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description | The present application is related to co-pending and co-owned U.S. patent applications Ser. Nos. 11/174,443, entitled LPP EUV PLASMA SOURCE MATERIAL TARGET DELIVERY SYSTEM, filed on Jun. 29, 2005, and 11/168,190, entitled EUV LIGHT SOURCE COLLECTOR LIFETIME IMPROVEMENTS, filed on Jun. 27, 2005, and 11/067,124, entitled METHOD AND APPARATUS FOR EUV PLASMA SOURCE TARGET DELIVERY, filed on Feb. 25, 2005; and 10/900,839, entitled EUV LIGHT SOURCE, filed on Jul. 27, 2004, the disclosures of which are hereby incorporated by reference. The present application claims priority to U.S. Provisional Application Ser. No. 60/733,658, entitled EUV LIGHT SOURCE, filed on Nov. 5, 2005 and co-owned by applicants' assignee, the disclosure of which is hereby incorporated by reference. The present invention related to laser produced plasma extreme ultraviolet light sources. Laser produced plasma (“LPP”) extreme ultraviolet light (“EUV”), e.g., at wavelengths below about 50 nm, using plasma source material targets in the form of a jet or droplet forming jet or droplets on demand comprising plasma formation material, e.g., lithium, tin, xenon, in pure form or alloy form (e.g., an alloy that is a liquid at desired temperatures) or mixed or dispersed with another material, e.g., a liquid. Delivering this target material to a desired plasma initiation site, e.g., at a focus of a collection optical element presents certain timing and control problems that applicants propose to address according to aspects of embodiments of the present invention. U.S. Pat. No. 6,541,786, entitled PLASMA PINCH HIGH ENERGY WITH DEBRIS COLLECTOR, issued on Apr. 1, 2003, to Partlo, et al, and co-owned by applicants' assignee, and patents issued on parent applications of the application from which the U.S. Pat. No. 6,541,786 patent issued, and U.S. Pat. No. 4,589,123, entitled SYSTEM FOR GENERATING SOFT X RAYS, issued to Pearlman et al. on May 13, 1986, and Japanese laid open applications 08-321395, published on Dec. 3, 1996, with Kamitaka et al. inventors and assigned to Nikon Corp, and 09-245992, published on Sep. 19, 1997, with inventors Kamitaka et al. and assigned to Nikon Corp., relate to debris management in the vicinity of the exit opening for plasma generated EUV light sources. An EUV light source and method of operating same is disclosed which may comprise: an EUV plasma production chamber comprising a chamber wall comprising an exit opening for the passage of produced EUV light focused to a focus point; a first EUV exit sleeve comprising a terminal end comprising an opening facing the exit opening; a first exit sleeve chamber housing the first exit sleeve and having an EUV light exit opening; a gas supply mechanism supplying gas under a pressure higher than the pressure within the plasma production chamber to the first exit sleeve chamber. The first exit sleeve may be tapered toward the terminal end opening, and may, e.g., be conical in shape comprising a narrowed end at the terminal end. The apparatus and method may further comprise an EUV light receiving chamber housing the first exit sleeve chamber; a suction mechanism having a suction mechanism opening in the vicinity of the EUV exit opening of the first exit sleeve chamber removing EUV production material entering the EUV light receiving chamber through the EUV exit opening in the first exit sleeve chamber. The apparatus and method may further comprise the EUV producing plasma production chamber comprising a second EUV exit sleeve comprising an exit opening facing an inlet opening of the first exit sleeve; a second exit sleeve chamber housing the second exit sleeve and having an EUV light exit opening; a suction mechanism removing EUV production debris from the second exit sleeve housing. The method and apparatus may comprise a plasma production chamber comprising an EUV utilization device connection mechanism attached to the plasma production chamber; the attachment of the utilization device connection mechanism to the plasma production chamber being through a flexible coupling. The flexible coupling may allow for positioning of a beam of EUV light produced in the plasma production chamber relative to the attachment utilization device connection mechanism, and may, e.g., be a bellows. The method and apparatus may comprise an EUV plasma production chamber; an EUV light collector within the chamber comprising a first focus and a second focus, plasma forming the EUV light being collected by the EUV light collector being formed in the vicinity of the first focus and as beam of exiting EUV light exiting the EUV light source chamber being focused to the second focus in the vicinity of an exit opening; a second focus alignment sensing mechanism comprising: an image detection mechanism imaging the second focus through the first focus and the collector; an alignment indicator indicating the position of the exiting beam in relation to the exit opening. The image detection mechanism may comprise a camera. The exit opening may comprise an exit aperture leading to an EUV light utilization apparatus and fixed in space in relation to the EUV utilization apparatus. The method and apparatus may further comprise the alignment indicator may comprise a target positioned at the exit aperture or a contrast detector detecting contrast between the image of the primary focus and the image of the intermediate focus. The second EUV exit sleeve exit opening may comprise a differential vacuum aperture. Turning now to FIG. 1 there is shown a schematic view of an overall broad conception for an EUV light source, e.g., a laser produced plasma EUV light source 20 according to an aspect of the present invention. The light source 20 may contain a pulsed laser system 22, e.g., a gas discharge excimer or molecular fluorine laser operating at high power and high pulse repetition rate and may be a MOPA configured laser system, e.g., as shown in U.S. Pat. Nos. 6,625,191, 6,549,551, and 6,567,450. The light source 20 may also include a target delivery system 24, e.g., delivering targets in the form of liquid droplets, solid particles or solid particles contained within liquid droplets. The targets may be delivered by the target delivery system 24, e.g., into the interior of a chamber 26 to an irradiation site 28, otherwise known as an ignition site or the sight of the fire ball, which is where irradiation by the laser causes the plasma to form from the target material. Embodiments of the target delivery system 24 are described in more detail below. Laser pulses delivered from the pulsed laser system 22 along a laser optical axis 55 through a window (not shown) in the chamber 26 to the irradiation site, suitably focused, as discussed in more detail below in coordination with the arrival of a target produced by the target delivery system 24 to create an x-ray releasing plasma, having certain characteristics, including wavelength of the x-ray light produced, type and amount of debris released from the plasma during or after ignition, according to the material of the target. The light source may also include a collector 30, e.g., a reflector, e.g., in the form of a truncated ellipse, with an aperture for the laser light to enter to the irradiation site 28. Embodiments of the collector system are described in more detail below. The collector 30 may be, e.g., an elliptical mirror that has a first focus at the plasma initiation site 28 and a second focus at the so-called intermediate point 40 (also called the intermediate focus 40) where the EUV light is output from the light source and input to, e.g., an integrated circuit lithography tool (not shown). The system 20 may also include a target position detection system 42. The pulsed system 22 may include, e.g., a master oscillator-power amplifier (“MOPA”) configured dual chambered gas discharge laser system having, e.g., an oscillator laser system 44 and an amplifier laser system 48, with, e.g., a magnetic reactor-switched pulse compression and timing circuit 50 for the oscillator laser system 44 and a magnetic reactor-switched pulse compression and timing circuit 52 for the amplifier laser system 48, along with a pulse power timing monitoring system 54 for the oscillator laser system 44 and a pulse power timing monitoring system 56 for the amplifier laser system 48. The system 20 may also include an EUV light source controller system 60, which may also include, e.g., a target position detection feedback system 62 and a firing control system 64, along with, e.g., a laser beam positioning system 66. The target position detection system 42 may include a plurality of droplet imagers 70, 72 and 74 that provide input relative to the position of a target droplet, e.g., relative to the plasma initiation site and provide these inputs to the target position detection feedback system, which can, e.g., compute a target position and trajectory, from which a target error can be computed, if not on a droplet by droplet basis then on average, which is then provided as an input to the system controller 60, which can, e.g., provide a laser position and direction correction signal, e.g., to the laser beam positioning system 66 that the laser beam positioning system can use, e.g., to control the position and direction of the laser position and direction changer 68, e.g., to change the focus point of the laser beam to a different ignition point 28. The imager 72 may, e.g., be aimed along an imaging line 75, e.g., aligned with a desired trajectory path of a target droplet 94 from the target delivery mechanism 92 to the desired plasma initiation site 28 and the imagers 74 and 76 may, e.g., be aimed along intersecting imaging lines 76 and 78 that intersect, e.g., alone the desired trajectory path at some point 80 along the path before the desired ignition site 28. The target delivery control system 90, in response to a signal from the system controller 60 may, e.g., modify the release point of the target droplets 94 as released by the target delivery mechanism 92 to correct for errors in the target droplets arriving at the desired plasma initiation site 28. An EUV light source detector 100 at or near the intermediate focus 40 may also provide feedback to the system controller 60 that can be, e.g., indicative of the errors in such things as the timing and focus of the laser pulses to properly intercept the target droplets in the right place and time for effective and efficient LPP EUV light production. Turning now to FIG. 2 there is shown schematically further details of a controller system 60 and the associated monitoring and control systems, 62, 64 and 66 as shown in FIG. 1. The controller may receive, e.g., a plurality of position signal 134, 136 a trajectory signal 136 from the target position detection feedback system, e.g., correlated to a system clock signal provided by a system clock 116 to the system components over a clock bus 115. The controller 60 may have a pre-arrival tracking and timing system 110 which can, e.g., compute the actual position of the target at some point in system time and a target trajectory computation system 112, which can, e.g., compute the actual trajectory of a target drop at some system time, and an irradiation site temporal and spatial error computation system 114, that can, e.g., compute a temporal and a spatial error signal compared to some desired point in space and time for ignition to occur. The controller 60 may then, e.g., provide the temporal error signal 140 to the firing control system 64 and the spatial error signal 138 to the laser beam positioning system 66. The firing control system may compute and provide to a resonance charger portion 118 of the oscillator laser 44 magnetic reactor-switched pulse compression and timing circuit 50 a resonant charger initiation signal 122 and may provide, e.g., to a resonance charger portion 120 of the PA magnetic reactor-switched pulse compression and timing circuit 52 a resonant charger initiation signal, which may both be the same signal, and may provide to a compression circuit portion 126 of the oscillator laser 44 magnetic reactor-switched pulse compression and timing circuit 50 a trigger signal 130 and to a compression circuit portion 128 of the amplifier laser system 48 magnetic reactor-switched pulse compression and timing circuit 52 a trigger signal 132, which may not be the same signal and may be computed in part from the temporal error signal 140 and from inputs from the light out detection apparatus 54 and 56, respectively for the oscillator laser system and the amplifier laser system. The spatial error signal may be provided to the laser beam position and direction control system 66, which may provide, e.g., a firing point signal and a line of sight signal to the laser beam positioner which may, e.g. position the laser to change the focus point for the ignition site 28 by changing either or both of the position of the output of the laser system amplifier laser 48 at time of fire and the aiming direction of the laser output beam. Applicants propose a method and apparatus to suppress the flow of HBr etch gas and other gasses in the EUV source plasma generation chamber 26 and other materials carried in such gas(es) from passing into the region behind the intermediate focus 40, This is necessary, e.g., in order to the exposure tool from influx of gases and contaminants from the EUV source chamber 26. According to aspects of an embodiment of the present invention, e.g., a noble gas, e.g., argon gas may be in the region of the intermediate focus 40, e.g., at an intermediate focus aperture 150. The noble gas may be introduced, e.g., in front of the intermediate focus (IF) 40 in a short region between two (or more) apertures, the intermediate focus aperture 150 and a cone aperture 152 at the terminus of an intermediate focus cone 160. The intermediate focus cone 160 may be a part of an intermediate focus region of the EUV chamber 26 and be an extension through an intermediate focus cone bulkhead 170 which may, e.g., be formed integrally with an intermediate focus bulkhead flange 172. The intermediate focus aperture 150 may, e.g., be formed in an intermediate focus aperture plate 174 attached by suitable means, e.g., by welding to an intermediate focus cone housing 176, which may in turn be attached, by suitable means, e.g., welding, to the intermediate focus cone bulkhead 170. The intermediate focus bulkhead flange 170 may be attached by suitable means, e.g., by welding to a generally cylindrical turbo pump housing 180 which may form a portion of a turbo pump 182, e.g., having an inlet 184 and an outlet 186. The opposing end of the cylindrical housing 180 may be attached by suitable means, e.g., by welding to a turbo pump attachment flange 190. Within the interior of the turbo pump housing 180 may be a differential vacuum aperture 200, formed in a differential vacuum aperture plate 202, which may from the terminus of a generally cylindrical differential vacuum aperture housing 204. The differential vacuum aperture plate housing 204 may be attached by a suitable means, e.g., by welding to a differential vacuum aperture plate housing attachment flange 210, The flange 210 may be attached by suitable means, e.g., by welding or bolting to the turbo pump attachment flange 190 at the opposite end of a differential vacuum aperture opening 212 from the cylindrical housing 180. It will be understood by those in the art that this arrangement of the vacuum pump 182 and the differential vacuum aperture 200 and housing 204 may be utilized to maintain a slightly higher vacuum pressure at the intermediate focus side of the aperture 200 than in the EUV source chamber 26, to thereby also discourage gas and entrapped debris from flowing toward the intermediate focus cone 160. A noble gas, e.g., argon can be inserted under pressure through an argon gas inlet 230 into an intermediate focus gas plenum 232 and removed through an argon gas outlet 234. It will be understood that the noble gas, e.g., argon gas can thus be passed into the plenum 232 around the exterior of the intermediate focus cone 160, between the aperture at the terminus of the intermediate focus cone 160 and both through the aperture at the terminus of the intermediate focus cone 160 and the intermediate focus aperture 150 in the intermediate focus aperture plate 174. This can be used, e.g., to further insure that the EUV source chamber 26 gas(s) and other debris does not reach the intermediate focus aperture and enter the lithography tool (not shown) that in operation can be affixed to the intermediate focus aperture plate 174 by suitable means, e.g., by bolting. The aforementioned flow of gas can also, therefore, e.g., act as a buffer gas curtain. The gas and debris which does manage to reach the space between the intermediate focus gas cone aperture 152 and the intermediate focus aperture plate 174, e.g., can be pumped out from the gas plenum 232 area through gas outlet 234 before reaching, e.g., the intermediate focus 40. Gas molecules and very small debris particles that would normally flow from the EUV source chamber 40 through these apertures 152, 150 and to the intermediate focus and, e.g., into the lithography tool (e.g., into the illuminator) and/or to intermediate focus metrology detectors, can, e.g., undergo collisions with the argon buffer gas and be slowed and changed in direction and pumped away. The gas curtain can, e.g., prevent the transmission of mainly etch and background gases, as well as contaminants and small debris particles from the source chamber, that may be flowing with and/or entrapped within the gas(es), from reaching the region past the intermediate focus aperture 174. The delicate optics in the exposure tool may thus be protected from the influx of debris particles, etch gases and other contaminants present in the source chamber 26. A more than 1000-fold suppression of transmission of gases from the source chamber 26 to the region beyond the intermediate focus is expected. Argon gas, e.g., may be chosen as a buffer gas since it is highly transparent to the 13.5 nm EUV radiation. A partial pressure of argon of up to a few mTorr can be tolerated in this region and in at least the light entrance environs of the lithography exposure tool. Helium and hydrogen gas are also highly transparent to 13.5 nm EUV radiation and may be considered, as well. However, argon atoms are believed now to be more efficient in deflecting other particles and gas molecules since argon atoms are heavier than helium atoms or hydrogen molecules. The gas curtain as illustratively shown in FIG. 3 is believed to be most advantageously located just before the intermediate focus, since the cone of EUV light is small in this region and thus, e.g., only a small buffer gas volume may be required. As has been shown illustratively in FIG. 3, e.g., several apertures, e.g., two, i.e., apertures 152, 150, may be installed in the intermediate focus region, e.g., just in front of the intermediate focus, which may, e.g., lie within the intermediate focus aperture 150, with, e.g., the intermediate focus cone 160 having, e.g., a diameter size only slightly larger than the usable EUV light cone, as shown, e.g., in the cross-sectional view of the apparatus of FIG. 3 in FIG. 4. Argon gas is introduced between apertures 150, 152 in a region of about 1 cm in length before the intermediate focus. The etch gas and the argon gas, etc., may first be almost completely effectively pumped away in another region defined by the apertures 152, 200, further in front of the intermediate focus, for example, in the housing of the turbo-molecular pump 182, which may be corrosion-resistant, due to the presence, e.g., of HBr etching gas. The second aperture 152 may be at the terminus of the intermediate focus aperture cone 160, which may be cone-shaped to define a gas collision region. For example, the pressure in the region of the apertures 152 may form, e.g., a region of diffusive flow, e.g., with small mean-free path (mm-range) between collisions, e.g., to ensure that the etch gas and debris and contaminants cannot pass through the region of the gas curtain between apertures 152 and 150 without undergoing collisions leading to a large suppression of unwanted gas(es) and contaminants. The intermediate focus aperture 150 may be selected to be smaller than the other apertures, e.g., aperture 152, the purging gas, e.g., argon gas may be caused to be mainly flowing towards the source chamber 26 and is further pumped away in the pumping region within the turbo-molecular pump. A small portion of the argon gas is flowing into the region behind the intermediate focus, i.e., into and through the intermediate focus aperture 150, however, this can be tolerated, since argon is highly transparent to 13.5 nm EUV radiation. Also almost all of the gas in the region between apertures 152, 150 just in front of the intermediate focus is argon. Remaining contaminants from the source chamber 26 can the undergo collisions with the argon atoms flowing towards the source chamber and are pumped away in the aperture region further in front or in the source chamber, or are pumped out with purge gas flow through the outlet 234. In a second embodiment, the argon can also be made to flow through other additional orifices (not shown) directed away from the intermediate focus aperture 150 towards the chamber 26 to establish a flow direction opposite to the gas flow direction of etch gas and debris from the source chamber. Typical parameters may be, e.g., for HBr etch gas in source chamber, 20-30 mTorr, argon flow and pressure in gas curtain region, 10-20 sccm, 10-100 mTorr, argon background gas in region beyond the intermediate focus, 1-5 mTorr For certain applications of utilization of EUV light produced as noted above, e.g., for semiconductor lithography, an EUV “point” source must be aligned, e.g., in 5 degrees of freedom with respect to the optical relay lensing housed within the litho stepper (not shown) to which it interfaces, e.g., as by being bolted to the intermediate focus aperture plate 174. Thus the intermediate focus aperture plate 174 and its associated structure, e.g., as illustrated by way of example in FIGS. 3 and 4, will, in operation, remain fixed in space with respect to the lithography tool (not shown) and its optics with their generally fixed optical train and optical axis for the passage of the EUV light from the source 20 to the integrated circuit fabrication wafer to be exposed with the EUV light. It will be understood that the bellows connection 250 illustrated in FIGS. 3 and 4 is not in place in operation of the EUV source 20, but may be attached for the connection of metrology apparatus and provides for such apparatus generally five degrees of freedom in motion needed to perform the metrology function. The EUV collector optic 30 may be, e.g., a reflectively coated elliptical substrate. Of the ellipse's two focal points, the one nearest the substrate is termed primary focus, since this is the point 28 where EUV energy is produced by plasma formation. The second focal point is termed the “Intermediate Focus” and represents the zone at which the EUV light source and an EUV lithography stepper interface. From a system perspective, maintaining energy focus at intermediate focus 40 can be of paramount importance (as the lithography tool—stepper/scanner—has its own optical relay lensing). To assure proper positioning of the intermediate focal point 40 it may be necessary to have adjustability with regard to the nominal placement of the collector optic (and thus the primary focal point, e.g., where the plasma formation point 28 is desired to be kept). With regard to heat loading or other dynamic deformation of the collector optic 30 during operation, it is likely that an active positioning system for the collector 30 will also be required. The bellows arrangement 302 shown in FIGS. 3 and 4 allows for six degrees of freedom in moving the collector and the primary focus 28 vis a vis the fixed in space (when connected to a lithography tool) intermediate focus 40. Such positioning requires active feedback from some sensing device(s) to determine positioning of the primary focus 28 with respect to the fixed intermediate focus position 40. According to aspect of an embodiment of the present invention, applicants propose to provide feedback with respect to alignment of primary and intermediate focal point 28, 40 in 3 axes, referred to as X, Y, and Z axes, with the Z axis being longitudinally along the beam (cone) of EUV light from the collector 30 to the intermediate focus 40 and the X and Y axis lying in a plane orthogonal to the X axis. Feedback may be in situ with regard to operation of the LPP device, i.e., from within the chamber 26, requiring no downtime to recalibrate the alignment. Turning to FIG. 5 there is shown by way of illustration a schematic view of an example of EUV metrology according to aspects of an embodiment of the present invention, where, e.g., a plurality of image detectors, e.g., a plurality of cameras 350, e.g., two cameras 350, illustrated in the present application for the sake of clarity. However, in order to collect feedback from three degrees of freedom (XYZ), or more, it is anticipated that at least three cameras 350 may be required. The cameras 350 may be positioned so that, e.g., their field of view includes a portion of the optical surface of the elliptical collector optic 30 (that relays focused EUV energy to intermediate focus 40). The cameras 350 may be lensed, e.g., with lenses on the cameras 350 and/or lenses 352 such that, e.g., a sharp image of the primary focus 28 and (via a bounce off of the elliptical collector 30) also the intermediate focus 40, and/or the intermediate focus aperture 150 is captured. When alignment is “true” the plasma event at or in the close vicinity of the primary focus 28 will be essentially coaxial with the physical aperture 150 at intermediate focus 40. Thus giving an indication of the positioning of the plasma formed at or in the near vicinity of the primary focus 28 vis-a-vis the fixed location of the intermediate focus 40. This may be possible with or without a third camera 350, e.g., with a focus or contrast detector, or both, viewing the image of the plasma event and the position thereof relative to the center of the aperture 150. The EUV energy detectors 400 positioned, e.g., at four quadrants of the plasma emission distribution, e.g., in the plane of the X and Y axis may also be useful in this regard. X and Y positioning of the primary focus 28, vis a vis the intermediate focus 40 may also be best viewed, e.g., via the two cameras illustrated in FIG. 5, e.g., oriented at 90 or 180 degrees with respect to one another. Other angular orientations are valid, but motion compensation loops become less intuitive. The viewing angle of these two cameras with respect to the central Z axis of the LPP device 20 should be identical. The viewing angle of a third camera 350 (not shown) could differ from the other two illustrated cameras 350, e.g., so as to detect errors along the Z axis. The greater the difference in viewing angle of this third camera 350 (not shown), the greater the resolution one could have with respect to determining the Z axis error. An alternate methodology (using fewer cameras) could include a camera/lensing (not shown), e.g., with high NA/short depth of focus located on the far side of the intermediate focus 40 aperture 150. Z axis error also could be made evident, e.g., if the plasma event at or in the near vicinity of the primary focus 28 is unfocused, e.g., with respect to the intermediate focus aperture 150. This type of measurement with a far side camera, at least located along the Z axis can likely be done only with the intermediate focus aperture 150 not connected to, e.g., a lithography tool. The bellows arrangement 250 (shown in FIGS. 3 and 4 can be used for connection of such a metrology device and for allowing it some freedom of movement in several axes, e.g., in the Z axis to, e.g., focus the image of the plasma event to, e.g., determine the Z axis error, without having to move the chamber 26, e.g., prior to actually moving the chamber 26. It will be understood by those skilled in the art that above an EUV light source and method of operating same is disclosed which, according to aspects of an embodiment of the present invention may comprise: an EUV plasma production chamber comprising a chamber wall comprising an exit opening for the passage of produced EUV light focused to a focus point, such as a wall of a unit meant to be attached to an EUV light utilization mechanism, e.g., a photolithography scanner or a wall that is integral with a chamber wherein plasma production of EUV light occurs and which may have other units or housings connected to it in series or nested or otherwise, e.g., as shown in FIGS. 3, 4 and 5. According to aspects of an embodiment of the present invention the apparatus and method may comprise a first EUV exit sleeve comprising a terminal end comprising an opening facing the exit opening; a first exit sleeve chamber which may house the first exit sleeve and may also have an EUV light exit opening. A gas supply mechanism may supply gas, such as a buffer gas, e.g., argon under a pressure higher than the pressure within the plasma production chamber to the first exit sleeve chamber, to thereby form, e.g., a gas curtain deterring the exit of material from the exit sleeve terminal aperture. The first exit sleeve may be tapered toward the terminal end opening, and may, e.g., be conical in shape comprising a narrowed end at the terminal end. The apparatus and method may further comprise an EUV light receiving chamber housing the first exit sleeve chamber and may include a suction mechanism, e.g., a pump, having a suction mechanism opening in the vicinity, e.g., near enough to most effectively remove the material that is not stopped by the buffer gas of the EUV exit opening of the first exit sleeve chamber. Such EUV production material prevented from entering the EUV light receiving chamber, which may in operation be attached to or a portion of an EUV light utilization apparatus, such as a photolithography scanner, may comprise gas constituents of the plasma production chamber contents, e.g., etching/cleaning gas(es), buffer gases(es), etc. or plasma formation debris, such as ions, plasma source material, or other materials, e.g., carried from or otherwise removed from surfaces in the chamber, e.g., bromine and/or hydrogen compounds. The apparatus and method may further comprise the EUV producing plasma production chamber comprising a second EUV exit sleeve comprising an exit opening facing an inlet opening of the first exit sleeve; a second exit sleeve chamber housing the second exit sleeve and having an EUV light exit opening; a suction mechanism, such as another pump, removing EUV production debris from the second exit sleeve housing. The method and apparatus may comprise a plasma production chamber comprising an EUV utilization device connection mechanism attached to the plasma production chamber, such as a mechanism including or connected to an intermediate focus aperture plate comprising an EUV intermediate focus aperture, positioned in the vicinity of the intermediate focus; the attachment of the utilization device connection mechanism to the plasma production chamber being through a flexible coupling. The flexible coupling may allow for positioning of a beam of EUV light produced in the plasma production chamber relative to the attachment utilization device connection mechanism, thus, to the desired position of the intermediate focus fixed in space as to the utilization device, and may, e.g., be a bellows. The bellows can allow, e.g., for several, e.g., six degrees of freedom of movement of the collector vis-a-vis the desired position of the intermediate focus, e.g., by moving the rest of the EUV plasma production chamber other than the portion(s) attached to the utilization mechanism. The method and apparatus may comprise an EUV plasma production chamber; an EUV light collector within the chamber comprising a first focus and a second focus, plasma forming the EUV light being collected by the EUV light collector being formed in the vicinity of the first focus and as beam of exiting EUV light exiting the EUV light source chamber being focused to the second focus in the vicinity of an exit opening, such as the intermediate focus aperture; a second focus alignment sensing mechanism comprising: an image detection mechanism imaging the second focus through the first focus and the collector; an alignment indicator indicating the position of the exiting beam in relation to the exit opening, such as the position of the actual second focus vis-a-vis the desired position of the second focus, e.g., in regard to the utilization tool, e.g., a indicated by the position of the EUV light exit aperture plate. The image detection mechanism may comprise a camera. The exit opening may comprise an exit aperture leading to an EUV light utilization apparatus and fixed in space in relation to the EUV utilization apparatus. The method and apparatus may further comprise the alignment indicator comprising a target positioned at the EUV intermediate focus aperture or a contrast detector detecting contrast between the image of the primary focus and the image of the intermediate focus. The second EUV exit sleeve exit opening may comprise a differential vacuum aperture, e.g., sized in relation to a pump drawing a suction on the downstream side of the second EUV light exit sleeve and to the pressure in the plasma production chamber to, e.g., maintain the downstream pressure higher than in the plasma production chamber, in order to, e.g., further discourage the passage of plasma production chamber material from the plasma production chamber toward the intermediate focus. It will be understood by those skilled in the art that the aspects of embodiments of the present invention disclosed above are intended to be preferred embodiments only and not to limit the disclosure of the present invention(s) in any way and particularly not to a specific preferred embodiment alone. Many changes and modification can be made to the disclosed aspects of embodiments of the disclosed invention(s) that will be understood and appreciated by those skilled in the art. The appended claims are intended in scope and meaning to cover not only the disclosed aspects of embodiments of the present invention(s) but also such equivalents and other modifications and changes that would be apparent to those skilled in the art. In additions to changes and modifications to the disclosed and claimed aspects of embodiments of the present invention(s) noted above others could be implemented. While the particular aspects of embodiment(s) of the EUV LIGHT SOURCE described and illustrated in this patent application in the detail required to satisfy 35 U.S.C. §112 is fully capable of attaining any above-described purposes for, problems to be solved by or any other reasons for or objects of the aspects of an embodiment(s) above described, it is to be understood by those skilled in the art that it is the presently described aspects of the described embodiment(s) of the present invention are merely exemplary, illustrative and representative of the subject matter which is broadly contemplated by the present invention. The scope of the presently described and claimed aspects of embodiments fully encompasses other embodiments which may now be or may become obvious to those skilled in the art based on the teachings of the Specification. The scope of the present EUV LIGHT SOURCE is solely and completely limited by only the appended claims and nothing beyond the recitations of the appended claims. Reference to an element in such claims in the singular is not intended to mean nor shall it mean in interpreting such claim element “one and only one” unless explicitly so stated, but rather “one or more”. All structural and functional equivalents to any of the elements of the above-described aspects of an embodiment(s) that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to he encompassed by the present claims. Any term used in the specification and/or in the claims and expressly given a meaning in the Specification and/or claims in the present application shall have that meaning, regardless of any dictionary or other commonly used meaning for such a term. It is not intended or necessary for a device or method discussed in the Specification as any aspect of an embodiment to address each and every problem sought to be solved by the aspects of embodiments disclosed in this application, for it to be encompassed by the present claims. No element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element in the appended claims is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited as a “step” instead of an “act”. |
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051961610 | claims | 1. A storage rack for retaining hazardous nuclear fuel rod assemblies normally disposed in liquid moderator filled pools while providing passive nuclear accident safety protection, comprising: a) a generally rectangular bottom plate; b) generally planar upstanding sidewalls conjoined along their vertical edges and joined along their lower edges to the periphery of said bottom plate to form an imperforate container; c) a plurality of vertically disposed, rectangular receiving tubes having lower ends which rest upon the bottom plate and upper ends of which are conjoined with an upper planar member defining the upper surface of said storage rack; d) a contiguous inner rectangular shell interposed between said conjoined sidewalls and the elongate receiving tubes disposed therein and spaced from the rack sidewalls to define a peripheral passageway with the sidewalls to permit convection liquid flowthrough of cooler moderator fluid entering from an ambient fluid pool to the rack bottom portion; e) at least one laterally disposed inlet port on the lower edges of each of said elongate tubes configured to permit moderator liquid entry and upflow therein fostered by the heat which is generated by the nuclear fuel assembly normally stored in said tubes; and f) at least one outlet port disposed in the upper planar member and overlying each of the elongate tubes to permit escape of warmed temperature moderator liquid from the rack to the ambient filled pool, such that the moderator liquid can circulate through said rack both while it is beneath the pool liquid level and while it is devoid of an ambient liquid envelope. a) a generally rectangular bottom plate; b) a plurality of generally upstanding sidewalls conjoined along their vertical edges and joined along their lower edges to the periphery of said bottom plate to form an imperforate container, wherein both said bottom plate and side walls are formed of a high chrome stainless steel; c) a plurality of vertically disposed, generally square cross section, open ended, elongate receiving tubes which, at their lower ends, rest upon the bottom plate surface and which at their upper ends intersect and are conjoined with an upper planar member defining the upper surface of the rack, said upper member having square edge covers each having one or more ports, and wherein said covers are coaxially aligned with the open ended tubes; d) a contiguous inner rectangular shell interposed between said conjoined sidewalls and the periphery of the array of elongate receiving tubes disposed therein, said shell being a substantially thinner gauge sheet metal than said bottom plate or sidewalls and said shell having slotted ports therein; e) the inner shell also being spaced from the rack sidewalls to define a peripheral passageway therebetween which permits convection liquid flowthrough of cooler moderator fluid entering from an ambient fluid pool to the rack bottom portion; f) one or more laterally disposed ports on the lower edges of each of said elongate tubes adapted for moderator liquid entry and upflow therein as fostered by waste heat generated by the nuclear fuel assemblies normally stored in said tubes; and g) one or more exit ports disposed in the upper planar member and overlying each of the elongate tubes to permit escape of warmer elevated temperature moderator liquid from the rack to the ambient filled pool, such that the moderator liquid can circulate through said rack both while it is beneath the pool liquid level and while it is devoid of ambient liquid. 2. The storage rack of claim 1 in which the upper member is provided with a plurality of hinged, squared edge covers having one or more ports, wherein the covers are coaxially aligned with the open tops of the elongate tubes. 3. The storage rack of claim 1 in which the rack bottom plate is provided with a resealable drain and refill orifice. 4. The storage rack of claim 1 in which the upper periphery of the rack is provided with two or more perforated lugs to facilitate hoisting and positioning of said rack in said filled pool. 5. The storage rack of claim 1 in which each receiving tube contains at least one fuel assembly, and the array is of elongate tubes is disposed in linear alignment and spaced to facilitate cooling fluid convection flow through the rack reservoir inlet and outlet ports. 6. The storage rack of claim 5 in which the inner rectangular shell has a plurality of generally vertical slots which facilitate moderator liquid flow into the ports on the lower edges of the elongate tubes. 7. The storage rack of claim 1 in which the upper member is provided with a linear array of peripheral ports which keep the rack liquid filled as warmed water escapes from the centrally located exit ports. 8. The storage rack of claim 7 in which the upper edges of the rack are provided with a perforated lug to facilitate lifting and resetting the rack in the liquid filled pool. 9. The storage rack of claim 1 in which the imperforate outer wall comprises high chrome stainless steel and the inner shell comprises a corrosion resistant, thinner gauge sheet metal. 10. A storage rack for retaining hazardous nuclear fuel rod assemblies normally disposed in liquid moderator filled pools and for further providing passive nuclear accident safety protection, said rack comprising: |
description | THIS INVENTION relates to a nuclear reactor plant. It further relates to a method of operating and to a method of constructing a nuclear reactor plant. It also relates to a cooling system. In a nuclear reactor plant, use is often made of a liquid coolant such as inhibited demineralized water, to cool the reactor and the cavity in which it is installed. Typically, use is made of a closed loop cooling system which includes one or more coolant chambers, arranged around at least part of the reactor, and pump means for pumping the coolant into and through the coolant chambers. A coolant inlet typically leads into the coolant chambers at a low level and a coolant outlet leads from the coolant chambers at a high level. A problem with this arrangement is that, should a breach occur in the inlet pipe, the coolant will drain from the coolant chambers which could lead to a potentially dangerous situation arising. It is an object of this invention to provide means which the Inventors believe will at least alleviate this problem. According to the invention there is provided a nuclear reactor plant which includes a heat source; at least one coolant chamber positioned in proximity to the heat source; a coolant inlet pipe which enters the coolant chamber at a high level and extends downwardly through the coolant chamber to a discharge end positioned at a low level within the coolant chamber; and an outlet leading from the coolant chamber at a high level. The nuclear reactor plant may include a plurality of coolant chambers arranged around the heat source, each of at least some of the coolant chambers having an inlet pipe which enters the coolant chamber at a high level and extends downwardly through the coolant chamber to a discharge end positioned at a low level within the coolant chamber. In one embodiment of the invention the heat source is a nuclear reactor. Preferably, the reactor may be a high temperature gas-cooled reactor of the type known as a Pebble Bed Reactor in which fuel, comprising a plurality of generally spherical fuel elements, is used. The fuel elements may comprise spheres of fissionable material in a ceramic matrix, or encapsulated in the ceramic material. In this embodiment of the invention gas coolant, eg helium, is fed through the reactor and liquid coolant is fed through the or each coolant chamber. In another embodiment of the invention the heat source is a used fuel storage facility. The plant may include anti-siphon means to reduce the risk that coolant will be siphoned from the coolant chamber, eg as a result of a breach occurring in the inlet pipe outside the coolant chamber. The anti-siphon means may include an anti-siphon valve mounted in the inlet pipe, typically at the highest point thereof. Instead, or in addition, the anti-siphon means may include at least one anti-siphon bleed opening provided in that portion of the coolant inlet pipe positioned within the coolant chamber at a position spaced from the discharge end whereby the coolant inlet pipe and the coolant chamber are connected or connectable in flow communication. Preferably, a plurality of anti-siphon bleed openings is provided in that portion of the coolant inlet pipe which is positioned at the highest level within the coolant chamber. The anti-siphon bleed openings may be in the form of holes in the pipe dimensioned to be sufficiently small so that, in normal use, the small amount of coolant flowing therethrough into the coolant chamber will have no or little detrimental effect on the cooling system and sufficiently large such that in the event of coolant being siphoned from the coolant chamber, when the coolant level in the coolant chamber falls below the level of the holes, sufficient gas, typically air, will be drawn from the coolant chamber into the coolant inlet pipe to break the vacuum and stop the siphoning. The anti-siphon bleed opening may be in the form of holes in the coolant inlet pipe which will have a combined area of between 1% and 10% of the cross-sectional area of the coolant inlet pipe. In an inlet pipe having a nominal diameter of 100 mm, typically between 4 and 8 anti-siphon bleed openings will be provided. The bleed openings will typically be circular and have a diameter of between 5 and 10 mm. The plant typically includes a pump, an outlet of which is connected to the or each coolant inlet pipe. The pump and the or each coolant chamber typically form part of a closed loop cooling system. The invention extends to a method of operating a nuclear plant having a heat source and at least one coolant chamber positioned in proximity to the heat source which method includes the steps of feeding coolant into the coolant chamber through a coolant inlet pipe which enters the coolant chamber at a high level and extends downwardly through the coolant chamber to discharge coolant into the coolant chamber at a low level; and removing coolant from the coolant chamber at a high level. The method may include inhibiting the draining of coolant from the coolant chamber by being siphoned from the coolant chamber through the coolant inlet pipe. The method may include the step of, in the event of coolant being siphoned from the coolant chamber through the coolant inlet pipe, bleeding gas into the coolant inlet pipe to stop the siphoning. The method may include bleeding gas from the coolant chamber through at least one bleed opening in the coolant inlet pipe into the coolant inlet pipe when the level of liquid coolant in the coolant chamber falls below the level of the at least one bleed opening. The invention further extends to a method of constructing a nuclear reactor plant having a reactor cavity and at least one coolant chamber positioned in proximity to the reactor cavity which method includes providing, a coolant inlet pipe which leads into the at least one coolant chamber at a high level and extends downwardly through the coolant chamber to a discharge position at a low level of the coolant chamber. The method may include the step of providing a plurality of coolant chambers around the reactor cavity. The method may include providing anti-siphon means in the inlet pipe. It will be appreciated that whilst the primary application of the invention is in respect of a nuclear reactor plant, the cooling system described may well have other applications. Hence, the invention extends to a cooling system which includes at least one coolant chamber; a coolant inlet pipe which enters the coolant chamber at a high level and extends downwardly through the coolant chamber to a discharge end positioned at a low level within the coolant chamber; and an outlet leading from the coolant chamber at a high level. The cooling system may include a plurality of coolant chambers arranged around a heat source, each of at least some of the coolant chambers having an inlet pipe which enters the coolant chamber at a high level and extends downwardly through the coolant chamber to a discharge end positioned at a low level within the coolant chamber. An advantage with this arrangement is that, should a breach in the inlet pipe occur, the coolant will not simply drain from the coolant chamber. In the drawings, reference numeral 10 refers generally to part of a cooling system of a nuclear reactor plant in accordance with the invention. In the embodiment shown the cooling system is used to cool the nuclear reactor part of which is generally indicated by reference numeral 11. It may however also be used for cooling a used fuel storage facility. The nuclear reactor 11 is positioned in a cavity defined within a concrete shell (not shown) and is at least partially surrounded by a plurality of coolant chambers 12, one of which is shown in the drawings. Each chamber 12 is defined by a circular cylindrical wall 13, typically in the form of a length of pipe, a top 14 and a bottom 15 sealing off the ends of the wall 13. The cooling system 10 includes a pump 16 having a suction or inlet side 18 and a discharge or outlet side 20. A coolant inlet pipe 22 is connected to the outlet 20 of the pump 16 and extends downwardly through the top 14 of the vessel to the bottom of the coolant chamber 12 at which it terminates in a upwardly directed discharge end 24. An outlet 26 leads from the vessel at a high level and is connected via piping 28 and other cooling circuit elements, generally indicated by reference numeral 30 to the inlet 18 of the pump 16. Hence, the cooling system is a closed loop cooling system. As can best be seen in FIG. 2 of the drawings, a plurality of anti-siphon bleed openings in the form of holes 32 provided in the highest portion of the coolant inlet pipe 22 positioned within the coolant chamber 12. In use, the pump 16 pumps coolant, typically in the form of inhibited demineralised water through the coolant inlet pipe 22 where it is discharged into each of the coolant chambers 12 at a low level through the discharge end 24 of the associated coolant inlet pipe 22. The coolant flows upwardly through the coolant chamber 12 extracting heat from the reactor and the reactor cavity and the heated coolant flows from the coolant chamber 12 through the pipe 28 where it is cooled and recycled. In the event of a breach or rupture in the coolant inlet pipe 22 the possibility exists that, depending upon the position of the breach, coolant will be siphoned from the coolant chamber 12 through the coolant inlet pipe 22. However, as the level of coolant in the coolant chamber 12 falls below the level of the holes 32, air from the coolant chamber 12 will flow into the coolant inlet pipe 22 thereby breaking the vacuum and stopping the siphoning to ensure that a relatively high level of coolant remains within the coolant chamber 12. The reactor can then be shut down, if necessary, and remedial action taken e.g. by repairing the breach. The holes 32 are typically dimensioned so that in normal use, coolant being pumped by the pump 16 which leaks through the holes 32 into the coolant chamber 12 will have no or little detrimental effect on the cooling system. However, the holes are sufficiently large to bleed enough air into the coolant inlet pipe 22 to break the vacuum and stop the siphoning process. Naturally, the dimensions may vary depending upon the intended application. However, the Inventors believe that in an inlet pipe 22 having a nominal diameter of 100 mm, typically between 4 and 8 holes of between 5 and 10 mm diameter will be provided. If desired, an anti-siphon valve 34 can be mounted in the inlet pipe 22. The anti-siphon valve 34 is typically positioned in the piping network at the highest point. The anti-siphon valve is configured to open when the pressure in the affected pipe drops below atmospheric pressure thereby permitting air to enter the affected pipe, equalising the pressure and stopping the siphoning action. The Inventors believe that by leading the inlet pipe into the coolant chamber from a high level, the risk that the coolant chamber will be drained as a result of a breach in the inlet pipe is reduced thereby substantially enhancing the safety of a nuclear reactor plant of which the cooling system forms part. Further, the provision of the anti-siphon means in the form of the bleed openings 32 and valve 34 serves to reduce the risk that coolant will be lost from the coolant chamber as a result of siphoning. The Inventors believe that, in particular, the provision of the anti-siphon bleed openings will provide a simple, reliable and cost effective method of reducing the risk of coolant being lost from the coolant chamber as a result of siphoning. |
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056617682 | abstract | A dry transfer system for spent nuclear fuel (SNF) assemblies includes a transfer container with a sliding sleeve for vertical translation therein. The sliding sleeve includes a number of compartments for receiving a corresponding number of fuel assemblies. The container includes an integral and remotely controllable hoist with a number of individually actuated grapples for latching onto a corresponding number of fuel assemblies. The system further includes a loading stand with an elevator for raising and lowering a fuel basket that also includes a number of compartments for moving fuel assemblies up to and in alignment with the sleeve of the transfer container that is landed on the loading stand. |
062883003 | abstract | Organic materials are mixed with metal oxide, such as hydrated metal oxides, prior to or during heat treatments in aerated or oxygenated environments to stabilize thermal decomposition or incineration of the organic materials and to suppress the emission of volatile, hazardous organic compounds. The organic materials may be ion exchange resins and polymeric sorbents, for example, and include contaminated materials such as hazardous wastes. The hydrated metal oxides may be hydrated ferric oxide, hydrated aluminum oxide or hydrated titania oxide, for examples. Ferrihydrite is preferred. The heat treatment may be a preparation for a waste disposal process, such as immobilization in ferric oxide, cement, concrete, a polymer, bitumen or glass, for example. Immobilization processes in ferric oxide are also discussed, including the use of additives such as magnesium oxide, ammonium dihydrogen phosphate and phosphoric acid, enabling consolidation at room temperature and pressures less than 15,000 psi. |
summary | ||
043303714 | abstract | A nuclear reactor of the type including a reactor vessel and a core assembly to be maintained in a fixed position within the vessel is disclosed herein along with a structural arrangement also located in the vessel, for supporting the core assembly in its fixed position. The structural arrangement disclosed utilizes a plurality of components including a grillage of I-beams interconnected to one another by welded joints so as to define a unitary structure capable of supporting the core assembly within the vessel. These components including the I-beams are also mechanically interlocked such that a total failure of the welded joints will result in a limited but readily detectable downward deflection of the unitary structure, thereby indicating such a failure while, at the same time, retaining sufficient structural integrity to maintain the core assembly in a supported position. |
abstract | The present invention provides a corrosion-resistant structure for a high-temperature water system comprising: a structural material 1; and a corrosion-resistant film 3 formed from a substance containing at least one of La and Y deposited on a surface in a side that comes in contact with a cooling water 4, of the structural material 1 which constitutes the high-temperature water system that passes a cooling water 4 of high temperature therein. Due to above construction, there can be provided the corrosion-resistant structure and a corrosion-preventing method capable of operating a plant without conducting a water chemistry control of cooling water by injecting chemicals. |
