors Nos. 2 and 5 are seen. FIG. 10 includes this data. FIG. 10 depicts a data table corresponding to the plots of FIGS. 9A-C. The data 1002 labeled as “NMS” corresponds to FIG. 9A; the data 1004 labeled as “UI” corresponds to FIG. 9B; and the data 1006 labeled as “TGC” corresponds to FIG. 9C. The differences in yield data may be attributed to the differences in the Activity Detector measurements. As seen in FIG. 10, the accuracy of the yield prediction varies between sites and particular synthesizers. In order to use the data for analysis of the synthesizer production for troubleshooting or other investigations, the data from the data collection files, e.g., log files, (as described above) are extracted from the synthesizer and analyzed. Plots, such as those in FIGS. 9A-C are created. However, since there are variations amongst synthesizers, even at the same site, the data analysis may be not be directly comparable. Activity trending may be a useful tool for monitoring reaction performance. A method of correcting activity detector measurements is described. A basic synthesizer sequence where a known amount of activity is passed in vicinity of the different Activity Detectors. This is accomplished by mating a cassette with the synthesizer (as would be done if a production run was being made. The cassette may be specifically configured cassette to support the required measurements or a production cassette may be used, possibly with modifications. No chemical reactions are required. The operations required are trapping and elution of the QMA cartridge with an accurately known volume followed by movement of the eluted 18F-fluoride solution around the cassette using syringe movements and gas pressure. A correlation factor for each detector can then be calculated as shown in the following example. When activity arrives from the cyclotron, the activity is accurately measured in an ion chamber. For illustration purposes, the net activity transferred on to the synthesizer in this example is 100 GBq. In the synthesizer, Activity Detector No. 1 reads 80 GBq, Activity Detector No. 2 reads 110 GBq, and Activity Detector No. 5 reads 90 GBq. The readings are then adjusted for decay. For simplification of the present example, the decay correction is not included. Based on the readings, the correlation factors for this particular synthesizer would then be: Correlation factor for Activity Detector No. 1: 100/80=1.25 Correlation factor for Activity Detector No. 2: 100/110=0.91 Correlation factor for Activity Detector No. 5: 100/90=1.11 Data for the other detectors including any custom placed additional detectors can of course be obtained in the same manner and correlation factors can be calculated. The correlation factors can then be used during the data analysis of the data collection file. This methodology does not require a modification to the synthesizer system's programming. It should be appreciated that calculation could be a part of a PET center set-up since the detector check is straightforward. This operation could be repeated on regular basis to see if detectors need to be calibrated. This operation can be repeated with different activities for control of the radio detector linearity. This operation can be carried out across multiple sites and, by using the correlation factors, activity detector readings can be compared across these multiple sites. It should further be appreciated that additional correlation factors can be calculated to compare data from synthesizers to other baselines or standards. While the foregoing description includes details and specific examples, it is to be understood that these have been included for purposes of explanation only, and are not to be interpreted as limitations of the present invention. While the embodiments have been particularly shown and described above, it will be appreciated that variations and modifications may be effected by a person of ordinary skill in the art without departing from the scope of the invention. Furthermore, one of ordinary skill in the art will recognize that such processes and systems do not need to be restricted to the specific embodiments described herein. Other embodiments, combinations of the present embodiments, and uses and advantages of the present invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The specification and examples should be considered exemplary. |
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description | This application is a continuation-in-part of pending application Ser. No. 10/620,954, filed Jul. 16, 2003, entitled “Multiple Hazard Protection Articles And Methods For Making Them,” which is a continuation-in-part of application Ser. No. 10/238,160, filed Sep. 9, 2002, entitled “Lightweight Radiation Protective Articles And Methods For Making Them,” and issued as U.S. Pat. No. 6,828,578 B2 on Dec. 7, 2004, which is itself a continuation-in-part of application Ser. No. 09/940,681, filed Aug. 27, 2001, entitled “Lightweight Radiation Protective Garments,” and issued as U.S. Pat. No. 6,459,091 B1 on Oct. 1, 2002, which was a continuation-in-part of application Ser. No. 09/206,671, filed Dec. 7, 1998, entitled “Lightweight Radiation Protective Garments,” and issued as U.S. Pat. No. 6,281,515 on Aug. 28, 2001. The disclosures in each of these priority applications are hereby incorporated by reference. The present invention relates to radiation detectable and protective articles. The radiation detectable articles of the present invention can be easily detected through the use of x-rays and other radioactive emissions. The processes and compositions for producing such radiation detectable articles can also be applied to creating articles which protect against radiation as well as other types of hazards, such as fire, chemical, biological and projectile hazards. Radiation has been used by humans in numerous ways. The most well known destructive application of radiation is atomic bombs. The electromagnetic radiation released by an atomic bomb can penetrate deeply into human tissue to damage human cells. The threat posed by atomic bombs has arguably increased in recent years with the growth of terrorism and the very real possibility that a “dirty bomb” can be made by terrorists through use of readily available nuclear waste materials. The destructive threat to humanity of such nuclear bombs has given rise to a need for cost-effective radiation protection, including the need for lightweight radiation protective garments. Ideally, such lightweight radiation protective garments would simultaneously provide protection against other types of hazards, such as fire, chemical, biological, projectile hazards and other forms of electromagnetic radiation. In this way, first responders, such as firemen, paramedics, policemen or the military, could use a single garment to provide them with protection against any type of hazard they might foreseeably confront. Such “universal” protective garments are addressed in Applicants' co-pending application Ser. No. 10/620,954, filed Jul. 16, 2003, entitled “Multiple Hazard Protection Articles And Methods For Making Them”, the disclosure of which is incorporated by reference. A number of constructive uses have also been developed for harnessing radiation. These constructive uses include medical x-rays and nuclear power plants. Other constructive uses of radiation, though, remain undiscovered. For example, in many industries, automated, high-speed machines are used to manufacture products quickly and inexpensively. The food industry is one such industry. For example, machines largely do the manufacture and packaging of the many popular brands of breakfast cereals. To market this mass-produced breakfast cereal, the breakfast cereal manufacturers often include a prize or “premium” inside the cereal box, such as a model of a popular superhero. This premium is typically inserted and sealed into the box by machine during the packaging process. Where high speed, automated manufacturing processes are used, there is a need for quality control procedures. Returning to the cereal box example, if the cereal box assembly machine runs out of premiums or has its premium insertion apparatus jammed, a number of cereal boxes might be sealed, shipped and sold without the premium. Since, for children's cereals, the cereal box is often purchased for the primary purpose of receiving the premium inside, the manufacturer's failure to include the premium in the cereal box can lead to angry and disillusioned customers. As such, there is a need, particularly in the high speed manufacturing art, to be able to quickly check to see if the manufactured product is made in full compliance with the company's manufacturing standards (e.g., including any premium) and that the product is also free of foreign contaminants. In the case of cereal boxes, this includes making sure that all of the cereal boxes which are supposed to have premiums actually have them and lack foreign contaminants, such as stones and metals, which can inadvertently enter the final assembly. While visual inspection by humans is often performed to maintain quality control, visual inspection is difficult to effectively perform for products manufactured on a high-speed assembly line. One problem with visual inspection is giving the human inspector enough time to perform a proper inspection without slowing down the manufacturing process. In the case of trying to detect premiums in cereal boxes, this problem is compounded by the fact that the cereal box is visually opaque and, as such, not amenable to visual inspection of items, such as premiums, which are inside the cereal box. The present invention includes compositions and processes for forming radiopaque polymeric articles. When these radiopaque polymeric articles are used in high speed, automated manufacturing processes, their attributes and presence can be easily confirmed through the use of radiation inspection apparatuses. A radiopaque polymeric article of the present invention can be created by mixing a radiopaque material, such as barium, bismuth, tungsten or their compounds, with a powdered polymer, palletized polymer or liquid solution, emulsion or suspension of a polymer in solvent or water. The polymer may advantageously be selected from a broad range of plastics including, but not limited to, polyurethane, polyamide, polyvinyl chloride, polyvinyl alcohol, natural latex, polyethylene, polypropylene, ethylene vinyl acetate, polyester, acrylonitrile-butadiene-styrene, acrylic, polycarbonate, polyoxymethylene, acetal, polytetrafluoroethylene (TEFLON™), ionomers, celluloses, polyetherketones, silicones, epoxy, elastomers, polymer foams and other polymer compounds. The radiopaque polymeric mixture can then be used to form a radiopaque polymeric article through a number of existing commercial processes, such as injection molding, extrusion and thermoforming. For example, in the case of injection molding, the radiopaque polymeric mixture can be heated in an extruder and then injected into a mold until it assumes the shape of the mold. After the radiopaque polymeric mixture has hardened into the appropriate molded shape, it is removed from the mold. In the case of a superhero model, the molded model can then be wrapped in cellophane and inserted, as a premium, into a cereal box. The radiopaque article may also be advantageously formed by spraying, adhering or coating a radiopaque adhesive mixture onto a pre-existing article. For example, mixing a lightweight radiopaque material with an adhesive, such as a gum adhesive or a liquid polymer, can form the radiopaque adhesive mixture. The radiopaque adhesive mixture may then be applied to the pre-existing article either by spraying the radiopaque adhesive mixture onto the article or dipping the article in the radiopaque adhesive mixture. During the manufacturing process, a radiation inspection apparatus can be used to detect the presence and attributes of a radiopaque polymeric article. In one embodiment, x-rays are passed through the radiopaque polymeric article itself or a radiation transmissible package containing the radiopaque polymeric article. An x-ray detector is then positioned on the opposite side of the radiopaque polymeric article to detect where the radiation has been attenuated and where it has been transmitted. Through this x-ray detector, the presence of the radiopaque polymeric article can be confirmed and, if desired, the attributes of the radiopaque polymeric article (e.g., proper dimensions, quantity, lack of defects etc.) can be ascertained. This x-ray detector can also make sure that undesired foreign contaminants, such as stones or metal debris, are not included in the finished product. A number of the processes and compositions used for creating radiopaque detectable objects may also be used to provide protection against a wide spectrum of ionizing radiation, such as neutron, ultraviolet, gamma and radio frequency radiation. For example, in the inventor's co-pending priority application Ser. No. 10/620,954, the disclosure of which is incorporated by reference, the radiopaque polymeric compounds of the present invention are used to create radiation protective garments, which, in some cases, can also provide protection against other hazards (e.g., fire, chemical, biological, projectile etc.). Similarly, in the same way an adhesive mixture of radiation protective materials can be sprayed onto a pre-existing object to make it radiation detectable, the same type of mixture can be sprayed onto a garment to make it attenuate radiation. As another part of the present invention, recent advances in nanotechnology can be used to create better radiation detectable and radiation attenuating articles. In certain embodiments, these radiation attenuating articles can also provide protection against other types of hazards, such as fire, chemical, biological, projectile hazards, and a wide range of electromagnetic radiation energies. Owing to their small size and high surface area to volume ratio, these nano-materials have demonstrated unique electrical, mechanical and optical properties. In this invention, various types of nano-materials can be utilized to enhance mechanical, thermal, attenuating and barrier protection properties of a product. In the present invention, nano-materials are used in at least three different ways. In one embodiment, nano-materials are added to the previously disclosed radiation protective polymeric mixtures to either enhance the radiation protection or provide additional protections, such as fire, chemical, biological and/or projectile protection. In a second embodiment, nanoparticles formed from radiopaque materials (e.g., barium, bismuth, tungsten etc.) are used in the radiation protective mixture instead of more bulky forms of the same or similar radiopaque materials. Use of such radiopaque nano-materials allows more even dispersion of radiopaque materials in the polymeric mixture, with the attendant possibility of allowing higher concentrations of radiopaque materials before the polymer becomes embrittled. In a third embodiment, the nano-materials are formed into a discrete nano-material layer. Such a discrete nano-material layer could either be added to a product or formed into a stand alone product. Nano-materials for use in the present invention include nanoparticles, nanotubes and nano-platelets. Nanoparticles are predominantly formed as solid grains, but may also consist of hollow nanospheres, nano shells, hemi-spheres, parabolas and so forth. Nanoparticles can be formed of various metal/non-metal powders including oxides, sulphides and ceramic powders. Nano-platelets are layered nano-materials which include natural nanoclays and synthetic nano-clays, such as silicic acids and transition-metal dichalcogenides (i.e. tantalum dichalcogenides interacted with lithium). Nanotubes are tube like nano-materials that have a diameter of a few nanometers but yet could be several microns in length. To attenuate electromagnetic radiation such as radio waves, ultra-violet rays and ionizing radiation, nano-particles can be formed of conventional radiopaque materials such as tungsten, tantalum, barium or their compounds, shell structures such as metal coated magnetic particles like Fe2O3/Au, SiO2/Au or other coated semiconducting particles like PbS/CdS. Hollow metal, metal oxide/sulphides nanospheres or nanospheres of other compounds; nanoparticles having shapes of parabolas, hemi-spheres and shell structures can also be used in this current invention. Shaped nanoparticles (e.g., nanoparabolas, nano hemi-spheres, nanospheres etc.) are believed to deflect, reflect and capture radiation in a manner similar to the way mirrors deflect, reflect and capture lightwaves. Since these shaped nanoparticles are believed to attenuate radiation differently than powdered radiopaque nanoparticles, these shaped nanoparticles do not need to be formed from radiopaque materials, but may instead be formed from such materials as metal/semiconductor hybrid particles. For example, the hybrid CdS-coated Ag nanoparticles exhibit red-shifted plasmon resonance absorption. This resonance absorption band of the metal nanoparticles is a function of particle size. As the particle size decreases, the theoretical wavelength of maximum absorption intensity can be approached. By creating these nano-spheres, nano-hemispheres, and nano-parabolic structures in specific shapes and curvatures, the optical properties can be used against smaller wavelengths of the light spectrum to attenuate electromagnetic radiation in the radiowaves, ultraviolet rays and ionizing radiation frequencies. Rather than absorbing the electromagnetic radiation as in the case of heavy metals, the electromagnetic radiation is effectively redirected, shifted, or reflected to allow its energy to be reduced to a lower level or converted to heat. To enhance the chemical and fire-retardant properties of a polymeric mixture, nano-materials of suitable composition can be evenly dispersed in the polymeric mixture. For instance, nanoclays when properly dispersed in a polymer enhances its chemical properties by creating a tortuous path in the polymer matrix, which makes hard for the harmful chemicals, biological agents and other gases, such as oxygen, to penetrate the polymer. To increase the fire-retardant properties of the polymer, a small percentage of nanoclays or other nano platelets in the range of 2 to 10% could be added along with conventional fire retardants, such as alumina trihydrate, magnesium hydroxide or other organic brominated and organic chlorinated compounds either in the nanoscale or micron range. Nanotubes can be used to enhance the mechanical properties such as tensile strength, flexibility, modulus and electrical conductivity of a polymeric mixture. There are three general ways of dispersing nano-materials into the polymeric mixture. The first is direct mixing of the polymer and the nano-materials either as a discrete phase or in solution. The second is in-situ polymerization in the presence of a nano material, and the third is in-situ particle processing which involves both in-situ formation of the nano-materials and in-situ polymerization. Also, nanomaterials could be coated on a number of substrates by several techniques such as evaporization, sputtering (glow-discharge, ion-beam, laser), ion-plating, chemical vapor deposition (CVD), plasma enhanced CVD, thermal spraying, dip coating, fluidized bed and atomized liquid spray. It should also be noted that nano-materials tend to agglomerate to reduce their surface area and, therefore, without proper dispersion and distribution in the polymer matrix the desired properties of the resulting nano-composite cannot be achieved. In order to disperse nano-materials into a polymer and process the resulting mixture by standard manufacturing techniques, they should preferably be surface modified. For instance, in the case of nanoclays, the clay surface is modified by a process known as compatibilization so that they are attracted to the resin matrices and thus get thoroughly dispersed. The two most common compatibilization methods known are onium ion modification and the ion-dipole interaction. By incorporating nano-materials into polymeric mixtures of the present invention or creating a pure nanolayer, a radiation protective shield can be created to either make an article radiation detectable, radiation protective (ultraviolet, radiofrequency, electromagnetic, x-radiation, or gamma radiation) or “universally” protective (i.e., protective against one or more hazards such as neutron radiation, fire, chemical, biological, or projectile hazards). The resultant radiopaque polymeric mixture, with or without the nano-materials, can additionally be laminated to a chemical film, anti-ballistics fabric, woven or non-woven, or flame retardant material as described in our previously referenced patent applications. Referring now to FIG. 1, an example of a radiopaque polymeric article 10 of the present invention is shown. In this case, the radiopaque polymeric article 10 is a premium which can be inserted into cereal boxes taking the form of a plastic toy model. The radiopaque polymeric article 10 is preferably formed from a polymeric mixture, which includes one or more radiopaque materials and one or more polymers. The inclusion of one or more radiopaque materials is important for this polymeric mixture because polymers themselves are largely transparent to many forms of radiation, such as x-rays, and, as such, using a polymer alone will not produce an effective radiopaque polymeric article. For the radiopaque materials, barium sulfate, tungsten and bismuth are preferred choices for the present invention because, as compared with lead, for example, they have fewer known heath hazards. Other radiopaque materials can also be used, including, but not limited to, barium, other barium compounds (e.g., barium chloride), tungsten compounds (e.g., tungsten carbide and tungsten oxide), bismuth compounds, tantalum, tantalum compounds, tin, titanium, titanium compounds, Diatrizoate Meglumine Inj. USP (sold by Nycomed Corporation under the trade name HYPAQUE™), Acetrizoate Sodium, boron, boric acid, boron oxide, boron salts, other boron compounds, beryllium, beryllium compounds, Bunamiodyl Sodium, Diatrizoate Sodium, Ethiodized Oil, Iobenzamic Acid, Iocarmic Acid, Iocetamic Acid, Iodipamide, Iodixanol, Iodized Oil, Iodoalphionic Acid, o-Iodohippurate Sodium, Iodophthalein Sodium, Iodopyracet, Ioglycamic Acid, Iohexol, Iomeglamic Acid, Iopamidol, Iopanoic Acid, Iopentol, Iophendylate, Iophenoxic Acid, Iopromide, Iopronic Acid, Iopydol, Iopydone, Iothalamic Acid, Iotrolan, Ioversol, Ioxaglic Acid, Ioxilan, Ipodate, Meglumine Acetrizoate, Meglumine Ditrizoate Methiodal Sodium, Metrizamide, Metrizoic Acid, Phenobutiodil, Phentetiothalein Sodium, Propryliodone, Sodium Iodomethamate, Sozoiodolic Acid, Thorium Oxide and Trypanoate Sodium. These radiopaque materials can be purchased from a variety of chemical supply companies, such as Fisher Scientific, P.O. Box 4829, Norcross, Ga. 30091 (Telephone: 1-800-766-7000), Aldrich Chemical Company, P.O. Box 2060, Milwaukee, Wis. (Telephone: 1-800-558-9160) and Sigma, P.O. Box 14508, St. Louis, Mo. 63178 (Telephone: 1-800-325-3010). Those of skill in the art will readily recognize that other radiopaque materials incorporating the same metals can be used interchangeably with the ones listed. The polymer used in the polymeric mixture of the present invention may preferably be selected from a broad range of plastics including, but not limited to, polyurethane, polyamide, polyvinyl chloride, polyvinyl alcohol, natural latex, polyethylene, polypropylene, ethylene vinyl acetate, polyester, polyisoprene, polystyrene, polysulfone, acrylonitrile-butadiene-styrene, acrylic, polycarbonate, polyoxymethylene, acetal, polytetrafluoroethylene (TEFLON™), ionomers, celluloses, polyetherketone, silicones, epoxy, elastomers, polymer foams and other polymer compounds. Conventional additives may be included in the polymeric mixture to improve the flexibility, strength, durability or other properties of the end product and/or to help insure that the polymeric mixture has an appropriate uniformity and consistency. These additives might be, in appropriate cases, plasticizers (e.g., epoxy soybean oil, ethylene glycol, propylene glycol, etc.), emulsifiers, surfactants, suspension agents, leveling agents, drying promoters, adhesives, flow enhancers, and flame retardants. The proportions of these various polymeric mixture ingredients can vary. Using a greater proportion of conventional sized radiopaque materials will generally allow the presence and attributes of the radiopaque polymeric article to be more easily ascertained through radiation detection techniques. Nonetheless, if the proportion of conventional sized radiopaque materials compared to the polymer is too high, the polymeric mixture will become brittle when dried or cooled and easily crumble apart. The inventors have found from their work that over 50% of the polymeric mixture, by weight, can be barium sulfate, tungsten, bismuth or other conventional sized radiation protective materials, with most of the rest of the mixture consisting of the polymer. In one preferred embodiment, the polymeric mixture contains approximately 85% by weight of conventional sized radiopaque materials and approximately 15% by weight of polymer. In this preferred embodiment, the radiopaque materials used in the polymeric mixture are tungsten (75%), barium sulfate (20%) and bismuth (5%). The currently preferred polymers for this preferred embodiment are a mixture of ethyl vinyl acetate (EVA) and polyethylene. It may be appropriate to consider the use of lead as one of the radiopaque materials for the polymeric mixture. While, because of its potential health hazards, lead would not be as preferred as many of the other radiopaque materials previously listed, lead nonetheless might have a role in some radiopaque polymeric mixtures. A number of known manufacturing processes may advantageously be used to create the radiopaque polymeric articles of the present invention. For example, the radiopaque polymeric mixture of the present invention can first be melted in an extruder and then pushed by a piston in molten form into the mold of an injection-molding machine. FIG. 2 illustrates such an injection-molding machine 20. In the FIG. 2 embodiment, the radiopaque polymeric mixture 24 is inserted into a hopper 26. The hopper 26 then feeds the radiopaque polymeric mixture 24 into an extruder 30, which, through use of extrusion heaters 32, melts the polymeric mixture 24 into dough like consistency. The extrusion screw 34 moves the melted polymeric mixture toward the mold 40. As the melted polymeric mixture leaves the extruder 30, it is injected under pressure through extruder nozzle 36 into mold 40. When the polymeric mixture has cooled inside the mold 40, it can be popped out of the mold 40 in finished form. A further example of an injection molding apparatus and process is described in Walter's U.S. Pat. No. 6,572,801 B1, the disclosure of which is hereby incorporated by reference. Thermoplastics, thermosets and elastomers can all be injection molded. By using multiple inlets to the mold 40 (not shown), a co-injection molding process allows molding of components with different materials, colors and/or features. Moreover, other types of molding techniques can be used depending on the shape, thickness, weight range, allowable tolerance, surface roughness and economic batch size of the injection-molded articles. These other types of molding techniques include, but are not limited to, rotational molding for large hollow closed or semi-closed structures, blow molding, foam molding, compression molding, resin transfer molding, die-casting, sand casting, investment casting, polymer casting, shape rolling, die forging, extrusion, press forming, roll forming, spinning, thermoforming, lay-up methods, powder methods, laser prototyping and deposition. Many other known plastic forming techniques can be used to form the radiopaque polymeric articles of the present invention. For example, the polymeric mixture of the present invention could again be put into the hopper of an extruder, heated and, in this case, deposited in molten form as a thin film on a conveyor belt. Vacuum pressure could then be applied to the thin film so as to draw the molten film into intimate contact with a mold impression to form the thin film into its desired shape. An example of such vacuum forming techniques is described in greater detail in Gilbert's U.S. Pat. No. 6,319,456 B1, the disclosure of which is hereby incorporated by reference. Alternatively, instead of drawing the thin film into a vacuum mold, the thin film sheet could simply be cut into a desired planar shape. As a further alternative, the article, such as the superhero, could be pre-formed and subsequently made radiopaque through the application of a thin radiopaque layer. In such case, mixing a lightweight radiopaque material with an adhesive, such as a gum adhesive or a liquid polymer, could advantageously form the radiopaque layer. The radiopaque adhesive mixture could then be applied to the pre-formed article either by spraying the radiopaque adhesive mixture onto the outside of the article or dipping the article in a solution of the radiopaque adhesive mixture. The mold used in the injection molding process shown in FIG. 2 might, for example, be in the shape of the superhero model 10 illustrated in FIG. 1. In addition to premiums, injection molding is used today to produce many other types of plastic articles, which could benefit from becoming radiopaque polymeric articles of the present invention. For example, a plastic straw is often attached to children's juice cartons in order to allow the child to drink the juice without spilling. Similarly, a plastic utensil, such as a spoon or fork, might be attached to a serving of food embedded in a plastic container. If the straw or other utensil is missing from the food container, the user will either have to throw the product away or manually try to eat from the container, thereby dealing with an attendant mess. If the straw or other utensil in this example were made of a radiopaque polymer of the present invention, a radiation inspection apparatus could be used to make sure that all the containers leaving the assembly line have radiopaque straws or other utensils attached. Since the straw or other utensil in this example touches the mouth of the user, it would be important to choose a non-toxic radiopaque material for the polymeric mixture, such as barium sulfate, iodine, bismuth or some combination of them or their compounds, rather than a toxic material, such as lead. A further factor to be considered in selecting a suitable radiopaque material is the degree of radiation attenuation which the material would provide. For example, in the straw and juice box example, the cardboard juice box freely transmits radiation. As such, one would not need a radiopaque compound with strong attenuating properties to create a sufficient radiation contrast between the straw and the box. More specifically, a radiopaque compound with relatively weaker attenuation properties, such as iodine compounds, could be used for the straw and juice box example or a radiopaque compound with stronger attenuation properties, such as a bismuth compound, could be used in lower concentrations. Other packaging industries would also benefit from the principles of the present invention. In disposable medical products, most of the devices are made of plastic and, if any of the contents were missing, the entire device would likely fail. Using radiopaque plastics of the present invention, an x-ray inspection of the sealed medical package at the factory could insure that all the contents of the medical device were present. Also in the field of medicine, a catheter could be manufactured with radiopaque materials using the principles of the present invention, which would allow the catheter's insertion into the human body to be carefully monitored using an x-ray machine. By so monitoring the catheter insertion, the doctor could make sure that the catheter reaches the correct position in the patient's body. As a further application, guns, knives and explosives are now being produced from plastics, which cannot be detected by the x-ray scanning machines used at airports. If such plastic guns, knives and/or explosives were in the hands of terrorists, they could be used to pose a threat to airplane crews and passengers. Using the principles of the present invention, the government could require that all plastic guns, knives and explosives incorporate one and more radiopaque materials of the present invention so that they would be readily detectable by the x-ray scanning machines used at airports. Given the great importance of detecting guns, knives and explosives at airports, the government would likely want to require that radiopaque compounds with high attenuating properties, such as bismuth compounds, be used for these applications. Referring now to FIG. 3, a radiation inspection apparatus 50 and process is illustrated for detecting radiopaque polymeric articles 10 of the present invention. In the process shown in FIG. 3, boxes or other containers 52 incorporating the radiopaque polymeric articles 10 are moving along a conveyor belt 60 in a high speed manufacturing process. In this preferred embodiment, an x-ray tube 70 is used to generate radiation for detecting the presence or absence of the radiopaque polymeric articles 10 in the box or other container 52. The x-ray tube 70 is controlled by an x-ray controller 72, which sends control signals to a high-voltage generator 74. The high voltage generator 74 applies a high voltage between the anode and the cathode of the x-ray tube 70 to produce x-rays 76. A lead plate 78 with a slit 79 is interposed between the x-ray tube 70 and the box or other container 52. This lead plate 79 serves to focus the x-rays on the box or other container 52 being inspected and prevent extraneous x-rays from harming manufacturing workers. After the x-rays pass through the box or other container 52 being examined, the x-rays are detected by an x-ray detector 80. The x-ray detector 80 can include a scintillator and one or more MOS image sensor(s). In such an arrangement, incident x-rays are converted by the scintillator into visual light, which is detected by the MOS image sensor(s). The MOS image sensor, in turn, outputs a detection signal 82 whose characteristics correspond to the amount of incident x-ray radiation detected. A data processor 84 is used to analyze the detection signal 82 received from the x-ray detector 80. Since the box 52 itself would evenly transmit x-ray radiation, a detection signal with no discontinuities would indicate that the radiopaque polymeric article 10 is missing from the box 52. By contrast, since the radiopaque polymeric article 10 would block a portion of the radiation, a detection signal with sharp discontinuities would usually indicate the presence of the radiopaque polymeric article 10 in the box. Further confirmation that the radiopaque polymeric article 10 is actually in the box 52 can be made by measuring the level or pattern of x-rays detected by the x-ray detector 80. For example, the amount of radiation detected by the x-ray detector 80 for a box 52 having a radiation detectable article 10 can be measured and loaded into the memory of the data processor 84 as a template. The data processor 84 could then compare the level for each subsequent box 52 on the conveyor 60 with the memorized template value and, if the two values match within a pre-determined tolerance, the data processor 84 could conclude that the box 52 indeed contains the radiopaque polymeric article 10. If, by contrast, the data processor 84 concludes that the box 52 is missing the radiopaque polymeric article 10, it could send a signal to alarm 86 to alert an attendant to the defective box 12. Alternatively, the data processor 84 could direct an operation unit 88 to either stop the assembly line or eject the defective box from the assembly line. For even greater precision of inspection, the x-ray detector 80 could have a pattern of detection pixels which each would detect the transmission of x-ray radiation over a small defined area. To establish a template, a box 52 with a radiopaque polymeric article 10 could be x-rayed with the x-rays being detected by the pattern of pixels. The level of detected x-rays for each pixel would then be stored in the memory of the data processor 84 as a template for future inspections. The data processor 84 could then, for each pixel, compare the level of detected radiation for each box 52 inspected during the manufacturing process with the memorized template to first determine, within a predetermined tolerance, whether the inspected box 52 contains a radiopaque polymeric article 10. The data received from the detailed detection pixels could then be used to determine the shape (e.g., outside contours) of the radiopaque polymeric article. Moreover, use of the detection pixels also allows analysis of whether there is a crack, nick or other defect in the radiopaque polymeric article 10. The use of pixel data in a radiation inspection apparatus to detect the presence of cracks or nicks in an article is described in greater detail in Sawada's U.S. Pat. No. 6,574,303 B2, the disclosure of which is incorporated herein by reference. In addition to detecting the presence and attributes of a desirable object in a box, the radiation inspection apparatus 50 shown in FIG. 3 could simultaneously, or alternatively, detect unwanted contaminants, such as stones, dirt or metal debris. Since such contaminants are likely to attenuate radiation differently from both the box and the radiopaque polymeric article, the data processor 84 could use a suspicious difference in detected radiation attenuation to either sound alarm 86 or use operation unit 88 to stop the conveyor 60. Thus far, the focus has been on methods and compositions for forming radiopaque detectable articles. Nonetheless, many of the same principles can be applied to making articles which protect against the harmful effects of radiation, including ultraviolet, electromagnetic, radiofrequency, neutron, x-ray and gamma radiation, as well as other hazards (e.g., fire, chemical, biological, and ballistic). For example, in the inventor's co-pending priority application Ser. No. 10/620,954, the disclosure of which is incorporated by reference, the radiopaque polymeric compounds of the present invention are used to create garments which protects against radiation and other hazards. Similarly, in the same way an adhesive mixture of lightweight radiation protective materials can be sprayed, adhered or coated onto a pre-formed object to make it radiation detectable in the previous examples, the same type of mixture can also be sprayed, adhered or coated onto a garment to make it radiation protective. FIG. 4 shows a full body suit 100, which is constructed from radiation protecting polymeric mixtures of the present invention. To provide complete surface protection, the full body suit 100 should preferably be a one-piece jumpsuit, which covers every portion of the human body. Elastic bands 112, 114 can be used around the hand and foot areas to help insure a tight fit. Alternatively, the gloves 116, booties 118 and hood 120 can be separate pieces, which overlap with the rest of the jumpsuit so as to leave no skin surface exposed. The full body suit 110 can also include hook and loop fasteners or a zipper flap 119 to allow the user to easily enter the full body suit 110. A transparent eye shield 124 is preferably included with the full body suit 110 to provide protection for the face. For convenience, the eye shield 124 could be hinged, such as with corner rivets 126, in order to allow the user to flip the shield 124 up and down. Alternatively, the eye protection can be a stand alone device, such as safety glasses (not shown). To provide radiation protection, the eye shield 124 preferably incorporates lead or other radiopaque compounds that are capable of attenuating radiation. Turning to FIG. 6, a composite material cross-section 200 is illustrated which, when fashioned into an article, can provide protection against numerous life threatening hazards, including toxic chemicals, infectious biological agents, fire and metal projectile hazards, in addition to the hazards posed by radiation. As part of this multiple hazard protection composite material, there can be two layers of fabric 204, 208 with a radiation protective polymer mixture 206 sandwiched between them. Added to these three layers 204, 206, 208 can be additional layers 210, 220, 230 to protect against different hazards. For example, a nonporous chemical protective layer 210 and/or 220 can be added to the three radiation protective layers 204, 206, 208. This nonporous chemical layer can either be a polymer film 210 laminated onto the three radiation protective layers 204, 206, 208 and/or a chemical protective fabric 220 which is sewn or otherwise adhered onto the three radiation protective layers. This chemical protective layer 210, 220 can be constructed of known chemical protective polymers and/or fabrics. For example, one known class of chemically protective fabrics are non-woven textiles, such as the flashspun polyethylene fabric sold by DuPont under the tradename Tyvek®, polypropylene fabrics such as Kimberly-Clark's Kleenguard™, Kappler's Proshield 1™, Lakeland's Safeguard 76™, fabrics mixing polyethylene with polypropylene and cellulose based fabrics such as DuPont's Sontara™ and Kimberly Clark's Prevail™. A similar type of non-woven textile would be the class of plastic films laminated onto one or both sides of a nonwoven fabric including DuPont's TyChem® series of fabrics, Kimberly Clark's HazardGard I, II™ fabrics, Kappler's CPF™ and Responder series of fabrics and ILC Dover's Ready 1 fabric™. These non-woven textiles would typically be combined with the three radiation protective layers 204, 206, 208 by sewing or otherwise adhering the fabrics together. Chemical protection can also be imparted by using polyvinyl chloride and/or chlorinated polyethylene films, such as ILC Dover's Chemturion™. These films could be laminated or extruded onto the three radiation protective layers 204, 206, 208. Another class of chemical protective layers are polymer films with microscopic pores laminated onto fabrics such as Gore-tax® or polypropylene based fabrics such as DuPont's NexGen™, Kimberly Clark's Kleenguard Ultra™, Lakeland's Micro-Max™ and Kappler's Proshield 2™. Chemical protection can further be provided by materials incorporating an absorbent layer, such as the carbon/fabric combinations sold by Blucher GmbH and Lanx. Another class of chemically protective fabrics are woven fabrics coated with rubber or plastic on one or both sides. These coated chemically protective fabrics include polyvinyl chloride and nylon composites, polyurethane/nylon composites, neoprene/aramid composites, butyl/nylon composites, chlorinated polyethylene/nylon composites, polytetrafluoroethylene (i.e., Teflon®/fiberglass composites and chlorobutyl/aramid composites. Because the chemical protective layers 210, 220 is preferably nonporous, it will also provide protection against infectious biological agents. While the fabric shown in FIG. 6 can provide a broad measure of protection with only the addition of one or more chemical protective layers 210, 220 to the three radiation protective layers 204, 206, 208, further or alternative layers 210, 220, 230 can nonetheless also be chosen to protect against additional hazards or promote heat dissipation. For example, where the chemically protective layer 210 is a plastic laminate, layer 220 in FIG. 6 could be another woven or nonwoven fabric layer and layer 230 could be a fire protection layer, such as a layer produced from the Nomex® fire resistant aramid fabric manufactured by DuPont. Other types of fire resistant materials include combinations of the Nomex® and Kevlar® aramid fabrics such as that sold by Southern Mills, combinations of melamine resin with aramid fibers, combinations of polytetrafluoroethylene (i.e., Teflon®) with aramid fibers, combinations of rayon with aramid fibers, combinations of polybenzimidazole with aramid fibers, combinations of polyphenylenebenzobisoxazole with aramid fibers, combinations of polyimide with aramid fibers and Mylar™ plastic films. Moreover, traditional fire retardant additives include aluminum trihydrate (ATH), magnesium hydroxide or organic brominated or chlorinated compounds. Alternatively, layer 230 could be a bullet or shrapnel resistant layer produced from bullet stopping aramid and/or polyethylene fibers. It may alternatively be prudent to form layer 230 of a heat dissipation material. One way of forming such a heat dissipation layer is to mix compounds with high thermal conductivity, such as silver, copper, gold, aluminum, beryllium, calcium, tungsten, magnesium, zinc, iron, nickel, molybdenum, carbon and/or tin, with a polymer in the same way that the radiation protective materials are mixed with polymers to form radiation protective layer 206. While a six layer hazard protecting fabric 200 is illustrated in FIG. 6, those of skill in the art will readily recognize that a multiple hazard protecting fabric can be created with more or less than six layers. For example, the woven or non-woven fabric layers 204, 208 illustrated in FIG. 6 can be omitted. It is also possible to combine different hazard protecting or heat dissipating layers together into a single layer. For example, while the radiation protective layer 206 of the present invention has been found to provide superior heat dissipating properties on its own, these heat dissipating properties can be enhanced by adding strong thermal conductors, such as silver, copper and/or aluminum, to the mixture of radiopaque materials in the radiation protective layer 206. Turning now to FIG. 7, a bullet proof vest 300 is illustrated which has additional hazard protecting properties. Most of the bullet proof vest 300 is of conventional design, similar to that shown in Borgese's U.S. Pat. No. 4,989,266, the disclosure of which is hereby incorporated by reference. The bullet proof protection is primarily provided by layers of polyethylene fibers 314 and/or aramid fibers 316. Commercially available polyethylene fabrics used for bulletproof vests include Honeywell's Spectra™ series of ultra high molecular weight polyethylene fabrics and Honeywell's Spectraguard™ ultra high molecular weight polyethylene fabrics which also include fiberglass. Commercially available aramid fabrics used in bulletproof vests include DuPont's Kevlar® series of aramid fabrics and Akzo's Twaron™ series of aramid fabrics. In this preferred example, the bullet proof vest has one or more layers of aramid fibers 316 sandwiched between layers of polyethylene fibers 314. To obtain greater levels of protection against bullets and shrapnel, one typically creates a greater number of layers of aramid fibers 314 and/or polyethylene fibers 316. Additional strength can be created by laying plies of the bulletproof material at 90 degree orientations to one another and encapsulating them between layers of thermoplastic. Ceramics and plates can be added to provide even higher levels of protection. The bullet proof vest 300 shown in FIG. 7 is preferably held together by a fabric insert casing 312. To add additional hazard protection to the bullet proof vest 300 shown in FIG. 7, an additional layer 320 can be inserted. This additional layer 320 can, in one embodiment, be a radiation protecting layer. By adding such a radiation protecting layer to the bullet proof vest, the bullet proof vest would achieve protection against radiation as well as bullets and shrapnel. Similarly, one could impart fire, chemical and/or biological protection by using a multiple layer material of the type described in connection with FIG. 6. In the case of radiation protection alone, one would usually want the added layer 320 to be situated close to the user's body in order to take advantage of the superior heat dissipation properties of the radiation protective layer. By contrast, in the case of a fabric imparting fire, chemical and/or biological protection, one would typically want that layer near the outside of the bullet proof vest in order to prevent those contaminants from permeating into the bullet proof vest 300. Turning now to FIG. 8, a multipiece protective garment 400 is illustrated which can be used as an undergarment. In certain applications, it is best to disguise the fact that one may be wearing a protective garment. For example, a policeman or other first responder may want to be protected against radiation and other hazards while not alarming others that such hazards may be present. Similarly, the attendant who operates an x-ray inspection machine at an airport would want to be protected against continuous exposure to radiation throughout the work day while not causing airline passengers to panic about their own incidental contact with the same x-ray inspection machine. In the FIG. 8 embodiment, this multipiece protective garment includes a vest 410, two shoulder flaps 420, a rear groin flap 430, a front groin flap 440 and two thigh flaps 450. Through a head hole 412, the vest 410 would fit over the user's head so that the front vest panel 414 would cover the user's chest and the rear vest panel 415 would cover the user's back. To achieve a snug fit, the front vest panel 414 is attached to the rear vest panel 415 using straps 416. The straps 416 can be fastened in a number of well known ways, including snap buttons, VELCRO™ fasteners, tie straps, buckles are the like. Rear groin flap 430 and front groin flap 440 are used to protect the waist and groin area of the user. The rear groin flap 430 would be fitted over the user's buttocks while the front groin flap 440 would be fitted over the user's groin. Upper straps 434, 444 are provided so that the rear groin flap 430 and front groin flap 440 can be attached to the bottom of the vest 410 so that they can hang from the vest. For a snug fit, lower straps 432, 442 are provided on both groin flaps 430, 440 which can be pulled under the groin to connect with the lower straps 432, 442 from the mating groin flap 430, 440. To protect the user's thighs, two thigh flaps 450 are provided. These thigh flaps 450 are curved so that they can wrap around the user's left and right thighs. Four straps 452, 454 are provided for each of these thigh flaps. The lower thigh flap straps 452 would wrap around the user's upper leg and fasten onto the mating lower thigh flap strap 452. By contrast, the upper thigh flap straps 454 could either be fastened to the lower portion of the front groin flap 440 or, like the lower thigh flap straps 452, could wrap around the user's upper leg and fasten onto the mating upper thigh flap strap 454. The user's