Split (2)

train · 33.5k rows

patent_number stringlengths 0 9	section stringclasses 4 values	raw_text stringlengths 0 954k
	summary
062597566	description	DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawing, there is schematically illustrated in FIG. 2 a nuclear reactor core, generally designated 10, with a control blade pattern indicated by the square boxes disposed in the core 10. Each box of FIG. 2 represents a control blade 12 and an associated fuel assembly, generally designated 13, comprised of four fuel bundles 14 as illustrated in FIG. 1. The fuel bundles 14 are only partially illustrated with each bundle having fuel rods 16, e.g., in a 10.times.10 array, and associated vertically spaced spacers 18 as is conventional, only one spacer 18 being illustrated in each fuel bundle 14. Fuel channels 19 surround each fuel bundle 14 and define a cruciform opening between the fuel assemblies. As will be appreciated, each control blade 12 is cruciform in cross-section and is generally receivable within the core of the nuclear reactor in the cruciform openings between the four fuel bundles 14, the blades being movable from below the fuel assemblies, i.e., withdrawn positions, to positions within the cruciform openings adjacent the fuel assemblies. Hence, each box illustrated in FIG. 2 and represented by any one of the control blades A1, A2, B1 and B2 includes a single control blade 12 and four associated fuel bundles 14 arranged in quadrants defined by the cruciform spaces therebetween. Control blade sequences are generally divided into two groups known as A sequence blades and B sequence blades. Thus, the A and B control blades constitute first and second main groups A and B, respectively, of control blades. The first and second main groups A and B form a checkerboard pattern throughout the core as illustrated in the plan view of the core of FIG. 2. From a review of FIG. 2, it will be appreciated that the first main group of blades A is symmetric relative to the center of the core. The second main group of control blades B is asymmetric relative to the core. It will also be appreciated from a review of FIG. 2 that the respective main groups of blades A and B are each further divided into two sub-groups. For example, main group A is divided into sub-groups A1 and A2. Main group B is divided into sub-groups B1 and B2. A control blade of the sub-group A2 always lies at the center of the core. From a detailed review of FIG. 2, each first sub-group A1 of the first main group A is flanked by sub-groups B1 of the second main group B in a first or X direction. Each sub-group A1 of the first main group A is also flanked by second sub-groups B2 of the second main group B in a second or Y direction normal to said first or X direction. Also, each sub-group A2 of the first main group A is flanked by second sub-groups 82 of the second main group B in the first or X direction. Each second sub-group A2 of first main group A is also flanked by first sub-groups B1 of the second main group B in the second or Y direction. Similarly, each sub-group B1 of the second main group B is flanked by a sub-group A1 of the first main group A in the first or X direction. Each sub-group B1 of the second main group B is also flanked by the second sub-group A2 of the first main group A in the second or Y direction. Finally, each second sub-group B2 of the second main group B is flanked by a second sub-group A2 of the first main group A in the first or X direction and by the first sub-group A1 of the first main group A in the second or Y direction. Thus, it will be appreciated that each sub-group at any one control blade location within the core is located alternately in both X and Y directions. In each control cell formed by the single control blade 12 and four associated fuel bundles 14, the control blades 12 are movable from a withdrawn position below the core to either a shallow position or a deep position or both, depending upon their status as sequence A or B blades. The movement of the control blades relative to the fuel assemblies is indicated by the double-ended arrow in FIG. 1. Blades whose tips are inserted more than two-thirds into the core are referred to as deep blades. Blades inserted less than one-third into the core are referred to as shallow inserted blades. Deep blades are used to control the total reactor power, as well as the global radial power shape. Shallow blades are used to control the reactor axial power shape. Generally, blades are not inserted into the middle third of the core because they would tend to create axial power distribution problems. In accordance with a preferred embodiment of the present invention, and instead of using the first and second main groups A and B, respectively, of blades alternately as in the prior art, the first and second main groups A and B are at times employed simultaneously with the second main group B only used as shallow blades and the first main group A used either as deep or shallow blades. Moreover, the sequences are constructed to enable each fuel bundle a period of operation in an uncontrolled state without its associated control blade that is at least twice as long as the previous period of operation in a controlled state with its associated blade. That is, each fuel bundle is operated with its associated control rod withdrawn from the core for a period of time at least twice as long as the previous period of operation with its associated control rod inserted into the core. Additionally, each sub-group A1 and A2 of the first main group includes operational sub-groups A1' and A2', respectively. Consonant with a preferred embodiment of this invention, the sequence pattern for control of the core repeats at least every three consecutive time periods and any one blade is fully withdrawn for at least two consecutive periods after it has been inserted. With these criteria, there are a number of possibilities for control blade sequence patterns to optimize the BWR power control. For example, a control blade sequence pattern is illustrated in the chart below. CHART I Deep Shallow Time Period Blades Blades Not Used (Withdrawn) 1 A1 A1' A2, A2', B1, B2 2 A2 B2 A1, A2', B1 3 A2' B1 A1, A2, B2 4 A1 A1' A2, A2' B1, B2 5 A2 B2 A1, A2', B1 6 A2' B1 A1, A2, B2 7 A1 A1' A2, A2', B1, B2 8 A2 B2 A1, A2', B1 9 A2' B1 A1, A2, B2 As can be seen from Chart I, during the first time period, the first sub-groups A1 of the first main group A have their control blades inserted as deep blades. The first operational sub-groups A1 ' of the first sub-groups A1 have their blades inserted to shallow depths. The remaining blades of sub-groups A2, A2', B1 and B2 are totally withdrawn and not inserted. At the end of the first time period of reactor operation, the blades of A1 and first operational sub-group A1 ' are withdrawn, while the second sub-groups A2 of the first main group A are inserted into the core as deep blades. The blades of the second sub-groups B2 of the second main group B are also inserted into the core as shallow blades. The remaining blades of sub-groups A1 and B1 and operational sub-groups A2' are or remain withdrawn as applicable. The reactor is then operated for the predetermined time period 2. At the end of the second time period of reactor operation, the blades of the operational sub-groups A2' are inserted into deep positions, while the blades of the sub-groups B1 are inserted into shallow positions. The remaining blades of sub-groups A1, A2 and B2 are either withdrawn or remain withdrawn as applicable. The reactor is then operated for the third predetermined time period. At the end of the third time period, the preferred pattern preferably repeats itself, although it will be appreciated that the pattern may extend to periods beyond three consecutive time periods before repeat. Note that with this pattern, each fuel bundle is operational in an uncontrolled state without insertion of its associated control blade for at least two consecutive time periods before the associated control blade is inserted. Stated differently, any one control blade is fully withdrawn for at least two consecutive time periods after it has been inserted. Moreover, it will be appreciated that the control blades of the second main group B are used only as shallow blades, not as deep blades, and are movable only between positions withdrawn or into shallow positions apart from a scram condition. It will be appreciated that other sequences of operation of the control blades using the criteria stated above may be used. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
051951207	abstract	In a radiological apparatus using an antiscatter grid, this grid is kept fixed instead of being movable, and its image is removed by irradiating it as well as the object to be examined by two X-ray sources that have to be separated by a distance b determined by the first zero of the modulation transfer function of this two-source system. To take account of the magnification G, the distance b can be adjusted by means of a cathode emitting two electron beams with adjustable deflection.
	description	1. Field of the Invention The present invention relates to feedwater spargers in boiling water reactors and, more particularly, to clamps for the end bracket assemblies of feedwater spargers. 2. Description of the Related Art While the present invention may be used in a variety of industries, the environment of a boiling water reactor (BWR) nuclear power plant will be discussed herein for illustrative purposes. In a BWR, a steam-water mixture is produced when reactor coolant (water) moves upward through the core, absorbing heat produced by the fuel. The steam-water mixture leaves the top of the core and enters a moisture separator, where water droplets are removed before the steam is allowed to enter the steam line. The steam line directs the steam to the main turbine, causing it to turn the turbine and the attached electrical generator. The steam is then exhausted to a condenser where it is condensed into water. The resulting water is pumped out of the condenser back to the reactor vessel as feedwater. Recirculation pumps and jet pumps allow the operator to vary coolant flow through the core and change reactor power. Within the BWR vessel, core shrouds surround the core to provide a barrier to separate the downward coolant flow through the annulus/downcomer (the space between the core shroud and the reactor vessel wall) from the upward flow through the core and fuel bundles. The feedwater is injected through nozzles in the reactor vessel and distributed by feedwater spargers. The feedwater spargers are located inside the reactor vessel and include a central T-connection with two pipe branches that are curved concentric with the inside radius of the reactor vessel. Each curved pipe has a set of nozzles through which the feedwater is injected. Each curved pipe has an end bracket that is welded to the pipe. The end brackets are C-shaped and surround an attachment lug that is welded to the reactor vessel wall. Pins having relatively large diameter heads are inserted through the end brackets and the attachment lug. Each pin has a securing nut on the bottom that is installed tightly against a shoulder of the pin but allows a gap between the nut and the bottom of the end bracket white the head of the pin rests against the top of the bracket. The sparger end brackets are secured axially to the attachment lug, but the end brackets are slotted to allow for relative thermal expansion and contraction of the feedwater sparger assembly. FIG. 7 shows a partially cut-away isometric view of a typical sparger end bracket assembly, including the pin 2 and bracket 3. Visual inspection of the spargers has revealed wearing of the end brackets and pin heads. The wear is caused by vibration of the pin relative to the bracket, which is believed to be caused by flow induced vibration. The present invention provides a solution to the wear problems discussed above, and includes several components that collectively act as a clamp that is installed on the feedwater sparger end bracket pin to increase the bearing area of the pin head without removing the feedwater sparger pin. The increased surface area of the clamp spreads the weight of the sparger pin over a larger area of the bracket, thereby reducing the load per unit area of the pin head relative to the surface of the bracket. The larger contact area will reduce future bracket and/or pin wear. In addition, the device also restores the position of the sparger pin head relative to the contact surface of the end bracket if the original pin head or bracket is worn. The clamp assembly includes abuse and cooperating bolt, a reaction arm, and a cross pin. With the exception of the cross pin, the parts are pre-assembled and then installed over the sparger pin head after lifting the pin head above the surface of the sparger bracket. The cross pin is then installed through the clamp base and through the (pre-existing) hole in the sparger pin head. The clamp bolt is then tightened, forcing the reaction arm against the top surface of the sparger pin head. This captures the dowel pin (which locks the reaction arm to the clamp bolt) within the clamp base and pushes the sparger pin head against the cross pin, forcing the cross pin against the contact surfaces on the clamp base. A predefined torque is then applied to the bolt to secure the clamp to the sparger pin head. Tightening the clamp bolt lowers the reaction arm, causing the distal end of the reaction arm to capture the cross pin and lock it with the clamp base. To prevent movement of the bolt during plant operation, the crimp cup is deformed into features in the bolt shank. The clamp can be removed from the sparger pin by de-torqueing the bolt. To accommodate the de-torqueing process, the crimp cup is secured to the clamp base with the lock pin to prevent movement of the cup. Re-installation of the clamp is possible after replacing the crimp cup. FIG. 1 shows an exploded perspective view of the components of a clamp assembly 1 of the present invention, and FIG. 2 shows a cross-sectional view of the clamp assembly 1 in a use position on the head of a sparger bracket pin 2. The clamp 1 includes a base 10 with a body that defines a chamber 101 configured to fit over and around the head of the sparger pin 2. In a preferred embodiment, the base 10 includes one or more side walls 110 and a top wall 112. While the embodiment of the base 10 illustrated in FIGS. 1 and 2 has an angular shape with multiple side walls 110, the base 10 may have alternate profiles such as a round or circular shape in which it may have only a single side wall 110. In any event, the base 10 has a body defining a chamber 101, which may be chamfered or beveled to facilitate positioning the base 10 over the sparger pin 2. The body of the base 10 defines a plurality of holes therethrough. The base body 10 defines a hole 102 passing through the side wall 110. Preferably, a corresponding hole 102 passes through the opposite side wall 110 to define a path completely through the base 10. The base 10 further defines a hole 104 passing through the top wall 112. This top hole 104 is threaded to engage corresponding threads on the bolt 12. The clamp assembly 1 further includes a reaction arm 14 that is configured to engage with the base 10 through the side wall opening 102. In a preferred embodiment, the reaction arm 14 has an L-shape defining substantially perpendicular arms 141 and 142. The reaction arm is configured to pass over a ledge of the base side wall 110 formed by the side hole 102 such that proximal arm 142 extends downward adjacent the base side wall 110. As seen in FIG. 2, the reaction arm 14 is thus cantilevered relative the base 10. The reaction arm 14 extends through a majority of the thickness of the base 10 such that the reaction arm 14 overlies the sparger pin 2. The reaction arm 14 has a first surface 145 configured to engage the top surface of the sparger pin head. In a preferred embodiment, this may include an engagement portion that extends away from body 141 of the reaction arm 14. The reaction arm 14 further comprises a second surface 146 configured to engage the clamp bolt 12 as is discussed in more detail below. The clamp assembly further includes a bolt 12 that is configured to matingly engage the threaded opening 104 through the base top wall 112. An abutment surface 121 is provided at the lower end of the bolt 12. By engaging the threaded region 122 of the bolt 12 with corresponding threads in the upper base opening 104, the bolt abutment surface 121 can be lowered into contact with the reaction arm upper surface 146. A force can thus be applied to the reaction arm 14, which is transferred through the reaction arm lower surface 145 to the sparger pin 2. This locks the clamp assembly 1 to the cross pin 18, as is discussed further below. The reaction arm upper surface 146 may contain an indentation or depression therein configured to engage the bolt abutment surface 121. The clamp assembly 1 further includes a cross pin 18 that is configured to extend through the base 10 and a hole 21 provided in the head of the sparger pin 2. Preferably, as shown in the illustrated embodiment of FIG. 1, the base side opening 102 contains V-channels in the lower ledges of the side wall 110 in which ends of the cross pin 18 rest. The V-channel on the side opposite the reaction arm 14 does not extend completely through the base side wall 110, however, so that the opposite end of the cross pin 18 contacts an internal surface of the base side wall 110 to lock the cross pin 18 within the base 10 and prevent it from becoming dislodged from the clamp assembly 1. The cross pin 18 may include a ridged recess 181 in an end thereof to facilitate insertion and, if desired, removal of the cross pin 18 from the clamp assembly 1. With the cross pin 18 positioned within the base 10 and sparger pin 2, the bolt is torqued to lower its abutment surface 121 into contact with the reaction arm upper surface 146. Continued torqueing of the bolt 12 causes the reaction arm 14 to lower, causing the reaction arm lower surface 145 to lower and exert a force against the top surface of the sparger pin 2. The sparger pin 2 and cross pin 18 are thus forced downward. When the bolt 12 is tightened to a predetermined torque, the clamp assembly 1 is fixedly locked to the sparger pin 2. A lower flange 114 of the base 10 is thus positioned to engage an upper surface of the sparger end bracket with an increased surface area with respect to the original contact surface area provided by the head of the sparger pin 2. Additionally, the clamp assembly 1, and the flange 114 in particular, provides 360° contact around the sparger pin 2. This provides assurance of contact regardless of whether discrete areas of the end bracket top surface have been worn or eroded through operation of the reactor prior to installation of the inventive clamp assembly 1. A crimp cup 16 may be included with the clamp assembly 1. The crimp cup 16 is configured to be positioned intermediate the base 10 and the bolt 12. A cylindrical portion 161 contains external threads 162 that matingly engage the threaded upper base opening 104 and internal threads 163 that matingly engage the bolt threads 122. A non-threaded region 165 of the cylindrical portion 161 extends beyond threaded region 162. The crimp cup 16 is inserted into the base upper opening 104 from the lower side thereof; that is, through the base internal chamber 101. The external threads 162 are matingly engaged with the base upper opening 104 until a flange 166 on the lower portion of the crimp cup 16 comes into contact with an internal surface of the base upper wall 112. The bolt is then coupled to the internal threads 163 of the crimp cup 16. As shown in FIG. 2, the non-threaded region 165 of the crimp cup 16 will extend beyond the base upper wall 112 when the flange 166 abuts the base 10. The crimp cup 16 is formed of a malleable material, such as stainless steel. Once the bolt 12 is torqued to the prescribed force and the clamp assembly 1 is locked to the sparger pin 2, the non-threaded region 165 of the crimp cup 16 can be plastically deformed into channels 123 formed on the shaft of the bolt 12. This crimping locks the bolt 12 in place, preventing it from backing out and becoming dislodged from the clamp assembly 1. Preferably, the thermal 163 and external 162 threads of the crimp cup have opposite thread configurations. For example, the external threads 162 may be left-handed and the internal threads 163 may be right-handed. This help ensure the crimp cup 16 remains in place during engagement of the bolt 12 as rotation of the bolt 12 into the crimp cup 16 will work to tighten the coupling of the crimp cup 16 to the base 10. The clamp assembly 1 can be removed from the sparger pin 2 by exerting a torque of enough magnitude, such as 20-25 foot-pounds, to release the crimped portion 165 of the crimp cup 16 from the bolt channels 123. The bolt 12 can then be backed out of the clamp assembly 1, relieving the force exerted against the cross pin 18 and freeing it for removal from the assembly 1. The clamp assembly 1 can be re-used with the replacement of the crimp cup 16. A dowel pin 20 may be provided with the clamp assembly 1. The dowel pin 20 is inserted through a hole 103 in the base 10 into a groove 201 cooperatively formed by a groove 124 formed in the bolt 12 and a groove 143 formed in a distal end of the reaction arm 14. The hole 103 is located such that the bolt groove 124 is aligned with the hole 103 when the bolt 12 is partially inserted into the base 10. Further tightening of the bolt 12—with the dowel pin 20 within the groove 201—lowers the dowel pin 20 below the hole 103. The dowel pin 20 is thus captured within the base 10 such that it cannot become dislodged or separated from the clamp assembly 1. The hole 103 can also be deformed such as by striking its edge with a tool to provide further assurance that the dowel pin 20 does not become dislodged. With the dowel pin 20 in place within the groove 201, the reaction arm 14 is locked to the bolt 12. This prevents the reaction arm 14 from becoming dislodged from the clamp assembly 1 prior to full torqueing of the bolt 12 to clamp the assembly 1 to the sparger pin 2. Thus, the reaction arm 14 is fixed to the clamp assembly 1 during installation of the clamp 1 into the reactor prior to insertion of the cross pin 18. A lock pin 22 may be provided with the clamp assembly 1. The lock pin 22 is inserted into a hole provided in the base top wall 112 and into an upper surface of the crimp cup flange 166. The lock pin 22 prevents rotation and decoupling of the crimp cup 16 from the base 10 if the bolt 12 is detorqued (that is, rotated in a direction to remove it from the base 10). The hole into which the lock pin 22 is inserted may be deformed such as by striking its edge with a tool to prevent it from becoming dislodged from the clamp assembly 1. The lock pin 22 may include a ridged recess in an end thereof to facilitate insertion and, if desired, removal of the lock pin 22 from the clamp assembly 1. In use, the clamp 1 is partially pre-assembled prior to its installation into the reactor. First, the crimp cup 16 is coupled into the base 10 by threading it into the top wall hole 104 such that the flange 166 abuts a lower surface of the base upper wall 112. The bolt 12 is then coupled to the crimp cup 16 by threading it into the crimp cup internal threads 163. The bolt 12 is inserted to the point when its groove 124 is aligned with the base dowel pin hole 103. The reaction arm 14 is then inserted into the base side opening 102 such that its groove 143 is adjacent the bolt groove 124, thereby forming the dowel pin groove 201. The dowel pin 20 is then inserted through the base hole 103 into the groove 201. This insertion may be performed in known manner, such as via a plunger or air cylinder. The bolt 12 is then threaded further into the base 10, capturing the dowel pin 20 within the base 10 and locking the reaction arm 14 to the bolt 12. The bolt 12 is inserted far enough to capture the dowel pin 20, but to still leave clearance between the reaction arm 14 and the V-channel of the lower edge of the base side opening 102. The base 110, bolt 12, reaction arm 114, crimp cup 16, and dowel pin 20 are now fixed together as a subassembly or unit. The preassembly is then loaded into a specially designed tool for insertion into the reactor. Additional openings in the base 10 may be provided to facilitate gripping of the subassembly by the tool. The tool also holds the cross pin 18, such as by the positioning of a detent within the recess 181. The tool and clamp assembly components are then lowered into the reactor to the location of the sparger pin 2 of interest. Arms of the tool are engaged to lift the sparger pin bolt, creating clearance between the sparger pin head and the sparger bracket. With the subassembly positioned atop the sparger pin head, the cross pin 18 is inserted through the base side opening 102 and sparger pin 2. An air cylinder or plunger of the tool may be used to insert the cross pin 18. With the cross pin 18 in place, the bolt 12 is torqued to lock the clamp assembly 1 to the sparger pin 2. This is accomplished by the tooling, which torques the bolt 12 to approximately 20 foot-pounds. Torqueing the bolt 12 also lowers the reaction arm such that its proximal arm 142 covers the cross pin 18, capturing it within the clamp assembly 1. A notch 144 in a lower surface of the proximal arm 142 allows the tooling to be engaged with the cross pin 18 while the bolt 12 is being torqued. However, the notch 144 is smaller than the cross pin 18 and will not allow it to pass therethrough. Finally, the upper portion 165 of the crimp cup 16 is crimped, locking the bolt 12 in place. The clamp assembly is thus fixedly locked to the sparger pin 2, and the tooling is removed from the reactor. Sparger pins 2 are typically formed of 304 stainless steel. The materials of the clamp assembly 1 components are chosen such that thermal expansion caused by engagement and operation of the reactor will cause the clamp 1 to tighten on the sparger pin 2 rather than becoming loose. Thus, the clamp assembly material has a lesser coefficient of thermal expansion than the sparger pin 2. One preferred material for the clamp assembly 1 is XM19 stainless steel. While directional references such as top, bottom, upper, and lower have been referenced herein, they are used for explanatory purposes relative the illustrated embodiments shown in the drawing figures only and should not be construed as limiting. While the preferred embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. Furthermore, while certain advantages of the invention have been described herein, it is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.
	claims	1. A displacement detecting element for detecting displacement in a leaf of a multi-leaf collimator, the multi-leaf collimator defining a shape contour of a collimated radiation beam, the displacement detecting element comprising: a voltage source; a displacement dependent voltage pick-off; and a resistive strip connected between said voltage source and said voltage pick-up, said resistive strip having a length which is greater than or equal to a maximum length of displacement of the leaf, wherein one of said pick-off and said strip is connected to the leaf and the other one of said pick-off and said strip is stationary, with both said strip and said pick-off being disposed outside of the collimated radiation beam. 2. The displacement detecting element of claim 1 , wherein the element is directly connected to the leaf. claim 1 3. The displacement detecting element of claim 1 , wherein said pick-off and said strip are disposed on a side of the leaf facing away from a radiation source. claim 1 4. The displacement detecting element of claim 1 , wherein said pick-off and said strip are disposed in a rear region of said leaf which is not exposed to the collimated beam. claim 1 5. The displacement detecting element of claim 4 , wherein said rear region is shielded by a pre-collimator. claim 4 6. The displacement detecting element of claim 1 , wherein a linearity of said strip is adjusted through partial removal of material from said strip. claim 1 7. The displacement detecting element of claim 1 , further comprising a housing which can be mounted to the leaf. claim 1 8. The displacement wherein detecting element of claim 7 , wherein said housing is inserted into a recess in the leaf. claim 7 9. The displacement detecting element of claim 8 , wherein said housing defines a housing recess which extends along a length thereof, and further comprising a fixed tongue displaceably disposed in said housing recess with an amount of displaceability which is at least a maximum length of leaf displacement, wherein one of said strip and said pick-off communicates with said housing and the other one of said pick-off and said strip communicates with said tongue. claim 8 10. The displacement detecting element of claim 9 , wherein said strip is located in a gap between said housing and said tongue. claim 9 11. The displacement detecting element of claim 9 , wherein said strip is disposed on said tongue and said voltage pick-off is disposed on said housing. claim 9 12. The displacement detecting element of claim 11 , wherein said voltage pick-off is effected via a window in said housing. claim 11 13. The displacement detecting element of claim 12 , wherein said housing and said tongue are formed as flat plastic parts. claim 12 14. The displacement detecting element of claim 13 , wherein said strip is connected to said voltage source by connecting one terminal of said voltage source to one end of said strip with the other end of said strip communicating with a conductor path which is disposed parallel to said strip and which is connected to the other terminal of said voltage source. claim 13 15. The displacement detecting element of claim 14 , wherein said strip and said conductor path are disposed on said tongue with said strip being formed as a first slide contact path, and further comprising a second slide contact path disposed parallel to said strip, wherein said voltage pick-off comprises two electrically connected wipers disposed on said housing which slide along first and second slide contact paths, and further comprising converting means connected between said second slide contact path and said voltage source for converting a signal into displacement information. claim 14 16. The displacement detecting element of claim 15 , wherein said wipers are disposed on an outer side of said housing and slide on said first and said second slide contact paths by passing through said window of said housing. claim 15 17. The displacement detecting element of claim 16 , wherein said means for converting said signal into displacement information is a voltage meter calibrated to a displacement to be detected, said voltage meter evaluating a voltage across a resistor communicating with a terminal of said voltage source. claim 16 18. The displacement detecting element of claim 17 , wherein said housing has a shielding conducting layer on an outer side thereof. claim 17 19. The displacement detecting element of claim 18 , wherein said housing has a dove-tailed outer contour for mounting to the leaf, wherein the leaf has a complementary recess for insertion therein. claim 18 20. A multi-leaf collimator comprising displacement detecting elements according to claim 1 , wherein each leaf has at least one displacement detecting element and all displacement detecting elements can be connected to a control of the multi-leaf collimator. claim 1
	summary
	claims	1. A radiation shield securing and covering system comprising:a radiation shield comprising a sheet of radiation attenuation material for preventing passage of all ionizing radiation through the shield to protect a patient from all ionizing radiation exposure on areas of the patient covered by the shield, the shield further comprising a means for handling the sheet of material during use with a patient and a means for hanging the material on an X-ray machine component;a retractable cable attached at a first end by a means for permanently securing the cable to a radiation shield and at a second end to a retractable spool in a cable casing locked onto an X-ray machine component to insure that the shield is always with the X-ray machine to shield each patient being X-rayed from all ionizing radiation exposure on areas of the patient covered by the shield;a plurality of sanitary disposable bags structured to encompass the radiation shield, the plurality of disposable bags removably stored within a dispenser of the disposable bags secured to an X-ray machine component for dispensing one of the plurality of disposable bags for each patient being X-rayed and mounting the disposable bag over the shield for each use of the shield with a patient and for disposing of the disposable bag after each use of the shield with a patient to prevent the spread of contagious diseases between patients using the shield and from technologists handling the shield. 2. The system of claim 1 further comprising at least one hook attached to the X-ray machine component and the means for handling the shield and means for hanging the shield comprises an opening adjacent to a top end of the shield to receive at least one hand of a user during use of the shield and alternately to receive the at least one hook for hanging the shield on the X-ray machine component. 3. The system of claim 2 wherein the at least one hook is attached to the cable casing. 4. The system of claim 3 wherein the opening comprises an elongated horizontal opening and the cable casing comprises a rigid structure having two hooks horizontally spaced on the casing to fit within the elongated horizontal opening to support the shield hanging on the hooks for storage of the shield. 5. The system of claim 1 wherein the cable casing houses a spring loaded spool to retract the cable after use of the shield. 6. The system of claim 1 wherein the cable casing further comprises a means for locking the cable casing onto the X-ray machine component.
	claims	1. A method for inspecting an irradiated fuel element having a spacer with two outer surfaces in a nuclear power plant, the method which comprises: measuring, with a measuring device, a respective relative position of the two outer surfaces of the spacer of the fuel element; measuring, with the measuring device, a calibration rod for providing measurements of the calibration rod, the calibration rod having known dimensions; and calibrating, with a computing device connected to the measuring device, the measurements of the spacer by comparing the measurements of the calibration rod with the known dimensions of the calibration rod. 2. The method according to claim 1 , which comprises: claim 1 forming, for respective two points situated opposite one another on two outer surfaces of the spacer pointing in opposite directions and respectively situated opposite one another on two subareas of the calibration rod pointing in the opposite directions, a measured value for a spacing between the outer surfaces and a further measured value for a spacing between the subareas; and converting the measured value for the spacing between the outer surfaces into a calibrated measured value by using the known dimensions of the calibration rod and the further measured value for the spacing between the subareas. 3. The method according to claim 2 , which comprises measuring further subareas of the calibration rod, the further subareas pointing in the opposite directions and being provided offset relative to the subareas of the calibration rod. claim 2 4. The method according to claim 2 , which comprises measuring further subareas of a further calibration rod, the further subareas pointing in the opposite directions and being provided offset relative to the subareas of the calibration rod. claim 2 5. The method according to claim 1 , which comprises: claim 1 disposing the measuring device with the calibration rod under water; providing the measuring device with a video camera and with at least two probes disposed opposite from one another; evaluating the measurements of the spacer and of the calibration rod with the computing device; and displaying, on a display screen, an image picked up by the video camera and displaying at least one calibrated measured value, calculated in the computing device, indicating a maximum spacing between outer surfaces of the spacer disposed opposite from one another. 6. The method according to claim 1 , which further comprises: claim 1 carrying out the step of measuring the respective relative position of the two outer surfaces of the spacer extending along a y-direction of the Cartesian reference system with the measuring device, carrying out the step of measuring the calibration rod by corresponding subareas of the calibration rod with the measuring device, providing the fuel element with a bundle of fuel rods, end pieces respectively configured as a foot piece and a head piece at respective ends of the bundle, penetrating the spacer by the fuel rods between the end pieces; positioning the fuel element with one of the end pieces or the spacer against a frame, the frame defining a z-axis of a Cartesian reference system; holding, on the frame, the calibration rod having known dimensions in an x-direction of the Cartesian reference system; and deriving, by using the known dimensions of the calibration rod and the value for the respective relative position of two outer surfaces of the spacer, at least one calibrated maximum value for a spacing between the two outer surfaces of the spacer. 7. The method according to claim 6 , which comprises: claim 6 performing the measuring step by guiding two probes disposed opposite one another synchronously along the outer surfaces of the spacer and along the subareas of the calibration rod and, in the process, sequentially generating at least measuring signals corresponding to respective spacings between two opposite points on the outer surfaces of the spacer and on the subareas of the calibration rod; and automatically converting the measuring signals corresponding to the respective spacings between the two opposite points on the outer surfaces of the spacer into calibrated measured values with the computing device by using the measuring signals of a known spacing between the subareas of the calibration rod. 8. The method according to claim 7 , which comprises varying a relative position of the fuel element in the Cartesian reference system for scanning further outer surfaces of the spacer by using the probes and the calibration rod. claim 7 9. The method according to claim 6 , which comprises using a plurality of probes for the measuring step, the plurality of probes being situated opposite one another in pairs and simultaneously measuring a plurality of points situated opposite one another in pairs on the outer surfaces of the spacer and on the corresponding subareas of the calibration rod. claim 6 10. The method according to claim 9 , which comprises scanning, with the plurality of probes, further outer surfaces of the spacer and corresponding further subareas of the calibration rod, the further outer surfaces and the further subareas extending along the x-direction. claim 9 11. The method according to claim 9 , which comprises measuring, with the plurality of probes, subareas of a further calibration rod, the subareas of the further calibration rod extending along the x-direction. claim 9 12. The method according to claim 6 , which comprises measuring further subareas of the calibration rod, the further subareas being offset relative to the subareas of the calibration rod. claim 6 13. The method according to claim 6 , which comprises: claim 6 measuring given subareas of a further calibration rod; and measuring further given subareas of the further calibration rod, the further given subareas being offset relative to the given subareas of the further calibration rod. 14. The method according to claim 1 , wherein the step of measuring the calibration rod is performed every time the respective relative position of the outer surface of the spacer of the fuel element is measured. claim 1 15. A method for inspecting an irradiated fuel element having a spacer with two outer surfaces in a nuclear power plant, the method which comprises: measuring, with a measuring device, a respective relative position of the two outer surfaces of the spacer of the fuel element; measuring, with the measuring device, a calibration rod for providing measurements of the calibration rod, the calibration rod having known dimensions; and calibrating the measurements of the spacer by comparing the measurements of the calibration rod with the known dimensions of the calibration rod. 16. A device for inspecting an irradiated fuel element having a spacer with two outer surfaces, comprising: a measuring device having a calibration rod with known dimensions, said measuring device being directed toward the two outer surfaces of the spacer and said calibration rod for forming measuring values defining relative positions of the outer surfaces and said calibration rod; and a computing device connected to said measuring device for calibrating the measurements of the spacer by comparing the measurements of the calibration rod with a known dimensions of the calibration rod. 17. The device according to claim 16 , further comprising a positioning device for positing the fuel element relative to said measuring device, said positioning device having a holder for receiving the fuel element to cause the fuel element to be inserted, with respect to a longitudinal axis thereof, in a vertical direction and to cause the fuel element to be fixed in a horizontal direction, and said positioning device including a positioning drive for moving said measuring device with said calibration rod in the vertical direction. claim 16 18. The device according to claim 16 , wherein said measuring device includes two probes disposed opposite from one another and a drive for moving said probes, and said drive moves said probes synchronously along the outer surfaces of the spacer and said calibration rod. claim 16 19. The device according to claim 16 , wherein said measuring device includes a plurality of mutually oppositely disposed probes, said probes simultaneously generating measured values for a plurality of points on the outer surfaces of the spacer and said calibration rod. claim 16 20. The device according to claim 19 , wherein said measuring device includes further probes and a further calibration rod pointing in opposite directions, said further probes are directed toward mutually oppositely disposed points on two further outer surfaces of the spacer, and the two further outer surfaces respectively point in a same direction as said further calibration rod. claim 19 21. The device according to one of claim 16 , wherein said measuring device includes a drive for positioning said calibration rod against the spacer. claim 16
	abstract	A molten salt reactor includes a nuclear reactor core for sustaining a nuclear fission reaction fueled by a molten fuel salt. A molten fuel salt control system removes a volume of the molten fuel salt from the nuclear reactor core to maintain a reactivity parameter within a range of nominal reactivity. The molten fuel salt control system includes a molten fuel salt exchange system that fluidically couples to the nuclear reactor core and exchanges a volume of the molten fuel salt with a volume of a feed material containing a mixture of a selected fertile material and a carrier salt. The molten fuel salt control system can include a volumetric displacement control system having one or more volumetric displacement bodies insertable into the nuclear reactor core. Each volumetric displacement body can remove a volume of molten fuel salt from the nuclear reactor core, such as via a spill-over system.
	summary
047568739	abstract	A single loop nuclear power plant with a helium cooled high temperature reactor for generation of electric current, designed for a capacity of 1-5 MWe. The plant, which in addition to the high temperature reactor includes a gas turbine assembly and a heat exchange apparatus, is housed in two pressure vessels located above each other and connected in a releasable manner. The lower pressure vessel contains the high temperature reactor and is charged with the primary gas. The other circulation components are located in the upper pressure vessel which is filled with a protective gas. The gas turbine, the radiators, the high temperature compressor, the intermediate radiators, and the low pressure compressor, are arranged above each other in this sequence and aligned with the high temperature reactor. the recuperator is laterally arranged. A generator may also be located in the upper pressure vessel or in a container set upon the upper pressure vessel.
	abstract	The present invention provides a plasma processing apparatus. The apparatus includes a vacuum chamber, a plasma reactor arranged in the vacuum chamber for plasma processing, an RF power source for providing RF signals to 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 includes a transmission line for transmitting RF signals and an outer conductor for shielding the electromagnetic field around the transmission line. The invention can effectively avoid the problem of electric discharge when RF signals transmit in a vacuum chamber, resulting in more security and less transmission power loss.
052672832	description	SPECIFIC DESCRIPTION In FIGS. 1 and 2 of the drawing, we have shown a reactor containment vessel 1 enclosing the reactor core of a boiling-water reactor, for example, which is surrounded by an annular structure 2 to define an annular space 3 extending substantially all around the containment. Adjacent the structure 2 is an auxiliary apparatus building 4 and, spaced from the latter, a chimney or stack 5 opening into the atmosphere. Both in the embodiment of FIG. 1 and in the embodiment of FIG. 2, a system 6 is provided for depressurization of the containment vessel 1. In addition, a system 7 is provided for the emergency evacuation of the space 3 and for maintaining a subatmospheric pressure therein in the case of design-exceeding events involving melting of the core. The latter system 7 comprises a blower system 8 which may include a plurality of parallel blowers for redundancy purposes or to generate the necessary evacuation flow, these blowers discharging into the chimney or stack 5. As represented by the line 20, the atmosphere wherein building 4 is also vented through the stack 5. The various lines and flow directions carrying the discharge gases to the stack are shown in heavy lines and with arrows. The pressure-relief system 6, for venting the pressure in the containment 1, comprises a metal-fiber filter 9 and a molecular sieve 10 downstream thereof, the molecular sieve trapping any radioactive gases, such as fission products, which may pass the metal-fiber filter. The emergency filter of the evacuation system 7 also includes metal-fiber filters 11 and molecular sieves 12 downstream thereof as can be seen from FIG. 1. In the embodiment of FIG. 2, an emergency filter comprises not only the metal-fiber filter 11 and the molecular sieve 12 downstream thereof, but a suspended-matter filter 13 and an active-coal filter 12 in succession. In both embodiments, pluralities of the filter assemblies 11, 12 or 11, 12, 13, 14 are connected in parallel. In the embodiment of FIG. 2, moreover, at the downstream side of each filter assembly, a further suspended-matter filter 15 is provided. The filter capacities of the aerosol filters 11, 13, 15 can be stepped. In the embodiments of FIGS. 1 and 2, in which both systems 6 and 7 have metal-fiber filters and molecular sieves, these can be provided as modular units which can be interchanged for the two systems and provided in as great or small a number as required. The filter units can include other components such as missed separators, droplet separators and heaters as the design requirements dictate.
	summary
062597671	claims	1. An X-ray device comprising: an X-ray imaging apparatus, an X-ray source, an X-ray generator for powering the X-ray source which co-operates with the X-ray imaging apparatus, a programmable control system, a diaphragm unit which is connected to the X-ray source and includes an adjustable diaphragm aperture in order to preset an exposure field on an X-ray image detection device, the diaphragm aperture being adjustable on the one hand by a drive unit which is controlled by the control system and on the other hand by adjusting means for manual adjustment of the diaphragm aperture, and a storage device which co-operates with the control system and in which a respective set of exposure parameters is stored for each of a number of organs, wherein each set includes, in addition to the exposure parameters for the X-ray generator, an adjustment value for adjusting the exposure field, and wherein, when an organ is selected, the adjustment value is fetched and the exposure field is adjusted, by way of the control system and the drive unit, in conformity with the adjustment value associated with the selected organ. 2. An X-ray device as claimed in claim 1, wherein the control system is programmed in such a manner that, after actuation of the adjusting means, the manual adjustment of the exposure field is carried out or preserved independently of an adjustment value fetched before or after that. 3. An X-ray device as claimed in claim 2, wherein the control system is programmed in such a manner that after an X-ray exposure or a change of a patient to be examined an exposure field adjusted by actuation of the adjusting means is adjusted in conformity with the relevant adjustment value fetched. 4. An X-ray device as claimed in claim 1, wherein the distance between the X-ray source and the X-ray image detection device is adjustable, further comprising means for measuring this distance, and wherein the control system is programmed in such a manner that in dependence on the measured distance the diaphragm aperture has a value such that the size of the exposure field on the image detection device assumes its preset value. 5. An X-ray device as claimed in claim 1, wherein X-ray image detection device comprises a flat detector with light-sensitive or X-ray sensitive detector elements which are arranged in the form of a matrix.
	abstract	The present invention relates to a method of confining pollution generated in the top volume and/or in the bottom volume of an enclosure filled with a fluid, i.e. either a gas, which is in general air, or a liquid, which is in general water, the method confining the pollution by thermal stratification. In said method the mean temperature of said top volume is maintained higher than the mean temperature of said bottom volume by an amount that is sufficient to ensure that said two volumes are separated by a turbulent intermediate zone of narrow width, referred to as the xe2x80x9cmixing zonexe2x80x9d, within which a steep temperature gradient is maintained; said intermediate zone constituting a virtual confinement barrier in a horizontal plane. The present invention also relates to apparatus associated with the method.
	summary
	summary
	description	The present invention relates to a method for providing a neutron source. Nuclear power stations transform nuclear energy into heat which may be passed to a working fluid running through and driving turbines to produce electricity. The heat is generated by nuclear fission reactions created by nuclear fuel elements within a nuclear reactor core. The nuclear reactor core is used to initiate and control a sustained nuclear chain reaction. The principal part of the nuclear reactor core is the active zone, where the nuclear fuel elements are situated and the nuclear reaction takes place. More specifically, within the active zone heavy nuclides of the nuclear fuel element undergo fission reaction into lighter ones, called fission products upon absorption of a neutron. Each fission event releases large amounts of energy, in the order of 200 MeV, in the form of kinetic energy of the fission fragments, gamma rays and several fast neutrons. The nuclear fuel element may, for example, be U-233, U-235, Pu-239 or Pu-241. To increase the efficiency of the fission reactions, the nuclear fuel elements may be arranged inside a neutron moderator, such as light or heavy water, or graphite arranged to thermalize neutrons for which the fission reaction has a maximum cross-section. Nuclear reactors may also serve other purposes than energy production such as production of neutron beams to be used in fundamental and applied research, material testing, characterization and analysis, neutron radiography, isotope production, etc. Many of these experiments or, procedures are based on neutrons being scattered from the material or system under study. The use of neutron scattering has many advantages. Neutron interaction with matter is confined to the short-range nuclear and magnetic interaction. The neutrons usually penetrate well through matter, due to their small interaction probability, making neutrons a unique probe for investigating bulk condensed matter. Neutrons can also be used as a surface probe, since the neutrons can be reflected by some surfaces when incident at glancing angles. Hence, neutrons may be both a bulk and a surface probe for investigating structures and dynamics. A few advantages are: Neutrons interact through short-range nuclear interactions and with the atomic magnetic moments; neutrons are penetrating matter efficiently and do not heat up, or damage most samples. Neutrons are good probes for investigating structures in condensed matter as neutron wavelengths are comparable to atomic sizes and interatomic spacing. Neutron energies are comparable to normal mode energies in materials, for example, phonon modes. Neutrons are good probes to investigate the dynamics of solid state and liquid materials. Neutron interaction with hydrogen and deuterium are widely different making the deuterium labelling method an advantage. The large interaction of neutrons with protons makes the neutron a very sensitive probe of hydrogen in many environments, such as living matter. As of today, the majority of neutron sources for neutron scattering research purposes are based on nuclear reactors. Fission fragments are heavy and remain inside the nuclear fuel elements therefore producing the major source of heat while energetic gammas and fast neutrons penetrate most everything and are carefully shielded against. Gamma rays and fast neutrons are a nuisance to neutron scattering work and are, as much as possible, not allowed to reach the detectors. After being slowed down by the moderator materials, the neutrons are used to sustain the fission reaction as well as beams extracted through beam tubes for low energy, i.e. hot, thermal and cold neutron scattering. There is, however, a need to improve the efficiency at which the neutrons are produced. There is also a demand for brighter neutron sources producing a higher flux of neutrons. It is desirable to reduce the inventory of radioactive and fissionable materials to increase safety and to reduce proliferation concerns. In view of the above, it is an object of the present invention to provide an improved neutron source. The method further takes advantage of pre-existing infrastructure of a nuclear reactor based neutrons source reducing costs associated with providing the improved neutron source. A reduction of the inventory of radioactive and fissile material may further be provided. According to an aspect of the invention a method for providing a neutron source is provided. The method comprising: providing a nuclear reactor neutron source, the nuclear reactor neutron source comprising: an enclosure delimiting a chamber, a nuclear reactor core arranged inside the chamber, the nuclear reactor core is configured to produce neutrons from a nuclear fuel element inside the nuclear reactor core; installing a beam generator arranged to generate a beam directed into the chamber; and installing, inside the chamber, a target arranged to eject neutrons upon impact of the beam such that neutrons are ejected from the target and emitted from the chamber. The term “beam generator” shall in this context be construed as a generator configured to generate a beam of charged particles or a beam of electromagnetic radiation. The charged particles are selected from the group of charged particles comprising ions, electrons and positrons. Non-limiting examples of ions are protons and deuterons. The beam generator may be an accelerator. Non-limiting examples of energy of the beam are 50-500 keV for electromagnetic radiation, 10-100 MeV for electrons, and 1-3000 MeV for ions. An advantage of the method is that a more efficient neutron source may be provided. The amount of energy needed for forming the neutrons may thereby be reduced. A larger flux of neutrons may, moreover, be provided. Pulsing of the provided neutrons may further be provided. By utilizing parts of a nuclear reactor neutron source when providing of the neutron source additional advantages are obtained. The method substantially reduces the investment costs by the conversion of the nuclear reactor neutron source, i.e. the “nuclear” into a “non-nuclear”, that is non-fission based, neutron source. The method further allows for re-use of infrastructure such as primarily buildings, shielding, beam lines, irradiation ports, neutron scattering instruments or parts of neutron scattering instruments and other experimental or production stations for neutron beam use, utilities, and safety and security functions. The method may further comprise removing the nuclear fuel element of the nuclear reactor core from the chamber. The replacement of the nuclear reactor source by the non-nuclear neutron sources reduces operational cost and enhances security. The time and cost needed for constructing a non-fission based neutron source may further be reduced. This since at least a portion of expenses of the decommissioning, dismantling and disposal of the nuclear reactor source is reduced. To this end, the provided neutron source allows for cheaper operation, including the reduced costs for nuclear fuel elements, a longer lifetime, i.e. extending the lifetime of the nuclear reactor neutron source. A larger flexibility in providing different neutron fluxes is further provided. This is advantageous as different experiments and applications require different neutron fluxes, even a lower flux source may be advantageous as and will be seen as an improved, if it has longer lifetime, lower costs, lower gamma ray production. The provided nuclear reactor neutron source may comprise a neutron beam outlet arranged through the enclosure to provide a neutron passage for neutrons from the chamber and the act of installing the target may comprise arranging the spallation target such that neutrons ejected from the target are emitted from the chamber via the neutron passage. An efficient output of neutrons from the chamber may thereby be achieved. Pre-existing infrastructure such as experimental station for conducting neutron scattering experiments or parts of such experiments may thereby be reused. Hence, the costs associated with providing the improved neutron source, are thereby reduced. The act of removing the nuclear fuel element of the nuclear reactor core from the chamber may form a void inside the chamber, and the act of installing the target may comprise arranging the target inside the void. The target may thereby be placed at a centre location that, for example, inside the active zone of the provided nuclear reactor core of the nuclear reactor neutron source. The freed space may efficiently be used for installing the target. The act of removing the nuclear fuel element of the nuclear reactor core may comprise removing the nuclear reactor core. The chamber of the provided nuclear reactor neutron source may further comprise a moderator, and the act of installing the target may comprise arranging the target inside the moderator. The moderator, also referred to as a neutron moderator, may thereby slow down the neutrons ejected from the target allowing for low neutron energy, i.e. hot, thermal and cold neutron scattering. In nuclear reactor neutron sources the moderator(s) that primarily assure the maintenance of the chain reaction are called “moderator”, they may have large volumes of several m3 and they operate in the temperature range between room temperature and typically smaller than 100° C. This moderator temperature range is called “thermal”. Moderators that are designed to emit slow neutrons of a particular energy range are called “source” and they are typically of volumes between 1-50 litres. A “hot source” has temperature above 1000° C. and a “cold source” below 150° C. In spallation and compact neutron sources these structures are called “hot moderator” and “cold moderator”, respectively, and there may also be “thermal moderators” installed, with typical volumes of 1-5 litre. The chamber of the provided nuclear reactor neutron source may further comprise a reflector, and the act of installing the target may comprise arranging the target inside the reflector. The reflector is arranged to reduce neutrons from leaking out of the enclosure, by being reflected back into the centre of the nuclear reactor core. A more flexible arrangement of the target may thereby be achieved. The reflector may enhance the intensity of the slow neutrons emitted by the moderators by reflecting neutrons into the moderators that would otherwise escape without interacting with the moderators. In nuclear reactor neutron sources the same structure may have both the function of moderator and reflector and called either moderator or reflector as above or “moderator-reflector”. Water moderator and moderator-reflector is often also used for cooling the nuclear fuel elements. The provided nuclear reactor neutron source may further comprise an additional neutron beam outlet arranged through the enclosure to provide an additional neutron passage for neutrons from the chamber, and the act of installing of the beam generator may comprise directing the beam into the chamber via the additional neutron passage onto the target. The use of the existing additional neutron passage reduces cost and provides an efficient passage for the beam to reach the target. The enclosure of the provided nuclear reactor neutron source may further comprise a thermal column or an access shaft, and the act of installing of the beam generator comprises directing the beam into the chamber via the thermal column or the access shaft onto the target. The use of the existing column or an access shaft reduces cost and provides an efficient passage for ions to reach the target. The act of installing a beam generator may comprise installing the beam generator or a portion of the beam generator inside the chamber. A more compact neutron source may thereby be provided. The nuclear reactor core of the provided nuclear reactor neutron source may comprise fissile material. The moderator of the provided nuclear reactor neutron source may comprise a material selected from the group consisting of H2O, D2O, liquid or solid hydrogen or deuterium, liquid or solid methane, mesithelene, and ice. The reflector of the provided nuclear reactor neutron source may comprise a material selected from the group consisting of graphite, beryllium, steel, tungsten carbide, nickel, tungsten, heavy water, lead or alloys of these. The act of installing a target may comprise installing a target comprising a material selected from the group consisting of mercury, tantalum, lead, liquid lead-bismuth alloy, tungsten, rhenium, or alloys of these, or beryllium or lithium. The act of installing a beam generator arranged to generate a beam directed into the chamber, may comprise installing the beam generator to form part of a spallation neutron source for providing the neutrons. The act of installing a beam generator arranged to generate a beam directed into the chamber, may comprise installing the beam generator to form part of a compact neutron source for providing the neutrons. The wording “spallation” should be construed as a nuclear reaction process in which light particles such as neutrons are ejected as the result of bombardment as by high-energy particles such as ions, e.g. protons. Spallation based replacement can be applied in a higher power range than other particle or lower energy (<200 MeV) accelerator based systems. As a non-limiting example, 1-GeV proton is capable of producing approximately 25 neutrons from a target such as lead, with heat deposition in the target of about half of the proton beam power—meaning one order of magnitude less heat must be dissipated than in a fission reaction producing the same time-averaged neutron flux. Hence a more effective production of neutrons is achieved. “Compact neutron sources” comprise beam generators arranged to generate a beam, of radiation or ions, with an energy range of 1-100 MeV. The generated beam may, for example, comprise protons which when colliding with a target create light particles such as neutrons. Advantages of the compact neutron sources are that have a small footprint, typically in the range of 3-20 m long and 20-60 cm in diameter. The length can be longer, if the energy is higher, say up to 50 m to reach 100 MeV. The compact neutron sources also considerable cheaper, to construct and handle, than for instance reactor based neutron sources. By use of a compact neutron source, additional construction work as for example to strengthen the shielding system of a reactor based neutron source is reduced in extent. The chamber of the provided nuclear reactor neutron source may further comprise a hot or cold neutron source, and the act of installing a target may comprise arranging the target adjacent to the hot or cold neutron source. Neutrons ejected from the target may thereby interact with the cold neutron source. After interaction the typically Maxwellian neutron spectral distribution may thereby be shifted to lower energies by neutrons slowing down through inelastic scattering processes with the cold neutron source. The cold neutron source may be arranged within the peak flux position within the reflector region. A further scope of applicability of the present invention will become apparent from the detailed description given below. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description. Hence, it is to be understood that this invention is not limited to the particular component parts of the device described or steps of the methods described as such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claim, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to “a unit” or “the unit” may include several devices, and the like. Furthermore, the words “comprising”, “including”, “containing” and similar wordings do not exclude other elements or steps. The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and to fully convey the scope of the invention to the skilled person. In the following a method for providing a neutron source is described with reference to FIG. 1 and FIGS. 3-7. FIG. 2 illustrates a nuclear reactor neutron source according to prior art. FIG. 1 shows a flow chart illustrating the method 100 for providing a neutron source. FIG. 3 illustrates a pre-stage of the neutron source. FIGS. 4-7, illustrates neutron sources provided by the method 100. Referring to FIGS. 1 and 2, the method 100 comprises the act of providing 102 a nuclear reactor neutron source 200. FIG. 2 illustrates a schematic top view of a nuclear reactor neutron source according to prior art. The nuclear reactor neutron source 200 comprises an enclosure 202 delimiting a chamber 204. A shielding 205 is further provided to prevent undesired radiation such as neutrons and gamma rays to exit through the enclosure 202 of the chamber 204. A for a user securer environment surrounding the nuclear reactor neutron source is thereby provided. A nuclear reactor core 206 is arranged inside the chamber 204. The nuclear reactor core 206 is configured to produce neutrons from a nuclear fuel element 207 inside the nuclear reactor core 206, i.e. heavy nuclides of the nuclear fuel element 207, comprising a fissile material, may undergo a fission reaction into lighter ones, so called fission products upon absorption of a neutron. Each fission event releases large amounts of energy in the form of kinetic energy of the fission fragments, gamma rays and neutrons. Hence, the nuclear fuel element 207 forms an active part of the nuclear reactor core 206. The nuclear reactor core 206 may thereby be referred to as an active zone. The chamber 204 of the provided nuclear reactor neutron source 200 may further comprise a moderator 208. The moderator 208 is arranged to slow down the neutrons ejected from the nuclear fuel element 207. The nuclear reactor neutron source 200 may further comprise a neutron beam outlet 209 arranged through the enclosure 202 to provide a neutron passage for neutrons from the chamber 204. An output of neutrons, generated by the fission events, from the chamber 204 may thereby be achieved. The method 100 may comprise the action of removing 104 the nuclear fuel element 207 of the nuclear reactor core 206 from the chamber 204, see the pre-stage 300 of the neutron source in FIG. 3. As a non-limiting example, the nuclear reactor core 206 comprises a plurality of nuclear fuel elements 207, which are all removed in the action of removing 104. The skilled person in the art, however, realizes that one or more of the fuel elements may be removed in the act of removing. It should further be noted that the nuclear reactor core 206 may be removed in the act of removing 104, not shown. It should further be noted that operation and decommissioning of nuclear reactor neutrons sources are internationally regulated and supervised by the International Atomic Energy Agency for both safety and worldwide non-proliferation purposes. Hence, by removing 104 the nuclear fuel element 207 or the nuclear reactor core 206 from the chamber 204 a reduction of nuclear fuel elements and other radioactive materials within the chamber 204 is achieved. In other words, a fissile material of the nuclear reactor core is thereby removed. A neutron source requiring less governmental inspection and regulations may thereby be provided. The method 100 further comprises the act of installing 106 a beam generator 402, see FIG. 4. The beam generator 402 is arranged to generate a beam of charged particles or a beam of electromagnetic radiation and to direct the beam into the chamber 204. The beam generator may, for example, form part of a spallation neutron source or a compact neutron source as will be described further below. The method 100 further comprises the action of installing 108, inside the chamber 204, a target 404 arranged to eject neutrons upon impact of the beam such that neutrons are ejected from the target 404 and emitted from the chamber 204. The provided neutron source 400 is illustrated in FIG. 4. The neutrons generated may be emitted from the chamber 204 via the neutron beam outlet 209. The generated neutrons may, moreover, be directed via a beam line 214 to an experimental station 216 for conducting neutron scattering experiments or investigations. The beam line 214 and the experimental station 216 may form parts of the pre-existing infrastructure of the nuclear reactor neutron source 200 which then may be reused. Hence, a cost reduction is associated with providing the improved neutron source. A new beam line and/or an experimental station may alternatively be provided. In the above description the act of removing 104 at least the nuclear fuel element 207 of the nuclear reactor core 200 from the chamber 204 forms a void 218 inside the chamber 204, see FIGS. 3 and 4. The act of installing 106 the target 404 may further comprise arranging the target 404 inside the void 218. The target 404 may thereby be arranged at the location where neutrons are generated in the nuclear reactor neutron source 200. Hence, the provided neutron source may efficiently take advantage of the design of the reactor core neutron source from the target. The target 404 may be arranged at other locations as will be described below. The provided nuclear reactor neutron source 200 may also comprise an additional neutron beam outlet 224 arranged through the enclosure 202 to provide an additional neutron passage for neutrons from the chamber 204 see FIG. 2-4. The act of installing 106 of the beam generator 402 may then comprise directing the beam into the chamber 204 via the additional neutron passage onto the target 404. The use of an existing neutron beam outlet 224 reduces cost and provides an efficient passage for the beam to reach the target 404. For the purpose of neutron scattering investigations neutrons having different kinetic energies may be used. The neutron energies may be referred to as epithermal, >500 meV, hot, about 100 meV-500 meV, thermal, about 10-100 meV, and cold, <10 meV. Hot, thermal and cold neutrons may be referred to as “slow” neutrons. For investigating materials by neutron scattering techniques the slow neutrons are preferably used. As non-limiting examples, the generated neutrons from the target may be emitted from the moderators, the moderators having different temperatures, typically but not limiting to 25-40 K hydrogen or methane for cold, 300 K water for thermal and 2000 K graphite for hot neutrons. Here the word “moderator” is used in the sense of slowing down neutrons for use in emitted beams, which are described by the word “source” for reactor neutron sources, e.g. “cold source”. We note that the moderator, the any of the controlled temperature “sources” of the originally provided nuclear reactor neutron source may be used as moderators for the beam generator based neutron production according to this invention. Epithermal neutrons up to several MeV energies may also be used, for example for the purposes of radiography of massive objects, such as concrete structures and emulating cosmic radiation conditions for testing electronic equipment. Generally, most epithermal neutrons are directly ejected by the target, but may also be present in the spectra of the neutrons emitted from the moderators. A reduction of epithermal neutrons and gamma radiation neutron passage may thereby be provided. This arrangement may, for example, be desirable for nuclear reactor neutron source having a split-core geometry whereby the neutron passage is provided by a thermal neutron beam tube which is not directed at the nuclear fuel elements directly. Thus, the chamber 204 of the provided nuclear reactor neutron source 200 may further comprise a moderator 208 as discussed above. The act of installing 108 a target may then comprise arranging a target 502 inside the moderator 208, see the provided neutron source 500 of FIG. 5. The moderator 208 may thereby slow down the neutrons ejected from the target 502 allowing for low energy, i.e. thermal and cold, neutron scattering. The neutron beam outlet 209 and the additional neutron beam outlet 224 are for clarity illustrated at different locations than the ones shown in FIG. 2. The skilled person in the art realizes that the neutron beam outlet 209 and the additional neutron beam outlet 224 may be the same as in FIG. 2 or be formed by additional neutron beam outlets of the nuclear reactor neutron source 200. Alternatively, new neutron beam outlets may be provided to form the neutron source 500 of FIG. 5. To this end, the beam generator 402 may be arranged to direct the beam into the chamber 204 and onto the target 502 through different neutron passage. The chamber 204 of the provided nuclear reactor neutron source 200 may further comprise a reflector 226. The act of installing 108 a target may then comprise arranging the target 602 inside the reflector 226, see the provided neutron source 600 of FIG. 6. The neutron beam outlet 209 and the additional neutron beam outlet 224 are here for clarity illustrated at different locations than in the previous figures. The skilled person in the art realizes that the neutron beam outlet 209 and the additional neutron beam outlet 224 may be the same as in, for example, FIG. 5 or be formed by other neutron beam outlets of the nuclear reactor neutron source 200. Alternatively, new neutron beam outlets may be provided to form the neutron source 600 of FIG. 6. To this end, the beam generator 402 may be arranged to direct the beam into the chamber 204 and onto the target 602. The reflector 226 may enhance the intensity of slow neutrons emitted by a target directly, or via the moderator 208 by reflecting neutrons back into the moderator 208 that would otherwise escape the chamber 204 without interacting with the moderator 208. A larger population of neutrons may thereby be provided for experiments such as neutron scattering or other neutron based investigations. The chamber 204 of the provided nuclear reactor neutron source 200 may further comprise a hot or cold neutron source 230, see for example FIGS. 2 and 7. The act of installing 108 a target 702 may comprise arranging the target 702 adjacent to the hot or cold neutron source 230. The target 702 may, for example, be arranged inside the void 218 as illustrated in neutron source 700 of FIG. 7. It should, however, be noted that the cold neutron source may in other arrangements be arranged outside the void, such as in the moderator or the reflector. The hot or cold neutron source may, for example, be arranged within the peak flux position within the reflector region. Neutrons ejected from the target may thereby interact with the cold neutron source. After interaction the typically Maxwellian neutron spectral distribution may thereby be shifted to lower energies by neutrons slowing down through inelastic scattering processes with the cold neutron source. The act of installing a beam generator arranged to generate a beam directed into the chamber, may comprise installing a spallation neutron source for providing the beam of the beam generator. The spallation neutron source may, for example, be arranged to produce protons and to accelerate these protons to energies above a threshold of 120 MeV. The spallation neutron source may be referred to as a spallation accelerator. Efficient spallation processes may thereby be achieved by directing the beam of protons on a target. The target may for such processes be referred to as a spallation target. An efficient generation of neutrons may be provided by the spallation processes. To achieve an efficient spallation process, the act of installing a target may comprise installing a target, i.e. a spallation target, comprising a material selected from the group consisting of mercury, tantalum, lead, liquid lead-bismuth alloy, tungsten, rhenium, or alloys of these. The act of installing a beam generator arranged to generate a beam directed into the chamber, may comprise installing a compact neutron source for providing the beam of the beam generator. The act of installing a target may then comprise installing a target comprising a material selected from the group consisting of beryllium or lithium. It should be noted that spallation sources allow for us to produce the highest neutron fluxes. They are more expensive than the compact sources, in particular compact sources below 10 MeV proton energy, which require lesser shielding. The compact sources are cheaper to build and operate than spallation sources. With state of the art target-moderator-reflector design they may deliver sufficient amount of neutrons for a number of uses, where it is then not desirable to use the more intense, but also more expensive spallation sources. The beam generator may be arranged to provide a pulsed beam. An efficiently pulsed neutron source may thereby be provided. For a pulsed neutron source, the repetition rate of the proton acceleration is an important parameter to be considered. The pulsed nature of the neutron sources may offer an advantage for experiments using a time-of-flight, TOF, method, in which the speed of the neutron is measured by timing its flight from the source to the detector. When a long neutron flight path is used for improved TOF resolution, a slow repetition rate is moreover, desirable to minimize frame overlap, i.e. where fast neutrons from one pulse overlap with the slow neutrons from the previous pulse. For pulsed neutron sources heat is predominantly produced in the target during the pulses. This allows the heat to dissipate slowly in the period between pulses, so the instantaneous power and neutron flux can be increased. As non limiting examples, short-pulse spallation neutron sources, typically delivering 1-μs proton pulse widths, have predominated because of the good timing resolution provided for TOF measurements of the neutron energy. The neutron source may further comprise ring structures, i.e. synchrotrons or accumulator/storage rings to provide high proton intensities in such short pulses. Alternatively, long-pulse sources, typically having 1 or a few ms proton pulse widths, may be used to provide a neutron source with higher power and with high timing resolution provided by other means, for example by mechanical choppers acting on the slow neutron beams In the above description, the moderator, reflector, and/or cold neutron source, have been described to form parts of the provided nuclear reactor neutron source 200. The skilled person in the art, however, realizes that the moderator, reflector, and/or hot, thermal and cold neutron source may be added, according to the present method, to a provided nuclear reactor neutron source not comprising these elements, or as additions to improve the slow neutron production from the target. The target may be installed together with a surrounding structure that may comprise cooling, reflector and moderator structures and other materials structures in order to adapt to and complement the structures re-used from the nuclear reactor neutron source. To this end, additional elements such as a neutron beam outlet may further be added to the provided nuclear reactor neutron source. Hence, the neutron source may comprise a plurality of neutron beam outlets. The neutron source may further comprise a plurality of targets with a plurality of moderators and reflectors or parts of reflector systems. A plurality of targets may be provided by a plurality of beam generators and the beam of a beam generator may be shared by several targets both simultaneously or alternatively in time, including sending subsequent beam pulses from the beam generator to different targets. A plurality of experimental stations, and a plurality of neutron beam outlets may be used. Hence, neutron may be provided to the plurality of experimental stations via one or more neutron beam outlets. It should further be understood that the compact neutron source or part of it can also be placed within in a thermal column, or in the vertical access shaft previously used to access the nuclear reactor core, including changing nuclear fuel elements of the previous nuclear reactor neutrons source. The act of removing the nuclear fuel element of the nuclear reactor core from the chamber may be temporary or permanent. The temporary or permanent removal of the nuclear fuel element may comprise, but is not limited to, replacing the nuclear fuel element with other structures, which can be dummy containers, space holders to keep out fluids, reflector or moderator materials. Parts of the old reactor can be re-used or replaced according to case by case analysis. In a swimming pool type of nuclear reactor neutron source, the installed equipment, such as the beam generator, may be placed inside a tube structure, such that a tube arranged to be watertight. Alternatively, the water can be replaced by solid shielding material. Reflectors, moderators, cold sources also can be re-used, partially re-used, modified or replaced. The beam generator may alternatively be arranged to generate electromagnetic radiation such as gamma rays. The beam generator may alternatively be arranged to generate electrons. The electron beam generator may produce neutrons in a target material using the Bremsstrahlung photo-neutron reaction. The beam generated from the beam generator is generally provided in a vacuum tube of about 5-10 cm diameter a few meters away from the target. To this end, a portion of the chamber surrounding the target may be evacuated such that a vacuum is formed. The beam generator may be arranged to generate a plurality of beams directed into the chamber. A plurality of targets may be installed inside the chamber, the targets being arranged to eject neutrons upon impact of the beam such that neutrons are ejected from the targets and emitted from the chamber. Hence, several targets may be placed inside the chamber. To operate these multiple targets one may use a beam of a beam generator divided between several targets or alternatively one may use several beam generators. The plurality of targets may be operated simultaneously in time. A target may be arranged in vicinity to or adjacent to a neutron beam outlet to enhance the neutron output. The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the act of installing a beam generator may comprise installing the beam generator or a portion of the beam generator inside the chamber, not shown. A neutron source having smaller foot print may thereby be provided. The provided reactor neutron source may comprise several beam outlets or other shafts, openings for such use. In addition, new beam outlets can be provided by opening by drilling, cutting holes through the enclosure, shielding, chamber, and other structures. The enclosure of the provided nuclear reactor neutron source may further comprise a thermal column or an access shaft, not shown. The act of installing of the beam generator may then comprise directing the beam into the chamber via the thermal column or the access shaft onto the target. The use of the existing column or an access shaft reduces cost and provides an efficient passage for ions to reach the target. The moderator of the provided nuclear reactor neutron source may comprise a material selected from the group consisting of H2O, D2O, liquid or solid hydrogen or deuterium, liquid or solid methane, mesithelene, and ice. The reflector of the provided nuclear reactor neutron source may comprise a material selected from the group consisting of graphite, beryllium, steel, tungsten carbide, nickel, tungsten, heavy water, lead, alloys of these. It should be noted that when target is installed somewhere inside the chamber, e.g. in the nuclear reactor core or inside the moderator or the reflector, the target may be surrounded by an additional target moderator, an additional target reflector and/or an additional target shielding structure, in order to complement pre-existing reflector and/or shielding or to fill a void formed for example by the act of removal disclosed above. The shielding may be lead, steel, and concrete on the one hand and borated polyethylene on the other. The footprint of the shielding may for example be 2-3 m across for proton energies below 10 MeV, but as the energies go higher, the target shielding needs to increase in size, since the generated fast neutron energies are getting higher. As noted above, neutron production utilizing a beam generator and a target inside the chamber may be provided without removing all or any nuclear fuel elements of the nuclear reactor neutrons source. An advantage of the method is that a neutron source is provided where the neutrons may be provided by nuclear reactions by the nuclear fuel element or by the target. Hence, a dual source for neutron production is provided. The lifetime of the nuclear reactor based neutron source may be increased as the amount of nuclear fuel needed for producing neutrons is reduced. Less nuclear waste will thereby be produced. The nuclear fuel material may further remain in the chamber reducing cost associated with decommissioning of the nuclear reactor core or parts thereof. The target may, for example, be installed in the reflector as illustrated in FIG. 8, the advantages are described above. The skilled person in the art, however, realizes that the target or targets may be arranged at other locations in the chamber as discussed above. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.
048225550	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a container capable of holding plate-like objects including angle-like objects easily in a compactly laminated state, and more particularly to a container for plate-like objects, which is suitably used to hold, for example, plate-like wastes resulting from cutting of a used fuel channel box taken out of a boiling-water nuclear reactor. 2. Description of the Related Art In order to place the largest possible number of plate-like objects in a container, it is necessary that the plate-like objects be laminated therein as closely as possible but laminating plate-like objects in such a manner in a container cannot always be done with ease. The conventional operation for placing plate-like objects in a container will now be described taking as an example an operation for placing in a container plate-like wastes of cut pieces of a used fuel channel box taken out of a boiling water reactor. A fuel channel box for a boiling-water reactor is a cross-sectionally square cylinder enclosing a fuel assembly (bundle of fuel rods), having a height of about 410 cm, a width of about 15 cm and a wall thickness of 2 mm and consisting of zircaloy. When a used fuel assembly is reprocessed, the fuel channel box is removed therefrom and cut along a diagonal line of a cross section thereof in the water in a waste storage pool so as to obtain angle-like or L-shaped objects 1 of about 410 cm in length shown in FIG. 4 (accordingly, one fuel channel box is divided into two angle-like objects 1). As shown in FIG. 5, this plate-like object 1 is suspended in the water in a waste storage pool 2 from a hoist 4, which is set on a service platform 3 provided above the pool 2 so that the platform 3 can be horizontally moved. The suspended plate-like object 1 is transferred to the position in the water and above a container 5 in the pool 2 and placed therein. Needless to say, the purpose of handling the plate-like object 1 in a waste storage pool is to prevent the radiation exposure. In order to utilize a waste storage space with a higher efficiency, it is necessary that the largest possible number of plate-like objects 1 be placed in each container 5. Accordingly, in the conventional techniques of this kind, a worker on the service platform 3 holds an elongated rod and pushes at its free end the plate-like object 1 being placed in the container 5, in such a manner that the plate-like objects therein contact each other as closely as possible. However, moving an elongated rod in the water causes the operation efficiency to lower, and it is difficult to place plate-like objects in the container compactly by this method. Therefore, by this method, only thirty pieces of plate-like objects 1 can be placed in a container of 300 mm in length and 227 mm in width. SUMMARY OF THE INVENTION An object of the present invention is to provide a simply-constructed container for plate-like objects, which is capable of holding plate-like objects in a tightly laminated state, whereby the utilization of the hollow in the container and the efficiency of placing plate-like objects in the container can be improved. The features of the container for plate-like objects according to the present invention reside in that elongated springs are provided in the container so as to extend thereacross in such a manner that one end of each of the springs is fixed to one inner wall surface of the container with the other end thereof being free and able to urge the introduced plate-like objects to the opposite inner wall surface of the container. Owing to these springs, plate-like objects can be placed in the container in a laminated state so that the plate-like objects tightly contact each other and the inner surface of the container closely. The above and other objects as well as advantageous features of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.
	abstract	A scintillator panel includes a substrate made of an organic material, a barrier layer formed on the substrate and including thallium iodide as a main component, and a scintillator layer formed on the barrier layer and including cesium iodide as a main component. According to this scintillator panel, moisture resistance can be improved by providing the barrier layer between the substrate and the scintillator layer.
042630975	claims	1. In apparatus for generating and confining a toroidal plasma comprising means for providing a toroidal magnetic field in a plasma zone, said toroidal field being of increasing strength with decreasing radial distance from the major toroidal axis, and means for generating a plasma in the plasma zone, said plasma having a dynamic trapped particle population of electrons, which reflect back and forth along the minor toroidal axis without contributing to the net toroidal plasma current, the improvement comprising means for asymmetrically altering the trapped electron particle population with respect to the minor toroidal axis to produce an ohmic plasma current along the minor toroidal axis. 2. Apparatus in accordance with claim 1 wherein said trapped particle population altering means comprises means for asymmetrically trapping plasma electrons. 3. Apparatus in accordance with claim 2 wherein said trapping means comprises means for providing an r-f field which propagates in a direction parallel to the plasma-confining magnetic field, said r-f field having an electric field vector perpendicular to said confining field, and being at resonance with a plasma resonance frequency, to increase electron perpendicular velocity. 4. Apparatus in accordance with claim 3 wherein said frequency is an electron cyclotron resonance frequency. 5. A method for providing a toroidal plasma current comprising the steps of providing a toroidal magnetic field in a plasma confinement zone, said toroidal field being of increasing magnetic strength with decreasing distance from the major toroidal axis, providing a plasma in said plasma zone and an initial toroidal current in said plasma to produce a poloidal field, said toroidal field and said poloidal field producing a plasma confining magnetic field, said plasma having a dynamic trapped particle population of electrons which reflect back and forth along the minor toroidal axis without contributing to the net toroidal plasma current, and increasing the electron perpendicular velocity to asymmetrically trap plasma electrons with respect to the minor toroidal axis to produce a net current in said plasma. 6. A method in accordance with claim 5 wherein said electron perpendicular velocity is increased by applying an r-f field which propagates in a direction parallel to the plasma confining magnetic field, said r-f field having an electric field vector perpendicular to said confining field and being at resonance with a plasma resonance frequency to increase electron perpendicular velocity. 7. A method in accordance with claim 6 wherein said frequency is an electron cyclotron resonance frequency. 8. Apparatus in accordance with claim 1 further including means for applying counter-current r-f ion cyclotron resonance energy to cancel ion momentum resulting from electron friction. 9. A method in accordance with claim 5 further including the step of applying counter current r-f ion cyclotron resonance energy for cancelling ion momentum from electron friction.
050139452	abstract	A linearly operating motor for stepwise advance of a driven member (11), such as a shaft, comprises an elongated body (10) with length variable properties, and means (15) for changing the length of said body (10). The driven member (11) is provided with at least one locking member (12), whereby at length increase of said body (10) the locking member (12) is arranged, by means of said length increase, to be brought into engagement with said driven member (11) and said body (10) is adapted to act upon the locking member (12) in such a manner the locking member and the driven member (11) are displaced at length increase of the elongated body (10).
	claims	1. A radiation source container that accommodates a radiation source, comprising:a radiation source capsule;a radiation source holder including an aperture that emits unidirectionally radiation emitted from a radiation port of said radiation source capsule, that provides screening such that no leakage of said radiation takes place except from said aperture, and that fixes said radiation source capsule in a manner that is difficult to attach or detach;an irradiation window that transmits radiation emitted from said aperture;an attenuation plate provided between said radiation port of said radiation source capsule and said irradiation window, that attenuates an amount of radiation emitted from said radiation source capsule prior to reaching said irradiation window;a shutter provided between said attenuation plate and said irradiation window and that screens a radiation emitted from said irradiation window; anda capsule cover whereby, when a recommended use period in respect of a sealing performance of said radiation source capsule has expired, said attenuating plate is removed and said radiation port of said radiation source capsule is resealed with one having same material properties and same thickness as said removed attenuating plate, entirely covering said radiation source capsule. 2. The radiation source container according to claim 1,wherein said attenuating plate is provided on said radiation source capsule and thickness and material properties of said attenuating plate are equivalent to those of a sealing weld of said radiation source capsule. 3. A radiation source container said comprising:a radiation capsule including a radiation port;an attenuating plate that comprises:a first capsule cover including a plurality of metal plates, wherein, when a recommended period of use in regard to sealing performance of said radiation source capsule has expired, one of said metal plates is removed and said radiation source capsule is entirely resealed with one having same material properties and same thickness as said one metal plate that was removed from said radiation port of said radiation source capsule; anda second capsule cover, wherein, when a guaranteed life in regard to sealing performance of said first capsule cover has expired, another one of said metal plates is removed and said first capsule cover is entirely resealed with one having same material properties and same thickness as said another one metal plate that was removed,so that said radiation source capsule can be reused a plurality of times. 4. A method of extending a sealing life of a radiation source capsule that seals a radiation source accommodated in a radiation source container, comprising:providing an attenuating plate that produces attenuation beforehand so as to present a value corresponding to an amount of attenuation of an amount of radiation emitted from said radiation source capsule of said radiation source container in a recommended period of use of sealing said radiation capsule; andremoving said attenuating plate and resealing a radiation port of said radiation source capsule with one having same material properties and same thickness as said removed attenuating plate so as to cover said radiation source capsule entirely, when a recommended use period in respect of the sealing performance of said radiation source capsule has expired.
	abstract	A canister for storing spent nuclear fuel includes an elongated shell, baseplate enclosing the bottom end of the shell, and removable top lid bolted to the shell. The shell may have a dual thickness comprising a lower portion with first thickness and upper portion with greater second thickness by comparison. The upper portion is formed by an annular boss defining a fastening portion of the shell including plural threaded bores for engaging the lid bolting. The fastening portion may protrude radially outwards or inwards in different embodiments. The lid has a mounting flange receiving the bolts and is seated on the top end of shell. The mounting flange does not protrude radially beyond the outer surface of the fastener portion to minimize the diameter of the canister for placement inside an outer radiation shielded overpack or cask for transport/storage. The shell may optionally include cooling fins.
	claims	1. An apparatus comprising:a radiation absorption layer comprising an electrode;a counter;a controller configured to cause a number registered by the counter to change, in response to an absolute value of an electrical signal on the electrode equaling or exceeding an absolute value of a second threshold during a time delay that is started from a time at which the absolute value of the electrical signal equals or exceeds an absolute value of a first threshold. 2. The apparatus of claim 1, further comprising a capacitor module electrically connected to the electrode, wherein the capacitor module is configured to collect charge carriers from the electrode. 3. The apparatus of claim 1, wherein the absolute value of the second threshold is greater than the absolute value of the first threshold. 4. The apparatus of claim 1, further comprising a meter, wherein the controller is configured to cause the meter to measure the electrical signal upon expiration of the time delay. 5. The apparatus of claim 4, wherein the controller is configured to determine an energy of the radiation particles based on a value of the electrical signal measured upon expiration of the time delay. 6. The apparatus of claim 1, wherein the controller is configured to connect the electrode to an electrical ground. 7. The apparatus of claim 1, wherein a rate of change of the electrical signal is substantially zero at expiration of the time delay. 8. The apparatus of claim 1, wherein a rate of change of the electrical signal is substantially non-zero at expiration of the time delay. 9. The apparatus of claim 1, wherein the radiation absorption layer comprises a diode. 10. The apparatus of claim 1, wherein the radiation absorption layer comprises silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. 11. The apparatus of claim 1, wherein the apparatus does not comprise a scintillator. 12. The apparatus of claim 1, wherein the apparatus comprises an array of pixels. 13. The apparatus of claim 1, wherein the radiation particles are photons. 14. The apparatus of claim 13, wherein the photons are X-ray photons. 15. The apparatus of claim 1, wherein the electrical signal is a voltage. 16. A system comprising the apparatus of claim 1 and a radiation source. 17. A system comprising the apparatus of claim 1 and an electron source.