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052251497 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a schematic elevation view of a BWR 10, wherein the main constituents of interest in the present invention are the reactor vessel 12 and reactor core 14. It is commonly understood in the field of nuclear power reactor design, that the core 14 comprises a multiplicity of fuel assemblies or bundles, each containing a regular array of nuclear fuel rods (not shown) that are spaced laterally from each other on a substantially uniform pitch. Water under pressure is pumped axially through the flow channels defined by the spaces between neighboring fuel rods. This water acts as a moderator, to slow down fast neutrons generated during nuclear fission in the fuel, and thereby provide a supply a thermal neutrons necessary for sustaining the criticality of the fission process. The water also acts as a coolant for removing heat from the fuel rods. In a BWR, the coolant moderator itself is converted to steam at the core exit for delivery to a turbine generator set. The performance of the core 14 is monitored with a variety of instruments situated both within the core 14 and outside the vessel 12. Among such conventional instruments are a type of elongated instrument assembly, commonly referred to as local power range monitors 16 (LPRM) which, prior to reactor start-up, are passed upwardly through the bottom of the vessel 12 and secured in position. Each LPRM is typically situated in a guide tube that is part of a fuel assembly, and thus extends through wire in parallel with the fuel rods. Conventional LPRM assemblies 16 are available from several vendors including Imaging and Sensing Technology Corporation, Horseheads, N.Y. FIG. 2 is a schematic representation of the BWR reactor core 14 figuratively divided into sixteen regions symmetrically disposed about a longitudinal axis 18. The core has an entrance end 20 for admitting coolant, and an exit end 22 above which the working fluid no longer absorbs heat from the fuel rods (not shown). The core is axially divided into four zones 24, 26, 28 and 30 (also designated A, B, C and D, respectively), each of which is for simplicity in the form of an upright cylinder. The core is also figuratively divided azimuthally into first, second, third and fourth quadrants 32, 34, 36 and 38. The four axial zones and the four quadrants in each zone, define sixteen spatially distinct, volumetric regions of the core. In the present description, each region may be uniquely identified by an alphanumeric designation, such as D2, which identifies the second quadrant in the uppermost axial zone D. It is typical of the conventional BWR design to provide in the core 14, at least two and more commonly, at least eight, LPRM assemblies in each quadrant. For example, as shown in FIG. 2, the third quadrant 36 has two LPRM 16a, 16b axially spanning the core. FIG. 3 shows additional details for a conventional LPRM assembly 16. The assembly 16 includes an elongated, outer housing or sheath 40 connected at its lower end to a sealing surface 42 which is secured to a mating surface (not shown) at the penetration of the assembly 16 through the lower wall of vessel 12. Within the sheath 40, a plurality, typically four, detector strings 44, 46, 48 and 50 are encapsulated. Each detector string has an active, sensor portion located within the sheath 40, such that when the assembly 16 is in place, each sensor will be located in one of the four axially distinct zones A, B, C and D, respectively. Below the sealing surface 42, the detector strings 44, 46, 48 and 50 terminate in connectors 52, 54, 56 and 58, respectively, which mate with signal amplification, and conditioning equipment. Typically, each sensor in the LPRM assemblies 16 is in the form of a miniature fission chamber which generates an electrical signal proportional to the local neutron flux. This provides a measure of the local power density. In the present context, "local" should be understood to mean the average power produced by the fission events within a distance from the sensor corresponding to less than about two fuel rod pitches. As mentioned in the background portion of the present specification, the local power density as measured by conventional LPRM, has been utilized to detect thermal hydraulic oscillations in the core 14. When installed, a LPRM is exposed to a spectrum of neutron and gamma energies. A percentage of the incident thermal neutrons interact with the uranium coating causing a fission event to occur. Equation 1 describes the fission event, where x and y stand for two fragments of roughly the same mass. As a fragment traverses the gas, it gives up a portion of its kinetic energy to the gas atoms. If sufficient energy is imparted to a given atom an electron is ejected (ionized) from the atom leaving a positive ion. The ionized electrons and positive ions between the electrodes are collected to form the measured LPRM element signal. EQU U.sup.235 +n (slow).fwdarw.x+y (1) In a fashion similar to fragments, incident gamma ray interactions will result in the detector's gas being ionized. On average the number of ionizations occurring due to gamma ray interaction are considerably lower than that of a fission fragment. However, as the neutron sensitive material is depleted, the gamma induced ionizations become an increasingly significant portion of the element's signal. To increase lifetime, IST mixes U.sup.234 with its U.sup.235 coating to form a regenerative neutron sensitive material. Core thermal hydraulic instability is a result of an imbalance in the local relationship between power (heat) generated in the fuel rods and the heat absorbing capability of the working fluid at the given location. Such imbalances are often caused by a rapid runback or trip of one or more of the fluid recirculation pumps (not shown). The imbalance can also occur during certain start-up conditions, before coolant pumps are started, while operating in the power range under natural circulation flow. The phenomena of instability for a BWR core was established early in the design process for this type of reactor. At low flow conditions, the reactor power transfer function can show a trough at the low frequency end (<0.8[Hz]) indicating a resonance hydraulic system. As flow increases, the trough disappears indicating stable hydraulics. This condition of resonance can be defined as the in-core fuel channel flow response to a reactivity disturbance. First reactivity is added; then, the core's reaction to this reactivity addition is to modulate flow. If the reactivity feedback is in sympathy with the hydraulic modulation, undampened oscillations can occur. Because the undampened oscillations have the potential to exceed fuel design limits under unique circumstances, operating BWRs in the United States are under direction to avoid the operating space where hydraulic oscillations can occur. When a power to flow condition exists that could initiate core wide oscillations, field data shows that when increasing oscillations occur, there is a shift in the void distribution axially and that, as a consequence, the power distribution is peaked at the bottom of the core. If this axially oscillation of the voids and the power distribution is at the resonance hydraulic frequency, the flux oscillations can become undampened. As represented in FIGS. 2, 4 and 5, the present invention provides a method and apparatus for improving the detection of such thermal hydraulic oscillations in the core. This is accomplished by not only measuring the local power density, but also separately detecting an associated regional power density, as manifested for example by the gamma radiation resulting from the fission process within a distance from the sensor corresponding to at least about ten fuel rod pitches. The ability to measure neutron and gamma flux simultaneously provides a qualitative measure of void fraction in a local region. Since both the neutron flux and gamma flux are modified by voids to different degrees, the relative signal difference is used to detect and correlate the magnitude and changes in voids. With differing power or flow conditions, voids redistribute within a BWR fuel channel affecting the local fluid density. This change in fluid density alters the flux attenuation. Both the neutron and gamma sensor reaction is essentially real time and is sufficient to measure the redistribution of voids with local power or flow changes. FIG. 5 shows the calculated relative response between a LPRM fission chamber and a gamma chamber of equal dimensions, versus void fraction. The relative response changes with fuel burnup and depletion of detector's neutron sensitive material. Since one can infer the void fraction from the signal difference, it is possible to correlate this information with average channel flow velocity within the instrumented fuel bundle. The fission chamber and paired gamma chamber sensors offers a means to sense the onset of undampened oscillations. During normal operations, natural reactor noise will excite both sensors and they will show normal 1-5% output signal amplitude oscillations over time. Because of their fast response times, these oscillations should be in phase and a phase detection system between the two signals will be near zero phase difference. With increasing hydraulic/flux oscillations, the signal phase difference between the two sensors begins to shift in response to the axially shifting voids. This is because the gamma flux is developed from a greater fuel area than the neutron flux and would tend to be delayed because of the greater source field. Therefore, a phase shift will occur between the two signals. Proper signal processing will then allow for detecting and monitoring the core oscillations. In one embodiment of the invention represented in the third quadrant (FIG. 2) two conventional LPRM assemblies 16a, 16b, and a separate gamma radiation intensity detector string 60 provided. Each detector assembly 16a, 16b, and 60 contains a sensor in each zone, A, B, C and D of the third quadrant. In this embodiment of the invention, each of the other quadrants 1, 2, and 4 would be similarly instrumented. Thus, a plurality of neutron flux sensors are positioned at a respective plurality of first locations in the core, and a plurality of gamma flux sensors are positioned at a respective plurality of second locations in the core. In the presently described embodiment, the first and second locations do not necessarily have a one-to-one correspondence. For example, gamma assembly 60 has four axially spaced sensors 62, 64, 66, and 68. Each of the neutron sensors 44a, 44b, is associated with sensor 62; likewise sensors 46a, 46b and sensor 64; 48a, 48b and 66; and 50a, 50b and 68 are associated as pairs. Each of the neutron sensors in a given assembly 16, generates an output signal commensurate with the local neutron flux at the sensor. Similarly, each of the sensors in the gamma assembly 16 generates an output signal commensurate with the gamma flux in the region surrounding the gamma sensor. In accordance with the present invention, the output signals generated from the neutron sensors are compared with the output signals generated by the gamma sensors to produce spatially-depended comparison value data. The comparison value output data are monitored during the flow of coolant through the reactor core. Preferably, the comparison value data are continually compared with established acceptance criteria. When the output data falls outside the acceptance criteria, another output signal indicative of actual or incipient core thermal hydraulic oscillations is generated and displayed or used to actuate an alarm or other corrective action. The apparatus for carrying out this method is shown schematically in FIG. 6. The system 300 includes a plurality of neutron flux sensors each of which generates a raw signal n.sub.i as represented in block 302. In the presently described embodiment, there would be a total of 32 neutron detectors in the core, with detector signals 50a and 50b as shown in FIG. 2, being represented by, for example, n.sub.29 and n.sub.30. The signals n.sub.i are delivered through the respective connectors to a signal conditioning circuitry of any conventional design, as represented in block 304. The signal from sensor n.sub.i, after conditioning, appears as neutron flux signal n.sub.j commensurate with the neutron flux at the sensor. In similar fashion, each gamma sensor represented at block 308 produces a signal g.sub.k, which is conditioned at block 310 into a output signal g.sub.l commensurate with the gamma radiation. In the present embodiment, the core would have 16 gamma sensors, with sensor 68 producing a signal g.sub.k of g.sub.15. A key feature of the present invention is that the neutron flux signals indicative of fluctuations in the local power density are normalized to the output signal of a gamma sensor, which is significantly less sensitive to local power variations. The normalization can take a variety of forms, but in a general sense, the normalization begins with establishing a paired association of measurement values, as indicated in block 314 by the notation (n.sub.j ; g.sub.l). The pairing is between the neutron signal(s) preceding the semicolon, and the gamma flux signal following the semicolon. In the present example, the conditioned signals originating as n.sub.29 and n.sub.30 are paired with the gamma sensor signal originating as g.sub.15 (i.e., (n.sub.29, n.sub.30 ; g.sub.15)). The level of pairing or association can itself take several forms of normalization. For example, a bias (i.e., difference), between each of the neutron signals of the pair and the gamma signal of the pair, can be determined. Similarly, a ratio between each neutron signal and the gamma signal can be determined. Although not preferred, the neutron signals indicated at the left of the colon could be combined or averaged before the comparison with the gamma signal. Thus, block 316 is generally characterized as comparing the paired measurement values, this comparison being represented in a functional form f(n.sub.j ;g.sub.l). As stated above, this comparison may be a difference, a ratio, or correlation. Moreover, a paired measurement value comparison is established for each of the gamma sensors throughout the core. Further, as stated above, at least one neutron sensor is paired with each gamma sensor. Thus, the processing associated with block 316 would, in the preferred embodiment, result in a matrix or output data table, in which for each of a plurality of spatially distinct volume representations in the core, the variables of time and the paired measurement comparison values are related. For example, a multi-dimensional vector containing the following entries is preferred: time (seconds); zone (A, B, C or D); quadrant (1, 2, 3 or 4); and the paired measurement value comparison (v.sub.c) from block 316. Of course, it may be understood that the present description based on 16 gamma sensors located respectively in 16 core regions, is merely an example, and that preferably more detectors and spatially smaller regions of the core would be utilized in an actual working system. As stated above, the nature of the comparison between the paired measurement values n.sub.j ;g.sub.l, is somewhat flexible. In a straightforward implementation of the present embodiment, the comparison would simply be a difference in signal amplitude, which in the steady state can be viewed as a bias, and, as such, can be adjusted to any desired reference bias. During core behavior that deviates from the steady state, and particularly upon the occurrence of voiding in the core, the bias will diverge or converge, depending on whether the voids are growing or collapsing. If the difference in signals exceeds a predetermined tolerance, the comparison value v.sub.c can be set to equal +1. Similarly, if the difference converges by more than a tolerance amount, the value v.sub.c can be set equal to -1. Thus, the output of block 316 would be a matrix containing, for example, one column vector for each of the regions of the core with the variable of time changing continually, for example at a convenient sampling rate of one Herz, and the variable v.sub.c assuming the value 0, +1 or -1 according to whether the bias between the neutron and gamma sensors of a pair is within the nominal range, diverging, or converging in excess of a predefined tolerance. In block 318, an analogous matrix F(n.sub.j ;g.sub.l) is stored, for defining the boundaries of an operating envelope, within which any core instabilities are considered insignificant, and outside of which the operator should be warned of the likelihood of incipient, or actual, core thermal hydraulic oscillations. Thus, in block 320, the time, space, and measured value matrix f(n.sub.j ;g.sub.l) is compared with the acceptance criteria matrix F(n.sub.j ;g.sub.l). In the event the comparison indicates a developing or actual oscillation, an alarm data signal is delivered to the alarm actuator 322, which may be a combination of one or more visual, auditory or other humanly perceptible actions. Furthermore, for record retention purposes, data generated in blocks 316, 320, and perhaps 322, may be stored in digital form in an output device 324 such as on a magnetic memory storage device, on paper printout, or the like, for future retrieval and analysis. Moreover, with the embodiment described immediately above, the utilization of the comparison value V.sub.c in the form of 0, +1, or -1, is well suited to visual representation of the core behavior by means of a gray scale image that is presented to the operator as it evolves in time. A straightforward information code calculation such as a gray code, can be made symbolic of the precursor of the pattern of precursor behavior to thermal hydraulic oscillations. The number of +1's versus the numbers of -1's are the operatives and need not be quadrant related to point to a high probability of instability. Event theory justifies high confidence on the number of +1's and -1's in any time frame and whether this pattern is increasing toward instability, based on the next time sample. Such processing is very fast, within the time constraints of the system. It should be appreciated that, as shown in FIG. 2, a particular gamma sensor 68 and its paired neutron sensors remain in fixed spatial relationship corresponding to the relationship upon which the reference or acceptance criteria F(n.sub.j ;g.sub.l) was established. As stated above, although each pair need not be supported within the core at exactly the same location, it is desirable that a given gamma sensor and its paired neutron sensor(s) be supported within a distance of each other no greater than the equivalent of about ten per cent of the core axial dimension. FIGS. 2 and 4 depict a second, preferred embodiment of the invention. In this embodiment, a conventional LPRM of the type shown in FIG. 3, is modified to include within the same sheath or housing, at least one gamma sensor. Such a combined monitoring assembly 200 is shown in cross-section in FIG. 4, as seen in the direction of the arrows indicated on the section line 4-4 in FIG. 2. At that section line, looking upward through the assembly 200, the cables for neutron sensors 50c, 48c, and 46c are visible, as is the calibration tube 70 that traverses the housing 40. In accordance with the modification of the present embodiment, a mounting lug 202 is secured to the calibration tube 70, and at least one gamma sensor 204 is supported by the mounting lug. In practice, the combination assembly shown in FIG. 4 has a sheath 40 having a 0.750 inch O.D. and a 0.048 inch wall thickness. Within this sheath 40, it is possible to support the gamma sensor within one inch (i.e., preferably within 0.50 inch) of a paired neutron sensor. As shown in FIG. 2, a given combination assembly 200 may have only one gamma sensor 204. In practice, a BWR core 14 may have up to 10 LPRM's per quadrant and any four of the LPRM in each quadrant could be modified to serve as a combined assembly such as 200, with each one of the four carrying the gamma sensor such as 204, for positioning in a different axial zone A, B, C, D of the quadrant. Preferably, at least two gamma sensors are provided in each quadrant, at each of at least four axial zones. Thus, it may be appreciated that the gamma sensors and neutron sensors can be supported in different housings, as described in the first embodiment and shown in the third quadrant of FIG. 2, or at least one neutron sensor and one gamma sensor can be supported within a common housing. Preferably, one neutron sensor is paired with one gamma sensor, and supported within a common housing. Moreover, the most desirable configuration would provide that each of up to 232 neutron sensors and respective paired gamma sensor be physically abutting or connected in tandem at each of the fission chamber locations such as 44, 46, 48 and 50 (FIG. 3), using a common cable such as 52, 54, 56 and 58 respectively. FIG. 7 is a flow diagram of the preferred embodiment, wherein a given gamma sensor 308 is located substantially adjacent to its paired neutron sensor 302, such as shown in the second quadrant in FIG. 2. Ideally, the gamma sensor would have a sensitivity substantially identical to the gamma sensitivity of the fission chamber of the neutron sensor. For example, a typical fission chamber would have a neutron sensitivity of 4.6.times.10.sup.-18 amps/nv, and the inherent gamma sensitivity would be 2.5.times.10.sup.-14 amps/R/hr. If the intimately located, yet distinct gamma sensor 308 is designed to have the same sensitivity, i.e., 2.5.times.10.sup.-14, the signal conditioning indicated at 304 in FIG. 6 can be accomplished by a differential amplifier 326 as shown in FIG. 7. This signal processing subtracts from the output signal n.sub.i of neutron sensor 302, the output signal g.sub.k from the gamma sensor 308, which therefore has the effect of generating and output signal n.sub.j that is free of the influence of gamma radiation. Moreover, the gamma flux signal g.sub.k from detector 302 does not require the kind of signal processing represented in block 310 of FIG. 6 because it has, in essence, been normalized as a result of the preestablished matching of sensitivity to the gamma response of the neutron sensor 302 and the proximity to the neutron sensor in the core. The output signals n.sub.i and g.sub.k from the neutron sensor 302 and gamma sensor 308 are also delivered, without differentiation, to a phase detector 328 where, for reasons discussed above, the different effect due to changes in voids, is most pronounced as between the gamma and neutron sensors. Thus, in the embodiment represented by FIG. 7, the phase detector 328 performs a particular type of comparison, which is indicated more generically at block 316 of FIG. 6. Moreover, it should also be appreciated that the function performed by block 314 of FIG. 6, whereby a particular neutron sensor is associated as a pair with a particular gamma sensor 308, is in the embodiment of FIG. 7, inherently achieved by using the signals from the adjacent sensors having output leads that are physically adjacent. The function performed by block 330 in FIG. 7 is an implementation of the functions indicated in blocks 318 and 320 in FIG. 6. The oscillation condition that warrants an alarm or other desirable action on the part of the operator or plant control system, is indicated at block 332. The modeling of the reactor core for determining the acceptance criteria 318 and the criterial comparison 320 as indicated in FIG. 6, can be achieved in any number of ways. The void model represented at 334 in FIG. 7 includes input signals indicative of the gamma response G.sub.l and neutron response n.sub.j, as well as the information concerning the axial power distribution in the channel from block 336 and the predicted channel flow from block 338. Tests at several operating reactors have shown that prior to the onset of divergent oscillations, there is a marked shift of power distribution toward the bottom of the core. This is attributed to a significant shift in void co-efficient in the center of the fuel assemblies. The gain margin of a BWR system is in effect not only a measure of the system stability but also a measure of how much the void coefficient of reactivity could be increased before divergent oscillations occurred. For an oscillation detection system based on shift in void fraction, the key information from FIG. 5 is the change in signal ratios (neutron/gamma) with a shift in void fraction. At the beginning of the fuel cycle, this shift is about 4% from 25% void to 75% void. At the end of the cycle (46,000 MWD/MT), the shift in signal ratio is as high as 12%. These shifts are readily detectable using signal processing electronics. Standard process noise is in phase between both detectors if located in the same axial plane. Therefore, process noise (about 2-5%) would not mask the shift. Given inputs from blocks 326 and 336, and a measured void fraction from a family of curves such as FIG. 5, a determination of channel flow can be made. This determination is compared to a prediction model of flow from 338 and a corrected value of channel flow is then used as a bias against the phase difference between the two signals n.sub.i and g.sub.k. If the local channel flow is low and the phase difference between n.sub.i and g.sub.k in the adverse direction is large, a truth level +1 is set. A balanced condition generates a truth level 0, whereas unbalance in the safe direction sets a -1. Only a truth level +1 "arms" the oscillation bistable 332 and with sufficient numbers of +1's from other detector pairs, alarm and automatic action is taken. |
summary | ||
048470368 | abstract | An apparatus for the inspection of a nuclear reactor fuel assembly in a water-filled pool having fuel rods with spaces therebetween includes an encapsulated housing having walls and being disposed in the water-filled pool. A lever drive mechanism is disposed in the housing. A rotary transmission connected to the lever drive mechanism extends through one of the walls of the housing toward the surface of water in the pool. A plurality of stationarily disposed lever linkages jut out from the rotary transmission outside the housing. Each of the lever linkages has an end facing away from the rotary transmission. Carriers are each connected to a respective one of the ends of the lever linkages. Probes are each disposed on a respective one of the carriers. Ultrasonic test heads are each disposed on a respective one of the probes for insertion into the spaces between the fuel rods. |
claims | 1. A semiconductor wafer inspection method comprising the steps of:placing a semiconductor wafer on a sample stage of an electron beam apparatus having a first electron beam optical system for irradiating an electron beam from a direction normal to a surface of a sample, and a second electron beam optical system for irradiating an electron beam from a direction tilted from the direction normal to the surface;obtaining defect position data on the semiconductor wafer from an inspection apparatus;moving the stage to a position corresponding to a defect position obtained from the inspection data, and capturing a scanned image of a defect by using the first electron beam optical system;discriminating a mode of the defect on the basis of the captured defect image;determining whether or not there is a defect which has been discriminated as one of a peeling mode; andcapturing a scanned image of an edge portion of the semiconductor wafer by using the second electron beam optical system, when it is determined in the above determination that there is a defect of the peeling mode. 2. The semiconductor wafer inspection method according to claim 1, wherein an area of an edge portion of the semiconductor wafer is determined on the basis of a distribution of defects of the peeling mode on the semiconductor wafer, the area to be imaged by using the second electron beam optical system. 3. A defect review apparatus comprising:a sample stage which moves with a semiconductor wafer held thereon;a first electron beam optical system for irradiating an electron beam from a direction normal to a surface of the semiconductor wafer held on the sample stage;a second electron beam optical system for irradiating an electron beam from a direction tilted from the direction normal to the surface;a display unit for displaying an image of the surface of the semiconductor wafer, the image generated by the irradiation of the electron beam; andmeans which classifies defects on the basis of an image of the defects captured by using the first electron beam optical system, which causes the display unit to display a wafer map showing the positions of defects of a peeling mode on the semiconductor wafer in a manner discriminating the defects of the peeling mode from the defects of the other modes, and which causes the display unit to display a scanned image of an edge of the semiconductor wafer, the image captured by using the second electron beam optical system. |
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abstract | The test elements are provided that are adapted to detect at least one analyte in a sample. At least some of the test elements are provided with a defect marking which contains information about defectiveness of the test elements. The test elements include at least one radiation-sensitive material. The test elements are exposed to at least one radiation, the radiation being adapted to induce marking in the form of at least one optically detectable change in the radiation-sensitive material. |
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description | A seal arrangement and method for sealing an ICI housing according to the present invention will now be explained in detail with reference to FIGS. 1 to 8 of the drawings. FIG. 1 shows a portion of a nuclear reactor system 10 having a reactor 12 including a substantially upright cylindrical vessel 14 and a substantially hemispherical head 16. The vessel has an upper flange 18, and the head 16 has a lower flange 20. The flanges 18 and 20 are bolted together in a known manner for normal operation of the reactor system 10. As is well known in the field of nuclear engineering, the operating conditions within the reactor 12 can be monitored by ICIs, such as thermocouples and so forth. This is typically accomplished by a plurality of ICIs 23 that pass through respective nozzles 22 into the reactor 12. For the purpose of simplifying the present description, only one of the reactor vessel nozzles 22 on the head 16 is shown, but it should be appreciated that normally there are several nozzles 22 positioned in an organized array across the head 16. Each ICI 23 is housed in an ICI housing 24 connected to a respective one of the nozzles 22. The ICI 23, ICI housing 24, and other components shown in FIG. 1 are conventional. As explained above, the ICIs 23 must be partially withdrawn at every refueling outage to allow for movement of the fuel, The process of withdrawing the ICIs 23 often results in damage to the sealing surfaces of the O-rings installed in the grooves 25 (FIG. 2) of the ICIs 23 and/or to the ICI seal housing 24. The present invention provides seal arrangements for resealing the interface between the ICI 23 and the ICI housing 24 after the ICIs 23 are reinserted following the refueling. Three embodiments of seal arrangements according to the present invention are described herein and shown in FIGS. 2 to 8 of the drawings. All three embodiments utilize external seal rings, preferably made of a graphite material, on the external surfaces of the existing ICI 23 and ICI housing 24. To effect a seal against full system design pressure of up to 2500 psi, the seal rings must be compressed under very high loads to prevent leakage. The sealing principle is the same in each of the three embodiments. The method used to compress the seal rings differs. As shown in FIGS. 2 to 4, a seal arrangement 30 according to the first embodiment of the present invention includes a first lower seal assembly 31 surrounding an outer portion 32 of the ICI housing 24, and a second upper seal assembly 33 surrounding an outer portion of an ICI 23 contained within the ICI housing 24. The lower seal assembly 31 includes a first pair of seal rings 34, 35 positioned in abutting relationship with each other. The upper seal assembly 33 includes a second pair of seal rings 36, 37 positioned in abutting relationship with each other. The seal rings 34, 35 of the lower seal assembly 31 have an inside diameter that fits closely to the external surface of the ICI housing 24. The seal rings 36, 37 of the upper seal assembly 33 have an inside diameter that fits closely to the external surface of the ICI 23. The seal rings 34-37 are preferably fabricated of a graphite material. A seal housing 38 is provided which spans the interface between the ICI 23 and the ICI housing 24. The seal housing 38 has a first recess 39 formed in a first lower end 40 and a second recess 41 formed in a second upper end 42. The lower seal assembly 31 is positioned in the first recess 39 so as to be enclosed by the lower end 40 of the seal housing 38. The upper seal assembly 33 is positioned in the second recess 41 so as to be enclosed by the upper end 42 of the seal housing 38. The seal housing 38 has a housing portion 43 and an integral retainer portion 44. The retainer portion 44 has an inner diameter 45 that fits closely around the external surface of the ICI 23, and an outer diameter having external male threads 46. The retainer portion 44 is secured to the ICI housing 24 by threadably engaging the external threads 46 of the retainer portion 44 to corresponding internal threads 47 formed in the upper end of the ICI housing 24. The retainer portion 44 has an abutment seat 48 at the top of the external threads 46 that engages and seats against an upper end surface 49 of the ICI housing 24. A lower end of the retainer portion 44 has an abutment surface 50 against which the existing spacers 51 surrounding the ICI 23 can be engaged. A lower end 52 of the lowest spacer 53 is engaged by an annular shoulder 54 formed on the ICI 23. Thus, the retainer portion 44 provides positive retention against slipping of the ICI 23 and other parts relative to the ICI housing 24 when system pressure is applied. The housing portion 43 of the seal housing 38 is molded together with the retainer portion 44 in a single, integral piece. The housing portion 43 has external male threads 55 on each end, which threads may extend along the entire length of the housing portion 43, as shown in FIG. 2. The seal housing 38 is preferably fabricated from a stainless steel alloy that resists galling and seizing of threads, such as NITRONIC 60(trademark) Stainless Steel. A first lower compression assembly 56 and a second upper compression assembly 57 are positioned on the lower and upper ends 40, 42 of the seal housing 38, respectively. The lower compression assembly 56 includes a first lower drive nut 58 and a first lower compression collar 59. The lower drive nut 58 has internal threads 60 threadably engaged on the external threads 55 of the housing portion 43, and a flange 61 that extends inwardly at a lower end. The lower compression collar 59 has a first annular portion 62 engageable by the flange 61 of the lower drive nut 58, a second annular portion 63 which extends through the flange 61 and protrudes from a lower end of the lower drive nut 58, and a third annular portion 64 facing the lower seal assembly 31. A first lower spacer ring 65 is positioned between the third annular portion 64 and the seal rings 34, 35 of the lower seal assembly 31. The lower compression collar 59 is axially movable against the lower spacer ring 65 using a compression tool, which will be described below, to compress the lower seal assembly 31 to form a seal between the ICI housing 24 and the seal housing 38. The lower drive nut 58 is threaded onto the housing portion 43 of the seal housing 38 until the flange 61 is engaged snugly against the first annular portion 62 of the lower compression collar 59 to maintain the compressed seal between the ICI housing 24 and the seal housing 38. The upper compression assembly 57 includes a second upper drive nut 66 and a second upper compression collar 67. The upper drive nut 66 has internal threads 68 threadably engaged on the external threads 55 at the upper end of the housing portion 43, and a flange 69 that extends inwardly at an upper end of the upper drive nut 66. The upper compression collar 67 has a first annular portion 70 engageable by the flange 69 of the upper drive nut 66, a second annular portion 71 which extends through the flange 69 and protrudes from an upper end of the upper drive nut 66, and a third annular portion 72 facing the upper seal assembly 33. A second upper spacer ring 73 is positioned between the third annular portion 72 of the upper compression collar 67 and the seal rings 36, 37 of the upper seal assembly 33. The upper compression collar 67 is axially movable against the upper spacer ring 73 using a compression tool, which will be described below, to compress the upper seal assembly 33 to form a seal between the ICI 23 and the seal housing 24. The upper drive nut 66 is threaded onto the housing portion 43 of the seal housing 38 until the flange 69 is engaged snugly against the first annular portion 70 of the upper compression collar 67 to maintain the compressed seal between the ICI 23 and the seal housing 38. As shown in FIG. 2, the diameters of the threaded portions 60, 68 of the lower and upper drive nuts 58, 66 are the same. The inner diameter of the flange 69 of the upper drive nut 66 and the corresponding portions of the upper compression collar 67 are smaller than the inner diameter of the flange 61 of the lower drive nut 58 and the corresponding portions of the lower compression collar 59. An installation tool 74 for installing the seal arrangement 30 shown in FIG. 2 over the existing ICI 23 and ICI housing 24 during a refueling outage is shown in FIG. 3. The installation tool 74 includes a pair of leg assemblies 75, 76 each having a lower end 77 with a gripping portion 78 protruding inwardly toward the ICI housing 24, and an upper end 79 supporting a hydraulic cylinder 80. The gripping, portions 78 at the lower end 77 of the leg assemblies 75, 76 engage the protruding second annular portion 63 of the lower compression collar 59. The pair of leg assemblies 75, 76 can be easily positioned over and removed from the seal arrangement 30 after the compression assemblies 56, 57 are installed with the drive nuts 58, 66 threaded hand tight. The installation tool 74 also includes an upper compression plate 81 surrounding the ICI 23 above the upper compression collar 67. A lower surface 82 of the compression plate 81 engages the protruding second annular portion 71 of the upper compression collar 67. A piston 83 protrudes from each of the hydraulic cylinders 80 into engagement with the upper compression plate 81. When the tool 74 is placed over the seal arrangement 30, as shown in FIG. 3, a predetermined pressure can be introduced into the hydraulic cylinders 80 to force the respective pistons 83 against the upper compression plate 81, which in turn pushes the upper compression collar 67 against the upper seal assembly 33. At the same time, a corresponding force is transmitted through the leg assemblies 75, 76 to force the gripping portions 78 against the lower compression collar 59 to compress the lower seal assembly 31. The tool 74 is thus operable to provide a compression load to the lower and upper seal assemblies 31, 33 simultaneously. While the tool 74 is installed and a compression preload is applied to the seal assemblies 31, 33, the lower and upper drive nuts 58, 66 can be threaded further along the seal housing 38 until the flanges 61, 69 of the drive nuts 58, 66 are engaged snugly against the respective lower and upper compression collars 59, 67. For example, the drive nuts 58, 66 can be seated hand tight while the seal assemblies 31, 33 are under compression from the installation tool 74. When the hydraulic pressure is released from the tool 74, the drive nuts 58, 66 pick up the load and maintain the compression preload on the seal assemblies 31, 33. Having explained the construction of the seal arrangement 30 according to a first embodiment of the present invention, a method of installing the seal arrangement 30 during a nuclear reactor refueling outage will now be described. After the seal welds have been cut (where applicable) and the surfaces cleaned, the existing retainer nut (not shown) is removed and discarded. The ICI 23 is partially withdrawn in accordance with existing procedures. The existing ICI O-rings in the grooves 25 can be discarded because they are not required with the seal arrangement 30 of the present invention. The refueling is then completed in accordance with existing procedures. The ICI 23 is then reinserted to the proper depth. The reinsertion can be done by hand without using an insertion tool because the grooves 25 do not have O-rings causing a friction drag during reinsertion. Spacers 51 are added according to the existing procedure to a defined height so that the seal housing 38 will seat properly. The lower drive nut 58, lower compression collar 59, lower spacer ring 65. and lower seal assembly 31 are lowered over the outside of the ICI housing 24. The retainer portion 44 of the seal housing 38 is threaded (e.g., hand tight) into the internal threads 47 of the ICI housing 24 until the seal housing 38 is seated on the ICI housing 24. After the seal housing 38 is installed, the ICI 23 is pulled up slightly by hand to close any gaps with the spacers 51. The lower seal assembly 31, lower spacer ring 65, lower compression collar 59 and lower drive nut 58 are then installed to the lower end 40 of the seal housing 38 (e.g., hand tight), as shown in FIG. 2. The upper seal assembly 33 and upper spacer ring 73 are installed in the upper end 42 of the seal housing 38. The upper compression collar 67 and upper drive nut 66 are then installed (e.g., hand tight), as shown in FIG. 2. The installation tool 74 shown in FIG. 3 is used to seat the lower and upper seal assemblies 31, 33, preload the seal arrangement 30 during installation, and unload the seal arrangement 30 for removal. Because the tool 74 loads both seal assemblies 31, 33 simultaneously, the number of operations required to install or remove the seal arrangement 30 is reduced, thereby saving installation and removal time. The upper and lower compression collars 59, 67 are axially loaded simultaneously by the hydraulic tool 74 to compress the lower and upper seal assemblies 31, 33 to the desired preload. While under compression with the hydraulic tool 74, both drive nuts 58, 66 are seated (e.g., hand tight). When the hydraulic pressure is released from the tool 74, the drive nuts 58, 66 pick up the load and maintain the preload on the seal assemblies 31, 33. The tool 74 can then be removed. A seal arrangement 85 according to a second embodiment of the invention will now be described with reference to FIG. 5. The seal arrangement 85 shown in FIG. 5 is similar in most respects to the seal arrangement 30 shown in FIGS. 2 to 4. The main difference is that the seal arrangement 85 of FIG. 5 includes a retainer nut 86 as a separate component from the seal housing 87. The retainer nut 86 has external threads 88 which are threaded into the internal threads 47 of the ICI housing 24 until the retainer nut 86 is seated against the upper end of the ICI housing 24. The seal housing 87 is installed over the retainer nut 86 after the retainer nut 86 is seated in the ICI housing 24. An inwardly directed flange 89 at the upper end of the seal housing 87 engages an upper surface of the retainer nut 86 to maintain the vertical positioning of the seal housing 87. The seal housing 87 and retainer nut 86 are both preferably fabricated from a stainless steel alloy that resists galling and seizing of threads, such as NITRONIC(trademark) 60 Stainless Steel. The installation tool 74 shown in FIG. 3 is used for installing and removing the seal arrangement 85 of FIG. 5 in the same manner described above. A seal arrangement 90 according to a third embodiment of the invention will now be described with reference to FIGS. 6 to 8. The seal arrangement 90 shown in FIGS. 6 to 8 is similar in many respects to the seal arrangement 85 shown in FIG. 5. The main difference is that the seal arrangement 90 of FIGS. 6 to 8 relies upon the torque applied to the lower and upper drive nuts 91, 92 to compress and load the lower and upper seal assemblies 93, 94 during installation, rather than a hydraulic installation tool. The seal arrangement 90 of FIGS. 6 to 8 includes a first lower seal assembly 93 enclosed by a lower end of a seal housing 95, and a second upper seal assembly 94 enclosed by an upper end of the seal housing 95. A first lower compression collar 96 and a second upper compression collar 97 are installed against the respective lower and upper seal assemblies 93, 94. The lower and upper compression collars 96, 97 each have anti-rotation keys 98, 99 protruding radially outwardly, as shown in FIG. 8, for example. The lower and upper ends of the seal housing 95 have mating keyways 100, 101 formed therein into which the anti-rotation keys 98, 99 of the compression collars 96, 97 are received. The compression collars 96, 97 act as a bearing surface for the applied thrust loads and prevent rotational loads on the seal rings of the respective seal assemblies 93, 94. Thrust bearing rings 102, 103 are installed between each of the drive nuts 104, 105 and the respective compression collars 96, 97. The thrust bearing rings 102, 103 reduce the rotational frictional drag as the drive nuts 104, 105 are tightened. The thrust bearing rings 102, 103 can be eliminated if the compression collars 96, 97 are fabricated of a good bearing material. The seal housing 95 has at least a pair of flat surfaces 106, 107 formed intermediate its ends on an external perimeter for engagement by a wrench (not shown) to prevent rotation during torquing of the upper and lower drive nuts 104, 105. For example, the external perimeter of the seal housing 95 can be hexagonal shaped. As shown in FIG. 6, the diameter of the threaded portion of the lower drive nut 104 is larger than the diameter of the threaded portion of the upper drive nut 105. The inner diameter of the flange 108 of the lower drive nut 104 and the corresponding portions of the lower compression collar 96 are also larger than the inner diameter of the flange 109 of the upper drive nut 105 and the corresponding portions of the upper compression collar 97. A method of installing the seal arrangement 90 of FIGS. 6 to 8 will now be described. As in the embodiments described above, the existing O-rings in the grooves 25 on the ICI 23 can be removed and discarded because they are not required with the seal arrangement 90 of the present invention. After the refueling is completed, the ICI 23 is reinserted to a proper depth. Spacers 51 are added according to the existing procedure to a defined height. The retainer nut 86 is then seated in the upper end of the ICI housing 24. The lower drive nut 104, lower thrust bearing ring 102, lower compression collar 96, and seal rings of the lower seal assembly 93 are lowered over the outside of the ICI housing 24. The seal housing 95 is then placed over the retainer nut 86 with its upper flange 110 seated against the upper surface of the retainer nut 86. The lower seal assembly 93, lower compression collar 96, lower thrust bearing ring 102, and lower drive nut 104 are then installed to the lower end of the seal housing 95. The lower drive nut 104 is torqued using a wrench (not shown) until a sufficient load is placed on the lower seal assembly 93 to prevent leakage under full system pressure. A second wrench (not shown) is used to engage the flat surfaces 106, 107 on the seal housing 95 to prevent rotation of the seal housing 95 when the lower drive nut 104 is being torqued. The upper seal assembly 94, upper compression collar 97, and upper thrust bearing ring 103 are then installed over the ICI 23 and seated into the upper end of the seal housing 95. While pulling the ICI 23 up slightly by hand to close any gaps with the spacers 51, the upper drive nut 105 is threaded onto the upper end of the seal housing 95 and torqued using a wrench until a sufficient load is placed on the upper seal assembly 94 to prevent leakage under full system pressure. The seal arrangements 30, 85, 90 described above provide the following advantages over the existing technology: (1) no field cutting or welding are required; (2) the existing ICIs and ICI housings can be reused, even with damaged O-ring sealing surfaces; (3) the seal assemblies will seal the expected pressure without machining or polishing the existing parts; (4) the seal arrangements can be assembled quickly and easily by hand; (5) the ICIs do not need to be withdrawn any further than normal to install the seal arrangements; (6) the existing O-rings can be eliminated making the ICI removal and insertion process easier; (7) the seal arrangements can be fit and installed into smaller areas of access; and (8) the seal arrangements can be reused throughout the life of the plant. While the invention has been specifically described in connection with specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit. |
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051030950 | abstract | This invention is a scanning probe microscope which uses three separate motorized legs to adjust the distance between the probe and sample and to adjust the tilt between the probe and the sample. The microscope is shown configured in various ways. One form is a scanner on a base in which the base contains the sample and legs. Another is a scanner which contains the legs and rests on the sample, or may also rest on a support that spans a larger sample allowing translation of the sample independent of the scanner. Another is a scanner which contains the legs and is mounted so that a sample holder sits on the legs. The latter configuration allows for easy access to the sample. One variation of this configuration has provision for the mounting of several samples which can be sequenced for probing automatically. |
063296624 | claims | 1. A combination for radiation image formation which comprises a silver halide photographic material having a support and at least one silver halide emulsion layer provided on each side of the support, and two radiographic intensifying screens each having a support and at least one phosphor layer provided thereon, wherein said phosphor layer contains a rare earth phosphor represented by the following formula: EQU M.sub.w O.sub.w X:M' in which M represents at least one rare earth atom selected from the group consisting of Y, La, Gd and Lu; X represents at least one chalcogen atom selected from the group consisting of S, Se and Te, or at least one halogen atom selected from the group consisting of F, Br, Cl and I; M' represents a rare earth atom which activates M; and w is 2 when X is a chalcogen atom or w is 1 when X is a halogen atom, said radiographic intensifying screen contains a fluorescent dye or pigment which absorbs a portion of luminescence emitted by the rare earth phosphor and then emits light in a visible region, and said photographic material shows a cross-over of 10% or less when it is placed between the two radiographic intensifying screens and exposed to radiation. said phosphor layer contains a rare earth phosphor represented by the following formula: EQU M.sub.w O.sub.w X:M' in which M represents at least one rare earth atom selected from the group consisting of Y, La, Gd and Lu; X represents at least one chalcogen atom selected from the group consisting of S, Se and Te, or at least one halogen atom selected from the group consisting of F, Br, Cl and I; M' represents a rare earth atom which activates M; and w is 2 when X is a chalcogen atom or w is 1 when X is a halogen atom, said radiographic intensifying screen contains a fluorescent dye or pigment which absorbs a portion of luminescence emitted by the rare earth phosphor and then emits light in a visible region, and said photographic material shows a cross-over of 10% or less when it is exposed to radiation in the system. forming a combination by placing a silver halide photographic material having a support and at least one silver halide emulsion layer provided on each side of the support between two radiographic intensifying screens each having a support and at least one phosphor layer provided thereon, said phosphor layer containing a rare earth phosphor represented by the following formula: EQU M.sub.w O.sub.w X:M' in which M represents at least one rare earth atom selected from the group consisting of Y, La, Gd and Lu; X represents at least one chalcogen atom selected from the group consisting of S, Se and Te, or at least one halogen atom selected from the group consisting of F, Br, Cl and I; M' represents a rare earth atom which activates M; and w is 2 when X is a chalcogen atom or w is 1 when X is a halogen atom, said radiographic intensifying screen containing a fluorescent dye or pigment which absorbs a portion of luminescence emitted by the rare earth phosphor and then emits light in a visible region, and said photographic material showing a cross-over of 10% or less when it is exposed to X-ray radiation; imagewise exposing the combination to X-ray radiation; separating the exposed photographic material from the intensifying screens; and developing the exposed photographic material in a developing solution. 2. The combination of claim 1, wherein the rare earth phosphor in the radiographic intensifying screen is a terbium activated gadolinium oxysulfide phosphor. 3. The combination of claim 2, wherein the terbium activated gadolinium oxysulfide phosphor contains terbium atom in an amount of 0.001 to 0.02 mol. per 1 mol. of Gd. 4. The combination of claim 1, wherein the fluorescent dye or pigment shows a light absorption peak in a wavelength region of shorter than 500 nm and an emission peak in the wavelength range of 450 to 600 nm under the condition that the wavelength of emission peak is longer than the wavelength of light absorption peak by at least 10 nm. 5. The combination of claim 4, wherein the emission peak of the fluorescent dye or pigment has a halfwidth of 100 nm or less. 6. The combination of claim 1, wherein the fluorescent dye or pigment shows a light absorption peak in a wavelength region of 400 to 490 nm and an emission peak in the wavelength range of 500 to 600 nm. 7. The combination of claim 1, wherein the fluorescent dye or pigment in the radiographic intensifying screen is a carbocyanine dye, a xanthene dye, a triarylmethane dye, a coumarin dye, a phthalimide compound, a naphthalimide compound, a diketopyrrolopyrrole compound or a perylene compound. 8. The combination of claim 1, wherein the fluorescent dye or pigment in the radiographic intensifying screen is contained in the phosphor layer. 9. The combination of claim 1, wherein the silver halide photographic material contains a dye which shows a light absorption peak in the wavelength region of 500 to 600 nm. 10. The combination of claim 9, wherein the dye in the silver halide photographic material is decolorizable in a developing process. 11. The combination of claim 10, wherein the decolorizable dye shows an absorption coefficient at 550 nm which is twice or more larger than that at 450 nm. 12. The combination of claim 1, wherein the silver halide photographic material contains a dye in a layer provided on the support. 13. A radiation image-forming system comprising two radiographic intensifying screens each having a support and at least one phosphor layer provided thereon and a silver halide photographic material which is interposed between the two intensifying screens and has a support and at least one silver halide emulsion layer provided on each side of the support, wherein 14. The radiation image-forming system of claim 13, wherein the rare earth phosphor in the radiographic intensifying screen is a terbium activated gadolinium oxysulfide phosphor. 15. The radiation image-forming system of claim 13, wherein the fluorescent dye or pigment shows a light absorption peak in a wavelength region of shorter than 500 nm and an emission peak in the wavelength range of 450 to 600 nm under the condition that the wavelength of emission peak is longer than the wavelength of light absorption peak by at least 10 nm. 16. The radiation image-forming system of claim 13, wherein the fluorescent dye or pigment shows a light absorption peak in a wavelength region of 400 to 490 nm and an emission peak in the wavelength range of 500 to 600 nm. 17. The radiation image-forming system of claim 13, wherein the silver halide photographic material contains a dye in a layer provided on the support, said dye showing a light absorption peak in the wavelength region of 500 to 600 nm and being decolorizable in a developing process. 18. A method for forming a radiation image which comprises the steps of: 19. The method of claim 18, wherein the rare earth phosphor in the radiographic intensifying screen is a terbium activated gadolinium oxysulfide phosphor. 20. The method of claim 18, wherein the fluorescent dye or pigment shows a light absorption peak in a wavelength region of shorter than 500 nm and an emission peak in the wavelength range of 450 to 600 nm under the condition that the wavelength of emission peak is longer than the wavelength of light absorption peak by at least 10 nm. 21. The method of claim 18, wherein the fluorescent dye or pigment shows a light absorption peak in a wavelength region of 400 to 490 nm and an emission peak in the wavelength range of 500 to 600 nm. 22. The method of claim 18, wherein the silver halide photographic material contains a dye in a layer provided on the support, said dye showing a light absorption peak in the wavelength region of 500 to 600 nm and being decolorizable in the developing step. |
abstract | An assembly including a base and first and second spaced-apart shafts secured to the base and extending generally perpendicular to an elongated aperture of the base. A carrier includes a first support member slidingly receiving the first shaft, a second support member receiving the second shaft, and an elongated opening extending between the support members and generally perpendicular to the shafts. The elongated opening of the carrier is for aligning with the aperture of the base and an elongated slit of a collimator supported on the carrier for passage of an x-ray beam therethrough. A backlash-resistant nut assembly is threadingly received on a threaded portion of the second shaft and secured to the second support member. |