shoulders are protected by shoulder flaps 420. These shoulder flaps 420 are used to cover the user's left and right shoulders while being attached to the upper portions 418 of the vest 410. By leaving the sides of the vest 410 open and using shoulder flap 420 attachments, the multipiece protective garment 400 of the present invention allows for free arm movement while providing protection for vital organs. Similarly, by separating the vest 410 from the groin flaps 430, 440 and thigh flaps 450, the user is allowed to freely move his legs and torso while again obtaining protection for vital organs. The multipiece protective garment 400 is constructed from the same type of radiation and hazard protecting materials previously described. For radiation protection alone, a radiation protective polymeric film can be applied to fabric in the manner described in co-pending application Ser. No. 10/620,954 and then cut into the shapes illustrated in FIG. 8. Alternatively, a multilayer material of the type shown in FIG. 6 or a multilayer composite of the type shown in FIG. 7 could be cut into the shapes illustrated in FIG. 8 to provide protection against multiple hazards including radiation, chemical, biological, fire and projectile hazards. In addition to undergarments, these same principles could be applied to producing a hazard protection blanket, “dirty” or nuclear bomb suppression blanket, jacket, pants, shirt, drape, x-ray apron, vest, cap, glove and similar protective articles. These same principles could also be applied to the manufacture of liners or coatings for vehicles, walls, vessels, airplanes, spacecraft, house foundations and containers to shield against a wide spectrum of electromagnetic and ionizing radiation. FIG. 9 shows an alternate embodiment to constructing components of the multipiece protective garment 400. In this embodiment, the rear groin flap 530 is constructed from standard fabric in the form of a pocket. The protective layer or layers are then made in the form of an insert 540 which can fit into the top of the pocket. Straps 536 are sewn into the bottom of the fabric pocket 530 in order to prevent the insert 540 from falling out of the pocket after insertion. This pocket 530 and insert 540 approach allows different types of inserts to be used depending upon the expected hazard. For example, if the user is likely to encounter only a radiation hazard, an insert can be used which protects only against radiation hazards. On the other hand, if projectile, chemical or biological hazards are also possible, a more bulky insert can be used which would provide protection against these additional hazards. This type of pocket 530 and insert 540 may also be used to form a pocket on the back of vest 410 (see, FIG. 8), for example, to provide additional protection for the spine or as a belt loop to accept a belt or lumbar support brace. Additionally, recent advances in nanotechnology can be used to create better radiation detectable and protective articles In certain embodiments, these radiation attenuating articles can also provide protection against other types of hazards, such as fire, chemical, biological and projectile hazards as well as against a wide range of electromagnetic radiation energies. Nano-materials are materials that have structural features (particle size or grain size, for example) in the range of 1-100 nanometers in at least one dimension. Owing to their small size and high specific surface area to volume ratio, these materials demonstrate unique mechanical, electrical, electronic and optical properties. In addition, nano-materials, unlike conventional micron-sized materials, are less likely to create large stress concentrations, which in turn increases their yield strength, tensile strength and Young's modulus. In the present invention, nano-materials are used in at least three different ways. In one embodiment, nano-materials are added to the previously disclosed radiation protective polymeric mixtures to either enhance the radiation protection or provide additional protections, such as fire, chemical, biological and/or projectile protection. In a second embodiment, nanoparticles formed from radiopaque materials (e.g., barium, bismuth, tungsten etc.) or other hazard protecting materials are used in the polymeric mixture instead of more bulky forms of the same or similar protective materials. Use of radiopaque nano-materials allows more even dispersion of radiopaque materials in the polymeric mixture with the attendant possibility of allowing higher concentrations of radiopaque materials before the polymer becomes embrittled. In a third embodiment, the nano-materials are formed into a discrete nano-material layer. Such a discrete nano-material layer could either be added to a product or formed into a stand alone product. Nano-materials used in the present invention include nanoparticles, nanotubes and nano platelets. The first type of nanomaterials used in the present invention are nanoparticles. Suitable nanoparticles include nanopowders of conventional radiopaque materials, nano ceramics, nano shells, nanospheres and other nanoparticles in the shape of hemispheres and parabolas. Relative proportions of radiopaque materials could be increased in a polymeric mixture by replacing bulky radiopaque materials with radiopaque nanopowders or by incorporating a mixture of both nano-sized and micron-sized radiopaque powders. By incorporating a greater proportion of radiopaque nanopowders into the polymeric mixture, the resultant product could have enhanced electromagnetic radiation attenuating capabilities. Nanopowders of radiopaque materials are commercially available and could be incorporated into a polymer using standard compounding techniques. The types of radiopaque nano-powders that could be used include: tungsten, barium, boron, lead, tin, bismuth, depleted uranium, cerium, yttrium, tantalum, lanthanum, neodymium and their compounds. Tungsten (APS: 100 nm) and tantalum (APS: 100 nm) nanopowders can be purchased, for example, from Argonide Nanomaterial Technologies, Sanford, Florida. Rare earth radiopaque nanomaterials of cerium oxide, yttrium oxide or neodymium oxide can be purchased at NanoProducts Corporation, Longmont, CO. Moreover, nanoparticles formed in the shape of hollow nanospheres, nano-hemi spheres, nano parabolas and nano shells could be used in the present invention to achieve radio pacification and attenuation of a wide spectrum of electromagnetic radiation. These shaped nanoparticles are believed to deflect, reflect and capture radiation in a manner similar to the way mirrors deflect, reflect and capture lightwaves. Since these shaped nanoparticles are believed to attenuate radiation differently than powdered radiopaque nanoparticles, these shaped nanoparticles do not need to be formed from radiopaque materials, but may instead be formed from such materials as metal/semiconductor hybrid particles. For example, hybrid CdS coated gold nanoparticles have been found to exhibit red-shifted plasmon resonance absorption. This resonance absorption band of the metal nanoparticles is a function of the particle size. As the particle size decreases, the theoretical wavelength of maximum absorption intensity could be approached. By creating these metal nano spheres, hemi spheres and parabola structures in specific shapes and curvatures, the optical-like properties can be used to attenuate against smaller wavelengths of the electromagnetic spectrum including radio waves, ultraviolet rays, and ionizing radiation, such as x-rays and gamma rays. Unlike conventional heavy metals, which absorb or scatter the electromagnetic radiation, these nanoparticles effectively redirect, shift or reflect the electromagnetic radiation, later converting it into a lesser energy or heat. Referring to FIG. 5A, the deflection of radiation 132 by the concave inner surface 134 of a nano-hemisphere is illustrated. In FIG. 5B, radiation 142 passes through the concave outer surface 144 of a nanosphere 140, but is internally reflected and, thereby, captured by the concave inner surface 146 of the same nanosphere 140. As is known in the art, resonating antennas in a parabolic or semi-spherical shape have very sharp directional characteristics. By analogy, when creating similar resonating characteristics for radiation at a nano level, one would preferably want to orient the position of the nano-materials in space to create a layer which would block radiation coming from a particular direction (e.g., the outside of a garment). Nonetheless, by applying a coating of randomly positioned particles in hundreds of layers, one can effectively achieve shielding from all directions. For better performance, such a coating of nano-materials should have a minimum of voids. As such, when making a mixture of nano-materials with a binder, the nano-materials should preferably be the bulk of the coating, for example, over 70% and, more preferably, between 85% and 95% by weight. Ceramic nanoparticles could also be added to the radiopaque polymeric mixture to enhance not only mechanical strength, like tensile strength and creep resistance, but also enhance heat resistance, anti-ballistic, electromagnetic attenuation and neutron emission attenuation. Ceramic nano-powders, which include, but are not limited to, oxides of aluminum, zirconium, silicon, titanium, mullite and spinel as well as carbides/nitrides such as boron carbide, silicon carbide, titanium carbide, tungsten carbide, boron nitride, silicon nitride, titanium diboride, zirconium diboride and other intermetallics like nickel aluminide, titanium aluminide and molybdenum disilicate could be advantageously incorporated into the polymeric mixture to provide radiation attenuation. These ceramic nanomaterials can be prepared by a number of methods including chemical vapor deposition, pulsed laser deposition, conventional powder processing (i.e. sol-gel processing), plasma synthesis, pyrolysis, carbothermal reduction, hydrothermal processes, emulsion processes, combustion synthesis, NIST process, precipitation, electrical arc, and ball milling. Adding metallic second phase particles into ceramics can also be done to enhance mechanical, thermal and electromagnetic attenuation properties. Metals such as tungsten, molybdenum, nickel, copper, cobalt and iron can be added to the ceramics using conventional powder metallurgical techniques and solution chemical processes like sol-gel, as well as co-precipitation methods. Alternatively, nanoparticles could be synthesized by several additional techniques. One such technique is colloidal templating in which an inner removable template particle, such as silica or polymer beads, are coated with metal materials in a multi-step colloidal or vapor-phase assembly and can later be removed to create empty metallic shells. Creating uniform coating on a particle template by colloidal self-assembly is based on the concept of self-assembled organic molecular species. The two ends of the molecules to be joined have specific functional groups (i.e. Thiols, amines, carboxylic groups) that can be targeted for specific interactions with the template and the clusters that are used to make the coatings. Uniform dense packing of the molecules around the templates leads to close packing of the clusters that form a porous but space filled shell around the template. Non-interacting metal-coated magnetic particles, which include SiO2/Au, Fe3O4/Au, NiO/Co, silver, platinum, tantalum, tungsten, aluminum and copper or coated semi-conducting particles, such as PbS/CdS, are examples of such composite particle structures. Alternatively PbS-coated CdS nanocomposite particles that are a few nanometers in diameter can be synthesized by ion displacement in inverse micro emulsions. The refractive nonlinearity in these nano-composite particles may be attributed to the optical Stark effect and to strong interfacial and inter nano-particle interactions. Hollow nanospheres could be synthesized by taking advantage of the nanoscale Kirkendall effect. When nano-crystals, such as cobalt, are exposed to sulfur, there is a differential in diffusion in which the cobalt atoms move outward more quickly that then sulfur atoms thus creating a hollow nanosphere of cobalt sulfide. Cobalt oxide and cobalt selenide could also be synthesized by this technique. Similarly, it may be possible to synthesize other metals such as silver, gold, platinum, aluminum, copper and tungsten using this technique. Nanoparticles could also be made via in-situ particle formation/in-situ polymerization. In this method, a stable suspension of metal particles is prepared in the presence of a polymer. Once in solution, the composite can be cast, or additional monomers of the same or different polymer type can be added to form a nano-composite. The reaction occurs in the presence of a protective polymer, which limits the size of the resultant nano-composite. Particle size is also controlled by the choice of metal precursor and the metal/polymer interaction. For example, if PdCl2 is compared with (NH4)2PdCl4, the former tends to form halogen-bridged complexes and thus tends to form agglomerates of nano-particles, but the latter does not. The interaction of the metal precursor with the polymer is also important in controlling particle size. If the polymer has a stronger interaction with the precursor, then the particle size tends to be reduced because the metal precursors are prevented from phase separating. Using this technique, nanoparticles could also be formed through the use of micelles formed from amphiphilic block polymers or cross-linked gelled matrices. Using copolymers to form micelles, metal salts are introduced that can either penetrate the micelle or are stable in the micelle corona. A reducing agent can be added and metal particles form either within the micelles or in the corona resulting in several morphologies. In general, nanoparticle size is controlled in several ways depending on the synthesizing technique used. For instance, in gas phase, synthesis particle size is controlled by varying the system parameters such as temperature, gas flow rate and system pressure. In other methods such as sol-gel technique, the particle size can be varied by changing the concentration of the solutions and temperature. In mechanical milling, the particle size depends more on the speed of the grinding media and milling time. Hollow nano-crystals can be commercially obtained from the Molecular Foundry at the Berkeley National Laboratory in Berkeley California, which specializes in synthesizing hollow metal, metal oxide/sulphide nano-crystals. The second type of nano-materials used in the present invention are nano-tubes. Nano-tubes are typically formed from carbon. When added to a polymeric mixture, nano-tubes represent another way to enhance mechanical properties like modulus, chemical resistance, flame resistance, strength and also electrical conductivity of the mixture. Carbon nano-tubes have unique electrical properties because the electronic conduction process in nano-tubes is confined in the radial direction and, as a result, they can also be used to attenuate electromagnetic radiation. The methods to produce these nanotubes includes chemical vapor deposition techniques using catalysts and hydrocarbon precursors to grow the nano-tubes. Nano-tubes can also be made by electric arc, laser ablation, chemical vapor deposition and high pressure carbon monoxide conversion (HiPCO). HiPCO uses high-pressure disproportionation of carbon monoxide gas in the presence of iron carbonyl catalyst vapor to produce nano-tubes of 80% purity in large quantities. Other types of nano-tubes include the hexagonal boron nitride nano-tubes, nano-tubes made of dichalcogenides (i.e. MoS2, WS2), nano-tubes of oxides (i.e. V2O, MoO3), gold nanotubes and organic nano-tubes. Nano-tubes may be commercially purchased from Materials and Electrochemical Research Corporation of Tucson, Ariz. Once produced, nano-tubes should undergo purification procedures before they can be incorporated into a radiopaque polymeric mixture of the present invention. Methods of purification and processing include preliminary filtration, dissolution, micro-filtration, settling and chromatography. The resultant nano-tube product is then preferably dispersed in the polymeric mixture with a surfactant, such as sodium dodecyl sulfate. The third type of nano-materials that could be added to the radio opaque polymeric mixture are nano platelets (i.e., plate-like nano-fillers). Nano platelets are layered materials that typically have a high aspect ratio and a thickness on the order of about 1 nm. When added to a polymeric mixture in quantity, nano-platelets would enhance the mixture's chemical, ballistic, fire, electromagnetic radiation and neutron resistance. Nano-platelets include nano-clays, such as montmorillonites clays. Montmorillonite clays belong to the smectite group which also includes clays like bentonite, hectorite, pyrophyllite, talc, vermiculite, sauconite, saponite and nontronite, layered silicic acids (i.e. kanemite and makatite) and layered double hydroxides. Clays from other groups, such as kaolinites and chlorites, and other phyllosilicates, such as mica, could also be used. Transition-metal dichalcogenides (i.e. tantalum dichalcogenides intercalated with lithium) could also be dispersed in a polymer mixture not only to provide the mixture with nanoclay like properties (because of its similar layered structure), but also to enhance the electromagnetic radiation attenuation. Natural nano-clays, such as smectites clays, are highly layered weakly bonded materials. Each layer consists of two sheets of silica tetrahedra with an edge shared octahedral sheet of either alumina or magnesia. Due to the isomorphic substitution of alumina into the silicate layers or magnesium for aluminum, each unit cell has a negative charge. The natural nano-clay layers are held together with a layer of charge compensating cations such as Lithium (Li+), Sodium (Na+), Potassium (K+), and Calcium (Ca+). These charge-compensating cations provide a route to the rich intercalation chemistry and surface modification that is required to disperse nanoclays into the polymer. Synthetic clays, such as hydrotalcite, carry a positive charge on the platelets. For these layered nano-clays to become useful within the radiopaque polymeric mixture, the layers should be separated and dispersed properly within the mixture. In the case of nano-clays, such as silicate clays, they are inherently hydrophilic while the polymers tend to be hydrophobic. To get intercalation and exfoliation of these clays, the galleries or layers of these clays must be opened and the polarities of the resultant clay must match the polarity of the polymer so that the polymer will intercalate between the layers. This is done by exchanging an organic cation for an inorganic cation. The larger organic cation will swell the layers and increase the hydrophobic properties of the clay. The organically modified clay can then be intercalated with the polymer by several routes. For positively charged clays, such as hydrotalcite, an anionic surfactant can be used. Other types of clay modifications can be used depending on the choice of polymer. These include ion-dipole interactions, the use of silane coupling agents and the use of block polymers. An example of ion-dipole interactions is the intercalation of a small molecule, such as dodecylpyrrolidone, into the clay. Unfavorable interactions of clay edges with polymers can be overcome by the use of silane coupling agents to modify the edges. Alternatively, compatibilization of clays and polymers can be done through the use of copolymers where one component of the copolymer is compatible with the clay and the other component of the copolymer is compatible with the polymer. The resistance of a polymeric mixture to harmful chemicals could be improved substantially by incorporating a small amount of nanoclays (about 2 to 5% by weight) into the polymer mixture. The level of chemical resistance improvement depends on many factors, though, such as the degree of exfoliation of the nano platelets in the polymer mixture, the percentage of the nano-material filler, its aspect ratio, and the alignment of the platelets. By incorporating nano-clays within the polymeric mixture, oxygen transmission through the mixture is particularly reduced which then reduces polymer degradation by reducing oxidation of the resins and hence improving its flame retardancy property as well. In addition, the inorganic phase can act as a sink to prevent polymer chains from decomposing. To enhance flame retardance in polymeric mixtures of the present invention, traditional fire retardant additives, such as alumina trihydrate (ATH), magnesium hydroxide or organic brominated and chlorinated compounds are often added. Nonetheless, very high levels of these fire retardant additives are usually needed to achieve acceptable levels of fire retardancy (e.g., for cable or wires). These high additive levels make the manufacturing process more difficult and therefore embrittles the polymeric end product. In the present invention, nanomaterials can be used in the polymeric mixture to overcome this fire retardant embrittlement problem. More specifically, a small weight percent of nanoclays (e.g., 2 to 10%) can be added with the traditional bulky fire-retardant additives, such as ATH or magnesium hydroxide, to drastically lower the additive loading levels needed to achieve the same or an improved level of flame resistance in a polymeric mixture. Other nano sized fire-retardant additives which could be added to the polymeric mixture are nano/micron-sized oxides such as antimony oxide, nano/micron-sized compounds of molybdenum, titanium, zirconium and zinc. Silicon carbide, silicon nitrate, aluminum nitride, silicon nano-tubes, carbon nano-tubes, boron nitride nano-tubes also could be used to enhance the fire resistant properties of a polymer. Moreover, conventional fire resistant additives, such as ATH or magnesium hydroxide, could be added in the nano-size range to more effectively achieve fire resistance in a polymeric mixture. Through use of these nanomaterials, the resultant polymeric mixture would be more strong, light and flexible. One of the key limitations in the use of nano-materials in polymeric compositions is processing. More specifically, nanomaterials tend to agglomerate to reduce their surface area and, therefore, without proper dispersion and distribution in the polymer mixture, the desired properties of the resulting nano-composite cannot be achieved. In order to effectively disperse nanomaterials into a polymer and process the resulting mixture by standard manufacturing techniques, the nanomaterials should be surface modified. For instance, in the case of nanoclays, the clay surface can be modified by a process known as compatibilization so that the nanoclays are attracted to the polymeric resin matrices and thus get thoroughly dispersed. The two most common compatibilization methods are onium ion modification and the ion-dipole interaction. Once the nano-material agglomeration problem is overcome, there are three general ways of dispersing nano-materials into the polymeric mixture. The first is direct mixing of the polymer and the nano-materials either as a discrete phase or in solution. The second is in-situ polymerization in the presence of a nano-material, and the third is in-situ particle processing which involves both in-situ formation of the nano-materials and in-situ polymerization. For example, to prepare a chemical-fire resistant nano-composite, a polymer, such as ethyl vinyl acetate (EVA), can be directly mixed with nano-platelets such as nano-clays, silicic acids, or transitional metal dichalcogenides. Such a mixture can be made with or without conventional fire retardants, such as ATH and magnesium hydroxide. The resultant polymeric mixture can then be processed in a twin-screw extruder and formed into a desired product using blow molding, or injection molding. Compounding with twin-screw extruder creates a great amount of shear force, which helps exfoliate the nano-materials in the polymer mixture. The addition of nanoclays or nanotubes would increase the viscosity of the polymeric mixture. Therefore, the rheology of the mixture should be closely monitored and controlled, though, by adding Theological additives that are compatible to the polymer and filler used (i.e. nanoclays or nanotubes). To produce the protective products of the present invention, nano-materials can also be coated on several different substrates, including polymeric substrates. Using known techniques, such as evaporation, sputtering (glow discharge/ion and beam/laser), ion plating, chemical vapor deposition (CVD), plasma enhanced CVD, thermal spraying, dip coating, fluidized bed, and atomized liquid spray, nano-composites can be coated on several different substrates. Also, nano-materials could be applied as a coat on different substrates by other techniques like unassisted spraying, spraying assisted by a high voltage electrical field, liquid coating by such existing technologies as roll stock, extrusion, coating and co-extrusion. Alternatively, nano-materials can be applied to a flexible film, which can then be coated with a pressure sensitive adhesive to produce a self-adhering material with shielding properties. For protection of human skin from the sun's ultraviolet rays, for example, nano-materials can be mixed with binders to form a spray or ointment to be applied directly to the skin. Further, since the thickness of several hundred rows of nano-materials is on the order of a single micrometer, the nano shielding materials of the present invention can be made transparent to visible light and thereby allow its use in the manufacture of goggles and other clear shields, with excellent optical properties. Turning now to FIG. 10, a bomb containment vessel 760 is shown which includes bomb containment sphere 762, front hatch 764, wheel assembly 766 and bomb tray 768. The sphere 762 and front hatch 764 of the bomb containment vessel 760 are constructed out of a hard explosion resistant material, such as hardened steel. While existing bomb containment vessels 760 are constructed to contain conventional bomb explosions, they are not designed to also trap or attenuate nuclear radiation, such as gamma and neutron emissions or rays. Using the principles of the present invention, though, the bomb containment vessel 760 can be reconfigured to also protect against the nuclear hazards produced by, for example, a “dirty” or radiological bomb. In the preferred embodiment, a radiation protective polymeric layer 770 is applied to the outside of the bomb containment vessel 760. As before, the radiation protective polymeric layer 770 is formed from a mixture, which includes one or more of the previously mentioned radiopaque materials and one or more of the previously mentioned polymers. In the preferred embodiment illustrated in FIG. 10, the radiopaque polymeric mixture is used to form curved radiopaque tiles 772. These radiopaque tiles 772 can be formed by any number of known manufacturing processes, including injection molding, extrusion, vacuum forming, drape forming, pressure forming and plug assisted forming. The radiopaque tiles 772 are then adhered to the outside surface of the bomb containment vessel 760 and to each other. To enhance the appearance of the bomb containment vessel 760, a smooth decorative layer (not shown) can then be applied over the radiopaque tiles 772. Alternatively, a radiopaque polymeric layer can be formed in one piece, or can be evenly coated on the outside or within the bomb containment vessel through adhesive spraying, rotational molding, injection molding, dipping in a liquid bath, painting or other known coating and injection molding processes. In operation, the hardened materials of the bomb containment vessel 760 will contain the explosive force of the bomb while the radiation protective layer 770 of the present invention will contain any radiation emitted by the bomb. While the radiation protective layer of the present invention could also be applied to the inside of the bomb containment vessel 760, the inventors believe that this would be less effective because of the damage an explosion could do to the radiation protective layer 770. In the foregoing specification, the invention has been described with reference to specific preferred embodiments and methods. It will, however, be evident to those of skill in the art that various modifications and changes may be made without departing from the broader spirit and scope of the invention as set forth in the appended claims. For example, those of skill in the art will recognize that the principles of the present invention would apply to many types of articles besides the toys, utensils, weapons and medical devices previously described. More specifically, the relatively lightweight radiopaque materials of the present invention could be incorporated into virtually any type of plastic product (e.g., auto parts, phones, storage containers etc.) to allow the presence and/or attributes of such products to be assessed using x-rays. Further, the principles of the present invention would apply to virtually all types of manufacturing processes for plastic products. While x-ray inspection has been described in the preferred embodiments, other types of radiation, such as alpha, beta or gamma radiation could alternatively be used to detect the radiopaque polymeric articles. In the case of nano-materials, since many nano-materials have been found to have minimal toxicity, nano-composites could be added intravenously or orally to the human body to provide enhanced tissue contrast for use in radiography. The specification and drawings are, accordingly, to be regarded in an illustrative, rather than restrictive sense; the invention being limited only by the appended claims. |
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abstract | An intelligent with abnormality alarm which may comprise a housing, jacks in the surface of the housing and a conductive component arranged within the housing, wherein the housing is internally provided with a single chip processor as well as a current detection module, a voltage detection module, an outdoor temperature detection module, an indoor temperature detection module, a display module and a power supply module which are electrically connected with the single chip processor respectively. The power supply module is connected with the display module to power it. The socket may be used to carry out a real-time monitoring without making modification to the software and hardware. After applying the air conditioner socket of the present invention, the user may replace the socket of the air conditioner of a corresponding model him or her, i.e., the monitoring of an installed air conditioner may be accomplished with a minimum cost. |
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043354670 | description | The invention will be described hereinafter with respect to a typical variant of a semi-integrated fast reactor. It is, however, to be noted that the features concerning the connection between the reactor vessel and the, or each, exchanger could be applied as well to fast or thermal neutron reactors with cooling loops, since, in the latter case, the same expansion problems concerning the outlet duct ant the vessel are raised and similar solutions might be adopted. FIG. 1 diagrammatically represents the main elements of the reactor. Inside a concrete enclosure 2 are to be found the reactor main vessel 4 with its safety shell and a heat-exchanger 6 with its shell for the retention of sodium leaks. It is, of course, to be understood that the reactor might comprise several cooling loops, comprising each a heat-exchanger 6 associated to vessel 4. In the specific example disclosed, heat-exchanger 6 ensures the heat-exchange directly between the liquid metal issuing from vessel 4 and the water-steam fluid. Quite obviously it would not be going beyond the scope of the invention to use exchanger 6 for ensuring a heat-exchange between the sodium issuing from the vessel (viz. the primary sodium, in the present instance) and secondary sodium. Moreover, with a view to rendering the whole plant less cumbersome, pump 6' for the circulation of liquid metal is integrated to the heat-exchanger. The so-called main vessel 4 is supported by supporting peripheral flanges or brackets such as 12 resting on supporting members 14 connected to concrete structure 2. The vessel is closed by a roof slab 4a resting on the upper peripheral flange of main vessel 4. The latter contains a primary vessel 16 coaxial therewith provided with a bottom portion 18. Said primary vessel 16 is provided, along its periphery, with supporting members 20 adapted to cooperate with supporting members 22 integral with the main vessel inner surface. It is to be noted that the supporting members of the main vessel and of the primary vessel are substantially in the same horizontal plane. Inside primary vessel 16 are to be found core 24 resting on diagrid 19, together with the neutronic lateral protective means 26. The liquid metal circulation between vessel 4 and exchanger 6 is achieved by means of an outlet conduit 28 adapted to connect the inside of primary vessel 16 with the inlet of exchanger 6, and of a liquid metal inlet duct 30 adapted to connect the heat-exchanger integrated pump outlet with the annular space 32 defined by the primary vessel and the main vessel. It should be noted that duct 28, in which flows a hot liquid metal that has passed through the core, passes through annular space 32. The fuel handling devices and the reactor control devices are of known types and, therefore, are not shown in the diagrammatic view. These various component parts are such that the reactor center of gravity be at a lower level than supporting means 12. According to the invention, and as shown in FIG. 1 in simplified form, steam generator 6 is supported by supporting means 40 integral with concrete enclosure 10. These supporting means 40 allow the generator to move freely in the direction of the axis of duct 28 due to the expansion of said duct and of the vessel. Of course, in addition to ducts 28 and 30 connecting heat-exchanger 6 with vessel 4, ducts relating to the exchanger secondary circuit, and diagrammatically shown at 42 and 44, are also provided. According to the preferred embodiment, the latter ducts (42,44) are water-vapour ducts. In a conventional exchanger, these ducts would be used for the circulation of the secondary liquid metal. It is important to note that, in all cases, it is indeed in duct 28 for hot active sodium that it is intended to minimize the stresses resulting from expansion or generated by earth tremors. Indeed, in return duct 30 flows a liquid metal that is "colder" by about 200.degree. C., which limits the temperature differentials between standstill and normal operation and, in addition, allows the metal to be submitted to higher stresses. It is to be noted that duct 30 is provided with elbows 30a, 30b giving thereto the requested flexibility. As regards ducts 42 and 44, the fluids they carry, whether it is secondary liquid metal or steam water, are not radioactive, so that the problems of expansion can be solved by the conventional methods, and all the more easily as said ducts are, along a major portion of their length, outside the radioactive protection zone. It is also to be noted that the level of the supporting-plane of the pump-exchanger assembly 6 determined by supporting members 40 is only slightly different from the levels of the supporting planes of the main vessel and of the primary vessel determined by supporting elements 14 and 22, the spacing between said levels being appropriately selected by calculation so as to minimize the stresses generated by the reactions of the "hot" duct and of the "cold" duct that open into the vessel as well as to the pump-exchanger assemblies at different levels. Indeed, as disclosed in French Pat. No. 78 18823 in the name of the applicant, tubing 28 is attached to the main vessel, whereas tubing 28 is extended between the main vessel and the primary vessel by separate fittings. In other words, the difference between the displacements resulting from thermal expansions in the vessel portion between supporting member 22 and the junction of tubing 28 with vessel 4, on the one hand, and in the shell portion between the extremity of the junction of tubing 28 with the exchanger inlet and supporting device 40, on the other hand, is negligible since the heights of said vessel portion and of said shell portion are rather small. Accordingly, the stresses resulting from the reactions of the piping on the main vessel and on the pump-exchanger assembly will readily assume acceptable values for the various temperature distributions. As explained in the above-mentioned patent, the main vessel, in that zone, is cooled by colder liquid metal. As will be explained later on, the exchanger containing the primary pump is supported by a member that is rather cold with respect to the liquid metal flowing in the exchanger. The effect of expansion variations in the vertical direction can thus be rendered substantially negligible. As shown in FIG. 1, damping jacks 46 integral with the concrete wall are attached to the lower portion of the exchanger outer shell. The function of these jacks is to damp out the oscillations likely tube imparted to the exchanger in the case of earth tremors, the exchanger center of gravity being, of course, at a lower level than the exchanger supporting plane. With reference to FIGS. 2 to 5, the following description will explain in more detail how the supporting device of the, or of each, exchanger is operated to allow the movements of said exchanger or exchangers in the direction of the axis of duct 28. The upper portion of the heat-exchanger outer shell 50 is surrounded by a sleeve 52, the upper extremity of which is fixed to outer shell 50. Said sleeve 52 is capable of withstanding the overall weight of the exchanger. Said sleeve 52 is, of course, at a temperature substantially lower than that of shell 50, the latter being provided with an outer heat-insulator (not shown). In the example described, the exchanger support is obtained through two supporting members, both of which are designated by reference numeral 40; of course, a portion 40a of each supporting member is integral with sleeve 52 (and, accordingly, with the exchanger), whereas another portion 40b is integral with concrete block 2. A notch 51 permits duct 28 to pass through sleeve 52. Portion 40a comprises a lug 60 arranged along a radius of sleeve 52 and welded or bolted to said sleeve. A so-called horizontal "backing plate" is rigidly fixed to its free end. Portion 40b comprises a horizontal supporting plate 64 anchored to concrete block 10, said plate 64 being situated under plate 62. Between these two plates is mounted a first series of cylindrical rollers 66 having horizontal axes. More specifically, the horizontal axes of rollers 66 are at right angles to the axis of duct 28. The extremities 68 of said rollers are conventionally retained in a cage 70, so that the various rollers form a solid assembly. It can thus be easily understood that, when backing-plate 62 moves horizontally with respect to supporting plate 64 as a result of the expansion undergone by the main vessel, duct 28 and the exchanger shell 50, a rolling movement of rollers 66 with respect to both plane surfaces is obtained. Thus, the free expansion of the various parts as a result of thermal stresses is not accompanied by any substantial mechanical stress. In fact, two sets of rollers (66a, 66b) are provided, which increases the resistance to the stresses applied. By way of example, it can be mentiond that, in the variant under examination, the normal temperature of the hot liquid metal is in the vicinity of 530.degree. C., whereas the temperature of the liquid metal at the moment of filling the vessel is in the vicinity of 150.degree. C., which, as regards the 1200 MW reactor described, results in a displacement of the pump-exchanger assembly of about 125 mm with respect to its position at the mounting temperature. Such a displacement, in the absence of the appropriate device, would lead to high stresses in duct 28. In addition, each supporting member is provided with means adapted to prevent any movement of the exchanger, e.g. in case of earth tremors. In this respect, it is to be noted that the pump-exchanger assembly 6 weighs about 265 metric tons, so that, under such conditions as earth tremors, the amount of energy involved might be considerable and, thus, lead to unacceptable movements and stresses. With a view to counteracting the consequences of earth tremors, each supporting member comprises a second series of rollers 72 with their horizontal axes in parallel relationship with the axes of rollers 66. These rollers 72 are bound to supporting plate 64 and so mounted that, in normal operation, there be no contact between the upper surface of plate 62 and said rollers 72. The latter are put in action only in case of earth tremors, for counteracting any substantial tilting or rising movements of the heat-exchanger. In fact, a horizontal upper plate 73 is made integral with the supporting plate, and, should the exchanger be unexpectedly caused to tilt, thus raising plate 62, rollers 72 would be brought into contact with backing plate 62 and with upper plate 73. Thus, stresses are absorbed by the whole cross-section of the rollers and not merely by the stub-axles at both ends of said rollers. Similarly, a third series of rollers 74 with vertical axes are pivotally mounted in part 76 integral with supporting plate 64. In normal operation, there is a clearance between rollers 74 and the vertical surface 62a of plate 62. In case of earth tremors, the function of said rollers is to restrict any horizontal movement at right angles to the axis of duct 28 to an acceptable value. Thus is obtained a system for supporting the movable pump-exchanger assembly, said system providing the mobility required for absorbing expansions in the direction of duct 28, the latter being itself so designed as to withstand any transient stresses resulting from components of the maximum earthquake contemplated for the site of the plant. Such a system permits to minimize the stresses applied to the connecting ducts between the vessel and the exchanger, while ensuring the stability of said exchanger in case of earth-tremors. As already specified, such a supporting system could be applied both to the primary or intermediate exchangers of a reactor with loops, and to the pumps, when the latter are not integrated to the corresponding exchanger, as is usual in reactors with loops. |
claims | 1. A ventilated cask for transporting and/or storing radioactive materials comprising: a vertically elongated overpack body comprising a longitudinal axis, an outer shell defining an outer surface, an inner shell defining an inner surface, a gap extending radially between the inner and outer shells, and an internal cavity configured for holding a nuclear fuel canister;a base enclosing a bottom end of the cavity;a lid enclosing a top end of the cavity;a plurality of outlet ducts each forming an air outlet passageway from a top portion of the cavity to an external atmosphere;a plurality of arcuately curved structures forming air inlet ducts extending radially between the outer and inner surfaces at a bottom portion of the overpack body, the air inlet ducts configured for admitting ambient cooling air into a lower portion of the cavity;the air inlet ducts spaced circumferentially apart around the longitudinal axis and the bottom portion of the overpack body in a symmetric arrangement;a plurality of wall segments comprising a radiation shielding material filled in the gap between each pair of air inlet ducts, each wall segment comprising a circumferentially projecting convex portion and an opposing circumferentially recessed concave portion. 2. The ventilated cask according to claim 1, wherein each of the wall segments has a convex outer wall that adjoins the outer shell of the overpack body and a concave inner wall that adjoins the inner shell of the overpack body. 3. The ventilated cask according to claim 2, wherein each of the wall segments is a singular uninterrupted monolithic structure. 4. The ventilated cask according to claim 3, wherein each wall segment is separated from every other wall segment by the air inlet ducts. 5. The ventilated cask according to claim 2, wherein the wall segments are arranged in an intermeshing configuration such that the convex portion of each wall segment is at least partially nested within the concave portion of an adjacent wall segment. 6. The ventilated cask according to claim 5, wherein each air inlet duct is interspersed between the convex and concave portions of adjacent wall segments. 7. The ventilated cask according to claim 5, wherein the wall segments are formed of poured concrete mass. 8. The ventilated cask according to claim 7, wherein the concrete mass is a monolithic mass extending from a top of the gap between the inner and outer shells to a bottom of the gap between the air inlet ducts. 9. The ventilated cask according to claim 1, wherein a straight line of sight does not exist from the cavity to the external atmosphere through each of the air inlet ducts. 10. The ventilated cask according to claim 5, wherein each air inlet duct includes a radially straight outer section, a radially straight inner section, and a curved section extending therebetween. 11. The ventilated cask according to claim 5, wherein each air inlet duct includes a vertically elongated outer opening formed in the outer surface of the outer shell of the overpack body, and a vertically elongated inner opening formed in the inner surface of the inner shell of the overpack body. 12. The ventilated cask according to claim 11, wherein the outer and inner openings have a rectangular configuration. 13. The ventilated cask according to claim 1, wherein each air inlet duct is defined by a pair of metal inter-shell connectors, each pair of inter-shell connectors extending between an outer opening formed in the outer surface of the outer shell of the overpack body, and an inner opening formed in the inner surface of the outer shell of the overpack body. 14. The ventilated cask according to claim 13, wherein the inter-shell connectors in each pair are complementary configured and spaced circumferentially apart, and a roof extends between tops of and covers each pair of inter-shell connectors to form one of the air inlet ducts. 15. The ventilated cask according to claim 1, wherein each of the air inlet ducts comprises a first radial section extending inwards from the outer shell into the gap, a second radial section extending outwards from the inner shell into the gap, and an arcuately curved section extending between the first and second radial sections. 16. The ventilated cask according to claim 1, wherein the air inlet ducts are C-shaped. 17. The ventilated cask according to claim 1, wherein each of the air inlet ducts are vertically elongated slots having a height and a width, and wherein a ratio of height to width is at least 10:1. 18. The ventilated cask according to claim 1, wherein for each segment, the convex portion comprises an arcuately curved first end wall adjoining a first air inlet duct, and the concave portion comprises an arcuately curved second end wall adjoining a second air inlet duct. 19. The ventilated cask according to claim 18, wherein the first end wall further comprises a first angled shoulder on an outer end adjacent to the outer shell of the overpack body, and a second angle shoulder on an inner end adjacent to the inner shell of the overpack body. 20. A ventilated cask for transporting and/or storing radioactive materials comprising:a vertically elongated overpack body comprising a longitudinal axis, an outer shell defining an outer surface, an inner shell defining an inner surface, a gap extending radially between the inner and outer shells, and an internal cavity configured for holding a nuclear fuel canister;a base enclosing a bottom end of the cavity;a lid enclosing a top end of the cavity;a plurality of outlet ducts each forming an air outlet passageway from a top portion of the cavity to an external atmosphere;a plurality of arcuately curved metallic air inlet ducts extending radially between the outer and inner surfaces at a bottom portion of the overpack body, the air inlet ducts configured for admitting ambient cooling air into a lower portion of the cavity;the air inlet ducts spaced circumferentially apart around the longitudinal axis and the bottom portion of the overpack body; anda plurality of wall segments comprising a radiation shielding material filled in the gap between each pair of air inlet ducts, each wall segment comprising a circumferentially projecting convex portion at one end extending into a concavity formed by a first one of the air inlet ducts, and a circumferentially recessed concave portion at an opposite end receiving a convexity of a second one of the air inlet ducts. |