042007941	description	DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 is a sectional view taken through plane 1--1 of FIG. 2 of a preferred form of micro lens array and micro deflector assembly according to the invention. As shown in FIGS. 1 and 2, the assembly is comprised by a micro lens array sub-assembly shown generally at 11, a micro deflector sub-assembly 12, a target assembly shown generally at 13, and a plurality of elongated glass support rods two of which are shown at 14 and all of which extend at substantially right angles to the plane of the micro lens array plates comprising the micro lens array sub-assembly and the plane of the micro deflection bars comprising the micro deflector assembly. In addition, the assembly further includes a termination plate shown at 15 which comprises a part of the micro lens array sub-assembly as will be explained more fully hereafter. The construction of the micro lens array sub-assembly is best seen in FIG. 3 and FIG. 4 of the drawings wherein it is shown in FIG. 3 that the micro lens array is comprised essentially of a plurality of three (3) (but could be four (4), five (5) or more or less such as 2 or one as needed for a particular application) of spaced-apart, stacked, parallel, thin, planar, apertured lens plates 16, 17 and 18 each of which is fabricated from silicon semiconductor material which preferably is single crystal silicon. As will be described more fully hereafter, each of the thin apertured silicon lens plates has an array of micro lens aperture openings formed therein by photo-lithographic semiconductor microcircuit fabrication techniques with the remaining surfaces of the plates being highly conductive. The apertured silicon lens plates 16, 17 and 18 are secured by thermal bonding or otherwise to glass support rods 19 arrayed around their outer periphery for holding the lens plates in stacked, parallel, spaced-apart relationship. While securing the lens plates 16, 17 and 18 in assembled relationship on the glass support rods 19, the lens aperture openings in all of the silicon lens plates are axially aligned along longitudinal axes passing through the center of each aperture opening and which are at right angles to the plane of the plates. This is achieved by means of alignment notches formed in the starting silicon wafers from which the apertured lens plates are fabricated in a manner to be described more fully hereafter or alternatively may be achieved by means of electron optical or light optical alignment techniques. Axial alignment of the lens aperture openings in each of the respective thin silicon plates 16, 17 and 18 commences with the placement of photo resist patterns employed in forming the aperture openings on the starting thin silicon wafers and are used right on through to assembly of the several lens plates together onto the supporting glass rods 19. In mounting the thin silicon plates to the glass support rods, the peripheral edge portions of the thin silicon plates are thermally bonded onto the glass rods by heating the glass rods to substantially their melting point. At the temperature where the glass rods commence to soften, the rod is phsically pressed into the periphery of the stacked and aligned plates supported in a suitable holding fixture with the array of aperture openings therein axially aligned as described above and thereafter the glass rod is allowed to cool. Different electrical excitation potentials are supplied to the thin silicon plates in the manner best shown in FIGS. 19 and 19A of the drawings. In FIG. 19 it will be seen that a small conductive wire such as nichrome has one exposed end shown at 20 trapped between the edge of the thin silicon plate 17 and the supporting glass rod 19 during thermal bonding. The remaining end of wire 20 is bent over as shown by dotted lines at 20A to connect to the exposed end of a conventional insulated lead-in conductor 20B for the excitation potential to be applied to plate 17. In FIG. 19A a small nichrome washer 20C that contacts the outer conductive surface of plate 17 is seated between a pair of nesting, coaxially aligned, glass rod insulator segments having two different diameter, cylindrically-shaped end portions. By clamping a suitable number of such insulator segments together and tailoring their longitudinal extent, proper spacing between the lens plates can be obtained. By thus assembling the micro lens array, the respective thin apertured silicon lens plates 16, 17 and 18 (which may have a thickness of the order of 1/2 millimeter in thickness and are spaced-apart approximately one and one-half millimeters) are capable of sustaining a voltage difference between plates of the order of 5 to 10 kilovolts without breakdown and conduction between adjacent plates. In place of nichrome, a metal which alloys with silicon could be used to form the contacts 20 or 20C, thereby assuring secure electrical contact of the lead-in conductor to the thin silicon plates. With the stacked, parallel apertured thin silicon plates comprising the lens array secured to the glass support rods 19 in the above described fashion, the glass support rods in turn are fastened by suitable mounting tabs shown at 21 to an annularly-shaped outer support ring 22 which also supports the termination plate 15. The mounting tabs 21 are generally trapezoidal in configuration as shown and have an essentially half-heart shaped depression formed in the end thereof for engaging the glass support rods to assure permanent and solid securement to the glass support rods after cooling. Placement of the mounting tabs 21 in the glass support rods may of course take place concurrently with the securement of the thin apertured silicon plates 16-18 to avoid the necessity for thermal recycling of the glass support rods in two different operations, however, in advance of securing the mounting tabs 21 to the glass rods, the mounting tabs are first brazed, or otherwise secured to the annularly-shaped, support rings 22 which may be formed from molybdenum, tungstem, or other suitable metal for providing electron optically clean surfaces after bake-out within an evacuated housing enclosure. The construction and purpose of the termination plate 15 is described more fully in a paper entitled "Computer-Aided Design and Experimental Investigation of an Electron-Optical Collimating Lens" by C. T. Wang, K. J. Harte, N. Curland, R. K. Likuski and E. C. Dougherty appearing in the Journal of the Vacuum Society Technology, Vol. 10, no. 6, November/December 1973, pages 110-113. Briefly, it can be stated that the termination plate 15, sometimes referred to as "tuning plate" serves to terminate electric fields employed in the coarse deflection section of the fly's eye type electron beam so that such fields do not enter and adversely influence the behavior of the micro lens array and micro deflector assembly. Upon assembly of the micro lens array in a fly's eye electron beam tube, electron beams transiting the sub-assembly enter through the termination plate 15 and exit through the lens aperture openings of the last or uppermost silicon plate 18. Thus, plate 18 is physically disposed adjacent the micro deflector sub-assembly and may be subject to the influence of the relatively high frequency (of the order of megahertz or perhaps even gigahertz frequency) deflection potentials applied to the respective deflector plates of the micro deflector assembly. To assure that plate 18 remains rigid, a stiffening ring 23 of molybdenum, tungsten or other suitable compatible metal is secured to the outer periphery of the uppermost thin silicon plate 18 by means of the additional mounting tab 21A. For the best thermal match, stiffening ring 23 should be fabricated from polycrystalline silicon of sufficient thickness to provide the required stiffening. As best shown in FIG. 17 of the drawings, lens aperture openings (hereinafter referred to as apertures) can be provided which are of exceptional symmetry (e.g., roundness) due primarily to the etching qualities of single crystal high purity silicon. By using boron diffusion patterns to provide sharp etching outlines in the silicon substrate, it is possible to provide these exceptional symmetry apertures in the lens plates for each set of axially aligned micro lens apertures, and to do so for the entire array of apertures to be formed in a single thin silicon wafer (e.g., 128 by 128 array of apertures) in a single processing operation. The sets of axially aligned apertures in the respective thin silicon lens plates 16, 17 and 18 are axially aligned with a respective set of micro deflector elements for any given channel. A channel is defined as an electron beam path provided by an axially aligned set of micro lens apertures and the coacting axially aligned micro deflector elements as described more fully hereinafter. A preferred axial profile for each axially aligned set of micro lens apertures defining any given channel is shown in FIG. 17. Referring to FIG. 17 it will be seen that each channel is comprised of four lens plates 16, 17, 18 and 18A. The fourth plate 18A may or may not be used depending upon the storage density desired. A very small aperture 31 of about 100 microns (100.mu.) diameter is formed on the top surface of the top thin silicon aperture plate 16 on the electron beam entrance side of the assembly. This small aperture 31 is formed through a highly conductive surface portion 33 of the lens plate 16 that is produced as a result of the process in which the aperture 31 was formed. As stated above, because of the process and the manner in which it was formed (to be described hereafter) the aperture 31 is of exceptional symmetry about a central axis extending through the center of the aperture 31 and perpendicular to the planar surfaces of the thin silicon plate 16. A second or outlet aperture 32 likewise of exceptional symmetry and centered about the same central axis as aperture 31, is formed on the bottom surface of the lens plate 16 which also has a highly conductive surface area 34. Intermediate portions of the silicon wafer extending between the apertures 31 and 32 are etched back away a slight distance as shown at 35 in order to assure that only the highly conductive aperture sides 31 and 32 which are precisely formed and of exceptional evenness and symmetry are effective to produce an electric field that influences an electron beam passing through the lens element. The second apertured thin silicon lens plate 17 has apertures 36 and 37 formed in the respective top and bottom surfaces thereof which are of substantially equal diameter and likewise are formed within highly conductive surface portions 33 and 34 of the thin silicon lens plate 17. In this plate, the outwardly sloping side surfaces 38 and 39 of each aperture project outward into the body of the semiconductor plate 17 from the respective apertures 36 and 37 and intersect at some mid-point spaced outwardly from the peripheral circumference of the equal diameter apertures 36 and 37 so as again not to influence the electron beam and assure that only the sides of the apertures 36 and 37 which are designed for that purpose, produce electric fields that affect the electron beam. The third plate 18 of the stacked parallel lens plate has a larger diameter aperture 41 formed in its upper or electron beam entrance side in contrast to a very small diameter exit aperture 42 formed on its lower conductive surface portion 34. Here again, the sloping side surfaces 43 of the intervening silicon semiconductor body portion of plate 18 are etched a sufficient distance back away from the peripheral edges of the apertures 41 and 42 to assure that the intervening semiconductor of the silicon plate does not influence an electron beam passing therethrough. The last plate 18A in the array (if used) is identical in construction to the top plate 16. In assembling the stacked, parallel silicon lens plates 16, 17, 18 and 18A in the manner described previously, the respective longitudinal axis passing through the aperture 31 in lens plate 16 also constitutes the common axis for all of the axially aligned apertures further comprised by 32 in plate 16, 36 and 37 in plate 17, 41 and 42 in plate 18 and 31 and 32 in plate 18A (if used). Further, it should be kept in mind that an entire array of such axially aligned lens apertures are provided by the assembled micro lens plates wherein if there is a 128 by 128 matrix of lens elements provided in the array, FIG. 17 would have to be projected outwardly from each side to illustrate the additional 127 axially aligned lens elements arrayed along a single plane. Again, ideally, the center axis passing through each axially aligned set of array elements is parallel to all of the other center axes and all in turn are perpendicular to the plane of the thin silicon plates 16, 17, 18 and 18A, respectively. The lens plates shown in FIG. 17 provide uniformity and exceptional symmetry in the placement of the small diameter lens apertures such as 31 and 42 in the small diameter regions of the axial profile shown in FIG. 17. It is also necessary that the plates 16, 17, 18 and 18A exhibit great rigidity because while in use they are in high field gradients and are thus subjected to strong deflection forces. The deflection forces can strongly influence the lens performance if the apertures do not possess a high degree of axial symmetry. This is due to the fact that the lens plates tend to deflect under the pull of the electric field applied between the plates so that the spacing of the lenslet elements near the center of the plate will be less than the spacing of the lenslet elements near the edges. To a first approximation, the spacing change does not cause any great disturbance since the stronger field created by the shorter distance in the center is in part offset by the shorter distance over which the field is applied. However, the outer lenslet elements experience a tilt as well as an infinitesimal radial displacement and this can cause some lens error of the type known as comma. For this reason, it is desirable that the plates be designed to deflect as little as possible upon being placed in operation. The axial profile shown in FIG. 17 permits a high stiffness or rigidity to weight ratio for optimum array densities versus center to center spacing of the lenslet elements thus providing a structure with a small mass which is required for use of the glass rodding assembly technique but which also possesses the required stiffness to prevent excessive deflection under electric field stress. By way of illustration, a silicon lens plate of approximately 3 inches in diameter and 1/2 millimeter thickness with a spacing between plates of about 1 millimeter, the total unbalanced forces on the plate are of the order of 1/2 lb. and the centered displacement is of the order of 50 micrometers (50.mu.) leading to a maximum tilt of less than 1/2 milliradian which gives an acceptable lens performance. The required aperture profile can be provided by a variety of known photolithographic and etching techniques used in the fabrication of semiconductor microcircuits. A preferred technique for fabricating apertured micro lens array thin silicon plates is illustrated in FIGS. 18A through 18J. For starting material, an N-type single crystal silicon wafer 17 of approximately 1/2 millimeter thickness and 100 orientation shown at 17 is provided. Suitable alignment notches shown at 51 are cut into the periphery of the wafer to facilitate positioning of the photomasks employed in forming masking areas on the surface of the silicon wafer and also in subsequently aligning the wafer with other apertured lens plates used in the micro lens array. A wet silicon oxide layer then is grown on both sides of the silicon wafer as shown at 52 and 53 in FIG. 18B of the drawings. After growing the oxide layers on each side of the wafer, chromium alignment dots are formed on one surface at the outer edges by photolithography masking techniques and exposure of one surface of the wafer, such as 52, to a chromium vapor atmosphere to thereby produce the chromium alignment dots 54, as shown in FIG. 18C. Using the chromium alignment dots and the notches in the periphery of the wafer, and again using photolithography techniques, an array of silicon oxide dots are produced where apertures are to be formed in the wafer as shown at 55 in FIG. 18D. Each of the silicon oxide dots in the array should be of the same size and shape as the apertures to be formed in the wafer. After the oxide layer has been processed to form the oxide dots 55, the chromium alignment dots are removed. During this process the notches and back side of the wafer are protected with wax or other suitable protective coating. The next step in the processing is to produce an array of oxide dots on the remaining untreated side of the wafer which, as shown in FIG. 17, may be of the same size or different size from the oxide dots formed on the previously treated side. If the wafer in question is being processed to produce an end plate, the oxide dots on the two sides of the wafer will be of different size but will have the same centers (e.g., axially aligned) as described previously. This is achieved using infrared techniques to assure alignment of the silicon oxide dots on both sides of the wafer during the photolithographic processing to produce the second set of oxide dots. The resultant array of oxide dots on the remaining surface are shown at 56 in FIG. 18E. At this point in the processing, the wafer is spin coated with a boron containing emulsion with the emulsion being spin coated on both sides of the wafer. The boron containing emulsion coated wafer then is fired in a furance at about 1100.degree. C. in a nitrogen atmosphere. During this processing, the boron dopant contained in the emulsion will diffuse into the surface of the silicon wafer to a depth of about 2 microns at which point the firing is discontinued as shown in FIG. 18F to result in a boron coated surface layer 33 where no apertures are to appear as best seen in FIG. 18H. The excess boron coating is removed in a hydrofluoric bath followed by a second bath in fresh hydrofluoric acid to remove the oxide buttons. This processing step leaves a deep and heavy boron layer formed in the surface areas of the wafer where it is desired that no apertures be formed and results in sharply defining the undoped silicon aperture opening areas as shown at 55A and 56A in FIG. 18G which are of quite even symmetry since the boron diffusion step is extremely uniform throughout. In a final processing step, the boron doped wafer is etched in a hot pyrocatechol and ethylene diamine bath as described in the article entitled "Ink Jet Printing Nozzle Arrays Etched in Silicon" by E. Bassous, et al. reported in Applied Physics Letters, Vol. 31, no. 2, July 15, 1977, pages 135-137, the teaching of which hereby expressly is incorporated. As taught in this article, the orientation rate dependence causes the etching action to stop when the sloping planes from under the two apertures being formed on opposite sides of the silicon wafer, meet. Consequently, the underlying silicon support for the apertures defined by the boron doped layer that now constitutes the remaining surface areas of the silicon wafer 17 is somewhat undercut below the boron doped layer 33 as shown in FIGS. 17, 18 and 18I to result in apertures of exceptional symmetry and evenness as depicted in FIGS. 18I and 18J of the drawings. In this respect, it should be noted that the profile of the silicon support underlying the thin boron doped layer 33 is not critical. The key factor is the thin surface boron doped layer 33 that defines the aperture (opening or hole) which must not be destroyed by the etchant used in etching away the silicon support intermediate the axially aligned aperture openings or each of the opposite sides of the silicon wafer. While there are a variety of ways known to the art for accomplishing differential etching action as described above, the preferred method is as disclosed. The above description was with relation to the production of the center lens plate wherein the aperture openings on each side of the plate have substantially the same diameter. The technique described is not limited to fabrication of lens aperture plates of this type for it may also be used in fabricating the end plates wherein the aperture on one side of the plate is smaller than the aperture on the opposite side of the plate, as well as other configurations as depicted in FIG. 28. FIG. 5 is an end plan view of a micro deflector sub-assembly constructed in accordance with the invention and FIG. 6 is a partial cross-sectional view of the deflector sub-assembly taken through plane 6--6 of FIG. 5. As best seen in FIG. 5, the micro deflector sub-assembly comprises two orthogonally arrayed sets of parallel, spaced-apart, deflector bars 61 and 62 which are arrayed at right angles to each other so as to define a plurality of orthogonally arrayed sets of micro deflector elements. As will be described more fully hereafter, alternate ones of each set of orthogonally arrayed deflector bars 61 and 62 are electrically interconnected for common connection to a respective source of fine x-y deflection potential for deflecting an electron beam passing through any selected one of the micro deflector elements in a direction at substantially right angles to the path of the electron beam in either the x or y direction. For example, considering the x and y axis to be as indicated in FIG. 5, then the x axis deflection potential applied between alternate ones of the deflector bars 62 will cause an electron beam passing through any selected one of the micro deflector elements to be deflected right or left as viewed in FIG. 5 along the x axis depending upon the polarity and magnitude of the fine x deflection potential. Similarly, the fine y deflection potentials applied to alternate ones of the deflector bars 61 cause deflection of an electron beam passing through any selected one of the micro deflector elements along the y axis in a manner dependent upon the polarity and magnitude of the fine y deflection potentials applied to alternate ones of the deflector bars 61. Thus, it will be appreciated that the intersection of the orthogonally arrayed sets of deflector bars 61 and 62 at their points of intersection define an entire array of fine deflector elements since the deflector bars are spaced apart one from the other and at each intersection point of the orthogonally arrayed bars an essentially square-shaped, fine open space exists which defines the micro deflector element within the points of intersection. This micro deflector element or open space is arranged so that it is axially aligned with a corresponding set of micro lens aperture element formed in the micro lens array sub-assembly as previously described. For this purpose, extreme care must be taken when assembling the micro deflector sub-assembly with the micro lens sub-assembly as described hereafter in order to assure the proper axial alignment of each respective micro deflector element with its corresponding micro lens axially aligned aperture openings. Each of the micro deflector bars 61 and 62 preferably is fabricated from polycrystalline silicon as will be described hereafter in connection with FIGS. 20, 20A through 20F and the surfaces thereof may be metalized with a platinum coating or other suitable highly conductive metallic material. As best seen in FIG. 20, the fine deflection bars 61, 62 preferably are sawed from a rectangular-shaped block 63 of polycrystalline silicon having grooves shown at 64 and 65 sawed or otherwise formed in each of the ends thereof. As best shown in the end view of FIG. 20A, the groove 64 is spaced from the end of the block of silicon 63 a greater distance "a" than is the groove 65 which is shown as being spaced a smaller distance "b" from the end of the block of polycrystalline silicon. The purpose for making the dimensions "a" and "b" different from one another will become apparent hereafter but it should be noted that the fine deflector bars 62 are fabricated in an identical manner and with essentially the same "a" and "b" dimension. Thus, after forming the grooves 64 and 65 in the block of polycrystalline silicon 63, the individual blades 61, 62 are sawed from block 63 in the manner indicated in FIG. 20. In contrast to aluminum oxide or other comparable ceramic, silicon is not nearly so hard so that tool wear in sawing the individual silicon deflector bars 61, 62 from the block of silicon is not a significant problem. At this point in the fabrication, the deflector bars 61, 62 are plated with about a 2000 Angstrom units thick coating of heavy metal such as platinum or gold preferably by an ion plating technique such as described in the article entitled "Electron Beam Techniques for Ion Plating" by D. Chambers and D. C. Charmichael reported in Research/Development, vol. 22, May 1971, or alternatively by vapor deposition as described in the article entitled "Physical Vapor Deposition" by Airco Temescal Staff (1976), R. J. Hill, Director (page 60). Other known metalization techniques and procedures also may be employed to provide the metal coating having good adherence and thickness of the order of about 2000 Angstrom units. Prior to metalizing the surfaces of the sawed deflector bars, it may be necessary to lap finish each of the bars to remove burrs and other surface irregularities prior to the metalization step. FIGS. 20B and 20C are a plan view and side end view, respectively, of a suitable holding fixture for assembling the micro deflector plates together in a spaced-apart, parallel assemblage. In FIG. 20B, a square or rectangular block of silicon shown at 66 again is employed and has a plurality of slots such as shown at 67 cut therein to a suitable depth that will insure mechanical rigidity of holding action upon the respective metalized deflector bars fabricated as shown at 20 and 20A inserted therein in the manner indicated in FIG. 20C. The slotted silicon block 66 after fabrication forms a fixture that can be reused in assembling further micro deflector sub-assemblies as described hereinafter. Because it likewise is formed of silicon, it is thermally compatible with the blades which are being held by the fixture and hence will reduce or minimize stresses which might otherwise be encountered in the assemblage steps to be followed as described hereafter. FIG. 20D shows a preferred procedure for assembling one set of the deflector blades such as 61 together in a parallel spaced-apart relationship by means of a glass supporting rod shown at 68. The metalized silicon bar or blades 61 (or 62) are held upside down in the slots 67 cut in the silicon holding fixture 66 with the grooves 64 and 65 facing upwardly and aligned along an axis looking into the plane of the paper. In so placing the blades, they are alternated end for end so that alternate bars have the groove 64 axially aligned with the grooves 65 in the remaining set of alternate bars. A glass support rod 68 then is placed in the axially aligned, alternate grooves 64 and 65 formed at each end of the parallel array of deflector bars as shown in FIG. 20D. A thin conductor wire or ribbon of platinum shown at 69 is then placed adjacent the elongated ends of alternate bars having the dimension "a" between the grooves 64 and the ends of the bars and a pressure pad 71 is applied to force the conductor wire 69 into positive engagement with the elongated ends of alternate ones of the blades 61. At the opposite side of the fixture, a similar arrangement is employed to bond a corresponding conductor wire 69 to the end of the remaining alternate sets of deflector bars 61. The fixture 66 is supported on a table of adequate strength and a second pressure pad indicated at 72 is applied downwardly across all of the deflector bars 61 to be assembled and concurrently heat is applied through a suitable heating tool to cause the glass support rods 68 to become heated to a temperature close to its melting point so that it softens and thermally bonds to the individual deflector bars at their points of contact with the glass support rod. Concurrently, heating current is supplied through the thin platinum conductor wire 69 to cause it to thermally bond to the ends of the metalized silicon bars and form good positive electric contact therewith. Upon cooling of the glass support rod 68, all of the deflector bars 61 will be thermally bonded to the glass support rods. Thereafter, the holding fixture 66 can be removed and used again in the assemblage of a second set of deflector bars. Because the holding fixture 66 is of the same material as the deflector bars, mechanical discrepancies and stresses due to thermal differences in the materials that might otherwise be built in during the heating and cooling phases of the assemblage operation, are avoided. A similar assemblage technique then is employed in mounting the second set of deflector bars 62 to their corresponding glass support rods thus resulting in the two sets of spaced-apart, parallel deflector bars 61 and 62 required to form the micro deflector sub-assembly first described with respect to FIGS. 1, 5 and 6 of the drawings. FIG. 20D also illustrates schematically an alternative scheme for applying the required lead-in conductor wires to alternate deflector blades or bars and employing an alternative form of conductor wire 69A. The alternative conductor wire 69A can be circular in cross section, flat or any desired cross-sectional configuration since it is designed to fit into the groove 64 below the glass support rod 68 and extend along the top edges so as to contact and fuse to alternate blades or bars 62. For this purpose, it would be necessary to machine the two grooves 64 and 65 to different depths rather than different end displacements "a" and "b" and arrange them alternatively. The alternate conductor wire 69A then should have sufficient thickness to be engaged by and compressed somewhat by the glass support rod 68 upon being pressured into engagement with the sides of the groove 64 during thermal bonding of the glass support rod to the blades or bars 61. With the alternate lead-in contact arrangement using the alternate conductor wire 69A it would not be necessary to provide the additional pressure pad 71 except for end alignment purposes. While two alternate methods for applying excitation potentials to the alternate micro deflector bars have been disclosed, it is believed obvious to one skilled in the art that a cross bar connector could be used across the tops of the sets of bars wherein alternate deflection bars would be brazed or otherwise connected to the cross bar connector and the intervening bars where no electrical connection is to be provided an insulating space would be provided. Other suitable arrangements likewise could be employed and would be obvious to those skilled in the art in the light of the above teachings. In addition to the metalized silicon deflection bars fabricated in two orthogonally arrayed sets as described above and shown in FIG. 5 of the drawings, each set of spaced-apart parallel deflector bars include elongated, end bars 61A and 61B which are parallel to the deflector bars 61 and elongated, end deflector bars 62A and 62B which are parallel to the deflector bars 62. The elongated, end deflector bars 61A, 61B, 62A and 62B all preferably comprise a suitable polished nonmagnetic metal bar such as molybdenum, tungsten or other similar metal that can be made electron optically clean and which provides sufficient rigidity to serve as a mounting means for mounting the sets of spaced-apart parallel metalized silicon deflector bars in place within the evacuated housing of an electron beam tube. It is also desirable that at least the ends of the elongated, end deflector bars 61A-62B be malleable to the extent that they can be bent to conform to a configuration whereby they can be clamped to a mounting ring or other supporting member located at a particular point within an electron beam tube housing. The micro deflector sub-assembly shown in FIG. 5, however, utilizes elongated, end deflector bars 61A, 61B, 62A and 62B wherein the ends of the bars project well beyond the glass support rods 68 to which they are likewise thermally bonded in the same heat treating process by which the metalized silicon deflector bars were secured to the glass support rods. The ends of the elongated, end deflector bars serve as mounting tabs for securement to an annularly-shaped metallic support ring 73 whereby each of the sets of the orthogonally arrayed, parallel, spaced-apart metalized silicon deflector bars 61 and 62 can be mounted in spaced-apart and juxtaposed relation. In order to minimize the spacing between the two sets of deflector bars 61 and 62, the ends of the elongated end deflector bars 61A and 61B are mounted to the upper surface of the support ring 73 as viewed by the reader, while the ends of the elongated, end deflector bars 62A and 62B are secured to the under-surface of the support ring as shown in FIG. 5. FIG. 6 of the drawings is a cross-sectional view of the micro deflector sub-assembly wherein it can be seen that the two sets of orthogonally arrayed, spaced-apart, parallel deflector bars 61 and 62 are spaced apart a short distance relative to the width of the bars, which distance may be of the order of only several milliinches. FIG. 7 of the drawings is a cross-sectional view of the target electrode sub-assembly employed with the overall micro lens array and micro deflector assembly shown in FIG. 1. The target electrode sub-assembly 13 comprises a metal-oxide semi-conductor memory capacitor structure which may be of the type described in U.S. Pat. No. 4,079,358 issued Mar. 14, 1978 for a "Buried Junction MOS Memory Capacitor Target for Electron Beam Addressable Memory and Method of Using Same," Floyd O. Arntz, inventor, the teaching of which hereby is expressly incorporated in this disclosure. The MOS memory capacitor target member indicated generally at 13 is mounted for support on a fairly massive donut-shaped ceramic mounting member 81 having the MOS memory capacitor target member 13 supported over a central opening 13A therein. Bias potential as well as signals derived during read-out of the MOS memory capacitor target member are supplied through an insulating terminal (not shown) for application to the upper (closest to the mircro deflector sub-assembly) conductive surface of the MOS capacitive target member as described in the above-referenced U.S. Pat. No. 4,079,358. The backing support member 81 and a cup-shaped shield 83 are secured to an annularly-shaped outer support ring 84 for mounting to the axially extending common glass support rods 14. As best seen in FIG. 1 considered in conjunction with FIG. 8 of the drawings, the metallic mounting ring 22 for the micro lens array sub-assembly is brazed or otherwise secured to the inner peripheral edge of a cup-shaped outer support ring 85 that in turn is secured by trapezoidally-shaped mounting tabs 86 to the axially extending, peripherally arrayed glass support rods 14. In a similar manner, the outer support ring 73 for the micro deflector sub-assembly has its outer peripheral edge brazed or otherwise secured to the inner peripheral edge of a disc-shaped, metallic outer support ring 87 that is secured to the axially extending, peripherally arrayed glass support rods 14 by mounting tabs 88. Lastly, the support ring 84 for the target electrode sub-assembly 13 is brazed or otherwise secured at its outer periphery to the inner periphery of a second annular disc-shaped metallic mounting ring 89 that in turn is secured to the axially extending glass support rods 14 by mounting tabs 90. During assembly of each of the micro lens array sub-assemblies to axially extending glass support rods 14 by brazing or otherwise securing the support ring 22 to the outer mounting or support ring 85, proper axial alignment of the array apertures relative to the lens elements of the micro deflector sub-assembly 12 and to the target electrode member 13, is maintained by insertion of alignment rods in alignment notches or aperture openings formed in the respective mounting rings 22 as shown at 91 in FIG. 4, in mounting ring 73 as shown at 92 in FIG. 5, and in mounting ring 84 (the alignment notch of which is not shown). If desired, electron optical and/or light optical alignment procedures could be used in place of or to augment the mechanical alignment procedures noted above. After assembly together in the above-described manner as shown in FIGS. 1 and 2 of the drawings, the resulting micro lens array and micro deflector assembly together with termination plate for the coarse deflection section and target electrode member will be seen to have been fabricated from silicon either in single crystal or polycrystalline form and glass to the greatest extent possible so that all parts of the assembly have comparable thermal properties and possess essentially the same thermal coefficient of expansion to the greatest possible extent. A number of the parts are processed in accordance with semiconductor micro-circuit fabrication techniques which provide exceptional quality roundness, symmetry and evenness of the aperture openings in the micro lens array together with exceptional symmetry in the spacing between openings. The entire assembly is held together by glass rodding or other similar material insofar as possible. The advantages obtained by fabrication of the assembly in this manner are that it reduces the cost and complexity of measures otherwise required to guard against rapid temperature changes between different parts of the electron optical assembly since the glass and silicon parts have substantially the same temperature coefficient of expansion. Silicon employed in the fabrication of most of the parts has greater stiffness and much better dimensional stability and can be used without closeby support rings or belts thereby making possible any desired lens plate thickness and any lens plate to lens plate spacing. It is much easier to cut and metalize silicon than fired ceramic or other material heretofore used thereby making the problem of fine deflector plate fabrication much less costly and better controlled. However, it should be understood that the use of ceramic deflector plates is not precluded. The fabrication techniques herein described result in an electron optically clean structure and, in addition, allows flexibility in forming the deflector bars so as to facilitate later assemblage and connection of deflection potentials to the bars. FIGS. 9 and 10 of the drawings illustrate the new and improved micro lens array and micro deflector assembly used in conjunction with a different type of target member from that shown in FIG. 1. The arrangement shown in FIG. 1 of the drawings is for use with electron beam accessed memories employed in computer systems. The arrangements shown in FIGS. 9 and 10 of the drawings are intended for use in semiconductor microcircuit fabrication or other comparable electron beam defined art work. For this reason, the arrangement shown in FIG. 9 includes a removable, electron sensitive target member 91 which is disposed immediately adjacent the micro deflector assembly on the electron beam exit side thereof for impingement of electrons thereon after deflection of the electron beam by the micro deflector sub-assembly 12. The electron sensitive target member 91 may comprise a photo-sensitive plate where the apparatus is being used for imaging or for alignment purposes, or the like, or alternatively, it may comprise an electron sensitive photo resist covered wafer having its electron sensitive surface placed opposite the exit side of the micro deflector assembly 12. The electron sensitive member 91 is clamped in place on a plate holder 92 by a set of clamps indicated at 93 which are arranged around the periphery of the plate or member 91. The electron sensitive plate or member 91 together with the plate holder 92 are held in place over the end of an evacuated tube, the outer housing or envelope of which is shown partially at 94 by reason of the vacuum produced within the interior of housing 94 by a vacuum apparatus (not shown) connected to the housing for the purpose of drawing down the atmosphere of the housing to low vacuum levels. In order to facilitate changing of the electron sensitive plates 91, a gate valve structure is provided which is designed to close over a central opening in the end wall 95 of the tube housing 94. During operation of the tube, the central opening in end wall 95 will be closed by the plate holder 92 and the electron sensitive member 91 held in place over the opening through the force of the spring clip 93. In order to change the electron sensitive plate member 91 after processing of the same, a linearly translatable gate valve member 96 is provided which can be slid into place over the central opening in end wall 95 and sealed against an O-ring seal 97 through actuation of a set of locking cam members shown at 98. With the gate valve member 96 in place over the central opening in the end wall 95, the electron sensitive target member 91 and plate holder 92 can be removed without complete loss of vacuum within the tube housing 94. Upon completion of the change of the electron sensitive target member 91, the gate valve 96 can be linearly withdrawn to the position indicated in FIG. 9 by appropriate actuation of the cam members 98 after placement of the new electron sensitive target member 91 and plate holder 92 back in position so that they are exposed to the interior of the housing as gate valve member 96 is withdrawn and the area above plate 91 in the housing again pumped down to a suitable level of evacuation. The micro lens array and micro deflector target assembly 11, 12 is secured by means of a support ring 99 to a glass mounting ring or belt 101 thermally bonded to the exterior periphery of the coarse deflector cone 100 at a point adjacent the end 95 of tube 94. Support ring 99 forms a "housekeepers seal" by means of a thin depending skirt portion that is embedded in the glass mounting ring 101 during thermal bonding. A spring metal bond is disposed between the external periphery of support ring 99 and the internal circumference of outer housing envelope 94 completes the structures. By this construction, the amount of metal contained within the interior of the housing 94 is reduced to a minimum for purposes discussed above and the overall weight of the assembly and the effect of different temperature coefficients of expansion in the material used in constructing the assembly, are reduced to a minimum. In the embodiment of the invention shown in FIG. 9, the coarse deflector section 102 of the coarse deflector cone 100 is disposed intermediate an electron gun assembly 103 for producing a fine, pencil-like beam of electrons and the micro lens array and micro deflector assembly (11,12). The coarse deflector section 102 preferably is designed pursuant to the teachings of U.S. patent application Ser. No. 812,981, filed July 5, 1977, Kenneth J. Harte, inventor, the disclosure of which hereby is incorporated in its entirety. The electron beam projected from the electron gun assembly 103 through the coarse deflector section 102, is selectively deflected by the coarse deflector to pass through a selected one of the 128 by 128 array of aligned openings in the termination plate 15. The electron beam then passes through the corresponding axially aligned lenslet apertures in micro lens array sub-assembly 11 and the axially aligned micro deflection element in the micro deflector sub-assembly 12 to thereafter selectively impinge upon the electron sensitive target member 91 at a point determined by the fine x-y deflection voltages applied to the micro deflector sub-assembly. By this means, extremely fine control over the positioning of the point of impingement of the electron beam on the electron sensitive target member 91 is achieved. The embodiment of the invention shown in FIG. 10 differs from that of FIG. 9 in that it employs a different form of electron gun assembly 103. The FIG. 10 species preferably uses a field emission type of electron gun for producing a flood of electrons that are directed through a graded field structure shown at 104 which completely circumscribes the interior surface of the coarse deflector cone 100, and which is used in place of the coarse deflectors 102 employed in the FIG. 9 arrangement. The graded field structure 104 is designed to produce a uniform flood of electrons that covers the entire surface of the termination plate 15, and hence uniformly simultaneously passes electron beams of reduced beam current through all the micro lenslets in the sub-assembly 11 and corresponding micro deflector elements in the micro deflector sub-assembly 12. After passing through the micro deflector sub-assembly 12 there will be a multiplicity of essentially parallel electron beams all of which will be deflected uniformly by the micro deflector 12 onto discrete areas of the electron sensitive target member 91. Assuming, for example, that the micro lens array provides a matrix or array of lenslets numbering 128 by 128, then a corresponding number of target areas will be traced on the electron sensitive target member 91 within the scope of deflection of the respective micro deflection elements and it becomes possible to uniformly control fabrication of up to 128 by 128 (16,384) microcircuit assemblies simultaneously. Referring now to FIGS. 11-16 of the drawings, a different embodiment of a micro lens array and micro deflector assembly is shown which is somewhat different from the species of the invention described with relation to FIGS. 1-10. The FIGS. 11-16 species employs metal support rings and cup-shaped outer supports for holding the various sub-assemblies together in a complete structure. In FIG. 11, the micro lens array sub-assembly is shown as comprising a plurality of stacked, parallel, thin silicon plates 16, 17 and 18 fabricated in somewhat the same manner as described with relation to FIGS. 17 and 18 of the drawings. In the micro lens array shown in FIGS. 11-14, the required lens aperture (hole) profile as shown in FIG. 17, can be obtained by a variety of known photolithographic and etching techniques employed in the fabrication of semiconductor integrated microcircuits. For example, in a manner similar to that shown in FIGS. 18A-18J, an N-type wafer of single crystal silicon of approximately 1/2 millimeter thickness and 100 orientation has a periodic oxide pattern produced on its two surfaces as shown in FIG. 18E. The pattern is the negative of the desired hole pattern and is produced by well-known oxidation and photo resist techniques. The patterns on the two sides of the silicon wafer may be the same size as shown but also may be different where one is fabricating the end plates as illustrated in FIG. 17. For end aperture plates the smaller holes are essentially the required aperture diameter while the larger holes on the opposite side are made as large as practicable without completely undercutting the underlying silicon supporting the aperture during the etching step. Having established the oxide pattern, a P+ dopant material is diffused into the exposed surfaces of the silicon wafer by thermal diffusion through the oxide mask as shown in FIG. 18E. The wafer is then etched using an orientation sensitive etch, for example, a hot pyrocathecol and ethylene diamene bath, is employed so that differential etching progresses from the two side of the undoped silicon as illustrated in FIGS. 18H and 18J. The geometrically perfect outline of the aperture opening is determined by the perfection of the crystal planes of the silicon which produces intersecting square based pyramids as shown in the combined views of FIGS. 18I and 18J. FIG. 18J is a plan view looking toward the bottom of FIG. 18I and thus shows the two circular boundary apertures 36 and 37 supported on the thin P+ boron doped layer with the pyramidal opening in the intervening undoped N-type silicon wafer intersection to form essentially square-shaped openings in the center of the thickness of the silicon wafer. Having established the correct structure for the aperture opening in the thin silicon plate, a coating of metal may then be placed over the entire structure to make it conductive. Any of the well-known metalization techniques may be employed so long as there is adequate metal to stop the electron beam completely. The method of ion plating identified earlier in the "Electron Beam Techniques For Ion Plating" article and in the "Physical Vapor Deposition" article, are preferred because the plating metal reaches internal surfaces and adheres well. For a 10 kilovolt lens, a thickness of 2000 Angstrom units of heavy metal such as gold or platinum is adequate. The key item for the apertures is the profile of the small circular openings as illustrated in FIG. 17. The profile of the intervening underlying silicon support is not critical. The key factor then is the doped, thin surface layer 33 which defines and determines the areas of differential etching action for production of the aperture openings and which must not be destroyed by the etchant used in forming the aperture openings. There are a variety of different, known ways in the art for accomplishing the above-described differential etching action other than that described earlier with relation to FIGS. 18A through 18J. For example, the thin surface layer may be produced by epitaxial growth of a P+ layer on an N-type silicon wafer. The hole structure is defined by ion implantation of N-type material through an oxide mask with holes where implantation is desired or by thermal diffusion of N-type material through the holes. Etching can then follow in the same manner as described with relation to FIGS. 18A-18J. To form the desired holes, since the form of the intervening supporting undoped silicon is not critical, one could substitute an isotropic etch for the orientation dependent etch in which case the silicon supports could follow a generally hemispherical outline rather than the pyramidal outline illustrated. In producing the center lens plate 17 shown in FIG. 17, a further restriction must be observed in that the symmetry of the supporting intervening silicon must be maintained with a high degree of accuracy due to the fact that the aperture holes 36 and 37 on both sides of the plate are equal in diameter. Because the orientation sensitive etching procedure described above maintains four-fold symmetry of the intervening supporting silicon, it is preferred because it may be so oriented as to correct the four-fold pattern of interaction between neighboring lenslets in an array of micro lenslets. By alternating orientation sensitive etching steps with other etching techniques, it is also possible to produce different configurations within the intervening supporting silicon but of course the processing procedures become more complex requiring greater skill and care in the fabrication. In the embodiment of the invention shown in FIGS. 11-16, the micro lens array is made as a stand-alone sub-assembly and for this purpose is provided with top and bottom support rings as best shown in FIGS. 13 and 14 at 111 and 112, respectively. The support rings 111 and 112 are thermally bonded or otherwise secured to the axially extending glass support rods 19 along with the apertured thin silicon lens plates 16, 17 and 18 (and 18A if provided) with the lower support ring 112 contacting and physically bracing the lens plate 18A to prevent microphonics being induced therein by deflection frequency fields produced by the adjacent micro deflector sub-assembly. The micro lens array sub-assembly shown in FIGS. 13 and 14 then is mounted in the overall assembly as best seen in FIGS. 11 and 12 by means of a central, annular cup-shaped mounting member 113. This annular, cup-shaped mounting member 113 serves to hold the entire assembly together along with the termination plate 15 which is secured to the outermost end portion of member 113 with its aperture openings axially aligned with corresponding apertures in the micro lens array sub-assembly. Excitation potentials of about 5-10 kilovolts are supplied to the inner thin silicon lens plate 17 by means of an insulator mounted conductor connected by means of an intermediate conductor wire to the conductive upper surface of the central lens plate 17. The end plates 16 and 18 can be operated at essentially ground potential for the equipment and suitable lead-in conductors to plates 16 and 18 are provided for this purpose. The micro deflector sub-assembly employed in the embodiment of the invention shown in FIGS. 11 and 12 is best seen in FIGS. 15 and 16. In this micro deflector sub-assembly, the fine deflector blades are made of individual molybdenum blades which are sawed from a block of molybdenum or alternatively, individually blanked from sheet stock, and are stacked alternately with spacers and then bonded together at their ends to glass support rods 114 and 115, respectively. The resulting sets of parallel, spacedapart fine deflector bars are provided with elongated end bars as shown at 61A, 61B, 62A and 62B, the elongated ends of which extend beyond the points of connection to the glass support rods 114 and 115, respectively. The elongated end portions 61A-62B are brazed or otherwise secured to an outer annular support ring 116 for the micro deflector sub-assembly. As best seen in FIG. 11 of the drawings, the outer support ring 116 is secured to the central annular cup-shaped mounting member 113 for holding the micro deflector sub-assembly in spaced-apart, parallel relationship with respect to the micro lens array sub-assembly with the individual micro deflector elements of the sub-assembly axially aligned with the individual lenslets apertures of the micro lens array. The complete fly's eye electron beam tube deflector/lens combination is assembled by spot welding the mounting tabs from each of the micro lens array and fine deflector sub-assemblies to the central, annular, cup-shaped mounting member 113. To assure proper registration and axial alignment of the respective lenslets and micro deflector elements, "V" notches are placed in the peripheral edge portion of the mounting rings and these are registered against round alignment pins at each stage of fabrication and assembly starting with the photo mask registration during fabrication of the thin apertured silicon lens plates 16, 17 and 18. The V notches and round alignment pins or rods are best seen in FIG. 12 at 117, 118, 119 and 121. FIG. 15 in conjunction with FIG. 12 illustrates the manner of connection of deflection potentials to alternate ones of the sets of spaced-apart, parallel deflector bars 61M and 62M. Referring to FIG. 15, the +X deflection potential is applied through a cross bar conductor 122 which is spot welded to alternate ones of the micro deflector blades or bars 62M and the -X deflection potential is connected through a conductor 123 to the remaining alternate ones of the micro deflector bars 62M. In a similar manner, the +Y deflection potential is connected through a cross bar type conductor 124 which is spot welded to the tops of alternate ones of the micro deflector bars 61M while the -Y deflection potential is connected through a cross bar conductor 125 spot welded to the top of the remaining alternate ones of the deflector bars 61M. By this construction, suitable deflection potentials are applied to all of the micro deflector elements simultaneously for appropriate fine deflection of an electron beam passing through any one of the elements as described previously. During final assembly, the locating or alignment rods are held in precisely machined holes in the central annular cupshaped mounting member 113 while assembly takes place. After spot welding the mounting tabs of the micro lens array and micro deflector sub-assemblies to the central mounting member, the locating or alignment rods are removed otherwise they would give redundant constraints, and if metallic, would electrically short circuit certain of the elements. It is also possible to obtain better alignment by use of electron optical or light optical registration and alignment techniques instead of the notches and alignment rods as described. As mentioned previously, to make the micro lens array a stand-alone sub-assembly, it was necessary to add two stiffening rings which as indicated, are formed from molybdenum. It is also possible to use metallic coated ceramic, metallic coated polycrystalline silicon, tungsten, or metallic coated amorphous carbon. Of the metals, tungsten most closely matches the termal coefficient of expansion of silicon; however, for ultimate thermal match, polycrystalline silicon having its surfaces metalized would be the best. The polycrystalline silicon is preferred for use as a stiffening member not only because it is cheaper to fabricate, but also it is stronger than single crystal silicon which has a tendency towards easy fracture in certain directions. In operation, the assembly shown in FIGS. 12-16 functions in precisely the same manner as the assembly described with relation to FIGS. 1-10. It should be noted, however, that because of the use of the rather massive central, annular, cup-shaped mounting member 113, the arrangement of FIGS. 11-16 requires the use of more metal whose temperature coefficient of expansion is considerably different from that of silicon and glass. Thus, creation of thermally induced stresses are more likely to be encountered with the arrangement of FIGS. 11-16 than is true with the assembly shown in FIGS. 1-10. For this reason alone, the FIGS. 1-10 species is preferred but in addition, it is considerably cheaper to manufacture and lighter in weight also. FIG. 20E of the drawings illustrates an alternative form of micro deflector sub-assembly construction which is different from that described with relation to FIGS. 20-20D and the FIG. 1 and FIG. 11 species of the invention. In FIG. 20E a set of spaced-apart, parallel metalized silicon deflector bars or blades 61 are permanently set in a block of silicon 66 having a through opening 66A shown in FIG. 20B and having slots 67 to accept the deflector bars 61. This is achieved in much the same manner as described with relation to FIG. 20C. However, in FIG. 20E the block 66 is made insulating as by growing a silicon oxide layer thereover, and the deflector bars 61 are permanently secured within the block of silicon 66 by means of glass frit or thermal bonding as shown at 131. In a similar manner the metalized silicon deflector bars 62 are permanently mounted in an insulating block 132 having a physical configuration similar to that shown in FIG. 20B but formed from ceramic, or silicon oxide coated silicon so that it is electrically insulating. The metalized silicon deflector bars 62 again are permanently secured in the slots in block 132 by glass frit, thermal bonding or otherwise. Deflection potentials are applied to alternate ones of the deflector bars 61 and 62 as described previously through the conductors 133, 134, 135 and 136. The entire assembly can be held together by thermally bonding the top surfaces of the second insulating block 32 to the lower edge portions of the deflector bars 61 and a suitable mounting ring secured thereto by mounting tabs as described earlier whereby the structure can be mounted in assembled relationship adjacent with a micro lens array sub-assembly similar to FIGS. 1 or 11. While the fine micro deflector structure shown in FIG. 20E has certain advantages, it is expensive to fabricate in that the silicon and ceramic or oxide coated silicon blocks 66 and 132 are not reuseable and hence the design requires a substantial amount of rather expensive material. For this reason, the fine deflector structure shown in FIG. 20D is preferred wherein the respective sets of orthogonally arrayed deflector bars 61 and 62 are thermally bonded to transversely extending glass support rods 68 at the ends thereof as described earlier. The blocks of silicon 66 having the slots 67 sawed therein then may be reused as holding fixtures thereby economizing greatly from a material viewpoint. FIG. 20F illustrates still another modified form of micro deflector sub-assembly constructed according to the present invention. In FIG. 20F the orthogonally arrayed sets of spaced-apart, parallel micro deflector bars are held in assembled relationship by respective glass support rods 68 extending at right angles to the bars and connected thereto at respective ends of the bars as described earlier with respect to the FIG. 20D species of the invention. In FIG. 20F, however, in place of securing the metallic elongated ends of the end deflection plates 61A, 61B, 62A and 62B to an annular support ring for securement to the axially extending main glass support rods 14, the elongated ends 61A-62B are fabricated from a malleable material such as tungsten so that they can be bent at substantially right angles to directly contact and be thermally bonded to axially extending glass support rods 14 in the manner shown in FIG. 20F and in FIG. 21. With the micro deflector sub-assembly secured to the main axially extending glass support rods 14, the peripheral edges of thin silicon lens plates 16, 17, 18 and 18A (if used) can be directly thermally bonded to the axially extending main glass support rods 14 as shown in FIGS. 21 and 21A. The structure thus greatly simplified by the absence of the mounting rings, is completed by directly thermally bonding the peripheral edge of the target electrode member 13 to the axially extending main glass support rods 14 and the termination plate 15 likewise is directly thermally bonded to the main glass support rods 14. The assembly thus comprised may then be secured to the inner peripheral edge of a suitable mounting ring support such as shown in FIG. 25 for support within the housing or other envelope of an electrode beam tube of the fly's eye type. The resulting assembly would comprise essentially only silicon and glass components and minimizes to the greatest possible extent the use of materials having temperature coefficients of expansion widely different from those of silicon and glass. In addition to this rather substantial benefit, the cost of the components is greatly reduced as is the cost of their processing not to mention the reduction in weight and ability to minimize the size of the entire assembly. In the effort to miniaturize the size of the combined micro lens array and micro deflector assembly in the manner depicted in FIG. 21 and FIG. 21A of the drawings, the physical spacing between the thin, apertured silicon lens plates 16, 17 and 18 can become critical. In order to overcome this problem, and still at the same time insure an adequate amount of insulator between adjacent edges of the spaced-apart lens plates whereby they will be able to withstand substantial potential differences of the order of 5-10 kilovolts or perhaps even greater, the plates can be mounted to modified glass support rods as shown in FIGS. 22 and 22A of the drawings. In each of these Figures the glass support rods are provided with suitable inwardly extending projections which contact the peripheral edge portions of the silicon plates at the point of thermal bonding whereby the effective insulator distance between adjacent silicon plates can be made to be much greater than the plate separation distance. For this purpose, the axially extending, main glass support rods such as 14A in FIG. 22 are provided with inwardly extending branches 137. As an alternative, the main axially extending glass support rods, such as 14B in FIG. 22A, may be bowed outwardly as shown at 138 for the extent thereof corresponding to the space between adjacent lens plates. FIGS. 23 and 23A of the drawings illustrate another alternative method of securing together the orthogonally disposed, metalized silicon micro deflector bars 61 and 62 having the ends thereof secured to glass support rods 68A and 68B, respectively, as described previously. In FIG. 23 and and FIG. 23A, the glass support rods 68A and 68B to which the respective ends of the micro deflector bars 61, 62 are thermally bonded, are extended sufficiently so that they intersect one over the other and are thermally bonded together at the point of intersection. A small, insulating, sapphire ball shown at 139 may be interposed and thermally bonded to the intersecting glass support rods 68A and 68B at the points of intersection to adjust the spacing between the sets of deflector bars. With the construction shown in FIGS. 23 and 23A, it is possible to get the closest possible spacing between the orthogonally disposed metalized silicon deflector bars 61,62 without requiring the need for elongated, metal end deflector bars as discussed in earlier described arrangements. To mount the micro deflector sub-assembly, the glass support rods 68A and 68B may be extended sufficiently to allow one or both to be secured to a mounting ring. Alternatively, an axially extending glass rod 14 can be directly thermally bonded to the intersection of 68A and 68B for mounting within an electron beam tube as indicated by dotted lines at 14 in FIG. 23. As described earlier with respect to FIG. 1 and FIG. 11 species of the invention, for holding the micro lens array and micro deflector assembly together or for mounting the assembly in a fly's eye electron beam tube structure, one may use any of the standard fastening means such as spot welding, brazing or even bolting together, all of which have been used in prior art devices. For example, it is not unusual to use a combination of machine screws and spot welding for assembly. Spot welding the component parts of a fly's eye electron beam tube has disadvantages in that it is limited to joining conducting materials. Thus for joining silicon and ceramics or glass, an additional step of providing mounting tabs or flanges is required. Spot welding also creates debris and is not suited to ready disassembly for realignment or replacement or component parts. Additionally, spot welding segregates alloys, causing instability and magnetic combinations to be formed during the spot welding procedure in nearby metal parts that are magnetizable. Finally, spot welding produces stretching at certain points of the metal parts being joined thereby resulting in distortion and leaves rough surfaces which can cause corona and arc-over during operation of the electron beam tube. Brazing of the sub-assemblies together for mounting the resulting micro lens and micro deflector assembly within the electron beam tube has disadvantages in that it requires complex fixturing to maintain alignment through a high temperature cycle required to braze the parts together. Additionally, the brazing process may require fluxes which are difficult to remove after the brazing operation in order to make the assembly electron optically clean. It is difficult to retain the brazed filler at the desired locations where jointures are to be accomplished and finally, the resulting structures cannot be readily disassembled non-destructively. Bolting or assembly through machine screws had disadvantages in that the bolts or screws generally are conductors and thus require complex insulator sleeving, spacers, etc. to avoid shorting out different parts of the assembly. Tightening of the bolts or machine screws tends to force the assembly out of alignment just as it approaches final position unless very elaborate means are employed through complex and bulky clamps and fixturing to separate the clamping force from the rotation which produces the force. Additionally, available screws and bolts have thermal coefficients of expansion which are not close enough to the coefficient of expansion of silicon and ceramic insulators to maintain the assembly integrated throughout the bake-out cycle. To produce screws and machine bolts of special materials such as tungsten in order to overcome this problem, removes the cost advantage of using bolts and screws in the first place. In the products herein described, glass rodding as a means for assembling the various component parts together into sub-assemblies and thereafter joining the sub-assemblies into a complete assembly, is preferred since the cost and integrity of the resulting structures are quire acceptable and the techniques for glass rodding well known and proven. In the case of faulty assembly, by "cracking the glass" the expensive parts of the assembly such as the thin silicon lens plates and micro deflector bars generally can be reclaimed. Since the glass rodding is not too expensive, this method of disassembly is acceptable for realignment and replacement problems. As noted in the preceding paragraph, the glass rodding technique of assembly does not lend itself readily to easy nondestructive disassembly. In those applications for a fly's eye electron beam tube where disassembly is a key factor, as for example in use of the fly's eye electron beam tube for art work generation in the fabrication of microcircuits, and the like, an assembly method employing precision sapphire balls mounted in conical recesses can be employed. This basic method of assembly is disclosed in FIGS. 24, 24A, 26, 26A, 26B and 27 of the drawings. As may be expected, the thin, apertured silicon lens plates are too brittle to be clamped between precision sapphire balls without taking special steps to accommodate this technique of assembly. As shown in FIG. 24, one procedure is to fuse the peripheral edges of the thin silicon lens plates such as 16, 17 and 18 to axially extending glass rods 14. The micro lens array sub-assembly thus comprised can then be separately mounted on a mounting ring such as shown at 141 in which circular openings 142 are formed. A small insulating sapphire ball 143 is inserted in the hole or opening 142 in mounting ring 141 and the end of the supporting glass rod then thermally shaped to form sockets for seating the insulating sapphire balls 143. FIG. 24A of the drawings illustrates a technique for fabrication of the structure shown in FIG. 24 using a vacuum chuck and gas flame to heat the glass support rods 14 to approaching their melting temperature. The thin, apertured silicon lens plates 16, 17 and 18 are then pressed into engagement with the glass support rod 14 by suitable holders (not shown) and either concurrently or sequentially, the insulating sapphire balls mounted in suitable holders 145 and 146 are brought into engagement with the heated ends of the glass support rods 14 to simply press a ball seat in the ends of the glass rods. The glass support rods 14 cool slowly enough to permit forming the ball sockets all in one operation immediately after pushing the glass support rod into proper mounting position with relation to the balls and thin silicon plates 16-18. The sequence of operations are (1) the glass rod 14 is moved to the right to engage the ends of the thin apertured silicon lens plates 16, 17 and 18 after being heated by the glass flame. Downward motion of the sapphire ball holder 145 and upward motion of the sapphire ball holder 146 indicated as motions 3 and 6 may occur simultaneously with motion 1 with these motions being sequentially followed by motions 2, 4 and 5 to withdraw the furnace and holders from the glass rodded sub-assembly shown in FIG. 24. The resulting structure then is mounted as shown in FIG. 24 on mounting ring 141 having apertures 142 for receiving the small insulating sapphire balls 143. In place of using the gas flame heating, one could use heating methods employing electron heat fusion, laser heat fusion or radio frequency heating of the glass rod prior to pressing the thin apertured silicon lens plate and sapphire balls into position on the rods. The inexpensive, artificial sapphire spheres used as the insulating balls 143 are ideal as forming tools for fabrication in accordance with this technique. FIG. 25 illustrates a preferred method for attaching a flange to a coarse deflector cone for electron beam tubes of the fly's eye type wherein the coarse deflector cone 90 has the coarse deflector electrode 102 formed thereon by any suitable known metalization glass technique. The ends of the coarse deflector cone 90 on the outer surfaces thereof are shaped to receive and coact with a metal mounting band 147 having an outwardly extending flange portion 148 to which are secured suitable glass rod mounting tabs such as 86, 88 and 90 described with relation to FIG. 1 of the drawings. The flanged metal band 147,148 is secured to the ends of the glass tube envelope 90 by heat shrinking the band 147 over the end of the glass tube. The metal band 147,148 may be prefinished in advance of the heat shrinking process, or alternatively may be finished after securement to the sides of the glass tube. The structure shown in FIG. 24 may be mounted on a mounting flange similar to that shown in FIG. 25 and which corresponds to the mounting ring 141 shown in FIG. 24. To heat the metal band 147, it could be heated with radio frequency electric fields or electron, or laser beam heating as well as by a gas fired furnace while the glass envelope 90 of the tube is maintained substantially at normal room or ambient temperature. The dimensions of the metal band 147 are proportioned so that upon being heated it can just be slipped over the end of the tube glass envelope 94 and upon cooling will shrink fit to a tight bond. FIGS. 26, 26A and 26B illustrate still other forms of the invention for use in fly's eye electron beam tubes of the type that must be easily broken down and taken apart for operational use. In the embodiment shown in FIG. 26, the central thin apertured silicon lens plate 17 is provided with a set of relatively thick pads shown at 151 and 152 secured on both sides of an outer peripheral edge portion thereof. Each of the pads 151 and 152 has a pyramidal or conical shaped opening indicated at 153 formed therein for receiving and seating a small, insulating sapphire ball such as shown at 143 and 143A. The sapphire ball 143 itself is seated in a circular opening formed in the peripheral edge portion of one of the outer thin apertured silicon lens plates 16. The sapphire ball 143 also seats in a pyramidal or conical shaped cavity 153 in a thick pad 154 secured to a peripheral edge portion of the termination plate indicated at 15. The sapphire ball 143A is designed to seat in the pyramidal or conical opening 153 formed in the lower pad 152 and in turn seats in an opening formed in the peripheral edge of the lower thin apertured silicon lens plate 18. The lower end of the lower insulating sapphire ball 143A in turn is seated in a circular opening in the annular mounting ring member 87 of a micro deflector sub-assembly 12 which may be fabricated as described with relation to FIG. 1 of the drawings. The entire assembly including the termination plate 15 and mounting ring 87 may then be supported within an evacuated electron beam tube housing in a manner to be described hereinafter with respect to FIG. 27, for example. Thus, it will be appreciated that with the arrangement of FIG. 26, disassembly of the components of the micro lens array for realignment purposes, etc. is facilitated without requiring breakage of glass support rods, or the like. FIGS. 26A and 26B illustrate modified constructions for the insert washers to be placed between the thin apertured silicon lens plates in order to control the spacing distance between plates and at the same time provide an adequate thickness to facilitate use of the small sapphire balls employed in assembling the elements in a composite structure such as shown in FIG. 26. In FIG. 26A the insert is shown as a relatively thick, flat annular washer type of spacer 155 having a central opening of sufficient dimension to accommodate the ends of the small sapphire insulating spacer balls 143. In the FIG. 26B species, the additional washer-like spacer 156 is provided with rimmed edge portions to accommodate the peripheral surfaces of openings formed in the thin apertured silicon lens plates. In each of these species, if the lens plates to be spaced apart are to be maintained at different potentials, the spacers 155 and 156 would be fabricated from electrical insulating material such as glass, aluminum oxide or silicon dioxide coated silicon or other similar compatible material. If the adjacent plates to be spaced apart are to be maintained at the same potential, then the spacers may be fabricated from a suitable metal such as molybdenum or tungsten. The easily disassembled "ball alignment" structure can be used for silicon plates if the plate separation is large enough to hold the potential difference across the ball surface. For example, at least a 5 kilovolt potential difference is generally required to be placed between adjacent plates. With sapphire balls, the minimum diameter corresponding to sound design practice lies in the range of 4-5 millimeter diameter balls. With the "ball alignment" structure, one of the constraints encountered is that the balls must be aligned and must not touch one another. This requirement in turn places a requirement for the use of the additional thick pads or spacer elements placed between adjacent siliconplates. The angle of contact of the balls with the peripheral edge portions of the holes in the silicon plates designed to accommodate the balls must be approximatelyat the point of equal division between vertical and horizontal loading. Typical numbers derived as exemplary are: ball diameter=5.00 mm., contact angle=45.degree., plate separation=3.54 mm., leakage path=3.93 mm., and minimum plate thickness=1.46 mm. FIG. 27 shows a micro lens array and micro deflector sub-assembly similar to those shown in FIGS. 23 or 24 mounted on the end of the coarse deflector cone 90 of an electron beam tube together with termination plate 15 and target electrode member 13 to provide a readily disassembled and remounted assembly employing both "ball alignment" and "glass rodding" techniques. For conveninece, only one side of the structure is shown with the end of the coarse deflector cone 90 terminating in a shrink fitted metal mounting flange 147 having an outwardly extending rim 148 constructed according to FIG. 25 of the drawings. The rim 148 of mounting flange 147 has a lip which receives and seats the termination plate 15 having ball seats formed therein for accommodating alignment balls 143 for seating and supporting the lower ends of the support rods 14 for the micro lens array 11. The micro lens array 11 may be fabricated as shown in FIG. 24 of the drawings and has its upper sapphire balls seating and supporting the lower ends of the axially extending glass support rod 14 of a micro deflector 12 constructed as described with relation to FIG. 23 of the drawings. An alignment ball 143 seated on the top of the axially extending glass support rods 14 of the micro deflector in turn is seated in the pyramidal shaped opening of a set of spacer pads 151 and 152 are spaced on either side of the target electrode member 13 in a manner similar to that described with relation to FIG. 26. The spacer ball 143 seated in the opening on the top of the spacer pad 151 in turn seats in an opening in an annular compression plate 157 that may comprise an integral part of the end cap structure 158 for the array optics assembly. The combined end cap and compression plate 157,158 is provided with an outer mounting flange 159 having openings therein that form seats for the alignment sapphire spheres 143. The entire structure comprising compression plate 157, end cap 158 and mounting flange 159 may be fabricated from glass or an electron optically clean metal such as tungstem or molybdenum, ceramic or other suitable material having the required imperviousness to gases and structural rigidity. Mounting flange 159 has a grooved surface around its outer periphery in which the sapphire balls 160 seat in the upper flange 161 of an outer housing envelope member 162 for the micro lens array and micro deflector assembly. Housing member 162 also has a lower mounting flange 163 coacting with the rim portion 148 of metal band 147 to seat and support the assembly on sapphire balls 164. The mounting flanges 159 and 161 and 163 and 148 are compressed together against the sapphire balls 160 and 164 by a set of Inconel steel compression springs shown at 165 inserted by means of a loading tool 166. After insertion with the loading tool, the clamping springs 165 rigidly hold the entire structure in assembled relationship. As an alternative to the arrangement shown in FIG. 27, where the intended application of the fly's eye, electron beam tube does not require ready disassembly for changing target members 13, such as where the intended application is for use as an electron beam accessible computer memory, the combined micro lens array and micro deflector assembly including target member 13 shown in FIG. 21 of the drawings could be inserted bodily in place of the three part assembly comprised by sub-assemblies 11, 12 and 13 of FIG. 27. With such an arrangement, the ends of the axially extending glass support rods 14 shown in FIG. 21 would be compressed to receive the alignment balls 143 employed in mounting the micro lens array and micro deflector assembly between compression plate 157 and termination plate 15 of the structure shown in FIG. 27. Needless to say, the termination plate arrangement 15 illustrated in FIG. 21 would not be required in any such modification since it would be redundant in view of the use of the plate 15 as a compression member in the modified FIG. 27 structure. The technique and apparatus for fabricating thin, apertured silicon lens plates for micro lens arrays according to the invention lends itself to improved methods for reduction of third order spherical aberration of the lens (which varies as the cube of the lens aperture in radius or angle). It has been established that third order aberrations in electron lenses can be corrected by one of three methods: (1) Use of some unround apertures. PA1 (2) Place a source of charge near the lens axis. PA1 (3) Vary the lens power with time. The last method described in (3) above requires impracticably high rates of variation. The second method described in (2) becomes progressively less attractive as the beam energy is reduced and is best suited to electron beam energies above 30 kilovolts. The unround aperture technique described in (1) is the most attractive since it will work at any voltage and is not restricted in use to higher beam energies. The double, thin conducting film cross-sectional configuration of the silicon lens plates 16, 17 and 18, is well adapted to the formation of unround lens apertures on either side of the plates as best illustrated in FIGS. 28 and 28A of the drawings. Referring to FIG. 28, an upper silicon lens plate 16 is fabricated with a small diameter circular aperture 171 formed in its upper surface and an elliptical or semi-elliptical aperture 172 formed in its lower conducting surface. When viewed from below, the plane of the lens plate would then appear as shown in FIG. 28 to provide the unround aperture openings 172 for correction of the undesired third order aberrations. The unround (elliptical or semi-elliptical) openings 172 may of course be fabricated by appropriate design of the photo-resist pattern employed in defining the undoped silicon surfaces to be etched by the etchant as described previously with respect to FIGS. 18A-18J of the drawings. FIG. 28A is a cross-sectional view through one of the unround apertures shown in FIG. 28. An additional advantage of fabricating the thin lens plates as shown in FIGS. 28 and 28A is that by use of such unround apertures, the number of plates that will be required in the stacked, parallel array of lens plates possibly can be reduced, perhaps by a factor of 2. In the embodiments of the invention described above, it should be understood that the thin conductive layer 33 on each side of the thin, apertured silicon lens plates (for dual-sided lens plates) or on the single side of the extremely thin lens plates (as shown in FIGS. 30 and 31 to be described hereafter) may comprise the highly conductive doped layer of silicon resulting from the processing of the starting silicon wafer without requiring that a further conductive coating or metalized layer of platinum, gold, silver or other heavy metal be disposed over the remaining surfaces of the thin, apertured silicon lens plates. Further, while the invention has been described primarily with relation to assemblies employing 3 or 4 lens plates, it is not limited to such structures. FIG. 29 of the drawings illustrates the preferred axial profile of a single channel of a micro lens array sub-assembly according to the invention which employs five (5) lens plates in the stacked array of parallel lens plates. In FIG. 29 the top plate 16 has the large diameter opening 32 in the highly conductive boron doped layer 33 exposed to the incoming electron beam with the smaller diameter beam limiting aperture 31 being located on the exit side of the plate. A second inlet lens plate 16A of similar construction is arranged in the same manner as 16. The center plate 17 to which the high focusing potential is applied has equal diameter apertures 36 and 37 formed on opposite sides thereof in the same manner as described with relation to FIG. 17. The two exit plates 18 and 18A have the small diameter limiting apertures 31 disposed on the upper surfaces thereof that are exposed to the incoming electron beam and the larger diameter apertures 32 are located on the beam exit side of the plates. FIGS. 30 and 31 illustrate a somewhat different cross-sectional configuration for the lens plates of the micro lens array whereby extremely fine spacing between the plates can be obtained. The starting material is a wafer 181 of single crystalline silicon having a diameter of about 7-9 centimeters and a thickness of 1/2 millimeters. The wafer 181 is processed in a manner similar to the method described with relation to FIGS. 18A-18J using quite different masking patterns for the two sides of the wafer. On one side (which may be the upper side exposed to the incoming electron beam) a comparatively large rectangular opening 182 is left open to the action of the etchant and an array of fine aperture openings 31 having diameters of the order of one to two microns (1-2.mu.) is formed in the lower boron doped surface 33 of the wafer. The boron doped surface extends around the edges and over a substantial upper peripheral portion of the wafer as shown at 183 to provide sufficient rigidity and strength for mounting the resulting lens plate. Etching action through the top surface opening 182 is allowed to proceed all the way through the thickness of the wafer to the lower boron doped layer 33 defining the lens apertures 31. This action results in the formatiion of the tapered shoulders 184 extending between the matrix of apertures 31 on the lower surface and the upper peripheral portion 183. The resulting lens plate in the active area of the electron beam may have a thickness of the order of one to two microns (1-2.mu.) while defining lens apertures having diameters of the order of one to two microns (1-2.mu.) each thereby maximizing to the greatest possible extent the number of data bearing channels that can be designed into an electron beam accessed memory tube. The lens plate construction shown in FIGS. 30 and 31 could be used in any of the micro lens array sub-assemblies described in the preceding portions of the specification and even makes possible the design of practical assemblies employing only a single micro lens plate as the micro lens array sub-assembly. In such constructions, only the single lens plate shown in FIGS. 30 and 31 would be inserted for the micro lens sub-assembly 11 employed in the structures of FIGS. 1, 11, 21, 24, etc. While it might be possible to use a single lens plate fabricated as described withrelation to plate 16 in FIGS. 18A-18J of the drawings as a micro lens array sub-assembly, the construction of FIGS. 30 and 31 is preferred for single lens plate structures. From the foregoing description, it will be appreciated that the perfection of the silicon etched symmetry and the precise geometrical control in three dimensions which is made possible by the boron diffusion and pyrocatechol and ethylene diamine etching action to limit the etching to predetermined locations, makes possible the fabrication of dramatically new and different lens plates for use on micro lens array elements. The steps in the preferred method of lens plate production are shown in FIG. 18 of the drawings. The technique employed makes possible the fabrication of two-layer structures where the aperture formed on one side of the lens plate has a different configuration from the aperture formed on the other, as described with relation to FIG. 28. Different shaped apertures "piggy-backed" on a single lens plate have been tried previously with photoetched metal plates. The problems encountered, however, were that the thin metal plates were not providing sufficiently round holes, were not staying in the plane and (being of a different metal in order to give selective etching characteristics) was also a bi-metallic plate subject to thermal warping. The doped silicon lens plates provided differential etching capability whereby different shaped apertures can be formed on opposite sides of the plate without introducing bi-thermal properties. Furthermore, where the apertured different configurations are "piggybacked" on the single lens plate, it is difficult to make the plate thick enough to cause the aperture to be placed outside the fringe field of the lens. Using boron doping and differential etching for definition of the aperture opening, sufficiently high quality holes can be formed on a "piggybacked" structure to make their use practical whereby fewer lens plates may be required in place of a larger number usually required in micro lens arrays fabricated from metal plates. This is made possible because control of the positioning of the aperture openings, their symmetry and size is of an order of magnitude improved over prior known constructions. It should also be noted that in the fabrication of the micro deflector assembly, the fine micro deflector bars or blades are sawed from a solid block of silicon and the resulting blades or bars subsequently metalized. This procedure also is true for blades made from aluminum oxide ceramic or vitreous carbon as a starting material. Needless to say, the sawing of the individual blades and subsequent metalization of the blades requires individual processing of these parts and hence increases the cost of the micro deflector sub-assembly. For very large volume use, the cost per fine deflector unit can be reduced and the advantages of unitary construction achieved, i.e., pure materials, no bake-out limitations, stress free, and no vacuum pockets, by pyrolytic formation of polycrystalline silicon from halogen vapor into a graphite master mold conforming to the desired micro deflector sub-assembly sets of bladed structures. The process of such pyrolytic silicon formation of large complex objects is well established in the manufacture of polycrystalline silicon furnace tubes and furnace boats as described in the article entitled "The Preparation and Properties of CVD-Silicon Tubes and Boats for Semiconductor Device Technology", Journal of the Electrochemical Society, Vol. 121 (1974), page, 112-115, by W. Dietnze, L. P. Hunt and D. H. Sawyer. Thus, for large volume fabrication of the fine deflector sub-assemblies, in place of sawing out the individual blades and mounting them in two separate sets of interdigited, orthogonally arrayed, spaced-apart parallel bars as described above, four individual sets of bars can be fabricated initially from a master mold as described in the above-referenced article. Two sets may then be interdigited and mounted for x axis deflection and the remaining two sets interdigited and mounted for y axis deflection. The two sets of interdigited bars produced by the polycrystalline silicon then are arrayed at right angles to each other and alternate ones of the interdigited sets of bars appropriately interconnected electrically to operate in the previously described manner to provide -x, +x and -y, +y deflection. Having described several embodiments of a new and improved micro lens array and micro deflector assembly for fly's eye type electron beam tubes constructed according to the invention, it is believed obvious that other modifications, variations and changes in the invention will be suggested to those skilled in the art in the light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention described which are within the full intended scope of the invention as defined by the appended claims.
043702961	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The invention is in the field of fusion reactor designs and particularly relates to ohmic heating coils for toroidal-type fusion reactors. The invention is also applicable to fusion-fission hybrid type reactors. 2. Description of the Prior Art A large number of studies have been directed to the design of toroidal-type fusion reactors as well as to the design of fusion-fission reactors. Representative studies include the following: Tokamak Experimental Power Reactor Conceptual Design, Volumes I and II, Argon National Laboratory, ANL/CTR-76-3, August 1976; Proceedings US-USSR Symposium on Fusion-Fission Reactors, July 13-16, 1976; and DCTR Fusion-Fission Energy Systems Review Meeting, Dec. 3-4, 1974, ERDA-4. In typical prior art toroidal-type fusion experiments and designs, the ohmic heating coil takes the form of a transformer positioned in the center of the toroidal configuration as illustrated, for example, in U.S. Pat. No. 3,778,343. It has long been desired to decrease the size of this OH transformer, particularly in view of the rather stringent space requirements present in existing machines. Attempts have been made, for example, to specifically design the toroidal field coils surrounding the plasma region to optimize space requirements within the toroidal region center along the main axis of the toroid. Such studies are exemplified by U.S. Pat. No. 3,859,615. The ability to utilize the interior space of a toroid would greatly relax the stringent design requirements imposed on toroidal-type fusion reactors and permit the utilization of lower current densities within the TF coils. SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to increase the operating efficiency of toroidal-type fusion reactors. It is a further object of the invention to remove the ohmic heating transformer from the region of the main axis of the toroidal field coils to thereby enable radial expansion of the TF coil cross-sectional area within the region of the main axis. Yet another object of the invention is to provide a more efficient ohmic heating coupling to the plasma region of a fusion device of the toroidal-type. A further object of the invention is to provide a more efficient ohmic heating coupling for fusion-fission type reactors or power generating devices. In accordance with the principles of the invention there is provided a fusion reactor of the toroidal-type having a plasma containing toroidal fusion region for producing energy from fusion reactions. The fusion reactor comprises toroidal field generating means for producing a toroidal magnetic field in the plasma fusion region upon the passage of current therethrough. The toroidal field generating means is positioned proximate the toroidal fusion region. Ohmic heating coils are provided for ohmically heating the plasma within the plasma fusion region, and the ohmic heating coils are positioned between the fusion region and the toroidal field generating means on the side nearest the main axis of the toroidal fusion region. There is also disclosed in accordance with the principles of the invention a method of increasing efficiency of a fusion reactor of a toroidal configuration having toroidal field coils positioned substantially adjacent a toroidal fusion region and ohmic heating coils for ohmically heating plasma within the toroidal fusion region. The method comprises the step of positioning the ohmic heating coils between the toroidal fusion region and the toroidal field coils on a side nearest the main axis of the toroidal fusion region. There is also disclosed in accordance with the principles of the invention a fusion power generating means comprising a fusion power core having a toroidal fusion region, a toroidal field generating means positioned proximate the toroidal fusion region and an ohmic heating means positioned between the toroidal fusion region and the toroidal generating means. Further, the power generating means comprises means for extracting thermal energy from the fusion power core and is constructed such that the fusion power core is removable from the power generating means for replacement thereof by a replacement fusion power core.
	claims	1. A device for disposing nuclear waste using a deep geological repository, comprising a raw material conveyor, a raw material mixer, a liquid waste conveying pipeline, an additive tank, a powder waste conveyor, an output pump, a liquid supply pump, a liquid supply manifold, an output manifold, a mixed liquid conveying pipeline, a high-pressure injection pump, a high-pressure pipeline, a wellhead sealing device, a supply-discharge pump connecting pipe, a first valve, and a second valve,wherein the raw material conveyor is arranged at the left side of the raw material mixer, the raw material conveyor has an output end thereof communicated with a top of the raw material mixer, the liquid waste conveying pipeline has an output end thereof communicated with a lower part of the raw material mixer, the liquid waste conveying pipeline has an input end thereof connected to a liquid waste source, the additive tank is deposited above the raw material mixer, the additive tank has a lower end thereof communicated with the top of the raw material mixer, the powder waste conveyor has an output end thereof communicated with an upper part of the raw material mixer, the liquid supply pump has an input end thereof connected to the liquid supply manifold, the liquid supply pump has an output end thereof connected to the raw material mixer, the output pump has an input end thereof connected to the raw material mixer, the supply-discharge pump connecting pipe is arranged between an output pipeline of the liquid supply pump and an input pipeline of the output pump, the first valve is located on the output pipeline of the liquid supply pump at the left side of the supply-discharge pump connecting pipe, the second valve is located on the supply-discharge pump connecting pipe, the output pump has an output end thereof connected to an input end of the output manifold, the output manifold has an output end thereof connected to an input end of the mixed liquid conveying pipeline, the mixed liquid conveying pipeline has an output end thereof connected to an input end of the high-pressure injection pump, the high-pressure injection pump has an output end thereof connected to an input end of the high-pressure pipeline, and the wellhead sealing device is located at a terminal of the high-pressure pipeline. 2. The device for disposing nuclear waste using a deep geological repository of claim 1, wherein the raw material conveyor and the powder waste conveyor are each a screw-type conveyor. 3. The device for disposing nuclear waste using a deep geological repository of claim 1, wherein the liquid supply manifold is provided with a plurality of liquid supply holes that are connected to a liquid source through a pipeline. 4. The device for disposing nuclear waste using a deep geological repository of claim 1, wherein the high-pressure injection pump is driven by a shaft. 5. The device for disposing nuclear waste using a deep geological repository of claim 1, wherein the powder waste conveyor and the liquid waste conveying pipeline have input ends thereof connected to a conveying-pump connecting end and another conveying-pump connecting end, respectively. 6. The device for disposing nuclear waste using a deep geological repository of claim 1, wherein the device can be compressed and buried after one-time use. 7. The device for disposing nuclear waste using a deep geological repository of claim 1, wherein the device is a vehicle-mounted type.
060693614	summary	FIELD OF THE INVENTION The invention relates generally to the field of X-Ray sensors and in particular to increasing the resolution of digital X-Ray sensors. BACKGROUND OF THE INVENTION U.S. Pat. No. 5,391,879 to Tran et al. discloses a radiation detector which includes an array 16 of pixelized sensors 15 and an overlying array 12 of phosphor pixels 11 with a fiber optic network in between (elements 17 and 17 in FIG. 1). See Col. 1, lines 10-23. This reference discloses one layer of sensor elements rather than a pair of sensor arrays on either side of a phosphor layer. Therefore, this device suffers from loss of efficiency due to loss of a portion of the light emanating from the phosphor layer in a direction away from the pixelized sensors. U.S. Pat. No. 5,220,170 to Cox et al. discloses an X-ray imaging system and a solid state detector used therewith. FIG. 16 shows a scintilator positioned between two layers, one containing a sensor element and another containing preprocessors. See Col. 1, lines 25-30. From the foregoing discussion, it should be apparent that the prior art devices suffer from a loss in resolution because the spaces between adjacent pixels are not active as detectors. The present invention is directed to overcoming one or more of the problems set forth. SUMMARY OF THE INVENTION A solid-state X-ray detector for use in a digital X-Ray imaging system wherein a detector employs a phosphorescent layer to convert x-radiation to visible light and have the visible light detected by an image sensing device. The preferred embodiment employs silicon charge coupled devices (CCDs) "sandwiched" face-to-face with a phosphor screen or phosphor layer between them to enhance overall sensitivity of the device to X-rays. X-rays normally would pass through a CCD device and not be efficiently detected. X-rays striking the phosphor layer in this detector will generate visible light which will then be efficiently detected by the surrounding CCDs (FIG. 1). In a related embodiment, the two CCDs are offset relative to one another so that the pixels of one cover the spaces between the pixels of the other, thereby increasing the resolution of the device. In a multiple sensor array embodiment, the sensor arrays can be placed next to, and offset from, each other to further increase the resolution, or allow additional predetermined bandwidths to be captured, or both. In a further related embodiment, the phosphorescent screen is combined with an opaque mask containing holes corresponding to the positions of the pixels in the CCDs. This improves image quality by preventing light resulting from an X-ray striking the screen in a particular location from "bleeding" and exposing adjacent pixels. One screen is placed on each side of the phosphorescent layer with holes aligned with the corresponding CCD. Or, alternatively, the screen is affixed directly to the CCD prior to assembly of the device, or "spots" of phosphor material are applied directly to the CCDs over each pixel to substitute for the screen. Briefly summarized, one aspect of this invention will provide the means of capturing high-resolution X-Ray images onto sensors including a solid state X-ray detector comprising: a plurality of pixellated array sensors each sensitive to a bandwidth selected for that sensor; a phosphorescent layer applied to at least one of the sensors and aligned with the pixels of that sensor, the phosphorescent layer being sensitive to X-rays and emitting light in response to X-rays within the bandwidth of the sensor to which it is applied. These and other aspects, objects, features, and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings. Advantageous Effect Of The Invention The present invention offers the following advantages: 1) enhanced efficiency of X-Ray detection by summing the response of multiple layers of pixels surrounding a phosphor layer; 2) increased resolution resulting from multiple sensor arrays positioned to overlap spaces between pixels; 3) the possibility of generating images from multiple X-Ray bandwidths simultaneously.
	description	This application claims priority to U.S. Provisional Application No. 62/359,746, filed on Jul. 8, 2016, which is incorporated herein by reference in its entirety. There is disclosed a physical isolation chamber that forms an integral part of a Hot Isostatic Press (“HIP”), which is located between a component to be Hot Isostatically Pressed and a furnace. There is also disclosed a method of physically containing and preventing migration of any hazardous/radioactive particulate, powder, and/or gas that may escape from a HIP can to the furnace or HIP vessel. In a HIP process a material to be consolidated is exposed to both elevated temperature and isostatic gas pressure in a high pressure containment vessel. The pressurizing gas is an inert gas, such as nitrogen or argon, so that the material does not chemically react. The chamber is heated, causing the pressure inside the vessel to increase, such that pressure is applied to the material in an isostatic manner. There remains a need to avoid contaminantion of HIP systems from potentially harmful elements found in the materials undergoing consolidation. One apparatus for containing radioactive and/or toxic substances to be subjected to high pressures and/or temperatures is referred to as an Active Containment Over Pack” system (“ACOP”). The ACOP system is not an integral part of an HIP system. Rather, it is a containment device which is a can inside of a can design that must be placed into a furnace chamber for each use. In addition to the potential of damaging the furnace due to alignment issues and thermal expansion differences as compared to the furnace materials, the ACOP system must be placed in a high temperature region of the furnace for it to operate, which leads to operation deficiencies. For example, as the entire ACOP system is located in the high temperature region of a HIP furnace, there are technical problems associated with thermal expansion and creep distortion of a seal area. In addition, filters of an ACOP system are also necessarily located in the high temperature region of a HIP furnace, which can cause problems in containing radioactive and/or toxic materials. This is because the continual use of these filters at high temperature causes the filter pore size to change. Therefore, the ability to maintain consistent performance over time is compromised. In addition, the filters have low strength at high temperatures and when fast decompression of the HIP occurs the filters can rupture and breach containment of which they were designed to maintain. Loss or reduction of gas pressure at high temperature can also cause a porous metal filter to sinter and close off through-holes; this could cause a potential problem as gas pressure will be trapped in the ACOP chamber. The pressure inside the ACOP may lead to a pressurized container that presents a hazard for an operator trying to unload the HIP can/component. The resultant problems associated with the combination of locating the seals and filters in the high temperature region of the furnace increases the possibility that that the contents of the ACOP system can contaminant the HIP system. For at least the foregoing reasons, ACOP systems typically require a high degree of maintenance/replacement. Thus, there is a possibility that during a HIP cycle, through either thermal gradients or pressure differential across the filters, a break could form in the sealing area. Furthermore, ACOP systems are made of metal, and at HIP process temperatures, the mechanical strength of the ACOP is low. As a result, the thickness of the ACOP may be increased in order to provide some strength, which makes the unit heavy. In addition, depending on the closure type, the ACOP takes up space in the HIP system. For example, in a bolted flange design the flange occupies space that reduces the working size of the ACOP cavity; meaning either a smaller part or a larger HIP needs to be used to maintain the cavity size. The end closure of an ACOP system may be done by a flange/lid with a series of spaced apart and threaded bolts. Alternatively, the flange/lid can be attached by screwing it on as a lid, similar to a jar lid, or other mechanical clamps or locks that effectively sandwich a sealing material/gasket to create a seal. The metal mating surfaces, whether threads or flat faces, have intimate contact at high temperatures and pressures. This may cause them to diffusion bond or stick/weld, making them difficult to get apart and, consequently, difficult to remove the component. Although coatings can be used to prevent bonding, coatings have limited life span and often need to be re-applied regularly. Moreover, applying coatings in a radioactive environment remotely is difficult and adds complexity to the HIP process. The disclosed Active Furnace Isolation Chamber (“AFIC”) for containing a component to be Hot Isostatically Pressed (“HIPed”) addresses one or more of the problems set forth above and/or other problems of the prior art. In one aspect, the present disclosure is directed to a furnace isolation chamber for containing a component to be HIPed. In an embodiment, the chamber comprises: longitudinally cylindrical sidewalls; a top end extending between and permanently connected to the sidewalls, thereby closing one end of the chamber; and a movable bottom end, which is opposite the top end and forms a base end of the chamber. The movable bottom end is adapted to receive the component, and comprises a mechanism for raising and lowering the component from a cold temperature zone outside the furnace in a HIP system to a high temperature zone of the furnace in the HIP system. Unlike an ACOP device typically used in HIP systems, the described isolation chamber forms an integral part of the HIP system with the base end of the chamber being located outside of the high temperature zone of the furnace. The disclosed inventive isolation chamber allows for integral components to be located outside the high temperature zones, such as critical seals and filters, which may be compromised by the extreme pressures and temperatures of the HIP process. There is also disclosed a method of HIPing a component using the furnace isolation chamber described herein. In a non-limiting embodiment, the method comprises consolidating a calcined material comprising radioactive material, the method comprising: mixing a radionuclide containing calcine with at least one additive to form a pre-HIP powder; loading the pre-HIP powder into a can; sealing the can; loading the sealed can into the furnace isolation chamber as described herein, closing said HIP vessel; and hot-isostatic pressing the sealed can within the furnace isolation chamber of the HIP vessel. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. In one embodiment, the Active Furnace Isolation Chamber described herein overcomes problems and limitations of currently used systems that are meant to protect a furnace from radioactive/hazardous material. The described Active Furnace Isolation Chamber overcomes limitations of currently used systems in at least the following ways: There are no flanges or seal faces in the hot zone, thereby allowing the use of high strength materials; High strength materials allow thinner sections to be used; The integrated design guarantees alignment, thereby allowing for remote loading/unloading; As there is no need for sealing flanges or special opening end closures there is no wasted space in the furnace hot zone; Sealing is in the lower temperature zone, thereby overcoming diffusion bonding issues between the sealing; Filters in the hot zone area are optional and not essential, therefore even if rapid depressurization occurs, the pressure has a path way through the lower temperature filter thereby reducing pressure differential across the filters in the hot zone, thus preventing filter rupture; and When a lower filter is used, it will not close off and therefore a path for gas to equalize with the vessel pressure is provided for preventing pressurized chamber scenarios. With reference to FIGS. 1A and 1B, the Active Furnace Isolation Chamber according to the present disclosure is an integral part of an HIP furnace design. As used herein, forming an “integral part of the HIP system” is intended to mean that the AFIC is not loaded and unloaded for each process, as required for an ACOP system, but which is a permanent component of the HIP furnace design. In FIG. 1, a chamber 110, within which the part to be HIPed 120 is contained. The AFIC contains a high temperature chamber 110, at least part of which is contained within the hot zone of the HIP furnace 130. In one embodiment, shown in FIGS. 1A and 1B, the bottom end of the AFIC is located outside the furnace, which forms a cool zone 140. According to the exemplary embodiment, the complete assembly further contains one or more insulation and/or thermal barrier layers 150, 160. FIG. 2 shows an expanded view of the furnace isolation chamber according to the embodiment of the present disclosure shown in FIG. 1B. In various embodiments, the chamber 110 can be made of a wide range of high temperature high strength materials. A non-limiting list of such materials includes tungsten (W), molybdenum (Mo), as well as super alloys and ceramics. With further reference to FIG. 2, there is shown an area 210 integral to the disclosed AFIC, which is designed to contain particulate release and melt that may escape from a HIP can. In addition, there are a number of advantages of the disclosed design of the furnace and AFIC, particularly with the bottom end of the AFIC being located outside the furnace, which forms a cool zone 140. As a result of this design, any escaped volatile gas is contained by condensation in the cool zone 140 before reaching filters located at the bottom of the chamber. In the exemplary embodiment of FIG. 2, to ensure a thermal gradient, it is possible to include an insulator 220 between the hot zone 130 and the cool zone 140. In one embodiment, the cool zone 140 contains at least one device for measuring the presence of radioactivity from a radioactive containing gas that condenses on the walls of the chamber within the cool zone 140. By having such a measuring device, it is possible to immediately detect relatively small breaches in the HIP can and/or the AFIC before a catastrophic unwanted escape of radioactive gas. The furnace design according to the present disclosure may also ensure the working volume is maximized. In particular, as the bottom end of the AFIC is located outside the hot zone 130 of the furnace, which forms the cool zone 140, there is no loss of volume due to flanges or seals being in the hot zone 130. In an embodiment shown in FIG. 3, the AFIC may contain porous metal or ceramic filters. In the exemplary embodiment, the filters are shown as primary filters 310, in the hot zone 130, as well as secondary filters 320 in the cool zone 140. When such primary and/or secondary filters are present, the pressurizing gas associated with the HIP system is able to communicate with and act on the part through filter material. As shown, the filters 310, 320 can be located either solely in the base of the chamber outside of the furnace zone 320 and/or may be incorporated in the walls and top of isolation chamber 310. In the exemplary embodiment, the AFIC contains an over-pressure relief valve 330, which may control or limit the pressure in an HIP system that may build up during HIPing. Relief valve 330 may be designed or set to open at a predetermined pressure in order to protect the AFIC and other equipment from being subjected to pressures that exceed their design limits FIG. 4 is an expanded view of an additional inventive embodiment of the bottom, end cool zone of the furnace isolation chamber shown in circle in FIG. 2. This embodiment also shows sealing plug 410 and a located seat 420, configured to ensure proper alignment of the AFIC and facilitate robotic or remote handling of the AFIC system. As shown, the AFIC described herein may contain filters in the hot zone 130 (primary filters 310) and in the cold zone 140 (secondary filters 320) of a reactor. The exemplary embodiment of FIGS. 5A and 5B show expanded views of AFIC filters and seals. In particular, FIG. 5A is a perspective view of a sealing plug and FIG. 5B is a perspective of the sealing plug after being coupled with chamber 110. FIGS. 5A and 5B show the location of primary filters 310 (sintered metal) and secondary filters 330 (sintered metal). The exemplary embodiment further shows an O-ring 530 that seals against the inside of chamber wall 510. Exemplary gas flow paths 520 through the AFIC are shown. At least one benefit of locating primary filters 520 in the hot zone is that heat is able to transfer through them via convective flow of gas. Without these filters, heat transfer will be via radiant and conductive heat transfer. A potential disadvantage of having the filters in the hot zone, of which the present disclosure overcomes, is the loss of mechanical strength at high temperature and the changing in filter pore size over time at varying temperatures. However, when filters 520 primary function is to prevent particulates from escaping the chamber, it may inadvertently compromise the intended function of the chamber. Ceramic-based filters can, in part, overcome this problem in many respects. An advantage of alternatively and/or additionally having filters 330 in the lower temperature zone 140 of the HIP allows the mechanical strength and the filter pore size to be maintained throughout use. Additional advantages may be realized by the disclosed embodiments when the chamber 110 is made of high temperature high strength materials such as: molybdenum, tungsten, carbon-carbon materials, with no separable parts in the hot zone. In the exemplary embodiment according to FIG. 6 an expanded view of the bottom, end cool zone of the furnace isolation chamber with particular reference of uncompressed O-ring 610 being shown. FIG. 7 illustrates the same embodiment of FIG. 6 but having compressed O-ring 720. The O-ring 720 may be compressed by tightening of compression nut 730. In some embodiments, multiple O-rings 720 may be used (not shown). In other embodiments still, a gasket or other similarly situated material configured to provide a sealing surface upon compression may be used. FIG. 7 further shows gas flow paths 710 through the bottom, end cool zone of the furnace isolation chamber. As shown in FIG. 8, which is an expanded view of an additional inventive embodiment of the bottom, end cool zone of the furnace isolation chamber shown in circle in FIG. 6. In the exemplary embodiment of FIG. 8, there is shown a spring-loaded mechanism that allows the O-ring 610 to remain uncompressed and the AFIC to remain in an open position. As shown in FIG. 8, compression nut 730 is not tightened. As a result, the uncompressed spring 810 allows plates 820 to remain separated by applying a biasing force, and thus O-Ring 610 remain in an uncompressed state. In contrast, FIG. 9 shows the spring loaded mechanism shown in FIG. 8, with O-ring 720 compressed. In this embodiment, compression nut 730 is tightened, thereby causing top plates 910A and bottom plates 910B to approach one another resulting in O-ring 720 being in a compressed state. In the exemplary embodiment, the inclined angle of the radial outermost face of the plates, respectively, pushes the O-ring 720 outward. In this way, the plates are configured to compress and position the O-ring such that it seals against three surfaces, the two outermost faces of the plates and an interior face of chamber 110 thereby ensuring sealing on three faces. This advantageously assists the O-ring with deforming to a compressed state and minimizing the possibility of leakage and/or O-ring fatigue/failure. Reference is made to FIGS. 10A and 10B, which are perspective views of locking mechanisms and filter assemblies according to an exemplary embodiment of the present disclosure. The locking mechanisms and filter assemblies may work in tandem with the various embodiments disclosed throughout this disclosure and described herein for removable coupling of discrete parts. FIGS. 10A and 10B show a location of a high temperature chamber 1010 and a filter sealing assembly 1020, with the secondary filters 320. In the exemplary embodiment, the high temperature chamber 1010 is keyed to lock and unlock with filter sealing assembly 1020 by an upper limiting locking mechanism (also referred to as a twist-lock). In other embodiments, snap locks, ridges, dove-tails, and etc. may be used to removably couple filter sealing assembly 1020 to high temperature chamber 1010. With particular reference to FIG. 10B, the upper limiting locking mechanism 1025A moves into the locked position by twisting of filter sealing assembly 1020 in direction 1030 relative to high temperature chamber 1010. In the exemplary embodiment, the upper limiting locking mechanism 1025A has a series (four) of protruded ends spaced equidistant around the upper portion of the filter sealing assembly 1020 and the the lower limiting locking mechanism 1025B has a series (four) of protruded ends spaced equidistant around the lower portion of the filter sealing assembly 1020. FIGS. 11A and 11B are elevation views of the embodiment of FIGS. 10A and 10B with lower limiting locking mechanism 1025B in an unlocked state (FIG. 11A) and in a locked state (FIG. 11B). With particular reference to FIG. 11B the lower limiting locking mechanism 1025B and filter sealing assembly 1020 are locked to filter support assembly 1110 by rotatable engagement. In the exemplary embodiment, the filter end support 1110 is keyed to lock and unlock with filter end support 1110 via lower limiting locking mechanism 1025B. In the exemplary embodiment, upper and lower limiting locking mechanisms 1025A, 1025B are configured to lock and unlock in opposing directions, thereby facilitating safety and ease of understanding. Filter support assembly 1110 is shown in FIGS. 10A and 10B, respectively with relation to the bottom of the AFIC system. Furthermore, cooling fins 1120 are shown. An exploded view of various aspects of an embodiment of the disclosed AFIC is provided in FIG. 12A with approximate corresponding locations of the elements of FIG. 12A shown in FIG. 12B. There is shown high temperature chamber 110, the HIP can 120, the pedestal 1210, and the filter sealing assembly 1020. As one of skill in the art would appreciate, if the HIP can fails during processing, components within the HIP can that are volatile at the HIP processing temperatures (T>850° C.) will escape from the failed HIP can. Currently available containment systems, such as the ACOP system described earlier, have no mechanism for dealing with the escape of volatile gases. This is largely because in an ACOP system, the filters are at a same process temperature as the HIP can during use, and thus will not contain any volatile gases. In contrast to an ACOP system, the AFIC system described herein has a thermal gradient between the high temperature zone within the furnace where HIP'ing occurs, and the much cooler zone located at the bottom of the HIP vessel and furnace. For example, in one embodiment, the temperature difference between the hot zone of the high temperature furnace and the cool zone at the bottom of the HIP vessel is at least 500° C. In other embodiments, the temperature differential is at least 750° C., or even at least 1000° C., cooler than the hot zone of the furnace. In another embodiment still, the temperature difference between the hot and cool zones is at least 1250° C. This may be accomplished, in part, by the customization of parts disclosed throughout this disclosure, for example, in FIG. 12A and the cooling fins shown in FIGS. 11A and 11B. The existence of a thermal gradient allows hot gases to escape from a failed HIP can, and the radioactive elements contained therein, to condense on the cool inside walls of the AFIC chamber prior to reaching the filters in the cool zone. As previously disclosed, the thermal gradient is a passive containment feature that is not present in an ACOP system. In addition to the passive containment feature created by the temperature gradient along the AFIC tube/chamber length from high temperature in the hot zone e.g. 1350° C. to the lower region of the AFIC tube/chamber at 50° C., it is possible to incorporate active cooling features by extending the lower portion of the AFIC to the bottom head of the HIP and including a cooling plate cooled by circulating a coolant. With regard to this embodiment, reference is made to FIG. 13, which shows a designed thermal gradient formed from a lower cooled head comprising a heat sink having a high thermally conductive material 1310. Non-limiting embodiments of such a material include aluminum, copper or alloys of such materials. These heat sinks may be made in the form of plates, blocks or fingers 1320, and may include one or more cooling channels located therein 1330 configured to directly cool the lower area of the AFIC system and cause the above mentioned temperature gradient. In this embodiment, active cooling features are incorporated into the system by having cooling plate/heat sink extending to the vessel wall 1310 and a cooled lower head 1340 where heat is transferred to the recirculating coolant for the HIP vessel. In yet another embodiment, active cooling features are incorporated by the addition of a collar that fits around the lower part of the AFIC tube/chamber to transfer heat to an existing cooled part of the HIP vessel or an additional cooling circuit. Although not essential, the advantage of the “forced” or “active” cooling features is that it works independent of gas pressure, as heat transfer efficiency changes as a function of the density of the gas. Active cooling may also assist in achieving the temperature gradients disclosed herein, but active cooling is not necessarily required to achieve such gradients. As disclosed herein, the chamber provides mechanical strength for expansion containment, should the can or component expand uncontrollably and protects the furnace/vessel from being mechanically damaged while the filters prevent the spread of radioactive/hazardous material contaminating the furnace, the HIP vessel, and the gas lines. Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope of the invention being indicated by the following claims.
	summary
047391731	claims	1. A collimator apparatus for producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: (a) support plate means having a central opening around a beam axis through which the beam of radiation can pass; (b) a bundle of nested rods mounted adjacent the support plate means each rod being movable into the beam at an angle to the beam axis to interfere with the beam, the rods having first ends which together define a first surface for shaping the beam around the beam axis and opposite second ends from the first ends of the rods; (c) a holder means including spaced apart blocks mounted on the support plate, each block having axially aligned holes mounting the rods so that the first surface is defined and the beam is shaped by the first ends of the rods; and (d) releasable clamping means for moving the blocks so that the blocks or means between the blocks adjacent the rods are in engagement with the rods to secure the rods together in the shape defined by the first ends of the rods. (a) support plate means having a central opening around a beam axis through which the beam of radiation can pass; (b) a bundle of nested rods mounted adjacent the support plate means each rod being movable into the beam at an angle to the beam axis to interfere with the beam, the rods having first ends which together define a first surface for shaping the beam around the beam axis and opposite second ends from the first ends of the rods; (c) a holder means with two spaced apart blocks mounted on the support plate, each block having axially aligned holes mounting the rods so that the first surface is defined and the beam is shaped by the first ends of the rods and at least one block being movable relative to the other block; (d) releasable clamping means mounted on the support plate means and engaging the blocks and rods between the first and second ends to secure the rods together in the shape defined by the first ends of the rods, wherein the releasable clamping means includes multiple coil spring means which have opposed ends which engage the blocks and which are positioned and mounted between the rods so that when at least one of the blocks is moved on the rods towards the other block and coil spring means is compressed and engages the rods surrounding the spring means to clamp the surrounding rods together and wherein the clamping means includes drive means mounted on the holder means and connected to at least one of the blocks for moving the blocks together to compress the coil spring against the rods to prevent movement of the rods in the holes in the blocks and for moving the blocks apart to release the spring means from the rods to allow movement of the rods in the holes in the blocks. (a) support plate means having a central opening around a beam axis through which the beam of radiation can pass; (b) a bundle of nested metal rods mounted adjacent the support plate means each rod having a longitudinal axis perpendicular to the beam axis and having first ends which together define a first surface for shaping the beam around the beam axis and opposite second ends from the first ends; (c) a holder means with two spaced apart blocks mounted adjacent the support plate means each block having axially aligned holes mounting the rods; (d) rod shaping means adjacent the opposite second ends of the rods, wherein the rod shaping means has a second surface corresponding to the first surface which defines varying positions of the first ends of the rods so that the first surface is defined and the beam is shaped by the first ends of the rods; and (e) releasable clamping means engaging the blocks for securing the rods together in the shape defined by the shaping means, wherein the releasable clamping means includes multiple coil spring means which have opposed ends which engage the blocks and which are positioned and mounted between the rods so that when the blocks are moved on the rods towards each other the coil spring means are compressed and engage the rods surrounding each of the spring means to clamp the surrounding rods together and wherein the clamping means includes drive means mounted on the holder means and connected to one of the blocks for moving the blocks together to compress the coil spring means against the rods to prevent movement of the rods in the holes in the blocks and for moving the blocks apart to release the spring means from the rods to allow movement of the rods in the holes. (a) providing a collimator apparatus which comprises support plate means having a central opening around a beam axis through which the beam of radiation can pass; a bundle of nested rods mounted adjacent the support plate means each rod being movable into the beam at an angle to the beam axis to interfere with the beam, the rods having first ends which together define a first surface for shaping the beam around the beam axis and opposite second ends from the first ends of the rods; a holder means including spaced apart blocks mounted on the support plate, each block having axially aligned holes mounting the rods so that the first surface is defined and the beam is shaped by the first ends of the rods and at least one block being movable relative to the other block; releasable clamping means engaging the rods between the first and second ends to secure the rods together in the shape defined by the first ends of the rods, wherein the releasable clamping means includes multiple coil spring means which have opposed ends which engage the blocks and which are positioned and mounted between the rods so that when at least one of the blocks is moved on the rods towards the other block the coil spring means is compressed and engages the rods surrounding the spring means to clamp the surrounding rods together and wherein the clamping means includes drive means mounted on the holder means and connected to one of the blocks for moving the blocks together to compress the coil spring against the rods to prevent movement of the rods in the holes in the blocks and for moving the blocks apart to release the spring means from the rods to allow movement of the rods in the holes in the blocks; (b) moving the rods in the holes in the blocks so that the rods define the first surface; (c) clamping the rods with the releasable clamping means by moving the blocks so that the spring means is compressed to prevent movement of the rods; and (d) producing the shaped beam defined by the first ends of the rods. (a) providing a collimator apparatus which comprises support plate means having a central opening around a beam axis through which the beam of radiation can pass; a bundle of nested metal rods mounted on the support plate means each rod having a longitudinal axis perpendicular to the beam axis and having first ends which together define a first surface for shaping the beam around the beam axis and opposite second ends from the first ends; a holder means with two spaced apart blocks mounted on the support plate each block having axially aligned holes mounting the rods; rod shaping means adjacent the opposite second ends of the rods, wherein the rod shaping means has a second surface corresponding to the first surface which defines varying positions of the first ends of the rods so that the first surface is defined and the beam is shaped by the first ends of the rods; and releasable clamping means for securing the rods together in the shape defined by the shaping means, wherein the releasable clamping means includes multiple coil spring means which have opposed ends which engage the blocks and which are positioned and mounted between the rods so that when the blocks are moved on the rods towards each other the coil spring means is compressed and engages the rods surrounding the spring means to clamp the surrounding rods together and wherein the clamping means includes drive means mounted on the holder means and connected to at least one of the blocks for moving the blocks together to compress the coil spring against the rods to prevent movement of the rods in the holes in the blocks and for moving the blocks apart to release the spring means from the rods to allow movement of the rods in the holes; (b) moving the opposite rods in the holes in the blocks with the second ends against the rod shaping means to define the first surface; (c) clamping the rods with the releasable clamping means by moving the blocks so that the spring means is compressed to prevent movement of the rods; and (d) producing the shaped beam defined by the first ends of the rods. (a) providing a collimator apparatus for producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: support plate means having a central opening around a beam axis through which the beam of radiation can pass; a bundle of nested rods mounted adjacent the support plate means each rod being movable into the beam at an angle to the beam axis to interfere with the beam, the rods having first ends which together define a first surface for shaping the beam around the beam axis and opposite second ends from the first ends of the rods; a holder means including spaced apart blocks mounted adjacent the support plate, each block having axially aligned holes mounting the rods so that the first surface is defined and the beam is shaped by the first ends of the rods; releasable clamping means for moving the blocks so that the blocks or means between the blocks adjacent the rods are in engagement with the rods to secure the rods together in the shape defined by the first ends of the rods; (b) moving the rods in the holes in the block so that the rods define the first surface; (c) clamping the rods with the releasable clamping means by moving the blocks to prevent movement of the rods; and (d) producing the shaped beam defined by the first ends of the rods. 2. The apparatus of claim 1 wherein the blocks can be compressed together around the rods by the clamping means to reduce the diameter of the holes and thus secure the rods together. 3. The apparatus of claim 1 wherein coil springs are provided between the rods and blocks which can be compressed by moving the blocks along the rods towards each other to hold the rods in position and can be uncompressed to release the rods. 4. A collimator apparatus for producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: 5. The collimator apparatus of claim 4 wherein there are two opposed bundles of rods mounted on the support plate means with the first ends opposite each other and axially displaced relative to each other. 6. The collimator apparatus of claim 4 wherein the rods are circular in cross-section and have a diameter of between about 1 mm and 10 mm. 7. The collimator apparatus of claim 4 wherein rods have a composition for interfering with a neutron beam. 8. The collimator apparatus of claim 4 wherein the rods have a composition for interference with a photon beam. 9. A collimator apparatus for producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: 10. The collimator apparatus of claim 9 wherein there are two opposed bundles of rods mounted on the support plate means with the first ends opposite each other and with the opposed rods having parallel longitudinal axis offset from each other on the axis. 11. The collimator apparatus of claim 9 wherein the rods are circular in cross-section and have a diameter of between about 1 mm and 10 mm. 12. The collimator apparatus of claim 9 wherein the metal composition of the rods is selected from the group consisting of tungsten and stainless steel. 13. The collimator apparatus of claim 9 wherein the rod shaping means is composed of polystyrene foam which is mounted on the holder means. 14. The collimator apparatus of claim 9 wherein the rods have a composition for interference with a neutron or photon beam. 15. The collimator apparatus of claim 9 wherein the rods have a polygonal cross-section. 16. The collimator apparatus of claim 9 wherein the rods have a circular cross-section and wherein the rod shaping means is composed of a polystyrene foam. 17. The apparatus of claim 9 wherein there are two opposed bundles of rods and blocks mounted on the support plate means with the first ends opposite each other and with the opposed rods having parallel longitudinal axis and wherein one bundle of rods and blocks is movable relative to the other bundle of rods and blocks so that the bundle of rods is shaped by a first shaping means, and wherein a second rod shaping means is movable with the movable bundle of rods and blocks to engage the opposite ends of the rods so that the first surfaces are defined and wherein motive means is provided on the support plate means to move the movable bundle of rods, and blocks and second rod shaping means. 18. The apparatus of claim 17 wherein the movable bundle of rods, blocks and shaping means are moved by an arm of a hydraulic or pneumatic cylinder as the motive means which is mounted on the support plate means. 19. The method for producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: 20. The method for producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: 21. The method of claim 20 wherein there are two bundles of rods and blocks each with a rod shaping means mounted on the support plate means with the first ends opposite each other and with the opposed rods having parallel longitudinal axis offset from each other wherein one bundle of rods and blocks are movable together relative to the other bundle of rods and blocks and wherein one bundle of rods and blocks is moved relative to the other bundle of rods and blocks so that the one bundle of rods is shaped by a first of the shaping means and wherein a second rod shaping means is moved with the movable bundle of rods so that the opposite second ends of the rods in the other bundle of rods engages a second of the rod shaping means so that the first surfaces are defined for each of the bundles of rods and wherein motive means mounted on the support plate means moves the second bundle of rods and blocks and second rod shaping means together and wherein the bundles of rods are secured together by the clamping means when each of the first surfaces are defined by the first ends of the rods. 22. The method for producing a cross-sectionally shaped beam of radiation from a radiation source which comprises:
	claims	1. An electron microscope specimen holder comprising a body, a clipping means, and at least one guide mechanism, wherein the clipping means comprise an article of manufacture having a top surface, a bottom surface, a first end, a securing means, a second end, and at least one electrical contact integrated on and/or in the bottom surface of the article, wherein the specimen holder further comprises a spring cantilever and a means of contacting said spring cantilever with the bottom surface of the first end of the article, wherein the spring cantilever provides constant tension to the first end of the article. 2. The specimen holder of claim 1, wherein the securing means comprise a pivot positioned between the first end and the second end of the article. 3. The specimen holder of claim 1, wherein the second end of the article is pivotally raised by applying downward pressure to the top surface of the first end of the article for insertion of a specimen support device between the bottom surface of the second end of the article and a top surface of the body. 4. The specimen holder of claim 1, wherein the article is pivotally lowered such that at least one electrical lead of a specimen support device substantially contacts at least one electrical contact of the article. 5. The specimen holder of claim 1, wherein the at least one electrical contact extends from the second end of the article, terminates at the second end of the article, or terminates before the second end of the article. 6. The specimen holder of claim 1, wherein the at least one electrical contact of the clip extends from the clip to a barrel, from the barrel to an end, and onto an electrical connector. 7. The specimen holder of claim 1, further comprising a specimen support device mechanically secured between the clipping means and the body. 8. A method of using a specimen holder in electron microscopy, said method comprising:positioning a specimen support device in the specimen holder of claim 1; andinserting said specimen holder in an electron microscope. 9. The method of claim 8, wherein a specimen is on the specimen support device and an electron beam is controlled to form an image of the specimen. 10. The specimen holder of claim 1, wherein the means of contacting said spring cantilever with the bottom surface of the first end of the article comprise a post. 11. The specimen holder of claim 1, wherein the specimen holder comprises a viewing region. 12. The specimen holder of claim 1, wherein the guide mechanism is selected from the group consisting of guide screws, guide pins, and guide posts. 13. The specimen holder of claim 1, wherein the specimen holder further comprises a depth stop to align the at least one electrical contact of the specimen holder with at least one electrical lead of a specimen support device. 14. The specimen holder of claim 13, wherein the depth stop further aligns a viewing region of the specimen holder with a membrane region of the specimen support device. 15. The specimen holder of claim 1, comprising 2 to 12 electrical contacts. 16. The specimen holder of claim 15, wherein the electrical contacts are electrically isolated from one another. 17. A method of providing an electrical contact between a specimen and a specimen holder of an electron microscope, said method comprising:positioning a specimen on a specimen support device, wherein the specimen support device comprises a frame, at least one electrical lead and at least one membrane region; andinserting the specimen support device in a specimen holder, wherein the specimen holder comprises a body, a clipping means, and at least one guide mechanism, wherein the clipping means comprise an article of manufacture having a top surface, a bottom surface, a first end, a securing means, a second end, and at least one electrical contact integrated on and/or in a bottom surface of the article, wherein the specimen holder further comprises a spring cantilever and a means of contacting said spring cantilever with the bottom surface of the first end of the article, wherein the spring cantilever provides constant tension to the first end of the article; and wherein at least one electrical lead of the device substantially contacts at least one electrical contact of the clipping means. 18. The specimen holder of claim 1, wherein the guide mechanism provides lateral alignment to a device as it is loaded.
	description	FIG. 1 schematically shows the arrangement of one embodiment of the proximity exposure device in accordance with the invention in which a workpiece W, for example, a liquid crystal display element substrate or the like, is placed on a workpiece carrier WS. Furthermore, a mask M is located spaced above the workpiece W with a predefined gap G between them (in the drawing, the size of the gap is shown exaggerated). On the mask M and the workpiece W, mask alignment marks (hereinafter called xe2x80x9cmask marks MAMxe2x80x9d) and workpiece alignment marks (hereinafter called xe2x80x9cworkpiece marks WAMxe2x80x9d) are recorded for positioning and are viewed using an alignment microscope 7 which is described below. In this way, positioning of the mask M relative to the workpiece W is performed. The workpiece carrier WS is driven by means of an X-Y-"THgr" drive device 1 in the X-Y-"THgr" directions (for example, X: to the right and left in FIG. 1; Y: in and out of the plane of the drawing, "THgr": in a direction of rotation around an axis perpendicular to the X-Y plane, i.e., an axis extending in a Z-direction, up and down in the drawings) and by means of a Z-drive device 2 is driven in the Z-direction (up and down in the drawings). A lamp housing 3 in which a lamp L for emitting light which contains UV radiation, and an oval reflector R and the like are located. Parallel exposure light is emitted from an exit opening 3a of the lamp housing 3. The lamp housing 3 is furthermore supported by an arc-shaped guide 4, as is shown in the drawings. The lamp housing 3 is arranged to be able to move along the guide 4. Therefore, the angle of incidence xcex4 of the exposure light can be changed with respect to the mask M and the workpiece W by the lamp housing 3 being moved along the guide 4 by means of a lamp housing drive device 5. The lamp housing 3, the guide 4 and the lamp housing drive device 5 are made such that they can be turned as a whole around an axis T. The irradiation direction of the exposure light can be changed with respect to the mask M and workpiece W by turning the lamp housing 3 around the axis T by means of the lamp housing drive device 5 (hereinafter the angle of rotation around the axis T is called the xe2x80x9cirradiation angle "PHgr"xe2x80x9d). By moving the lamp housing 3 along the guide 4, the angle of incidence 6 can be changed in the range 0 less than xcex4 less than 90xc2x0. Furthermore, the irradiation angle "PHgr" can be changed in the range from 0xe2x89xa6"PHgr"xe2x89xa6360xc2x0 by the lamp housing 3 being turned around the axis T. For the above described lamp housing, the lamp housing already proposed by in published Japanese patent application HEI-10-154658 can be used. Above the mask M, there are a gap measuring device 6 for measuring the gap size G between the mask M and the workpiece W and an alignment microscope 7 for positioning of the mask M relative to the workpiece W. The measuring device already proposed in published Japanese patent application HEI 10-268525 (EP 0 867 775 A2) can be used as the gap measuring device. Furthermore, a control element 10 controls driving of the X-Y-"THgr" drive device 1 and the Z-drive device 2 based on the outputs of the gap measuring device 6 and the alignment microscope 7 and moves the workpiece carrier WS in the X-Y-"THgr"-Z directions. The control element 10 has a storage part 10a which stores an adjustment value Go of the gap size G as the light irradiation gap between the mask M and the workpiece W and the adjustment values xcex4o, "PHgr"o of the angle of the light which is incident on the workpiece W. These adjustment values which are input by an input part 11 are adjusted in the storage part 10a. In the following, the process for positioning of the mask relative to the workpiece in accordance with the invention is described. Here, an example in described in which the mask pattern shown in FIG. 2 is formed on the mask M (a mask pattern which corresponds to a pixel), the mask M is attached and the workpiece is moved. Using the mask M, the mask M and the workpiece W are arranged with a predefined gap G between them, as is illustrated in FIG. 3, and using the alignment microscope 7, the coordinates of the mask marks MAM and of the workpiece marks WAM are determined. In FIG. 3, the alignment microscope 7 has a CCD camera 7a and a light source 7b for emitting alignment light. The alignment light emitted from the light source 7b is emitted onto the mask marks MAM and the workpiece marks WAM. By means of the CCD camera 7a of the alignment microscope 7, the mask marks MAM and the workpiece marks WAM are recorded. The recorded video signals are sent to the above described control element 10. Before positioning, in the alignment microscope 7, the mask mark MAM and the workpiece mark WAM are viewed, as is shown in FIG. 4. The mask M and the workpiece W can be positioned in the vertical direction when the workpiece is moved in the X-Y-"THgr" directions such that the mask mark MAM and the workpiece mark WAM are aligned with one another (such that the workpiece mark WAM is located at the site shown in the mask mark MAM in FIG. 4 using the broken line). FIG. 3 shows this state. Specifically, the correlation is determined between the amount of movement of the workpiece carrier WS and the amount of movement in the video processing coordinates of the workpiece mark WAM which corresponds to the movement of the workpiece carrier WS, beforehand. The positional information about the alignment marks obtained by the alignment microscope 7 according to FIG. 3 is subjected to video processing in the control element 10 and the position coordinates for the video processing coordinates of the respective alignment mark are computed. The above described processing makes it possible to compute the amount of displacement (xcex94X, xcex94Y, xcex94"THgr") in the X-Y-"THgr" directions with which the workpiece mark WAM which is originally located at coordinates (Xn, Yn) moves to the coordinates in which it is aligned with the mask mark MAM. The amount of displacement in the X-Y-"THgr" directions (xcex94X, xcex94Y, xcex94"THgr") is computed as the amount of movement of the workpiece carrier WS in the X-Y directions and as the amount of rotation "THgr" of the workpiece carrier WS in which the positions of the two mask marks MAM shown in FIG. 5 and the workpiece marks WAM are aligned with one another. When based on the above described computation, the workpiece carrier WS moves and positioning of the mask M relative to the workpiece W is performed in the vertical direction, the workpiece mark WAM has position coordinates of (Xn+xcex94X, Yn+xcex94Y). In the case of oblique light irradiation of the mask M, the position at which the mask pattern is projected on the workpiece W is shifted, depending on the xe2x80x9cangle (angle of incidence) xcex4 with which the irradiation light is incident in the mask M,xe2x80x9d the xe2x80x9cangle (irradiation angle) with which the irradiation light is incident with respect to the X-direction of the mask patternxe2x80x9d and xe2x80x9cthe size of the gap G between the mask M and the workpiece Wxe2x80x9d because the irradiation light is parallel light as is shown in FIGS. 6(a) and 6(b). Within the mask pattern surface, the X-Y coordinate axes are defined. The angle of the light incident with respect to the X-axis is called the irradiation angle "THgr". The direction of the X-Y coordinate axes of the mask pattern and the direction of the X-Y coordinate axes of the workpiece carrier are brought into alignment with one another. In this way, the movement of the workpiece carrier is regulated. Therefore, by moving the workpiece W by the amount of displacement described above, the mask pattern can be projected onto a predetermined area and a desired area can be irradiated with light, as is shown in FIG. 6(c). The above described amount of displacement is computed as follows: With reference to the positions (X, Y) to which the mask pattern is shifted as shown in FIG. 6(b), these positions are described with the following formulas where (Xo, Yo) are the position coordinates at which any mask pattern MAM is projected onto the workpiece W when light is incident vertically on the mask M, G is the size of the gap between the mask M and the workpiece W, xcex4 is the angle of incidence of the irradiation light with respect to the mask, and "PHgr" is the irradiation angle with which the irradiation light is incident with respect to the X-direction of the mask pattern: X=Xoxe2x88x92Gxc2x7tan xcex4xc2x7cos "PHgr" Y=Yoxe2x88x92Gxc2x7tan xcex4xc2x7sin "PHgr" Here, it can be imagined that the coordinates (Xo, Yo) are the position coordinates of the workpiece mark when the mask M is positioned relative to the workpiece W in the vertical direction. Therefore, the following applies: (Xo, Yo)=(Xn+xcex94X, Yn+xcex94Y) Therefore, for oblique light irradiation, only a desired area can be irradiated with light when the workpiece carrier is subjected to movement control in the X-Y-"THgr" directions such that the workpiece mark WAM is moved from the coordinates (Xn, Yn) to the coordinates (X, Y). In the following, the processes of positioning and exposure using the above described process are described using the exposure device which is shown above in FIG. 1. (1) The adjustment value Go of the size of the light irradiation gap between the mask M and the workpiece W, the adjustment value xcex4o of the angle of incidence with respect to the workpiece W and the adjustment value "PHgr"o of the irradiation angle are input by the input part 11. These values are all stored in the storage part 10a of the control element 10. (2) The control element 10, based on the input information about the angle of incidence xcex4o and the irradiation angle "PHgr"o, drives the lamp housing drive device 5 and moves the lamp housing 3 which emits the light. (3) The output of an encoder which is located in the device 5 is input into the control element 10. The control element 10 determines the amount of movement of the lamp housing 3 and computes the actual angles xcex4, "PHgr" of the light which is incident in the actual workpiece. These values are stored in the storage part 10a of the control element 10. (4) On the other hand, the workpiece carrier Ws is lifted by the Z-drive device 2. The locations of the mask marks MAM and the workpiece marks WAM are determined by the alignment microscope 7 at the alignment gap position. The determined signals are subjected to video processing. Based on this information, in the control element 10, the position coordinates of the workpiece carrier WS (Xn+xcex94X, Yn+xcex94Y)=(Xo, Yo) are determined in which positioning of the mask relative to the workpiece in the X-Y-"THgr" directions is to be produced in the vertical direction. (5) Then, the workpiece carrier WS is lifted according to the adjustment gap size Go as far as the position of the adjustment gap size G. After movement, the gap measuring device 6 measures the gap size G between mask M and the workpiece W at several locations. These values are returned to the control element 10. The position of the workpiece carrier WS in the Z-direction is moved back and forth by means of an adjustment device (not shown) for movement back and forth such that it is in a predetermined area with respect to the adjusted gap size GO. The substrate of the LCD element is large, as described above. The mask M used for this purpose is also large. In the mask M, sagging occurs due to its weight. Therefore, it is necessary to measure again whether the gap size G with respect to the adjustment value Go lies in an allowable range in order to regulate the sagging of the mask M when necessary. (6) The actual gap size at the conclusion of adjustment is G. This gap size G is stored in the storage part 10a of the control element 10. (7) Based on the actual values xcex4 and "PHgr" of the light angle and of the gap size G stored in the storage part 10a, i.e., the values stored in the storage part 10a, the control element 10 computes the position coordinates (X, Y) to which the workpiece carrier should move using the formulas described above. Based on this computation result, the control element 10 moves the workpiece W by means of the X-Y-"THgr" drive device 1 such that the workpiece mark WAM is moved to coordinates (X, Y). (8) After completion of the movement of the workpiece carrier WS, light is emitted from the lamp housing 3 and the mask pattern is exposed onto the workpiece W. In the case of a device in which the lamp housing 3 is manually moved, the movement position of the workpiece W is determined by the fact that the adjustment values xcex4o and "PHgr"o of the angle of the light which is incident in the workpiece W is used unchanged. (9) After completion of exposure of the first zones of the pixel on the substrate of the LCD element in the above described manner, the workpiece is turned, for example, by 180xc2x0, as was described above. The mask M and the workpiece W are positioned relative to one another in the above described manner. Then, the third zones which are located point-symmetrically with respect to the first zones around the pixel center are irradiated with light with a predetermined angle of incidence and a preset irradiation angle. The mask M is replaced. The second and fourth zones of the pixel on the substrate of the LCD element are exposed in the above described manner. As was described above, in accordance with the invention, in a proximity exposure device in which a mask and a workpiece are arranged with a predetermined gap between them and the workpiece is irradiated obliquely with light via the mask, based on the gap size G between the mask and the workpiece, on the angle of incidence xcex4 of the irradiation light with respect to the mask and based on the irradiation angle "PHgr" with which the irradiation light is incident with respect to the X-direction of the mask pattern, the displacement position of the mask pattern to be projected is computed, and according to the result of this computation, the workpiece is moved and the light is emitted. In this way, the mask pattern can be projected onto the predetermined position of the workpiece and the desired area can be irradiated with light.