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claims | 1. An X-ray imaging apparatus, comprising:a source for generating X-ray radiation emitting a polychromatic spectrum of X-ray energies;an object receiving space for arranging an object of interest for X-ray imaging;an X-ray collimator arrangement; andan X-ray mirror arrangement;wherein the X-ray collimator arrangement comprises at least a pre-collimator arranged between the source and the object receiving space for providing collimated X-ray radiation to the object receiving space;wherein the X-ray mirror arrangement is arranged between the source and the pre-collimator;wherein the X-ray mirror arrangement comprises a set of two mirrors for guiding X-ray radiation of the source by providing total reflection of the whole polychromatic spectrum of X-ray energies of a part of the X-ray radiation in order to deflect the part of the X-ray radiation towards the pre-collimator such that in the region of the object receiving space enhanced radiation is provided in form of unreflected primary X-ray radiation in combination with secondary X-ray radiation by total reflection; andwherein the mirrors of the set of two mirrors are facing one another with an angle of spread (θm) larger than zero, such that the set of mirrors providing an X-ray entrance having an entrance width and an X-ray exit having an exit width, which is smaller than the entrance width. 2. The apparatus according to claim 1, wherein the primary X-ray radiation forms a primary beam cone between the source and the pre-collimator,wherein the mirrors of the set of mirrors abuts outside on the primary beam cone, andwherein the angle of spread corresponds to a cone angle (θk) of the primary beam cone with a maximum deviation to the cone angle of 10%. 3. The apparatus according to claim 2, wherein a length LM of each of the mirrors of the set of mirrors is arranged, such that the inequalityLM≤LMmax=LW/(Θc2−Θm)holds, wherein:LW is the width of the exit of the set of mirrors,Θc2 is the critical angle of reflection at a mirror of the set of mirrors,Θm is the angle of spread of the mirrors of the set of mirrors. 4. The apparatus to claim 1, wherein the exit of the set of mirrors abuts to an aperture of the pre-collimator. 5. The apparatus according to claim 1, wherein the aperture of the pre-collimator is formed by the set of mirrors. 6. The apparatus according to claim 1, wherein the set of mirrors are arranged such that for the part of the X-ray radiation of the source to be reflected at the set of mirrors, a maximum of one or two total reflections at the mirrors of the set of mirrors occur. 7. The apparatus according to claim 1, wherein the pre-collimator comprises at least two apertures; andwherein, for each aperture of the pre-collimator, the mirror arrangement comprises an associated set of mirrors. 8. The apparatus according to claim 1, wherein the collimator arrangement further comprises a post-collimator; andwherein the object receiving space is arranged between the pre-collimator and the post collimator. 9. The apparatus according to claim 1, wherein each mirror of the sets of mirrors comprises a substrate with a coating layer for providing the total reflection; andwherein, between the coating layer and the substrate, a boundary is provided that is configured to reduce scatter radiation from incoming radiation that is not reflected but passes a mirror surface and enters the coating layer. 10. The apparatus according to claim 9, wherein, between the coating layer and the substrate, an uneven interface region is provided as the boundary. 11. The apparatus according to claim 10, wherein the interface has a randomly rough structured surface profile. 12. The apparatus according to claim 10, wherein the interface has a periodical profile with a periodical height between 0.05 mm and 1.5 mm, and a period between 0.5 mm and 5 mm. 13. The apparatus according to claim 12, wherein a thickness of the coating layer is between 10 nm and 25 nm. 14. An X-ray imaging system, comprising:an apparatus comprising:a source for generating X-ray radiation emitting a polychromatic spectrum of X-ray energies;an object receiving space for arranging an object of interest for X-ray imaging;an X-ray collimator arrangement; andan X-ray mirror arrangement;wherein the X-ray collimator arrangement comprises at least a pre-collimator arranged between the source and the object receiving space for providing collimated X-ray radiation to the object receiving space;wherein the X-ray mirror arrangement is arranged between the source and the pre-collimator;wherein the X-ray mirror arrangement comprises a set of two mirrors for guiding X-ray radiation of the source by providing total reflection of the whole polychromatic spectrum of X-ray energies of a part of the X-ray radiation in order to deflect the part of the X-ray radiation towards the pre-collimator such that in the region of the object receiving space enhanced radiation is provided in form of unreflected primary X-ray radiation in combination with secondary X-ray radiation by total reflection; andwherein the mirrors of the set of two mirrors are facing one another with an angle of spread (θm) larger than zero, such that the set of mirrors providing an X-ray entrance having an entrance width and an X-ray exit having an exit width, which is smaller than the entrance width;a detector for detecting X-ray radiation passing the object receiving space;an imaging processing unit; andan image data output unit;wherein the imaging processing unit is configured to receive signals from the detector; and to compute image data of an object based on the signals; andwherein the image data output unit is configured to provide the image data for further purpose. 15. An X-ray imaging system according to claim 14, further comprising:a mounting arrangement for mechanically connecting the source, the mirror arrangement, the collimator arrangement and the detector,an actuator coupled to the mounting arrangement to displace the mounting arrangement, anda control unit to control the actuator,wherein the control unit is configured to receive signals from the detector and to compute a control signal based on the received signals from the detector. |
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049903047 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to fuel assemblies for a nuclear reactor and, more particularly, is concerned with instrumentation tube features for reducing coolant flow-induced vibration of a flux thimble tube within the instrumentation tube. 2. Description of the Prior Art In a typical pressurized water nuclear reactor (PWR), the reactor core includes a large number of fuel assemblies each of which is composed of top and bottom nozzles with a plurality of elongated transversely spaced guide thimbles extending between the nozzles and a plurality of transverse grids axially spaced along the guide thimbles. Also, each fuel assembly is composed of a plurality of elongated fuel elements or rods transversely spaced apart from one another and from the guide thimbles and supported by the grids between the top and bottom nozzles. The fuel rods each contain fissile material and are grouped together in an array which is organized so as to provide a neutron flux in the core sufficient to support a high rate of nuclear fission and thus the release of a large amount of energy in the form of heat. A liquid coolant is pumped upwardly through the core in order to extract some of the heat generated in the core for the production of useful work. Further, in each fuel assembly, a provision is made to enable actual flux measurements to be taken under reactor operating conditions. For this purpose a hollow instrumentation tube is located in the approximate center of each fuel assembly and extends between the bottom and top nozzles. The instrumentation tube is open at its bottom end through the adapter plate of the bottom nozzle for insertion of a flux thimble tube into the instrumentation tube. The thimble tube is adapted to take the flux measurements. Coolant flow passes upward through an annulus formed between the outside diameter of the flux thimble tube and the inside diameter of the instrumentation tube, the coolant entering this annulus from the underside of the bottom nozzle adapter plate. The coolant exits through a bleed orifice formed by the top end of the instrumentation tube and the adapter plate of the top nozzle. The coolant flow induces vibrations in the thimble tube due to the existence of radial clearance and lack of mechanical connection between the instrumentation and thimble tubes. Vibration of the thimble tube frequently results in wall degradation in both the instrumentation tube and the thimble tubes. Instrumentation tube wall degradation, in turn, increases annular coolant flow rate, thereby increasing the jetting of coolant onto surrounding fuel rods. This jetting is known to cause erosion and breakdown of the fuel rod pressure boundary Wear-through of the tubes is presently minimized by placing a coolant flow-limiting seal between the underside of the bottom nozzle adapter plate and a nozzle attached to the core support plate. Although this has been generally successful in preventing wear-through of the tubes, it does not work in all cases. Other proposed solutions are use of small spring devices located at the entrance to the instrumentation tube. However, these devices are subject to coming loose and falling off and thus creating debris in the coolant system. Consequently, a need exists for an alternative approach to reducing coolant flow-induced vibrations and resultant wear to the instrumentation and thimble tubes. SUMMARY OF THE INVENTION The present invention provides vibration reducing features for the instrumentation tube designed to satisfy the aforementioned needs. The present invention is set forth in a fuel assembly having a hollow instrumentation tube and a flux thimble tube inserted in the instrumentation tube for taking flux measurements. The flux thimble tube is radially spaced inwardly at its exterior surface from an interior surface of the instrumentation tube so as to define a coolant flow annulus therebetween. The present invention relates to means for reducing coolant flow-inducing vibration of the thimble tube. The vibration-reducing means preferably is mechanical elements on the instrumentation tube which constrain the flux thimble tube within the instrumentation tube to maintain physical contact of the exterior of the thimble tube with the interior of the instrumentation tube at a plurality of points. The points are staggered on a single-diametral plane and spaced substantially throughout the length of the instrumentation tube. The staggered mechanical elements induce a controlled elastic sinuous deflection of the inner thimble tube. The mechanical elements of the present invention can take several different forms, for example, dimples or cantilevered spring fingers formed in the wall of the instrumentation tube and projecting radially inwardly therefrom. These and other features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention. |
claims | 1. A hybrid indirect-drive/direct drive apparatus for inertial confinement fusion, comprising:a central fusion fuel component;a first portion of a shell surrounding said central fusion fuel component, said first portion of a shell having a first thickness;a second portion of a shell surrounding said fusion fuel component, said second portion of a shell having a second thickness that is greater than said thickness of said first portion of a shell; anda hohlraum containing at least a portion of said fusion fuel component and at least a portion of said first portion of a shell,said hohlraum adapted to produce X-rays that are directed to said first portion of a shell and said fusion fuel component; andwherein said at least a portion of said fusion fuel component and said second portion of a shell are not contained in said hohlraum. 2. The hybrid indirect-drive/direct drive apparatus for inertial confinement fusion of claim 1 further comprising a fill tube extending through said first portion of a shell and said second portion of a shell to said fusion fuel component. 3. A hybrid indirect-drive/direct drive apparatus for inertial confinement fusion, comprising:a central fuel unit;a first portion of a shell surrounding said central fuel unit, said first portion of a shell having a first thickness;a second portion of a shell surrounding said central fuel unit, said second portion of a shell having a second thickness that is greater than said thickness of said first portion of a shell; anda hohlraum containing at least a portion of said central fuel unit and at least a portion of said first portion of a shell,said hohlraum adapted to produce X-rays that are directed to said first portion of a shell; andwherein said at least a portion of said central fuel unit and said second portion of a shell are not contained in said hohlraum. 4. The hybrid indirect-drive/direct drive apparatus for inertial confinement fusion of claim 3 further comprising a fill tube extending through said first portion of a shell and said second portion of a shell to said central fuel unit. 5. A hybrid indirect-drive/direct drive apparatus for inertial confinement fusion, comprising:a central fuel unit;a shell surrounding said central fuel unit, said shell having a first portion partially surrounding said central fuel unit and a second portion partially surrounding said central fuel unit;wherein said first portion has a first thickness and said second portion has a second thickness that is greater than said first shell thickness; anda hohlraum containing at least a portion of said first portion of said shell having a first thickness,said hohlraum adapted to produce X-rays that are directed to said first portion of said shell having a first thickness; andwherein said at least a portion of said central fuel unit and said second portion of said shell having a second thickness that is greater than said first shell thickness are not contained in said hohlraum. 6. The apparatus for inertial confinement fusion utilizing laser beams from a first direction and laser beams from a second direction of claim 5 further comprising a fill tube extending through said shell to said central fuel unit. 7. A hybrid indirect-drive/direct drive apparatus for inertial confinement fusion, comprising:a central fuel unit;a first portion of a shell surrounding said central fuel unit, said first portion of a shell having a first thickness;a second portion of a shell surrounding said central fuel unit, said second portion of a shell having a second thickness that is greater than said thickness of said first portion of a shell, said second portion of a shell comprising fuel; anda gold hohlraum containing at least a portion of said central fuel unit and at least a portion of said first portion of a shell,said gold hohlraum adapted to produce X-rays that are directed to said first portion of a shell; andwherein said at least a portion of said central fuel unit and said second portion of a shell are not contained in said gold hohlraum. 8. The hybrid indirect-drive/direct drive method for inertial confinement fusion of claim 7 wherein said second portion of a shell comprising fuel is solid deuterium-tritium. |
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description | The invention relates to improvements provided to the sealed junction and the sealed transfer between two chambers for the purpose of aseptic transfer between them, limiting the risks of contamination at the locations of the inside and outside critical lines. The invention more specially has as its object a sealed junction device between two chambers, an aseptic transfer device that comprises such a sealed junction device, and a first chamber and a second chamber that are part of such an aseptic transfer device, the process for implementing the sealed junction device, and the process for implementing the sealed transfer device. Double-door-type aseptic transfer devices are already known. Purely by way of example, it is possible to cite the devices that are known under the trademark BIOSAFE® and the document EP-A-0688020 that describes a sealed junction device between two chambers that are isolated from an external environment. With such an embodiment, a structure that includes a first wall that is equipped with a first opening that is bordered by a first annular flange that forms, on the one hand, an interface (with a second flange), and, on the other hand, a seat for a first panel of a first door, are part of a first chamber—for example, a chamber that is stationary, rigid and of relatively large size. The first door is supported by the structure by means of carrying means, of a mechanical, movable or deformable nature. The first panel is mounted to move—namely in rotation—and arranged to be in the closed state or in the open state or, respectively, it closes or opens the first opening. Movement actuation means are able to move the first panel. A second wall that is equipped with a second opening that is bordered by a second annular flange that forms, on the one hand, an interface (with the first flange), and, on the other hand, a seat for a second panel of a second door that is mounted to move and arranged to be in the closed state or in the open state, where, respectively, it closes or opens the second opening, are part of a second chamber—for example a movable, disposable, and at least partly flexible container that is of smaller size. The first flange, the first panel, the second flange, and the second panel each have an inside surface that is located toward the inside, respectively, of the first chamber, the second chamber, and an outside surface that is in contact with the external environment with two chambers. The first flange and the second flange are complementary and able to be held in a removable way, flattened against one another by their outside surfaces, hermetically sealed, by thus being isolated from the external environment, owing to removable holding means with which they are equipped, for example a cam mechanism. The first door and the second door are complementary, and their panels are able to be flattened against one another by their outside surfaces, hermetically sealed, by thus being isolated from the external environment, and to be kept thus flattened in a removable way, owing to removable interlocking means with which they are equipped. For this purpose, the flanges and the panels have respective surfaces that are designed to be flattened against one another and of which the shapes are complementary, and sealing joints can be provided where necessary. Movement actuation means are also provided, and said means are able to move the first panel of the first door, with which the second panel of the second door can be made integral, between its closed and open states, as well as monitoring means of these movement actuation means. The process for implementing a sealed junction device of the preceding type comprises the following successive operating stages: The first chamber of which the first panel of the door is in the closed state and the second chamber of which the second panel of the second door is in the closed state are available; The two chambers are brought close to one another, and the first flange and the second flange are flattened against one another in a hermetically sealed way by their outside surfaces, and the panel of the first door and the panel of the second door are brought to be flattened against one another in a hermetically sealed way; The first flange and the second flange, on the one hand, and the first panel and the second panel, on the other hand, are held, and the first panel is actuated to move it and to bring it into the open state and thus also to bring the second panel into the open state. Thus, the first chamber and the second chamber are in communication with one another via their respective openings in the open state, with a communication space being made between the two chambers, making it possible to pass certain contents between them and thus to transfer said contents from one to the other of the two chambers. This communication space consists of an entrance/exit space in the first chamber and an entrance/exit space in the second chamber, whereby these two entrance/exit spaces are in communication with one another. The process for implementing a device for sealed transfer between two chambers including such a sealed junction device comprises the following successive operating stages: Two chambers in the closed state, one originally containing certain contents to be transferred, are available; The sealed junction device is implemented as it was just indicated; Once the first panel of the first door and the second panel of the second door are in the open state and once the first chamber and the second chamber are in communication with one another via the communication space, the certain contents of the chamber are passed from where they were located originally to the other chamber where they are to be located ultimately; Once this transfer is carried out, the panels of the first door and the second door are brought into the closed state; Then, the two chambers are separated. As appropriate, the certain contents are originally in the first chamber or in the second chamber. Transfers such as those in question here may be needed in a number of technical fields, in particular but not exclusively the biopharmaceutical field. The invention quite especially focuses on this field, as with those that can be considered as analogous in relation to the imposed requirements. The contents—to be transferred or that have been transferred—are not per se crucial to the invention if they are only to be transferred and therefore are supposed to be capable of being transferred. In the biopharmaceutical field, it may be a matter of, for example, a sterile object such as a receptacle, a receptacle element such as a stopper, or a syringe, but also environmental monitoring elements, and even waste produced during the manufacturing or treatment operation, waste that is to be transferred so as to dispose of it . . . . More complex transfers, such as those considered here, most often are involved within the process framework in which the certain contents experience one or more operations before and/or after the transfer. These operations consist of manufacturing, assembly, treatment, handling, use, measurement, monitoring, analysis, etc. In the case of an operating line, a first chamber may be provided that comprises a wall that is equipped with both the same number of first openings and first doors, as well as sealed junction devices with a multiplicity of second chambers. In the case of the embodiment that is known under the trademark BIOSAFE®, the carrying means and the movement actuation means of the first door and its panel comprise a hinge of which the axis—vertical and lateral—is located in the first chamber itself (inside space of this first chamber), in or close to the inside surface of its wall, close to its opening and its flange, with the rotation around the hinge being implemented manually or in a motorized way (actuator, motor, . . . ). In the closed state, the first panel is retracted in the plane of the first wall or in its vicinity, the first opening, and the first flange. In the open state, the first panel, which is designed to then support the second panel, is projecting, in the first chamber, in particular arranged more or less perpendicularly to the plane of the first wall, the first opening, and the first flange. The movement of the panel between its closed state and its open state (and vice versa) is on the order of one-third of a turn. As for the movement actuation means, such as an actuator, motor, . . . , they are able to move the first panel in rotation over this path. In the embodiments described in the document EP-A-2091051 where the axis is also vertical and lateral, in the documents EP-A-1 141 974, EP-A-1 454 328, EP-A-0 730 907, EP-A-0 830 896 where the axis is horizontally below (below the opening and the flange) and in the document EP-A-0 662 373 where the axis is horizontally above, in the open state, the first panel, which then supports the second panel, is projecting as above into the first chamber and more or less perpendicular to the plane of the first wall, the first opening, and the first flange. As the document EP-A-1141672 states, one skilled in the art knows that with the type of aseptic transfer device considered, there exists what one calls a “critical line” with residual contamination by the external environment with two chambers. It is possible that this line comes into contact with the external environment that is in the passage between the two chambers or in contact with the contents that pass through this passage to be transferred from one chamber to the next, with consequent contamination. This critical line is sometimes called “critical zone” or “ring of concern” (see PIC/S—Pharmaceutical Inspection Convention—RECOMMENDATION—ISOLATORS USED FOR ASEPTIC PROCESSING AND STERILITY TESTING). More specifically, there are two approximately concentric critical lines when the two doors are in the closed state. An inside critical line is on the outside surface of the first door, more specifically its panel, in contact with the external environment and not overlapped by the outside surface of the second door, more specifically its panel, when the two panels are flattened against one another. An outside critical line is on the outside surface of the second flange in contact with the external environment and not overlapped by the outside surface of the first flange, when the two flanges are flattened against one another. In the embodiments cited above, in the open state of the first panel, the first panel, which supports the second panel, is laterally adjacent to the lateral boundary of the entrance/exit space of the first chamber. Thus, the first panel and/or the second panel can be found to be brought into contact with the certain contents during its passage into the entrance/exit space, with risks of contamination by the inside critical line. Several solutions have been proposed for the purpose of remedying this risk of contamination, also mentioned in ISOLATION TECHNOLOGY—A PRACTICAL GUIDE, published by CRC Press in 2004. The document EP-A-0960698 provides decontamination means using ultraviolet, pulsed-ultraviolet, or pulsed-light radiation. The document EP-A-0662373 provides that a flanged ring of the aseptic transfer device comprises a heat-resistant annular element whose purpose is to maintain maximum integrity of the device against possible contamination. Variants of the heating technology are described in the documents EP-A-730907 and EP-A-830907. The technology of sterilization by dry heat was indicated as being the preferred solution according to the presentation made by the Barrier Users Group Symposium (BUGS) at the conference of Jan. 17 and 18, 1995. The document EP-A-1454328 describes an aseptic transfer device that comprises a device for protection of the single outside critical line. This protective device comprises an annular part and a support arm. The annular part comprises a tapered portion and a circular portion. The tapered portion is sized in such a way as to be able, when the first panel of the first door is in the open state, to be engaged through the seat that is bordered by the flange of the first chamber, in such a way as to overlap the areas of the flange forming this seat, while the circular portion is shaped in such a way as to rest against the surface of the flange that is turned toward the inside of the first chamber so as to position the tapered portion axially with respect to the flange, by overlapping and without contact. For this purpose, the arm is mounted to pivot on a wall of the first chamber. Such a protective device is mounted inside the first chamber, and it is structurally independent of the first door and not integrated therein. This embodiment is therefore complex and bulky, in addition to the fact that it involves having to act on the support arm that is located in the first chamber. Ultimately, this embodiment does not provide any solution regarding the inside critical line. Concerning the outside critical line, it has also been proposed to provide a flexible horn that is supported by the second chamber and that is unfolded after the second chamber is brought into the open state, or a rigid horn that is installed after opening, or else a removable funnel. These solutions are only palliatives. The technology that uses a horn poses several problems: risk of failing to install or of mis-positioning the horn during the manufacturing of the second chamber, errors during use, risk of contamination during the installation of a flexible horn . . . . The technology that uses a funnel poses other problems: space requirement in the first chamber, risk of particles . . . . Whether it involves a horn or a funnel, such an element is connected to the first door, being structurally independent of it and not integrated into it. The state of the art also comprises the documents U.S. Pat. No. 3,489,298, EP 0586307, FR 2833745, EP 0830 896, FR 2787 235, US 2009/212054, WO 96/21615, WO 03/041087 and WO 95/34078. However, none of these documents provides an arrangement such that there is a separation between the communication space and both the inside critical annular line and the outside critical annular line. The problem on which the invention is based is therefore to equip a sealed junction device between two chambers that are isolated from an external environment that is integrally protected against the risks of contamination both for the outside critical line and for the inside critical line, and that does not have the drawbacks or the boundaries of the partial solutions proposed thus far. For this purpose and according to a first aspect, the invention has as its object a sealed junction device between a first chamber and a second chamber that are isolated from the external environment, such as: Being part of a first chamber: A structure that includes a first wall that borders a first inside space is equipped with a first opening that is bordered by a first annular flange; A first door that is supported by the structure by means of the movable or deformable carrying means, of which the panel is arranged and mounted so as to be able to be moved to be either in the closed state where it works with the first flange by closing the first opening or in the open state where it is detached from the first flange and placed in the inside space by opening the first opening; Being part of a second chamber: A second wall is equipped with a second opening that is bordered by a second annular flange; A second door of which the panel is arranged and mounted to move, able to be in the closed state or in the open state, where, respectively, the second panel closes or opens the second opening; The first flange and the second flange are complementary and able to be held in a removable way, flattened against one another by their end surfaces by removable holding means; The first panel and the second panel are complementary and able to be flattened against one another, hermetically sealed, by their outside surfaces; Removable interlocking means are able to hold the two panels in a removable way, flattened against one another in a hermetically-sealed way by their outside surfaces; Movement actuation means are able to move the first panel between its closed and open states, and monitoring means are able to monitor the movement actuation means; Such that when the first door and the second door, respectively their panels, are in the open state, the first chamber and the second chamber are in communication with one another via their respective openings in the open state, with a communication space that consists of an entrance/exit space in the first chamber and an entrance/exit space in the second chamber being made between the two chambers that make it possible to pass certain contents from one to the other; An inside critical annular line of contamination risk exists on the first panel of the first door, and an outside critical annular line of contamination risk exists on the second flange; And protective means are provided against the risks of contamination for the outside critical line. This device comprises means that are structurally integrated into the first door and/or means that are structurally integrated into the second flange, able—when the first door and the second door, respectively their panels, are in the open state—to form a separation between the communication space and the inside critical annular line and the outside critical annular line. According to another characteristic, the structurally integrated means that can form a separation constitute protective means against any contamination at the location of the inside critical annular line and/or the outside critical annular line. According to one embodiment, the structurally integrated means are completely integrated into the first door and/or into the second flange. According to a first embodiment, the structurally integrated means that can form a separation come in the form of an annular deflector that is placed between the communication space and the critical line, whereby the latter thus normally cannot be reached during the passage into the communication space. According to a second embodiment, the structurally integrated means that can form a separation come in the form of a separation space of appropriate size, placed between the communication space and the critical line, whereby the latter thus normally cannot be reached during the passage into the communication space. As appropriate, one or the other or both embodiments exist. According to a first variant embodiment, the structurally integrated means that are able to form a separation come in the form of an annular deflector that is integrated into the second flange, bordering the second opening and projecting from the free frontal plane of the second flange that forms an interface with the first flange. According to one possibility, the annular deflector has a general cylindrical shape or a slightly tapered free distal edge, or it forms an annular cavity with the outside peripheral part of the second flange in the bottom or in the vicinity of the bottom of which the critical line is located. According to one possibility, the panel of the second door comprises an annular groove that opens toward the inside of the second chamber, able to accommodate the deflector of the second flange, for example, able to comprise—toward the inside—the annular groove, and to form toward the outside a part in the shape of a tenon that can be housed in a complementary part in the shape of a mortise provided on the outside surface of the panel of the first door. According to a second variant embodiment, the structurally integrated means that can form a separation come in the form of an annular deflector that is integrated into the first door, supported by or being part of the carrying means or movement actuation means of the first door or panel of the first door in the open state and arranged around the first door. According to several possibilities, the annular deflector has a general cylindrical shape and with a central part of the carrying means or movement actuation means of the first door forms a cavity for protection of the inside critical line with a larger axial size, in particular a considerably larger size, than the axial space requirement of the panel of the first door or the axial space requirement of the unit that comprises the panel of the first door and the panel of the second door flattened on the panel of the first door. According to one possibility, the carrying means and the movement actuation means of the first door are means to rotate around an axis that is at least approximately parallel to the first opening, and the first flange. This axis is, for example, separated in the inside space of the first chamber in such a way as to allow the deflector—in the open state of the first panel—to be placed between the central part of the carrying means or the movement actuation means and the inside surface of the wall of the first chamber around the first opening. This axis, however, is separated laterally from the panel of the first door, in such a way as to separate the deflector, the panel of the first door, and the inside critical line of the communication space when the first panel is in the open state. According to a third variant embodiment, the structurally integrated means that can form a separation come in the form of a separation space of appropriate size, with the carrying means and the movement actuation means of the first door being arranged in such a way that in the open state of the first panel, the first panel is substantially separated beyond the boundary of the first entrance/exit space, with the separation space thus being made between the first entrance/exit space and the first panel in the open state. According to different possibilities, the first door is supported by means of carrying means in such a way that the first panel is arranged and mounted so as to be able to be moved to be located, in the open state, either in a primary open state where a primary separation space is made or in a final open state where a final separation space is made, larger than the primary separation space. As appropriate, the separation space is located beyond the lateral boundary or beyond the distal end boundary of the entrance/exit space of the first chamber, opposite to the first opening, and to the first flange. According to one possibility, the separation space is an empty space. According to another possibility, a stationary or movable separation wall is provided for the first chamber, said wall which, in the open state of the first panel, is placed and extends, at least partly, between the first panel and the first entrance/exit space. According to the possibilities, in the open state of the first panel, the separation between any area of the first panel and the closest boundary of the first entrance/exit space is at least equal to one-fourth, more particularly is at least equal to one-half, and more particularly still is at least equal to the size of the first entrance/exit space computed in the direction of this separation. According to the possibilities, in the open state of the first panel, the first panel is arranged in a position that is at least approximately parallel or at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state. According to the possibilities, in the open state of the first panel, the first panel is arranged in a position that is at least approximately opposite or in a lateral position in relation to the first opening, the first flange, and the position of the first panel in the closed state. According to the possibilities, the carrying means and the movement actuation means of the first door are arranged to be able to move the first panel between its closed and open or primary open states, in a movement that comprises an initial movement of separation from the first panel of the first flange, which is an at least essentially initial translational movement along an axis that is at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state, or an initial rotational movement around an axis that is at least approximately parallel to the first opening, the first flange, and the position of the first panel in the closed state. According to the possibilities, the carrying means and the movement actuation means of the first door are arranged to be able to move the first panel between its closed and open or primary open and final open states, in a movement that comprises an initial movement of separation of the first panel from the first flange and at least a subsequent movement that is a subsequent translational movement and/or at least one subsequent rotational movement. According to the possibilities, the carrying means and the movement actuation means of the first door are arranged to be able to move the first panel in a subsequent translational movement along an axis of translation that is at least approximately rectilinear or curvilinear, or in a subsequent rotational movement around an axis that is at least approximately parallel to or at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state. According to a first family of embodiments, the carrying means and the movement actuation means of the first door are arranged to be able to move the first panel from its closed state in a movement that comprises an initial translational movement along an axis that is at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state, to separate the first panel from the first flange, and at least one subsequent translational movement along an axis that is at least approximately parallel to the first opening, the first flange, and the position of the first panel in the closed state and/or a rotational movement around an axis that is at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state, to bring the first panel into its position in the open or primary open or final open state, where it is then arranged in a lateral position in relation to the first opening, the first flange, and the position of the first panel in the closed state, at least approximately orthogonal to the axis of the first entrance/exit space, with the separation space being located beyond the lateral boundary of the first entrance/exit space. According to a second family of embodiments, the carrying means and the movement actuation means of the first door are arranged to be able to move the first panel from its closed state in a movement that comprises at least one translational movement along an axis that is at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state, for separating the first panel from the first flange, and then to bring the first panel into its position in the open, primary open, or final open state, where it is then arranged in a position that is at least approximately opposite the first opening, the first flange, and the position of the first panel in the closed state, at least approximately orthogonal to the axis of the first entrance/exit space, whereby the separation space is located beyond the end boundary of the entrance/exit space that is opposite to the first opening and the first flange. According to a third family of embodiments, the carrying means and the movement actuation means of the first door are arranged to be able to move the first panel from its closed state in a movement that comprises a rotational movement around an axis that is at least approximately parallel to the first opening, the first flange, and the position of the first panel in the closed state, to bring the first panel into its position in the open or primary open or final open state where it is then arranged in a lateral position in relation to the first opening, the first flange, and the position of the first panel in the closed state, at least approximately orthogonally to the axis of the first entrance/exit space, whereby the separation space is located beyond the lateral boundary of the first entrance/exit space. According to a fourth family of embodiments, the carrying means and the movement actuation means of the first door are arranged to be able to move the first panel from its closed state in a movement that comprises a translational movement along a curvilinear axis that corresponds at least approximately to an arc with an axis that is at least approximately parallel to the first opening, the first flange, and the position of the first panel in the closed state, to bring the first panel into its position in the open or primary open or final open state where it is then arranged in a lateral position in relation to the first opening, the first flange, and the position of the first panel in the closed state, at least approximately orthogonally to the axis of the first entrance/exit space, with the separation space being located beyond the lateral boundary of the first entrance/exit space. According to a second aspect, the invention has as its object a process for implementing a sealed junction device as just described, comprising the following successive operating stages: A first chamber of which the first door that comprises a first panel is in the closed state, and a second chamber of which the second door that comprises a second panel is in the closed state are available; The two chambers are brought into proximity with one another, and the first flange and the second flange are flattened against one another, hermetically sealed, by their outside surfaces, and the first panel of the first door and the second panel of the second door are brought to be flattened against one another, hermetically sealed; The first flange and the second flange and the two panels are made integral, and the first panel is actuated to move it and to bring it into the open state and thus also to bring the second panel into the open state, in such a way that the first chamber and the second chamber are in communication with one another via their respective openings in the open state, with a communication space being made between the two chambers, making it possible to pass certain contents between them. This process is such that when the first panel of the first door and the second panel of the second door are in the open state, the means that are structurally integrated into the first door and/or the means that are structurally integrated into the second flange are implemented, and a separation is formed between the communication space and the inside critical annular line and the outside critical annular line of the sealed junction device. According to a third aspect, the invention has as its object a first chamber, specially designed with a second chamber to be part of a device for sealed transfer between the two chambers, comprising: A structure that includes a first closed wall that borders an inside space, At least a first opening that is made in the first wall and bordered by a first annular flange of which the outside surface is able to provide the hermetically-sealed flattening on itself of the outside surface of a second complementary flange that is part of the second chamber, Removable holding means, combined at least in part with the first flange, able to hold in a removable way the first flange and the second flange that are flattened against one another by their outside surfaces, A first door that is supported by the structure by means of the movable or deformable carrying means, of which the first panel is arranged and mounted so as to be able to be moved to be either in the closed state where it works with the first flange by closing the first opening or in the open state where it is released from the first flange and placed in the first inside space by opening the first opening, and of which the outside surface is able to ensure the hermetically-sealed flattening on itself from the outside surface of the second panel of a second complementary door that is part of the second chamber, Means for removable interlocking combined at least in part with the first door, able to hold the first panel and the second panel, flattened against one another by their outside surfaces, in a removable way, Movement actuation means that can move the first panel between its closed and open states, and means for monitoring these movement actuation means, And, when the first panel is in the open state, a first entrance/exit space in/of the first inside space, in the general shape of a truncated cylinder, cone or pyramid, extending into the first inside space at least approximately axially from the first opening, and the first flange, whereby this first entrance/exit space is part of a communication space between the two combined chambers and is able to make it possible to pass certain contents into/out of the first inside space, from one to the other of the two chambers, Able to be attached to the second chamber by a sealed junction device as described, And comprising means that are structurally integrated into the first door that are able, when it is in the open state, to form a separation between the communication space and the inside critical annular line. According to a first embodiment, the means that are structurally integrated into the first door come in the form of an annular deflector that is supported by or is part of the carrying means of the first door or the first panel of the first door in the open state and arranged around the first door. In this first embodiment, the deflector can have a larger axial size, in particular a considerably larger size, than the axial space requirement of the first panel and can form a cavity for protection of the inside critical line with a central part of the carrying means of the first door. In this first embodiment, the carrying means of the first door can be carrying means to rotate around an axis that is approximately parallel to the first flange. For example, this axis of rotation is separated from the first flange toward the inside of the first chamber in such a way as to make it possible for the deflector to be placed between the central part of the carrying means and the inside surface of the wall of the first chamber, around the first opening. This axis of rotation can be separated laterally from the first panel, in such a way as to separate the deflector, the first panel, and the inside critical line of the communication space when the first door is in the open state. According to a second embodiment, the means that are structurally integrated into the first door come in the form of a separation space of appropriate size, with the carrying means and the movement actuation means of the first door being arranged to be able to move the first panel between its closed and open or primary open and final open states in such a way that in the open state of the first panel, the first panel is substantially separated beyond the boundary of the first entrance/exit space for making this separation space between the first entrance/exit space and the first panel in the open state. According to the modes of execution of this second embodiment, the carrying means and the movement actuation means of the first door comprise initial separation means of the first panel from the first flange that are translational means along an axis that is at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state, or rotational means around an axis that is at least approximately parallel to the first opening, the first flange, and the position of the first panel in the closed state. However, the carrying means and the movement actuation means comprise initial separation means of the first panel from the first flange and subsequent movement means that are translational means and/or rotational means. For example, the carrying means and the movement actuation means comprise subsequent translational movement means along an axis of translation that is at least approximately rectilinear or curvilinear or subsequent rotational means around an axis that is at least approximately parallel to or at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state. According to one possibility, the first panel is extended laterally projecting, in an at least essentially coplanar way, by at least one mechanism plate that is part of the carrying means and that makes possible the movement of the first panel as a result of the implementation of the movement actuation means. According to one possibility, the first wall comprises one or more through slots that can allow sealed and aseptic passage of carrying means and/or movement actuation means. In the second embodiment (separation space) and according to a first family, the carrying means and the movement actuation means comprise at least a first actuator that is arranged along an axis that is at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state and that ensures the initial translational movement and either at least a second actuator along an axis that is at least approximately parallel to the first opening, the first flange, and the position of the first panel in the closed state, or at least one rotational movement system along an axis that is at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state. According to the possible embodiments of this first family, the initial course of translational movement is just that necessary, aside from the necessary degrees of play, to make possible subsequent translational or rotational movement, without the first panel interfering with the first wall of the first chamber on its inside surface. In its open or primary open or final open state, the outside surface of the first panel is turned toward and close to the inside surface of the first wall of the first chamber. The first panel is extended laterally projecting by at least one mechanism plate that is supported at least approximately orthogonally by the at least one first actuator that passes through the at least one through slot of the first wall with the at least one first actuator being supported by the at least one second actuator or the at least one rotational movement system. In the second embodiment (separation space) and according to a second family, the carrying means and the movement actuation means comprise at least one actuator that is arranged along an axis that is at least approximately orthogonal to the first opening, the first flange, and the position of the first panel in the closed state. According to the possible embodiments of this second family, the course of translational movement is that necessary to the production of the separation space and, in its open or primary open or final open state, the outside surface of the first panel is turned toward and removed from the first opening and the first flange. In the second embodiment (separation space) and according to a third family, the carrying means and the movement actuation means comprise at least one rotational movement system along an axis that is at least approximately parallel to the first flange and to the position of the first panel in the closed state. According to the possible embodiments of this third family, the course of rotational movement is close to a half-turn; in its open or primary open or final open state, the outside surface of the first panel is turned opposite the inside surface of the first wall of the first chamber, and the first panel is extended laterally projecting by a mechanism plate that is supported by the rotational movement system. In the second embodiment and according to a fourth family, the carrying means and the movement actuation means comprise at least one system with a deformable parallelogram along an axis that is at least approximately parallel to the first flange and to the position of the first panel in the closed state. According to the possible embodiments of this fourth family, the course of rotational movement of the deformable parallelogram is on the order of a half-turn, and in its open or primary open or final open state, the outside surface of the first panel is turned toward the inside surface of the first wall of the first chamber. According to a fourth aspect, the invention has as its object a second chamber, specially designed to be part of a first chamber of a sealed transfer device between the two chambers, Comprising: A second wall that is equipped with a second opening that is bordered by a second annular flange, A second door of which the panel is arranged and mounted to move, able to be in the closed state or in the open state or, respectively, the second panel closes or opens the second opening, Able to be attached to the first chamber by a sealed junction device as described above, And comprising suitable means that are structurally integrated into the second flange that can, when the second door, respectively the second panel, is in the open state, form a separation between the communication space and the outside critical annular line. According to one embodiment, the means that are structurally integrated into the second flange come in the form of an annular deflector that borders the second opening, projecting from the free frontal plane of the second flange that forms an interface with the first flange. According to the embodiments, the annular deflector has a general cylindrical shape or a slightly tapered free distal edge, and with the outside peripheral part of the second flange, it forms an annular cavity in the bottom or in the vicinity of the bottom of which the outside critical line is located. According to the embodiments, the panel of the second door comprises an annular groove that opens toward the inside of the second chamber, able to accommodate the deflector of the second flange, and the panel of the second door comprises a rounded annular peripheral part that can comprise the annular groove toward the inside and that can form a part in the shape of a tenon toward the outside. According to a fifth aspect, the invention has as its object a device for sealed transfer between a first chamber as described and a second chamber as described, comprising a sealed junction device between the two chambers that is equipped with means that are structurally integrated into the first door and/or means that are structurally integrated into the second flange, able—when the first door and the second door, respectively the panels of the doors, are in the open state—to form a separation between the communication space and the inside critical annular line and/or the outside critical annular line. According to a sixth aspect, the invention has as its object a process for implementing a sealed transfer device between a first chamber and a second chamber comprising a sealed junction device, as described, which comprises the following successive operating stages: A first chamber of which the first door, respectively the first panel, is in the closed state and a second chamber of which the second door, respectively the second panel, is in the closed state, are available, with one of the chambers originally