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06326627& | description | DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG. 1, a device for separating ions in accordance with the present invention is shown and generally designated 10. As shown, the device 10 includes a substantially cylindrical-shaped chamber 12 that defines a longitudinal axis 14, and has a first end 16 and a second end 18. Magnetic coils 20a and 20b are shown mounted on the chamber 12 at its first end 16, and magnetic coils 22a and 22b are shown mounted on the chamber 12 at its second end 18. Together, these magnetic coils 20a,b and 22a,b create a magnetic field (B) inside the chamber 12. The particular magnetic coils 20a,b and 22a,b that are shown in the Figures are, however, only exemplary and additional magnetic coils can be incorporated as desired. The magnetic coils 20a,b, and 22a,b are, however, shown in the Figures to illustrate that the magnetic field (B) will be strongest at the ends 16 and 18. Also, they are configured to illustrate that the coils 20a and 20b at the first end 16 are to be positioned at a greater distance from the axis 14 than are the magnetic coils 22a and 22b at the second end 18. The consequence of all this is that the magnetic field (B) will generate so-called "magnetic mirrors" at both the first end 16 and at the second end 18. Thus, in comparison with each other, there will be a full magnetic mirror across the whole cross section at the second end 18 (r<b), and a generally annular-shaped magnetic mirror at the first end 16 (c<r<b). The exit 24 shown in FIGS. 1 and 2 is specifically positioned around the center of the annular-shaped mirror at the first end 16. Additional features of the device 10 will, perhaps, be best appreciated with reference to FIG. 2. There it will be seen that the device 10 includes a substantially rod-shaped, metallic electrode 26 that extends along the longitudinal axis 14 through the center of the chamber 12. For purposes of the present invention, this centrally located electrode 26 will preferably include two elements. One of the elements is preferably a light metal that has a mass "m.sub.1 ". As envisioned for the present invention, the second element of the central electrode 26 will be a relatively heavy impurity having a mass "m.sub.2." FIG. 2 also shows that a plurality of ring electrodes 28 are positioned in a plane around the longitudinal axis 14 at the first end 16. The electrodes 28a, 28b and 28c are only exemplary. FIG. 2 also shows that there are a plurality of ring electrodes 30 which are positioned in a plane around the longitudinal axis 14 at the second end 18. Again, the electrodes 30a, 30b, 30c, 30d and 30e are only exemplary. Together, the central electrode 26 and the ring electrodes 28 and 30 create an electric field inside the chamber 12 that will vary radially from the longitudinal axis 14 to provide a desirable radial distribution as described below. Recall, "e" is the ion charge, "m" is the mass of an ion, and "r" is a radial distance from the longitudinal axis 14. For the device 10, wherein "a" is the radius of the central electrode 26, "b" is the radius of the chamber 12, and "c" is the radius of the exit 24 (see FIG. 2), a critical potential U.sub.o can be expressed as U.sub.o =e.sup.2 B.sup.2 (b.sup.2 -a.sup.2).sup.2 /8a.sup.2 m. Desirable radial profiles 34 and 38 of the electric potential are shown in FIG. 3. For the purpose of explanation, several other profiles are also shown. For example, the radial profile 32 shown in FIG. 3 is representative of the cut-off potential for an ion of heavy mass, m.sub.2. The radial profile 34, on the other hand, is representative of the cut-off potential for an ion of light mass, m.sub.1. Stated differently, with a radial profile 32 for the electrical potential, U(r), in the chamber 12, the ions of mass m.sub.2 will be directed back toward the axis 14 for collision with the central electrode 26. The ions of light mass m.sub.1, however, will not be so directed. Further, with a radial profile 34 for the electrical potential, U(r), in the chamber 12, both the ions of mass m.sub.1 and mass m.sub.2 will be directed into collision with the central electrode 26. Thus, operationally, in order to separate the ions of mass m.sub.1 from the ions of mass m.sub.2, the device 10 is preferably operated with a radial profile 36 that is somewhere between the radial profiles 32 and 34. In some instances, as explained more fully below, it may be necessary or desirable to operate with a radial profile 38. With a radial profile 36 in the chamber 12, the heavier ions of mass m.sub.2 will generally follow a path similar to the trajectory 40 shown in FIG. 4. Thus, the heavier ions (m.sub.2) will be accelerated back into collision with the central electrode 26. The result of this is additional sputtering of the central electrode 26. At the same time, because the radial profile 36 is below the cut-off potential for the lighter ions of mass m.sub.1 (i.e. radial profile 34), the lighter ions (m.sub.1) will be confined within the chamber 12. In FIG. 4, the trajectory 42 is exemplary of a cold light ion and the trajectory 44 is exemplary of a hot light ion. In both instances, the trajectories 42 and 44 indicate that the ion does not collide with the central electrode 26. Stated differently, the ions on trajectories 42 and 44 are confined in the chamber 12. Inside the chamber 12, the sputtered particles of heavier mass m.sub.2 can either be ionized and return to the central electrode under the influence of the electric field, or, as neutrals, reach a collector 46. As seen in FIG. 2, the collector 46 is preferably a cylindrical-shaped plate that is located near the wall of the chamber 12, at a distance from the central electrode 26. The lighter ions of mass m.sub.1, which are confined within the chamber 12, will be expelled from the chamber 12 through the exit 24. This can be caused to happen by properly configuring the magnetic field (B) inside the chamber 12. In accordance with the present invention, the configuration of the magnetic field (B) inside the chamber 12 can, perhaps, be best appreciated by reference to FIG. 5. In FIG. 5, consider that the axial position Z=0 is at the first end 16 of the chamber 12, and that "z" increases along the longitudinal axis 14 in a direction from the first end 16 to the second end 18. The axial profiles 48, 50 and 52 are illustrative of magnetic field strengths for B inside the chamber 12. Recall, the device 10 incorporates respective magnetic mirrors at the first end 16 and the second end 18 of the chamber 12. Specifically, due to the configuration of the magnetic coils 20a and 20b at the first end 16 of the chamber 12 (i.e. where z=0), the field strength B will vary as shown. At the exit 24, where r<c, where c is the radius of the exit 24, the magnetic field B will have the axial profile 52. At the r>c, the magnetic field B will have the axial profile 52. Thus, there is a diverging magnetic field at r<c which effectively creates an annular shaped magnetic mirror at the first end 16. On the other hand, due to the magnetic coils 22a and 22b at the second end 18 of the chamber 12 (i.e. where z=L), the field strength will be relatively high over the entire second end 18. The consequence here is that the magnetic mirror at the second end 18 will tend to redirect charged particles away from the second end 18 and toward the first end 16. The annular-shaped magnetic mirror at the first end 16 will, however, allow the charge particles to exit from the chamber 12 through the exit 24. In operation, the magnetic field, B, is established as described above. A vacuum of around 10.sup.-4 Torr is drawn inside the chamber 12 and a gas, such as hydrogen (H.sub.2) or Argon (Ar) is introduced into the chamber 12. The electric field, E, is then activated to initiate a plasma discharge in the chamber 12. Specifically, the electric field, E, is established with a potential that will effectively accelerate ions in the chamber 12 to an energy in the range of one to three thousand electron volts (1-3 KeV). The resultant sputtering of the central electrode 26 will then cause both light ions (M.sub.1) and heavy ions (m.sub.2) to be present in the chamber 12. With an electric field having a radial profile (e.g. radial profile 36) the heavier ions (m.sub.2) will be directed toward the central electrode 26 for further sputtering. The lighter ions (m.sub.1) will be confined inside the chamber 12 and eventually expelled through the exit 24 by the effect of the magnetic mirrors disclosed above. Heavier neutrals with mass m.sub.2 that reach the outer wall without ionization shall be collected on the collector 46. It is to be appreciated that the operation disclosed above will be effective so long as there is a sufficient amount of the heavier ions of mass m.sub.2. If the central electrode 26 contains only a minority of an impurity (i.e. the ions of mass m.sub.2 are less than 10-30% of the electrode 26), it may be necessary to adjust the electric field. Specifically, for this case, the ring electrodes 28 and 30 can be adjusted so that the radial profile 38 is established inside the chamber 12. With this potential, a fraction of the light ions that reach the plasma periphery will be directed by the electric field back to the central electrode to take part in further sputtering. Subsequently, as the proportion of heavier ions in the electrode 26 is increased, it will be possible to establish the radial profile 36 inside the chamber 12. While the particular Mass Filtering Sputtered Ion Source as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims. |
052689417 | abstract | A system is directed for remotely securing a canopy seal about a broken omega seal site between the control drive mechanism and the adapter tube of a nuclear reactor vessel so as to contain any radioactive leakage therebetween. The system includes a stalk measuring device for initially measuring the diameter of the adapter tube, a split canopy installation fixture which is adjusted according to the measurement detected by the stalk measuring device to position a two-piece canopy seal about the omega seal site, and a robotic weld arm for performing the upper and lower radial welds about the canopy seal as well as C-shaped vertical welds between the two-piece canopy seal. |
claims | 1. A method for determining a position of a tumor in a patient for treatment of the tumor using positively charged particles in a treatment room, comprising the steps of:providing a set of fiducial indicators, comprising:a set of fiducial markers, a first fiducial marker of said set of fiducial markers mechanically affixed to a first object of a set of objects in the treatment room, a second fiducial marker of said set of fiducial markers affixed to a second object of said set of objects; anda set of fiducial detectors configured to detect photons from said set of fiducial markers, wherein at least one reference element of a union of said set of fiducial markers and said set of fiducial detectors comprises a mechanical connection to an element of said set of objects;using a known position of the reference element of said set of objects in establishing a reference line;determining relative positions, using a controller, of each object in the treatment room relative to the reference line using all of said reference element, said set of fiducial markers, and said set of fiducial detectors;targeting the tumor of the patient with the positively charged particles using the determined relative positions of each object in the treatment room; andconnecting a synchrotron to an exit nozzle with a first beamline, said reference line defined relative to a zero-vector path of the positively charged particles passing through said exit nozzle absent electromagnetic steering in said exit nozzle. 2. A method for determining a position of a tumor in a patient for treatment of the tumor using positively charged particles in a treatment room, comprising the steps of:providing a set of fiducial indicators, comprising:a set of fiducial markers, a first fiducial marker of said set of fiducial markers mechanically affixed to a first object of a set of objects in the treatment room, a second fiducial marker of said set of fiducial markers affixed to a second object of said set of objects; anda set of fiducial detectors configured to detect photons from said set of fiducial markers, wherein at least one reference element of a union of said set of fiducial markers and said set of fiducial detectors comprises a mechanical connection to an element of said set of objects;using a known position of the reference element of said set of objects in establishing a reference line;determining relative positions, using a controller, of each object in the treatment room relative to the reference line using all of said reference element, said set of fiducial markers, and said set of fiducial detectors;targeting the tumor of the patient with the positively charged particles using the determined relative positions of each object in the treatment room; andcalibrating position of at least two fiducial detectors of said set of fiducial detectors to a zero vector of a treatment beam, said treatment beam comprising the positively charge particles, wherein the zero vector passes through an exit nozzle in the absence of electromagnetic steering of the treatment beam in said exit nozzle, said exit nozzle comprising at least one steering magnet. 3. The method of claim 1, further comprising the step of:defining the reference line as overlapping at least two points of the zero-vector path of a treatment beam passing through said exit nozzle absent electromagnetic steering in said exit nozzle. 4. The method of claim 3, the zero-vector path not passing through an isocenter point of a rotatable gantry positioning said exit nozzle. 5. The method of claim 1, said step of determining relative positions further comprising the steps of:determining a current position of a proton scintillation detector using a scintillation detector fiducial indicator set of said set of fiducial indicators;determining a current position of the patient using a patient fiducial indicator set of said set of fiducial indicators;generating an image of the tumor using the positively charged particles; anddetermining a current position of the tumor of the patient relative to the reference line using the scintillation detector fiducial indicator set, the patient fiducial indicator set, and the image. 6. The method of claim 5, further comprising the steps of:moving said proton scintillation detector out of the zero-vector path; andconfirming movement of said scintillation detector out of the zero-vector path using said set of fiducial indicators. 7. The method of claim 6, further comprising the steps of:determining a current position of an X-ray imaging system detector using a set of X-ray detector fiducial indicators; andguiding the positively charged particles to the tumor using the set of X-ray detector fiducial indicators, an X-ray image from said X-ray imaging system, the reference line, and fiducial indicators associated with a current position of the patient. 8. The method of claim 6, further comprising the steps of:dynamically determining a current position of a moveable X-ray imaging system detector using a set of X-ray detector fiducial indicators; andguiding the positively charged particles to the tumor using: (1) an X-ray from said X-ray detector and (2) a position of said X-ray detector relative to the positively charged particles determined using the set of X-ray detector fiducial indicators. 9. The method of claim 1, said step of connecting further comprising the steps of:disconnecting said exit nozzle from said first beamline; andsubsequent to said step of disconnection, coupling said synchrotron to said exit nozzle through a second beamline, wherein a first focusing magnet of said first beamline is not physically present in said second beamline. 10. The method of claim 9, further comprising the step of:establishing an updated vector of the zero-vector path. 11. The method of claim 10, wherein said zero-vector path and said updated vector do not intersect at an isocenter point of a treatment volume in the treatment room. 12. The method of claim 1, said step of determining not reliant upon a calculation using an isocenter point of a moveable gantry supporting said exit nozzle. 13. The method of claim 1, further comprising the steps of:providing an imaging system configured with a set of imaging system fiducial indicators of said set of fiducial indicators;developing an irradiation plan of the tumor using output from said imaging system and output of said set of fiducial detectors without computational reliance on an isocenter point. 14. The method of claim 1, further comprising the step of:confirming a clear field vector from said exit nozzle to the patient using said fiducial indicators. 15. An apparatus for determining a position of a tumor in a patient for treatment of the tumor using positively charged particles in a treatment room, comprising:a set of fiducial indicators, comprising:a set of fiducial markers, a first fiducial marker of said set of fiducial markers mechanically affixed to a first object of a set of objects in the treatment room, a second fiducial marker of said set of fiducial markers affixed to a second object of said set of objects; anda set of fiducial detectors configured to detect photons from said set of fiducial markers, wherein a least one reference element of a union of said set of fiducial markers and said set of fiducial detectors comprises a mechanical connection to a reference element of said set of objects, a known position of said reference element used to establish a reference line during use;a controller configured to determine relative positions of each object in the treatment room relative to the reference line using all of said reference element, said set of fiducial markers, and said set of fiducial detectors, said controller configured to target the tumor of the patient with the positively charged particles using the determined relative positions of each object in the treatment room; anda synchrotron connected to an exit nozzle via a first beamline, said reference line defined relative to a zero-vector path of the positively charged particles through said exit nozzle absent electromagnetic steering in said exit nozzle. 16. The apparatus of claim 15, further comprising:a gantry configured to support said exit nozzle, said nozzle configured to move along an arc, said arc comprising an isocenter point. 17. The apparatus of claim 15, further comprising:an arc, said nozzle configured to move along an said arc, said arc not comprising an isocenter point. |
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abstract | A nuclear reactor includes a nuclear core comprising a fissile material, and a pressure vessel containing the nuclear core immersed in primary coolant water. Turbo pumps disposed in the pressure vessel provide active circulation of primary coolant water in the pressure vessel. Each turbo pump includes a turbine driving an impeller. A manifold plenum chamber is disposed in the pressure vessel, and is in fluid communication with inlets of the turbines of the turbo pumps. An electrically driven pump operatively connected with the manifold plenum chamber to pressurize the manifold plenum chamber with primary coolant water. The turbo pumps may be disposed in openings passing through the manifold plenum chamber. The pressure vessel may be vertically oriented and cylindrical, with a cylindrical riser oriented coaxially inside, and the manifold plenum chamber may be annular and disposed in a downcomer annulus defined between the cylindrical riser and the cylindrical pressure vessel. |
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040574660 | claims | 1. In a fuel core of a nuclear reactor wherein said fuel consists of a plurality of cylindrical pellets of fuel in oxide form of about 0.49 inches in diameter contained in a plurality of elongated zirconium alloy cladded tubular fuel elements with a cladding thickness of about 0.032 inches and having a range of power output and a maximum power rating, a method of conditioning said fuel elements to withstand subsequent rapid power changes without cladding failure comprising: (1) increasing the power produced by said fuel elements through a fuel pellet-cladding interaction range of power wherein expansion of said pellets and consequent pellet-cladding interaction causes said pellets to exert forces upon said cladding to a selected power level no greater than said maximum power level at a first rate of power increase below a critical rate which causes cladding damage due to said fuel pellet-cladding interaction, said critical rate being about 0.125 kw/ft/hr, and stepwise increases in power at said first rate comprising steps no greater than about 0.5 kw/ft, whereby said fuel elements are conditioned for subsequent rapid power changes up to said desired power level with minimized danger of cladding damage; (2) decreasing the power produced by said fuel elements from said selected power level to a lower power level; and (3) subsequently increasing the power produced by said fuel elements over any portion of the power range of said fuel elements up to said selected power level at a second rate of power increase greater then said critical rate, said second rate of power increase being at least 16 kw/ft/hr. 2. The method of claim 1 wherein said second rate of power increase is at least 15 percent of said maximum power rating per minute. 3. The method of claim 2 wherein power increases at said first rate toward said selected power level are made at a rate no greater than about 0.1 kw/ft/hr. 4. The method of claim 2 wherein power increases at said first rate toward said selected power level are made at a rate of 0.08 - 0.1 kw/ft/hr. 5. The method of claim 2 wherein power increases at said first rate toward said selected power level are made as a series of step increases in power and each of said steps is no greater than about 0.1 kw/ft with a time of no less than 1 hour between said step increases. 6. In a fuel core of a nuclear reactor wherein said fuel consists of a plurality of cylindrical pellets of fuel in oxide form contained in a plurality of elongated zirconium alloy cladded tubular fuel elements having a range of power output and a maximum power rating, a method of operating said fuel elements comprising: (1) increasing the power produced by said fuel elements through a fuel pellet-cladding interaction range of power wherein expansion of said pellets and consequent pellet-cladding interaction causes said pellets to exert forces upon said cladding to a selected power level no greater than said maximum power level at a first rate of power increase below a critical rate which causes cladding damage due to said fuel pellet-cladding interaction, said critical rate being about 0.125 (0.49).sup.3 /D.sub.n.sup.3 times T.sub.n /0.032 kw/ft/hr and stepwise increases in power at said first rate comprising steps no greater than about 0.5 (0.49).sup.3 /D.sub.n.sup.3 times T.sub.n /0.032 kw/ft/hr where D.sub.n is the diameter of the fuel pellets and T.sub.n is the thickness of the cladding, whereby said fuel elements are conditioned for subsequent rapid power changes up to said selected power level with minimized danger of cladding failure; (2) decreasing the power produced by said fuel elements to a lower power level below said selected power level; and (3) subsequently increasing the power produced by said fuel elements over any portion of the power range of said fuel elements up to said selected power level at a second rate of power increase above said critical rate, said second rate of power increase being at least about 16 kw/ft/hr. 7. The method of claim 6 wherein said second rate of power increase is at least 15 percent of said maximum power rating per minute. 8. The method of claim 7 wherein said maximum power rating is about 16 kw/ft. 9. The method of claim 6 wherein said critical rate is about 0.125 kw/ft/hr for fuel pellets of about 0.49 inches in diameter. 10. The method of claim 8 wherein power increases at said first rate toward said selected power level are made at a rate no greater than about 0.1 kw/ft/hr. 11. The method of claim 8 wherein power increases at said first rate toward said selected power level are made at a rate of 0.08 - 0.1 kw/ft/hr. 12. The method of claim 8 wherein power increases at said first rate toward said selected power level are made as a series of step increases in power and each of said steps is no greater than about 0.1 kw/ft with a time of no less than 1 hour between said step increases. 13. The method of claim 6 wherein power increases at said first rate toward said selected power level are made at a rate no greater than 0.1 (0.49).sup.3 /D.sub.n.sup.3 times T.sub.n /0.032 kw/ft/hr. 14. The method of claim 6 wherein power increases at said first rate toward said selected power level are made at a rate of (0.08 to 0.1) (0.49).sup.3 /D.sub.n.sup.3 times T.sub.n /0.032 kw/ft/hr. 15. The method of claim 6 wherein power increases at said first rate toward said selected power level are made as a series of step increases in power and each of said steps is no greater than about 0.1 (0.49).sup.3 /D.sub.n.sup.3 times T.sub.n /0.032 kw/ft with a time of no less than 1 hour between said step increases. |
047626658 | summary | This invention relates to the location of bodies end-to-end to form a stack of predetermined length. One application of the invention is in the formation of stacks of nuclear fuel pellets for loading into the sheath of a fuel pin. Because of variations in pellet length, difficulties may be encountered in securing the required stack length and, in the past, reliance has been placed on manual handling of the pellets so that the operator by trial and error can correct for drift away from the required length by substituting pellets in the stack with longer or shorter pellets depending upon whether the stack length is below or above the required length. Manual handling is considered undesirable since it tends to be time consuming and laborious and may, with certain types of nuclear fuel, such as reprocessed uranium or plutonium, give rise to radiological hazards for operators. The object of the present invention is to provide a method of and apparatus for automatically effecting stacking of bodies end-to-end to form stacks of predetermined length. According to one aspect of the present invention we provide a method of stacking bodies in end-to-end relation to form a stack of predetermined length said method including the steps of mechanically segregating said bodies according to length into a plurality of groups, initially drawing on said groups to build-up the stack part-way towards its overall length, measuring the length of the partly-formed stack and, depending on the extent (if any) to which the measured length deviates from a predetermined value, compensating for any such deviation by selecting between said groups in continuing to build up the stack. According to a second aspect of the invention we provide apparatus for stacking bodies in end-to-end relation to form a stack of predetermined length, said apparatus comprising means for feeding said bodies from a supply to a stacking zone, means upstream of the stacking zone for measuring the lengths into a plurality of lanes, means for measuring the stack length in said stacking zone and selector means responsive to said stack measuring means for selectively supplying bodies from said lanes to the stacking zone. |
claims | 1. A measuring apparatus, comprising:light receiving means for receiving EUV light diverging from a light convergent point;an optical system for directing the EUV light toward said light receiving means;a first light blocking member disposed at a pupil plane of said optical system and having a plurality of openings;a second light blocking member having an opening and being detachably mountable at the position of the light convergence point: andmeans for detecting a spatial distribution of the EUV light at the light convergent point, on the basis of reception of EUV light by said light receiving means. 2. An apparatus according to claim 1, wherein, when L is the distance between the light convergent point and the openings, λ is the wavelength of light to be measured, and R is a desired resolving power, the size d of the openings of the first light blocking member satisfies a relation d>1.22·λ·L/R. 3. An apparatus according to claim 1, wherein, when L is the distance between the light convergent point and the openings, λ is the wavelength of light to be measured, and D is a diameter of the light convergent point, the size d of the openings of the first light blocking member satisfies a relation d>6.1·λ·L/D. 4. An apparatus according to claim 1, wherein said second light blocking member has a thickness in an optical axis direction and wherein the opening of said second light blocking member has extension from an incidence direction of the EUV light to an exit direction thereof, with a predetermined angle. 5. A measuring apparatus, comprising:light receiving means for receiving EUV light diverging from a light convergent point;a gas filter disposed in a portion of a light path of the EUV light and being filled with a predetermined gas; andmeans for detecting a spatial distribution of the EUV light at the light convergent point, on the basis of the reception of EUV light by said light receiving means. 6. An apparatus according to claim 5, wherein the gas is a mixed gas comprising mixture of gases having positive and negative differential coefficients, to wavelength, of an absorption coefficient with respect to light of a predetermined wavelength. 7. An apparatus according to claim 5, wherein the gas consists of at least one of xenon Xe, sulfur hexafluoride SF6, krypton Kr, and mixture of them. 8. An apparatus according to claim 5, further comprising a light blocking member having an opening and being detachably mountable at the position of the light convergence point. 9. An apparatus according to claim 8, wherein said light blocking member has a thickness in an optical axis direction and wherein the opening of said second light blocking member has extension from an incidence direction of the EUV light to an exit direction thereof, with a predetermined angle. |
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summary | ||
claims | 1. A device for removing foreign objects from nuclear reactor vessel, comprising:a suction pipe capable of extending into the nuclear reactor vessel;a suction opening structure disposed at a lower end of the suction pipe, wherein the suction opening structure has a suction opening thereon and an upper end of the suction opening structure is connected to the suction pipe;an electric valve disposed at a connection of the suction pipe and the suction opening structure;a filter mesh located in the suction pipe and above the electric valve;a suction pump located in the suction pipe and above the filter mesh; anda drainage pipe; wherein a water inlet of the suction pump is communicated with the suction opening of the suction opening structure, a water outlet of the suction pump is communicated with an outside space of the suction pipe though the drainage pipe, and the device further comprises a touch switch disposed on the filter mesh, wherein the touch switch is in operative connection with the electric valve, and wherein a foreign object impact force to the filter mesh triggers the touch switch to close which causes the electric valve to close which prevents escape of the foreign object from the device. 2. The device for removing foreign objects from nuclear reactor vessel according to claim 1, the electric valve comprising a spool with mesh structure. 3. The device for removing foreign objects from nuclear reactor vessel according to claim 1, further comprising a controlling switch disposed on a top portion of the suction pipe. 4. The device for removing foreign objects from nuclear reactor vessel according to claim 1, further comprising an operating handle disposed on the top portion of the suction pipe. 5. The device for removing foreign objects from nuclear reactor vessel according to claim 1, wherein the drainage pipe comprises an upward outlet, preventing the foreign objects flowing with water. 6. The device for removing foreign objects from nuclear reactor vessel according to claim 1, further comprising an alarm disposed on the top portion of the suction pipe, wherein the alarm is connected to and controlled by the touch switch, when the touch switch is triggered and closed, the alarm will inform the operator to check whether there are foreign objects sucked. 7. The device for removing foreign objects from nuclear reactor vessel according to claim 2, further comprising an alarm disposed on the top portion of the suction pipe, wherein the alarm is connected to and controlled by the touch switch, when the touch switch is triggered and closed, the alarm will inform the operator to check whether there are foreign objects sucked. 8. The device for removing foreign objects from nuclear reactor vessel according to claim 3, further comprising an alarm disposed on the top portion of the suction pipe, wherein the alarm is connected to and controlled by the touch switch, when the touch switch is triggered and closed, the alarm will inform the operator to check whether there are foreign objects sucked. 9. The device for removing foreign objects from nuclear reactor vessel according to claim 4, further comprising an alarm disposed on the top portion of the suction pipe, wherein the alarm is connected to and controlled by the touch switch, when the touch switch is triggered and closed, the alarm will inform the operator to check whether there are foreign objects sucked. 10. The device for removing foreign objects from nuclear reactor vessel according to claim 5, further comprising an alarm disposed on the top portion of the suction pipe, wherein the alarm is connected to and controlled by the touch switch, when the touch switch is triggered and closed, the alarm will inform the operator to check whether there are foreign objects sucked. |
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041742931 | claims | 1. A process for the disposal of aqueous solutions containing radioactive waste material comprising; (a) densifying dry particulate portland cement in a sealable leak-proof container to a bulk density ranging from about 1.3 to about 1.8 grams per cubic centimeter, said cement having a particle size ranging from about 120 mesh to about 400 mesh; (b) dispersing without mechanical agitation from about 15 weight percent to about 30 weight percent of the aqueous solution based upon the weight of the densified cement in-situ within the densified cement; (c) sealing said densified cement containing said aqueous solution off from the atmosphere until the said aqueous solution is hydrated with said cement; (d) impregnating the hydrated cement with a mixture of monomer and a polymerization catalyst and polymerizing the monomer in-situ within the pregnant hydrated cement; (e) storing said pregnant hydrated cement in a suitable storage area; (f) maintaining the temperature of the materials utilized in the process at a temperature below 99.degree. C. throughout steps a thru e of the process. 2. The process of claim 1 wherein type III portland cement is used. 3. The process of claim 2 wherein the temperature of the materials utilized in the process are maintained at a temperature below 90.degree. C. throughout steps a through e of the process. 4. The process of claim 3 wherein said monomer is styrene. 5. The process of claim 4 wherein the polymerization catalyst is 2,2 Azobis-2-methylpropionitrile. 6. The process of claim 5 wherein a safety seal of solid polystyrene is formed on the surface of said pregnant hydrated cement. 7. The process of claim 6 wherein the leak-proof container is a 55 gallon drum having leak-proof plastic liner. |
description | 1. Field of the Invention The present invention relates to the area of medicine known as radiation oncology which uses radiation to treat cancer and, more specifically, to a method for mounting radiation treatment blocks on a radiation treatment block mounting tray, an adjustable radiation block mounting tray and a template and method for making a form for casting a radiation treatment block. 2. Description of Related Art and Other Considerations Radiation produced in a machine and directed towards cancer in humans and animals was found to be effective by the early 1900's. Original machines did not have apertures to control the size of the radiation beam, but later improvements in the form of blocking apertures were placed around the radiation beam to reduce the size of the emanating beam and to provide some protection to uninvolved body structures and anatomy of the patient. The ability to provide protection to uninvolved body structures is highly desirous and allows physicians to increase the radiation dose with the aim of obtaining enhanced results in the treatment of the cancer. To that end, radiation treatment blocks were developed. Radiation treatment blocks are blocks of metal placed in the path of the radiation beam to shape the radiation beam so that the beam is applied to the prescribed area of treatment for the patient. Historically, radiation blocks were produced in standard shapes without regard to the specific anatomy of a patient. This often required that multiple blocks be utilized to shape the radiation beam to the desired field. This is labor intensive as typically the blocks are heavy. Also, because the blocks were available only in preformed geometric shapes, it also made it difficult to precisely shape the radiation beam to the anatomy of each patient. More recent technology allows a radiation treatment block to be custom fabricated to precisely shape the radiation beam to a specific patient's anatomy. However, even with the development of custom fabricated radiation treatment blocks, problems with mounting and adjusting the blocks within the radiation beam have persisted. The present methods and apparatuses solve these problems. Custom blocking structures, or radiation treatment blocks, must be tailored to precisely fit patients and their anatomies. Therefore, for each patient, each block is cut or configured with an aperture which is precisely shaped to “fit” the specific patient's anatomy and is placed in the path of the radiation treatment beam to provide further protection to uninvolved anatomy, thereby allowing even higher doses of radiation to be delivered to the cancer. As higher and higher doses are administered to the patient, the exact position of these blocks in the beam is of paramount importance, because even small deviations of the block aperture and, thus, the beam configuration can lead to permanent, irreversible damage to uninvolved anatomy of the patient. There are several conventionally employed block positioning techniques and devices for shaping the radiation beam, but all have deficiencies as more fully discussed below, such as block misalignment and inaccurate positioning, the potential for radiation contamination of the treatment facility with toxic and carcinogenic heavy metals, and creating environmentally toxic waste. A. Misalignment/Inaccuracy Problems Currently, blocks are typically set on a clear plastic plate known as a block mounting tray or plate, which fits into the radiation treatment machine. The block is typically held in position by gravitational force when the tray is in its horizontal position with respect to the treatment machine. Typically, a radiation technologist, that is the person who administers the radiation to the patient on a day-to-day basis, places and aligns the block each day by hand. This is a tedious, time-consuming procedure, which often results in significant day-to-day variation in positioning the block, all of which are undesirable. Due to the constant handling of radiation treatment blocks by the technologist, there is a potential for the technologist to be exposed to the toxic heavy metals in the block. An article entitled “Potential Exposure to Metal Fumes, Particulates, and Organic Vapors During Radiotherapy Shielding Block Fabrication” appearing in the September/October 1986 edition of Medical Physics identified potential hazards to block handling personnel as including: (1) bruises to hands or feet from dropped blocks, (2) inhalation of metallic dust particles and fumes, (3) ingestion of metal alloy, (4) skin absorption of metal alloy, and (5) lifting hazards posed by placing very heavy blocks into position. When the tray is in a more vertical position and, therefore, not supported by the block mounting tray, the block will move or slide off of the tray unless the block is held onto the tray. Accordingly, various methods and devices have been used to mount the block to the tray. The most widely-used method involves the drilling of a hole in the bottom of the block and screwing it to the tray with a simple sheet metal screw. However, many technologists have difficulty in performing this task because it requires a certain degree of skill and careful positioning of the block on the tray, and the effective use of a drill and sheet metal screws. In addition, because the metals and alloys most commonly utilized to form the block are relatively soft, the screw threads in the block can easily be stripped, making it difficult to securely affix the block to the tray. The result is often that the block is poorly secured to the tray, and is loose and slightly misaligned with respect to the beam. Efforts to correct these problems create further difficulties. When a block is misaligned but fixed to the tray, some technologists often simply compensate for the misalignment by moving the patient, who is already laying or positioned on the treatment machine, with respect to the beam. However, such movement of the patient may create an aberration in the geometry calculated for the treatment and result in a significant change in the dose of radiation delivered to the patient. Furthermore, such compensation may not be communicated to another technologist who provides subsequent treatment. As a result, uninvolved structures or radiation sensitive body parts in the patient may be over-irradiated and permanently damaged. Other technologists, when confronted with a fixed, but misaligned block, usually elect to cancel treatment on that day and have the patient return for treatment on a subsequent day, after the tray has been dismantled and the block re-affixed to the tray. Such cancellation results in wasted time and effort for both the patient and the technologist, including lost treatment days for the patient. In addition, this subsequent effort to re-affix the block to the tray may also result in a misaligned block. Remounting the block also requires additional handling of the block, which increases the risk that the radiation technologist may be exposed to the toxic metals that are present in the block. Another method, in an effort to improve the alignment of the block with respect to the tray, involves the milling of slots through the tray. With this method, the sheet metal screw is loosened, the block is slid with respect to the tray, and the screw is then retightened. This procedure allows the block to be adjusted in one direction, with the goal of regaining the proper alignment. Unfortunately, because such milled slots allow an adjustment in only a single direction, their use does not allow the block to be adjusted in a direction perpendicular to that of the slots. Furthermore, the milling of intersecting perpendicular slots in a tray may weaken its structural integrity and, because the blocks are relatively heavy, they can cause the tray to sag, resulting in the misalignment of the block or even fracture, possibly causing injury to the patient or attending personnel. A less-commonly used system to affix a block to a tray involves the use of a double-sided, adhesive, foam tape. This system suffers from the alignment-of-the-tray-to-block problem described above, as well as from an inability to adjust the block once it is fixed to the tray. In addition, it is possible that a block, which can weigh as much as twenty-five pounds, could fall on a patient or a technologist, which renders this tape-fixing system a less-favored solution due to safety concerns. B. Contamination of the Radiation Treatment Facility In addition to the above-described problems, most blocks are formed from an alloy of toxic heavy metals, specifically lead and cadmium, both of which have known health risks. Cadmium is also known to be highly carcinogenic. The repeated handling of these blocks potentially exposes the technologists to these toxic and carcinogenic metals. Additionally, any drilling of them creates an even greater health risk in the form of fine toxic and carcinogenic dust which, without proper handling, can rapidly permeate the radiation treatment facility and, thus, create a hazardous environment for patients and personnel within the facility. A variation of the sheet-metal-screw method described above is directed to avoid the drilling of the block and, therefore, the contamination of the radiation treatment facility. In this variation, a sheet metal screw is sunk into the alloy while it is still molten to form a properly molded hole. Once the alloy has solidified, the sheet metal screw is removed and replaced by a shorter sheet metal screw for securing the block to the tray. Although this method avoids the generation of fine, toxic dust from drilling, it still suffers from the other disadvantages of the previously-described method, that is, the metal of the block being softer than the metal of the screw creates the chance that the threads produced in the block can become stripped, which can cause misalignment of the block or result in the block falling off the tray and injuring the patient or technologist. Correction of misalignment problems is difficult and time consuming. If the threads become stripped, a new block has to be cast and/or a new hole has to be drilled. If a new hole is drilled, toxic shavings and dust are created. C. Environmentally Toxic Waste Another known method to affix a block to a tray is by sinking a one or more threaded rod into the molten alloy while the alloy is in the block forming mold. After the alloy has cooled a nut can be screwed onto each threaded rod protruding through a hole or slot in the tray in order to affix the block to the tray. This technique again requires an alignment of the tray to the block and can result in possible misalignment inaccuracies due to a single attachment point when one rod is used which can allow the block to shift or rotate on the tray. If more than one rod is used it creates multiple attachment points which makes it difficult to adjust the position of the block on the tray. Furthermore, after the block is no longer needed, the block is melted, whereupon each threaded rod will float to the top of the molten alloy where they can be retrieved. Retrieved threaded rods, however, are usually coated with solidified hazardous alloy or metals and are therefore, unusable. As a result, the rods must be disposed of in accordance with environmental regulations. This creates additional hazardous materials that must be disposed of at licensed disposal facilities. Proper disposal of toxic materials is both costly and time consuming for the facility staff due to the documentation required by environmental regulations. In the past, improper disposal of toxic metals into the general waste system of the local municipality has resulted in toxic pollution to the environment. As an example, many species of trees and the white-tailed ptarmigan of the Rocky Mountains have thereby been exposed to cadmium toxicity as a result of improper disposal or containment of materials containing cadmium. D. Current Radiation Block Forming Techniques Currently, radiation treatment blocks are typically prepared by a technologist drawing the perimetric outline of a block around a prescribed treatment area that has been drawn on an x-ray film of a patient by an oncologist. The technologist first draws the outline of the appropriate size radiation treatment block and then traces that pattern on a foam block cutting machine to cut the outline of a radiation treatment block. This procedure is difficult because the technologist has to decide on the correct perimetric outline of a block and oftentimes has no specific guidelines for making the decision. As a result, the sides of a resultant block are oftentimes not square, not properly oriented and of insufficient thickness resulting in the radiation beam spilling over the outer edge of the block. This can result in radiation being applied to uninvolved structures and patient anatomy. The template of the present invention allows a technologist to overlay a template on the marked x-ray film or vice versa. The technologist then can readily observe the appropriate perimetric outline on the template and simply trace the outline using the stylus of the foam block cutting machine. A hot wire present in the machine cuts the perimetric outline of the foam block to correspond with the perimetric outline on the template. A designated beam shaping area can also be cut within the body of the block that will shape the radiation beam for the prescribed treatment. The use of the template saves the technologist time in the preparation of a form for casting a radiation treatment block. The template optionally also provides notches on the sides and corners of the perimetric outlines of the blocks. Tracing of the notches with the stylus of the foam block cutting machine when the perimetric outline of the block is being cut in the foam block will create notches in the block when it is cast. The notches in the block will accept the shaft of a clamping device of the present invention to assist in aligning and clamping a block to a mounting tray or plate. E. Description of the Art The patent literature includes a description of technology encompassing the above-described problems. U.S. Pat. No. 5,115,139 (“Cotter patent”) discloses a slotted bracket attached to the underside of a block, through which a connecting bolt passes to run in a slot milled into a tray. The device of the Cotter patent allows the block to be adjusted in a lateral direction and to rotate the block on the tray. However, the device disclosed in the Cotter patent is not applicable to most modern blocks now commonly used, which are specifically cast to match the anatomy of a unique patient undergoing treatment. Furthermore, the device involves only a single point-of-attachment for these heavy blocks that allows for possible unintended rotation or migration of the block on the tray under the influence of gravity. The device also requires that holes be drilled into or cast into the block. If holes are drilled, the Cotter device creates toxic metal dust and particulate matter. If the holes are drilled or cast, they are prone to stripping due to the softness of the metal that is most commonly used to form the blocks. U.S. Pat. No. 4,266,139 (“'139 patent”) describes a base plate that moves in parallel mounting rails. The device disclosed in the '139 patent allows a plate with a masking overlay to be mounted on a radiation machine. The device, however, does not allow precise multidirectional adjustment of the masking overlay. In addition, the device uses Velcro strips to attach thin metal shield plates thereto. Such a system is incompatible with most custom cast blocks in use today, which can be very heavy and would raise safety concerns if the block fell from the tray. U.S. Pat. No. 4,472,637 (“'637 patent”) discloses a base plate that can be mounted in slots on a radiation machine. The device allows only bi-directional movement of blocking shields. The '637 patent also discloses a shield with a single attachment point which can be prone to misalignment or rotational movement of the shield on the tray resulting in inaccurate and potentially injurious treatment of the patient. U.S. Pat. No. 5,056,128 (“'128 patent”) discloses a metal base plate and allows the magnetic mounting of radiation shielding devices. The apparatus would likely not work with the radiation treatment blocks currently in use because: (1) they are not magnetic, and (2) the size and weight of the blocks may make magnetic mounting unsafe. U.S. Pat. No. 4,700,451 (“'451 patent”) describes a method for indexing a block to a tray. The method, however, uses screws to attach the custom cast block to the tray. This method requires that holes be drilled into the block to secure the screws. This creates toxic dust and particulate matter