043205283	claims	1. In the art of maintaining a steam generator for a nuclear power plant in which the steam generator is characterized by an enclosed tank containing a plurality of heat exchanger tubes and a plurality of support plates arranged transverse to and sequentially spaced along the longitudinal axis of the tubes and forming junctions therewith, where crevices exist between the heat exchanger tubes and the support plates at the site of the junctions, the junctions being thereby arranged in a series of groups, and also containing an outer shell and a metal wrapper inside the tank which envelops the plurality of tubes and support plates, and wherein magnetite tends to build up within the crevices at the junctions over a period of time, the process of removing the magnetite from the crevices and the junctions while the heat exchanger tubes and support plates remain in their operative position inside the steam generator, comprising the steps of: a. selecting a chemical solvent which when heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit dissolves magnetite exposed to fresh chemicals at a rate equal to or greater than about 1.0 inch per 24 hours; b. adding a metal corrosion inhibitor to said chemical solvent; c. at least partially filling the tank with said chemical solvent, so as to establish an initial level which is only a few inches above the level of the uppermost group of junctions and their uppermost group of crevices; d. selecting a plurality of sonic transducers wherein each sonic transducer has a power output greater than about 0.2 watts per square centimeter at room temperature; e. placing said plurality of sonic transducers at a level which is below the surface of said chemical solvent, substantially in the plane of said uppermost group of junctions and uppermost group of crevices and in spaced locations around the circumference of and in contact with said metal wrapper; f. running a hot fluid through said heat exchanger tubes so that the chemical solvent in the region adjacent said junctions and crevices reaches a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit; g. activating said sonic transducers to a frequency in the range of about 2 KHZ to 200 KHZ so that sonic energy is transmitted through said chemical solvent to said junctions and into and laterally of said crevices whereby cavitation induced at said junctions and at said crevices by said sonic energy cooperates with said chemical solvent so as to enhance and accelerate the removal of the magnetite from said junctions and crevices; h. continuing the cooperative action of said hot chemical solvent and said transducers upon said uppermost group of junctions and crevices until the magnetite is removed from the junctions and crevices; i. maintaining said chemical solvent at a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit; j. then lowering the level of said chemical solvent to a height which is only a few inches above the next group of junctions and crevices from which magnetite is to be removed, lowering said plurality of transducers to a corresponding lower location on said metal wrapper in a plane substantially in alignment with said next group of junctions and crevices, and again applying said cooperative effort between said hot chemical solvent and said transducers until the magnetite is removed from said next group of junctions and next group of crevices; and k. continuing in this fashion at the level of each successive group of junctions and crevices until all of said junctions and crevices have been cleaned. a. selecting a chemical solvent which when heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit dissolves magnetite exposed to fresh chemicals at a rate equal to or greater than about 1.0 inch per 24 hours; b. adding a metal corrosion inhibitor to said chemical solvent; c. at least partially filling the tank with said chemical solvent, so as to establish an initial level which is only a few inches above the level of the lowermost group of junctions and their lowermost group of crevices; d. selecting a plurality of sonic transducers wherein each sonic transducer has a power output greater than about 0.2 watts per square centimeter at room temperature; e. placing said plurality of sonic transducers at a level which is below the surface of said chemical solvent, substantially in the plane of said lowermost group of junctions and lowermost group of crevices and in spaced locations around the circumference of and in contact with said metal wrapper; f. running a hot fluid through said heat exchanger tubes so that the chemical solvent in the region adjacent said junctions and crevices reaches a temperature between 120 degrees Fahrenheit and 220 degrees Farenheit; g. activating said sonic transducers to a frequency in the range of about 2 KHZ to 200 KHZ so that sonic energy is transmitted through said chemical solvent to said junctions and into and laterally of said crevices whereby cavitation induced at said junctions and at said crevices by said sonic energy cooperates with said chemical solvent so as to enhance and accelerate the removal of the magnetite from said junctions and crevices; h. continuing the cooperative action of said hot chemical solvent and said transducers upon said lowermost group of junctions and crevices until the magnetite is removed from the junctions and crevices; i. maintaining said chemical solvent at a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit; j. then raising the level of said chemical solvent to a height which is only a few inches above the next group of junctions and crevices from which magnetite is to be removed, raising said plurality of transducers to a corresponding higher location on said metal wrapper in a plane substantially in alignment with said next group of junctions and crevices, and again applying said cooperative effort between said hot chemical solvent and said transducers until the magnetite is removed from said next group of junctions and next group of crevices; and k. continuing in this fashion at the level of each successive group of junctions and crevices until all of said junctions and crevices have been cleaned. a. selecting a chemical solvent which when heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit dissolves magnetite exposed to fresh chemicals at a rate equal to or greater than about 1.0 inch per 24 hours; b. adding a metal corrosion inhibitor to said chemical solvent; c. at least partially filling the tank with said chemical solvent, so as to establish an initial level which is only a few inches above the level of the uppermost group of junctions and their uppermost group of crevices; d. selecting a plurality of sonic transducers wherein each sonic transducer has a power output greater than about 0.2 watts per square centimeter at room temperature; e. placing said plurality of sonic transducers at a level which is substantially in the plane of each of said groups of junctions and in spaced locations around the circumference of and in contact with said metal wrapper; f. running a hot fluid through said heat exchanger tubes so that the chemical solvent in the region adjacent said junctions and crevices reaches a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit; g. activating all the transducers simultaneously at each level substantially in the plane of each group of junctions and each group of crevices to a frequency in the range of about 2 KHZ to 200 KHZ so that sonic energy is transmitted through said chemical solvent to each group of junctions and into and laterally of each group of crevices whereby cavitation induced at each group of junctions and each group of crevices cooperates with said chemical solvent so as to enhance and accelerate the removal of the magnetite from the all of the junctions and crevices; h. continuing the cooperative action of said hot chemical solvent and said transducers upon each group of junctions and crevices until the magnetite is removed from all of the junctions and all of the crevices. a. selecting a chemical solvent which when heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit dissolves magnetite exposed to fresh chemicals at a rate equal to or greater than about 1.0 inch per 24 hours; b. adding a metal corrosion inhibitor to said chemical solvent; c. selecting a plurality of sonic transducers wherein each sonic transducer has a power output greater than about 0.2 watts per square centimeter at room temperature; d. placing said plurality of sonic transducers at a level substantially in the plane of the uppermost group of junctions and uppermost group of crevices and in spaced locations around the circumference of and in contact with said metal wrapper; e. heating said chemical solvent to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit at a location outside of said steam generator; f. at least partially filling the tank with said heated chemical solvent, so as to establish an initial level which is only a few inches above the level of the uppermost group of junctions and their uppermost group of crevices; g. activating said sonic transducers to a frequency in the range of about 2 KHZ to 200 KHZ so that sonic energy is transmitted through said chemical solvent to said junctions and into and laterally of said crevices whereby cavitation induced at said junctions and at said crevices by said sonic energy cooperates with said chemical solvent so as to enhance and accelerate the removal of magnetite from said junctions and crevices; h. continuing the cooperative action of said hot chemical solvent and said transducers upon said uppermost group of junctions and crevices until the magnetite is removed from the junctions and crevices; i. maintaining said chemical solvent at a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit; j. then lowering the level of said chemical solvent to a height which is only a few inches above the next group of junctions and crevices from which magnetite is to be removed, lowering said plurality of transducers to a corresponding lower location on said metal wrapper in a plane substantially in alignment with said next group of junctions and crevices, and again applying said cooperative effort between said hot chemical solvent and said transducers until the magnetite is removed from said next group of junctions and next group of crevices; and k. continuing in this fashion at the level of each successive group of junctions and crevices until all of said junctions and crevices have been cleaned. a. selecting a chemical solvent which when heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit dissolves magnetite exposed to fresh chemicals at a rate equal to or greater than about 1.0 inch per 24 hours; b. adding a metal corrosion inhibitor to said chemical solvent; c. selecting a plurality of sonic transducers wherein each sonic transducer has a power output greater than about 0.2 watts per square centimeter at room temperature; d. placing said plurality of sonic transducers at a level substantially in the plane of the lowermost group of junctions and lowermost group of crevices and in spaced locations around the circumference of and in contact with said metal wrapper; e. heating said chemical solvent to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit at a location outside of said steam generator; f. at least partially filling the tank with said heated chemical solvent, so as to establish an initial level which is only a few inches above the level of the lowermost group of junctions and their lowermost group of crevices; g. activating said sonic transducers to a frequency in the range of about 2 KHZ to 200 KHZ so that sonic energy is transmitted through said chemical solvent to said junctions and into and laterally of said crevices whereby cavitation induced at said junctions and at said crevices by said sonic energy cooperates with said chemical solvent so as to enhance and accelerate the removal of the magnetite from said junctions and crevices; h. continuing the cooperative action of said hot chemical solvent and said transducers upon said lowermost group of junctions and crevices until the magnetite is removed from the junctions and crevices; i. maintaining said chemical solvent at a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit; j. then raising the level of said chemical solvent to a height which is only a few inches above the next group of junctions and crevices from which magnetite is to be removed, raising said plurality of transducers to a corresponding higher location on said metal wrapper in a plane substantially in alignment with said next group of junctions and crevices, and again applying said cooperative effort between said hot chemical solvent and said transducers until the magnetite is removed from said next group of junctions and next group of crevices; and k. continuing in this fashion at the level of each successive group of junctions and crevices until all of said junctions and crevices have been cleaned. a. selecting a chemical solvent which when heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit dissolves magnetite exposed to fresh chemicals at a rate equal to or greater than about 1.0 inch per 24 hours; b. adding a metal corrosion inhibitor to said chemical solvent; c. selecting a plurality of sonic transducers wherein each sonic transducer has a power output greater than about 0.2 watts per square centimeter at room temperature; d. placing said plurality of sonic transducers at a level which is substantially in the plane of each of said groups of junctions and in spaced locations around the circumference of and in contact with said metal wrapper; e. heating said chemical solvent to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit at a location outside of said steam generator; f. at least partially filling the tank with said heated chemical solvent, so as to establish an initial level which is only a few inches above the level of the uppermost group of junctions and their uppermost group of crevices; g. activating all the transducers simultaneously at each level substantially in the plane of each group of junctions and each group of crevices to a frequency in the range of about 2 KHZ to 200 KHZ so that sonic energy is transmitted through said chemical solvent to each group of junctions and into and laterally of each group of crevices whereby cavitation induced at each group of junctions and each group of crevices cooperates with said chemical solvent so as to enhance and accelerate the removal of the magnetite from all of the junctions and crevices; h. continuing the cooperative action of said hot chemical solvent and said transducers upon each group of junctions and crevices until the magnetite is removed from all of the junctions and all of the crevices. a. selecting a chemical solvent which when heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit dislodges the sludge from the base plate within 24 hours; b. at least partially filling the tank with said chemical solvent, so as to establish an initial level which is only a few inches above the level of said base plate; c. adding a metal corrosion inhibitor to said chemical solvent; d. selecting a plurality of sonic transducers wherein each sonic transducer has a power output greater than about 0.2 watts per square centimenter at room temperature; e. placing said plurality of sonic transducers at a level which is below the surface of said chemical solvent, substantially in the plane of said base plate, and in spaced locations around the circumference of the tank; f. heating said chemical solvent to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit adjacent said base plate; g. activating said sonic transducers to a frequency in the range of about 2 KHZ to 200 KHZ so that sonic energy is transmitted through said chemical solvent and into said sludge pile whereby cavitation induced at said base plate by said sonic energy cooperates with said chemical solvent so as to enchance and accelerate the removal of said sludge pile from said base plate; h. continuing the cooperative actions of said hot chemical solvent and said transducers upon said base plate for several hours until the sludge pile is removed from said base plate; and i. flushing said steam generator with a liquid to remove said sludge pile from said steam generator. a. selecting a chemical solvent which when heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit dislodges the sludge from the base plate within 24 hours; b. adding a metal corrosion inhibitor to said chemical solvent; c. selecting a plurality of sonic transducers wherein each sonic transducer has a power output greater than about 0.2 watts per square centimenter at room temperature; d. placing said plurality of sonic transducers at a level which is substantially in the plane of said base plate, and in spaced locations around the circumference of the tank; e. heating said chemical solvent to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit at a location outside of said steam generator; f. at least partially filling the tank with said chemical solvent, so as to establish an initial level which is only a few inches above the level of said base plate; g. activating said sonic transducers to frequencies in the range of about 2 KHZ to 200 KHZ so that sonic energy is transmitted through said chemical solvent and into said sludge pile whereby cavitation induced at said base plate by said sonic energy cooperates with said chemical solvent so as to enhance and accelerate the removal of said sludge pile from said base plate; h. continuing the cooperative actions of said hot chemical solvent and said transducers upon said base plate for several hours until the sludge pile is removed from said base plate; and i. flushing said steam generator with a liquid to remove said sludge pile from said steam generator. a. selecting a chemical solvent which when heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit dissolves magnetite exposed to fresh chemicals at a rate equal to or greater than about 1.0 inch per 24 hours; b. at least partially filling the tank with said chemical solvent, so as to establish an initial level which is only a few inches above the level of the uppermost group of junctions and their uppermost group of crevices; c. adding a metal corrosion inhibitor to said chemical solvent; d. selecting a high boiling point fluid and placing the fluid in a plurality of thin flexible containers, wherein the combination of fluid and the thin flexible container has the same acoustic impedance as said metal wrapper; e. placing said plurality of high boiling point fluid filled containers at a level which is below the surface of said chemical solvent, substantially in the plane of said uppermost group of junctions and uppermost group of crevices and in spaced locations around the circumference of and in contact with said metal wrapper; f. selecting a plurality of sonic transducers wherein each sonic transducer has a power output greater than about 0.2 watts per square centimeter at room temperature; g. placing said plurality of sonic transducers in alignment with and in contact with corresponding ones of said plurality of high boiling point fluid filled containers and also in contact with said metal wrapper; h. running a hot fluid through said heat exchanger tubes so that the chemical solvent in the region adjacent said junctions and crevices reaches a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit; i. activating said sonic transducers to a frequency in the range of about 2 KHZ to 200 KHZ so that sonic energy is transmitted through said fluid filled containers, through said metal wrapper and through said chemical solvent, and to said junctions and into and laterally of said crevices whereby cavitation induced at said junctions and at said crevices by said sonic energy cooperates with said chemical solvent so as to enhance and accelerate the removal of the magnetite from said junctions and crevices; j. continuing the cooperative action of said hot chemical solvent and said transducers upon said uppermost group of junctions and crevices until the magnetite is removed from the junctions and crevices; k. then lowering the level of said chemical solvent to a height which is only a few inches above the next group of junctions and crevices from which magnetite is to be removed, lowering said plurality of high boiling point fluid filled containers and said plurality of transducers to a corresponding lower location on said metal wrapper in a plane substantially in alignment with said next group of junctions and crevices, and again applying said cooperative effort between said hot chemical solvent and said transducers until the magnetite is removed from said next group of junctions and next group of crevices; and l. continuing in this fashion at the level of each successive group of junctions and crevices until all of said junctions and crevices have been cleaned. a. cutting a plurality of windows in said metal wrapper such that a number of the windows are substantially in the plane of each group of junctions and in spaced locations around the circumference of and in contact with said metal wrapper; b. selecting a plurality of sonic transducers wherein each sonic transducer has a power output greater than about 0.2 watts per square centimeter at room temperature; c. placing said plurality of sonic transducers at a level which is substantially in the plane of each group of junctions, in spaced locations around and in contact with the circumference of said metal wrapper, and substantially in alignment with corresponding ones of said plurality of windows; d. at least partially filling the tank with said chemical solvent so as to establish a level which is only a few inches above the level of the uppermost group of junctions; e. adding a metal corrosion inhibitor to said chemical solvent; f. running a hot fluid through said heat exchanger tubes so that the chemical solvent in the region adjacent said junctions reaches a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit; g. activating all the transducers simultaneously at each level substantially in the plane of each group of junctions and each group of crevices to a frequency in the range of about 2 KHZ to 200 KHZ so that sonic energy is transmitted through said chemical solvent to each group of junctions and into and laterally of each group of crevices whereby cavitation induced at each group of junctions and each group of crevices cooperates with said chemical solvent so as to enhance and accelerate the removal of the magnetite from all of the junctions and crevices; h. continuing the cooperative action of said hot chemical solvent and said transducers upon each group of junctions and crevices until the magnetite is removed from all of the junctions and all of the crevices. 2. In the art of maintaining a steam generator for a nuclear power plane in which the steam generator is characterized by an enclosed tank containing a plurality of heat exchanger tubes and a plurality of support plates arranged transverse to and sequentially spaced along the longitudinal axes of the tubes and forming junctions therewith, where crevices exist between the heat exchanger tubes and the support plates at the site of the junctions, the junctions being thereby arranged in a series of groups, and also containing an outer shell and a metal wrapper inside the tank which envelops the plurality of tubes and support plates, and wherein magnetite tends to build up within the crevices at the junctions over a period of time, the process of removing the magnetite from the crevices and the junctions while the heat exchanger tubes and support plates remain in their operative positions inside the steam generator, comprising the steps of: 3. In the art of maintaining a steam generator for a nuclear power plant in which the steam generator is characterized by an enclosed tank containing a plurality of heat exchanger tubes and a plurality of support plates arranged transverse to and sequentially spaced along the longitudinal axes of the tubes and forming junctions therewith, where crevices exist between the heat exchanger tubes and the support plates at the site of the junctions, the junctions being thereby arranged in a series of groups, and also containing an outer shell and a metal wrapper inside the tank which envelops the plurality of tubes and support plates, and wherein magnetite tends to build up within the crevices at the junctions over a period of time, the process of removing the magnetite from the crevices and the junctions while the heat exchanger tubes and support plates remain in their operative positions inside the steam generator, comprising the steps of: 4. In the art of maintaining a steam generator for a nuclear power plant in which the steam generator is characterized by an enclosed tank containing a plurality of heat exchanger tubes and a plurality of support plates arranged transverse to and sequentially spaced along the longitudinal axes of the tubes and forming junctions therewith, where crevices exist between the heat exchanger tubes and the support plates at the site of the junctions, the junctions being thereby arranged in a series of groups, and also containing an outer shell and a metal wrapper inside the tank which envelops the plurality of tubes and support plates, and wherein magnetite tends to build up within the crevices at the junctions over a period of time, the process of removing the magnetite from the crevices and the junctions while the heat exchanger tubes and support plates remain in their operative positions inside the steam generator, comprising the steps of: 5. In the art of maintaining a steam generator for a nuclear power plant in which the steam generator is characterized by an enclosed tank containing a plurality of heat exchanger tubes and a plurality of support plates arranged transverse to and sequentially spaced along the longitudinal axes of the tubes and forming junctions therewith, where crevices exist between the heat exchanger tubes and the support plates at the site of the junctions, the junctions being thereby arranged in a series of groups, and also containing an outer shell and a metal wrapper inside the tank which envelops the plurality of tubes and support plates, and wherein magnetite tends to build up within the crevices at the junctions over a period of time, the process of removing the magnetite from the crevices and the junctions while the heat exchanger tubes and support plates remain in their operative positions inside the steam generator, comprising the steps of: 6. In the art of maintaining a steam generator for a nuclear power plant in which the steam generator is characterized by an enclosed tank containing a plurality of heat exchanger tubes and a plurality of support plates arranged transverse to and sequentially spaced along the longitudinal axes of the tubes and forming junctions therewith, where crevices exist between the heat exchanger tubes and the support plates at the site of the junctions, the junctions being thereby arranged in a series of groups, and also containing an outer shell and a metal wrapper inside the tank which envelops the plurality of tubes and support plates, and wherein magnetite tends to build up within the crevices at the junctions over a period of time, the process of removing the magnetite from the crevices and the junctions while the heat exchanger tubes and support plates remain in their operative positions inside the steam generator, comprising the steps of: 7. In the art of maintaining a steam generator for a nuclear power plant in which the steam generator is characterized by an enclosed tank containing a base plate on the lower portion of its interior surface, and wherein the products of corrosion, oxidation, sedimentation and comparable chemical reactions form a sludge pile over a period of time on the base plate, the process of removing the sludge pile while the base plate remains in its operative position inside the steam generator, comprising the steps of: 8. In the art of maintaining a steam generator for a nuclear power plant in which the steam generator is characterized by an enclosed tank containing a base plate on the lower portion of its interior surface, and wherein the products of corrosion, oxidation, sedimentation and comparable chemical reactions form a sludge pile over a period of time on the base plate, the process of removing the sludge pile while the base plate remains in its operative position inside the steam generator, comprising the steps of: 9. In the art of maintaining a steam generator for a nuclear power plant in which the steam generator is characterized by an enclosed tank containing a plurality of heat exchanger tubes and a plurality of support plates arranged transverse to and sequentially spaced along the longitudinal axes of the tubes and forming junctions therewith, where crevices exist between the heat exchanger tubes and the support plates at the site of the junctions, the junctions being thereby arranged in a series of groups, and also containing an outer shell and a metal wrapper inside the tank which envelopes the plurality of tubes and support plates, and wherein magnetite tends to build up within the crevices at the junctions over a period of time, the process of removing the magnetite from the crevices and the junctions while the heat exchanger tubes and support plates remain in their operative positions inside the steam generator, comprising the steps of: 10. The process as defined in claim 9 wherein said high boiling point fluid is oil and said container is a thin plastic bag. 11. The process as defined in claim 9 wherein said chemical solvent is heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit at a location outside said steam generator before it is placed into said steam generator as described. 12. In the art of maintaining a steam generator for a nuclear power plant in which the steam generator is characterized by an enclosed tank containing a plurality of heat exchanger tubes and a plurality of support plates arranged transverse to and sequentially spaced along the longitudinal axes of the tubes and forming junctions therewith, where crevices exist between the heat exchanger tubes and the support plates at the site of the junctions, the junctions being thereby arranged in a series of groups, and also containing an outer shell and a metal wrapper inside the tank which envelops the plurality of tubes and support plates, and wherein magnetite tends to build up within the crevices at the junctions over a period of time, the process of removing the magnetite from the crevices and the junctions while the heat exchanger tubes and support plates remain in their operative positions inside the steam generator, comprising the steps of: 13. The process as defined in claim 12 wherein said plurality of windows are each slightly smaller than the face of said transducers. 14. The process as defined in claim 12 wherein said plurality of windows are each slightly larger than the face of said transducer so that a portion of each transducer may protrude through said wrapper. 15. The process as defined in claim 12 wherein said chemical solvent is heated to a temperature between 120 degrees Fahrenheit and 220 degrees Fahrenheit before it is placed into the steam generator as described.
039714446	summary	SUMMARY OF THE INVENTION The present invention is directed to reaction vessels of the kind having a charge of spherical reaction elements, for example fuel elements forming a core of a pebble bed nuclear reactor in which control and/or shutdown rods are provided for insertion into and retraction from the charge to control the reaction with the rods being in direct contact with the elements. Further, during operation of the reaction vessel, the charge is continuously circulated. In the operation of reaction vessels of this type, especially pebble bed nuclear reactors, it is necessary to advance and retract the control rods quite frequently, that is, to vary their depth of penetration into the charge in direct contact with the elements. Such movements of the control rods involve a number of difficulties in reactors containing a bulk charge of spherical reaction elements as will be described. During the operation of the reaction vessel, the spherical elements are moved about by a variety of influences, that is, not only by the circulation of the elements through the vessel, but also by the movement of the control rod, while the heat movements in the charge, as well as the pressure drop of the coolant gas additionally affect the stresses within the charge of elements. Due to the movement of the elements, they tend to adopt an arrangement corresponding to the maximum possible density of the charge, that is, the most tightly packed arangement of the elements. This makes it different to manipulate and control the charge because the elements become too tightly packed together to allow necessary movements of the control rods to take place. Where the elements are all of the same diameter, they adopt an ordered pattern or arrangement corresponding to the maximum bulk density in which each spherical element is in contact with the twelve neighboring spherical elements. In practice, this means that the most dense packing of the elements corresponds to the most rigid charge which is a highly undesirable condition. With the elements in the most rigid arrangement, moving the control rods into the charge can result in damage to either or both rods and the elements. To obtain an almost homogenous distribution of the more or less burnt up fuel elements in the pebble bed and thereby a well-controlled nuclear reaction in a pebble-bed reactor, the spherical elements must circulate through the core in a desired manner, each individual element traveling through the core at a desired velocity. If the elements become too densely packed together it will interfere with the relative velocities of travel of the elements near the outer surface of the core and also in the central region, particularly if there is only one central tube through which the elements are removed from the reaction vessel. Attempts have been made to counteract this undesirable influence on the flow of the charge by milling interference structure into the lateral surface of the reflector enclosing the core, the intention being to prevent the outer layers of the core from becoming too densely packed. However, these interference structures influence only the outer part of the charge. The difficulty remains that when the control and shutdown rods are advanced into the charge very high stresses are applied to the elements by the tips or leading ends of the advancing rods. If the charge is too densely packed the stresses become excessive, particularly with deep penetration of the rods, possibly fracturing the elements and even damaging the rods. It has not been possible, for constructional as well as operational reasons, to install structural parts in the reactor to prevent the charge from becoming too densely packed in the interior of the core. The only remedy available today has been to avoid direct contact of the control rods with the elements forming the core by installing stationary guide tubes which extend permanently through the core, with the control rods being advanced and retracted within the guide tubes. However, among other reasons, this remedy is not only costly, but by adding other structural members into the core, interferes with the circulation of the elements in an undesirable manner. The primary object of the present invention is to ensure that a charge of spherical reactions elements in a reaction vessel, for example a charge of spherical fuel elements forming the core of a pebble bed reactor, does not become too densely packed, and especially to ensure that the arrangement of the spherical elements does not approach the maximum density, even under the most unfavorable circumstances, without this involving the use of additional structures in the reaction vessel. In accordance with the present invention, a charge of spherical reaction elements are circulated through the core of the nuclear reactor during operation and the charge contains at least two groups of spherical elements uniformly mixed together. All of the elements in each group are of the same diameter but each group of elements has a different diameter from the other. The difference in diameter between the groups is selected in a range of 5 to 35 %, and preferably 5 to 20 %, to afford the desired relation between the different sized elements. Further, with the elements uniformly mixed together within the selected range of diameters, the continuous circulation of the elements through the core does not cause their substantial segregation into separate groups. The provision of the groups of elements of different diameter within a selected range prevents the elements from adopting an arrangement which corresponds to the most dense possible packing, in which each sphere is in contact with twelve neighboring spheres, and accordingly, when the control rods are advanced into the charge it is possible for the elements to be displaced relative to one another and the stresses applied to the elements and to the tips of the rods are considerably reduced. Therefore, it is not necessary to use special means for the up th charge, for example introducing additional structures into the space containing the spherical elements which would interfere with the circulation of the elements and the optimum operation of the reaction. While previously the use of interferences structures were considered necessary to avoid dense packing of the core members, it has been appreciated that such structures disturb the movement of the core members and result in additional production costs. Further, it has been discovered that the use of different diameter sized balls affords the result intended by the utilization of interference structures without the disadvantages of such structures. The use of different diameter sized balls provides a surprising effect, since normally it would be expected that such different sized members would result in a tighter packing of the core. However, merely using different sizes of the balls is not sufficient because with improper size selection a tightly packed segregated arrangement would occur. It is known from concrete technology that in a mixture of coarse and fne aggregate, the fine aggregate tends to fill the interstices between the coarse aggregate and, as a result, there is a segregation of the different sizes of aggregate. Further, in such an arrangement of the aggregate a densification of the mixture takes place. Accordingly, persons familiar with such technology would not expect the result obtained by the present invention. This is particularly true where it is considered that the balls are continuously circulated through the core which would tend to cause segregation and packing and the repeated insertion of rods into the core would also cause packing. It is sufficient to use elements of only two different diameters as long as they are selected of sizes which provide the desired effect. If the diameters of the elements are too close in size it will be not possible to avoid dense packing of the core. If the diameters are too far apart difficulties will develop in conveying the different diameters, and segregation may occur or the proper spacing with the ability to absorb the stresses developed during the insertion of the control rods will not result. Tests have been made which indicate the effectiveness of the use of two different sizes of reaction elements as compared with a core made up all of one diameter size of elements. Additional factors to be considered in selecting the element diameters include the reactor core size, the recirculation apparatus to be used with the reactor, and the characteristics of the elements under irradiation, for example, the degree of expansion they undergo and their elasticity. The range of elements to be effective is between 5 and 35 %. with the preferred range being between 5 and 20 %. As an example, if a reactor core is designed to operate with a standard size element of 60 mm, then one group of elements would have the size of 60 mm and the other group, based on the preferred size range, would be between 48 mm and 57 mm, if smaller, and between 63 mm and 72 mm, if larger. With such an arrangement of the elements, it is impossible for any element to rest in contact with twelve neighboring spheres. The smaller spherical elements necessarily produce extra empty spaces and the resulting arrangement makes it easier for the elements to move out of the way of the control rods when the rods are advanced into the charge. After establishing a standard element diameter for use in a particular reactor, the selection of the diametral size of the elements is based first on obtaining, to the highest degree possible, the effect intended by the invention, which is to prevent the elements from becoming too densely packed together, and secondly to prevent any serious segregation of the elements of different diameters during the circulation of the charge. With conventional charges, experiments have shown that, during advancement of the control rods into the charge, mechanical stresses applied to the individual elements by the rod tips vary in such a way that, particularly at greater depths of penetration, thrusts supplied radially to the elements by the rod tips almost reach the ultimate compressive strengths of the elements. By means of the invention, the occurrence of these very high stresses is prevented, the highest stresses developed between the rod tips and the elements being reduced sufficiently to ensure that they cannot reach values high enough to fracture the elements by excessive stresses applied in compression or to damage the control rods. Therefore, the invention is applicable to all reaction vessels with bulk charges, such as pebble bed nuclear reactors, which employ spherical elements and which are required to circulate in a controlled way and may also be required to withstand the penetration of bodies the dimension and shapes of which are different from those of the elements. The invention can be applied with advantage to all reaction vessels containing a bulk charge of spherical elements which are being circulated during the operation of the reaction vessel. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.
052020843	abstract	A nuclear reactor with a recirculating heat transfer fluid has a bi-level core which provides enhanced flexibility in fuel arrangement. The bi-level core includes a first core, a plurality of steam separators disposed above the first core, and a second core disposed above the steam separators all inside a single pressure vessel. The steam separators receive a steam and water mixture from the first core and separate the water from the steam. The separated steam is channeled to the second core which cools the second core resulting in the generation of superheated steam. Preferably, fuel bundles of the second core are arranged in vertical alignment with fuel bundles of the first core. This permits a fuel bundle of the first core to be accessed by removing only the adjacent fuel bundle of the second core. During refueling operations, fuel bundles can be shifted from one core to the other, providing additional flexibility in arranging units at various states of burnup. The bi-level core allows fuel to be initially positioned in the second core for conversion of fertile fuel to fissile fuel, and then repositioned to the first core for more complete axial burnup. The steam separators disposed between the first and second cores control the quality of steam channeled into the second core, and allow any crud to remain in solution in the separated water for being removed without buildup in the cores during operation.
	description	The invention relates to detection systems and methods, particularly in the field of diagnostics. One example of a detection system is based on creation of fluorescence radiation in a sample that may be detected to analyse the sample with respect to its constitution, and an example of the use of fluorescence detection is in nucleic acid testing (NAT). This is a core element in molecular diagnostics for detecting genetic predispositions for diseases, for determining RNA expression levels or identification of pathogens, like bacteria and viruses that cause infections. Such bio-sensing methods can also be used to detect other analytes such drugs (therapeutic or abuse) or markers for disease in bodily fluids such as for example blood, urine or saliva. The detection of fluorescence can be used both for a qualitative or a quantitative determination of the presence of a particular target analyte in a sample (e.g. DNA, protein or drug. The present invention relates to the apparatus used to detect fluorescence, and the method of use. Many examples of chemical or biological assay methods for specific binding, capturing and even isolating such targets using for example antibodies immobilised or not are generally known form handbooks such as for example Immunology 5th edition 1998 ISBN 0723429189 see for example chapters 6, 9 29). Often used in this respect are the so called competition and sandwich assays. In a typical molecular diagnostic experiment, a bio-sample is screened for detection of certain biological components (the “target”), such as genes or proteins, the latter often providing markers for specific diseases. This is done by detecting the occurrence of selective bindings (known as hybridisation) of the target to a capture probe, such as for example an antibody. The hybridisation step is typically followed by a washing step, where all unbound target molecules are flushed away, and finally a detection step is carried out. DNA, or RNA detection is generally performed using a replication phase performed before the detection. In this replication phase the DNA or RNA to be detected and present in only small amount within the sample is replicated to larger amounts in order to facilitate reliable detection. Since, the replication step is costly in time and energy, a low detection boundary is important. The apparatus of the invention is useful in that respect. There are two general detection approaches: homogeneous tests (in solution), and heterogeneous tests (on a surface). Heterogeneous tests are more widespread for several reasons, the most important being the fact that they allow the use of special surface sensitive techniques which yield a more sensitive detection. The detection is based on fluorescent detection of fluorescent labels attached to the target molecules. The fluorescent detection needs to be very sensitive, and for heterogeneous tests, the detection must be surface specific so as to minimize the biological background. Ideally, the fluorescent detection needs to be capable of single fluorescent label detection, while the process is kept time effective. The capture probes can be applied in a patterned fashion which allows multiplexing (i.e. detecting many different targets in parallel). The main disadvantages of such heterogeneous, i.e. surface immobilized capture immunoassays, is that the analytes need to diffuse and bind to the surface which usually is the rate limiting step in the analysis. Magnetic beads with surface immobilized capture probes are used frequently to extract components such as the analytes referred to above, from a solution. The beads can be pulled towards the surface by external magnets. In a second step, the beads can be re-dispersed in the fresh solution by removing the magnetic attraction. The actuation force depends on the field strength and the magnetic volume of the bead. Magnetic beads can also be used as labels. The sensitive detection of the presence of target molecules can either be based on the signal generated by the magnetic beads (either based on optical, electrical or magnetic properties) or a signal which is generated by any other label attached to the magnetic beads. A currently implemented solution of magnetic actuation with optical detection is the detection of the attenuation of an excitation beam entering at an oblique angle The inventors have recognized that in the currently implemented solution described here above a small change of a large signal needs to be detected which may have noise limitations. An improved sensitivity may be obtained from a detection of luminance emitted from the bound labels. For fast and efficient detection, which is mandatory in point-of-use applications, not only sensitive detection is important but also compact construction is of paramount importance as such devices must be handled in the field often in chaotic environment and/or by one person. Thus there is a practical constructive limitation for the combination of improved optical read out and magnetic actuation when related to a device suitable for point of care use. It is an object of the invention to provide a detection system that at least partly obviates the aforementioned problem. The invention is defined by the independent claims. The dependent claims provide advantageous embodiments. The arrangement according to the invention enables and makes use of magnetically activated displacement of captured targets towards a detection surface, selective excitation of these captured targets at the detection surface from and detection the response of the excitation in order to know the presence of the target. This surface localized excitation gives an enhanced surface specificity, so that a sensitivity enhancement in detection is achieved. The invention combines the advantages of surface detection with a simple low cost magnetic system for bringing the target to the surface. The magnetic system provides a high speed transport mechanism. In addition, both excitation and detection are done from one side of the detection surface so that a compact construction of the device is achieved. Accordingly, the device can be produced as a low cost compact arrangement by providing a fixed magnet and radiation guidance system. Magnetic actuation allows attracting beads towards (up-concentration) and away from (washing) the surface efficiently, while the dimensions of the beads ensure that strong radiation signals can be generated. In an embodiment the excitation radiation is evanescent with the advantage to have increased selectivity of excitation at the detection surface. A magnetic field guide arrangement is preferably provided for focusing the magnetic field from the magnet to the analysis region. This enables the magnet to be located away from the analysis region, so that there is sufficient space for the magnet and the excitation source and detector. The magnetic field guide arrangement can be arranged in a horse-shoe configuration (essentially a linear arrangement), with the collected radiation passing down the centre of the field guide to the detector. This provides a compact arrangement. The radiation coupling arrangement can then provide the excitation radiation to the analysis region up the central opening of the horse-shoe field guide arrangement, and has a radiation coupling arrangement for focusing the radiation onto the analysis region to generate the evanescent radiation in the sample. The radiation coupling arrangement can then also be for focusing the collected radiation to the detector, and the radiation coupling arrangement can comprise a beamsplitter for providing different radiation paths for the collected radiation and the excitation radiation. This provides a compact combined excitation and detection radiation system, partly housed within the centre of the annular magnetic field guide. The detector can instead be mounted at the top surface of the magnet arrangement. The detector and the magnet arrangement can instead be side by side on a carrier, and wherein the carrier is movable between a magnetic actuation position and a detection position. This can improve the image quality. The actuator will need to be scanned only a small number of times during an assay. Generally, the detector preferably comprises a radiation focusing arrangement. In one arrangement, the radiation focusing arrangement comprises a radiation guide. The detector can comprise a radiation band pass or high pass filter, to remove background noise from the detected radiation signal. In another arrangement, the radiation coupling arrangement comprises a radiation coupling arrangement associated with the excitation radiation source for directing the excitation radiation to the analysis region at an acute angle with respect to the detection surface or, if that is parallel to the substrate surface, parallel to the substrate surface, such that the detection surface provides total internal reflection. This total internal reflection provides the evanescent wave in the sample. The acute angle means that the radiation paths close to the analysis region do not occupy a large depth, so that the magnet can be kept close to the analysis region. The detection is effectively confined to a thin layer above the detection surface. In another arrangement, the radiation coupling arrangement comprises an evanescent radiation guide at the detection surface which is in contact with the sample, again confining excitation to a very thin layer of the sample near or at the detection surface. The excitation radiation may be coupled into this waveguide at a distance from the detection surface and hence from the magnet and radiation coupling equipment/and/or detector so that they do not have to interfere with each other with respect to space available in the device. A compact device is enabled having the advantageous of sensitive measurement at the surface using the magnetic actuation. In another arrangement, the radiation coupling arrangement generates a non-evanescent, travelling wave confined in a shallow volume close to the surface which is in contact with the sample This is known as “double refraction detection”. The shallow volume can have a depth of several to tens of microns. The detection and/or excitation radiation may be optical radiation including or excluding near infrared radiation and/or UV radiation. The interaction of the sample with the excitation radiation may include reflection, absorption or luminescence, where luminescence includes phosphorescence and/or fluorescence. Preferably the excitation radiation is optical radiation while the detection radiation is luminescence radiation as that provides increased sensitivity. Most preferably the detection radiation is fluorescence radiation which provides extremely sensitive detection. In cases where the method relies on absorption of excitation radiation followed by the emittance of the converted excitation radiation such as for example in luminescence generation, the sample may be provided with suitable species for conversion. The detector may comprise a pixilated radiation detector. The system preferably comprises a biological component screening system, for screening for a particular analyte such as for example a protein, drug, DNA, RNA or other molecule. The combination of detection of fluorescence light and the use of magnetic actuation is known per se (Anal. Chim. Acta 564, 2006, 40). However, the solution disclosed is not compact in the sense of the present invention. The same reference numbers are used to denote the same components in different Figs. When a Fig. includes the same components as a previous Fig., the description is not repeated. Where reference numbers are used in the claims, this is only to assist in an understanding of the invention and is not intended to limit the scope of the claims. The invention relates to an optical analysis apparatus and method which combines surface localized excitation with magnetic bead capture. Making use of surface localized excitation gives an enhanced surface specificity, so that a selectivity enhancement in fluorescence detection is achieved. The magnetic bead capture provides a low cost and compact way of enabling surface measurement, with high speed movement of particles to the surface. One way to achieve surface localized excitation is to use evanescent excitation. The principle of evanescent excitation will first be explained with reference to FIG. 1. The sample 14 to be investigated is confined into a given volume forming a micro-fluidic part by a substrate 16. A light source 18 directs excitation light 10 to the surface of the substrate 16. By providing an angle of incidence of this excitation light larger than the critical angle, there is total internal reflection of the light. This removes the bulk excitation. An evanescent wave travels into the sample, with a decaying field amplitude as a function of propagation distance z, as schematically illustrated by plot 21. Since this evanescent wave is rapidly decaying, it can be used to probe only those molecules that are present near the surface of the interface. Upon excitation with a (short wavelength) laser, the fluorescent molecules will start radiating light in all directions. The wavelength of the fluorescent light will be longer than the excitation wavelength. FIG. 2 shows a first example of device of the invention. Generally, the device comprises a reader instrument and a disposable cartridge. The reader instrument has a magnet arrangement for bringing the magnetic beads to the surface and pulling them away from the surface, an optical excitation system for inducing fluorescence, and an optical detector. As explained with reference to FIG. 1, the sample 14 to be investigated is confined into a given volume forming a micro-fluidic part by a substrate 16. The sample includes magnetic beads 15. Excitation light 10 generated by a source such as a laser (or LED) 18 is used to excite fluorescence 19. The induced florescence emitted by the bound labels, (as a result of the evanescent excitation light provided into the sample) is collected by a collection lens arrangement 20, and is directed towards a detector 22. The detector is a photodetector, which can be a diode or an array of diodes or charge-coupled devices (CCD). The amount of light which reaches the sensor surface can be further increased by introducing optical elements such as lenses between the disposable part of the device (the substrate) and the detector 22. As shown in FIG. 2, the disposable substrate can also include optical surfaces 26, 28 defining part of the optics 23. To reduce a background signal from scattering light, a color selective filter 32 (bandpass or highpass; where “high” refers to the wavelength of the light) is provided on top of the detector. The filter can be absorbing or reflecting (dichroic), and can be in optical contact with the detector. The optical elements 20 can also be used to image the binding surface on the detector surface. In this way, a spatial image of the emitted light is created which allows simultaneous detection of different targets on different spots at the binding surface. This represents a multiplexed detection scheme. The magnetic field for the magnetic bead capture is guided towards the bottom of the optical substrate 16 by using high permeability material forming guides 24. The magnetic field needs to be provided close to the binding surface of the optical substrate, in order to achieve sufficiently large forces (typically <1.5 mm between the top of the magnet and the substrate sensor area). The electromagnetic sources themselves are located at a larger distance, not shown in FIG. 2. This creates sufficient space between the magnetic field guides 24 to position the optical detection system. In the example shown, the guides form an horse-shoe shaped ring, and the central opening is used for housing the detection optical components. A large optical aperture of the magnetic guiding structure is desired for an increased light collection. The opening angle of the cone of light that has to be collected by the imaging optics should be large, for example corresponding to a numerical aperture of 0.5 of more. The excitation light 10 enters the substrate 16 via window 26 which is integrated in the disposable part of the device. An exit window 28 is also shown, and an optional detector 30 used for feedback control of the excitation source, for example for reference and quality control. In the example of FIG. 2, the excitation is achieved with an incident beam which is totally reflected at the interface between the substrate and the analyte solution at the spot of the biological binding. This creates the desired evanescent field at the surface with exponentially decaying intensity. Only labels in proximity of the surface (distance order of 100 nm or less) will become excited. Such a surface selective excitation creates a very low background from the supernatant solution and consequently allows real-time detection with high sensitivity. By providing the excitation source and associated lenses laterally of the analysis region of the sample, and with a small acute angle between the direction of incidence and the plane of the substrate, a small space can be provided between the magnetic field guides and the lower surface of the substrate. In the arrangement of FIG. 2, the detector and associate optics are provided within a space at least partially surrounded by the magnetic field guides. In a second embodiment shown in FIG. 3, the emitted light is transported from the analysis region by a light guide 40, for example fibre bundles. The detector 22 is placed at the lower end of the light guide 40 outside the magnetic head. This enables a more compact design of the magnetic field guides and allows the use of standard components for the optical elements. In a third embodiment shown in FIG. 4, the photodetector 22 is positioned directly on top of the magnet 50 that is used for actuation of the magnetic labels. The photodetector 22 is still however located in the reader instrument to keep costs of the disposable part of the apparatus low. FIG. 4 shows a flat underside of the substrate in the analysis region, but an optical component such as a single refractive or diffractive lens, or a 1D- or 2D-lenslet array (providing imaging functionality), could again be moulded in the bottom of the optical substrate to increase the collection efficiency, as shown in FIG. 2. To keep the photodetector slim, it is preferably a semiconductor element (e.g. photodiode, CCD, CMOS) or a polymeric element. Excitation by total internal reflection as shown in the examples above can be replaced by excitation with an evanescent light guide, as shown in FIG. 5. In this way, no components are required at the location of the analysis region for coupling the light to the analysis region. This leaves more area for the magnetic head. The excitation source 18 provides light to the light guide 60 by means of a grating structure 62. FIG. 6 shows an arrangement in which the excitation light is guided through the optical elements inside the magnetic head. In this way, an optical arrangement is used which provides the excitation light to the analysis region up the centre of the field guide arrangement (for example again in a horse shoe configuration). The light is focused onto the analysis region to generate the radiation in the sample. The excitation light is directed to the sample by a dichroic mirror or beamsplitter 70. This enables different optical paths to be defined for the excitation lights and the fluorescence. The excitation light is subsequently focused in the sample by means of an excitation lens 72. Any reflected stray laser light (having the excitation wavelength) is reflected again by the dichroic mirror or beam splitter 70, whereas the fluorescence luminance is passed through the mirror/beam splitter 70 to the detector 22. A band pass filter can provide further filtering for rejection of the excitation light, and the filtered light is focused on the detector 22 by an imaging lens 74 which images the sample onto the detector 22. The read-out can be implemented in a quasi-confocal mode by introducing a pinhole in the focal point of the collecting lens in the read out path or using the pixelated detector as a quasi-pinhole to suppress luminance from other parts outside the binding array. However, no pinhole arrangement is required when an evanescent field is present only at an excitation spot. The examples above have fixed magnetic and optical components, and the magnetic and optical functions are performed with the same cartridge position. In an arrangement shown in FIG. 7, the coaxial arrangement of magnetic and optical elements replaced with a parallel arrangement with the advantage of having a better imaging quality. The arrangement of FIG. 7 has an actuated sledge 80 containing the magnet arrangement 82 and the imaging and detection optics 18, 22, next to each other. FIG. 7A shows the device in side view and top view. FIG. 7B shows the two positions of the sledge 80. The top part of FIG. 7B shows the analysis region 90 in the path of the excitation source and above the magnetic field. The bottom part of FIG. 7B shows the analysis region over the optical detector arrangement for detecting the fluorescence. The excitation of fluorescence, and light detection are at the same time (the relaxation time of fluorescence is a few nanoseconds). The arrangement of FIG. 7 separates the magnetic attraction function from the excitation/detection. The magnetic attraction is a comparatively slow process and once the beads are bound they remain in place sufficiently for the cartridge movement. This arrangement uses the same conceptual approach as the examples of FIGS. 2 and 3, in that imaging of the analysis region is through the center of the magnet. The example of FIG. 7 provides movement of the sledge 80 during actuation between two positions. A position is provided in which the magnet is exactly below the analysis region of the cartridge. When the actuation protocol has ended (magnetic attraction to bring particles to the surface), the sledge is moved to a second position such that the optical axis of the imaging/detection optics coincides with the center of the analysis region and excitation and fluorescence detection can take place. In all examples above, the target molecules attach to the beads (in the same way as in existing bead capture systems), and the fluorescent labels attach to the target molecules (in the same way as in existing optical systems), so that magnetically drawing the beads to the surface provides the required fluorescent labels at the surface. Beads which are attracted to the surface but have no attached target molecule will not bind and can be pushed away by reversing the magnetic gradients. The technology of 1D and 2D moving mechanical stages is well-known from optical storage and these devices can be made reliably, at low-cost and in high volumes. Furthermore, 1D actuated sledges can be moved fast (up to 100 Hz) and with high accuracy (tens of microns). A possible disadvantage of this method is the lack of signal during magnetic actuation. However, for an end-user product this would be no problem since the dynamics of the bio-assay is known from research. The actuation protocol can thus be performed without requiring feedback or analysis. The various examples of the invention enable a system with compact imaging optics and detector, and with high image quality. A compact and efficient magnet arrangement is provided. The supply of the sample to the analysis region can be entirely conventional, for example using microfluidic pumping. Multiple channels can be in parallel with different antibodies immobilized. Temperature control of the device can be provided by integrated heating. Fluorescent beads of different spectrum can be used. The background fluorescence can be read from unbound labels. The background will result mainly from unintentionally bound labels and other particles that stick to the surface, as well as some intrinsic fluorescence from the substrate and all components in the light path. Measuring the density of beads by absorption (FTIR) or scattering is an alternative which can be measured instead of or in addition to fluorescence. This can use essentially the same arrangement except the filters. Premixing of the beads and labelled antibodies with the sample can take place before injection. Preferably, the mixing and reaction would take place inside the disposable cartridge for a point of care application. In the examples above, the system is used for fluorescence detection. However, the invention more generally relates more generally to the excitation of a sample and the detection of resulting light. The substrate may be a flat plate of any suitable material, e.g. may be of glass or a polymer, and may have capture elements with a surface density between 0.01 and 106 elements per μm2, preferably between 10 and 104 elements per μm2. The sample, the substrate with capture elements in contact with the sample or the substrate after it has been in contact with the sample, typically is screened for certain components, e.g. biological components such as oligonucleotides, DNA, RNA, genes, proteins, carbohydrates, lipids, cells, cell components such as external cell membranes or internal cell membranes, bacteria, viruses, protozoa, etc. also called the target particles. Luminescent labels typically are attached to the target particles and thus assist in the detection of target particles. In some embodiments the sample thus includes at least one luminescent label, also referred to as an “optically variable particle”. Such optically variable particles can be, for instance, fluorescent (as described above), electroluminescent or chemiluminescent particles. The optical variable particles may be any entity that is capable to bind to a binding site chemically or otherwise. The binding is due to screening effects (i.e. ionic, dispersive and hydrogen bonding interactions). Covalent bonding is an alternative In the examples above, the fluorescence detection takes place through the substrate. However, the fluorescence detection can be implemented above the sample. The applications of the invention are generally in the field of molecular diagnostics: clinical diagnostics, point-of-care diagnostics, advanced bio-molecular diagnostic research—biosensors, gene and protein expression arrays, environmental sensors, food quality sensors, etc. Various other modifications will be apparent to those skilled in the art.
055984533	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be detailed with reference to the accompanying drawings. (Embodiment 1): FIG. 1 shows schematic perspective view and FIG. 2 shows front views, in model form, of a cone-beam X-ray CT apparatus in accordance with the first embodiment of the present invention. The X-ray imaging apparatus of the present embodiment 1 includes an imaging-sequence controller 1, an X-ray tube 2, an X-ray grid 3, an X-ray image intensifier 4, an optical lens unit 5, a television camera 6, an image acquisition and processing unit 7, a rotatory gantry 8, a bed board 9, a gantry-rotation controller 10, a board transfer controller 11, an angle encoder 12 for measuring a rotation angle of the rotatory gantry, a linear encoder 13 for measuring a position of the bed board, and an image display unit 21. The other units and mechanisms of the X-ray imaging apparatus are known and thus explanation thereof is omitted. An X-ray detection unit 4' includes the X-ray image intensifier 4, optical lens unit 5 and television camera 6. An imaging unit includes the X-ray detection unit 4', X-ray tube 2 and rotatory gantry 8. A subject 14 to be examined is positioned on the bed board 9, which standard posture is assumed to be supine position. And the center of a part of the subject 14 to be imaged is set to be in the vicinity of the rotation center of the imaging unit. The optical lens unit 5 is made up of optical lenses and mirrors. In FIG. 2, the X-ray tube 2 has a rotation radius of 720 mm, a distance between the X-ray tube 2 and an input phosphor screen (X-ray input screen (assumed plane) 4") of the X-ray image intensifier 4 is 1100 mm, and the X-ray input screen (assumed plane) 4" of the X-ray image intensifier 4 has a diameter of 380 mm. A fan angle at the X-ray tube 2 toward the X-ray input screen (assumed plane) 4" is equal to 19.6 degrees. The X-ray tube 2 and X-ray detection unit 4' have a rotation period of 5 seconds as a typical example. The television camera 6 comprises a high-resolution image-pick-up tube as an imaging device. Explanation will be made to the respective elements. The imaging-sequence controller 1 defines a movement sequence for rotating the rotatory gantry 8 having a pair of the X-ray detection unit 4' and X-ray tube 2 fixed thereto and a movement sequence for periodically moving the bed board 9. The imaging-sequence controller 1 also defines an imaging sequence for controlling the X-ray generation of the X-ray tube 2 and the imaging operation of the X-ray detection unit 4'. The gantry rotation angle encoder 12 outputs rotation angle data. The bed board 9 sets a fluoroscopic and radiographic posture of the subject 14. The bed board 9 is horizontally positioned, and in a rotation imaging mode it is moved in a direction parallel to the rotation plane, on which the X-ray detection unit 4' is mounted. The bed-position measuring encoder 13 outputs positional data on the bed board 9. Explanation will be made as to the operation of the cone-beam X-ray CT apparatus in accordance with the embodiment 1 of the present invention. In FIGS. 1 and 2, X rays emitted from the X-ray tube 2 are transmitted through the subject 14, scattered components of which are shielded by the X-ray grid 3, converted into a visible ray image by the X-ray image intensifier 4, and then imaged on the television camera 6 by the optical lens unit 5. The image is converted into a video signal by the television camera 6 and applied to the image acquisition and processing unit 7. Although the CT scanning operation of the television camera 6 is carried out with 60 frames/sec. and a scanning line number (number of scanning lines) of 525 in a standard scanning mode, the scanning or imaging may be carried out with 30 frames/sec. and a scanning line number of 1050. The imaging can be realized with 7.5 frames/sec. and a scanning line number of 2100 in a high-resolution imaging mode. In the standard CT scanning mode, 60 images/sec. are measured for every 1.25 degrees to obtain 288 images per 4.8 sec. The image acquisition and processing unit 7 converts the video signal to a digital signal, stores in its internal frame memory the digital signal together with the rotation angle data and bed board position data, subjects the respective projection images to corrections of geometric distortion and shading of the pixel value (intensity) thereof, and then performs 3-D image reconstruction thereover. In this case, a series of tasks ranging from the geometric image distortion correction to the 3-D reconstruction may be sequentially carried out simultaneously with acquisition of each projection image or may be carried out after the acquisition of all the projection images. The image display unit 21 displays thereon a 3-dimensional X-ray image subjected to the 3-D reconstruction. In this connection, the display of the 3-D X-ray image may be carried out sequentially with an intermediate result of the reconstruction during the reconstruction, or may be carried out after the reconstruction is completely finished. The image obtained by the television camera 6 in a fluoroscopic or radiographic mode is displayed on the image display unit 21 as it is or after subjected to the aforementioned corrections. FIG. 3 shows front views, in model form, of the imaging unit and subject 14 for explaining examples of relationship between the motion of the imaging unit and the movement of the subject 14. In FIG. 3, a displacement (which direction is shown by an arrow in the vicinity of the subject 14) in the periodical reciprocating movement of the subject 14 in the horizontal direction is expressed by a sine wave with respect to time. With regard to the rotation direction of the pair of the X-ray tube 2 and X-ray detection unit 4', the counterclockwise direction is defined as + rotation direction. Explanation will then be made as to the above relationship between the rotation of the imaging unit and the movement of the subject 14. At a start stage A in FIG. 3, the X-ray tube 2 and X-ray detection unit 4' in pair are horizontally positioned and the center (body axis) of the subject 14 is positioned at the center of rotation of the X-ray tube 2. Simultaneously with the fact that the pair of the X-ray tube 2 and X-ray detection unit 4' starts to rotate counterclockwise, the subject 14 starts to move rightwardly in the horizontal direction in a horizontal plane including the rotation center of X-ray tube and detection unit to start the fluoroscopic or radiographic operation. At a B stage that the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated by +90 degrees from the start stage A, the movement direction of the subject 14 is reversed and directed to the left in the horizontal direction. At a C stage that the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated by +180 degrees from the start stage A, the center (body axis) of the subject 14 returns to the rotation center. At a D stage that the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated +270 degrees from the start stage A, the movement direction of the subject 14 is reversed and directed to the right in the horizontal direction. At a E stage that the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated +360 degrees from the start stage A, i.e., again at the start stage A, the pair of the X-ray tube 2 and X-ray detection unit 4' is reversed in the rotation direction to the clockwise direction. When the pair of the X-ray tube 2 and X-ray detection unit 4' starts to rotate clockwise, the subject 14 starts to move to the right in the horizontal direction of the horizontal plane including the rotation center. At a F stage that the pair of the X-ray tube 2 and X-ray detection unit 4' are rotated -90 degrees from the start stage A, the movement direction of the subject 14 is reversed to the left in the horizontal direction. At a G stage that the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated -180 degrees from the start stage A, the center (body axis) of the subject 14 returns to the rotation center. At a H stage that the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated -270 degrees from the start stage A, the movement direction of the subject 14 is reversed to the right in the horizontal direction. At a I stage that the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated -360 degrees from the start stage A, that is, again at the start stage A, the rotation of the pair of the X-ray tube 2 and X-ray detection unit 4' and the movement of the subject 14 are stopped, terminating the fluoroscopic or radiographic operation or CT scanning. Shown in FIG. 4 is a block diagram for schematically explaining a flow of the fluoroscopic or radiographic operation or CT scanning procedure in the present invention. The 3-D image reconstruction in FIG. 4 will be detailed later separately in connection with FIG. 14. In FIG. 4, imaging conditions are first set (step 301). The imaging conditions determine the position of the bed board 9 and the position of the imaging unit when X-ray exposure is carried out. The i-th imaging conditions are expressed by a horizontal movement distance x.sub.i of the bed board 9 and by a rotation angle .beta..sub.i of the imaging unit corresponding to a difference with the (i-1)-th imaging position. The imaging conditions are held in the memory in the form of a table, from which imaging condition data are sequentially read out as the imaging operation proceeds so that once movement and rotation are carried out before the next X-ray exposure. The sequence for executing the movement and rotation is controlled by the imaging-sequence controller 1. When the imaging operation is started, this causes first the bed board 9 and imaging unit to move. While the position of the bed board 9 is horizontally moved by x.sub.1 from the imaging start position, the imaging unit is rotated by .beta..sub.1 so that at a stage (step 302) that the positions of the bed board 9 and imaging unit are set at first imaging positions X-ray exposure is carried out (step 303) and then data collection is carried out (step 304). In the case of the fluoroscopic or radiographic mode (A), the collected data are displayed on the image display unit 21 (step 305) and at the same time, the bed board and imaging unit are moved for use in the next imaging operation. In the case of the CT mode (B), the collected data are used for the 3-D image reconstruction (step 306) and also displayed on the image display unit 21 (step 307), and at the same time, the bed board and imaging unit are moved for use in the next imaging operation. At the same time the position of the bed board 9 is horizontally moved by x.sub.2 from the first imaging position, the imaging unit is rotated by .beta..sub.2 so that the second X-ray exposure is carried out (step 303) and then data collection is carried out (step 304) when the positions of the bed board 9 and imaging unit are set at second imaging positions (step 302). The above procedure is sequentially repeated until the imaging operation is completed. Also supplementarily depicted in FIG. 3 are variations in the x coordinate of the bed board 9 and in the x and y coordinates with time. Assuming that T denotes notes a rotation period of the pair of the X-ray tube 2 and X-ray detection unit 4', then .beta. at a time t is expressed by the following equation (1). ##EQU1## The x and y coordinates of the X-ray tube 2 is written as Rcos.beta. and Rsin.beta., respectively, where R is the radius of X-ray source orbit. Further, the position of the bed board 9 is varied according to a sine wave function with respect to the horizontal direction (x direction) together with the rotation angle .beta. of the X-ray tube 2. When the movement distance D (one side) of the bed board 9 is set at (R/2)tan.alpha. corresponding to about 1/2 of a view field radius when the bed board 9 is not moved, the x coordinate d of the bed board 9 is expressed as follows. ##EQU2## The x and y coordinates of the X-ray tube 2 is expressed in the coordinate system fixed to the subject by the following equations (3). ##EQU3## When scanning is carried out during the A and I stages in FIG. 3, over the entire view field data is measured with the both up and down and the both of right and left position of the X-ray tube 2, as in the prior art cone-beam X-ray CT apparatus. In the embodiment 1, a movement (one side) of about 1/2 of the view field radius when the bed board 9 is not moved is carried out in the horizontal direction, so that the view field in the horizontal direction is increased by about 1/2 of the view field radius and the view field in the vertical direction does not vary substantially. In general, the view field in the horizontal direction is increased by an amount corresponding to the movement distance of the bed board 9. The imaged projection image is subjected to corrections of geometric distortion and non-uniform sensitivity at the image acquisition and processing unit. Three-dimensional reconstruction is carried out with use of the projection image after the corrections. Further, two of the fluoroscopic or radiographic images may be used to perform stereoscopic vision. Furthermore, only part of the scanning during the A and I stages in FIG. 3 may be performed. For example, the scan range can be set to be during the A and E stages or during the E and I stages to realize the equivalent view field with half of the measurement time, and such simple and convenient scan can be realized that eliminates the need for the reversing operation of the pair of the X-ray tube 2 and X-ray detection unit 4' in the course of the scan. When the scan range is set to be during the A and E stages in FIG. 3, the measured data in the left peripheral area of the view field are the data when imaging is carried out only under a condition that the X-ray tube 2 is at its upper position and the X-ray detection unit 4' is at its lower position, on the other hand, the measured data in the right peripheral area of the view field are the data when imaging is carried out only under a condition that the X-ray tube 2 is at its lower position and the X-ray detection unit 4' is at its upper position. As a result, the left lung of a patient as the subject is imaged from the top side while the right lung is imaged from the bottom side. On the other hand, when the scan range is set to be during the E and I stages in FIG. 3, the measured data in the left peripheral area of the view field are the data when imaging is carried out only under a condition that the X-ray tube 2 is at its lower position and the X-ray detection unit 4' is at its upper position, while the measured data in the right peripheral area of the view field are the data when imaging is carried out only under a condition that the X-ray tube 2 is at its upper position and the X-ray detection unit 4' is at its lower position. When the scan range is set to be during the C and G stages in FIG. 3, the measurement time can be made half with substantially the same view field and the scan with the same imaging direction in the entire view field can be realized. That is, in this case, data measurement is carried out only from one direction, though data measurement is carried out from two direction, with the both of up and down or both of right and left position of the X-ray tube, the entire view field with the prior art cone-beam X-ray CT apparatus in which the bed board 9 is not moved or with the sequence ranging during the A and I stages in FIG. 3. When the start stage of the movement sequence is set at any stages but the A stage in FIG. 3, various movement sequences may be considered. FIGS. 5A to 5E are diagrams showing relationships between a position of an X-ray source (X-ray tube 2) on the rotation orbit and the view field of the transaxial sectional plane in a coordinate system fixed to the subject 14. More specifically, FIG. 5A corresponds to the prior art when the subject is not moved, while FIGS. 5B to 5E correspond to the present invention when the subject is moved. In FIGS. 5A to 5E, a point S represents the X-ray source (X-ray tube 2), a point O represents the center of the view field which, when the subject 14 is not moved, coincides with the rotation center of the pair of the X-ray source and X-ray detection unit 4'. It is assumed that lines m and n indicate boundary lines limiting areas to be measured by the X-ray detection unit 4' and a distance between the boundary line m or n and the view field center O is defines as a view field radius. A view field radius a.sub.0 when the subject 14 is not moved is independent of .beta. as shown at the start stage A in FIG. 3, and FIG. 5A, and written by the following equation (4). EQU a.sub.0 =R sin .alpha. (4) When the subject 14 is moved by .vertline.d.vertline. in the negative direction of the x axis, the view field is enlarged on one side (right side) of the x axis direction, while the view field is reduced on the other side (left side) thereof, as shown in FIG. 5B. View field radii a and b are given as follows. EQU a=R sin .alpha.+.vertline.d.vertline. sin (.beta.+.alpha.) (5) EQU b=R sin .alpha.-.vertline.d.vertline. sin (.beta.-.alpha.) In FIG. 5B, the boundary lines m and n when the subject 14 was not moved are denoted by dotted lines, FIGS. 5D and 5E. For the purpose of preventing generation of missing of measured data nearly in the center of the view field, it is required that smaller one (b in FIG. 5B) of the boundary lines a and b is prevented from having a negative value. In other words, the .vertline.d.vertline. is required to satisfy the following relation (6). EQU .vertline.d.vertline..ltoreq.R sin .alpha. (6) The d is set as its typical example to meet such a function that varies in a sine wave manner in the x-axis direction as shown by the following equation (7), and in FIG. 5C the rotation angle .beta. of the pair of the X-ray source 2 and X-ray detection unit 4' is equal to zero degrees. EQU d=kR tan .alpha. sin .beta. (7) (k: constant in 0.ltoreq.k.ltoreq.1) In this case, both of the view field radii a and b are expressed by R.multidot.sin.alpha., which is the same as when the prior art system with the subject being not moved. When .beta.=180.degree., it is the same as .beta.=0.degree.. Meanwhile, when .beta.=90.degree. (FIG. 5D), the following equation (8) is satisfied so that the view field is reduced on the right side of the x axis direction, while the view field is enlarged on the left side thereof. EQU a=(1-k)R sin .alpha. (8) EQU b=(1+k)R sin .alpha. When .beta.=270.degree. (FIG. 5E), the following equation (9) is satisfied so that the view field is enlarged on the right side of the x axis direction, while the view field is reduced on the left side thereof. EQU a=(1+k)R sin .alpha. (9) EQU b=(1-k)R sin .alpha. Hence, when the position of the subject 14 is controlled so that the X coordinate varies according to a sine wave function together with the rotation angle .beta. of the pair of the X-ray source 2 and X-ray detection unit 4', and measurement is carried out with the rotation angle .beta. varied in a range from 0.degree. to 360.degree., the measurement can be realized with the view field enlarged in the x axis direction than the case when the measurement with the stationary subject 14 is carried out. Mutually lacking projection images can be made complementary by controlling the X-ray source and the subject as follows. That is, as will be clear from FIG. 3, when the X-ray source 2 is located at a point-symmetric position with respect to the rotation center O during the rotation of the X-ray source, for controlling a position of the bed board to be located at a point-symmetric position with respect to a middle point of the reciprocating movement of the bed board, and when the X-ray source is located at a line-symmetric position with respect to a straight line passing through the rotation center, parallel to the rotation plane and vertical to said reciprocating movement direction, for controlling the bed position to be located at a point-symmetric position with respect to the middle point of the reciprocating movement. When the pair of the X-ray source 2 and X-ray detection unit 4' is rotated one turn along a circular orbit starting with their horizontal position, the bed board is reciprocated in the horizontal direction starting with the center position of the reciprocating movement. At the same time the rotation direction of the pair of the X-ray source 2 and X-ray detection unit 4' is reversed along the same circular orbit, the bed board again performs the above reciprocating movement. As result, the X-ray source 2 can acquire projection images of the subject 14 in all the directions during the reciprocating rotation. And since the X-ray detection unit 4' is made up of a 2-dimensional detector, the projection images can be acquired at high speed. By subjecting the respective imaged projection images to the corrections of geometric distortion and nonuniform sensitivity, accurate reconstructed images having high resolution can be obtained. Since displacement in the reciprocating movement of the subject 14 follows a sinusoidal wave varying with time, the movement of the subject 14 can be made smooth and thus the physical and mental burden of the subject 14 can be lightened. Although the rotation of the pair of the X-ray source 2 and X-ray detection unit 4' as well as the reciprocating movement of the subject 14 have been made continuous in the foregoing explanation, intermittent (stepwise) movement may be employed when necessary, as a matter of course. Explanation will next be made as to how to display X-ray fluoroscopic or radiographic images in the present imaging system. And explanation will be made in connection with a general case where the subject 14 is arbitrarily moved in a direction parallel to the rotation plane of the imaging unit. Accordingly, the following explanation can hold true even for the earlier-mentioned moving system as it is. FIG. 7 is a front view, in a model form, showing a positional relationship between the subject 14 and imaging unit in an (X,Y) coordinate system fixed to the subject 14. In the present embodiment, since a relative positional relationship between a rotation axis 1a of the imaging unit and the subject 14 sequentially varies in the course of imaging operation, a projection position 72b of a central axis 72a (body axis) of the subject 14 projected onto the X-ray input screen 4' (assumed plane) sequentially varies leftwards or rightwards relative to a center position 7lb of the X-ray input screen 4". In FIG. 7, O.sub..phi. is a vector indicative of the position of the rotation center expressed in the (X,Y) coordinate system, and the subject 14 is moved along the X axis. In general, the center position 7lb of the rotation axis of the imaging unit to the X-ray input screen 4" is fixed always to the center of a display screen 73 as shown in FIG. 8A. For this reason, when an X-ray transmission image of the subject 14 through the X-ray detection unit 4' is displayed on the display screen 73 as it is, the rotation of the imaging unit causes the projection position 72b of the central axis of the subject 14 to be sequentially shifted to the left or the right, as shown in FIG. 8A. In this way, there occurs a problem that the position of the subject incessantly varies rightwards or leftwards on the display screen 73, which makes it difficult for the inspector to observe the image. To avoid this, in accordance with the present embodiment, the projection position 72b of the central axis of the subject 14 is set to always coincide with the center position 7lb of the rotation axis of the imaging unit, as shown in FIG. 8B. More in detail, this can be easily realized by, e.g., correcting image information stored in the memory with respect to its lateral shift on the basis of a relationship with the display screen 73. That is, in FIG. 7, when the quantities .phi. and O.sub..phi. are known, an offset in the position of the projection position 72b relative to the center position 7lb of the detection plane is also found, for which reason the correction can be carried out based on the offset. Since the correction is carried out based on the offset for image display, the inspector can observe the projection image with the projection position 72b of the central axis of the subject 14 always fixed to the central position of the screen on the display screen 73. In this case, since display portion 74 indicative of the X-ray transmission image of the subject 14 in such an image as shown in FIG. 8B is displayed as varied leftwards or rightwards with respect to the display screen 73, the display screen 73 becomes laterally elongated when compared to the prior art one. For this reason, all the X-ray transmission image of the subject 14 can be displayed within the display screen 73 without any missing of the image. In general, an X-ray transmission image is handled, in many cases, as a digital image signal, and shifting a display image to the left or right corresponding to shifting the pixels of the image on the display screen to the left or right. However, since the amount of such pixel shift is in units of an interval between the adjacent pixels of the image and thus has not always an integer value, it is difficult to accurately shift the image. For the purpose of realize the above accurate shift, in the present embodiment, an inter-pixel data interpolation method is employed to cause the above shift amount to have an integer value based on the inter-pixel spacing units to thereby realize an accurate image shift. The shift amount may be approximated as an integer value closest thereto. Explanation will then be made as to how to reconstruct an X-ray CT image in the present imaging system. And explanation will be made in connection with a case where the subject 14 is arbitrarily moved in a direction parallel to the rotation plane of the imaging unit. Accordingly, the following explanation can hold true for the earlier-mentioned moving system as it is. For easy understanding of this, explanation will be done in conjunction with a case where a reconstruction area in the 3-dimensional reconstruction is limited to a 2-dimensional area on the rotation orbit plane of the X-ray source. First, FIG. 9A shows, in an (X,Y) coordinate system fixed to a subject, a relationship among a position on the rotation orbit plane of the X-ray source S, a locus 16 of the X-ray source S, and a reconstructible area 15 in an X-ray tomographic image in a prior art cone-beam X-ray CT apparatus where a relative positional relationship between the rotation center O.sub..phi. of an imaging unit and the subject is stationary. In FIG. 9A, a point O denotes the origin of the (X,Y) coordinate system fixed to the subject, a hatched area denotes an area in which the X-ray tomographic image can be reconstructed, and D denotes the rotation radius of the X-ray source S. The word "reconstructible area" used here refers to a boundary area in which the X-ray image of the subject can be reconstructed only when the subject is included completely therein. In such a prior art cone-beam X-ray CT apparatus, the X-ray detection unit 4' collects X-ray transmission data necessary for reconstruction of images of the subject while the imaging unit is rotated by one turn around the rotation center fixed to the subject. Assuming now that the rotation center has a position O, then the reconstructible area corresponds to the area of a circle having a diameter 2d in FIG. 9A. Assume that, as in the foregoing apparatus for example, the X-ray source S has the rotational radius D of 720 mm, a distance between the X-ray source S and detector is 1100 mm, and the X-ray input screen 4" of the X-ray detection unit 4' has a diameter of 380 mm. Then the reconstructible area has the diameter 2d of 250 mm. According to a projection theorem present in a paper "New X-ray Imaging Method and Computer Tomographic Imaging" of a book "Medical Electronics and Bioengineering", Vol. 14, No. 5, p.375 of pp. 369-378, 1976; a condition necessary and sufficient for an area in which an X-ray tomographic image is reconstructible is that, in the area in question, a transmission image of a subject formed by X-ray parallel beams 17 shown in FIG. 9B is present with respect to a given angle direction .THETA..sub.1. Accordingly, in the present imaging system, when the rotation of the imaging unit by a plurality of turns and relative positional relationships between the O.sub..phi. and subject are arbitrarily combined, all data sufficient for obtaining such parallel beams as mentioned above, i.e., for reconstruction can be acquired for a reconstructible area having a given size in the rotation orbit plane. FIGS. 10A and 10B show, in an (X,Y) coordinate system fixed to a subject, a relationship among a position on the rotation orbit plane of the X-ray source S, the loci 16 (which 2 loci correspond to movements of the subject in positive and negative directions) of the X-ray source S, the reconstructible area 15 of the X-ray tomographic image when the subject is moved according to the aforementioned moving system in the cone-beam X-ray CT apparatus of the present embodiment. In FIG. 10A, .phi. denotes an angle between the X axis and a straight line connecting the X-ray source S and the rotation center O.sub..phi., and 2c denotes the amplitude of a bade movement. In this case, the positions of the rotation center O.sub..phi. at 1st and 2nd rotations in the above moving system are expressed in the (X,Y) coordinate system as: EQU First rotation: 0.sub..PHI.1 =(-c sin .PHI..sub.1,0) (10) EQU Second rotation: 0.sub..PHI.2 =(c sin .PHI..sub.2, 0) where .phi..sub.1 and .phi..sub.2 correspond to rotational angles at the 1st and 2nd rotations of .phi. and are expressed as follows. ##EQU4## The then movement locus of the X-ray source S is shown in FIG. 10A. The then reconstructible area is the area surrounded by boundary lines 22 of view field of the X-ray detection unit 4' in FIG. 10B. It will be appreciated from comparison between FIGS. 10B and 9A that the reconstructible area is expanded in the X axis direction in the present moving system. Assuming that, as in the case of FIG. 9A, the X-ray source S has the rotational radius D of 720 mm, a distance between the X-ray source S and detector is 1100 mm, the X-ray input screen 4" of the X-ray detection unit 4' has a diameter of 380 mm, and the amplitude (2c in FIG. 10A) of a bed movement is 100 mm; then the size of the reconstructible area in FIG. 10B becomes 343.3 mm in the X axis direction and 250 mm in the Y axis direction, which is increased by 93.3 mm in the X direction when compared to that in FIG. 9A. With the cone-beam X-ray CT apparatus of the present embodiment, in this way, when the imaging unit including the X-ray tube 2 and X-ray detection unit 4' is rotated about the subject by a plurality of turns and at the same time, when a relative positional relationship between the rotation center O.sub.100 and subject 14 is varied in a direction parallel to the rotation plane, all data necessary for the reconstruction can be acquired for the enlarged reconstructible area. Accordingly, in the imaging mode, the rotation center of the imaging unit is always moved with respect to the subject (which coordinate system fixed to the imaging unit and having the O.sub.100 as its origin will be referred to as the moving center coordinate system, in the present specification). In contrast, with the prior art cone-beam X-ray CT apparatus, the rotation center O.sub..phi. of the imaging unit is always fixed to the subject and calculations for the reconstruction are carried out based on the coordinate system fixed to the imaging unit and having the rotation center O.sub..phi. as its origin (which coordinate system will be referred to as the fixed center coordinate system, in the present specification). In general, prior art reconstruction methods in CT scan apparatuses and reconstruction methods for expanding the reconstruction method of the CT scan to 3-dimensional space in cone-beam X-ray CT apparatuses are all based on the use of the aforementioned fixed center coordinate system. Therefore, in order to apply to the prior art reconstruction method the projection data of a subject collected in the imaging system of the present embodiment, it is necessary to convert all data in the moving center coordinate system to data in the fixed center coordinate system. However, such conversion of all the collected projection data requires highly troublesome works with much calculation time. This also involves a corresponding complex processing device. To avoid this, in accordance with the present embodiment, such a special coordinate system as called the moving center coordinate system is used to realize the reconstruction to be explained later. FIG. 11 shows the position of a target beam in an X-ray transmission image of a subject in the (X,Y) coordinate system fixed to the subject. In FIG. 11, the position of the X-ray beam issued from the X-ray source S and passed through a reconstruction point 18 is uniquely expressed with use of two parameters u and .theta.. In other words, the X-ray beam passed through the reconstruction point 18 can be uniquely specified by the parameters u and .theta.. In this connection, the u axis is the axis which passes through the origin O and which is perpendicular to a straight line connecting the X-ray source S and reconstruction point 18, and u indicates a position on the u axis. Further, .theta. is an angle between the u axis and X axis. According to the equation (9) set forth in the aforementioned journal "Optical Society of America", p. 613, an X-ray factor f(X,Y) for the subject at a point (X,Y) is written as follows, assuming that the X-ray transmission image of the subject by the X-ray beams expressed in terms of the parameters u and .theta. has an intensity p(u,.theta.): ##EQU5## u.sub..theta. : Unit vector in .mu. axis direction .smallcircle.: Inner product PA1 y.sub..phi. : Unit vector in y-axis direction PA1 (1) Procedure for filter correction of projection data: This is expressed by the following equation. ##EQU11## (2) Procedure for back projection of data subjected to filter-correction: PA1 (1) With respect to each of the plurality of rotation turns, sequential reconstruction is carried out within the reconstructible area and projection data not detected for each turn is not processed. This is for the purpose of avoiding such a problem that the projection data not detected are used as data for the image reconstruction. PA1 (2) With regard to the detected projection data, an overlapping degree of the projection data for the overall rotation turns is found for averaging and selection. The projection data which may or may not be overlapped for the plural rotation turns are modified by the averaging or selection. PA1 (3) Of the above detected projection data, the projection data present in the peripheral area of view field are handled as not detected in the operation (1). In other words, the unsuitable projection data are not used as the image reconstruction data. In the equation (12), r represents a vector indicative of the position of the reconstruction point 18 when viewed from the origin O of the (X,Y) coordinate system, and u.sub..theta. represents a unit vector in the u axis direction. A filter for correction of projection data is expressed in terms of the following equation (13). ##EQU6## Such filters include, as typical ones, a Ramachandran filter and a Shepp and Logan filter. Shown in FIG. 12 represents position of the target beam in the X-ray transmission image for the subject in the moving center coordinate system. In FIG. 12, the position of the X-ray beam irradiated from the X-ray source S and passed through the reconstruction point 18 is expressed in terms of two parameters y and .phi. of the moving center coordinate system. In this case, the x axis has the O.sub..phi. as its origin and pointed toward a direction of a straight line connecting the X-ray source S and rotation center O.sub..phi.. Further, the y axis has the O.sub..phi. as its origin and pointed toward a direction perpendicular to the x axis. Parameter y represents a position on the y axis. Parameter .phi. denotes a rotational angle relative to the X axis of the X-ray source S. In FIG. 12, such a fixed center coordinate system (X,Y) as shown in FIG. 11 is also depicted as overlapped. In this way, in order to uniquely express the position of the X-ray beam in terms of the parameters y and .phi. in the moving center coordinate system, it is necessary that at least the locus of the X-ray source S forms a closed loop on the (X,Y) plane. This means that, when the imaging unit is rotated by one turn with respect to the X axis, that is, when the parameter .phi. varies from 0 radians to 2.pi. radians, the rotation center O.sub..phi. is required to return to its original position on the (X,Y) plane. Accordingly, if this condition is satisfied, and if and only if all the X-ray beams passed through the reconstructible area are uniquely expressed in terms of the parameters of the moving center coordinate system; p(u,.theta.) indicative of the intensity of the X-ray transmission image can be rewritten as p.sub..phi. (y) with use of the parameters y and .phi. of the moving center coordinate system. In this case, the parameters u and .phi. can be given as follows. ##EQU7## 0.sub..phi. : Rotation center vector .smallcircle.: Inner product x.sub..phi. : Unit vector in x-axis direction In the equation (14), O.sub..phi. represents a vector indicative of the position of the rotation center expressed in the (X,Y) coordinate system, r represents a vector indicative of the position of the reconstruction point 18 as viewed from the origin O of the (X,Y) coordinate system, and x.sub..phi. and y.sub..phi. represent unit vectors in x and y directions respectively. Considering the following relationships (15), ##EQU8## .smallcircle.: Inner product the equation (12) is rewritten as follows with use of the parameters y and .phi.. ##EQU9## .smallcircle.: Inner product The position of the reconstruction point 18 as viewed from the origin 0 of the (X,Y) coordinate system moving together with the rotation is expressed as: EQU .rho..sub.101 =r-O.sub..PHI. (17) The f.sub.2 in the equation (16) is rewritten as the following equation (19) with use of the following equation (18). ##EQU10## Hence, when one-turn rotation of the imaging unit including the X-ray source S and X-ray detection unit 4' around the subject causes the rotation center O.sub..phi. to return to the original position relative to the subject, f.sub.2 is expressed in terms of line integral and has a value of 0 according to the Cauchy integral theorem. This movement condition, which is the condition necessary to uniquely express the position of the X-ray beam with use of the parameters y and .phi. in the moving center coordinate system, is required to be always satisfied. Thus, it will be appreciated that reconstruction is only required to perform the reconstruction according to the equation (16) when f(X,Y)=f.sub.1. Although explanation has been made as to the reconstruction method based on the use of the moving center coordinate system, explanation will next be directed to a calculation method when the imaging unit is rotated by a plurality of turns to enlarge the reconstructible area in the imaging system of the present embodiment. In general, since the view field (input plane of the X-ray) of an X-ray detector is smaller than the size of a subject, it is impossible to collect all the data necessary for the reconstruction in the enlarged reconstructible area in each of the plurality of turns of the imaging unit. Thus, the reconstruction requires all the projection data separately collected through the plurality of turns to be rearranged in the form of projection data in a unified coordinate system. As the unified coordinate system, a fixed center coordinate system or a moving center coordinate system with respect to a certain rotation may be considered. Either case, however, involves such a difficulty that all the projection data must be rearranged. Further, in a cone-beam X-ray CT apparatus for performing reconstructing operation over an 3-dimensional image of a subject with use of a 2-dimensional X-ray detector, the reconstruction is carried out with use of the projection data of the subject based on X rays irradiated from an X-ray source in a cone shape, which results in that it is impossible in the unified coordinate system to rearrange the projection data in an identical spatial plane. This is a problem inherent in the cone-beam X-ray CT apparatus, which means that the reconstruction method based on the rearrangement of the projection data cannot be applied to the cone-beam X-ray CT apparatus. In accordance with the present embodiment, with regard to each of a plurality of rotation turns of the imaging unit, the aforementioned moving center coordinate system is employed to perform sequential reconstructing operation, and as projection data insufficient for each turn rotation, projection data obtained in another rotation are approximately used. As a result, the reconstruction for obtaining the X-ray 3-dimensional image for the subject can be realized while eliminating the need for rearranging the projection data. Here, the equation f(X,Y)=f.sub.1 for reconstruction of the moving center coordinate system includes two procedures (1) and (2) which follow. This is expressed by the following equation. ##EQU12## The filter correction procedure of projection data is expressed in terms of a convolution integral having the projection data and correction filter, so that, during the reconstruction, this procedure is carried out as a preprocessing over X-ray projection images in every angle direction .phi.. In the back projection procedure, on the other hand, the projection data subjected to the filter correction are back-projected as the projection data irradiated from the X-ray source S and passed through the reconstruction point 18 are overlapped from every direction within 360.degree.. FIG. 13 shows positional relationships between the X-ray transmission image and X-ray detector (X-ray input screen) in the present imaging system. The two loci 16 of the X-ray source S correspond to movements of the subject in positive and negative directions. In this case, with regard to a plurality of rotation turns of the imaging unit, the reconstruction is carried out based on the respective moving center coordinate systems and includes such procedures as mentioned above, i.e., the projection-data filtering and back-projecting procedures. In the illustrated example, in the back-projection procedure of each turn rotation, there may exist such a situation that, as shown in FIG. 13A for example, projection data is present for a turn rotation but not present for another. There may occur such another situation that, as shown in FIG. 13B, projection data in the respective turn rotations are overlapped. Another situation may be present where projection data is present for a turn rotation but is present in a peripheral area 19 of view field on the X-ray input screen of the X-ray detector. In the case of FIG. 13C, the projection image breaks off in the peripheral area of the view field and thus is influenced by the projection-data correcting filter. To avoid this, in the present embodiment, back-projection is carried out taking the following processings into consideration. Of the projection data necessary for the image reconstruction, the projection data not obtained due to the fact that the presence outside the view field or in the peripheral area of the view field for one rotation turn, are built in another rotation turn through the above operation (1). Further, Of the projection data necessary for the image reconstruction, the projection data overlapped for the plural rotation turns are previously averaged or selected through the above operation (2), whereby no overlapping will take place in the reconstruction. In this way, in the above image reconstruction method, projection data obtained in one rotation turn are substituted for projection data lacking in another rotation turn. However, in the (X,Y) coordinate system moving together with the rotation, the locus of movement of the rotation center O.sub..phi. of the imaging unit varies from rotation to rotation and thus the moving center coordinate system correspondingly varies from rotation to rotation, with the result that, in the strict sense, projection data collected for one rotation turn cannot be substituted for projection data lacking for another rotation. More specifically, such influence to the projection data by the coordinate system difference takes place in the course of the filtering operation. In the (X,Y) coordinate system moving together with the rotation, however, since the displacement distance of the rotation center O.sub..phi. with respect to the rotation radius of the imaging unit is not so large, this influence is highly light and thus can be practically negligible. FIG. 14 is a flowchart for explaining the back projection procedure in the reconstruction method of the present invention. In the drawing, n denotes n-the rotation and N denotes a total number of rotations. Further, .DELTA..phi. represents a rotational step angle in the imaging unit. In the earlier-explained apparatus in connection with the foregoing embodiment, N=2, .DELTA..phi.=1.25.degree.. The back projection is carried out for the first to N-the rotations in this order. In FIG. 14, the back projection is started at a step 101 and initialized for the first rotation at a step 102, and control is shifted to the next rotation at a step 107. When it is judged at a step 103 that the N-turn rotation was completed, the back projection is terminated at a step 104. In the respective rotation turns, the rotational angle .phi. is increased from 0.degree. to 360.degree. and the back projection is carried out for each angle of the rotation turns. In FIG. 14, the rotational angle .phi. is initialized at 0 degrees at a step 105 and is increased at a step 113 in increments of .DELTA..phi.. When the rotational angle .phi. becomes 360.degree. at a step 106, control goes to the step 107 for the next rotation. At each of the rotational angles, it is judged whether projection data based on the X-ray emitted from the X-ray source S and passed through the reconstruction point 18 is present (step 108). The presence of the projection data is determined, it is judged whether the projection data is present in the peripheral area of view field on the X-ray input screen 4" of the X-ray detection unit 4'(step 109). Projection data not present in the peripheral area then is subjected to calculation of its overlapping degree (step 110) for its previous averaging or selection (step 111), and then subjected to a back projection (step 112). When it is judged at the step 108 that the projection data is not present, no back projection is carried out and control goes to the step 113 to move to the next rotational angle. The determination of the presence of the projection data at the step 108 causes control to go to the next step 109 where it is judged whether the projection data is present in the peripheral area of the X-ray input screen 4" of the X-ray detection unit 4'. In this case, the projection data judged as present in the peripheral area break off on the way, which may possibly involve the influence of the projection data correcting filter. To avoid this, no back projection is carried out and control is shifted to the step 113 for the operation of the next rotational angle. Data for the rotational angle of another rotation is instead used for the back projection. That is, the projection data influenced by the correcting filter is not used as the data of the image reconstruction. The projection data is judged as not present in the peripheral area, it is examined at the step 109 whether the projection data is overlapped with the projection data of another rotation and also its overlapping degree is examined. At the step 111, further, the averaging or selection of the projection data is carried out on the basis of the overlapping degree. Such operation is carried out because the information detected through the rotation of the X-ray source S include the projection data obtained as multiple-overlapped depending on the position (area) of the subject and the projection data obtained as not multiple-overlapped depending thereon. In addition, the averaging is for the purpose of improving the S/N ratio. Thereafter, back projection is carried out at the step 112. Finally, control is moved to the step 113 for the operation of the next rotation angle. Shown in FIGS. 15A to 15C are target beams in the X-ray transmission image of a subject which pass through the peripheral area of view field of the X-ray input screen 4" of the X-ray detection unit 4', for explaining how to judge at the step 109 of FIG. 14 whether the projection data is present in the peripheral area. In FIGS. 15A to 15C, the two loci 16 of the X-ray source S correspond to movements of the subject in positive and negative directions. As mentioned above, the reconstruction procedure of the X-ray image includes the filter correction procedure of the projection data and the back projection procedure of the projection data subjected to the filter correction. The filter correction procedure of the projection data, as shown by the equation (20), is expressed in terms of a convolution integral of the projection data and correcting filter, so that, when the projection image of the subject is out of the view field of the X-ray input screen 4" of the X-ray detection unit 4', the projection image breaks off in the peripheral area of the view field and thus is influenced by the projection data correcting filter. When a Shepp and Logan filter for example is employed as the projection data correcting filter, the correction function takes such a digital signal as shown by FIG. 15A. In this case, the amplitude of the correction function decrements in proportion to the square of a distance from the center. In FIG. 15A, when the amplitude at the center is "1" for example, the amplitude decrements to 1/99 at a point away from the center by 5 channels and to 1/1599 at a point away from the center by 20 channels, with a sampling pitch as a unit. For this reason, the influence of the projection data correcting filter caused by the break-off of the projection image appears in the ranges 19a of the view field peripheral area corresponding to about 20 channels as shown in FIG. 15B, the distance corresponding to the about 20 channels depends on the channel interval on the detector. For example, in the case of the apparatus previously explained in connection with the present embodiment, when the detector has a width of 380 mm and the number of channels is 512 points, a distance corresponding to 20 channels is 14.8 mm and the detector has an effective width of 350.3 mm. Since the projection data in the peripheral area are discharged (which corresponds to the shift of control to the step 113 of FIG. 14), and in order to prevent the effective width of the detector from being decreased as mentioned above, the projection data are subjected to an extrapolation by some means in ranges 19b located outside the view field peripheral area of the X-ray input screen 4" of the X-ray detection unit 4' as shown in FIG. 15C. In this connection, simple examples of the extrapolation include, for example, a method for using, as extrapolation data, the data obtained at outermost ends of the X-ray input screen 4" of the X-ray detection unit 4' as they are and a method for approximating the shape of a subject as a simple geometrical figure such as ellipse to estimate extrapolation data. In this way, all the projection data detected within the X-ray input screen 4" of the X-ray detection unit 4' can be effectively used. FIG. 16 is a diagram for explaining how to find the overlapping degree of the projection data in the reconstruction method based on the moving center coordinate system (, which corresponds to the step 110 in FIG. 14). In FIG. 16, n denotes the n-th rotation in a total of N rotations. For the sake of explanation simplicity, only (n-1)-th, n-th, and (n+1)-th rotations are illustrated- Symbol 16(n) denotes the n-th rotation locus (rotation orbit), and along which the X-ray source S (which is indicated by S(n) on the n-th rotation orbit) is moved. Here is how to find the overlapping degree of the projection data when the X-ray source S is located in the n-th rotation with a rotational angle .phi.. In FIG. 16: (a1) Draw a half line 20 from the reconstruction point 18 toward the position S(n) of the X-ray source at the n-th rotation. (a2) Assume that there is an X-ray source S(k) on an intersection of the half line 20 and the k-th rotation orbit 16(k) (k=1-N). (a3) Examine whether the reconstruction point 18 is located within the view field with respect to the X-ray source S(k). (a4) When the total number of S(k) which contains the reconstruction points 18 within their view field is M (M=1-N), the overlapping degree of the reconstruction point 18 for the rotational angle .phi. is M. In this case, the above steps (a1) to (a4) are carried out according to a previously-set sequence and selection of the M is carried out on the basis of the sequence. With regard to the overlapping degree M thus obtained, for the purpose of making the most of the projection data as much as possible, the projection data are divided by M and then subjected to a back projection to previously find an average of the projection data. When the projection data are selected on the basis of some unified judgement criteria, the projection data not selected are regarded as has not been present and thus not subjected to the back projection and only the selected data are subjected to the back projection (, which corresponds to the step 111 in FIG. 14). Although explanation has been made from the viewpoint of explanation simplicity in connected with the reconstruction area in the 3-dimensional reconstruction is limited only to the 2-dimensional area on the rotation orbit of the X-ray source, explanation will next be expanded to the three-dimensional area. The earlier-cited journal "Optical Society of America" describes a Feldkamp's 3-dimensional reconstruction method wherein, of all the reconstruction points of an X-ray 3-dimensional image of a subject, a fixed center coordinate system is directly used with respect to the reconstruction points included within the rotational plane of an imaging unit; whereas, the fixed center coordinate system is also used with respect to the reconstruction points not included within the rotational plane, under the assumption that a plane, which includes the X-ray generation point and the reconstruction points and a line parallel to the rotation plane at the same time, is regarded approximately as the rotational plane, whereby the fixed center coordinate system is expanded to the entire 3-dimensional space for reconstruction. Accordingly the calculation method is based on the two-dimensional calculation method. In reconstruction equation f(X,Y)=f.sub.1 defined in the moving center coordinate system in the present invention, when the position of the rotation center O.sub..phi. to the subject is set always at 0, this equation indicates a prior art 2-dimensional reconstruction in the fixed center coordinate system. Here, the equation (17) indicative of the position of the reconstruction point as viewed from the rotation center O.sub..phi. is written as follows, indicating the position of the reconstruction point as viewed from the origin O of the absolute coordinate system fixed to the subject. EQU .rho..sub..PHI. =r (22) This means that, when the equation (22) is replaced by the equation (17), the reconstruction equation defined in the prior art fixed center coordinate system is converted to a reconstruction equation defined in the moving center coordinate system. Therefore, in the above Feldkamp's method in which the fixed center coordinate system is expanded to the 3-dimensional space, when the equation (22) is replaced by the equation (17), the moving center coordinate system can be expanded to a 3-dimensional space as in the above case. FIG. 17 shows the beam of a target beam in an X-ray transmission image of a subject in a moving center coordinate system expanded to a 3-dimensional space, corresponding to FIG. 12 expanded to the 3-dimensional space. In FIG. 17, z axis passes through the rotation center O.sub..phi. and intersects the X-Y plane perpendicular thereto. In this case, in the Feldkamp's reconstruction method shown by the equations (28) to (32) and explained on page 615 of the above journal "Optical Society of America", when the equation (22) is replaced by the equation (17), its result is as follows. ##EQU13## z.sub..phi. : Unit vector in z-axis direction .smallcircle.: Inner product In the equation, p.sub..phi. (y,z) indicates the intensity of an X-ray transmission image of a subject based on an X-ray beam which is irradiated from the X-ray source S and which passes through a point (y,z) in a moving center coordinate system, and rotation center z.sub..phi. indicates a unit vector in the z direction. Reconstruction of a 3-dimensional X-ray transmission image can be realized with use of the equation (23). FIG. 18 is a diagram for explaining how to find the overlapping degree of projection data in the reconstruction method based on the moving center coordinate system expanded to the 3-dimensional space, corresponding to a representation of FIG. 16 expanded to the 3-dimensional space. In FIG. 18, n denotes the n-th rotation in a total of N rotations and only the (n-1)-th, n-th and (n+1)-th rotations are illustrated for simplicity of the drawing. Assume now that the X-ray source S is present with a rotational angle .phi. at the n-th rotation. Then, how to find an overlapping degree is as follows. In FIG. 18: (b1) First, set a line extended from the reconstruction point 18 perpendicular to the rotation orbit plane of the X-ray source S so as to intersect the rotation plane at a pseudo reconstruction point 18a. (b2) Draw the half line 20 from the pseudo reconstruction point 18a toward the position S(n) of the X-ray source at the n-th rotation. (b3) Assume that and X-ray source S(k) is present at an intersection of the half line 20 and the rotation orbit 16(k) of the k-th rotation (k=1-N). (b4) Examine the X-ray source S(k) to see if the reconstruction point 18 is within the view field. (b5) When the total number of S(k) which contains the reconstruction points within the view field is M (M=1-N), the overlapping degree at the rotational angle .phi. for the reconstruction point 18 is M. When the overlapping degree M thus found is used for the averaging or selection of projection data, this can be carried out in substantially the same manner as in the 2-dimensional space. In the above 3-dimensional reconstruction method of FIG. 18, the projection data based on beams irradiated from the X-ray source S(n) (n=1-N) and passed through the reconstruction point 18 are handled as if they were obtained from the beams irradiated from the X-ray source S(n) and passed through the pseudo reconstruction point 18a, so that the 2-dimensional reconstruction method can be expanded approximately to the 3-dimensional reconstruction method. Thus, the smaller an offset a(n) in the projection angle of the above 2 projections is the higher the above approximated accuracy is. Therefore, when one of overlapped M projection data emitted from the X-ray source located at the farmost position from the pseudo reconstruction point 18a is always selected as one example of the above projection data selection, the reconstruction can be realized with the optimum approximate accuracy. The 3-dimensional reconstruction method has been explained in the above. The reconstruction method of the present invention includes a correction procedure of projection data and a back projection procedure of a projected image subjected to the filter correction. When the overlapping degree of the projection data is found, data lacking or overlapped for the respective rotations can be estimated based on the overlapping degree. Accordingly, reconstruction can be carried out simultaneously with the collection of X-ray projection data while eliminating the need for awaiting the completion of collection of all the data, a series of works from the data collection to the reconstruction of the X-ray 3-dimensional image can be concurrently carried out efficiently at high speed. Further, with regard to the X-ray 3-dimensional image sequentially being reconstructed by the back projection, when intermediate results of the reconstruction are sequentially displayed, the user can quickly confirm the state of the subject. As will clear from the foregoing explanation, in the X-ray CT scan of the present embodiment, the subject 14 is reciprocated along a straight line that is parallel to the rotation plane while the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated around the subject 14, and the X-ray transmission images are detected from a plurality of directions, as a result there can be obtained an X-ray CT image which has an area wider than the view field of the X-ray input screen 4" of the X-ray detection unit 4' in a direction parallel to the rotation plane of the X-ray tube 2. As a result, since the view field of a transaxial sectional plane of the X-ray CT image can be enlarged, such diagnostic ability as lung cancer can be improved. (Embodiment 2) FIG. 6 is a front view, in model form, of a second embodiment of the present invention for explaining the operation of the second embodiment. In the present embodiment, as shown in FIG. 6, at the A stage (start stage), the pair of the X-ray tube 2 and X-ray detection unit 4' is in the vertical direction and the center (body axis) of the subject 14 is located at the left end. At the same time the X-ray tube 2 and X-ray detection unit 4' in pair start to rotate in the clockwise direction, the subject 14 also starts to move rightwardly in the horizontal direction on the rotation plane passing through the rotation center O, to start the fluoroscopic or radiographic operation. At the B stage to which the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated by -90.degree. from the start stage A, the pair of the X-ray tube 2 and X-ray detection unit 4' is reversed in the rotation direction to the counterclockwise direction. At the C stage to which the pair is rotated +90.degree. from the start stage of the counterclockwise rotation, that is, at the stage that the pair of the X-ray tube 2 and X-ray detection unit 4' returns to the start stage A, the movement direction of the subject 14 is reversed to the horizontal, leftward direction. At the stage E to which the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated +180.degree. from the start stage A, the movement direction of the subject 14 is reversed to the horizontal, rightward direction. At the F stage to which the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated +270.degree. from the start stage A, the pair of the X-ray tube 2 and X-ray detection unit 4' is reversed in the rotation direction to the clockwise direction. At the G stage to which the pair is rotated -90.degree. from the start stage of the clockwise rotation, the movement direction of the subject 14 is reversed to the horizontal, leftward direction. At the I stage after another -180.degree. rotation, that is, again at the start stage A, the rotation of the pair of the X-ray tube 2 and X-ray detection unit 4' as well as the movement of the subject 14 are stopped to terminate the fluoroscopic or radiographic operation. In the present embodiment, the position of the moving subject 14 varies with time in accordance with a sinusoidal wave function as in the embodiment 1. In accordance with the present invention, the imaging area of the subject 14 can be estimated on the basis of the fluoroscopic or radiographic image at the A stage and the image at the C stage, returned after the -90.degree. rotation and then reversion of the pair of the X-ray tube 2 and X-ray detection unit 4' from the start stage A. The reconstruction of the X-ray CT image when the imaging system follows the present embodiment can be realized in the same manner as the method set forth in the embodiment 1. (Embodiment 3) In a third embodiment of the present invention, the pair of the X-ray tube 2 and X-ray detection unit 4' is rotated and at the same time, reciprocated in one direction so that a relative positional relationship between the pair of the X-ray tube 2 and X-ray detection unit 4' and the subject 14 becomes equal to that in the foregoing embodiment 1 or 2 without moving the subject 14. Further, the pair of the X-ray tube 2 and X-ray detection unit 4' may be reciprocated in two directions at the same time. In this way, since the subject 14 is not moved, the mental and physical pain of the subject 14 can be softened. (Embodiment 4) In a fourth embodiment of the present invention, the position of the moving subject 14 varies with time in accordance with a rectangular or trapezoidal wave function, or such an orbit that the moving subject 14 describes number "8", though the position of the moving subject 14 varies with time in accordance with the sinusoidal wave function in the foregoing first and second embodiments. The reconstruction of the X-ray CT image when the imaging system follows the present embodiment can be carried out in the same manner as in the embodiment 1. (Embodiment 5) In a fifth embodiment of the present invention, the subject 14 is moved not only in a plane parallel to the rotation plane of the pair of the X-ray tube 2 and X-ray detection unit 4' but also in the vertical direction. Explanation will be made as to the reconstruction method of an X-ray CT image when the imaging system follows the present embodiment. As a generalized method corresponding to a generalization of the Feldkamp's 3-dimensional reconstruction method described in the aforementioned journal "Optical Society of America", there is a Ge Wang's method set forth in the aforementioned IEEE transactions on medical imaging. In this method, a subject is moved in the direction of the rotation axis of an imaging unit including the X-ray tube 2 and X-ray detection unit 4' to thereby enlarge the view field of the subject with respect to the rotation axis direction, which reconstruction algorithm basically utilizes the Feldkamp's reconstruction algorithm. Accordingly, in the present invention, the moving center coordinate system can be applied even to the above Ge Wang's reconstruction method in the same manner as the moving center coordinate system is applied to the above Feldkamp's reconstruction method. Though specific reconstruction equations are omitted here, its brief explanation is that, in the equation (10) set forth on page 489 of the aforementioned IEEE transactions on medical imaging, the above equation (22) is replaced by the equation (17), that is, the position of a reconstruction point expressed in an absolute coordinate system fixed to the subject is replaced by a relative position when viewed from the rotation center O.sub..phi.. As a result, the moving center coordinate system can be applied the above Ge Wang's reconstruction method. Descriptions of the "Optical Society of America" and "IEEE transactions on medical imaging" are incorporated herein by reference. In this case, the imaging is carried out by rotating the imaging unit around the subject by a plurality of turns and at the same time, by moving the subject in directions vertical to the rotation plane of the subject and parallel thereto. In this way, the imaging view field to the subject can be expanded to the directions parallel and vertical to the rotation plane. For example, when the rotation of the imaging unit is carried out 4 turns, the position of the rotation center O.sub..phi. of the imaging unit at each turn rotation is expressed as follows in an (X,Y,Z) coordinate system fixed to the subject. ##EQU14## where l denotes a movement distance of the rotation center O.sub..phi. of the imaging unit in the direction of the rotation axis when the imaging unit rotates by one turn. Further, .phi..sub.1,2 and .phi..sub.3,4 denote rotational angles at the first, second and third, fourth rotations of the imaging unit, respectively, and vary with time in accordance with the following equations (25). ##EQU15## Such movement can be easily realized by moving the bed board carrying the subject sinusoidally in left or right direction and at the same time, by reciprocating it in the body axis direction. Shown in FIG. 19 is a relationship between the X-ray source S and the moving locus 16 of the X-ray source S when the movement of the rotation center O.sub..phi. follows the above equations (24). In FIG. 19, the locus of the X-ray source S is a spiral locus surrounding the subject. Also shown in FIG. 20 is a diagram for explaining how to find an overlapping degree of projection data in the above imaging system wherein the subject is moved in the directions horizontal and vertical to the rotation plane of the imaging unit. In FIG. 20, n denotes the n-th rotation of a total N of rotations, but for the sake of drawing simplicity, only (n-1)-th, n-th and (n+1)-th rotations are illustrated. When the X-ray source S is assumed to be located with a rotational angle .phi. at the n-th rotation, an overlapping degree is found in the following manner. (c1) Consider in FIG. 20 a half plane 23 which passes through the reconstruction point 18 and the position S(n) of the X-ray source at the n-th rotation, which intersects the XY plane vertically thereto and also has the reconstruction point 18 in its boundary. (c2) Assume that the X-ray source S(k) is present at an intersection of the half plane 23 and the k-th rotation orbit 16(k) (k=1.about.N). (c3) With respect to each X-ray source S(k), examine whether the reconstruction point 18 is within the view field, (c4) When the total number of S(k) which contains the reconstruction points 18 within the view field is M (M=1.about.N), an overlapping degree at the reconstruction point 18 for the rotational angle .phi. is M. When the overlapping degree M thus found is used for the averaging or selection of the projection rdata, this is carried out in the same manner as in the 2-dimensional method already explained above. Although the present invention has been detailed in connection with the specific embodiments of the invention, it will be appreciated that the invention is not restricted to the specific embodiments but may be modified in various ways without departing from the gist of the invention. It goes without saying that the present invention can be applied, for example, to general X-ray fluoroscopic systems, X-ray radiographic systems, stereoscopic X-ray imaging systems, and the like.