containing certain contents; The sealed junction device is implemented as described; Once the first door and the second door, respectively the panels, are in the open state and the first chamber and the second chamber are in communication with one another via a communication space, certain contents of the chamber where they are located are passed to the other chamber, without the certain contents, during this transfer between the two chambers, being in contact with the inside critical annular line and/or the outside critical annular line; Once this transfer is done, the first door and the second door, respectively the panels, are brought into the closed state; Then, the two chambers are separated. According to the embodiments, the certain contents are originally in the first chamber or they are originally in the second chamber. A sealed and aseptic transfer device between a first chamber 1 and a second chamber 2 such as the one under consideration here is called “double-door.” By way of example, but not limiting, such a device is of the type of the one that is known under the trademark BIOSAFE® and described in the document EP-A-0688020. Such a transfer may be necessary in a number of technical fields, in particular but not exclusively the biopharmaceutical field. The first chamber 1—for example stationary, rigid and of relatively large size—comprises a structure that includes a first closed wall 3, solid and rigid, but equipped with a first opening 4, itself bordered by a first annular flange 5, with an outside surface 5a, with one and the other of the opening 4 and the flange 5 being, for example, circular, whereby this embodiment is not limiting. According to one embodiment, the first wall is vertical or inclined to the vertical by an angle on the order of 30° to 45°. The wall 3, having an inside surface 3b, borders the inside space 1a of the chamber 1. That which is in or toward the inside space 1a that is bordered by the wall 3 is termed “interior” in connection with the first chamber 1. That which is beyond its inside space 1a that is bordered by the wall 3 is termed “outside” in connection with the first chamber 1. The first chamber 1 also comprises a first door 6 that is supported by the structure, in particular by the wall 3, by means of movable or deformable carrying means 11a. The panel 6v of the first door 6 (or first panel 6v) is mounted to move in relation to the first flange 5 that forms a seat, and arranged to be moved and brought either into the closed state where it works with the flange 5 by closing the opening 4 or in the open state, where it is released from the flange 5 and placed in the inside space 1a by opening the opening 4. By synecdoche, it will be said that the first door 6 is mounted to move in relation to the first flange 5 to be in the closed state or in the open state, where, respectively, it closes or opens the first opening 4. The panel 6v comprises an outside surface 6a. If applicable, the first chamber 1 comprises several first doors such as the first door 6, with the transfer device being part of an operating line that is suitable for making it possible to implement one or more operations before and/or after the transfer, such as manufacturing, treatment, handling, use, measurement, monitoring, analysis, or the like . . . . The second chamber 2—for example, a movable pouch that is disposable, at least partially flexible and of a smaller size—comprises a structure that includes a second closed wall 7, solid and flexible, but equipped with a second opening 8, itself bordered by a second annular flange 9, with the outside surface 9a, one and the other of the opening 8 and the flange 9 being, for example, circular, with this embodiment not being limiting. The wall 7 borders the inside space 2a of the chamber 2. That which is in or toward its inside space 2a that is bordered by the wall 7 is termed “interior” in connection with the second chamber 2. That which is beyond its inside space 2a that is bordered by the wall 7 is termed “outside” in connection with the second chamber 2. The second chamber 2 also comprises a second door 10, having a second panel 10v, an outside surface 10a and an inside surface 10b. The panel 10v, mounted to move in relation to the second flange 9 that forms a seat, and arranged to be in the closed state or in the open state, where, respectively, it closes or opens the second opening 8. As above, by synecdoche, it will be said that the second door 10 is mounted to move in relation to the second flange 9 to be in the closed state or in the open state, where, respectively, it closes or opens the second opening 8. The sealed and aseptic transfer device is such that several second chambers, such as the second chamber 2, can be combined with the same first chamber 1, when necessary, successively if the first chamber 1 comprises a single opening and a single door 4 and 6 and/or simultaneously if the first chamber 1 comprises several openings and doors 4 and 6. One of the chambers 1, 2 originally contains certain contents C. For example, certain contents C are originally in the first chamber 1 or in the second chamber 2, with the object of the transfer being to bring said contents finally, respectively, into the second chamber 2 or into the first chamber 1, and in so doing passing the certain contents C into a communication space 13 that is made between the two chambers 1 and 2. The certain contents C have as a characteristic to have a purpose to be, and therefore to be able to be, transferred via the communication space 13. In the biopharmaceutical field, the certain contents C can be, for example, a sterile object such as a receptacle, a receptacle element such as a stopper, a syringe, but also environmental monitoring elements, and even waste produced during the operation of manufacturing or treatment, waste that it is a matter of transferring so as to eliminate it . . . . Transfers, such as those considered here, take place within the framework of more complex processes in which the certain contents C experience one or more operations before and/or after the transfer These operations consist of manufacturing, assembly, treatment, handling, use, measurement, monitoring, analysis, or the like, with the asepsis requirement having to be met. In contrast, it is important that the transfer of the certain contents C via the communication space 13 not be impeded by the panel 6v of the first door 6 in the open state, that the certain contents C not deteriorate this first panel 6v, and conversely that this first panel 6v not deteriorate the certain contents C, therefore that the first panel 6v cannot be reached by the certain contents C during their transfer. The invention has as its object both this sealed junction device, and the transfer device that includes it, and the first chamber 1 and the second chamber 2, and, finally, the process for implementing this sealed junction device and this transfer device. The first flange 5 and the second flange 9 are complementary with one another both structurally and functionally. They are designed so that the panels 6v and 10v are able to be held in a removable way flattened against one another by their outside surfaces 5a and 9a, hermetically sealed, by thus being isolated from the external environment. For this purpose, it is provided to equip the flanges 5 and 9 with assembly means such as, for example, the complementary shapes provided to their respective surfaces 5a and 9a having to be flattened against one another and one or more sealing joints on the second flange 9. On the other hand, it is provided to combine a removable interlocking mechanism, for example with cams, not shown, with flanges 5 and 9. The first door 6 and the second door 10—more specifically their panels 6v and 10v—are complementary with one another both structurally and functionally. They are designed so as to be able to be flattened against one another by the outside surfaces 6a and 10a of their respective panels 6v and 10v, hermetically sealed, by thus being isolated from the external environment. For this purpose, it is provided to equip the doors 6 and 10—more specifically their panels 6v and 10v—with assembly means such as, for example, the complementary shapes given to their respective outside surfaces 6a and 10a having to be flattened against one another and one or more sealing joints. Movement actuation means 11b that can move the first door 6—more specifically its panel 6v—between its closed and open states are also provided. Monitoring means 11c of the movement actuation means 11b are also provided. The movable or deformable carrying means 11a, the movement actuation means 11b, and the monitoring means 11c are integrated into one another and integrated into the first door 6. Removable interlocking means that are combined with two doors 6 and 10, not shown, able to keep, in a removable way, the two doors 6 and 10—more specifically their panels 6v and 10v—flattened against one another are also provided. Such a sealed transfer device is implemented as follows. A start is made from a situation where the first chamber 1 of which the first door 6, or the panel 6v, is in the closed state and a second chamber 2 of which the second door 10, or the panel 10v, is in the closed state are available, whereby one of the chambers 1, 2 originally contains the certain contents C, as indicated above. When the first panel 6v is in the closed state, it works with the first opening 4, in such a way that the first opening 4, the first flange 5, and the first panel 6v in the closed state are essentially coplanar aside from thicknesses, with the first panel 6v being retracted, in the direction where it does not project substantially from the first wall 3. The sealed junction device is implemented between the two chambers 1 and 2, and for this purpose, the successive operating stages that are described below are carried out. The two chambers 1 and 2 are brought to be placed at least essentially coaxially, facing one another and close together (arrows F1 of FIGS. 1 and 6). Then, the first flange 5 and the second flange 9 are flattened against one another, hermetically sealed, by their outside surfaces 5a and 9a, and the first panel 6v of the first door 6 and the second panel 10v of the second door 10 are brought to be flattened against one another, hermetically sealed, by their outside surfaces (FIGS. 2, 7, 12, 18, 21, 24). The flanges 5 and 9 and the doors 6 and 10 are then coaxial with axis AA. On the one hand, the first flange 5 and the second flange 9 are rigidly combined, and on the other hand, the two panels 6v and 10v of the first door 6 and the second door 10, flattened as was just indicated, are rigidly combined, and then the first panel 6v is actuated to move it from its original closed state and to bring it into the final fully open state. By so doing, the second panel 10v is moved, and it is also brought from its original closed state to its final fully open state. A movement—or a combination of movements—of the latter that is illustrated in the figures by the arrows F2 corresponds to this movement of the two panels 6v and 10v. In this situation, the first chamber 1 and the second chamber 2 are in communication with one another via their respective openings 4, 8, with, in the open state, the communication space 13 being provided between the two chambers 1 and 2. In this situation, the certain contents C of the chamber 1 or 2 where they were originally located are passed to the other chamber 2 or 1, respectively, where it is desired that they be ultimately located (arrows F3). Once this transfer of the certain contents C is made, the first door 6 and the second door 10, respectively the panels 6v and 10v, are brought into the closed state, at least the door of the chamber where the certain contents C are finally located. Then, the two chambers 1 and 2 can be separated. It is understood that the first door 6—more specifically the first panel 6v—can pass through and be at a given instant in an intermediate open state, but not fully open, between the closed state and the open state (FIGS. 8, 9, 10, 13, 16B, 17B, 19, 22, 25, 27). The communication space 13 has a general shape that corresponds to that of a truncated cylinder with an axis AA that passes through the edges of the openings 4 and 8 or a shape that is close to that of such a truncated cylinder, for example a shape of a double truncated cone or a double truncated pyramid that has a small median base that corresponds to the edge of the openings 4 and 8 and two large bases on both sides, respectively in the chambers 1 and 2, in particular in the inside space 1a that is removed from the first opening 4. The communication space 13 consists of a first entrance/exit space 13a in the inside space 1a of the first chamber 1 and a second entrance/exit space in the inside space of the second chamber 2. The first entrance/exit space 13a has a general shape of a truncated cylinder, cone or pyramid, extending into the inside space 1a at least essentially axially with axis AA, starting from the opening 4 and the flange 5. The first entrance/exit space 13a, shown diagrammatically, is virtually bordered by a proximal end boundary that is formed by the first opening 4 and the first flange 5, by a distal end boundary 13b that is opposite to the first opening 4 and the first flange 5, and by a lateral boundary 13c that is between the proximal and distal end boundaries 13b. The sealed junction device exhibits in operation what one skilled in the art knows by the term of critical line. An inside critical line LCi is found on the outside surface 6a of the panel 6v of the first door 6 in contact with the external environment and not overlapped by the outside surface 10a of the panel 10v of the second door 10, when the panels 6v and 10v of the two doors 6 and 10 are applied against one another. An outside critical line LCe is found on the outside surface 9a of the second flange 9 in contact with the external environment and not overlapped by the outside surface 5a of the first flange 5, when the flanges 5 and 9 are applied against one another. These critical lines LCi and LCe constitute areas where there is a risk of contamination because they are in contact with the external environment. These critical lines LCi and LCe are therefore unavoidable because it is impossible that the panel 10v of the second door 10 fully overlaps the panel 6v of the first door 6 and that the outside surface 5a of the first flange 5 fully overlaps the outside surface 9a of the second flange 9, even if the shape and the sizing of the flanges 5 and 9 and of the panels 6v and 10v of the doors 6 and 10, respectively, are selected so that these critical lines LCi and LCe are minimal. The sealed junction device also comprises means 25 that are structurally integrated into the first door 6 and/or means 26 that are structurally integrated into the second flange 9 that are able—when the first door 6 and the second door 10, respectively the panels 6v and 10v, are in the open state—to form a separation 25, 26 between the communication space 13 and the inside critical annular line LCi and/or the outside critical annular line LCe. The sealed transfer device that incorporates the sealed junction device therefore itself also comprises the means 25 and/or 26 that can—when the first door 6 and the second door 10, respectively the corresponding panels 6v and 10v, are in the open state—form a separation 25, 26 between the communication space 13 and the inside critical annular line LCi and/or the outside critical annular line LCe. Integrated—in relation to the means 25 and 26 and to the first door 6 and the second flange 9—is defined as the fact that these means 25 and 26 are, respectively, incorporated in or at least included in the door 6 and the flange 9 in such a way as to form a coherent whole with it. In other words, the means 25 and 26 are not, respectively, extraneous to, connected to, or exterior to the door 6 and the flange 9. Preferably, the means 25 and 26 are completely integrated into the first door 6 and in the second flange 9. The process for implementing the sealed junction device is such that when the first door 6 and the second door 10 are in the open state, the above-indicated integrated means 25 and/or 26 are implemented, and said separation 25, 26 thus is formed. This separation 25, 26 constitutes by itself the means for protection against any contamination at the location of the inside critical annular line LCi and/or the outside critical annular line LCe. Preferably, protection is ensured for the inside critical annular line LCi and the outside critical annular line LCe. However, in certain situations, it is possible to consider only ensuring protection of only one of the two critical lines LCi and LCe. Each of the integrated means 25 and 26 can be the object of one of the two following embodiments. In a first possible embodiment that in particular FIGS. 1 to 10 illustrate, the integrated means 25, 26 come in the form of an annular deflector, more generally a barrier that forms an obstacle, placed between the communication space 13 and the critical line LCi, LCe. In a second possible embodiment that in particular FIGS. 11 to 28 illustrate, the integrated means 25, 26 come in the form of a separation space 12 of adequate appropriate size placed between the communication space 13 and the critical line LCi, LCe. In both cases, the critical line LCi, LCe thus normally cannot be reached while the certain contents C are passing into the communication space 13. Expressing that a critical line LCi, LCe normally cannot be reached during the passage of the certain contents C into the communication space 13 means that when the certain contents C are passed from one to the next chamber 1, 2 under normal conditions of use of the sealed transfer device, the certain contents C do not come into contact with the critical line LCi, LCe. Normal conditions of use of the sealed transfer device are defined by the fact that the certain contents C are transferred along the path that is adapted to the shape of the communication space 13, for example in the median part of this space. More specially, a variant embodiment of means 26 integrated into the second flange 9 according to the first embodiment (barrier that forms an obstacle in the form of an annular deflector) will now be described with reference to FIGS. 1 to 5. In this variant, means 26 are provided in the form of an annular deflector that is integrated into the second flange 9 and that borders the second opening 8 on its periphery. This deflector 26 projects from the free frontal plane of the second flange 9 that forms an interface with the first flange 5 that consists of the outside surface 9a. The deflector 26 has a general cylindrical shape that corresponds to the shape of the second opening 8. If applicable, according to a possibility that is not shown, its free distal edge 27 (separated from the body of the flange 9) is slightly tapered laterally. With the outside peripheral part of the second flange, the deflector 26 forms an annular cavity 28 in the bottom or in the vicinity of the bottom from which there is an outside critical line LCe. This structure reinforces the separation exerted by the deflector 26 between the communication space 13 and the outside critical line LCe. Taking into account the presence of the projecting deflector 26 and that the second flange 9 forms a seat for the second door 10, it is provided that the panel 10v of the second door 10 comprises on its inside surface 10b an annular groove 29 that opens toward the inside of the second chamber 2. This groove 29 is arranged in such a way as to be able to accommodate the deflector 26 of the second flange 9 when the second door is in the closed state on the second flange 9 (FIGS. 1 and 2). The groove 29 is advantageously made toward the inside of a rounded annular peripheral part 30 of the panel 10v of the second door 10. Toward the outside surface 10a of the second panel 10v, this rounded part 30 forms a part that is shaped like a tenon and that can be housed in a complementary part in the shape of a mortise 31 that is made on the outside surface 6a of the panel of the first door 6. More specially, a variant embodiment of the means 25 that are integrated into the first door 6 will now be described, according to the first embodiment (barrier that forms an obstacle in the form of an annular deflector) with reference to FIGS. 6 to 10. In this variant, means 25 are provided in the form of an annular deflector that is integrated into the first door 6. In the case that is shown in the figures, this deflector 25 is part of the carrying means 11a of the panel of the first door 6 when the latter is at least in the open state. The deflector 25 is arranged around the first door 6. Alternately, the deflector 25 is supported by the carrying means 11a. According to another possibility, not shown, the deflector 25 is made part of the panel 6v itself of the first door 6. The deflector 25 has a general cylindrical shape that is broader than the shape of the panel 6v of the first door 6 and the panel 10v of the second door 10 and broader than the openings 4 and 8. If applicable, according to a possibility, not shown, its free distal edge 32 (separated from the carrying means 11a of the panel of the first door 6 or the panel of the first door 6) is slightly tightened laterally. With the central part 33 of the carrying means 11a, the deflector 25 forms a cavity 34 for protection of the inside critical line LCi. Means are provided for passing the panel 6v of the first door 6 and the panel 10v of the second door 10 that is flattened on itself from the closed state to an intermediate open state where the two panels 6v and 10v are separated from the openings 4 and 8 and placed—and held—in the cavity 34 (FIG. 8). The deflector 25 defines the axial depth of the cavity 34. This axial size is larger, and in particular is considerably larger, than the axial space requirement of the panel 6v of the first door 6 and even in the axial space requirement of the unit that comprises the panel 6v of the first door 6 and the panel 10v of the second door 10 flattened on the panel 6v of the first door 6. Thus, the inside critical line LCi is placed deeply enough in the cavity 34, which ensures the separation function filled by the deflector 26. In this variant, it is provided that the carrying means 11a of the first door 6 are means to rotate around an axis 35 arranged approximately parallel to the outside surface 5a of the flange 5 and orthogonally to the axis AA. Thus, the panel 6v of the first door 6 and the panel 10v of the second door 10, flattened on it, are moved in concert from the intermediate open state to the fully open state. The course of rotation of the carrying means 11a of the first door 6 and the panel 6v of the first door 6 itself is such that the panel 6v of the first door is separated from the communication space 13. For example, the course of rotation is on the order of one-quarter turn. According to another possibility, this course is on the order of a half-turn. With this arrangement, it is possible to produce a separation space 12 of a large enough size between the communication space 13 and the inside critical line LCi when the first door 6 is in the open state. The axis 35 is separated orthogonally from the plane of the first flange 5 toward the interior of the first chamber 1, in such a way as to allow the deflector 25 to be placed between the central part 33 of the carrying means 11a and the inside surface 3b of the wall 3 of the first chamber 1, around the first opening 4. For this purpose, the axis 35 can be supported by a bracket 36 that projects from the wall 3 toward the interior of the chamber 1 over a length that corresponds to the axial length of the deflector 25. In contrast, the axis 35 is separated laterally (parallel to the wall 3) from the panel 6v of the first door 6 by a mechanism plate 15, in such a way as to separate the deflector 25, the panel 6v of the first door 6 and the inside critical line LCi of the communication space 13, when the first door 6 is in the open state. For this purpose, the bracket 36 is offset laterally in the removal from the first opening 4, the first flange 5, and the position of the first panel 6v in the closed state. With this arrangement, it is possible to produce a separation space 12 of large enough size between the communication space 13 and the inside critical line LCi. If the lateral spacing that results from the separation and/or the movement of the panel 6v of the first door 6 is significant enough, this separation space will reinforce the separation that is exerted by the deflector 25 between the communication space 13 and the outside critical line LCe. More specially, in a general way—and according to different variant embodiments—the second embodiment of means 25 that are integrated into the first door 6 and that assume the shape of a separation space 12 of appropriate size will now be described, with reference to FIGS. 11 to 28. In these variants, means 25 are provided in the form of a separation space 12 of an appropriate size, with the carrying means 11a and the movement actuation means 11b of the first door 6 being arranged in such a way that in the open state of the first panel 6v, the first panel 6v is substantially separated beyond the boundary 13b, 13c of the first entrance/exit space 13a, with the separation space 12 thus being made between the first entrance/exit space 13a and the first panel 6v in the open state. According to the embodiments that can be considered, the separation space 12 is located beyond the lateral boundary 13c of the entrance/exit space 13a (FIGS. 14, 15, 16C, 17C, 20, 26, 28) or is located beyond its distal end boundary 13b (FIG. 23). “Substantially separated” is defined as the fact that the first panel 6v is removed and separated beyond the boundary 13b, 13c of the first entrance/exit space 13a, and that between any area of the first panel 6v and the boundary 13b, 13c that is the closest of the first entrance/exit space 13a, there is an interval that consists of a distance e that, on the scale of the size E of the first entrance/exit space 13a that is computed in the direction of this interval or is computed at this distance e, not only is not insignificant but even is noteworthy and noticeable. When the separation space 12 is located beyond the lateral boundary 13c of the first entrance/exit space 13a, the direction in which e and E are computed is a direction that is orthogonal to the axis AA and parallel to the first opening 4, the first flange 5, and the position of the first panel 6v when it is in the closed state. When the separation space 12 is located beyond the distal end boundary 13b of the first entrance/exit space 13a, the direction in which e and E are computed is the axial direction AA, i.e., orthogonal to the first opening 4, the first flange 5, and the position of the first panel 6v when it is in the closed state. In the applications that are more specially considered where the first opening 4 has a diameter on the order of 10 to 40 centimeters, E can be of the same order of magnitude (10 to 40 centimeters), and the separation e that constitutes the separation space 12 can be between a minimum value on the order of 3 centimeters and can go up to 40 centimeters. Although the separation e is not directly proclaimed the size E, it turns out that the separation e can be at least equal to one-quarter of E, or even at least equal to one half of E, or even at least equal to E. It should be noted that the invention that is intended for the biopharmaceutical field makes it possible to consider openings 4 and 8 and panels 6v and 10v of which the diameter is larger than the current diameters, let us say a diameter that is larger than 40 centimeters. The word “diameter” is to be understood as the largest width of the first opening 4, the latter not necessarily being circular. “Open state of the first panel 6v” is defined as the state in which the separation space 12 is made as defined or a primary open state where a primary separation space 12 is made as defined, with the first panel 6v also being able to be in a final open state in which an interval that constitutes a greater distance than that of the primary open state is made between it and the entrance/exit space 13a. According to the embodiments that can be considered, the separation space 12 is an empty space (FIGS. 14, 16C, 20, 23, 26, 28) or else the chamber 1 also comprises a separation wall 14 that is stationary or movable that, in the open state of the first panel 6v, is placed and extends, at least partially, between the first panel 6v and the entrance/exit space 13a (FIGS. 17A, 17B, 17C). According to the embodiments that can be considered, such a separation wall 14 is stationary (FIGS. 17A, 17B, 17C) or it is movable. According to an embodiment that can be considered, such a separation wall 14 can be combined structurally with the structure of the first chamber 1, in particular with the first wall 3, in which case the separation wall can be stationary (FIGS. 17A, 17B, 17C) and can form with the wall 3 a protective cavity 14a of the first panel 6v in the open state—and therefore the second panel 10b—and therefore also a protective cavity of the inside critical line LCi in this state of the first panel 6v and the second panel 10v. Such a protective cavity 14a comprises an entrance/exit opening by which the first panel 6v and the second panel 10v are able to enter into or exit from the protective cavity 14 by sliding and translational movement in their own planes, such as a slot. According to another embodiment that can be considered, such a separation wall 14 can be combined structurally with the first door 6 and/or with its carrying means 11a or movement actuation means 11b, in which case the separation wall 14 is movable. For example, an annular deflector that is integrated into the first door 6, analogous to the deflector 25, described above in relation to the first embodiment (barrier forming an obstacle in the form of an annular deflector) and FIGS. 6 to 10, can be provided. According to the embodiments that are shown, the first panel 6v in the open state is arranged in a position that is at least approximately parallel to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state. In this case, the first panel 6v is arranged in a position that is at least approximately orthogonal to the axis AA of the first entrance/exit space 13a. According to another embodiment, not shown, the first panel 6v in the open state is arranged in a position that is at least approximately orthogonal to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state. In this case, the first panel 6v is arranged in a position that is at least approximately parallel to the axis AA of the first entrance/exit space 13a. According to the embodiment that is shown in FIG. 23, the first panel 6v in the open state is arranged in a position that is at least approximately opposite the first opening 4, the first flange 5, and the position of the first panel 6v in the closed state. This embodiment corresponds to the case where the separation space 12 is located beyond the distal end boundary 13b of the first entrance/exit space 13a. According to the embodiments that are shown in FIGS. 15, 16C, 17C, 20, 26, 28, the first panel 6v in the open state is arranged in a lateral position in relation to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state. This embodiment corresponds to the case where the separation space 12 is located beyond the lateral boundary 13c of the first entrance/exit space 13a. It is understood that when the first chamber 1 is combined with a second chamber 2, within the framework of a sealed junction device and an aspetic transfer device, the first panel 6v supports the second panel 10v, with the two panels 6v and 10v being made integral, flattened against one another by their respective outside surfaces 6a and 10a that are in contact. The carrying means 11a and the movement actuation means 11b of the first door 6, just like the arrangement and the kinematics of the first door 6, in particular its panel 6a, can be the object of several embodiments that are structurally different but all having the effect of ensuring that in the open state of the first panel 6, the latter is substantially separated beyond the boundary 13b, 13c of the first entrance/exit space 13, with the creation of the separation space 12. In a general way, the carrying means 11a and the movement actuation means 11b are arranged to be suitable for moving the first panel 6v between its closed and open or primary open states, in a movement that comprises an initial separation movement of the first panel 6v from the first flange 5. In one embodiment, this initial separation movement is an at least essentially initial translational movement along an axis that is at least approximately orthogonal to the first opening 4, the first flange 5, and the position of the first panel 6v in the closed state (FIGS. 13, 16B, 17B, 19, 22). In another embodiment, this initial separation movement is an initial rotational movement around an axis that is at least approximately parallel to the first opening 4, the first flange 5, and the position of the first panel 6v in the closed state (FIG. 24). In another embodiment, this initial separation movement is an at least essentially initial translational moment of the first panel along a curvilinear axis (FIG. 28). In a no less general way, the carrying means 11a and the movement actuation means 11b are arranged to be able to move the first panel 6v between its closed and open or primary open and final open states, in a movement that comprises an initial separation movement of the first panel 6v from the first flange 5, as it was just indicated, and at least one subsequent movement that is a subsequent translational movement and/or at least one subsequent rotational movement. This subsequent translational movement or rotational movement can be the object of several embodiments. In one embodiment, the axis of translation of the subsequent translational movement is an axis that is at least approximately rectilinear. For example, this axis of translation can be at least approximately parallel to the first opening 4, the first flange 5, and the position of the first panel 6v in the state that is closed and approximately orthogonal to the axis AA (FIG. 20). Or, alternately, this axis of translation can be approximately orthogonal to the first opening 4, the first flange 5, and the position of the first panel 6v in the closed state and approximately parallel to the axis AA (FIG. 23). Or, according to another embodiment, not shown, this translational axis may be not orthogonal or parallel to the first opening 4, the first flange 5, and the position of the first panel 6v in the closed state or parallel or orthogonal to the axis AA, but inclined in relation to the first opening 4, the first flange 5, and the position of the first panel 6v in the state that is closed and inclined in relation to the axis AA. In another embodiment, the axis of translation of the subsequent translational movement is a curvilinear axis (FIGS. 27 and 28). In another embodiment, the subsequent movement is not a translational movement, but a rotational movement around an axis. For example, this axis of rotation can be at least approximately parallel to the first opening 4, the first flange 5, and the position of the first panel 6v in the state that is closed and approximately orthogonal to the axis AA (FIGS. 24, 25, 26, 27, 28). Or, this axis of rotation can be at least approximately orthogonal to the first opening 4, the first flange 5, and the position of the first panel 6v in the state that is closed and approximately parallel to the axis AA (FIGS. 13, 14, 16A, 16B, 16C, 17A, 17B, 17C). The structure and the arrangement of the carrying means 11a and the movement actuation means 11b are suitable for the desired kinematics. Thus, the carrying means 11a and the movement actuation means 11b comprise initial separation means of the first panel 6v from the first flange 5 that are translational means along an axis that is at least approximately orthogonal to the first opening 4, the first flange 5, and the position of the first panel 6v in the closed state (i.e., approximately orthogonal to the axis AA), or rotational means around an axis that is at least approximately parallel to the first opening 4, the first flange 5, and the position of the first panel 6v in the closed state (i.e., approximately orthogonal to the axis AA), as indicated above. Likewise, the carrying means 11a and the movement actuation means 11b comprise such initial separation means of the first panel 6v and the first flange 5 and subsequent movement means that are translational means and/or rotational means, as indicated above. The first panel 6v is extended laterally projecting, in an at least essentially coplanar way, by one or more mechanism plates (or arms or appendices) 15 that are part of the carrying means 11a and that make possible the movement of the first panel 6v, following the implementation of the movement actuation means 11b. According to the embodiments, the first wall 3 comprises one or more through slots 16 that can make possible and ensure the sealed and aseptic passage of the carrying means 11a and/or movement actuation means 11b on both sides of the wall 3, in such a way that from the outside of the first chamber 1, it is possible to monitor the movement of the means 11a and 11b. More specially, a first family of means 25 integrated into the first door 6 according to the second embodiment (separation space 12 of appropriate size) will now be described, with reference to FIGS. 11 to 20. More specially, a first embodiment of this first embodiment family will now be described, with reference to FIGS. 11 to 17C. In this case, the carrying means 11a and the movement actuation means 11b of the first door 6 are arranged to be able to move the first panel 6v from its closed state in a movement that comprises an initial translational movement along an axis that is at least approximately orthogonal to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., parallel to the axis AA), so as to separate the first panel 6v from the first flange 5 as it was indicated above, and at least one subsequent rotational movement around an axis that is at least approximately orthogonal to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., parallel to the axis AA), so as to bring the first panel 6v into its position in the open or primary open or final open state. In the embodiment of FIG. 15, the rotational movement is at least approximately a half-turn. In the embodiments of FIGS. 16C and 17C, the rotational movement is at least approximately a quarter-turn. In this open or primary open or final open state, the first panel 6v is arranged in a lateral position in relation to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state, with this position being at least approximately orthogonal to the axis AA, while the separation space 12 is located beyond the lateral boundary 13c of the first entrance/exit space 13. In this embodiment, the carrying means 11a and the movement actuation means 11b of the first door 6 comprise at least a first actuator 17 that is arranged along an axis that is at least approximately orthogonal to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state and ensuring the initial translational movement and at least one rotational movement system 18 along an axis that is at least approximately orthogonal to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., parallel to the axis AA). Such a rotational movement system 18 can comprise a shaft that comprises a contoured slot having an axial part and an inclined part over the axis of the shaft, with which a pin works. In the embodiment shown, the course of initial translational movement that is carried out using a first actuator 17 is just that necessary, aside from the necessary degrees of play, to make possible, on the one hand, the subsequent rotational movement, without the first panel 6v and the second panel 10v interfering with the first wall 3 of the first chamber 1 on its inside surface 3b and, on the other hand, the inside surface 10b of the second door 10 (or more precisely the panel 10v of the second door 10) is in the vicinity of the inside surface 3b of the first wall 3, so as not to occupy a useful part of the interior space 1a of the first chamber 1 and to see to it that the interior critical line LCi of the first open door 6 is located toward the inside surface 3b of the first wall 3. In the embodiment shown, the outside surface 6a of the first panel 6v in its open or primary open or final open state is turned toward—and in particular close to—the inside surface 3b of the first wall 3 of the first chamber 1. Thus, the inside surface 10b of the second panel 10v in its open or primary open or final open state is turned toward and located in the proximity, in particular in the immediate proximity, of the inside surface 3b of the first wall 3 of the first chamber 1. In this embodiment, the first panel 6v of the first door 6 is extended laterally by a mechanism plate 15, which is supported at least approximately orthogonally at the end of the shaft, arranged along an axis that is at least approximately orthogonal to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., parallel to the axis AA). Furthermore, this shaft passes through a through slot 16 of the first wall 3, where the contoured slot and the pin of the rotational movement system 18 are provided. The first actuator 17 acts on the shaft to cause it to slide along its axis. The shaft is laterally offset away from the first opening 4 and the first flange 5. On the other hand, it is laterally (parallel to the first wall 3) separated from the first panel 6v of the first door 6 because of the presence of the mechanism plate 15. With a mechanism plate 15 of adequate length and an adequate course of rotation, it is possible to produce a separation space 12 of sufficiently large size, as indicated. According to a possibility (FIGS. 16A, 16B, 16C), the panels 6v and 10v of the two doors 6 and 10 in the open state are simply located in the inside space 1a of the first chamber 1, adequately separated from the entrance/exit space 13a, as indicated. According to another possibility (FIGS. 17A, 17B, 17C), a protective cavity 14a of the panels 6v and 10v of the two doors 6 and 10 in the open state, whereas they are flattened against one another, is provided in the first chamber 1. Such a protective cavity 14a is made between the inside surface 3b of the first wall 3 and a separation wall 14 that is arranged parallel to and separated from it. Such a protective cavity 14a comprises an entrance/exit opening of the two panels 6v and 10v by sliding and translational movement in their own planes, such as a slot. With such a structure, the distance separation is reinforced by a separation barrier. More specially, a second embodiment of this first embodiment family will now be described, with reference to FIGS. 18 to 20. In this case, the carrying means 11a and the movement actuation means 11b of the first door 6 are arranged to be able to move the first panel 6v from its closed state in a movement comprising an initial translational movement as in the first mode of execution described above, and at least one subsequent translational movement along an axis that is at least approximately parallel to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., orthogonal to the axis AA) so as to bring the first panel 6v into its position in the open or primary open or final open state. In this open or primary open or final open state, the first panel 6v is arranged as in the first embodiment, described above. In this embodiment, the carrying means 11a and the movement actuation means 11b of the first door 6 comprise at least the first actuator 17 that is arranged along an axis that is at least approximately orthogonal to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., parallel to the axis AA) and ensuring the initial translational movement and at least a second actuator 19 along an axis that is at least approximately parallel to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., orthogonal to the axis AA). In the embodiment shown, the course of the initial translational movement that is carried out using the first actuator 17 is like that of the first embodiment described above. In the embodiment shown, the outside surface 6a of the first panel 6v in its open or primary open or final open state is arranged as in the first embodiment described above. The same is true for the surfaces of the second panel 10v. In this embodiment, the first panel 6v of the first door 6 is also laterally extended by at least one mechanism plate 15, which is supported at least approximately orthogonally by the first actuator 17 passing through a through slot 16 of the first wall 3. The first actuator 17 is supported by the second actuator 19. More specially, a second family of means 25 that are integrated into the first door 6 according to the second embodiment (separation space 12 of appropriate size) will now be described, with reference to FIGS. 21 to 23. In this case, the carrying means 11a and the movement actuation means 11b of the first door 6 are arranged to be able to move the first panel 6v from its closed state in a movement comprising at least one translational movement along an axis that is at least approximately orthogonal to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., parallel to the axis AA), so as to separate the first panel 6v from the first flange 5, and then to bring the first panel 6v into its position in the open or primary open or final open state. In this open or primary open or final open state, the first panel 6v is arranged in a position at least approximately facing the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state, this position being at least approximately orthogonal to the axis AA, while the separation space 12 is located beyond the distal end boundary 13b of the first entrance/exit space 13a. In this embodiment, the carrying means 11a and the movement actuation means 11b of the first door 6 comprise at least one actuator 20 that is arranged along an axis that is at least approximately orthogonal to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., parallel to the axis AA) and ensuring both the initial translational movement and the subsequent translational movement. The course of translational movement is that necessary to make the separation space 12. In the embodiment shown, the outside surface 6a of the first panel 6v in its open or primary open or final open state is turned toward and removed from the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state. Thus, the inside surface 10b of the second panel 10v in its open or primary open or final open state is turned toward and also removed from the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state. In the embodiment shown, the first panel 6v of the first door 6 is laterally extended by a mechanism plate 15, which is supported at least approximately orthogonally at the end of the actuator 20. Preferentially, two diametrically opposite mechanism plates 15 and two actuators 20 are provided. More specially, a third family of means 25 that are integrated into the first door 6 according to the second embodiment (separation space 12 of appropriate size) will now be described, with reference to FIGS. 24 to 26. In this case, the carrying means 11a and the movement actuation means 11b of the first door 6 are arranged to be able to move the first panel 6v from its closed state in a rotational movement around an axis that is at least approximately parallel to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., orthogonal to the axis AA), and this so as to separate the first panel 6v from the first flange 5 and then to bring the first panel 6v into its position in the open or primary open or final open state. In this open or primary open or final open state, the first panel 6v is arranged in a lateral position in relation to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state, with this position being at least approximately orthogonal to the axis AA, while the separation space 12 is located beyond the lateral boundary 13c of the entrance/exit space 13a. In this embodiment, the carrying means 11a and the movement actuation means 11b of the first door 6 comprise at least one rotational movement system 21 along an axis 21a that is at least approximately parallel to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., orthogonal to the axis AA) and ensuring both the initial movement and the subsequent rotational movement. The rotational movement system 21 comprises a hinge with an axis 21a and a means for driving in rotation around the axis 21a. The course of rotational movement is close to a half-turn. In the embodiment shown, the outside surface 6a of the first panel 6v in its open or primary open or final open state is turned opposite the inside surface 3b of the first wall 3 of the first chamber 1. Thus, the inside surface 10b of the second panel 10v in its open or primary open or final open state is turned toward and located in the proximity, in particular in the immediate proximity, of the inside surface 3b of the first wall 3 of the first chamber 1. In the embodiment shown, the first panel 6v of the first door 6 is laterally extended by a mechanism plate 15, which is supported by the articulation of the rotational movement system 21. With a mechanism plate 15 of sufficient length, it is possible to produce a separation space 12 of sufficiently large size, as indicated. More specially, a fourth family of means 25 that are integrated into the first door 6 according to the second embodiment (separation space 12 of appropriate size) will now be described, with reference to FIGS. 27 and 28. In this case, the carrying means 11a and the movement actuation means 11b of the first door 6 are arranged to be able to move the panel from its closed state in a movement comprising a translational movement along a curvilinear axis 22 corresponding at least approximately to an arc with an axis 23 that is at least approximately parallel to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state (i.e., orthogonal to the axis AA). In this embodiment, the carrying means 11a and the movement actuation means 11b of the first door 6 comprise at least one deformable parallelogram system 24 along an axis 23 that is laterally offset in relation to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state. For example, the course of rotational movement of the deformable parallelogram 24 is on the order of a half-turn. In the embodiment shown, the outside surface 6a of the first panel 6v in its open or primary open or final open state is turned toward the inside surface 3b of the first wall 3 of the first chamber 1. Thus, the inside surface 10b of the second panel 10v in its open or primary open or final open state is turned toward and located in the proximity, in particular in the immediate proximity, of the inside surface 3b of the first wall 3 of the first chamber 1. With an axis 23 that is sufficiently offset laterally in relation to the first opening 4, the first flange 5, and the first panel 6v when it is in the closed state, it is possible to produce a separation space 12 of sufficiently large size, as indicated. |