which exposes technologists to toxic metal. This method also creates the potential for the screws to strip out of the holes resulting in possible misalignment of the block or could result in the block falling off the tray and injuring a patient or technologist. The method for mounting a radiation treatment block on a radiation treatment block mounting tray of the present invention comprises providing a radiation treatment block mounting plate, providing a radiation treatment block for mounting on the plate, providing a plurality of external clamping devices to secure the block to the plate, securing the external clamping devices to the plate, and securing the block to the plate by adjusting the external clamping devices. An adjustable radiation treatment block mounting tray of this invention is comprised of a substantially rigid frame body, a plate, and one or more releasable fastener to releasably secure the plate to the frame body when at least one releasable fastener is in a fastened position and to allow the plate to move relative to the frame body when each fastener is in a released position. More specifically, in one embodiment of the invention, orifices are drilled or otherwise formed into the plate. A releasable fastener, such as a thumbscrew, is positioned through each orifice for holding the plate to the frame body. The orifices allow the plate to move in any direction on the surface of the frame body, thereby allowing the desired adjustment of the radiation treatment block in any direction when the fasteners are in a released position. A method for adjusting a radiation treatment block in a radiation treatment beam of this invention comprises providing a radiation treatment block mounted on an adjustable radiation treatment block mounting tray with releasable fasteners to releasably secure the plate of the tray to the frame body of the tray. The tray is mounted in a radiation treatment machine. The block can be aligned within the radiation treatment beam by adjusting the releasable fasteners to a released position allowing the plate and the block to move relative to the frame body. The plate is moved until the block is correctly aligned within the radiation beam for treatment of the patient. The releasable fasteners can be adjusted to a fastened position compressibly securing the plate to the frame body, thereby securing the block within the radiation beam. A template of this invention for use with a foam block cutting machine for making a form to cast a radiation treatment block comprises a transparent sheet or plate having perimetric outlines of radiation treatment blocks of varying sizes marked or inscribed thereon. A method of this invention for making a foam form to cast a radiation treatment block comprises using a template with the perimetric outlines of varying sizes of radiation treatment blocks with a commercially-available foam block cutting machine to cut the perimetric outline of a radiation treatment block. Other objects and advantages, as well as a more complete understanding of the present invention, will appear from the following explanation of preferred embodiments and the accompanying drawings thereof. Specific apparatuses and methods within the scope of the present invention include, but are not limited to, the apparatuses and methods discussed in detail herein and/or illustrated in the drawings that are present herein. Contemplated equivalents of the apparatuses and methods described and illustrated herein and/or illustrated in the drawings contained herein include apparatuses and methods which otherwise correspond thereto, and which have the same general properties and/or components thereof, wherein one or more simple or other variations of components, materials or steps are made. All of the structures and components used in the apparatuses and methods of the current invention and to carry out the methods of the present invention, are commercially-available from sources known by those of ordinary skill in the art. The different components and structures that may be employed in the methods and apparatuses of the present invention may be generally arranged in the manner shown in the drawings, or described hereinbelow. However, the present invention is not limited to methods and apparatuses shown in the drawings and specifically described herein having the precise arrangements, configurations, dimensions and/or instrumentalities shown in these drawings, or described hereinbelow. These arrangements, configurations, dimensions and instrumentalities may be otherwise, as circumstances require. Different specific embodiments of that may be employed in the methods and apparatuses of the present invention will now be described with reference to the drawings. In a first aspect the present invention provides for a method for mounting at least one radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface; (b) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face, a lower face and at least one mounting hole or slot that extends at least partially through the radiation treatment block mounting plate from its upper surface, and wherein said mounting hole or slot is positioned to permit radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate; (c) providing at least one affixing means for compressibly affixing said radiation treatment block to said radiation treatment block mounting plate, wherein said affixing means has an upper portion and a lower portion; (d) placing the bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate; (e) attaching said upper portion of said affixing means to said radiation treatment block; (f) placing said lower portion of said affixing means through said mounting hole or slot present in said radiation treatment block mounting plate; (g) securing said lower portion of said affixing means to said radiation treatment block mounting plate; and (h) adjusting said affixing means to compressibly and releasably affix said radiation treatment block to said radiation treatment block mounting plate. In a second aspect the present invention provides for a method for mounting at least one radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face and at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving one or more external clamping means, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate; (b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface; (c) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate; (d) providing external clamping means for compressibly affixing each radiation treatment block to said upper face of said radiation treatment block mounting plate; (e) attaching said external clamping means to said radiation treatment block mounting plate; (f) positioning said external clamping means on each radiation treatment block; (g) adjusting said external clamping means to compressibly affix said radiation treatment block to said upper face of the radiation treatment block mounting plate. In a third aspect the present invention provides for a method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate; (b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface; (c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, at least one clamping device having an end portion sized and shaped to fit within a mounting hole or slot for securing said clamping device to said radiation treatment block mounting plate and an opposite end portion sized and shaped to engage said top surface of said radiation treatment block; (d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate; (e) positioning said end portion of said clamping device through a mounting hole or slot and securing said clamping device to said radiation treatment block mounting plate; (f) positioning said opposite end portion of said clamping device above and adjacent to said top surface of said radiation treatment block; and (g) adjusting said clamping device until at least part of said opposite end portion of said clamping device engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. In a fourth aspect the present invention provides for a method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate; (b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface; (c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, wherein at least one clamping device comprises a shaft and a threaded nut, said shaft having a threaded end portion and an opposite end portion sized and shaped to engage said top surface of said radiation treatment block; (d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate, (e) inserting said threaded end portion of said shaft through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to at least one side surface of said radiation treatment block; (f) attaching a threaded nut onto said threaded end portion of said shaft; (g) positioning said shaft until said opposite end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block; (h) adjusting said threaded nut on said threaded end portion of said shaft until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. In a fifth aspect the present invention provides for a method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate; (b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface, at least one side surface having at least one groove positioned therein, said groove extending from said top surface to said bottom surface and projecting from said side surface into said radiation treatment block, said groove being sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove; (c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, wherein at least one clamping device comprises a shaft and a threaded nut, said shaft having a threaded end portion and an opposite end portion sized and shaped to engage said top surface of said radiation treatment block; (d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate; (e) inserting said threaded end portion of said shaft through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to a groove in a side surface of said radiation treatment block; (f) attaching a threaded nut onto said threaded end portion of said shaft; (g) positioning said shaft of said clamping device until said shaft is positioned at least partially in said groove and said opposite end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block; (h) adjusting said threaded nut on said threaded end portion of said shaft until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. In a sixth aspect the present invention provides for a method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate; (b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least one side surface; (c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, at least one clamping device comprising a rod, a shaft, and a threaded nut, said rod having one end portion hingeably connected to said shaft and an opposite threaded end portion, said shaft having an end portion hingeably connected to said rod and an opposite end portion sized and shaped to engage said top surface of said radiation treatment block; (d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate, (e) inserting said threaded end portion of said rod of said clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to at least one side surface of said radiation treatment block; (f) attaching a threaded nut onto said threaded end portion of said rod; (g) pivoting said shaft of said clamping device until said opposite end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block; (h) adjusting said threaded nut on said threaded end portion of said rod until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. In a seventh aspect the present invention provides for a method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate; (b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface, and at least one side surface, at least one side surface having at least one groove positioned therein, said groove extending from said top surface to said bottom surface and projecting from said side surface into said radiation treatment block, said groove being sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove; (c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, at least one clamping device comprising a rod, a shaft, and a threaded nut, said rod having one end portion hingeably connected to said shaft and an opposite threaded end portion, said shaft having an end portion hingeably connected to said rod and an opposite end portion sized and shaped to engage said top surface of said radiation treatment block; (d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate; (e) inserting said threaded end portion of said rod of said clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to a groove in a side surface of said radiation treatment block; (f) attaching a threaded nut onto said threaded end portion of said rod; (g) pivoting said shaft of said clamping device until said shaft is positioned at least partially in a groove in a side surface of said radiation treatment block and said opposite end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block; (h) adjusting said nut on said threaded end portion of said rod until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. In an eighth aspect the present invention provides for a method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having a plurality of mounting holes or slots extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting holes or slots being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate; (b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface, and four side surfaces, each side surface having a groove positioned therein, said groove extending from said top surface to said bottom surface and projecting from said side surface into said radiation treatment block, said groove being sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove; (c) providing four clamping devices to externally affix said radiation treatment block to said radiation treatment block mounting plate, each clamping device comprising a rod, a shaft, and a threaded nut, said rod having one end portion hingeably connected to said shaft and an opposite threaded end portion, said shaft having an end portion hingeably connected to said rod and an opposite substantially hook shaped end portion; (d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate; (e) inserting said threaded end portion of each rod of each clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to a groove in a side surface of said radiation treatment block; (f) attaching a threaded nut onto said threaded end portion of each rod; (g) pivoting said shaft of each clamping device until said shaft is positioned at least partially in a groove in a side surface of said radiation treatment block and said substantially hook shaped end portion of each shaft is positioned above and adjacent to said top surface of said radiation treatment block; (h) adjusting said nut on said threaded end portion of each rod until at least part of each substantially hook shaped end portion of each shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. In a ninth aspect the present invention provides for a method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting hole or slot being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting plate; (b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least three side surfaces, the intersection of a side surface with another side surface forming a corner edge, said radiation treatment block having a groove positioned on at least one corner edge, said groove extending from said top surface to said bottom surface and projecting from said corner edge into said radiation treatment block, said groove sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove; (c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, said clamping device comprising a rod, a shaft, and a threaded nut, said rod having one end portion hingeably connected to said shaft and an opposite threaded end portion, said shaft having an end portion hingeably connected to said rod and an opposite end portion shaped and sized to engage said top surface of said radiation treatment block; (d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate; (e) inserting said threaded end portion of said rod of said clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot positioned proximate to a groove in a corner edge; (f) attaching a threaded nut onto said threaded end portion of said rod; (g) pivoting said shaft of said clamping device until said opposite end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block; and (h) adjusting said nut on said threaded end portion of said rod until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. In a tenth aspect the present invention provides for a method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate having a plurality of mounting holes or slots extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving a clamping device, said mounting holes or slots being positioned to allow radiation treatment blocks having different sizes to be affixed to said radiation treatment block mounting tray. (b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface and at least three side surfaces, the intersection of a side surface with another side surface forming a corner edge, said radiation treatment block having a groove positioned on at least one corner edge, said groove extending from said top surface to said bottom surface and projecting from said corner edge into said radiation treatment block, said groove sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove; (c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, said clamping device comprising a shaft and a threaded nut, said shaft having a threaded end portion and an opposite end portion sized and shaped to engage said top surface of the radiation treatment block; (d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate; (e) inserting said threaded end portion of said shaft of said clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot positioned proximate to a groove in a corner edge; (f) attaching a threaded nut onto said threaded end portion of said shaft; (g) positioning said shaft of said clamping device until said shaft is positioned at least partially in said groove and said opposite end portion of said shaft is positioned above and adjacent to said top surface of radiation treatment block; (h) adjusting said threaded nut on said threaded end portion of said shaft until at least part of said opposite end portion of said shaft engages said top surface of said radiation treatment block and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. In an eleventh aspect the present invention provides for a method for mounting a radiation treatment block on a radiation treatment block mounting plate comprising: (a) providing a radiation treatment block mounting plate, said radiation treatment block mounting plate having an upper face and a lower face, said radiation treatment block mounting plate further having at least one mounting hole or slot extending through said radiation treatment block mounting plate from said upper face to said lower face for receiving an external clamping device, said mounting hole or slot positioned to allow the mounting of radiation treatment blocks having different sizes to said radiation treatment block mounting plate; (b) providing at least one radiation treatment block, said radiation treatment block having a top surface, a bottom surface, and at least one side surface, at least one side surface having at least one groove positioned therein, said groove extending from said top surface to said bottom surface and projecting from said side surface into said radiation treatment block, said groove being sized and shaped to allow a shaft of a clamping device to fit at least partially within said groove; (c) providing at least one clamping device to externally affix said radiation treatment block to said radiation treatment block mounting plate, at least one clamping device comprising a rod, a shaft, and a threaded nut, said rod having one end portion hingeably connected to said shaft and an opposite threaded end portion, said shaft having an end portion hingeably connected to said rod and an opposite oversized end portion, at least one dimension of said oversized end portion being greater than a dimension of said groove; (d) positioning said bottom surface of said radiation treatment block on said upper face of said radiation treatment block mounting plate; (e) inserting said threaded end portion of said rod of said clamping device through a mounting hole or slot in said radiation treatment block mounting plate, said mounting hole or slot being positioned proximate to a groove in a side surface of said radiation treatment block; (f) attaching a threaded nut onto said threaded end portion of said rod; (g) pivoting said shaft of said clamping device until said shaft is positioned at least partially in a groove in a side surface of said radiation treatment block and said oversized end portion of said shaft is positioned above and adjacent to said top surface of said radiation treatment block; (h) adjusting said nut on said threaded end portion of said rod until said oversized end portion of said shaft engages said top surface of said radiation treatment block or one or more face of said groove and compressibly affixes said radiation treatment block to said upper face of said radiation treatment block mounting plate. In a twelfth aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening; (b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one radiation treatment block mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate; (c) means to releasably secure said plate to said frame body, said means allowing said plate to move relative to said frame body when in a released position and when in a fastened position said means compressibly secures said plate to said frame body. In a thirteenth aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, and at least one bore for receiving a releasable fastener therein; (b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate, and at least one orifice extending through said plate from said upper face to said lower face, with at least one orifice being positioned over at least one bore in said frame body; (c) at least one releasable fastener to releasably secure said plate to said frame body, said releasable fastener having a head portion at one end and a shank portion at an opposite end, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, wherein a diameter of said orifice is larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said head portion being larger than a diameter of said orifice such that when said releasable fastener is in a fastened position said head portion compressibly secures said plate to said frame body. In a fourteenth aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, a generally central opening and least one bore for receiving a releasable fastener therein; (b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate and at least one orifice extending through said plate from said upper face to said lower face, with at least one orifice being positioned over at least one bore in said frame body; (c) at least one releasable fastener to releasably secure said plate to said frame body, said releasable fastener having a head portion at one end, a shank portion at an opposite end and a washer positioned on said shank portion adjoining said head portion, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said washer being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position said releasable fastener and washer compressibly secure said plate to said frame body. In a fifteenth aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, opposing side frame body members, a generally central opening, and a plurality of bores for receiving a releasable fastener therein; (b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate, and four orifices extending through said plate from said upper face to said lower face, each orifice positioned over a bore in said frame body; (c) four releasable fasteners to releasably secure said plate to said frame body, each releasable fastener having a head portion at one end, a shank portion at an opposite end and a washer positioned on said shank portion adjoining said head portion, each shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said washer being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position, said releasable fasteners and washers compressibly secure said plate to said frame body. In a sixteenth aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, and at least one bore for receiving a releasable fastener therein; (b) a plate having an upper face and a lower face, said bottom face of said frame body being positioned on said upper face of said plate, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate, and at least one orifice extending through said plate from said upper face to said lower face, with at least one orifice being positioned over at least one bore in said frame body; (c) at least one releasable fastener to releasably secure said plate to said frame body, said releasable fastener having a head portion at one end and a shank portion at an opposite end, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, wherein a diameter of said orifice is larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said head portion being larger than a diameter of said orifice such that when said releasable fastener is in a fastened position said head portion compressibly secures said plate to said frame body. In a seventeenth aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, a generally central opening and least one bore for receiving a releasable fastener therein; (b) a plate having an upper face and a lower face, said bottom face of said frame body being positioned on said upper face of said plate, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate and at least one orifice extending through said plate from said upper face to said lower face, with at least one orifice being positioned over at least one bore in said frame body; (c) at least one releasable fastener to releasably secure said plate to said frame body, said releasable fastener having a head portion at one end, a shank portion at an opposite end and a washer positioned on said shank portion adjoining said head portion, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said washer being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position said releasable fastener and washer compressibly secure said plate to said frame body. In an eighteenth aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a plate having an upper face and a lower face, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having a plurality of bores for receiving a releasable fastener therein; (b) a substantially rigid frame body having a top face and a bottom face, said bottom face of said frame body being positioned on said upper face of said plate, said frame body having an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having at least one orifice extending through said frame body from said top face to said bottom face, at least one orifice being positioned over at least one bore in said plate; (c) at least one releasable fastener to releasably secure said frame body to said plate, said fastener having a head portion at one end and a shank portion at an opposite end, said shank portion of each releasable fastener being positioned through an orifice in said frame body and inserted into a bore in said plate, a diameter of said orifice being larger than a diameter of said shank portion to allow said frame body to move relative to said plate when said releasable fastener is in a released position, a diameter of said head portion being larger than a diameter of said orifice such that when said releasable fastener is in a fastened position said head portion compressibly secures said frame body to said plate. In a nineteenth aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a plate having an upper face and a lower face, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having a plurality of bores for receiving a releasable fastener therein; (b) a substantially rigid frame body having a top face and a bottom face, said bottom face of said frame body being positioned on said upper face of said plate, said frame body having an upper frame body member, a lower frame body member, opposing side frame body members, said frame body having a generally central opening, said frame body further having at least one orifice extending through said frame body from said top face to said bottom face, at least one orifice being positioned such that said orifice is aligned over at least one bore in said plate; (c) at least one releasable fastener to releasably secure said frame body to said plate, said releasable fastener having a head portion at one end, a shank portion at an opposite end and a washer positioned on said shank portion adjoining said head portion, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said washer being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position said releasable fastener and washer compressibly secure said frame body to said plate. In a twentieth aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having a plurality of threaded bores for receiving a threaded rod therein; (b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having at least one orifice extending through said plate from said upper face to said lower face, at least one orifice being positioned over at least one threaded bore in said frame body; (c) at least one rod having opposing end portions, both of said end portions of said rod being threaded, one end portion of said rod being inserted into a threaded bore in said frame body, an opposite exposed end portion of said rod being positioned through an orifice in said plate, a diameter of said rod being less than a diameter of said orifice in said plate, a threaded nut being attached to said exposed end portion of said rod, a diameter of said nut being greater than a diameter of said orifice such that when said nut is in a fastened position said nut compressibly secures said plate to said frame body and when said nut is in a released position allowing said plate to move relative to said frame body. In a twenty-first aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having a plurality of threaded bores for receiving a threaded rod therein; (b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having at least one orifice extending through said plate from said upper face to said lower face, at least one orifice being positioned over at least one threaded bore in said frame body; (c) at least one rod having opposing end portions, both of said end portions of said rod being threaded, one end portion of said rod being inserted into a threaded bore in said frame body, an opposite exposed end portion of said rod being positioned through an orifice in said plate, a diameter of said rod being less than a diameter of an orifice in said plate, a washer being positioned over said exposed end portion of said rod and positioned on said upper face of said plate, a diameter of said washer being greater than a diameter of said orifice, a nut being attached to said exposed end portion of said rod, such that when said nut is in a fastened position said nut and washer compressibly secure said plate to said frame body and when said nut is in a released position allowing said plate to move relative to said frame body. In a twenty-second aspect the present invention provides for an adjustable radiation treatment block mounting tray comprising: (a) a substantially rigid frame body, said frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having at least one tray adjustment slot extending through said frame body from said top face to said bottom face; (b) a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having at least one tray adjustment slot extending through said plate from said upper face to said lower face, at least one tray adjustment slot in said plate being generally perpendicular to a tray adjustment slot in said frame body and being positioned to overlap a tray adjustment slot in said frame body; (c) at least one releasable fastener to releasably secure said plate to said frame body, said releasable fastener having a head portion at one end, a shank portion at an opposite end, said shank portion of each releasable fastener positioned through both a tray adjustment slot in said plate and a tray adjustment slot in said frame body wherein when said releasable fastener is in a fastened position said releasable fastener compressibly secures said plate to said frame body and when said releasable fastener is in a released position said releasable fastener allows said plate to move relative to said frame body. In a twenty-third aspect the present invention provides for a method for adjusting a radiation treatment block in a radiation beam comprising: (a) providing a radiation treatment block mounted on a plate of an adjustable radiation treatment block mounting tray, said adjustable radiation treatment block mounting tray being installed on a radiation treatment machine, said adjustable treatment block mounting tray comprising: a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening; a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate; means to releasably secure said plate to said frame body, said means allowing said plate to move relative to said frame body when said means is in a released position and when said means is in a fastened position said means compressibly securing said plate to said frame body; (b) adjusting said means to a released position so that said plate and said radiation treatment block affixed thereto can move relative to said frame body; (c) aligning said radiation treatment block within said radiation beam by moving said plate until said radiation treatment block is correctly aligned within said radiation beam for a prescribed treatment of a patient; (d) adjusting said means to a fastened position compressibly securing said plate to said frame body and securing said radiation treatment block within said radiation beam. In a twenty-fourth aspect the present invention provides for a method for adjusting a radiation treatment block in a radiation beam comprising: (a) providing a radiation treatment block mounted on a plate of an adjustable radiation treatment block mounting tray, said adjustable radiation treatment block mounting tray being installed on a radiation treatment machine, said adjustable radiation treatment block mounting tray comprising: a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having at least one bore for receiving a releasable fastener therein; a plate having an upper face and a lower face, said lower face of said plate being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face of said plate, said plate further having at least one orifice extending through said plate from said upper face to said lower face, at least one orifice being positioned over at least one bore in said frame body; at least one releasable fastener to releasably secure said plate to said frame body, at least one releasable fastener having a head portion at one end, a shank portion at an opposite end, said shank portion of said each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said head portion being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position said head portion compressibly secures said plate to said frame body; (b) adjusting each releasable fastener to a released position so that said plate and said radiation treatment block affixed thereto can move relative to said frame body; (c) aligning said radiation treatment block within said radiation beam by moving said plate until said radiation treatment block is correctly aligned within said radiation beam for a prescribed treatment of a patient; (d) adjusting at least one releasable fastener until said releasable fastener is in a fastened position compressibly securing said plate to said frame body and securing said radiation treatment block within said radiation beam. In a twenty-fifth aspect the present invention provides for a method for adjusting a radiation treatment block in a radiation treatment beam comprising: (a) providing a radiation treatment block mounted on a plate of an adjustable radiation treatment block mounting tray, said adjustable radiation treatment block mounting tray being installed on a radiation treatment machine, said adjustable radiation treatment block mounting tray comprising: a substantially rigid frame body having a top face and a bottom face, an upper frame body member, a lower frame body member, and opposing side frame body members, said frame body having a generally central opening, said frame body further having at least one bore for receiving a releasable fastener therein; a plate having an upper face and a lower face, said lower face being positioned on said top face of said frame body, said plate having at least one mounting hole or slot extending through said plate from said upper face to said lower face for use in mounting a radiation treatment block to said upper face, said plate further having at least one orifice extending through said plate from said upper face to said lower face, at least one orifice being positioned over at least one bore in said frame body; at least one releasable fastener to releasably secure said plate to said frame body, at least one releasable fastener having a head portion at one end, a shank portion at an opposite end and a washer positioned on said shank portion adjoining said head portion, said shank portion of each releasable fastener being positioned through an orifice in said plate and inserted into a bore in said frame body, a diameter of said orifice being larger than a diameter of said shank portion to allow said plate to move relative to said frame body when said releasable fastener is in a released position, a diameter of said washer being greater than a diameter of said orifice such that when said releasable fastener is in a fastened position said releasable fastener and washer compressibly secure said plate to said frame body; (b) adjusting each releasable fastener to a released position so that said plate and radiation treatment block can move relative to said frame body; (c) aligning said radiation treatment block within said radiation beam by moving said plate until said radiation treatment block is correctly aligned within said radiation beam for a prescribed treatment of a patient; (d) adjusting at least one releasable fastener until said fastener is in a fastened position compressibly securing said plate to said frame body and securing said radiation treatment block within said radiation beam. In a twenty-sixth aspect the present invention provides for a template for use with a commercially available foam block cutting machine for making a form to cast a radiation treatment block, comprising a sheet, said sheet having marked or inscribed thereon at least one perimetric outline of a radiation treatment block. In a twenty-seventh aspect the present invention provides for a template for use with a commercially-available foam block cutting machine for making a form to cast a radiation treatment block, said template comprising a transparent sheet, said sheet having marked or inscribed thereon perimetric outlines of radiation treatment blocks having different sizes, each perimetric outline of a radiation treatment block present on said template having four sides, being rectangular in shape, and having four corners, each of said sides having a rectangular notch positioned thereon, each perimetric outline of a radiation treatment block present on said template having a rectangular notch present on each corner of said perimetric outline, said template further having a horizontal and a vertical line that intersect at a center of said perimetric outlines of said template, said template further having a radiation treatment block alignment line marked or scribed thereon, said radiation treatment block alignment line being positioned such that it intersects with one side of each perimetric outline of a radiation treatment block present on said template, said side having a protrusion thereon extending from said side at the intersection of said side with the radiation treatment block alignment line. In a twenty-eighth aspect the present invention provides for a method for making a foam form to cast a radiation treatment block comprising: (e) providing a commercially-available foam block cutting machine for making a form to cast a radiation treatment block, said foam block cutting machine having a light table, a hot wire frame, said hot wire frame having an upper hot wire frame member and a lower hot wire frame member, and a hot wire for cutting a foam block, said hot wire being positioned between said upper and lower hot wire frame members, said foam block cutting machine further having a stylus connected to said hot wire frame for tracing a perimetric outline of a radiation treatment block, and a tray for holding a foam block; (f) positioning a template for use with a foam block cutting machine for making a form to cast a radiation treatment block on said light table, said template comprising a transparent sheet, said sheet having marked or inscribed thereon a perimetric outline of at least one radiation treatment block; (g) placing a foam block for casting a radiation treatment block on said tray; (h) tracing a perimetric outline of a radiation treatment block present on said template with said stylus causing said hot wire to cut said foam block in a same perimetric dimension as said perimetric outline of said radiation treatment block on said template. In a twenty-ninth aspect the present invention provides for a ruler for use with a template for use with a commercially available foam block cutting machine for making a form to cast a radiation treatment block, said ruler having an elongated rectangular shape, said ruler having four sides, two of said sides being elongated, at least one elongated side having a tab protruding from an elongated side. In a thirtieth aspect the present invention provides for a ruler for use with a template for use with a commercially available foam block cutting machine for making a form to cast a radiation treatment block, said ruler having four sides, two of said sides being elongated, at least one elongated side having a notch present therein. FIGS. 1 and 2 generally show a radiation treatment block affixed to an adjustable radiation block mounting tray, however, specific elements present in the adjustable radiation block mounting trays and radiation treatment blocks may best be observed by reference to FIGS. 1–14 in total. FIG. 1 shows an adjustable radiation block mounting tray 1 (“tray”) with a radiation treatment block 25 (“block”) affixed to a plate 12. The plate 12 is releasably secured to a frame body 2 by at least one releasable fastener 13. In the embodiment shown, the releasable fasteners 13 are knurled head screws. It is recognized by those skilled in the art that other releasable fasteners, including but not limited to thumb screws, knob screws, adjustable diameter pins, cam clamps, bolts, and screws are equally suitable. The plate 12 has an upper face 14 and a lower face 101 (shown in FIG. 6). The block 25 is affixed to an upper face 14 of the plate 12 by a plurality of external clamping devices 40 inserted through block mounting holes 15 in the plate 12. It is recognized by those skilled in the art that external clamping devices 40 other than the embodiments shown in the drawings are suitable, including but not limited to clamps, pivot clamps, hook clamps, toggle clamps, swing clamps and nylon ties. The adjustable radiation block mounting tray 1 can be inserted into guide channels 100 present on a radiation machine 150. With the adjustable radiation block mounting tray 1 positioned in the guide channels 100, the position of the block 25 within a radiation beam 90 can be aligned by adjusting the releasable fasteners 13 to a released position until the plate 12 can move relative to the frame body 2. This allows the block 25 to be easily and precisely aligned so that the radiation beam 90 is correctly and accurately applied to a patient 200. The releasable fasteners 13 can then be adjusted to a fastened position thereby securing the radiation block 25 in the correct alignment. FIG. 2 shows an adjustable radiation treatment block mounting tray 1 having a radiation treatment block 25 mounted on an upper face 14 of the plate 12. The block 25 is compressibly secured to the upper face 14 of the plate 12 of the adjustable radiation block mounting tray 1 using a plurality of external clamping devices 40. The threaded end portion 44 of the rod 41 that is present on the external clamping device 40 can be inserted through a block mounting hole 15 or slot 16 positioned proximate a groove 29 (shown in FIG. 7) in a side surface 28 of the block 25, and a threaded nut 43 can be attached to the threaded end portion 44 of the rod 41 (see FIGS. 7, 8 and 11). An opposite hingeable connection end portion 45 of the rod 41 is hingeably connected to the hingeable connection end portion 46 of the shaft 42 present on the clamping device 40 (see FIGS. 7, 8). The shaft 42 is pivoted until an opposite substantially hook shaped end portion 47 present on the shaft 42 is positioned above a top surface 26 of the radiation treatment block 25 and the shaft 42 is at least partially in the groove 29 (FIGS. 7 & 8). The threaded nut 43 present on the threaded end 44 portion of the rod 41 of the clamping device 40 can be adjusted so that at least part of the substantially hook shaped end portion 47 of the shaft 42 engages the top surface 26 of the block 25 to compressibly secure the block 25 to the upper face 14 of the plate 12 (shown in FIGS. 7 & 8). The lower face 101 (shown in FIG. 6) of the plate 12 is positioned on a top face 102 (shown in FIG. 6) of the substantially rigid frame body 2. The frame body 2 has one or more bores 6 (see FIG. 10) to receive a releasable fastener 13 therein. A releasable fastener 13 is positioned through at least one orifice 17 present in the plate 12 and inserted into a bore 6. The releasable fastener 13 can be adjusted to a fastened position until the plate 12 is compressibly secured to the frame body 2. The releasable fastener 13 can be adjusted to a released position to allow the plate 12 to be moved relative to the frame body 2. This allows a radiation technologist to adjust and align the position of a radiation treatment block 25 for use in a radiation beam 90 by moving the plate 12 relative to the frame body 2. Once the correct alignment of the block 25 is achieved within the radiation beam 90, the releasable fasteners 13 can be adjusted to a fastened position to compressibly secure the plate 12 to the frame body 2 and fix the block 25 in a correct position. The bores 6 can either be threaded or non-threaded, but are preferably threaded. In the embodiment shown in FIG. 2 a side frame body member 5 has a slotted orifice 8 that forms a handle portion 9 in a side frame body member 5. A handle fitting 38 can optionally be affixed to the handle portion 9. In the embodiment shown in FIG. 2, a compressible washer 49 is positioned on the threaded end portion 44 of the rod 41 and is positioned at least partially between the upper face 14 of the plate 12 and the bottom surface 27 of the block 25. In the embodiment shown, the adjustable radiation block mounting tray 1 has one or more spring mounting fitting 20 affixed to both a top face 102 of an upper frame body member 3 and to the upper face 14 of the plate 12. The plate 12 has notches 19 that extend from an outer edge 18 of the plate 12 into the plate 12. The notches 19 are positioned to align over a spring attachment fitting 20 affixed to a top face 102 of an upper frame body member 3. A spring mounting fitting 20 affixed to a top face 102 of an upper frame body member 3 is connected to a spring attachment fitting 20 affixed to the upper face 14 of the plate 12 by a spring 21. The spring 21 absorbs some of the weight of the block 25 when the adjustable radiation treatment block mounting tray 1 is installed in a radiation treatment machine 150 (shown in FIG. 1) and the releasable fasteners 13 are in a released position. This allows a radiation technologist to more easily move the plate 12 relative to the frame body 2 and align the position of the block 25. It is recognized by those skilled in the art that various types of springs 21 are suitable, for this purpose, including but not limited to coiled springs and elastomeric bands or strips. Although the embodiment in FIG. 2 shows that the lower face 101 of the plate 12 is positioned on a top face 102 of a substantially rigid frame body 2, other embodiments of the invention are also suitable. In an alternative embodiment, the bottom face 103 (bottom face shown in FIG. 6) of the frame body 2 can be positioned on the upper face 14 of the plate 12. In another alternative embodiment of an adjustable radiation treatment block mounting tray 1, not shown in a drawing, the adjustable radiation treatment block mounting tray 1 comprises a plate 12 that has an upper face 14 and a lower face 101. The plate has a plurality of bores 6 present therein receiving a releasable fastener 13. The plate 12 further has at least one mounting hole 15 or slot 16 extending through the plate 12 from the upper face 14 to the lower face 101. The adjustable radiation treatment block mounting tray 1 further comprises a substantially rigid frame body 2 having a top face 102 and a bottom face 103. The frame body 2 has at least one orifice 17 extending through the frame body 2. The bottom face 103 of the frame body 2 can be positioned on the upper face 14 of the plate 12 such that at least one orifice 17 in the frame body 2 is positioned over at least one bore 6 in the plate 12. The adjustable radiation treatment block mounting tray 1 further comprises at least one releasable fastener 13 to releasably secure the frame body 2 to the plate. A shank portion 75 of a releasable fastener 13 is positioned through an orifice 17 in the frame body 2 and is inserted in a bore 6 in the plate 12. A diameter of the orifice 17 is larger than a diameter of the shank portion 75 so the plate 12 can move relative to the frame body 2 when the releasable fasteners 13 are in a released position to allow a radiation block 25 affixed to the upper face 14 of the plate 12 to be adjusted in a radiation beam 90. The head portion 76 of the releasable fastener 13 has a diameter larger than a diameter of the orifice 17 such that when a releasable fastener 13 is in a fastened position the head portion 76 compressibly secures the frame body 2 to the plate 12. A releasable fastener 13 can alternatively be provided that has a head portion 76 with a diameter less than a diameter of the orifice 17. In that case a rigid washer 65 with a hole present therein, and that