	claims	1. A nuclear fuel assembly storage rack sleeve assembly for refurbishing a fuel rack having cells in which fresh or spent nuclear fuel assemblies may be stored, the cells defined by elongate rack walls extending from a rack base plate, the rack base plate having flow holes extending therethrough communicating with the cells, comprising: a sleeve having at least one elongate wall fixedly attached to a sleeve base plate, the sleeve base plate having a first side disposed above a second opposed side and defining a flow hole extending from the first side to the second opposed side, the elongate wall extending upwardly from the first side of the sleeve base plate; and a pin assembly disposed in the sleeve base plate flow hole and hating at least one resilient tab, the resilient tab extending downwardly through the flow hole in the sleeve base plate and beyond the second opposed side of the sleeve base plate for extending into a rack base plate flow hole and resiliently engaging the rack base plate when the sleeve assembly is installed in one of the cells. 2. The sleeve assembly of claim 1 , wherein the at least one resilient tab is one of a plurality of resilient tabs that extend beyond the second side of the sleeve base plate for resiliently engaging the rack base plate when the tabs extend into a rack base plate hole. claim 1 3. The sleeve assembly of claim 1 , wherein the at least one tab has an intermediate section with a surface facing and substantially parallel to the second side of the sleeve base plate for engaging the rack base plate when the tab extends into the rack flow hole. claim 1 4. The sleeve assembly of claim 3 , wherein the at least one tab has an end section which extends from the intermediate section at an acute angle. claim 3 5. The sleeve assembly of claim 1 , wherein the at least one tab extends from a tubular portion of the pin assembly. claim 1 6. The sleeve assembly of claim 5 , wherein the at least one tab has an intermediate section with a surface facing and substantially parallel to the second side of the sleeve base plate. claim 5 7. The sleeve assembly of claim 6 , wherein the intermediate section of the at least one tab extends outwardly of the tubular portion of the pin assembly. claim 6 8. The sleeve assembly of claim 7 , wherein the at least one tab has an end section which extends from the intermediate section at an acute angle inwardly of the tubular portion of the pin assembly. claim 7 9. The sleeve assembly of claim 1 , wherein the pin assembly is of integral construction. claim 1 10. The sleeve assembly of claim 1 , wherein the pin assembly is welded to the sleeve assembly base plate. claim 1 11. The sleeve assembly of claim 1 , wherein the sleeve assembly comprises an extrusion comprised of boron carbide and aluminum. claim 1 12. The sleeve assembly of claim 11 , wherein the sleeve base plate is comprised of boron carbide and aluminum. claim 11 13. The sleeve assembly of claim 12 , wherein the sleeve base plate has at least one undercut keyway for receiving an installation tool. claim 12 14. The sleeve assembly of claim 2 , wherein the plurality of resilient tabs are spaced apart and the spaces between adjacent resilient tabs extend above the second opposed side of the sleeve base plate. claim 2 15. The sleeve assembly of claim 3 installed in a fuel rack cell defined by elongate walls extending above a fuel rack base plate, with the sleeve assembly base plate and the elongate walls of the fuel rack cell defining a clearance width wherein the tab intermediate section of the pin assembly is longer than the clearance width. claim 3 16. The sleeve assembly of claim 15 , wherein the pin assembly has a plurality of spaced apart resilient tabs and each tab has an intermediate section that is longer than the clearance width defined by the sleeve assembly base plate and the elongate walls of the fuel rack cell. claim 15
	claims	1. A debris trap for separating debris from water in a flowpath of an Emergency Core Cooling System (ECCS) of a nuclear power plant, the debris trap comprising:filtration media for separating at least some of the debris from the water in response to the water flowing through said filtration media;a plurality of filtration flowpaths at least partially defined by said filtration media, whereinfor each filtration flowpath of said plurality of filtration flowpaths, said filtration flowpath extends from upstream of said filtration media to downstream of said filtration media, andmultiple filtration flowpaths of said plurality of filtration flowpaths extend through both a first portion and a second portion of said filtration media, so that said first portion and said second portion of said filtration media are arranged in series with respect to one another in said filtration flowpath;a bypass flowpath at least partially defined by said filtration media, wherein said bypass flowpath extendsbetween said first portion and said second portion of said filtration media, andalong each of said first portion and said second portion of said filtration media; andsaid plurality of filtration flowpaths being configured for at least initially having a lower head loss than said bypass flowpath, and said plurality of filtration flowpaths and said bypass flowpath being in fluid communication with one another, so that the debris trap is operative for automatically, passively decreasing flow through said plurality of filtration flowpaths and increasing flow through said bypass flowpath in response to said filtration media collecting increasing amounts of the debris. 2. The debris trap according to claim 1, wherein said plurality of filtration flowpaths and said bypass flowpath being in fluid communication with one another comprises:upstream ends of said plurality of filtration flowpaths and said bypass flowpath being in fluid communication with one another; anddownstream ends of said plurality of filtration flowpaths and said bypass flowpath being in fluid communication with one another. 3. The debris trap according to claim 2, wherein said plurality of filtration flowpaths and said bypass flowpath being in fluid communication with one another further comprises midstream segments of said plurality of filtration flowpaths and said bypass flowpath being in fluid communication with one another. 4. In combination, the debris trap according to claim 1, and a strainer, wherein the strainer and the debris trap are both positioned in the flowpath of an ECCS, wherein:said debris trap is in a position selected from the group consisting ofupstream of said strainer in the flowpath of the ECCS, anddownstream of said strainer in the flowpath of the ECCS; andsaid debris trap is adapted for at least initially separating relatively small debris from the flowpath, whereas said strainer is adapted for separating relatively large debris from the flowpath. 5. The combination according to claim 4, wherein:said debris trap is positioned upstream of said strainer in the flowpath of the ECCS; andsaid debris trap extends at least partially around said strainer. 6. The combination according to claim 5, wherein said debris trap comprises a plurality of debris trap modules that extends at least partially around said strainer. 7. The debris trap according to claim 1, comprising first and second filtration partitions that are in opposing face-to-face configuration with respect to one another, wherein:said first filtration partition comprises said first portion of said filtration media; andsaid second filtration partition comprises said second portion of said filtration media. 8. A debris trap for separating debris from water in a flowpath of an ECCS of a nuclear power plant, the debris trap comprising:a plurality of filtration partitions, wherein each filtration partition of said plurality of filtration partitions is configured for separating at least some of the debris from the water in response to the water flowing through said filtration partition, and said plurality of filtration partitions comprises first and second filtration partitions;a plurality of filtration flowpaths at least partially defined by said plurality of filtration partitions, wherein said plurality of filtration flowpaths extends through both of said first and second filtration partitions, and said first and second filtration partitions are arranged in series in said plurality of filtration flowpaths;a bypass flowpath at least partially defined by said plurality of filtration partitions, wherein said bypass flowpath extends along each of said first and second filtration partitions; andsaid plurality of filtration flowpaths being configured for at least initially having a lower head loss than said bypass flowpath, and said plurality of filtration flowpaths and said bypass flowpath being in fluid communication with one another, so that the debris trap is operative for automatically, passively decreasing flow through said plurality of filtration flowpaths and increasing flow through said bypass flowpath in response to said plurality of filtration partitions collecting increasing amounts of the debris. 9. The debris trap according to claim 8, wherein:with regard to said plurality of filtration flowpaths, each of said first and second filtration partitions has an upstream side and a downstream side; andsaid bypass flowpath extends along each of said upstream and downstream sides of each of said first and second filtration partitions, so that each of said upstream and downstream sides of each of said first and second filtration partitions partially define said bypass flowpath. 10. The debris trap according to claim 8, wherein: each of said first and second filtration partitions includes opposite first and second edges; said first edge of said first filtration partition is closer to said first edge of said second filtration partition than to said second edge of said second filtration partition; said bypass flowpath extends around both said first edge of said first filtration partition and said second edge of said second filtration partition; and the debris trap includes a structure for restricting said bypass flowpath from extending around said second edge of said first filtration partition. 11. The debris trap according to claim 10, wherein:said second edge of said first filtration partition is selected from the group consisting of a bottom edge of said first filtration partition, a side edge of said first filtration partition, and a top edge of said first filtration partition; andsaid structure is selected from the group consisting of a basement floor proximate said second edge of said first filtration partition, an upright structural member proximate said second edge of said first filtration partition; and a top cover proximate said second edge of said first filtration partition. 12. The debris trap according to claim 8, wherein:said plurality of filtration partitions comprises a third filtration partition;said first and third filtration partitions are spaced apart from one another and extend away from structure so that said first and third filtration partitions together with said structure at least partially define a cavity; andsaid second filtration partition extends into said cavity, is recessed from said structure, and is spaced apart from said first and third filtration partitions so thatan upstream segment of said bypass flowpath is at least partially defined between said first and second filtration partitions,an intermediate segment of said bypass flowpath is at least partially defined between said second filtration partition and said structure, anda downstream segment of said bypass flowpath is at least partially defined between said second and third filtration partitions. 13. A debris trap for separating debris from water in a flowpath of an ECCS of a nuclear power plant, the debris trap comprising:a plurality of filtration partitions, wherein each filtration partition of said plurality of filtration partitions is configured for separating at least some of the debris from the water in response to the water flowing through said filtration partition, and said plurality of filtration partitions comprises first, second and third filtration partitions;a plurality of filtration flowpaths at least partially defined by said plurality of filtration partitions, wherein said plurality of filtration flowpaths extends through each of said first, second and third filtration partitions, and said first and second filtration partitions are arranged in series in said plurality of filtration flowpaths;a bypass flowpath at least partially defined by said plurality of filtration partitions, wherein said first and third filtration partitions are spaced apart from one another and extend away from a structure so that said first and third filtration partitions together with said structure at least partially define a cavity, and wherein said second filtration partition extends into said cavity, is recessed from said structure, and is spaced apart from said first and third filtration partitions so that an upstream segment of said bypass flowpath is at least partially defined between said first and second filtration partitions,an intermediate segment of said bypass flowpath is at least partially defined between said second filtration partition and said structure, anda downstream segment of said bypass flowpath is at least partially defined between said second and third filtration partitions. 14. The debris trap according to claim 13, wherein said first, second and third filtration partitions are substantially parallel to one another. 15. The debris trap according to claim 13, wherein:each of said first, second and third filtration partitions is substantially cylindrical;said first filtration partition extends at least partially around said second filtration partition; andsaid second filtration partition extends at least partially around said third filtration partition. 16. The debris trap according to claim 15, wherein said first, second and third filtration partitions are substantially concentric with respect to one another. 17. The debris trap according to claim 13, wherein:each of said first, second and third filtration partitions is substantially rectangular in top plan view;said first filtration partition extends at least partially around said second filtration partition;said second filtration partition extends at least partially around said third filtration partition; andsaid first, second and third filtration partitions are substantially concentric with respect to one another.
	abstract	Charged-particle-beam (CPB) mapping projection-optical systems and adjustment methods for such systems are disclosed that can be performed quickly and accurately. In a typical system, an irradiation beam is emitted from a source, passes through an irradiation-optical system, and enters a Wien filter (“E×B”). Upon passing through the E×B, the irradiation beam passes through an objective-optical system and is incident on an object surface. Such impingement generates an observation beam that returns through the objective-optical system and the E×B in a different direction to a detector via an imaging-optical system. An adjustment-beam source emits an adjustment beam used for adjusting and aligning the position of, e.g., the object surface and/or the Wien's condition of the E×B. The adjustment beam can be off-axis relative to the objective-optical system. For such adjusting and aligning, fiducial marks (situated, e.g., in the plane of the object surface) can be used that are optimized for the CPB-optical system and the off-axis optical system. Desirably, the image formed on the detector when electrical voltage and current are not applied to the E×B is in the same position as the image formed on the detector when electrical voltage and current are applied to the E×B. Also provided are “evaluation charts” for use in such alignments that do not require adjustment of the optical axis of the irradiation-optical system, and from which the kinetic-energy distribution of the emitted adjustment beam is stable.
	description	The present application is a continuation-in-part of U.S. patent application Ser. No. 29/383,507 filed Jan. 19, 2011, and having the title “Radiation Shielding Container Lid.” The present disclosure relates generally to a radiation shielding lid for an auxiliary shield assembly of a radioisotope elution system. Nuclear medicine uses radioactive material for diagnostic and therapeutic purposes by injecting a patient with a dose of the radioactive material, which concentrates in certain organs or biological regions of the patient. Radioactive materials typically used for nuclear medicine include Technetium-99m, Indium-111, and Thallium-201 among others. Some chemical forms of radioactive materials naturally concentrate in a particular tissue, for example, radioiodine (I-131) concentrates in the thyroid. Radioactive materials are often combined with a tagging or organ-seeking agent, which targets the radioactive material for the desired organ or biologic region of the patient. These radioactive materials alone or in combination with a tagging agent are typically referred to as radiopharmaceuticals in the field of nuclear medicine. At relatively low doses of radiation from a radiopharmaceutical, a radiation imaging system (e.g., a gamma camera) may be utilized to provide an image of the organ or biological region in which the radiopharmaceutical localizes. Irregularities in the image are often indicative of a pathology, such as cancer. Higher doses of a radiopharmaceutical may be used to deliver a therapeutic dose of radiation directly to the pathologic tissue, such as cancer cells. A variety of systems are used to generate, enclose, transport, dispense, and administer radiopharmaceuticals. One such system includes a radiopharmaceutical generator, including an elution column, and an input connector (e.g., an input needle) and an output connector (e.g., an output needle) in fluid communication with the elution column. Typically, a radiopharmacist or technician fluidly connects an eluant vial (e.g., a vial containing saline) to the input connector and fluidly connects an empty elution vial (e.g., a vial having at least a partial internal vacuum) to the output connector. The vacuum in the empty elution vial draws the eluant (e.g., saline) from the eluant vial through the elution column, and into the elution vial. The saline elutes radioisotopes as its flows through the elution column so that radioisotope-containing saline fills the elution vial. The elution vial is typically housed in its own radiation shielding container, sometimes referred to as an elution tool or an elution shield. To reduce the amount of radiation exposure on the radiopharmacist or technician, the radiopharmaceutical generator is housed within a radiation shield assembly, sometimes referred to as an auxiliary shield, that includes a removable radiation shielding lid to allow the generator to be inserted into and removed from the shield assembly. The radiation shielding lid is disposed over the input connector and output connector of the generator, and includes an eluant opening and an eluate opening that are respectively aligned with the input connector and output connector of the generator and are sized and shaped for respectively receiving the eluant vial and the elution tool so that the respective vials can be fluidly connected to the input and output connectors. Although this type of system generally tends to work well, one problem associated with this type of system is that the input connector and/or output connector of the generator—particularly where the input and output connectors are hollow needles—may be bent, crushed, or broken due to misalignment of the eluant vial and/or the elution vial with the respective input and/or output connectors when making the fluid connection(s). As a result of the broken or deformed needles, the system operates less effectively or become completely useless. If the system contains radiopharmaceuticals, then the damaged connectors can result in monetary loss and/or delays with respect to nuclear medicine procedures. Another result of this misalignment problem can be that the input connector and/or output connector of the generator may undesirably puncture a retaining ring/collar of the respective eluant vial and/or elution vial causing damage to the vial(s). This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. One aspect of this disclosure relates to a radiation shielding lid for a radiation shielding container that includes a body having an upper surface and an opposing lower surface. A vial opening is defined in the body of the lid. This vial opening has a lower end found at the lower surface of the body and an upper end intermediate the upper and lower surfaces of the body. A finger recess is defined in the upper surface of the body and is sized and shaped to allow at least a distal portion of each of at least two digits (e.g., thumb/fingers of a technician) to enter the finger recess. This finger recess has an upper edge adjacent the upper surface of the body and a lower edge adjacent the upper end of the vial opening. First and second wings extend upward from adjacent the upper end of the vial opening. Each of these first and second wings has opposite sides, a top portion, and an inner surface extending partially around a circumference of the upper end of the vial opening. The inner surfaces of the first and second wings and the vial opening together define a vial passageway extending from the top portion of each of the first and second wings through the lower surface of the body. The vial passageway is sized and shaped for receiving a vial therein. Respective adjacent sides of the first and second wings are spaced apart from one another around the vial opening to partially define first and second finger channels leading from the finger recess to the vial passageway. Each of the first and second finger channels are sized and shaped to allow at least the distal portion of each of at least two digits to enter the corresponding finger channel from the finger recess. One benefit of this arrangement may be to facilitate gripping of the vial during insertion of the vial into the vial passageway and/or removal of the vial from the vial passageway. In some embodiments of the first aspect, the inner surface of each of the first and second wings extends at least 45 degrees and less than 180 degrees around the circumference of the upper end of the vial opening. The top portions of the first and second wings may extend above the upper surface of the body. The inner surface of each of the first and second wings may extend at least 60 degrees around the circumference of the upper end of the vial opening, or may extend at least 90 degrees around the circumference of the upper end of the vial opening. The inner surfaces of the first and second wings may be diametrically opposed to one another with respect the vial opening. In some embodiments of the first aspect, the sides of the respective first and second wings extend into the finger recess. The finger recess may include first and second finger recesses, and the first and second finger recesses may be diametrically opposed to one another with respect to the vial opening. The lower edge of the first finger recess may extend between the corresponding adjacent sides of the first and second wings to partially define the first finger channel, and the lower edge of the second finger recess may extend between the corresponding adjacent sides of the first and second wings to partially define the second finger channel. The top portions of the first and second wings may extend above the upper surface of the body, and at least one of the first and second wings may have a notch in the corresponding top portion. In some embodiments of the first aspect, the upper end of the vial opening may be substantially circular, and the inner surfaces of the first and second wings may be generally arcuate. A portion of the vial passageway defined by the inner surfaces of the wings may taper from the top portions of the wings toward the vial opening. Each of the first and second wings may include a plurality of ribs on the inner surface of each wing projecting inward into the vial passageway, and the ribs on each wing may be spaced apart from one another between the opposite sides of each wing. The ribs may project generally toward a centerline of the passageway from the inner surface of the corresponding wing, such that each rib has a terminal, guiding surface generally facing a centerline of the vial passageway, and each guiding surface may be uniformly spaced from the centerline of the vial passageway along its length. The body may be substantially disk-shaped and may be formed, at least in part, from a radiation shielding material including at least one of depleted uranium, tungsten, tungsten impregnated plastic, or lead. An elution tool opening may be defined in the body, and the elution tool opening may be spaced apart and separate from the vial opening. A second aspect of this disclosure also relates to a lid for a radiation shielding container that includes a body having upper and lower surfaces. In this second aspect, a vial opening in the body has a centerline extending through the upper and lower surfaces of the body. The vial opening is sized and shaped to accommodate insertion of a vial therein and removal of the vial therefrom. First and second alignment wings extend upward from the vial opening. Each of these first and second alignment wings has opposite sides, a top portion, and an inner surface extending partially around a circumference of the vial opening. In some embodiment, the first and second alignment wings may be said to enable or promote alignment of a longitudinal axis of a vial with the centerline of the vial opening as the vial is inserted into the vial opening. Respective adjacent sides of the first and second alignment wings partially define at least one finger channel sized and shaped to allow at least a distal portion of at least one finger (e.g., a finder of a technician) to enter the finger channel. Such an arrangement may be found by users to facilitate insertion of the vial into and/or removal of the vial from the vial opening. In some embodiments of the second aspect, the inner surface of each alignment wing extends at least 45 degrees and less than 180 degrees around the circumference of the vial opening, and the finger channel may include at least a first finger channel and a second finger channel. First and second finger recesses may be in the upper surface of the body. Each of the first and second finger recesses may have an upper edge adjacent the upper surface of the body and a lower edge leading to the vial opening. The first and second finger recesses may be diametrically opposed to one another with respect to the vial opening. An elution tool opening defined in the body may be spaced apart and separate from the vial opening. Yet a third aspect of this disclosure also relates to a radiation shielding lid that includes a body having upper surface and an opposing lower surface. In this third aspect, the body of the lid includes at least one appropriate radiation shielding material (e.g., a material capable of shielding radiation emitted by medical radioisotopes (e.g., beta and/or gamma radiation)). Examples of such radiation shielding material include depleted uranium, tungsten, tungsten impregnated plastic, and lead. A first opening is defined in the body of the lid. This first opening has a lower end at the lower surface of the body and an upper end intermediate the upper and lower surfaces of the body. A second opening is also defined in the body of the lid. However, this second opening has a lower end at the lower surface of the body and an upper end at the upper surface of the body. The second opening is spaced apart and separate from the first opening. In addition, a recess is defined in the body of the lid. At least a portion of an upper end of this recess is located at the upper surface of the body, and at least a portion of a lower end of this recess is located at the upper end of the first opening. Further, first and second wings extend upward (e.g., away from the lower surface of the body) and only partially about a circumference of the upper end of the first opening such that a gap is defined between the first wing and the second wing. In some embodiments of the third aspect, the first and second wings have top portions extending above the upper surface of the body. A diameter of the first opening may be less than a diameter of the second opening. The first and second wings may be diametrically opposed to one another with respect the first opening. The finger recess may include first and second recesses, and the first and second recesses may be diametrically opposed to one another with respect to the vial opening. The gaps may be diametrically aligned with the first and second recesses relative to the first opening. At least one of the first and second wings may have a notch in a top portion thereof. Still a fourth aspect of this disclosure relates to a method of using a radiation shielding lid. In this method a first container having non-radioactive medical fluid (e.g., saline) therein is inserted into a first opening defined in and extending entirely through the radiation shielding lid. The insertion of the first container into the first opening includes the first container being passed between first and second opposing wings that extend away from a bottom of the lid upward beyond a top of the radiation shielding lid. A second container is inserted into a second opening defined in and extending entirely through the radiation shielding lid. This second opening is separate and distinct from the first opening. A user (e.g., a technician) may contact the first container (e.g., a substantially cylindrical side wall thereof, as opposed to the top or bottom of the first container) with first and second digits while the first container is located in the first opening. More particularly, while the first container is in the first opening, the user may contact the first container such that at least a portion of his/her first digit is located in a first gap between the first and second wings of the lid, and at least a portion of his/her second digit is located in a second gap between the first and second wings of the lid that is separate and distinct from the first gap. In some embodiments of the fourth aspect, the contacting may further include the first digit being located within a first recess defined in the lid, and the second digit may be located within a second recess defined in the lid. The first recess may be separate and distinct from the second recess. An interior of the second container may be at least partially evacuated. The non-radioactive medical fluid in the first container may include saline. The method may further include drawing the non-radioactive medical fluid from the first container, through the radioisotope generator, and into the second container after the inserting of the first container and the inserting of the second container. The non-radioactive medical fluid elutes a radioisotope as it flows through the radioisotope generator so that it includes the radioisotope prior to entering into the second container. The inserting of the second container may occur while the first container is in the first opening. Various refinements exist of the features noted in relation to the above-mentioned aspects of the present disclosure. Further features may be incorporated in the above-mentioned aspects of the present disclosure as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments of the present disclosure may be incorporated into any of the above-described aspects of the present disclosure, alone or in any combination. Referring to FIGS. 1-4, one embodiment of a radioisotope elution system 10 includes a radioisotope generator 12 (FIGS. 3 and 4), which is removably receivable in an auxiliary shield assembly 14. As explained in more detail below, an elution tool 16, which houses an elution vial 17 (broadly, a container), and an eluant vial 18 (broadly, a container) are fluidly connectable to the radioisotope generator 12. Herein, “fluidly connectable” refers to the ability of first component and a second component to be connected (either directly or indirectly) or interface in a manner such that fluid (e.g., eluate, eluant) may flow therebetween in a substantially confined flow path. The auxiliary shield assembly 14 includes a radiation shielding body 20 that defines a cavity 22 in which the generator 12 is removably receivable, and a radiation shielding lid 24 that may be positioned on the body 20 toward a top thereof to substantially enclose the cavity 22 defined in the body 20. In general, the radiation shielding lid 24 facilitates proper alignment of the eluant vial 18 with the radioisotope generator 12 when fluidly connecting the eluant vial with the radioisotope generator. Additional disclosure of the radiation shielding lid 24 is set forth in detail herein below. The illustrated elution tool 16 may be of any appropriate configuration (e.g., size, shape, design), as is known to one having ordinary skill in the art, and may include one or more suitable radiation shielding materials, such as depleted uranium, tungsten, tungsten impregnated plastic, or lead. The illustrated elution vial 17 is a generally cylindrical container, made from glass or other material (e.g., plastic), which includes a septum (not shown) secured to a top portion thereof by a metal ring or cap (not shown), as is generally known in the art. The elution vial 17 may be a different type of container suitably connectable to a radioisotope generator and/or may have a shape other than generally cylindrical. In one embodiment, the interior of the elution vial 17 is at least partially evacuated such that the elution vial has a reduced internal pressure (i.e., at least a partial vacuum). The eluant vial 18, like the elution vial 17, may be a generally cylindrical container, which includes a septum (not shown) secured to a top portion thereof by a metal ring or cap (not shown), as is generally known in the art. The eluant vial 18 may be a different type of container suitably connectable to a radioisotope generator and/or may have a shape other than generally cylindrical. The eluant vial 18 is filled with an eluant fluid, such as saline. In one embodiment, the volume of eluant fluid is less than the volume of the elution vial 17. In another embodiment, the interior volume of eluant vial 18 is less than the interior volume of the elution vial 17. For example, the eluant vial 18 may have an internal volume of about 26 milliliters, and the interior volume of the elution vial 17 may be about 36 milliliters. The elution vial 17 and/or the eluant vial 18 may be of other configurations without departing from the scope of the present disclosure. Referring to FIGS. 3-5, the radioisotope generator 12 includes: a housing 26; an elution column assembly 28 (FIG. 3) disposed within the housing; and input and output connectors 30, 32, respectively, in fluid communication with the elution column assembly 28; and a hood or cap 38 secured to the housing. The generator housing 26 is generally cylindrical and defines an axially extending cavity in which the elution column assembly 28 is received. The housing cap 38 may be snap-fit on the housing 26, or secured thereto in any other appropriate manner. The housing cap 38 has a recessed portion 40 extending downward from an upper surface of the cap. The cap 38 also has a generally U-shaped channel 42 extending downward from the upper surface and through a sidewall of the cap to the recessed portion 40. As explained in more detail below, the recessed portion 40 and the channel 42 together constitute an alignment structure, more specifically female alignment structure, for facilitating proper alignment of the radiation shielding lid 24 on the generator 12. The generator housing 26 and cap 38 may be formed from plastic (such as by molding) or from other suitable, preferably lightweight, material. Moreover, the generator housing 26 itself may be free from lead, tungsten, tungsten impregnated plastic, depleted uranium, or other radiation shielding material, such that the housing provides little or only nominal radiation shielding. The generator 12 includes a generator handle 44 pivotally secured to the cap 38. The handle 44 is pivotable between a stored position, in which the handle lies in a plane substantially transverse to the axis A1 of the housing 26 (FIG. 3) and below the upper surface of the cap 38, and a carrying position, in which the handle lies in a plane substantially parallel to the axis of the housing and above the upper surface of the cap. The generator handle 44 allows a radiopharmacist or technician to lift the generator 12 for placement of the generator in the auxiliary shield assembly 14 and removal of the generator from the auxiliary shield assembly. The generator handle 44 may be formed from plastic or any other appropriate material and may be pivotally connected to the generator housing 26 by pivot connectors 46 (FIG. 5) or in any other appropriate manner of connection. Referring to FIG. 3, the input and output connectors 30, 32 extend upward from the elution column assembly 28 and through respective openings 50, 52 in a bottom surface 53 of the recessed portion 40 of the generator cap 38 such that respective terminal ends or tips 30a, 32a of the input and output connectors are disposed within the recessed portion. In the illustrated embodiment, the input and output connectors 30, 32 respectively include input and output needles for piercing respective septums of the elution vial 17 and the eluant vial 18, although it is contemplated that the connectors may be of other configurations/types. In addition to the input and output connectors 30, 32, a venting connector 54, in fluid communication with atmosphere, extends through the bottom surface 53 of the recessed portion 40 of the cap 38. The venting connector 54 is adjacent to the input connector 30 and extends through the same opening 50 in the generator cap 38. In the illustrated embodiment, the venting connector 54 includes a venting needle having a terminal end or tip 54a disposed within the recessed portion 40 of the generator cap 38. The venting needle 54 pierces the septum of the eluant vial 18, like the input needle 30, to vent the eluant vial 18 to atmosphere. Referring to FIG. 3, the elution column assembly 28 may be any appropriate type of elution column assembly known to those having ordinary skill in the art, such as, the elution column assembly disclosed in U.S. Pat. No. 5,109,160 or the elution column assembly found in the Ultra-Technekow™ dry-top eluting (DTE) generator distributed by Mallinckrodt LLC. For example, the elution column assembly 28 may include a radioactive column (not shown) including source of radioactive material (e.g., molybdenum-99, adsorbed to the surfaces of beads of alumina or a resin exchange column), and input and output conduits (not shown) fluidly connecting the input needle 30 to the column and the output needle 32 to the column. The elution column assembly 28 may include a column radiation shield (not shown) having a cavity in which the radioactive column is received, and a conduit radiation shield (not shown) surrounding the input and output conduits. The respective radiation shields may include (e.g., be made from or have in their construct) lead, tungsten, tungsten impregnated plastic, depleted uranium and/or another suitable radiation shielding material. Referring back to FIG. 1, the illustrated auxiliary shield assembly body 20 includes a top ring 56, a base 58, and a plurality of step-shaped or generally tiered, modular rings 60, which are disposed one over the other between the base 58 and the top ring 56. Substantially all or part of the illustrated auxiliary shield assembly body 20 may be made of one or more suitable radiation shielding materials, such as depleted uranium, tungsten, tungsten impregnated plastic, or lead. The modular aspect of the rings 60 may tend to enhance adjustment of the height of the auxiliary shield assembly body 20, and the step-shaped configuration may tend to contain some radiation that might otherwise escape through a linear interface between the modular rings. It is understood that the auxiliary shield assembly body 20 may be of other configurations. Referring now to FIGS. 6-11, the radiation shielding lid 24 includes: a generally cylindrical lid body 72 having upper and lower surfaces, 74, 76, respectively; an elution tool opening 78; and an eluant vial opening 80. In one example (of which an exemplary method of making is explained in more detail below), the lid body 72 includes a radiation shielding core 124 that is overmolded with a plastic material 126, 128. As an example, the radiation shielding core 124 may include depleted uranium, tungsten, tungsten impregnated plastic, or lead. The upper and lower surfaces 74, 76, respectively, are generally planar, although the surfaces may be other than generally planar. A male alignment structure, generally indicated at 81, is provided on the lower surface 76 of the lid body 72 to facilitate proper alignment of the lid 24 on the generator 12. More specifically, the male alignment structure 81 has a shape generally corresponding with the combined shape of the recessed portion 40 and the channel 42 of the generator 12 (together, these recessed portion 40 and the channel 42 constitute a female alignment structure) so that the male alignment structure mates with the generator in order to align the elution tool opening 78 with the output needle 32 and the eluant vial opening 80 with the input needle 30 and the venting needle 54. As such, it may be said that the lid 24 is keyed with the generator 12 (e.g., the cap 38 thereof) such that proper positioning of the lid 24 atop the generator 12 results in alignment of the respective openings 78, 80 with the corresponding needles 32, 30. The structure 81 enables only one position of the lid 24 relative to the generator 12. The illustrated male alignment structure 81 includes a wall 81a projecting outward from the bottom surface 76 and surrounding the elution tool opening 78 and the eluant vial opening 80. A plurality (e.g., a pair) of handles 82 on the upper surface 74 of the lid body 72 allows the radiopharmacist or technician to properly place the lid 24 on the generator 12 and remove the lid from the generator. The elution tool opening 78 extends through the lid body 72 from the upper surface 74 through the lower surface 76 thereof. The elution tool opening 78 is sized and shaped for removably receiving the elution tool 16 therein. For example, in the illustrated embodiment, the elution tool opening 78 has a generally circular circumference that is substantially uniform along its axis. In one embodiment, the elution tool opening 78 has a diameter slightly larger than an outer diameter of the elution tool 16 such that the opening effectively aligns the septum (not shown) of the elution vial 17 (FIG. 4) with the output needle 32 as the elution tool is inserted into the opening. For example, the elution tool opening 78 may have a diameter that is from about 0.25 mm (0.01 in) to about 1.0 mm (0.04 in) larger than the outer diameter of the elution tool 16. In one embodiment, the elution tool opening 78 may have a diameter from about 46 mm (1.8 in) to about 48 mm (1.9 in), although it may alternatively have a diameter falling outside this range. Other shapes and sizes of the elution tool opening 78 may be appropriate; however, it tends to be preferred that the shape and size of the elution tool opening 78 be at least generally complimentary to the shape and size of the elution tool 16 being used with the radiation shielding lid 24 to reduce the likelihood of misalignment between the elution vial 17 and the output needle 32. As shown in FIGS. 9 and 10, the eluant vial opening 80 is spaced apart and separate from the elution tool opening 78, and is sized and shaped for removably receiving an eluant vial 18 (FIG. 2), such as a vial containing saline or other eluants. In the illustrated embodiment (FIG. 10), the eluant vial opening 80 has a lower end 86 at the lower surface 76 of the lid body 72 and an upper end 88 intermediate the upper and lower surfaces 74, 76, respectively. In one example, the eluant vial opening 80 may have a diameter from about 34.0 mm (1.34 in) to about 34.5 mm (1.36 in), although it may alternatively have a diameter falling outside this range. As with the elution tool opening 78, other shapes and sizes of the eluant vial opening 80 may be appropriate; however, it tends to be preferred that the shape and size of the eluant vial opening 80 be at least generally complimentary to the shape and size of the eluant vial 18 being used with the radiation shielding lid 24 to reduce the likelihood of misalignment between the eluant vial 18 and the input needle 30 and venting needle 54. Referring to FIGS. 2, 6, 8, and 11, the illustrated lid 24 has two finger recesses 90 formed in the upper surface 74 of the lid body 72, which are diametrically opposite one another with respect to the eluant vial opening 80. The finger recesses 90 are defined by respective recessed surfaces extending downward from the upper surface 74 of the lid body 72 to the eluant vial opening 80, and are sized and shaped to allow at least distal portions of two fingers of a radiopharmacist or other appropriate technician to enter the finger recesses. Recessed surfaces defining illustrated finger recesses 90 are curved and generally in the shape of a half-bowl such that the recessed surfaces lead the radiopharmacist's or technician's fingers toward the eluant vial opening 80. It is understood that in other embodiments the lid 24 may have a single finger recess, such as a finger recess that completely or partially surrounds the eluant vial opening 80, or more than two finger recesses. Referring to FIG. 8, each illustrated finger recess 90 has an upper edge 92 adjacent the upper surface 74 of the lid body 72 and a lower edge 93 that is coextensive with a portion of the upper end 88 of the eluant vial opening 80. Referring to FIG. 11, the lid 24 of the auxiliary shield assembly 14 includes first and second wings, each designated generally at reference numeral 100, extending upward from adjacent the upper end 88 of the eluant vial opening 80 within the finger recesses 90. Each of the first and second wings 100 has opposite sides 104, a top portion 106, and an inner surface 108 extending partially around a circumference of the upper end 88 of the eluant vial opening 80. In the illustrated embodiment, the top portion 106 of each of the wings 100 is disposed above the upper surface 74 of the lid body 72 (as seen best in FIGS. 7 and 10), and the inner surface 108 of each of the wings 100 is generally arcuate, although it is understood that the wings 100 may be of other shapes and relative dimensions. Together, the inner surfaces 108 of the wings 100 and the eluant vial opening 80 define a vial passageway 107 extending from the top portions 106 of the wings 100 through the lower surface 76 of the lid body 72. The wings 100 preferably enable alignment of the eluant vial septum with the input needle 30 and venting needle 54 as the eluant vial 18 is inserted into the vial passageway 107. As such, the wings 100 preferably make it is less likely that the input needle 30 or venting needle 54 will contact the metal ring or other hard part of the vial and damage the needle. In one example, the inner surface 108 of each wing 100 may extend at least 45 degrees and less than 180 degrees around the circumference of the upper end 88 of the eluant vial opening 80. In other examples, the inner surface 108 of each wing 100 may extend at least 60 degrees, or at least 90 degrees, and less than 180 degrees around the circumference of the upper end 88 of the eluant vial opening 80. Other configurations of the wings 100 do not depart from the scope of the present disclosure. To facilitate gripping of the eluant vial 18 during at least one of insertion of the vial into the vial passageway 107 and removal of the vial from the vial passageway, the respective adjacent sides 104 of the first and second wings 100 are spaced apart from one another about the eluant vial opening 80 to define gaps or first and second finger channels, each indicated at 112 (FIGS. 6 and 10), leading from the finger recesses 90 to the vial passageway. In the illustrated embodiment, the finger channels 112 are diametrically aligned, relative to the vial opening 80, with the finger recesses 90, and the respective sides 104 of the wings 100 extend into the associated finger recesses 90. Each of the first and second finger channels 112 are sized and shaped to allow at least the distal portion of one of the two fingers to enter the corresponding finger channel from the associated finger recess 90. For example, a minimum width of each of the finger channels 112 (i.e., the distance between the respective adjacent sides 104 of the first and second wings 100) may measure from about 19 mm (0.75 in) to about 21 mm (0.83 in), and more specifically, from about 19.0 mm (0.748 in) to about 19.6 mm (0.772 in), although the minimum width of each finger channel may fall outside this range. Thus, the finger channels 112 allow the radiopharmacist or technician to grip the eluant vial 18, such as by using his/her thumb and forefinger, during at least one of insertion of the vial in the vial passageway 107 and removal of the vial from the vial passageway. In the illustrated embodiment (FIGS. 8, 10, and 11), a diameter of a portion of the vial passageway 107 defined by the inner surfaces 108 of the wings 100 tapers from the top portions 106 of the wings toward the eluant vial opening 80. Tapering the inner surfaces 108 of the wings 100 facilitates molding of the wings when overmolding the lid 24 in one example, as described below. Although this diameter of the vial passageway 107, as defined by the inner surfaces 108, tapers along the length of the passageway, a plurality of alignment ribs 114 are provided on the inner surfaces to define an effective inner diameter of the vial passageway that is substantially uniform along the length of the passageway. The ribs 114 are spaced apart from one another between the sides 104 of the wings and extend longitudinally along the respective wings 100. The wings 100 project inwardly, generally toward a centerline of the passageway 107, such that each rib 114 has a terminal, guiding surface 115 (FIG. 11) generally facing the centerline of the passageway. Each guiding surface 115 is uniformly spaced from the centerline of the vial passageway 107 along its length. In other words, the guiding surface 115 of each rib 114 does not taper or flare with respect to the axis of the vial passageway 107. Through this configuration, the guiding surfaces 115 effectively align the elution vial 18 with the input needle 30 and venting needle 54 even though the inner surfaces 108 of the wings 100 are tapered. The ribs 114 have depths projecting into the vial passageway 107 relative to the respective inner surfaces 108. Because the diameter of the vial passageway 107 defined by the inner surfaces 108 of the wings 100 tapers, yet the guiding surfaces 115 do not taper or flare relative to the centerline of the vial passageway, the depths of the ribs relative to the respective inner surfaces 108 taper toward the eluant vial opening 80. The wings 100 may not include the ribs 114 without departing from the scope of the present disclosure. As illustrated in FIG. 3, a bottom 116 of the eluant vial 18 lies slightly below or at the top portions 106 of the wings 100 when the eluant vial is received in the vial passageway 107 and fluidly connected to the input needle 30. Notches 118 in the top portions 106 of the wings 100 allow the radiopharmacist or technician to view the eluant vial 18 in the passageway without having to position his/her head above the upper surface 74 of the lid 24. In one example, the auxiliary shield lid 24 may be formed by a two-step overmolding process. In such a process, a radiation shielding core 124 (FIG. 10)—which may include a suitable radiation shielding material such as depleted uranium, tungsten, tungsten impregnated plastic, or lead—is provided. The core 124 may be generally disk-shaped, having first and second openings, which will form the elution tool and eluant vial openings, 78, 80, respectively, and recesses, which will form the finger recesses 90. A first molded part is molded with a first thermoplastic material 126 to form the bottom surface 76, the male alignment structure 81, and the sidewall of the body 72, and at least lower portions of the elution tool opening 78 and the eluant vial opening 80. Next, the core 124 is placed into the first molded part. Finally, this assembly is overmolded with a second thermoplastic material 128 to form the top surface 74, the handles 82, the finger recesses 90, the wings 100, and an upper portion of at least the elution tool opening 78. The first and second thermoplastic materials 126, 128, respectively, may include polypropylene and polycarbonate, or other material, and the first and second thermoplastic materials may be of the same material. Other methods of making the auxiliary shield lid 24 may be used. In an exemplary method of using the radioisotope elution system 10, the radiopharmacist or technician manually inserts the radioisotope generator 12 into the cavity 22 of the auxiliary shield body 20. The auxiliary shield lid 24 is manually placed in the cavity, on top of the radioisotope generator 12. The lid 24 may be rotated to thereby mate the male alignment structure 81 on the lid with the female alignment structure (i.e., the recessed portion 40 and the U-shaped channel 42) in the cap 38 of the generator 12. Upon mating, the eluant vial opening 80 is disposed over and generally vertically aligned with the input needle 30 and the venting needle 54, and elution tool opening 78 is disposed over and generally vertically aligned with the output needle 32. The eluant vial 17 is manually inserted into the passageway defined by the wings 100 and the eluant vial opening 80. The passageway guides the eluant vial 17 in a substantially vertical direction, such that the longitudinal axis of the eluant vial is generally aligned with the axes of the input needle 30 and the venting needle 54. More specifically, the passageway guides the eluant vial 17 such that the input needle 30 and the venting needle 54 pierce the septum of the vial to fluidly connect the interior of the eluant vial to the generator 12. Accordingly, the wings 100 give the radiopharmacist or technician confidence that the input needle 30 and venting needle 54 will pierce the septum, and therefore, the radiopharmacist or technician does not have to position his/her head directly above the lid 24 to confirm that the needles will properly pierce the eluant vial septum. To this effect, the radiopharmacist or technician reduces any likelihood of radiation exposure from the generator 12 when positioning his/her head over the eluant vial opening 80. The elution tool 16, which includes the elution vial 17 therein, is manually inserted into the elution tool opening 78 such that the output needle 32 pierces the septum of the elution vial to fluidly connect the elution vial to the generator 12. The vacuum (or reduced pressure) in the elution vial 17 draws the saline from the vial 18 through the radioisotope column and into the elution vial 17. The radiopharmacist or technician can view the bottom 116 of the eluant vial 18 through the notches 118 in the respective wings 100 when the vial is received in the passageway 107 to confirm that the eluant vial 18 is fully inserted onto the generator 12. Accordingly, the radiopharmacist or technician does not have to position his/her head directly above the lid 24 to confirm that the needles 30, 54 actually pierced the eluant vial septum. Once confirmation is made that the vial is properly placed, an eluant vial shield (not shown) may be placed over the bottom of the eluant vial. After the elution vial 17 is filled with the desired quantity of radioisotope-containing saline, the elution tool 16 can be manually removed from the lid 24. A vial (not shown) containing a sterile liquid may be placed on the output needle 32. The eluant vial 18 may remain on the radioisotope generator 12 until a subsequent elution in order to keep the needles 30, 54 sterile. When it is time for a subsequent elution, the eluant vial 18 can be manually removed from lid 24, such as by the radiopharmacist or technician inserting his/her thumb and forefinger into the respective finger recesses 90 and then into the respective finger channels 112 to grip (or pinch) the eluant vial. The radiopharmacist or technician can then lift the eluant vial 18 upward and out of the lid 24. When introducing elements of the present invention or the embodiment(s) thereof, the articles “a”, “an”, the and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. As various changes could be made in the above apparatus and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying figures shall be interpreted as illustrative and not in a limiting sense.
	abstract	A moderator temperature coefficient measurement apparatus includes: an input section receiving plant data including a coolant temperature signal being time series data on a temperature of a coolant of a light water reactor, and a reactivity signal indicating time series data on a reactivity calculated based on a detection value of a neutron flux in the light water reactor; a singular value decomposition section decomposing the coolant temperature signal into N components T′1 (t) to T′N (t), and the reactivity signal into M components ρ′1 (t) to ρ′M (t) by a singular value decomposition method; a combination section generating a selected combination being a combination of T′i (t) selected from the N components T′1 (t) to T′N (t) and ρ′j (t) selected from the M components ρ′1 (t) to ρ′M (t); and a temperature coefficient calculation section calculating a moderator temperature coefficient based on auto and cross power spectral density functions obtained by applying a Fourier transformation to the selected combination. The moderator temperature coefficients can be detected at high precision without changing states of the plant.
056174560	description	DESCRIPTION OF PREFERRED EMBODIMENTS The principle of the present invention will first be described prior to illustrating embodiments of the present invention. FIG. 1 illustrates the structure. Fundamentally, the fuel assembly is provided with a water rod 1 which has a coolant ascending path 2 of which a coolant inlet port 4 is open in a region lower than a resistance menber such as fuel supporting portion of a lower tie plate) 6 provided at a lower portion of the fuel assembly, and which further has a coolant descending path 3 that downwardly guides the coolant from the coolant ascending path and that has a coolant delivery port 5 open in a region higher than the resistance member 6. The resistance member 6 has a plurality of coolant passage ports 7. The pressure differential .DELTA.P changes between the region lower than the resistance member 6 and the region higher than the resistance member 6 depending upon the change in the flow rate of the coolant (cooling water) that flows through the coolant passage ports 7 formed in the resistance member 6. The differential pressure caused by narrowing or broadening of the coolant path varies nearly in proportion to the square power of the flow rate of the cooling water. Therefore, if the flow rate of the cooling water passing through the resistance body 6 changes from 80% to 120%, the pressure differential .DELTA.P increases by about 2.25 times. FIG. 2 illustrates a relationship between the flow rate of cooling water in the water rod 1 and the pressure differential between the inlet and the outlet of the water rod 1 (pressure differential between the coolant inlet port 4 and the coolant delivery port 5). If the flow rate of the cooling water is increased starting from zero, the pressure differential between the outlet and the inlet of the water rod 1 once reaches a maximum value. As the flow rate of the cooling water is further increased, the pressure differential between the outlet and the inlet of the water rod 1 once drops to a minimum value, and then increases monotonously. This is due to the phenomenon shown in FIGS. 3A to 3C. FIG. 3A shows the condition in the water rod 1 at a point S in FIG. 2, FIG. 3B shows the condition in the water rod 1 at a point T in FIG. 2, and FIG. 3C shows the condition in the water rod 1 at a point U in FIG. 2. Being irradiated with neutrons and gamma rays from the fuel rods around the water rod 1, the cooling water in the water rod 1 generates the heat at a rate of about 0.5 to 2 W/cm.sup.2. When the flow rate of the cooling water flowing through the water rod 1 is very small (condition of point S in FIG. 2), the cooling water in the water rod 1 generates the heat and evaporates being irradiated with neutrons and the like. The upper portions of the coolant ascending path 2 and the coolant descending path 3 are then filled with the vapor as shown in FIG. 3A. A liquid level L.sub.1 is established in the coolant ascending path 2, and the pressure differential between the outlet and the inlet of the water rod 1 is generated by the difference in the static water head between the liquid level L.sub.1 and the liquid level L.sub.2 of the coolant delivery port 5 (outlet of the coolant descending path 3) of the water rod 1. The flow rate of the cooling water that flows into the coolant ascending path 2 maintains balance with respect to the flow rate by which the vapor flows out through the coolant delivery port 5. As the flow rate of the cooling water is further increased from the point S in FIG. 2, the cooling water flows into the coolant ascending path 2 at a rate that is greater than the amount by which the cooling water is vaporized. In such a case (e.g., at the point T in FIG. 2), the cooling water flows down through the coolant descending path 3 as shown in FIG. 3B. At this moment, the static head in the coolant ascending path 2 is partly cancelled by the weight of the cooling water that flows through the coolant descending path 3, and the pressure differential between the outlet and the inlet of the water rod 1 becomes smaller that the maximum value S.sub.0. As the flow rate of the cooling water further increases, however, the unsaturated water introduced through the coolant inlet port 4 is not boiled in the coolant ascending path 2 and the coolant descending path 3 (void fraction is very reduced), and is permitted to flow out through the coolant delivery port 5 (condition of point U in FIG. 2, FIG. 3C). Therefore, the water flows through the coolant ascending path 2 and the coolant descending path 3 almost in the form of a single phase stream. Under the condition of FIG. 3A, therefore, the static water heads at the level of the coolant ascending path 2 and at the level of the coolant delivery port 5 in the coolant descending path 3 are cancelled by each other, so that the difference in the static water head becomes very small. However, since the cooling water flows at a large rate in the water rod 1, the pressure loss increases due to friction and inversion in the flow of the cooling water, and the pressure differential increases again between the outlet and the inlet of the water rod 1. Owing to the above-mentioned phenomenon, the flow rate of the cooling water in the water rod 1 varies greatly and the void fraction varies greatly even though the pressure differential varies little between the outlet port and the inlet port of the water rod 1. Therefore, the void fraction can be changed greatly by changing the flow rate of the cooling water (flow rate in the reactor core) that flows in the fuel assembly, if the resistance of the resistance member 6 is so adjusted that the pressure differential between the outlet and the inlet of the water rod 1 is smaller than a pressure differential between the outlet and the inlet of the water rod 1 that corresponds to the minimum value T.sub.0 of FIG. 2 when the flow rate in the reactor core is 80% and that the pressure differential between the outlet and the inlet of the water rod 1 is in excess of a pressure differential between the outlet and the inlet of the water rod 1 that corresponds to the maximum value S.sub.0 of FIG. 2 when the flaw rate in the reactor core is 120%. In the above example, the flow rate of 80% in the reactor core lies on the left side of the maximum value S.sub.0 and, preferably, lies on the left side of a point Q (pressure differential between the outlet and the inlet same as the minimum value T.sub.0) in FIG. 2, and the flow rate of 120% in the reactor core lies on the right side of the minimum value T.sub.0 and, preferably, lies on the right side of the point R (pressure differential between the outlet and the inlet same as the maximum value S.sub.0) in FIG. 2. An example of a fuel assembly utilizing the above-mentioned principle, i.e., an example of the structure of a fuel assembly to be used in a boiling-water reactor, will now be described in conjunction with FIGS. 4, 5, 6, 7A and 7B. A fuel assembly 10 of this example is comprised of fuel rods 11, an upper tie plate 12, a lower tie plate 13, a fuel spacer 16, a channel box 17, and a water rod 19. The upper and lower ends of the fuel rods 11 are held by the upper tie plate 12 and the lower tie plate 13. The water rod 19, too, is held at its both ends by the upper tie plate 12 and the lower tie plate 13. Several fuel spacers 16 are arranged in the axial direction of the fuel assembly 10 to maintain an appropriate distance among the fuel rods 11. Between the fuel rods 11. Spaces 50 (second cooling water path) of a cooling water path is formed. The fuel spacers 16 are held by the water rod 19. The channel box 17 is mounted on the upper tie plate 12 to surround the outer periphery of a bundle of fuel rods 11 that are held by the fuel spacers 16. The lower tie plate 13 has a fuel rod supporting portion 14 at the upper end and has therein a space 15 under the fuel rod supporting portion 14. The lower ends of the fuel rods 11 and the water rod 19 are supported by the fuel rod supporting portion 14. With reference to FIG. 5, a number of fuel pellets 33 are loaded in a covering tube 30 whose both ends are sealed with an upper end plug 31 and a lower end plug 32. A gas plenum 34 is formed at an upper end of the covering tube 30. The water rod 19 has a diameter (outer diameter of an outer tube 21 that will be mentioned later) which is greater than the diameter of the fuel rod 11, and is arranged at the central portion in the cross section of the fuel assembly 10. Structure of the water rod 19 will now be described in detail with reference to FIGS. 7A and 7B. The water rod 19 consists of an inner tube 20, an outer tube 21 and a spacer 22. The outer tube 21 and the inner tube 20 are arranged in concentric with each other, and the outer tube 21 surrounds the outer periphery of the inner tube 20. The upper end of the outer tube 21 is sealed with a covering portion 23, and the upper end of the covering portion 23 is held by the upper tie plate 12 being inserted therein. The covering portion 23 covers the upper end of the inner tube 20 so as to form a gap with respect to the upper end of the inner tube 20. The upper rod of the inner tube 20 is secured to the inner surface of the outer tube 21 via plate-like spacers 22 that are radially arranged from the axis of the water rod 19. The lower end of the outer tube 21 is sealed with a sealing portion 24. The lower end of the inner tube 20 penetrates through the sealing portion 24 to protrude downwardly. The lower end of the inner tube 20 penetrates through the fuel rod supporting portion 14 of the lower tie plate 13. A coolant inlet port 28 formed in the lower end of the inner tube 20 is open in the space 15 of the lower tie plate 13. The interior of the inner tube 20 forms a coolant ascending path 25. An annular path formed between the inner tube 20 and the outer tube 21 defines a coolant descending path 26. A plurality of cooling water delivery ports 29 are formed in the wall at the lower end of the outer tube 21 in the circumferential direction. The cooling water delivery ports 29 are formed in the circumferential direction maintaining an equal distance and are open in the space 50 over the fuel rod supporting portion 14. In this embodiment, the fuel rod supporting portion 14 exhibits the function of the resistance member 6 of FIG. 1. The cooling water ascending path 25 and the cooling water descending path 26 are communicated with each other through an inverting portion 27 formed at an upper end of the water rod 19. Thus, the water rod 19 contains therein a cooling water path (first cooling water path) of an inverted U-shape which consists of the cooling water ascending path 25, the cooling water descending path 26 and the inverting portion 27. When the fuel assembly 1 of this embodiment is loaded in the reactor core of the boiling-water reactor (the whole fuel assemblies are represented by the fuel assemblies 1) to operate the boiling-water reactor, most of the cooling water is directly introduced into space 80 among the fuel rods 11 of the fuel assembly 10 loaded in the reactor core passing through space 15 of the lower tie plate 13 and penetration holes 18 (FIG. 74) formed in the fuel rod supporting portion 14. The remainder of the cooling water that flows into space 15 in the lower tie plate 13 flows through the coolant inlet port 28 into the coolant ascending path 25 of the water rod 19, and is delivered into the space 80 over the fuel rod supporting portion 14 through the inverting portion 27, the coolant descending path 26 and the coolant delivery ports 29. The cooling water delivered from the cooling water delivery ports 29 may be in the form of a liquid or a gas (vapor) depending upon the flow rate of the cooling water that flows into the water rod 19 through the cooling water inlet port 28 as described earlier. According to this embodiment, the pressure loss by the fuel rod supporting portion 14 and the specifications of the inner tube 20 and the outer tube 21 have been selected in advance, so that the condition of FIG. 3A develops in the water rod 19 when the flow rate in the reactor core is smaller than 100% (flow rate at the maximum value S.sub.0 of FIG. 2 in the water rod 19), and the condition of FIG. 3C develops in the water rod 19 when the flow rate in the reactor core is 110% (flow rate at the point R of FIG. 2 in the water rod 19). Concretely described below is how to operate the boiling-water reactor while changing the void fraction in the water rod 19 under the condition where the fuel assembly 10 is loaded in the reactor core of the boiling-water reactor. This operation method applies for one fuel cycle (operation period of a nuclear reactor from when the fuel in the reactor core is replaced and operation of the nuclear reactor is started to when the nuclear reactor is stopped for renewing the fuel, i.e., usually, one year). In the boiling-water reactor as disclosed in Japanese Patent Publication No. 11038/1982, Col. 8, line 19 to Col. 10, line 31, the control rods are operated and the flow rate in the reactor core is adjusted to raise the atomic output up to 100% (point N in FIG. 7 of the above publication and 80% flow rate in the reactor core in this embodiment) in order to prevent the fuel from breaking. The flow rate in the reactor core is increased to compensate the reduction of reactor output as the nuclear fuel substance is consumed, i.e., to maintain the reactor output at 100%. When the flow rate in the reactor core has reached 100% owing to the compensation operation, the flow rate in the reactor core is decreased to 20% and the control rods are pulled out until the nuclear reactor produces a predetermined output as disclosed in Japanese Patent Publication No. 11038/1982, Col. 11, line 23 to Col. 12, line 40 (Col. 9, line 47 to Col. 10, line 51 of U.S. Pat. No. 4,279,698). Thereafter, the flow rate in the reactor core is increased to 80% to maintain the reactor output at 100%. To maintain the reactor output at 100%, the control operation is repeated. According to this embodiment, the output of the nuclear assembly is flattened in the axial direction by utilizing nuclear characteristics. After the flow rate in the reactor core has been decreased, therefore, the control rods are pulled out; i.e., there is no need of pulling out the control rods or there is no need of inserting other control rods unlike the art disclosed in Japanese Patent Publication No. 11038/1982 Col. 12, lines 19 to 29 (U.S. Pat. No. 4,279,698, Col. 10, lines 21 to 34), and what is needed is to pull out only those control rods that are deeply inserted. As described above, the operation for obtaining 100% of reactor output with the flow rate in the reactor core of smaller than 100% is continued for about 70% of a fuel cycle period. During the period of about 70%, the water rod 19 in the fuel assembly 1 assumes the condition as shown in FIG. 3A. That is, the upper portion of the coolant ascending path 25 and the interior of the coolant descending path 26 are filled with the vapor; i.e., the liquid cooling water does not almost exist in the vapor region which is formed in the water rod 19 in the fuel assembly 1 loaded in the reactor core. Therefore, up to 70% of the fuel cycle, the vapor region is formed in the water rod 19, and the cooling water in the reactor core is partly expelled. It can be said that the fuel assembly 10 according to this embodiment is provided with a water rod that has a vapor reservoir. The coolant descending path 26 works as a vapor reservoir until the flow rate in the reactor core exceeds 100% as will be described later. Formation of the vapor region in the water rod 19 suppresses the effect for decelerating neutrons and promotes the conversion of uranium 238 into plutonium 239 in the nuclear fuel substance. Suppression of the neutron deceleration effect results in the suppression of nuclear fission such as of uranium 235 and results in the decrease in the reactivity. Decrease in the reactivity, however, can be alleviated by pulling out the control rods by an increased amount. During this period, new core materials such as plutonium 239 and the like may be formed, and the core material in the reactor core decreases at a reduced rate. According to this embodiment as described above, the surplus reactivity (surplus neutrons) is absorbed by uranium 238 in the nuclear fuel substances to form a new core material. By the time when the operation period of the boiling-water reactor reaches about 70% of the fuel cycle, the surplus reactivity in the reactor core will have been lowered to a minimum level for maintaining the criticality. In this case, the flow rate in the reactor core is gradually increased in excess of 100%; i.e., the flow rate in the reactor core is increased to 120% at the time when the operation of a fuel cycle is stopped. The recirculation pump does not hinder the operation at all if the flow rate in the reactor core does not exceed 120%. The output of the nuclear reactor is maintained at 100% from when the flow rate in the reactor core exceeds 100% until when it reaches 120%. When the flow rate in the reactor core is greater than 110%, the interior of the water rod 19 assumes the condition of FIG. 3C where the liquid flows in the form of a single-phase stream and no vapor stays in the coolant descending path 26. As the flow rate in the reactor core becomes greater than 110%, therefore, the amount of cooling water (the number of hydrogen atoms) in the reactor core increases remarkably compared with when the flow rate in the reactor core is smaller than 100%, and whereby the effect increases for decelerating the neutrons, and hence nuclear fission of uranium 235 and the like becomes active. Accordingly, the infinite multiplication factor of the fuel assembly increases and it is made possible to effectively utilize the core materials. The fuel assembly 1 experiences the fuel cycle operation four times in the reactor core. Therefore, the conditions of FIG. 3A and 3B are alternatingly repeated four times each. According to the fuel assembly 10 of this embodiment as described above, the water rod is made up of a simply constructed double tube. Therefore, the phase condition of the cooling water in at least the coolant descending path 26 can be successively changed from the gaseous state to the liquid state by means which controls the output of the nuclear reactor (by means which adjusts the flow rate in the reactor core and which may be a recirculation pump). That is, the range in which the average void fraction changes in the fuel assembly 10 can be greatly broadened being added up with the range of void fraction change due to the water rod 19. Concretely speaking, the flow rate in the reactor core in this embodiment is increased to 80 to 120%, so that the average void fraction of the fuel assembly 10 changes as shown in FIG. 8. This is due to the change of void fraction outside the water rod 19. The fuel assembly 10 exhibits an average void fraction change on which is superposed an average void fraction change produced by the water rod 19. Therefore, the nuclear fuel substances can be effectively utilized with a simply constructed structure, and the operation period of a fuel cycle can be greatly extended. Described below is another operation control to substitute for the aforementioned operation control. According to Japanese Patent Publication No. 44237/1983 (U.S. Pat. No. 4,285,769), a fuel cell constituted by four adjoining fuel assemblies is divided into a controlled cell and a noncontrolled cell, the average enrichment of the controlled cell is selected to be smaller than that of the noncontrolled cell, and the output of the nuclear reactor under the ordinary operation condition is controlled by the control rods only that are inserted in the controlled cell. On Col. 27, line 29 to Col. 28, line 43 of Japanese Patent Publication No. 44237/1983 (U.S. Pat. No. 4,285,769, Col. 16, lines 6 to 65), there is described that the control rods inserted in the controlled cell (c cell) are driven by a control rod driving device of the type of fine movement. After the boiling-water reactor is started, the control rods in the controlled cell and the flow rate in the reactor core are adjusted to maintain 100% output of the nuclear reactor with a 80% flow rate in the reactor core. Reduction of the reactor output due to the consumption of the core material is compensated by increasing the flow rate in the core before the flow rate in the core reaches 100% and after the flow rate has reached 100%, by gradually pulling out the control rods from the controlled cell by the Control rod drive device while maintaining the flow rate in the reactor core at 100%. After 70% period of the fuel cycle, operation of the control rods is stopped and the flow rate in the reactor core is gradually increased up to 120%. During the period of up to 70% of the fuel cycle, the water rod 19 is filled with the water vapor as mentioned earlier and after 70% of the fuel cycle, the void fraction in the water rod 19 can be markedly reduced. In the aforementioned embodiment, the inverting portion 27 is arranged at a position over the position of a gas plenum 34 of the fuel rod 11, i.e., over the upper end of the fuel pellet-filled region. The lower end of the coolant descending path 26 is located at a position at least under the upper end (lower end of gas plenum 34) of the fuel pellet-filled region (region filled with fuel pellets 33) of the fuel assembly 1. In other words, the vapor reservoir of the water rod 19 should be located at a position at least lower than the upper end of the fuel pellet-filled region of the fuel assembly. In particular, in order that the vapor region is uniformly distributed in the axial direction of the fuel pellet-filled region where nuclear fission takes place in the nuclear assembly, the cooling water delivery ports 29 (or vapor delivery ports of the vapor reservoir) of the coolant descending path 26 (vapor reservoir) should be located near the lower end of the fuel pellet-filled region or desirably at a position (near the fuel rod supporting portion 14) under the fuel pellet-filled region. Namely, the vapor region under the condition of FIG. 3A is formed over the full length in the axial direction of the fuel pellet-filled region, and the output distribution of the fuel assembly 1 is flattened in the axial direction. In this embodiment in which the coolant descending path 26 surrounds the periphery of the coolant ascending path 25, the neutron deceleration effect of when the coolant ascending path 25 and the coolant descending path 26 are substantially filled with liquid cooling water and the effect of converting into plutonium of at least when the coolant descending path 26 is filled with the vapor, can be uniformly imparted to the fuel rods that surround the water rod 19. By lowering the position of the inverting portion 27 from the upper end of the fuel pellet-filled region, furthermore, there can be employed a short water rod 19 having a length shorter than the fuel rods 11. In this case, pressure loss in the fuel assembly can be decreased. Referring to FIG. 2, difference in the flow rates in the reactor core between the maximum value S.sub.0 and the minimum value T.sub.0, pressure differential between the outlet and the inlet of the water rod 19 for the maximum value S.sub.0, and pressure differential between the outlet and the inlet of the water rod 19 for the minimum value T.sub.0, undergo the change depending upon the sizes of the inner tube 20 and the outer tube 21. This will now be described. FIGS. 9, 11 and 13 illustrate changes of pressure differential between the outlet and the inlet of the water rod 19 for the flow rate of cooling water supplied into the water rod 19 when the outer tube 21 has an inner diameter of 30 mm and when the inner diameter and outer diameter of the inner tube 20 are changed. FIG. 9 shows the characteristics when the inner tube 20 has an outer diameter of 14 mm and an inner diameter of 12 mm, FIG. 11 shows the characteristics when the inner tube 20 has an outer diameter of 17 mm ant an inner diameter of 15 mm, and FIG. 13 shows the characteristics when the inner tube 20 has an outer diameter of 20 mm and an inner diameter of 18 mm. FIGS. 10, 12 and 14 illustrate changes of the average void fraction in the water rod for the flow rate of cooling water supplied into the water rod, that correspond to FIGS. 9, 11 and 13. When the inner tube 20 is thin as will be obvious from FIG. 9, a maximum value is reached with a flow rate of cooling water which is greater than that of the thick inner tube 20 (FIGS. 11 and 13), and the pressure differential thereafter changes suddenly. Therefore, the range for changing the flow rate of the cooling water is small compared with the range for changing the pressure differential. This is due to the fact that since the inner tube 21 is thin, the heat is generated in small amounts in the inner tube 20 and the flow rate of the cooling water decreases, that surpasses the amount of vapor generated in the inner tube 20, and that the fluid flows through the inner tube 20 at such a high speed that the flow resistance increases. When the sectional area of the coolant descending path 26 between the inner tube 20 and the outer tube 21 is great and the flow rate is small, however, the void is almost 100% in the coolant descending path 26. Therefore, the range in which will change the average void fraction of the water rod having a thin inner tube 20 is little different from that of the water rod having a thick inner tube 20. On the other hand, the thicker the inner tube 20 of the water rod, the smaller the variable range of the pressure differential relative to the variable range of the cooling water. In any case, however, the average void fraction decreases sharply as a maximum value of the pressure differential is exceeded as will be obvious from FIGS. 10, 12 and 14. Referring to FIGS. 9, 11 and 13, furthermore, the average void fraction in the water rod for the flow rate of cooling water greater than a point R is conspicuously smaller than the average void fraction for the flow rate of cooling water smaller than the maximum value S.sub.0. FIG. 15 illustrates a relationship between the average void fraction in the water rod 19 and the pressure differential between the outlet and the inlet of the water rod 19, such that the contents of FIGS. 9 to 14 can be easily comprehended. As will be obvious from FIG. 15, the average void fraction of the water rod drops from 76% to 2% when the pressure differential is changed from 0.015 MPa to 0.03 MPa between the outlet and the inlet of the water rod 19 which employs the inner tube having an outer diameter of 20 mm. The pressure loss of the fuel rod supporting portion 14 of the lower tie plate 2 varies nearly in proportion to the square power of the flow rate of cooling water that flows in the fuel assembly 1 as mentioned earlier. Therefore, if the pressure differential between the outlet and the inlet of the water rod is set to be 0.015 MPa when the flow rate of cooling water that flows through the fuel assembly 1 is 80%, the pressure differential becomes 0.034 MPa when the flow rate of cooling water is 120%, and the average void fraction becomes 1% in the water rod. Therefore, the variable range of average void fraction in the water rod 19 is 75%; i.e., the variable range of average void fraction is 7.5% with the fuel assembly 10 as an average. Accordingly, a net variable range of average void fraction of the fuel assembly 10 is 16.5% being added up with 9% by the flow rate in the reactor core of FIG. 8. As shown in FIG. 6, the water rod 19 occupies about one-tenth the sectional area of the coolant path of the fuel assembly 10. Here, the variable range of average void fraction of the fuel assembly can be increased by providing two or more water rods 19 in the fuel assembly. To improve fuel economy, there has been proposed a fuel assembly which is provided with nine water rods. In this case, the water rods as a whole occupy about 30% the sectional area of the coolant path of the fuel assembly. A fuel assembly 35 of this embodiment is shown in FIG. 16. The fuel assembly 35 is the one in which the water rods of the fuel assembly disclosed in Japanese Patent Application No. 167972/1986, page 9, line 4 to page 11, line 5, and FIG. 1 are all replaced by the above-mentioned water rods 19. The fuel assembly 35 of this embodiment further exhibits the effect of the fuel assembly 1 of Japanese Patent Application No. 167972/986 (effect of reactivity gain shown in FIG. 3 of this prior application). Described below is the operation of the boiling-water reactor in which the fuel assembly 35 of this embodiment is loaded in the reactor core. The whole fuel assemblies in the reactor core is represented by the fuel assembly 35. FIG. 17 illustrates the change of characteristics of the case when the boiling-water reactor loaded with the fuel assembly 35 is operated with two continuous fuel-cycles. Broken lines indicate the case of this embodiment and solid lines indicate the case when use is made of the fuel assembly 35 which has conventional rods 19 (without coolant descending path 26). In the former case, the spectrum shift operation is carried out while changing the void fraction and in the latter case, no spectrum shift operation is carried out. The output of the nuclear reactor during the fuel cycle period is controlled by using the method disclosed in Japanese Patent Publication No. 44237/1983. The flow rate in the reactor core should range from 80 to 120% to maintain the output of the nuclear reactor at 100%. According to this embodiment, the inner tube 20 and the outer tube 21 have been so specified that the condition of FIG. 3A is established in the water rod 19 when the flow rate in the reactor core is smaller than 80% and that the condition of FIG. 3C is established in the water rod 20 when the flow rate in the reactor core is 110%. The flow rate of 80% in the reactor core is the one which corresponds to the maximum value S.sub.0 of FIG. 2 at which the cooling water is supplied into the water rod 19, and the flow rate of 110% in the reactor core is the one which corresponds to the point R of FIG. 2 at which the cooling water is supplied into the water rod 19. During the period of up to 70% of both the first fuel cycle and the second fuel cycle, the flow rate in the reactor core is maintained at 80% as shown in FIG. 17(d) and the change in the output of the nuclear reactor due to the consumption of the core material is compensated by gradually pulling out the control rods using a finely-driving control rod driving device. From 70% of the fuel cycle to the end of the fuel cycle, the flow rate in the reactor core is gradually increased from 80% to 120% while halting the operation of the control rods. With the output of the nuclear reactor being controlled as described above, the surplus reactivity in this embodiment is maintained at a minimum level necessary for criticality for a predetermined period of time (FIG. 17(b)) at the end of each of the fuel cycles. Furthermore, the ratio of hydrogen atom density to uranium atom density greatly increases toward the end of each of the fuel cycles (FIG. 17(c)). The core material in the nuclear fuel material loaded in the reactor core is consumed in small amounts during the period B of from the start of the fuel cycle to 70% of the fuel cycle, and is consumed in large amounts during the period E of from 70% of the fuel cycle to the end of the fuel cycle, as shown in FIG. 17(a). In this embodiment which employs nine water rods 19, the whole water rods occupy 30% of the sectional area of the coolant path of the fuel assembly 35 as mentioned above, and the variable range of the average void fraction of the fuel assembly 35 is increased by as great as 22.5% owing to the function of nine water rods 19. In practice, however, to this value is further added 9% of FIG. 8. Therefore, the nuclear fuel substances can be very effectively utilized, the period of a fuel cycle can be markedly extended for operating the nuclear reactor, and the fuel assembly 5 can be simply constructed. It is further possible to change the shape of nine water rods 19 of the fuel assembly 35 (e.g., to differ the inner diameter of the inner tube 20 of nine water rods 19) to vary the transition period from the state of FIG. 3A to the state of FIG. 3C. FIGS. 18A and 19 illustrate further embodiments of the water rod 19 employed for the fuel assembly 10 and the fuel assembly 35. In the water rod 19A of FIGS. 18A and 18B, a coolant ascending tube 40 and a coolant descending tube 41 are coupled together through a coupling tube 42, thereby to form a coolant ascending path 43 and a coolant descending path 44. The water rod 19A exhibits the function same as that of the water rod 19, but presents an advantage in that the metal has a small sectional area with respect to the area occupied by the water rods. In this embodiment, the coolant delivery port 29 is opened downwardly and may be affected by the dynamic pressure of the cooling water that flows upwardly in the fuel assembly. In the similar way as in the embodiment shown in later-appearing FIG. 21, the coolant ascending tube 40 of this embodiment changes from a large diameter tube portion to a small diameter tube portion (the outside diameter of which is smaller than that of the large diameter tube portion) between the fuel spacer located at the lowermost position and the fuel rod supporting portion 14. The small diameter tube portion is positioned below the large diameter tube portion. The cooling water descending tube 41 is coupled to the cooling water ascending tube 40 by a support member 45. Therefore, flow vibration of the cooling water descending tube 41 due to cooling water flowing through the outside of the water rod 19A can be restricted. Further, in the similar way as the embodiment shown in later-appearing FIG. 21, the outer peripheral surfaces of both the cooling water ascending tube 40 and the cooling water descending tube 41 come into contact with cooling water. Therefore, even when these tubes are full of the vapor, the temperature of the cooling water ascending tube 40 and the cooling descending tube 41 can be lowered. In the water rod 19B of FIG. 19, the lower end of the descending tube 16 is closed and delivery ports 29 are formed in the side surface of the descending tube 16 so as not to be affected by the dynamic pressure. Finally, the structure of the boiling-water reactor in which the above-mentioned fuel assembly is loaded will now be described in conjunction with FIG. 20. A boiling-water reactor 60 has a reactor pressure vessel 61, a recirculation pump 70 and a reactor core 67 loaded with the fuel assembly 10. A reactor core shroud 62 is arranged in the reactor pressure vessel 61 and is mounted therein. Jet pumps 68 are arranged between the reactor pressure vessel 61 and the reactor core shroud 62. A lower support plate 63 of the reactor core is mounted on the lower end of the reactor core shroud 62 and is arranged therein. A plurality of fuel support metal fittings 65 penetrate through the lower support plate 63 of the reactor core and are installed on the lower support plate 63 of the reactor core. Upper lattice plates 64 are arranged in the reactor core shroud 62 and are mounted thereon. A plurality of control rod guide tubes 72 are installed in a lower plenum 71 under the lower support plate 63 of the reactor core. Housings 74 of control rod drive devices are mounted on the bottom of the reactor pressure vessel 61. A recirculation conduit 69 which communicates the reactor pressure vessel 61 with the reactor core shroud 62 it open at the upper end of the jet pumps 68. The recirculation conduit 69 is provided with the recirculation pump 70. Control rods 73 are arranged in the control rod guide tubes 72, and are linked to control rod driving devices (not shown) installed in the housings 72 of the control rod drive devices. The lower tie plates 13 of the fuel assembly 10 are inserted in and are held by the fuel support metal fittings 65, and the upper ends thereof are supported by the upper lattice plates 62. Being driven by the control rod drive devices, the control rods 73 are inserted among the fuel assemblies 10 penetrating through the fuel support metal fittings 65. The cooling water is supplied into the reactor core 67 as described below. That is, the recirculation pump 70 is driven, and the cooling water between the reactor pressure vessel 61 and the reactor core shroud 62 is injected to the upper end of jet pump 68 through the recirculation couduit 69. The cooling water between the reactor pressure vessel 31 and the reactor core shroud 62 is further intaken by the jet pump 68 as the cooling water is injected. The cooling water delivered from the jet pump 68 flows into the lower plenum 71 and into the cooling water paths 66 of the fuel support metal fittings 65, and is supplied into the fuel assembly 10 via the lower tie plate 13. When the nuclear reactor is producing the output of a low level, the control rods 72 are pulled out from the reactor core to increase the output of the nuclear reactor. The output of a high level of the nuclear reactor can be controlled by changing the number of revolutions of the recirculation pump 70 and by increasing or decreasing the flow rate in the reactor core. By pulling out the control rods and by adjusting the flow rate in the reactor core, the nuclear reactor produces a rated 100% output with a flow rate in the reactor core of 80%. The operation for compensating the decrease of reactor output due to the consumption of the core material and the poeration for shifting the flow condition in the water rod 19 from the condition of FIG. 3A to the condition of FIG. 3C, are performed by increasing the flow rate in the reactor core, i,e., by increasing the number of revolutions of the recirculation pump 70. With the recirculation pump running at a speed that produces the flow rate of smaller than 100% in the reactor core, the condition of FIG. 3A is established in the water rod 19 whereby the vapor is built up in the coolant descending path 26. With the recirculation pump running at a speed that produces the flow rate of greater than 110% in the reactor core, the condition of FIG. 3C is established in the water rod 19, and no vapor is built up. It can therefore be said that the recirculation pump 70 serves as means that controls the accumulating amount of voids (vapor) in the water rod 19. The fuel assembly 35 may be loaded in the reactor core 67 instead of the fuel assembly 10. Furthermore, the recirculation pump 70 may be replaced by an internal pump that is mounted in the reactor pressure vessel 61. The water rod 19A shown in FIG. 18A has an inverted U shape, and includes the cooling water ascending tube 40 and the cooling water descending tube 41. However, this water rod 19A is not free from the following problems. To assemble the water rod 19A, there is a way to couple the cooling water ascending tube 20 and the cooling water descending tube 41 by welding using the coupling tube 22. When they are welded, the cooling water ascending tube 20 and the coupling tube 22 are welded from outside throughout their entire preiphery and then the cooling water descending tube 21 and the coupling tube 42 are welded from outside. However, if the gap between the cooling water ascending tube 40 and the cooling water descending tube 41 is small, welding between the cooling water descending tube 41 and the coupling tube 42 on the cooling water ascending tube side cannot be carried out. The reason is that since the gap between the cooling water ascending tube 40 and the cooling water descending tube 41 is small, a welding torch or a welding rod cannot be inserter into this gap. Accordingly, the cooling water ascending tube 40 and the cooling water descending tube 41 must be spaced apart from each other by a gap large enough to carry out the welding work described above. However, this results in the increase in the distance between the axes at both ends of the coupling tube 42 for individually coupling the cooling water ascending tube 40 and the cooling water descending tube 41. The fuel assembly according to still another embodiment of the present invention which solves this problem will be explained next. The fuel assembly according to still another preferred embodiment of the present invention for the boiling-water reactor will be explained with reference to FIGS. 21 and 22. The fuel assembly 10A of this embodiment includes the water rod 19C, the fuel rod 11, the upper the plate 12A, the lower tie plate 13A and the fuel spacer 16A. The upper and lower end portions of the fuel rod 11 are supported by the upper tie plate 12A and the Lower tie plate 13A, respectively. A plurality of fuel spacers 16A are disposed in the axial direction of the fuel assembly 10A and keep the gap between the adjacent fuel rods 11 under a suitable condition. The fuel spacer 16A is held by the water rod 19C. The channel box 17 is fitted to the upper tie plate 12A and encompasses the outer periphery of the bundle of the fuel rods 11 held by the fuel spacers 16A. The lower tie plate 13A is equipped with the fuel rod supporting portion 12A at its upper end and moreover has the space 15 thereinside below the fuel rod supporting protion 14A. The fuel rod supporting portion 12A supports the lower end portion of each of the fuel rods 11 and water rod 19C. The water rod 19C includes a lower end plug 49, an ascending tube 46, a coupling portion 47, a descending tube 48 and an upper end plug 52. The water red 19C constituted by these components is made of a zirconium alloy. The ascending tube 46 has a large diameter tube portion 46A, a small diameter tube portion 46B having an outside diameter smaller than that of the large diameter portion 46A and a taper portion 46C. The taper portion 46C has a through-hole 53 therein the outside is tapered. The lower end of the large diameter tube portion 46 is coupled to the upper end of the taper portion 46C by welding. The upper end of the small diameter portion 46B is coupled to the lower end of the taper portion 46C by welding. The lower end of the small diameter tube portion 46B is coupled to the lower end plug 49 by welding. The upper end of the large diameter tube portion 46A is coupled to the coupling portion 47 by welding. The descending tube 28 is disposed in parallel with the ascending tube 26, and its upper end is coupled to the coupling portion 27 by welding. The upper end plug 52 is fitted to the upper end of the coupling portion 47. The lower end plug 49 under the condition where the water rod 19C is supported by the fuel rod supporting portion 14A is shown in magnification in FIG. 23. A path 49A is defined inside the lower end plug 49, and a coolant inlet port 51 is made in the end of the lower end plug 49. The coolant inlet port 51 is made in the side wall of the lower end plug 49 and communicates with the path 49A. The lower end plug 49 includes a projecting portion 49B the upper end of which is sealed. An opening 56 is so made on the side wall of the projecting portion 49B as to be directed sideways. The projecting portion 49B is disposed inside the small diameter tube portion 46B concentrically with the portion 46B and is positioned above the weld portion between the small diameter tube portion 46B and the lower end plug 49. Accordingly, a clad reservoir 54 is annularly formed between the small diameter portion 46B and the lower end plug 49. This clad reservoir 54 is positioned below the opening 56. The lower end plug 49 is fitted into a hole 58 defined in a boss 57 which is disposed on the lower surface of the fuel supporting portion 14A of the lower tie plate 13A. The lower end of this hole 58 is sealed. In the side wall of the boss 57, an opening 59 directed sideways and leading to the hole 58 is made. The outer diameter of the lower end plug 49 is substantially the same as the inner diameter of the hole 58. The lower end of the path 49A extending inside the lower end plug 49 in the axial direction of the plug 49 is closed by the bottom of the boss 57. When the radiation growth of the water rod 19C due to radiation with the increase in the burnup of the fuel assembly is taken into consideration, it is preferable that the opening 59 has a margin on the higher side than the coolant inlet port 51 of the lower end plug 59 to be of greater size. Furthermore, when the possibility of the change of the positional relationship between the lower end plug 49 and the fuel supporting portion 14A from the relationship at the time of production due to combustion of the nuclear fuel, etc, is taken into consideration, it is preferable that the opening 59 has also a margin on the lower side of the coolant inlet port 51. The cooling water ascending path 25 is defined inside the lower end plug 49 and the ascending tube 46. In other words, it includes the path 49, the opening 56, the space inside the small diameter tube portion 46B, the through-hole and the inside of the large diameter tube portion 46A. The coolant inlet port 51 is positioned below the fuel supportion portion 14A and communicates with the space 15. The lower end of the descending tube 48 is sealed, and a delivery port 55 is formed in the side wall of the lower end portion of this tube 48. The delivery port 55 is positioned above the fuel supporting portion 14A. The cooling water descending path 26 is defined inside the descending tube 48. The delivery port 55 communicates with the descending path 26 and communicates with the coolant path 38 defined between the fuel rods 11 above the fuel supporting portion 14A. The coupling portion 47 has a coupling portion lower part 47A and a coupling portion upper part 47B as shown in FIG. 22. The couping portion lower part 47A and coupling portion upper part 47B are coupled to each other by welding. The large diameter tube portion 46A and the descending tube 48 are welded to the coupling portion lower part 47A. The path 36 defined inside the coupling portion 47 is for communication of the cooling water ascending path 25 with the cooling water descending path 26. Accordingly, the water rod 19C has an inverted U shape as shown in FIG. 22. Reference numeral 37A denotes a weld portion between the coupling portion lower part 47A and the ascending tube 46, 37B denotes a weld portion between the coupling portion lower part 47A and the descending tube 48, and 37C denotes a weld portion between the coupling portion lower part 47A and the coupling portion upper part 47B. The fuel spacer 16A includes a plurality of cylindrical round cells 75 that are arranged in a square grid. The round cells 75 are mutually coupled by welding. Each round cell 75 has two rigid supporting portions 75A that protrude inward. Flexible supporting members 76 are disposed on the adjacent round cells 75. The fuel rod 11 inserted into each round cell 75 is supported at three points by the two rigid supporting portions 75A and the flexible supporting member 76. Two water rods 19C and 19D are inserted into a region formed between the round cells 75 at the center of the fuel spacer 16A. The ascending tube 46 of the water rod 19C and the ascending tube 46a of the water rod 19D are positioned on one of the diagonals of the fuel spacer 16A and adjacent to each other. The descending tube 48 of the water rod 19C is positioned between a round cell 75E and a round cell 75F that are adjacent to the ascending tube 46. Similarly, the descending tube 48a of the water rod 19D is positioned between the two round cells adjacent to the ascending tube 46a and adjacent to each other. Since the descending tubes 48 and 48a are disposed between the adjacent round cells, the outside diameter of the large diameter tube portion 46A of each of the water rods 19C and 19D can be increased within such a range that seven fuel rods 11 can be disposed. This results in the increase in the transverse sectional area of the coolant ascending path 13 inside the large diameter tube portion 46A. The descending tubes 48 and 48a are positioned in mutually opposite directions in the direction of the other diagonal of the fuel spacer 16A perpendicularly crossing the diagonal described above on which the ascending tubes 46 and 46a are positioned. The ascending tube 46 is supported at three points by the rigid supporting members 27A and 27B fitted to a plurality of round cells 25 opposing to the ascending tube 46 or 46a and by the flexible supporting member 78A disposed on a bridging member fitted to the adjacent round cells 75. The ascending tube 46a is supported at three points by the rigid supporting members 27A and 27B and a flexible supporting member 78B disposed on a bridging member fitted to the adjacent round cells 75. The ascending tubes 46 and 46a supported in this manner is not in contact with each other. The descending tube 48 (having an outside diameter of about 5 mm) is supported at the large diameter tube portion 46A of the ascending tube 46 by supporting members (for example, the supporting member 45 shown in FIG. 18A), not shown in the drawings. A narrow gap is defined between the descending tube 48 and the large diameter tube portion 46A. The descending tube 48a is supported similarly by the large diameter portion 46A of the ascending tube 46a. The cross-sectional area of the cooling water descending path 26 inside the water rod 19C and the descending tube 19D is smaller than 1/25 of the cross-sectional area of the cooling water ascending path 25 (at the large diameter tube portion 46A) inside the ascending tube. Therefore, the fuel assembly 10A can have the characteristics shown by the solid line in FIG. 6 and by the single dot and dash line in FIG. 7 of U.S. Pat. No. 5,023,047. When the fuel assemblies 10A are loaded in the core, the boiling-water reactor can operate as shown in FIG. 15 of U.S. Pat. No. 5,023,047 by regulating the flow rate of cooling water supplied to the core. When the quantity of the cooling water supplied into the fuel assembly 10A having the water rods 19C and 19D each equipped thereinside with the cooling water ascending path 25 and the cooling water descending path 26 is changed, the flow condition of the fluid inside the water rods 19C and 19D changes as shown in FIGS. 3A, 3B and 3C. In other words, the fuel assembly 10A is loaded in the core of the boiling-water reactor. The flow rate of the cooling water supplied to the core is regulated by controlling the number of revolutions of a recirculation pump, not shown in the drawing. The cooling water is first guided to the space 15 of the lower tie plate 13A. The major proportion of this cooling water passes through the through-hole 18A bored in the fuel supporting portion 14A, flow into the coolant path 38 above the upper surface of the fuel supporting portion 14A and cool the fuel rod 11. Part of the rest cooling water flows into the coolant ascending path 25 of the water rod 19C through the opening 59 and the coolant inlet port 51. This also holds true for the water rod 19D. The flow of the fluid inside the cooling water ascending path 25 will be explained. The cooling water guided to the path 49A as a part of the cooling water ascending path 25 reaches the large diameter tube portion 46A through the opening 56, the small diameter tube portion 46B and the taper portion 46C. When the flow rate of cooling water supplied into the fuel assembly 10A is low, the cooling water existing inside the cooling water ascending path 25, particulary in the large diameter tube portion 46A, is heated by radiation of gamma rays generated from nuclear fission of the nuclear fuel. When the flow rate of cooling water supplied into the fuel assembly 10A is low, the cooling water turns to vapor, and a vapor region is formed inside the cooling water ascending path 25 as shown in FIG. 3A. Consequently, a liquid surface is formed inside the cooling water ascending path 25. The generated vapor is discharged from the coolant delivery port 55 into the cooling water path 38 throuhg the path 36 and cooling water descending path 26. As the flow rate of cooling water increases, the liquid level inside the cooling water ascending path 25 rises and the vapor region decreases. Through the condition shown in FIG. 3C, that is, the condition where the cooling water ascending path 25 and the cooling water descending path 26 are fully filled with cooling water, is finally established. Accordingly, since the change of the voidity inside the fuel assembly 10A can be enlarged between the initial stage and the final stage of the fuel cycle in this way, the effect of the spectrum shift can be increased and the period of one fuel cycle can be drastically lengthened. It is around the final stage of the fuel cycle when the insides of the cooling water ascending path 25 and the cooling water descending path 26 are fully filled with cooling water, and the vapor region is formed inside the cooling water ascending path 25 through the major proportion of the fuel cycle. Accordingly, when the cooling water descending path is so disposed as to encompass the cooling water ascending path as shown in FIG. 7A, the tube wall disposed between the cooling water ascending path and the cooling water descending path comes into contact with the vapor and its temperature becomes high because cooling is not sufficient. In this embodiment, the ascending tube 46 and the descending tube 48 are so arranged as to define the inverted U shape and moreover, the gap exists between these ascending and descending tubes 46, 48 as already described. Accordingly, the peripheries of both of the ascending and descending tubes 46, 48 are cooled by cooling water ascending in the cooling water path 38. Therefore, the temperatures of the ascending tube 46 and the descending tube 48 drop and the problem involved in the water rod and shown in FIG. 7A can be solved. The reason why the condition where the liquid surface is formed inside the water rod 19C shifts to the condition where the liquid surface is not formed by the regulation of the flow rate of cooling water supplied into the fuel assembly 10A is that the fuel supporting portion 14A functions as a resistance to the cooling water path 38 and the total cross-sectional-area of all the through-holes 18A provided in the fuel supporting portion 14A is so determined that the liquid surface can be moved. In other words, the total cress-sectional area of all the through-holes 18A is so determined as to correspond to the static head corresponding to the difference between the level at the upper end of the cooling water ascending path 25 and the level of the coolant delivery port 55. The total cross-sectional area of all the through-holes 18A made in the fuel supporting portion 14A is smaller than the cross-sectional area of the cooling water path 38. The fuel supporting portion 14A having such a construction serves as the resistance to the cooling water path As described above, the cross-sectional area of the cooling water ascending path 25 inside the large diameter tube portion 46A can be increased by disposing the descending tubes 48 and 48a between the adjacent round cells 75. Accordingly, when the vapor region is formed inside the large diameter tube portion 46A, the quantity of plutonium produced increases so much more, and when the insides of the cooling water ascending path 25 and the cooling water descending path 26 are filled with the cooling water (moderator) near the end of the fuel cycle, nuclear fission of plutonium and other fission substances can be activated. Accordingly, the reactivity at the center of the cross-section of the fuel assembly 10A can be much more improved and effective utilization of the nuclear fuel can be accomplished. In other words, the effect of the improvement in fuel economy due to the spectrum shift can be further improved. The descending tubes 48 and 48a are positioned in the mutually opposite directions on the other diagonal crossing perpendicularly the diagonal on which the ascending tubes 46 and 46a are positioned. Therefore, even when the descending tubes 48 and 48a are filled with the vapor, the vapor region does not locally concentrate on the cross-section of the fuel assembly, and the fuel assemblies can be disposed in a good balance. In this way, uneven burnup of the nuclear fuel on the cross-section of the fuel assembly can be prevented. In the water rod shown in FIG. 7A, one coolant inlet port is disposed at the lower end of the cooling water ascending path. For this reason, there is the possibility that the coolant inlet port is clogged by solid matters such as clads that flow with the coolant. The smaller the diameter of the coolant inlet port, the higher becomes this possibility. In this embodiment, the cooling water inlet port 51 is so disposed as to be perpendicular to the axial direction of the cooling water ascending path, and a plurality of such inlet parts 51 are disposed in the circumferential direction of the lower end plug 49. Accordingly, cooling water flowing into the cooling water inlet ports 51 must turn at right angles immediately before the ports 51, and the possibility of clogging of the cooling water inlet port 51 by the clad, etc. is by far smaller than the possibility in the water rod shown in FIG. 7A. Furthermore, since the cooling water inlet port 51 is not disposed in the axial direction of the lower end plug 49, there is no opening in the flowing direction of the core coolant when the lower end is closed. Therefore, the influence of the dynamic pressure due to the flow can be suppressed, and variation of the liquid level inside the water rod due to variation of the dynamic pressure can be remarkably suppressed. As described above, the vapor region is formed inside the cooling water ascending path 25 in the major portion of the fuel cycle, cooling water existing inside the cooling water ascending path 25 is considered to concentrate. Therefore, the clads contained in cooling water may aggregate and settle. The opening 56 is transversely disposed lest it is clogged by the settling clads, and is positioned above the bottom surface of the path formed inside the small diameter tube portion 46B. The settling clads are gradually deposited inside the clad reservoir 54 formed between the small diameter portion and the projecting portion 49B. The capacity of the clad reservoir 54 is determined by estimating the quantity of the clads deposited during the life of the fuel assembly 10A. Next, the assembling process of the ascending tube 46, the coupling portion 47 and the descending tube 48 in this embodiment will be explained with reference to FIGS. 26A to 26D. The lower portion 47A of the coupling portion 47 has through-holes 47E and 47F as shown in FIGS. 26A to 26D, and is lower than the upper end of the lower portion 47A of the coupling portion at which the upper end of the side wall between the through-holes 47E and 47F is formed. The inside diameter of the through-hole 47E is greater than that of the through-hole 47F. FIG. 26D is a sectional view taken along line X--X of FIG. 26C. First of all, the ascending tube 46, that is, the upper end portion of the large diameter tube portion 46A, is fitted to the lower end portion of the side wall encompassing the through-hole 47E of the lower portion 47A of the coupling portion having such a construction by welding over the whole periphery of the large diameter tube portion 46A (FIG. 26A). The lower portion 47A of the coupling portion and the large diameter tube portion 46A are coupled through the weld portion 37A. Thereafter, the upper end portion of the descending tube 48 is fitted into the through-hole 47F of the lower portion 47A of the coupling portion, and the side wall encompassing the through-hole 47F of the lower portion 47A of the coupling portion and the whole periphery of the upper end portion of the descending tube 48 are coupled by welding from above (FIG. 26B). The lower portion 47A of the coupling portion and the descending tube 48 are coupled through the weld portion 37B. The lower portion 47A of the coupling portion is a coupling member for coupling the ascending tube 46 and the descending tube 48 at their upper ends. Finally, the upper portion 47B of the coupling portion is provided on the lower portion 47A of the coupling portion in such a manner as to cover the through-hole 47E of the lower portion 47A of the coupling portion and the cooling water descending path 26 inside the descending tube 48. Under such a condition, the upper end of the lower portion 47A of the coupling portion is fitted to the upper portion 47B of the coupling portion over the whole periphery by welding (FIG. 26C). The lower portion 47A of the coupling portion is integrated with the upper portion 47B of the coupling portion through the weld portion 37C. The upper portion 47B of the coupling portion is a cover member for covering the cooling water ascending path 25 and the cooling water descending path 26 from above. The upper end plug 52 is fitted to the upper portion 47B of the coupling portion by welding. As described above, in the water rod 19C used in this embodiment, the descending tube 48 is fitted into the through-hole 47F and the upper end of the descending tube 48 is fitted to the lower portion 47A of the coupling portion through the weld portion 37C. Accordingly, the whole periphery of the descending tube 48 can be easily welded to the lower portion 47A of the coupling portion. Even when the ascending tube 46 is thin, particularly the gap formed between the large diameter tube portion 46A and the descending tube 48 is thin, the whole periphery of the descending tube 48 can be easily welded to the lower portion 47A of the coupling portion. The descending tube 48 is disposed as shown in FIG. 25, and the width of the gap defined between the descending tube 48 and the large diameter tube portion 46A cannot be much increased. If the width of this gap is increased, the outside diameter of the large diameter tube portion 46A must be reduced. Since this results in the decrease in the cross-sectional area of the cooling water ascending path 25 inside the large diameter tube portion 46A, the effect of the aforementioned spectrum shift is weakened and the degree of improvement in fuel economy drops. In FIG. 25, the descending tubes 48 and 48a cannot be moved further deeply into the gap defined between the round cells 75 from the positions described above because support structural members (not shown) for supporting the descending tubes 48 and 48a on the corresponding large diameter tube portions 46A strike the adjacent round cells 75. By the weld structure of the large diameter tube portion 46A, the descending tube 48 and the lower portion 47A of the coupling portion which is obtained by the assembly method of FIGS. 26A to 26D and is shown in FIG. 24, the width of the gap between the large diameter tube portion 46A and the descending tube 48 can be reduced and the outsider diameter of the large diameter tube portion 46A can be increased. Accordingly, the cross-sectional area of the cooling water ascending path 25 can be increased, and the degree of improvement in fuel economy due to the spectrum shift effect can be increased so much more. Incidentally, since the water rod 19C receives external force through the fuel spacer 16A during earthquake, etc, a bending moment is produced in the water rod 19C. In this embodiment, the structural strength of the water rod 19C is governed by the large diameter tube portion 46A. Accordingly, from the aspect of soundness of the water rod structure, the welding between the large diameter tube portion 46A and the lower portion 47A of the coupling portion is preferably of an ordinary type. Further, the size of the lower portion 47A of the coupling portion can be reduced much more greatly by welding the large diameter tube portion 46A to the lower portion 47A of the coupling portion in the state that the lower end of the lower portion 47A of the coupling portion is inserted into the upper end of the large diameter tube portion 46A as shown in FIG. 26C than by welding contrarily the large diameter tube portion 46A to the lower portion 47A of the coupling portion in the state that the lower portion 47A of the coupling portion encompasses the outside of the large diameter tube portion 46A. This welding is preferable from the aspect of the reduction of the size of the coupling portion 4, too. In the water rods 19C and 19D used in this embodiment, the lower end plug 49 having a smaller outside diameter than that of the large diameter tube portion 46A and the small diameter tube portion 46B are arranged above the upper surface of the lower tie plate 13A (the upper surface of the fuel supporting portion 14A). Therefore, the outside diameter of the ascending tube 46 near the lower end portion, that is, at the portion which is lower than the fuel spacer 16A at the lowermost level is reduced. The portion having this reduced outside diameter has a length of about 3 to 4% of the full length of the water rods 19C, 19D in the axial direction. Even when the bending stress acts on the ascending tube 46 of each water rod 19C, 19D during an earthquake, etc, excessive stress at the lower end of the ascending tube 46 can be prevented by reducing the outside diameter of the ascending tube 46 of each water rod 19C, 19D over the range of 3 to 4% of the full length of the water rod 19C, 19D in the axial direction upward from the upper surface of the lower tie plate 13A. Besides the assembly method of the ascending tube 46, the coupling portion 47 and the descending tube 48 described above, the ascending tube 46 and the descending tube 48 can be easily welded to the lower portion 47A of the coupling portion over the whole periphery by the following method even when the gap defined between the large diameter portion 46A and the descending tube 48 is small. In this assembly method, the inside diameter of the through-hole 47E of the lower portion 47A of the coupling portion is equal to the outside diameter of the large diameter tube portion 46A of the ascending tube, 46, the large diameter tube portion 46A is inserted into the through-hole 47E, and the upper end of the large diameter tube portion 46A is welded to the lower portion 47A of the coupling portion. The descending tube 48 is welded to the side wall on the lower surface side of the lower portion 47A of the coupling portion under the state where a part of the side wall encompassing the through-hole 47F is inserted into the descending tube as shown in FIG. 26A. The upper end of the lower portion 47A of the coupling portion is welded to the upper portion 47B of the coupling portion over the whole periphery as shown in FIG. 26C. By this second method, the coupling portion 47 is large and the pressure loss of the fuel assembly increases in comparison with the assembly method shown in FIGS. 26A to 26D. The reason is that since the large diameter tube portion 46A is inserted into the through-hole 47E, the side wall encompassing the through-hole 47E becomes necessary. The inside diameter of the through-hole 47F becomes smaller than that of the descending tube 48. In the assembly method shown in FIGS. 26A to 26D and in the method described above, the weld portions of the large diameter tube portion 46A and the descending tube 48 to the lower portion 47A of the coupling portion are shifted from each other in the axial direction. Accordingly, welding of one of them does not adversely affect welding of the other, and does not either hinder the insertion of the tube used for the other welding into the corresponding through-hole (into the lower portion 47A of the coupling portion). Another embodiment of the lower end plug of the water rod used in the embodiment described above is shown in FIG. 27. This lower end plug 49E is the one in which the lower end of the lower end plug 49 is closed. In other words, the lower end of the passage 49A is closed. The upper structure of the lower end plug 49E, not shown in the drawing, is the same as that of the lower end plug 49. The lower end plug 49E has the same effect as that of the lower end plug 49. Further, by the use of this lower end plug 49E, the boss 57 is not necessary for the fuel supporting portion 14B, and the structure of the lower tie plate 13A can be simplified. It is also possible to use a lower end plug 49F shown in FIG. 28 which is produced by swaging the lower end plug 49 described above. In this case, a round plate member for closing the passage 49 is fitted to the lower end of the lower end plug 49F. The projecting portion 49B formed on the lower end plug 49 is fitted to the upper part of the lower end plug 49F. This lower end plug 49, too, can has the same effect as that of the lower end plug 49F. FIG. 29 shows still another embodiment of the lower end plug. The lower end plug 49 of this embodiment has an opening 51A of the passage 49A. The upper structure of the lower end plug 49G is the same as that of the lower end plug 49. The lower end plug 49G has a tapered part outside the side wall encompassing the passage 49A. The formation of this taper can prevent clogging of the opening 51A by solid matters such as the clads flowing with the cooling water. However, since the opening 51A is directed in the flowing direction of cooling water, the effect of reducing the influence of the dynamic pressure is low like the opening 51 of the lower end plug 49. Another embodiment of the structure at and near the delivery port 55 of the descending tube 48 is shown in FIG. 30. In the embodiment shown in FIG. 21, the delivery port 55 is formed in the side surface of the descending tube 48 so as to suppress the influences of the dynamic pressure due to cooling water flowing outside the water rods. However, from the aspect of the suppression of the influences of the dynamic pressure due to the flow of cooling water, it is preferable to form a plurality of openings 55A in the upper surface of the header 79 in which the lower end portion of the descending tube 48A is enlarged like an inverted corn. The cooling water or the vapor descending inside the cooling water descending passage 26 flows out through the openings 55A in the flowing direction of cooling water inside the cooling water path 38. Since the delivery direction of the fluid through the openings 55A and the flowing direction of the cooling water inside the cooling water path 38 become substantially the same, discharge of the fluid through the openings 55A becomes smooth. FIG. 32 shows another example of the structure at and near the delivery port of the descending tube 48B shown in FIG. 30. This structure includes the header 79A having a slant inclining outward from the descending tube 48B on the upper surface thereof, at the lower end portion of the descending tube 48B. Four openings 55B are made on the upper slant of the header 79A in the same way as in FIG. 31. A water rod 19E as another embodiment of the water rod 19C shown in FIG. 22 is shows in FIG. 33. This water rod 19E includes a supporting portion 81 extending downward at the lower end of the descending tube 48. This supporting portion 81 is inserted into the fuel supporting portion 14A of the lower tie plate 13A. According to such a structure, the supporting force of the descending tube 48 can be increased, and the possibility of flow vibration of the descending tube 48 due to the flow of cooling water flowing inside the cooling water descending tube 38 can be reduced. Since the radiation growth quantity of the fuel rod 11 due to the radiation is greater than that of the water rod 19E, the water rod 19E moves upward through the fuel spacer 16A depending on the difference of the radiation growth quantity between the water rod 19E and the fuel rod 11. The lower end plug 49 of the ascending tube 46 has a sufficient length such that it does not come off the fuel supporting portion 14A due to the upward movement described above.