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description | This application claims priority to and the benefit of Korean Patent Application No. 2013-0071776, filed on Jun. 21, 2013, the disclosure of which is incorporated herein by reference in its entirety. 1. Field of the Invention The present invention relates to an apparatus and method for separating radioactive nuclides in a waste salt and recovering a refined salt from the waste salt, which are able to maximize process efficiency and operating efficiency of a process of regenerating a waste salt generated from a pyrochemical process of used nuclear fuel by converting radioactive nuclides in the waste salt into a thermally stable form and distilling the waste salt under a reduced pressure using a single apparatus having two top covers which are mountable for converting radioactive nuclides or distillation a waste salt, and highly improve applicability and utility in a remote operation facility for the waste salt treatment by further simplifying operation/handling compared with conventional processes. 2. Discussion of Related Art Rare earth nuclides in a LiCl—KCl eutectic salt generated from a pyrochemical process of used nuclear fuel is converted into an insoluble compound and precipitated to the bottom of the eutectic salt, the eutectic salt containing the insoluble compound is divided into an upper refined salt and a precipitate layer, and rare earth nuclides and refined salt are recovered from the precipitate layer using technology of regenerating a LiCl—KCl eutectic waste salt, which was developed from a combination of an oxidative (or phosphorylative) precipitation process and a vacuum distillation process. Such technology of regenerating a eutectic waste salt has been evaluated as world-leading technology in the process of disposing of a eutectic waste salt since it is used to separate at least 99% of the rare-earth nuclides and recover at least 95% of the eutectic salt. However, such conventional technology of regenerating a eutectic waste salt is specifically divided into four processes: a chemical conversion and precipitation process, a process of separating a solid eutectic salt, a process of separating a precipitate layer, and a process of distilling a eutectic salt in a precipitate layer. Since the same number of apparatuses are required to perform the processes, operations of the apparatuses for performing the processes cause an increase in operating time and cost of equipment, which results in a decrease in operating efficiency. Also, a process of separating a solid eutectic salt includes separating a solid salt in a reaction container, to which the eutectic salt in a solid state discharged after being subjected to a chemical conversion and precipitation process and being cooled at room temperature is stuck, by heating an outer wall of the reaction container using an electric heater in a state in which the reaction container is turned upside down. In this separation process, upper and lower portions of the solid salt are separated as a precipitate layer and a refined salt layer, respectively, in the reaction container. In such a process of separating a solid eutectic salt, the eutectic salt present in the precipitate layer may intermittently flow down and contaminate the lower refined salt layer. In this case, since it is difficult to separate the refined salt layer and the precipitate layer, the separated salt should often be repeatedly processed. Meanwhile, since a refined salt layer and a precipitate layer including a rare-earth compound are separated by cutting the top of the precipitate layer using an electric cutter in the case of a process of separating a solid eutectic salt discharged in the process of separating a solid eutectic salt into a refined salt layer and a precipitate layer, fine salt particles may be scattered, and salt debris may be precipitated. Therefore, an additional apparatus for collecting and recovering these salts is required. Also, when the separated precipitate layer and refined salt layer are subjected to a process considering remote operations from facilities handling a radioactive material in a cylindrical shape, the precipitate layer and the refined salt layer may not be easily handled during a transfer process. Also, the loss of salts may occur during the process of separating a solid eutectic salt and the process of separating a precipitate layer, thereby causing a decrease in salt recovery ratio. As the loss of salts is accumulated, the problems regarding operations of the apparatus and an increase in amount of waste to be further disposed may be caused. Patent document: Korean Patent Publication No. 2012-0021568, Korean Registered Patent No. 0861262 The present invention is directed to an apparatus and method for separating radioactive nuclides in a waste salt and recovering a refined salt from the waste salt, which are able to separate radioactive nuclides in a waste salt and recover most of the salts in the form of a pure renewable refined salt by converting the radioactive nuclides in the waste salt into a thermally stable form and distilling the waste salt under a reduced pressure, using a single reaction/distillation apparatus having two replaceably mountable top covers. Also, the present invention is directed to an apparatus and method for separating radioactive nuclides in a waste salt and recovering a refined salt from the waste salt, which are able to reduce the operating time and the cost of equipment by simplifying apparatuses and processes to perform conventional processes for separating radioactive nuclides from a waste salt and recovering a refined salt (two processes on LiCl waste salt in two apparatuses/four processes on LiCl—KCl eutectic waste salt in four apparatuses) in two processes in a single apparatus, maximize process efficiency and operating efficiency of a process of regenerating a waste salt produced from a pyrochemical process of used nuclear fuel by enhancing purity of salts recovered with no loss of the salts or contamination of the refined salt, which are problematic in the conventional processes, and highly improve applicability and utility in a remote operation facility for disposal of a radioactive waste by further simplifying operation/handling, compared with the conventional processes. According to an aspect of the present invention, there is provided a method of separating radioactive nuclides from a waste salt and recovering a refined salt, which includes a first operation of agitating radioactive nuclides in the waste salt and a chemical additive by installing a first top cover provided with a stirrer in a reaction/distillation apparatus and rotating the stirrer, and converting the radioactive nuclides in the waste salt into an insoluble compound in the waste salt, and a second operation of detaching the first top cover provided with the stirrer from the reaction/distillation apparatus, replaceably mounting a second top cover provided with a heater in the reaction/distillation apparatus, distilling the waste salt under a reduced pressure to separate the radioactive nuclides, and recovering a renewable refined salt when a chemical conversion reaction in the first operation is completed. Here, the radioactive nuclides included in the waste salt in the first operation may be dissolved in the form of a chloride, and may be converted into a thermally stable form by reaction with the chemical additive introduced into the waste salt. In this case, a reaction temperature required to convert the radioactive nuclides in the waste salt into the thermally stable form may be set within a temperature range in which the waste salt is able to be present in a molten state. Also, the agitating of the radioactive nuclides in the waste salt and the chemical additive using the stirrer may be performed at 300 rpm for at least one hour. In addition, when a chemical conversion reaction in the first operation is completed, the stirrer may be lifted upward, and the reaction container storing the waste salt may be cooled to a temperature of 200° C. or less prior to replacing the first top cover with the second top cover. Here, the distilling of the waste salt under a reduced pressure in the second operation may include (a) decompressing an inner part of the reaction/distillation apparatus to a predetermined pressure using a decompression device while heating a vaporization chamber in the reaction/distillation apparatus to a predetermined temperature at which the waste salt is not volatilized, (b) closing a valve of the decompression device in a state in which the inner part of the reaction/distillation apparatus remains decompressed to a predetermined pressure, suspending an operation of the decompression device, and producing conditions for closed systems under a reduced pressure, and (c) heating the vaporization chamber to a temperature at which the waste salt is able to be smoothly volatilized, heating the condensation chamber to a temperature lower than that of the vaporization chamber, and distilling the waste salt under a reduced pressure by means of a temperature gradient formed between the vaporization chamber and the condensation chamber. In this case, the decompressing of the inner part of the reaction/distillation apparatus in operation (a) may be performed at a pressure of 0.005 Torr or less. In addition, the vaporization chamber in operation (c) may be heated to a temperature of 850° C. or higher, and the condensation chamber may be heated to a temperature of 700° C. Additionally, the bottom of the recovery container in which the refined salt produced in the vacuum distillation process in operation (c) is recovered may be maintained at a temperature of 50° C. or lower to facilitate separation of the recovered salt deposited in the recovery container. According to another aspect of the present invention, there is provided an apparatus for separating radioactive nuclides from a waste salt and recovering a refined salt, which includes a vaporization chamber having a reaction container installed therein for accommodating a waste salt, a first top cover provided with a stirrer configured to agitate the waste salt accommodated in the reaction container of the vaporization chamber, a second top cover provided with a first electric heater configured to distill the waste salt under a reduced pressure and mutually replaceable with the first top cover provided with the stirrer when a chemical conversion reaction of the waste salt using the stirrer is completed, a condensation chamber in which salt steam produced by heating the vaporization chamber is condensed and liquefied, a decompression device configured to decompress inner parts of the vaporization chamber and the condensation chamber to a predetermined pressure, a recovery container which is disposed at the bottom of the condensation chamber and in which the salt steam liquefied at the condensation chamber precipitates by gravity to be recovered in the form of a refined salt, and a bottom cover switchably installed at the bottom of the condensation chamber to unload the recovery container. Here, a baffle coupled to the stirrer may be installed to be adjacent to an inner wall of the reaction container. Also, the apparatus for separating radioactive nuclides from a waste salt and recovering a refined salt may further include an upward/downward driving device driven to lift the stirrer and the baffle upward and downward at the same time. In addition, the apparatus according to the present invention may further include a top cover opening/closing device configured to automatically open and close the first top cover or the second top cover. Additionally, the apparatus according to the present invention may further include a bottom cover opening/closing device configured to automatically open and close the bottom cover. Meanwhile, the apparatus for separating radioactive nuclides from a waste salt and recovering a refined salt according to the present invention may further include a second electric heater configured to heat the vaporization chamber, and a third electric heater and a fourth electric heater configured to heat upper and lower portions of the condensation chamber, respectively, wherein the heating by the second electric heater, the third electric heater and the fourth electric heater is controlled in sequentially decreasing temperatures so that a temperature gradient in the vaporization chamber and the condensation chamber is formed to facilitate the flow of salt steam. In this case, the vaporization chamber may be decompressed to a predetermined pressure by means of the decompression device while the waste salt is heated by the second electric heater to a predetermined temperature at which the waste salt is able to be smoothly volatilized. Also, a cooling water circulation passage may be formed at the bottom of the recovery container. Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. While the present invention is shown and described in connection with exemplary embodiments thereof, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. The present invention is directed to an apparatus for separating radioactive nuclides from a waste salt and recovering a refined salt, which is a single reaction/distillation apparatus having two top covers and one bottom cover, the top covers being provided with an impeller which is a waste salt agitating unit and an electric heater which is a waste salt heating unit, wherein the radioactive nuclides are separated and the renewable refined salt is recovered by performing a process of converting the radioactive nuclide in the waste salt into an insoluble compound in the waste salt using the top cover provided with the impeller, followed by distilling the waste salt under a reduced pressure using the top cover provided with the electric heater. FIGS. 1 and 2 are systemic block diagrams showing a reaction/distillation apparatus for separating radioactive nuclides from a waste salt and recovering a refined salt according to one exemplary embodiment of the present invention. Here, FIG. 1 shows the reaction/distillation apparatus having a first top cover installed therein for performing physical and chemical reactions to convert the radioactive nuclides in the waste salt into an insoluble compound in the waste salt, and FIG. 2 shows that the first top cover shown in FIG. 1 is detached and a second top cover is replaceably mounted in the reaction/distillation apparatus to distill the waste salt under a reduced pressure. Referring to FIGS. 1 and 2, the apparatus for separating radioactive nuclides from a waste salt and recovering a refined salt according to the present invention has a vaporization region 140 formed therein for vaporizing salts in a reaction/distillation apparatus 100 configured as a single apparatus (a left region indicated by a dotted line, hereinafter referred to as a ‘vaporization chamber’) and a condensation region 150 formed therein for condensing the salts (a right region indicated by a dotted line, hereinafter referred to as a ‘condensation chamber’), and also further includes a decompression device 170 installed to maintain decompression of inner parts of the vaporization chamber 140 and the condensation chamber 150 under a predetermined pressure upon vaporization of the salts. A reaction container 142 accommodating a waste salt is disposed inside the vaporization chamber 140 in a state in which the reaction container 142 is anchored onto the reaction container holder 144, and a first top cover 110 provided with a stirrer, which is able to agitate a waste salt accommodated in the reaction container 142 disposed inside the vaporization chamber 140, is mounted above the reaction/distillation apparatus 100 in which the vaporization chamber 140 is arranged. Also, a heat insulator 111 is provided at a lower surface of the first top cover 110 to maintain heat insulation upon heating of the vaporization chamber 140. The stirrer 116 includes a motor 112 disposed above an outer side of the first top cover 110, a shaft 113 coupled to the motor 112, and an impeller coupled to a lower end of the shaft 113. In this case, the shaft 113 coupled to the motor 112 is vertically formed through the first top cover 110, the heat insulator 111 and the vaporization chamber 140 to extend to an inner lower end of the reaction container 142, and an impeller 114 having four pitched blades is coupled to a lower end of the shaft 113. The impeller 114 serves to uniformly mix the waste salt stored in the reaction container 142 while rotating with the shaft 113 upon rotation of the motor 112. In this case, a baffle 115 having a plurality of through holes (not shown) formed therein for enhancing agitation efficiency upon agitation of the waste salt is installed in the reaction container 142 to be adjacent to an inner wall of the reaction container 142, and such a baffle 115 is installed so that the baffle 115 can be mutually coupled to the stirrer. Also, when agitation of the waste salt using the stirrer 116 is completed, an upward/downward driving device 120 which is able to be driven in a vertical direction to unload the stirrer 116 and the baffle 115 by lifting the stirrer 116 and the baffle 115 together is installed. As shown in FIG. 2, a second top cover 130 that is mutually replaceable with the first top cover 110 provided with the stirrer 116 as shown in FIG. 1 to distill a waste salt under a reduced pressure when the agitation of the waste salt using the stirrer 116 is completed is installed at the reaction/distillation apparatus 100 according to the present invention. Like the above-described first top cover 110, a heat insulator 131 is installed at a lower surface of the second top cover 130, and a first electric heater 132 configured to electrically heat the vaporization chamber 140 is installed under the heat insulator 131. Also, a second electric heater 146 configured to heat an inner part of the vaporization chamber 140 with the first electric heater 132 arranged above the vaporization chamber 140 is installed at the sidewalls and outer bottom portion of the vaporization chamber 140. Although not shown in the drawings, a top cover opening/closing device may also be further installed to automatically open and close the first top cover 110 and the second top cover 130 from the reaction/distillation apparatus 100. Meanwhile, salt steam produced by heating the waste salt in the vaporization chamber 140 by means of the first and second electric heaters 132 and 146 is introduced into the condensation chamber 150, condensed and liquefied at an upper portion of the condensation chamber 150, caused to flow down again by gravity to precipitate in the recovery container 152 arranged at the lower bottom surface of the condensation chamber 150, and recovered in the form of a refined salt. In this case, a third electric heater 154 and a fourth electric heater 156 configured to heat an inner part of the condensation chamber 150 under different temperature conditions are installed at upper and lower portions of a circumferential sidewall of the condensation chamber 150, respectively. Here, the heating of the inner parts of the vaporization chamber 140 and the condensation chamber 150 by the first electric heater 132, the second electric heater 146, the third electric heater 154, and the fourth electric heater 156 may be controlled in sequentially decreasing temperatures so that a temperature gradient in the vaporization chamber 140 and the condensation chamber 150 can be formed to facilitate the flow of salt steam. Also, the decompression device 170 serves to decompress the inner parts of the vaporization chamber 140 and the condensation chamber 150 to a predetermined pressure to maintain the inner parts of the chambers under a constant reduced pressure upon heating the vaporization chamber 140 and the condensation chamber 150. In this way, the inner part of the vaporization chamber 140 may remain to be decompressed to a predetermined pressure by means of the decompression device while the waste salt is heated by the first electric heater 132 and the second electric heater 146 to a predetermined temperature at which the waste salt is able to be smoothly vaporized. In this case, the decompression device 170 includes a vacuum pump 171 mutually coupled to a lower end of the condensation chamber 150 via a connection pipe 176, a filter 174 installed above the connection pipe 176 to filter impurities included in the circulating air, two valves 172 and 173 installed respectively at front and rear portions of the filter 174, and a pressure sensor 175 configured to sense a pressure in the connection pipe 176. When the inner parts of the chambers are in a decompressed state under a predetermined pressure by means of the decompression device 170, the valve 173 arranged at the rear portion of the pressure sensor 175 is closed in a state in which the decompressed state is maintained in the chambers, and an operation of decompression device 170 is suspended to produce conditions for closed systems under a reduced pressure. In the reaction/distillation apparatus 100, a bottom cover 160 configured to unload the recovery container 152 is switchably installed at a lower end of the condensation chamber 150 having the recovery container 152 disposed therein. In this case, the bottom cover 160 is coupled via a bottom cover opening/closing device 190, which is vertically driven by force acting on a piston of a cylinder, so that the bottom cover opening/closing device 190 can be configured to automatically open and close the bottom cover 160. In addition, a cooling water circulation passage 180 is formed at the bottom of the condensation chamber 150 having the recovery container 152 arranged therein to circulate cooling water supplied from the outside, preventing a refined salt precipitated in the recovery container 152 from being heated to a predetermined temperature by means of the cooling water circulating through the cooling water circulation passage 180. Reference numerals 161 and 162, which have yet to be described, represent temperature sensors configured to detect temperatures in upper and lower inner sides of the condensation chamber 150 heated respectively by the third electric heater 154 and the fourth electric heater 156, reference numeral 163 represents a temperature sensor configured to detect a temperature in an inner part of the recovery container 152 in which a refined salt is precipitated, and reference numeral 164 represents a temperature sensor configured to detect a temperature in the bottom of the recovery container 152 cooled by the cooling water. Hereinafter, processes of the method of separating radioactive nuclides from a waste salt and recovering a refined salt according to the present invention will be described. FIG. 3 is a flowchart sequentially illustrating processes of a method of separating radioactive nuclides from a waste salt and recovering a refined salt according to one exemplary embodiment of the present invention. Referring to FIG. 3, the method of separating radioactive nuclides from a waste salt and recovering a refined salt according to the present invention includes, first, installing the first top cover 110 provided with the stirrer 116 in the reaction/distillation apparatus 100 (S201), agitating a radioactive nuclide in a waste salt and a chemical additive by rotating the stirrer 116 provided in the first top cover 110 and converting the radioactive nuclides in waste salt into an insoluble compound in the waste salt (S202), detaching the first top cover 110 provided with the stirrer 116 from the reaction/distillation apparatus 100, replaceably mounting the second top cover 130 provided with the heater 132 in the reaction/distillation apparatus 100 (S203) when the chemical conversion reaction is completed, distilling the waste salt under a reduced pressure to separate the radioactive nuclides, and recovering a renewable refined salt (S204). Operations S201 and S202 are operations of converting the radioactive nuclides into thermally stable forms (an oxide, a phosphate, a sulfate or a carbonate) by injecting a proper amount of chemical additives (an oxidizing agent, a phosphorylating agent, a sulfating agent or a carbonating agent) into the waste salts including the radioactive nuclides. To convert the radioactive nuclides into the thermally stable forms by injecting the chemical additive into the waste salt as described above, this conversion process may be performed at a predetermined temperature (610 to 650° C. in the case of LiCl, and 450 to 550° C. in the case of LiCl—KCl) at which the waste salt can be present in a molten state. However, since salts are highly volatile, the operating temperature may be controlled so that the operating temperature does not exceed the predetermined temperature. Here, the radioactive nuclides in the waste salt are dissolved in the form of a chloride, but at least a predetermined equivalent amount of a chemical additive should be added to convert the radioactive nuclides into thermally stable forms. In this case, the equivalent amount of the added chemical additive may be different according to the kind of chemical additives and the nuclides. Therefore, the highest equivalent amount of the chemical additive required for chemical conversion may be calculated in consideration of all the radioactive nuclides, and almost all the radioactive nuclides in the form of a chloride may be converted into the thermally stable forms only when necessary chemical additives should be added. To perform this chemical conversion reaction effectively, agitation may be performed for a predetermined period of time to allow the radioactive nuclides to effectively react with the chemical additives in the waste salt after addition of the chemical additives. In this case, the stirrer 116 used to agitate the waste salt may be adopted in the form of an impeller 114 having four pitched blades in consideration of uniform mixing in a solid-liquid reaction. In addition, two baffles 114 may be installed near the wall of the reaction container 142 so as to enhance stability and agitation efficiency in agitating a medium (i.e., a molten salt) as described above. When the chemical reaction of the waste salt using the stirrer 116 is completed, an upward/downward driving device 120 may be installed to unload the stirrer 116 and the baffle 115 from the medium. The agitation rate and the agitation time required to agitate the waste salt using the stirrer 116 may vary according to the reaction capacity, but an effective conversion rate of the radioactive nuclides may be obtained when the agitation is performed for at least 2 hours. Meanwhile, since the radioactive nuclide compound (an oxide, a phosphate, a sulfate or a carbonate) produced in the waste salt through the above-described chemical conversion reaction is melted or precipitated in the waste salt, it is difficult to separate only the radioactive nuclide compound, and it is necessary to completely separate the radioactive nuclide compound from the waste salt so as to promote ease of preparing a stable solid form for minimizing and finally disposing of a radioactive waste and a handling property for recycling the separated nuclides. Operations S203 and S204 are operations of separating the radioactive nuclides and recovering a renewable refined salt by distilling the waste salt under a reduced pressure using the second top cover 130 provided with the first electric heater 132 when the chemical conversion reaction of the waste salt is completed as in Operations S201 and S202. In this case, when the chemical conversion reaction of the waste salt after Operations S201 and S202 is completed, the waste salt should be cooled to a temperature of 200° C. or lower to smoothly perform replacement of the top covers 110 and 130 and handling of the reaction container 142. The radioactive nuclide compound produced through the chemical conversion reaction as described above is thermally stable. However, the salts (LiCl and LiCl—KCl) are more volatile than the radioactive nuclide compound. That is, the radioactive nuclide compound and the salts may be separated through a vacuum distillation method using physical properties of the highly volatile salts. In this case, the vacuum distillation method has an advantage in that no additional waste is produced. In particular, distillation of such salts under a reduced pressure has an advantage in that purity of the recovered refined salt may be improved, and no additional waste is produced. To cool the reaction container 142 to 200° C. or lower, separate the radioactive nuclide compound and the salts through distillation under a reduced pressure and recover a renewable refined salt when the chemical conversion reaction in Operations S201 and S202 is completed, conditions of constant reduced pressure in the chambers should be produced, followed by causing an increase in temperature at which the salts are volatile. The above-described vacuum distillation is a method of reducing an operating temperature for vaporization by vaporizing a target compound under constant reduced pressure conditions. In the case of such a vacuum distillation method, the vapor pressure of the target compound according to a temperature is important data used to set the operating conditions. The vapor pressure of a salt (LiCl or LiCl—KCl) according to a temperature may be calculated based on the context disclosed in a non-patent document: Handbook of Vapor Pressure (C. L. YAWS, Handbook of Vapor Pressure, Volume 4, Inorganic Compounds and Elements, Gulf Publishing, Houston, Tex., USA, 1995), p 360. The results are listed in the following Tables 1 and 2. TABLE 1Vapor pressure of LiCl according to temperatureTemperature 600650700750800850900(° C.)Pressure0.0090.0470.1750.5261.3483.0776.445(Torr) TABLE 2Vapor pressure of LiCl—KCl eutectic salt (LiCl:KCl = 44.2 wt %:55.8 wt %) according to temperatureTemperature 600650700750800850900(° C.)Pressure0.0070.0330.1190.3590.9452.2324.847(Torr) The distillation of the salts under a reduced pressure is performed using the reaction/distillation apparatus 100 composed of one single apparatus including a vaporization chamber 140, a condensation chamber 150 and a decompression device 170, and the shapes of the salts are as shown in FIGS. 1 and 2. To separate the radioactive nuclide compound and the salts through the distillation of the salts under a reduced pressure, the operating temperature of the vaporization chamber 140 and the pressure conditions in the reaction/distillation apparatus 100 are determined based on the vapor pressure of the LiCl or LiCl—KCl eutectic salt listed in Tables 1 and 2, and the details of operating procedures for distillation of salts under a reduced pressure are as follows. First, an inner part of the reaction/distillation apparatus 100 is decompressed to a predetermined pressure using the decompression device 170 while heating the vaporization chamber 140 to a predetermined temperature, and remains in a decompressed state. In this case, the predetermined temperature refers to a temperature at which a salt introduced into the vaporization chamber 140 is not vaporized under a reduced pressure. In addition, an inner part of the condensation chamber 150 is heated to a temperature lower than that of the vaporization chamber 140 to form a temperature gradient between the vaporization chamber 140 and the condensation chamber 150. In this case, the predetermined pressure should be set to 0.005 Torr or less in consideration of maintenance of a hermetic state of an apparatus and hence reduced pressure conditions for vaporization of salts. When the reduced pressure conditions at a predetermined temperature and a predetermined pressure are produced in the vaporization chamber 140 as described above, the rear portion of the pressure sensor 175 as shown in FIG. 1 is closed while maintaining the reduced pressure conditions, and an operation of the decompression device 170 is suspended to produce conditions for closed systems in a state in which inner parts of the chambers in the reaction/distillation apparatus 100 are maintained under a reduced pressure. Then, the vaporization chamber 140 in which the salts are present is heated to a temperature (850° C. or higher) at which the salts are able to be smoothly vaporized, and the condensation chamber 150 is heated to a temperature lower than this temperature range so that the vaporized salt (salt steam) can be allowed to rapidly move from the vaporization chamber 140 to the condensation chamber 150 by means of a temperature gradient. In this case, the temperature in the bottom of the recovery container 152 is possibly controlled to exceed 50° C. so as to promote liquefaction and gravity precipitation of the salt vapor transferred to the condensation chamber 150, and cooling of the salt vapor into a solid state, and easily separate the recovered salt in a solid state precipitated in the recovery container 152. When the distillation of the salts under a reduced pressure is completed in this way, salts are hardly present in the remaining nuclide compound. In this case, the nuclide compound is in a thermally stable form, and thus easily subjected to solidification for final disposal. Also, the recovered salt is discharged in a solid phase having the same shape as the inner part of the recovery container, and can be recycled as a high-purity refined salt including almost no nuclides. As described above, the method of separating radioactive nuclides from a waste salt and recovering a refined salt according to the present invention can be useful in highly curtailing the economic costs in construction and use of facilities by performing the conventional processes, which have heretofore been performed in a plurality of processes and apparatuses, in two processes (i.e., a process of converting radioactive nuclides in a waste salt into an insoluble compound, and a process of separating the radioactive nuclide through distillation of salts under a reduced pressure and recovering a renewable refined salt) in a single apparatus (i.e., a reaction/distillation apparatus), and highly improving operating efficiency by highly reducing (50% or more) the process operating time. Also, since there are no processes of separating a solid salt in the reaction container and separating a precipitate layer like the conventional processes, the contamination of refined salt produced in these processes and the loss of salts can be prevented, fine salt particles necessary to be further processed are not formed, unlike the conventional processes, and the recovery ratio (99% or more) and purity (nuclide separation efficiency of greater than 99.9%) of salts can be enhanced. Also, since the finally recovered salt is easily separated in the recovery container and its entire operation/handling is simply performed, applicability in remote operation facilities for disposal of radioactive waste can be highly improved. Hereinafter, the method of separating radioactive nuclides from a waste salt and recovering a refined salt according to the present invention will be described with reference to the following Examples. However, it should be understood that the following Examples are given by way of illustration of the present invention only, and are not intended to limit the scope of the present invention. First Operation of Converting Rare-Earth Nuclides In Eutectic Waste Salt into Insoluble Compound (Phosphide) in Eutectic Waste Salt using First Top Cover 110 Provided with Impeller 114 A simulated LiCl—KCl eutectic waste salt ingot including 2.5 kg of a LiCl—KCl eutectic salt and 125 g of rare-earth chlorides (YCl3, LaCl3, CeCl3, PrCl3, NdCl3, SmCl3, EuCl3, and GdCl3) was put into a reaction container 142, and one equivalent amount of a Li3PO4—K3PO4 mixed phosphorylating agent (at the same mixing ratio as a weight ratio of Li and K in the eutectic salt) was added to an upper portion of the reaction container 142. Then, the resulting mixture was charged into an apparatus. When a stirrer (an impeller) was positioned at the highest position, a first top cover 110 was closed, heated to 450° C. with respect to a temperature of the eutectic salt, and then maintained at 450° C. After a lapse of predetermined time, when the simulated eutectic waste salt was converted into a liquid phase, the stirrer 116 was lowered, and the impeller 114 was rotated at approximately 300 rpm. Agitation was performed for approximately one hour in consideration of a complete chemical conversion reaction. When the agitation was completed, a temperature in the vaporization chamber 140 was cooled to approximately 200° C. in a state in which the stirrer 116 was allowed to move to the highest end of the first top cover 110 (the first top cover was in a closed state). Second Operation of Separating Radioactive Nuclides and Recovering Renewable Refined Salt by Distilling Salts Under a Reduced Pressure Using Second Top Cover 130 Provided with Electric Heater After the temperature in the apparatus was cooled to 200° C. in the first operation, the reaction container 142 was unloaded, the first top cover 110 was replaced with a second top cover 130 provided with an electric heater, and the reaction container 142 was then put on a container holder 144, and loaded into the apparatus. After loading the reaction container 142, a first electric heater 132 and a second electric heater 146 disposed at upper and lower sides of the vaporization chamber 140 were heated to 500° C., and maintained at 500° C. Also, an inner part of the apparatus was decompressed to a pressure of approximately 0.003 Torr using a decompression device 170. Next, when the reduced pressure state was maintained at a set temperature, a valve 173 arranged upstream from the decompression device 170 was closed, and an operation of the decompression device 170 was suspended to control the apparatus so that closed systems in the apparatus could be operated. Thereafter, the first and second electric heaters 132 and 146 disposed at the vaporization chamber 140 were heated to approximately 960° C. (about 900° C. based on an inner part of the chamber), and the third electric heater 154 disposed at an upper portion of the condensation chamber 150 was heated to approximately 700° C. In this case, the heating rate was approximately 10° C./min. During heating of the apparatus, cooling water was also circulated to prevent a temperature of the bottom of the recovery container 152 from exceeding 50° C. Almost all the eutectic salt (99.9% or more) which was present at a content of 2.5 kg in the reaction container 142 was vaporized in this procedure. Then, the vaporized salt was condensed along a temperature gradient formed in the apparatus, and precipitated in the recovery container 152. A time required for condensation and precipitation was approximately 2 hours based on a point of time at which the electric heater reached a set temperature. Subsequently, after the distillation of the eutectic salt was confirmed to be completed, the apparatus was cooled to room temperature. Thereafter, an inner part of the apparatus cooled to room temperature was compressed to atmospheric pressure, and the second top cover 130 was then opened to unload a remaining distillate. From X-ray diffraction analysis (see FIG. 4), it was confirmed that all the rare-earth chlorides were converted into phosphates. Also, it was revealed that the eutectic salt in the remaining distillate was present at a content of less than 0.1%. Then, the bottom cover 160 was opened to recover a refined salt remaining in the recovery container 152, and a concentration of the rare-earth nuclides in the refined salt was assayed to determine separation efficiency of the rare-earth nuclide compound. As a result, it could be seen that the separation efficiency of the rare-earth nuclide compound was greater than or equal to 99.9%. As described above, the method of separating radioactive nuclides from a waste salt and recovering a refined salt according to the present invention can be useful in highly improving economic feasibility as a radioactive waste disposal technique and applicability in a remote operation facility since the method can be used to maximize process efficiency and operating efficiency of technology of regenerating a waste salt produced during a pyrochemical process of used nuclear fuel, separate the radioactive nuclides in a form in which the radioactive nuclides are easily solidified under a condition in which the loss of salts is minimized, simplify apparatuses and processes, and improve nuclide separation efficiency and purity of a recovered salt. According to the present invention configured thus, the economic costs in construction and use of facilities can be highly curtailed by simplifying apparatuses and processes to perform the conventional processes, which have heretofore been performed in a plurality of processes and apparatuses (two processes on LiCl waste salt in two apparatuses/four processes on LiCl—KCl eutectic waste salt in four apparatuses) for separating radioactive nuclides from a waste salt and recovering a refined salt, in two processes in a single apparatus, and operating efficiency may be highly improved by highly reducing the process operating time. Also, since there are no additional processes of separating a solid salt in a reaction container and separating a precipitate layer as known in the prior art, the loss of salts, the contamination of refined salt, and formation of fine particles necessary to be further processed, all of which are problematic in the conventional processes, are not caused, thereby maximizing process efficiency and operating efficiency of technology of regenerating a waste salt produced during a pyrochemical process of used nuclear fuel, and improving a recovery ratio and purity of salts. Finally, applicability and utility in a remote operation facility for disposal of a radioactive waste can be highly improved since the recovered salt can be easily separated in the recovery container and the entire operation/handling is simpler than the conventional processes. It will be apparent to those skilled in the art that various modifications can be made to the above-described exemplary embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers all such modifications provided they come within the scope of the appended claims and their equivalents. |
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description | This application claims the benefit of Provisional Application Ser. No. 60/619,858, filed Oct. 18, 2004 and is a Continuation In Part of Utility Application Ser. No. 11/106,744 filed Apr. 15, 2005. This invention relates to stellar imaging systems and in particular to such systems useful for position location and platform attitude determination. Global positioning systems (GPS) are widely used for navigating ships and aircraft. However, these systems are vulnerable and have other shortcomings. Their space components are subject to hostile attack and the systems may be jammed. The systems also suffer from reliability failures and these GPS systems do not provide absolute azimuth positioning needed for attitude determination. Inertial navigation systems (INS) mitigate GPS deficiencies; however, these inertial navigation systems are not accurate over long time periods. Errors may accumulate at rates of about an arc-seconds per hour to an arc-minutes per hour. Periodic alignment of the inertial navigation systems is required using an external reference system such as a GPS system. For centuries navigators have used the sky for the most fundamental and accurate inertial system available, in which each star is a benchmark. Cataloged positions and motions of the stars define the celestial reference frame. The problem is stars are hard to see during the daytime. Efforts have been made to navigate by stars during daytime using very sensitive visible light charge couple device (CCD) cameras, but these efforts as far as we know, have been unsuccessful due to the very limited number of stars that can be seen with this sensor. A need exists for a backup to GPS systems and an absolute azimuth reference for fast alignment of INS systems. The present invention provides an automatic celestial navigation system for navigating both night and day by observation of K-band or H-band infrared light from multiple stars. In a first set of preferred embodiments three relatively large aperture telescopes are rigidly mounted on a movable platform such as a ship or aircraft with each telescope being directed at a substantially different portion of sky. Embodiments in this first set tend to be relatively large and heavy, such as about one cubic meter and about 60 pounds. In a second set of preferred embodiments one or more smaller aperture telescopes are pivotably mounted on a movable platform such as a ship, airplane or missile so that the telescope or telescopes can be pivoted to point toward specific regions of the sky. Embodiments of this second set are mechanically more complicated than those of the first set, but are much smaller and lighter and are especially useful for guidance of aircraft and missiles. Telescope optics focus (on to a pixel array of a sensor) H-band or K-band light from one or more stars in the field of view of each telescope. Each system also includes an inclinometer, an accurate timing device and a computer processor having access to cataloged infrared star charts. The processor for each system is programmed with special algorithms to use image data from the infrared sensors, inclination information from the inclinometer, time information from the timing device and the cataloged star charts information to determine position of the platform. Direction information from two stars is needed for locating the platform with respect to the celestial sphere. The computer is also preferably programmed to use this celestial position information to calculate latitude and longitude which may be displayed on a display device such as a monitor. These embodiments are jam proof and insensitive to radio frequency interference. Also these embodiments work in those areas with poor GPS coverage or where GPS is not available at all. These systems provide efficient alternatives to GPS when GPS is unavailable and can be used for periodic augmentation of inertial navigation systems. These systems also provide absolute azimuth measurements for platform attitude determination. The invention is based upon Applicants' discovery that, at infrared wavelengths, a large number of stars (at positions offset by more than about 30 to 80 degrees from the sun) “out-shine” the sky background even at mid-day. Preferred embodiments of the present invention operate autonomously during daytime and nighttime, utilize observations of stars, and in combination with an inertial navigation system, provide a secondary means, independent of radios and GPS, for navigation of aircrafts and ships. Preferred processor software includes a background subtraction and a special signal to noise enhancement algorithm, star pattern recognition software, software for mapping of star direction, and an algorithm for computation of the lines of positions, celestial fix, and latitude and longitude. Preferred software also includes instrument-control code. The combination of the present invention with an inertial navigation system is a synergistic match. The accuracy of the inertial navigation system degrades with time from initial alignment, while the celestial fix accuracy is not time dependent. The inertial navigation systems are oblivious to bad weather, whereas a celestial fix is sensitive to cloud conditions. Both the inertial navigation systems and systems of the present invention are passive, jam-proof, and do not depend on shore or space components. If a run of bad weather interferes with star sights, the inertial navigation system serves as a bad-weather “flywheel” that essentially carries the stellar fix forward until new observations can be obtained. Thus, a combination of the inertial navigation system and the present invention will provide an independent alternative to radios and GPS. Systems designed by Applicants include very efficient optical sensors, which increase the probability of detecting stars during daytime by several orders of magnitude, as compared with a prior art approach based on CCD cameras operating at visible wavelengths. The latter is due to several factors including: a) The number of infrared sources exceeds the number of stars in the visible waveband, b) The daytime sky background is by a factor of 6-18 lower in the infrared wavebands than in the visible waveband, and c) The full well capacity of selected infrared sensors is more than one order of magnitude higher than that for comparable visible sensors. Additional advantages of this design approach are associated with the fact that atmospheric obscurants including haze and smoke affect infrared sensors less than sensors operating in the visible waveband, and the effect of daytime turbulence on the infrared sensor is lower. In each embodiment of the first set of preferred embodiments each of three telescopes are mounted on a moving ship and views a 0.5×0.4 degree region of the sky for H-band starlight. Located stars, usually those with brightness greater than 6.4 H-band magnitude, are then compared with star positions from the star catalog within a selected 5×5 degree region of the sky. A correlation of the data from at least two of the three telescopic measurements determines the position of the platform to a precision of 30 meters. The computer uses this position and the speed of the ship or aircraft, direction and attitude (pitch and roll) to establish the 5×5 degree region for the next correlation. Applicants have determined that there are an average of about 300 to 400 daytime visible infrared stars in these 5×5 degree regions of the Milky Way portion of the sky and an average of about 30 to 40 visible infrared stars in the 5×5 degree regions in other portions of the sky. Embodiments in this first set of embodiments have no moving parts and use automatic star detection and star pattern recognition algorithms. These preferred embodiments utilize three infrared telescopes imaging simultaneously three small areas of the sky, about 45 degrees in elevation with each telescope separated from the others by 120 degrees in azimuth. System software detects and identifies stars and calculates three crossing lines of position and a latitude/longitude celestial fix. Ship or aircraft positions may be up-dated every 5 to 10 minutes with position errors of less than 30 meters. Embodiments of the second set of preferred embodiments utilize telescopes with aperture diameter to less than 10 cm to provide much smaller and lighter systems. For example, with an aperture diameter of 5 cm, the dimensions of the system can be reduced to less than 20 cm×15 cm×12 cm. Such a system will fit applications of navigating missiles and aircraft. However, reduction of the telescope aperture diameter will reduce the number of received star photons and the signal-to-noise ratio (SNR). This will reduce the star detection limit, or star-limited magnitude. In addition, in order to avoid star image blur due to aircraft or missile motion and vibration, camera exposures on the order of a few milliseconds should be used. If the camera exposure is reduced to a few milliseconds, then once again the SNR is reduced. Applicants utilize two techniques to compensate for the above SNR losses caused by reduction of the telescope aperture diameter and camera exposure time. The first technique is to increase the star brightness by pointing a telescope to selected bright infrared stars. In preferred embodiments Applicants use a two-axis precision rotary stage to point one or more telescopes at selected bright stars. In these preferred embodiments Applicants limit the size of search windows to be equal, or less, than the 15°×15° square area angular distance over which the selected commercially available rotary stage maintains a one arc-second absolute accuracy or less. This provides an optical scan of up to 30°×30° when used with a reflecting mirror. The second approach is to utilize infrared cameras with reduced readout camera noise. Applicants have determined that for short camera exposures, the SNR is limited by the camera readout noise rather than the sky background noise. In some preferred embodiments an “all sky” CCD camera views the entire sky so that on “partly cloudy days the telescope can be quickly pointed to a cloudless region of the sky. A first preferred embodiment of the present invention is shown in FIGS. 1A(1) and 1A(2). This is a stellar imaging system useful for day and night accurate stellar navigation for ships. The system is a “strap down” system (i.e., it is mounted or “strapped down” on a platform, in this case a ship) with no moving parts. Three telescopes, separated by 120 degrees in azimuth and directed at 45 degrees in elevation, provide images of stars on three infrared 256×320 pixel cameras designed for operation in the infrared waveband at about 1.6 micron wavelength. The instantaneous field of view of each camera is 0.4×0.5 degrees, which provides a very high probability of imaging stars that are recognized by a computer system programmed with special algorithms, a star catalog, and star pattern recognition software. The camera is a fast frame rate camera operating at frame rates up to 30 Hz with a full well capacity of 5 million electrons, with thermoelectric cooling. A second preferred embodiment is shown in FIG. 1B. This embodiment is similar to the ship version but is designed for aircraft day and night navigation. In this embodiment a fewer pixel camera is used providing shorter exposure times to prevent blurring due to faster aircraft motion The third preferred embodiment is shown in FIG. 1C. This embodiment uses a single telescope to provide accurate azimuth reference for at-sea inertial navigation system calibration for attitude determination. Many more details on the features of these embodiments are provided in the section below that discusses Applicant's research and these specific features and design choices made by Applicants. Almost all celestial navigation at sea level using starlight has in the past been at night with observations at visible wavelengths. During the day, sunlight scattered in the earth's atmosphere produces background illumination that makes detection of starlight difficult. Also, strong daytime sky background quickly fills small electron collection “wells” of visible sensors, thus limiting the aperture diameter and/or exposure time. As a consequence, visible sensors have small signal to noise ratios and poorer overall sensor performance. Atmospheric transmittance at wavelengths between about 0.2 microns to about 3.2 microns is shown in FIG. 2A. Applicants have evaluated and compared the performance of three candidate sensor systems: one operating in the red portion of the visible spectrum (I-band, 0.8 micron wavelength, indicated at 2 in FIG. 2A) and two near-infrared spectral bands (H-band, 1.6 microns wavelength, indicated at 4 in FIG. 2A and K-band 2.2 microns wavelength, indicated at 6 in FIG. 2A). The analysis included several analytic studies: 1) Examination of star statistics, 2) Evaluation of the atmospheric transmittance and daytime sky background in three spectral wavebands; 3) Evaluation of the effects of atmospheric turbulence, and atmospheric obscurants on three candidate sensor systems; 4) Development of a novel star detection algorithm, 5) Testing of the developed algorithm using simulated and field data; 6) Evaluation of commercially available electronic and optical components and 7) A trade-off study to select the best design approach. Applicants characterized the overall sensor performance by the probability of detection of a given number of stars within the field-of-view of each telescope. They found that the probability of detecting stars at daytime with infrared sensors is much higher than that with a visible sensor. They determined, therefore, the infrared sensors operating at 1.6 microns or 2.2 microns are the best candidate systems for the hardware prototype. Star Statistics Applicants evaluated the star statistics in the visible I-band by using the Catalog of Positions for Infrared Stellar Sources and in the H-band and K-band by using the 2-Micron All Sky Survey catalog. Both of these catalogs are well known and are available on the Internet. They found that the number of stars in the infrared wavebands at similar intensity levels is an order of magnitude greater than the number of stars in the visible waveband. As an example, FIGS. 2C(1), (2) and (3) show the probability of detecting at least 1, 2 or 3 stars within a field of view of 1 degree versus star magnitude in the three spectral wavebands. For all star magnitudes the probability of detecting stars in the infrared wavebands is about an order of magnitude higher than in the visible waveband. This defines the first principal advantage of the infrared sensor. Atmospheric Transmission and Sky Background Using a MODTRAN3 computer model available from M. E. Thomas & L. D. Duncan, which is described in “Atmospheric Transmission”, in Atmospheric Propagation of Radiation, F. G. Smith, ed, Vol-2 of The Infrared and Electro-Optical Systems Handbook, J. S. Accetta & D. L. Shumaker, eds, ERIM, Ann Arbor, Mich., and SPIE Press, Bellingham, Wash. (1993), and MODTRAN & FASCOD references cited therein, Applicants evaluated the atmospheric transmission and daylight sky background in three candidate spectral wavebands (1.6 micron-0.25 micron bandwidth, 2.2 micron-0.2 micron bandwidth and 0.8 micron-0.1 micron bandwidth). The total atmospheric transmission in the infrared wavebands is 20 to 30 percent higher than the visible. Sky background radiation based on Applicants' calculations is shown in FIG. 3. The sky background radiation at potential wavelength ranges is plotted versus angular distance between the sun and the detector pointing direction for two atmospheric conditions (23 kilometers visibility and 10 kilometers visibility). They found that the daylight sky radiance in the infrared wavebands is significantly lower than that in the visible waveband. The sky radiance in the H-band and K-band is lower by a factor of 6 and 18, respectively, than that in the I-band. In addition, the average atmospheric transmittance in the infrared wavebands is higher and effects of atmospheric obscurants including haze, smoke, and clouds that can attenuate starlight is also lower in the infrared waveband than that in the visible. Thus, in the IR waveband there is less atmospheric scattering and higher transmission. This provides the second principal advantage of the infrared sensor. Total sea-level transmission through the atmosphere as a function of wavelength is shown in FIG. 2A. Daytime Sea Level Turbulence The effect of daytime sea-level turbulence on the infrared sensor is lower than that in the visible waveband. In particular, turbulence-induced scintillation at daytime can cause strong signal fades at the detector and thus degrade the performance of the visible sensor. The scintillation index, or normalized log amplitude variance, that characterizes the effect of turbulence on the star image brightness is reduced by a factor of 2.2 and 3.2 in H-band and K-band, as compared to I-band. Consequently, the effect of scintillation on an infrared sensor is expected to be small. Also the atmospheric coherence diameter, or Fried parameter, that characterizes turbulence-induced image blur, is increased by a factor of 2.3 and 3.4 in H-band and K-band, as compared to I-band. This defines the third advantage of the infrared sensor. Full Well Camera Capacity The fourth principal advantage of the infrared sensors is associated with the fact that the infrared cameras typically have a large full well capacity. The full well capacity of the infrared sensors exceeds the value for the CCD visible sensors by more than one order of magnitude (5 to 20 million electrons in the infrared waveband vs 0.1 million electrons in the I-band). A large full well capacity is extremely important for daytime operations. It allows Applicants to increase the signal to noise ratio for the infrared sensors by increasing the aperture diameter (up to 20 cm) and/or integration time to successfully detect stars in the presence of a strong sky background. Conversely, the small full well capacity of the visible sensor limits the aperture diameter and the total exposure and thus limits the signal to noise ratio, star detection limit, and probability of detecting stars. Large full well capacity is the fourth advantage of the infrared sensor. Camera Frame Rate The infrared sensors have much higher full frame rate, than visible sensors. Due to large pixel count (4096×4096 pixels) required to image a large field of view, the frame readout period is 3.5 sec in the visible, while it is typically 30 msec in the infrared waveband. This allows Applicants to increase the signal to noise ratio by averaging multiple frames. The accuracy of the image centroid calculations is determined by the image spot diameter Dstar and the signal to noise ratio. σ = 3 π 16 D star SNR The signal to noise ratio is given by SNR = N S N S + 4 ( n B + n D + n e 2 ) ,where Ns is the total number of signal photoelectrons detected in a frame (assuming within an area of 4 pixels and that the spot size full width at half maximum is approximately 1 pixel), nB is the number of sky background photoelectrons detected per pixel, nD is the number of dark current electrons per pixel, and ne is the number of read noise electrons per pixel. Averaging of multiple data frames by using a shift-and-add technique provided an additional way to increase the signal to noise ratio. The signal to noise increases proportionally to √{square root over (N)}, where N is the number of averaged frames. An implementation of this technique with the infrared sensors is straightforward because the frame rate for the IR cameras is approximately 5 to 30 Hz, depending on the exposure time. This provides the fifth advantage of operating in the infrared spectrum. H-Band and K-Band are the Spectral Ranges of Choice The above performance analysis revealed that the infrared sensor, as compared to the visible sensors, have a much higher probability of detecting stars. In particular, in a clear atmosphere for optimal aperture diameter and optimal angular pixel size the star detection limit for the I-band sensor is magnitude 3.3, whereas for the H-band and K-band sensors it is 6.8 and 5.8, respectively. The optimum field of view of the I-band sensor is 7×7 degrees, whereas the optimum field of view of the H-band and K-band sensors is 0.86×0.86 degrees and 1.3×1.3 degrees. For given sensor parameters, Applicants found that the probability of detecting at least 1 star with a 4096×4096 pixel I-band sensor is 0.18, whereas the probability of detecting at least 2 stars is 0.03. Under the same conditions, using a 512×512 pixel H-band sensor, the probability of detecting at least 1 star is 0.86 and probability of detecting at least 2 stars is 0.62. The number of infrared sources (H-band or K-band) of magnitude 7 is about 350, 000 in the entire sky, whereas the number of I-band stars of magnitude 3.3 in the sky is only about 300. Thus, the probability of detecting stars using infrared sensor is higher than using the sensor operating in the visible waveband. Therefore, in sense of performance and utility for the surface fleet and aircraft navigation, the infrared sensors have greater value than the visible sensors. Each of the three telescopes scan a region of the sky and the region grows with time. (The sky appears to rotate 1.25 degrees each five minutes.) FIG. 6 shows probability of detecting of at least 1, 2 and more stars in a 1×1 degree field of view with an infrared sensor that has star detection limit of 6.4 magnitude. The probability of detecting stars is shown versus observation time. The probability of detecting at least 1 star in the field of view exceeds 90% for the observation time of 5 minutes. For comparison, a strap-down system operating in the visible waveband and having field of view of 7×7 degrees and star detection limit of 3.3 magnitude will require 4-6 hours to detect at least one star. In summary, Applicants' trade-off study revealed that the infrared sensor has an inherent advantage, based on the laws of physics, over the prior art visible sensor in probability of detecting stars. Applicants' trade-off studies included a comparison of the H-band and K-band sensors in terms of detector format, cost, and cooling requirements. Applicants found that the H-band (InGaAs) sensor from Sensors Unlimited, which operates in the 0.9 -1.7 micron spectral band, has sensor performance somewhat (but not much) better than to the K-band in terms of star detection probabilities, but this H-band sensor has several more important advantages over the K-band sensor. First, it is less expensive ($25K for a 320×256 InGaAs array from Sensors Unlimited versus $120K for a 256×256 HgCdTe sensor from Rockwell). Second, it requires only TE cooling to obtain low dark current levels for low noise performance and does not use liquid nitrogen. Third, its full well capacity of 5 million electrons is greater than the full well capacity of K-band sensors considered. For these reasons, the Sensors Unlimited Minicamera 320×256 pixels camera was selected for the hardware prototype of Applicants' first preferred system. Applicants also determined the optimal number of fields of view to be simultaneously viewed, optimal sensor pixel size, and the field of view angular size. We found that the optimal pixel size in the H-band is approximately 6 arc-sec. Regarding the number of fields of view, Applicants considered two options: a) using one field of view and taking sequential stellar measurements at different areas of the sky, or b) using 3 fields of view and three cameras and doing simultaneous measurements. Due to the effects of vibration and ship/aircraft motion on the line-of-sight between sequential stellar measurements, Applicants determined that simultaneous measurements with three fields of view are preferred for a hardware prototype. Each field of view is 0.4×0.5 degree. A single aperture telescope was constructed and star observations were performed at sea level at daytime. Images of known stars were taken and stored for post-processing to determine photon flux levels in the K-band or minimum detectable stellar magnitudes. Multiple data sets were collected for various atmospheric transmittance and angular distance from the sun. FIG. 10 shows one example of the daytime K-band detection of stars with brightness values ranging from about 6.3 to 1.8 at an angular distance of 100 degrees from the sun. Seven stars are detected in the field of view of 0.4×0.5 degrees. These measurements confirm that minimum detectable stellar magnitude for the K-band sensor at daytime is about 6.4 to 6.9. A first preferred embodiment is a device which can autonomously determine its geographical position with a horizontal position error of less than 30 meters both day and night purely from observations of stars and deliver a latitude/longitude fix every 5 minutes. This embodiment is shown in FIGS. 4A and 4B. It is a prototype designed as a multi-aperture, strap down system without moving parts. The multi-aperture optical-mechanical design is a direct extension of the single aperture design. The same 20 cm telescope system and three infrared cameras are used. Each of the three apertures are mounted to a Holtzen parallelpiped, providing a line-of-sight that is at the same zenith angle of 45 degrees (from the horizon) with a 120 degrees offset in azimuth between each of the three apertures. The use of three independent apertures allows for both increased positional accuracy due to the ability to triangulate the measurements and redundancy in case one of the apertures line of sight is close to the sun. The structural support of the optics can be a simple aluminum or fiberglass tube, but carbon fiber composites may be desired for better thermal performance. The tube extensions (beyond the first optical element) act as sun baffles. The performance of the system is maintained so long as direct sunlight does not scatter into the telescope. An even longer baffle would allow operation slightly closer to the sun, but the 30 degree baffle shown is adequate under most circumstances. FIG. 4B shows the optical components of one of the three telescopes. As shown in FIG. 4A the optical axes of three telescopes are intersected to minimize the system foot print and total dimensions. The cameras are fastened to the telescope structure normal to the optical axis as indicated at 10 in FIG. 4B. A triangular frame at the bottom as shown at 12 in FIG. 4A provides structure rigidity. The entire assembly is meant to have the same low expansion coefficient, so if the entire structure is shaded from direct sunlight and if the structure remains isothermal, then the angle between the telescopes should remain fixed. The total weight of this strap down assembly is about 120 to 140 pounds. Star measurements with a single telescope can provide absolute azimuth reference for platform attitude determination. Once a star in the field view is detected and identified, a corresponding line of sight is accurately known. A projection of this line of sight on the horizontal plane defined as cos(star azimuth angle) provides an absolute azimuth reference. A sensor system with three telescopes provides three independent azimuth references that can be averaged together to reduce the measurement noise. Platform attitude determination does not require measurement of a local vertical with an inclinometer. To further improve the sensor performance and reduce the star detection limit, Applicants developed a robust image processing algorithm. This algorithm allows Applicants to accurately determine star position in the imagery data recorded in the presence of a strong sky background and having low contrast and low signal to noise ratio. The basic concept is the following. The algorithm uses the fact that the pixels which include the star image are illuminated with spatially correlated light (photons all coming from the same source, a single star), whereas pixels that are illuminated with only sky background are illuminated with spatially uncorrelated light (randomly scattered photons from the sun). Therefore, if the signals in the neighboring pixels are summed up, pixels with the star image and the noisy pixels will have different gain, and thus can be distinguished. If Np pixels are summed up, then the signal level in the super-pixel with the star light will increase proportionally to, Np, whereas the signal level in the super-pixel that include noise increases proportional to √{square root over (Np)}. Thus, the signal to noise ratio increases by a factor of √{square root over (Np)}. Similarly, when N image frames are summed up, the signal to noise ratio increases by a factor of √{square root over (N)}. The image processing algorithm includes two stages: a) background subtraction and noise reduction stage and b) star detection and centroid determination stage. For Applicants' prototype unit, each data frame is time stamped using a time reference instrument provided by Inter-Range Instrumentation Group (IRIG) and an off-the-shelf personal computer interface card. The IRIG system relies on GPS for time determination but has an AM radio backup in the case GPS is not available. The time is accurate to within 1 microsecond, which is very small compared to preferred timing requirement of 10 milliseconds (corresponding to 5 meters in platform position error). Since it is important for many applications that the system be independent of GPS, Applicants will replace the IRIG time base with an alternate clock source which is independent of GPS. Atomic clocks are standard equipment on many ships could provide the alternate clock with sufficient accuracy. These alternate timing sources can be reset with GPS or radio when the reset sources become available. The image processing algorithm includes the following steps: 1. Median value subtraction. This step reduces the fixed pattern camera noise. Consider the data set that consists of 20 frames. First, using 20 data frames that precede the first frame in the data set, the median data is calculated to for each pixel. Then, the median frame of pixels is subtracted from each frame in the data set, pixel by pixel. 