has a diameter greater than an orifice 17 can be positioned on the shank portion 75 adjoining the head portion 76 of the releasable fastener 13. When the releasable fastener 13 is in a fastened position the rigid washer 65 engages the top face 102 of the frame body 2 and the rigid washer 65 and the releasable fastener 13 compressibly secure the frame body 2 to the plate 12. Although FIG. 2 shows a radiation treatment block 25 affixed to a plate 12 of an adjustable radiation treatment block mounting tray 1 it is recognized that the methods for mounting radiation treatment blocks on a radiation treatment block mounting plate of this invention can also be used to affix a radiation treatment block 25 on a commercially available radiation treatment block mounting plate or tray. FIG. 3 shows a range of movement of the plate 12 relative to the frame body 2. A shank portion 75 of a releasable fastener 13 is positioned through a rigid washer 65 and an orifice 17 present in the plate 12 and is inserted into a bore 6 in the frame body 2. In the embodiment shown a shank portion 75 of a releasable fastener 13 and the bore 6 are threaded. However, it is recognized by those skilled in the art, that depending on the releasable fastener 13 selected, a shank portion 75 and a bore 6 do not have to be threaded. The rigid washer 65 is positioned between the upper face 14 of the plate 12 and a head portion 76 of the releasable fastener 13. When the releasable fastener 13 is in a released position, the plate 12 can move relative to the frame body 2 within a range determined by the dimensions of the orifice 17, which can be varied in a manner known by those of skill in the art. In the embodiment shown, a plurality of measuring gauges 23 are marked or scribed on the frame body 2. The measuring gauges 23 allow a technologist to observably measure the amount of movement that occurs between the plate 12 and the frame body 2 when the position of a block 25 is being adjusted. FIG. 4 shows an alternative embodiment of the adjustable radiation block mounting tray 1. The plate 12 preferably has at least one tray adjustment slot 70 that is positioned to overlap a tray adjustment slot 70 present in the frame body 2. The tray adjustment slot 70 present in the plate 12 is generally perpendicular to the tray adjustment slot 70 present in the frame body 2. A shank portion 75 present in a releasable fastener 13 is positioned through the tray adjustment slots 70 present in the plate 12 and the frame body 2. In the embodiment, shown the releasable fastener 13 is a knob screw and the shank portion 75 is threaded. A threaded nut 71 can be affixed to the shank portion 75 of the releasable fastener 13. In the embodiment shown, the threaded nut 71 is a T-nut, however, it is recognized by those skilled in the art that other types of nuts are equally suitable for this purpose, including but not limited to a wing nut, a lock nut, a finger nut, a knurled nut, a handle nut or a push nut. It is also recognized that other types of releasable fasteners 13 are suitable, including but not limited to a thumb screw, a knurled head screw, a bolt, a screw and an adjustable diameter pin. The head portion 76 present in the releasable fastener 13 can be adjusted to a fastened position to compressibly secure the plate 12 to the frame body 2. In an alternative embodiment a rigid washer 65 can be positioned between the head portion 76 of the releasable fastener 13 and the upper face 14 of the plate 12. FIG. 5 shows a cam clamp 80 as an alternative embodiment of a releasable fastener 13 to releasably secure the plate 12 to the frame body 2. In the embodiment shown, the shank portion 82 of the cam clamp 80 is positioned through a rigid washer 65 having a diameter larger than the orifice 17 that is present in the plate 12 and is inserted into a bore 6 (shown in FIG. 10) present in the frame body 2. In the embodiment shown the shank portion 82 of the cam clamp 80 is threaded and the bore 6 is threaded. The rigid washer 65 is positioned between the cam clamp handle 83 and the upper face 14 of the plate 12. The cam clamp handle 83 is shown in the fastened position. In the fastened position, the cam clamp 80 compressibly secures the rigid washer 65 to the upper face 14 of the plate 12, and the plate 12 to the frame body 2. In the released position, the cam clamp 80 allows the plate 12 to move relative to the frame body 2 so that a radiation treatment block 25 can be properly aligned in the radiation beam 90 (see FIG. 1). It is recognized that a cam clamp 80 can also be used without a rigid washer 65. FIG. 6 shows a releasable fastener 13 as a means to releasably secure the plate 12 to the frame body 2. A lower face 101 of the plate 12 is positioned on a top face 102 of the frame body 2. A shank portion 75 present in the releasable fastener 13 is inserted through a rigid washer 65 having a diameter larger than an orifice 17 that is present in the plate 12. The rigid washer 65 is positioned between an upper face 14 of the plate 12 and a head portion 76 of a releasable fastener 13. The shank portion 75 of the releasable fastener 13 is positioned through an orifice 17 present in the plate 12 and is inserted into a threaded bore 6 present in the frame body 2. The releasable fastener 13 can be adjusted until the head portion 76 of the releasable fastener 13 engages the rigid washer 65 and compressibly secures the plate 12 to the frame body 2. In the embodiment shown, the releasable fastener 13 is a knurled head screw which is used to releasably secure the plate 12 to frame body 2, however, it is recognized by those skilled in the art that other types of releasable fasteners 13 can be used. It is recognized that a diameter of the head portion 76 of the releasable fastener 13 can be larger than a diameter of an orifice 17 in which case a rigid washer 65 can, optionally, be omitted. FIG. 7 shows an external clamping device 40 positioned proximate to a groove 29 present in a side surface 28 of a radiation treatment block 25. In the embodiment shown, the external clamping device 40 is comprised of a rod 41, a shaft 42, and a threaded nut 43. The rod 41 has a threaded end portion 44 and an opposite hingeable connection end portion 45. The shaft 42 has a hingeable connection end portion 46 and an opposite substantially hook shaped end portion 47. The hingeable connection end portion 45 of the rod 41 is hingeably connected to the hingeable connection end portion 46 of the shaft 42. The threaded end portion 44 of the rod 41 is inserted through a mounting hole 15 or slot 16 present in the plate 12 positioned proximate to a side surface 28 of the block 25. The threaded nut 43 is attached to the threaded end portion 44 of the rod 41. The shaft 42 is sized and shaped so that it fits at least partially into a groove 29 present in a side surface 28 of a radiation treatment block 25. The groove 29 extends from the top surface 26 to the bottom surface 27 of the radiation treatment block 25 and projects from a side surface 28 into the radiation treatment block 25. In one embodiment, the threaded nut 43 is a wing nut, however, it is recognized by those of skill in the art that other types of nuts including but not limited to a lock nut, a finger nut, a knurled nut, a handle nut and a push nut can be utilized. In one embodiment, the threaded end portion 44 of the rod 41 is inserted through a compressible washer 49 and the compressible washer 49 is positioned at least partially between the bottom surface 27 of the radiation treatment block 25 and the upper face 14 of the plate 12. It is recognized that the compressible washer 49 does not need to be positioned on the threaded end portion 44 of the rod 41. It is also recognized that one or more compressible washer 49 can be placed between the bottom surface 27 of the radiation treatment block 25 and the upper face 14 of the plate 12. In the preferred embodiment, the compressible washer 49 is made from an elastomeric material such as rubber; however other materials, such as plastic, wood, leather are equally suitable as known by those skilled in the art. It is also recognized by those skilled in the art that alternatively, one or more pieces of compressible material can be positioned between the bottom surface 27 of the radiation treatment block 25 and the upper face 14 of the plate 12. In the embodiment shown, the shaft 42 is rectangular in shape. However, it is recognized the other shapes are equally suitable, including but not limited to a round or triangular shaft. The groove 29 in the embodiment shown is rectangular in shape, however it is recognized that other shapes of grooves are equally suitable including but not limited to U-shaped or V-shaped grooves. It is recognized that in other embodiments of the clamping device 40 of the present invention, the end portion of the shaft 42 opposite the hingeable connection end portion 46 of the shaft 42 does not have to be substantially hook shaped but can be sized and shaped to engage the top surface 26 of the radiation treatment block 25. It is also recognized that in an alternative embodiment of the clamping device 40 of the present invention, the end portion of the shaft 42 opposite the hingeable connection end portion 46 of the shaft 42 can be oversized such that one or more dimension of the opposite end portion of this shaft 42 is greater than one or more dimension of a groove 29 present in a side surface 28 of a radiation treatment block 25. The opposite oversized end portion of the shaft 42 can be positioned over and adjacent to the top surface 26 of the radiation treatment block 25. The threaded nut 43 can be adjusted until the opposite oversized end portion of the shaft 42 engages the top surface 26 of the radiation treatment block 25 or one or more face of the groove 29 and compressibly secures the radiation treatment block 25 to the upper face 14 of the plate 12. FIG. 8 shows the external clamping device 40 (shown in FIG. 7) after the shaft 42 has been pivoted so that the substantially hook shaped end portion 47 of the shaft 42 is positioned above and adjacent to the top surface 26 of the block 25 and at least part of the shaft 42 is present within the groove 29 in a side surface 28 of the block 25. The threaded nut 43 can be adjusted until at least part of the substantially hook shaped end portion 47 of the shaft 42 engages the top surface 26 of the block 25 and compressibly secures the block 25 to the upper face 14 of the plate 12. FIG. 8 further shows an alternative embodiment of a radiation treatment block 25. In the embodiment shown, the radiation treatment block 25 further comprises a ridge 31 protruding from a side surface 28 of a radiation treatment block 25. The ridge 31 extends from the top surface 26 to the bottom surface 27 of a radiation treatment block 25. The ridge 31 can be positioned on a side surface 28 of a radiation treatment block 25 so that it is aligned over a radiation treatment block alignment line 32 that is marked or scribed on an upper face 14 of a plate 12 of an adjustable radiation treatment block mounting tray 1. The ridge 31 and the radiation treatment block alignment line 32 can assist a radiation technologist to correctly position and orient a radiation treatment block 25 on the plate 12. FIG. 9 shows an alternative embodiment of a clamping device 40 and a radiation treatment block 25. The rod 41 has a threaded end portion 44 and at its opposite end a hingeable connection end portion 45. The shaft 42 has a hingeable connection end portion 46 and at its opposite end a substantially hook shaped end portion 47. The hingeable connection end portion 45 of the rod 41 and the hingeable connection end portion 46 of the shaft 42 are hingeably connected. The radiation treatment block 25 has a groove 29 located at at least one corner edge 30, said corner edge 30 formed by the intersection of two side surfaces 28. The groove 29 extends from the top surface 26 to the bottom surface 27 of the radiation treatment block 25 and projects from the corner edge 30 inward into the radiation treatment block 25. In the embodiment shown, the threaded end portion 44 of the rod 41 can be inserted through a compressible washer 49 and the compressible washer 49 is positioned at least partially between the bottom surface 27 of the radiation treatment block 25 and the upper face 14 of the plate 12. In the embodiment shown, the threaded end portion 44 of the rod 41 is inserted in a mounting hole 15 or slot 16 positioned proximate to a groove 29 in a corner edge 30 of radiation treatment block 25. A threaded nut 43 is attached to the threaded end portion 44 of the rod 41. The shaft 42 is pivoted until the substantially hook shaped end portion 47 of the shaft 42 is positioned above and adjacent to the top surface 26 of the radiation treatment block 25 and at least part of the shaft 42 is positioned within the groove 29 in the radiation treatment block 25. The threaded nut 43 can be adjusted until at least part of the substantially hook shaped end portion 47 of the shaft 42 engages the top surface 26 of the radiation treatment block 25 and compressibly secures the radiation treatment block 25 to the upper face 14 of the plate 12. The clamping device 40 shown in FIG. 9 can also be used to affix a radiation treatment block 25 without a groove 29 to the upper face 14 of the plate 12. The threaded end portion 44 of the rod 41 can be inserted in a mounting hole 15 or slot 16 positioned proximate to at least one side surface 28 of a radiation treatment bock 25. A threaded nut 43 can be attached to the threaded end portion 44 of the rod 41. The shaft 42 can be pivoted until the substantially hook shaped end portion 47 is positioned above and adjacent to the top surface 26 of the radiation treatment block 25. The threaded nut 43 can then be adjusted on the threaded end portion 44 until at least part of the substantially hook shaped end portion 47 engages the top surface 26 of the radiation treatment block 25 and compressibly secures the radiation treatment block 25 to the upper face 14 of the plate 12. FIG. 10 shows the substantially rigid frame body 2. The frame body 2 has an upper frame body member 3, a lower body frame member 4, and opposing side frame body members 5. The frame body 2 has a generally central opening 7. In the embodiment shown, at least one side frame body member 5 has a slotted orifice 8 that forms a handle portion 9 in a side frame body member 5. It is recognized that the frame body 2 can be fabricated without a slotted orifice 8 and a handle portion 9. In the embodiment shown, a plurality of holes 10 are provided in the handle portion 9 to mount handle fitting 38 (shown in FIGS. 1 and 2). The frame body 2 also has a plurality of bores 6 for receiving a releasable fastener therein for compressibly securing the plate 12 to the frame body 2. A plurality of rail mounting bores 11 are also provided in the upper and lower frame body members 3, 4. In one embodiment, the rail mounting bores 11 can be used to affix a spring attachment fitting 20 (shown in FIG. 2) to the upper frame body member 3. In the embodiment shown, a plurality of measuring gauges 23 are marked or scribed on the frame body 2. The gauges 23 allow a radiation technologist to observably measure the amount of movement between the plate 12 and the frame body 2 when the position of a block 25 is being adjusted. It is also recognized that optionally one or more measuring gauge 23 can be marked or scribed on the plate 12. In the embodiment shown, the frame body 2 is fabricated from metal, however, it is recognized by those skilled in the art that other materials, for example, plastic, fiberglass, wood, carbon fiber, graphite or composites are also suitable. FIG. 11 shows a plate 12 of an adjustable radiation block mounting tray 1. The plate 12 has a plurality of mounting holes 15 and slots 16 for receiving clamping means to affix a radiation treatment block 25 to said plate 12, said mounting holes and slots extending through said plate from said upper face 14 to said lower face 101 the holes and slots can be positioned to allow radiation treatment block 25 having different sizes to be affixed to the plate 12. In the embodiment shown, the plate 12 has both mounting holes 15 and slots 16, however the plate can also be fabricated with one or more mounting hole 15 or one or more mounting slot 16. Although it is preferable that the mounting holes 15 or slots 16 extend through the plate 12, in an alternative embodiment the mounting holes 15 or slots 16 can extend only partially through the plate 12 from the upper face 14 depending on the means selected to affix a radiation treatment block 25 to a radiation treatment block mounting plate 12. The plate 12 also has a plurality of orifices 17 extending through the plate 12 from the upper face 14 to the lower face 101 (shown in FIG. 6), said orifices 17 are positioned so that at least one orifice 17 is aligned over a bore 6 in the frame body 2 for receiving a releasable fastener 13 when the lower face 101 of plate 12 is positioned on the top face 102 of the frame body 2. In the embodiment shown, the plate 12 has a plurality of notches 19 extending from an outer edge 18 of the plate 12 into the plate 12. In the embodiment shown, the notches 19 are semi-circular, however, notches of other shapes, such as rectangular and triangular are also suitable. The notches 19 in the plate 12 are sized and positioned so that when the lower face 101 of the plate 12 is positioned on the top face 102 of the frame body 2 the notches 19 can be aligned over spring attachment fittings 20 affixed to the upper frame body member 3 and allow the plate 12 to move relative to the frame body 2 when the releasable fasteners 13 are in a released position. In the embodiment shown, the plate 12 is made from polycarbonate, however, other material such as acrylic, plastics, composites and perforated metal are also suitable. FIG. 11 also shows an optional radiation treatment block alignment line 32 scribed or marked on an upper face 14 of the plate 12. The radiation treatment block alignment line 32 is positioned such that a ridge 31 positioned on a side surface 28 of radiation treatment blocks 25 having different sizes will be positioned over the radiation treatment block alignment line 32 when the radiation treatment blocks 25 are affixed on the upper face 14 of the plate 12. FIG. 12 shows an alternative embodiment of a clamping device 40. The embodiment of the clamping device 40 shown is comprised of a rod 41, a shaft 42 and a threaded nut 43. The rod 41 has a threaded end portion 44 and at its opposite end, a hingeable connection end portion 45. The shaft 42 has a hingeable connection end portion 46 and at its opposite end, a substantially lever shaped end portion 50. The substantially lever shaped end portion 50 and the shaft 42 forming an angle α, which is between about 60 and about 120 degrees, and is preferably about 90 degrees. The hingeable connection end portion 45 of the rod 41 hingeably connects to the hingeable connection end portion 46 of the shaft 42. The threaded end portion 44 of the rod 41 can be inserted in a mounting hole 15 or slot 16 (shown in FIG. 11) present in the plate 12 that is located proximate to a groove 29 that is present in a side surface 28 of the radiation treatment block 25. A threaded nut 43 can be positioned on the threaded end portion 44 of the rod 41. The shaft 42 can be pivoted until the substantially lever shaped end portion 50 is positioned above the top surface 26 of the block 25 and the shaft 42 is at least partially within the groove 29. The threaded nut 43 can be adjusted on the threaded end portion 44 of the rod 41 so that at least part of the substantially lever shaped end portion 50 engages the top surface 26 of the radiation treatment block 25 and compressibly secures the radiation treatment block 25 to the upper face 14 of the plate 12. In the embodiment shown, at least one side surface 28 of a radiation treatment block 25 has groove 29 present therein, however, it is recognized that the clamping device 40 shown in FIG. 12 can be used to affix a radiation treatment block 25 without a groove 29 present therein, to an upper face 14 of a plate 12. The threaded end portion 44 of the rod 41 can be inserted in a mounting hole 15 or a slot 16 positioned proximate at least one side surface 28 of a radiation treatment block 25. A threaded nut 43 can be attached to the threaded end portion 44 of the rod 41. The shaft 42 can be pivoted until the substantially lever shaped end portion 50 is positioned above and adjacent to the top surface 26 of the radiation treatment block 25. The threaded nut 43 can be adjusted on the threaded end portion 44 until at least part of the substantially lever shaped end portion 50 engages the top surface 26 of the radiation treatment block 25 and compressibly secures the radiation treatment block 25 to the upper face 14 of the plate 12. In the embodiment shown, a compressible washer 49 is positioned on the rod 41 and is located at least partially between the upper face 14 and the bottom surface 27 of the radiation treatment block 25. FIG. 13 shows an alternative embodiment of a clamping device 40. The embodiment of the clamping device 40 shown is comprised of a flexible shaft 55 and a threaded nut 43. The flexible shaft 55 has a threaded end portion 56 and at an opposite end, an end portion sized and shaped to engage the top surface 26 of the radiation treatment block 25. In the embodiment shown in FIG. 13 the opposite end portion of the flexible shaft 55 is a substantially hook shaped end portion 57. The threaded end portion 56 can be inserted in a mounting hole 15 or slot 16 (shown in FIG. 11) in the plate 12 that is located proximate to a groove 29 present in a side surface 28 of a block 25. A threaded nut 43 can be positioned on the threaded end portion 56 of the flexible shaft 55. The flexible shaft 55 can be flexed so that the substantially hook shaped end portion 57 of the flexible shaft 55 is positioned above the top surface 26 of the block 25 and the flexible shaft 55 is at least partially within a groove 29. The threaded nut 43 can be adjusted on the threaded end portion 56 of the flexible shaft 55 so that the substantially hook shaped end portion 57 of the flexible shaft 55 engages the top surface 26 and compressibly secures the block 25 to the upper face 14 of the plate 12. In the embodiment shown in FIG. 13 at least one side surface 28 of a radiation treatment block 25 has a groove 29 present therein. It is recognized that the clamping device 40 shown in FIG. 13 can be used to affix a radiation treatment block 25 without a groove 29 positioned therein, to an upper face 14 of a plate 12. The threaded end portion 56 of the flexible shaft 55 can be inserted in a mounting hole 15 or slot 16 positioned proximate to at least one side surface 28 of a radiation treatment block 25. A threaded nut 43 can be positioned on the threaded end portion 56 of the flexible shaft 55. The flexible shaft 55 can be flexed until the substantially hook shaped end portion 57 of the flexible shaft 55 is positioned above and adjacent to the top surface 26 of the radiation treatment block 25. The threaded nut 43 can be adjusted on the threaded end portion 56 until at least part of the substantially hook shaped end portion 57 of the flexible shaft 55 engages the top surface 26 of the radiation treatment block 25 and compressibly secures the radiation treatment block 25 to the upper face 14 of the plate 12. It is also recognized that the flexible shaft 55 of the clamping device 40 can optionally be provided with a substantially lever shaped end portion 50 instead of a substantially hook shaped end portion 57. The substantially lever shaped end portion 50 and the flexible shaft 55 forming an angle α. The angle α being between about 60 degrees and about 120 degrees and is preferably about 90 degrees. In the embodiment shown, a compressible washer 49 is positioned on the flexible shaft 55 and is located at least partially between the upper face 14 of the plate 12 and the bottom surface 27 of the radiation treatment block 25. FIG. 14 shows an alternative embodiment of a clamping device 40. The embodiment of the clamping device 40 shown in FIG. 14 is comprised of a bent shaft 58 and a threaded nut 43. The bent shaft 58 has a threaded end portion 59 and an opposite end portion sized and shaped to engage the top surface 26 of the radiation treatment block 25. In the embodiment shown in FIG. 14 the opposite end portion is a substantially hook shaped end portion 60. The threaded end portion 59 can be inserted into a mounting hole 15 or slot 16 (shown in FIG. 11) in the plate 12 that is located proximate to a groove 29 present in a side surface 28 of a radiation treatment block 25. A threaded nut 43 can be positioned on the threaded end portion 59. The bent shaft 58 can be manipulated so that the substantially hook shaped end portion 60 of the bent shaft 58 is positioned above the top surface 26 of the radiation treatment block 25 and the bent shaft 58 is positioned at least partially within a groove 29. The threaded nut 43 can be adjusted on the threaded end portion 59 so that the substantially hook shaped end portion 60 of the bent shaft 59 engages the top surface 26 of the radiation treatment block 25 and compressibly secures the radiation treatment block 25 to the upper face 14 of the plate 12. In an alternative embodiment, the clamping device 40 shown in FIG. 14 can be used to affix a radiation treatment blocks 25 without a groove 29 positioned therein to an upper face 14 of a plate 12. The threaded end portion 59 of the bent shaft 58 can be inserted in a mounting hole 15 or slot 16 positioned proximate at least one side surface 28 of a radiation treatment block 25. A threaded nut 43 can be positioned on the threaded end portion 59 of the bent shaft 58. The bent shaft 58 can be manipulated until the substantially hook shaped end portion 60 of the bent shaft 58 is positioned above and adjacent to the top surface 26 of the radiation treatment block 25. The threaded nut 43 can be adjusted until at least part of the substantially hook shaped end portion 60 of the bent shaft 58 engages the top surface 26 of the radiation treatment block 25 and compressibly secures the radiation treatment block 25 to the upper face 14 of the plate 12. It is also recognized that the bent shaft 58 of clamping device 40 can be fabricated with a substantially lever shaped end portion 50 instead of a substantially hook shaped end portion 60. The substantially lever shaped end portion 50 and the bent shaft 58 forming an angle α. The angle α being between about 60 degrees and about 120 degrees and is preferably about 90 degrees. In the embodiment shown, a compressible washer 49 is positioned on the bent shaft 58 and is positioned at least partially between the upper face 14 of the plate 12 and the bottom surface 27 of the radiation treatment block 25. FIG. 15 shows an alternative embodiment of a releasable fastener 13. The releasable fastener 13 is comprised of a rod 75, a rigid washer 65 and a threaded nut 76. Both end portions of the rod 75 are threaded, one end portion is positioned through an orifice 17 present in the plate 12 and is inserted into a threaded bore 6 (shown in FIG. 10) present in the frame body 2. The rigid washer 65 has a diameter greater than the orifice 17 and can be positioned over the exposed threaded end portion of the rod 75 such that the exposed threaded end portion of the rod 75 projects through a hole in the rigid washer 65. The rigid washer 65 rests on the upper face 14 of the plate 12. The threaded nut 76 can be adjusted on the exposed threaded end portion of the rod 75 until the threaded nut 76 engages the rigid washer 65 and compressibly secures the plate 12 to the frame body 2. FIG. 16 shows the frame body 2 having a rail 95 mounted on a lower frame body member 4 to adapt a dimension of a frame body 2 of an adjustable radiation treatment block mounting tray 1 to fit a radiation machine 150 and demonstrates how a rail 95 can be mounted on an upper frame body member 3. Rails 95 can be mounted to the upper and lower frame body members 3, 4 by positioning a fastener 52, such as a screw, through a hole 53 present in the rail 95 and inserting an end of the fastener 52 into a rail mounting bore 11. The fastener 52 is then adjusted to secure the rail 95 to the upper and lower frame body members 3, 4. It is recognized by those skilled in the art that, depending on the radiation machine 150 being utilized, no rail 95 may be required, a different size rail 95 may be required, or an additional rail 95 may be necessary. A rail 95 can also be affixed to the upper frame body member 3 or, optionally, to both the upper and lower frame body members 3, 4. A rail 95 can be fabricated from metal or other rigid material including but not limited to wood, plastic, fiberglass, carbon fiber or composite. A rail 95 can be marked or colored to correlate said rail 95 to a particular manufacturer or model number of a radiation machine 150. FIG. 17 shows a template 310 for use with a foam block cutting machine for making a form to cast a radiation treatment block 25. In the embodiment shown, the template 310 is made from a transparent sheet 311. In the embodiment shown, the template 310 is made from a sheet 311 of plastic, however, it is recognized that other materials such as polymers, acrylics and glass would also be suitable. Although it is preferable that the sheet 311 be transparent a non-transparent or translucent sheet can also be suitable. The transparent sheet 311 has marked or scribed thereon perimetric outlines 312 of radiation treatment blocks 25 having different sizes. This allows a radiation technologist or oncologist to select the perimetric outline 312 to correspond with the required size of a radiation treatment block 25 to be fabricated. The template 310 can be provided with a horizontal line 314 and a vertical line 315 that intersect at the center of a perimetric outline 312 present on a template 310. The horizontal and vertical lines 314 and 315 can be utilized to align the template 310 with corresponding horizontal and vertical lines 316, 317 that can be present on a light table 301 of the foam block cutting machine 300 (each shown in FIG. 18). In the embodiment shown, each side of a perimetric outline 312 has a notch 313 positioned therein. In the embodiment shown, each corner of a plurality of perimetric outlines 312 have a notch 313 positioned therein. In the embodiment shown, the notch 313 is rectangular, however, it is recognized that the notch can also be U-shaped or V-shaped. It is recognized that the perimetric outlines 312 of radiation treatment blocks 25 present on the template 310 can be provided without notches 313 positioned therein. The template 310 can optionally have a radiation treatment block alignment line 32 scribed or marked thereon. At an intersection of the radiation treatment block alignment line 32 with a side of a perimetric outline 312 of a radiation treatment block 25, a ridge 325 is marked or scribed on the template 310. The ridge 325 protrudes from a side of a perimetric outline 312 of a radiation treatment block 25. When a radiation technologist traces over a ridge 325 present on a perimetric outline 312 of a radiation treatment block 25, a ridge 325 will be formed in foam block 307 form that can be used to cast a radiation treatment block 25. When the radiation treatment block 25 is cast in the foam block 307 form a ridge 31 will protrude from a side surface 28 of the radiation treatment block 25. FIG. 18 shows a commercially-available foam block cutting machine 300 for cutting a foam form for casting a radiation treatment block 25. A template 310 for tracing a perimetric outline 312 of a radiation treatment block 25 can be placed on a light table 301 of a foam block cutting machine 300. A radiation technologist can trace a selected perimetric outline 312 of a radiation treatment block 25 on the template 310 with a stylus 302 present on the foam block cutting machine 300. The stylus 302 is connected to a hot wire frame 303 that has a hot wire 304 positioned between an upper hot wire frame member 305 and a lower hot wire frame member 306. A foam block 307 is positioned in a foam block mounting tray 308. As a radiation technologist traces a perimetric outline 312 of a radiation treatment block 25 on the template 310 the hot wire 304 cuts the foam block 307 to the same perimetric outline 312 of the radiation treatment block 25 on the template 310. If required by the prescribed treatment, the technologist can also cut the foam block 307 to create an opening in the foam block 307 that will create a beam shaping opening in the radiation treatment block 25 when a radiation treatment block 25 is cast in the foam block 307 form. FIG. 19 shows two embodiments of a ruler 400 and 401. One embodiment of a ruler 400 has a notch 402 present therein. An alternative embodiment of a rule 401 has a tab 403 present thereon. The rulers 400 and 401 can be used by a technologist to guide a stylus 302 of a foam block cutting machine 300 while tracing a perimetric outline 312 of a radiation treatment block 25 on the template 310. The notch 402 and the tab 403 facilitate the tracing of one or more notches 313 present on a template 310. It is also recognized that a ruler 400 or 401 can have both a notch 402 and a tab 403 present therein. The methods and apparatuses of the present invention allow radiation blocks of varying sizes to be quickly and accurately prepared using a template in conjunction with a commercially-available foam block cutting machine to cut the perimetric outline of a form for casting a radiation treatment block. A block can be mounted to a block mounting tray according to methods of this invention for the duration of the patient's treatment. Once a block is mounted, it does not have to be repeatedly handled by the technologist. If adjustments of a block in the radiation beam are required, the adjustable radiation block mounting tray of the present invention allows such adjustments to be made without further handling of the block. Upon completion of the treatment of a patient, the radiation block can be melted and used to cast another block. This eliminates the creation of hazardous materials and waste. |
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claims | 1. A core of a boiling water reactor comprising:multiple fuel assemblies arranged in a square lattice shape in the core,wherein an arrangement of fuel assemblies adjacent to a fuel assembly having a shortest loading period among the multiple fuel assemblies arranged in the core is arranged in the core so as to satisfy a relationship X=Ta/Tb, where X is a parameter representing a core residence period of the arrangement of fuel assemblies that is 0.8 or more and 1.0 or less, where,Ta: T in a case where fuel exchange is performed,Tb: T in a case where fuel exchange is not performed,T: an average value oft of a fuel assembly arranged in an inside-core region of the core having the shortest loading period,t: (ΣTs+0.5×ΣTx)/(4+0.5×4),Ts: a number of residence cycles, in the core, of fuel assemblies laterally and longitudinally adjacent to the fuel assembly having the shortest loading period in core cross section, andTx: a number of residence cycles, in the core, of fuel assemblies diagonally adjacent to fuel assembly having the shortest loading period in core cross section. 2. The core of a boiling water reactor according to claim 1,wherein the parameter X is 0.8 or more and 0.9 or less. 3. The core of the boiling water reactor according to claim 1,wherein the core is configured by the inside-core region and an outside-core region. 4. The core of the boiling water reactor according to claim 1,wherein, in the core cross section, an inside of a circle having a radius of 70% of a radius of a circumscribed circle circumscribing the fuel assemblies arranged in an outermost periphery of the core is the inside-core region. 5. The core of the boiling water reactor according to claim 2,wherein, in the core cross section, an inside of a circle having a radius of 70% of a radius of a circumscribed circle circumscribing the fuel assemblies arranged in an outermost periphery of the core is the inside-core region. 6. The core of the boiling water reactor according to claim 3,wherein, in the core cross section, an inside of a circle having a radius of 70% of a radius of a circumscribed circle circumscribing the fuel assemblies arranged in an outermost periphery of the core is the inside-core region. |
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abstract | An assembly part for constituting a unit in a vacuum column is provided with wirings and wiring terminals. Each wiring is provided on a first insulating film, and is covered with a second insulating film made of an electro-deposited polyimide film. The assembly part is used to constitute a semiconductor manufacturing system such as an electron beam exposure system. |
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description | A description is made of a first embodiment in which the present invention is applied to replacement of a reactor vessel in a pressurized water reactor plant (hereinafter abbreviated to a xe2x80x9cPWR plantxe2x80x9d). In this embodiment, after removing a polar crane within a reactor containment vessel (simply called a containment vessel), a reactor vessel (hereinafter abbreviated to xe2x80x9cRVxe2x80x9d) and core internals are carried out together and replaced with a new set of reactor vessel and core internals. FIG. 2 is a schematic vertical sectional view of a reactor shielding building in the PWR plant to which the present invention is applied. As shown in FIG. 2, a reactor shielding building 1 is of a reinforced concrete structure, and a steel-made containment vessel (hereinafter abbreviated to xe2x80x9cCVxe2x80x9d) 3 is installed inside the reactor shielding building 1. Walls and floors of a reinforced concrete structure or a steel-framed concrete structure are provided in a lower portion of the CV 3 to define a reactor cavity 5, and the RV 2 is installed at the center of a bottom portion of the reactor cavity 5. An operation floor 7, on which various kinds of works in the CV 3 are performed, is formed in an upper portion of the reactor cavity 5. An equipment carrying-in opening 4 is provided on the upper side of the operation floor 7 so that various types of equipment may be carried out to the exterior of the reactor shielding building 1 through the opening 4. A steam generator (hereinafter abbreviated to xe2x80x9cSGxe2x80x9d) 8 is arranged in a space surrounded by a shied wall 6. An annular rail 10 is installed just below a dome-shaped ceiling of the CV 3, and a polar crane 9 is mounted on the annular rail 10. The polar crane 9 is an overhead traveling crane comprising a girder 9a and a trolley 9b, and it is used to move large-weight components in the CV 3. FIG. 3 is a perspective view, partly broken away, of the RV 2 shown in FIG. 2. As shown in FIG. 3, an upper lid 2a is fixed to a body of the RV 2 through a flange 2b using bolts 2c. The RV 2 has a height of about 10 m and a diameter of about 4 m. Core internals 50, described later, are installed inside the RV 2. A core tank 12 is arranged at the center of the RV 2, and a fuel assembly 13 is arranged inside the core tank 12. The core tank 12 is a cylindrical core internal arranged in the RV 2 so as to surround a rector core. An upper core support plate 17 is detachably provided at an upper end of the core tank 12 and is attached to an upper core plate 16 by a plurality of upper core support posts 19. The upper core plate 16, the upper core support plate 17, a control rod cluster 18, and the upper core support posts 19 constitute upper core internals 20. A lower core support plate 14 and a lower core plate 15 are provided in a lower portion of the core tank 12. The core tank 12, the lower core support plate 14, and the lower core plate 15 constitute lower core internals 21. The core internals 50 comprise the upper core internals 20 and the lower core internals 21. The core internals 20 and 21 can be separately taken out to the exterior of the RV 2. An inlet nozzle 22 and an outlet nozzle 23 both provided in the RV 2 are connected via pipes to the SG 8 installed in the CV 3. FIG. 1A and FIG. 1B are flowchart showing a method for replacing the RV according to the first embodiment. First, work for making the reactor open is performed in step S1. In the reactor opening work, the upper lid 2a of the RV 2 is removed. FIG. 4 is a schematic vertical sectional view of the RV 2 and surroundings thereof during the reactor opening work. Numeral 18a denotes a control rod driving mechanism. Then, in step S2, the upper core internals 20 are removed. This work is performed in a state in which a core water level is raised to fully fill the reactor cavity 5 with water. FIG. 5 is a schematic vertical sectional view of the RV 2 and surroundings thereof during the work for removing the upper core internals 20. The upper core plate 16, the upper core support plate 17, the control rod cluster 18, and the upper core support posts 19, which constitute the upper core internals 20, are removed together. Then, in step S3, all fuel is taken out and moved to a fuel pool. This work is performed while the core water level is kept raised to fully fill the reactor cavity 5 with water. FIG. 6 is a schematic vertical sectional view of the RV 2 and surroundings thereof during the work for taking out a fuel assembly 13 with a fuel replacing apparatus 13a. Then, in step S4, the upper core internals 20 are returned into the RV 2 and mounted in place. When the upper core internals 20 are not replaced, this step can be omitted. Then, in step S5, the interior of the RV 2 is decontaminated to eliminate radioactive materials deposited on an inner wall of the RV 2 and the core internals 50. Chemical decontamination using chemicals is one example of decontaminating methods. Performing the decontamination makes it possible to simplify a shield that is used when carrying out the RV 2 to the exterior of the reactor shielding building 1. When the decontamination is not performed, this step can be omitted. Then, in step S6, pipes 24 and 25 connected to the inlet nozzle 22 and the outlet nozzle 23 respectively are cut off. On that occasion, for reducing an exposure rate of workers engaged in the pipe cutting work, water sealing plugs 22a and 23a are attached to the inlet nozzle 22 and the outlet nozzle 23 respectively from the inside of the reactor while the reactor cavity 5 is kept fully filled with water. Subsequently, the reactor water level is lowered to a position of the flange 2b in the upper portion of the RV 2. Thereafter, for shutting off radiations from the inner side of the reactor, a shield lid 26 having a radiation shielding capability is attached to the flange 2b by bolts 26a. Then, after securing a space for the pipe cutting work, structural members, such as sealing materials, located above the nozzles and thermal insulating materials located around the nozzles are removed. With removal of those materials, the RV 2 is prevented from interfering with the nozzles when it is carried out. FIG. 7 is a schematic vertical sectional view of the RV 2 and surroundings thereof, showing a state after cutting off the pipes 24 and 25 connected respectively to the inlet nozzle 22 and the outlet nozzle 23. To prevent radioactive materials in the reactor from flowing out to the exterior of the RV 2, closure plates 22b and 23b are attached to the respective nozzles after the pipe cutting work from the outer side of the RV 2. Then, in step S7, a radiation shielding material, such as mortar, is filled in the reactor. The shielding material is filled through a hose or the like inserted in a hole, which is formed in the shield lid 26 beforehand. Filling the shielding material into a reactor bottom portion makes it possible to omit a bottom plate of a radiation shield 28, described later, for the RV 2. After filling the shielding material, the hole formed in the shield lid 26 is plugged. When the radiation dose from the reactor bottom portion is not more than a transport standard value, this step may be omitted. Then, in step S8, cables 37 connected to the bottom portion of the RV 2 for in-core instrumentation are removed. In step S9, a heavy-duty crane 30 for carrying out (in) the RV 2 is set up outside the reactor shielding building 1. Then, in step S10, a temporary opening 31, through which the RV 2 can be carried out (in), is formed in the ceiling (top wall) of the reactor shielding building 1 and the containment vessel 3. A shutter 32 capable of opening and closing is provided above the temporary opening 31 for protection against rain. FIG. 8 is a schematic vertical sectional view of the reactor shielding building 1 after setting up the heavy-duty crane 30 and forming the temporary opening 31. Then, in step S11, the polar crane 9 is removed and, in step S12, the radiation shield 28 is carried in. When carrying in the radiation shield 28, reinforcing members 27 are first placed at the bottom of the reactor cavity 5 so as to surround the RV 2. The reinforcing members 27 serve to distribute the weight of the radiation shield 28 over the bottom of the reactor cavity 5. Subsequently, the shutter 32 is opened, and the radiation shield 28 is carried into the CV 3 through the temporary opening 31 and temporarily placed on the reinforcing members 27 by using the heavy-duty crane 30. To that end, the temporary opening 31 is set to a size allowing the radiation shield 28 to be carried in (out) through it. The radiation shield 28 has a cylindrical shape and is provided at its upper end with a shield upper lid 28a in the form of a disk. The radiation shield 28 serves to shut off radiations from the RV 2. FIG. 9 is a schematic vertical sectional view of the RV 2 and surroundings thereof, showing a state in which the radiation shield 28 is temporarily placed in the reactor cavity 5 and a sling 30a is attached to the shield lid 26. Then, in step S13, the RV 2 is lifted up and united with the radiation shield 28. The strongback (sling) 30a as a jig for lifting up the RV2 is attached to the shield lid 26 using eight to ten pieces of bolts 26a. The sling 30a is suspended by the heavy-duty crane 30. The shield upper lid 28a has a slit-like opening through which the sling 30a is able to pass, and has hooks 28b provided on its upper side for hanging the radiation shield 28. By raising the sling 30a with the heavy-duty crane 30, the RV 2 is lifted up. The RV 2 is combined with the radiation shield 28 just by lifting up the RV 2 such that the shield lid 26 is brought into abutment with the shield upper lid 28a. Subsequently, the opening of the shield upper lid 28a is covered with a protective sheet 28c, and ends of the protective sheet 28c are fixedly attached in a sealed-off manner using a sealing tape. Likewise, a lower end of the radiation shield 28 is covered with a protective sheet 28d whose ends are also fixedly attached in a sealed-off manner using a sealing tape. Each of the protective sheets 28c and 28d can be formed of, e.g., a polyvinyl chloride sheet. FIG. 10 is a schematic vertical sectional view of the RV 2 and surroundings thereof, showing a state in which the RV 2 is lifted up and united with the radiation shield 28. Thus, the radiation shield 28 can be easily combined with the RV 2 in a surrounding relation in a short time just by lifting up the core internals 50 together (in union) with the RV 2. Also, since the openings of the radiation shield 28 are sealed off with the protective sheets 28c and 28d, radioactive dust deposited on the surface of the RV 2 can be prevented from scattering to the exterior. Next, in the state of the radiation shield 28 being combined with the RV 2, the surfaces of the shield and the protective sheets are decontaminated. The fact that the surface dose rate has been lowered to such a level as not affecting an external environment of the containment vessel is confirmed by a contamination test. FIG. 11 is a schematic vertical sectional view of the CV 3, showing a state immediately before lifting up a large-size block 51, which includes the radiation shield 28 and the RV 2 united into one, by the heavy-duty crane 30 and carrying out the large-size block 51 through the temporary opening 31. As shown in FIG. 11, the radiation shield 28 covers the whole of the RV 2 from the top to the bottom thereof. Since the bottom portion of the RV 2 generates a lower radiation dose than a core portion located above the bottom portion of the RV 2 and is filled with the radiation shielding material, it is not required to attach a radiation shield to the bottom portion of the RV 2 in most cases. When it is required to attach such a shield to the bottom portion of the RV 2, the shield is attached to the reactor bottom portion in step S13. A method for attaching the shield is now described with reference to FIGS. 12A and 12B. FIG. 12A shows a state before attaching a bottom shield 29, and FIG. 12B shows a state after attaching the bottom shield 29. As shown in FIG. 12A, the large-size block 51 is lifted up by the heavy-duty crane 30 to a level above the operation floor 7, rails 29a are set at the top of the reactor cavity 5, and a flatcar 29b including the bottom shield 29 laid thereon is rested on the rails 29a. Then, as shown in FIG. 12B, the flatcar 29b including the bottom shield 29 laid thereon is moved to a position right below the large-size block 51, and the large-size block 51 is descended to a height at which it contacts the bottom shield 29. Thereafter, the large-size block 51 and the bottom shield 29 are joined to each other by, e.g., bolts. In such a way, when carrying the RV 2 out of the reactor shielding building 1, the surface dose rate of the radiation shield 28 can be reduced to a level lower than a reference value (limit value). Then, in step S14, the RV 2 is carried out. More specifically, the RV 2 is lifted up as the large-size block 51 in union with the radiation shield 28 and the core internals 50. The large-size block 51 is carried out to the exterior through the temporary opening 31 of t he re actor shielding building 1. After carrying out the large-size block 51 to the exterior of the reactor shielding building 1, the shutter 32 is closed. FIG. 13 is a view showing a state in which the large-size block 51 is carried out by the heavy-duty crane 30 through the temporary opening 31 of the reactor shielding building 1. Then, in step S15, the large-size block 51 carried out of the reactor shielding building 1 is carried into a storage container 40. On that occasion, a fore end 30b of the heavy-duty crane 30 is moved from a position right above the temporary opening 31 of the reactor shielding building 1 to a position right above the storage container 40 while keeping the large-size block 51 hanged by the heavy-duty crane 30. Thereafter, the large-size block 51 is descended and