	claims	1. An exoskeleton frame comprising:a frame body made of a single flat continuous piece of flexible material configured to be manipulated such that in a first position, the single flat continuous piece of flexible piece of material is bent and includesa front torso member positioned such that when the exoskeleton frame is worn by a user the front torso member is located along a front of a torso of the user;a back torso member positioned such that when the exoskeleton frame is worn by a user the back torso member is located along a back of the torso of the user;a first shoulder band located at a bend of the single flat continuous piece of material, the first shoulder band extending from the front torso member to the back torso member;a second shoulder band located at the bend of the single flat piece of material, the second shoulder band extending from the front torso member to the back torso member; andan opening positioned between the first shoulder band and second shoulder band such that when the exoskeleton frame is worn by a user, a neck of the user is located within the opening,wherein the single flat continuous piece of flexible material is configured to be manipulated such that in a second position, the single flat continuous piece of flexible material is at least partially unbent such that the front torso portion is moved away from the back torso portion; andan adjustable belt removably attached to the front torso and back torso member,wherein the adjustable belt is configured to direct a weight of apparel that is worn by the user over the exoskeleton frame to a weight-bearing area of the user located between knees and abdomen of the user, and wherein the first shoulder band and second shoulder band are configured to support the weight of the apparel such that the weight of the apparel is held off of a first shoulder and a second shoulder of the user. 2. The exoskeleton frame of claim 1, wherein the front torso member and back torso member each include at least one belt attachment structure configured to attach the adjustable belt to the exoskeleton frame. 3. The exoskeleton frame of claim 2, wherein the at least one belt attachment structure includes a plurality of slits configured to securably receive the adjustable belt. 4. The exoskeleton frame of claim 1, wherein the back torso member includes a first vertical element having a first end, wherein the front torso member includes:a chest plate positioned such that when the exoskeleton frame is worn by the user the chest plate is located in front of a chest area of the user;a second vertical element having a second end; anda third vertical element having a third end,wherein the first shoulder band and second shoulder band extend from the chest plate to the back torso member,wherein the second vertical element and third vertical element extend from the chest plate opposite the first shoulder band and second shoulder band. 5. The exoskeleton frame of claim 4, wherein the first vertical element includes a first plurality of slits located proximate to the first end, wherein the second vertical element includes a second plurality of slits located proximate to the second end, wherein the third vertical element includes a third plurality of slits located proximate to the third end, wherein the first plurality of slits, second plurality of slits, and third plurality of slits are configured to receive the adjustable belt such that the adjustable belt is securable to the exoskeleton frame at different locations along the first vertical element, second vertical element, and third vertical element. 6. The exoskeleton frame of claim 1, wherein the front torso member includes a space positioned such that when the user is wearing the exoskeleton frame, the space is located in front of a stomach area of the user. 7. The exoskeleton frame of claim 1, wherein when the exoskeleton frame is worn by a user, a first gap is located between the first shoulder of the user and the first shoulder band, and a second gap is located between the second shoulder of the user and the second shoulder band. 8. The exoskeleton frame of claim 7, wherein the first shoulder band and second shoulder band are configured to compress while maintaining the first gap and second gap by holding the apparel off of the first shoulder and the second shoulder of the user when apparel is worn over the exoskeleton frame by the user. 9. The exoskeleton frame of claim 1, wherein a space between the front torso member and back torso member is adjustable to fit differently sized users by lengthening or shortening a length of the adjustable belt. 10. A method comprising:providing a single flat continuous piece of flexible material configured to be manipulated such that in a first position, the single flat continuous piece of flexible piece of material is bent and includesa front torso member positioned such that when the exoskeleton frame is worn by a user the front torso member is located along a front of a torso of the user;a back torso member positioned such that when the exoskeleton frame is worn by a user the back torso member is located along a back of the torso of the user;a first shoulder band located at a bend of the single flat continuous piece of material, the first shoulder band extending from the front torso member to the back torso member;a second shoulder band located at the bend of the single flat piece of material, the second shoulder band extending from the front torso member to the back torso member; andan opening positioned between the first shoulder band and second shoulder band such that when the exoskeleton frame is worn by a user, a neck of the user is located within the opening,wherein the single flat continuous piece of flexible material is configured to be manipulated such that in a second position, the single flat continuous piece of flexible material is at least partially unbent such that the front torso portion is moved away from the back torso portion;forming a preformed frame body out of the single flat continuous piece of flexible material by bending the single flat continuous piece of flexible material, such that the preformed frame body includes a first shoulder band located at a bend of the single flat continuous piece of flexible material, the first shoulder band, a second shoulder band located at the bend of the single flat piece of flexible material, the second shoulder band, an opening between the first shoulder band and second shoulder band, a front torso member, and a back torso member; andmanipulating the preformed frame body into a frame body such that when the frame body is worn by a user, the front torso member is located in front of a torso of the user and the back torso member is located along a back of the torso of the user, and the first shoulder band and second shoulder band are configured to support the weight of apparel that is worn by the user over the frame body such that the weight of the apparel is held off of a first shoulder and a second shoulder of the user. 11. The method of claim 10, including attaching an adjustable belt to the front torso member and back torso member. 12. The method of claim 10, including forming the preformed body out of the single flat continuous piece of flexible material such that the back torso member includes a first vertical element having a first end, and such that the front torso member includes:a chest plate;a second vertical element having a second end; anda third vertical element having a third end,wherein the first shoulder band and second shoulder band extend from the chest plate to the back torso member,wherein the second vertical element and third vertical element extend from the chest plate opposite the first shoulder band and second shoulder band. 13. The method frame of claim 12, including forming the preformed body out of the piece of material such that a space is located between the second vertical element and the third vertical element. 14. The method frame of claim 10, including forming at least one belt attachment structure in each of the front torso member and back torso member. 15. The method frame of claim 10, wherein the manipulating the single flat continuous piece of flexible material into a frame body includes bending the preformed frame body such that a first end of the back torso member is aligned with a second end of the front torso member. 16. The method of claim 15, including applying heat to the preformed frame body while the preformed frame body is bent. 17. The method of claim 10, wherein the single flat continuous piece of flexible material is a high-density polyethylene. 18. The method of claim 10, wherein the forming a preformed frame body out of the single flat continuous piece of flexible material includes at least one of cutting and stamping the piece of material. 19. An exoskeleton frame comprising:a frame body made of a single flat continuous piece of flexible material configured to be manipulated such that in a first position, the single flat continuous piece of flexible piece of material is bent and includesa front torso member positioned such that when the exoskeleton frame is worn by a user the front torso member is located along a front of a torso of the user;a back torso member positioned such that when the exoskeleton frame is worn by a user the back torso member is located along a back of the torso of the user;a first shoulder band located at a bend of the single flat continuous piece of flexible material, the first shoulder band extending from the front torso member to the back torso member;a second shoulder band located at the bend of the single flat continuous piece of flexible material, the second shoulder band extending from the front torso member to the back torso member; andan opening positioned between the first shoulder band and second shoulder band such that when the exoskeleton frame is worn by a user, a neck of the user is located within the opening,wherein the single flat continuous piece of flexible material is configured to be manipulated such that in a second position, the single flat continuous piece of flexible material is at least partially unbent such that the front torso portion is moved away from the back torso portion,wherein the front torso member and back torso member are configured to receive an adjustable belt that is configured to direct a weight of apparel that is worn by the user over the exoskeleton frame to a weight-bearing area of the user located between knees and abdomen of the user, and wherein the first shoulder band and second shoulder band are configured to support the weight of the apparel such that the weight of the apparel is held off of a first shoulder and a second shoulder of the user. 20. The exoskeleton frame of claim 19, wherein the back torso member includes a first vertical element having a first end, wherein the front torso member includes:a chest plate positioned such that when the exoskeleton frame is worn by the user the chest plate is located in front of a chest area of the user;a second vertical element having a second end; anda third vertical element having a third end,wherein the first shoulder band and second shoulder band extend from the chest plate to the back torso member,wherein the second vertical element and third vertical element extend from the chest plate opposite the first shoulder band and second shoulder band. 21. A method comprising:providing the exoskeleton frame of claim 19; andwearing the exoskeleton frame, by a user, such that the first shoulder band and second shoulder band are positioned above a first shoulder and second shoulder of the user, and such that a first gap is between the first shoulder and first shoulder band, and a second gap is between the second shoulder and second shoulder band. 22. The method of claim 21, wherein the first shoulder band and second shoulder band are compressible such that the first gap and second gap are maintained when the apparel is worn by the user over the exoskeleton frame, and decompressible when the apparel is taken off by the user.
044951388	summary	SUMMARY OF THE INVENTION The invention relates to a junction device between the delivery duct of a primary pump and a duct joined to the core support of a liquid metal cooled fast neutron nuclear reactor. BACKGROUND OF THE INVENTION In a liquid metal cooled fast neutron nuclear reactor, the liquid metal constitutes the primary fluid permitting the cooling of the fuel element assemblies which give off heat and which form the core of the reactor. The heat from the core is taken off by the liquid metal, generally liquid sodium, which is pumped to the bottom of the core by the primary pumps, which may be immersed in the liquid sodium filling the reactor vessel in the case of an integrated nuclear reactor, or be disposed outside the vessel in the case of a loop type nuclear reactor. The liquid sodium heated by the reactor core enters heat exchangers permitting the heating of a second liquid metal constituting the secondary fluid, which in turn is used to produce steam in the steam generators. On leaving the heat exchangers, the cooled primary fluid enters a zone of the vessel where, with the aid of the primary pumps, it is re-injected at the base of the reactor core. The sodium cooled in the heat exchangers, i.e., cold sodium, is nevertheless at a temperature higher than 300.degree., so that the primary pumps undergo expansions when the nuclear reactor is in operation. Furthermore, the temperature of the primary fluid is not constant in the course of the operation of the reactor, and consequently the expansion of the different parts of the pump is variable. In addition, the pumps and their accessories undergo vibrations, which are in particular due to the circulation of the liquid sodium at high speed. In nuclear reactors of the integrated type, and in particular, in which the primary pumps inject the liquid metal into ducts joined to the core support, it is necessary to assure continuity of circulation of this liquid sodium between the pump and the duct joined to the support, and at the same time to permit displacements of the pump relative to the core support or bed on which the fuel element assemblies rest and which enables them to be supplied with sodium. In order to carry out these functions, use is generally made of a connecting sleeve having its ends fixed on the pump delivery duct and on the bed respectively, in a non-rigid manner, and leading into the duct joined to the bed. A cylindrical sleeve of this kind nevertheless does not enable the speed of flow of the liquid metal to be controlled before it is injected into the duct joined to the bed. Moreover, in order to permit transverse displacements relative to the flow, it is necessary to provide a universal joint arrangement for the entire pump, thereby complicating the construction and the fastening of the latter. Finally, it is not possible to mount the pump sufficiently flexibly to absorb the displacements and at the same time sufficiently rigidly and with sufficient mechanical strength to withstand the various stresses (particularly earthquakes). OBJECT OF THE INVENTION An object of the invention is therefore a junction device between the delivery duct of a primary pump and a duct fastened to the core support of a liquid metal cooled fast neutron nuclear reactor, in which the liquid metal constituting the primary fluid of the reactor is pumped to the base of the core by primary pumps which inject the liquid metal into ducts joined to the core support for the purpose of cooling the core, this junction device permitting adequate displacements of the pump relative to the core support during the operation of the reactor while assuring a stable junction and withstanding mechanical stresses, particularly vibrations, and effecting a degree of regulation of the speed of the liquid metal before its injection into the duct joined to the core support. To this end, the junction device according to the invention comprises: a sleeve of frusto-conical shape disposed as an extension of the pump deliver duct and having its smaller base situated near the outlet of the delivery duct and its larger base near the inlet of the duct joined to the core support; PA1 a connecting member joined to the sleeve at its smaller base and symmetrical in revolution around the axis of the sleeve, this member carrying in its central portion, near the axis of symmetry, the movable portion of an articulated connection means whose fixed portion is carried by the pump, thus permitting at one and the same time lateral displacements and the retention of the sleeve on the pump duct despite the axial force exerted thereon, while the peripheral portion of the connecting member, which has a diameter larger than the diameter of the smaller base of the sleeve, has a spherical surface, symmetrical around the axis of the sleeve, which is complementary to a corresponding surface machined on the end of the pump delivery duct, fluid-tightness between these two surfaces disposed against one another being achieved with the aid of a labyrinth seal, while the pressure of the liquid metal delivered by the pump, applied to the portion of the connecting member which lies between its peripheral portion and its portion fixed to the sleeve, makes it possible to exert an axially directed force on the sleeve; PA1 a sealing device inserted between the outlet end of the sleeve and the duct joined to the core support, the end of this device on which the outlet end of the sleeve is engaged being of a different diameter from that of the end of the sleeve; PA1 an elastic means inserted between the end of the sleeve and a bearing member joined to the core support, this elastic means extending over the entire periphery of the sleeve for the lateral support of the sleeve, the outlet end of which can move freely in the axial direction relative to the duct joined to the core support.
043303676	summary	The following allowed and issued patents are herein incorporated by reference: U.S. Pat. No. 3,752,735 issued on Aug. 14, 1973 entitled "Instrumentation for Nuclear Reactor" invented by Charles R. Musick and Richard P. Remshaw. U.S. Pat. No. 3,356,577 issued to Ygal Fishman on Dec. 5, 1967 entitled "Apparatus for Determining the Instantaneous Output of a Nuclear Reactor." BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to safety systems for nuclear reactors. More specifically, this invention is directed to the prediction of internal reactor conditions commensurate with maintaining the integrity of the fuel element cladding. Accordingly, the general object of the present invention is to provide novel and improved apparatus and methods of such character. The performance of a nuclear reactor, like that of many other energy conversion devices, is limited by the temperature which component materials will tolerate without failure. In the case of a reactor with a core comprising an assemblage of fuel assemblies which in turn consist of an array of fuel rods or pins, the upper limit of temperature is imposed by the fuel rod or fuel pin cladding material employed. In order to adequately protect the reactor core against excessive temperatures, it is necessary to examine the temperature of the "hottest" fuel pin or the "hottest" coolant channel between adjacent fuel pins of the core, since damage will first occur in the "hottest" fuel pin. Thus the "hottest" pin or channel becomes the limiting pin or channel for the reactor core. As is well known, heat is generated in a reactor by the fission process in the fuel material. The fission process, however, produces not only heat but radioactive isotopes which are potentially harmful and which must be prevented from escaping to the environment. To this end, the fuel is clad with a material which retains the fission products. In order to prevent clad overheating and in the interest of precluding release of the fission products which would occur on clad damage or failure, a coolant is circulated through the reactor core. Heat transferred to the circulating coolant from the fuel elements is extracted therefrom in the form of usable energy downstream of the reactor core in a steam generator. Thus, for example, in a pressurized water reactor system, the water flowing through the core is kept under pressure and is pumped to the tube side of a steam generator where its heat is transferred to water on the shell side of the generator. The water on the shell side is under lower pressure and thus the thermal energy transfer causes the secondary water to boil and the steam so generated is employed to drive the turbine. To summarize, in the design and operation of a nuclear reactor, the basic objective of removing heat from the fuel must be obtained without allowing the temperature of the fuel cladding of the limiting fuel pin to rise to such a degree that the clad will fail. As the coolant circulates through the reactor core, heat will be transferred thereto either through subcooled convection, often referred to as film conduction, or through nucleate boiling. Nucleate boiling occurs at higher levels of heat flux and is the preferred mode of operation since it permits more energy to be transferred to the coolant thereby permitting the reactor to be operated at higher levels of efficiency. Nucleate boiling is characterized by the formation of steam bubbles at nucleation sites on the heat transfer surfaces. These bubbles break away from the surface and are carried into the main coolant stream. If the bulk coolant enthalpy is below saturation, the steam bubbles collapse with no net vapor formation in the channel. This phenomenon is called subcooled boiling or local boiling. If the bulk fluid enthalpy is at or above the enthalpy of saturated liquid, the steam bubbles do not collapse and the coolant is said to be in bulk boiling. If the heat flux is increased to a sufficiently high value, the bubbles formed on the heat transfer surface during nucleate boiling are formed at such a high rate that they cannot be carried away as rapidly as they are formed. The bubbles then tend to coalesce on the heat transfer surface and form a vapor blanket or film. This film imposes a high resistance to heat transfer and the temperature drop across the film can become very large even though there is no further increase in heat flux. The transition from nucleate boiling to film boiling is called "departure from nucleate boiling," hereinafter referred to as DNB, and the value of the heat flux at which it occurs is called the "DNB heat flux" in a pressurized water reactor or the "critical heat flux" in a boiling water reactor. A factor also to be considered is the creation of flow instabilities resulting from excessive coolant void fractions. Another condition which requires protective action is the occurrence of a high local power density in one of the fuel pins. An excessive local power density initiates centerline fuel melting which may lead to a violation of the fuel clad integrity. In addition, a condition of excessive local power density is unacceptable in the event of a Loss of Coolant Accident (LOCA) since excessive local power densities would cause the clad temperature to exceed allowable limits if the coolant were lost. As the result of analyses of Loss of Coolant Accidents, values are established by the reactor designers for the maximum allowable local power densities at the inception of a LOCA such that the criteria for acceptable consequences are met. The maximum local power density or local limit is generally specified as a kilowatt per foot (KW/ft) limit. A third condition which acts as an operating limit is the licensed power at which the particular reactor is permitted to run. All three of these "limiting conditions for operation" must be monitored in order to make reactor operations safe. Since clad damage is likely to occur because of a decrease in heat transfer coefficient and the accompanying higher clad temperatures which may result when DNB occurs, or because of an excessive local power density, the onset of these conditions must be sensed or predicted and corrective action in the form of a reduction in fissions rate promptly instituted. Restated, in reactor operation DNB must be prevented since the concurrent reduction in clad strength as temperature increases can lead to a clad failure because of the external coolant pressure or because of the internal fission gas pressures in the fuel rod. One way of monitoring DNB in the reactor is to generate an index or a correlation which indicates the reactor condition with respect to the probability of the occurrence of DNB. (See L. S. Tong, "Prediction of DNB for an Axially Non-Uniform Heat Flux Distribution," Journal of Nuclear Energy, 21:241, 1967). This correlation is alternatively called Departure from Nucleus Boiling Ratio (DNBR) or Critical Heat Flux Ratio and is defined as the ratio of the heat flux necessary to achieve DNB at specific local coolant conditions to the actual local heat flux. The two correlations stem from slightly differing statistical derivations so that the critical values of DNBR and critical heat flux ratio are defined to be 1.3 and 1 respectively. These are the statistically established limiting values above which DNB has a very small probability of occurring. In the following discussion and claims, it should be understood that DNBR will be used, for the sake of simplicity, as describing both of the correlations. Thus, DNBR for the purposes of this discussion and description, shall mean both the Tong W-3 correlation for Departure from Nucleate Boiling Ratio and the Critical Heat Flux Ratio Correlation. Additionally, an excessive KW/ft. in the limiting or "hottest" fuel pin in the core must be avoided in order to maintain the integrity of the cladding or to prevent violation of the limiting conditions for operation established by a Loss Coolant Accident analysis. It is known that DNB occurs as a function of the reactor operating parameters of heat flux or power distribution, primary coolant mass flow rate, primary coolant pressure and primary coolant temperature. In order to prevent an excessive KW/ft. or DNB (also called "burn-out") or "boiling crisis," reactor protective systems must be designed to insure that reactor operation is rapidly curtailed, a condition known in the art as "reactor trip" or "reactor scram," before the combination of conditions commensurate with DNB or excessive local power density can exist. Departure from nucleate boiling and DNB Ratio may be expressed for one fuel pin or channel as: EQU DNBR=f(0, Tc, P, m, F.sub.r, R.sub.z (z), T.sub.r) (1) and the LOCA or centerline fuel melt limit may be expressed as: EQU KW/FT limit=f(0, F.sub.r, F.sub.z (z)) (2) where: 0=Core Power in Percent of Fuel Power PA1 T.sub.c =Coolant Inlet Temperature PA1 P=Coolant Pressure PA1 m=Coolant Mass Flow Rate PA1 F.sub.r =Integral Radial Power Peaking Factor PA1 F.sub.z (z)=Axial Power Distribution in the Pin which has the Integral Radial Power Peaking Factor PA1 T.sub.r =Azimuthal tilt magnitude which is a measure of side to side xenon oscillation Core power in percent of full power may be determined in a manner similar to that disclosed in the referenced U.S. Pat. No. 3,752,735 entitled "Instrumentation for Nuclear Reactor." Integral radial power peaking factor is defined as the maximum ratio of power generated in any fuel pin in the core to the average fuel pin power. Axial power distribution is defined for each fuel pin as a curve of local pin power density versus axial distance up the pin divided by the total power generated in the pin. See the "Description of the Preferred Embodiment" and the "Appendix to the Description of the Preferred Embodiment" for a more detailed discussion. The other parameters of coolant inlet temperature, reactor coolant system pressure and coolant mass flow rate may be determined in conventional manners. For example, see co-pending U.S. Pat. No. 3,791,922 entitled "Thermal Margin Protection System" filed Nov. 23, 1970, for methods for obtaining coolant inlet temperature. An accurate measure of coolant mass flow rate may be obtained from the speed of the coolant pumps. A very accurate and low noise signal may be obtained from the shaft associated with the coolant pumps to determine the pump speed. Each shaft is provided with a large number of teeth or notches around its periphery. Means such as a transducer are provided for detecting the passage of the teeth past a fixed position. The output signal from the transducer consists of an extremely regular pulsed signal with a frequency directly related to the pump speed which is, in turn, directly related to the coolant flow. In the first equation for DNBR, it is important to recognize that a value of DNBR above 1.3 results in a high probability that acceptable thermal values would exist in the core such that a departure from nucleate boiling would not occur. However, when the DNBR falls below this value, the probability of DNB and clad failure would be expected to increase to unacceptable values. Similarly in equation (2) the KW/ft. limit on the left hand side of the equation is a fixed number determined either by LOCA or the local power density that causes the degree of centerline fuel melting which is adopted as the fuel design limit by the reactor designers. For purposes of generalization and for the purposes of this disclosure, both the DNBR and KW/ft. can be thought of as indices which are indicative of the proximity of operation to the appropriate design limit. The same or similar treatment can be made for any design limit which is amendable to a mathematical representation. Therefore, this invention is applicable to any design limit and any index which can be generated mathematically from parameters of the system. DESCRIPTION OF THE PRIOR ART Heretofore, the prior art has attempted core protection through means and methods that have sacrificed plant capacity and availability. Various schemes with different degrees of sophistication were implemented, none of which enabled the utilization of the plant's full potential. The least sophisticated system consisted of the establishment of a series of independent limits for each of the parameters upon which the design limit in question depended. By so doing, this prior art method could not account for the functional interdependence of all of the variables. Thus, the situation could arise in which one parameter deviated from its optimum value, without causing an approach to the design limit since the other parameters on which the design limit depended might have compensated for the one bad parametric value. Nevertheless, under this prior art system, a reactor trip would have been initiated if the deviation of the one parameter caused the parametric value to exceed the independently determined envelope for that parameter. A second more sophisticated prior art scheme attempted to utilize, to a greater degree, the functional dependence of the design limit index on the plurality of parameters. However, even in this more sophisticated scheme, certain approximations and assumptions were made to render the functional dependence simple enough so that it could be easily reproduced in analogue circuitry. A typical type of assumption which had to be made was to assume that as many as two or three parameters were either constants held at their design values or were variables which varied only within their allowed envelopes. This second more sophisticated prior art scheme increased the plant availability and capability but, nonetheless, could not approach the optimum operating conditions since the calculations were limited by the degree of refinement which was allowed by the analogue circuitry. Another common failing of the prior art systems was that there was often no recognition of the fact that it is not sufficient merely to avoid design limit violation on steady state operation, but design limit violation must also be avoided on the occurrence of accidents which cause rapid approach to the design limit. Thus, prior art systems often permitted operation close to the design limit on a steady state basis, without provision for avoiding design limit violation on the occurrence of an anticipated operational occurrence (which is defined as a condition of normal operation which is expected to occur one or more times during the life of a nuclear power plant). The trend toward very large and high power nuclear reactors results in core dynamics not previously considered a problem. Axial and azimuthal xenon oscillations, as well as xenon redistribution after power changes, must be taken into consideration. With reactors operating close to thermal - hydraulic limits, these transient conditions must be coped with relatively quickly. Because of the complexity of determining the core power distribution, an on-line computer is necessary to aid the operator in determining the control actions necessary to maintain the reactor within operational limits. Only by use of plant computers can surveillance and assimilation of the large quantity of plant parameters be handled. Demands for greater reactor availability and increased emphasis placed on safety requirements designed to protect the reactor's core and the integrity of fuel rod cladding cogently point out for the need for a flexible and rapid system which not only prevents the core from exceeding its safety limits but also allows operation of the reactor close to those limits in order to maximize reactor efficiency and availability. Such a protection system must consist of two components: One system sensing reactor conditions and tripping the reactor when a safety limit violation is imminent, and a second system for calculating the appropriate operating limits which would insure that the protection system has sufficient time to safely trip the reactor while at the same time allowing maximum use of the reactor. In the following discussion, the first system will be called the "core protection calculator" and the second system will be called the "Core Operating Limit Supervisory System" (COLSS). The teaching which is required for an understanding of the mathematical deviations of some of the inputs to these two systems is to be found in the "Appendix to the Description of the Preferred Embodiment." SUMMARY OF THE INVENTION The instant invention involves a protection apparatus and method whose function it is to ensure the safe operation of a nuclear reactor. In order to achieve the safe operation of a nuclear reactor, the reactor and its collateral systems must be operated so as to avoid violation of certain safety design limits. This involves not only avoiding the actual violation of these design limits when operating on a steady-state basis, but also operating the system in such a manner as to avoid design limit violation on the occurrence of an incident of the type which is expected to occur at least once in the life of the system. In order to be able to prevent the violation of the design limits on the occurrence of an incident, the protection system must be capable of not only calculating an operating limit which ensures that there exists sufficient margin to the design limits so that corrective and protection action can be initiated and completed before the design limit violation, but also it must be capable of monitoring the appropriate parameters and predicting a design limit violation sufficiently in advance of the actual violation to allow the initiation and completion of the protective action. If either capability is not present, it can be expected that a critical design limit such as those calculated to maintain the fuel cladding integrity will be violated on the occurrence of one of these incidents. The invention herein disclosed includes a method and apparatus for calculating the reactor system operating limit based on the margin that must be maintained in order to allow operation of the nuclear reactor in a safe manner and a method and apparatus for calculating and predicting the imminent violation of a design limit so that corrective action may be timely initiated. The method for calculating a reactor system operating limit, briefly stated, is as follows: 1. The reactor parameters are measured. 2. One of the parameters is modified by an amount which builds in a margin. 3. The operating limit is calculated from the modified and unmodified parameters in an equation that relates the measured parameters to an appropriate design limit. The degree of modification of the modified parameter depends on: the one accident which could cause the most rapid approach to the design limit; the length of time required to sense and calculate the occurrence of an accident; and the length of time required to adequately initiate and complete effective control measures. The method for calculating and predicting the imminent violation of a design limit, briefly stated, is as follows: 1. The reactor parameters are measured; 2. Periodic samples of these parameters are taken and a periodic detailed calculation made of an index representation of the proximity of violation of the appropriate design limit; 3. Continuous updates to this calculated index are made; 4. Various parameters are projected into the future over a time (T) on the basis of the instanteous rate of change of the parameter; and 5. Continuous projections of the calculated index are obtained from the projected parameters. Once a projected value of the index is obtained, that projected value can be compared to a critical value of the index of design limit violation and protective action initiated when the projected index is equal to the critical value.
054901880	abstract	System and method for evaporating moisture from a gap defined between a heat transfer tube surrounding a repair sleeve in a nuclear steam generator. The nuclear steam generator has a heat transfer tube surrounding a repair sleeve that has been hydraulically expanded into engagement with the tube. The tube and the sleeve define a gap therebetween having moisture residing therein. The system includes an air compressor in communication with the gap for supplying air to the gap and a dryer in communication with the air compressor for drying the gas supplied to the gap. A heater in communication with the air compressor may also be provided for heating the air supplied to the gap, so that the moisture residing in the gap evaporates into the heated air. A vacuum pump in communication with the gap may be provided for decreasing the pressure of the heated air in the gap, so that substantially all the moisture evaporates from the gap and into the heated air.
	summary
	claims	1. An electronic emission device including plural electron beams comprising:a first structure including a plurality of emitting sources of electron beams;a second structure including a plurality of diaphragm openings; andmetallic balls made from at least one of fusible metal alloys and gold interposed between the first structure and the second structure and hybridizing the first structure with the second structure. 2. The device according to claim 1, in which the second structure includes an electrode or a metallic or conductive or semiconductive membrane. 3. The device according to claim 1, in which at least one diaphragm opening has two different opposite opening surfaces, the opening surface of a first side of the diaphragm having an area greater than an area of the opening surface of a second side of the diaphragm. 4. The device according to claims 1, in which each diaphragm opening comprises a bevelled, flat, concave, or convex opening edge profile. 5. The device according to claim 1, in which each of the first structure and the second structure comprises a periodic arrangement of sources of emission of electrons or diaphragm openings, the structures having a matrix arrangement or a multilinear arrangement or a linear arrangement, regular or irregular. 6. The device according to claim 1, in which the sources of electron beam emission and the diaphragm openings are arranged with a spacing of about a few microns to one millimeter. 7. The device according to claim 1, further comprising electrostatic or magnetic or electromagnetic means for focusing electron beams. 8. The device according to claim 1, further comprising means for magnetic projection. 9. The device according to claim 1, further comprising a polarized anode or electrode structure arranged outside the second structure of diaphragm openings. 10. The device according to claim 1, in which the second structure comprises at least one conductive part and at least one dielectric part. 11. The device according to claim 1, in which the second structure comprises two levels of electrodes or membranes, which are metallic, conductive, and attached to at least one dielectric layer. 12. The device according to claim 1, in which the second structure includes, around zones of the diaphragm openings, a thickness of about a fraction of a micrometer to a few hundred micrometers. 13. The device according to claim 1, in which the second structure includes, outside zones of the diaphragm openings, a thickness of about one micrometer to around one millimeter. 14. The device according to claim 1, in which the second structure includes an alveolar structure insulating each opening or plural groups of openings from one another, such that each opening or each group of openings is subjected to a respective polarization potential. 15. The device according to claim 1, in which at least one side of the diaphragm of the second structure is disposed in an electric field for acceleration or focusing of electrons. 16. The device according to claim 1, in which the second structure of diaphragm opening comprises two opposite sides, a first side facing an electric field, and a second side facing another electric field. 17. The device according to claim 1, in which at least one diaphragm opening has two different opposite opening surfaces, the opening surface of a first side of the diaphragm having an area greater than an area of the opening surface of the second side of the diaphragm, at least one side of the diaphragm of the second structure is disposed in an electric field for acceleration or focusing of electrons, the diaphragm openings are oriented such that the opening surface of greater area faces the electric field of greater value, and the opening surface of lesser area facing the electric field of less value or in absence of an electric field. 18. The device according to claim 1, in which each diaphragm opening comprises a bevelled, flat, concave, or convex opening edge profile, at least one side of the diaphragm of the second structure is disposed in an electric field for acceleration or focusing of electrons, the diaphragm openings are oriented such that the opening surface of greater area faces the electric field of greater value, and the opening surface of lesser area facing the electric field of less value or in absence of an electric field. 19. The device according to claim 1, in which at least one diaphragm opening has two different opposite opening surfaces, the opening surface of a first side of the diaphragm having an area greater than an area of the opening surface of a second side of the diaphragm, in which the second structure of diaphragm opening comprises two opposite sides, a first side facing an electric field, a second side facing another electric field, the diaphragm openings are oriented such that the opening surface of greater area faces the electric field of greater value, and the opening surface of lesser area facing the electric field of less value or in absence of an electric field. 20. The device according to claim 1, in which each diaphragm opening comprises a bevelled, flat, concave, or convex opening edge profile in which the second structure of diaphragm opening comprises two opposite sides, a first side facing an electric field, a second side facing another electric field, the diaphragm openings are oriented such that the opening surface of greater area faces the electric field of greater value, and the opening surface of lesser area facing the electric field of less value or in absence of an electric field. 21. The device according to claim 1, wherein the second structure is disposed completely above the emitting sources of the electron beams, and the second structure controls divergence of the electron beams.
	summary
	summary
	claims	1. An apparatus for detection of radiation comprising: at least a first collimator arranged to transmit radiation, emitted from a radiation source, through at least a first slit in a Z-direction and prevent radiation in said Z-direction apart from through said at least first slit, at least a first array of at least two radiation detecting elements, each of said radiation detecting elements having a width xcex1 in an X-direction, where said X-direction is the direction of said array of radiation detecting elements, each of said radiation detecting elements having a length xcex2 in a Y-direction, said at least first slit, for letting through radiation in the Z-direction, having a length in said second X-direction which is at least as long as said array of radiation detecting elements, said at least first slit having a length in said Y-direction which is substantially shorter than said length xcex2 of said radiation detecting elements, and displacement means arranged to move said collimator and/or said array of radiation detecting elements. 2. The apparatus according to claim 1 , wherein claim 1 at least a second array of radiation detecting elements, having said width xcex1 in said X-direction and said length xcex2 in said Y-direction, said at least first array of radiation detecting elements and said at least second array of radiation detecting elements being displaced in relation to each other substantially only in the Y-direction with a distance substantially equal to xcex2, said collimator comprise at least a second slit having a length in said second X-direction which is at least as long as said at least second array of radiation detecting elements, and a length in said Y-direction which is substantially shorter than said length xcex2, said at least first and at least second slits being displaced in relation to each other substantially only in the Y-direction with a distance substantially equal to xcex2, and said first and second slits are fixed in relation to each other, and said first and second arrays of radiation detecting elements are fixed in relation to each other. 3. The apparatus according to claim 1 , wherein claim 1 said displacement means is arranged to move said collimator in relation to said radiation detecting elements in said Y-direction over substantially the complete length xcex2 of said radiation detecting elements. 4. The apparatus according to claim 1 , wherein claim 1 said displacement means is arranged to move said collimator in relation to said radiation detecting elements in said Y-direction over a length substantially longer than the length xcex2, e.g. 2xcex2, 3xcex2 or any multiple of xcex2. 5. The apparatus according to claim 1 , wherein claim 1 each of said radiation detecting elements is arranged to repeatedly detect values during the relative movement of said collimator and radiation detecting elements so as to obtain multiple values for the radiation admitted through said slit to said corresponding radiation detecting elements. 6. The apparatus according to claim 1 , wherein claim 1 said movement is a translation of said collimator in the Y-direction over said at least first array of radiation detecting elements. 7. The apparatus according to claim 1 , wherein claim 1 said movement is a pivoting movement of the collimator and radiation source in relation to the radiation detecting elements. 8. The apparatus according to claim 1 , wherein said collimator is arranged to substantially completely cover each of said radiation detecting elements, during said movement, from radiation, apart from radiation admitted through said slit to said radiation detecting elements. claim 1 9. The apparatus according to claim 8 , wherein claim 8 a second collimator, having at least two elongated openings separated by a distance xcex2, is arranged at a distance xcex3 in the Z-direction from said first collimator, wherein said distance xcex3 is selected to allow an object to be positioned between said first and second collimator, and said first and second collimator is fixed in relation to each other so that X-rays emitted from the X-ray source and transmitted through said slits in the second collimator are transmitted through the corresponding slits in the first collimator. 10. The apparatus according to claim 1 , wherein said width xcex1 is substantially shorter than said length xcex2, and said length of said array is substantially longer than said length xcex2. claim 1 11. The apparatus according to claim 1 , wherein said radiation detection means is a CCD. claim 1 12. The apparatus according to claim 1 , wherein said radiation detecting elements is a TFT array. claim 1 13. The apparatus according to claim 1 , wherein said radiation detecting elements is a C-mos detector. claim 1 14. The apparatus according to claim 1 , wherein said radiation detecting elements is PIN-diodes. claim 1 15. The apparatus according to claim 1 , wherein said apparatus comprises a gas detector having an ionisable gas arranged between an anode and an cathode and being arranged to detect electrons emitted by said gas due to said radiation and accelerated by a voltage across said anode and cathode. claim 1 16. The apparatus according to claim 15 , wherein said gas detector comprises means for electron avalanche amplification. claim 15 17. The apparatus according to claim 1 , wherein said detector elements comprise a radiation detection area which is substantially as wide in the X-direction as said distance xcex1. claim 1 18. The apparatus according to claim 1 , wherein said detector elements comprise a radiation detection area, which has a width xcex5 in X-direction that is substantially shorter than said distance xcex1. claim 1 19. The apparatus according to claim 18 , wherein claim 18 said displacement means is arranged to repeatedly move said collimator in relation to said radiation detecting elements back and fourth in said Y-direction over substantially the complete length xcex2 of said radiation detecting elements, and said displacement means is arranged to move said radiation detecting elements and said collimator substantially a distance xcex5 in the X-direction for each repetition of movement in said Y-direction. 20. An X-ray imaging device comprising the detector apparatus according to claim 1 , comprising claim 1 an X-ray source arranged displaced in the Z-direction in relation to said collimator and arranged to emit X-rays in at least said Z-direction towards said radiation detection means and said radiation is arranged to pass through an object to be imaged, said collimator being arranged to scan over substantially the complete object, and said radiation detection device being arranged to repeatedly detect the radiation reaching said radiation detection device so as to construe a scanned image of the X-rayed object. 21. A method for detection of radiation comprising: at least a first collimator arranged to transmit radiation through at least a first slit in a Z-direction and prevent radiation in said Z-direction at other positions, at least a first array of radiation detecting elements comprising at least two radiation detecting elements, that each of said radiation detecting elements having a width xcex1 in a X-direction, where said X-direction is the direction of said array of radiation detecting elements, that each of said radiation detecting elements having a length xcex2 in a Y-direction, that said at least first slit, for letting through radiation in the Z-direction, has a length in said second X-direction which is at least as long as said array of radiation detecting elements, that said at least first slit has a length in said Y-direction which is substantially shorter than said length xcex2 of said radiation detecting elements, and comprising the step of: moving said collimator in relation to said radiation detecting elements in the Y-direction over substantially the complete length xcex2 of said radiation detecting elements. 22. The method according to claim 21 , comprising claim 21 at least a second array of radiation detecting elements, having same characteristics as said at least first radiation detecting elements, said collimator comprise at least a second slit having same characteristics as said at least first slit, and comprising the further steps of: displacing said at least first and at least second slit in relation to each other substantially only in the Y-direction with a distance substantially equal to xcex2, displacing said at least first array of radiation detecting elements and said at least second array of radiation detecting elements in relation to each other substantially only in the Y-direction with a distance substantially equal to xcex2, and fixing said first and second slit, and said first and second array of radiation detecting elements in relation to each other. 23. The method according to claim 21 , comprising the further step of: claim 21 continuously detecting a value corresponding to the detected radiation during the relative movement of said collimator and radiation detecting elements, so as to obtain multiple values for the radiation admitted through said slit to said corresponding radiation detecting elements. 24. The method according to claim 21 , wherein claim 21 said movement is a translation of said collimator in the Y-direction over said at least first array of radiation detecting elements. 25. The method according to claim 21 , wherein claim 21 said movement is a pivoting movement of the collimator and radiation source in relation to the radiation detecting elements. 26. The method according to claim 21 , wherein said width xcex1 is substantially shorter than said length xcex2, and said length of said array is substantially longer than said length xcex2. claim 21 27. The method according to claim 21 , wherein said radiation detection means is a CCD. claim 21 28. The method according to claim 21 , wherein said radiation detecting elements is a TFT. claim 21 29. The method according to claim 21 , wherein said radiation detecting elements is a C-mos detector. claim 21 30. The method according to claim 21 , wherein said radiation detecting elements is PIN-diodes. claim 21 31. The method according to claim 21 , wherein said radiation detection means comprises a gas detector having an ionisable gas arranged between an anode and an cathode and being arranged to detect electrons emitted by said gas due to said radiation and accelerated by a voltage across said anode and cathode. claim 21 32. The method according to claim 31 , wherein said gas detector is arranged to perform electron avalanche amplification. claim 31 33. The method according to claim 21 , wherein claim 21 a second collimator, having at least two elongated openings separated by a distance xcex2, is arranged at a distance xcex3 in the Z-direction from said first collimator, wherein said distance xcex3 is selected to allow an object to be positioned between said first and second collimators, and said first and second collimator is fixed in relation to each other so that X-rays emitted from the X-ray source and transmitted through said slits in the second collimator are transmitted through the corresponding slits in the first collimator. 34. The method according to claim 21 , wherein said detector elements comprise a radiation detection area which is substantially as wide in the X-direction as said distance xcex1. claim 21 35. The method according to claim 21 , wherein said detector elements comprise a radiation detection area, which has a width xcex5 in X-direction that is substantially shorter than said distance xcex1. claim 21 36. The method according to claim 35 , wherein claim 35 said displacement means is arranged to repeatedly move said collimator in relation to said radiation detecting elements back and fourth in said Y-direction over substantially the complete length xcex2 of said radiation detecting elements, and said displacement means is arranged to move said radiation detecting elements and said collimator substantially a distance xcex5 in the X-direction for each repetition of movement in said Y-direction.
	summary
	summary
045049645	description	DETAILED DESCRIPTION X-ray system 2 in FIGS. 1 and 2 includes a pair of electrodes 4 and 6 spaced by an axial gap 8 therebetween. Electrode 6 is a cylindrical member having a plurality of circumferentially spaced axial passages such as 10 and 12 therethrough. A plurality of laser sources such as 14 and 16 direct laser beams axially through the axial passages such as 10 and 12 such that a cylindrical array of laser beams impinge on electrode 4 in an annular pattern as shown at 18. Electrode 6 may alternatively have an annular passage therethrough, in place of plural passages such as 10 and 12. Electrode 4 is a target electrode of a given substance, for example aluminum, for producing plasma vapor in response to laser impingement thereon. Upon closing switch 20, a large storage capacitor 22, charged from voltage source 24, discharges electrode 4 across axial gap 8 to electrode 6. This passes high current through the plasma annulus in gap 8, causing magnetic field pinching of the plasma radially inwardly. This radial inward pinching of the plasma further heats the plasma and causes X-ray emission from the pinched plasma. Referring to FIG. 2, the annular pattern of the plasma before pinching is shown at 18, and the constricted pinched plasma is shown at 26. The X-rays are emitted through an axial passage 28 in the target electrode 4 coaxially aligned with the centrally pinched plasma 26. Alternatively, the X-rays may be emitted back through a central axial passage 30 through the other electrode 6. The axial emission orientation of the X-rays enables placement of a masked semiconductor substrate 32 normal to the axial direction of emission for impingement by the X-rays. An additional laser beam from another laser source 34 may be directed through central axial passage 30, regardless of which direction X-rays are emitted. This additional central laser beam impinges on the radially inwardly pinched central plasma 26 in gap 8 and further heats the pinched plasma. In an alternative, a single laser source may be used with a beam splitter, such as mirror or prism means, to provide a plurality of circumferentially spaced laser beams. It is recognized that various modifications are possible within the scope of the appended claims.
	claims	1. Process for creating a predetermined three-dimensional structure in the bulk of a radiation-sensitive material (40) comprising the steps of:directing a beam (818) of penetrating radiation to said radiation-sensitive material,providing a mask (810) introducing a space-variable energy loss, in said beam (818),deposing energy by said beam (818) locally into said bulk of said material (40) according to a predetermined three-dimensional pattern (612). 2. Process according to claim 1, whereas said energy deposited into said bulk of said material (40) is substantially higher than an energy deposited to an outer surface of said material. 3. Process according t claim 1, wherein said radiation energy is deposited by a radiation beam having a penetration range in which the deposited energy is sensibly higher towards the end of the penetration range. 4. Process according to the previous claim, wherein said radiation beam comprises charged ions. 5. Process according to the previous claim, wherein said charged ions belong to one of the following species: H; He; Li; Be; B; C; N; O. 6. Process according to claim 1, further comprising a development step for removing a predetermined portion of said material. 7. Process according to claim 1, wherein a predetermined portion of said material is evaporated or ablated without a development step. 8. Process according to claim 1, wherein a predetermined portion of the target is directly etched with the aid of a reactive component introduced in the material or in a gas surrounding said material, without need of a subsequent development step. 9. Process according to claim 1, wherein said predetermined three-dimensional structure comprises at least one internal channel. 10. Process according to claim 1, wherein the refractive index of a predetermined region of said material is altered by said radiation. 11. Process according to claim 1, wherein a magnetic or optic or thermal property of a predetermined region of said material are altered by said radiation. 12. Process according to claim 1, wherein the mask (810) has variable thickness. 13. Process according to claim 1, wherein the mask (810) comprises materials of variable dE/dx coefficient. 14. Process according to claim 1, wherein the energy loss in the mask (810) varies in such a way that the energy is deposited at variable depth in the bulk of the material (40). 15. Process according to the previous claim, wherein the energy loss in the mask (810) varies in such a way that the energy is deposited in the bulk of the material (40) according to a 3D structure. 16. Process according to claim 1, wherein the energy loss in the mask (810) varies stepwise. 17. Process according to claim 1, wherein the energy loss in the mask (810) varies in a continuous fashion in such a way that the energy is deposited in the bulk of the material (40) according to a slanted pattern. 18. Process according to claim 1, wherein the energy deposited in said bulk of said material (40) is substantially higher than energy deposited to an outer surface of said material, whereby said predetermined three-dimensional structure comprises at least one internal channel. 19. Process according to claim 1, wherein the delivered energy dose is chosen for obtaining an open structure. 20. Miniaturized device comprising a three-dimensional structure realizable by the process of one of the preceding claims. 21. Device according to the preceding claim, comprising at least one internal channel for micro- or nano-fluidic applications and/or for micro- or nano-gas flow applications. 22. Device according to claim 20, comprising a magnetizable structure. 23. Device according to claim 20, comprising a light guide structure. 24. Process for creating a predetermined three-dimensional structure in the bulk of a photoresist material, comprising the steps of:directing a beam (818) of penetrating radiation to said photoresist material,providing a mask (810) introducing a space-variable energy loss, in said beam (818),deposing energy by said beam (818) locally into said bulk of said material according to a predetermined three-dimensional pattern. 25. Process according to the previous claim, wherein said photoresist material is a negative photoresist material, and further comprising a step of developing said negative photoresist material for obtaining a three-dimensional micro-structure corresponding to the three-dimensional pattern of energy deposited in the photoresist material. 26. Process for creating a predetermined structure in a diamond substrate, the process comprising the steps of:directing a beam (818) of radiation to said diamond substrate,deposing energy by said beam (818) locally into said diamond substrate, according to a predetermined pattern,selectively removing those parts of the diamond substrate in which said energy has been deposited.
	claims	1. A control rod/fuel support grapple comprising: a control rod holding mechanism adapted to hold a hoist handle provided at a top end of a control rod comprising a pivotable hook adapted to be hooked onto said hoist handle, and means for pivoting said pivotable hook actuated by a working fluid from a source provided to the grapple by a single fluid connection; a fuel support holding mechanism adapted to hold a fuel support which supports a bottom end of a fuel assembly; a coupling releasing mechanism adapted to uncouple said control rod from a control rod drive mechanism coupled by a spud coupling, said coupling releasing mechanism comprising a pivotable lever adapted to lift a release handle on said control rod, and means for pivoting said lever when actuated by said working fluid from said source so that when actuated by said working fluid said lever is pivoted causing it to lift said release handle, said coupling releasing mechanism comprising an L-shaped arm dimensioned so that it can be inserted into a clearance between said control rod and said fuel support and positioned away from said fuel support holding mechanism such that said coupling releasing mechanism can lift said release handle when said control rod is descended to a full pull-out state; a main body frame to which said control rod holding mechanism, said fuel support holding mechanism, and said coupling releasing mechanism are attached, said main body frame adapted so that said control rod holding mechanism, said fuel support holding mechanism, said coupling releasing mechanism and said main body frame may be inserted into a reactor pressure vessel as an integral unit; and means for delaying actuation of said coupling releasing mechanism such that said coupling releasing mechanism fully actuates after said control rod holding mechanism hooks onto said control rod when said working fluid is provided from said source simultaneously to said coupling releasing mechanism and said control rod holding mechanism. 2. A control rod/fuel support grapple according to claim 1 , wherein said coupling releasing mechanism further comprises a coupling releasing link mechanism adapted to operate said release handle of said control rod, and a coupling releasing cylinder adapted to drive said coupling releasing link mechanism. claim 1 3. A control rod/fuel support grapple according to claim 1 , wherein the control rod holding mechanism can be is placed relative to the main body frame along a longitudinal direction of the control rod by a predetermined width. claim 1 4. A control rod/fuel support grapple according to claim 2 , wherein said means for delaying actuation after comprises a damper mechanism for applying resistance to a piston rod of said coupling releasing cylinder in its operation. claim 2 5. A control rod/fuel support grapple according to claim 2 , wherein said means for delaying actuation further comprises a flow restrict mechanism which is provided in a working fluid pipe connected to said coupling releasing cylinder. claim 2 6. A control rod/fuel support grapple according to claim 1 , wherein said pivotable hook is formed of a hook-shaped member, and the weight of said control rod maintains a hooked state of said hoist handle by said pivotable hook after said control rod has been lifted up via said pivotable hook. claim 1 7. A control rod/fuel support grapple according to claim 1 , wherein said fuel support holding mechanism comprises a fuel support holding link mechanism adapted to hold a top end of an orifice of said fuel support, and a fuel support holding cylinder adapted to drive said fuel support holding link mechanism. claim 1 8. A control rod/fuel support grapple according to claim 7 , wherein said fuel support holding link mechanism comprises a moveable contact piece, said contact piece adapted for contacting an upper portion of said orifice, said contact piece comprising a stepped portion and wherein said contact piece can be positioned such that said upper portion of said orifice contacts said stepped portion of said contact piece when said control rod/fuel support grapple is raised. claim 7 9. A control rod/fuel support grapple according to claim 1 , further comprising detecting means for checking a holding state of said control rod holding mechanism, a holding state of said fuel support holding mechanism, and a releasing state of the coupling releasing mechanism respectively. claim 1 10. A control rod/fuel support grapple according to claim 1 , wherein said control rod holding mechanism and said coupling releasing mechanism are detachably attached to said main body frame, said fuel support holding mechanism and both said control rod holding mechanism and said coupling releasing mechanism can be employed independently respectively as separate bodies by detaching said control rod holding mechanism and the coupling releasing mechanism from said main body frame. claim 1 11. A control rod/fuel support grapple comprising: means for holding a top end of a control rod actuated by air from a source provided to the grapple by a single air connection; a fuel support holding mechanism adapted to hold a fuel support which supports a bottom end of a fuel assembly; a coupling releasing link mechanism for uncoupling a control rod and a control rod drive mechanism coupled by a spud coupling mechanism, said coupling releasing mechanism comprising a spud coupling releasing mechanism adapted to operate a control rod release handle, said spud coupling releasing mechanism comprising a pivoting lever dimensioned so that it can be inserted into a clearance between said control rod and said fuel support and positioned away from said fuel support holding mechanism so that said coupling releasing link mechanism can operate said control rod release handle when said control rod is descended to a full pull-out state; a main body frame, comprising fitting bolts and a separating frame, to which said means for holding a top end of a control rod, said fuel support holding mechanism, and said coupling releasing link mechanism are attached, said main body frame adapted so that said means for holding a top end of a control rod, said fuel support holding mechanism, said coupling releasing link mechanism and said main body frame may be inserted into a reactor pressure vessel as an integral unit, wherein said separating frame is detachable from said main body frame by releasing said fitting bolts such that said fuel support holding means can be removed from said reactor pressure vessel separate from an assembly comprising said coupling releasing link mechanism and said means for holding a top end of a control rod; a coupling releasing cylinder adapted to drive said coupling releasing link mechanism, said coupling releasing cylinder actuated by air from said source; and an operational timing control mechanism adapted to delay actuation of said coupling releasing link mechanism until after said means for holding a top end of a control rod is fully actuated when air is provided from said source simultaneously to said coupling releasing cylinder and said means for holding a top end of a control rod, wherein said fuel support holding mechanism includes a fuel support holding cylinder and a contact piece that has a stepped portion, said contact piece being capable of being inserted into an orifice of said fuel support by a link mechanism such that an upper surface of said orifice is aligned with said stepped portion of said contact piece and said upper surface of said orifice is placed in contact with said stepped portion when said control rod/fuel support grapple is raised, said contact piece being arranged at a position corresponding to said orifice when said main body frame is inserted into a reactor pressure vessel. 12. A control rod/fuel support grapple comprising: a main body frame; a separating frame connectable to said main body frame; means for holding a hoist handle provided at a top end of a control rod, said means for holding a hoist handle connected to said separating frame; means for holding a fuel support which supports a bottom end of a fuel assembly, said means for holding a fuel support connected to said main body frame; and a coupling releasing mechanism attached to said separating frame via a vertical arm and adapted to uncouple a control rod and a control rod drive mechanism coupled by a spud coupling mechanism, said vertical arm comprising an L-shaped arm dimensioned so that it can be inserted into a clearance between said control rod and said fuel support and positioned away from said means for holding a fuel support so that said coupling releasing mechanism can release said spud coupling mechanism when said control rod is descended to a full pull-out state, wherein said separating frame and said main body frame are adapted such that when said separating frame is connected to said main body frame, said means for holding a hoist handle, said means for holding a fuel support, and said coupling releasing mechanism form an integral unit. 13. A control rod/fuel support grapple comprising: means for holding a hoist handle provided at a top end of a control rod; means for holding a fuel support which supports a bottom end of a fuel assembly; means for uncoupling a control rod and a control rod drive mechanism coupled by a spud coupling mechanism, wherein said means for uncoupling a control rod comprises a spud coupling releasing mechanism that engages a control rod release handle on said control rod and thereby uncouples said spud coupling mechanism, said spud coupling releasing mechanism comprising an L-shaped arm dimensioned so that it can be inserted into a clearance between said control rod and said fuel support and positioned away from said means for holding a fuel support such that said spud coupling releasing mechanism can operate said control rod release handle when said control rod is descended to a full pull-out state; and a main body frame to which said means for holding a hoist handle, said means for holding a fuel support, and said means for uncoupling a control rod are attached.
	claims	1. A tritium production element for use in a nuclear reactor, comprising:a substantially cylindrical cladding having a length and an inner diameter;a plurality of tritium producing burnable absorber pellets disposed within the cladding, each pellet of the plurality including a first surface, a second surface, and a substantially cylindrical sidewall extending between the first surface and the second surface, the sidewall including an outer diameter dimensioned to fit within the inner diameter of the cladding, the plurality of pellets arranged in an end-to-end relation; andat least one silicon carbide barrier substantially hermetically sealing tritium within the pellets of the plurality, each of the at least one silicon carbide barriers including a first portion arranged radially over the first surface of at least one of the pellets of the plurality, a second portion arranged radially over the second surface of at least one of the pellets of the plurality, and a sidewall portion axially extending between the first portion and the second portion, the sidewall portion being concentrically arranged between the substantially cylindrical sidewall of at least one of the pellets of the plurality and the substantially cylindrical cladding,wherein the at least one silicon carbide barrier comprises a free-standing container into which one or more of the tritium producing burnable absorber pellets are sealed. 2. The tritium production element of claim 1, wherein each one of the plurality of tritium producing burnable absorber pellets is sealed within a corresponding silicon carbide barrier. 3. The tritium production element of claim 1, wherein a plurality of tritium producing burnable absorber pellets is sealed within a corresponding silicon carbide barrier. 4. The tritium production element of claim 1, wherein at least some of the plurality of tritium producing burnable absorber pellets have an annular configuration. 5. The tritium production element of claim 1, wherein the sidewall portion of each of the at least one silicon carbide barriers contacts the substantially cylindrical cladding. 6. The tritium production element of claim 1, wherein the at least one silicon carbide barrier has a thickness of between about 200 micron and 500 micron. 7. The tritium production element of claim 1, wherein the cylindrical cladding has outer dimensions substantially the same as the outer dimensions of a fuel rod used within the nuclear reactor. 8. The tritium production element of claim 1, wherein the tritium producing burnable absorber pellets comprise lithium aluminate. 9. A tritium production assembly for use in a nuclear reactor, comprising:a plurality of tritium production elements arranged in a bundle, the bundle having hydraulic characteristics substantially the same as a fuel bundle used in the nuclear reactor, wherein each tritium production element comprises:a substantially cylindrical cladding having a length and an inner diameter;a plurality of tritium producing burnable absorber pellets disposed within the cladding, each pellet of the plurality including a first surface, a second surface, and a substantially cylindrical sidewall extending between the first surface and the second surface, the sidewall including an outer diameter dimensioned to fit within the inner diameter of the cladding, the plurality of pellets arranged in an end-to-end relation; andat least one silicon carbide barrier substantially hermetically sealing tritium within the pellets of the plurality, each of the at least one silicon carbide barriers including a first portion arranged radially over the first surface of at least one of the pellets of the plurality, a second portion arranged radially over the second surface of at least one of the pellets of the plurality, and a sidewall portion axially extending between the first portion and the second portion, the sidewall portion being concentrically arranged between the substantially cylindrical sidewall of at least one of the pellets of the plurality and the substantially cylindrical cladding,wherein, within each tritium production element, the at least one silicon carbide barrier comprises a free-standing container into which one or more of the tritium producing burnable absorber pellets are sealed. 10. The tritium production assembly of claim 9, wherein, within each tritium production element, each one of the plurality of tritium producing burnable absorber pellets is sealed within a corresponding silicon carbide barrier. 11. The tritium production assembly of claim 9, wherein, within each tritium production element, a plurality of tritium producing burnable absorber pellets is sealed within a corresponding silicon carbide barrier. 12. The tritium production assembly of claim 9, wherein, within each tritium production element, at least some of the plurality of tritium producing burnable absorber pellets has an annular configuration. 13. The tritium production assembly of claim 9, wherein, within each tritium production element, the sidewall portion of each of the at least one silicon carbide barriers contacts the substantially cylindrical cladding. 14. The tritium production assembly of claim 9, wherein, within each tritium production element, the at least one silicon carbide barrier has a thickness of between about 200 microns and 500 microns. 15. The tritium production assembly of claim 9, wherein the tritium producing burnable absorber pellets comprise lithium aluminate. 16. The tritium production assembly of claim 15, wherein a majority of the tritium production elements within the assembly have cylindrical cladding having outer dimensions substantially the same as the outer dimensions of fuel rods used within the nuclear reactor.
	abstract	A nuclear thermoacoustic device includes a housing defining an interior chamber and a portion of nuclear fuel disposed in the interior chamber. A stack is disposed in the interior chamber and has a hot end and a cold end. The stack is spaced from the portion of nuclear fuel with the hot end directed toward the portion of nuclear fuel. The stack and portion of nuclear fuel are positioned such that an acoustic standing wave is produced in the interior chamber. A frequency of the acoustic standing wave depends on a temperature in the interior chamber.
	description	This application is based upon and claims the benefits of priority from the prior Japanese Patent Application No. 2009-082103, filed in the Japanese Patent Office on Mar. 30, 2009. 1. Technical Field The present invention relates to a boiling water reactor having a reactor pressure vessel equipped with an openable upper lid. 2. Background Art A typically known boiling water reactor will be described below by referring to FIG. 5. FIG. 5 is a schematic diagram of a known boiling water reactor, showing a cross-sectional elevation of a principal part of the reactor pressure vessel and the system configuration of the vent line and the head spray line thereof. The vent line 21 of the reactor pressure vessel 1 of a conventional nuclear power plant is installed to exhaust gas and steam from or supply gas and steam to the inside of the reactor pressure vessel 1 when the nuclear reactor is shut down, and penetrates a reactor pressure vessel upper lid 2. The vent line 21 arranged at a top part of the reactor pressure vessel 1 includes a non-condensable gas exhaust line 23 arranged to exhaust non-condensable gas that can be accumulated in the top part of the reactor pressure vessel 1 while the nuclear reactor is operating. An end of the vent pipe is connected to a main steam pipe 20. A head spray line 22 is branched from the vent line 21 as disclosed in Japanese Patent Application Laid-Open Publication No. 11-231088, the entire content of which is incorporated herein by reference. When the nuclear reactor is shut down, the steam discharged from a dryer 26 can be cooled by spraying water into the gas phase section in the reactor pressure vessel upper lid 2 by way of the head spray line 22. Additionally, the water level in the inside of the reactor pressure vessel 1 needs to be raised and lowered when the nuclear reactor is started and shut down, and a reactor water level gauge 7 is provided to monitor the water level. An upper take-out point of the reactor water level gauge 7 is branched out from the top part of the reactor pressure vessel 1. The fuel in the reactor core 34 in the reactor pressure vessel 1 keeps on emitting decay heat after the nuclear reactor is shut down. In order to remove the decay heat, the reactor water in the reactor pressure vessel 1 is partly taken out, pressurized by a reactor water circulation pump 16 and cooled by way of a reactor water cooling heat exchanger 17. Then, the cooled water is returned to the inside of the reactor pressure vessel 1. Besides, water can be fed to the head spray line 22 from the downstream of the reactor water cooling heat exchanger 17. More specifically, steam can be cooled in the reactor pressure vessel 1 by partly utilizing the water to be returned to the reactor pressure vessel 1 so as to spray the water into the gas phase section in the reactor pressure vessel upper lid 2. The piping of the reactor pressure vessel vent line 21 and the head spray line 22 is disposed on the heat insulating material 15 of the reactor pressure vessel 1. Therefore, the heat insulating material 15 cannot be removed unless the reactor pressure vessel flanges 24 are uncoupled and the piping on the reactor pressure vessel upper lid 2 is taken away. It is required to reduce the shut down period of the nuclear reactor of a nuclear power plant in order to improve the operation rate of the power plant. In recent years, the head spray line has been employed to cool the upper part of the nuclear reactor in order to improve the cooling rate of the nuclear reactor and to open the reactor pressure vessel as soon as possible. When the nuclear reactor is shut down and the temperature of the reactor water is 100 degrees Celsius or higher, the piping connected to the reactor pressure vessel 1 cannot be removed because the inside of the reactor pressure vessel upper lid 2 is filled with steam. The heat insulating material 15 of the reactor pressure vessel 1 cannot be removed in such a condition. Therefore, in order to open the reactor pressure vessel 1 early, it is desirable to remove the reactor pressure vessel heat insulating material 15 early and, when the reactor water temperature falls well below 100 degrees Celsius, quickly take away the reactor pressure vessel upper lid 2. To take away the reactor pressure vessel upper lid 2, the operation of loosening the stud bolts 11 tightly binding the reactor pressure vessel flanges 5 together needs to be conducted quickly. However, since the head spray line 22 is not so designed as to directly spray water to the inner wall of the reactor pressure vessel 1, it takes time to cool the reactor pressure vessel 1 even by using the head spray line 22. In view of the above-identified circumstances, it is therefore an object of the present invention to make it possible to open the reactor pressure vessel upper lid of a boiling water reactor early when the reactor is shut down. According to the present invention, there is provided a boiling water reactor comprising: a reactor pressure vessel that includes a main body trunk having an upper open end and an openable upper lid covering the upper open end of the main body trunk from above; and a through piping that penetrates lateral side of the main body trunk and has an opening section at a same level with or higher than the upper open end of the main body trunk in the reactor pressure vessel. Now, embodiments of the boiling water reactor according to the present invention will be described below by referring to FIGS. 1 through 4. The components same as or similar to those of the conventional art shown in FIG. 5 are denoted by the same reference symbols and will be not described repeatedly. The vent line in the inside of the reactor pressure vessel of this embodiment will be described below. FIG. 1 is a schematic diagram of the first embodiment of the boiling water reactor according to the present invention, showing a cross-sectional elevation of a principal part of the reactor pressure vessel and the system configuration of the vent line thereof. A containment vessel 30 is partitioned to form a dry well 31 and a wet well 32 that communicate with each other. A reactor pressure vessel 1 is disposed in the dry well 31. A suppression pool 33 is disposed in the wet well 32. The reactor pressure vessel 1 is a substantially cylindrical container with a vertical axis, and has a main body trunk 38 with an upper open end formed at the top thereof and a pressure vessel upper lid 2 arranged to cover the upper open end. The junction of the main body trunk 38 and the pressure vessel upper lid 2 has a flange structure such that the main body trunk flange 5a formed at the upper end of the main body trunk 38 and the upper lid flange 5b formed at the lower end of the pressure vessel upper lid 2 are coupled together by means of a plurality of stud bolts 11. The pressure vessel upper lid 2 is covered at the outside thereof with a heat insulating material 15. Although not shown, the main body trunk 38 is also covered by a heat insulating material at the periphery thereof. A reactor core 34, separators 27 and dryers 26 are arranged in the reactor pressure vessel 1. At least the reactor core 34 and the separators 27 are disposed below the main body flange 5a. A main steam pipe 20 is connected to the main body trunk 38 and a valve 18 (normally open) is arranged at an intermediate position thereof. A reactor pressure vessel vent line 3 penetrates the main body trunk 38. The reactor pressure vessel vent line 3 extends upward along the inner wall surface of the reactor pressure vessel upper lid 2 in the reactor pressure vessel 1. The reactor pressure vessel vent line 3 is connected to a condensation tank 8 for the reactor water level gauge by gas phase piping 40 extending substantially horizontally outside the reactor pressure vessel 1. Water piping 41 extending downward from the condensation tank 8 passes through the reactor water level gauge 7 and is connected to the reactor pressure vessel 1 below the gauge 7. Piping 42 branched from the gas phase piping 40 is connected to a dry well sump 6 through a drain valve 19 (normally closed). Piping 43 branched from the piping 42 at the downstream side (lower side) of the drain valve 19 is connected to a vacuum breaker 28. Piping 44 branched from the piping 42 at the downstream side of the drain valve 19 is connected to the suppression pool 33 by way of a valve 45 (normally closed). A nitrogen gas filling line 50 is branched from the gas phase piping 40 at an intermediate position thereof so that nitrogen gas can be supplied from a nitrogen gas cylinder 9 to the gas phase piping 40 by way of a nitrogen gas supply valve 52. With the above described arrangement of the reactor pressure vessel vent line 3, the reactor pressure vessel vent line 3 can be used to raise the water level in the reactor pressure vessel 1 at the time of a pressure resistance test or an operation of filling the nuclear reactor with water without penetrating the reactor pressure vessel upper lid 2. Additionally, since the reactor pressure vessel upper lid 2 is free from any penetrations, the heat insulating material 15 of the reactor pressure vessel upper lid 2 and the reactor pressure vessel vent line 3 do not interfere with each other. Therefore, the heat insulating material 15 of the reactor pressure vessel upper lid 2 can be taken off to open the reactor pressure vessel 1 early while the nuclear reactor is under depressurization after it is shut down. The vent line is installed in the reactor pressure vessel upper lid 2 and is connected to the piping 40 that penetrates the main body trunk 38 below the main body trunk flange 5a at flanges 4. If the water level of the nuclear reactor is raised only to the vicinity of the level of the main body trunk flange 5a, it can be so arranged that the opening of the vent line is positioned at or above the level of the main body trunk flange 5a and no vent is formed at the reactor pressure vessel upper lid 2. Steam can be prevented from dispersing from the inside of the dry well 31 when the vent of the reactor pressure vessel is opened, by connecting the discharge line to the dry well sump 6 at the time of venting the reactor pressure vessel 1. Alternatively, the steam from the reactor pressure vessel vent line 3 can be discharged into the suppression pool 33 that is operated as heat sink in case of accident, instead of discharging the steam into the dry well sump 6 The reactor water level gauge 7 is arranged to monitor the water level when the reactor water level is raised or lowered during start up or shut down operation of the nuclear reactor. Because of this arrangement, the vent line 3 can be connected to the condensation tank 8 disposed at the reactor water level gauge 7, utilizing the vent line 3 as upper taking out point for gauging the water level by the reactor water level gauge 7. The reference water level can be held to a constant value by opening the drain valve 19. When the nuclear reactor is shut down and the reactor water level is raised, nitrogen gas can be fed into the reactor pressure vessel vent line 3 by way of the nitrogen gas filling line 44 and fill the vent line 3 with nitrogen gas in order to replace steam with nitrogen gas so as to raise the water level stably. By filling with nitrogen gas, the non-condensable gas accumulated in a top part of the reactor pressure vessel 1 can be diluted and replaced when the nuclear reactor is shut down. FIG. 2 is a schematic diagram of the second embodiment of boiling water reactor according to the present invention, showing a cross-sectional elevation of a principal part of the reactor pressure vessel and the system configuration of the head spray line thereof. FIG. 3 is a schematic partial cross-sectional elevational view of the head spray line of FIG. 2, showing the configuration thereof. FIG. 4 is a schematic partial cross-sectional plane view of the head spray line of FIGS. 2 and 3, showing the configuration thereof. The head spray line in the inside of the reactor pressure vessel of this embodiment will be described below. The reactor pressure vessel head spray line 10 penetrates the lateral side of the main body trunk 38 and not the reactor pressure vessel upper lid 2. Additionally, spray nozzles 12 may be arranged so as to directly spray water toward the inner surface of the main body trunk flange 5a and that of the upper lid flange 5b from the head spray line 10 in order to improve the rate of cooling the nuclear reactor when the nuclear reactor is shut down. The head spray line 10 is installed in the reactor pressure vessel upper lid 2 and connected to the piping penetrating the main body trunk 38 at the flanges 4. The spray nozzles 12 are directed obliquely downward so that the sprayed water hits the inner wall surface of the reactor pressure vessel 1 to form a liquid film on the wall surface and cool the wall surface. When the nuclear reactor is cooled, if the temperature of the stud bolts 11 that tightly bind the flanges of the reactor pressure vessel 1 including the main body trunk flange 5a and the upper lid flange 5b together falls slowly, operation of loosening the stud bolts 11 to open the reactor pressure vessel 1 cannot be started early, because such an operation cannot be conducted until the temperature of the stud bolts 11 falls sufficiently. However, in this embodiment, the flanges 5a and 5b can be cooled at an accelerated rate by arranging spray nozzles 12 for spraying water to the insides of the flanges 5a and 5b at the head spray line 10. Similarly, spray nozzles 13 may be arranged so as to directly spray water toward the inner wall surface of the reactor pressure vessel upper lid 2 located above the flanges 5a and 5b and cool the steam in the inside of the reactor pressure vessel upper lid 2 at an accelerated rate when the nuclear reactor is cooled. Additionally, a liquid film is formed at the insides of the flanges 5a and 5b to cool the flanges as the water sprayed to the reactor pressure vessel upper lid 2 flows down. Furthermore, spray nozzles 12 may be installed separately. Spray nozzles 14 for spraying water to the gas phase section in the inside of the reactor pressure vessel upper lid 2 may be installed as part of the spray nozzles for discharging water from the head spray line 10 in order to absorb sensible heat of steam. Spray nozzles 13 for cooling the reactor pressure vessel upper lid 2 and spray nozzles 12 for cooling the inside parts of the flanges 5 may be installed separately. Thus, since the reactor pressure vessel upper lid 2 of this embodiment is free from any penetrations, the heat insulating material 15 on the reactor pressure vessel and the reactor pressure vessel vent line do not interfere with each other so that the heat insulating material 15 can be taken off to open the reactor pressure vessel early while the nuclear reactor is shut down and subsequently depressurized. The above-described embodiments are only examples and the present invention is by no means limited to them. For instance, as for the connections of the reactor pressure vessel vent line 3 outside the reactor pressure vessel 1 of the first embodiment, it may not necessarily be connected to all of the water level gauge 7, the nitrogen gas filling line 50, the dry well sump 6 and the suppression pool, and may be connected only to some of them. Additionally, all the nozzles of the head spray line 10 of the second embodiment including the spray nozzle 12 for cooling the insides of the flanges, the spray nozzles 13 for cooling the reactor pressure vessel upper lid and the spray nozzles 14 for cooling the gas phase section of the reactor pressure vessel upper lid may not necessarily be installed, and only some of them may be installed. Finally, any of the variously combined arrangements of the reactor pressure vessel vent line 3 of the first embodiment and any of the variously combined arrangements of the head spray line 10 of the second embodiment may be appropriately combined and connected.