2. Next, to reduce noise, five sequential data frames in the data set are blindly summed up. This typically spreads star illumination over a few pixels. 3. Then a “super pixeled” image is created by down sampling the image generated in step 2 at the rate of 1:4 (i.e., four adjacent pixels are summed across the pixel array) 4. Determine the brightest super pixel in the first frame from step 1 and create a small (9×9 regular pixel size) window about the brightest super-pixel location (81 pixels with the brightest 4×4 in the middle). 5. To increase the centroid accuracy, up sample the image within the window at the rate 10:1 using cubic spline fit algorithm. (The computer produces a digital array of 90×90 [8100] virtual pixels and fits them with the cubic spline fit algorithm into a Gaussian-like shape.) 6. Calculate the intensity weighted centroid. Under this step an expected star location in the first data frame is determined. 7. Repeat steps 5-6 for each subsequent data frame in the data set. 8. Once an expected star location in all subsequent data frames are determined, shift all 20 frames to the star position in the first frame, and sum up all frames. This step produces the final image for star detection within the 9×9 pixels window. The extent of the shift is based on the location of the centroid. 9. Once an expected star location in all subsequent data frames are determined, shift all 20 frames to the star position in the first frame, and sum up all frames, The final image for the entire frame is based on the shifts obtained from the 9×9 pixel centroiding window. The extent of the shift is based on the location of the centroid. 10. Create a “super pixel” representation of the shifted and added frame obtained from step 8 by down sampling at the rate of 1:4 (i.e., four adjacent pixels are summed across the pixel array). Determine brightest super pixel and create a small (9×9 regular pixel size) window about that location. 11. Up sample the image within the small 9×9 pixel window with a ratio of 10:1 by using cubic spline fit algorithm. Remove background by chopping at noise ceiling, calculate intensity weighted centroid position as well as total intensity in the image. Make an estimation of the rms noise by taking the standard deviation σ of all pixels [other than pixels illuminated by bright stellar objects] in the entire image frame. Remove the data within the small window in order to search for the next dimmest star. Repeat steps 9 and 10 until all potential stellar objects within the frame are found. 12. For each potential star location, the pixel SNR is calculated: SNR = I S - 〈 I 〉 σ , where Is is the total signal intensity divided by number of pixels in the image, <I> is the mean intensity in the image, and σ is the rms noise. If the SNR≧10, then the star is detected. The star coordinates are determined by intensity weighted centroid calculated in step 11. If SNR<10, then this potential star location is rejected and treated as a noise. 13. The star coordinates alone with the star intensity calculated in step 11 are used further by automated star pattern recognition algorithm. Also the coordinates of the brightest star in the field of view are used in calculations of the latitude/longitude celestial fix and absolute azimuth determination. The above algorithm was tested on both simulated data and field data. Applicants found that the algorithm allows us to detect 6.4 magnitude stars in the imagery data recorded at sea level at daytime. They also found that the measured distances between stars agree with their catalog values to the accuracy of 0.5 arc-seconds. Stellar identification and celestial latitude/longitude fix calculations require the infrared star catalog that includes accurate star positions, motions, and magnitudes (apparent brightness). Researchers from US Naval Observatory based on the 2MASS catalog and other sources available provided the IR star catalog that includes about 350,000 stars down to 7th magnitude. The H band magnitude corresponds to the 1.6 μm waveband where the camera is sensitive. Only objects brighter than or equal to the 7th magnitude were included in order to limit the disk space required to store the data. Using star positions and star relative brightness alone with the triangle patterns, the stars in each field-of-view are identified using reference catalog of positions and relative brightnesses, which is a subset of the infrared catalog. The reference star catalog currently covers the entire sky with 350,000 stars visible in the infrared. The field of view of each of the three telescopes is an area of the sky of 5×5 degrees centered about the pointing direction for each telescope determined based on the inclinometer measurements of the local horizon, and the angular separation of the three fields. When looking at the Milky Way the number of stars in the 5×5 field is about 300 to 400 and in regions of the sky other than the Milky Way the number of stars is about 30 to 40. In another embodiment the fields of view are increased to 10×10 degrees. All star catalog positions are corrected to the current epoch and corrected for proper motion. The distances between all star pairs in the reference catalog are calculated. After that the measured distances between all star pairs detected in the field of view are calculated. The stars detected within the field of view are listed in descending order, where the brightest stars are listed first. The first star pair would represent the brightest two stars. Position of each star is corrected for atmospheric effects and stellar aberration. Then the distances between all star pairs are calculated. Next the measured distances between stars are compared with the distances from the reference catalog. In order to accommodate the centroid measurement errors and effects of turbulence of a star image, a 5 arc-seconds error is allowed. In addition to the distances, each observed pair of stars also include a ratio of the relative intensities. The measurements performed by the Applicants revealed that individual star measurements fit the curve M 2 - M 1 = 0.4 * log 10 ( I 1 I 2 ) ( 1 ) with an error of 0.5 star magnitude. Here M1 and M2 are the star magnitudes from infrared catalog, and I1 and I2 are the measured star intensities. By using these two criteria, only the star pair, which matches the catalog distance within the accuracy of 5 arc-sec, and also their measured relative intensities match the ratio of the catalog intensities within the error of 0.5 star magnitude are accepted. If there are more than two stars in the field of view, then once the pair 1-2 is correctly identified, the search for each subsequent star's distance as related to star one and two, i.e. 1-3, 2-3, 1-4, 2-4, etc, is performed. The major change in the identification of these stars is the use of an additional conditional statement that includes a triangle pattern. Each subsequent pair must include either star one or star two, otherwise this star is rejected. This creates a form of a triangle pattern, where stars one and two present two of the three points. The third point in each triangle is the next star in question. This algorithm was successfully tested on the field data recorded at both day and night. FIGS. 7A and 7B show one example of the stars identified from the field data recorded at daytime (FIG. 7B) and compared with the star map (FIG. 7A) from the infrared catalog. Six stars having brightnesses varying from 3.4 to 6.6 magnitude are detected and identified. The 7th star in the field of view that has a brightness of 7th magnitude was not easily detected. Finally, if a single star is detected in the field of view, then the algorithm will use the relative magnitudes and positions of stars in all three fields for star identification. A simple block diagram of the electronics is shown in FIG. 8. All of the components are controlled by software written on a standard personal computer 40. The interface to the camera 41 is achieved using a frame grabber board (not shown) on the personnal computer interface bus with off-the-shelf software drivers provided by Sensors Unlimited. Each frame is time stamped. A commercial inclinometer 46, currently base lined as a unit from Jewel Instruments, is used to provide the local horizon measurement necessary to determine the elevation angle of the detected stars. The inclinometer provides a pair of analog voltages proportional to the tilt in each of two axes. The tilt meter output is digitized by an off the shelf analog to digital converter 48 synchronized to the camera frame acquisition. The analog to digital converter is also used to digitize the output of an off-the-shelf Meteorological Station system. The temperature and pressure are preferably used to correct the stellar position measurements for atmospheric refraction. For elevation angles (greater than 10 degrees), the atmospheric refraction is a function only of the local index of refraction which can be predicted accurately knowing only the wavelength of light, and the temperature and pressure. All software runs on standard personal computer 40. As a baseline the software is written in C++. A flow chart of the software to operate the camera, to process the frames, and to determine the longitude/latitude celestial fix is shown in FIG. 9. A single exposure from the camera is transferred from the frame grabber board to the personal computer using software drivers, and is time stamped from the IRIG time base. Using the image processing algorithm described above, the stars in each field of view are detected. The stellar positions within each field are then corrected for atmospheric refraction. Then using the stellar positions and relative brightness along with the triangular patterns the stars are identified. After that longitude and latitude celestial fix is determined using the measured stars elevations from at least two of the three fields. Applicants use all three when they are available. When several stars are detected within the field of view, the elevation of the brightest star is used in position fix calculations. The fix calculations are performed using the engine from the STELLA software developed at the US Naval Observatory. (J. A. Bangert, “Set Your Sights on STELLA: New Celestial Navigation Software from US Naval Observatory, Chips, Vol. 14, No. 5, pp 5-7 (1996). This software calculates both celestial positions and latitude and longitude for the platform, as well as the platform speed and direction. The obtained celestial position fix provides a back up for GPS, when the GPS is not available. In addition, it will provide periodic alignments for the inertial navigation system to correct for the drifts and latitude bias. In preferred applications the present invention is integrated with the inertial navigation system. This helps to mitigate an impact of a cloud cover on the performance of the present invention. If bad weather separates star sights, the inertial navigation system will carry the stellar fix forward until new observations can be obtained. Finally, each star measurement provides an absolute azimuth needed for platform attitude determination. Kalman filtering is a preferred method for estimating, or updating the previous estimate of a system's state by: (1) using indirect measurements of the state variables, and (2) using the covariance information of both the state variables and the indirect measurements. The basic idea is to use information about how measurements of a particular aspect of a system are correlated to the actual state of the system. The Kalman filter estimates a process by using feedback control: the filter estimates the process state at some time and then obtains feedback in the form of (noisy) measurements. Accordingly, the equations for the Kalman filter fall into two groups: time update equations and measurement update equations. The time update equations are responsible for projecting forward (in time) the current state and error covariance estimates to obtain the a priori estimates for the next time step. The measurement update equations are responsible for the feedback, i.e., for incorporating a new measurement into the a priori estimate to obtain an improved a posteriori estimate. Kalman filtering is an important tool in many navigation systems. Indeed, the Kalman filter can be used to integrate the present invention with an inertial navigation system (INS). The INS is considered to be the system model and its outputs are regarded as the referenced trajectory. Measurement aids, including data from the present invention, are used to compute errors and they are applied to the reference to generate the combined output. The filter can accept as data the estimates and covariance matrices for vessel coordinates and source positions generated from the analysis of the primary observations. Similarly, it can be used as an observer in a feedback system for disturbance rejection (and hence smoothing a vessel's motion) using estimates of the vessel coordinates, since tracking and output disturbance attenuation are essentially equivalent problems (at least for linear models). Alternate Telescope Designs An alternative design approach for the multi-aperture unit uses a single infrared camera with large pixel count and is required to combine the light from each of the three independent apertures on a single detector array. The preferred technique uses a small turning mirror and 3-sided pyramid mirror to combine the light from the different apertures. FIGS. 5A and 5B show the design of a pyramid mirror combining system for combining three celestial beams onto a single infrared sensor 40 located at the focal plane of each telescope. The light from each lens assembly is first reflected off a small turning mirror and then a three-sided pyramid shaped mirror placed directly in front of the camera array. These pyramid assemblies are typically polished from a solid glass substrate and are generally used in the opposite direction as solid retro-reflectors. In this design, the outer glass surfaces will be coated with an enhanced aluminum coating for high reflectivity in the H-band. FIG. 5B also indicates how a larger 640×512 array is separated into the three distinct regions for the different apertures with the pyramid mirror. Only two regions 40A and 40B are shown. Each individual aperture uses approximately ⅓ the entire array area with an effective field of view of a 0.55 degree square (or 0.62 degree circular). Another aperture combining technique investigated by Applicants involves the use of bent fiber image conduit. This requires the infrared camera to be modified so that the thermoelectric cooler package (that normally has a window in front of the array) would be replaced with a fiber window bonded directly to the array. Due to this additional expense, the pyramid mirror technique was selected as the preferred aperture combiner for the alternative preferred embodiment. Embodiments of the present invention described above tend to be relatively large and heavy, such as about one cubic meter and about 60 pounds. A need exists for embodiments of the present invention that are small enough to fit easily in an aircraft or missile. Described in detail below are a second set of preferred embodiments utilizing one or more smaller aperture telescopes that are pivotably mounted on a movable. platform such as a ship, airplane or missile so that the telescope or telescopes can be pivoted to point toward specific regions of the sky. Embodiments of this second set are mechanically more complicated than those of the first set, but are much smaller and lighter and are especially useful for guidance of aircraft and missiles. In addition, these embodiments have high update rates. This second set of embodiment like the first set is based upon Applicants' discovery that, at infrared wavelengths, a large number of stars (at positions offset by more than about 30° from the sun) “out-shine” the sky background at sea level even at mid-day. The midwave infrared cameras provide several principal advantages compared to the visible waveband sensors. This includes: The number of bright infrared stars exceeds the number of stars in the visible waveband by about one order of magnitude There is less atmospheric scatter and higher transmission at longer wavelengths. The daytime sky background at 1.6 μm and 2.2 μm is lower by a factor of 8 and 16, respectively, compared to the visible waveband The effects of atmospheric obscurants and daytime turbulence are lower at longer wavelengths compared to the visible The full well capacity of infrared cameras is about one order of magnitude greater than for visible waveband sensors (CCDs). This allows us to increase the aperture diameter and/or the exposure time, thus increasing the signal to noise ratio. However, a large (20 cm) diameter aperture leads to large sensor dimensions and large weight because size of the stellar imager, as well as its weight, depends on the telescope aperture diameter. In order to provide a compact and light-weight optical sensor, Applicants reduce the telescope aperture diameter to less than 10 cm. For example, if the aperture diameter is 5 cm, then the sensor dimension can be reduced to less than 20 cm×15 cm×12 cm. Such a sensor will fit applications of navigating missiles and aircraft. However, reduction of the telescope aperture diameter will reduce the number of received star photons and the (SNR). This will reduce the star detection limit, or star-limited magnitude. In addition, in order to avoid star image blur due to aircraft or missile motion and vibration, camera exposures on the order of a few milliseconds should be used. If the camera exposure is reduced to a few milliseconds, then once again the SNR is reduced. The implication is that a reduction of a telescope aperture diameter and camera exposure time will reduce the SNR and thus will limit our ability to detect stars in the presence of strong sky background. One can compensate for the above SNR losses caused by reduction of the telescope aperture diameter and camera exposure time by using two approaches. The first approach is to increase the star brightness by pointing a telescope to selected bright IR stars within a search window. The second approach is to reduce the readout camera noise because for short camera exposures, the SNR is limited by the camera readout noise rather than the sky background noise. Both techniques are discussed below. In order to detect stars at sea level in the presence of strong daytime sky background with a small-aperture telescope and short camera exposures, Applicants use a strap-down optical system with a limited degree of freedom, which includes a two-axis precision rotary stage and allows us to point the FOV of a telescope at selected bright stars within a search window. Applicants limit the size of a search window to be equal, or less, than the angular distance over which the selected rotary stage maintains a one arc-second absolute accuracy or less. Commercially available single axis rotary stages (from Aerotech, Inc., for example) provide a 1 arc-second absolute accuracy over a mechanical angle of 15°×15° square area, providing an optical scan of up to 30°×30° when used with a reflecting mirror. By combining two stages with a right angle bracket and performing a calibration, we can provide biaxial performance with 1 arc-second accuracy. Applicants use these rotary stages, or similar devices, in their compact stellar trackers. Also, Applicants limit the size of a search window to 15°×15° to minimize possible calibration errors. Because precision rotary stages have very high absolute accuracy (1 arc-second) over a limited optical angle of 15°, the search window is limited to a 15°×15° square area. In order to evaluate the sensor performance, Applicants determined the average number of bright infrared stars within a 15°×15° area of the sky. FIG. 11 depicts the number of H-magnitude stars vs. star magnitude over the entire sky. Using the data from FIG. 11, one can calculate the average number of stars of a given magnitude in the area of the sky of any size. If N is the number of stars in the sky, and A is the area of the sky in square degrees that corresponds to the search window, then the average number of stars in this area isn=N×A/41253since there are 41253 square degrees on the sky. Here A=V2, where V is the width of the search window in degrees. The average number of stars of different H-band magnitude in a 15°15° window is shown in Table 1. TABLE 1Average Number of Stars of Different H-magnitudein a 15° × 15° windowStar Magnitude1234Average Number of Stars3113098 As indicated in Table 1, there are on average 3 to 30 stars of first to third H-band magnitude in the 15°×150 square window. Since only a few stars are required to determine a celestial fix, this means that there are enough bright infrared stars in the 15°×15° search window for navigating missiles and aircraft using a proposed compact optical GPS unit. Next, Applicants determined the star detection limit for the proposed stellar tracker, or H-band star magnitude that the proposed stellar tracker can detect at daytime at sea level. Applicants performed SNR calculations using field data acquired with an H-band sensor with an equatorial mount that can be pointed at any direction on the sky. The number of star photoelectrons versus H-band star magnitude measured at sea level at daytime at 80° angular distance from the sun is shown in FIG. 12. The measurements were performed at daytime at sea level at angular distance from the sun of 80° using a 20 cm aperture telescope and an infrared camera, which is sensitive in the spectral waveband from 1400 nm to 1700 nm. The measured signal intensities in FIG. 12 in photoelectrons/millisecond are compared with the corresponding values from an infrared catalog. The measured signal intensities agree with a catalog values with an accuracy of 0.5 magnitude. FIG. 13 compares the measured daytime sky background with the theoretical prediction using MODTRAN3 code for 23 km visibility. The measurements were performed using the same infrared camera and a 20 cm aperture telescope at sea level. The number of measured background photoelectrons in photoelectrons/pixel/millisecond is shown versus angular distance from the sun. The measurements and theoretical predictions are consistent with each other. By using the measured data shown in FIGS. 12 and 13, SNR calculations were performed. The signal to noise ratio was calculated using the equation: SNR = N S N S + 4 ( n B + n D + n e 2 ) ,where NS is the total number of signal photoelectrons detected in a frame (assuming an area of 4 pixels and that the spot size full width at half maximum is approximately 1 pixel), nB is the number of sky background photoelectrons detected per pixel, nD is the number of dark current electrons per pixel, and ne is the number of read noise electrons per pixel. The measured signal intensities and solar background was re-scaled to smaller aperture diameters (5 cm to 10 cm) and an exposure time of 5 milliseconds. The calculated values of the SNR for three aperture diameters (D=10 cm, 7.5 cm, and 5 cm) and two cameras (with readout noise of 150 photoelectrons/pixel and 13 photoelectrons/pixel) at sea level and 20,000 ft altitude are shown in FIGS. 14, 15, and 16 versus H-band star magnitude. For the 10 cm aperture diameter telescope, the exposure time is 5 msec, the pixel field of view is 16 microradians, and the angular distance from the sun is 80°. For the 7.5 cm aperture diameter telescope, the exposure time is 5 msec, the pixel field of view is 21 microradians, and angular distance from the sun is 80°. For the 5 cm diameter telescope, the exposure time is 5 msec, the pixel field of view is 27 microradians, and angular distance from the sun is 80°. Using a commercial infrared camera from CEDIP Infrared Systems (JADE SWIR HgCdTe focal plane array, 320×2450 pixels, 1.2 million electrons full well capacity, 150 electrons read out noise, thermoelectric cooler) and a 10 cm telescope at sea level, the sensor can detect (with SNR greater than 10) stars equal or brighter than 2.3 magnitude during the day. At night, much dimmer stars are visible. Using a 5 cm aperture telescope, the daytime star detection limit at sea level is the first H-band star magnitude. According to Table 1, on average there are three first H-band magnitude stars in the 15°×15° search window. Using a low noise infrared camera (13 photoelectrons/pixel), the daytime star detection limit reduces to the second H-band magnitude. This shows that a small aperture (D=5 cm) optical GPS unit can operate at sea level during both daytime and night time. The first compact embodiment of the present invention uses a single telescope equipped with a two-axis high precision rotary stage to point the field of view at a selected bright infrared star within a search window. It also includes a temporary mirror which turns the telescope field of view by 90°. The latter is necessary because a geographical position determination requires that the star measurements be separated by an angular distance of between 90° and 120° in azimuth. This design concept is shown in FIG. 17. When a temporary mirror 50 is inserted into the optical train, the field of view is deflected by 90°. A small telescope 52, nominally 5 cm aperture, points toward a mirror 54 mounted onto a precision stage 56 that has a 7.5° rotation capability, for example, the ARA125 from Aerotech, Inc. This rotary stage has an absolute accuracy of 1 arc-second. The telescope is fitted with an infrared camera to view stars within a field of view of nominally 0.44°×0.4°. The telescope uses a negative Barlow lens to increase the effective focal length while keeping the total length as short as 15 cm. The field of view of the telescope is changed in one direction by 15° by rotating the stage by 7.5°. The stage and mirror are connected to a second precision rotary stage mounted at a right angle, allowing the telescope to point directly to any particular stellar field within a 15° field in both directions. After the stage-mounted mirror is the temporary mirror 50 mounted at a fixed angle. This mirror can be quickly inserted into the optical path. The field of view of the telescope is then deflected by a fixed amount (nominally 90°), but is still able to point over a 15° field of view. The temporary mirror is inserted into a precise location to maintain the angular precision. This allows a single telescope and camera to sequentially view two fields of view. Alternatively, this temporary mirror may have two or more fixed orientations, including an angle 90° orthogonal to that shown. This provides even more sky coverage, which is especially useful in the case of partly cloudy skies or when the solar angle is not far enough from the original directions. An advantage of this approach is that it has few components (a single telescope and one two-axis rotating stage). A possible disadvantage is that sequential (time separated) star measurements may be affected by the platform motion and vibration more than the simultaneous measurements. The second compact embodiment of the present invention uses two identical telescopes mounted to a dual-axis precision rotary stage. In the design shown in FIG. 18, the two telescopes 60 and 62 are pointed at 90° with respect to each other, sharing a common focal plane. Small fold mirrors near the focal plane, not shown, are used to combine the fields of view onto one infrared camera. An alternate design would add a 45° fold mirror at the output of one of the telescopes, so that the two telescope bodies are essentially parallel, and the different fields of view are provided by the 45° fold mirror. A single infrared camera is used for both telescopes. Two approaches for combining two images in a single focal plane array have been described above and shown in FIG. 5B. This design also includes two temporary fold mirrors that can be inserted at a precise angle. These temporary mirrors increase the sky coverage for the cases where the solar angle is too close to the original direction, or in the case of partly cloudy skies, where there is an advantage to pointing toward holes in the clouds. The key benefits of the proposed strap-down stellar imaging system with limited degree of freedom are: compact sensor design (5 cm aperture, 20 cm×15 cm×12 cm dimensions). Such a sensor with small dimensions is well suited for navigating flying platforms such as unmanned arial vehicles, aircrafts, and missiles, light weight, high probability of detecting stars because the telescope is pointed at selected stars, high update rate of the celestial fix (a few to several tens of seconds), and increased accuracy and reliability of the estimates for a celestial fix. This last advantage is due to two factors: a) increased signal to noise ratio of the stellar imagery data and b) elimination of the need for star identification using star pattern recognition (there is no need to identify a star because a telescope will be pointed at the selected star using a two-axis rotating stage). The sensor operates as follows. First, by using an infrared star catalog, first H-band magnitude stars are selected within two search windows separated at 90° in azimuth. Second, using the local vertical measured with an on-board inclinometer as a reference (for example, the LCF 2000 series from Jewel Instruments), the sensor software generates control commands for the two-axis rotary stage and points the telescopes at the selected stars. (Since the instantaneous field of view of the telescope is 153 arc-seconds×192 arc-seconds, at this stage the star position is known within about the same accuracy, i.e. 153 arc-seconds×192 arc-seconds). Third, the sensor acquires the star images and processes the imagery data. Fourth, the sensor software calculates the image centroid with sub-arc-second accuracy. Then, the on-board software calculates the star height with respect to local horizon and a line of position (LOP). At the same time, the second telescope acquires star imagery within the second 15°×15° search window separated from the first search window at about 90° in azimuth, processes the imagery data, and calculates the second line of position. The intersection of the two lines of position defines a celestial fix (latitude and longitude). The accuracy of the centroid measurements with an infrared sensor, as well as the accuracy of the longitude and latitude calculations using site reduction software is a fraction of an arc-second. Thus, the accuracy of the proposed stellar tracker is limited by the absolute accuracy of the rotary stage, which is one arc-second. Applicants expect that an update rate for a celestial fix will be on the order of a few seconds In order to convert the measured angular positions of the stars into a geo position, accurate measurements of the local vertical are required. Applicants will use a commercial Jewel LCF-196 inclinometer. This sensor is designed for applications with high level of shock and vibration. Its resolution is 3 micro-radian and the bandwidth is 30 Hz. With a lower band width of 1 Hz, an accuracy of about 1 micro radian is estimated. The first preferred embodiment shown in FIG. 4A includes three telescopes mounted to have their optical axes separated at 120 degrees. The use of three telescopes allows for both increased position accuracy due to the ability to triangulate the measurements and redundancy in case one of the telescope optical axes is close to the sun. A similar approach may be used in a compact unit. Two telescopes (four field-of-views using temporary mirrors) will share a single infrared focal plane array. Two techniques may be used to combine the light from each of the two telescopes onto a single focal plane array. A preferred technique uses a small turning mirror and two-sided pyramid mirror to combine the light from three telescopes. Another aperture combining technique involves the use of a fiber image conduit. In order to increase the operational utility of the above compact systems, a visible-band “all sky” CCD camera may be included. This visible camera would optimize the sensor performance. It would image the sky over an area of 180°×180° to determine the approximate sun position with respect to the optical axes of the one or more infrared telescopes as well as positions of clouds. Then, the sensor software will select those telescopes (one, two or three) whose optical axes are separated at angular distances from the sun greater than 80° and have a clear line of sight. Thus, an “all sky” camera will allow users to minimize the effects of clouds on the star imaging system. An Optical GPS unit will be integrated with the on-board inertial navigation unit. As in the earlier described embodiments, if bad weather separates star sightings, the inertial navigation unit will carry the stellar fix forward until new star observations can be obtained. Marine Environment A marine environment provides the challenge of the sensor operating autonomously over large variations in humidity and temperature, along with requiring additional protection from condensation and corrosion due to fog and saline conditions. Some of the modifications that could be required would be to change the lens housing or mechanical structure material to lower the coefficient of thermal expansion in order to maintain the system focus while operating over an increased temperature range. Additionally, the sensor covering will be reviewed to provide for increased weatherproofing protection for the optical system. The lens assembly is preferably designed so that the system can be nitrogen purged which will prevent condensation on the internal surfaces of the optics. Similarly, the entire sensor head could also be nitrogen purged or a desiccant material placed internally to reduce condensation. A large mechanical shutter assembly is preferably placed on each of the three lens apertures to provide protection of the optics during periods of rain, ice, or snow, fog when the system would be prevented from operating due to poor atmospheric transmission. To increase the reliability and maintainability of the unit while deployed at sea, several other designs should be considered. The wire cabling connection between the sensor head and electronics can be redesigned to use a single fiber optic cable. This could be an important upgrade for the sensor head to improve reliability and ruggedness while reducing the possible electromagnetic interference from external shipboard hardware such as radars. To improve the maintainability of the sensor, an increased set of built-in diagnostic capabilities could be implemented for a deployed system. This would also include an autonomous calibration diagnostic that can be run during favorable atmospheric conditions (clear night time) when the probability of observing several stars in each aperture is high. This diagnostic would recalibrate the line of sight of each of the apertures with respect to each other and the inclinometer by knowing the ship location via GPS. In this way, the system could autonomously calibrate out small thermal and/or mechanical drifts during periods of opportunity to increase the system reliability, maintainability and accuracy. The accuracy of the local horizon measurements using the inclinometer will require review. Specifically, the update rate requirement along with the suppression of angular acceleration effects should be reviewed. The addition of angular rate sensors may be required to permit removal of platform motion effects in multiple frame averages. Aircraft Issues Peculiarities of the present invention for the aircraft include: a) Effect of atmospheric obscurants including clouds is reduced (50% probability of clear line of site at sea level, and 90% probability at 30,000 ft). The use of multiple measurement channels increases the probability of clear line of sight; b) Daytime sky background is reduced by a factor of 10 for every 20,000 ft; c) Simultaneous measurements with four optical channels may be preferred to reduce the effect of aircraft vibration and motion; d) Short exposure time (1 msec or lower) may be required to prevent star blurring due to aircraft vibration; and e) A multiple-frame averaging technique should be used to reduce noise and increase the signal to noise ratio in the imagery data. For the aircraft application, it is likely important to reduce the size and weight of the unit while also having an increased vibrational operating specification for the sensor. Due to reduced sky background at altitude, the sensor apertures could be designed for a smaller diameter with a shorter focal length to maintain the same f-number. Similarly, the mechanical structure could be designed with composite materials to increase stiffness and reduce susceptibility in a harsh vibrational environment, lower sensor head weight, and reduce the system thermal susceptibility. Although the present invention has been described above in terms of specific preferred embodiments persons skilled in this art will recognize that many changes and variations are possible without deviation from the basic invention. For example, platform position can be determined with only two telescopes. With three telescopes at least two will always be pointed more than 30 degrees away from the sun. If only two telescopes are used, preferably they would be mounted with a 90 degree azimuthal separation at an elevation of 45 degrees to the horizon. There could also be situations where four telescopes would be preferred. Many infrared sensors other than the ones specifically referred to are available for operation in the transmission windows shown as 4 and 6 in FIG. 2A. The systems could have applications other than ship or airplane navigation. Various additional components could be added to provide additional automation to the system and to display position information. Star catalogs may include celestial objects other than stars such as planets and asteroids. Otherwise, if one of these objects shows up in an image, it could confuse the system. The CCD camera discussed above for looking for cloudless regions of the sky (or another visible light camera) can be very useful for both the strap-down embodiments as well as the embodiments with the pointing telescopes. To take advantage of clear regions of the sky for the strap-down embodiments three temporary fold mirrors such as the ones described for the pointing telescopes may be provided for temporary insertion in each of the three strap-down telescopes to change each field of view by fixed angles. The computer processor will be programmed to cause the insertion of the temporary fold mirrors if the CCD camera data shown that the insertion will provide a clearer line of sight to infrared stars. Accordingly, the scope of the invention should be determined by the appended claims and their legal equivalents. |
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claims | 1. A spacer for a fuel assembly of a nuclear reactor cooled by light cooling water, comprising:a multiplicity of crisscrossing webs forming a grid, each of said webs formed of interconnected first and second sheet-metal strips having corrugations shaped asymmetrically in relation to a vertical middle plane running between said sheet-metal strips such that in each case neighboring corrugations form an enclosed flow sub-channel for receiving the cooling water;said flow sub-channel running oblique to a vertical and having a shape being asymmetric in relation to said vertical middle plane thereby imparting to the cooling water emerging from said flow sub-channel a flow component perpendicular to said vertical middle plane running between said sheet-metal strips; andsaid asymmetric shape of said enclosed flow sub-channel and said asymmetric shape of said corrugations being predefined. 2. The spacer according to claim 1, wherein said flow sub-channel has a first partial channel with a cross section formed by a first corrugation decreasing in a flow direction of the cooling water, and a second partial channel having a cross section formed by a second, neighboring corrugation increasing in the flow direction. 3. The spacer according to claim 1, wherein:said first sheet-metal strips have first corrugations alternately disposed in a longitudinal direction of said first sheet-metal strips;said second sheet-metal strips have second corrugations alternately disposed in a longitudinal direction of said second sheet-metal strips; andsaid first and second sheet-metal strips are assembled to form said webs such that each said flow sub-channel is formed by said first and second corrugations. 4. The spacer according to claim 1, wherein said flow sub-channel has a downstream end and runs oblique to the vertical at least at said downstream end. 5. The spacer according to claim 4, wherein the cooling water respectively emerging from said flow sub-channels which are mutually neighboring and inclined to a crossing point of two of said webs, have mutually opposed flow components perpendicular to the vertical middle plane such that a swirl flow is produced around said crossing point. 6. The spacer according to claim 5, wherein swirl flows around mutually neighboring crossing points are respectively directed in an opposed fashion to each other along said web. 7. A fuel assembly comprising:at least one spacer, containing:a multiplicity of crisscrossing webs forming a grid, each of said webs formed of interconnected first and second sheet-metal strips having corrugations shaped asymmetrically in relation to a vertical middle plane running between said sheet-metal strips such that in each case neighboring corrugations form an enclosed flow sub-channel running oblique to a vertical and having a shape being asymmetric in relation to said vertical middle plane thereby imparting to cooling water emerging from said flow sub-channel a flow component perpendicular to said vertical middle plane running between said sheet-metal strips;said asymmetric shape of said enclosed flow sub-channel and said asymmetric shape of said corrugations being predefined. 8. The fuel assembly according to claim 7, wherein: said asymmetric shape of said corrugations is formed by predefined offset arches. 9. The spacer according to claim 1, wherein: said asymmetric shape of said corrugations is formed by predefined offset arches. |
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summary | ||
summary | ||
claims | 1. A system for controlling a main feed-water pump and a main feed-water control valve including a downcomer feed-water valve and an economizer feed-water valve to control a steam generator level of a nuclear power plant, comprising:a proportional-integral (PI) controller which performs a PI operation on a compensated steam generator error signal generated according to a deviation between the steam generator level and level setpoints of the steam generator and generates a flow demand signal according to the result of the PI operation;a power determiner which determines a power section to which reactor power belongs, among low and high power sections and determines a transfer time when the determined power section transfers;a main feed-water controller which generates a main feed-water control signal for controlling the main feed-water pump and the main feed-water control valve according to the flow demand signal and the determined power section;an information provider which provides PI information comprising a gain and an integral time constant set according to the reactor power; andan information transformer which provides the PI information to the PI controller and provides transformed PI information comprising a transformed gain and a transformed integral time constant to the PI controller only for a predetermined timer time at the transfer time,wherein the transformed gain and the transformed integral time constant are preset to vary with the timer time. 2. The system of claim 1, wherein the information transformer comprises:a transformation information provider which provides the transformed gain and the transformed integral time constant to the PI controller; anda first timer which provides the PI information to the PI controller and provides the transformed PI information to the PI controller only for a predetermined first timer time at a first transfer time when the transfer time transfers from the low power section to the high power section. 3. The system of claim 2, wherein the information transformer comprises:a second timer which provides the PI information to the PI controller and provides the transformed PI information to the PI controller only for a predetermined second timer time at a second transfer time when the transfer time transfers from the low power section to the high power section. 4. The system of claim 1, wherein the transformed gain is set to a value greater than a gain set according to the reactor power, and the transformed integral time constant is set to a value smaller than an integral time constant set according to the reactor power. |
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claims | 1. A method of operating a nuclear power plant that includes a pressurized water reactor (PWR), a steam generator, a turbine, an electric generator, and a condenser, the method comprising:operating the PWR to heat primary coolant flowing through a nuclear reactor core comprising fissile material immersed in the primary coolant water;operating the steam generator to convert secondary coolant feedwater to steam using primary coolant water heated by the operating PWR;operating the turbine by flowing steam from the steam generator through the turbine and then through the condenser;driving the electric generator using the turbine to generate electricity;conveying the generated electricity to an electrical switchyard; andresponsive to a station blackout, transitioning the nuclear power plant to an island mode over a transition time interval by transition operations including:at the beginning of the transition time interval, disconnecting the electric generator from the electrical switchyard and opening a bypass valve to convey bypass steam flow from the steam generator to the condenser wherein the bypass steam flow does not flow through the turbine;after opening the bypass valve, gradually closing the bypass valve over the transition time interval; andgradually reducing the thermal power output of the PWR over the transition time interval,wherein the transition time interval comprises at least a plurality of minutes. 2. The method of claim 1 further comprising:concurrently with conveying the generated electricity to the electrical switchyard, also conveying the generated electricity to an electrical power system of the nuclear power plant; andin the transitioning, continuing to convey the generated electricity to the electrical power system of the nuclear power plant after the disconnecting of the electric generator from the electrical switchyard. 3. The method of claim 2 wherein the gradual reducing comprises gradually reducing the thermal power output of the PWR over the transition time interval such that the thermal power output of the operating PWR at the end of the transition time interval is 20% or less of the thermal power output of the operating PWR before the transition time interval. 4. The method of claim 2 wherein the gradual closing of the bypass valve over the transition time interval comprises:controlling the bypass valve over the transition time interval to convey bypass steam flow from the steam generator to the condenser that is sufficient to enable said gradual reducing of the thermal power output of the PWR over the transition time interval without approaching steam generator or pressurizer safety valve setpoints and while continuing to convey the generated electricity to the electrical power system of the nuclear power plant after the disconnecting of the electric generator from the electrical switchyard. 5. The method of claim 1 wherein the transition operations further include:at the beginning of the transition time interval, opening a supplemental bypass valve to convey supplemental bypass steam flow from the steam generator to a feedwater system of the PWR wherein the supplemental bypass steam flow does not flow through the turbine and does not flow through the condenser. 6. The method of claim 5 wherein the transition operations further include: after opening the supplemental bypass valve, gradually closing the supplemental bypass valve over the transition time interval. 7. The method of claim 1 wherein the transition operations do not include venting the steam from the steam generator to atmosphere. 8. The method of claim 1 wherein the operating of the steam generator includes:disposing the steam generator inside a pressure vessel of the PWR; andflowing the secondary coolant feedwater into a feedwater inlet of the PWR and through the steam generator where primary coolant water heated by the operating PWR heats the secondary coolant feedwater to convert the secondary coolant feedwater to steam that exits a steam outlet of the PWR. 9. The method of claim 1 wherein the gradual closing of the bypass valve over the transition time interval results in the bypass valve being fully closed at the end of the transition time interval. 10. A method operating in conjunction with a nuclear power plant comprising a pressurized water reactor (PWR) operating to heat primary coolant water, a steam generator using the heated primary coolant water to convert secondary coolant feedwater to steam, a turbine driven by steam from the steam generator and operatively connected with an electric generator, and a condenser connected with the turbine to condense steam after flowing through the turbine, the method comprising:transitioning the nuclear power plant to an island mode over a transition time interval by transition operations including:responsive to detecting a station blackout, electrically isolating the nuclear power plant and opening a bypass valve to convey bypass steam flow from the steam generator to the condenser without flowing through the turbine;after opening the bypass valve, gradually closing the bypass valve over the transition time interval; andgradually reducing the thermal power output of the PWR over the transition time interval,wherein the transition time interval comprises at least a plurality of minutes. 11. The method of claim 10 wherein the transition operations further include:responsive to detecting the station blackout, opening a supplemental bypass valve to convey supplemental bypass steam flow from the steam generator to a feedwater system supplying the secondary coolant feedwater to the steam generator;wherein the supplemental bypass steam flow does not flow through the turbine and does not flow through the condenser. 12. The method of claim 10 wherein the transition operations do not include venting steam from the steam generator to atmosphere. 13. The method of claim 10 wherein the transition operations further include conveying electricity generated by the generator to an electrical power system of the nuclear power plant during the transition time interval, the method further comprising:after the transition time interval, continuing to convey electricity generated by the generator to an electrical power system of the nuclear power plant. 14. The method of claim 10 wherein the gradual reducing of the thermal power output of the PWR over the transition time interval comprises:gradually reducing the thermal power output of the PWR over the transition time interval to a level that is 20% or less of the thermal power output of the PWR prior to detecting the station blackout. |