carried into the storage container 40. FIG. 14 is a view showing a state immediately before carrying the large-size block 51 into the storage container 40 in step S15. The storage container 40 is provided under the ground near the reactor shielding building 1, and has a structure capable of containing the large-size block 51 in an upright posture. Thus, the large-size block 51 can be carried into the storage container 40 by using g the heavy-duty crane 30 while the large-size block 51 is kept in the same state as that just after being carried out of the reactor shielding building 1. After carrying the large-size block 51 into the storage container 40, a lid is attached to the storage container 40 for bringing it into a sealed-off condition. As an alternative, in step S15, the large-size block may be loaded on a trailer, transported to the storage container, and then carried into it. This method is effective when the storage container is remote from the reactor shielding building. Also, the storage container may be provided in a building of a ridge continuation with the reactor shielding building. The storage container may be provided on the ground to be able to contain the large-size block in a horizontally laid state. A method for loading the large-size block on a trailer (flatcar) in a horizontally laid state is now described. The large-size block 51 hanged by the heavy-duty crane 30 is moved to a tilting-down apparatus provided on a trailer 34, which is stopped near the reactor shielding building 1. Then, the large-size block 51 is horizontally laid by the tilting-down apparatus to be loaded on the trailer 34. FIG. 15A is a view showing a state in which the large-size block 51 is tilted down to be laid on the trailer 34, and FIG. 15B is a view showing one example of the tilting-down apparatus provided on the trailer for tilting down the large-size block. In such a case, a tilting-down shaft 28g is attached to the radiation shield 28 beforehand. The large-size block 51 is slowly descended toward a tilting-down bearing 35 while being vertically hanged by heavy-duty crane wires 30c, and at the same the trailer 34 is slowly moved in a direction corresponding to the direction in which the large-size block 51 is to be tilted down. As a result, the radiation shield 28 is rotated about the tilting-down shaft 28g, and the large-size block 51 is gradually tilted down from the vertically hanged state. On that occasion, the distance and speed by and at which the trailer 34 is moved and the distance and speed by and at which the large-size block 51 is descended, are adjusted in a proper combination so that the weight imposed on the tilting-down shaft 28g is reduced to, e.g., about a half the total weight of the large-size block. In such a way, the large-size block 51 is gradually horizontally laid on a platform 36 of the trailer 34 while avoiding excessive loads from being imposed on the tilting-down shaft 28g and the tilting-down bearing 35. After horizontally laying the large-size block 51 on the platform 36 of the trailer 34, the large-size block 51 is fixed in place by, e.g., wires. The work for tilting down the large-size block is thus completed. Through the procedures described above, the work for carrying out, as the large-size block 51, the RV 2 in union with the radiation shield 28 and the core internals 50 is completed. Then, in step S16, a new reactor vessel (new RV) 2 is lifted up by the heavy-duty crane 30 and is carried in to a predetermined position within the containment vessel 3 (i.e., the bottom portion of the reactor cavity 5) through the temporary opening 31. At this time, the new RV 2 is carried in together with the lower core internals 21 mounted in the new RV 2. Alternatively, the new RV 2 and the lower core internals 21 may be carried in separately. Then, in step S17, the removed polar crane 9 is carried into the containment vessel 3 through the temporary opening 31 for restoration to the same state as that before removal. Subsequently, the temporary opening 31 is closed in step S18, and the heavy-duty crane 30 is dismantled in step S19. Further, in step S20, an outlet pipe and an inlet pipe to be connected to the new RV 2 are connected respectively to the outlet nozzle and the inlet nozzle for restoration to the same state as that before replacement. In step S21, the cables are attached to a bottom portion of the new RV 2 for restoration to the same state as that before replacement. Then, fuel is charged in step S22 and the upper core internals 20 are mounted in step S23 for restoration to the same state as that before removal. Thereafter, in step S24, the operation of the reactor is started. A series of work steps for replacing the reactor vessel is completed through the procedures described above. Another example of the radiation shield 28 to be combined with the RV 2 will be described below with reference to FIGS. 16A and 16B. A radiation shield 28 of this example differs from that shown in FIG. 9 in having, instead of the shield upper lid 28a, stopper beams 28e that are brought into abutment with the upper lid of the RV 2. The remaining structure is the same as that shown in FIG. 9, and hence a description thereof is omitted here. FIG. 16A and FIG. 16B show a state in which the RV 2 is lifted up and combined with the radiation shield 28 of this example. Specifically, FIG. 16A is a side view, partly broken away, showing details of an attachment unit for the radiation shield 28, and FIG. 16B is a top plan view of FIG. 16A. As shown in FIG. 16B, opposite ends of each of four stopper beams 28e are fixed to an upper surface of the radiation shield 28 by set bolts 28f. The stopper beams 28e are arranged at positions almost evenly spaced from each other in the circumferential direction such that the stopper beams will not interfere with the sling 30a. A hook 28h for hanging the radiation shield 28 is provided at the center of each stopper beam 28e. In the radiation shield 28 of this example, since central portions of the stopper beams 28e are brought into abutment with the shield lid 26, the radiation shield 28 can be easily combined with the RV 2 just by lifting up the RV 2. Depending on cases, the height of the radiation shield 28 can be reduced to a height enough to cover nearly a level of the outlet nozzle (or the inlet nozzle) by filling a shielding material in the RV 2. In such a case, the height of the radiation shield 28 may be reduced to such an extent that the stopper beams 28e are brought into abutment with the outlet nozzle (or the inlet nozzle). In that case, the radiation shield 28 can also be easily combined with the RV 2 in a short time just by lifting up the RV 2. With the embodiment described above, the reactor vessel can be carried out and in with high efficiency in a short time in a state where the polar crane is removed. It is therefore possible to shorten the term of work for replacing the reactor vessel and hence to shorten the downtime of the nuclear power plant. Further, when carrying out the reactor vessel, the surface dose rate of the shield for the reactor vessel can be reduced to a level lower than the limit value. Moreover, since workers are less required to access the reactor vessel when the shield is combined with the reactor vessel, the radiation exposure rate of the workers can be reduced during the work for carrying out the reactor vessel. Additionally, in the embodiment described above, work for draining reactor water in the RV 2 after the end of step S6 may be omitted. In that case, the remaining reactor water is effective to shut off radiations from the core internals 50. It is therefore possible to further reduce the surface dose rate of the RV 2, and hence to omit the step S7 of filling mortar (shielding material). Also, instead of mortar, powder (or fine particles) of, e.g., lead or steel may be sealed off in the reactor. While, in the embodiment described above, the polar crane is removed in step S11, this step is not limited to removal of the polar crane. For example, the polar crane may be operated to move aside for creating a space, through which the reactor vessel and the shield are able to pass, in an area within the reactor containment vessel where the polar crane is installed. In that case, the polar crane is restored to the original state in step S17. Next, a description is made of a second embodiment in which the present invention is applied to replacement of a reactor vessel in a PWR plant. In this embodiment, after reinforcing a polar crane, a large-size block including a reactor vessel (RV) is lifted up by the reinforced polar crane and then carried out through an opening formed so as to penetrate side walls of a containment vessel (CV) and a reactor shielding building for replacement with a new reactor vessel. FIG. 17A and FIG. 17B are flowchart showing a method for replacing the RV according to the second embodiment. Steps T1-T8 and T21-T25 in FIGS. 17A and 17B are the same as steps S1-S8 and S20-S24 in FIGS. 1A and 1B. This second embodiment differs from the first embodiment in steps T9-T20 in FIGS. 17A and 17B. Other procedures are the same as those in the first embodiment and a description thereof is omitted here. Steps T9-T20 in this embodiment will be described below. In step T9, a temporary opening 4a is formed so as to penetrate side walls of a CV 3 and a reactor shielding building having 1, the temporary opening 4a having a size allowing a large-size block 51 including an RV 2 to be carried out through it in a horizontally laid state. FIG. 18 shows a state in which the temporary opening 4a enabling the large-size block 51 (not shown in FIG. 18) to be carried out therethrough is formed in the side wall of the CV 3 at a level above an operating floor 7. Although an equipment carrying-in opening 4 is provided in the CV 3 for carrying out/in large-size equipment through it, the size of the equipment carrying-in opening 4 is not enough to carry out the large-size block 51 including a radiation shield 28 and the RV 2, as described above. Therefore, the temporary opening 4a is newly formed so as to penetrate both the CV 3 and the reactor building 1. A shutter 4b capable of opening and closing is provided to close the temporary opening 4a. The temporary opening 4a may be formed at a different position from the equipment carrying-in opening 4, but the term necessary for the work can be cut down by enlarging the existing equipment carrying-in opening 4 to such an extent that the temporary opening 4a is formed. Then, in step T10, a polar crane 9 is reinforced. The existing polar crane has a capacity of about 100 tons. On the other hand, the weight of the large-size block 51 including core internals 50, the RV 2 and the radiation shield 28 amounts to 400 to 500 tons. For that reason, the polar crane 9 is reinforced to be capable of lifting up the large-size block 51 having such a large weight. FIG. 19 shows a state in which the polar crane 9 is reinforced by erecting reinforcing members 33 on the operating floor 7 in the CV 3. The reinforcing members 33 may be provided with pulleys or the likes so that the reinforcing members are able to freely move on the operating floor 7 in conjunction with the polar crane 9. Then, in step T11, an auxiliary trolley 9c with a reinforced lifting apparatus is mounted. More specifically, the auxiliary trolley 9c comprising a chain jack (or a hydraulic jack, etc.), which has a capacity capable of lifting up the large-size block with the weight of 400 to 500 tons, is mounted on a girder 9a. Then, in step T12, the radiation shield 28 is carried in through the temporary opening 4a. As with step S12 in the first embodiment, the radiation shield 28 is temporarily placed on the RV 2 (or reinforcing members 27) in a bottom portion of a reactor cavity 5. The radiation shield 28 is provided with a tilting down shaft 28g, which is similar to that shown in FIGS. 15A and 15B, for tilting down the RV 2. Then, in step T13, the RV 2 and the radiation shield 28 are combined with each other. The RV 2 is lifted up by the reinforced polar crane 9. As with step S13 in the first embodiment, the RV 2 and the radiation shield 28 can be easily united into one in a short time by just lifting up the RV 2 to such an extent that a shield lid 26 of the RV 2 is brought into abutment with a shield upper lid 28a. Then, in step T14, a flatcar (trailer) 34a provided with a tilting-down bearing 35 is carried into the CV 3 and set up on the operating floor 7 for tilting down the RV 2. Then, in step T15, the large-size block 51 including the RV 2 combined with the radiation shield 28 is tilted down. The tilting-down of the large-size block 51 is performed in a similar manner as described above in connection with FIGS. 15A and 15B. FIG. 20 is a view showing a state in which the large-size block 51 is tilted down in the CV 3 to be laid on the flatcar 34a. Then, in step T16, the large-size block 51 in a state of being horizontally laid on the flatcar 34a is carried out of the reactor shielding building 1 through the temporary opening 4a. In step T17, while keeping the large-size block 51 horizontally laid on the flatcar 34a, the large-size block 51 is transported to a storage container 40 for the RV 2, which is installed in, e.g., the nuclear power plant site, and then carried into the storage container 40. Then, in step T18, a new reactor vessel (new RV) 2 is carried into the CV 3 through the temporary opening 4a by using the flatcar 34a. After carrying the new RV 2 into the CV 3, the new RV 2 is tilted up by the reinforced polar crane 9 in accordance with the procedure reversal tot that in step T15. Further, the new RV 2 is lifted up by the reinforced polar crane 9 and is installed in the reactor cavity 5. Then, the reinforcing members 33 and the auxiliary trolley 9c for the polar crane 9 are removed in step T19, and the temporary opening 4a is closed in step T20. Subsequent steps T21 to T25 are performed in the same manners as in steps S20 to S24 shown in FIGS. 1A and 1B. The work for carrying out the large-size block 51, which includes the core internals 50, the RV 2 and the radiation shield 28 united into one, and the work for carrying the new RV 2 are thereby completed. With this embodiment, carrying-out and -in of the reactor vessel can be implemented in a short time with high efficiency by using the reinforced polar crane. It is therefore possible to shorten the term of work for replacing the reactor vessel and hence to shorten the downtime of the nuclear power plant. Further, as with the first embodiment, when carrying out the reactor vessel, the surface dose rate of the shield for the reactor vessel can be reduced to a level lower than the limit value, and the radiation exposure rate of workers can be reduced. |
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claims | 1. An ion implantation system, comprisingan ion source;an electrode, maintained at a first voltage different than ground; anda power supply in communication with said electrode, wherein said power supply is configured to detect a glitch when said first voltage changes by more than a predetermined amount, and in response to said detection, said power supply increases a current output to attempt to restore said first voltage. 2. The ion implantation system of claim 1, wherein said predetermined amount is between 20% and 40% of said first voltage. 3. The ion implantation system of claim 1, wherein said power supply utilizes a control loop to establish and maintain said first voltage and wherein said control loop has a time constant of less than 10 milliseconds. 4. The ion implantation system of claim 1, further comprising a resistance located in series between said electrode and said power supply so as to create a filter. 5. The ion implantation system of claim 4, wherein said resistance is between 1 kilo-ohm and 5 kilo-ohms. 6. The ion implantation system of claim 1, further comprising at least one additional component, maintained at a second voltage, different than ground and said first voltage, and a second power supply in communication with said additional component wherein said second power supply is configured to detect a glitch when said second voltage changes by more than a predetermined amount, and in response to said detection, said second power supply increases a current output to attempt to restore said second voltage. 7. A method of manufacturing a solar cell from a substrate, comprising:directing a beam of ions having a beam current toward a substrate, wherein at least one power supply supplies a first voltage, different than ground, in order to direct said beam toward said substrate;scanning said beam relative to said substrate for as to implant a surface of said substrate;monitoring changes in said beam current of said beam;allowing said scanning to continue if said monitored beam current changes by less than a predetermined value, said value greater than zero, whereby said predetermined value guarantees a dose uniformity acceptable for a solar cell. 8. The method of claim 7, wherein said predetermined value is about 3%. 9. The method of claim 7, wherein said changes in said beam current are caused by changes in said first voltage, and further comprising configuring said power supply to minimize durations of said changes in said first voltage. 10. The method of claim 9, wherein said power supply reduces glitch duration to between 20 and 40 milliseconds. 11. The method of claim 9, comprising configuring said power supply to detect a glitch when said first voltage changes by more than a predetermined amount, and in response to said detection, to increase a current output to attempt to restore said first voltage. 12. The method of claim 11, wherein said predetermined amount is between 20% and 40% of said first voltage. 13. The method of claim 9, wherein said power supply utilizes a control loop to establish and maintain said first voltage and wherein said control loop has a time constant of less than 10 milliseconds. 14. The method of claim 7, further comprising a resistance located at an output of said power supply so as to create a filter. 15. The method of claim 14, wherein said resistance is between 1 kilo-ohm and 5 kilo-ohms. 16. The method of claim 7, further comprising stopping said scanning if said monitored changes in beam current are greater than said predetermined value. |
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abstract | A method of injecting mortar into a container fastened to a first tank and to a second tank, the first tank communicating with the container via a first orifice and the second tank communicating with the container by a second orifice, the method comprising the following operations: a continuous circulation of a first stream of mortar is made to flow in a circulation loop; during the continuous circulation, a second stream of mortar is drawn off from the circulation loop, the second stream being smaller than the first stream of mortar; the second stream of mortar is injected into the container, ensuring that there is dynamic confinement of the gaseous effluents; and the appearance of mortar in the second tank is monitored and, when this appearance is detected, the removal of mortar from the circulation loop is brought to an end. |
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claims | 1. A focused ion beam system for processing a specimen by irradiating the specimen with a focused ion beam, said focused ion beam system comprising:an ion beam source for producing the ion beam;condenser lenses for focusing the produced ion beam;multiple variable apertures for selectively limiting current of the ion beam focused by the condenser lenses;a deflection portion for deflecting the focused ion beam whose current has been selectively limited by the apertures;an objective lens for focusing the deflected ion beam at a desired position on the specimen;a specimen stage for moving the specimen;an input portion for accepting data entered by a human operator;a control portion comprising a computer readable medium containing instructions to cause said control portion to first select optical conditions for the condenser lenses, the multiple variable apertures, the deflection portion, and the objective lens for establishing a beam size based on the data entered into said input portion comprising the size of the processed region and the degree of precision wherein the beam size is increased for larger processing regions but not so as to provide unacceptable precision, and second automatically calculate processing and scanning conditions including dwell time per hit position, dwell position spacing and frame in accordance with said selected optical conditions and cut depth and specimen kind or dose entered into the input portion wherein the dwell position spacing is reduced sufficient to suppress discontinuous processing, the frame time is increased to reduce blanking tail to a minimum, and the hit position spacing and dwell time per hit position are set so the scan speed does not decrease below a threshold value at which the specimen is disfigured;a setting condition data output portion for outputting data based on the optical conditions and processing and scanning conditions selected and calculated by said control portion; anda driver portion for driving the condenser lenses, the multiple variable apertures, the deflection portion, and the objective lens based on the data output from said setting condition data output portion about the optical conditions and the processing and scanning conditions. 2. A focused ion beam system as set forth in claim 1, wherein said processing and scanning conditions automatically set by said control portion include a dwell time of the ion beam per hit point on the specimen and a dwell point spacing. 3. A focused ion beam system as set forth in claim 1, wherein said control portion calculates a diameter of the ion beam used for processing according to the size of the processed region on the specimen, the size being entered into said input portion, and first selects an optical condition file matched to the calculated beam diameter and based upon the degree of finish selected the optical condition file adjacent the first selected file is selected. 4. A focused ion beam system as set forth in claim 2, wherein said control portion calculates a diameter of the ion beam used for processing according to the size of the processed region on the specimen, the size being entered into said input portion, and selects an optical condition file matched to the calculated beam diameter. 5. A focused ion beam system as set forth in claim 1, wherein said control portion calculates a diameter of the ion beam used for processing according to the size of the processed region on the specimen, the size being entered into said input portion, and selects an optical condition file matched to the calculated beam diameter. 6. A focused ion beam system as set forth in claim 3, wherein said control portion automatically selects said optical condition file based on the calculated diameter of the beam, the file defining a mode of operation in which the condenser lenses, objective lens, multiple variable apertures, and deflection portion are driven by the driver portion. 7. A focused ion beam system as set forth in claim 4, wherein said control portion automatically selects said optical condition file based on the calculated diameter of the beam, the file defining a mode of operation in which the condenser lenses, objective lens, multiple variable apertures, and deflection portion are driven by the driver portion. 8. A focused ion beam system as set forth in claim 5, wherein said control portion automatically selects said optical condition file based on the calculated diameter of the beam, the file defining a mode of operation in which the condenser lenses, objective lens, multiple variable apertures, and deflection portion are driven by the driver portion. |
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description | This application is a continuation of U.S. patent application Ser. No. 10/853,835, filed May 26, 2004, now abandoned entitled “METHOD AND APPARATUS FOR ONLINE SAMPLE INTERVAL DETERMINATION”, which is herein incorporated by reference in its entirety. The present invention relates generally to computing systems, and relates more particularly to performance and systems management of computing systems. Specifically, the invention is a method and apparatus for online determination of sample intervals for optimization and control operations in a dynamic, on-demand computing environment. FIG. 1 is a block diagram illustrating a typical data processing system 10. The data processing system 10 comprises a database server 100 which serves one or more database clients 150. The database server 100 includes a plurality of memory pools 121-125 that is adapted to cache data in a plurality of storage media 111-119. Database agents 101-109 access copies of storage media data through the memory pools 121 to 125 in order to serve the clients 150. Central to the performance of the data processing system 10 is the management of the memory pools 121-125. Increasing the size of a memory pool 121-125 can dramatically reduce response time for accessing storage media data, since there is a higher probability that a copy of the data is cached in memory. This reduction in response time, measured in terms of saved response time per unit memory increase, is referred to as the “response time benefit” (or “benefit”). A benefit reporter and a memory tuner operate to optimize the benefit derived from the system 10. At regularly scheduled intervals (referred to as “sample intervals”), the benefit reporter 130 collects measured output data (e.g., data indicative of system performance metrics) and transmits the data to the memory tuner 140, which is adapted to adjust memory pool allocations, based on analysis of the measured output data, with the intent of reducing overall response time for data access. Due to the stochastic and dynamic nature of computing systems, the size of these sample intervals can be critical. For example, too small a sample interval may yield an insufficient collection of samples, and significant measurement noise may be generated during optimization, resulting in controller-introduced oscillation. On the other hand, too large a sample interval may reduce the optimization responsiveness as measured by time-response characteristics, such as system settling time. Effective online optimization therefore requires a substantially precise sample interval in order to provide fast response without introducing unwanted oscillation. A drawback of conventional systems for determining sample intervals, such as the benefit reporter and memory tuner system discussed above, is that the determinations tend to be based on static workloads. However, in a dynamic, on-demand environment, the workload characteristics and system configurations change drastically with time, and statically derived intervals may therefore yield less than optimal results. Thus, there is a need in the art for a method and apparatus for online sample interval determination. In one embodiment, the present invention is a system for online determination of sample intervals for dynamic (i.e., non-stationary) workloads. In one embodiment, functional system elements are added to an autonomic manager to enable automatic online sample interval selection. In another embodiment, a method for determining the sample interval by continually characterizing the system workload behavior includes monitoring the system data and analyzing the degree to which the workload is stationary. This makes the online optimization method less sensitive to system noise and capable of being adapted to handle different workloads. The effectiveness of the autonomic optimizer is thereby improved, making it easier to manage a wide range of systems. To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. In one embodiment, the present invention provides a method for online determination of a sample interval for collecting measured output data of computing systems dealing in dynamic (e.g., non-stationary) workloads. In one embodiment, the method is implemented in a data processing system such as that illustrated in FIG. 1, and operates to adjust memory allocation to a plurality of memory pools. Since the total size of a system's memory pools is fixed, increasing the size of one memory pool necessarily means decreasing the size of another pool. Care must be taken in determining when and how frequently to adjust the allocations to the memory pools. If adjustments are made too frequently, the benefit data can be corrupted by substantial random factors in memory usage; however, because, the workload varies over the time and the memory tuner needs to be responsive in determining the optimal memory allocations, memory allocation adjustments must not be made too infrequently either. Determination of proper sample intervals is therefore critical. FIG. 2 is a block diagram illustrating one embodiment of a data processing system 200 in which a method for online determination of a sample interval may be executed according to the present invention. The system 200 comprises an interval tuner 210, a resource optimizer 220, and a data processing system 230. The data processing system 230 receives workload 240 in the form of client requests, and transmits measured output data (in the form of a plurality of data points) to both the resource optimizer 220 and the interval tuner 210. As described above, the measured output data is data indicative of system performance metrics, and in one embodiment, the measured output is benefit information. However, those skilled in the art will appreciate that the measured output data generally reflects many different aspects of the data processing system 200. The resource optimizer 220 functions in a manner similar to the memory tuner 140 in FIG. 1, and analyzes the measured output data collected from the data processing system 230 to determine new resource allocations for the data processing system at specified intervals of time. The challenge for the resource optimizer is that different workloads 240 will affect the data processing system 230 differently, and will thus require tuning at different intervals. The interval tuner 210 uses the measured output data collected from the data processing system 230 to determine the operating frequency (e.g., the sample interval for collecting the measured output data and the control interval for changing the resource allocation; generally, the sample interval is equal to the control interval) of the resource optimizer 220. The interval tuner 210 is adapted to automatically select and adjust the sample interval in real time. For example, in one embodiment the workload 240 is an online transaction processing (OLTP) workload. Since each of the transactions take less than a second to run, it may be reasonable for the resource optimizer 220 to tune the resource allocation of the data processing system 230 every one or two minutes (or after several hundred thousand transactions). However, the same resource optimizer 220 and data processing system 230 may need to handle different type of workload 240, such as a decision support (DSS) workload. Since the transactions from a DSS workload usually take several minutes to run (e.g., some transactions can take up to half an hour to run), if the resource optimizer 220 were to tune the data processing system 230 with the same one or two minutes interval, it would be performing intra-query tuning which is much more difficult (and in some cases impossible). Furthermore, if the data processing system 230 is tuned too quickly, it will cause unnecessary measurement and resizing overheads. Alternatively, if changes are made too infrequently, the system will exhibit poor response time to changing workload demands. The workload characteristics and system configurations in a dynamic on-demand environment differ from customer to customer, and can change drastically during normal operation. FIG. 3 is a flow diagram illustrating one embodiment of a method 300 for determining sample intervals in a dynamic environment according to the present invention. In one embodiment, the method 300 is executed by the interval tuner 210 of the system 200. The individual steps 310-340 in the method 300 are described in greater details below. The method 300 is initialized at step 305 and proceeds to step 310, where the method 300 collects measured output data. In one embodiment, the measured output data is benefit information. In step 320, the method 300 uses the measured output data to determine whether to start interval tuning. Once the interval tuning process is started, the resource optimizer (e.g., 220 in FIG. 2) is overridden and current resource allocations are fixed. In step 330, the method 300 determines whether sufficient measured output data has been collected for performing interval tuning. In one embodiment, the collected measured output data is sufficient if it is representative of system characteristics. In one embodiment, the determination of whether sufficient measured output data has been collected is made in accordance with a method 500, described in more detail below with regard to FIG. 5. If the collected measured output data is insufficient for interval tuning, the method 300 returns to step 310 and collects additional data. Alternatively, if the method 300 determines in step 330 that sufficient measured output data has been collected, the method 300 proceeds to step 340, where the method 300 analyzes the system workload and characteristics, as indicated by the collected measured output data, and determines a sample interval that is suitable for the system 200 and workload 240. The method 300 continually characterizes the workload behavior and statistically determines the sample interval based on the collected measured output data. This allows the resource optimizer 220 to be less sensitive to system noise and to adapt to different workloads 240, since interval tuning is conducted regularly during the period in which automatic resource allocation is active for the data processing system 200. FIG. 4 is a flow diagram illustrating one embodiment of a method 320 for determining whether to start interval tuning. The method 320 is initialized at step 400 and proceeds to step 402, where the method 320 determines whether a system workload 240 exists. Since a workload 240 must exist (e.g., at least one of the measured output data must be non-zero) in order for interval tuning to begin, if the method 320 determines at step 402 that a workload 240 does not exist, the method 320 concludes that the system 200 is not ready for interval tuning. Alternatively, if a workload 240 does exist, the method 320 proceeds to step 404, where the method 320 determines whether the system 200 is attempting to start interval tuning for the first time. Those skilled in the art will appreciate that at a particular time interval, some of the data points of the measured output data can be zero; for example, one or more databases may not be needed by the database agents for handling the client requests. However, in one embodiment, if all of the data are zero, the workload 240 most likely does not exist, e.g., the data processing system 200 is not connected to handle incoming workloads 240. Since the workload 240 does not exist, the interval tuning process should not be started. If the system 200 has completed interval tuning for the first time, since the workload may change over time, the system 200 may attempt to perform interval tuning again. Therefore, the method 320 proceeds to step 410 and waits for the next scheduled interval tuning. If the system 200 is attempting to perform interval tuning for the first time, the method 320 proceeds to step 406 to determine whether the system resource allocation has reached a steady state. In one embodiment, a steady state implies that the system 200 is working in a normal operating state, so that the measured output (benefit) data collected is representative of system characteristics and so that interval tuning is necessary. FIG. 7 is a flow diagram illustrating one embodiment of a method 700 for determining whether the system 200 has reached a steady state. The method 700 is initialized at step 702 and proceeds to step 704, where the method 700 determines whether the resize amount falls below some minimum threshold, thereby implying that the system 200 has converged and the system resource is not aggressively reallocated by the resource optimizer 220 (that is, a steady state is reached). In one embodiment, the system resource is memory, and the resize amount is the percentage of memory reallocation with respect to the total available memory. If the resize amount is insignificant (e.g., below a threshold of 0.5%), the system is assumed to have converged since less than 0.5% memory reallocation will not significantly impact system performance. If the method 700 determines that the resize amount does fall below the minimum threshold, the method 700 determines that the steady state has been reached or is close to being reached. Alternatively, if the method 700 determines that the resize amount does not fall below the minimum threshold, the method 700 proceeds to step 706. In step 706, the method 700 determines whether a relatively small number of tuning intervals has passed since the start of workload 240 and resource allocation from the resource optimizer 220, thereby implying that convergence of the system 200 may not be possible with the current sample interval. In one embodiment, this “relatively small number” of tuning intervals is based upon the desired converging speed of the resource optimizer. In one embodiment, it is desirable for the resource optimizer to converge at approximately twenty intervals. If the method 700 determines that a relatively small number of tuning intervals has passed, the method 700 determines that the system 200 has reached a steady state, e.g., a normal operating state where the system 200 can oscillate and not necessarily need to be converged. That is, the data collected at the steady state is representative of system characteristics and may be used for interval tuning purposes. Thus, referring back to FIG. 4, if the method 700 indicates that the system resource allocation has reached the steady state, the method 320 determines that the system is ready for interval tuning and proceeds to step 330 of FIG. 3 (illustrated in further detail in FIG. 5). Alternatively, if the method 700 determines that the system 200 has not reached a steady state, interval tuning should not be started. FIG. 5 is a flow diagram illustrating one embodiment of a method 330 for determining whether sufficient measured output data has been collected for interval tuning. The method 330 is initialized at step 500 and proceeds to step 502, where the method 500 determines whether the system 200 is ready for interval tuning (e.g., based on the results obtained by the method 320 of FIG. 4). If the method 330 determines that the system 200 is not ready for interval tuning, the method 330 returns to step 402 of FIG. 4 and repeats the method 320. If the method 330 determines that the system 200 is ready for interval tuning, the method 330 proceeds to step 504 to determine whether enough measured output data has been collected to perform interval tuning. If the method 330 determines that sufficient data has been collected, the method 330 determines that the system 200 is ready for analysis of the measured output data, and proceeds to step 340 of FIG. 3 (illustrated in further detail in FIG. 6). Alternatively, if the method 330 determines that sufficient data has not been collected, the method 330 proceeds to step 506, where the method 330 overrides any resource allocation decisions from the resource optimizer. In one embodiment, no resource reallocation is conducted while measured output data is collected for analysis (e.g., in step 340 of the method 300), thereby ensuring that the system 200 is able to base data analysis on a stable data set. This helps to remove autocorrelation of the measured output data due to closed loop tuning. Next, the method 330 proceeds to step 508, where a small sample interval is set. In one embodiment, a small sample interval size is used in order to shorten the data collection process, but still collect enough data points for analysis. In one embodiment, this “small” sample interval size is the minimum sample interval that can be reasonably applied in the data processing system. For example, a data processing system handling a combination of online transaction processing (OLTP) and decision support system (DSS) workloads (e.g., transactions that may take less than a second or more than an hour) may select a minimum sample interval between five and thirty seconds. In one embodiment, this minimum sample interval is large enough to include dozens of transactions, but not too small in light of the resizing time and central processing unit cycles. The method 330 then collects more measured output data in step 510 using this sample interval, and proceeds to step 340 of FIG. 3 (illustrated in further detail in FIG. 6). FIG. 6 is a flow diagram illustrating one embodiment of a method 340 for analyzing the workload and system characteristics and determining the sample interval. The method 340 is initialized at step 600 and proceeds to step 602, where the method 340 determines whether the system 200 is ready for analysis of the collected measured output data. If the system 200 is not ready for data analysis, the method 340 returns to step 310 of FIG. 3, to repeat the method 300. If the method 340 determines that the system 200 is ready for data analysis, the method 340 proceeds to step 604, where the method 340 separates the “good” collected measured output data from the data that may have been affected by an abrupt workload change. To accomplish this separation, the method 340 separates the collected data into two groups (e.g., halves) and only analyzes the group with the smaller standard deviation. The method 340 then proceeds to step 606, where, if the method 340 determines that the data processing system 200 reports more than one measured output data point for the purpose of resource optimization, the method 340 selects the measured output data group whose standard deviation is the largest, for performing interval tuning. In step 608, the method 340 determines the sample interval based on the measured and desired statistical properties of the system 200. In one embodiment, the sample interval is determined by considering the confidence of the measured output data. For example, given P measured benefit samples from a database server, which are represented by benefit (i) for i=1, 2, . . . , P, the sample mean is: mean benefit = [ benefit ( 1 ) + benefit ( 2 ) + … + benefit ( P ) ] P ( EQN . 1 ) and the sample standard deviation is std benefit = { [ benefit ( 1 ) - mean benefit ] 2 + … + [ benefit ( P ) - mean benefit ] 2 } P - 1 ( EQN . 2 ) Both the mean benefit and the std benefit values are used to calculate the interval size as follows: desired sample interval = [ T ( std benefit desired confidence range ) ] 2 ( current sample interval ) ( EQN . 3 ) where “desired confidence range” is an accuracy measure of the desired maximum difference between the measured sample benefit and the statistically “real” mean benefit, and “current sample interval” is the sample interval that is currently used to collect benefit data (e.g., benefits 1-P). In one embodiment, the desired confidence range is plus or minus 10% of the measured sample benefit. In another embodiment, the desired confidence range is plus or minus 20% of the measured sample benefit. In one embodiment, the benefit data is noisy but the accuracy requirement is high, resulting in a large desired sample interval. Note that the random variable (benefit−mean benefit)/(std benefit) follows the student distribution, which is different to the normal distribution because mean benefit and std benefit are estimated. The constant T is used to compensate for the estimated benefits. Those skilled in the art will appreciate that more details on student and normal distributions can be found in most statistics textbooks, including Walpole et al., Probability and Statistics for Engineers and Scientists, Prentice Hall, 1997. For convenience, a subset of a table for determining T is illustrated in Table I. TABLE ISubset of table for determining T0.9123450.9512.7064.3033.1822.7762.5710.96.3142.922.3532.1322.0150.83.0781.18861.6381.5331.476In Table I, each row corresponds to one confidence interval (0.95, 0.0, 0.8, etc.) and each column corresponds to a degree of freedom (1, 2, 3, 4, 5, etc.), e.g., the number of measured benefit samples. For example, if 90% confidence in the accuracy of the measured data is desired, and the decision is based on P=3 measured benefit samples, a T of 2.353 is chosen. Increasing the confidence (e.g., from 90% to 95%) will result in a larger value for T; in addition, achieving a greater confidence score will require a larger sample interval. Decreasing the number of measured benefit samples (e.g., from three to two) will also result in a larger value for T, indicating that a larger sample interval is required. This is because a sample interval size that is determined based on a smaller sample is subject to more errors; to achieve the same confidence level, a larger desired sample interval would be required. FIG. 8 is a high level block diagram of the present dynamic resource allocation system that is implemented using a general purpose computing device 800. In one embodiment, a general purpose computing device 800 comprises a processor 802, a memory 804, a dynamic resource optimizer or module 805 (e.g., capable of performing online sample interval determination) and various input/output (I/O) devices 806 such as a display, a keyboard, a mouse, a modem, and the like. In one embodiment, at least one I/O device is a storage device (e.g., a disk drive, an optical disk drive, a floppy disk drive). It should be understood that the dynamic resource optimizer 805 can be implemented as a physical device or subsystem that is coupled to a processor through a communication channel. Alternatively, the dynamic resource optimizer 805 can be represented by one or more software applications (or even a combination of software and hardware, e.g., using Application Specific Integrated Circuits (ASIC)), where the software is loaded from a storage medium (e.g., I/O devices 806) and operated by the processor 802 in the memory 804 of the general purpose computing device 800. Thus, in one embodiment, the resource optimizer 805 for allocating resources among entities described herein with reference to the preceding Figures can be stored on a computer readable medium or carrier (e.g., RAM, magnetic or optical drive or diskette, and the like). In further embodiments, resources may be shared among a plurality of clients, e.g., web content providers, and dynamic resource allocation and optimization may be provided to the clients according to the methods of the present invention. In such cases, the workload of each individual client may be continually monitored so that resources allocated to any individual client are sufficient to meet, but do not greatly exceed, the needs of the client, thereby substantially achieving optimal resource allocation. Thus, the present invention represents a significant advancement in the field of dynamic resource allocation. A method and apparatus are provided that enable a data processing system to dynamically determine a sample interval for analyzing resource allocation by continually characterizing the system workload. This makes the online optimization method less sensitive to system noise and capable of being adapted to handle different workloads. The effectiveness of a system resource optimizer is thereby improved, making it easier to manage a wide range of systems. While foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. |
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summary | ||