054917328	description	DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, and particularly to FIG. 1, there is illustrated a schematic flow diagram of a decontamination clean-up system operable in conjunction with the chemical decontamination of a nuclear reactor primary system to remove dissolved and suspended solids from the fluids flowing through the nuclear reactor primary system. The decontamination clean-up system, which is generally designated by the numeral 10, is operable to receive primary system fluids circulating through a nuclear reactor primary system or containment chamber such as schematically illustrated by the numeral 12 and remove suspended and dissolved solids from the fluids generated as a result of the primary system being subjected to a conventional chemical decontamination process. The primary system fluids containing the suspended and dissolved solids are introduced into the clean-up system 10 via piping 14 and a pair of residual heat removal (RHR) pumps 16. The residual heat removal pumps 16 provide a pressure head for the primary system fluids as the fluids flow through the piping 18 and into the clean-up system 10. The pressure head needed for operation of the chemical decontamination clean-up system 10 is preferably provided by the residual heat removal pumps 16 since these pumps are already in use in a reactor auxiliary system. The primary system fluids flowing through the piping 18 are introduced into a valve network 20 which includes a throttle valve 22 and shut off valves 24, 26, 28 and 30. With the valves 24, 26 and 28 in the open position, valve 30 in the closed position and throttle valve 22 either partially or fully open, a portion of the primary system fluids discharged from the residual heat removal pumps 16 are directed to the clean-up system 10 wherein suspended and dissolved solids contained within the primary system fluids are removed. The suspended and dissolved solids contained within the primary system fluids are generated by a conventional decontamination process. In general, suspended solids or particulates will consist of metals (chromium, iron and nickel) and manganese dioxide. Although the exact quantity of metals will depend upon the crud film thickness, the total quantity will typically be between 400 and 1,000 pounds (180 and 450 kg) for a standard four loop reactor system. In normal operation of the decontamination system, the majority of this mass will be dissolved by the decontamination chemicals. As for the undissolved particulates which form the suspended solids, tests have shown that about 70% of the particulates will be in a range of between 2 and 8 microns, and their concentration within the primary system fluids will be in the range of between 10 and 15 parts per million. The manganese dioxide contained in the primary system fluids is generated during the alkaline/permanganate step that is common to both the known CAN-DEREM and LOMI chemical decontamination processes. It was originally thought to be desirable to remove all manganese dioxide in particulate form rather than allowing it to become a dissolved solid. Since the expected particle size of the manganese dioxide is in a range of between 0.7 and 1.7 microns, filtration had heretofore been believed to be the preferred removal process. After further evaluation, however, it has been determined that manganese dioxide filtration is, in most instances, neither practical nor economical. It has been determined that the manganese dioxide is best treated chemically with oxalic acid, which is injected into the clean-up system 10 via a chemical injection pump 33. The oxalic acid chemically reacts with the manganese dioxide carried by the primary system fluids circulating through the clean-up system 10. The oxalic acid reduces the manganese dioxide to manganous ions and these manganous ions are removed by ion exchange within downstream demineralizer resin beds. Regarding the removal of suspended solids or particulates from the primary system fluids, based on the relatively high particulate or solids concentration, it had been thought that the large volume of solids would normally have an adverse affect on these downstream demineralizer resin beds in terms of excessive pressure drop or coating of the resins. Therefore, it was believed to be preferable to remove at least a substantial portion of the suspended solids via a filtering system prior to utilization of any ion-exchange beds. However, it has been determined that the removal of suspended solids prior to utilization of any ion-exchange beds is not required. Eliminating the initial filtering system does not adversely affect the clean-up system 10 so long as a sufficient number of ion-exchange beds are utilized during the clean-up process. For example, for a conventional 4 loop reactor system, it has been found that a minimum of 14 ion-exchange beds are required. Properly quantifying the total amount of resin and demineralizer vessels required for the clean-up process eliminates the need to backflush the demineralizers during operation of the clean-up system 10 and allows the operators of the clean-up system 10 to postpone resin bed replacement until after the clean up process is complete. After the primary system fluids have passed through the piping 18 and the open valves 24, 28, the fluids are directed via piping 32 to a network of first demineralizer banks generally designated by the numeral 34. The network of first demineralizer banks 34 includes one or more cation demineralizer banks 36 which may be selectively chosen by means of the plurality of upstream and downstream valves 38. If desired, the cation demineralizer banks 36 may be totally bypassed using bypass piping 40 and valve 42. The cation demineralizer banks 36 are operable to remove metals such as iron, chromium and nickel, and radioactive materials, such as cobalt and cesium, which are dissolved by the decontamination chemicals, as well as manganous ions and cation species of the decontamination chemicals themselves. In addition to demineralizing primary system fluids flowing through each of the cation demineralizer banks via ion-exchange, each of the demineralizer banks 36 also serves to some degree as a filtration device. Within the cation demineralizer banks 36, larger solids suspended in the primary system fluids are removed as they are trapped within the resin beds of the individual demineralizers forming each bank 36. After passage through the cation demineralizer banks 36, the primary system fluids are directed via the piping 44 to an anion demineralizer bank 46 which also forms a portion of the network of first demineralizer banks 34. The anion demineralizer bank 46 is used primarily to remove the anionic species of the decontamination chemicals. As with each of the cation demineralizer banks 36, the anion demineralizer bank 46 also serves as a filtration device to trap solids suspended in the primary system fluids. If desired, the anion demineralizer bank may also be bypassed using bypass piping 48 and valve 50. Eliminating the need to replace resin beds during the clean-up process eliminates the potential delays in the overall decontamination process due to equipment malfunctions or operator errors in operating the resin replacement subsystems during the decontamination process (i.e., on critical path). Delays are obviously very costly due to the impact on the utilities outage schedule. Another advantage of the demineralizer arrangement described above is the segregation of cation and anion resins in separate demineralizers. In known systems which included approximately nine demineralizer vessels, cation and anion resins were mixed in certain demineralizer vessels. Although this arrangement provides acceptable ion exchange performance, resin performance is less than optimum. That is, ion exchange is slightly more efficient, when for example, process fluids are directed through separate cation and anion beds in series rather than directed through one demineralizer with both cation and anion resins mixed. In addition, this system also provides the flexibility of using only cation or anion resin in the event that unexpected chemistry conditions occur which must be corrected using the resins. When used with a CAN-DEREM chemical decontamination process, the cation and anion demineralizer banks 36, 46 are arranged as shown in FIG. 1. Two of the cation demineralizer banks 36 are utilized for the alkaline/permanganate steps and the third bank, containing vessels referred to as REGEN beds, are dedicated to the regeneration step (when 70-80% of the curies will be removed from the primary system fluids). When the CANDEREM chemical decontamination process is utilized on a four loop reactor system, primary system fluids may be treated without replacing the cation and anion demineralizer bank resin beds. When operating with the LOMI chemical decontamination process, the same two banks of cation demineralizer banks 36 can be used. The REGEN beds are not required for the LOMI decontamination process. After passage through the anion demineralizer bank 46, the primary system fluids are directed via the piping 52 to a "finish" demineralizer bank 54 wherein the primary system fluids are "polished" to remove substantially all of the dissolved solids (trace levels of dissolved solids) from the primary system fluids. Finish demineralizer bank 54 includes two demineralizers each containing mixed resin, i.e., a mixture of cation and anion resins. If desired, the finish demineralizer bank 54 may be totally bypassed using the bypass piping 56 and bypass valve 58. After the primary system fluids are demineralized within the cation and anion demineralizer banks 36, 46, and finish demineralized in the demineralizer bank 54, they are returned to the primary system 12 via a return apparatus generally designated by the numeral 60. Return apparatus 60 includes a pair of resin traps 62 connected in parallel flow relationship. The traps resin 62 may be selectively placed in the clean-up system 10 by operation of the upstream and downstream valves 64. Each trap resin 62 is designed to prevent large quantities of resin from entering the reactor primary system in the event that any of the upstream individual demineralizer vessels forming each of the banks 36, 46 and 54 fail. Typically, only one of the resin traps 62 is on line at any given time. After passing through at least one of the resin traps 62, the primary system fluids are directed via the piping 66 to a pair of filters 68. Each of the filters 68 is preferably a high dirt-holding capacity depth filter in a pre-shielded container, and at least two filters 68 are recommended so that one can serve as a backup while the other is in service. Each of the filters 68 includes upstream and downstream valves 70 so that an individual filter 68 can be operated, or maintenance performed thereon, independently of the operation of the other filter 68. One preferred filter media is polypropylene or glass fiber. Pleated paper is typically not acceptable because the decontamination chemicals of the standard processes will dissolve the paper. The filters will typically have a nominal rating of 3 microns or less to allow for fine filtration of solids suspended in the primary system fluids. This nominal 3 micron rating is acceptable since, as previously described, larger particles suspended in the primary system fluids are trapped within the resin beds of the network of first demineralizer banks 34 and the finish demineralizer bank 54. After the primary system fluids pass through the filter 68, these fluids are reintroduced into the primary system 12 by piping 72, open valve 26 and piping 73. As seen in FIG. 1, each of the cation demineralizer banks 36 and the anion demineralizer bank 46 is formed from three individual demineralizers 74 connected in parallel flow relationship. The finish demineralizer bank 54 is formed from a pair of individual demineralizers 74 connected in parallel flow relationship. Each of the individual demineralizers 74 in the clean-up system 10 is arranged in order to optimize a variety of factors including: total resin volume requirements; resin bed removal after primary system fluids clean-up; adequate flow rate to achieve the proper clean-up within a viable time period; use of multiple units for operating flexibility and ease of transport; and proper resin loading. The arrangement and number of individual demineralizers 74 are selected so that no resin bed replacement is required during the operation of the clean-up system. The amount of resin loading should allow for sufficient residence time to obtain efficient ion exchange. It is preferable to achieve roughly 99% removal of any chemicals injected within the primary system in less than about 8 hours. Thus, a flow rate in the range of between 1,000 and 1,500 gallons (38,000-57,000 liters) per minute will be necessary for a system volume of approximately 100,000 gallons (380 cubic meters). The clean-up system 10 is operable to remove suspended and dissolved solids from the primary system fluids subjected to a chemical decontamination process. As previously described, the number of demineralizer banks utilized within the clean-up system 10 is chosen so that resin bed replacement is not necessary until the primary system fluids clean-up is complete. Further, since the demineralizer beds themselves are utilized to trap larger suspended solids, filtering primary system fluids prior to demineralization is not required. For an in-depth explanation of the operation of the clean-up system 10 and each of the individual demineralizers 74, reference is made to copending patent application Ser. No. 07/983,503, filed Nov. 30, 1992, now U.S. Pat. No. 5,325,410, which is assigned to the assignee of the present invention and incorporated herein by reference. Now referring to FIG. 2, the various components of the chemical decontamination clean-up system 10 described with reference to FIG. 1 are illustrated schematically and located outside of containment in existing on-site support buildings and areas adjacent to the support buildings. As seen in FIG. 2, the primary system or containment chamber 12 provides primary system fluids via piping 14 to the pair of residual heat removal pumps 16. As described with reference to FIG. 1, the primary system fluids exiting the pair of residual heat removal pumps 16 pass through open valve 24 and into the chemical decontamination clean-up system 10. Since FIG. 2 is presented to illustrate the layout of the various components of the clean-up system 10, all piping and valving extending between various components of the clean-up system 10 have been eliminated for clarity. The layout configuration of the present invention as illustrated in FIG. 2 provides for supplying the components necessary for full system decontamination clean-up in divisible units. In most instances, these units are placed upon skids which are easily transported by tractor/trailers to the reactor site. These components are also easily installed and dismantled for removal when not in use. Another key design feature of the present invention is that almost all of the individual components forming the cleanup system 10 can fit upon an individual skid, or a plurality of skids which would be situated in close proximity to one another. Since the chemical decontamination clean-up process on a full scale basis may only be needed two to three times per reactor life, a particular nuclear facility using the clean-up system may desire to remove the equipment when not in use. Therefore, a modular design facilitates easy component set-up and removal. The preferred outside of containment layout design utilizing existing on-site support buildings is shown in FIG. 2 for a typical 4-loop pressurized water nuclear reactor. In this layout design, skid positions are established for various components forming the decontamination clean-up system. Those components handling the radioactive fluids are positioned within shielded rooms in existing on-site support buildings, while those components of the clean-up system 10 which do not contain radioactive primary system fluids are located outside of the buildings. As seen in FIG. 2, the network of first demineralizer banks generally designated by the numeral 34 is positioned within a fuel storage building 80 which forms a portion of the nuclear power plant. Each of the individual demineralizers 74 of the cation banks 36 and anion bank 46 is positioned on an individual skid 82 located within a shielded room 84 of the fuel storage building 80 and defined by the temporary shields 86, 87, and the building wall 90. As seen in FIG. 2, three of the individual demineralyzers are positioned within a dotted-line box 89. These three demineralizers 74, which form the REGEN bed referred to with regard to FIG. 1, are located in the left corner 85 of the shielded room 84 since they will accumulate most of the dissolved radioactivity and will be shielded from personnel within the fuel storage building providing 80 by the remaining demineralyzers 74 within the room 84. The temporary shields 86, 87, 88 are formed from a twenty-four inch thick concrete or equivalent wall and the building wall 90 is six feet thick. The shielded room 84 is equipped with floor drains and a retaining curb extending around the perimeter of the room as well known in the art to collect and contain radioactive fluids in the event any of the individual demineralizers 74 or piping/valve arrangements experience leakage. The individual demineralizers 74 forming the second or finish demineralizer bank 56 are positioned on skids 92 located in a shielded room 94 forming a portion of the nuclear power plant primary auxiliary building 96. The shielded room 94 is defined by the walls 98, 100, 102 and 104. The walls 98, 100 and 102 are formed from twenty-four inch thick concrete or equivalent. The wall 104 is formed from thirty-six inch thick concrete or equivalent. An additional twenty-four inch thick concrete or equivalent shield wall 106 is positioned within the shielded room 94 so that no direct line of site exists between the pair of individual demineralizers 74 positioned on the skids 92 and the outer area 108 of the shielded room 94. Also positioned within the shielded room 94 are the pair of resin traps 62 and the pair of filters 68. Both of the resin traps 62 are positioned on a skid 110. The individual demineralizers 74 positioned on the skids 92 are located adjacent to the wall 100, the pair of filters 68 are located adjacent to the wall 104 and the pair of resin traps 62 positioned on the skids 110 are disposed between the pair of demineralizers 74 and the pair of filters 68. As is evident from FIG. 2, those components of the clean-up system 10 which handle radioactive fluids are positioned within the shielded rooms 84 and 94. Those components of the clean-up system 10 which do not directly come in contact with radioactive fluids are located outside the shielded rooms 84, 94. For example, the chemical injection pump 33 utilized to inject oxalic acid into the primary system is positioned on a trailer 114 located in an outdoor corridor 116 extending between the fuel storage building 80 and the primary auxiliary building 96. In addition, a trailer 118 which houses electrical control equipment utilized to operate the various electrically controlled valves of the clean-up system 10 and also houses monitoring equipment may also be located within the outdoor corridor 116. A motor control trailer 120 which houses electrical starters for the various motors used in clean-up system 10 may be positioned in the corridor 116 or in an outdoor staging area 122. As previously described with reference to FIG. 1, the clean-up system 10 utilizes a sufficient number of individual demineralizers 74 such that resin replacement is not required during the chemical decontamination clean-up process. As a result, spent resin storage tanks typically used with prior clean-up systems are not required. Prior to chemical decontamination clean-up, each of the individual demineralizers 74 are devoid of resin. Prior to commencing decontamination clean-up operations, a portable device such as a trailer 124 carrying one or more fresh resin containers 126 is parked in the staging area 122. The trailing 124 is then moved into the truck bay 125 and the individual resin containers 126 are connected via suitable piping (not shown) to the individual demineralizers 74 located in both the fuel storage building 80 and the primary auxiliary building 96. Thereafter, fresh resin is either pumped as a scurry into the individual demineralizers 74 or pulled in under vacuum. In this manner, each of the individual demineralizers 74 may be filled remotely. After each of the individual demineralizers 74 is filled with resin, the individual containers 126 may be disconnected from the fill piping and the trailer 124 removed from the truck bay 125 and the staging area 122. After the chemical decontamination clean-up process is complete, a second portable unit generally designated by the numeral 128 is initially positioned in the staging area 122. The second portable unit 128 includes a pair of trailers 130 and 132 which are then moved into the truck bay 125. The trailer 130 carries one or more pumps schematically illustrated by the numerals 134 which are connected with each of the individual demineralizers 74 in the fuel storage building 80 and primary auxiliary building 96 via suitable piping (not shown). The pumps 134 are operable to pump sluicing water through one or more of the individual demineralizers 74 to flush out the spent resin contained within the selected demineralizers 74 after clean-up is complete. The spent resin/sluicing water mix is returned from the selected demineralizers 74 to high integrity containers 136 positioned on the trailer 132. The high integrity containers 136 are shielded and thus contain radioactivity within their interiors. When the high integrity containers are filled, they may be removed from the staging area 122 and transported to a burial site for final disposal. It is thought that the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts of the invention described herein without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof.
	claims	1. A method for producing an iodine radioisotopes fraction, comprising the following steps:(i) dissolving enriched uranium targets by contacting with base to obtain an alkaline slurry containing aluminium salts, uranium, and isotopes generated by the fission of enriched uranium and a gaseous phase of Xe-133, wherein the alkaline slurry comprises a solid phase containing uranium and an alkaline solution comprising molybdate and salts of iodine radioisotopes,(ii) filtering said alkaline slurry to separate the solid phase containing the uranium and the alkaline solution of molybdate and salts of iodine radioisotopes,(iii) adsorbing said salts of iodine radioisotopes on an alumina resin doped with silver and recovering an alkaline solution of molybdate depleted of iodine radioisotopes by passing the alkaline solution of molybdate and salts of iodine radioisotopes through said alumina resin doped with silver, and(iv) recovering said iodine radioisotopes fraction,wherein said recovering of said iodine radioisotopes fraction comprises washing of the alumina resin doped with silver with a solution of NaOH at a concentration of between 0.2 and 1.5 mol/l, between 0.3 and 1 mol/l, or about 0.5 mol/l, and eluting the iodine radioisotopes by a thiourea solution having a thiourea concentration of between 0.5 mol/l and 1.5 mol/l , between 0.8 and 1.2 mol/l, or of about 1 mol/l , collecting an eluate containing said iodine radioisotopes in a thiourea solution wherein the iodine radioisotope fraction is an iodine radioisotope fraction comprising I-131. 2. The method according to claim 1, wherein said uranium targets are low enriched uranium targets. 3. The method according to claim 2, further comprising, before said filtering, an addition of alkaline-earth nitrate selected from strontium nitrate, calcium nitrate, and barium nitrate, and sodium carbonate to said alkaline slurry. 4. The method according to claim 1, further comprising acidifying said eluate containing said iodine radioisotopes in a thiourea solution by the addition of a buffer solution, wherein the buffer solution comprises a solution of phosphoric acid with a concentration of between 0.5 and 2 mol/l, between 0.8 and 1.5 mol/l, or about 1 mol/l with a recovery of an acidified solution of iodine radioisotope salts. 5. The method according to claim 4, further comprising purifying said acidified solution of iodine radioisotope salts comprising loading said acidified solution of iodine radioisotope salts on an ion-exchange column, washing said ion-exchange resin with water, and eluting said ion-exchange resin with NaOH at a concentration of between 0.5 and 2.5 mol/l, between 0.8 mol/l and 1.5 mol/l or about 1 mol/l with a recovery of said iodine radioisotopes fraction in a solution of NaOH. 6. The method according to claim 5, wherein said ion-exchange resin is a weak anionic resin. 7. The method according to claim 1, further comprising an acidification of the alkaline solution of molybdate depleted of iodine radioisotopes comprising I-131, passing through said alumina resin doped with silver, with formation of an acid solution of molybdenum salts and release of residual iodine radioisotopes comprising I-131, in the form of gas for the purpose of the recovery thereof. 8. The method according to claim 7, further comprising, before said acidification of the alkaline molybdate solution depleted of iodine radioisotopes comprising I-131, passing through said alumina resin doped with silver, a cooling of the alkaline molybdate solution depleted of iodine radioisotopes, passing through said alumina resin doped with silver to a temperature below or equal to 60° C., below or equal to 55° C., or below or equal to 50° C. 9. The method according to claim 7, further comprising, after acidification, heating of the acid solution of molybdenum salts to a temperature greater than 93° C., greater or equal to 95° C., between 96° C. and 99° C., or below 100° C., accompanied by air bubbling. 10. The method according to claim 7, wherein said recovery of the iodine radioisotopes comprising I-131 as the release thereof is carried out by a transfer of the iodine radioisotopes comprising I-131 in the form of gas in a pipe connected at one end to an acidifier wherein the acidification occurs and at another end to a closed container containing an aqueous phase and a surrounding medium, said transfer of iodine radioisotopes comprising I-131 in the form of gas being carried out so as to result directly in the aqueous phase wherein the iodine radioisotopes comprising I-131, in the form of gas pass through the aqueous phase and escape in the form of bubbles in the surrounding medium of the aqueous phase, contained in the closed container. 11. The method according to claim 10, wherein said closed container is connected by a pipe to a second closed container that contains an NaOH trap and wherein the surrounding medium of the aqueous phase is transferred from the closed container to the second closed container containing the NaOH trap in the form of a solution at a concentration from 2 to 4 mol/l or about 3 mol/l , with discharge of the surrounding medium containing the iodine radioisotopes comprising I-131 of the pipe into the solution of the NaOH trap, with solubilisation of the iodine radioisotopes I-131 in the form of gas into iodide of iodine radioisotopes comprising I-131 in the aqueous solution of the NaOH trap. 12. The method according to claim 11, wherein the aqueous solution of the NaOH trap containing the iodides of the iodine radioisotopes comprising I-131, forms a crude iodine solution, which is then purified by a second acidification to form gaseous iodine. 13. The method according to claim 12, wherein said second acidification is carried out in the presence of H2SO4 and H2O2. 14. The method according to claim 12, wherein the gaseous iodine is captured in NaOH 0.2 M bubblers to form said fraction of iodine radioisotopes comprising I-131. 15. The method according to claim 5, wherein said fraction of iodine radioisotopes in an NaOH solution containing iodides of the iodine radioisotopes, forms a crude iodine solution and is then purified by a second acidification. 16. The method according to claim 15, wherein said second acidification is carried out in the presence of H2SO4 and H2O2. 17. The method according to claim 15, wherein the gaseous iodine is captured in NaOH 0.2 M bubblers to form said fraction of iodine radioisotopes comprising I-131. 18. The method according to claim 12, wherein said iodine radioisotopes fraction comprising I-131 in an NaOH solution and the aqueous solution of the NaOH trap containing the iodides of iodine radioisotopes comprising I-131, are collected and purified together by a second acidification.
	summary
	claims	1. A two-dimensional position map correcting method used when detecting with radiation detectors each formed of a plurality of scintillator elements arranged in one dimension, two dimensions or three dimensions, and a light sensor optically coupled thereto, for correcting a two-dimensional position map presenting, in two dimensions, signal strengths obtained with the light sensor as corresponding to incident positions of the radiation incident on the scintillator elements, the two-dimensional position map correcting method comprising a peak separating step for drawing boundaries based on peaks of the signal strengths, and separating respective positions by the boundaries, and a number determining step for determining, by using spatial periodicity of the peaks, the number of peaks having failed to be separated in the peak separating step, with a plurality of the peaks connecting to each other. 2. The two-dimensional position map correcting method according to claim 1, comprising a boundary determining step for separating respective positions having failed to be separated in the peak separating step, by setting the boundaries so that as sensitivity ratio of each of the scintillator elements and a total ratio of pixels in a peak area be in agreement. 3. The two-dimensional position map correcting method according to claim 1, wherein the separating step is executed to compare the signal strengths and obtain respective local minimal values, and to draw positions of the local minimal values as the boundaries, and separate the respective positions by the boundaries. 4. The two-dimensional position map correcting method according to claim 1, wherein the separating step is executed to compare the signal strengths and obtain respective local maximal values, and to draw positions of the local maximal values as the boundaries, and separate the respective positions by the boundaries. 5. A radiation detecting apparatus having radiation detectors each formed of a plurality of scintillator elements arranged in one dimension, two dimensions or three dimensions, and a light sensor optically coupled thereto, the apparatus comprising a storage device, in relation to a two-dimensional position map presenting, in two dimensions, signal strengths obtained with the light sensor as corresponding to incident positions of the radiation incident on the scintillator elements, for storing a table having, in a corresponding relationship, each position in the two-dimensional position map and each scintillator element, and an arithmetic processing device for carrying out arithmetic processes for correcting the two-dimensional position map, radiation detecting positions being determined by discriminating the incident positions based on the two-dimensional position map corrected and results of radiation detection, wherein the arithmetic, processing device has a peak, separating step for drawing boundaries based on peaks of the signal strengths, and separating respective positions by the boundaries, and a number determining step for determining, by using spatial periodicity of the peaks, the number of peaks having failed to be separated in the peak separating step, with as plurality of the peaks connecting to each other, and carries out arithmetic processes relating to these steps. 6. The two-dimensional position map correcting method according to claim 2, wherein the separating step is executed to compare the signal strengths and obtain respective local minimal values, and to draw positions of the local minimal values as the boundaries, and separate the respective positions by the boundaries. 7. The two-dimensional position map correcting method according to claim 2, wherein the separating step is executed to compare the signal strengths and obtain respective local maximal values, and to draw positions of the local maximal values as the boundaries, and separate the respective positions by the boundaries.
	description	FIG. 1 is a top sectional view of a boiling water nuclear reactor pressure vessel 10. Reactor pressure vessel 10 includes a vessel wall 12 and a shroud 14 which surrounds the reactor core (not shown) of pressure vessel 10. An annulus 16 is formed between vessel wall 12 and shroud 14. The space inside annulus 16 is limited with most reactor support piping located inside annulus 16. Cooling water is delivered to the reactor core during a loss of coolant accident through core spray distribution header pipes 18 and 20 which are connected to downcomer pipes 22 and 24 respectively. Downcomer pipes 22 and 24 are connected to shroud 14 through sparger T-boxes 26 and 28 respectively, which are attached to shroud 14 and internal sparger pipes 30. Distribution header pipes 18 and 20 diverge from an upper T-box 32 coupled to a safe end 42 of core spray nozzle 44. Header pipes 18 and 20 are coupled to upper T-box by pipe connectors 46 and 48 respectively. Pipe connectors 46 and 48 may be any pipe connectors known in the art, for example, ball flange connectors. FIG. 2 is a side sectional view of a sparger T-box attachment assembly 50 in accordance with an embodiment of the present invention. Sparger T-box attachment assembly 50 couples downcomer pipes 22 and 24 to sparger T-boxes 26 and 28 respectively, and clamps sparger pipes 30 to sparger T-boxes 26 and 28 to prevent separation of sparger pipes 30 from sparger T-boxes 26 and 28 in the event of a connecting weld failure. The sparger T-box attachment assembly includes a downcomer pipe coupling 52 and a sparger T-box clamp 54. Referring also to FIG. 3, downcomer pipe coupling 52 includes a cylindrical outer housing 56 having a first end 58 and a second end 60. First end 58 is configured to couple to downcomer pipe 22 by any suitable means, for example by welding. A flange 62 extends from second end 60 of outer housing 56. Flange 62 is received into a circular groove 64 machined into shroud 14. Groove 64 is located so as to be concentric with sparger T-box 26 penetration through shroud 14. A center portion 66 having a threaded axial bore 68 therethrough is connected to outer housing 56 by a plurality of vanes 70 extending from an inner surface 72 of outer housing 56 to center portion 66. A draw bolt 74 threadedly engages axial bore 68 of said center portion 66. Draw bolt 74 connects downcomer pipe 52 to sparger T-box clamp 54. Of course, coupling 52 can be used to connect downcomer pipe 24 to sparger T-box 28. Referring to FIGS. 2, 4, 5, and 6, sparger T-box clamp 54 includes an anchor 76 having a draw bolt opening 78, and a plurality of legs 80 extending from a first face 82 of anchor 76. Legs 80 are configured to engage an inside surface 84 of shroud 14 and are machined or trimmed so that anchor face 82 is parallel to an exterior surface 86 of sparger T-box 26. A first and a second clamp block 88 and 90 are connected to opposite sides 92 and 94 of anchor 76. Clamp blocks 88 and 90 are positioned to be substantially aligned with one another. Specifically, clamp blocks 88 and 90 are connected to sides 92 and 94 of anchor with dove-tail joints 96 and 98 respectively. Dove-tail joints 96 and 98 permit clamp blocks to move relative to anchor 76 which eliminates the imposition of any stress on the sparger pipe to sparger T-box welds. Clamp blocks 88 and 90 partially surround sparger pipe 30. Each clamp block 88 and 90 includes a threaded stop bolt opening 100 extending therethrough. A stop bolt 102 extends through each stop bolt opening 100. Each stop bolt 102 has a conical shaped distal end 104 which is sized to mate with a conical shaped opening 106 machined in sparger distribution header pipes 30. The conical shape of stop bolt end 104 and mating opening 106 minimizes interference with the flow stream in pipe 30 and also seals opening 106 to minimize leakage. Referring also to FIG. 7, clamping elements 108 and 110 are connected to clamp blocks 88 and 90 respectively by clamp bolts 112. Clamp bolts 112 extend through clamp bolt openings 114 in clamp blocks 88 and 90, and clamp bolt openings 116 in clamping elements 108 and 110. Spherical nuts 118 secure clamp bolts 112. Clamping elements 108 and 110 oppose clamp blocks 88 and 90 to provide a clamping action as clamp bolts 112 are tightened. A clamp bolt keeper 120 couples to clamp bolt head 122 to prevent clamp bolt 112 from loosening. Keeper 120 includes a crimp collar 124 threaded into a spherical collar 126. Crimp collar 124 to spherical collar 126 threads are opposite of the threads on clamp bolt 112. Specifically, in one embodiment, clamp bolt 112 has right hand threads, and spherical collar 124 has left hand threads. In an alternate embodiment, clamp bolt 112 has left hand threads, and spherical collar 124 has right hand threads. To hold clamp bolt 112 in place, crimp collar 124 is deformed into flutes 128 in clamp bolt head 122. Referring also to FIGS. 8, 9, 10, and 11, spherical seats 130 are machined into clamp blocks 88 and 90, and into clamping elements 108 and 110. Spherical seats 130 are concentrically aligned with clamp bolt openings 114 and 116. Also, spherical nut 118 and spherical collar 126 are keyed to clamp blocks 88 and 90 and clamping elements 108 and 110. Specifically, spherical nut 118 and spherical collar 126 includes a key portion 129, and spherical seats include a keyway 131 sized to receive key portion 129. The interface of key portion 129 with keyway 131 prevents spherical nut 118 and spherical collar 126 from rotating. Spherical seats 130 mitigate any bending forces imposed on clamp bolts 112 and provide flexibility to sparger T-box clamp 54 by permitting clamping elements 108 and 110 to move slightly to adjust and conform to the exterior contour of sparger pipe 30. Further clamping elements 108 and 110 include base portions 132 and 134 and engagement portions 136 and 138 respectively. Engagement portions 136 and 138 include cut-outs 140 sized to receive a sparger nozzle 142. Referring again to FIG. 4, a seal plate 144 is coupled to anchor 76 with adjusting screws 146. Seal plate 144 includes adjusting screw openings 148 and a draw bolt opening 150 sized to receive draw bolt 74 in a close tolerance fit. Anchor 76 includes threaded adjusting screw openings 152 sized to receive adjusting screws 146. A distal end portion 154 of adjusting screws 146 includes a circumferential groove 156 sized to receive a dowel pin 158 pressed into seal plate 144 to attach adjusting screws 146 to seal plate 144. A shank portion 160 of adjusting screws 146 are threaded into adjusting screw openings 152. As adjusting screws are torqued, seal plate 144 is advanced into close contact with exterior surface 86 of sparger T-box 26 to seal draw bolt opening 151 in T-box 26. Keepers 162 prevent adjusting screws from loosening. Keepers 162 mate with seats 164 concentric with adjusting screw openings 152. Keepers 162 include left hand threads (not shown) to mate with threads 165 in seats 164. Referring to FIGS. 4 and 5, anchor 76 further includes a rectangular depression 166 in a second face 168 of anchor 76. Draw bolt opening 78 is located in rectangular depression 166. A draw bolt keeper 170 having a rectangular portion 172 is received in rectangular depression 166 to prevent draw bolt 74 from loosening. Draw bolt keeper 170 also includes a crimp collar 173. FIG. 12 is perspective view of anchor 76. FIG. 13 is a perspective view of an anchor 174 in accordance with another embodiment of the present invention. Anchor 174 is similar to anchor 76 and includes a draw bolt opening 78, legs 80, keeper depression 166, adjusting screw openings 152, and adjusting bolt seats 164. To install a replacement downcomer pipe 22, the original piping is severed in close proximity to the outside surface of shroud 14. Circular groove 64 is machined into shroud 14 by any suitable method, for example electrode discharge machining (EDM). Groove 64 is concentric with sparger T-box 26 penetration through shroud 14. A draw bolt opening is machined in T-box 26 and conical stop bolt openings 100 are machined in sparger pipes 30 equidistant from the center of sparger T-box 26. First end 58 of outer housing is coupled to downcomer pipe 22 by any suitable means, for example welding. Flange 62 is then positioned in groove 64. T-box clamp 54 is positioned around sparger pipes 30 and sparger T-box 26 with anchor legs 80 engaging inner surface 72 of shroud 14. Draw bolt 74 with keeper 170 is inserted through draw bolt opening and threaded into axial bore 66 of coupling center portion 68 and tightened. Stop bolts 102 are threaded through stop bolt openings in clamp blocks 88 and 90 and tightened so as to seat in conical stop bolt openings 100 in sparger pipes 30. Clamp bolts extending through clamp bolt openings 114 and 116 in clamp blocks 88 and 90 and clamping elements 108 and 110 are tightened to exert a clamping force on sparger pipes 30. Adjusting screws are tightened to move seal plate 144 into contact with exterior surface 86 of sparger T-box 26. The crimp collars of all the keepers are deformed into flutes of the corresponding bolt heads to prevent the bolts from loosening. The above described core spray sparger T-box attachment assembly 50 mechanically couples downcomer pipe 22 to shroud 14 and sparger T-box 26. Also, the above described core spray sparger T-box attachment assembly 50 provides a clamping system to provide structural integrity to sparger T-box 26 and to hold the sparger pipes 30 to T-box 26 welded joints together in the event that one or more welds fail. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
	description	The present invention is directed to radiation powered devices comprising diamond material, and electrical power sources for radiation powered devices. One of the alternatives to current battery technology is the use of radiation powered batteries, also known as atomic batteries, nuclear batteries, radioisotope batteries, or radioisotope generators. These devices directly convert nuclear decay products (e.g. alpha or beta particles or gamma radiation) into electricity. Various device structures and materials have been developed to extract electrical energy from nuclear sources. Methods can generally be grouped into two main types: thermal and non-thermal. In thermal devices the radioactive source heats up a cathode electrode causing emission of electrons which flow to a cooler anode electrode generating electricity, e.g. thermoelectric or thermionic generators. In non-thermal devices radioactive decay products from a radioactive source generate electron-hole pairs in a semiconductor disposed adjacent the radioactive source in order to generate electricity, e.g. alphavoltaic or betavoltaic devices. Thermal and non-thermal processes can also be combined in device structures using both a thermal gradient and radiation induced electron-hole pair generation to produce electricity. Compared to chemical battery technologies, radioisotope batteries tend to have low power output. However, they have the advantage of long lifetimes, reduced size, and high energy density. As such, they are useful as power sources for equipment that must operate for long periods of time, particularly in environments which are difficult to access such as spacecraft, medical implants (e.g. pacemakers), underwater systems, automated scientific stations in remote parts of the world, high radiation environments, harsh chemical or physical environments, etc. They are also useful as power sources in miniaturized systems where the size of the power source is of importance. Examples of several prior art radioisotope batteries are briefly discussed below. US2013264907 (A1) discloses a betavoltaic battery which includes a beta particle source configured to provide beta particles and a diamond moderator configured to convert at least some of the beta particles into lower-energy electrons. The betavoltaic battery further includes a PN junction configured to receive the electrons and to provide electrical power to a load. The diamond moderator is located between the beta particle source and the PN junction. The beta source is comprised of tritium, nickel, krypton, promethium or strontium-yttrium isotopes which can be embedded in a substrate adjacent the diamond moderator. The PN junction is formed using a semiconductor such as silicon, silicon carbide, gallium nitride, boron nitride, or other materials with suitable p-type and n-type dopants. US2013033149 (A1) discloses a betavoltaic cell that has been fabricated using a semiconductor that includes, but is not limited to, Silicon Carbide (SiC), Silicon (Si), Gallium Arsenide (GaAs), Indium Gallium Arsenide (InGaAs), Gallium Nitide (GaN), Gallium Phosphide (GaP), or Diamond, and uses through wafer via holes or other fabrication techniques to form both positive (+ve) and negative (−ve) contacts on the front and back sides of the cell. A beta radiation source is provided as a separate layer or incorporated into a substrate adjacent the semiconductor. The beta radiation source is selected from Phosphorus-33, Ni-63, Promethium, and Tritium. US2011031572 (A1) discloses a betavoltaic battery comprising a semiconductor that includes, but is not limited to, Si, GaAs, GaP, GaN, diamond, and SiC. Tritium is referenced as an exemplary beta radiation source and SiC is referenced as an exemplary semiconductor material. The beta radiation source is provided as a separate layer or incorporated into a substrate adjacent the semiconductor. The beta radiation source is selected from Phosphorus-33, Ni-63, Promethium, and Tritium. “Designing CVD Diamond Betavoltaic Batteries” (https://www.researchgate.net/publication/235130192) discloses that diamond is a wide band-gap semiconductor characterized by exceptional physical properties and represents an appropriate material for applications involving the use of intense beams of high-energy (hv) radiation and electrons. It is disclosed that devices are being designed for the conversion of high-energy radiation into electrical power. Specifically, it is disclosed that efforts are focused on the interaction between diamond and beta particles which are simulated using an electron beam rather than a radioisotope. “Single crystal CVD diamond membranes for betavoltaic cells” (http://dx.doi.org/10.1063/1.4954013) discloses a single crystal diamond large area thin membrane assembled as a p-doped/Intrinsic/Metal (PIM) structure and used in a betavoltaic configuration. Beta particles are simulated using an electron beam rather than a radioisotope. “Comparative study of different metals for Schottky barrier diamond betavoltaic power converter by EBIC technique” (http://onlinelibrary.wiley.com/doi/10.1002/pssa.201533060/abstract) discloses betavoltaic converters based on synthetic IIb diamond Schottky structures. The structures were tested using an electron beam rather than a radioisotope. RU2595772 (C1) discloses a radioisotope photo-thermoelectric generator comprising a closed gas-dynamic circuit with working gas-xenon, a radioisotope radiator, photo- and thermoelectric converters, heat-eliminating plates and a radiator. U.S. Pat. No. 5,859,484 (A) discloses a radioisotope-powered semiconductor battery. The battery comprises a substrate of a crystalline semiconductor material and a radioactive power source comprising at least one radioactive element. The power source is positioned relative to the substrate to allow for impingement of emitted particles on the substrate. It is disclosed that the radioactive element is preferably impregnated within or immediately adjacent the semiconductor material. The semiconductor material is selected from the group consisting of III-V and II-VI semiconductor materials and mixtures thereof. The radioactive element is selected from the group consisting of tritium, promethium-147, americium-241, carbon-14, krypton-85, cesium-137, radium-226 or -228, curium-242 or -244, and mixtures thereof. KR20140129404 (A) discloses a radioisotope battery including a semiconductor layer, a seed layer which is formed on the semiconductor layer, a radioisotope layer which is formed on the seed layer, and a radiation shielding layer which is formed on the radioisotope layer and shields the radiation of the radioisotope layer from the outside. Ni-63 is used as the radiation source. In light of the above, it is evident that various materials and device structures have been proposed in the art. However, there is still an ongoing need to provide radioisotope batteries which have improved performance including one or more of: electrical efficiency; electrical power output; safety and/or radiation leakage; inertness, toxicity and/or biocompatibility; and lifetime. The present inventors have identified that diamond is in many ways the ideal material for use in radiation powered devices such as radioisotope batteries and related devices. First, diamond is extremely radiation hard and therefore has a higher tolerance to ionising radiation than other semiconductor materials improving stability and lifetime. Secondly, the large band-gap of diamond enables a significant improvement in the internal efficiency of the device. Thirdly, diamond is chemically inert, non-toxic, has high thermal conductivity, and is stable up to very high temperatures. Non-toxicity for example is highly important for human handling and sub-dermal implantation of devices for applications including pace makers and/or hearing aids. As discussed in the background section, the possibility of using diamond material in radioisotope batteries has already been proposed in several documents, either as a moderating material in combination with another semiconductor material or as the active semiconductor component of the device. However, the present inventors have identified several problems with prior art configurations as discussed below. First, diamond based devices discussed in the background section are configured such that the radioactive source is positioned outside of the diamond semiconductor material. This has been found to be an inefficient configuration for diamond based devices in terms of converting radiation into electron flow within the diamond material. Losses occur at surface interfaces and any air gaps. Furthermore, the dense atomic packing in the diamond structure means that radiation, such as alpha or beta radiation, does not effectively penetrate far through the diamond structure. Secondly, because the radioactive source is positioned outside of the diamond material then such a configuration can be prone to radiation leakage. Thirdly, because the radioactive source is positioned outside of the diamond material then the radioisotope material component may be damaged and leak from the device. This can lead to degradation in device performance, lack of chemical inertness, increased toxicity and/or biocompatibility issues. Fourthly, the diamond based devices utilize tritium or heavy metal radiation sources. These can be prone to leakage and/or be highly toxic. Fifthly, the configuration described in the background section have a low output voltage. The aim of certain embodiments of the present invention is to at least partially solve one or more of these problems. The term “diamond material” is used herein to refer to a material composed of diamond. The skilled person understands that diamond can be described as a crystalline material (a polycrystalline material or a single crystal material). The skilled person also understands that diamond can be described as the diamond allotrope of carbon in which carbon atoms are arranged in a cubic Bravais lattice over which is laid a four-atom tetrahedral motif. In certain embodiments, the diamond material may comprise n-type diamond (e.g. nitrogen doped diamond or phosphorous doped diamond) and/or p-type diamond (e.g. boron doped diamond). In certain embodiments the diamond material may comprise boron doped diamond. The diamond material may contain at least about 90% sp3 bonds, for example at least about 95% sp3 bonds, at least about 97% sp3 bonds, at least about 98% sp3 bonds, at least about 99% sp3 bonds, at least about 99.5% sp3 bonds, at least about 99.9% sp3 bonds, or about 100% sp3 bonds. The sp3 bond content in the diamond material may be determined by methods known to the skilled person, for example using X-ray photoelectron spectroscopy (XPS) (for example, as described by Yan et al., “Quantitative study on graphitization and optical absorption of CVD diamond films after rapid heating treatment”, Diamond and Related Materials, 14 Apr. 2018 (available online at https://doi.org/10.1016/j.diamond.2018.04.011); or Taki et al., “XPS structural characterization of hydrogenated amorphous carbon thin films prepared by shielded arc ion plating”, Thin Solid Films, Volume 316, Issues 1-2, 21 Mar. 1998, Pages 45-50). The skilled person understands that diamond may have a single active Raman mode at 1332 cm−1. The diamond material may have a band gap at room temperature (about 25° C.) of greater than about 5.3 eV, or about 5.4 eV or greater, or about 5.5 eV. The diamond material may have a thermal conductivity measured at room temperature (about 25° C.) of greater than about 100 W/mK, for example, greater than about 500 W/mK, greater than about 1000 W/mK, greater than about 1500 W/mK, or greater than about 2000 W/mK, or about 2200 W/mK or greater. Thermal conductivity of diamond may be determined according to the 3ω method (as described by Frank et al., in “Determination of thermal conductivity and specific heat by a combined 3ω/decay technique”, Review of Scientific Instruments 64, 760 (1993)). The diamond material may have a density of greater than about 3300 kg/m3, for example greater than about 3400 kg/m3, or greater than about 3500 kg/m3. According to a first configuration, a radiation powered device is provided which comprises: a first electrode; a second electrode; a semiconductor disposed between the first and second electrodes; and a radioactive source configured to generate a flow of electrons through the semiconductor between the first and second electrodes; wherein the semiconductor comprises diamond material; and wherein the radioactive source is embedded within the diamond material. According to a second configuration, an electrical power source (e.g. a radioisotope electrical power source or a beta-emitting radioisotope electrical power source) is provided. The electrical power source may comprise a semiconductor comprising a diamond material and a radioactive source embedded within the diamond material, wherein the radioactive source comprises a beta-emitting radioisotope and atoms of the radioisotope are substitutionally or interstitially integrated into the diamond material. The electrical power source may further comprise an ohmic contact as described herein. The ohmic contact may comprise a first electrode in contact with the semiconductor. The electrical power source may further comprise a Schottky contact as described herein. The Schottky contact may comprise a second electrode in contact with the semiconductor. The radiation powered devices and electrical power sources described herein may comprise a first electrode and a second electrode and a semiconductor disposed between the first electrode and the second electrode. The semiconductor may be disposed between first and second electrodes such that electrons may flow between the first and second electrodes via the semiconductor. In certain embodiments, the semiconductor may comprise first and second opposing faces, the first electrode contacting the first face and the second electrode contacting the second face (e.g. such that the semiconductor disposed between the first and second electrodes is sandwiched between the first and second electrodes). In certain embodiments, the semiconductor may be disposed between the first and second electrodes in any arrangement that allows electrons to flow between the first and second electrodes via the semiconductor. For example, the semiconductor may comprise first and second opposing faces, and the first and second electrodes may both contact the first face of the semiconductor. In certain embodiments, provided herein is a radiation powered device comprising an electrical power source as described herein. In certain embodiments, the radiation powered device is a battery, e.g. a betavoltaic battery. Also described herein is a battery, e.g. a betavoltaic battery, comprising an electrical power source described herein. In certain embodiments, the semiconductor comprises diamond material comprising p-type diamond and diamond material comprising n-type diamond such that the semiconductor comprises a p-n junction. According to a third configuration, a radiation powered device is provided which comprises: a first electrode; a second electrode; and a semiconductor disposed between the first and second electrodes, wherein the semiconductor comprises diamond material which generates a flow of electrons between the first and second electrodes when exposed to radiation, and wherein the diamond material includes a 13C diamond region which comprises isotopically purified diamond material having an increased 13C content compared to natural isotopic abundance. According to a fourth configuration, an electrical power source is provided which comprises a semiconductor comprising a diamond material and a radioactive source embedded within the diamond material, wherein the radioactive source comprises a beta-emitting radioisotope and atoms of the radioisotope are substitutionally or interstitially integrated into the diamond material, and the diamond material comprises a 13C diamond region which comprises isotopically purified diamond material having an increased 13C content compared to natural isotopic abundance. According to a fifth configuration, a radiation powered device is provided which comprises: a first electrode; a second electrode; a semiconductor disposed between the first and second electrodes; and a radioactive source configured to generate a flow of electrons through the semiconductor between the first and second electrodes; wherein the semiconductor comprises diamond material; and wherein the radioactive source is formed of 14C. According to a sixth configuration, an electrical power source is provided which comprises a semiconductor comprising a diamond material and a radioactive source embedded within the diamond material, wherein the radioactive source comprises 14C atoms which are substitutionally integrated into the diamond material. According to a seventh configuration, a radiation powered device is provided which comprises: a first electrode; a second electrode; and a semiconductor disposed between the first and second electrodes, wherein the semiconductor comprises diamond material which generates a flow of electrons between the first and second electrodes when exposed to radiation without the application of a biasing voltage, and wherein the radiation powered device further comprises a charge storage device coupled to the first and second electrodes for storing charge flowing out of the diamond material. The radioactive source may comprise radioisotopes, for example, beta-emitting radioisotopes. Examples of beta-emitting radioisotopes are tritium, 14C, 10Be and 33P. In certain embodiments, the radioactive source comprises tritium, 14C, 10Be, and/or 33P. In certain embodiments, the radioactive source comprises tritium, 14 and/or 10Be. In certain embodiments, the radioactive source comprises 14C and/or 10Be. In certain embodiments, the radioactive source comprises 14C and/or tritium. In certain embodiments, the radioactive source comprises 14C. The radioactive source may be embedded within the diamond material such that, for example, atoms of a radioisotope of the radioactive source are either substitutionally or interstitially integrated into the diamond material, that is substitutionally or interstitially integrated into the crystal lattice of the diamond material, to form a constituent part of the diamond material. For example, the semiconductor may comprise diamond material with 14C and/or 10Be substitutionally integrated into the diamond material, and/or the semiconductor may comprise diamond material with tritium interstitially integrated into the diamond material. In certain embodiments, atoms of a radioisotope, e.g. tritium, of the radioactive source may also be entrapped on grain boundaries (if present) within the diamond material. In certain embodiments the diamond material in which a radioactive source is embedded is a synthetic diamond material in which the radioactive source (e.g. radioisotopic atoms) is integrated during formation of the diamond material. For example, tritium and/or 14C may be integrated into the diamond crystal lattice during formation of the diamond material. In certain embodiments, the diamond material may comprise 13C such that the 13C content of the diamond material comprises an increased 13C content compared to natural isotopic abundance of 13C. In certain embodiments, the diamond material includes a 13C diamond region which comprises isotopically purified diamond material having an increased 13C content compared to natural isotopic abundance. In certain embodiments, the diamond material comprises a 13C diamond layer, where the 13C diamond layer is a layer of diamond material comprising 13C such that the 13C content of the 13C diamond layer comprises an increased 13C content compared to natural isotopic abundance of 13C. In certain embodiments, the diamond material comprises a 13C diamond layer which is positioned at an outer surface of the diamond material. In certain embodiments, the diamond material comprising 13C is a synthetic diamond material in which 13C is integrated during formation of the diamond material. In certain embodiments, the diamond material is a synthetic diamond material in which 13C and a radioactive source (e.g. radioisotope atoms) are integrated during formation of the diamond material. In certain embodiments, the diamond material comprises a 12C diamond region. In certain embodiments, the 12C diamond region is a 12C diamond layer. The In certain embodiments, the diamond material comprises a 12C diamond layer. The term “12C diamond” may be used herein to refer to diamond material comprising a substantially natural abundance of carbon isotopes. In certain examples, the 12C diamond region/layer comprises boron-doped 12C diamond, i.e. the diamond material may comprise a boron-doped 12C diamond region/layer. In certain embodiments, the diamond material comprises 14C diamond. In certain embodiments, the diamond material comprises a 14C diamond region. In certain embodiments, the diamond material comprises a 14C diamond layer. The term “14C diamond” may be used herein to refer to diamond material comprising atoms of 14C substitutionally integrated within the diamond structure such that the 14C content of the 14C diamond comprises an increased 14C content compared to natural isotopic abundance of 14C. In certain embodiments, the 14C diamond also comprises an increased 13C content compared to natural isotopic abundance of 13C. In certain embodiments, the diamond material comprises a 12C diamond region, a 14C diamond region, and/or a 13C diamond region. The 12C diamond, 14C region, and/or 13C diamond regions of the diamond material may be described as isotopic regions within a continuous diamond crystal lattice (i.e. as opposed to a structure with different regions with physical boundaries/discontinuous structures between the different regions. In certain embodiments, the diamond material comprises a bi-layer structure. The bi-layer structure of the diamond material may be described as isotopic layers within a continuous diamond crystal lattice (i.e. as opposed to a bi-layer structure comprising a discontinuous structure (or a physical boundary) across the two layers). In certain embodiments, a diamond material having a bi-layer structure may comprise a layer of diamond in which a radioactive source is embedded (for example, a layer of diamond in which atoms of a radioisotope (such as 14C) are substitutionally or interstitially integrated) and a layer of 12C diamond. In certain embodiments, a diamond material having a bi-layer structure may comprise a 14C diamond layer and a 12C diamond layer (e.g. a boron-doped 12C diamond layer). In certain embodiments, a diamond material having a bi-layer structure may comprise a layer of diamond in which a radioactive source is embedded (for example, a layer of diamond in which atoms of a radioisotope (such as 14C) are substitutionally or interstitially integrated) and a 13C diamond layer. In certain embodiments, a diamond material having a bi-layer structure may comprise a 14C diamond layer and a 13C diamond layer. In certain embodiments, the diamond material comprises a tri-layer structure. The tri-layer structure of the diamond material may be described as isotopic layers within a continuous diamond crystal lattice (i.e. as opposed to a tri-layer structure comprising a discontinuous structure (or physical boundaries) across the three layers). In certain embodiments, the diamond material having a tri-layer structure may comprise a layer of diamond in which a radioactive source is embedded (for example, a layer of diamond in which atoms of a radioisotope (such as 14C) are substitutionally or interstitially integrated), a 12C diamond layer (e.g. a boron-doped 12C diamond layer) and a 13C diamond layer. In certain embodiments, the diamond material having a tri-layer structure may comprise a 14C diamond layer, a 12C diamond layer and a 13C diamond layer. In certain embodiments, the tri-layer structure may be arranged such that the 12C diamond layer is positioned between the layer of diamond in which a radioactive source is embedded (e.g. the 14C diamond layer) and the 13C diamond layer. In certain embodiments, the diamond material comprises a region comprising an embedded radioactive source (for example a 14C diamond region or a 14C diamond layer). In certain embodiments, the diamond material comprises a region comprising an embedded radioactive source (for example a 14C diamond region or a 14C diamond layer) and the first electrode contacts the region comprising the embedded radioactive source (for example the first electrode contacts the 14C diamond region) of the diamond material of the semiconductor, for example to form an ohmic contact. In certain embodiments, the diamond material comprises a bi-region structure. The bi-region structure of the diamond material may be described as isotopic regions within a continuous diamond crystal lattice (i.e. as opposed to a bi-region structure comprising a discontinuous structure (or a physical boundary) across the two regions). In certain embodiments, a diamond material having a bi-region structure may comprise a region of diamond in which a radioactive source is embedded (for example, a region of diamond in which atoms of a radioisotope (such as 14C) are substitutionally or interstitially integrated) and a region of 12C diamond. In certain embodiments, a diamond material having a bi-region structure may comprise a 14C diamond region and a 12C diamond region (e.g. a boron-doped 12C diamond region). In certain embodiments, a diamond material having a bi-region structure may comprise a region of diamond in which a radioactive source is embedded (for example, a layer of diamond in which atoms of a radioisotope (such as 14C) are substitutionally or interstitially integrated) and a 13C diamond region. In certain embodiments, a diamond material having a bi-region structure may comprise a 14C diamond region and a 13C diamond region. In certain embodiments, the diamond material comprises a tri-region structure. The tri-region structure of the diamond material may be described as isotopic regions within a continuous diamond crystal lattice (i.e. as opposed to a tri-region structure comprising a discontinuous structure (or physical boundaries) across the three regions). In certain embodiments, the diamond material having a tri-region structure may comprise a region of diamond in which a radioactive source is embedded (for example, a region of diamond in which atoms of a radioisotope (such as 14C) are substitutionally or interstitially integrated), a 12C diamond region (e.g. a boron-doped 12C diamond region) and a 13C diamond region. In certain embodiments, the diamond material having a tri-region structure may comprise a 14C diamond region, a 12C diamond region and a 13C diamond region. In certain embodiments, the tri-region structure may be arranged such that the 12C diamond region is positioned between the region of diamond in which a radioactive source is embedded (e.g. the 14C diamond region) and the 13C diamond region. In certain embodiments, the 12C diamond region is a 12C diamond layer. In certain embodiments, the 13C diamond region is a 13C diamond layer. In certain embodiments, the region of diamond in which a radioactive source is embedded is a layer of diamond in which a radioactive source is embedded. In certain embodiments, the 14C diamond region is a 14C diamond layer. In certain embodiments, the diamond material comprises a 13C diamond region (e.g. a 13C diamond layer) and a second electrode contacts the 13C diamond region of the diamond material of the semiconductor, for example to form a Schottky contact. In certain embodiments, the diamond material comprises a 12C diamond region (e.g. a 12C diamond layer) and a second electrode contacts the 12C diamond region of the diamond material of the semiconductor, for example to form a Schottky contact. In certain embodiments, the diamond material comprises a region in which a radioactive source is embedded (e.g. a 14C diamond region or layer) and a first electrode contacts the region in which a radioactive source is embedded (e.g. a 14C diamond region or layer) of the diamond material of the semiconductor, for example to form an ohmic contact. In certain embodiments, the diamond material of the semiconductor comprises 14C diamond and a first electrode contacts the 14C diamond of the diamond material to form an ohmic contact and a second electrode contacts the 14C diamond of the diamond material to form a Schottky contact. In certain embodiments, the diamond material of the semiconductor comprises a diamond region in which a radioactive source is embedded (e.g. a 14C diamond region or layer), and a 12C diamond region (e.g. a boron doped 12C diamond region), and a first electrode contacts the diamond region in which a radioactive source is embedded (e.g. a 14C diamond region or layer) to form an ohmic contact and a second electrode contacts the 12C diamond region to form a Schottky contact. In certain embodiments, the diamond material of the semiconductor comprises a diamond region in which a radioactive source is embedded (e.g. a 14C diamond region or layer), and a 13C diamond region, and a first electrode contacts the diamond region in which a radioactive source is embedded (e.g. a 14C diamond region or layer) to form an ohmic contact and a second electrode contacts the 13C diamond region to form a Schottky contact. In certain embodiments, the diamond material of the semiconductor comprises a diamond region in which a radioactive source is embedded (e.g. a 14C diamond region or layer), a 12C diamond region (e.g. a boron doped 12C diamond region) and a 13C diamond region, and a first electrode contacts the diamond region in which a radioactive source is embedded (e.g. a 14C diamond region or layer) to form an ohmic contact and a second electrode contacts the 13C diamond region to form a Schottky contact. The present inventors have found that embedding a radioactive source, for example a beta-emitting radioisotope, into a diamond material such that atoms of a radioisotope of the radioactive source are either substitutionally or interstitially integrated into the diamond material (that is substitutionally or interstitially integrated into the crystal lattice of the diamond material, to form a constituent part of the diamond material) advantageously provides a sealed (and therefore safe) and long life electrical power source. The inventors have also found that embedding a radioactive source in a diamond material such that atoms of a radioisotope of the radioactive source are either substitutionally or interstitially integrated into the diamond material also provides a power source having improved efficiency) due to atoms of a radioactive isotope of the radioactive source being positioned within the continuous crystal lattice of the diamond material which provides a structure in which there is no break in the atomic architecture between the emitting and collecting material) compared to conventional systems which exhibit a physical gap or discontinuous structure between the radioactive source and the collecting material. The aforementioned configurations can be combined in various ways according to requirements and details of several specific configurations are given in the detailed description of this specification. It may also be noted that certain features of diamond based radiation powered devices have been disclosed by the present inventors [see, for example, http://www.bristol.ac.uk/news/2016/November/diamond-power.html and https://en.wikipedia.org/wiki/Diamond_battery]. However, details for putting the present invention into effect have not been disclosed by the inventors prior to filing of the present specification. It should be noted that in the drawings like reference numerals have been used for corresponding components to illustrate common features of the various device configurations. Device Configurations FIG. 1 shows a radiation powered device which comprises: a first electrode 10; a second electrode 12; and a semiconductor 14 disposed between the first and second electrodes, wherein the semiconductor comprises diamond material which generates a flow of electrons between the first and second electrodes when exposed to radiation. An external radiation source 18, such as a gamma-radiation source, is shown in the configuration of FIG. 1 with the device placed in a radiation field such that electron-hole pairs are generated in the diamond material. The device may be placed adjacent the radiation source 18 or configured to surround the radiation source, e.g. by providing a cylindrical device structure within which the radiation source is disposed. An alternative to the external radiation source is to provide a radioisotope within the layered device structure as illustrated in the FIG. 2a which shows a radiation powered device comprising: a first electrode 10; a second electrode 12; a semiconductor 14 disposed between the first and second electrodes; and a radioactive source 20 configured to generate a flow of electrons through the semiconductor between the first and second electrodes, wherein the semiconductor comprises diamond material. The radioactive source 20 can be embedded within the diamond material rather than provided as a separate layer of material (see for examples the pictorial representations of the semiconductor shown in FIGS. 10 and 11). It has been found that if the radioactive source is embedded within the diamond material then losses associated with surface interfaces, air gaps, and limited penetration into the diamond structure are reduced. This provides much higher energy conversion efficiency than previous devices. Furthermore, the dense atomic packing in the diamond structure means that radiation does not effectively escape from the diamond material thus reducing radiation leakage. The embedded radioactive source may be, for example, tritium, 14C, 10Be, or Phosphorus-33; or tritium, 14C, or 10Be, more preferably tritium and/or 14C. While it is possible to encapsulate relatively small radioisotopes such as tritium, 14C, 10Be and phosphorus-33 into the diamond lattice, the present inventors have found that it is difficult to incorporate larger atoms into the high atomic number density diamond lattice without causing significant damage to the diamond crystal structure which negatively impacts electronic charge transporting performance. The present inventors have found that embedding 14C, 10Be and/or tritium into the diamond material is particularly advantageous in terms of providing a diamond material in which a radioactive source is embedded whilst also maintaining the diamond crystal structure. FIG. 2b shows a radiation powered device similar to the device described in FIG. 2a, although the device of FIG. 2b has an alternative arrangement. The device of FIG. 2b comprises a semiconductor 14 comprising a diamond material in which a radioactive source is embedded. Both of the devices shown in FIGS. 2a and 2b comprise a semiconductor having first and second opposing faces. In the device shown in FIG. 2a, the first electrode 10 contacts a first face of the semiconductor and the second electrode 12 contacts the second face of the semiconductor. In the device shown in FIG. 2b, both the first and second electrodes 10, 12 contact a first face of the semiconductor. Both arrangements shown in FIGS. 2a and 2b allow electrons to flow between the first and second electrodes via the semiconductor. Furthermore, encapsulation of the radioisotope material within the hard, chemically inert diamond structure reduces the possibility of damage and leakage of radioactive material from the device thus improving device stability and performance and increasing the robustness and chemical inertness of the device thus reducing problems associated with toxicity and/or biocompatibility. An additional advantage of using tritium or 14C is that both hydrogen and carbon are conventionally used in a diamond synthesis process and readily incorporate into the diamond lattice during synthesis. Accordingly, introducing tritium (a hydrogen isotope) and/or 14C into the diamond synthesis process will not unduly affect the diamond synthesis chemistry. Yet a further advantage of using tritium or 14C is that they are both bi-products of nuclear power plants. Using this approach, radioactive bi-products of nuclear power plants can be encapsulated into diamond material to render them safe and the resultant diamond material utilized to construct radioisotope batteries thus converting problematic waste materials into a useful power source. The diamond material optionally has a layered structure with at least one layer comprising the radioactive source and at least one layer which does not comprise the radioactive source. The layered structure may have a plurality of layers comprising the radioactive source and a plurality of layers which do not comprise the radioactive source. Such a layered structure enables the provision of thin layers of diamond material comprising a radioactive source separated by diamond layers which do not have the radioactive source. This can be advantageous as radiation does not penetrate far through the diamond lattice and so a layered structure can provide alternating layers of charge generating material and charge propagation and/or charge multiplication material. For example, the radioactive source can be provided in a layer or layers of diamond having a thickness in a range 50 nanometres to 150 micrometres, optionally 500 nanometres to 50 micrometres. The layer(s) of diamond material comprising the radioactive source may be a layer(s) of diamond material in which atoms of a radioisotope of the radioactive source are either substitutionally or interstitially integrated into the diamond material (that is substitutionally or interstitially integrated into the crystal lattice of the diamond material, to form a constituent part of the diamond material). In certain embodiments, the diamond material comprises a plurality of regions, where the plurality of regions are isotopic regions within the diamond material (i.e. isotopic regions within the continuous crystal lattice of the diamond material). In certain embodiments, the diamond material comprises a plurality of layers, where the plurality of layers are isotopic layers within the diamond material (i.e. isotopic layers within the continuous crystal lattice of the diamond material). It will be appreciated that the natural abundance of carbon isotopes is approximately 98.9% 12C, 1.1%′13C and a trace amount of 14C (approximately 1 part per trillion). When we talk about 14C configured to generate a flow of electrons through diamond material, the 14C concentration must be significantly higher than the 1 part per trillion trace amount occurring naturally. For example, the radioactive source can be provided within the diamond material at an atom concentration of at least 0.1%, 1%, 5%, 10%, 20%, 50%, 75%, 85%, 95%, 99%, or 99.9%. Since beta region from 14C does not penetrate large distances within a diamond lattice, a relatively thin layer of material can be provided. This can also potentially reduce production costs. However, sufficient 14C must be provided to generate the required electrical power output. FIG. 3 shows another radiation powered device configuration which comprises: a first electrode 10; a second electrode 12; and a semiconductor 14 disposed between the first and second electrodes, wherein the semiconductor comprises diamond material which generates a flow of electrons between the first and second electrodes when exposed to radiation, and wherein the diamond material includes a 13C diamond region 16 which comprises isotopically purified diamond material having an increased 13C content compared to natural isotopic abundance. An external radiation source 18, such as a gamma-radiation source, is shown in the configuration of FIG. 3 with the device placed in a radiation field such that electron-hole pairs are generated in the diamond material. The device may be placed adjacent the radiation source 18 or configured to surround the radiation source, e.g. by providing a cylindrical device structure within which the radiation source is disposed. An alternative to the external radiation source is to provide a radioisotope within the layered device structure as illustrated in FIG. 4 which comprises: a first electrode 10; a second electrode 12; a semiconductor 14 disposed between the first and second electrodes; a radioactive source configured to generate a flow of electrons through the semiconductor between the first and second electrodes, wherein the semiconductor 14 comprises diamond material and includes a region 20 in which the radioactive source is embedded and a 13C diamond region 16 which comprises isotopically purified diamond material having an increased 13C content compared to natural isotopic abundance. Surprisingly, it has been found that the provision of a diamond material which has at least one region which is isotopically purified to increase its 13C leads to a significant increase in output voltage when compared to a corresponding device which does not contain such a 13C diamond layer. It is known that isotopic substitution of 12C by 13C increases the band-gap energy in diamond [see, for example, H Watanabe, “Isotope composition dependence of the band-gap energy in diamond” Phys. Rev. B, 88, 2013]. Providing a larger band gap region of diamond material has been found to significantly increase output voltage in a radiation powered device and can function as an electron multiplication region or layer. For example, a diamond beta-voltaic device having an output voltage of 1.4 V has been found to have an increased output voltage of 2.1 V with the introduction of a thin 13C diamond termination layer. By way of illustration, for a single diode device with an effective volume of 1.47×10−6 m3 (15 μm thick×25 mm diameter) containing 0.343 g of C-14 radiating half of its output into the diode, the open circuit voltage is approximately 2.0 V and the short circuit current is estimated to be 10 μA in a diamond diode using an integral 49 keV radioisotope beta source. When the diamond device structure is repeated many times in a single device then this imbues the capability for the device to act as an efficient gamma-voltaic when exposed to a high intensity gamma radiation fields. While not being bound by theory a betavoltaic cell voltage depends on the diode leakage current which in turn depends on the Schottky barrier height and its homogeneity. The choice of high purity C-13 influences the Schottky barrier height due to the band gap of C-13 being 17 meV larger than C-12, which also influences the magnitude of the diode leakage current. The 13C diamond region can be provided in the form of a layer having a thickness in a range 2 nm to 2 mm, optionally 200 nanometres to 2 millimetres. Isotopically purified carbon source material is relatively expensive and thus fabricating a thick layer of isotopically purified 13C is not desirable. In this regard, it has been found that a thin layer of such isotopically purified diamond material can provide a significant increase in output voltage without duly increasing expense. The 13C diamond region may can have an atomic concentration of 13C of at least 1.1%, 5%, 10%, 20%, 50%, 75%, 85%, 95%, 99%, or 99.9%. The 13C diamond region may can have an atomic concentration of 13C of at least 1.5%, 2%, 3%, 4%, 5%, 10%, 20%, 50%, 75%, 85%, 95%, 99%, or 99.9%. Sufficient 13C should be incorporated into the diamond lattice in order to increase the diamond band gap to achieve the desired increase in output voltage. However, increasing isotopic purification also increases expense in requiring a higher degree of isotopic separation of the carbon source material utilized in the diamond synthesis process. The diamond material can also include a 12C diamond layer (or region) which comprises a layer (or region) of diamond material which has a natural abundance of carbon isotopes to, for example, within 1.1% (or at least has a 13C content lower that the 13C diamond region and/or a 14C content lower than the 14C diamond region). The 12C diamond layer (or region), if present, may comprises a layer (or region) of diamond material which has a substantially natural abundance of carbon, for example, within 1.1% of natural abundance of each carbon isotope. For example, the diamond material can include a tri-layer structure comprising a layer of 14C containing diamond, a layer of 12C diamond, and a layer of 13C diamond. Alternatively, a more simple bi-layer device structure may be provided comprising diamond material including a layer in which a radioisotope is embedded and a layer of conventional 12C diamond. As discussed above, the layers (or regions) of the diamond material maybe isotopic layers (or regions) within the diamond material (i.e. isotopic layers within the continuous crystal lattice of the diamond material). The 12C diamond layer can have a thickness in a range 200 nanometres to 2 millimetres, optionally 1 micrometre to 10 micrometres. The specific layer thickness will depend to some extent on the device configuration and application. For example, in betavoltaic configurations the diamond layer can be thin as the beta radiation does not penetrate through large thicknesses of diamond material. Alternatively, for gammavoltaic configurations the diamond layer may advantageously be thick as gamma radiation will penetrate through larger distances and a large volume of diamond material will lead to more electron-hole pairs being generated and a larger charge output. For example, the diamond material may have a thickness in a range 20 micrometres to 25 millimetres, optionally 20 micrometres to 20 millimetres, optionally 50 micrometres to 1500 micrometres. The diamond material preferably has a single substitutional nitrogen concentration of no more than 5 ppm, 1 ppm, 500 ppb, 300 ppb or 100 ppb in at least one of the aforementioned regions thereof. Impurities, of which nitrogen is the most important, reduce charge carrier performance within the diamond lattice as is known, for example, from WO0196633. As such, the diamond material can be engineered to increase charge generation and also charge mobility and lifetime. The electrodes may be formed of materials to generate a bias for flow of electrons from the first electrode to the second electrode via a Schottky effect. The first electrode can form an ohmic contact. Such an electrode may comprise a layer of carbide forming material and a noble metal layer. The second electrode can form a Schottky contact. Such an electrode can be formed of a low atomic number metal or alloy. For example, a metal or metal alloy formed of a metal or metals having an atomic number z of no more than 20, e.g. Al or LiAl. In certain embodiments, the second electrode can form a Schottky contact and may be formed of a metal or metal alloy formed of a metal or metals having an atomic number z of 40 or less, e.g. Zr, Al or LiAl. It should be noted that the choice of metal used to construct the Schottky contact can be a significant factor impact device performance. Furthermore, the quality of the interface between the metal and diamond can also be important. For example, one reason for a low barrier height is the lack of homogeneity of a Schottky metal interface with an oxygen-terminated diamond surface. While certain metals can be selected based on their ability to bond to diamond material and provide a Schottky biasing effect, it is also envisaged that electrically conductive boron doped diamond could also be used either as one or both of the first and second electrodes or as a layer within the diamond layer structure. The electronic bias may also be provided or enhanced by configuring the radiation powered device to provide a thermal bias between the first and second electrodes. While the previous configurations have been described in relation to device structures which comprise a layer of 13C diamond which can function as an electron multiplication layer and increase output voltage, it is also envisaged that certain devices may comprise one or more of the features as described herein without such a region of 13C diamond. For example, according to one configuration, a radiation device is provided comprising: a first electrode; a second electrode; a semiconductor disposed between the first and second electrodes; and a radioactive source configured to generate a flow of electrons through the semiconductor between the first and second electrodes; wherein the semiconductor comprises diamond material; and wherein the radioactive source is embedded within the diamond material. As previously described, the radiation source may be, for example, tritium, 14C, 10Be or Phosphorus-33. Even if a region of 13C diamond is not provided, encapsulating the radioactive source still has benefits in terms of reducing losses associated with surface interfaces, air gaps, and limited penetration into the diamond structure and reducing radiation leakage and the possibility of damage and leakage of radioactive material from the device thus improving device stability and performance and increasing the robustness and chemical inertness of the device thus reducing problems associated with toxicity and/or biocompatibility. That said, it is advantageous to combine the encapsulation configuration with the performance enhancing 13C diamond layer so as to provide a diamond material which has a region in which a radioactive source is embedded and a region of 13C diamond which functions as an electron multiplication layer and increases output voltage. According to yet another configuration, a radiation powered device is provided which comprises: a first electrode; a second electrode; a semiconductor disposed between the first and second electrodes; and a radioactive source configured to generate a flow of electrons through the semiconductor between the first and second electrodes; wherein the semiconductor comprises diamond material; and wherein the radioactive source is formed of 14C. In this configuration it has been noted that several advantageous features can also be achieved by replacing the external radioactive source with a lower toxicity radioisotope in the form of 14C such that both the radioactive source and the semiconductor are formed of carbon material even if the 14C is not embedded within the diamond lattice, e.g. provided as a layer of 14C containing graphite adjacent the diamond material. Such an “all carbon” radiation source and semiconductor structure is preferable to one which, for example, uses a separate heavy metal radioisotope. However, most preferably, the radioactive source is both embedded within the diamond material forming at least a part of the diamond lattice structure and most preferably is still used in combination with a 13C diamond layer or region for charge multiplication and increased voltage output. It is possible to provide multiple device structures by providing multiple layered structures in a single layer stack. An example of such a configuration is shown in FIG. 5 which includes two beta-voltaic structures in a single layer stack and sharing a common central electrode. The configuration comprises: a central electrode 10; end electrodes 12; carbon-14 diamond layers 20; carbon-12 diamond layers 14; and carbon-13 diamond layers 16. The structure thus provides two beta-voltaic devices comprising a layer structure: electrode/14C diamond/12C diamond/13C diamond/electrode. Multi-layered stacked device structures and/or use of thicker layers of diamond material are particularly useful in conjunction with external gamma-radiation sources as gamma radiation can penetrate through the thicker diamond layers and produce an increase in charge generation. FIG. 6 shows another configuration of a radiation powered device including a super capacitor layered structure and a beta-voltaic layered structure. The layer structure is similar to that shown in FIG. 5 with the difference that one of the two beta-voltaic devices has been modified by reversing the 13C and 12C layers such that one of the devices is transformed into a super capacitor. The configuration comprises: a central electrode 10; end electrodes 12; carbon-14 diamond layers 20; carbon-12 diamond layers 14; and carbon-13 diamond layers 16. The structure thus provides a beta-voltaic device 24 comprising a layer structure: electrode/14C diamond/12C diamond/13C diamond/electrode. The structure further comprises a super capacitor comprising the layer structure: electrode/14C diamond/13C diamond/12C diamond/electrode. FIG. 7 shows a thermionic diamond energy converter configuration. The device configuration is similar to that shown in FIG. 4 and comprises: a first electrode 10; a 14C diamond layer 20; a 12C diamond layer 14; a 13C diamond layer 16; and a second electrode 12. An electric load 26 is also shown coupled between the first and second electrodes with current flow as illustrated by the arrows to and from the electric load 26. In this configuration the first electrode 10 is heated 22 and the second electrode 12 is cooled 24. As such, a hot cathode 12 and a cooled collector 12 are provided to provide a thermal bias between the cathode 12 and collector 12. In one configuration heating of the cathode is provided by sunlight in order to provide a solar thermionic diamond energy converter. FIG. 8 shows a thermionic beta Schottky emitter configuration. Again, the device configuration is similar to that shown in FIG. 4 and comprises: a first electrode 10; a 14C diamond layer 20; a 12C diamond layer 14; a 13C diamond layer 16; and a second electrode 12. The difference here is that through holes are provided in the second electrode such that hot electrons 28 can be emitted into a vacuum gap or chamber. FIG. 9 shows a diamond Schottky diode beta-voltaic configuration comprising a capacitor for storing up charge. Again, the device configuration is similar to that shown in FIG. 4 and comprises: a first electrode 10; a 14C diamond layer 20; a 12C diamond layer 14; a 13C diamond layer 16; and a second electrode 12. A capacitor 30 is provided to collect a trickle charge from the layered structure such that a useful quantity of charge can be built up for subsequent use. In general terms, a device structure can be provided which comprises: a first electrode; a second electrode; and a semiconductor disposed between the first and second electrodes, wherein the semiconductor comprises diamond material which generates a flow of electrons between the first and second electrodes when exposed to radiation without the application of a biasing voltage, and wherein the radiation powered device further comprises a charge storage device coupled to the first and second electrodes for storing charge flowing out of the diamond material. In this regard, it has been found that diamond based configurations can provide charge flow when exposed to radiation without a biasing voltage. However, the charge flow is still relatively small for certain applications and thus it is advantageous to provide a charge storage device, such as a capacitor, coupled to the first and second electrodes for storing charge flowing out of the diamond material. Charge can thus be accumulated and then utilized. Charge flow can also be enhanced for charging up the charge storage device. Examples include use of a Schottky biasing effect via an electrode/diamond interface and/or thermal biasing by heating the first electrode and/or cooling the second electrode. The radiation source may be external to the device and in use the device is placed in a radiation field such as a gamma irradiation field. Alternatively, the radiation source may be incorporated into the device, for example in a manner as previously described. While the device structures illustrated in the figures are shown in a planar layered geometry, it is also envisaged that non-planar layered structures may be provided for certain applications. For example, for radioactive waste stored in cylinders it is envisaged that the device structures as described herein can be fabricated in a cylindrical configuration such that they surround the radioactive cylinders. It will also be understood that all the preceding configurations can be combined in a variety of different ways depending on application requirements. Power Sources FIG. 10 provides a pictorial representation of an electrical power source 100 as described herein. The power source 100 is a radioisotope electrical power source comprising a semiconductor 14 comprising a diamond material and a radioactive source embedded within the diamond material. In the configuration shown in FIG. 10, the radioactive source is 14C which is substitutionally integrated into the diamond material, in this example a boron-doped diamond material. The electrical power source 100 provides electrical power as the radioactive source 14C decays via beta emission (e−). FIG. 11 provides a pictorial representation of an electrical power source 100 as described herein. The power source 100 is a radioisotope electrical power source comprising a semiconductor 14 comprising a diamond material and a radioactive source embedded within the diamond material. In the configuration shown in FIG. 10, the radioactive source is 14C which is substitutionally integrated into the diamond material, in this example a boron-doped diamond material. The electrical power source 100 provides electrical power as the radioactive source 14C decays via beta emission (e−). FIG. 12 is a diagram of an electrical power source 100 as described herein. The power source 100 is a radioisotope electrical power source comprising a semiconductor 14 comprising a diamond material and a radioactive source embedded within the diamond material. The electrical power source 100 shown in FIG. 12 also comprises a Schottky metal layer 12 to provide a Schottky contact. Methods of Manufacture A chemical vapour deposition (CVD) technique can be used to fabricate the diamond material for incorporation into devices according to the various configurations described herein. CVD diamond synthesis is well known in the art. An example is described in WO0196633 for fabricating high purity electronic grade single crystal CVD diamond material. Such high purity synthetic diamond material is particularly useful for the devices as described herein as it has better charge mobility and charge lifetime characteristics when compared with lower purity diamond material in which impurities act as charge traps. However, it is also envisaged that other well-known diamond synthesis techniques can be used including, for example, those to produce nitrogen doped single crystal diamond materials, boron doped single crystal CVD diamond materials, and polycrystalline diamond materials. The fabrication techniques are modified compared with standard diamond synthesis processes by utilizing isotopically purified starting materials which are incorporated into the growing diamond lattice. For example, methane or an alternative carbon containing gas can be provided in C-12, C-13, and/or C-14 form to provide a continuous single crystal CVD diamond lattice with a layered structure with varying carbon isotope concentration. Fabrication of isotopically purified layers of single crystal CVD diamond material is known in the art. What is different here is the finding that specific combinations of C-12, C-13, and C-14 diamond layers can be used to provide improved radiation powered devices with, for example, increased output voltage. A diamond material embedded with a radioactive source may be provided by synthetically producing a diamond material in which atoms of a radioisotope are integrated (e.g. substitutionally or interstitially) during formation of the synthetic diamond material, for example by chemical vapour deposition (CVD). In certain embodiments a diamond material may be synthetically obtained by: providing a carbon containing gas comprising carbon atoms and a radioisotope source gas comprising radioisotope source atoms; and depositing carbon atoms and radioisotope source atoms by chemical vapour deposition to form a diamond material. The carbon containing gas may comprise 12C, 13C, and/or 13C. In certain embodiments the carbon containing gas comprises 12C and/or 13C. In certain embodiments the carbon containing gas comprises 12C. The radioisotope source gas may comprise deuterium, tritium, 13C, 14C, and/or 33P. In certain embodiments, the radioisotope source gas is a radioisotope containing gas. The radioisotope containing gas may containing may contain tritium, 14C, and/or 33P. The radioisotope containing gas may containing may contain tritium and/or 14C. The radioisotope containing gas may containing may contain 14C. The radioisotope source gas may comprise atoms of a radioisotope atoms (i.e. a radioisotope containing gas) or atoms of a non-radioactive isotope that may be converted to a radioisotope by neutron irradiation. For example, the radioisotope source gas may comprise tritium, 14C, and/or 33P as radioisotope atoms; and/or 13C and/or deuterium as atoms which may be converted to a radioisotope on neutron irradiation (deuterium can be converted to tritium using neutron irradiation and 13C can be converted to 10Be using neutron irradiation). In certain embodiments the carbon containing gas comprises 12C and/or 13C, and the radioisotope source gas comprises 14C, deuterium and/or tritium. In certain embodiments the carbon containing gas comprises 12C and/or 13C, and the radioisotope source gas comprises 14C and/or tritium. In certain embodiments the carbon containing gas comprises 12C, and the radioisotope source gas comprises 14C and/or tritium. In certain embodiments the carbon containing gas comprises 12C, and the radioisotope source gas comprises 13C and/or deuterium. In certain embodiments the process of synthetically producing a diamond material further comprises neutron irradiating the diamond material produced by chemical vapour deposition to produce a diamond material embedded with a radioactive source. For example, the process may comprises providing a carbon containing gas comprising 12C and a radioisotope source gas comprising 13C and/or deuterium; depositing carbon atoms and radioisotope source atoms by chemical vapour deposition to form a diamond material; and neutron irradiating the diamond material deposited by chemical vapour deposition to form a diamond material embedded with a radioactive source, where the radioactive source is 10Be, 14C and/or tritium. Electrode contacts can be provided on the diamond material using a physical vapour deposition (PVD) process to permit connection to an electrical circuit. Again, metallization techniques for providing electrical contacts to diamond material are known in the art. Certain embodiments of the present invention select particular metals for the electrodes based on their ability to bias charge flow through diamond material when exposed to radiation without application of a biasing voltage. An advantage of using tritium and/or 14C as the radioisotope is that they are both bi-products of nuclear power plants. Tritium is formed in coolant water in nuclear power plants and water containing tritium is normally released from nuclear plants under controlled, monitored conditions. This tritium containing water can be electrolytically decomposed into oxygen and hydrogen gas including tritium. The tritium containing hydrogen gas can then be used in a hydrogen plasma chemical vapour deposition (CVD) diamond synthesis process. A hydrogen plasma CVD diamond synthesis process tends to incorporate a significant amount of hydrogen within the diamond lattice and thus using this approach a significant amount of tritium can be incorporated into the diamond lattice. In some examples, a hydrogen plasma for CVD diamond synthesis may comprise deuterium. Deuterium incorporated into the diamond lattice may be converted to tritium by neutron irradiation. 14C is also a bi-products of nuclear power plants and has been found to form as a surface layer on neutron irradiated graphite rods or blocks used to moderate the nuclear reaction. The 14C can be extracted from the blocks and then converted to methane via, for example, reaction with hydrogen or a catalysed reaction with water vapour. Methane is conventionally used as the carbon source in a hydrogen plasma CVD diamond synthesis process. As such, 14C can be used as the carbon source in such a hydrogen plasma CVD diamond synthesis process resulting in a diamond lattice incorporating 14C. Alternatively, solid 14C containing graphite can be placed in a CVD reactor in a location such that the plasma etches the graphite which is subsequently incorporated into the growing diamond lattice. Alternatively still, solid graphite material comprising 14C can be used in a high pressure high temperature diamond synthesis process which conventionally converts graphite to diamond under high pressure and temperature using a metal catalyst composition. Using the aforementioned approaches, radioactive bi-products of nuclear power plants can be encapsulated into diamond material to render them safe and the resultant diamond material utilized, for example, to construct radioisotope batteries thus converting problematic waste materials into a useful power source. An alternative approach to incorporate 14C into a diamond lattice is to nitrogen dope the diamond material during synthesis and then neutron irradiate the nitrogen doped diamond material to convert 14N into 14C. For example, a nitrogen doped C-13 layer of diamond can be grown and then irradiated to convert 14N into 14C. The advantage of using a C-13 layer of diamond in this approach is that a small proportion of C-13 is also converted into C-14. Alternatively, it may be sufficient to nitrogen dope a natural isotopic abundance diamond material during synthesis and then neutron irradiate the nitrogen doped diamond material to convert 14N into 14C. Alternatively still, beryllium-10 can be incorporated into a diamond lattice by introducing a 13C containing species into the growth plasma during CVD diamond synthesis and neutron irradiating the diamond material containing 13C to form 10Be. Alternatively still, it is also known that phosphorus can be incorporated into a diamond lattice by introducing a phosphorus containing species into the growth plasma during CVD diamond synthesis or by subsequent ion implantation. However, it should be noted that these doping/converting/implanting approaches will not achieve the same levels of isotopic purity as using isotopically purified starting materials. Applications The technology as described herein has been developed to use nuclear waste to generate electricity in a nuclear-powered batteries. The inventors have grown synthetic diamond samples that, when placed in a radioactive field, for example a gamma radiation field, are able to generate a useful electrical current. Furthermore, synthetic diamond samples have been grown which incorporate their own power source in the form of, for example, beta emitting 14C in the diamond lattice. These developments have the potential to solve some of the problems of nuclear waste, clean electricity generation, and battery life. Unlike the majority of electricity-generation technologies, which use energy to move a magnet through a coil of wire to generate a current, the synthetic diamond samples are able to produce a charge simply by being placed in close proximity to a radioactive source and/or incorporating their own radioisotope source. There are no moving parts involved, no emissions generated, and no maintenance required, just direct electricity generation. By encapsulating radioactive material inside diamonds, a long-term problem of nuclear waste has been turned into a nuclear-powered battery and a long-term supply of clean energy. Initial research work demonstrated a prototype diamond battery using Nickel-63 as the radiation source. However, significantly improved efficiency has been achieved by utilising carbon-14, a radioactive version of carbon, which is generated in graphite blocks used to moderate the reaction in nuclear power plants. Research has shown that the radioactive carbon-14 is concentrated at the surface of these blocks, making it possible to process it to remove the majority of the radioactive material. The extracted carbon-14 is then incorporated into diamond material to produce a nuclear-powered battery. The UK alone currently holds almost 95,000 tonnes of graphite blocks at the time of writing and by extracting carbon-14 from these blocks, their radioactivity decreases, reducing the cost and challenge of safely storing this nuclear waste. In accordance with certain configurations, carbon-14 is chosen as a source material because it emits a short-range radiation, which is quickly absorbed by a solid material. This make it dangerous to ingest or touch with naked skin, but when safely held within diamond material no short-range radiation can escape. In fact, since diamond is the hardest substance known to man it is the ideal material to provide safe storage of radioactive waste material. Despite their low-power, relative to current battery technologies, the life-time of the diamond batteries described herein could revolutionise the powering of devices over long timescales. The actual amount of carbon-14 in each battery will depend on application requirements. One battery containing 1 g of carbon-14, would deliver 15 Joules per day. This is less than a standard AA battery. However, standard alkaline AA batteries are designed for short timeframe discharge: one battery weighing about 20 g has an energy storage rating of 700 J/g. If operated continuously, this would run out in 24 hours. Using carbon-14 the battery would take 5,730 years to reach 50 percent power, which is about as long as human civilization has existed. It is envisaged that these batteries will be used in situations where it is not feasible to charge or replace conventional batteries. Applications include low-power electrical devices where long life of the energy source is needed such as pacemakers, satellites, high-altitude drones, spacecraft, seabed communications, monitoring devices etc. Another application is in systems for monitoring radioactive waste using self-powered devices. In this regard, a device as described herein could be adapted to function as both a battery and a detector by switching between non-voltage-biased and voltage-biased modes of operation. Self-powered sensor devices are envisaged for monitoring of radiation, humidity, temperature and gases, e.g. in high radiation environments. In essence, the technology is designed for applications where low power is required constantly to keep devices on/retain memory etc. and where changing a battery is not possible/inherently expensive due to the difficult location of the device. The markets include, but are not limited to: the civil nuclear sector; the ‘internet of things’; space exploration; vehicle tyre pressure monitoring; and certain implanted medical devices. It is also envisaged that when using diamond material in electronic applications, the diamond material can be used both as a power source and a heat spreader or heat sink. Yet another application is in downhole drilling. Diamond is already used as cutters on drill bits for improved drilling performance. Sensors are also provided on drill bits or drill strings for sensing numerous parameters for optimizing drilling performance. The downhole physical and chemical environment during drilling is challenging. As such, the provision of robust, radiation powered diamond devices in such applications would be advantageous in some respects over more standard power sources. It is also envisaged that beyond the radiation powered devices as described herein, other diamond products can be provided. That is, in general terms a method of disposing of radioactive waste is provided which comprises encapsulating the radioactive waste in diamond material. The diamond material can then be utilized in a range of applications as is known in the art. While this invention has been described in relation to certain embodiments it will be appreciated that various alternative embodiments can be provided without departing from the scope of the invention which is defined by the appending claims. Unless otherwise stated, the features of any dependent claim can be combined with the features of any of the other dependent claims, and any other independent claim. Aspects of the present invention may be described in the following numbered statements: 1. A radiation powered device comprising: a first electrode; a second electrode; a semiconductor disposed between the first and second electrodes; and a radioactive source configured to generate a flow of electrons through the semiconductor between the first and second electrodes; wherein the semiconductor comprises diamond material; and wherein the radioactive source is embedded within the diamond material. 2. A radiation powered device according to statement 1, wherein the radioactive source embedded within the diamond material is formed of one or more of tritium, 14C, and phosphorus-33. 3. A radiation powered device according to statement 2, wherein the radioactive source is 14C and/or tritium. 4. A radiation powered device according to statement 3, wherein the radioactive source is 14C 5. A radiation powered device according to any preceding statement, wherein the diamond material has a layered structure with at least one layer comprising the radioactive source and at least one layer which does not comprise the radioactive source. 6. A radiation powered device according to statement 5, wherein the layered structure has a plurality of layers comprising the radioactive source and a plurality of layers which do not comprise the radioactive source. 7. A radiation powered device according to any preceding statement, wherein the radioactive source is provided in a layer of diamond having a thickness in a range 50 nanometres to 150 micrometres, optionally 500 nanometres to 50 micrometres. 8. A radiation powered device according to any preceding statement, wherein the radioactive source is provided within the diamond material at an atom concentration of at least 0.1%, 1%, 5%, 10%, 20%, 50%, 75%, 85%, 95%, 99%, or 99.9%. 9. A radiation powered device according to any preceding statement, wherein the diamond material includes a 13C diamond region which comprises isotopically purified diamond material having an increased 13C content compared to natural isotopic abundance. 10. A radiation powered device according to statement 9, wherein the 13C diamond region is in the form of a layer having a thickness in a range 200 nanometres to 2 millimetres. 11. A radiation powered device according to statement 9 or 10, wherein the 13C diamond region has an atomic concentration of 13C of at least 0.1%, 1%, 5%, 10%, 20%, 50%, 75%, 85%, 95%, 99%, or 99.9%. 12. A radiation powered device according to any preceding statement, wherein the diamond material includes a 12C diamond layer which comprises a layer of diamond material which has a natural abundance of carbon isotopes to within 1.1%. 13. A radiation powered device according to statement 12, wherein the 12C diamond layer has a thickness in a range 200 nanometres to 2 millimetres, optionally 1 micrometre to 10 micrometres. 14. A radiation powered device according to any preceding statement, wherein the diamond material includes a tri-layer structure comprising a layer of 14C containing diamond, a layer of 12C diamond, and a layer of 13C diamond. 15. A radiation powered device according to any preceding statement, wherein the diamond material has a single substitutional nitrogen concentration of no more than 5 ppm, 1 ppm, 500 ppb, 300 ppb or 100 ppb in at least one region thereof. 16. A radiation powered device according to any preceding statement, wherein the first electrode forms an ohmic contact. 17. A radiation powered device according to statement 16, wherein the first electrode comprises a layer of carbide forming material and a noble metal layer. 18. A radiation powered device according to any preceding statement, wherein the second electrode forms a Schottky contact. 19. A radiation powered device according to statement 18, wherein the second electrode is formed of a metal or metal alloy, the metal or metal alloy being formed of a metal or metals having an atomic number z of no more than 20. 20. A radiation powered device according to statement 19, wherein the second electrode is formed of Al or LiAl. 21. A radiation powered device according to any preceding statement, wherein the diamond material has a thickness in a range 20 micrometres to 25 millimetres, optionally 20 micrometres to 20 millimetres, optionally 50 micrometres to 1500 micrometres. 22. A radiation powered device according to any preceding statement, wherein the radiation powered device is configured to provide a thermal bias between the first and second electrodes. 23. A radiation powered device according to any preceding statement, further comprising a charge storage device coupled to the first and second electrodes for storing charge flowing out of the diamond material. 24. A radiation powered device comprising: a first electrode; a second electrode; and a semiconductor disposed between the first and second electrodes, wherein the semiconductor comprises diamond material which generates a flow of electrons between the first and second electrodes when exposed to radiation, and wherein the diamond material includes a 13C diamond region which comprises isotopically purified diamond material having an increased 13C content compared to natural isotopic abundance. 25. A radiation powered device comprising: a first electrode; a second electrode; a semiconductor disposed between the first and second electrodes; and a radioactive source configured to generate a flow of electrons through the semiconductor between the first and second electrodes; wherein the semiconductor comprises diamond material; and wherein the radioactive source is formed of 14C. 26. A radiation powered device comprising: a first electrode; a second electrode; and a semiconductor disposed between the first and second electrodes, wherein the semiconductor comprises diamond material which generates a flow of electrons between the first and second electrodes when exposed to radiation without the application of a biasing voltage, and wherein the radiation powered device further comprises a charge storage device coupled to the first and second electrodes for storing charge flowing out of the diamond material. 27. A method of disposing of radioactive waste comprising encapsulating the radioactive waste in diamond material. 28. A method according to statement 27, wherein the radioactive waste is 14C or tritium.
039490270	abstract	Process for manufacturing improved nuclear fuel pellets, including compacting ceramic powder in the Compaction chamber of a pelletizing machine with only the lower punch moving on compaction, wherein the walls of the compaction chamber are widened on at least part of their height in the direction of a diameter increase towards the die-bearing table.
	summary
	summary
044951418	abstract	A tagging gas releasing element which is contained in a nuclear fuel rod to release a tagging gas for detecting a failed fuel. The element comprises an inorganic solid material holding the tagging gas therein. The tagging gas is composed of a rare gas, and is held in the inorganic solid material in an injected or adsorbed state.