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045333955 | description | EXAMPLE 1 A prepared solution representing an evaporation concentrate (MAW-concentrate) in accordance with the data as given in FIG. 1 was introduced into a heatable mixing auger. The composition of the concentrate is given in Table 1. A flow of 150 l/h was maintained into which Portland cement 35F was metered at a rate of 24 kg/h. A process temperature of between 130.degree. and 180.degree. C. was maintained. A fixation mixture was produced at a rate of 30 l/h which included 30 kg/h of salts, 24 kg/h of cement and 6 kg/h of water. The fixation mixture was discharged from the mixing auger into a waste container in which it hardened. The solid end product contained 50 wt.% of salts and the water-cement number was 0.25. The steam escaping during mixing and evaporation amounted to 134 kg/h of condensate. TABLE 1 ______________________________________ COMPOSITION OF THE MAW CONCENTRATE Element or Compound Concentration in g/l ______________________________________ NaNO.sub.3 300 Al 0.23 Ca 1.5 Cr 0.08 Cu 0.15 Fe 0.38 K 0.08 Mg 0.75 Mn 0.08 Mo 0.38 Ni 0.08 Ru 0.15 Zr 0.15 Sodium oxalate 5 Sodium tartrate 5 EDTA 1 NaF 1 Tensid (Marlox FK 64) 1 Tensid (Marlophen 812) 1 Na.sub.2 HPO.sub.4 5 Sodium citrate 5 Tributylphosphate (TBP) 0.2 Dibutylphosphate (DBP) 0.2 Kerosene 0.02 ______________________________________ All elements were introduced in the form of nitrates with the exception of Mo which was used as sodium molybdate. During non-active tests, 10 g/l inactive Cs or, respectively, Sr were introduced. EXAMPLE 2 161 g Portland cement (PC 35F) were mixed in a retort with 354 g NaNO.sub.3 solution (NaNO.sub.3 content of 90 g). Such a mixture has a water-cement number of 1.64 and contains 17.5% by weight of salt. In place of Portland cement, blast furnace cement, trass cement or pozzuolona cement may be used. Volume reduction by mixing/evaporation at 130.degree.-180.degree. C. resulted in evaporation of 215 g H.sub.2 O. The fixation mixture with a water-cement number of 0.3 and a salt content of 30 wt.% was easily transferred from the retort into prismatic forms wherein it hardened. After 28 days storage time, the end products had dynamic elasticity-module values of 18-25 N/mm.sup.2 ; the crash resistance was 25-35 N/mm.sup.2. The mechanical resistance of those products with a high salt content and low water-cement number is, consequently, comparable to, or better than, that of products with a 10% (by weight) salt content and water-cement numbers of 0.4 to 0.45 as they are known in the art. Before evaporation and mixing, for example, 0.01 to 0.2 wt.%, of a known setting retardant or of a liquifier may be added to the mixture if an evaporation temperature at the lower end of the given range is selected, that is, if the mixing and evaporation period is relatively long. It is also possible to perform the mixing and evaporation step under vacuum so that the operating temperature is relatively low which is advantageous if premature setting must be avoided. The results of this example show that solid products of cement with a low water-cement number (0.3) and a relatively high waste content (30% by weight), which values exceed those of products made in accordance with the state of the art, can be made in a continuous process in which the mixture of cement and aqueous waste has originally a high water-cement number (>1) but in which, during mixing, the water content is reduced, by evaporation, to the desired end value. With a continuous process, residence times of the mixture in the mixer-evaporator of about 5-10 minutes can be obtained without problems (for comparison: bitumination--3 minutes) so that, under the selected conditions, premature setting and solidification of the mixture can be avoided. Leach Resistancy Diffusion coefficient (m.sup.2 /s) for Co-137. TABLE 2 ______________________________________ Product Composition NaCl Solution Quinary Solution Water-Cement normal normal Number = 0.4 conditions) conditions) PC = Portland Cement (at RT) (at RT) ______________________________________ PC 35F + 10 wt. % NaNO.sub.3 8.1 .times. 10.sup.-3 8.5 .times. 10.sup.-14 PC 35F + 10 wt. % 1.2 .times. 10.sup.-13 1.5 .times. 10.sup.-14 NaNO.sub.3 +5 wt. % Bentonite PC 35F + 40 wt. % NaNO.sub.3 4.5 .times. 10.sup.-12 2.7 .times. 10.sup.-13 PC 35F + 40 wt. % 8.4 .times. 10.sup.-15 1.0 .times. 10.sup.-15 NaNO.sub.3 +5 wt. % Bentonite ______________________________________ The results show that the leach resistancy of products with or without addition of Bentonite is similar. Samples with a high salt content benefit by the addition of Bentonite since they show a lower Cs release. Corrosion Resistancy in Quinary Solution Changes in the attenuation of the resonance frequency, that is, changes in the dynamic elasticity module (which is calculated from the attenuation) and changes in the weight of the samples, are employed as a measurement for progress of corrosion. TABLE 3 ______________________________________ Sample weight (g) 10% Salt 45% Salt E-Module (N/mm.sup.2) Storage Time w/c = 0.4 w/c = 0.25 10% Salt 45% Salt ______________________________________ 0 days PC 35F 61.8 65.4 18.5 23.0 5 days 58.0 65.7 14.0 17.0 15 days 60.0 66.3 13.5 16.0 50 days 61.0 66.3 13.0 14.5 90 days 61.0 66.2 12.5 13.5 0 days BFC 35L 57.5 64.8 19.5 23.5 5 days 57.0 65.5 15.0 18.0 15 days 56.5 66.0 15.0 17.0 50 days 57.0 66.7 15.0 16.0 90 days 57.5 67.2 15.0 14.0 ______________________________________ w/c = watercement number (wt. ratio) PC = Portland cement BFC = blast furnace cement From the test results listed, it may be seen that samples of PC 35F exhibit no differences and samples of BFC 35L exhibit only small differences in corrosion resistancy for different salt contents. EXAMPLE 3 315 g of the concentrate (containing NaNO.sub.3) of Table 1 in Example 1 were mixed with 140 g Portland cement 35F (w/c=1.6) and heated in an oil bath of 140.degree. C., whereby 180 g H.sub.2 O were evaporated (in 4 hours). To the resulting viscous mixture 26 g of Na.sub.2 SiO.sub.3 .multidot.5H.sub.2 O was added and the mixture was then filled into prismatic forms. The samples showed the normal hardening progress. After 28 days hardening time, the dynamic E-module was comparable with that of products made in accordance with prior art methods. The composition of the solid end products was: ##EQU1## EXAMPLE 4 380 g of a borate-containing solution, according to borate-containing waste water of a pressurized water nuclear reactor (Table 4) were mixed with 175 g cement and subjected to an oil bath at a temperature of 140.degree. C. for 2 hours during which time 258 g H.sub.2 O was evaporated. The resulting flowable mixture was filled with prismatic forms wherein it exhibited a normal hardening progress. After 28 days, the dynamic E-module was 16 N/mm.sup.2. The composition of the solid end product was: ##EQU2## The method according to the invention presents a simple solution especially for the disposal of boric acid concentrates. It has been necessary so far, for the fixation of these concentrates, to adjust the pH value of 11-12 by additives (NaOH or Ca(OH).sub.2) in order to obtain a solid end product. However, these additives degraded the quality of the product. With the method according to the invention, solid fixation end products can be obtained without additives and these end products exhibit better quality and have a lower w/c number. TABLE 4 ______________________________________ CONCENTRATIONS IN g/l ______________________________________ NaOH 29 H.sub.3 BO.sub.3 180 Na.sub.2 SO.sub.4 30 Na.sub.2 HPO.sub.4 .times. 12H.sub.2 O 5 NaCl 5 Fe.sub.2 (SO.sub.4).sub.3 5 Cs.sub.2 SO.sub.4 10 Detergents (Hakar-Dekopur RS) 5 ______________________________________ |
041949480 | abstract | A locking device for supporting and locking a nuclear fuel assembly within a cylindrical bore formed by a support plate, the locking device including a support and locking sleeve having upwardly extending fingers forming wedge shaped contact portions arranged for interaction between an annular tapered surface on the fuel assembly and the support plate bore as well as downwardly extending fingers having wedge shaped contact portions arranged for interaction between an annularly tapered surface on the support plate bore and the fuel assembly whereby the sleeve tends to support and lock the fuel assembly in place within the bore by its own weight while facilitating removal and/or replacement of the fuel assembly. |
summary | ||
048760617 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the pressure vessel of a pressurized water reactor system of an advanced design in which plural rod guides are cantilever-mounted at their lower ends and extend in parallel, vertical relationship to dispose the upper ends thereof adjacent a calandria assembly and, more particularly, to an improved, resiliently loaded lateral support between the top, free ends of the cantilever-mounted rod guides and the calandria assembly of an advanced design, pressurized water reactor. 2. State of the Relevant Art Conventional pressurized water reactors employ a number of control rods which are mounted within the reactor vessel, generally in parallel axial relationship, for axial translational movement in telescoping relationship with the fuel rod assemblies. The control rods contain materials which absorb neutrons and thereby lower the neutron flux level within the core. Adjusting the positions of the control rods relatively to the respectively associated fuel rod assemblies thereby controls and regulates the reactivity and correspondingly the power output level of the reactor. Typically, the control rods, or rodlets, are arranged in clusters, and the rods of each cluster are mounted at their upper ends to a common, respectively associated spider. Each spider, in turn, is connected to a respectively associated adjustment mechanism for raising or lowering the associated rod cluster. In certain advanced designs of such pressurized water reactors, there are employed both control rod clusters (RCC) and water displacement rod clusters (WDRC), and also so-called gray rod clusters which, to the extent here relevant, are structurally identical to the RCC's and therefore both are referred to collectively hereinafter as RCC's. In an exemplary such reactor design, a total of over 2800 reactor control rods and water displacement rods are arranged in 185 clusters, each of the rod clusters having a respectively corresponding spider to which the rods of the cluster are individually mounted. Further, there are provided, at successively higher, axially aligned elevations within the reactor vessel, a lower barrel assembly, an inner barrel assembly and a calandria assembly, each of generally cylindrical configuration; a removable, upper closure dome seals the top of the vessel and is removable to gain access to the vessel interior. The lower barrel assembly has mounted therein, in parallel axial relationship, a plurality of fuel rod assemblies, comprising the reactor core. The fuel rod assemblies are supported at the lower and upper ends thereof, respectively, by corresponding lower and upper core plates. The inner barrel assembly comprises a cylindrical sidewall which is welded at its bottom edge to the upper core plate. Within the inner barrel assembly there are mounted a large number of rod guides disposed in closely spaced relationship, in an array extending substantially throughout the cross-sectional area of the inner barrel assembly. The rod guides are of first and second types, respectively housing therewithin the reactor-control rod clusters (RCC) and the water displacement rod clusters (WDRC); these clusters, as received in telescoping relationship within their respectively associated guides, generally are aligned with respectively associated fuel rod assemblies. One of the main objectives of the advanced design, pressurized water reactors to which the present invention is directed, is to achieve a significant improvement in the fuel utilization efficiency, resulting in lower overall fuel costs. Consistent with this objective, the water displacement rodlet clusters (WDRC's) function as a mechanical moderator and provide spectral shift control of the reactor. Typically, a fuel cycle is of approximately 18 months, following which the fuel must be replaced. When initiating a new fuel cycle, all of the WDRC's are fully inserted into association with the fuel rod assemblies, and thus into the reactor core. As the excess reactivity level of the fuel diminishes over the cycle, the WDRC's are progressively, in groups, withdrawn from the core so as to enable the reactor to maintain the same reactivity level, even though the reactivity level of the fuel rod assemblies is reducing due to dissipation over time. Conversely, the control rod clusters are moved, again in axial translation and thus telescoping relationship relatively to the respectively associated fuel rod assemblies, for control of the reactivity and correspondingly the power output level of the reactor on a continuing basis, for example in response to load demands, in a manner analogous to conventional reactor control operations. A reactor incorporating WDRC's is disclosed in application Ser. No. 217,503, filed Dec. 16, 1980 and entitled MECHANICAL-SPECTRAL SHIFT REACTOR and in further applications cited therein. A system and method for achieving the adjustment of both the RCC's and WDRC's are disclosed in the co-pending application of Altman et al., entitled "DISPLACER ROD DRIVE MECHANISM VENT SYSTEM." Each of the foregoing applications is assigned to the common assignee hereof and is incorporated herein by reference. A critical design criterion of such advanced design reactors is to minimize vibration of the reactor internals structures, as may be induced by the core outlet flow as it passes therethrough. A significant factor for achieving that criterion is to maintain the core outlet flow in an axial direction throughout the inner barrel assembly of the pressure vessel and thus in parallel axial relationship relative to the rod clusters and associated rod guides. The significance of maintaining the axial flow condition is to minimize the exposure of the rod clusters to cross-flow, a particularly important objective due both to the large number of rods and also to the type of material required for the WDRC's, which creates a significant wear potential. This is accomplished by increasing the vertical length, or height, of the vessel sufficiently such that the rods, even in their fully withdrawn (i.e., raised) positions within the inner barrel assembly, remain located below the vessel outlet nozzles, whereby the rods are subjected only to axial flow, and through the provision of a calandria assembly which is disposed above the inner barrel assembly thus above the level of the rods and which is designed to withstand the cross-flow conditions. In general, the calandria assembly comprises a lower calandria plate and an upper calandria plate which are joined by a cylindrical side wall, and an annularly flanged cylinder which is joined at its lower cylindrical end to the upper calandria plate and is mounted by its upper, annularly flanged end on an annular supporting ledge of the pressure vessel. The rod guides are cantilever-mounted at their lower ends to the upper core plate and at their upper ends to the lower calandria plate. Within the calandria assembly and extending between aligned apertures in the lower and upper calandria plates is mounted a plurality of calandria tubes, positioned in parallel axial relationship and respectively aligned with the rod guides. A number of flow holes are provided in the lower calandria plate, at positions displaced from the apertures associated with the calandria tubes through which the reactor core outlet flow passes as it exits from its upward passage through the inner barrel assembly. The Calandria assembly receives the axial core outlet flow, and turns the flow from the axial direction through 90.degree. to a radially outward direction for passage through the radially oriented outlet nozzles of the vessel. The calandria thus withstands the cross-flow generated as the coolant turns from the axial to the radial directions, and provides for shielding the flow distribution in the upper internals of the vessel. Advanced design pressurized water reactors of the type here considered incorporating such a calandria assembly are disclosed in the co-pending applications: Ser. No. 490,101 to James E. Kimbrell et al., for "NUCLEAR REACTOR"; application Ser. No. 490,059 to Luciano C. Veronesi for "CALANDRIA"; and application Ser. No. 490,099, "NUCLEAR REACTOR", all thereof concurrently filed on Apr. 29, 1983 and incorporated herein by reference. Maintenance of such reactors, for example, requires that the upper closure dome be removed to provide access to the calandria assembly which in turn is removed to afford access to the WDRC and RCC rod clusters for repair or replacement, and as well to the core for rearrangement or replacement of the fuel rod assemblies. To accomplish this, the calandria assembly typically is removable from the inner barrel assembly, withdrawing thereby the WDRC and RCC rods from within the corresponding rod guides. As before noted, the rod guides for each of the RCC and WDRC rod clusters are mounted rigidly at their bottom ends to the upper core plate, preferably by being bolted thereto, and extend in parallel axial relationship to dispose the upper, free ends thereof adjacent the lower calandria plate. This cantilever-type mounting is necessitated to accommodate axial (i.e., vertical) movement of the free ends of the rod guides, which occurs due to thermal expansion and thus axial elongation of the rod guides, and fixed end motion caused by vibration and/or flexing of the upper core plate to which the bottom, fixed ends of the rod guides are mounted. Because of these factors, it is not possible to rigidly and permanently secure the free ends of the rod guides to the lower calandria plate. Preferably, the design of the pressure vessel and particularly of the support structures which mount the free ends of the rod guides to the lower calandria plate permit both the assembly and removal of the calandria, relatively thereto, without special tools. Nevertheless, the mounting means for the free ends of the rod guides not only must constrain the same against lateral motion due to vibration, flow and thermal forces while accommodating the aforesaid axial movement of the free ends of the rod guides, but also must avoid wear of the reactor internals arising out of loads imposed on the guides and the previously discussed axial motion of the free ends of the guides. In some existing designs and as used with conventional reactors, split pins are employed at the free ends of the rod guides for restricting lateral motion while permitting a limited extent of axial motion. Such designs, however, present wear concerns for the reasons above-noted. In fact, due to the high loads and large axial motion of the free ends in the advanced design pressure vessels, the use of split pins for the free end supports is deemed not practical. There thus exists a substantial need for a top end support structure for the top, free ends of the rod guides in such advanced design reactors, which satisfies these complex structural and operational requirements but yet which is of simple design and employs a minimum number of parts, thereby to achieve cost economies both in the construction and also in the maintenance of such reactors. CROSS-REFERENCE TO RELATED APPLICATIONS The co-pending application of J. E. Gillett et al., entitled "TOP END SUPPORT FOR WATER DISPLACEMENT ROD GUIDES OF PRESSURIZED WATER REACTOR", assigned to the common assignee hereof and incorporated herein by reference, discloses a telescoping interconnection between a cylindrical support element which is affixed to and extends downwardly from the lower calandria plate and an apertured sleeve affixed to the top end of each rod guide. The configuration of the telescoping elements maximizes the area of the wear surface, thereby to resist wear during normal operation, while affording ease of removal of the calandria to gain access to the rod clusters and of reassembly of same, for the reasons aforenoted. An alternative top end support assembly is disclosed in the co-pending application of Gillett et al. entitled "FLEXIBLE ROD GUIDE SUPPORT STRUCTURE FOR INNER BARREL ASSEMBLY OF PRESSURIZED WATER REACTOR", assigned to the common assignee hereof and incorporated herein by reference. Respective, differently configured top support plates are mounted on the free ends of the RCC and the WDRC rod guides, respectively, and have mating, respective exterior and interior vertices to permit assemblage of same in an interdigitized array. Flexible linkages connect the top plates in a concatenated relationship, and serve to restrain relative, lateral movement therebetween while permitting independent axial movement. Stop pins are received in aligned bores of the contiguous interdigitated top plates and serve to limit the extent of load which can be applied to the linkages and thus the ultimate extent of relative movement between the concatenated top plates. The RCC top plates include openings, preferably of cylindrical configuration, which receive corresponding cylindrical extensions which are secured to and extend downwardly from the lower calandria plate, thereby establishing basic alignment of the concatenated and interleaved matrices of the plates. Leaf springs secured to the calandria bottom plate engage and exert a downward force on the top surfaces of the RCC top plates, thereby establishing a frictional force which further opposes lateral movement of the RCC top plates and correspondingly, through the concatenated and interleaved arrangement, any lateral movement of the WDRC top plates, as well, while permitting restrained axial displacement, or movement, of the individual RCC and WDRC rod guides. While the flexible support structure of the referenced Gillett et al. application satisfies many of the requirements of the rod guide top end supports, the structure is of complex design and requires the use of numerous elements, contributing to increased costs of construction and maintenance of the reactor. Accordingly, there remains a need for a lateral support for the top, free ends of the cantilever-mounted rod guides of the pressurized water nuclear reactors of the advanced designs herein contemplated, which is of simplified design and reduced cost, yet which affords the requisite support functions while reducing and/or substantially eliminating wear concerns. SUMMARY OF THE INVENTION In accordance with the present invention, an improved lateral support is provided at the interface between the upper, free ends of cantilever-mounted rod guides and the lower calandria plate of a calandria assembly, as employed in a pressurized water reactor of the advanced design type herein contemplated. While the improved lateral support of the invention is directed to the particular problems presented by such advanced design pressurized water reactors, it will be appreciated that the lateral support of the invention may be employed in other reactors with the alignment and lateral top end support requirements are imposed even though the further concerns of vibration and axial movement of the rod guides are not as severe a concern. More particularly, an extension element having a central aperture therethrough, corresponding to an aperture in the lower calandria plate which accommodates a drive rod for an associated rod cluster, is aligned axially with a respectively corresponding aperture in the lower calandria plate and secured to the lower calandria plate so as to depend downwardly therefrom. Plural pivotal mounting sockets defining horizontal axes of rotation are formed in the extension element, each socket receiving and pivotally mounting therein a first end of a corresponding link, the plurality of links extending generally radially and in angularly displaced relationship relatively to the common axis of the aligned apertures. The top end of each rod guide includes a plurality of corresponding receiving sockets, each receiving socket having a mating configuration with respect to the free end of a corresponding link for releasably receiving and engaging same. The number of links and associated mounting and receiving sockets, and the corresponding angular relationships thereof are determined in accordance with the configuration of the top end of the associated rod guide. Illustratively, for a rod guide top end of generally square cross-sectional configuration, four such links and respectively associated mating and receiving sockets are provided, the links being relatively angularly displaced at right angles and extending radially outwardly from the extension element so as to engage and be received in correspondingly disposed receiving sockets in the top end of the associated rod guide. In use, as the calandria assembly is lowered into the pressure vessel, the links are normally pivoted downwardly, through force of gravity, and thus disposed at radially inwardly, retracted or disengaged positions. The corresponding receiving sockets formed at the upper and inner portions of the corresponding rod guide top end define an engagement ledge which is aligned with the free end of the link in its inwardly retracted position. As the downward movement of the calandria assembly continues, the free end of each link contacts the engagement ledge and is pivoted thereby upwardly and thus moved radially outwardly, to a releasably engaged position in its corresponding receiving socket in the assembled position of the calandria. Removal of the calandria is performed simply by lifting the calandria this causes the links to pivot downwardly and the free ends to move inwardly, thereby being withdrawn from the receiving sockets to the normal, retracted positions. The links may assume any of various configurations, the principle requirement being that a limited degree of lateral, i.e., radially oriented, flexibility be afforded through the resulting connection between the extension element and the rod guide top end. This is afforded in different embodiments of the lateral support of the present invention, alternatively by use of link configurations which themselves afford a required degree of flexibility in the lateral, or radial direction, or by the use of links of more rigid configuration but wherein the receiving socket is flexibly mounted in the top end of the associated rod guide. In all of these embodiments of the invention, the links are loaded laterally into the top end of the rod guide, and serve to center same, both maintaining the intended alignment and preventing lateral motion of the rod guide; further, since the links remain capable of pivotal movement even in the engaged position, they accommodate, through slight pivotal movement, axial movement of the free ends of the rod guides as may be produced by axial thermal growth and vibrations. The resiliently loaded lateral supports of the present invention thus provide for substantially rigid lateral restraint of the rod guide top, free ends, translating lateral forces from the rod guides directly to the calandria bottom plate and thus maintaining alignment and eliminating lateral movement of the rod guide free ends, while allowing axial, vertical motion for accommodating axial thermal expansion growth and base plate and related rod guide axial vibrations. The support, moreover, facilitates both the installation and the removal of the calandria, as required for routine maintenance and inspection operations. These and other advantages of the present invention will become more apparent from the following detailed description, taken with reference to the enclosed figures, in which like reference numerals and letters refer to like parts throughout. |
claims | 1. A method operating in conjunction with video display units (VDUs) of a reactor control interface wherein the VDUs include a group of safety VDUs and an additional VDU that is not a safety VDU, the method comprising:detecting a malfunctioning safety VDU, the remaining safety VDUs being functioning safety VDUs;shifting the displays of the functioning safety VDUs to free up one of the functioning safety VDUs wherein the shifting transfers the display of one of the functioning safety VDUs to the additional VDU that is not a safety VDU; andtransferring the display of the malfunctioning safety VDU to the functioning safety VDU freed up by the shifting. 2. The method of claim 1 wherein the group of safety VDUs includes:a home screen VDU displaying a simplified diagrammatic representation of a nuclear power plant;a mimic VDU displaying a mimic of a component of the nuclear power plant;a procedures VDU displaying a stored procedure executable by the nuclear power plant;a multi-trend VDU displaying trends of data acquired from the nuclear power plant; andan alarms VDU displaying a list of alarms generated by the nuclear power plant. 3. The method of claim 1 wherein the group of safety VDUs includes at least three VDUs of a group consisting of:a home screen VDU displaying a simplified diagrammatic representation of a nuclear power plant;a mimic VDU displaying a mimic of a component of the nuclear power plant;a procedures VDU displaying a stored procedure executable by the nuclear power plant;a multi-trend VDU displaying trends of data acquired from the nuclear power plant; andan alarms VDU displaying a list of alarms generated by the nuclear power plant. 4. A non-transitory storage medium storing instructions executable by an electronic data processing device in communication with a video display unit (VDU) to perform a method comprising:displaying a home screen representing a nuclear power plant, the home screen including:blocks representing functional components of the nuclear power plant including at least (i) blocks representing functional components of a normal heat sinking path of the nuclear power plant and (ii) blocks representing functional components of at least one remedial heat sinking path of the nuclear power plant, andconnecting arrows of a first type connecting blocks that are providing the current heat sinking path wherein directions of the connecting arrows of the first type represent the direction of heat flow along the current heat sinking path; andin response to the nuclear power plant transitioning to a different heat sinking path, updating the connecting arrows of the first type by deleting and adding connecting arrows of the first type so that the updated connecting arrows of the first type represent the different heat sinking path. 5. The non-transitory storage medium as set forth in claim 4 wherein the method further comprises:in response to a malfunctioning functional component of the nuclear power plant, highlighting the block representing the malfunctioning functional component using a highlighting format. 6. The non-transitory storage medium as set forth in claim 5 further comprising:selecting the highlighting format for the malfunctioning functional component from a group of different highlighting formats including at least:a first highlighting format that is selected if the malfunctioning functional component is the root cause of a of the nuclear power plant entering an abnormal operating condition,a second highlighting format that is selected if the malfunctioning functional component is not the root cause of a of the nuclear power plant entering an abnormal operating condition. 7. The non-transitory storage medium as set forth in claim 6 further comprising:in response to a remedial functional component taking intended remedial action in response to a malfunctioning functional component, highlighting the block representing the remedial functional component using a third highlighting format that is different from the first and second highlighting formats. 8. The non-transitory storage medium as set forth in claim 4 wherein the method further comprises:receiving a user selection of a block of the home screen; anddisplaying a mimic view of the functional component represented by the user-selected block. 9. The non-transitory storage medium as set forth in claim 4 wherein the method further comprises:receiving a user selection of a block of the home screen; anddisplaying a list of stored procedures involving the user-selected block. 10. The non-transitory storage medium as set forth in claim 4 wherein the method further comprises:simultaneously displaying two side-by-side alarm lists wherein one alarm list is by chronological or reverse chronological order and the other alarm list is ordered by priority. 11. The non-transitory storage medium as set forth in claim 10 wherein the method further comprises reordering the alarms of the alarm list is ordered by priority based on a user selection of a different ordering criterion. 12. The non-transitory storage medium as set forth in claim 4 wherein the method further comprises:displaying a plurality of trends of data acquired from the nuclear power plant in peripheral windows of a multi-trend display area;receiving a user selection of one of the trends displayed in the peripheral windows of the multi-trend display area; anddisplaying the selected trend in a central window that is larger than the peripheral windows and that is surrounded by the peripheral windows. |
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claims | 1. A pressurized water nuclear reactor, comprising:a containment shield surrounding a reactor vessel in which a core having fuel assemblies that contain control rods and fuel rods filled with fuel pellets is disposed;a steam generator thermally coupled to said reactor vessel via a primary flow loop; anda pump for circulating a water-based heat transfer fluid through said core and said steam generator via said primary flow loop, where said water-based heat transfer fluid comprises a plurality of nanoparticles comprising at least one of pyrolytic carbon, carbon black, adamantanes, lonsdaleite, or amorphous carbon dispersed therein. 2. The pressurized water nuclear reactor of claim 1, wherein the plurality of nanoparticles are functionalized. 3. The pressurized water nuclear reactor of claim 1, wherein the plurality of nanoparticles are primarily colloidal. 4. The pressurized water nuclear reactor of claim 1, wherein the plurality of nanoparticles have a mean size that is in a range from 0.5 nm to 200 nanometers. 5. The pressurized water nuclear reactor of claim 1, wherein the plurality of nanoparticles have a mean size that is in a range from 1 nm to 100 nm. 6. The pressurized water nuclear reactor of claim 1, wherein the plurality of nanoparticles have a mean size that is in a range from 40 nm to 100 nm. 7. The pressurized water nuclear reactor of claim 1, wherein a concentration of said plurality of nanoparticles in said water-based heat transfer fluid is in a range from 0.0001 to 10 volume percent of said water-based heat transfer fluid. 8. The pressurized water nuclear reactor of claim 1, wherein a concentration of said plurality of nanoparticles in said water-based heat transfer fluid is in a range from 0.1 to 3 volume percent of said water-based heat transfer fluid. 9. A nuclear reactor, comprising:a containment structure surrounding a reactor vessel in which a core having fuel assemblies that contain control rods and fuel rods is disposed; anda pump that circulates heat transfer fluid comprising at least one of pyrolytic carbon nanoparticles, carbon black nanoparticles, nanoparticles comprising adamantanes, lonsdaleite nanoparticles, or amorphous carbon nanoparticles through a coolant loop that cools the core of the nuclear reactor. 10. The nuclear reactor of claim 9, wherein the pyrolytic carbon nanoparticles, carbon black nanoparticles, nanoparticles comprising adamantanes, lonsdaleite nanoparticles, or amorphous carbon nanoparticles are functionalized. 11. The nuclear reactor of claim 9, wherein the pyrolytic carbon nanoparticles, carbon black nanoparticles, nanoparticles comprising adamantanes, lonsdaleite nanoparticles, or amorphous carbon nanoparticles are primarily colloidal. 12. The nuclear reactor of claim 9, wherein the pyrolytic carbon nanoparticles, carbon black nanoparticles, nanoparticles comprising adamantanes, lonsdaleite nanoparticles, or amorphous carbon nanoparticles have a mean size that is in a range from 0.5 nm to 200 nanometers. 13. The nuclear reactor of claim 9, wherein the pyrolytic carbon nanoparticles, carbon black nanoparticles, nanoparticles comprising adamantanes, lonsdaleite nanoparticles, or amorphous carbon nanoparticles have a mean size that is in a range from 1 nm to 100 nm. 14. The nuclear reactor of claim 9, wherein the pyrolytic carbon nanoparticles, carbon black nanoparticles, nanoparticles comprising adamantanes, lonsdaleite nanoparticles, or amorphous carbon nanoparticles have a mean size that is in a range from 40 nm to 100 nm. 15. The nuclear reactor of claim 9, wherein a concentration of the pyrolytic carbon nanoparticles, carbon black nanoparticles, nanoparticles comprising adamantanes, lonsdaleite nanoparticles, or amorphous carbon nanoparticles within the heat transfer fluid is in a range from 0.0001 to 10 volume percent of the heat transfer fluid. 16. The nuclear reactor of claim 9, wherein a concentration of the pyrolytic carbon nanoparticles, carbon black nanoparticles, nanoparticles comprising adamantanes, lonsdaleite nanoparticles, or amorphous carbon nanoparticles within the heat transfer fluid is in a range from 0.1 to 3 volume percent of the heat transfer fluid. 17. The nuclear reactor of claim 9, wherein the coolant loop is contained within the containment structure. 18. The nuclear reactor of claim 17, further comprising a steam generator, wherein at least a portion of the coolant loop passes through the steam generator. 19. The nuclear reactor of claim 18, wherein a secondary flow loop connected to the steam generator is at least partially external to the containment structure. 20. The nuclear reactor of claim 9, further comprising:a steam generator within the containment structure;a turbine external to the containment structure;a condenser external to the containment structure; andwherein a secondary pump circulates a water-based heat transfer fluid through the steam generator, the turbine, and the condenser. |
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abstract | Systems and methods for managing aquifer operation are included. An exemplary method includes receiving at an analysis computing device, one or more water measurements from a plurality of sites in an aquifer, wherein water measurements are received at a plurality of time points. A site may include one or more groundwater extraction wells. The method may further include calculating well operational data for at least one groundwater extraction well based on the water measurements, wherein the well operational data includes a well efficiency over a time period. Further, the method may include receiving an aquifer objective input via a graphical user interface presented on the analysis computing device. The method may further include generating a pump operation signal based on the well operational data and the aquifer objective input. |
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050376055 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is generally related to a nuclear reactor fuel assembly and in particular to a debris filter used with the fuel assembly. 2. General Background Commercial nuclear reactors include multiple fuel assemblies. Each fuel assembly is comprised of a number of fuel rods radially spaced apart in a parallel array by grid assemblies spaced along the length of the fuel rods. Each grid assembly is formed in an eggcrate design by multiple metal strips that criss-cross at right angles to form individual cells for each of the fuel rods. The strips are provided with tabs that project into the cells against the fuel rods. The tabs serve the purposes of holding the fuel rods in their respective radial positions and providing maximum surface area contact of the fuel rods with coolant flowing through the cells. Control rod guide thimble tubes also extend through selected cells in the grid assembly and are attached at their upper and lower ends respectively to an upper end fitting and a lower end fitting. The upper and lower end fittings are also commonly referred to in the industry as nozzle plates since they are rigid plates that provide structural integrity and load bearing support to the fuel assembly and are provided with flow apertures therethrough for coolant flow. The lower end fitting or nozzle plate is positioned directly above openings in the lower portion of the reactor where coolant flows up into the reactor to the core. The ligaments between apertures in the end fittings coincide with the ends of the fuel rods and limit upward or downward movement of the fuel rods. Debris such as metal particles, chips, and turnings is generated during manufacture installation, and repair of the reactor, piping, and associated cooling equipment. The size and complexities of the equipment prevent location and removal of all such debris before operations are commenced. Also, some of this debris may not become loose matter in the system until the system is put into operation. It has been recognized that this debris presents a greater problem to the system than previously thought. These small pieces of debris have been found to lodge between the walls of the grid cells and the fuel elements. Movement and vibration of the lodged debris caused by coolant flow results in abrasion and removal of cladding on the fuel rods. This in turn leads to detrimental effects such as corrosion of the fuel rods and failure to retain radioactive fission gas products. Such damage, although not critical to safety of the surrounding environment, can reduce operating efficiency by the need to suspend operation while replacing damaged fuel rods. It can be seen that a need exists for a debris filter capable of filtering debris of a size which may lodge between the grid cell walls and the fuel rods. An important consideration besides that of filtration is that a substantial coolant pressure drop across the filter must be avoided in order to maintain an adequate coolant flow over the fuel rods for heat removal therefrom. Patented approaches to this problem of which applicant is aware include the following. U.S. Pat. Nos. 4,684,495 and 4,684,496 disclose debris traps formed from a plurality of straps aligned with one another in a crisscross arrangement and defining a plurality of interconnected wall portions which form a multiplicity of small cells each having open opposite ends and a central channel for coolant flow through the trap. U.S. Pat. No. 4,828,791 discloses a debris resistant bottom nozzle which is a substantially solid plate having cut-out regions in alignment with inlet flow holes in the lower core plate. Separate criss-cross structures fixed to the plate extend across the cut-out regions to act as a debris trap. U.S. Pat. Nos. 4,664,880 and 4,678,627 disclose debris traps mounted within a bottom nozzle that define a hollow enclosure with an opening so as to form a debris capturing and retaining chamber. U.S. Pat. No. 4,652,425 discloses a trap for catching debris disposed between the bottom nozzle and the bottom grid. The structure forms multiple hollow cells that receive the fuel rod lower end plugs with dimples in each cell for catching debris carried into the cells by the coolant flow. SUMMARY OF THE INVENTION The present invention provides a solution to the above problem in the form of a screen attached to the lower end fitting or nozzle plate. The lower end fitting is formed from a substantially square base having interconnecting ribs between the walls with openings thereon which receive control rod guide tubes. Legs extending downward from each corner support the end fitting on the lower reactor internals. A stamped screen sized to match the lower end fitting and provided with flow holes sized to filter debris is attached to the lower end fitting. |
description | This application is a continuation of U.S. patent application Ser. No. 11/003,857, filed Dec. 3, 2004 now U.S. Pat. No. 7,193,230, and entitled Low-Weight Ultra-Thin Flexible Radiation Attenuation Composition (which claimed priority of U.S. provisional application Ser. No. 60/527,326, filed Dec. 5, 2003). X-ray equipment is commonly found in hospitals, dentist and doctor offices, veterinarian facilities, industrial testing and QC laboratories and the like. Medical personnel, technicians, and patients wear X-ray shielding garments to protect them from both direct and secondary exposure to radiation. In addition, today various procedures of scientific and medical significance involve the use and handling of radioactive compounds. The use of radioactive compounds is now commonplace in laboratories, hospitals and physician's offices. The handling and use of these compounds exposes the user and subject to potentially harmful amounts of ionizing radiation. To date, many compositions have been utilized in an effort to reduce the risk associated with exposure to X-ray and ionizing radiation. Typically these compositions have been metallic lead powder-loaded polymeric or elastomeric sheet goods that are incorporated into garments designed to provide personal protection. For example, lead loaded aprons, thyroid shields, gonad shields, and gloves have been marketed for their protective properties. Attenuation garments are needed to protect the user from specified levels of radiation. Additionally, these garments should be light in weight and exhibit suitable mechanical properties such as tensile strength, tear and puncture resistance, crease and fold resistance, etc. Further, the garments need to be resistant to cleaning by detergents, alcohols and other agents typically used in medical environments. Finally, the garments should preferably maintain their properties without immediate or long term degradation, when subjected to radiation. Many polymeric materials, particularly those that contain unsaturated bonds, such as natural rubber, are susceptible to degradation from radiation, becoming brittle and cracking, thus possibly allowing radiation penetration. Lead filled polymers are most often used in the manufacture of protective garments. In these polymer compositions, the polymers serve as a matrix for incorporation of the powdered lead, or other high atomic weight metals or compounds. The polymers commonly employed include highly plastisized polyvinyl chloride (PVC), polyethylene and other olefins, elastomers, and many other flexible polymers. The process of forming the filled polymer composition usually includes mixing the metal into the plastic using standard thermoplastic compounding equipment such as two-roll mills. In the case of PVC, standard plastisol production equipment and processes are employed. The finished products are usually designed to provide protection equivalent to a sheet of lead 0.5 mm in thickness, but the degree of radiation attenuation may be adjusted to meet the final application, and normally ranges from 0.1 mm to 1.5 mm of lead equivalence. Commercially, single layers of cast sheets of lead-filled polymer compositions are available and provide different levels of protection, depending on the sheet thickness and lead loading. The most widely available protective sheet is made of plastisized PVC. A plastisol is prepared by mixing dispersion grade PVC with a plasticizer such as dioctyl phthalate (DOP). The metal powder is then added and the viscous mix de-aerated. The mixture is coated onto release paper using standard casting equipment such as a knife over roll process and heated in an oven to approximately 400° F. to cure the resin. Other filled polymers, such as polyethylene-lead formulations are blended using intensive mixers such as a Banbury or a two roll mill and formed into sheets using calenders or extruders using procedures well-known in the art of polymer compounding. Sheets of plastisized PVC are most often commercially available in thicknesses providing protection of 0.125 mm equivalence of lead, 0.167 mm equivalence of lead, 0.175 mm equivalence of lead, 0.25 mm equivalence of lead, and the like. Sheets may be combined to achieve desired radiation attenuation. For example, three cast sheets of 0.167 mm rating are combined to provide 0.50 mm of protection. One disadvantage of producing PVC based sheets is that the process necessarily involves mixtures which have very high viscosities which most often result in poor wetting of the metals and poor dispersions of the metal in the plasticizer. Poor dispersion of the metal will lead to lower and uneven radiation attenuation performance of the final product. Another disadvantage of using PVC sheet is the excess weight of the final product necessary to provide the equivalence of 0.5 mm of lead. Three layers of 0.0167 thick lead loaded PVC weigh approximately 1.35 pounds per square foot. An apron constructed of the three sheets and associated nylons shells, buckles and the like can weigh 20 pounds or more. As a result of the weight and the length of time the protective garments sometimes must be worn, as by x-ray technicians, it has long been an objective of designers and producers of radiation attenuation material to achieve lighter weight products while maintaining the standard attenuation of 0.5 mm of lead. An object of the invention is to provide an ultra thin, light-weight, flexible sheet product useful for radiation attenuation. The invention provides for a polymer latex composition from which sheets can be prepared that incorporate heavy weight and high volume loadings of one or more high atomic weight metals and wherein the cured sheets are thinner and of lower weight than currently available compositions, while maintaining the desired level of radiation attenuation and structural properties, in both the latex dispersion and final sheet product. Specifically, sheets can be prepared by admixing high atomic number elements or their related compounds and alloys, singly or preferably in combination, into polymer latexes, desirably at room temperature, forming a fluid mixture. Despite solids loadings in excess of 89 weight percent of the total loaded polymer, the latex based formulations are sufficiently low in viscosity to be able to be poured. This low viscosity allows the use of processing procedures, such as liquid casting, not previously available in the production of attenuation products. Additives known in the art to alter viscosity, aid in dispersion, and remove entrapped air can be added to the latex. Such additives are especially useful when dealing with latex having a higher pH, e.g., above about 8.5, and preferably above about 8. In one embodiment, high metal loadings may be achieved while maintaining the desired final polymer properties, by using metal fillers having an average particle size of greater than 5 microns, preferably at least about 8 microns, and most preferably at least about 10 microns. If a metal compound is used, it should be substantially insoluble in water. Suitable methods of determining average particle size are known, and include, but are not limited to, analyzing with a scanning electron microscope. In one embodiment, the resulting fluid mixture can be readily cast onto a non-adherent surface such as release paper at a thickness of as low as about 0.010 inches, or preferably at least about 0.015 in., dried into a flexible sheet, and removed from the paper. These resulting flexible sheets can be used in the manufacture of any product in which radiation attenuation properties are advantageous, e.g., aprons, thyroid shields, gonad shields, and gloves. However, the invention is not limited to these purposes and has numerous applications across a large spectrum of industries. In a further embodiment, casting the metal-filled blend as a sheet, onto an adherent substrate, which becomes part of the final product, results in a product with much higher tensile and strength properties. Such substrates, which can become part of the final structure, include, but are not limited to: polymer sheets such as those made from vinyl or polyolefin; woven fabrics such as those made from cotton, linen, polymeric fibers, carbon fibers or the like, as well as blends of different types of natural and synthetic fibers; and non-woven fabric made of natural, polymeric, or carbon-fiber materials. Products made based on the invention have been found to be as much as 40% lighter than corresponding products made from standard lead filled vinyl. Specific embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention are intended to be illustrative, and not restrictive. Further, the figures are not necessarily to scale, some features may be exaggerated to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. The present invention relates to radiation attenuation compositions that are low-weight, ultra-thin and flexible sheets and which are formed by heavy loading of high atomic weight metals into polymer latexes. For example, the loading of the high atomic weight metals exceeds about 89 percent by weight and, more particularly exceeds about 90 percent by weight of the combined final sheet product, and more preferably is at least about 92% by weight of the total sheet product. For the present invention, metals found to be effective include metallic elements having an atomic number greater than 45, and preferably greater than about 50, such as antimony, tin, barium, bismuth, cesium, cadmium, indium, rhodium, tungsten and uranium, and lead, (and their compounds and/or alloys), such as tin/lead, barium sulphate, gadolinium oxide, and other heavy metals that have non-radioactive isotopes, Other high atomic number elements or their compounds also include, but are not limited to: cerium and gadolinium. In yet another embodiment, suitable metals include tantalum, silver, gold and other precious metals. In a specific embodiment, the metal particles have a platelike appearance where one of the dimensions is an order of magnitude less than the other two dimensions, and the other two dimensions differ by no more than a factor of four, and more particularly by not more than a factor of three. Suitable thicknesses of the final sheet product include, but are not limited to, in the range of at least about 0.010 in., and more specifically in the range of at least about 0.015 in. and more specifically in the range of from about 0.030 to about 0.070 in. In yet another embodiment, the thickness can vary depending on the desired attenuation. Unless otherwise indicated, the term “latex” includes dispersions of a polymer into an aqueous liquid. Such liquid dispersions are well-known in the art and are commercially available. They can include both natural and synthetic polymers dispersed into the aqueous liquid. Suitable polymer latexes include, but are not limited to: acrylic, styrene/butadiene, vinyl acetate/acrylic acid copolymers, vinyl acetate, ethylene vinyl acetate, polybutene, and urethane, latexes are prepared by the polymerization of a monomer in an aqueous medium. Typically, the acrylic, styrene/butadiene, and acetate polymer latexes are made in this manner. In another embodiment, a coating of unfilled latex is applied to the surface of the dried filled polymer composition. In another specific example, Rohm & Haas acrylic, trade name “TR 38HS” was used as the coating. In another example, a natural rubber latex, from Firestone, trade name “HARTEX 101”, was used as the coating. The coating thickness can vary. Examples of the thickness of the coating is in the range of about 0.25 mils to about 4 mils. The additional coating layer can improve the strength, stretchiness andor tear resistance of the overall end product. In one embodiment, high metal loadings may be achieved while maintaining the desired final polymer properties, by using metal fillers having an average particle size of greater than 5 microns, preferably at least about 8 microns, and most preferably at least about 10 microns. If a metal compound is used, it should be substantially insoluble in water. Suitable methods of determining average particle size are known, and include, but are not limited to, analyzing with a scanning electron microscope. In a further embodiment, when tin is employed as the metal in the mixture, latexes of varying pH ranges (e.g. less than about 10) can be employed. In yet another embodiment, especially when dealing with latexes having a pH of above about 8 the order of addition of the components (e.g. latex and metal) can assist in the dispersion of the components. For example, adding tungsten after the latex