description | The first BWR plants used a steel containment in the shape of an inverted light-bulb, completely surrounding any reactor vessel pressure relief valves on all main steam lines, and also fully enclosing a coolant re-circulation system. Several containment designs are currently used, as shown in FIGS. 1a through 1c. The containment shown in FIG. 2 is the predominant type of BWR containment. With reference to FIGS. 1 and 2, wherein like numerals denote like structures, a BWR containment 20 generally is divided into two chambers: a dry-well 22 that houses a reactor vessel 24 and other primary system components; and a generally toroidal suppression chamber 26, also known as a xe2x80x9cwet-wellxe2x80x9d, which contains a pool of water 28 used for pressure suppression and as a heat sink. If a pipe rupture occurs inside a containment 20, the dry-well 22 becomes pressurized by steam blowing down from a primary coolant system. The steam enters a plurality of downcomers 30 and is routed to each wet-well 26 where it is discharged beneath the water surface 32 of a pool 28. The pool 28 is designed to condense the steam discharged to the wet-well 26 and thus mitigate a post-accident containment pressure transient. The pool 28 also provides a source of water for an emergency core cooling system (ECCS) (not shown). The ECCS is designed to inject water back into the reactor vessel to make up for lost water in the event of a loss of coolant accident (LOCA). The ECCS also re-circulates water through the core following a LOCA to provide for long term post-accident core cooling. A LOCA results from a high pressure coolant system pipe rupture. It is postulated that such a rupture will cause large quantities of debris, such as pipe and vessel insulating material, and other solids, to be washed into the wet-well 26. Conventional suction strainers 40 (see FIGS. 3 and 4) installed on ECCS suction lines 42 currently installed in BWR plants may not be able to handle the amount of debris expected to result from a LOCA. As a result, conventional strainers 40 are being replaced with replacement strainers 44 that are much larger and heavier. As best seen in FIG. 4, the replacement strainers 44 consist of multiple strainers 46 strainers formed into trains that connect to a suction pipe 48 through a penetration 50 in the wet-well wall 52. The larger replacement strainers 44 include more inertial mass than the conventional strainers 40 that may cause the strainers 44, and the attached suction pipe 48, to move significant amounts during seismic and other events in response to applied loads. In particular, when a large pressurized pipe ruptures with great force, resulting in an LOCA, the strainers 44 in the wet-well 26 are subjected to large hydrodynamic forces that can deflect the strainers 44 and subject the attached suction pipe 48 to large reactive forces. Forces may be applied to the strainers 44 and the suction pipe 48 in directions indicated by arrows A, B, C and D of FIGS. 3 and 4. The force indicated by arrow A in FIG. 3 acts in a transverse direction, causing the entire suction strainer assembly to move either towards or away from the penetration 50. Additionally, suction pipe 48 moves in response to the transverse force A. Forces applied in directions indicated by arrows B and D of FIG. 4 act on the penetration in a radial direction. Radial forces B and D may also combine to exert a rotational force upon penetration 50, indicated by arrow C in FIG. 4. As seen in the figures, the transverse force A, radial forces B and D and rotational forces C affected the conventional strainers 40. But, when the conventional strainers 40 are replaced by larger, heavier trains of strainers 44, the effect of forces A, B, C and D is magnified and has a greater effect on penetration 50 because the trains 44 have a larger inertial mass. Simply by increasing the size of the strainers 44, conventional penetration designs become unable to handle the expected inertial forces. Thus, the present invention is directed to a flexible penetration attachment that moves in response to postulated inertial forces acting upon either or both of the strainers 44 and the suction pipe 48. The flexible penetration attachment of the present invention is shown in FIG. 5. A flexible penetration attachment 60 is shown that allows the suction pipe 48 to communicate with liquid in the wet-well 26 through an aperture 62 in a wet-well wall 52. The penetration attachment 60 includes a boot 64, preferably fabricated, for defining an outer circumference 68 of the aperture 62. Suction pipe 48 extends through the boot 64 to fluidly communicate with the water in the wet-well 26. The outer circumference 68 of the aperture 62 is larger than the outer circumference 70 of the suction pipe 48. As a result, a space 66 is defined between the aperture outer circumference 68 and the outer circumference 70 of suction pipe 48. Because suction pipe 48 usually includes a circular cross-section, space 66 is usually annular, though other geometries may also fall within the objectives of the present invention. A resilient seal 72, also preferably annular, having a generally U-shaped cross section is placed within the annular space 66. More preferably, resilient seal 72 is fabricated from an elastomeric compound having high strength. The resilient seal 72 includes a first end 74 that is fixedly secured to the outer circumference 70 of the suction pipe 48, and a second end 76 that is fixedly secured to the outer circumference 68 of the aperture 62 defined by the fabricated boot 64. As can be seen from FIG. 5, the resilient seal 72 is fixed only at the first end 74 and at the second end 76. A central portion 80 of the seal 72 is able to flex between the first end 74 and the second end 76 of the seal such that the suction pipe 48 is allowed to move a pre-determined distance in response to a force in any direction. In particular, suction pipe 48 is able to move in the transverse, radial and rotational directions because the suction pipe 48 is not directly secured to the outer circumference 68 of the aperture 62. Instead, because the resilient seal 72 is fixedly attached with straps 78 between the outer circumference 68 of the aperture 62 and the outer circumference 70 of the suction pipe 48, the seal 72 allows the suction pipe to move in response to forces placed upon it. At the same time, the seal 72 prevents leakage from the suppression pool 26 through the annular space 66. It may be appreciated that the size of the seal 72 and the size of annular space 66 are dependent upon the size of the replacement strainers 44 in each individual plant. If the replacement strainers 44 and the suction pipe 48 are predicted to move a larger distance in response to predicted loads, then the size of both annular space 66 and central portion 80 of seal 72 may be larger. But, in any event, the seal 72 may be sized so that the suction pipe 48 is allowed sufficient room to move transversely, radially or rotationally in response to the largest predicted force placed upon the combined suction line 42 and the replacement strainers 44. In addition, both the boot 64 and the seal 72 may be sized to easily accommodate any installation differences that may be present due to existing penetrations and complicated piping systems. The seal 72 is also relatively easily disassembled to allow for penetration leakage testing or ECCS suction line repair. The present invention therefore provides a relatively simple replacement flexible penetration attachment 60 for connecting trains of strainers 44 submerged within a wet-well pool 26 to a suction pipe 48 through the existing apertures 62 in the wet-well wall 52. The flexible penetration attachment allows connection through an existing penetration without transferring significant loading for which the original penetration was not designed to absorb, and also minimizes leakage through the penetration. The features and objects of this invention have been disclosed. But it should be realized that the various changes and modifications that are possible will be self-evident to those of skill in the art in which the present invention pertains, and may be made without departing from the scope of the invention, which is limited only by the appended claims. |
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description | The present disclosure relates to a safety system shutdown including a passive electrical component that senses a system parameter and becomes tripped if a predetermined set point is reached so that a signal is sent to take an action in the system. The passive electrical component makes use of the principles of Gauss' Law of Magnetism. This section provides background information related to the present disclosure which is not necessarily prior art. Modern nuclear reactors use a variety of digital systems for both control and safety, referred to as a Distributed Control and Information System (DCIS). These systems must be redundant, diverse, fault tolerant, and have extensive self-diagnosis while the system is in operation. Meanwhile, the nuclear digital industry is concerned with common cause software failure. Even more damaging is a cyberattack to, or through, the system safety systems. In the digital industry, the desire to increase computational power while decreasing component size results in a very small digital device with embedded software. It is very difficult to convince a regulatory body that these systems cannot have a common cause failure. Even more damaging operations can occur when this compact digital system is subjected to a cyberattack. These extreme unknown conditions of a nuclear power plant safety system lead to the cause for redundancy, independence, and determinacy, all of which contribute to significant added cost. FIG. 6 schematically shows a conventional distributed control and information system (DCIS) 200 with both a safety portion 202 and non-safety portion 204 that are interfaced by a control panel 203. The present disclosure is directed to the safety portion 202 of the DCIS 200 which is shown in FIG. 7. The safety portion 202 of the DCIS 200 includes four independently designed divisions 202A-202D which each receive measured system signals that are collected and sent from a remote multiplexer unit RMU 205 which provides output to the digital trip module DTM 206 which each provide outputs to the trip logic units TLU 208 which each provide an output signal to the output logic unit OLU 210. The conventional safety portions 202 use a voting logic of at least 2 out of 4 of the different divisions 202A-202d receiving like signals in order to determine a fault (i.e. pressures and temperatures are not compared against each other). It becomes more difficult for the nuclear power plant control system designer, purchaser, installer, and operator to establish and trace the essential safety signals to ensure the system is performing as designed. A device and method is needed on a scale that humans can vary “signal flow” or “trace the flow of electrons/data so that the system is immune from cyber-attack. This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. The present disclosure provides electro-technical devices that, coupled to control systems, can provide passive system safety shutdown using Guass' Law of magnetism. These devices will solve the issue of common cause software failure or cyber security attacks that are inherent limitations of digital safety systems. The Gauss Law of magnetism contactor provides an electro-technical device that can be set up in multiple configurations to protect a nuclear power plant, or another sensitive infrastructure. The Gauss Law of magnetism contactor can be produced using metallic and plastic 3-D printing machines that can be utilized to ensure consistent manufacture of the electrotechnical device for which the manufacturing data can be captured and stored for utilization in confirming the device's consistent operational characteristics. The devices use a simple pass/fail or go/no-go check to convey to an electrical safety system to change state to safe shutdown. The printed device is placed into the safety system to perform 3 basic tasks: sense a system parameter (e.g. temperature, flow, pressure, power or rate of change), if the predetermined set point is reached—result in a “tripped” state, and lastly, if the safety system logic is met—send a signal to take an action in the system, such as shutdown. In the event of normal power supply loss, the Gauss Law of magnetism contactor can fail as either is or fail in a safe state, depending on user requirements. The system prevents any loss of the safety function of the digital device due to power outage. The device also eliminates failures due to software or digital cyber-attacks. According to an aspect of the present disclosure, an electro-technical device includes an input electrical connection supplied with an input signal and electrically isolated from an output electrical connection. A bar magnet is pivotally mounted on a pedicel between the input electrical connection and the output electrical connection. At least one coil is disposed adjacent the bar magnet and is supplied with an electronic signal from a sensor, the bar magnet being responsive to an electromagnetic filed generated by the at least one coil to cause the bar magnet to contact the input electrical connection and the output electrical connection and complete a circuit and send out a control signal. According to a further aspect, the at least one coil includes a pair of coils disposed on opposite sides of the bar magnet and each being supplied with an electronic signal from a sensor A fault detection system for a nuclear reactor includes a plurality of contactors each including an input electrical connection supplied with an input signal and electrically isolated from an output electrical connection. A bar magnet is pivotally mounted on a pedicel between the input electrical connection and the output electrical connection and a pair of coils are disposed on opposite sides of the bar magnet and each being supplied with an electronic signal from a sensor. The bar magnet is responsive to an electromagnetic field generated by the pair of coils to cause the bar magnet to contact the input electrical connection and the output electrical connection and complete a circuit and send out a control signal. Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. With reference to FIGS. 1-3, a Gauss Law of Magnetism contactor 10 according to the principles of the present disclosure will now be described. As shown in FIG. 1, the Gauss Law of Magnetism contactor 10 includes an input signal 12 having an electrical connection point 14 and an output signal 16 having an electrical connection point 18. In FIG. 1, an open state is shown. The Gauss Law of Magnetism contactor 10 includes a bar magnet 20 rotatably supported on a pedicel 22 between the input electrical connection point 14 and the output electrical connection point 18. A first coil 24 is positioned adjacent to the input electrical connection point 14 and a second coil 26 is positioned adjacent to the output electrical connection point 18. One or both of the coils 24, 26 can have an electrical current passing through them (i.e. 4 to 20 mA standard signal) from a pair of sensors 28, 30 that can sense one of a temperature, pressure, flow or other parameter. The engineered direction of current flow in both coils 24, 26 results in the south pole in the region of the input electrical connection point 14 and the north pole in the region of the output connection point 18. These externally induced magnetic fields result in the magnetic rotation of the bar magnet 20. FIG. 2 shows that repositioning of the bar magnet 20 due to increased current flow from the sensors 28, 30 passing through the coils 24, 26 causing the electrical connection between the input electrical connection 14 and output electrical connection point 18 so that a safety system action signal 32 can be sent. FIG. 3 provides a side view of the Gauss Law of Magnetism contactor 10 illustrating the magnet 20 placed inside a non-magnetic box 34 on the pedicel 22. The magnet 20 rotates about the pedicel 22, and the box 34 is sealed with a lid 36. As an alternative, the reverse circuit can be set up to open (rather than close) the Gauss Law of Magnetism contactor 10 to de-energize a system for a protective feature. FIGS. 4 and 5 provide a schematic view of a nuclear safety system 40 using Gauss' Law of Magnetism. The nuclear safety system 40 utilizes four independent divisions 42A-42D for each division of the safety system. In a 4-division safety system utilizing a 2 out of 4 logic of like signals (A, B, C, D), there are six states including AB, AC, AD, BC, BD and CD to reach a tripped state. FIG. 4 provides a side view in the X and Z plane. In the positive Z direction, the AB, AC and AD trip states are attained by the Gauss magnetism Law contactors 50A, 50B and 50C, respectively. The Gauss Magnetism law contactor 50A receives current through the respective coils 66A, 66B from the divisions 42A and 42B. The Gauss Magnetism law contactor 50B receives current through the respective coils 66A, 66C from the divisions 42A and 42C. The Gauss Magnetism law contactor 50C receives current through the respective coils 66A, 66D from the divisions 42A and 42D. In the negative Z direction the BC and BD trip states are attained by the Gauss Magnetism law contactors 50D, 50E, respectively. The Gauss Magnetism law contactor 50D receives current through the respective coils 66B, 66C from the divisions 42B and 42C. The Gauss Magnetism law contactor 50E receives current through the respective coils 66B, 66D from the divisions 42B, and 42D. FIG. 5 provides a side view in the positive Y direction which provides the CD tripped state. The Gauss Magnetism law contactor 50F receives current through the respective coils 66C, 66D from the divisions 42C and 42D. Thus, sensors from two out of four divisions 42A-42D can be activated causing an increased current to flow through the two respective coils 66A-66D and triggering one or more of the Gauss magnetism law contactors 50A-50F in any of 6 states so that an output signal is sent and a safety action occurs. The six Gauss magnetism law contactors 50A-50F replace the DTM, TLU and OLU of the safety divisions 202A-202D previously described in FIGS. 6 and 7. The present disclosure envisions the use of the following operating modes. During steady-state operation of the devices, a current (4 to 20 mA) is supplied to drive the devices. If the current exceeds the device baseline due to, for example, a sensed temperature rise above a predetermined level or a pressure rise above a predetermined level, the safety system response is actuated. If there is a loss of primary power, an uninterruptible power supply is used to maintain a constant voltage level within the circuitry. The electricity from this secondary supply will also be fed to the safety measuring devices, and the loss results in the safe shutdown of the system. In the event of a loss of all power, then the system either fails as is or to a safety state, depending on how the device is placed into an architecture by the circuit designer. The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. |
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060404914 | abstract | In a method and an apparatus for dewatering and containing radioactive, aqueous waste (44), the latter is introduced into a filtration container (12) and is ultimately disposed of in a disposable container structure (12, 48, 50), which comprises the filtration container (12) holding the dewatered waste (44), as well as an outer container (50) enclosing the filtration container (12). The filtration container is an inner sack (12) having a bottom (13) which is provided with a straining cloth and through which essentially all the dewatering is carried out. After the dewatering operation has been completed, the inner sack (12) is sealed and placed in the outer container (50) in order to be ultimately disposed of. For purposes of cleaning, the filtration water (17) may be recirculated through the waste during the dewatering operation. |
041773861 | abstract | A maximum density storage rack is provided for long term or semipermanent storage of spent nuclear fuel assemblies. The rack consists of storage cells arranged in a regular array, such as a checkerboard array, and intended to be immersed in water. Initially, cap members are placed on alternate cells in such a manner that at least 50% of the cells are left open, some of the caps being removable. Spent fuel assemblies are then placed in the open cells until all of them are filled. The level of reactivity of each of the stored fuel assemblies is then determined by accurate calculation or by measurement, and the removable caps are removed and rearranged so that other cells are opened, permitting the storage of additional fuel assemblies in a pattern based on the actual reactivity such that criticality is prevented. |
047088451 | abstract | A fuel assembly has a bundle of elongated fuel rods disposed in a side-by-side relationship so as to form an array of spaced fuel rods, an outer tubular flow channel surrounding the fuel rods so as to direct flow of coolant/moderator fluid along the fuel rods, a hollow water cross extending centrally through and interconnected with the outer flow channel so as to divide the channel into separate compartments and the bundle of fuel rods into a plurality of mini-bundles thereof being disposed in the respective compartments, and a plurality of spacers axially displaced along the fuel rods in each of the mini-bundles thereof. Each of the fuel rods includes an outer cladding tube with an inner clad surface and a plurality of fuel pellets contained within the tube. Each spacer is composed of a plurality of interleaved inner straps and an outer strap encompassing the inner straps. The interleaved inner straps and the outer strap have respective protrusions formed thereon and together define spacer cells into which the respective protrusions extend to maintain the fuel rods received through the spacer cells in laterally spaced relationships in respective corner, side and interior cells defined by the interleaved inner straps and the outer straps. The BWR fuel assembly includes several improvements which enhance its thermal-hydraulic performance. First, each of the fuel rods received through the corner cells of each spacer has a diametric size smaller than that of the fuel rods received through the side and interior cells of each spacer. Also, each of the protrusions in the corner cells extend a greater distance into the corner cells than the distance through which the protrusions in the side and interior cells extend into those cells, whereby increased coolant flow space is provided through the corner cells as compared to the side and interior cells so as to increase heat transfer from the corner fuel rods to the coolant. Second, perforations are formed in the outer strap at the locations of the corner and side cells of the spacer for reducing the amount of strap area adjacent the fuel rods received in the corner and side cells and thereby increasing coolant flow to the corner and side fuel rods. Third, a generally uniform poison coating, such as boron, is applied within at least a majority of the fuel rods, the poison coating being applied to either the fuel pellets or the inner clad surface of the cladding tube of each fuel rod in the majority. Additionally, a predetermined pattern of fuel enrichment is provided with respect to the fuel rods of each mini-bundle thereof which together with the uniform poison coatings within the fuel rods ensures that the peaking powers of fuel rods in the corner and side cells of the spacers are less than the peaking power of a leading one of the fuel rods in the interior cells of the spacers. |
claims | 1. A processor-based method for constructing an error map for a lithography process, the method comprising the steps of:using the processor, constructing a first error map using spatial error data, including lens signature data, compiled on a lithography tool used in the lithography process,using the processor, constructing a second error map using spatial error data, including pattern placement data, compiled on a mask used in the lithograph process, andcombining the first error map and the second error map to produce an overall error vector map for the lithography process. 2. The method of claim 1, further comprising the step of adjusting process variables to reduce errors represented in the overall error map. |
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description | This application is a divisional of U.S. patent application Ser. No. 10/164,460, filed Jun. 6, 2002, now U.S. Pat. No. 6,720,551, which is a divisional of U.S. patent application Ser. No. 09/824,452, filed on Apr. 2, 2001, now U.S. Pat. No. 6,410,907 and which is a continuation of U.S. patent application Ser. No. 09/398,698, filed on Sep. 20, 1999, now U.S. Pat. No. 6,246,052, issued Jun. 12, 2001, entitled “Flexure Assembly For A Scanner.” The present invention relates generally to a high resolution measuring device, and more particularly to a flexure assembly of a micro scanning device. Flexure carriages and devices are known in the art and are used for high resolution instrumentation and measuring equipment such as scanning probe microscopes and the like. These flexure devices typically carry thereon a probe or a sensor, or a specimen to be analyzed. Either the specimen or the probe is moved in very small increments in a plane relative to the other for determining surface or subsurface characteristics of the specimen. These devices are typically designed so as to move highly precisely and accurately in an X-Y plane and yet move very little in a Z direction perpendicular to the X-Y plane. The sensing probe typically measures surface defects, variation of the specimen's components, surface contour or other surface or subsurface characteristic. These types of devices may also be designed and utilized for other applications as well, such as imaging and measuring properties of computer microchips, computer disc surfaces, and other physical or chemical properties. The range of measurement for such devices is typically on the order of one Angstrom (Å) to several hundred microns (μ). In order to provide this type of extremely high resolution measurement, these devices require precise and minute micro-positioning capabilities within an X-Y plane and yet ideally permit no movement in a Z direction perpendicular to the plane. The flexure devices or carriages which hold the sensing probe or specimen of such devices are designed and utilized to provide just such movement. A known flexure carriage construction uses a piezoelectric actuator which utilizes an applied electric potential to micro-position portions of the flexure devices. Conventional or known devices typically can only provide very flat movement in an X-Y plane over a very small relative area. The larger the range of movement, the greater the out-of-plane movement becomes, (i.e., the motion becomes increasingly curved or less flat). This is because of the construction and arrangement of the piezoelectric element in the devices. The piezoelectric elements bend partially out of their longitudinal axis and therefore apply out of axis forces which induce errors. The out of axis forces and resultant errors increase with increased expansion of the piezoelectric elements. One device, disclosed in U.S. Pat. No. 5,360,974 and assigned to International Business Machines Corporation of Armonk, N.Y., provides a fairly flat movement in an X-Y direction or plane utilizing a dual frame arrangement where each frame is supported in opposite directions by flexible legs. Any Z direction motion perpendicular to the plane of one frame of the device is cancelled by movement of the other frame to maintain a very flat movement. However, the disclosed device utilizes long external piezoelectric elements which are oriented parallel to the plane of movement in order to eliminate or reduce rotation or yaw produced by the device. Such a device is much too large in certain applications. Applications that employ such minute micro-positioning and sensing technology increasingly demand higher resolution measurements. For example, computer technology continues to reduce the size and increase the package density for the electronic elements in microchips and circuits. Meanwhile, the volume in which they are being produced and thus the size of the wafers on which they are made is also increasing. It is therefore becoming increasingly necessary to provide flexure devices which are capable of relatively large ranges of movement in an X-Y plane, which prevent movement in a Z axis perpendicular to the plane, and which are relatively small in size so that they may be utilized in equipment that must be smaller, less expensive and more accurate. It should be understood that while measurement on a smaller scale is being discussed, changes to a sample on similar scales, such as nanolithography and micro-machining, may also need to be performed with this level of accuracy. Thus, the discussion herein is intended to encompass fabrication as well as measurement. The present invention is therefore directed to an improved flexure carriage and assembly useful in high resolution measurement and fabrication devices and instruments. The flexure carriage of the invention provides extremely flat and true movement in an X-Y direction or plane and prevents movement in a Z direction perpendicular to the X-Y plane. Additionally, the flexure carriage of the invention is capable of producing a relatively large range of motion in both the X and the Y direction while producing such a flat plane of motion. The flexure carriage of the invention produces such advantages and yet may be constructed in a relatively small and very sturdy or stiff package to produce the very flat plane of motion in the X and Y directions. To accomplish these and other objects, features and advantages of the invention, a flexure assembly or carriage is disclosed. In one embodiment the flexure carriage of the invention is formed of a substantially rigid material and has four elongate columns arranged spaced apart and parallel to one another. Each of the elongate columns has a first and a second end. The carriage also has four first cross members arranged so that each first cross member extends between and interconnects two first ends of the elongate columns. The carriage also has four second cross members arranged so that each second cross member extends between and interconnects two second ends of the elongate columns. The carriage has a translating section that is disposed within a space between the elongate columns generally equidistant between the first and second ends of the elongate columns. The translating section is interconnected to the elongate columns. The carriage has a plurality of flexures wherein one flexure interconnects each first end of each elongate column to each first cross member. One flexure interconnects each second end of each elongate column to each second cross member. At least one flexure interconnects each elongate column with a translating section. The flexures permit the translating section to move according to an applied force in a plane which is essentially perpendicular to the orientation of the elongate columns. The symmetry of the flexure carriage eliminates virtually any movement in a Z direction perpendicular to the X-Y plane. In one embodiment, a pair of flexures interconnect each elongate column with the translating section. One flexure of each pair is disposed adjacent the translating section on each elongate column nearer the first end. The other flexure of each pair is disposed adjacent the translating section on each elongate column nearer the second end. In one embodiment, each flexure of the flexure carriage includes a first pair of opposed slots formed transversely and extending toward one another into one of the elongate columns. A first web of the substantially rigid material is left remaining between the first pair of slots. A second pair of opposed slots are spaced from the first pair of slots in the same elongate column and formed transversely and extending toward one another into the elongate column. A second web of the substantially rigid material is left between the second pair of slots. The first web and the second web are arranged perpendicular to one another and spaced apart along the same elongate column. In one embodiment, a flexure carriage as described above, is provided with a first piezoelectric assembly connected to the translating section for moving the translating section along only a first linear path generally perpendicular to the elongate columns. A second piezoelectric assembly is connected to the translating section for moving the translating section along only a second linear path generally perpendicular to the elongate columns and perpendicular to the first linear path. In one embodiment, a high resolution measurement device is constructed according to the invention and has a support structure carrying various elements of the device. The measurement device also has a measuring instrument which is carried by the translating section of a flexure carriage provided as described above. Each of the piezoelectric assemblies is affixed at one portion to the support structure of the measurement device and affixed to a portion of the translating section of the flexure carriage for providing applied forces to the translating section for moving the translating section and the measuring instrument therewith. These and other objects, features and advantages of the present invention will be better understood and appreciated when considered in conjunction with the following detailed description and accompanying drawings. It should be understood however that the following description is given by way of illustration and not of limitation though it describes several preferred embodiments. Many changes and modifications may be made to the disclosed embodiments without departing from the spirit and scope of the present invention and the invention is intended to include all such modifications. The present invention generally discloses a micro-positioning motion transducer in the form of a flexure device. The flexure device includes a rigid frame or support structure securely carrying a flexure carriage assembly. The flexure carriage assembly includes a carriage having a plurality of structures which permit high precision translational movement in an X and a Y direction defining a substantially flat plane of movement. The structure precisely transmits forces at least partially applied in the X direction that are converted to translational movement of a translational section only in the X direction. The structure also transmits forces at least partially applied in the Y direction into translational movement of the translational section only in the Y direction. The structure essentially prevents any substantial movement of the translational section of the carriage in a Z direction perpendicular to the X-Y plane. The flexure carriage assembly includes a pair of piezoelectric assemblies that drive the translating section of the flexure carriage. One piezoelectric element drives the translating element in the X direction and the other piezoelectric element assembly drives the translating element in the Y direction. The piezoelectric assemblies are oriented substantially parallel to the Z axis, though they impart precision movement in the X-Y plane perpendicular to the Z axis. Referring now to the drawings. FIG. 1 illustrates generally a flexure device 20 having a frame or support structure 22 and a flexure carriage assembly 24 rigidly affixed to and supported by the frame. The carriage assembly 24 includes a carriage 25 and also includes a pair of piezoelectric assemblies 26 each having opposed distal end couplers 28 fixed to the frame 22. The piezoelectric assemblies 26 have a central coupler 30 fixed to a translating section 29 of the flexure carriage 25. In general, the frame or support structure 22 can be a separate frame element as is illustrated in FIG. 1 that is further attached to a suitable instrument or device. Alternatively, the frame 22 can be an integral portion of the instrument or device (not shown). The piezoelectric elements 26 are energized from a source of electric energy (also not shown) and, in accordance with known principles of such elements, the piezoelectric assemblies 26 move according to the applied energy. Since the elements have a central coupler 30 coupled to the translating section 29 of the flexure carriage 25, the translating section as described in detail below, moves in accordance with the motion of the piezoelectric assemblies 26. As described and shown herein, the movement of the piezoelectric assemblies 26 and the translating section 29 of the flexure carriage 25 is highly precise and has a relatively large range of motion. However, as discussed above, the typical and desirable range of motion for such a device is small in reality, for example, on the order of one Å to about a few hundred μ. FIG. 2A illustrates the flexure carriage assembly 24 in perspective view. FIG. 2B illustrates the carriage 25 in perspective view. FIGS. 3 and 4 illustrate two sides in plan view of the carriage 25 which have been arbitrarily selected for illustration. The carriage need not have a front, back and designated sides. However, for illustrative purposes, FIG. 3 illustrates a view arbitrarily shown as a back surface of the carriage 25, and FIG. 4 illustrates a side surface of the carriage which can be either side of the carriage when the carriage is rotated 90 degrees about a vertical axis relative to the views in FIGS. 3 and 4. Turning again to FIGS. 2–4, the flexure carriage 25 of the carriage assembly 24 is in the form of a rectangular three-dimensional structure. The carriage 25 is preferably made from a substantially rigid material such as stainless steel or the like wherein the material is not too brittle, soft or flexible so that it may perform the intended functions of the invention. The carriage 25 is comprised of a substantially symmetrical structure and is described herein including a top and bottom end as well as front, rear and side surfaces. However, these designations are arbitrarily selected and utilized only for simplicity of description. It will be obvious to one of ordinary skill in the art that the carriage as well as the flexure device 20 can be oriented in any manner and manipulated to any orientation without departing from the scope of the invention. With that in mind, FIG. 2A illustrates the flexure carriage assembly 24 and FIG. 2B illustrates the carriage 25. The carriage 25 includes four elongate vertical columns disposed parallel to one another and spaced equal distance from one another. Each of the elongate columns includes a first end, herein designated as a top end and a second end, herein designated as a bottom end. The four elongate columns are identified herein for simplicity as 32A, 32B, 32C and 32D. The respective top ends are identified as 34A, 34B, 34C and 34D. The respective bottom ends 36 are represented by 36A, 36B, 36C and 36D. Each of the elongate columns is essentially the same length and oriented so that catch of the top ends terminate in the same plane relative to one another and each of the bottom ends terminate in the same plane relative to one another. Each of the top ends of the carriage 25 are interconnected to adjacent top ends of corresponding elongate columns by first cross members 38A–D. For example, the cross member 38A extends between the top ends 34A and 34B of the adjacent elongate columns 32A and 32B. Similarly, the cross member 38B extends between the top ends 34B and 34C, the cross member 38C extends between the top ends 34C and 34D, and the cross member 38D extends between the top ends 34D and 34A. The first cross members 38A–D combine to define an arbitrary top 39 of the carriage 25. Similarly, four second cross members 40A–D extend between the bottom ends 36A–D of the elongate columns 32A–D in an identical manner. The four second cross members 40A–D combine to define an arbitrary bottom 41 of the carriage 25. Each of the cross members 38A–D and 40A–D are arranged at right angles relative to one another when viewed from either the top 39 or the bottom 41 of the carriage 25. Thus, the combination of the cross members 38A–D and 40A–D along with the elongate columns 32A–D define a right angle three dimensional parallelogram. In the present embodiment, all of the cross members are of equal length so that the top 39 and bottom 41 are square. A symmetrical shape is preferred for the carriage but the overall cross section need not be a square shape in order to fall within the scope of the invention. The elongate columns 32A–D and the cross members 38A–D and 40A–D are each preferably integrally formed with one another and therefore, without more, would form a rigid frame structure. However, the carriage 25 of the flexure device 20 must allow for certain flexible movements as described below in detail. The flexible nature of the carriage 25 is provided by adding a plurality of flexures 50 to the structure of the carriage 25. The construction of one flexure 50 is now described in detail below. Subsequently, the placement of the flexures 50 on the carriage 25 is described along with the function and flexible nature of the carriage. In order to simplify the description of the carriage 25, a coordinate system is arbitrarily chosen and utilized in conjunction with the discussion herein. Referring to FIG. 2B, an X axis or X coordinate is defined along one axis perpendicular to the four elongate columns 32A–D and perpendicular to arbitrary side surfaces 52 and surface 54. A Y axis as illustrated in FIG. 2B is perpendicular to the X axis and also perpendicular to an opposed front 56 and back 58 of the carriage 25. The front and back 56 and 58, respectively, are perpendicular to the sides 52 and 54. A Z axis is also illustrated in FIG. 2B disposed parallel to and between to the four elongate columns 32A–D and perpendicular to the X-Y plane. The arbitrary back 58 is illustrated in FIG. 4 and the arbitrary side 52 is illustrated in FIG. 3. FIG. 5 illustrates the construction of one flexure 50 taken at the juncture between the elongate column 32C at its top end 34C and the cross member 38B. FIG. 6 illustrates the same flexure 50 viewed 90 degrees relative to the flexure shown in FIG. 5. Each flexure 50 includes an interior first material web 60 nearer the X and Y plane and an exterior second material web 62 nearer either the top 39 or bottom 41 of the carriage and essentially perpendicular relative to the first material web 60. Each material web is formed by creating a pair of opposed slots 64 perpendicularly or transversely into opposed surfaces of the appropriate elongate column 32. Thus, each material web 60 and 62 is a thin web or membrane of material between the slots 64 and extends the entire width of the appropriate elongate column 32 when viewed into one of the slots 64. Therefore, the view of the flexure 50 in FIG. 5 shows the interior material web 60 on an end view so that the thin-walled construction is visible. The exterior material web 62 is illustrated lengthwise. The same flexure 50 is illustrated in FIG. 6 where the interior material web 60 is lengthwise and the exterior material web 62 is in an end view. Each flexure 50 permits linear movement in the X direction and the Y direction but not in the Z direction. The web 60 will permit slight lateral movement of the elongate column 32C relative to the cross member 38B when a force is applied in the X direction. The web 62, because it is oriented lengthwise in the X direction and rigidly connected to both the cross member 38B and the elongate column 32C, prevents movement in the X direction. However, when viewed at a 90 degree angle as shown in FIG. 6, the web 62 permits movement in the Y direction upon an applied Y direction force. Each flexure 50 therefore permits movement in the X direction and the Y direction upon an applied force, respectively, in the X or the Y direction. Each flexure 50 also prevents any movement in the Z direction based on the rigid connections between each structural element connected to each flexure 50. The construction of each flexure 50 also enhances direct movement only in the direction of the applied force in that one web is oriented to permit movement only in one linear direction wherein the other web is oriented to permit movement in only one linear direction perpendicular to the linear direction of movement for the other web. Each web is also constructed to prevent any movement at that web other than in its intended direction of movement. Therefore, each flexure 50 provides a precise X or Y flexure according to the applied force and prevents any other movement and particularly prevents movement in the Z direction. As best illustrated in FIG. 2A, a flexure 50 is disposed at each top end 34A–D and each bottom end 36A–D between the respective elongate columns 32A–D and cross members 38A–D and 40A–D. Each flexure 50 disposed at the top ends 34 of the elongate columns 32 is oriented so that all interior webs 60 are oriented in the same direction relative to one another and all exterior webs 62 are oriented in the direction relative to one another. Each of the flexures 50 disposed at the bottom ends 36 of the elongate columns 32 is also oriented identically relative to one another. Each flexure 50 disposed at opposite ends of each of the elongate columns 32A–D are preferably oriented as mirror images of one another to provide symmetry in the construction of the carriage 25. For example, the flexures 50 on ends 34A and 36A of the elongate column 32A each have the exterior material webs 62 oriented parallel relative to one another and have the interior material webs 60 oriented parallel relative to one another. Each of the elongate columns 32A–D also has at least one, and preferably, a pair of flexures 50 disposed near the center defined by the X axis and Y axis noted in FIG. 2A with one flexure 50 being disposed on each side of the mid-line or X-Y plane. Again, each of these interior flexures 50 are disposed so that they are mirror images relative to one another. Therefore, the interior material webs 60 are oriented parallel relative to one another and the exterior material webs 62 are also oriented parallel relative to one another. Additionally, each of the flexures disposed near the mid-line 50 is oriented identically on each of the elongate columns 32A–D to provide uniform flexure. The translating section 29 is connected to each of the mid-line flexures 50 of the carriage. The translating section 29 is disposed corresponding to the X-Y plane of the carriage 25 so that the carriage is essentially symmetrical on either the top portion or the bottom portion of the carriage 25 relative to the translating section 29. A force F applied to a back surface 68 of the translating member in the X direction will cause all of the flexures 50 to flex at the appropriate material web to permit movement in the X direction as seen in phantom lines in FIG. 7. Because the carriage 25 is constructed symmetrically, any small movement in a Z direction of any particular flexure 50 on one side of the X-Y plane is negated by mirror image movement of the corresponding flexure on the other side of the X-Y plane. This mirror image movement also offsets empirical strain on the carriage during microactuator actuation. Thus, the translating section 29 moves in a very flat movement along the X-Y plane at the center axis of the carriage. A force applied to a side surface 70 of the translating section 29 in the Y direction causes each flexure 50 to bend slightly about the appropriate material web oriented to permit movement in the Y direction. Again, because of the symmetry of the structure, movement in the Y direction of the translating section 29 will be a very flat planar movement along the X-Y plane. Because of the construction of the flexures 50 and the carriage 25, any load applied along the Y axis is transmitted as movement only in the Y direction and yields no movement in the X or the Z direction. Loads applied in both the X direction and the Y direction simultaneously will move the translating section 29 in both the X direction and the Y direction but only for a distance according to the force vectors in each direction respectively. An X direction force produces no substantial movement in the Y direction, and a Y direction force produces no substantial movement in the X direction. Therefore, extremely accurate results are produced by utilizing the carriage assembly 24 of the invention. As illustrated in FIGS. 3 and 4, the carriage 25 includes a plurality of stiffening beams 80 spanning each adjacent pair of elongate columns 32A–D and running essentially parallel to the top and bottom cross members 38A–D and 40A–D. Each stiffening beam 80 is connected to an elongate column 32A–D at its opposite ends 82 and 84 by a material web 86. Each material web 86 is formed similar to any one of the material webs 60 or 62 described above in that a pair of opposed notches or slots 88 are cut into the carriage material adjacent to each of the ends 82 and 84 to form a thin web of material interconnecting the stiffening beams 80 to the elongate columns 32A–D. Each stiffening beam 80 essentially locks the adjacent elongate columns 32A–D laterally relative to one another so that if they move in either the X or the Y direction, they will move in tandem and not move closer to or further away from one another. However, the web 86 at each end of each stiffening beam permits the stiffening beams to pivot slightly relative to the respective one of the elongate columns 32A–D so that the carriage 25 can perform its intended flexure function by allowing the translating section 29 to move in the X-Y plane. As illustrated in FIGS. 3 and 4, the front 56, back 58, and sides 52 and 54 can include a stiffening beam 80 adjacent to each of the flexures 50 to provide lateral support to the carriage structure. As illustrated in FIGS. 1 and 2B, one side, such as the front 56, can be devoid of a stiffening beam to permit access to the interior of the carriage 25. Access may be necessary in order to activate or install or replace a sensor probe (not shown) or other apparatus attached to or carried by the translating section 29 of the flexure device. The number of stiffening beams 80 as well as the position or location of the stiffening beams can vary considerably without departing from the scope of the present invention. The addition and strength of the stiffening beams is determined by the particular application for which the flexure device 20 is intended. Some applications may require a stiffer carriage 25 while other applications may require a more flexible structure. As illustrated in FIGS. 1 and 2A, the back 58 and one side 52 are coupled to the piezoelectric assemblies 26. In the present embodiment, each piezoelectric assembly 26 has a pair of piezoelectric elements 90 extending symmetrically outward from a central block coupler 30 as illustrated in FIGS. 2A and 8. The coupler 30 is rigidly affixed to the back surface 68 of the translating section 29 for movement therewith. The coupler 30 includes a pair of symmetrically opposed flexures 50 essentially identical in construction to those described above for the carriage 25. Each of the flexures 50 is attached to one of the piezoelectric elements 90. Each piezoelectric element 90 is attached at their opposite distal ends to a corresponding end coupler 28, which is rigidly affixed to the frame or support structure 22 and retained thereby. Each of the end couplers 28 also includes a flexure 50 for coupling the piezoelectric elements 90 to the end couplers 28. Each piezoelectric element 90 is electrically connected to a power supply (not shown) wherein the power supply is utilized to energize each piezoelectric element and to move each element and hence the translating section 29. The flexures at each coupler 30 and 28 permit the piezoelectric elements 90 to drive the central coupler 30 and hence the translating section 29 as described above in either the X direction or the Y direction or both depending on how the piezoelectric assemblies 26 are energized. The piezoelectric elements 90 are intended to be identical in nature for each piezoelectric assembly 26 so that each piezoelectric element 90 of a particular assembly produces an equivalent movement. This insures that no out of balance force is applied to the translating section 29. Additionally, the movement produced by each piezoelectric assembly 26 is essentially only in the X or the Y direction because of the symmetrical construction of the piezoelectric assemblies 26 and because each end coupler 28 is rigidly affixed to the frame 22. Any movement which would otherwise be created in the Z direction at one end of the piezoelectric assembly is cancelled by an opposite and equal reaction at the other end of the assembly 26. As illustrated in FIG. 2A, the central couplers 30 of each piezoelectric assembly 26 are different in construction. However, the only difference is in the size of the rigid central portion of the couplers 30 affixed to the translating section 29. The size of this central portion of the central couplers is merely adapted to coincide or correspond to the size and shape of the particular surface 68 or 70 of the translating section 29 to which the coupler is attached. The shape and construction of the end couplers 28 as well as the central couplers 30 may vary considerably without departing from the scope and spirit of the invention. Additionally, the particular size, type and configuration of the piezoelectric elements may also vary considerably. The invention is not intended to be limited to any particular piezoelectric element construction. To summarize the invention, the structure of the flexure carriage 25 transmits an applied force in the X direction into an X direction movement of the translating section 29 without producing any movement in the Y direction or the Z direction. Similarly, an applied force in the Y direction produces movement of the translating section 29 only in the Y direction without producing any movement in the X direction or the Z direction. An applied force by both of the piezoelectric assemblies 26 produces corresponding movement in both the X and the Y direction wherein the movement in the X direction corresponds only to the applied X direction force and movement in the Y direction corresponds only to the applied Y direction force. The construction of the flexure device of the invention produces a highly accurate X-Y coordinate movement and produces such movement in a very flat X-Y plane virtually over a relatively large area while eliminating any significant movement of the translating section in the Z direction. Many modifications and changes to the invention as described may be made without departing from the spirit and scope of the invention. For example, the size, shape and construction of each of the elongate columns 32A–D, cross members 38AD and 40A–D, flexures 50, material webs 60, 62, and 84, slots 64 and 86, and translating sections 29 may vary considerably without departing from the invention. The size, shape and construction as well as the materials utilized to produce the flexible carriage 25 may be selected and determined according to a particular application for which the device 20 is intended. The compact nature of the overall carriage assembly 24 including the piezoelectric elements 26 permits utilizing the invention in application environments smaller than previously possible. This is accomplished by the novel construction of the invention wherein the piezoelectric assemblies 26 are oriented in the Z direction relative to the X-Y plane of movement of the translating section produced by the piezoelectric assemblies. While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept. |