059075880	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a reactor pressure vessel (RPV) 1 which is disposed in a reactor cavity 3. The reactor cavity 3 in this case is formed by a concrete structure 5. Insulation 7, which encloses the RPV 1, is disposed between a wall of the reactor cavity 3 and the RPV. The RPV 1 contains a non-illustrated water-cooled reactor core. An upper part of the reactor cavity 3 is cylindrically constructed and a lower part thereof is constructed with a vaulted shape, especially frustoconically. In this case, the reactor cavity 3 has a crucible-shaped structure. The crucible shape is formed by a base unit 9. An intermediate space remaining between the RPV 1 and the base unit 9, which serves as a prechamber 11 for collecting core melt, is equipped with a packing unit 13 which serves to displace water out of the prechamber 11. This prevents a steam explosion when hot core melt escapes. The lowest point of the prechamber 11 is closed off by a barrier wall or dividing wall 15. The barrier wall or dividing wall 15 is constructed in such a way that it is destroyed by melting by the core melt after a predetermined time, as a result of which a path through a channel 17 into a spreading chamber 19 is opened. The spreading chamber 19 in this case is disposed laterally next to the RPV 1. The spreading chamber 19 in this case serves substantially as a cooling space and final accumulation space for the core melt. Further details regarding the function of the prechamber 11, of the channel 17 and of the spreading chamber 19, as well as their dimensioning, are disclosed by and can be found in German Published, Non-Prosecuted Patent Application DE 43 19 094 A1, corresponding to International Publication WO 94/29876 and U.S. application Ser. No. 08/569,676, filed Dec. 8, 1995, now U.S. Pat. No. 5,867,548, as mentioned above. The configuration of the base unit 9 and, where appropriate, of bottom regions of the spreading chamber 19 and the channel 17 are essential for the concept of the present invention. The base unit 9, which at least forms a bottom region of the prechamber 11 (optionally, the base unit 9 can also form the bottom region of the channel 17) is made of a material having high thermal conductivity. The base unit 9 in this case is annularly surrounded by the concrete structure 5. Preferably, the base unit 9 is made of a metal, as a result of which the high thermal conductivity is ensured. However, other materials are also conceivable, for example a high-density ceramic. The base unit 9 may be formed by non-illustrated individual base elements, for example elements with the shape of a sector of a circle or a sector of a circular annulus, which may also be disposed in slices or layers. This makes them easy to transport. The prechamber 11 then has the function of initially collecting the escaping core melt. To this end, the dividing or barrier wall 15 is initially closed. The dividing or barrier wall 15 must therefore be dimensioned in such a way that it remains functional for a time of approximately 10 to 30 minutes. The packing unit 13 is destroyed by the emergence of the core melt, so that the core melt can spread out in the prechamber 11 and can accumulate. The new function of the base unit 9 then sets in. By virtue of its high thermal conductivity, the core melt lying on top of the base unit 9 is strongly cooled, so that the latter forms a crust. An autogenous crucible, so to speak, is thereby formed, in which the core melt is held. In addition, an insulating effect for the core melt is also provided. The cooling is dimensioned in this case in such a way that, by virtue of the insulating effect of the crust, a sufficiently large volume of core melt accumulates in the prechamber 11. The purpose of this structure is to ensure that, when the barrier wall or dividing wall 15 is destroyed, all of the core melt flows steadily at once out of the prechamber 11 into the spreading chamber 19. In this case it is advantageous if, as far as possible, the entire core equipment has melted and is inside the prechamber 11 or inside the reactor cavity 3. The autogenous crucible formed by the core melt additionally prevents penetration or destruction of the base unit 9 and its structure. It is optionally possible to provide a special cooling device in or on the barrier wall or dividing wall 15, in order to more accurately determine the time of destruction of this wall. The timing of the entire process can be better controlled in this way. Additionally, the base unit 9 may be provided on its underside with a cooling device 21 which is constructed in the manner of integrated cooling pipes or cooling coils as shown. The cooling device 21 may also extend further, in the bottom region of the channel 17 and the spreading chamber 19. However, additional or alternative cooling systems may also be provided for the channel 17 and the spreading chamber 19, if appropriate. The concrete structure 5 in addition spreads out as a concrete foundation in the bottom region below the cooling device 21. The function of the cooling device 21 can be seen from FIG. 2. First and second coolant tanks 23a and 23b are disposed on both sides of the reactor cavity 3. These tanks may also be connected to each other or else formed by a common vessel. A cooling pipe 23, which is shown as an example of other cooling pipes of the device 21, in this case extends from a first end 24 in a lower bottom region 25 of the first coolant tank 23a, in cooling contact within or below the base unit 9, and along into the second coolant tank 23b. A second end 26 of the cooling pipe or line 23 is disposed in this case at a high level in the second coolant tank 23b, above a water level 28 in the latter, so that no coolant can flow back from the second tank 23b into the first tank 23a. Steam is formed when the cooling liquid inside the cooling tube 23 along the base unit 9 is heated, with the water pressure formed by the high water level in the first coolant tank 23a displacing the steam into the second coolant tank 23b, where it condenses and precipitates. A uniform flow of coolant in the direction from the first tank 23a to the second tank 23b is ensured in this way. The cooling device 23 can thus operate passively, without additional energy supply. Where appropriate, steam which is possibly still produced may be discharged into the atmosphere of the containment. If the cooling effect during passive operation is not sufficient, then additional active cooling, especially long-term cooling, may be provided, if appropriate, through a non-illustrated device. FIG. 3 shows the concrete structure 5 in a cross-section taken along the line III--III in FIG. 1. The channel 17 which connects the prechamber 11 to the spreading chamber 19 can be seen in this figure. In this case, the spreading chamber 19 essentially has a rectangular shape, with its corners being beveled. Its structural configuration is such that the core melt suddenly emerging from the channel 17 can spread out quickly and conformally, without piles or jams being formed. The bottom of the spreading chamber 19 is kept relatively thin, so that strong heat dissipation through the cooling device 21 is provided. Lasting cooling of the core melt in the spreading space 19 is thereby achieved. FIGS. 4, 5 and 6 show an alternative rectangularly constructed spreading chamber 19, having a bottom region 27 which is constructed as a cooling bottom. Other desired or technically required shapes may also be chosen for the spreading chamber 19. The bottom region is constructed underneath in this case in the manner of cooling fins, through which coolant of the cooling device 21 flows. Fast dissipation of residual heat in the core melt is possible in this way. The bottom region 27 has a ribbed structure providing a very stable structural configuration, so that the load of the core melt can be supported well. The coolant flow is indicated by arrows according to FIG. 5, with pipe ends 28a and 28b respectively corresponding to the ends 24 and 26 of the coolant line 23 in FIG. 2. As can be seen from the plan view of the bottom region 27 in FIG. 4, the bottom region 27 may preferably be formed by bottom elements 29. This makes transport and handling easier. It is thereby also possible to use standard bottom elements 29 for different sizes of spreading spaces. Further details and particular features of first, second and third bottom elements 29a, 29b and 29c are disclosed in the subsequent FIGS. 7 to 13. Firstly, FIGS. 7, 8 and 9 show proposed alternatives for bottom elements according to the portion X in FIG. 6. The first bottom element 29a according to FIG. 7 is supported, for example, on webs 31 similar to cooling fins. The bottom elements 29 in this case are also preferably made of a material having high thermal conductivity. A portion Z, which shows a connection technique or structure between the bottom elements 29, is dealt with in further detail below in the description of FIGS. 10 to 13. The same is true for the bottom elements according to FIGS. 8 and 9. A side of the bottom elements 29a to 29c remote from the core melt may optionally be provided with a coating 33 which preferably prevents penetration of the bottom elements 29. The coating 33 may be applied onto the bottom elements 29 or may be applied subsequently as a continuous coating onto the already laid bottom elements 29. In the embodiment of the second bottom elements 29b according to FIG. 8, webs 31a, which are constructed in the manner of cooling fins, are widened on their underside like a punch, so that improved support of the bottom elements 29b is provided. Furthermore, an area which is actually cooled in channels 35 formed by the fins 31a is increased as compared to the embodiment according to FIG. 7, as a result of which the cooling effect is improved. The connection technique between the cooling elements 29b according to the portion Z corresponds to that in FIG. 10. The third bottom elements 29c according to FIG. 9 differ from those in FIG. 8 by an alternative connection technique, as well as a different measure of division. It is conceivable in this case, for example, for the bottom elements 29b in FIG. 8 to be constructed rectangularly according to the plan view of FIG. 4. In contrast, the bottom elements 29c according to FIG. 9 may be constructed to be long profiled elements which, if appropriate, fill the spreading chamber 19 over its entire length. Considerable care must be taken in this case in the construction of the bottom elements 29a to 29c with regard to the connection technique or structure between the bottom elements. On one hand, they must have a sealing effect, so that the core melt cannot combine with the coolant. On the other hand, the elements must mechanically engage one another firmly, so that a structure with high mechanical load-bearing capacity is provided. Furthermore, the extent of the elements must be balanced by the temperature differences and temperature conditions which occur. The embodiments shown in FIGS. 10 to 13 are firstly divided into stepped connections (FIGS. 10, 11) and tongue and groove connections (FIGS. 12 and 13). A factor which is common to all of the embodiments in this case is that a sealing effect with respect to the upper side must be achieved. In the embodiments according to FIGS. 10, 11 and 12, this is achieved by using a packing material 37 which fills a gap possibly existing between the bottom elements 29. In this case, the packing material 37 fulfills two functions. On one hand, it has an extensible-joint effect and, on the other hand, it exerts a sealing effect. In addition, a sealing element 39 which is disposed between two adjoining surfaces 41 may be provided, for example. In this case, the sealing effect is the predominant function. In the embodiment according to FIG. 12, there is no sealing element since a labyrinth, which has the required sealing effect, is provided by the tongue and groove construction of the connection technique. In the embodiment according to FIG. 13, it is also additionally possible to do without packing material, since penetration of core melt into the intermediate space between two bottom elements is prevented by a beveled construction of the tongue and groove connection. Furthermore, a labyrinth effect is provided in this case as well, so that the requisite leak-tightness is likewise achieved. In this embodiment, a saving on additional material is possible by virtue of the increased outlay in the manufacturing technique. Of course, any desired combinations of the above-mentioned features are possible, within the scope of ability of the person skilled in the art, without departing from the fundamental spirit of the present concept.
052079767	claims	1. In an apparatus for inspecting nuclear fuel pellets for surface defects, said apparatus including a pellet infeed conveyor and a pellet discharge conveyor, a pellet slide and inspection assembly comprising: (a) a pellet slide defining an inclined track having an exit end adjacent to said discharge conveyor and an entry end adjacent to said infeed conveyor and at a higher elevation than said exit end; (b) an inspection station located along said inclined track between said entry and exit ends of said track, said station including lower and upper sound reflectors being configured to define an annular inspection chamber through which a pellet moves as the pellet slides down said inclined track, said lower and upper sound reflectors defining said annular inspection chamber completely surrounding the circumferential surface of the pellet as the pellet moves through said chamber; and (c) an ultrasonic inspection head mounted at said inspection station and being operable to transmit and receive sound energy to and from a pellet as it moves through said inspection chamber such that the sound energy completely surrounds the moving pellet being inspected within said chamber; (d) one of said lower and upper sound reflectors having an opening therethrough, said ultrasonic inspection head extending through said opening in said one of said lower and upper sound reflectors for transmitting and receiving sound energy to and from the pellet as it moves through said annular inspection chamber; (e) one of said lower and upper sound reflectors having a recess defined therein, a first semicircular cavity defined in said recess and a pair of first surface portions defined along opposite sides of said first semicircular cavity, the other of said lower and upper sound reflectors having a second semicircular cavity defined therein being complementary to said first semicircular cavity and a pair of second surface portions defined along opposite sides of said second semicircular cavity, said other of said lower and upper sound reflectors being inserted into said recess of said one of said lower and upper sound reflectors so as to mate therewith at said respective pairs of surface portions such that said first and second semicircular cavities together define said annular inspection chamber and completely surround the circumferential surface of the pellet as the pellet moves through said chamber. an upper portion extending from said entry end of said slide through said inspection chamber; and a lower portion extending from said inspection chamber to an exit end of said slide along which each pellet moves after passing through said inspection chamber, said lower portion having a shallower slope than said upper portion of said pellet slide so as to cause deceleration of the pellet as it moves from said upper portion to said lower portion of said track which reduces the velocity of the inspected pellet as it approaches said exit end of said pellet track. means disposed in one of said lower and upper sound reflectors for transmitting light across the inspection chamber and thus across the path of movement of a pellet through said chamber; and means disposed in one of said lower and upper sound reflectors for receiving the light transmitted across the inspection chamber and thereby sensing the position of a pellet in said chamber. means for retaining said light transmitting and receiving means on said one of said lower and upper sound reflectors. said track of said slide has a cutout located between and spaced from said entry and exit ends thereof; and said lower sound reflector is disposed within said cutout of said slide track. (a) a pellet slide defining an inclined track having an exit end adjacent to said discharge conveyor and an entry and adjacent to said infeed conveyor and at a higher elevation than said exit end; (b) an inspection station located along said inclined track between and spaced from said entry and exit ends of said track, said station including lower and upper sound reflectors being configured to define an annular inspection chamber through which a pellet moves as the pellet slides down said inclined track, one of said lower and upper sound reflectors having a recess defined therein, a first semicircular cavity defined in said recess and a pair of first surface portions defined along opposite sides of said first semicircular cavity, the other of said lower and upper sound reflectors having a second semicircular cavity defined therein being complementary to said first semicircular cavity and a pair of second surface portions defined along opposite sides of said second semicircular cavity, said other of said lower and upper sound reflectors being inserted into said recess of said one of said lower and upper sound reflectors so as to mate therewith at said respective pairs of surface portions such that said first and second semicircular cavities together define said annular inspection chamber completely surrounding the circumferential surface of the pellet as the pellet moves through said chamber; and (c) an ultrasonic inspection head mounted at said inspection station and being operable to transmit and receive sound energy to and from a pellet as it moves through said inspection chamber; (d) said track of said pellet slide having an upper portion extending from said entry end of said track through said inspection chamber and a lower portion extending from said inspection chamber to said exit end of said track along which each pellet moves after passing through said inspection chamber, said upper portion of said track defining a substantially linear path of movement of a pellet from said entry end of said track through said inspection chamber, said lower portion of said track defining a substantially linear path of movement of a pellet from said inspection chamber to said exit end of said track, said lower portion having a shallower slope than said upper portion of said track so as to cause deceleration of the pellet as it moves from said upper portion to said lower portion of said track which reduces the velocity of the inspected pellet as it approaches said exit end of said track. means disposed at said inspection chamber for transmitting light across the inspection chamber and thus across the path of movement of a pellet through said chamber; and means disposed at said inspection chamber for receiving the light transmitted across the inspection chamber and thereby sensing the position of a pellet in said chamber. (a) a pellet slide defining an inclined track having an exit end adjacent to said discharge conveyor and an entry end adjacent to said infeed conveyor and at a higher elevation than said exit end; (b) an inspection station located along said inclined track between and spaced from said entry and exit ends of said track, said station including lower and upper sound reflectors being configured to define an annular inspection chamber through which a pallet moves as the pellet slides down said inclined track, one of said lower and upper sound reflectors having a recess defined therein, a first semicircular cavity defined in said recess and a pair of first surface portions defined along opposite sides of said first semicircular cavity, the other of said lower and upper sound reflectors having a second semicircular cavity defined therein being complementary to said first semicircular cavity and a pair of second surface portions defined along opposite sides of said second semicircular cavity, said other of said lower and upper sound reflectors being inserted into said recess of said one of said lower and upper sound reflectors so as to mate therewith at said respective pairs of surface portions such that said first and second semicircular cavities together define said annular inspection chamber completely surrounding the circumferential surface of the pellet as the pellet moves through said chamber, said upper sound reflector having an opening therethrough; and (c) an ultrasonic inspection head mounted at said inspection station and extending through said opening of said upper sound reflector, said head being operable to transmit and receive sound energy to and from a pellet as it moves through said inspection chamber such that the sound energy completely surrounds the moving pellet being inspected within said chamber; (d) said track of said pellet slide having an upper portion extending from said entry end of said track through said inspection chamber and a lower portion extending from said inspection chamber to an exit end of said track along which each pellet moves after passing through said inspection chamber, said lower portion having a shallower slope than said upper portion of said track so as to cause deceleration of the pellet as it moves from said upper portion to said lower portion of said track which reduces the velocity of the inspected pellet as it approaches said exit end of said track. means disposed on said upper sound reflector for transmitting light across the inspection chamber and thus across the path of movement of a pellet through said chamber; and means disposed on said upper sound reflector for receiving the light transmitted across the inspection chamber and thereby sensing the position of a pellet in said chamber. means for retaining said light transmitting and receiving means on said upper sound reflector. said track of said slide has a cutout located between and spaced from said entry and exit ends thereof; and said lower sound reflector is disposed within said cutout of said slide track and includes a pair of rails mounted between opposite edges of said cutout portion of said track for supporting a pellet as it moves through said inspection chamber. 2. The assembly as recited in claim I, wherein said track of said pellet slide includes an upper portion defining a substantially linear path of movement of a pellet from said entry end of said slide through said inspection chamber. 3. The assembly as recited in claim 1, wherein said track of said pellet slide includes: 4. The assembly as recited in claim 1, further comprising: 5. The assembly as recited in claim 4, further comprising: 6. The assembly as recited in claim 1, wherein: 7. The assembly as recited in claim 6, wherein said a pair of rails are mounted in said lower sound reflector and extend between opposite edges of said cutout of said track for supporting a pellet as it moves through said inspection chamber. 8. In an apparatus for inspecting nuclear fuel pellets for surface defects, said apparatus including a pellet infeed conveyor and a pellet discharge conveyor, a pellet slide and inspection assembly comprising: 9. The assembly as recited in claim 8, further comprising: 10. In an apparatus for inspecting nuclear fuel pellets for surface defects, said apparatus including a pellet infeed conveyor and a pallet discharge conveyor, a pallet slide and inspection assembly comprising: 11. The assembly as recited in claim 10, wherein said upper portion of said track defines a substantially linear path of movement of a pellet from said entry end of said track through said inspection chamber. 12. The assembly as recited in claim 10, wherein said lower portion of said track defines a substantially linear path of movement of a pellet from said inspection chamber to said exit end of said track. 13. The assembly as recited in claim 10, further comprising: 14. The assembly as recited in claim 13, further comprising: 15. The assembly as recited in claim 10, wherein said lower and upper sound reflectors have respective semi-cylindrical cavities defined therein which together define said annular inspection chamber. 16. The assembly as recited in claim 10, wherein:
	abstract	Provided are a method and system for improving control of a steam generator level for preventing oscillation of the steam generator level in a nuclear power plant. In order to prevent oscillation of a steam generator level and resultant shutdown of a nuclear reactor, which may be caused when a high-level priority control function is frequently and repeatedly turned on/off as the steam generator level is excessively increased, by improving a feedwater control system in the nuclear power plant, a proportional integral control value may be controlled to be reduced, and thus, output while a certain condition is met after a high-level priority mode is deactivated or a signal instructing to enter the high-level priority control mode may be controlled not to be output.
	summary
	claims	1. A scanning apparatus for processing a substrate, the scanning apparatus comprising:a base portion; anda rotary subsystem comprising:a first link comprising a first joint, wherein the first link is rotatably coupled to the base portion by the first joint;a second link comprising a second joint, wherein the second link is rotatably coupled to the first link by the second joint, and wherein the first joint and the second joint are spaced a predetermined distance from one another, the second link further comprising an end effector whereon the substrate resides, wherein the end effector is operably coupled to the second link, and wherein the end effector is further spaced from the second joint by the predetermined distance;a first actuator operable to continuously rotate the first link about the first joint in a first rotational direction; anda second actuator operable to continuously rotate the second link about the second joint in a second rotational direction, wherein the second actuator comprises a servo motor fixedly mounted to the first link, and wherein the end effector is operable to linearly oscillate with respect to the base portion along a first scan path upon the rotation of the first and second actuators. 2. The scanning apparatus of claim 1, wherein the first rotational direction is opposite the second rotational direction. 3. The scanning apparatus of claim 1, wherein the base portion is operably coupled to a translation mechanism, wherein the translation mechanism is operable to move the base portion in one or more directions with respect to the translation mechanism. 4. The scanning apparatus of claim 3, wherein the translation mechanism is operable to move the base portion along a second scan path, wherein the second scan path is generally perpendicular to the first scan path. 5. The scanning apparatus of claim 3, wherein the translation mechanism comprises a linear drive system, wherein the linear drive system is operable to linearly translate the rotary subsystem in a direction generally perpendicular to the linear oscillation of the end effector. 6. The scanning apparatus of claim 1, wherein the end effector is operably coupled to the second link by a third joint, wherein the end effector is further operable to move in one or more directions with respect to the second link. 7. The scanning apparatus of claim 6, wherein the third joint provides the end effector with two or more degrees of freedom. 8. The scanning apparatus of claim 7, wherein the third joint is operable to provide a rotation and a tilt of the end effector with respect to the second link. 9. The scanning apparatus of claim 1, wherein the end effector comprises an electrostatic chuck. 10. The scanning apparatus of claim 1, wherein the first actuator comprises a servo motor fixedly mounted to the base portion. 11. The scanning apparatus of claim 1, wherein the first rotational velocity of the first actuator is operable to vary with respect to a location of the end effector. 12. The scanning apparatus of claim 1, wherein the second rotational velocity of the second actuator is operable to vary with respect to a location of the end effector. 13. The scanning apparatus of claim 1, wherein the base portion further comprises a prismatic joint, wherein the base portion is operable to move the rotary subsystem in one or more directions. 14. The scanning apparatus of claim 1, wherein the first link and the second link are generally parallel to a single plane. 15. The scanning apparatus of claim 14, wherein the end effector is further operable to rotate parallel to the single plane. 16. The scanning apparatus of claim 1, further comprising a controller operable to control a rotational velocity of the respective first and second links by controlling an amount of power provided to the respective first and second actuators. 17. The scanning apparatus of claim 16, further comprising one or more sensing elements associated with the first and second actuators, wherein the one or more sensing elements are operable to sense the rotational velocity of the respective first and second links and feed back the sensed rotational velocities to the controller. 18. The scanning apparatus of claim 17, wherein the one or more sensing elements comprise one or more encoders. 19. The scanning apparatus of claim 16, wherein the controller is operable to maintain the respective rotational velocities such that the linear oscillation of the end effector is generally constant within a predetermined scanning range of the end effector. 20. The scanning apparatus of claim 19, wherein the predetermined range of motion of the end effector is at least twice a diameter of the substrate. 21. The scanning apparatus of claim 19, wherein a maximum scan distance of the end effector is generally defined between maximum positions of the end effector when the first link and second link are fully extended, and wherein the maximum scan distance is larger than the predetermined scanning range of the end effector.
052271218	summary	A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. BACKGROUND OF THE INVENTION The present invention relates to apparatus and methods for monitoring and controlling the operation of commercial nuclear power plants. Conventionally, commercial nuclear power plants have a central control room containing equipment by which the operator collects, detects, reads, compares, copies, computes, compiles, analyzes, confirms, monitors, and/or verifies many bits of information from multiple indicators and alarms. Conventionally, the major operational systems in the control room have been installed and operate somewhat independently. These include the monitoring function, by which the components and the various processes in the plant are monitored; control, by which the components and the processes are intentionally altered or adjusted, and protection, by which a threat to the safety of the plant is identified and corrective measures immediately taken. The result of such conventional control room arrangement and functionality can sometimes be information overload or stimulus overload on the operator. That is, the amount of information and the variety and complexity of the equipment available to the operator for taking action based on such extensive information, can exceed the operator's cognitive limits, resulting in errors. The most famous example of the inability of operators to assimilate and act correctly based on the tremendous volume of information stimuli in the control room, particularly during unexpected or unusual plant transients, is the accident that occurred in 1978 at the Three Mile Island nuclear power plant. Since that event, the industry has focused considerable attention to increasing plant operability through improving control room operator performance. A key aspect of that improvement process is the use of human engineering design principles. Advances in computer technology since 1978 have enabled nuclear engineers and control room designers to display more information, in a greater variety of ways, but this can be counterproductive, because part of the problem is the overload of information. Improving "user friendliness" while maintaining the quantity and type of information at the operator's disposal has posed a formidable engineering challenge. SUMMARY OF THE INVENTION It is thus an object of the present invention to provide apparatus and method for nuclear power plant control and monitoring operations having the characteristics of concise information processing and display, reliable architecture and hardware, and easily maintainable components, while eliminating operator information overload. This objective should be accomplished while achieving enhanced reliability, ease of operation, and overall cost effectiveness of the control room complex. The solution to the problem is accomplished with the present invention by providing a number of features which are novel both individually and as integrated together in a control complex. The complex includes six major systems: (1) the control center panels, (2) the data processing system (DPS), (3) the discrete indication and alarm system (DIAS), (4) the component control system consisting of the engineered safeguard function component controls (ESFC) and the process component controls (PCC), (5) the plant protection system (PPS), and (6) the power control system (PCS). These six systems collect data from the plant, efficiently present the required information to the operator, perform all automatic functions and provide for direct manual control of the plant components. The control complex in accordance with the invention provides a top-down integrated information display and alarm approach that supports rapid assessment of high level critical plant safety and power production functions; provides guidance to the operator regarding the location of information to further diagnose high level assessments; and significantly reduces the number of display devices relative to conventional nuclear control complexes. The complex also significantly reduces the amount of data the operator must process at any one time; significantly reduces the operational impact of display equipment failures; provides fixed locations for important information; and eliminates display system equipment used only for off normal plant conditions. It is known that the nuclear steam supply system can be kept in a safe, stable state by maintaining a limited set of critical safety functions. The present invention extends the concept of the critical plant safety functions to include critical plant power production functions, in essence integrating the two functions so that the information presentation to the operator supports all high level critical plant functions necessary for power production as well as safety. The information display hierarchy in accordance with the invention includes a "big board" integrated process status overview screen (IPSO) at the apex, which provides a single dedicated location for rapid assessment of key information indicative of critical plant power production and safety functions. Further detail on the sources and trends of normal or abnormal parameter changes are provided by the DIAS. Both IPSO and the DIAS provide direct access and guidance to additional system and component status information contained on a hierarchy of CRT display pages which are driven by the DPS. The IPSO continually displays spatially dedicated information that provides the status of the plant's critical safety and power production functions. This information is presented using a small number of easily understood symbolic representations that are the results of highly processed data. This relieves the operator of the burden of correlating large quantities of individual parameter data, systems or component status, and alarms to ascertain the plant functional conditions. The IPSO presents the operator with high level effects of lower level component problems. The IPSO relies primarily on parameter trend direction, e.g., higher, lower, an alarm symbol color and shape, to convey key information. These are supplemented by values for selected parameters. The IPSO presents consolidated, simplified information to the operator in relatively small quantities of easily recognized and understood information. Furthermore, the IPSO compensates for the disadvantage inherent in recent industry trends towards presenting all information serially on CRTs, by enabling the operator to obtain an overview, or "feel" of the plant condition. Display of plant level overview on a large-format dedicated display addresses two additional operational concerns. First, operator tasks often require detailed diagnostics in very limited process areas. However, maintaining concurrent awareness of plant-wide performance is also necessary. Rather than relying on multiple operators in the control room to monitor respective indicators and the like on spatially separated panels, the IPSO can be viewed from anywhere in the control room and thus provides an operator a continuous indication of plant performance regardless of the detailed nature of the task that may be requiring the majority of his attention. In the preferred implementation, IPSO supports the assessment of the power and safety critical functions by providing for each function, key process parameters that indicate the functional status. For each function, key success paths are selected with the status of that success path The IPSO clearly relates functions to physical things in the plant. The critical functions are applied to power production, normal post trip actions, and optimal functional recovery procedures. The second level in the display information hierarchy in accordance with the present invention is the presentation of plant alarms from the DIAS. A limited number of fixed, discrete tiles are used with three levels of alarm priorities. Dynamic alarm processing uses information about the plant state (e.g., reactor power, reactor trip, refueling, shut-down, etc.) and information about system and equipment status to eliminate unnecessary and redundant alarms that would otherwise contribute to operator information overload. The alarm system provides a supplementary level of easily understood cueing into further information in the discrete indicators, CRTs and controls. Alarms are based on validated data, so that the alarms identify real plant process problems, not instrumentation and control system failures. The alarm features include providing a detailed message through a window to the operator upon the acknowledgment of an alarm and the ability to group the alarms without losing the individual messages. The tiles can dynamically display different priorities to the operator. The acknowledgment sequence insures that all alarms are acknowledged while at the same time reducing the operator task loading by providing momentary tones, then continuous alarm, followed by reminder tones to insure that the alarms are not forgotten. The operator has the ability to stop temporarily alarm flashing to avoid visual overload, and resume the flashing to insure that the alarm will eventually be acknowledged. The discrete indicators in the DIAS provide the third level of display in the hierarchy of the present invention. The flat panel displays compress many signal sources into a limited set of read-outs for frequently monitored key plant data. Signal validation and automatic selection of sensors with the most accurate signal ranges are also employed to reduce the number of control panel indicators. Information read-outs are by touch-screen to enhance operator interaction and include numeric parameter values, a bar form of analog display, and a plot trend. Various multi-range indicators are available on one display with automatic sensor selection and range display. The automatic calculation of a valid process representation parameter value, with the availability of individual sensor readings at the same display, avoids the need for separate backup displays, or different displays for normal operation versus accident or post-accident operation. Moreover, in another preferred feature of the invention, the parameter verification automatically distinguishes failed or multiple failed sensors, while allowing continued operation and accident mitigation information to the operator even if the CRT display is not available. Furthermore, the normal display information can be correlated to a qualified sensor, such as that used for post-accident monitoring purposes. At the information display level associated with control of specific components, dynamic "soft" controllers are provided with component status and control signal information necessary for operator control of these components. For the ESFC system, this information includes status lamp, on-off controls, modulation controls, open-closed controls, and logic controls. For the PCCS, the information includes confirm load, set points, operating range, process values, and control signal outputs. In the fourth level of the information hierarchy, dynamic CRT display pages are complementary to all levels of spatially dedicated control and information and can be accessed from any CRT location in the control room, technical support center, or emergency operations facility. These displays are grouped into a three level hierarchy that includes general monitoring (level 1), plant component and systems control (level 2), and component/process diagnostics (level 3). Display implementation is driven by the DPS and duplicates and verifies all discrete alarm and indicator processing performed in the DIAS. In the preferred implementation of the invention, the indicator, alarm, and control functions for a given major functional system of the plant are grouped together in a single, modularized panel. The panel can be made with cutouts that are spatially dedicated to each of the displays for the indicators, alarms, controls, and CRT, independent of the major plant functional system. This permits delivery, installation, and preliminary testing of the panels before finalization of the plant specific logic and algorithms, which can be software modified late in the plant construction schedule. This modularization is achievable because the space required on the panel is essentially independent of the major plant functional system to which the plant is dedicated. Both the alarms and indicators can be easily modified in software. The number of indicators and alarm tiles that can be displayed to the operator are not significantly limited by the available area of the panel, so that standardization of panel size and cutout locations for the display windows is possible.
	summary
047215968	claims	1. A method of decreasing the amount of relatively long lived fission products in radioactive waste materials in excess of that due to their natural radioactive decay by producing relatively short lived radioactive nuclides and stable nuclides from said relatively long lived fission products comprising the steps of: (a) separating said fission products into at least (1) a plurality of physically separate groups, each of said groups having at least one relatively long lived fission product nuclide selected from the group comprising Se.sup.79, Kr.sup.85, Sr.sup.90, Zr.sup.93, Tc.sup.99, Pd.sup.107, Sb.sup.125, Sn.sup.126, I.sup.129, Cs.sup.135, Cs.sup.137, Pm.sup.147, Sm.sup.151 +Eu, and actinides, and (2) relatively short lived fission product radioactive nuclides and stable nuclides; (b) storing said relatively short lived radioactive nuclides and stable nuclides; (c) exposing at least the groups containing Kr.sup.85, Sr.sup.90, Zr.sup.93, Tc.sup.99, Pd.sup.107, I.sup.129, Cs.sup.135, Sm.sup.151 +Eu, and actinides, to a high thermal neutron flux for separate, different predetermined periods of time selected in accordance with the long lived fission product nuclide in said corresponding group for inducing predetermined transformations of said relatively long lived fission product nuclides to produce relatively short lived radioactive nuclides and stable nuclides; (d) removing each exposed group containing said produced relatively short lived radioactive nuclides and stable nuclides from said high thermal neutron flux; (e) separating said removed group into (1) said produced short lived radioactive nuclides and stable nuclides, and (2) a plurality of further groups having long lived fission product nuclides respectively corresponding to at least some of the long lived fission product nuclides or said plurality of groups of step (a); (f) storing said produced short lived radioactive nuclides and stable nuclides; (g) joining at least one of said plurality of further groups to at least one of said plurality of groups of step (a) having a corresponding long lived fission product nuclide; (h) repeating steps (c)-(f) at least one time; (i) for at least one other further group, maintaining same separate from said plurality of groups of step (a) while re-exposing same to a high thermal neutron flux for a predetermined period of time selected in accordance with said long lived fission product nuclide contained therein for inducing predetermined transformations of said long lived nuclide to further produce relatively short lived radioactive nuclides and stable nuclides; (j) removing said at least one other further group containing said further produced relatively short lived radioactive nuclides and stable nuclides from said high thermal flux; (k) separating said removed other further group into (1) said further produced short lived radioactive nuclides and stable nuclides, and (2) yet another group containing said long lived fission product nuclides of step (i); (l) storing said further produced short lived radioactive nuclides and stable nuclides; and (m) storing said long lived radioactive nuclides of steps (e) and (k) after they have reached a reduced level of radioactivity over their natural decay. 2. A method as recited in claim 1, wherein a component comprises Se.sup.79. 3. A method as recited in claim 1, wherein a component comprises Krypton. 4. A method as recited in claim 1, wherein a component comprises Strontium. 5. A method as recited in claim 1, wherein a component comprises Zr.sup.93. 6. A method as recited in claim 1, wherein a component comprises Tc.sup.99. 7. A method as recited in claim 1, wherein a component comprises Pd.sup.107. 8. A method as recited in claim 1, wherein a component comprises Sn.sup.126. 9. A method as recited in claim 1, wherein a component comprises Sb.sup.125. 10. A method as recited in claim 1, wherein a component comprises Iodine. 11. A method as recited in claim 1, wherein a component comprises Cs.sup.135. 12. A method as recited in claim 1, wherein a component comprises Cs.sup.137. 13. A method as recited in claim 1, wherein a component comprises Pm.sup.147. 14. A method as recited in claim 1, wherein a component comprises Sm.sup.151. 15. A method as recited in claim 1, wherein a component comprises Europium.
	abstract	The invention relates to an X-ray imaging apparatus (2), comprising: a source (4) for generating X-ray radiation, an object receiving space (6) for arranging an object of interest for X-ray imaging, an X-ray collimator arrangement (8) arranged between the source (4) and the collimator arrangement (8), and an X-ray mirror arrangement (10). The mirror arrangement (10) comprises for example two tapered mirrors (22) facing each other and adapted for guiding X-ray radiation of the source (4) to the collimator arrangement (8). Consequently, the X-ray intensity at the object receiving space (6) is increased. In order to limit the X-ray radiation to an area, where the X-ray radiation can be utilized form imaging, an angle of spread Θm between the mirrors (22) and a length LM of each mirror (22) is adapted, such that a number of total reflections of X-ray radiation, provided by the source (4), at the mirrors (22) is limited. The limitation provides the effect that an angle of reflection Θr of the totally reflected X-ray radiation is limited. Consequently, an X-ray intensity at the object receiving space (6) is increased while constrains are provided, which prevent a large increase of a width of the X-ray radiation provided at the object receiving space (6), which effectively improves an imaging quality of an object of interest being arrangeable at the object receiving space (6).
050283839	summary	FIELD OF THE INVENTION This invention relates to power generating nuclear fission reactor plants and equipment therefor. The invention is particularly concerned with an improvement in means used for depressurizing steam within the nuclear reactor pressurized system of a power generating plant. Water cooled nuclear fission reactors utilized for electrical power generation, as with any steam producing boiler, require valve means to reduce excessively high pressures within the system, through venting, to maintain and insure system integrity and safety. Safety or relief, and combination safety-relief valves commonly used in many nuclear reactor plants, typically open at a specified pressure and reclose after the pressure of the system is reduced to a prescribed safe level. Anticipated nuclear reactor plant designs contemplate the use of "depressurization valves" to reduce excessively high pressures. Once opened, such valves have the unique feature of remaining open down to zero pressure without any further operator action and without need to provide power to maintain a valve in open position. Typically, the nature of the steam producing unit will determine the type and requirements for such depressurizing safety relief valves. This is especially so in the nuclear reactor field due to the distinctive conditions encountered with nuclear fission and the stringent safety requirements imposed in this industry, among other reasons. BACKGROUND OF THE INVENTION A unique aspect of nuclear reactors and a foremost safety consideration, is the inherent presence of radiation and radioactive materials. This highly significant condition requires the most strict design and safety conditions with respect to many components and functions of a nuclear reactor plant and imposes numerous requirements in operating and maintaining nuclear plants. For example, reactor components and related equipment which become significantly radioactive in service generally must be capable of long term, trouble free and positive functions, as well as being amenable to operation and maintenance by personnel in remote locations. Steam depressurization and/or pressure relief valves or means are especially critical devices in any type of high pressure hot water and/or steam producing units, and when employed in a nuclear reactor plant the standards and demands must be applied to design and fabrication of such valves. Various valve designs and operating modes have been proposed and considered in an effort to meet the stringent demands for such steam depressurization and pressure relief valves. For example, one proposed category of depressurization valves has been explosive/propellant-activated valves. In theory this type of valve should comply with the required design properties. This type of valve is fast operating, and routine valve maintenance and replacement of consumed parts of an opened valve can be quickly performed. However, it appears that with such explosive/propellant-activated valves, there are significant concerns such as limits upon the effective life of the explosive material as a result of exposure to heat and radiation, and flow rates obtainable with the current designs. SUMMARY OF THE INVENTION This invention comprises an improved steam depressurization valve for service in power generating, water cooled nuclear fission reactor plants. The valve of this invention, which will meet the requirements for nuclear reactor service, is maintained in the normal operating closed position by fluid pressure which can be sourced and controlled from outside the reactor containment and thus beyond any source of radiation, and opens to permit depressurization venting by release of the externally applied and controlled fluid pressure. OBJECTS OF THE INVENTION It is a primary object of this invention to provide an improved steam depressurization valve suitable for service in a nuclear fission reactor plant. It is also an object of this invention to provide a mechanically uncomplicated and reliable, light-weight and leak-tight valve for steam depressurization in a nuclear fission reactor plant. It is a further object of this invention to provide a steam depressurization valve which utilizes a positive source of fluid pressure to maintain the valve in its normal operating closed position such that the valve can be opened to its pressure relieving position simply by terminating the positive fluid pressure force applied thereto. It is a still further object of this invention to provide a steam depressurization valve for which the source of the actuating medium for opening the valve and the control of the opening medium can be located outside the reactor plant safety containment.
	description	1. Field of the Invention The present invention relates to an X-ray CT apparatus that controls a collimator for restricting the irradiation field of X-rays (or X-ray beam). 2. Description of the Related Art X-ray computed tomography apparatuses are known by which X-rays are irradiated at a patient and image data is reconstructed from the permeation data. An X-ray computed tomography apparatus for multi-slicing makes it possible to collect data regarding a plurality of slices from different positions all together at a time by using an X-ray detector in which detecting elements (e.g., an assembly of a scintillator and photo diode) for detecting X-rays are arranged in a row. The combined use of multi-slice scanning (also referred to as cone-beam scanning) and helical scanning makes it possible to collect data of an extremely wide scanning range within a short time, so propagation in the future is anticipated. One important objective in the case of the combined use of multi-slice scanning and helical scanning is the reduction of exposure to radiation dose. For example, there is technology in which a scanning range is set so as to include the region of a subjected organ on a scanogram and the opening of a collimator is set in accordance with the scanning range so that the scanning is restricted to the subjected organ within the patient (e.g., Japanese Unexamined Patent Application Publication No. 2002-17716 and Japanese Unexamined Patent Application Publication No. H10-248835). However, in reality, a part of the targeted organ is left out from the scanning range, resulting in missing data. Therefore, a situation may occur in which rescanning becomes necessary. In this respect, it is possible to reconstruct a scanned image even if the data is missing, but in reality, noise ends up being inserted into the portion of the reconstructed scanned image where the data was missing. In addition, when a doctor uses the scanned image as a reference for diagnosis, the area of the diagnosis such as cancer is extremely small. Therefore, it is difficult to distinguish the difference of the noise that has been inserted into the scanned image from a diseased site, so there is a risk of misdiagnosis. For this reason, it is necessary to reduce the amount of exposure to radiation without missing data. Accordingly, technology has been proposed in the past for reducing the radiation exposure of a patient at the time of helical scanning by changing the opening degree (size of the irradiation field) of the opening of a collimator in accordance with the position on a body axis in the progressing course of the helical scanning (e.g., Japanese Unexamined Patent Application Publication No. 2006-51233). However, with the conventional method of changing the opening degree of the opening of a collimator, only the coordinate of the direction of movement of the bed of the collimator opening is acquired, and the opening degree of the opening of the collimator is preliminarily determined with respect to said coordinate. Thus, it is difficult to say that the timing of data collection via a data collection system corresponds to the control of the opening of the collimator, the data collection system including an imaging part such as an X-ray irradiator or an X-ray detector. Therefore, correlation of the collected data and the opening degree of the collimator is unclear, and there is a risk of missing data or of subjecting a patient to excessive radiation exposure. Furthermore, in recent years, technology referred to as variable speed helical scanning has been proposed, whereby scanning is performed by changing the speed of movement in the body axis direction and the helical pitch while collecting data of a designated scanning range. In this respect, the collimator is simply controlled according to the distance by which the bed is moved, so with the conventional method of collimator control, it has been difficult to control the opening of the collimator with favorable accuracy with respect to the changes of the speed of movement or the helical pitch in such variable speed helical scanning. The purpose of the present invention is to provide an X-ray CT apparatus for conducting quantitative collimator control on the basis of a data collection system by synchronizing with the timing pulse of the data collection system and changing the size of the opening of the collimator. According to a first aspect of the present invention, the X-ray CT apparatus comprises the following functioning parts. A supporter supports a patient and is disposed movably along the body axis direction of said patient. An imaging part includes an X-ray-generator and an X-ray-detector. The X-ray-generator irradiates X-rays while rotating around the body axis. The X-ray-detector detects the X-rays that have permeated a patient. A collimator changes the irradiation field of X-rays to be irradiated. A scan controller controls the movement of the supporter and the imaging part. An image-constructing part reconstructs image data based on the X-rays that have been detected by the X-ray detector. A detector detects the amount of movement of a patient by the supporter. A collimator controller controls so as to change the size of the opening of a collimator based on the amount of movement. According to the first aspect, with this constitution, the quantitative control of the opening of a collimator is conducted by synchronizing with the timing pulse based on a starting signal of the data collection system including the imaging part such as an X-ray-generator or an X-ray-detector and then changing the size of the opening of the collimator based on the number of pulses. Therefore, the operation timing of the data collection system and the opening/closing of the collimator may accurately be matched, and it is possible to reduce the portion of the region that is subjected to excessive radiation exposure, but it is not used for the reconstruction, while preventing data from being missing. Furthermore, it becomes possible to control the opening of the collimator with favorably accuracy in accordance with the scanning range, even during variable speed helical scanning. Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a diagram representing the hardware constitution of the X-ray CT apparatus according to the present embodiment. The X-ray CT apparatus comprises: a mounting base 102 constituted for collecting projection data regarding a patient P, a bed 103 for moving the patient P thereon, and an operation console 104 for performing entry and image display for operating the X-ray CT apparatus. The mounting base 102 has an X-ray tube 105, X-ray detector 106, collimator plate 107a, collimator drive part 107b, rotary frame 108, high voltage-generating part 109, rotary drive device 110, mounting base control part 111, and data collection part 112. The X-ray tube 105 and X-ray detector 106 are attached to the rotary frame 108. With this constitution, rotation of the rotary frame 108 by the rotary drive device 110 enables rotation around the patient P while the X-ray tube 105 and X-ray detector 106 are opposing each other. Herein, the X-ray tube 105 is equivalent to the “X-ray-generating part” in the present invention. The X-ray tube 105 generates X-rays in accordance with tube voltage that is supplied from the high voltage-generating part 109. The X-ray detector 106 is a two-dimensional array type detector (also referred to as a multi-slice type detector). An X-ray detecting element has, for example, a square-shaped detecting surface of 0.5 mm×0.5 mm. For example, 916 X-ray detecting elements are arranged in the channel direction and, for example, more than 64 rows are arranged in parallel along the slicing direction (direction of the rows of the detector). An X-ray diaphragm device is constituted of a collimator plate 107a and a collimator drive device 107b. The X-ray diaphragm device is for adjusting the irradiation range in the slicing direction of the X-rays to be irradiated at a patient. The collimator drive device 107b moves the collimator plate 107a to change the X-ray irradiation range in the slicing direction. In general, the data collection part 112, referred to as a DAS (data acquisition system), amplifies signals that are output from the detector 106 for each channel and converts the same to digital signals. The projection data (raw data) is supplied to the operation console 104 external to the mounting base. The mounting base control part 111 controls the high voltage-generating part 109, collimator drive device 107b, rotary drive device 110, data collection part 112, etc., based on the control signal from a console control part 113. The bed 103 comprises a top plate on which to place a patient and a top plate drive device for moving the top plate along the slicing direction. The center portion of the rotary frame 108 has an opening, and a patient P that has been placed on the top plate, is introduced into the opening. It should be noted that the direction parallel to the rotating center axis of the rotary frame 108 is defined as the Z-axial direction (slicing direction), and the plane perpendicularly crossing it in the Z-axial direction is defined as the X-axial direction and Y-axial direction. The operation console 104 comprises: a console control part 113, input device 114, preprocessing part 115, projection data storage part 116, reconstructing part 117, image storage part 118, image-processing part 119, and display device 120. The reconstructing part 117 uses projection data that has been stored in the projection data storage part 116 and reconstructs images of information regarding the live body of a patient. This reconstruction may be performed by methods: of fan-beam reconstruction in which the passage of X-rays is presumed to be parallel in the slicing direction; and of cone-beam reconstruction in which the X-ray irradiation angle (cone angle) in the slicing direction is taken into consideration. The image storage part 118 stores the reconstructed images. The image-processing part 119 generates a display image by performing various types of image processing on the image data that has been stored in the image storage part 118. Setting various types of setting conditions, regions of interest, or the like, in the event of generating a display image, is performed based on entry into the input device 114 by the operator. The display device 120 displays the image that has been generated by the image-processing part 119. Furthermore, the console control part 113 is configured to send a control signal to the mounting base control part 111 so that scanning such as helical scanning is performed based on entry by the operator. It should be noted that the operation console 104 may be constituted of a proprietary hardware, or the same function may also be realized by software using a computer. Next, the collimator control of the X-ray CT apparatus according to the present embodiment is described in detail with reference to FIG. 2. FIG. 2 is a block diagram representing the function of the X-ray CT apparatus according to the present invention. The bed 103 in FIG. 2 is equivalent to the “supporting part” in the present invention, the X-ray tube 105 to the “X-ray-generating part” in the present invention, and the data collection part 112 to the “X-ray-detector” in the present invention. The mounting base control part 111 is constituted of a timing adjustment part 1 and a scan control part 2. Herein, the timing adjustment part 1 sends signals for operating the collimator drive part 107 by synchronizing with the operation of the imaging part 3 and is equivalent to the “detector” in the present invention. The scan control part 2 is configured to send the same pulse signals to the imaging part 3 and the bed 103 so that the two are synchronized and operated. Furthermore, the collimator part 107b is constituted of a collimator drive part 107b and a collimator plate 107a. The collimator plate 107a is equivalent to the “collimator” in the present invention. Moreover, the collimator drive part 107b is equivalent to the “collimator control part” in the present invention. Herein, the mounting base control part 111, collimator drive part 107b, and image-constructing part 117 each comprise a CPU (Central Processing Unit). FIG. 3 is a figure for explaining X-ray irradiation of a patient by the X-ray CT apparatus according to the present invention and the corresponding process of operations of the opening of a collimator 003 (the collimator 003 is equivalent to the collimator plate 107a in FIG. 2). The collimator 003 in the present embodiment is constituted of movable blades on the left and right, and thus, the opening is semi-closed, and the blades are arranged so that one each on the left and right is independently movable. The irradiation field of X-rays is restricted by the movement of the blades. FIG. 3(b) is a drawing in which the state of a patient 004 on the bed 103 is viewed from above. The bed 103 moves in the direction of a direction of movement 007. In this respect, the bed 103 is moved in the direction of movement 007 for imaging, but for convenience, FIG. 3 is a figure in which the bed 103 is fixed, while the imaging part 3 is moved along with the passage of time. Each triangle 001 shows X-ray irradiation from an X-ray-generating source 002. FIG. 3 shows a state in which the X-ray-generating source 002 as well as the data collection part 112 (not illustrated in FIG. 3) have moved toward the right of the figure along with the movement of the patient 004 toward the left of the figure. Furthermore, the X-ray-generating source 002 as well as the data collection part 112 are rotating in vertically with respect to the body axis of the patient 004. Herein, the irradiation field of the X-ray irradiated from the X-ray-generating source 002 is restricted by the blades of the collimator 003. The irradiated X-ray is made incident to the patient 004 in the range of an irradiation range 006. Furthermore, the range from point 005a to point 005f represents a position along the body axis of the patient 004. Point 005a is the starting position of the X-ray irradiation; point 005b is the foremost position of an imaging region 010 that is required for reconstructing an image of a region of interest 009; point 005c is the foremost position of the region of interest 009; point 005d is the end position of the region of interest 009; point 005e is the end position of the imaging region 010; and point 005f is the end position of the X-ray irradiation. Furthermore, FIG. 3(a) shows the degree of opening (size of the irradiation field) of the collimator 003 corresponding to the position of movement of the X-ray-generating source 002 and the data collection part 112. For example, position 008, taken as a reference, represents the state in which the opening of the collimator 003 is semi-closed at the position. Herein, the degree of opening of the collimator 003 is controlled via movement of the blades of the opening of the collimator 003. Herein, the regions from point 005a to point 005b and from point 005e to 005f are regions where X-ray is irradiated on half of the surface of the detector. Furthermore, the region from point 005b to point 005c is a region where the irradiation field becomes wider as the opening of the collimator 003 gradually opens, and the region from point 005d to point 005e is a region where the irradiation field becomes narrower as the opening of the collimator 003 gradually closes. Operators like a doctor or an operation engineer (hereinafter simply referred to as “operator”) uses the operation console 104 and designates an image-generating range (or scanning range) on the scanogram. That is, the region of interest 009 from point 005c to point 005b shown in FIG. 3 is designated. The mounting base control part 111 automatically ascertains point 005a, point 005b, point 005e, and point 005f shown in FIG. 3 based on the entered reconstructing conditions such as the slicing thickness, and sends the position of each point to the scan control part 2. Herein, in the present embodiment, the engineer enters two points corresponding to the region of interest 009 to ascertain the position of each point, but there is no particular limit for this as long as the five distances corresponding to the interval of each of the points is discovered. For example, with this constitution, an engineer may enter all of the distances, and it is also possible to enter some of the distances so that the remaining distances are obtained from other conditions. The scan control part 2 converts each entered distance to: a sequential number of pulses NVc from the starting position of the X-ray irradiation (point 005a) to the end position of the X-ray irradiation (point 005f); number of pulses NVa from the starting position of the X-ray irradiation (point 005a) to the forefront of the imaging region 008 (point 005b); and number of pulses NVb from the forefront of an imaging region 010 (point 005b) to the forefront of the region of interest 009 (point 005c). Herein, number of pulses NVa and number of pulses NVb are sequential, and number of pulses NVa and number of pulses NVb are part of the sequential number of pulses NVc. Furthermore, as for the number of pulses corresponding to the distance, for example, if the cycle of one pulse is T and the speed of movement of the bed 103 is v, the distance that the bed 103 moved during one pulse is represented as vT, so the number of pulses corresponding to the distance L is calculated by L/vT. Next, the scan control part 2 starts to move the bed 103. Based on the speed of movement of the bed 103 and the distance from the start position of moving the bed 103 (not illustrated) to the start position of X-ray irradiation (point 005a) (hereinafter, referred to as “operation start distance), the scan control part 2 calculates the number of pulses corresponding to the operation starting distance (from the start of moving the bed 103 until the X-ray irradiation is started by the X-ray tube 105). Furthermore, the scan control part 2 generates a timing pulse for driving the imaging part 3 and sends, to the timing adjustment part 1, number of pulses NVc, number of pulses NVb, number of pulses NVa, the number of pulses corresponding to the operation start distance, and the timing pulse. In the present embodiment, number of pulses NVa is the number of pulses of the first segment and the number of pulses of the fifth division. Number of pulses NVb is the number of pulses of the second division and the number of pulses of the fourth division. Subtraction of the two folds of the number of pluses NVa and number of pulses NVb from number of pulses NVc is equivalent to the number of pulses of the third division. Herein, according to the present embodiment, the distance from point 005a to point 005b is the same as the distance from point 005e to 005f, so the number of pulses thereof is regarded as NVa. Moreover, the distance from point 005b to point 005c is the same as the distance from point 005d to point 005e, so the number of pulses thereof is regarded as NVb. If these distances differ, the different number of pulses may be adapted. Furthermore, the starting position of the X-ray irradiation (point 005a) to the end position of the X-ray irradiation (point 005f) is clear, so the number of pulses equivalent to the distance is regarded as the number of pulses NVc. But whichever distance is used for the number of pulses is not particularly limited as long as all five distances that have been entered beforehand are represented by the number of pulses to be calculated herein. As for the number of pulses, for example, number of pulses NVc may also be the number of pulses from point 005c to point 005d. The timing adjustment part 1 receives, from the scan control part 2, the number of pulses that corresponds to the operation start distance, counts the timing pulse, and sends, to the X-ray tube 105, a signal for initiating the X-ray irradiation (hereinafter simply referred to as “starting signal”) when the count reaches the number of pulses that corresponds to the operation starting distance. The position for sending the starting signal is point 005a. Moreover, the timing adjustment part 1 counts the timing pulse after the starting signal is sent at point 005a, sends a signal for starting detection to the data collection part 112 when the count reaches number of pulses NVa, and sends, to the collimator drive part 107b, a signal to initiate full opening of the opening of the collimator plate 107a. Furthermore, number of pulses NVb is sent to the collimator drive part 107b. The position for sending the signal to start detection and the signal to start full opening of the opening is point 005b. Subsequently, once the count of the timing pulse since the starting signal is sent reaches the addition of number of pulses NVa and number of pulses NVb, the timing adjustment part 1 sends a signal to the collimator drive part 107a for maintaining a fully opened state. Point 005c is the position for sending the signal for maintaining a fully opened state. Subsequently, once the count of the operation reference pulse since the starting signal is sent reaches a number that is obtained by subtracting number of pulses NVa and number of pulses NVb from number of pulses NVc, the timing adjustment part 1 sends, to the collimator drive part 107b, a signal to start closing of the opening of the collimator plate 107a. Moreover, number of pulses NVb is sent to the collimator drive part 107b. Point 005d is the position for sending the signal to start closing. Subsequently, once the count of the timing pulse since the starting signal is sent reaches a number that is obtained by subtracting number of pulses NVa from number of pulses NVc, the timing adjustment part 1 sends, to the collimator drive part 107b, a signal for maintaining a semi-open state. Furthermore, the timing adjustment part 1 sends a signal to an X-ray detection device 112 for detecting the end. Point 005e is the position for sending the signal to stop operation and the signal to end detection. Subsequently, once the count of the operation reference pulse since the starting signal is sent reaches number of pulses NVc, the timing adjustment part 1 sends, to the x-ray tube 105, a signal for ending the X-ray irradiation (hereinafter, simply referred to as “ending signal”). Point 005f is the position for sending the ending signal. The X-ray tube 105 receives the starting signal at point 005a and starts the irradiation of X-rays. Furthermore, the X-ray tube 105 receives the ending signal at point 005f and ends the irradiation of X-rays. The data collection part 112 receives the signal to start detection at point 005a and starts the detection of X-ray data. Furthermore, the data collection part 112 receives the signal to end detection at the 005f and ends the detection of X-ray data. The data collection part 112 repeats the detection of X-ray data after receiving the signal to start detection until the signal to end detection is received. Herein, the detection of X-ray data means that X-rays are read out in accordance with the timing pulse by the data collection parts 112 that have been arranged in a row. Herein, according to the present embodiment, the data collection system including the imaging part 3 and the control of the opening of the collimator plate 107a are synchronized by the timing pulse. The synchronization also includes a case in which the phase is the same but the cycle is in integral multiples, (e.g., the first pulse is an integral multiple of the second pulse, or the second pulse is an integral multiple of the first pulse), in addition to the case in which the pulse (first pulse) for controlling the detection of X-ray data and the pulse (second pulse) for controlling the opening of the collimator plate 107a are exactly in the same cycle and the same phase. Alternatively, the case is included in which the cycle is same and the phase is displaced for certain amount. Once movement of the bed 103 is started by the scan control part 2, the collimator drive part 107b moves the blade on the side of the direction of movement 007 of the bed 103 (cf. FIG. 3) to realize a semi-open state by closing half of the opening of the collimator plate 107a on the side of the direction of movement 007 of the bed 103. Thereby, as shown in FIG. 3, the blade is to be maintained in a state in which the opening of the collimator plate 107a is semi-closed on the side of the direction of movement 007 of the bed 103, during the period from point 005a (which is the starting position of the X-ray irradiation) to point 005b. After receiving the signal to start full opening from the timing adjustment part 1, the collimator drive part 107b starts moving the blade on the side of the direction of movement 007 of the bed 103 (cf. FIG. 3) to fully open the opening of the collimator plate 107a. Then, the collimator drive part 107b receives number of pulses NVb, calculates the speed of the blade so as to be fully opened after the duration of number of pulses NVb, and moves the blade at that speed. Thereby, the movement of the blade starts from point 005b in FIG. 3, and the opening reaches a fully open state at point 005c. Next, the collimator drive part 107b receives the signal from the timing adjustment part 1 for maintaining a fully open state and maintains the blade in a state in which the opening of the collimator plate 107a is fully open during the period from point 005c to point 005d. Next, the collimator drive part 107b receives the signal from the timing adjustment part 1 to start closing and starts moving the blade on the side that is opposite the direction of movement 007 of the bed 103 (cf. FIG. 3), because the side opposite to the direction of movement 007 of the bed 103 of the opening of the collimator plate 107a is semi-closed at point 005d. Then, the collimator drive part 107b receives number of pulses NVb, calculates the speed of movement of the blade so that the opening of the collimator plate 107a becomes semi-closed after a duration of number of pulses NVb, and moves the blade at the speed. Thereby, the movement of the blade from point 005d in FIG. 3 starts and the side of the direction of movement of the bed 103 of the opening of the collimator plate 107a comes to a semi-closed state at point 005e. Next, the collimator drive part 107b receives the signal for maintaining semi-open state from the timing adjustment part 1 and maintains the blade in a state in which the side is semi-closed that is opposite to the direction of movement 007 of the bed 103 of the opening of the collimator plate 107a during the period from point 005e to point 005f. In the starting portion of the scanning shown in FIG. 3, the projection data of the portion from 005a to 005b (a portion of 005e to the 005f in the ending portion) is not used for the reconstruction of images. Therefore, as described above, it becomes possible to reduce the radiation exposure of the patient by controlling the collimator plate 107a so as not to irradiate X-rays to the patient 004 in that portion. Next, with reference to FIG. 4, data collection by X-ray irradiation and the corresponding flow of operations of the opening of the collimator plate 107a according to the present embodiment will be described. FIG. 4 is a flowchart showing the operations of the X-ray CT apparatus according to the present embodiment. In the flowchart, the left side divided by the dotted lines is primarily the flow of timing control, the center thereof divided by the dotted lines is the flow of operations of the collimator plate 107a, and the right side divided by the dotted lines is a flowchart showing the flow of operations of the X-ray tube 105 and the data collection part 112. Step S001: An engineer enters information such as information regarding positions, direction of movement 007 of the bed 103, irradiation range 006, and the like, from the operation console 104. Step S002: The scan control part 2 receives the information from the operation console 104, starts moving the bed 103, generates a timing pulse, and further obtains, from information of each position and the timing pulse, number of pulses NVa, number of pulses NVb, number of pulses NVc, and the number of pulses corresponding to the entrance length. Step S003: The collimator drive part 107b moves the blade so that the side of the direction of movement 007 of the bed 103 of the opening of the collimator plate 107a comes to a semi-closed state. Step S004: The timing adjustment part 1 receives, from the scan control part 2, number of pulses NVa, number of pulses NVb, number of pulses NVc, the number of pulses corresponding to the entrance length, and the timing pulse. Step S005: The timing adjustment part 1 counts the timing pulse. Hereinafter, the timing adjustment part 1 continues to count the timing pulse until the end. Step S006: The timing adjustment part 1 determines whether or not the count of the timing pulse has reached the number of pulses that corresponds to the entrance length. If not reached, the counting of the timing pulse is repeated, and if reached, the timing adjustment part 1 sends a starting signal to the X-ray generating part 105 and proceeds to Step S008. Step S007: On receipt of the starting signal from the timing adjustment part 1, the X-ray-irradiating part 105 starts X-ray irradiation, and the data collection part 112 starts detecting X-ray data. Thereafter, the data collection part 112 repeats the detection of the X-ray data until a signal to end detection is received from the timing adjustment part 1 in step S017. Step S008: The timing adjustment part 1 determines whether or not the count of the timing pulse has reached number of pulses NVa. If not reached, the counting of the timing pulse is repeated, and if reached, the timing adjustment part 1 sends a signal to start detection to the data collection part 112, sends a signal to start full opening for the collimator plate 107a to the collimator drive part 107b, and proceeds to step S010. Step S009: The collimator drive part 107b receives the signal to start full opening from the timing adjustment part 1, and starts opening the blade on the side of the direction of movement 007 of the bed 103 at the opening of the collimator plate 107a. Step S010: The timing adjustment part 1 determines whether or not the count of the timing pulse has reached number of pulses NVb. If not reached, the counting of the timing pulse is repeated, and if reached, the timing adjustment part 1 sends a signal of operation stop to the collimator drive part 107b and proceeds to step S012. Step S011: The collimator drive part 107b receives a signal of maintaining full opening from the timing adjustment part 1 and maintains the blade in a state in which the opening of the collimator plate 107a is fully open. Step S012: The timing adjustment part 1 determines whether the count of the timing pulse has reached the number of pulses that is obtained by subtracting number of pulses NVa and number of pulses NVb from number of pulses NVc. If not reached, the counting of the timing pulse is repeated, and if reached, the timing adjustment part 1 sends, to the collimator drive part 107b, a signal to start closing for the opening of the collimator plate 107a, and proceeds to step S014. Step S013: The collimator drive part 107b receives the signal to start closing from the timing adjustment part 1 and starts closing the blade that is on the opposite side to the direction of movement 007 of the bed 103 at the opening of the collimator plate 107a. Step S014: The timing adjustment part 1 determines whether the count of the timing pulse has reached the number of pulses that is obtained by subtracting number of pulses NVa from number of pulses NVc. If not reached, the counting of the timing pulse is repeated, if reached, the timing adjustment part 1 sends a signal of operation stop to the collimator drive part 107b, sends a signal to end detection to the data collection part 112, and proceeds to step S016. Step S015: The collimator drive part 107b receives a signal of maintaining semi-opening from the timing adjustment part 1 and maintains the blade in a state in which the opposite side to the direction of movement 007 of the bed 103 of the opening of the collimator plate 107a is semi-closed. Step S016: The timing adjustment part 1 determines whether or not the count of the timing pulse has reaches number of pulses NVc. If not reached, the counting of the timing pulse is repeated, and if reached, an ending signal is sent to the X-ray tube 105. Step S017: The X-ray tube 105 receives the ending signal from the timing adjustment part 1 and ends the X-ray irradiation. The data collection part 112 receives a signal to end detection from the timing adjustment part 1 and ends detecting the x-ray data. As described above, unlike the conventional control of the degree of opening of the collimator plate 107a which was being conducted, e.g. based on the position on the body axis of the X-ray-generating part with respect to a patient, as for the control of the opening of the collimator plate 107a according to the present embodiment, the control is conducted by synchronizing with the pulse of a signal for driving the data collection system including the imaging part 3 using a starting signal. Thereby, it becomes possible to quantitatively control the degree of opening of the collimator plate 107a (size of the irradiation field), and unnecessary radiation exposure with respect to the patient may be reduced. Furthermore, in recent years, among technologies for capturing X-ray CT images by returning to a region of interest, there has been technology for imaging while accelerating/decelerating within the region of interest to maintain the continuity of images (such technology is sometimes referred to as “shuttle helical”). In the case of shuttle helical imaging, if a collimator plate is simply controlled based on the generated timing pulse as in the past, because the control for the accelerated/decelerated portion becomes complicated, there is a risk of deterioration of the repeatability of the operation of the collimator plate with respect to the operation of a mounting base. On the contrary to this, in the X-ray CT apparatus according to the present embodiment, because even in the event of imaging by shuttle helical, the collimator plate is controlled by the position of the bed, the control becomes easier, thus, making it possible to enhance the repeatability of the operation of the collimator plate for the operation in objective. The X-ray CT apparatus according to the present embodiment is configured so as to issue a warning, in the X-ray CT apparatus according to the first embodiment, in the case when the synchronization of the operation of the bed 103 and the operation of the control of the data collection system including the imaging part 3 as well as the collimator plate 107a becomes insufficient. Hereinafter, the determination is described regarding whether the operation of the bed 103 and the operation of the control of the data collection system including the imaging part 3 as well as the collimator plate 107a are synchronized insufficiently or not, and the warning issue thereof is also described. As shown by the dotted line in FIG. 2, in addition to the X-ray CT apparatus in the first embodiment, the X-ray CT apparatus according to the present embodiment further comprises an encoder pulse-generating part 103a that is attached to the bed 103 and a pulse-comparing part 4. The bed 103 is moved by the pulse signal that is sent by the scan control part 2. Herein, because the pulse signal is the same pulse as the timing pulse for driving the imaging part 3 or the collimator plate 107a, the operation of the control of the data collection system including the imaging part 3 as well as the collimator plate 107a and the operation of the bed 103 are supposed to be synchronized. However, due to the load of the motor for driving the bed 103, etc., in reality, there is a risk that the operation of the bed 103 will not be completely synchronized with the pulse signal that is being sent. Therefore, the encoder pulse-generating part 103a is attached to the bed 103 and the encoder pulse-generating part 103a generates a pulse in accordance with the actual moved distance of the bed 103 (hereinafter, referred to as “support base encoder pulse”). The pulse-comparing part 4 receives an encoder pulse and a timing pulse. The pulse-comparing part 4 divides the frequency of the timing pulse for the timing pulse so as to have the same clock as the encoder pulse. Herein, the frequency of the timing pulse is divided in order to make the control simpler, but it is also possible to adjust the clock by multiplying the encoder pulse. By comparing the timing pulse and the encoder pulse in which the clocks have been adjusted, a warning is issued in the case of having a difference that exceeds a permissible preliminarily set value for the pulse cycle. The notice of the warning is issued, e.g., by displaying it in a display part (not illustrated) or by sounding an alert. Furthermore, according to the present embodiment, it is also possible to adjust the timing of the control of the collimator plate 107a by the pulse that is generated by the encoder pulse-generating part 103a. Herein, the control of the collimator plate 107a at the time of accelerating the speed of movement of the bed 103 by using either the support base encoder pulse or the timing pulse generated by the pulse generator, is described with reference to FIG. 5. FIG. 5 is a synchronous circuit for controlling a collimator at the time of accelerating the speed of movement of the support base. A CPU 606 constituting a mounting base control part 111 receives collection conditions 605 from the operation console 104. The CPU 606 instructs a pulse generator 602 to generate a timing pulse. Furthermore, a frequency divider/multiplier circuit 601 receives a support base encoder pulse from the encoder pulse-generating part 103a. The CPU 606 instructs the frequency divider/multiplier circuit 601 to adjust the cycle to be the same as the timing pulse that is generated by the pulse generator 602. The pulse generator 602 sends the generated timing pulse to a pulse selector 607. On receipt of the instruction, the frequency divider/multiplier circuit 601 divides or multiples the frequency of the support base encoder pulse to adjust the cycle with the timing pulse that is generated by the pulse generator. Furthermore, the frequency divider/multiplier circuit 601 sends, to the pulse selector 607, the support base encoder pulse that was subjected to the frequency division/multiplication. After receiving a selection instruction of the pulse to be used for the adjustment of the drive of the collimator plate 107a on receipt of the instruction from the CPU 606, the pulse selector 607 sends, to the timing adjustment part 1, either the support base encoder pulse or the timing pulse generated by the pulse generator 602. As described above, if there is a difference that exceeds a permissible value in the pulse cycle between the timing pulse generated by a pulse generator and the support base encoder pulse, the synchronization of the operation of the imaging part 3 as well as the collimator plate 107a and the operation of the bed 103 is insufficient. If the synchronization of the operation is insufficient, the reliability of an image that has been imaged then becomes dubious. Therefore, by issuing a warning in the case of a difference that exceeds a permissible value in the pulse cycle between the timing pulse generated by a pulse generator and a support base encoder pulse, re-imaging is possible for diagnosis without using an image with low reliability. Thereby, it becomes possible to eliminate diagnoses with X-ray images having low reliability, and the risk of misdiagnosis may thus be reduced. As the pulse used for driving the motor of the collimator, a pulse with the frequency divided (or multiplied) may be entered from the support base encoder pulse 604 to the driver circuit, thereby enabling the blade of the collimator to move accordingly even if the bed cannot move at a constant speed because of load variation. Further, when moving the collimator during accelerating/decelerating the bed, a pulse with the frequency divided (or multiplied) may be entered from the support base encoder pulse 604 to the motor driver, thereby enabling opening/closing with the blade accelerated/decelerated. Moreover, in the first and second embodiments, the control of the collimator plate 107a located on the bed 103 in the X-ray CT apparatus according to the present invention has been described. However, the X-ray CT apparatus according to the present invention may also be constituted so as to allow a selection of a mode in which an active collimator is used and a mode in which the active collimator is not used by changing the control mode of the collimator plate 107a. Operations are described of the X-ray CT apparatus in a case of having a constitution that allows the mode selection. In the case of performing helical scanning by using an active collimator, the operator selects a mode in which the active collimator is used as a control mode for the collimator plate 107a. In this case, the instruction to select a mode in which the active collimator is used is entered into the CPU 606 as a collection condition 605 as shown in FIG. 5. The CPU 606 sends, to the pulse selector 607 or the collimator drive part 107b, the instruction of the active collimator control according to the position of the bed 103 that has been stated in the first and second embodiments. On the other hand, in the case of helical scanning without using an active collimator, conventional scanning (a method of imaging by rotating the mounting base 102 only one rotation), or dynamic scanning (a method of imaging the same position by rotating the mounting base 102 at the same position), the operator selects, as a control mode for the collimator plate 107a, a mode in which the active collimator is not used. In this case, an instruction to select a mode in which the active collimator is not used is entered into the CPU 606 as a collection condition 605, and the CPU 606 sends, to the pulse selector 607 or the collimator drive part 107b, the instruction for control that is not according to the position of the bed 103 (the active collimator is not used). As described above, with a constitution that allows the selection of a mode in which an active collimator is used and a mode in which the active collimator is not used, it also becomes possible to deal with a scanning mode other than helical scanning in which an active collimator is used such as in conventional scanning.
	summary
	summary
	abstract	In an analyzing chamber for a mass analyzer, a body of the analyzing chamber may include an inlet through which an ion beam enters and an outlet through which the ion beam leaves. A shielding section may be installed on a sidewall. The shielding section may prevent the ion beam traveling along a path in the body from causing damage to the sidewall of the body. A detector may be interposed between the sidewall of the body and the shielding section. The detector may detect an ion beam leaking through the shielding section. Accordingly, damage to the sidewall of the body may be sufficiently reduced and/or prevented.
045227829	abstract	Fuel assembly for a nuclear reactor comprising at least two guide tubes (6) made of a material metallurgically compatible with the material of the spacer grids (9, 10). The guide tubes (6) are fixed rigidly to the plates (8) and to the spacer grids (9, 10). The other guide tubes (7), made of a material with a low neutron capture cross section, are secured to only one of the end plates and are movably engaged in the cells of the spacer grids (9, 10) so as to be able to move with respect to these under the effect of expansion.. The invention is particularly applicable to pressurized water nuclear reactors.
058964304	claims	1. A method in fuel handling for lifting fuel assemblies and/or control rods out of/into a reactor vessel in a nuclear reactor, wherein the reactor vessel comprises a reactor core with a plurality of fuel assemblies and control rods and wherein a fuel pool is arranged adjacent the reactor vessel, said method comprising the steps of: arranging a cassette comprising a plurality of storage positions for fuel assemblies and/or control rods adjacent the reactor core; lifting fuel assemblies and/or control rods out of the reactor core and arranging in the cassette; transporting the cassette to the fuel pool for temporary storage and transporting the cassette back to the reactor vessel for reinsertion into the reactor core of the fuel assemblies and/or the control rods arranged in the cassette. 2. A method according to claim 1, further comprising loading the cassette with fuel assembles and/or control rods in the lateral direction. 3. A device used for lifting fuel assemblies and/or control rods out of/into a reactor vessel in a nuclear reactor, the reactor vessel comprising a reactor core with a plurality of fuel assemblies and control rods, and a fuel pool being arranged adjacent the reactor vessel, the device comprising a cassette with at least two substantially vertically arranged sleeve-formed spaces, each of the sleeve-formed spaces being provided with an opening for loading at least one or more fuel assemblies and/or control rods for transporting the cassette with the fuel assemblies and/or control rods between the reactor vessel and the fuel pool and for temporary storage of the cassette with the fuel assemblies and/or control rods in the fuel pool. 4. A device according to claim 3, wherein each of the sleeve-formed spaces is formed of walls of a neutron-absorbing material and a bottom part. 5. A device according to claim 3, comprising four, eight or twelve sleeve-formed spaces arranged in one or two rows. 6. A device according to claim 3, wherein each of the sleeve-formed spaces is designed for accommodating a fuel assembly or a control rod, or a core module with four fuel assemblies and a control rod arranged therebetween. 7. A device according to claim 3, wherein at least one of the sleeve-formed spaces comprises an opening provided in the vertical wall portion of the sleeve-formed space for unloading and loading, respectively, the fuel assemblies and/or the control rods in the lateral direction and wherein the opening extends substantially along the whole vertical extent of the sleeve-formed space. 8. A device according to claim 7, wherein the opening is provided with a port for sealing the sleeve-formed space during transportation and storage.
	claims	1. A kit for preparing TEM sample holders, the kit comprising:at least one TEM coupon;the TEM coupon having a TEM sample holder form; and,a press, for joining a probe-tip point to the TEM coupon and for cutting a TEM sample holder from the coupon. 2. The kit of claim 1, where the coupon further comprises:a sheet of material; and,one or more paths through the sheet from the TEM sample holder form to the edge of the sheet. 3. The kit of claim 2, where the sheet comprises a metal, selected from the group consisting of copper, molybdenum, gold, silver, nickel and beryllium. 4. The kit of claim 2 where the sheet has surface corrugations. 5. The kit of claim 1 where the coupon further comprises alignment holes, for aligning the coupon in a press. 6. The kit of claim 1 further comprising:at least one hole in the coupon defining the outer boundary of a TEM sample holder form;the hole having a mouth;the mouth of the hole defining a land of material;the land connecting the TEM sample holder form to the sheet; and,at least one path through the sheet connecting the hole to the edge of the sheet. 7. The kit of claim 6, where the hole has a C-shape. 8. The kit of claim 6, where the TEM sample holder has a rectangular shape. 9. The kit of claim 1, where the press further comprises:an outer die;an inner die situated inside the outer die;a former rod opposing the inner and outer dies;a shear punch situated coaxially with the former rod;a hold-down spring biasing the former rod toward the inner die; and,an actuator for driving the shear punch toward the inner and outer dies. 10. The kit of claim 9, further comprising:teeth in the former rod for flowing the TEM sample holder material around the probe-tip point. 11. The kit of claim 10 where the press further comprises:an adjustment for setting the force of the hold-down spring against the former rod, so that the former rod applies sufficient force to ensure that the probe-tip point is embedded in the TEM sample holder form. 12. The kit of claim 9 where the actuator is pneumatic. 13. The kit of claim 10 further comprising:at least one hole in the coupon defining the outer boundary of a TEM sample holder form;the hole having a mouth;the mouth of the hole defining a land of material;the land connecting the TEM sample holder form to the sheet; and,at least one path through the sheet connecting the hole to the edge of the sheet; and,where the shear punch is sized to sever the land and cut an opening in the TEM sample holder form; thereby forming a TEM sample holder with one or more probe-tip points embedded therein. 14. The kit of claim 13 where the severance of the land and the cutting of the opening are simultaneous. 15. A kit for preparing TEM sample holders, the kit comprising:at least one TEM coupon; where the TEM coupon further comprises:a TEM sample holder form; and,one or more paths through the coupon from the TEM sample holder form to the edge of the coupon;at least one hole in the coupon defining the outer boundary of the TEM sample holder form;the hole having a mouth;the mouth of the hole defining a land of material;the land connecting the TEM sample holder form to the coupon;at least one probe tip, the probe tip having a probe-tip point; and,a press, where the press further comprises:an outer die;an inner die situated inside the outer die;a former rod opposing the inner and outer dies;a shear punch situated coaxially with the former rod;a hold-down spring biasing the former rod toward the inner die; and,an actuator for driving the shear punch toward the inner and outer dies;where the shear punch is sized to sever the land and cut an opening in the TEM sample holder form; thereby forming a TEM sample holder with one or more probe-tip points embedded therein.
047120142	claims	1. A radiation lamp unit, comprising: an elongate housing (1), a plurality of highly-polished concave reflectors (3) mounted in the housing, an equal plurality of light-orange radiation lamps (4) individually disposed at focal point areas of the reflectors, and two UV lamp units (9, 10) secured to mounting bases (7, 8) spaced apart from each other and symmetrically disposed about a center axis of the housing. 2. A lamp unit in accordance with claim 1, wherein the UV lamp units are individually disposed in front of the focal point areas of light-orange radiation lamps (4), and are shielded from the latter by mirrors reflective on both sides. 3. A lamp unit in accordance with claims 1 or 2, wherein five concave reflectors (3) are provided in a row, each with a light-orange radiation lamp, and the two UV lamp units are individually arranged in front of the second and fourth reflectors. 4. A lamp unit in accordance with claim 3, wherein each UV lamp unit contains a UV-B lamp and a UV-C lamp supported by a common base (7, 8). 5. A lamp unit in accordance with claim 4, further comprising means for swivelling the base (7, 8) of each UV lamp unit through a limited angular range in a longitudinal direction of the housing. 6. A lamp unit in accordance with claim 5, wherein the swivelling means comprises: (a) a drive motor (12), (b) a drive disk (13) rotatably driven by the motor, (c) a continuous circular groove (15) defined in the base of each UV lamp unit, (d) two adjustably tensioned clamping rings (16) individually disposed in each groove, extending therearound, and defining slip couplings with associated lamp unit bases, and (e) a pair of drive arms (14) individually connected at their one ends to the clamping rings and eccentrially connected at their other ends to the drive disk such that, upon startup with the two UV lamp units in unequal rotational positions, one of the clamping rings will slip until equal rotational positions are established. (a) two drive motors (12a, 12b), (b) two drive disks (13a, 13b) individually rotatably driven by the motors, (c) a continuous circular groove (15) defined in the base of each UV lamp unit, (d) two adjustably tensioned clamping rings (16) individually disposed in each groove, extending therearound, and defining slip couplings with associated lamp unit bases, and (e) a pair of drive arms (14) individually connected at their one ends to the clamping rings and individually eccentrically connected at their other ends to the drive disks such that, upon startup with the two UV lamp units in unequal rotational positions, one of the clamping rings will slip until equal rotational positions are established. 7. A lamp unit in accordance with claim 5, wherein the swivelling means comprises:
	abstract	A system, method and program product for determining parallelism of an ion beam using a refraction method, are disclosed. One embodiment includes determining a first test position of the ion beam while not exposing the ion beam to an acceleration/deceleration electrical field, determining a second test position of the ion beam while exposing the ion beam to an acceleration/deceleration electrical field, and determining the parallelism of the ion beam based on the first test position and the second test position. The acceleration/deceleration electrical field acts to refract the ion beam between the two positions when the beam is not parallel, hence magnifying any non-parallelism. The amount of refraction, or lateral shift, can be used to determine the amount of non-parallelism of the ion beam. An ion implanter system and adjustments of the ion implanter system based on the parallelism determination are also disclosed.
	description	The present application is a continuation pursuant to 35 U.S.C. §120 of U.S. patent application Ser. No. 13/642,224 filed Sep. 24, 2013 which claims priority under 35 U.S.C. §119(e) to U.S. Patent Application Ser. No. 61/325,688, filed Apr. 19, 2010, which is hereby incorporated by reference in its entirety. This invention was made with Government support under Grant No. DE-AC02-05CH11231 awarded by the United States Department of Energy. The Government has certain rights in the invention. The present invention relates to luminescent materials and, in particular, to scintillators and applications thereof. Scintillators are materials that absorb high-energy radiation (e.g. gamma rays, x-rays, high-energy particles) and emit light (low-energy photons) in response. To the extent that the number of emitted photons is proportional to the total energy of the stopped radiation, a scintillator provides the useful function of identifying the total energy of any radiation that is stopped. As the nucleus of every element (and each isotope of each element) emits a characteristic fingerprint of gamma-ray energies when suitably excited (usually by neutron activation), scintillator responses to such emissions provide value in security screening of shipping and trucking containers and baggage, where chemical elements and isotopes of elements can be identified (and imaged using arrays of segmented scintillators) without opening the container. This applies both to radioactive elements (nuclear nonproliferation and screening) and to ordinary non-radioactive elements via neutron activation of gamma emission. Scintillators are also widely used in medical imaging and diagnostics as well as oil-well logging, where energy resolution can often also be of value. Desirable energy resolution requires sufficient proportionality of light yield to ray energy. Non-proportionality of scintillator photonic emission to the stopped radiation can degrade resolution and produce significant inaccuracies in determining the total energy of the radiation received. It is generally accepted that non-proportionality in scintillators is associated with quenching (non-radiative electron-hole recombination) in parts of the particle/ray track wherein ionization density is high, coupled with the characteristic variability of dE/dx from beginning to end of an electron track. Prior scintillators, such as CsI:Tl as well as others, comprise crystalline materials doped with impurities. The impurities serve as radiative recombination centers for electron-hole pairs generated from the absorption of the high energy radiation. Impurities are doped throughout the host crystal to ensure efficient photonic output from the scintillator upon radiation absorption. As a result, an electron-hole pair does not have to travel far before contacting an impurity for radiative recombination. This limitation of carrier mobilities reduces the probability of linear (i.e. trap dominated) non-radiative electron-hole recombination, thereby maximizing the light output of the scintillator. Maximization of light output by this route, however, has associated costs as the limitation of carrier mobility by high dopant levels throughout the host crystal can result in or exacerbate non-proportional response of the scintillator to the absorbed radiation. In view of the foregoing, scintillators are described herein which, in some embodiments, may address one or more disadvantages of previous scintillators. In some embodiments, a scintillator described herein comprises at least one radiation absorption or stopping region and at least one spatially discrete radiative exciton recombination region for receiving excitons from the at least one radiation absorption region. In some embodiments, a scintillator described herein comprises a plurality of radiation absorption regions and a plurality of spatially discrete radiative exciton recombination regions for receiving excitons from the plurality of radiation absorption regions. In some embodiments, a radiative exciton recombination region operable to receive excitons from a radiation absorption region comprises one or more scintillation activators. In some embodiments of a scintillator described herein, a radiation absorption region comprises less scintillation activator than one or more spatially discrete radiative exciton recombination regions. In some embodiments, a radiation absorption region is free or substantially free of scintillation activator. Exciton(s), as used herein, refers to bound electron-hole pairs as well as free or independent holes and electrons. Additionally, radiation includes electromagnetic radiation, particle radiation, photons, electrons, heavy charged particles, neutrons or combinations thereof. In some embodiments, radiation comprises high energy radiation such as gamma rays, x-rays, other high energy particles or combinations thereof. In some embodiments, a scintillator described herein comprises a single-crystalline material. In some embodiments, a scintillator described herein comprises a polycrystalline material. In some embodiments, a scintillator described herein is optically transparent or substantially optically transparent. Moreover, in some embodiments, a radiation absorption region of a scintillator described herein comprises one or more metal halides. In embodiments described herein, a metal halide comprises an alkali halide, an alkaline earth halide or a transition metal halide or mixtures thereof. In some embodiments, a metal halide absorption region of a scintillator comprises less scintillation activator than one or more spatially discrete radiative exciton recombination regions. In some embodiments, a metal halide absorption region of a scintillator is free or substantially free of scintillation activator. In some embodiments, a radiation absorption region of a scintillator described herein comprises a semiconductor material including, but not limited to, II/VI semiconductors and/or III/V semiconductors. In some embodiments, a spatially discrete radiative exciton recombination region comprises a metal halide having incorporated therein one or more scintillation activators. In some embodiments, scintillation activators comprise transition metals, lanthanide series elements or actinide series elements or combinations thereof. In some embodiments, one or more scintillation activators can comprise dopants, impurities or intrinsic defects within the crystalline structure of the metal halide. In some embodiments, a spatially discrete radiative exciton recombination region comprises a semiconductor material having a bandgap less than the bandgap of a semiconductor material of the radiation absorption region. In some embodiments, a semiconductor material of a spatially discrete radiative recombination region comprises a II/VI semiconductor or a III/V semiconductor. In another aspect, crystalline particles or grains are provided. In some embodiments, crystalline particles or grains can be sintered to provide a scintillator having a construction described herein. A crystalline particle or grain, in some embodiments, comprises a radiation absorption region comprising at least one metal halide and a spatially discrete radiative exciton recombination region. In some embodiments, the spatially discrete radiative exciton recombination region comprises a metal halide comprising one or more scintillation activators. In some embodiments, a metal halide absorption region comprises less scintillation activator than one or more spatially discrete radiative exciton recombination regions. In some embodiments, a metal halide absorption region is free or substantially free of scintillation activator. In other embodiments, a crystalline particle or grain comprises at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region, the particle having a size ranging from about 20 nm to about 1 μm. In some embodiments, the at least one radiation absorption region of the crystalline particle comprises a metal halide free or substantially free of a scintillation activator, and the at least one radiative exciton recombination region comprises a metal halide comprising one or more scintillation activators. In some embodiments, the at least one radiation absorption region comprises a first semiconductor having a first bandgap, and the at least one radiative exciton recombination region comprises a second semiconductor having a second bandgap. In some embodiments, the second bandgap is smaller than the first bandgap. In another embodiment, a scintillation detector or counter is described herein. In some embodiments, a scintillation detector or counter comprises a scintillator and an electromagnetic radiation sensor, wherein the scintillator comprises any construction described herein. In some embodiments, for example, a scintillator of a scintillation detector has a construction comprising at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region comprising a scintillation activator, wherein excitons are received from the at least one radiation absorption region. In another aspect, methods of making scintillators are described herein. In some embodiments, a method of making a scintillator comprises providing a radiation absorption region comprising a first material having a first bandgap and locally modulating the first bandgap to trap excitons in a spatially discrete radiative exciton recombination region, wherein locally modulating the first bandgap comprises providing the radiative exciton recombination region in electrical communication with the radiation absorption region. In some embodiments, the first material comprises a metal halide and the second material comprises a metal halide having incorporated therein one or more scintillation activators. In some embodiments, the metal halide first material is free or substantially free of scintillation activator. A method of producing a scintillator, in some embodiments, comprises providing a radiation absorption region comprising a metal halide and providing a spatially discrete radiative exciton recombination region in electrical communication with the radiation absorption region, the radiative exciton recombination region comprising a metal halide comprising one or more scintillation activators. In some embodiments, the metal halide radiation absorption region comprises less scintillation activator than the spatially discrete radiative exciton recombination region. In some embodiments, the metal halide radiation absorption region is free or substantially free of scintillation activator. In some embodiments, a method of producing a scintillator comprises providing a mixture of metal halide particles and metal halide particles comprising one or more scintillation activators and sintering the particles of the mixture to provide a polycrystalline scintillator. In some embodiments, the polycrystalline scintillator comprises a radiation absorption region formed from sintered metal halide particles free or substantially free of scintillation activator. Moreover, in some embodiments, the polycrystalline scintillator comprises spatially discrete radiative exciton recombination regions formed from the metal halide particles comprising one or more scintillation activators. In some embodiments, for example, metal halide particles comprising one or more scintillation activators are dispersed throughout a sintered matrix of metal halide particles free or substantially free of scintillation activator to provide spatially discrete radiative exciton recombination regions. In some embodiments, a method of producing a scintillator comprises providing crystalline particles comprising a radiation absorption region and a spatially discrete radiative recombination region and sintering the crystalline particles to provide a polycrystalline scintillator. In some embodiments, the radiation absorption region of a crystalline particle comprises a metal halide free or substantially free of scintillation activator, and the spatially discrete radiative recombination region comprises a metal halide comprising one or more scintillation activators. In some embodiments, the radiation absorption region of a crystalline particle comprises a first semiconductor having a first bandgap, and the spatially discrete radiative recombination region comprises a second semiconductor having a second bandgap. In some embodiments, the second bandgap is less than the first bandgap. In another aspect, methods of converting radiation of a first energy into radiation of a second energy are described herein. In one embodiment, a method of converting radiation of a first energy into radiation of a second energy comprises providing a scintillator comprising at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region, absorbing the radiation of the first energy in the radiation absorption region to generate excitons and recombining at least some of the excitons in the spatially discrete radiative exciton recombination region to emit radiation of a second energy. In some embodiments, the radiation of the first energy has a wavelength less than the wavelength of the radiation of the second energy. As described herein, in some embodiments, the radiation absorption region of the scintillator comprises a metal halide, and the spatially discrete radiative exciton recombination region comprises a metal halide comprising one or more scintillation activators. In some embodiments, the metal halide radiation absorption region comprises less scintillation activator than one or more spatially discrete radiative exciton recombination regions. In some embodiments, the metal halide radiation absorption region is free or substantially free of scintillation activator. In a further aspect, methods of reducing non-proportional response in a scintillator are described herein. In one embodiment, a method of reducing non-proportional response comprises providing a scintillator comprising at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region, absorbing radiation of a first energy in the radiation absorption region to generate excitons, transferring at least some of the excitons out of the radiation absorption region and into the spatially discrete radiative exciton recombination region and recombining the excitons to emit radiation of a second energy from the radiative exciton recombination region. In some embodiments, the radiation absorption region of the scintillator comprises a metal halide free or substantially free of a scintillation activator, and the spatially discrete radiative exciton recombination region comprises a metal halide comprising one or more scintillation activators. These and other embodiments are described in greater detail in the detailed description which follows. The present invention can be understood more readily by reference to the following detailed description and drawings and their previous and following descriptions. Elements, apparatus and methods of the present invention, however, are not limited to the specific embodiments presented in the detailed description and drawings. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention. As described herein, the present invention provides scintillators and methods of making and using the same. In some embodiments, a scintillator comprises at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region for receiving excitons from the at least one radiation absorption region. In some embodiments, a scintillator comprises a plurality of radiation absorption regions and a plurality of spatially discrete radiative exciton recombination regions for receiving excitons from the plurality of radiation absorption regions. In keeping radiation absorption and radiative exciton recombination regions spatially discrete, at least some, if not substantially all, excitons generated in one or more radiation absorption regions are transferred to one or more radiative exciton recombination regions for recombination and photonic emission. As described herein, the absence of scintillation activator in the radiation absorption material facilitates transfer of excitons out of the absorption material to the radiative exciton recombination material. A scintillator architecture wherein a radiation absorption or stopping region is spatially discrete from an exciton recombination region is a fundamental departure from prior scintillator constructions wherein radiation absorption and exciton recombination occur in the same region or material. Prior scintillator constructions, for example, utilize a radiation absorption material doped throughout with impurities (scintillation activators) to induce radiative exciton recombination throughout the absorption material. FIG. 1 illustrates spatially discrete radiation absorption and radiative exciton recombination regions of a scintillator according to one embodiment described herein. The scintillator (100) illustrated in FIG. 1 comprises a plurality of radiation absorption or stopping regions (102) and a plurality of spatially discrete radiative exciton recombination regions (104). In the embodiment illustrated in FIG. 1, the spatially discrete radiative exciton recombination regions (104) are disposed as continuous layers between layered radiation absorption regions (102). As provided herein, excitons generated in the radiation absorption layers (102) are transferred to the radiative exciton recombination regions (104) for recombination and light emission. FIG. 2 illustrates spatially discrete radiation absorption and radiative exciton recombination regions of a scintillator according to another embodiment described herein. The scintillator illustrated in FIG. 2 comprises a plurality of radiation absorption or stopping regions (202) and a plurality of spatially discrete radiative exciton recombination regions (204). The spatially discrete radiative exciton recombination regions (204) are disposed as discontinuous layers of island structures positioned between layers of radiation absorption regions (202). The use of island structures for spatially discrete radiative exciton recombination regions (204), in some embodiments, permits excitons produced in the radiation absorption regions (202) to be confined in 3-dimensions. FIG. 3 illustrates spatially discrete radiation absorption and radiative exciton recombination regions of a scintillator according to another embodiment described herein. The scintillator illustrated in FIG. 3 comprises a continuous radiation absorption or stopping region (302) and a plurality of spatially discrete radiative exciton recombination regions (304). The spatially discrete radiative exciton recombination regions (304) are island structures disposed in the radiation absorption region (302). In some embodiments, the radiative exciton recombination regions (304) are randomly ordered in and/or dispersed throughout the radiation absorption region (302). In some embodiments, the radiative exciton recombination regions (304) are patterned in the radiation absorption region. A spatially discrete radiative exciton recombination region, in some embodiments, occupies a fraction of the space or volume occupied by a radiation absorption region. In some embodiments of a layered scintillator, such as that illustrated in FIG. 1 or FIG. 2 herein, the thickness ratio of a radiation absorption region to a radiative exciton recombination region is at least 10. In some embodiments, the thickness ratio of a radiation absorption region to a radiative exciton recombination region is at least 100. The thickness ratio of a radiation absorption region to a radiative exciton recombination region, in some embodiments, is at least 1000. In some embodiments, the thickness ratio of a radiation absorption region to a radiative exciton recombination region is at least 10,000. In some embodiments, spatially discrete radiative exciton recombination regions of a scintillator described herein have a spacing equal or substantially equal to the diffusion range of the least mobile carriers generated in the radiation absorption region. In some embodiments, spatially discrete radiative exciton recombination regions have a spacing less than the diffusion range of the least mobile carriers generated in the radiation absorption region. In some embodiments, the least mobile carriers generated in the radiation absorption region are holes. In some embodiments, the least mobile charge carriers generated in the radiation absorption region are electrons. As carrier mobility and carrier diffusion range varies from material to material, spacing of spatially discrete radiative exciton recombination regions can vary depending on the identity of the material of the radiation absorption region. In some embodiments, diffusion range of a carrier of a radiation absorption region is determined according to:r=(Dt)0.5 wherein D is the diffusion coefficient of the material forming the radiation absorption region and wherein D is related to carrier mobility (μ) by:D=kTμ/e wherein k is the Boltzman constant, T is temperature (K) and e is electron charge. With the carrier diffusion range of a radiation absorption region being determined according to the foregoing, the appropriate spacing of spatially discrete exciton recombination regions for a scintillator described herein can be set. In some embodiments, a radiation absorption region comprises one or more materials having a carrier (hole or electron) mobility of at least about 1·10−4 cm2/V·s. In some embodiments, a material of a radiation absorption region has a carrier mobility of at least about 1·103 cm2/V·s or at least about 0.1 cm2/V·s. In some embodiments, a material of a radiation absorption region has a carrier mobility of at least 1 cm2/V·s. In some embodiments, a material of a radiation absorption region has a carrier mobility of at least 100 cm2/V·s or at least 1000 cm2/V·s. In some embodiments, a material of a radiation absorption region has a carrier mobility ranging from about 1·10−4 cm2/V·s to about 1000 cm2/V·s. In some embodiments, a material of a radiation absorption region has a carrier mobility ranging from about 1·10−2 cm2/V·s to about 100 cm2/V·s. In some embodiments, a material of a radiation absorption region has a carrier mobility ranging from about 0.1 cm2/V·s to about 70 cm2/V·s or from about 1 cm2/V·s to about 50 cm2/V·s. In some embodiments, a material of a radiation absorption region has a carrier mobility ranging from about 5 cm2/V·s to about 100 cm2/V·s or from about 10 cm2/V·s to about 75 cm2/V·s. In some embodiments, a material of a radiation absorption region has a carrier mobility ranging from about 20 cm2/V·s to about 80 cm2/V·s. I. Metal Halide Scintillator In some embodiments, a scintillator described herein comprises at one radiation absorption region comprising a metal halide and at least one spatially discrete radiative exciton recombination region comprising a metal halide comprising one or more scintillation activators. In some embodiments, the metal halide of the radiation absorption region is free or substantially free of scintillation activator, thereby promoting the transfer of one or more photo-generated charge carriers or excitons to a spatially discrete radiative exciton recombination region for recombination and photonic emission. A. Alkali Halide Scintillators In some embodiments, metal halides suitable for use as the radiation absorption region of a scintillator described herein comprise alkali halides. In some embodiments, for example, a radiation absorption region comprises cesium iodide (CsI), sodium iodide (NaI) or potassium iodide (KI). In some embodiments, an alkali halide radiation absorption region comprises less scintillation activator than an alkali halide spatially discrete radiative exciton recombination region described herein. In some embodiments, an alkali halide radiation absorption region is free or substantially free of scintillator. Moreover, in some embodiments, metal halides suitable for use in a spatially discrete radiative exciton recombination region comprise alkali halides comprising one or more scintillation activators associated therewith. In some embodiments, a spatially discrete radiative exciton recombination region comprises CsI, NaI or KI comprising one or more scintillation activators. In some embodiments, a spatially discrete radiative exciton recombination region and a radiation absorption region comprise the same alkali halide. In some embodiments, a spatially discrete radiative exciton recombination region and a radiation absorption region comprise different alkali halides. In some embodiments comprising different alkali halides, the alkali halide of the spatially discrete radiative exciton recombination region has a lower bandgap than the alkali halide of the radiation absorption region. In some embodiments wherein the alkali halide of the spatially discrete radiative exciton recombination region has a lower bandgap, the alkali halide of the recombination region does not comprise a scintillation activator. As described herein, scintillation activators can comprise transition metals, lanthanide series elements, actinide series elements, alkali metals, impurities, intrinsic crystalline defects or combinations thereof. In some embodiments, a scintillation activator of an alkali halide comprises thallium (Tl+) or sodium (Na+) An alkali halide spatially discrete radiative exciton recombination region can comprise any amount of scintillation activator not inconsistent with the objectives of the present invention. In some embodiments, an alkali halide spatially discrete radiative exciton recombination region comprises one or more scintillation activators in an amount of at least about 0.1 mol %. In some embodiments, an alkali halide spatially discrete radiative exciton recombination region comprises one or more scintillation activators in an amount of at least about 0.3 mol %. In some embodiments, an alkali halide spatially discrete radiative exciton recombination region comprises one or more scintillation activators in an amount of at least about 0.5 mol %. In some embodiments, an alkali halide spatially discrete radiative exciton recombination region comprises one or more scintillation activators in an amount ranging from about 0.1 mol % to about 1 mol %. In some embodiments, spatially discrete radiative exciton recombination regions are incorporated into a single crystal radiation absorption host of an alkali halide. In some embodiments described further herein, spatially discrete radiative exciton recombination regions are provided as alkali halide particles doped with one or more scintillation activators. The doped alkali halide particles are mixed with undoped alkali halide particles and co-sintered to provide a polycrystalline scintillator material, wherein the undoped alkali halide particles form one or more radiation absorption regions of the polycrystalline scintillator. Additionally, in some embodiments described further herein, alkali halide particles comprising at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region are provided and sintered resulting in a polycrystalline scintillator. Moreover, in some embodiments of a scintillator described herein having a radiation absorption region comprising an alkali halide, the spatially discrete radiative exciton recombination regions have a spacing of up to about 40 nm. In some embodiments, the spatially discrete radiative exciton combination regions have spacing of up to about 30 nm or 20 nm. In some embodiments, the spatially discrete radiative exciton recombination regions have a spacing ranging from about 1 nm to about 40 nm or from about 5 nm to about 30 nm. In some embodiments, the spatially discrete radiative exciton recombination regions have a spacing ranging from about 10 nm to about 20 nm. B. Alkaline Earth Halide Scintillators In some embodiments, metal halides suitable for use as the radiation absorption region of a scintillator described herein comprise alkaline earth halides. In some embodiments, for example, a radiation absorption region comprises strontium iodide (SrI2), barium iodide (BaI2) or barium bromide iodide (BaBrI). In some embodiments, an alkaline earth halide radiation absorption region comprises less scintillation activator than an alkaline earth halide spatially discrete radiative exciton recombination region described herein. In some embodiments, an alkaline earth halide radiation absorption region is free or substantially free of scintillator. Additionally, in some embodiments, metal halides suitable for use in a spatially discrete radiative exciton recombination region comprise alkaline earth halides comprising one or more scintillation activators associated therewith. In some embodiments, a spatially discrete radiative exciton recombination region comprises SrI2, BaI2 or BaBrI comprising one or more scintillation activators. In some embodiments, a spatially discrete radiative exciton recombination region and a radiation absorption region comprise the same alkaline earth halide. In some embodiments, a spatially discrete radiative exciton recombination region and a radiation absorption region comprise different alkaline earth halides. In some embodiments comprising different alkaline earth halides, the alkaline earth halide of the spatially discrete radiative exciton recombination region has a lower bandgap than the alkaline earth halide of the radiation absorption region. In some embodiments wherein the alkaline earth halide of the spatially discrete radiative exciton recombination region has a lower bandgap, the alkaline earth halide of the recombination region does not comprise a scintillation activator. As described herein, scintillation activators can comprise transition metals, lanthanide series elements, actinide series elements, alkali metals, impurities, intrinsic crystalline defects or combinations thereof. In some embodiments, a scintillation activator of an alkali earth halide comprises europium (Eu2+). An alkaline earth halide spatially discrete radiative exciton recombination region can comprise any amount of scintillation activator not inconsistent with the objectives of the present invention. In some embodiments, an alkaline earth halide spatially discrete radiative exciton recombination region comprises one or more scintillation activators in an amount of at least about 0.1 mol %. In some embodiments, an alkaline earth halide spatially discrete radiative exciton recombination region comprises one or more scintillation activators in an amount of at least about 0.3 mol %. In some embodiments, an alkaline earth halide spatially discrete radiative exciton recombination region comprises one or more scintillation activators in an amount of at least about 0.5 mol %. In some embodiments, an alkaline earth halide spatially discrete radiative exciton recombination region comprises one or more scintillation activators in an amount ranging from about 0.1 mol % to about 10 mol % or from about 1 mol % to about 10 mol %. In some embodiments, an alkaline earth halide spatially discrete radiative exciton recombination region comprises one or more scintillation activators in an amount ranging from about 2 mol % to about 8 mol % or from about 3 mol % to about 7 mol %. In some embodiments, spatially discrete radiative exciton recombination regions are incorporated into a single crystal radiation absorption host of an alkaline earth halide. In some embodiments described further herein, spatially discrete radiative exciton combination regions are provided as alkaline earth halide particles doped with one or more scintillation activators. The doped alkaline earth halide particles are mixed with undoped alkaline earth halide particles and co-sintered to provide a polycrystalline scintillator material, wherein the undoped alkaline earth halide particles form one or more radiation absorption regions of the polycrystalline scintillator. Additionally, in some embodiments described further herein, alkaline earth halide particles comprising at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region are provided and sintered resulting in a polycrystalline scintillator. In some embodiments of a scintillator described herein having a radiation absorption region comprising an alkaline earth halide, the spatially discrete radiative exciton recombination regions have a spacing of up to about 500 nm. In some embodiments, the spatially discrete radiative exciton recombination regions have spacing of up to about 200 nm or 100 nm. In some embodiments, the spatially discrete radiative exciton recombination regions have a spacing ranging from about 10 nm to about 500 nm or from about 50 nm to about 200 nm. In some embodiments, the spatially discrete radiative exciton recombination regions have a spacing ranging from about 5 nm to about 200 nm or from about 10 nm to about 100 nm. C. Transition Metal Halide Scintillators In some embodiments, metal halides suitable for use as the radiation absorption region of a scintillator described herein comprise transition metal halides. In some embodiments, for example, a radiation absorption region comprises a transition metal halide, wherein the metal is selected from the group consisting of metallic elements of Groups IB, IIB, IIIB, IIIA, IVA and VA of the Periodic Table. Groups of the Periodic Table described herein are identified according to the CAS designation. In some embodiments, for example, the radiation absorption region comprises a lanthanum halide, copper halide, zinc halide, cadmium halide, mercury halide, indium halide, thallium halide, tin halide or a lead halide. In some embodiments, the radiation absorption region comprises LaBr3, LaCl3, CuI, ZnI2, CdI2, HgI2, InI, TlI, SnI4 or PbI2. In some embodiments, a transition metal halide radiation absorption region comprises less scintillation activator than a transition metal halide spatially discrete radiative exciton recombination region described herein. In some embodiments, a transition metal halide radiation absorption region is free or substantially free of scintillator. In some embodiments, a spatially discrete radiative exciton recombination region and a radiation absorption region comprise the same transition metal halide. In some embodiments, a spatially discrete radiative exciton recombination region and a radiation absorption region comprise different transition metal halides. In some embodiments comprising different transition metal halides, the transition metal halide of the spatially discrete radiative exciton recombination region has a lower bandgap than the transition metal halide of the radiation absorption region. In some embodiments wherein the transition metal halide of the spatially discrete radiative exciton recombination region has a lower bandgap, the transition metal halide of the recombination region does not comprise a scintillation activator. In some embodiments, metal halides suitable for use in a spatially discrete radiative exciton recombination region comprise transition metal halides comprising one or more scintillation activators associated therewith. In some embodiments, for example, a spatially discrete radiative exciton recombination region comprises a transition metal halide comprising one or more scintillation activators, wherein the transition metal is selected from the group consisting of metallic elements of Groups IB, IIB, IIIB, IIIA, IVA and VA of the Periodic Table. In some embodiments, a spatially discrete radiative exciton recombination region comprises a lanthanum halide, copper halide, zinc halide, cadmium halide, mercury halide, indium halide, thallium halide, tin halide or a lead halide. In some embodiments, the radiation absorption region comprises LaBr3, LaCl3, CuI, ZnI2, CdI2, HgI2, InI, TlI, SnI4 or PbI2 comprising one or more scintillation activators. In some embodiments, a spatially discrete radiative exciton recombination region and a radiation absorption region comprise the same transition metal halide. In some embodiments, a spatially discrete radiative exciton recombination region and a radiation absorption region comprise different transition halides. As described herein, scintillation activators can comprise transition metals, lanthanide series elements, actinide series elements, alkali metals, impurities, intrinsic crystalline defects or combinations thereof. In some embodiments, a scintillation activator comprises cerium (Ce3+) for use in a lanthanum halide (e.g. LaBr3 or LaCl3) exciton recombination region. In some embodiments, cerium can be present in a spatially discrete lanthanum halide exciton recombination region in an amount ranging from about 0.1 mol % to about 30 mol %. In some embodiments, a scintillation activator comprises one or more impurities and/or defects in the crystalline structure of a transition metal halide of a spatially discrete recombination region. In some embodiments, spatially discrete radiative exciton recombination regions are incorporated into a single crystal radiation absorption host of a transition metal halide. In some embodiments described further herein, spatially discrete radiative exciton recombination regions are provided as transition metal halide particles having one or more scintillation activators. These transition metal halide particles are mixed with transition metal halide particles substantially free of scintillation activator and co-sintered to provide a polycrystalline scintillator material, wherein the activator free transition metal halide particles form one or more radiation absorption regions of the polycrystalline scintillator. Additionally, in some embodiments described further herein, transition metal halide particles comprising at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region are provided and sintered resulting in a polycrystalline scintillator. In some embodiments of a scintillator described herein having a radiation absorption region comprising a transition metal halide, the spatially discrete radiative exciton recombination regions have a spacing of up to about 5 μm. In some embodiments, the spatially discrete radiative exciton recombination regions have a spacing ranging from about 10 nm to about 5 μm or from about 100 nm to about 1 μm. In some embodiments, the spatially discrete radiative exciton recombination regions have a spacing ranging from about 250 nm to about 750 nm. II. Polycrystalline Scintillators In another aspect, polycrystalline scintillators are described herein. In some embodiments, a scintillator comprises a polycrystalline material, the polycrystalline material having at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region. In some embodiments, the polycrystalline material of a scintillator comprises a plurality of radiation absorption regions and/or a plurality of spatially discrete radiative exciton recombination regions. In some embodiments, the at least one radiation absorption region comprises one or more crystalline grains free or substantially free of scintillation activator. Moreover, in some embodiments, the at least one spatially discrete radiative exciton recombination region comprises one or more crystalline grains comprising a scintillation activator. In some embodiments, one or more spatially discrete radiative recombination regions of a polycrystalline scintillator comprises more scintillation activator than a radiation absorption region. In some embodiments, crystalline grains comprising scintillation activator are present in a polycrystalline scintillator described herein in an amount of up to about 30 weight percent. In some embodiments, crystalline grains comprising scintillation activator are present in an amount ranging from about 0.01 weight percent to about 30 weight percent or from about 0.1 weight percent to about 20 weight percent. In some embodiments, crystalline grains comprising scintillation activator are present in an amount ranging from about 1 weight percent to about 10 weight percent. In some embodiments wherein a radiation absorption region comprises crystalline grains and spatially discrete radiative exciton recombination regions comprise crystalline grains, the polycrystalline scintillator material is a sintered material. In some embodiments, for example, crystalline grains of a radiation absorption region form a sintered host matrix in which crystalline grains comprising scintillation activator are dispersed. The dispersed crystalline grains comprising scintillation activator provide the spatially discrete radiative exciton recombination regions. In some embodiments, a polycrystalline scintillator material described herein has a density of at least about 95% of theoretical density (i.e., the density of a single crystal). In some embodiments, a polycrystalline scintillator material described herein has a density of at least about 97%. In some embodiments, a polycrystalline scintillator described herein has a density of at least about 99%. In some embodiments, crystalline grains of a radiation absorption region and crystalline grains of spatially discrete radiative exciton recombination regions comprise one or more alkali halides as set forth in section IA hereinabove. In some embodiments, alkali halide crystalline grains of a radiation absorption region have an average size less than about 40 nm. In some embodiments, alkali halide crystalline grains of a radiation absorption region have an average size ranging from about 1 nm to about 40 nm or from about 10 nm to about 20 nm. In some embodiments, crystalline grains of a radiation absorption region and crystalline grains of spatially discrete radiative exciton recombination regions comprise one or more alkaline earth halides as set forth in section IB hereinabove. In some embodiments, crystalline grains of one or more alkaline earth halides have a non-cubic crystalline structure. In some embodiments, alkaline earth halides for use in a polycrystalline scintillator demonstrate an orthorhombic crystalline structure. In some embodiments, for example, SrI2, BaI2 and BaBrI demonstrate orthorhombic crystalline structures. In some embodiments, alkali earth halide crystalline grains of a radiation absorption region have an average size less than about 500 nm. In some embodiments, alkaline earth halide crystalline grains of a radiation absorption region have an average size ranging from about 10 nm to about 500 nm or from about 50 nm to about 200 nm. In some embodiments, alkaline earth halide crystalline grains of a radiation absorption region have an average size ranging from about 10 nm to about 100 nm. In some embodiments, crystalline grains of a radiation absorption region and crystalline grains of spatially discrete radiative exciton recombination regions comprise one or more transition metal halides as set forth in section IC hereinabove. In some embodiments, crystalline grains of one or more transition metal halides have a cubic crystalline structure. In some embodiments, crystalline grains of one or more transition metal halides have a non-cubic crystalline structure. In some embodiments, transition metal halides for use in a polycrystalline scintillator demonstrate a tetragonal or rhombohedral crystalline structure. In some embodiments, for example, SnI4 and PbI2 demonstrate rhombohedral crystalline structures. In some embodiments, transition metal halide crystalline grains of a radiation absorption region have an average size less than about 5 μm. In some embodiments, transition metal halide crystalline grains of a radiation absorption region have an average size ranging from about 10 nm to about 5 μm or from about 100 nm to about 1 μm. In some embodiments, transition metal halide crystalline grains of a radiation absorption region have an average size ranging from about 250 nm to about 750 nm. In some embodiments, crystalline grains of a radiation absorption region and crystalline grains of spatially discrete radiative exciton recombination regions comprise one or more semiconductor materials. In some embodiments, crystalline grains of a radiation absorption region comprises a first semiconductor having a first bandgap, and crystalline grains of spatially discrete radiative exciton recombination regions comprise a second semiconductor having a second bandgap, wherein the first bandgap is greater than the second bandgap. In some embodiments, the first and/or second semiconductor material comprises a binary semiconductor. Binary semiconductors, in some embodiments, comprise II/VI semiconductors, III/V semiconductors or combinations thereof. In some embodiments, the first and/or second semiconductor material comprises ternary or quaternary semiconductor alloys. Ternary or quaternary semiconductor alloys, in some embodiments, comprise III/V alloys, II/VI alloys or combinations thereof. In some embodiments, semiconductor crystalline grains of a radiation absorption region have an average size of less than about 100 μm. In some embodiments, semiconductor crystalline grains of a radiation absorption region have an average size ranging from about 10 nm to about 10 μm or from about 50 nm to about 1 μm. In some embodiments, semiconductor crystalline grains of a radiation absorption region have an average size ranging form about 100 nm to about 750 nm. In some embodiments, a method of producing a polycrystalline scintillator comprises providing a mixture comprising metal halide particles free or substantially free of one or more scintillation activators and metal halide particles comprising one or more scintillation activators and sintering the mixture to provide a polycrystalline scintillator material comprising a radiation absorption region and spatially discrete radiative exciton recombination regions. In some embodiments, the radiation absorption region is formed from the metal halide particles free or substantially free of scintillation activator. In some embodiments, spatially discrete radiative exciton recombination regions are formed by metal halide particles comprising one or more scintillation activators. Metal halide particles suitable for use in methods of forming a polycrystalline scintillator can comprise any metal halide described herein. In some embodiments, metal halide particles comprising one or more scintillation activators are present in the mixture in an amount up to about 30 weight percent. In some embodiments, metal halide particles comprising scintillation activator are present in the mixture in an amount ranging from about 0.01 weight percent to about 30 weight percent or from about 0.1 weight percent to about 20 weight percent. In some embodiments, metal halide particles comprising scintillation activator are present in the mixture an amount ranging from about 1 weight percent to about 10 weight percent. The mixture of metal halide particles can be sintered under any conditions of temperature, pressure and time effective to provide a sintered polycrystalline scintillator having a construction described herein. Sintering conditions can be determined according to several factors including specific identity of the metal halide, particle size and particle shape. In some embodiments, for example, metal halide particles are sintered at a temperature below the melting point of the particles. In some embodiments, metal halide particles described herein are sintered at a temperature ranging from about 30° C. to about 650° C. In some embodiments, sintering temperature can be ramped at any desired rate. In some embodiments, the temperature is ramped at a rate ranging from about 1° C./min to about 10° C./min. Moreover, in some embodiments, metal halide particles are pressed or subjected to the application of an external pressure prior to and/or during sintering. In some embodiments, metal halide particles are sintered under a pressure ranging from about 1 kpsi to about 200 kpsi. In some embodiments, the external pressure is applied uniaxially. In some embodiments, the pressure is applied isostatically. In some embodiments, metal halide particles are sintered for a time period ranging from about 0.5 to 10 hours. In some embodiments, metal halide particles are sintered for a time period ranging from about 1 hour to about 6 hours. Additionally, in some embodiments, metal halide particles are sintered under vacuum conditions or in an inert, dry atmosphere to prevent water absorption by hygroscopic metal halides. In some embodiments, a method of producing a polycrystalline scintillator comprises providing a mixture comprising particles of a first semiconductor having a first bandgap and particles of a second semiconductor having a second bandgap and sintering the mixture to provide a polycrystalline scintillator material comprising a radiation absorption region and spatially discrete radiative exciton recombination regions. In some embodiments, the first bandgap is larger than the second bandgap. In some embodiments, the radiation absorption region is formed from the first semiconductor particles and the spatially discrete radiative exciton recombination regions are formed by the second semiconductor particles. Semiconductor particles suitable for use in methods of forming a polycrystalline scintillator can comprise any semiconductor described herein. Moreover, a mixture comprising particles of a first semiconductor and a second semiconductor can be sintered according to the principles set forth hereinabove for sintering a mixture of metal halide particles. III. Crystalline Particles In another aspect, crystalline particles or grains are described herein. In some embodiments, a crystalline particle or grain comprises a radiation absorption region comprising at least one metal halide and a spatially discrete radiative exciton recombination region. In some embodiments, the spatially discrete radiative exciton recombination region comprises a metal halide comprising one or more scintillation activators. In some embodiments, the metal halide radiation absorption region of a crystalline particle described herein has less scintillation activator than the spatially discrete radiative exciton recombination region. In some embodiments, the metal halide radiation absorption region of a crystalline particle described herein is free or substantially free of scintillation activator. In other embodiments, a crystalline particle described herein comprises at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region, the particle having a size ranging from about 20 nm to about 100 μm. In some embodiments, the crystalline particle has a size ranging from about 50 nm to about 100 μm or from about 100 nm to about 100 μm. In some embodiments, the crystalline particle has a size ranging from about 200 nm to about 50 μm. In some embodiments, the spatially discrete radiative exciton recombination region of a crystalline particle described herein is disposed between the radiation absorption region and an exterior surface of the crystalline particle. In some embodiments, for example, the spatially discrete radiative exciton recombination region is located at the periphery of the crystalline particle surrounding a core comprising the radiation absorption region. In some embodiments, a crystalline particle comprises a core radiation absorption region and a spatially discrete shell radiative exciton recombination region. FIG. 4 illustrates a cross-sectional view of a crystalline particle according to one embodiment described herein. As illustrated in FIG. 4, the crystalline particle (400) comprises a radiation absorption core (401) and a spatially discrete radiative exciton recombination shell (402) at least partially surrounding the core (401). In some embodiments, the spatially discrete radiative exciton recombination shell (402) completely or substantially completely surrounds the core (401). As described herein, excitons generated by the absorption of radiation by the core (401) are transferred to the spatially discrete shell (402) for radiative recombination and the release of photons. In some embodiments wherein the spatially discrete radiative exciton recombination region is disposed between the radiation absorption region and an exterior surface of the crystalline particle, an exciton confinement region or layer can be provided adjacent to the spatially discrete radiative exciton recombination region. In some embodiments, an exciton confinement layer can preclude or inhibit excitons transferred to a spatially discrete radiative exciton recombination region from undergoing non-radiative recombination at particle surface traps and/or surface defects. Moreover, in some embodiments, an exciton confinement region adjacent to a spatially discrete radiative exciton recombination region of a crystalline particle can protect the recombination region from damage during sintering of the crystalline particle as described herein. In some embodiments, an exciton confinement region has a bandgap higher than the bandgap of the material forming the spatially discrete radiative exciton recombination region. In some embodiments, an exciton confinement region can comprise the same material as the core radiation absorption region. In some embodiments, an exciton confinement region is a different material than the core radiation absorption region. FIG. 5 illustrates a cross-sectional view of a crystalline particle comprising an exciton confinement region adjacent to a spatially discrete radiative exciton recombination region according to one embodiment described herein. As illustrated in FIG. 5, the crystalline particle (500) comprises a radiation absorption core (501) and a spatially discrete radiative exciton recombination shell (502) at least partially surrounding the core (501). In some embodiments, the spatially discrete radiative exciton recombination shell (502) completely or substantially completely surrounds the core (501). As described herein, excitons generated by the absorption of radiation by the core (501) are transferred to the spatially discrete shell (502) for radiative recombination and the release of photons. An exciton confinement region or layer (503) is disposed adjacent to and at least partially surrounds the spatially discrete radiative exciton recombination shell (502). In some embodiments, the exciton confinement region (503) completely or substantially completely surrounds the spatially discrete radiative exciton recombination shell (502). While the particles illustrated in FIGS. 4 and 5 are spherical, crystalline particles described herein can have any shape including spherical, substantially spherical, non-spherical, elliptical or polygonal. In some embodiments, the radiation absorption core can comprise any metal halide described herein free or substantially free of scintillation activator. In some embodiments wherein the radiation absorption core comprises an alkali halide described herein, the core has a size less than about 40 nm. In some embodiments, an alkali halide core has a size ranging from about 1 nm to about 40 nm or from about 5 nm to about 30 nm. In some embodiments, an alkali halide core has a size ranging from about 10 nm to about 20 nm. In some embodiments wherein the core comprises an alkaline earth halide, the core has a size less than about 500 nm. In some embodiments, an alkaline earth halide core has a size ranging from about 10 nm to about 500 nm or from about 50 nm to about 200 nm. In some embodiments, an alkaline earth halide core has a size ranging from about 250 nm to about 750 nm. In some embodiments, an alkaline earth halide core has a size ranging from about 10 nm to abut 100 nm or from about 20 nm to about 80 nm In some embodiments, wherein the core comprises a transition metal halide, the core has a size less than about 5 μm or less than about 1 μm. In some embodiments, a transition metal halide core has a size ranging from about 100 nm to about 5 μm or from about 200 nm to about 1 μm. In some embodiments, a transition metal halide core has a size ranging from about 250 nm to about 750 nm In some embodiments, the radiation absorption core can comprise any semiconductor material described herein. In some embodiments wherein the core comprises a semiconductor material, core has a size less than about 100 μm. In some embodiments, a semiconductor core has a size ranging from about 20 nm to about 10 μm or from about 50 nm to about 1 μm. In some embodiments, a semiconductor core has a size ranging from about 100 nm to about 750 nm. In some embodiments of a crystalline particle, the spatially discrete radiative exciton recombination shell can comprise any metal halide described herein comprising one or more scintillation activators. In some embodiments, the spatially discrete radiative exciton recombination shell comprises an alkali halide having one or more scintillation activators described herein. In some embodiments wherein the spatially discrete radiative exciton recombination shell comprises an alkali halide having scintillation activator, the shell has a thickness up to about 5 nm. In some embodiments, an alkali halide shell has a thickness ranging from about 1 nm to about 5 nm or from about 2 nm to about 4 nm. In some embodiments, the spatially discrete radiative exciton recombination shell comprises any alkaline earth halide described herein having one or more scintillation activators. In some embodiments wherein the spatially discrete radiative exciton recombination shell comprises an alkaline earth halide having scintillation activator, the shell has a thickness up to about 10 nm. In some embodiments, an alkaline earth halide shell has a thickness ranging from about 1 nm to about 10 nm or from about 3 nm to about 7 nm. In some embodiments, the spatially discrete radiative exciton recombination shell comprises any transition metal halide described herein having one or more scintillation activators. In some embodiments wherein the spatially discrete radiative exciton recombination shell comprises a transition metal halide having scintillation activator, the shell has a thickness up to about 100 nm. In some embodiments, a transition metal halide shell has a thickness ranging from about 1 nm to about 100 nm or from about 5 nm to about 75 nm. In some embodiments, a transition metal halide shell has a thickness ranging from about 10 nm to about 50 nm. In some embodiments, the spatially discrete radiative exciton recombination shell comprises a semiconductor material described herein having a bandgap less than the bandgap of the core semiconductor material. In some embodiments wherein the shell comprises a semiconductor material, the shell has a thickness up to about 1 μm. In some embodiments, a semiconductor shell has a thickness ranging from about 5 nm to about 1 μm or from about 10 nm to about 500 nm. A crystalline particle having a spatially discrete radiative exciton recombination region located at the periphery of the crystalline particle surrounding a radiation absorption core region can be produced according to several methods. In some embodiments, a metal halide particle can be doped at the periphery of the particle with one or more scintillation activators to provide the spatially discrete radiative exciton recombination shell region and an undoped radiation absorption core region. In one embodiment, for example, a SrI2 particle can be doped at the periphery with Eu2+ activator to provide the spatially discrete radiative exciton recombination shell and an undoped SrI2 radiation absorption core. In such embodiments, the crystalline particle can demonstrate a gradient of scintillation activator wherein the amount of scintillation activator increases with increasing distance from the particle center or core. In some embodiments, a crystalline particle comprising a radiation absorption core and a spatially discrete radiative exciton recombination shell can be produced by providing host particles and diffusing scintillation activator into the host particles to a depth corresponding to the desired thickness of the spatially discrete radiative exciton recombination shell. In one embodiment, for example, particles of SrI2 are provided and placed in an oven or furnace at elevated temperature. A vapor comprising scintillation activator, such as Eu2+, can be flowed over the SrI2 particles at a temperature and time period sufficient to diffuse the scintillation activator into the SrI2 particles to the desired depth, thereby establishing a radiation absorption core and a spatially discrete radiative exciton recombination shell. Alternatively, in some embodiments, a crystalline particle can be produced by providing a metal halide particle free or substantially free of scintillation activator and coating the metal halide particle with a composition comprising scintillation activator. In such embodiments, the coating can serve as the spatially discrete radiative exciton recombination region and the metal halide particle can serve as the radiation absorption region. In some embodiments, for example, metal halide host particles are provided and exposed to vapor comprising precursors of the metal halide host and one or more scintillation activators to deposit a metal halide/scintillation activator coating on the host particles. In some embodiments, such depositions can be administered in chemical vapor deposition (CVD) apparatus or carried out in solution phase in liquid phase epitaxy apparatus. In some embodiments wherein the radiation absorption region comprises a first semiconductor, a spatially discrete radiative exciton recombination region comprising a second semiconductor can be deposited on the first semiconductor. In some embodiments, the second semiconductor is grown on the first semiconductor by one or more epitaxial methods such as chemical vapor deposition (CVD), atomic layer epitaxy (ALE), solution atomic layer epitaxy (SALE) or molecular beam epitaxy (MBE). In some embodiments, the foregoing construction of a crystalline particle can be reversed wherein the spatially discrete radiative exciton recombination region is provided as the particle core, and the radiation absorption region is disposed at the periphery of the particle at least partially surrounding the core. In some embodiments, the radiation absorption region is provided as a shell around a spatially discrete radiative exciton recombination core. In some embodiments, crystalline particles described in this section (section III) of the application can be sintered to provide a polycrystalline scintillator material having at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region. In some embodiments, the construction of the crystalline particles provides the polycrystalline scintillator a plurality of radiation absorption regions and a plurality of spatially discrete radiative exciton recombination regions. In some embodiments, a method of producing a scintillator comprises providing crystalline particles comprising a radiation absorption region and a spatially discrete radiative exciton recombination region and sintering the crystalline particles to provide a polycrystalline scintillator material. The crystalline particles sintered to provide the polycrystalline scintillator material can have any construction described in this section (section III) of the application. The crystalline particles can be sintered under any conditions of temperature, pressure and time effective to provide a sintered polycrystalline scintillator having a construction described herein. Sintering conditions can be determined according to several factors including specific identity of the metal halide or semiconductor material, particle size and particle shape. Moreover, sintering should be administered at temperature that does not induce substantial migration or diffusion of scintillation activator out of a spatially discrete radiative exciton recombination region and into the radiation absorption region. In some embodiments, for example, crystalline particles comprising a radiation absorption region and a spatially discrete radiative exciton recombination region are sintered at a temperature below the melting point of the particles. In some embodiments, metal halide crystalline particles described herein are sintered at a temperature ranging from about 30° C. to about 650° C. In some embodiments, sintering temperature can be ramped at any desired rate. In some embodiments, the temperature is ramped at a rate ranging from about 1° C./min to 10° C./min. Moreover, in some embodiments, crystalline particles are pressed or subjected to the application of an external pressure during sintering. In some embodiments, crystalline particles are sintered under a pressure ranging from about 1 kpsi to about 200 kpsi. In some embodiments, the external pressure is applied uniaxially. In some embodiments, the pressure is applied isostatically. In some embodiments, crystalline particles are sintered for a time period ranging from about 0.5 to 10 hours. In some embodiments, crystalline particles are sintered for a time period ranging from about 1 hour to about 6 hours. Additionally, in some embodiments, crystalline particles are sintered under vacuum conditions or in an inert, dry atmosphere to prevent water absorption by hygroscopic metal halides. In some embodiments, the resulting polycrystalline scintillator material has a density of at least about 97% or at least about 99%. IV. Scintillation Detector In another embodiment, the present invention provides a scintillation detector or counter comprising and an electromagnetic radiation sensor, wherein the scintillator comprises at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region for receiving excitons from the at least one radiation absorption region. A scintillator of any construction described herein can be used in a scintillator counter. In some embodiments, an electromagnetic radiation sensor comprises a photomultiplier tube (PMT) or a photodiode. An electromagnetic radiation sensor, in some embodiments, is operable to detect visible radiation, infrared radiation, ultraviolet radiation or combinations thereof. V. Methods of Producing Scintillators In another aspect, methods of producing scintillators are described herein. In some embodiments, a method of producing a scintillator comprises providing a radiation absorption region comprising a first material having a first bandgap and locally modulating the first bandgap to trap excitons in a spatially discrete radiative exciton combination region, wherein locally modulating the first bandgap comprises providing the radiative exciton recombination region in electrical communication with the radiation absorption region, the radiative exciton recombination region comprising a second material having a second bandgap different from the first bandgap. In some embodiments, the second bandgap is smaller or of lower energy than the first bandgap. In some embodiments, the first material comprises a metal halide free or substantially free of a scintillation activator and the second material comprises a metal halide having incorporated therein one or more scintillation activators as described herein. FIG. 6 illustrates the electronic structure of a scintillator comprising a metal halide radiation absorption region and a spatially discrete metal halide radiative exciton recombination region comprising scintillation activator according to one embodiment described herein. As illustrated in FIG. 6, the scintillation activator localized to the radiative exciton recombination region provides energy or dopant levels facilitating the acceptance of electron and hole carriers from the metal halide radiation absorption region for radiative recombination. Additionally, in some embodiments, a method of producing a scintillator comprises providing a radiation absorption region comprising a metal halide free or substantially free of a scintillation activator and providing a spatially discrete radiative exciton recombination region in electrical communication with the radiation absorption region, the radiative exciton recombination region comprising a metal halide comprising one or more scintillation activators. In some embodiments, the metal halide radiation absorption region is single crystalline, and the spatially discrete radiative exciton combination region comprises a phase of metal halide comprising scintillation activator within the single crystal. In some embodiments, for example, phases of metal halide comprising activator are precipitated from the single crystalline phase while cooling the metal halide crystal from melt. Moreover, in some embodiments, polycrystalline scintillators can be produced according to the methods disclosed in sections II and III hereinabove. In another aspect, the present invention provides methods of converting radiation of a first energy into radiation of a second energy. In one embodiment, a method of converting radiation of a first energy into radiation of a second energy comprises providing a scintillator comprising at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region, absorbing the radiation of the first energy in the radiation absorption region to generate excitons and recombining at least some of the excitons in the spatially discrete radiative exciton recombination region to emit radiation of a second energy. In some embodiments, the radiation of the first energy has a wavelength less than the wavelength of the radiation of the second energy. As described herein, in some embodiments, the radiation absorption region of the scintillator comprises a metal halide free or substantially free of a scintillation activator, and the spatially discrete radiative exciton recombination region comprises a metal halide comprising one or more scintillation activators. In a further aspect, the present invention provides a method of reducing non-proportional response in a scintillator. In one embodiment, a method of reducing non-proportional response comprises providing a scintillator comprising at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region, absorbing radiation of a first energy in the radiation absorption region to generate excitons, transferring at least some of the excitons out of the radiation absorption region and into the spatially discrete radiative exciton recombination region and recombining the excitons to emit radiation of a second energy from the radiative exciton recombination region. In some embodiments, the radiation absorption region of the scintillator comprises a metal halide free or substantially free of a scintillation activator, and the spatially discrete radiative exciton recombination region comprises a metal halide comprising one or more scintillation activators. Various embodiments of the invention have been described in fulfillment of the various objectives of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.
040640027	summary	CROSS-REFERENCES TO RELATED APPLICATIONS U.S. Patent application Ser. No. 259,327, filed June 2, 1972, by Erling Frisch and Harry Andrews, now abandoned, entitled "Emergency Core Cooling System for Nuclear Reactors," and assigned to the Westinghouse Electric Corp., discloses subject matter which relates to this application. BACKGROUND OF THE INVENTION The invention described herein relates to nuclear reactors and more particularly to an emergency core cooling system which operates to supply coolant from an emergency source to the reactor core under conditions of reduction in pressure of primary coolant in the reactor. The function of an emergency core cooling system for nuclear reactors is to immediately flood the reactor core with highly concentrated neutron absorber material which acts to terminate the fission process and simultaneously prevent heat damage to fuel and fuel rods in the event of a major rupture in the reactor primary coolant system piping. The Atomic Energy Commission general design criteria for nuclear reactors requires that all operating reactors include an emergency core cooling system and although different designs have been developed for this purpose, one well known system utilizes large pressurized tanks or accumulators which discharge highly concentrated borated water directly into a pressurized water reactor when the pressure of primary coolant circulated from the reactor through a heat exchanger or steam generator drops below about 660 psi. This emergency coolant normally is injected into the primary coolant inlet pipes near the reactor inlet nozzles to assure delivery directly into the area containing the reactor fuel assemblies. It has been determined that current emergency cooling systems are completely effective to cool the fuel and fuel rods under circumstances of minor breaks in any component, including piping in the reactor coolant flow paths. However, a major rupture, i.e., a full circumferential break and separation of the primary coolant inlet piping, creates unusual problems because the pressure of primary coolant still being circulated through the reactor from the other primary loops tends to cause the coolant to flow towards the area of reduced pressure which is represented by the pipe break. As the emergency coolant from the accumulator is then introduced into the inlet coolant pipes, the emergency coolant in-flow blocks the normal coolant attempting to escape through the fractured inlet pipe. Although the accumulator pressure is sufficient to overcome the out-flowing coolant, it is suspected that because of the tortuous inlet flow path in the reactor, the fuel and fuel rods comprising the core may become partially starved of coolant. Such starving and the accompanying drop in coolant pressure, allows the water circulating around the fuel rods to boil, thus generating bubbles which rise in the core and partially block flow laterally through the normal coolant outlet. Even though the likelihood or possibility of such a major rupture occurring is so extremely remote as to not dictate the need for designs to cover the situation, in view of the public interest, the systems are nevertheless designed to accommodate the most remote possibility of accidents. In recognition of this problem, the emergency core cooling system disclosed in the above Frisch et al. patent application was designed to handle all loss of coolant situations by conducting emergency coolant downwardly through unused control rod guide thimbles or tubes into the reactor core. According to that disclosure, water enters the upper end of each guide thimble and is discharged near the lower end thereof inside the core in the form of a spray which is directed radially outward against adjacent fuel rods. This direct contact with the fuel rods thus increases the cooling efficiency and assures delivery of the required volume of water into the core. Tests on this type system show its great effectiveness, efficiency and reliability and the only known drawback lies in the labor and material costs necessary for installation and for subsequent removal when the reactor is being refueled. The above discussion therefore suggests the need for a system which may independently be used for emergency cooling purposes, or alternatively, be used as a system supplemental to present emergency core cooling systems but of sufficient simplicity to eliminate the relatively high costs inherent in the Frisch et al design. SUMMARY OF THE INVENTION Briefly stated, the above disadvantages are eliminated in the present invention by providing an emergency core cooling system which discharges neutron absorber material, such as borated water, from a separate system of accumulators into the area beneath the reactor head and above the upper support plate structure for further distribution through coolant conducting devices to the top of the reactor core. The spaces above the reactor core provides a manifold-like chamber which serves to feed the emergency core coolant downwardly past the fuel rods in each fuel assembly, thus carrying away both residual heat in the fuel rods and that heat which is still being generated by the fuel. The system may be designed to supplement present emergency core cooling equipment incorporated in the reactor or it may independently serve as the sole emergency core cooling system for cooling the fuel rods under reactor loss or reduction of coolant conditions. An object of the invention therefore is to provide an emergency core cooling system which introduces emergency coolant into the closure head area of a nuclear reactor for distribution to the reactor core for core cooling purposes. Another object of the invention is to provide an emergency core cooling system for a nuclear reactor which is supplemental to an emergency cooling system used for core cooling purposes. Still another object of the invention is the provision of an emergency core cooling system which conducts coolant from the top of the reactor downwardly through the core and in a direction counter to the normal flow of primary coolant in the system.
	claims	1. An apparatus for providing additional radiation shielding to a container holding radioactive materials comprising:a tubular shell extending from a first end to a second end, the tubular shell constructed of a gamma radiation absorbing material and having an inner surface that forms a cavity;a first opening in the first end of the tubular shell that provides a passageway into the cavity;a second opening in the second end of the tubular shell that provides a passageway into the cavity, the second opening being larger than the first opening; anda plurality of spacers extending from the inner surface of the shell. 2. The apparatus of claim 1 wherein the spacers are circumferentially spaced from one another about an axis of the cavity. 3. The apparatus of claim 1 further comprising means on the first end of the tubular shell for lifting the apparatus. 4. The apparatus of claim 1 further comprising one or more channels that extend from along the inner surface of the tubular shell from the first end of the tubular shell to the second end of the tubular shell. 5. An apparatus for providing additional radiation shielding to a container holding radioactive materials comprising:a tubular shell constructed of a gamma radiation absorbing material and having an inner surface that forms a cavity having an axis, the cavity having an open top end and an open bottom end;a plurality of spacers extending from the inner surface of the shell toward the axis of the cavity, the spacers extending a first height from the inner surface of the tubular shell; andone or more flange members located at or near the open top end of the cavity extending from the tubular shell toward the axis of the cavity, the flange member extending a second height from the inner surface of the shell, the second height being greater than the first height. 6. The system of claim 5 further comprising one or more channels extending from the open bottom end of the cavity to the open top end of the cavity. 7. The system of claim 6 further comprising a ring-like member connected to a top of the tubular shell. 8. A system for handling and/or processing radioactive materials comprising:a container having a first cavity, the container having an outer surface and a top surface;a canister containing radioactive materials positioned within the first cavity;a tubular shell having an inner surface that forms a second cavity for receiving the container, the tubular shell comprising at least one spacer extending from the inner surface of the shell toward an axis of the second cavity;the container positioned in the second cavity of the tubular shell, the at least one spacer maintaining the inside surface of the tubular shell in a spaced relationship from the outer surface of the container; andwherein the tubular structure is non-unitary and slidably removable from the container. 9. The system of claim 8 wherein the second cavity of the tubular shell has an open top end defined by a first opening and an open bottom end defined by a second opening. 10. The system of claim 9 wherein the second opening is sized and shaped to allow a body portion of the container to slidably pass therethrough in an unobstructed manner. 11. The system of claim 10 wherein the container further comprises a lid positioned atop the body portion of the container that substantially encloses a top end of the first cavity; and wherein the first opening is sized and shaped to allow the lid to slidably pass therethrough in an unobstructed manner. 12. The system of claim 11 wherein the at least one spacer maintains the inside surface of the tubular shell in the spaced relationship from the outer surface of the container so as to form an annular gap between the tubular shell and the container. 13. The system of claim 12 wherein the annular gap comprises one or more channels that extend from an inlet at or near a bottom of the tubular shell to an outlet at or near a top of the tubular shell. 14. The system of claim 8 wherein the container comprises both gamma radiation absorbing material and neutron absorbing material and the tubular shell is constructed of a gamma radiation absorbing material.
	summary
	summary
	description	The instant application is a national phase of PCT International Application No. PCT/RU2014/000882 filed Nov. 21, 2014, and claims priority to Russian Patent Application Serial No. 2013152247, filed Nov. 26, 2013, the entire specifications of both of which are expressly incorporated herein by reference. The invention relates to nuclear power industry and specifically to reactor fuel elements and units thereof, in particular to the composition of solid ceramic fuel elements based on uranium dioxide intended for and exhibiting characteristics for application in various-purpose nuclear reactors. A pellet of nano-structured nuclear fuel (its embodiments) is known that contains pressed and sintered powder of a mixture of particles of a U compound and a nanodiamond uniform in effective size and density, in addition, it may contain pressed and sintered powder of a mixture of particles of the compound (U, Pu) and nanodiamond (Patent No. 2467411RU. Published Nov. 20, 2012). However, notwithstanding the improved strength and heat resistance of the known pellet, it has low thermal conductivity, moreover, introduction of more than 1% of nanodiamond in UO2 or (U,Pu)O2 results in a decreased effective density of the nuclear fuel and may cause an accident during reactor operation as diamond reacts to form graphite spontaneously and bursts to small fragments when heated to 2000° C. without access of air. A high-burnup nuclear fuel pellet and preparation method thereof (embodiments) are known, where a pellet based on uranium dioxide contains aluminum and silicon oxides evenly distributed within the pellet volume, wherein, in relation to uranium, the content of aluminum amounts to between 0.005 and 0.03 wt %, that of silicon between 0.003 and 0.02 wt %, the weight ratio of aluminum to silicon is between 1.5 and 4, the size of uranium dioxide grain varies between 20 and 45 μm. Additionally, the pellet may contain gadolinium oxide evenly distributed in the pellet volume as a solid solution with uranium dioxide, wherein the content of gadolinium oxide in relation to uranium is between 0.3 and 10.0 wt %, or contain erbium oxide evenly distributed in the pellet volume as a solid solution with uranium dioxide, wherein the content of erbium oxide in relation to uranium is between 0.3 and 0.8 wt % (Patent No. 2376665RU. Published Dec. 20, 2009). However, notwithstanding the fact that the known pellet results in an increased fuel burnup during its operation at up to 70 to 100 MW·day/kg U, it does not possess a simple structure, composition, or increased thermal conductivity. Moreover, it is not intended for load following operation of the reactor. Its preparation method is characterized by high production cost. A nuclear fuel pellet based on uranium dioxide is known containing pressed and sintered powder of a mixture of uranium dioxide with erbium oxide (Er2O3), the content of which in nuclear fuel is between 0.46 and 0.64 wt % by erbium at the nominal weight percentage of U-235 in nuclear fuel between 2.6 and 2.8 wt %. The effective porosity of the pressed and sintered mixture of uranium dioxide (UO2) with erbium oxide does not exceed 1% (Patent No. 2157568RU. Published Oct. 10, 2000). While fuel burnup is increased by adding erbium oxide, it results in decreased thermal conductivity of the fuel and, therefore, in increased radial temperature gradient of the pellet and does not contribute to stable load following operation of the reactor. A fuel composition of 40 wt. % of UO2+60 wt % of MgO is known having thermal conductivity of 5.7 W/m·deg. at 1000° C. (˜1.5 times higher than the design thermal conductivity) (I. S. Kurina, V. N. Lopatinsky, N. P. Yermolayev, N. N. Shevchenko. Research and Development of MgO based matrix fuel.—Proceedings of a Technical Committee meeting held in Moscow, 1-4 Oct. 1996. IAEA-TECDOC-970, 1997, p. 169-181). However, the known fuel composition of UO2+MgO comprises a significant amount of a diluent: MgO (60 wt %). Complete charging of existing reactors with fuel of such composition is not possible. For use in the existing fast or thermal reactors, the concentration of 235U in the UO2+MgO fuel must be increased. This would require considerable costs in connection with increased enrichment of fuel in 235U and modification of fuel production process instrumentation based on nuclear safety. A nuclear fuel pellet is known that is a composite uranium dioxide matrix with a heat-conducting phase located inside in a specific way. The fuel heat flux direction coincides with the heat-conducting phase orientation. Heat is transferred by monocrystalline particles of beryllium oxide of acicular or platelet shape, 40 to 200 μm in size, optically transparent, dispersed in the uranium dioxide matrix (U.S. Pat. No. 2,481,657. Published May 10, 2013). However, while the known pellet allows to improve thermal conductivity of its material due to the composite structure of fuel, it does not possess a special structure having nanopores inside grains and metal clusters of uranium. A nuclear fuel pellet (embodiments) is known containing pressed and sintered powder of a mixture of particles of a uranium compound and frame carbon structures uniform in density and effective particle size. One embodiment thereof is a zoned pellet, wherein the central cylindrical zone of the pellet has a lower volumetric content frame carbon structures, while the outer annular zone has a higher volumetric content. In particular cases, the content of frame carbon structures (fullerenes, carbon nanotubes, carbon nanofibers) in the mixture powder is between 1.5 and 12.5 vol. % for a mixture with UO2 and 1.2 to 10.4 vol. % for a mixture with UN. (Patent No. 2469427RU. Published Dec. 10, 2012). However, while the known pellet has improved strength, heat resistance, deceleration of occurrence and development of cracks, decreased probability of its destruction, it does not provide sufficient thermal conductivity at increased temperatures resulting from its reliable special structure and simple composition of uranium dioxide. A modeled composite nuclear fuel pellet is known with up to 3 wt % of particles of ordered graphite or silicon carbide with high thermal conductivity, which allows improving its thermal conductivity. In the known technical solution, a composite grain of nuclear fuel contains a composite body with a UO2 matrix and many particles of high proportions dispersed in the same, where these particles of high proportions have a higher thermal conductivity compared to that of the UO2 matrix (Application No. PCT/US2010/043307; International Publication Number WO/2011/014476. Published Feb. 3, 2011). However, particles of high thermal conductivity in the known pellet are fibers between 0.25 and 1.25 cm in length and between 5 and 15 μm in width (diameter) that are destroyed (broken, twisted, etc.) when mixed and pressed, thus losing their function of pellet thermal conductivity improvement. In addition, introduction of up to 3% of ordered graphite or silicon carbide in UO2 results in decreased uranium capacity of nuclear fuel, and addition of graphite may cause an emergency during reactor operation. A method of production of fuel pellets, fuel assemblies, and uranium powder applied therefor are known. Among fuel rods (13, 14, 15, 16, 17, 18, 19) the fuel assemblies are comprised of, fuel rods (16, 17, 18) are added each containing uranium oxide with a condensation rate of more than 5%, contain a Gd composite oxide. Gd composite oxide is an oxide containing gadolinium and a rare earth element B other than gadolinium and represented by chemical formula Al—XGdXO2-0, 5X or Al—XGdXO1.5. The rare earth element may be cerium (Ce), lanthanum (La), erbium (Er) (International Application Number: International Application Number: PCT/JP2009/001708, International Filing Date: Apr. 14, 2009; International Publication Number: WO/2009/128250, Publication Date: Oct. 22, 2009). A method of preparation of a fuel composition for fast-neutron reactors is known consisting in preparation of fissile material solutions of fissile materials, deposition with ammonia, powder thermal treatment to fissile material oxides followed by pellet pressing and sintering, wherein solutions of magnesium and iron are added at the solution preparation stage, and iron is restored to metallic state (Patent No. 2098870RU. Published Dec. 10, 1997). However, the known method does not produce a more reliable special structure and a simple composition of uranium dioxide of the fuel pellet with enhanced thermal conductivity of fuel, namely above the reference data, at temperature increase. A method of fabrication of ceramic products is known including the operations of deposition of metal carbonate, hydroxide, oxalate, etc. from a solution, residue thermal treatment, pressing and sintering, wherein the lower temperature limit of the residue thermal treatment is the recrystallization temperature, i. e that of the morphological change of particle shape (Patent No. 2135429 RU. Published Aug. 27, 1999). However, the known method does not produce a more reliable special structure and a simple composition of uranium dioxide of the fuel pellet with enhanced thermal conductivity of fuel, namely above the reference data, at temperature increase. A method of production of nuclear fuel pellets based on uranium dioxide is known consisting in addition of nanodispersed uranium hydride to the initial highly-dispersed uranium dioxide, thorough mixing of the components, vacuum drying of the mixture at 300 to 330° C., where uranium hydride decomposes to metal, pressing of pellets from the dries product and their dynamic vacuum sintering at 1500 to 1550° C. (Patent No. 2459289RU. Published Aug. 20, 2012). However, the known method does not produce a more reliable special structure and a simple composition of uranium dioxide resulting in enhanced thermal conductivity of fuel, namely above the reference data, at temperature increase. A modification of fuel pellets of uranium dioxide is known including addition of ammonia-containing additives to the standard UO2 powder and improvement of their production process, preparation of oxide ceramic materials, including obtaining a residue containing simultaneously particles of various sizes, including nanoparticles, followed by incinerating at the optimum temperature (Kurina I.S. Improvement of Uranium Dioxide Fuel Preparation Technology for Improved Performance//Digest of the 1st All-Russian Workshop of Undergraduate, Post-Graduate Students, Young Researchers in Topical Areas of Activities of the Functional Nanomaterials for Energy National Network for Nanotechnology. Moscow, National Research Nuclear University MEPhI, 2011. PP. 117-146). The said publication describes general approaches to modification of uranium dioxide fuel pellets that will not allow to obtain a reliable special structure of a fuel pellet and a simple composition of uranium dioxide with enhanced thermal conductivity of fuel, namely above the reference data, at temperature increase without their constructive elaboration. The closest analogous technical solution is based on the properties of a nuclear fuel pellet that is a composite uranium dioxide matrix with its heat-conducting BeO phase located inside in a specific way. The fuel heat flux direction coincides with the heat-conducting phase orientation. Heat is transferred by optically transparent monocrystalline particles of beryllium oxide of acicular or platelet shape dispersed in the uranium dioxide matrix, between 40 and 200 μm in size, its content in the fuel between 1 and 10 wt %. The calculation shows that the increase of thermal conductivity at 1000° C. and BeO content of 3% by weight as compared to fuel in the form of UO2 will be less than 21%. (U.S. Pat. No. 2,481,657. Published May 10, 2013). However, the enhanced conductivity in the known pellet is achieved only if the thermal flow coincides with the heat-conducting phase orientation, which is practically unachievable during pellet preparation (mixing, pressing). In addition, preparation of such a thermally conductive phase of the single-crystal beryllium oxide is a complicated and massive production process that significantly increases the cost of the nuclear fuel production, while introduction of a sufficiently large amount of BeO to UO2 leads to the decrease of the fuel uranium capacity. Moreover, the beryllium oxide is a reflector and moderator of neutrons and addition thereof will modify the reactor physics. The method of nuclear fuel pellet fabrication closest to the proposed one is the method of fabrication of oxide ceramic products with enhanced thermal conductivity, including operations of preparation of an acid solution containing at least one metal cation, including a fissile one, sedimentation of salts or hydroxide of at least one metal from the solution, thermal treatment of the residue at a temperature at least equal to that of the morphological change of the residue particle shape, product pressing and sintering, where the metal hydroxide is subsided with ammonia in two stages, wherein the first stage pH value is lower than the pH of complete metal sedimentation by at least 0.5, and the second stage pH is between 9.5 and 10.5, the salt in the form of a metal oxalate is subsided with a concentrated solution of oxalic acid with a stoichiometry surplus of at least 20%, wherein large particles of at least 0.1 μm and 0.05 to 2.0 wt % of nanoparticles with the size up to 30 nm are generated in the residue (Patent No. 2323912RU. Published May 10, 2008). However, the known method does not produce a nuclear fuel pellet of more reliable special structure and simple composition of uranium dioxide with enhanced thermal conductivity of fuel, namely above the reference data, at temperature increase. The purpose of this invention is to develop a more reliable special structure and a simple composition of uranium dioxide without heterogeneous additives in a fuel pellet, and a simple method of preparation thereof, both resulting in approaching monocrystalline properties and enhanced thermal conductivity of fuel, namely above the reference data, at temperature increase. Implementation of the invention yields the following technical results. The proposed pellet and preparation method thereof are simple and low-cost. The proposed pellet has a more reliable special structure and a simple composition of uranium dioxide without heterogeneous additives. The proposed pellet prepared using the proposed method is close to the monocrystalline properties and shows almost no porosity. In addition, it has enhanced thermal conductivity, namely above the reference data, at temperature increase. The proposed pellet has enhanced plasticity due to formation of metal clusters and provides stable load following operation of the reactor. Additionally, the method of its preparation is rather low-cost, when conditions for uranium metal formation are provided. The following essential features influence the achievement of the above technical results. The solution to the problem set consists in that a nuclear fuel pellet with enhanced thermal conductivity containing a structure of pressed and sintered uranium dioxide powder has its structure made up of pores evenly distributed along the grain boundaries and within the grains, wherein nanopores and metal clusters of uranium chemical compounds with a valency of 0 and 2+ are located inside the grains, and nanopores are between 1 and 200 nm in size and make up at least 50% of the total porosity, and metal clusters of a mixture of uranium chemical compounds with a valency of 0 and 2+ are surrounded by UO2, in addition, the total content of metal clusters in the form of a mixture of uranium chemical compounds with a valency of 0 and 2+ is between 0.01 and 2 wt %. To produce a nuclear fuel pellet with enhanced thermal conductivity, a method of its preparation is applied including deposition of metal hydroxides with pH in two stages, incinerating, sintering of a uranium dioxide mixture powder and pressing, application of an X-ray photon spectrometer, with deposition performed by simultaneous draining of uranyl nitrate and ammonia solutions to the buffer at 55-60±2° C. in two stages: at the first stage, pH is maintained between 6.5 and 6.7, at the second stage, final deposition of polyuranate ammonia (PUA) is performed at pH level between 9.0 and 10.5, the incinerating is performed at temperatures between 600 and 680° C. until UO2 reduction, uranium metal is melted at the temperature above 1150° C., the sintering is performed in a small amount of liquid phase in a hydrogen-nitrogen medium at temperatures between 1600 and 2200° C. until metal clusters are formed. In an embodiment with an extended range of method application, the deposition is performed by simultaneous draining of the nitric-acid solution with uranium and added metal and ammonia to the buffer at 55-60±2° C. in two stages: at the first stage, pH is maintained between 7.0 and 7.2, at the second stage, final deposition of polyuranate ammonia (PUA) is performed at pH level between 8.0 and 8.5, wherein chromium, tin, titanium, aluminum, etc. are used as added metals. When applying the standard technology, it is reasonable to stir in mechanically an ammonia-containing additive in the amount of 0.01 to 0.5% to the UO2 powder, wherein the following is used as such ammonia-containing additive: ammonia carbonate or bicarbonate, paraphenylenediamine, triazole, etc. The nuclear fuel pellet having enhanced thermal conductivity (hereinafter referred to as the “pellet”) has a structure of pressed and sintered uranium dioxide powder (FIG. 1). The pellet structure is made up of pores of 1 to 5 μm in size evenly distributed along the grain boundaries, and nanopores between measured between 1 and 200 nm in size located inside the grains (FIG. 2). The latter make up at least 50% of the total porosity. Metal clusters of uranium chemical compounds with a valency of 0 and 2+ are surrounded by UO2. The total content of metal clusters (the clusters) in the form of a mixture of uranium chemical compounds with a valency of 0 and 2+ is between 0.01 and 2 wt % and represent chemically bonded uranium cations (chemical bond U—U). Microhardness of such metal clusters is at least 1.5 time lower than the reference data. Due to metal clusters, the O/U ratio is reduced to 1.996-1.999 inside the grains, and O/U ratio is between 2.000 and 2.002 along the grain boundaries due to oxidation during storage in open air. This improves the pellet thermal conductivity. FIG. 3 shows the structure of the standard uranium dioxide nuclear fuel pellet without metal clusters for comparison. Pellet thermal conductivity increases as temperature increases above 500-600° C. and exceeds the reference and design data by 1.5 to 3 times at 1000° C. (FIG. 4, 5). It is attributable to the following. The nature of temperature dependence of thermal conductivity measured using the conventional axial thermal flux method for the proposed UO2 pellet is very similar to the nature of temperature dependence of thermal conductivity for monocrystalline UO2. For a monocrystal, thermal conductivity does not depend on its size or orientation. At 700° C., monocrystal thermal conductivity is 60% higher than the average thermal conductivity of the sintered polycrystalline UO2. At 1000° C., monocrystal thermal conductivity is 5.9 W/m.deg., which is 2.4 times higher than the thermal conductivity of the sintered polycrystalline uranium dioxide. To produce a nuclear fuel pellet with enhanced thermal conductivity, a method is applied that includes deposition of metal hydroxides in two stages with pH, incinerating, sintering of the uranium dioxide mixture powder, pressing, and application of an X-ray photon spectrometer. For the method implementation, deposition is performed by simultaneous draining of uranyl nitrate solutions and ammonia to the buffer at 55-60±2° C. in two stages. At the first stage, pH is maintained between 6.5 and 6.7, at the second stage, final deposition of polyuranate ammonia (PUA) is performed at pH level between 9.0 and 10.5. The incinerating is performed at temperatures between 600 and 680° C. until UO2 reduction. Uranium metal is melted at a temperature exceeding 1150° C., and sintering is carried out in an insignificant amount of liquid phase at temperatures between 1600 and 2200° C. in a hydrogen-nitrogen medium until metal clusters are formed. Sintering in a liquid phase results in the required porosity and pellet structure. Pores with the size of 1 to 5 μm are formed along the grain boundaries, and nanopores with the size of ≤1 to 200 nm are formed inside the grains making up at least 50% of total porosity. The O/U ratio reduces to 1.996-1.999 in the UO2-U system. Uranium dioxide is formed with dispersed metal clusters of uranium chemical compounds with a valency of 0-2+ surrounded by UO2. The new structure of the UO2 pellet and an additional U—U chemical bond are identified by means of an X-ray photon spectrometer showing that such metal clusters amount to from 0.01 to 2 wt % in the pellet. In an embodiment with an extended range of method application and preparation of catalysts, the deposition is performed by simultaneous draining of the nitric-acid solution with uranium and added metal and ammonia to the buffer at 55-60±2° C. in two stages as well: At the first stage, pH is maintained between 7.0 and 7.2, at the second stage, final deposition of polyuranate ammonia (PUA) is performed at pH level between 8.0 and 8.5. Chromium, tin, titanium, aluminum, etc. are used as metal additives. Additives are catalysts contributing to partial, in the areas near the additives, reduction of uranium dioxide nanoparticles to uranium metal during pellet sintering. When applying the standard technology, an ammonia-containing additive in the amount of 0.01 to 0.5% is stirred in mechanically to the UO2 powder, wherein the following is used as such ammonia-containing additive: ammonia carbonate or bicarbonate, paraphenylenediamine, triazole, etc. Nuclear fuel fillet having enhanced thermal conductivity was prepared as follows. Deposition was performed by simultaneous draining of uranyl nitrate solutions and ammonia to the buffer at 55-60±2° C. in two stages. The ammonium solution was supplied to the ammonium polyuranate sediment bowl. At the first stage, pH was maintained between 6.5 and 6.7, at the second stage, final deposition of polyuranate ammonia (PUA) was performed at pH level between 9.0 and 10.5. The incinerating was performed at temperatures between 600 and 680° C. until UO2 reduction. Uranium metal was melted at a temperature exceeding 1150° C., and sintering was carried out in an insignificant amount of liquid phase at 1750° C. in a hydrogen-nitrogen medium until metal clusters were formed. Sintering in a liquid phase resulted in the required porosity and pellet structure. The new structure of UO2 pellet and an additional U—U chemical bond were identified using an X-ray photon spectroscope. The pellet structure has pores evenly distributed along the grain boundaries and inside the grains. Pores with the size of 1 to 5 μm were identified along the grain boundaries, and nanopores with from ≤1 to 200 nm were identified inside the grains making up at least 50% of total porosity. In addition, it was noted that the size of nanopores is even smaller than the microscope resolution, i. e. less than 1 nm. A the same time, sintered pellets in the UO2—U system had a UO2 phase composition and O/U ratio of 2.002 at grain boundaries and 1.998 inside grains. Dispersed metal clusters of uranium chemical compounds with a valency of 0-2+ surrounded by UO2 were identified in the uranium dioxide structure. Such metal clusters of a mixture of uranium chemical compounds with a valency of 0 and 2+ amounted to 0.01-2 wt % of the pellet. Nuclear fuel fillet having enhanced thermal conductivity was prepared as follows. Deposition is performed by simultaneous draining of the nitric-acid solution with uranium and added metal and ammonia to the buffer at 55-60±2° C. in two stages as well. At the first stage, pH was maintained between 7.0 and 7.2, at the second stage, final deposition of polyuranate ammonia (PUA) was performed at pH level between 8.0 and 8.5. Chrome was used as an additive to metal. Additives contributed to partial, in the areas near the additives, reduction of uranium dioxide nanoparticles to uranium metal during pellet sintering. Then uranium metal was melted at a temperature exceeding 1150° C., and sintering was carried out in an insignificant amount of liquid phase at 1750° C. in a hydrogen-nitrogen medium until metal clusters were formed. Sintering in a liquid phase resulted in the required porosity and pellet structure. The new structure of UO2 pellet and an additional U—U chemical bond were identified using an X-ray photon spectroscope. The pellet structure has pores evenly distributed along the grain boundaries and inside the grains. Pores with the size of 1 to 5 μm were identified along the grain boundaries, and nanopores with from ≤1 to 200 nm were identified inside the grains making up at least 50% of total porosity. In addition, it was noted that the size of nanopores is even smaller than the microscope resolution, i. e. less than 1 nm. At the same time, sintered pellets in the UO2—U system had a UO2 phase composition and O/U ratio of 2.002 at grain boundaries and 1.998 inside grains. Dispersed metal clusters of uranium chemical compounds with a valency of 0-2+ surrounded by UO2 were identified in the uranium dioxide structure. Such metal clusters of a mixture of uranium chemical compounds with a valency of 0 and 2+ amounted to 0.01-2 wt % of the pellet. In a uranium dioxide powder prepared by the standard method, 0.5 wt % of 4-amino-1,2,4-triazole powder (the triazole) was added by mechanical stirring. Pellets were pressed and sintered in a hydrogen medium at 1750° C. During sintering, the ammonium-containing triazole radical ion decomposed emitting hydrogen that contributed to the reduction of adjacent areas of uranium dioxide within the pellet volume. As a result, metal clusters and substoichiometric composition were formed in the internal part of pellets. Then uranium metal was melted at a temperature exceeding 1150° C., and sintering was carried out in an insignificant amount of liquid phase at 1750° C. in a hydrogen-nitrogen medium until metal clusters were formed. Sintering in a liquid phase resulted in the required porosity and pellet structure. The new structure of UO2 pellet and an additional U—U chemical bond were identified using an X-ray photon spectroscope. The pellet structure has pores evenly distributed along the grain boundaries and inside the grains. Pores with the size of 1 to 5 μm were identified along the grain boundaries, and nanopores with from ≤1 to 200 nm were identified inside the grains making up at least 50% of total porosity. In addition, it was noted that the size of nanopores is even smaller than the microscope resolution, i.e. less than 1 nm. A the same time, sintered pellets in the UO2—U system had a UO2 phase composition and O/U ratio of 2.001 at grain boundaries and 1.999 inside grains. Dispersed metal clusters of uranium chemical compounds with a valency of 0-2+ surrounded by UO2 were identified in the uranium dioxide structure. Such metal clusters of a mixture of uranium chemical compounds with a valency of 0 and 2+ amounted to 0.01-2 wt % of the pellet.
055966152	description	EXPLANATION OF SYMBOLS 1: sheath tube, 2: liner, 3: end plug, 4: nuclear fuel pellet, 5: plenum spring, 6: welding portion, 7: lower end portion 10: fuel assembly, 11: channel box, 12: hanging handle, 13: spacer, 14: cell, 15: upper end plate, 16: control rod, 17: steam separator, 18: upper grating plate, 19: reactor core supporting plate, 20: corner, 21: side, 22: control rod guide tube, 25: follower, 26: sheath, 27: B.sub.4 C tube, 28: small diameter portion, 29: large diameter portion, 30: end plug, 31: fuel rod, 36: lower end tie plate. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION One specific feature of an embodiment of the present invention lies in that each of a fuel sheath tube (1), a spacer (13) and channel box (11) constituting a fuel assembly (10) for a nuclear reactor is formed of a Zr alloy; the Zr alloy is refined into an ultra-fine crystal particle size; and the Zr alloy contains alloy elements of Sn, Fe, Ni and Cr mostly dissolved in solid in amounts larger than those in a conventional alloy. In particular, by refining the Zr alloy into an ultra-fine crystal grain size of 100 nm or less, the irradiation damage can be substantially perfectly prevented. Additionally, each of the above-described alloy elements is added to enhance the strength and corrosion resistance. The crystal grain size of a Zr alloy of the present invention is in the range of 1000 nm or less, preferably, in the range of 300 nm or less, particularly, in the range from 10 to 100 nm. Sn is added in an amount of 15 wt % or less. It may be added in an amount of 1 to 2 wt % like a conventional Zr alloy; however, the added amount larger than 1 to 2 wt % gives a large effect, and is preferably in the range of from 3 to 7 wt %. Fe is added in an amount of 0.05 to 30 wt %. It may be added in an amount of 0.1 to 0.5% like a conventional Zr alloy. In a conventional Zr alloy, precipitations of Fe are formed by the repeating of cold-working and annealing, resulting in the reduced corrosion resistance. On the contrary, in the Zr alloy of the present invention, precipitations of Fe are difficult to be formed and are dissolved in solid, thus increasing the corrosion resistance. In particular, to obtain a high effect, the content of Fe is in range of 0.5% or more, preferably, in the range of from 1 to 5%. Ni is added in an amount of 5 wt % or less. Ni has a high hydrogen absorption property. However, since the Zr alloy of the present invention has an ultra-fine crystal grain size, Ni can be added in an amount of from 0.2% or more. Additionally, at least one kind of Cr, Nb, Mo, Te, Bi and Si may be added in an mount of 5 wt % or less for increasing the strength. In particular, there may be added at least one kind of 0.05-3% of Cr, 0.2-2.5% of Nb, 0.2-1% of Mo, 0.1-1% of Te, 1-2% of Bi and 0.1-0.5% of Si. Oxygen (O) is added in the alloying of the present invention. The addition of oxygen is effective to suppress the crystal grain growth due to the heating at a high temperature, which leads to the generation of ultra-fine crystal grains. The example of the Zr alloy composition (wt %) of an embodiment of the present invention is as follows: (1) A Zr alloy containing 1-5% of Sn and one kind of 0.1-30% of Fe, 0.01-5% of Ni and 0.1-5% of Te. (2) A Ze alloy containing the alloy elements shown in (1) and further 0.1-5% of Cr. (3) A Zr alloy containing 0.5-5% of Nb. (4) A Zr alloy containing the alloy element shown in (3) and further 0.1-5% of Bi. (5) A Zr alloy containing the alloy element shown in (3), and further 0.1-5% of Sn and one kind of 0.2-5% of Mo, 0.1-5% of Fe, 0.01-5% of Ni, and 0.1-5% of Te. In the usual process of melting, working and heat-treatment, the addition of a transient metal element such as Fe forms a large mount of a coarsened intermetallic compound in the Zr matrix. The Zr alloy having such a metal structure is brittle and is extremely difficult to be worked. However, by refining the Zr alloy having the composition containing such a brittle intermetallic compound in the usual state, the Zr alloy can ensure a high ductility. The feature of the present invention lies in manufacturing a structural member having an ultra-fine crystal state by working and heat-treatment by use of a material in an ultra-fine crystal state in which such an alloy element is dissolved in solid in Zr. A pure Zr powder and alloy powders (or a Zr alloy powder) are mechanically mixed and crushed, to form an alloy powder in a non-equilibrium state (super-saturated solid-solution). At this time, the pure metal powder may be replaced by a metal powder containing oxygen of 1,000 to 10,000 ppm. Moreover, an oxide powder such as ZrO.sub.2 may be added and mixed. The addition of the oxide powder is effective to enhance the crystallization temperature at the time of the subsequent HIP (hot isostatic pressing) for preventing the coarsening of crystal grains during HIP, hot-working and final annealing. The alloy powder thus obtained is sintered by HIP, to form a bulk material of a Zr alloy. The sintering may be performed at a temperature (<800 degrees C.) lower than a re-crystallization temperature for keeping at least part of the alloy powder in a non-equilibrium state after HIP and for preventing the coarsening of an intermetallic compound. In the case where the alloy powder is constituted of an amorphous alloy, the sintering may be performed at a temperature lower than the temperature higher than a crystallization temperature of the alloy by about 100 degrees C. for preventing the coarsening of crystals and the coarsening of the precipitated intermetallic compound. The solution treatment after HIP is not required and it may be omitted. The hot-plastic working may be performed at a temperature lower than a re-crystallization temperature, 650 degrees C. The cold-plastic working is performed at a draft of 80% or less, and the final annealing is performed at a temperature lower than 800 degrees C. Of the alloy elements, Sn and O are elements for increasing the strength; Fe is an element for reducing the resonance neutron capture cross-section; and Fe, Cr and Ni are elements for increasing the corrosion resistance. EXAMPLE 1 An alloy powder (Alloy No. 1) and raw powders of Zr, Fe, Sn Cr and Ni (Nos. 2 and 3), having a particle size of 100 .mu.m or less and having a composition shown in Table 1 (wt %), were subjected to metal alloying (MA) in a planetary bah mill for 101 hr and 155 hr respectively under an argon atmosphere at room temperature. The composition of each alloy powder after alloying was shown as an MA alloy powder in Table 1. In the ball mill, the vessel and balls are made of AISI 304 steel. Each of the alloy powder No. 1 and the Zr powder contains oxygen of about 900 ppm. TABLE 1 ______________________________________ raw powder alloy Sn Fe Cr Ni Zr ______________________________________ No. 1 1.5 0.25 0.14 0.10 bal. No. 2 1.3 0.05 0.05 0.03 bal. No. 3 10.0 30.0 -- -- bal. ______________________________________ MA alloy powder alloy Sn Fe Cr Ni Zr ______________________________________ No. 1 1.6 0.50 0.50 0.20 bal. No. 2 1.5 0.15 0.10 0.10 bal. No. 3 13.0 55.0 -- -- bal. ______________________________________ The alloy powder after mechanical alloying (MA) contained oxygen in an amount of about 4,000 ppm. The reason why the contents of Sn, Fe, Cr and Ni in the MA alloy powder are higher than those in the raw powder lies in that Zr is stuck on the wall of the vessel of the planetary ball mill, and in that the alloy elements are supplied from the vessel and balls. The MA alloy powder No. 1 was observed for the fine structure using a transmission electron microscope, which gave the result that the matrix of the MA alloy powder is made of amorphous crystal surrounding ultra-fine crystals having a crystal grain size of 10 nm or less, and that any dislocation does not exist in the crystal grains although the alloy powder is applied with a forcible work at room temperature. Moreover, although in the conventional Zr alloy, there exist intermetallic compounds such as Zr(Fe, Ni).sub.2, Zr.sub.2 (Fe, Ni), Zr(Fe, Cr).sub.2, these precipitation phases do not exist in the inventive alloy powder. This shows that the alloy elements are dissolved in the matrix as the super-saturated solid-solution. FIG. 1 is a graph showing the result of measuring the distribution of the crystal particle size of the MA alloy powder. As described above, the crystal structure was contained in the alloy powder only in an amount of about 5 vol %, and 90% or more of the crystal grain sizes were in the range of 2 to 10 nm. By increasing a period of time for mechanical alloying (MA) from 101 hr to 155 hr, the crystallized portion in the alloy powder is reduced, and the whole alloy powder becomes amorphous by the MA for about 200 hr. In the present invention, it is desirable that the whole MA alloy powder becomes substantially amorphous. FIG. 2 is a diagram showing the result in which the alloy powder No. 1 is subjected to scanning differential thermal analysis and the re-crystallization temperature is measured. The peak of the heat-generation appears at 719 degrees C., which shows a possibility that the holding of the alloy powder for a long period of time at the temperature higher than 719 degrees C. causes the re-crystallization of the above-described amorphous structure, leading to the growth of crystal grains. However, even when the MA alloy powder No. 1 was heated for 5 hr at 800 degrees C., it kept the ultra-fine structure yet while the crystal grains were slightly grown into a size of about 50 nm. Accordingly, it is revealed that the alloy powder No. 1 can keep the ultra-fine structure even by setting the powder processing (solidifying) temperature after MA at a temperature near 800 degrees C. When being actually heated at 800 degrees C., the alloy powder No. 1 was present substantially as a super-saturated solid-solution without any precipitation phase. FIG. 3 shows a damage preventive mechanism for ultra-fine crystals against neutron irradiation. As shown in the figure, atoms are repelled by neutrons and a pair of an interstitial atom and a vacancy are formed. In the usual crystal, the interstitial atoms are bonded to each other to form a loop of a dislocation, which causes the irradiation embrittlement, irradiation growth and the like. However, in the ultra-fine crystal alloy, interstitial atoms and vacancies are present near the crystal boundaries, and accordingly they move and disappear. Consequently, in the ultra-fine crystals in which the grain boundaries are present near interstitial atoms and vacancies, any defect is not generated in the crystal grains, thus preventing the generation of damages such as irradiation embrittlement, irradiation growth and the like. The relationship between the crystal grain size and the irradiation condition for preventing the irradiation damage is represented by the equation (1). EQU d=2.K.sub.0.sup.-1/4. exp.sup.(-Em/4 kT) (1) where d: crystal grain size (nm), K.sub.o : neutron irradiation rate (dpa/s), k: Boltsmann's constant, T: temperature (K), and Em: moving energy (eV) of interstitial atom. FIG. 4 shows the relationship between the neutron irradiation rate and the critical crystal grain size for preventing the irradiation damage. From the figure, it becomes apparent that in a light water reactor, the irradiation damage can be prevented by setting the crystal grain size to be in the rage of 100 nm or less. Moreover, in a high conversion reactor, the same effect can be obtained by setting the crystal grain size to be in the range of 50 nm or less. In the existing nuclear reactor, the neutron irradiation rate is 5.times.10.sup.-8 (dpa/s) and the quantity of irradiation is 7 dpa; and in a high conversion reactor, the former is 3.times.10.sup.-7 dpa/s and the latter is 20 dpa. FIGS. 5a and 5b show the result of the effect of Fe, Ni and Cr exerted on the corrosion resistance. Each of these elements exists at the position of Zr by the replacement with Zr in the oxide film. As the electronic conductivity of the oxide film becomes higher, the corrosion rapidly proceeds. Fe, Ni, and Cr act to trap these conductive electrons thereby lowering the electronic conductivity of the oxide film, resulting in the improved corrosion resistance. The probability of replacement of Zr by Fe, Ni, and Cr is significantly increased in a super-saturated solid-solution. Accordingly, in terms of corrosion resistance, the member of a fuel assembly (10), as shown in FIG. 17, of the present invention is extremely excellent. However, Nb having five valence electrons, and Mo and Te having six valence electrons increase the electronic conductivity, so that it seems to lower the corrosion resistance. The movement of electrons in the oxide film rate-determines the corrosion of Zr. FIG. 6 shows the relationship of a water-fuel volume ratio exerting an effect on the neutron absorption rate (%) represented by the resonance neutron capture cross-section based on the whole neutron generation rate. In the figure, the line shows the state that the resonance neutron capture cross-section of the Zr alloy is reduced by the change in the alloy composition and the strength. As is apparent from the figure, even when the water-fuel volume ratio is about 0.5 or less, by increasing the strength of the Zr alloy by two times and thus setting the thickness to be half, the resonance neutron absorption rate can be reduced to the value similar to that of stainless steel. Alternately, by adding Fe in an amount of 50 wt % or more, the resonance neutron capture cross-section is reduced, thus realizing the member of a fuel assembly (10) which has the same characteristics as those of stainless steel. In a high conversion reactor, the water-fuel volume ratio is set to be in the range of 1.5 or less. The ultra-fine crystal powder was subjected to electron irradiation for examining the irradiation resistance. Electron beams of imparting damages equivalent to those obtained by imparting the quality of neutron irradiation of 10 dpa were irradiated, and the fine structure was examined. The irradiation temperature was set at 280 degrees C. which was equivalent to the water temperature in a nuclear reactor. As a result, the ultra-fine crystal powder showed the very excellent irradiation resistance without any irradiation defect. The same experiments were performed for Nos. 2 and 3 alloy powders, which gave the same results as those of the alloy powder No. 1. Consequently, it is revealed that the ultra-refining of the crystal grains using the mechanical alloying (MA) method can provide a very excellent irradiation resistance. EXAMPLE 2 A fuel structural member was manufactured using the alloy powder No. 1 subjected to mechanical alloying for 155 hr in the manner described in Example 1. The MA alloy powder was formed and sintered in a cylindrical shape by a hot-isostatic pressing (HIP) at about 800 degrees C. The density was about 98% of the theoretical density. The sintered cylindrical body was perforated at the center, to form a hollow billet. A pure Zr tube was then inserted in the hollow billet and the end surfaces thereof were welded, thus integrating the alloy hollow billet and the pure Zr tube. The integrated tube was subjected to hot-extrusion at 650 degrees C., to form a raw tube. The density of the raw tube almost equals the theoretical density. The raw tube was repeatedly and alternately subjected to cold-rolling by a pilger mill and annealing by three times. The draft was set at 70%, and the final annealing temperature was set at 600 degrees C., thus obtaining a finished fuel sheath tube having an outside diameter of 12.3 mm and a wall thickness of 0.86 mm. In the sheath tube thus obtained, an average crystal grain size was smaller than 100 nm, and any precipitation was not recognized and all of the alloy elements are substantially dissolved in solid in the matrix. The pure Zr liner layer may be set at a desirable thickness in the range of from 10 to 100 .mu.m. The above-described billet may be set to have an outside diameter of 60 to 70 mm and a thickness of 10 to 12 mm. The pure Zr liner layer of the sheath-tube was removed by mechanical grinding. The resultant sheath tube was kept for 50 hr in steam of 10.3 MPa at 500 degrees C. for examining the corrosion resistance. As a result, the increment by the corrosion was 40 mg/dm.sup.2 or less, which showed the very good corrosion resistance. A conventional fuel sheath tube was also subjected to the corrosion test under the same condition, which gave the result of the increment of about 50 mg/dm.sup.2. A fuel rod, shown in FIG. 7 was manufactured using the above sheath tube (1) welded with end plugs made of the same alloy. The fuel rod includes an MA alloy sheath tube (1), a pure Zr liner (2), an upper end plug (3), a nuclear fuel pellet (4), a plenum spring (5), a welding portion (6), and a lower end portion (7). The welding was performed by a TIG welding method. The pure Zr liner (2) had a wall thickness of about 100 .mu.m. In this example, since the sheath robe (1) is thinned by repeating cold-working and annealing, the orientation of the crystal face of (0002) of Zr having the hexagonal crystal structure tends to be directed at right angles to the planar surface; however, the orientation is difficult to be generated because of the ultra-fine crystal grains. As a result, it seems that the crystal grains are distributed at random to the extent of a Fr value of about 0.25 to 0.35. EXAMPLE 3 The alloy powder No. 1 (MA: 155 hr) in Example 1 was formed and sintered by HIP, to manufacture a slab. The slab was hot-rolled, to enhance the density of the material substantially up to the theoretical value. The hot-rolled sheet was repeatedly and alternately subjected to cold-working at a draft of about 30% and vacuum annealing at 600 degrees C., to form a sheet having a thickness of 2 mm. The resultant sheet was bent in a U-shape. Two of these sheets were welded to each other, to form an angular cylinder. The angular cylinder was shaped in specified dimensions, to form a channel box. In the alloy of this example, any precipitation was not recognized, and alloy elements were dissolved in solid. FIGS. 8a-b and 9a-c are perspective views, wherein FIGS. 8a-b shows a straight structure having a constant thickness, and FIGS. 9a-c show a structure in which a corner (20) is thicker than that of a side (21). In FIG. 9b, the outside is thicker; and in FIG. 9c, the inside is thicker. The shaping was performed by suitably masking the channel box, followed by chemical etching by mixed acid solution of hydrogen fluoride and nitric acid or machining. Moreover, in the same manufacturing process, a hexagonal channel box may be obtained. In this hexagonal channel box the wall thickness may be made constant or corner portions may be made thicker. EXAMPLE 4 An alloy powder No. 3 of Table 1 in Example 1, was mechanically alloyed in the same manner as in Example 1, and was subjected to HIP, hot-working and cold-working, like the sheath tube, into a shape of a spacer. The inside diameter of the tubular spacer was larger than the outside of the sheath robe, and the inside diameter portion of the tubular spacer was not provided the pure Zr liner. It was subjected to hot-extrusion in the state where the pure Zr inner robe was not inserted. FIG. 10a shows a plan view and FIG. 10b shows a side view of a spacer (13) of 8.times.8 type. The spacer (13) is intended to regularly arrange fuel rods as an assembly. The spacers (13) in the number of seven pieces or more are disposed in the assembly, and control rods (16) are disposed between the assemblies so as to crossed to each other as shown in the figures. As shown in FIG. 11, the spacer (13) includes 8-10 pieces of cylindrical circular cells (14) for one row, for example, in the arrangement of 8.times.8, 9.times.9, and 10.times.10 (pieces). The cell (14) may be formed of the same material as in this example. It can be manufactured in the same process as that of the sheath tube in Example 1 except that the pure Zr was not provided in the hollow billet. In this example, since the spacer (13) and the cell (14) are formed of a high strength material having the above-described composition, either of the spacer (13) and the cell (14) can be thinned to a wall thickness of 0.35 to 0.6 mm. This reduces the average interval between fuels, thus achieving a high conversion reactor. FIG. 12 is a plan view of a spacer (13) of 9.times.9 type and cells (14) disposed therein. The average interval between the sheath tubes of 8.times.8 type shown in FIGS. 10a-b can be set at about 3.0 to 4.5 mm; and the average interval for the sheath tube of 9.times.9 type shown in FIG. 12 can be set at 1.0 to 2.5 mm. By strengthening the sheath tube, spacer (13) and cell (14) using an alloy containing alloy elements in increased amounts, the integration of the sheath tube of 9.times.9 type or 10.times.10 type can be further increased, and the average interval can be further reduced to be 1 to 2.0 mm. The circular cells (14) are welded to each other or fixed on the outer frame of the spacer (13), and spring made holding members are mounted to form a slight space between the sheath tubes. The spring made holding member can be also formed of a sheet of the Zr alloy or Ni alloy of the present invention. EXAMPLE 5 FIGS. 13 and 14 are partially sectional plan views each showing a water rod. The water rod in this example was manufactured by forming a hollow billet without a pure Zr liner tube by use of each of the alloy Nos. 1 and 2 shown in Table 1 of Example 1 in the same manner as in Example 1; and repeatedly applying, to the hollow billet, the cold-working by the pilger mill and annealing in the same manner as in Example 1. A small diameter portion (28) and a large diameter portion (29) shown in FIG. 14, were separately manufactured, and they were integrated with each other by welding. Reference numeral (30) designates an end plug. EXAMPLE 6 FIG. 15 is a sectional view of a fuel assembly for a boiling water type high conversion nuclear reactor according to the present invention. As shown in the figure, the fuel assembly includes a large number of fuel rods (31); seven steps or more of spacers (13) for holding the fuel rods (31) at specified intervals; an angular cylindrical channel box (11) for containing the fuel rods (31) held by the spacers (13); an upper end tie plate (15) and a lower end tie plate (36) for holding both the ends of the fuel rods (31) containing fuel pellets in the fuel sheath tubes (1); and a hanging handle (12) for carrying the whole assembly. The fuel channel box (11) contains the fuel rods (31) integrated with each other by the fuel spacers (13). The fuel channel box (11) is obtained by joining two-divided U-shaped plates manufactured in Example 2 by plasma welding into an angular cylindrical shape. The member acts to regularly run both steam generated on the surfaces of fuel rods (31) and high temperature water flowing between the fuel rods (31), and to forcibly introduce them upward. Since the channel box (11) has the internal pressure being slightly higher than the external pressure, it can be used for a long period in the state that a stress is applied so as to expand the angular cylinder outward. The channel box (11) in this example shows the arrangement in which 247 pieces of fuel rods (31) are disposed held by the spacers (13) as shown in FIG. 16. The circular cell (14) in the spacer (13) is the same as that in Example 4. As a high conversion type BWR fuel, there is used an MOX fuel in which plutonium is added to enrich depleted uranium or natural uranium. In the BWR, for enhancing the conversion ratio and increasing the produced amount of plutonium, it is required to lower the water-fuel ratio. This can be achieved by disposing fuel rods in a fuel assembly in a closed-pack manner for lowering the amount of a moderator to the fuel. In the case of realizing the same conversion ratio, the water density can be simply reduced by steam voids in the reactor core, so that the interval between fuel rods can be made large as compared with a pressurized water reactor. This is advantageous not only in cooling fuel but also in manufacturing the assembly. In consideration of application to a conventional type reactor core, the reactor core uses a fuel assembly having a square section and a cross-shaped control rod for minimizing the modification of the nuclear reactor structure. As the arrangement of fuel rods there is adopted a closed-pack triangular arrangement shown in FIG. 16 for lowering the water-fuel ratio. Moreover, the enlargement of the fuel assembly reduces the area of the water gap portion between fuel assemblies. Thus, it becomes possible to increase the number of fuel rods per unit area by about two times that of a conventional type BWR. Accordingly, in the case of the same reactor core equivalent diameter, by reducing the effective length of the fuel rod to be about half, the thermal output of the fuel rod per unit length can be made to be similar to that of a conventional reactor core. In this case, the pressure loss in the reactor core can be reduced by the shortening of the effective length of the fuel rod. The water-fuel ratio can be further reduced by adoption of a control rod with a follower (25) in which a zirconium made follower (25), shown in FIG. 18, is provided at the leading edge of an absorption material of the control rod, in addition of the arrangement of the fuel rods. Namely, when the reactor core is stopped, the absorption material portion of the control rod with a follower (25) is inserted in the reactor core; but in the operation, only the follower (25) portion is inserted for excluding water from the water gap portion, thereby reducing the water-fuel ratio, resulting in the increased conversion ratio. Moreover, the water-fuel ratio is increased by fully drawing the follower (25) portion of the control rod at the end of the cycle, as needed, thereby obtaining the gain of the reactivity. In this example, 247 pieces of the fuel rods are arranged in one channel box. FIG. 17 is a sectional view showing the structure of a high conversion reactor. The pressure vessel used in the nuclear reactor is not required to be changed in design from that used in a conventional type BWR; but the fuel assembly (10) loaded in the pressure vessel and a control rod guide tube, reactor core supporting plate (19) and an upper grating plate (18) in association with the enlarged control rod must be changed. As for the other parts such as an internal pump system and a steam separator (17), the existing structures may be used. The high conversion reactor shortens the fuel effective length. However, the control rod is provided with a follower and has the same length as conventional. Accordingly, the fuel channel box is set at the conventional length used for the supporting and guiding the control rod. Thus, the channel box can be supported by the upper end grating plate as in a conventional type BWR, and is not required to be changed in design.
048805963	claims	1. In a reactor control assembly utilizing electromagnetic means for retaining a control element in ready position for insertion into a reactor core containing a plurality of fuel assemblies having coolant flowing therethrough, the improvement comprising: first means responsive to temperature of reactor coolant passing through said fuel assemblies for releasing said control element, said first means including a quantity of thermionic material which changes from a high electrical resistance to a low electrical resistance upon an increase in reactor coolant temperature above a selected temperature; second means responsive to reactor neutron flux for releasing said control element, said second means including a quantity of material which is heated by neutron flux and a quantity of thermionic material that changes from a high electrical resistance to a low electrical resistance upon an increase in temperature above a selected temperature, said thermionic material being heated by the heating of said first-mentioned material by neutron flux; and an electrical circuit interconnecting a power source with said electromagnetic means, said first and second means being connected to said electrical circuit so as to be electrically in paralllel with said electromagnetic means; whereby under normal operating conditions electrical current flows from said power source to said electromagnetic means, and activation of either of said first means or said second means causes electrical current flowing to said electromagnetic means to be short-circuited resulting in release of said control element from said electromagnetic means for insertion of said control element into said reactor core. said control assembly having a guide tube within which is movably positioned an absorber element and a drive mechanism for positioning and retaining said absorber element exterior of the core region under normal reactor operating conditions, said drive mechanism including an electromagnetic means for retaining said absorber element, said absorber element, said guide tube, and said drive mechanism each being constructed so as to allow reactor coolant to pass therethrough, a first means responsive to reactor neutron flux, a second means responsive to coolant temperature exiting from said fuel assemblies, each of said first and second means being operatively connected to an electrical circuit connecting a power source to said electromagnetic means so as to be connected in parallel with said electromagnetic means for causing release of said absorber element upon activation of said first or second means, each of said first and second means containing a quantity of thermionic material which ionizes at a selected temperature causing said means to change from a high electrical resistance to a low electrical resistance, and said first means additionally including a quantity of material which is heated by reactor neutron flux causing heating of said thermionic material; whereby activation of said means, due to heating thereof to said selected temperature by either reactor neutron flux or coolant from the fuel assemblies, causes short-circuiting of said electromagnetic means so as to release said absorber element which falls into the reactor core region for reducing reactivity of the fuel assemblies. said guide tube and said control element each being constructed to allow reactor coolant to flow upwardly therethrough, said control element being provided with a magnetic armature at an upper end thereof, an electromagnet located within said guide tube, secured to a drive mechanism, and positioned so as to cooperate with said magnetic armature to retain or release said armature and said control element, and means responsive either to an increase in temperature of the coolant passing through at least one of said fuel assemblies, or to an increase in neutron flux for effecting deactivation of said electromagnet and release of said control element, said means comprising a plurality of switches connected to an electrical circuit connecting an electrical source to said electromagnet so as to be in parallel with said electromagnet and activated by ionization of a quantity of thermionic material contained therein, causing said switches to change from a high resistance to a low resistance thereby short-circuiting current flow through said electrical circuit to said electromagnet, said thermionic material being ionized by an increase in temperature above a selected temperature, one of said plurality of switches being additionally provided with a quantity of material capable of being heated by neutron flux which heats said thermionic material causing ionization thereof. 2. The improvement of claim 1, wherein said first means is positioned such that reactor coolant exiting from the fuel assemblies flows thereacross. 3. The improvement of claim 1, wherein said second means is positioned such that it is shielded from reactor coolant exiting from the fuel assemblies. 4. The improvement of claim 1, wherein each of said first and second means consists of at least one thermionic diode. 5. The improvement of claim 4, wherein at least one of said thermionic diodes constituting said first means is provided with a quantity of uranium comprising said first-mentioned quantity of material which is heated by neutron flux causing heating of said thermionic material and activation of the diode to short circuit electrical current flowing to said electromagnetic means. 6. The improvement of claim 4, wherein each of said thermionic diodes includes an emitter, a collector positioned with respect to said emitter to define a gap therebetween, said emitter and collector being mounted within a sealed container and provided with electrical leads extending therefrom through said sealed container for operative connection to said electrical circuit of said electromagnetic means, and said quantity of thermionic material being located within said sealed container, whereby heating of said thermionic material causes the diode to change from high electrical resistance to low electrical resistance whereupon the diode conducts electrical current causing short circuiting of the electromagnetic means and release of said control element. 7. A self-actuating shutdown system for a nuclear reactor having at least one fuel bundle positioned in a core region and provided with a control assembly and a plurality of fuel assemblies, 8. The system of claim 7, additionally including kinetic energy absorbing means positioned in said guide tube for stopping movement of said absorber element after it has entered the core region. 9. The system of claim 7, wherein said first and second means comprises a plurality of thermionic switches, at least one of said plurality of thermionic switches being responsive to coolant temperature of the fuel assemblies, and at least one of said plurality of thermionic switches being responsive to reactor neutron flux. 10. The system of claim 9, wherein at least one of said plurality of thermionic switches responsive to reactor neutron flux includes a quantity of uranium constituting said quantity of material for heating said thermionic material and activating said switch. 11. The system of claim 9, wherein said temperature responsive thermionic switch is positioned so as to be in direct contact with coolant exiting from said fuel assemblies. 12. The system of claim 9, wherein said neutron flux responsive switch is positioned so as to be substantially isolated from coolant exiting from said fuel assemblies. 13. The system of claim 12, additionally including neutron shield means positioned adjacent said neutron flux responsive switch. 14. The system of claim 9, wherein each of said thermionic switches are constructed as a thermionic diode having a spaced apart emitter and collector located within a sealed container, said quantity of thermionic material located within said sealed container, and electrical leads operatively connected to said emitter and collector plate and extending through said sealed container for electrical connection to said electrical circuit of said electromagnetic means. 15. The system of claim 14, wherein at least one of said thermionic diodes is additionally provided with a quantity of uranium attached to said emitter. 16. The system of claim 15, wherein said quantity of uranium consists of a uranium blanket positioned around said emitter. 17. The system of claim 9, wherein said temperature responsive thermionic switch is located on an exterior surface of said drive mechanism adjacent the exit of coolant from said fuel assemblies. 18. In a self-actuating reactor shutdown system including at least one control element located within a guide tube, a plurality of reactor fuel assemblies having coolant passing therethrough and positioned around the guide tube and the control element, and electromagnetic means for retaining the control element external to a reactor core region and for releasing said control element so as to enable same to enter into the reactor core region, the improvement comprising: 19. The improvement of claim 18, wherein said plurality of switches include one switch responsive to neutron flux and a plurality of switches response to temperature of the coolant passing through a plurality of said fuel assemblies. 20. The improvement of claim 18, additionally including neutron shield means positioned adjacent said neutron flux responsive switch. 21. The improvement of claim 18, wherein each of said switches is constructed to include a spaced apart emitter and collector located within a sealed container, said quantity of thermionic material being located within said sealed container, and electrical leads extending through said sealed container and operatively connecting each of said emitter and collector to said electrical circuit. 22. The improvement of claim 21, wherein one of said switches additionally includes a quantity of uranium within said sealed container said uranium constituting said material capable of being heated by neutron flux.

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.