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043205283 | abstract | The present invention relates to methods and apparatus for cleaning and removing the buildup of products of corrosion, oxidation, sedimentation and comparable chemical reactions from various portions of heat exchanger systems such as the location wherein the primary heat exchanger tubes come in contact with support plates for those tubes, and the base of said heat exchanger. The corrosive scale, oxides and other materials can cause denting of the primary heat exchanger tubes due to the compressive force of the oxides, scale, and other materials, and therefore adversely affects the heat exchanging ability of the heat exchanger system. |
052372332 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the preferred embodiment of the present invention will be described. An optoelectronic active circuit element 10 in accordance with the present invention comprises a light source means 12, an optical control means 14 and a photocell means 16. The optical control means 14 is a photorefractive material that is intimately interposed between a light emitting surface of the light source means 12 and a light receiving surface of the photocell means 16. Unlike the prior art secondary or intermediary electrical/optical hybrid devices having optical inputs and outputs with an electrical intermediary, the optoelectronic active circuit element 10 of the present invention is an electrical/optical hybrid device that has an electrical input 20 and an electrical output 22 with an optical intermediary in the form of light source means 12 and optical control means 14. Also, unlike the prior art photodetectors and photochoppers, the optoelectronic active circuit element 10 of the present invention is capable of emulating a traditional active element (i.e., a transistor or a diode) by operating in the active range of an I-V curve. The optoelectronic active circuit element 10 operates as an active circuit element by providing an input voltage V.sub.input 20 that controls the transmissivity of the optical control means 14. As a result, the photons 22 emitted by the light emitting surface of the light source means 12 are modulated before striking the light receiving surface of the photocell means 16. In the embodiment as shown in FIG. 1, the photons 22 are amplitude modulated to decrease the number of photons 24 that are allowed to pass through to the light receiving surface of the photocell means 16. In an alternative embodiment described in greater detail hereinafter, the photons 22 may also be frequency modulated by the optical control means 14 to produce the desired effect of the optoelectronic active circuit element 10. The photons 24 striking the light receiving surface of the photocell means 16, in this case a photovoltaic cell, generate an open circuit voltage V.sub.output that is dependent upon the frequency and intensity of the photon energy absorbed by the photo detector means 16. As such, the optoelectronic active circuit element 10 behaves like a traditional active circuit element (i.e., a triode vacuum tube, a transistor or a diode) in that the output voltage or current is a function of the input voltage or current. Unlike conventional semiconductor transistors or diodes, the optoelectronic active circuit element 10 exhibits the characteristic of a vacuum tube in that the energy source can be completely independent from the input voltage or current. This isolation of the input signal from the energy source results in a favorable signal-to-noise ratio (SNR) for the optoelectronic active circuit element 10 of the present invention. SELF-POWERED ACTIVE CIRCUIT ELEMENT In the preferred embodiment of the present invention shown in FIG. 2 and described in the previously identified parent application entitled LIGHT EMITTING POLYMER ELECTRICAL ENERGY SOURCE, the light source means 12 is a light emitting polymer (LEP) material 60 and the photocell means 16 are photovoltaic cells 62. By using the LEP material 60, the preferred embodiment of the present is self-powered in that the energy for the light source means 12 is contained within the light source itself. The LEP material 60 is optically separated from the photovoltaic cells 62 by an optical control means 64 for controlling the amount of light that may be absorbed by the photovoltaic cells 62. The optical control means 64 is a photorefractive material, such as a liquid crystal display (LCD) or lead lantium zirconium titinate (PLZT) or similar material, that is either transparent or opaque, depending upon the voltage or current applied to the material. By controlling the amount of light that may be absorbed by the photovoltaic cells 62, the optical control means 64 also controls the output of the photovoltaic cells 62 and, hence, operates as either a voltage or current regulator depending upon the particular circuit that utilizes the electrical energy source of the present invention. In the preferred embodiment, the LEP material 60 is a tritiated organic polymer to which an organic phosphor or scintillant is bonded. Such an LEP material was obtained from Amersham International plc, Amersham Place, Little Chalfont, Buckinghamshire, England, and, pending NRC regulatory approval, may be available from Amersham International plc. Such an LEP material is described in the United Kingdom patent application, Ser. No. 890,5297.1 by Colin D. Bell, entitled TRITIATED LIGHT EMITTING POLYMER COMPOSITION, filed in the British Patent Office on Mar. 8, 1989, the disclosure of which is hereby incorporated by reference herein. It should be recognized that other types of LEP material known in the prior art may also be utilized with the present invention. (e.g., U.S. Pat. Nos. 3,033,797, 3,325,420 and 3,342,743). Those aspects of the LEP material 60 that allow it to be used effectively in the present invention are discussed in greater detail in the previously identified parent application. LIGHT SOURCE MEANS Although the preferred embodiment of the light source means 12 is described in terms of the LEP material 60, it will be recognized that a variety of light sources are contemplated for use with the present invention. For example, the light source means 12 might be comprised of a light emitting diode or a semiconductor laser powered by an external power supply. Another variation on the self-powered aspect of the LEP material 60 is to provide a chemoluminiscient material that would be activated to operate the optoelectronic active circuit element 10 for a short period of time, for example, as an emergency transmitter. As discussed in greater detail hereinafter, the frequency bandwidth of the emitted light energy may also be used by the present invention, both in terms of its effect on the efficiency of the present invention and on the modulation of the photon energy by the optical control means 14. The preferred embodiment of the light source means 12 is described in terms of a light source having at least one light emitting surface. As will be appreciated by a person skilled in the art, the preferred embodiment of the present invention is well-suited for the type of planar construction techniques used with integrated circuits. The materials of the preferred embodiment are capable of being integrated using well-known deposition and sputtering techniques for constructing the integral combination of the LEP material 60, the photocell 62 and the photorefractive material 64. These techniques allow the optoelectronic active circuit element 10 to be miniaturized. It will also be seen that this embodiment of the present invention may be incorporated with traditional semiconductor integrated circuit devices. Although the preferred embodiment of the light source means 12 utilizes a planar light emitting surface, other shapes and configurations of light source may also be within the scope of the present invention. For example, the LEP material 60 may be cast as an entire volume about the combination of one or more photovoltaic cells 62 having a photorefractive optical control means 64 sputtered thereon. Alternatively, the light source may be optical intimate, but physically remote from the optical control means, provided that there is suitable optical mating means (e.g., bundled optical fibers, light pipes or light channels) to transport the known photon energy from the light source to the optical control means. PHOTOCELL MEANS In the preferred embodiment as described in the previously identified parent application, the photovoltaic cells 62 are amorphous thin-film silicon solar cells, Model No. 035-01581-01, available from ARCO Solar, Inc., Chatsworth, Calif., or their equivalent. These cells have their highest efficiency conversion (greater than 20%) in the blue range of the spectrum of visible light to match the frequency bandwidth of the emitted light of LEP material incorporating a phosphor that emits in the blue range. While the particular photovoltaic cells 62 in the preferred embodiment have been selected to match the blue range of the spectrum of visible light, it should be apparent that other photovoltaic cells may be selected to match the bandwidth of light emitted at other frequencies. In particular, as discussed below, it is known that a new solar cell, known as the Sunceram II (trademark), available from Panasonic's Industrial Battery Sales Div., is claimed to more efficient than conventional amorphous silicon solar cells, especially in the red range of the spectrum of visible light. A standard type of photovoltaic cell having a p-n junction is shown in FIG. 6. An incoming photon of energy hv creates an electron-hole pair and the junction field accelerates the electron toward the n-side of the junction and the hole toward the p-side of the junction. The separation of charge leads to a voltage across the junction, the maximum value of which is V.sub.oc. The ideal bandgap energy E.sub.g for a given photon energy should be one which is just a few tenths of an eV below the photon energy. Because the absorption coefficient for the photon increases as the photon energy increases above E.sub.g, the photon energy should be somewhat greater than E.sub.g to obtain good absorption of the photons. Referring to FIG. 7, an equivalent circuit for a photovoltaic cell and the diode equation which describes the operation of the photovoltaic cell are shown. As can be seen from the descriptive equation in FIG. 7, the current in the photovolatic cell at the operating point is the difference between the light generated current and oppositely direct currents because of diode currents and shunt currents. Clearly, the photovolatic cell will perform most efficiently when these oppositely-directed currents are minimized. This is especially important for the small light-generated currents that are experienced at low light intensities. Using the photovoltaic cell descriptive equation with the assumed diode parameters, the equation can be solved for the maximum power point parameters. This solution should yield an upper limit for the efficient of the photovoltaic cell with the given operating parameters. With the considerations understood, one embodiment of photocell mans 16 of the present invention is an amorphous silicon photovoltaic cell comprised of an intrinsic layer sandwiched between a p-layer and an n-layer. The emitted light energy enters through the p-layer. The entire photovoltaic cell is sandwiched between two conductive layers, one of which is transparent and forms the light absorbing surface of the photocell means 16. A 1/4".times.1/2" amorphous silicon cell was constructed and I-V curves were measured for a number of intensities at different wavelengths. The results of these measurements are shown in FIG. 8. From the I-V curves in FIG. 8, the quantum efficiency of the photovoltaic cell is plotted as a function of wavelength as shown in FIG. 9. Given the curve of FIG. 9, the cell current density J.sub.L can be integrated to predict a total short circuit current for a given intensity of each of the desired spectra. The cell power output can then be found from a characteristic curve for that cell. FIG. 10 shows the results of this determination indicating the incident intensity of the preferred embodiment of the present invention. The result for the cell shown in FIGS. 7-10 had a relatively thick i-layer in order to absorb the longer wavelengths in that spectrum. Further enhancement in efficiency may be achieved by reducing the cell i-layer thickness to a value more appropriate for the wavelengths of the preferred embodiment (615 nm). FIG. 11 shows the construction of such a cell for the 615 nm spectrum. The layer thickness in this cell which would provide the best efficiency for the 615 nm spectrum can be determined by experiment using the criteria just outlined. The applicant estimates that, when properly optimized, this cell should proved for a 12% or higher quantum efficiency. Although the preferred embodiment of the photocell means 16 is described in terms of the photovoltaic cells 62, it will be recognized that a variety of photovoltaic and photoconductive devices are contemplated for use with the present invention. For example, the photocell means 16 might be comprised of a semiconductor avalanche photodiode or phototransistor; or the photocell means 16 might be made of a metal-semiconductor type photocell or a Schottky-barrier type photocell. As will be appreciated by one skilled in the art, the selection of the type of photocell means 16 will depend upon numerous factors, including: the band gap energy, the material selected, the construction techniques, the desired efficiency. For a more detailed discussion of these considerations reference is made to J. Wilson and J. Hawkes, Optoelectronics: An Introduction, pgs. 286-327, Prentice Hall (1983). One of the more interesting alternative embodiments of the present invention involves the use of a phototransistor for the photocell means 16. In addition to the gain introduced by the optical control means 14, the phototransistor can provide an additional gain for the optoelectronic active circuit element 10. The net effect is a cascaded two-stage gain device that greatly increase the magnitude of the gain swing of the active circuit element. EQUIVALENT CIRCUIT Referring now to FIG. 3, the equivalent circuit for the optoelectronic active circuit element 10 will be described. The light source means 12 is shown as a voltage source and a transformer for isolating the energy source from the remaining portions of the equivalent circuit. The optical control means 14 acts as a transistor with the base current being supplied by the input voltage V.sub.input 20. The photocell means 16 is shown as its series resistance value connected to the emitter of the transistor with the output voltage V.sub.output 26 being measured across this resistance. In the equivalent circuit as shown, an external capacitor 30 is used to decouple the D.C. components of the output voltage V.sub.output 26. In general, the characteristic function of the optoelectronic active circuit element 10 is driven by the change in the refractive index of the optical control means 14 and the corresponding change in intensity, frequency or both of the photon energy incident upon the optical control means 14. The change in the index of refraction of a photorefractive material may be expressed in terms of the applied electric field as: EQU 1/.DELTA.n.sup.2 =r.epsilon.+P.epsilon..sup.2 where r is the linear electro-optic coefficient and P is the quadratic electrooptic coefficient. In solids, the linear variation in the refractive index is known as the Pockels effect and the non-linear variations in the refractive index is referred to as the Kerr effect. For a more detailed discussion of the implications of the Pockel and Kerr effects on the index of refraction of a photorefractive material, reference is made to J. Wilson and J. Hawkes, Optoelectronics: An Introduction, pgs. 85-124, Prentice Hall (1983). It will be appreciated that the characteristic function of any particular embodiment of the present invention will be a complex function dependent ultimately upon the atomic level interaction of the photons and electrons within the photorefractive material, as well as the optical relationships among each of the component materials of the optoelectronic active circuit element 10. Although the applicant has not provided a representative example of the various types of characteristic functions of the optoelectronic active circuit element of the present invention, it is believed that the characteristic function of the device will include, at least, a linear region, an active region and a saturation or cutoff region. The precise nature of the characteristic equation will depend upon the particular materials chosen for the device and the manner in which these material are fabricated, the mathematical representation of which is beyond the scope of the present application. Although the optoelectronic active circuit element of the present invention has been described in terms of an active circuit element, it will be recognized by one skilled in the art that the circuit element of the present invention is capable of emulating many types of active circuit elements such as a transistor/switch, a transistor/amplifier, a diode/rectifier, a diode/detector, and a Schmidt trigger, as well as numerous types of logic elements such as AND gates, OR gates, inverters, and memory cells. OPTICAL CONTROL MEANS The optical control means 14 of the preferred embodiment is comprised of a photorefractive material that modulates the light incident upon the surface of the optical control means adjacent the light emitting surface of the light source means 12. When an electrical field is applied across a photorefractive medium, the distribution of electrons within the medium is distorted so that the polarizability and hence the refractive index of the medium changes anisotropically. In the present invention, the electrical field is applied in the form of an input voltage or an input signal to the optical control means 14. As will be appreciated by one skilled in the art, the physical application of the electrical signal to the photorefractive medium (i.e., which surfaces are the electrical contacts applied to and the thickness of the dimension across which the electric field will propagate) will effect the photorefractive effect obtained from the medium. In the preferred embodiment, a high impedance device is used to drive the input signal to modulate optical control means 14, thereby decreasing the switching capacitance and the switching time of the optical control means 14. In the preferred embodiment, a small PLZT optical control means having dimensions of approximately 0.05".times.0.05" will have a capacitance in the 10 pF range. This device would be capable of switching speeds on the order of 400 MHz for input signals of 5 volts. The normal index of refraction of PLZT is on the order of 2.5. The index of refraction of thin film PLZT 280-100 is 2.6. These indices of refraction are desirable in that the typical index of refraction of the preferred polymer light source is in the range of 1.5 and the typical index of refraction of the preferred amorphous silicon photocell is in the range of 3.5. For a typical PLZT material, the photorefractive capabilities of the material are such that it can modulate 65% of the photon energy transmitted through the material in response to relatively low electrical fields. The switching speeds of the PLZT are also very fast, with modulation capabilities on the order of 10-20 GHz. Referring now to FIG. 4, a frequency plot of the frequency distribution of a frequency modulated embodiment of the present invention is shown. This plot demonstrates how the index of refraction of the optical control means 14 of the present invention could be used to alter the frequency of the transmitted light. Assuming that the photocell means 16 is responsive only to the narrow frequency band 50, the change in the frequency of the light passing through the optical control means 14 will produce a corresponding change in the voltage output of the photocell means 16. In this embodiment, the optical control means 14 is comprised of an interference filter 52 in combination with a photorefractive material 54. The interference filter means 52 polarizes the incident photon energy such that relatively small changes in the index of refraction of the photorefractive material 54 allow the optical control means 14 to function as a frequency bandpass filter. The interference filter means 52 may be any type of well-known polarizing filter, including an interdigitated grid. The PLZT material of the preferred embodiment may be capable of frequency modulation down to as fine a resolution as 2 nm wavelengths. Although the photorefractive material that comprises the optical control means 14 of the preferred embodiment is shown as being responsive to an electrical signal, it will also be recognized that other types of input signals may be used to activate a change in the index of refraction of certain types of photorefractive materials. For example, certain photorefractive materials may operate as magneto-optical devices, responding to a Farrady magnetic effect. Other types of photorefractive materials may be sensitive to pressure or to acoustical signals. Still other types of photorefractive materials may be sensitive to temperature variations. As a result, the present invention has numerous applications as a sensing device and, in particular, a self-powered sensing device that is capable of amplifying the sensed condition to enable easier detection. OPTICAL MATING MATERIALS Because the characteristic function of the optoelectronic active circuit element 10 is dependent upon the index of refraction of the optical control means 14, the optical mating of the light source means 12, the photocell means 16 and the optical control means 14 is an important consideration in both the efficiency of the device, as well as the characteristic function exhibited by the device. Although it would be possible to factor multiple changes in the indices of refraction of the various components into the characteristic function of the device, it is preferable to minimize the impact of any changes introduced into the device by changes in the indices of refraction of all materials other than the photorefractive material. To accomplish this, the preferred embodiment can include a first optical mating means optically interposed between the light emitting surface of the light source means 12 and the optical control means 14 and a second optical mating means optically interposed between the optical control means 14 and the light collecting surface of the photocell means 16. The purpose of the optical mating means is to maximize the transmisivity of the emitted light energy by minimizing the boundary condition reflections among the various materials. In the preferred embodiment, the first and second optical mating means are comprised of an optical gel, such as Rheogel 210C or Dow Corning Optical Fluid. The first optical gel should have an index of refraction equal to the square root of the product of the index of refraction of the light source means 12 and the index of refraction of the optical control means 14. The second optical gel should have an index of refraction to the square root of the product of the index of refraction of the optical control means 14 and the index of refraction of the photocell means 16. As an alternative to the use of a separate optical mating means, a first and second sputtering material may also be used. The first sputtering material should have an index of refraction equal to the square root of the product of the index of refraction of the light source means 12 and the index of refraction of the optical control means 14 and the second sputtering material should have an index of refraction to the square root of the product of the index of refraction of the optical control means 14 and the index of refraction of the photocell means 16. Another variation on the sputtering material is to define a sputtering region having a defined sputtering depth in the deposited material that comprise the light source means 12, the optical control means 14 or the photocell means 16 that will produce an equivalent effect as an optical mating means. Maximum absorption of the emitted light energy from the light source means is achieved by the intimate optical contact between the light emitting surface of the light source means and the light collecting surface of the photocell means, by matching the maximum absorption frequency bandwidth of the photovoltaic cell with the specified frequency bandwidth of the emitted light energy from the light emitting polymer material, and by the structural arrangement of the light emitting polymer material itself. To maximize the surface area between the light emitting polymer and the photovoltaic cell, the light emitting surface and the light collecting surface are preferably arranged so that they are generally parallel to and in intimate contact with each other. In addition, the light emitting polymer material and the photovoltaic cell may be arranged to allow the photovoltaic cell to be constructed in manner so as to absorb light energy at more than a single surface. Another feature that may be used to increase the efficiency of the present invention is to include a focal means optically interposed between the light emitting surface of the light source means 12 and the light collecting surface of the photocell means 16 for focusing the emitted light energy on the photocell means 16. The focal means may be interposed either prior to, or after, the optical control means 14. EXAMPLE APPLICATIONS Referring now to FIGS. 5a and 5b, two sample applications of the optoelectronic active circuit element of the present invention are shown. In FIG. 5a, the optoelectronic active circuit element 10 is used as both an amplifier and power source for the microphone 70 and voltage amplifier 72 of a sound detection device, the output of which may be fed to a transmitter logic, for example. In FIG. 5b, a frequency feedback control 82 is used in conjunction with a frequency modulated optical control means 14 to produce an oscillator 80 having a sinusoidal output signal. Although the description of the preferred embodiment has been presented, it is contemplated that various changes could be made without deviating from the spirit of the present invention. Accordingly, it is intended that the scope of the present invention be dictated by the appended claims rather than by the description of the preferred embodiment. |
claims | 1. An x-ray optical device comprising:an x-ray source generating an x-ray beam; anda reflective element for receiving the x-ray beam and having variable focal points such that the convergence of an x-ray output beam varies across a surface of the reflective element according to a pre-defined function the convergence varying from a near end of the reflective element to a far end of the reflective element, the near end and the far end being defined by the respective positions of the ends relative to the x-ray source. 2. The optical device of claim 1 wherein the reflective element has a curved surface and wherein the portion of the x-ray output beam with the lowest convergence is delivered from the far end of the reflective element. 3. The optical device of claim 1 wherein the reflective element has a curved surface and wherein the portion of the x-ray output beam with the lowest convergence is delivered from the near end of the reflective element. 4. The optical device of claim 1 wherein the optical device delivers a uniform x-ray output beam of x-rays toward a sample or a detector. 5. The optical device of claim 1 further comprising an adjustable aperture for selecting a portion of the x-ray output beam which optimizes the convergence and flux of the x-ray output beam. 6. The optical device of claim 5 wherein the aperture is made of four individual blades. 7. The optical device of claim 5 wherein the aperture is made of two angled blades. 8. The adjustable aperture in claim 5 wherein the aperture is a round pinhole, the portion of the x-ray output beam being selected by changing the size of the pinhole. 9. The optical device of claim 1 wherein a portion of the beam is occluded, the non-occluded portion of the x-ray output beam having a desired convergence. 10. The optical device of claim 1 wherein the surface of the reflective element varies according to a pre-defined function to provide the varying convergence. 11. The optical device of claim 10 wherein the convergence varies according to a linear function. 12. The optical device of claim 10 wherein the reflective element provides a uniform x-ray output beam at a certain location. 13. The optical device of claim 1 further comprising a second reflective element arranged relative to the first reflective element to provide a two-dimensional conditioned x-ray output beam. 14. The optical device of claim 1 wherein the reflective element is a two-dimensional curved surface, which provides a two-dimensional conditioned x-ray output beam. 15. The optical device of claim 1 wherein the varying convergence across the x-ray output beam produces the varying focal points simultaneously. |
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claims | 1. A solid state sub-nanometer-scale electron beam emitter comprising a nano-tip electron emitter and tunnel emission junction formed on substrate, an initial electron beam extraction electrode, and an electron beam lens wherein said electron beam lens includes a nano-sandwich Einzel lens electrode and wherein said nano-sandwich Einzel lens electrode includes a lower primary electron beam acceleration electrode, an annular metal electrode, and an upper metal membrane electrode. 2. The emitter as recited in claim 1, wherein said initial electron beam extraction electrode also forms said lower primary electron beam acceleration electrode of said nano-sandwich Einzel lens electrode. 3. The emitter as recited in claim 1, further comprising a spacing layer disposed between said initial electron beam extraction electrode and said lower metal membrane and primary electron beam acceleration electrode of said nano-sandwich Einzel lens electrode. 4. The emitter as recited in claim 1, wherein said lower primary electron beam acceleration electrode has a thickness between about 1 nanometer and about 10 nanometers, said annular metal electrode has a thickness between about 1 nanometer and about 10 nanometers, and said upper metal membrane electrode has a thickness between about 1 nanometer and about 10 nanometers. 5. The emitter as recited in claim 4, wherein said annular metal electrode has an opening through which electrons pass of between about 10 nanometers and about 100 nanometers in diameter. 6. The emitter as recited in claim 1, wherein said nano-sandwich Einzel lens electrode comprises an interior region devoid of material and forming a nano-vacuum chamber. 7. The emitter as recited in claim 1, wherein said nano-sandwich Einzel lens electrode comprises an interior region consisting essentially of an electron transparent material. 8. The emitter as recited in claim 1, further comprising an electron transparent protective layer disposed upon said nano-sandwich Einzel lens electrode. 9. The emitter as recited in claim 8, wherein said electron transparent protective layer consists essentially of a material selected from the group consisting of diamond, silicon nitride, and aluminum nitride. 10. The emitter as recited in claim 1, wherein said emitter is formed with a substantially cylindrical shape. 11. The emitter as recited in claim 1, wherein said substrate consists essentially of silicon. 12. The emitter as recited in claim 1, wherein said nano-tip electron emitter is embedded in a spacing layer that separates said nano-tip electron emitter from said initial electron beam extraction electrode. 13. The emitter as recited in claim 12, wherein said spacing layer consists essentially of diamond. 14. The emitter as recited in claim 1, wherein said nano-tip electron emitter is formed with a conical shape. 15. The emitter as recited in claim 14, wherein said nano-tip electron emitter extends from said substrate a distance of between about 20 nanometers and about 80 nanometers. 16. The emitter as recited in claim 1, wherein said nano-tip electron emitter comprises a tungsten tetrahedral tip. 17. The emitter as recited in claim 1, wherein said nano-tip electron emitter comprises a carbon nanotube. 18. The emitter as recited in claim 1, wherein said nanotip electron emitter comprises a C.sub.60 buckyball. 19. A solid state sub-nanometer-scale electron beam emitter comprising a nano-tip electron emitter and tunnel emission junction formed on substrate, an initial electron beam extraction electrode, and a protective layer disposed on said initial electron beam extraction electrode. 20. A nano-sandwich Einzel lens for directing an electron beam, said lens comprising a lower primary electron beam acceleration electrode, an annular metal electrode, and an upper metal membrane electrode. 21. The lens as recited in claim 20, wherein said lower primary electron beam acceleration electrode is separated from said annular metal electrode by a first electron transparent spacing layer and said annular metal electrode is separated from said upper metal membrane electrode by a second electron transparent spacing layer. 22. The lens as recited in claim 21, wherein said first electron transparent spacing layer and said second electron transparent spacing layer consist essentially of a material selected from the group consisting of diamond, silicon nitride, and aluminum nitride. 23. The lens as recited in claim 20, wherein an electron directing voltage is applied to said annular metal electrode. 24. The lens as recited in claim 20, wherein said annular metal electrode is unitary. 25. The lens as recited in claim 20, wherein said annular metal electrode is segmented into at least a first segment and a second segment. 26. The lens as recited in claim 25, wherein a first electron directing voltage is applied to said first segment of said annular metal electrode and a second electron directing voltage is applied to said second segment of said annular metal electrode. 27. The lens as recited in claim 25, wherein said annular metal electrode is segmented into four segments at approximately 90 degree intervals. |
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062326112 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiographic intensifying screen (hereinafter referred to as "intensifying screen"). More particularly, the present invention relates to an intensifying screen excellent in durability. 2. Discussion of Background An intensifying screen is used in intimate contact with an X-ray film in order to improve sensitivity of photographing in the field of medical radiographing for medical diagnosis or of industrial radiographing for non-destructive inspection of materials. Generally, on the surface of the intensifying screen, there are made abrasions or defects by an X-ray film, or dirt is attached thereon. Also, the surface of the intensifying screen is often damaged by contaminants including dust entered between the intensifying screen and the X-ray film, and also chemical materials contained in cleaners for the intensifying screen and the X-ray film are sometimes invaded into the intensifying screen to stain or color the screen. The above-mentioned various defects and damages cause unusual artifacts on a radiograph or make sensitivity lower. In order to prevent the performance of the intensifying screen from deteriorating, it is usual to provide a transparent protective layer on the surface of the intensifying screen which is brought into direct contact with an X-ray film. Heretofore, in a method for forming a protective layer, a protective layer-forming coating solution having an appropriate viscosity is prepared by dissolving cellulose derivatives such as cellulose acetate, nitro cellulose and cellulose acetate butyrate, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polycarbonate, polyvinyl butyral, polymethyl methacrylate, polyvinyl formal, polyurethane or other resins in a solvent, and the coating solution thus prepared is coated on a previously formed fluorescent layer and dried to form a protective layer thereon. Alternatively, a protective layer previously formed in the form of a film, such as an organic macromolecule film including polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyamide and the like, may be laminated on a fluorescent layer to form a protective layer. It is useful for improving durability of an intensifying screen to make a protective layer thick, but if the thickness of the protective layer increases, sharpness is lowered, and therefore it has been difficult to improve both durability and image quality at the same time. As a method for improving durability and handling property of an intensifying screen or a radiation image-conversion panel using an photostimulable phosphor, Japanese Unexamined Patent Publication No. 310900/1992, Japanese Unexamined Patent Publication No. 309898/1992 and Japanese Unexamined patent Publication No. 75097/1994 disclose a protective layer formed on the surface of a fluorescent layer by coating a protective layer-forming coating solution containing an organic solvent-soluble fluorocarbon resin having a polysiloxane-structured oligomer, a perfluoroalkyl group-containing oligomer, a perfluoroolefin resin powder or a silicone resin powder added therein. Among these protective layer-forming methods, when a coating solution prepared by dissolving a protective layer-forming resin in a solvent is coated on a fluorescent layer, a part of the coating solution is soaked into the inside of the fluorescent layer and accordingly a protective layer is formed on the fluorescent layer without making a boundary between the two layers. Thus, the protective layer is firmly bonded with the fluorescent layer, and peeling of the protective layer off the intensifying screen and occurrence of pinholes on the protective layer due to the presence of contaminants can be avoided. Also, when the above-mentioned organic solvent-soluble fluorocarbon resin is used as a protective layer-forming resin, anti-fouling property is improved and a coefficient of friction is lowered, thereby improving durability resistance. Further, since a contact angle between water and the resin is large, even if pinholes are produced, a chemical material from an X-ray film is hardly soaked and spot-like sensitivity degradation does not substantially occur, thus improving pinhole resistance. However, when a protective layer is formed by coating a solution, a starting material used is limited to a solvent-soluble resin, and accordingly durability resistance is poor as compared with a method wherein an organic macromolecule film such as polyethylene terephthalate is laminated on a fluorescent layer to form a protective layer. Further, when a binder resin content in a fluorescent layer is reduced in order to improve sharpness, a protective layer-forming coating solution is soaked into the fluorescent layer when the protective layer-forming coating solution is coated on the fluorescent layer, and a protective layer having a sufficient thickness can not be formed. On the other hand, when a protective layer-forming coating solution is coated in a large amount on a fluorescent layer in order to form a protective layer having a sufficient thickness, the protective layer-forming coating solution is soaked into the fluorescent layer, thereby causing such problems as lowering sharpness or generating foams during coating. Unlike the method for forming a protective layer by coating a solution, in the method for forming a protective layer by laminating an organic macromolecule film on a fluorescent layer, there is caused no problem of soaking with a protective layer-forming coating solution. Particularly when a polyethylene terephthalate film is used as a protective layer to be laminated, as compared with the method of using a protective layer-forming coating solution, abrasion resistance and solvent resistance are excellent and water vapor permeability and gas permeability are low, thereby providing excellent anti-staining property to a chemical material eluded from an X-ray film. However, as compared with a protective layer formed by coating a solution, adhesive strength of a protective layer laminated on a fluorescent layer is poor and therefore the laminated protective layer is liable to be peeled and pinholes are liable to occur when contaminants invade into between an intensifying screen and an X-ray film. Further, through the pinholes, various contaminants invade into the intensifying screen, thereby causing a problem of producing spot-like sensitivity degradation parts. Thus, both a protective layer formed by coating a solution on a fluorescent layer and a protective layer formed by laminating an organic macromolecule film on a fluorescent layer respectively provide various advantages and disadvantages, and it has been difficult to satisfy all of requirements. Also, recently, radiographing is automatically conducted in a labor saving manner, and an X-ray film is automatically conveyed and charged into a radiographing apparatus. Further, a film changer for automatically taking an X-ray film after radiographing and a film-conveying apparatus of a cassetteless X-ray TV are often used. Under these recent circumstances, an intensifying screen is demanded to be more improved in respect of anti-staining property, handling properties including an X-ray film-conveying property, and the like. An object of the present invention is to provide an intensifying screen which satisfies satisfactory image quality, durability and handling performances at the same time. In order to improve durability and handling performances of an intensifying screen without degrading image quality, the present inventors have studied about materials used for a protective layer of an intensifying screen and its structure, and have found that the material quality and the structure of the protective layer are closely related to durability and handling performances of the intensifying screen. The present invention is made on the basis of this finding. SUMMARY OF THE INVENTION The present invention provides a radiographic intensifying screen having at least a fluorescent layer and a protective layer on a support, wherein the protective layer has a multi-layer structure comprising at least one layer of an organic macromolecule film and a film-forming resin layer provided on the surface of the organic macromolecule film at least on the side which is not in contact with the fluorescent layer, and the resin of the film-forming resin layer is different from the resin of the organic macromolecule film. The intensifying screen having the protective layer of the above-mentioned structure is improved not only in image quality but also in pinhole resistance, anti-staining property, anti-fouling property, durability and handling performances including X-ray film-conveying performance, and the like. |
041750047 | claims | 1. In combination with a nuclear fuel assembly of the type having a plurality of vertically extending fuel elements and guide tubes maintained in a laterally spaced array by at least one cellular spacer grid assembly that is composed of a multiplicity of intersecting slotted grid plates disposed to form a plurality of cells through which the fuel elements and guide tubes extend; and, lower and upper end fitting assemblies, each being rigidly attached to the respective ends of the guide tubes, the improvement comprising a plurality of protuberancies integrally formed in the guide tubes in spaced relation, each guide tube having a cross-section at each protuberancy greater than a distance between the plates forming the cell through which the guide tubes extend, the protuberancies being longitudinally aligned with and spaced relative to at least part of of the plates such that the protuberancies engage the plates to restrain longitudinal movements of the spacer grid assembly relative to the guide tubes beyond the longitudinal spacing, and the spaced relation of the protuberancies being such that the guide tubes, including the protuberancies, may be inserted through a cell. 2. The improved nuclear fuel assembly of claim 1 further comprising saddles formed in the grid plates to project into the cells containing the guide tubes, said saddles generally conforming to the shape of the guide tubes, wherein said protuberancies are longitudinally aligned with the saddles such that the protuberancies engage the saddles to restrain movements of the plates. 3. The improved fuel assembly of claim 2 wherein at least two longitudinally spaced saddles are formed to project from each grid plate forming a guide tube cell and said protuberancies are spaced between said longitudinally spaced saddles. 4. The improved fuel assembly of claim 3 wherein groups of said longitudinally spaced protuberancies are equidistantly spaced about the perimeter of the guide tubes. 5. The improved fuel assembly of claim 4 wherein said guide tubes are cylindrical and groups of four protuberancies are equidistantly spaced about the circumference of the guide tubes at longitudinally spaced intervals. 6. The improved fuel assembly of claim 5 wherein said guide tubes protuberancies are cut to form a lip at the protuberance edge adjacent to the spacer grid plate saddle. 7. The improved fuel assembly of claim 2 wherein at least two longitudinally spaced saddles are formed to project from each grid plate forming a guide tube cell and said protuberancies are spaced to span the width of the spacer grid plates having the longitudinally spaced saddles. 8. The improved fuel assembly of claim 7 wherein groups of said longitudinally spaced protuberancies are equidistantly spaced about the perimeter of the guide tubes. 9. The improved fuel assembly of claim 8 wherein said guide tubes are cylindrical and groups of four protuberancies are equidistantly spaced about the circumference of the guide tubes at longitudinally spaced intervals. 10. The improved fuel assembly of claim 9 wherein each of said guide tube protuberancies are cut to form a lip at the protuberancy edge adjacent to the spacer grid plate saddle. 11. In combination with a fuel assembly of the type having a plurality of vertically extending fuel elements and at least one guide tube maintained in a laterally spaced array by at least one cellular spacer grid assembly that is composed of a multiplicity of intersecting slotted grid plates disposed to form a plurality of cells through which the fuel elements and guide tube extend; and lower and upper end fitting assemblies, each being rigidly attached to the respective ends of the guide tube, the improvement comprising a plurality of protuberancies integrally formed in the guide tube in spaced relation, the guide tube having a cross-section at each protuberancy greater than a distance between the plates forming the cell through which the guide tube extends, the protuberancies being longitudinally aligned with and longitudinally spaced relative to at least part of the plates such that the protuberancies engage the plates to restrain longitudinal movements of the spacer grid assembly relative to the guide tube beyond the longitudinal spacing, and the spaced relation of the protuberancies being such that the guide tube, including the protuberancies, may be inserted through cell through which the guide tube extends. |
059986905 | abstract | A unique method for solidification of solutions containing boric acid and/or borates is disclosed in this invention. The boron species in the solutions are polymerized to form polyborates, and the solutions are then solidified by mixing with solidification agents which are prepared completely from inorganic materials. Therefore, the solid form produced by this method has no aging problem. The boron species in the solution are not merely wastes to be encapsulated or embedded, they take part in the solidification reaction and share a major portion of total reactants. Thus, the total volume of solid forms produced in this invention is less than 1/10 of that produced in conventional cementation. |
abstract | An in-core neutron monitor that employs vacuum microelectronic devices to configure an in-core instrument thimble assembly that monitors and wirelessly transmits a number of reactor parameters directly from the core of a nuclear reactor without the use of external cabling. The in-core instrument thimble assembly is substantially wholly contained within an instrument guide tube within a nuclear fuel assembly. |
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