mixture is prepared, including the addition of all dispersion additives, produced will assist in the overall dispersion of the tungsten, and the tin is added after the tungsten is dispersed, an improved attenuation will be achieved. In yet a further embodiment, when a combination of metal fillers of differing particle sizes, is added to the latex, e.g., tin and tungsten, latexes of varying pH ranges (e.g. pH of not more than about 10) can be employed. In yet another embodiment, the order of addition of the several metal filler components can improve the dispersion of the metal filler components, preferably adding the finer particle filler first. As a further improvement the average combined particle size should preferably be at least about 8. For example, for the tin/tungsten composition, where the tungsten is available in a very small particle size, e.g., 1 micron or smaller, first dispersing the tungsten alone, after the polymer latex is fully mixed with the additives to be used, and thereafter adding the tin particles to the mixture , will allow the formation of the combined tin-tungsten overall dispersion of the composition of this invention while maintaining the suitable characteristics of the latex dispersion and the final dried polymer product, even at higher pH values. Specifically, a suitable casting dispersion comprising natural rubber latex can be formed with the tin/tungsten filler, by a method following this order of addition. Specifically, a vacuum dispersion mixer, manufactured by Shar Systems, Inc., of Fort Wayne, Ind., can be used to prepare the casting mixture. First, all the liquids are added to the mixer tank, including the latex dispersions and any desired additives; a vacuum of at least 26 inches is drawn, and the liquids are mixed for one minute, at a blade speed of 400 rpm. The vacuum is broken and the tungsten particles (having a particle size of less than one micron) are added, followed by vacuuming and one minute mixing. The mixer is again opened and the metal particles (particle size of about 20 microns) are added to the mixture, followed by a three-minute mix cycle at 1000 rpm and a second metal particle addition, where suitable would follow, with further mixing under vacuum. The mix cycles and blade rotation speed can be varied depending on the latex, metals, solids loading, and shear sensitivity of the latex. All mixing is carried out at ambient temperature, little heat is generated. In yet another embodiment, additives can be employed so as to aid in the preparation of the mixes and to adjust the end physical properties and structure of the end product. Of particular interest are those materials that aid in the uniform dispersion of the metals, to prevent the incorpation of air, and to defoam if necessary. Suitable additives include, but are not limited to, surfactants, defoamers, antifoaming agents, dispersing aids, stabilizers (e.g., Rohm & Haas trade name “Accumer, an alkoxylated alkylphenol and Rohm & Haas Tamol, a sulfonated naphthalene) plasticisizers (e.g. Rohm & Haas's plastisizer “Paraplex WP-1, a proprietary polymeric plastisizer”, aqueous ammonia). Other additives that can be used in the manufacture of different formulations include: Foamaster VF®, a proprietary defoamer from Cognis Corporation; Daxad 30™, a sodium polymethacrylate from Hampshire Chemical; Aersol® LF-4, a proprietary surfactant from Cytec Industries; Surfynol DF-210, a defoamer from Air Products; Troykyd™ D729, a silicone-based antifoam agent from Troy Chemical; Aersol® OT-75%, a sodium dioctyl sulfosuccinate from Cytec Industries; and Solsperse 27000, an aromatic polymeric alkoxylate from Avecia Limited. In another embodiment, a blend of latexes can be employed. Suitable blends of latexes include, but are not limited to, ethylene vinyl acetate and acrylic polymers, acrylic and styrene acrylic polymers, polybutene and natural rubber polymers, polybutene and acrylic polymers, styrene-butadiene polymers, and styrene acrylic polymers, isoprene and acrylic polymers, and similar blends. Each of these blends have to be modified with appropriate additives for best performance. In a specific example, natural rubber latex and other latexes can be employed so that the latex mixture can be vulcanized, if desired. In a further embodiment, in addition to using elements and compounds, alloys of the heavy metals can also be employed. Suitable alloys of attenuation metals include, but are not limited to, tin/lead, antimony/lead, tin/antimony, tin/silver, and bismuth/tin, lead/bismuth, tin/bismuth and bismuth/lead/tin/cadium/indium. In one example of a standardized test for determining the radiation attenuation equivalent to 0.5 mm thickness of a pure lead sheet, i.e., the lead equivalence, an X-ray attenuation sheet material is made from a loaded polymer, by casting into a sheet having a desired thickness, e.g., 0.0167 inches. The sheet is then cut into test squares measuring 4.5 inches. The cut squares are tested in accordance with the following protocol. The test sample is placed between the output beam from a standard medical x-ray generator and a detector, exposing the sample to x-ray radiation of known properties. Specifically, the sample is placed on a lead test shelf that is 23 inches below the x-ray tube and 13 inches above the detector. The shelf has a 2.0 inch diameter opening. For non-lead attenuating materials, the beam energy is set to 100 Kvp, at 100 milliamperes, and exposure times set to 1 second for a one-layer test. The sample is exposed to the x-rays and the non-absorbed energy, i.e., the x-ray energy passing through the sample, is measured. An x-ray exposure meter is used to measure the non-absorbed beam energy. The performances of pure lead control samples of known attenuation effectiveness are measured by this same procedure. The lead controls were selected to have attenuation just above, just below, and approximately the same as the attenuation of the test piece. The performance of the sample is compared to the known lead controls and the exact attenuation of the sample is calculated via interpolation. It should be noted that where the following examples used tin or tungsten particles, the tin product used was Grade 140 manufactured by Accupowder International, LLC (having an average particle size of about 20 microns), and the Tungsten powder used was Tungsten Powder Grade, manufactured by Buffalo Tungsten, Inc. (having an average particle size of less than 1 micron). A mixture of the following formulation was prepared: Rohm & Haas TR38 HS (pH 7-8)25gramsTin powder150grams.Tungsten powder60grams. To form the final product the polymer latex and metals were weighed in separate cups. The metals were poured into the latex and mixed using a small spatula. The fluid mixture was stirred until a smooth, pourable mixture was obtained. The mixture was poured onto release paper and knifed over shims of known thickness. The sheet was then dried for ten minutes in a convection oven at 160° F. The product of Example 1 weighed 57.1 grams, equivalent to 0.89 pounds per square foot at an equivalence of 0.50 mm of lead. The metals loading was 93.8% by weight or 65% by volume. The product was soft and supple and could be used for manufacturing a garment having highly effective attenuation properties. Using the above procedures, the following formulation was prepared. Air Products Air Flex 400 ethylene vinyl acetate25gramscopolymer latex (having a pH of 4.5, a Solids Contentof 52%) -Tin Powder150gramsTungsten Powder60gramsWater7grams The product of Example 2 at an equivalence of 0.50 mm of lead would weigh 54.2 grams, equivalent to 0.85 pounds per square foot. The metals loading was 93.8% by weight or 65% by volume. The product was soft and supple and both top and bottom surfaces had an excellent, smooth appearance. This product could be used for manufacturing an attenuation garment. Using the above procedures, the following formulation was prepared. Air Products Air Flex 400 ethylene vinyl acetate25gramscopolymer latexTin powder120grams.Tungsten powder40grams.Bismuth powder40gramsWater3.8grams The product of Example 3 would weigh 55 grams, equivalent to 0.86 pounds per square foot at a pure lead equivalence of 0.50 mm. The metals loading is 94.1% by weight or 65.5% by volume. The sheet product was soft and supple. Both top and bottom surfaces had an excellent, smooth appearance. The resulting product could be used for manufacturing an attenuation garment. Blending different latexes improved the overall appearance and strength of the final product. One such blend formulation was: Rohm & Haas TR38 HS Acrylic polymer latex0.175pounds(pH 7-8; Solids Content 50%-52%)Air Products Air Flex 920 Acrylic polymer latex0.0925pounds(pH 4 - Solids Content 55%)Tin Powder3.3poundsTungsten Powder1.1pounds This blend was mixed in a five quart Hobart mixer. The mixture was cast on release paper using a production knife over roll coating system. The material was dried at 160° F. The product of Example 4 was found to have a weight of 50.4 grams at an equivalence of 0.50 mm of lead. This weight corresponds to a weight of 0.79 pounds per square foot. The metals loading was 94.3% by weight and 67.7% by volume. The product was soft and supple and both top and bottom surfaces had an excellent, smooth appearance. This product had sufficient strength that it could be used for an attenuation garment. Preferably, excellent results have been obtained by coating the fluid mixture onto a substrate to improve tear strength. A vinyl film (PVC) approximately 0.007 inch thick was cast onto release paper. The latex blend was prepared as outlined above, and coated onto the vinyl film (still on the release paper). The casting was then dried in a convection oven. The latex formula prepared was: Rohm & Haas 1845 Styrene Acrylic copolymer latex32grams(pH 6.7, Solids Content 56%)Tin Powder150gramsTungsten Powder60grams The product of Example 5 was found to have a weight of 56.3 grams at an attenuation equivalence of 0.50 mm of lead. This weight corresponds to 0.88 pounds per square foot. The metals loading was 92% by weight and 59% by volume. Equally useful products can be obtained using as a substitute nylon, muslin, rag cloth and non-woven fabrics of several types. In this example, the addition of glycerin and water (50 parts of each) to the fluid latex mixture resulted in the final product having increased flexibility. The following formulation was prepared and knife coated onto a polyolefin non-woven substrate supplied by Crane Paper, product number BC-9. The formulation was: Rohm & Haas 1845 Styrene Acrylic copolymer latex18grams(pH 6.7 - Solids Content 56%)Air Products Air Flex 920 Acrylic polymer latex7gramspH 4 - Solids Content 55%Tin160gramsTungsten40gramsGlycerine USP0.75grams The product of Example 6 was found to have a weight of 55 grams at an attenuation equivalence of 0.50 mm of lead including the weight of the substrate. For comparison purposes and excluding the substrate, this weight corresponds to a weight of 0.86 pounds per square foot. The metals loading was 93.9% by weight and 67% by volume. The following formulation was prepared and knife coated onto a polyester non-woven, calendered substrate supplied by Crane Paper, product number RS-21. The formulation: Rohm & Haas 1845 Styrene Acrylic copolymer latex18gramspH 6.7 - Solids Content 56%Air Products Air Flex 920 Acrylic polymer latex7gramspH 4 - Solids Content 55%Tin powder160gramsTungsten powder40gramsGlycerine USP0.75grams The product of Example 7 was found to have a weight of 54 grams at an attenuation equivalence of 0.50 mm of lead, including the weight of the substrate. For comparison purposes and excluding the substrate, this weight corresponds to a weight of 0.84 pounds per square foot. The metals loading was 93.9% by weight and 67% by volume. In another example, additives can be employed so as to adjust the end physical properties and structure of the end product. In this example, Rohm & Haas dispersing aid, trade name “Accumer, an alkoxylated alkylphenol” was added to the mix as was Rohm & Haas's plastisizer “Paraplex WP-1,” to make the end products more flexible. X-ray attenuation products are compared to the lead equivalence. A formulation using these additives was: Rohm & Haas 184520gramsAir Products Air Flex 9204gramsTin150gramsTungsten55gramsAccumer0.3gramsWPI0.3grams Samples of this formulation averaged a 0.5 mm lead equivalence weight of 57 grams, or about 0.88 pounds per square foot. In a further example, excellent products can be made using a blend of natural rubber latex and other latexes. An advantage of the natural latex is that the product can be vulcanized to improve the physical properties. One such formulation uses Firestone's “Hartex 101” having a pH of 9.78 and a solids content of 62%, and includes a Vanderbilt dispersion aid, “Darvan 7” (a sodium polymethacrylate), a sulfur composition from Akreochem grade W-9944 and a zinc oxide accelerator from Akrochem, grade w-9989, is as follows: Rohm & Haas 18450.6poundsHartex 1010.4poundsTin9.2poundsDarvan 735gramsSulfur (additive)1.6gramsAccelerator (zinc oxide)2.2grams A test piece having a 0.5 mm lead equivalence weighs about 59 grams and has desirable physical properties, namely tensile strength and elasticity. In another example, in addition to using elements and compounds, alloys of attenuation materials can also be employed. A tin/lead alloy with 40 weight % tin and 60 weight % lead from Cookson Industries, grade 113918, was used in the following formulation: Rohn & Haas 18450.6poundsHartex 1010.4poundsAlloy9.13poundsDarvan 735grams The weight of the standard test piece to achieve a 0.5 mm lead equivalence was 71 grams. Whereas particular embodiments of the present invention have been described above as examples, it will be appreciated that variations of the details may be made without departing from the scope of the invention. One skilled in the art will appreciate that the present invention can be practiced by other than the disclosed embodiments, all of which are presented in this description for purposes of illustration and not of limitation. It is noted that equivalents of the particular embodiments discussed in this description may practice the invention as well. Therefore, reference should be made to the appended claims rather than the foregoing discussion of examples when assessing the scope of the invention in which exclusive rights are claimed. For mixing the filled latex dispersions of the present invention it is preferred to use a a low shear, high pumping action dispersion blade, well known to the art. In this example, a Shar vacuum dispersion mixer with a three gallon capacity mixing bowl is used. A latex premix is prepared according to the following formula: Rohm & Haas TR-38HS10poundsHartex 10110poundsDarvan 71.6poundsAmmonia 3%0.7poundsGlycerin80grams The ammonia solution is an additive serving to stabilize the final mix. The Hartex 101 latex is initially mixed with the Darvan 7, ammonia and glycerin. This combination was hand stirred using a spatula. The Rohm & Haas latex is then added to form the latex premix. The casting formulation includes: Latex premix8.8poundsTin56poundsTungsten16pounds The premix is added to the mixing bowl of the Shar mixer followed by the Tungsten powder. A vacuum of at least 26 in. Hg, is pulled on the mixing bowl and the tungsten is mixed into the latex premix for one minute. The vacuum is then broken and the tin added. After drawing a vacuum, the material is mixed to disperse the metals for a further three minutes. The mixture is cast on release paper and oven dried. The standard test piece of the final product has a weight of 58 grams, or 0.88 pounds per square foot, with a single layer thickness of 0.022 inches. After applying a latex coating of approximately 0.5 mils, to the dried sheet, the resulting product is strong with good tensile strength and elasticity. |
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claims | 1. A removable rail assembly for a spent fuel handling machine, comprising: a shim plate; a support rail coupled to the shim plate for adjusting the height level of the support rail; a removable rail guide carried by the support rail, said rail guide having a first end and a second end; a first rail joint connector supported by the rail guide for coupling the rail guide first end to a first adjacent fixed rail, the joint connector including a tongue and groove joint with a tapered parting line; and at least one jacking screw supported by the support rail and extending through the shim plate for lifting the support rail. 2. The removable rail assembly as defined in claim 1 , wherein the tongue portion of the tongue and groove joint is supported by the removable rail guide. claim 1 3. The removable rail assembly as defined in claim 1 , wherein the ends of the removable rail guide extend beyond the support rail and are supported by a rail trench. claim 1 4. The removable rail assembly as defined in claim 1 , wherein the first end of the removable rail guide is coupled to a first rail end support member and the second end of the removable rail guide is coupled to a second rail end support member. claim 1 5. The removable rail assembly as defined in claim 4 , wherein the first rail end support member is a threaded rod embedded in a structure that supports the support rail. claim 4 6. The removable rail assembly as defined in claim 1 , wherein the support rail includes an I-beam cross-section. claim 1 7. The removable rail assembly as defined in claim 1 , wherein the support rail receives an alignment pin. claim 1 8. The removable rail assembly as defined in claim 1 , wherein the rail support is embedded in a floor surface. claim 1 9. A removable rail assembly for a spent fuel handling machine, comprising: a. a support rail; b. a removable rail guide carried by the support rail; c. a rail joint connector supported by the support rail and having a tongue with a tapered parting line for coupling the removable rail guide to an adjacent fixed rail; d. a shim plate coupled to the support rail; and e. means supported by the support rail and extending through the shim plate for at least loosening the joint connector for lifting the support rail to facilitate removal of said support rail. 10. The removable rail assembly of claim 1 , further comprising a second rail joint connector supported by the rail guide for coupling the rail guide second end to a second adjacent fixed rail. claim 1 11. The removable rail assembly as defined in claim 10 , wherein the second rail joint connector is a tongue and groove joint with a tapered parting line. claim 10 12. The removable rail assembly as defined in claim 4 , wherein the second rail end support member is a threaded rod embedded in a structure that supports the support rail. claim 4 |
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039430367 | claims | 1. Fluid-cooled fast breeder reactor comprising an outer cylindrical boundary wall, a plurality of canless fuel elements and breeder material elements received within said boudnary wall and being in an array therein forming a fissionable fuel zone and a breeder material zone coaxially surrounding said fissionable fuel zone, a coolant supply system for applying fluid coolant at uniform pressure to the entire cross section within said cylindrical boundary wall, and flow guide devices extending substantially horizontally and disposed at different levels one above the other within said breeder material zone which coaxially surrounds said fissionable fuel zone, means for elastically securing the flow guide devices at alternate levels within said breeder material elements to said boundary wall, the flow guide devices at the levels intermediate said alternate levels being spaced by an annular gap from said boundary wall. 2. Fast breeder reactor according to claim 1 wherein said flow guide devices are formed of spacer supports, said flow guide devices being disposed in gaps respectively at the levels of said spacer supports for said breeder material elements and the ends of the latter, said spacer support being of such dimension as to fill the gaps between individual breeder material rods forming said elements and the end pieces of said elements to an extent that a limited longitudinal flow of the coolant along said rods is possible. 3. Fast breeder reactor according to claim 1 wherein said flow guide devices are annular in shape and are formed with radially extending heat expansion joints. 4. Fast breeder reactor according to claim 1 including devices for producing turbulent coolant flow disposed in said annular gap. 5. fast breeder reactor according to claim 4 including mounting structures for holding said flow guide devices, said mounting structures being disposed in breeder element positions and extending in axial direction through said breeder material zone. 6. Fast breeder reactor according to claim 1 wherein said flow guide devices are formed of spacer supports for said breeder material elements, said spacer supports being disposed in substantially horizontal planes. 7. Fast breeder reactor according to claim 6 wherein the spacer supports of adjacent breeder material elements abut one another elastically in a sealing manner. |
048636754 | claims | 1. An inherently safe modular nuclear power system for producing electrical power at acceptable efficiency levels using working fluids at relatively low temperatures and pressures, said system comprising: a reactor module for heating a first fluid; a heat exchanger module for transferring heat from said first fluid to a second fluid; a first piping system effecting flow of said first fluid in a first fluid circuit successively through said reactor module and said heat exchanger module; a power conversion module comprising a turbogenerator driven by said second fluid, and means for cooling said second fluid upon emergence thereof from said turbogenerator; a second piping system comprising means for effecting flow of said second fluid in a second fluid circuit successively through said heat exchanger module and said power conversion module; and a plurality of pits for receiving said modules; each of said modules being elongated and having an upper end and a lower end, and being disposed in a substantially vertical orientation with a lower portion contained in one of said pits; said reactor module and said heat exchanger module having means for connection with said first piping system near their respective upper ends; each of said modules including a tank having support means thereon enabling said tank to be installed in an associated pit from above; said modules being located side-by-side in close proximity to one another to provide compactness for the system while permitting overhead access to each of the modules without interference from any other module; said reactor module comprising a tank, a core supported within said tank and disposed near the lower end of said tank, a pool of relatively cool liquid contained within said tank surrounding said core, means to selectively permit circulation of said liquid from said pool through said core by natural convection in the event of interruption of flow of said first fluid through said reactor module while inhibiting intermixing of said liquid from said pool with said primary coolant under normal conditions, and a plurality of coolers disposed within said reactor module to remove heat from said pool; the pit which receives said reactor module being lined with a relatively impermeable material so as to provide secondary containment for said pool so that said core will remain surrounded by said relatively cool liquid in the event of a rupture of said tank; said piping systems and modules maintaining separation between said first and second fluids; said core comprising a fuel which imparts a large prompt negative temperature coefficient to the core, which inherently shuts down the reactor in the event of a large reactively insertion; said second fluid being a member of the group consisting of R-113 and R-114. 2. A system in accordance with claim 1 wherein said means for cooling said second fluid is a recuperator which cools said second fluid without change of phase, said system further comprising a condenser module, said second piping system further comprising means for effecting flow of said second fluid through said condenser. 3. A system in accordance with claim 2 wherein said means for effecting flow of said second fluid through said condenser includes a substantially horizontal straight pipe extending from said recuperator to said condenser to enable said second fluid to flow directly from said recuperator to said condenser without changing direction. 4. A system in accordance with claim 1 wherein said turbogenerator comprises a turbine and a generator supported for rotation on a common vertical shaft, and wherein said means for cooling said second fluid upon emergence thereof from said turbogenerator includes an annular tube bundle defining a central plenum directly beneath said turbine, whereby said second fluid flows downwardly from said turbine into said inlet plenum without changing direction. 5. A system in accordance with claim 4 wherein said means for cooling said second fluid upon emergence thereof from said turbine is configured so that said second fluid flows downwardly into said inlet plenum from said turbine and thence radially outwardly through said tube bundle. 6. A system in accordance with claim 1 wherein said means for cooling said second fluid is a condenser. 7. A system in accordance with claim 1 wherein said means for cooling said second fluid upon emergence thereof from said turbogenerator includes an annular tube bundle defining a central plenum for receiving said second fluid, and wherein said power conversion module is configured to enable said second fluid to flow from said turbine into said central plenum without changing direction. 8. A modular nuclear power system in accordance with claim 1 wherein said fuel comprises uranium zirconium hydride fuel. |
claims | 1. An X-ray diagnostic apparatus, comprising:an X-ray tube configured to radiate X-rays;an X-ray collimator configured to change an irradiation region of the X-rays radiated by the X-ray tube;an X-ray detector that includes a first detector and a second detector having a smaller detection area than a detection area of the first detector, and is configured to be able to detect the X-rays radiated to a fixed irradiation region, after being changed by the X-ray collimator, with the first detector and the second detector at the same time by arranging the first detector and the second detector so as to overlap in an irradiation direction of the X-rays and detecting the X-rays radiated to an overlapping region where the first detector and the second detector overlap with each other; andprocessing circuitry configured togenerate a synthesized image obtained by synthesizing a first X-ray image generated based on an output from the first detector in the fixed irradiation region, and a second X-ray image generated based on an output from the second detector in the fixed irradiation region, the synthesized image having an image size corresponding to an aspect ratio of the fixed irradiation region, andcause a display to display the synthesized image. 2. The X-ray diagnostic apparatus according to claim 1, wherein the processing circuitry is configured todetermine a side serving as a reference of the image size of the synthesized image in accordance with the aspect ratio of the fixed irradiation region, andgenerate the synthesized image obtained by synthesizing the first X-ray image and the second X-ray image with an image size corresponding to a length of the determined side. 3. The X-ray diagnostic apparatus according to claim 2, wherein the processing circuitry is configured to determine a long side of the fixed irradiation region to be a side serving as a reference of the image size. 4. The X-ray diagnostic apparatus according to claim 2, wherein the processing circuitry is configured to generate the synthesized image obtained by synthesizing the first X-ray image and the second X-ray image so that the length of the side serving as a reference of the image size of the synthesized image is matched with a length of a corresponding side of a display region of the synthesized image on the display. 5. The display method according to claim 2, comprising:generating the synthesized image obtained by synthesizing the first X-ray image and the second X-ray image so that the length of the side serving as a reference of the image size of the synthesized image is matched with a length of a corresponding side of a display region of the synthesized image on the display. 6. The X-ray diagnostic apparatus according to claim 1, wherein the second detector has a pixel size smaller than that of the first detector. 7. The X-ray diagnostic apparatus according to claim 1, wherein the processing circuitry is configured to sequentially acquire the first X-ray image and the second X-ray image, and sequentially generate the synthesized image based on the acquired first X-ray image and the acquired second X-ray image. 8. The display method according to claim 1, wherein the second detector has a pixel size smaller than that of the first detector. 9. The display method according to claim 1, comprising sequentially acquiring the first X-ray image and the second X-ray image, and sequentially generating the synthesized image based on the acquired first X-ray image and the acquired second X-ray image. 10. An X-ray diagnostic apparatus, comprising:an X-ray tube configured to radiate X-rays;an X-ray collimator configured to change an irradiation region of the X-rays radiated by the X-ray tube;an X-ray detector that includes a first detector and a second detector having a smaller detection area than a detection area of the first detector, and is configured to be able to detect the X-rays radiated to a fixed irradiation region, after being changed by the X-ray collimator, with the first detector and the second detector at the same time by arranging the first detector and the second detector so as to overlap in an irradiation direction of the X-rays and detecting the X-rays radiated to an overlapping region where the first detector and the second detector overlap with each other: andprocessing circuitry configured togenerate a synthesized image obtained by synthesizing a first X-ray image generated based on an output from the first detector in the fixed irradiation region, and a second X-ray image generated based on an output from the second detector in the fixed irradiation region, andcause a display to display the synthesized image, whereinthe processing circuitry is configured tochange a size of a display region of the synthesized image on the display in accordance with the fixed irradiation region, andcause the synthesized image to be displayed in the changed display region. 11. The X-ray diagnostic apparatus according to claim 10, wherein the processing circuitry is configured tochange at least one of a size and a position of the display region for displaying a display target other than the synthesized image on the display to change the size of the display region of the synthesized image, andcause the synthesized image to be displayed in the changed display region. 12. The X-ray diagnostic apparatus according to claim 10, wherein the processing circuitry is configured to change a size of the display region so that a size of an image obtained by the second detector is kept to be substantially constant on the display. 13. The X-ray diagnostic apparatus according to claim 10, wherein the second detector has a pixel size smaller than that of the first detector. 14. The X-ray diagnostic apparatus according to claim 10, wherein the processing circuitry is configured to sequentially acquire the first X-ray image and the second X-ray image, and sequentially generate the synthesized image based on the acquired first X-ray image and the acquired second X-ray image. 15. A display method for displaying an X-ray image generated based on an output from an X-ray detector that includes a first detector and a second detector having a smaller detection area than a detection area of the first detector, and is configured to be able to detect X-rays radiated to a fixed irradiation region, after being changed by an X-ray collimator for changing an irradiation region of the X-rays radiated by an X-ray tube, with the first detector and the second detector at the same time by arranging the first detector and the second detector so as to overlap in an irradiation direction of the X-rays and detecting the X- rays radiated to an overlapping region where the first detector and the second detector overlap with each other, the display method comprising:generating a synthesized image obtained by synthesizing a first X-ray image generated based on an output from the first detector in the fixed irradiation region, and a second X-ray image generated based on an output from the second detector in the fixed irradiation region, the synthesized image having an image size corresponding to an aspect ratio of the fixed irradiation region, anddisplaying the synthesized image on a display. 16. The display method according to claim 15, comprising:determining a side serving as a reference of the image size of the synthesized image in accordance with the aspect ratio of the fixed irradiation region, andgenerating the synthesized image obtained by synthesizing the first X-ray image and the second X-ray image with an image size corresponding to a length of the determined side. 17. The display method according to claim 16, comprising determining a long side of the fixed irradiation region to be a side serving as a reference of the image size. |
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051260980 | summary | FIELD OF THE INVENTION This invention relates to a method of straightening a bowed nuclear fuel assembly. BACKGROUND OF THE INVENTION Nuclear reactor cores contain a large number of nuclear fuel assemblies. Typically the fuel assemblies are approximately twelve feet long, eight and one-half inches square and weigh about 1,500 pounds. The fuel assemblies have top and bottom end fittings (also referred to as nozzles) and a plurality of longitudinally extending thimble tube members interconnecting top and bottom end fittings to form a skeleton framework. Typically, seven or eight transverse fuel rod support grids, are axially spaced along the thimble tube members. A plurality of fuel rods are supported in an organized array by the grids. Each bottom end fitting includes at opposing corners two positioning holes for interfacing onto core pins positioned on the bottom core plate of the nuclear reactor core so that each fuel assembly can be positioned in a predetermined location in closely spaced relation on the core plate. As many as 180 fuel assemblies are contained in some reactor cores. The fuel assemblies are closely packed under water in the reactor core and a large amount of heat-transfer surface for removal of the high power produced per unit volume is provided. Spacing of the fuel assemblies can be critical and is based on a predetermined inter-assembly water gap. The fuel assemblies contained in a reactor core are removed from the core during refueling cycles. Typically, about every eighteen months, one-third of the fuel assemblies will be replaced with new fuel assemblies. In another eighteen months, another one-third will be replaced. This cycle repeats approximately every eighteen months. During refueling, all the fuel assemblies are transferred to a separate fuel assembly storage area, also referred to as a spent fuel pit, located adjacent to the containment building surrounding the reactor core. Each fuel assembly is raised by a crane positioned in the containment building and then transferred in vertical orientation onto an upender. The upender typically is supported on narrow gauge rails. The upender is turned to orient the fuel assembly in a horizontal position, and the upender and fuel assembly thereon are transferred on the rail through a small access opening positioned in the wall of the containment building and into the spent fuel pit adjacent to the reactor core. New fuel assemblies are moved into the spent fuel pit and then transferred together with the other two-thirds of the fuel back into the reactor core by the upender. The crane in the containment building places the fuel assemblies onto the proper core pins. During reactor shut-down and start-up, the fuel assemblies change temperature. Because the zirconium alloy fuel rods contain heavy uranium pellets, the fuel rods cool and heat more slowly than the other zirconium alloy grids and thimble tube members. This differential cooling rate of the fuel rods from the thimble tube members causes an expedited contraction of the thimble tubes. Subsequent contraction of the fuel rods puts the thimble tubes in compression which results in the fuel assembly becoming bowed. This bow can become as large as 0.500 inch over the twelve foot length of the fuel assembly. This amount of bow makes it difficult to interface the bottom end fitting of the fuel assemblies with the core pins during refueling. In severe cases of fuel assembly bow, adjacent fuel assemblies already positioned on core pins can become damaged as bowed fuel assemblies are reinserted into the reactor core. As the crane moves the bowed fuel assembly into position over the core pins, the bowed fuel assembly sometimes will contact other adjacent fuel assemblies and in some cases, damage the other fuel assemblies. Additionally, a bowed fuel assembly adversely impacts the performance of the nuclear fuel reactor. The inter-assembly water gap may change resulting in higher thermal neutron flux on the outer fuel rods in the reactor. This could lead to reduced thermal margins for the fuel rod cladding and result in plant operational problems. In U.S. Pat. No. 4,678,625 to Wilson et al., a method of straightening bowed irradiated fuel assemblies is disclosed which teaches determining the length adjustment required for shortening the bowed tubular structural member and forming at least an expansion in the bowed member to shorten the length. This method of straightening bowed fuel assemblies is complex. It is more desirable to provide a more simple and less costly method of straightening the bow in a fuel assembly. SUMMARY OF THE INVENTION In accordance with the present invention, a method is disclosed of removing the bow in a nuclear fuel assembly. The fuel assembly includes top and bottom end fittings and a plurality of longitudinally extending thimble tube members interconnecting top and bottom end fittings. At least two transverse fuel rod support grids are axially spaced along the thimble tube members, and a plurality of fuel rods are transversely spaced and supported by the fuel rod support grids. In one embodiment, a weight of known magnitude is secured onto the bottom end fitting. The fuel assembly is raised with the weight secured onto the bottom end fitting so that the weight exerts a downward, longitudinal force onto the fuel assembly for eliminating the compressive stresses previously imparted in the thimble tubes straightening the fuel assembly. In a second embodiment, one of the end fittings is held stationary. The other end fitting is pulled for exerting a longitudinally extending force onto the fuel assembly for eliminating the compressive stresses previously imparted in the thimble tubes straightening the fuel assembly. This can be accomplished when the fuel assembly is moved onto the upender used in transporting fuel assemblies into the containment building. The bottom end fitting is secured to the upender and the fuel assembly is pulled with a predetermined amount for straightening the fuel assembly. In the method of the present invention, a fuel assembly is transferred from a fuel assembly storage area, i.e., the spent fuel pit, and onto the upender. The upender is moved into the containment building where it is upended so that the fuel assembly is positioned in a vertical orientation. In the first embodiment the fuel assembly is moved onto a weight positioned in the containment building and secured thereto. The fuel assembly then is lifted. Alternatively, the bottom end fitting of the fuel assembly is pulled upward while the bottom end fitting is secured to the upender for straightening the fuel assembly. |
abstract | A ventilation system operating method for a service personnel-accessible operations room or control room in a nuclear plant or nuclear power plant enables a supply of decontaminated fresh air at least for a few hours in the event of serious incidents involving the release of radioactive activity. The content of radioactive inert gases in the fresh air supplied to the operations room should be as low as possible. Therefore, an air supply line is guided from an external inlet to the operations room, a first fan and a first inert gas adsorber column are connected into the air supply line, an air discharge line is guided from the operations room to an external outlet, a second fan and a second inert gas adsorber column are connected into the air discharge line, and a switchover device interchanges the roles of the first and second inert gas adsorber columns. |
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claims | 1. An electromagnetic wave-absorbing composition comprising a curable organopolysiloxane as a base polymer and a magnetic powder coated with electrically insulating inorganic submicron fines in an RF thermal plasma method, dispersed therein,said composition having an Asker C hardness of up to 80 when cured. 2. The composition of claim 1 wherein the magnetic powder is of a magnetic metal material containing at least 15% by weight of iron. 3. The composition of claim 1 which exhibits a breakdown voltage of at least 50 V when molded into a sheet of 1 mm thick. 4. An electromagnetic wave-absorbing composition comprising a curable organopolysiloxane as a base polymer, and a magnetic powder coated with electrically insulating inorganic submicron fines in an RF thermal plasma method and a heat conductive powder, both dispersed therein, said composition having an Asker C hardness of up to 80 when cured. 5. The composition of claim 4 wherein the magnetic powder is of a magnetic metal material containing at least 15% by weight of iron. 6. The composition of claim 4 which exhibits a breakdown voltage of at least 50 V when molded into a sheet of 1 mm thick. 7. The composition of claim 4 wherein the base polymer is a curable organopolysiloxane. 8. The composition of claim 4 which has an Asker C hardness of up to 80 when cured. 9. A sheet obtained by molding and heat curing an electromagnetic wave-absorbing composition comprising a curable organopolysiloxane as a base polymer and a magnetic powder coated with electrically insulating inorganic submicron fines in an RF thermal plasma method, dispersed therein, said composition having an Asker C hardness of up to 80 when cured. 10. A sheet obtained by molding and heat curing an electromagnetic wave-absorbing composition comprising a curable organopolysiloxane as a base polymer, and a magnetic powder coated with electrically insulating inorganic submicron fines in an RF thermal plasma method and a heat conductive powder, both dispersed therein, said composition havening an Asker C hardness of up to 80 when cured. 11. The composition of claim 1 or 4 wherein the composition when cured has a thermal conductivity of at least 1.0 W/mk. 12. A sheet of claim 9 or 10 wherein the composition when cured has a thermal conductivity of at least 1.0 W/mk. 13. The composition of claim 1 or 4 wherein the curable organopolysiloxane has at least two alkenyl radicals per molecule and has the average compositional formula (1)R1aSiO(4−a)/2 (1)wherein, R1, which may be the same or different, stands for substituted or unsubstituted monovalent hydrocarbon radicals having 1 to 10 carbon atoms, and the subscript “a” is a positive number from 1.98 to 2.02, and the composition further comprises a combination of an organohydrogenpolysiloxane and an addition reaction catalyst or an organic peroxide so that a silicone rubber or silicone gel having an Asker C hardness of up to 80 is obtained when cured. 14. The sheet of claim 9 or 10 wherein the curable organopolysiloxane has at least two alkenyl radicals per molecule and has the average compositional formula (1)R1aSiO(4−a)/2 (1)wherein, R1, which may be the same or different, stands for substituted or unsubstituted monovalent hydrocarbon radicals having 1 to 10 carbon atoms, and the subscript “a” is a positive number from 1.98 to 2.02, and the composition further comprises a combination of an organohydrogenpolysiloxane and an addition reaction catalyst or an organic peroxide so that a silicone rubber or silicone gel having an Asker C hardness of up to 80 is obtained when cured. |
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046631186 | description | DESCRIPTION As shown in the longitudinal cross section view of FIG. 1, a fuel assembly 11 includes a plurality of elongated fuel rods 12 supported between a lower tie plate 13 and an upper tie plate 14. Although not shown herein, ordinarily a plurality of fuel rod spacers are positioned intermediate the lower and upper tie plates for lateral support of the fuel rods 12. Each of the fuel rods 12 comprises an elongated tube containing the fissile fuel, usually in the form of pellets, sealed in the tube by lower and upper end plugs 16 and 17. Lower end plugs 16 are formed with a taper for registration and support in support cavities 18 formed in the lower tie plate 13. Upper end plugs 17 are formed with shanks 19 which register with support cavities 21 in the upper tie plate 14. Several of the support cavities 18 (for example selected ones of the edge or peripheral cavities, such as a cavity 18') in the lower tie plate 13 are formed with threads to receive fuel rods having threaded lower end plugs, such as an end plug 16'. The shanks 19' of the upper end plugs of these same fuel rods are elongated to pass through their respective cavities 21 in the upper tie plate 14 and are formed with threads to receive threaded retaining nuts 22. Springs 23 mounted on the shanks 19 urge the upper tie plate 14 upward with respect to the fuel rods 12. In this manner the lower and upper tie plates and the fuel rods are formed into a unitary structure or fuel bundle, the upper tie plate 14 being formed with an upwardly extending handle or bail 20 for handling of the fuel assembly. The fuel assembly is surrounded by a thin-walled tubular flow channel 24 of substantially square cross section which is open at its upper end. The fuel assembly 11 is a sliding fit in the flow channel 24 so that it readily can be inserted and removed. At its upper end the channel 24 may be formed with holes 25 or the like for handling. At its bottom end the flow channel 24 is secured, as described in detail hereinafter, to a tapered nose piece 26 adapted to fit into a socket of the lower core support structure (not shown). The lower part (not shown) of nose piece 26 is formed with openings to receive pressurized coolant which is directed by the nose piece 26 and the flow channel 24 upward past the fuel rods 12 (see U.S. Pat. No. 3,697,376). The nose piece 26 is formed with a shoulder 27 upon which the lower tie plate 13 rests for support of the fuel assembly 11. An upstanding rim 28 surrounds and provides lateral location of the lower tie plate 13. Typically the flow channel 24 is formed of a material having a low neutron absorption cross section such as an alloy of zirconium while the nose piece 26 is formed of a corrosion resistant iron alloy such as stainless steel. As a practical matter such different materials cannot be welded together. Previous channel-to-nozzle attachments include attachment of the channel directly to the nozzle with screws or rivets as shown in U.S. Pat. No. 3,697,375. Although simple, the drawback of this arrangement is the possibility that the screws or rivets may loosen or be overstressed and fail because of differential thermal expansion of the flow channel and nozzle due to their different material. The drawbacks of prior arrangements are avoided by the channel-to-nozzle attachment of the present invention which, as shown in FIGS. 1-3, includes tapered attachment bars 29 secured to the inside lower edges of the channel 24 and fitted into similarly tapered grooves 31 formed in the outside surfaces of the nozzle 26. The material of the attachment bars 29 is selected to have the same or a very similar thermal coefficient of expansion as the material of the channel 24. Typically, the channel 24 and the attachment bars 29 are formed of an alloy of zirconium having a thermal coefficient of expansion of about 3.2.times.10.sup.-6 inch per inch per degree F. while the stainless steel of the nozzle 26 has a substantially greater thermal coefficient of expansion of about 9.45.times.10.sup.-6 inch per inch per degree F. The temperature range experienced by these parts varies from room temperature to an operating temperature in the reactor core of 600 degrees F. or greater. As the temperature increases it is evident that the channel 24 expands, i.e. the distance D.sub.c from the center line CL.sub.v to the inside surface of the channel 24 increases. Also the width W of the attachment bars 29 increases. At the same time, the nozzle 26 expands outward a greater amount and the width of the tapered grooves 31 increases a greater amount. If the channel 24 was firmly attached to the nozzle 26, as in the prior art arrangement, the greater expansion of the nozzle 26 would cause the lower end of the channel 24 to be bent outward thereby stressing this lower end and the attachment screws or rivets. However, with the illustrated attachment arrangement of the present invention, the tapered attachment bars 29 simply move further into the more rapidly expanding tapered grooves 31, a clearance space C being provided to allow this inward movement. With proper selection of the angle of taper A the bars 29 can move more or less deeply into the grooves 31 as differential thermal expansion occurs, without any bending of the lower end of the channel 24 and with the bars 29 remaining tightly fitted in the grooves 31. The optimum angle of taper is illustrated graphically in FIG. 1. A part (the nozzle 26) under thermal expansion will change shape along lines (such as lines 32 and 33) radiating from a center point 34. Thus the grooves 31 change size along the lines 32 and 33 and, therefore, the lines 32 and 33 define the optimum angle of taper A, i.e. the angle between the opposite tapered surfaces of the grooves 31. In other words, the angle of the taper A is selected such that the tapered upper surface of the groove 31 on one side is in the same plane as the tapered lower surface of the groove 31 on the opposite side of the nozzle 26. While in the usual case the nozzle 26 has a greater thermal coefficient of expansion than the channel 24 and attachment bars 29, the invention is not so limited and can be used with any combination of different materials. Mathematically, the optimum angle of taper A can be determined as follows with reference to FIG. 3. The change in part size due to temperature change dD is given by the following relationship: EQU dD=a dT D (1) where: a is the thermal coefficient of expansion. PA0 dT is the temperature range. PA0 D is the length of part. PA0 Y is the axial (vertical from CL.sub.r) thermal growth of bar 29. PA0 X' is the radial thermal growth of nozzle 26. PA0 Y' is the axial thermal growth of groove 31. PA0 a.sub.z is the termal coefficient of expansion of the material of the channel 24 and bars 29. PA0 a.sub.s is the thermal coefficient of expansion of the material of the nozzle 26. PA0 D.sub.c is the distance from the vertical centerline CL.sub.v to the inside surface of channel 24. PA0 D.sub.n is the distance from the centerline CL.sub.v to the outside surface of nozzle 26. PA0 W is the distance from radial centerline CL.sub.r to point P. PA0 D.sub.n approximates D.sub.c =D. For any point P on the interface line between the bar 29 and groove 31. ##EQU1## where: X is the radial (lateral from CL.sub.v) thermal growth of bar 29. From relationship (1): EQU X=a.sub.z dT D.sub.c EQU X'=a.sub.s dT D.sub.n EQU Y=a.sub.z dT W EQU Y'=a.sub.s dT W where: Substituting in relationship (2): ##EQU2## Assuming that D.sub.n and D.sub.c are insignificantly different then: Thus simplifying: ##EQU3## In a practical example of the invention for use in a typical BWR (boiling water reactor), W=0.3 inches (7.62 mm) and D=2.63 inches (66.8 mm). Therefore ##EQU4## As shown in FIGS. 1 and 2, the attachment bars 29 may be secured to the lower end of the flow channel 24 by flat head screws 36. Alternatively, rivets or welding may be used for this purpose. As illustrated in FIG. 2, the ends of the grooves 31 are shown rounded since this configuration results from the tapered rotary cutting tool normally used to make the grooves 31. Although not shown, the ends of the attachment bars 29 may be similarly rounded but, in any event, the length L of the bars 29 is selected to be slightly less (depending on manufacturing tolerances) than the length of the grooves 31. This is to allow the bars 29 to find their natural and laterally unrestrained position in the grooves 31. With reference to FIG. 2, the channel 24 is assembled to the nozzle 26 by placing the attachment bars 29 in the grooves 31, slipping the lower end of the channel 24 over the bars 29 with screw holes in alignment, and then inserting and tightening the screws 36. Thus what has been described is a flow channel-to-nozzle attachment which remains tightly fitted with temperature changes without stressing the parts. An additional benefit of this arrangement is excellent control of bypass leakage flow (discussed in U.S. Pat. No. 3,697,376). The only open or leakage flow area is between the nozzle and channel at the four corners and this area tends to remain constant throughout design life. |
046438670 | description | DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Referring now to the drawings, and more particularly to FIG. 1 thereof, there is shown a first embodiment of the new and improved nuclear reactor refueling machine of the present invention as generally indicated by the reference character 10. The refueling machine 10 is seen to include, in part, a vertically disposed outer stationary mast 12 upon the lower end of which there is mounted a support sleeve 14. The sleeve 14 is annularly disposed about the mast 12 so as to completely encircle the same, and flanged edge portions 16 of the sleeve 14 are secured together in a butt-contact mode by means of suitable bolt fasteners 18. The stationary mast 12 has conventionally mounted thereon three roller bracket assemblies 20 which are equiangularly disposed about mast 12 in a circumferential array, although only two of the roller bracket assemblies 20 are shown in this figure. The roller bracket assemblies 20 project radially outwardly of mast 12, and also extend radially inwardly of mast 12 so as to mount thereon suitable roller mechanisms, not shown, internally of the stationary mast 12 for operatively engaging the refueling machine inner mast or gripper tube, also not shown, for facilitating the telescopic movement of the inner mast or gripper tube relative to the outer stationary mast during performance of refueling operations. Sleeve 14 is therefore provided with suitable apertures or windows 22 so as to accommodate the locations of the roller bracket assemblies 20 when the sleeve 14 is mounted upon the stationary mast 12. In accordance with the particularly unique features of the fuel assembly scanning system and/or fuel assembly-reactor core alignment system of the present invention, sleeve 14 has four, upwardly extending finger portions 23 upon which are respectively mounted four television cameras 24 by means of suitable brackets 26, although only three camera mounting systems are disclosed in this figure. The cameras 24 are oriented vertically with their axes disposed parallel to the axis of the stationary mast 12 and with the camera lenses oriented vertically downwardly. The cameras 24 are also disposed in a circumferential array about the stationary mast 12, and are substantially equiangularly spaced, although the accommodation of the existing roller bracket assemblies 20 of the otherwise conventional refueling machine may dictate a slight modification of the precise angular spacing or separation between adjacent television camera systems. Each camera 24 has operatively associated therewith a respective light source 28, and consequently, the scanning system of the present invention will include four light sources 28 substantially equiangularly disposed in a circumferential array about the longitudinal axis of stationary mast 12, although only one light source 28 is shown in FIG. 1. Each light source 28 is secured to the lower end of support sleeve 14 by means of suitable brackets 30 and serves to project its light beam in a substantially horizontal direction transverse or perpendicular to the longitudinal axis of stationary mast 12 in order to illuminate a sector portion of a reactor core fuel assembly 32 of at least 90.degree.. The fuel assembly 32 and its grid strap 34 are illustrated as being retracted into the stationary mast 12 by means of the inner mast or gripper tube, not shown, as would be the case during a refueling operation. In addition to the cameras 24 and the light assemblies 28, the scanning system of the present invention is completed by the further provision of four mirror assemblies 36 secured to the lower end of support sleeve 14 by suitable bracket assemblies 38. The mirror assemblies 36 are disposed about the axis of stationary mast 12 in a substantially equiangularly array, however, for clarity purposes, only one mirror assembly is illustrated in FIG. 1. Each of the mirror assemblies 36 is disposed directly beneath its respective television camera 24, and is inclined with respect to a horizontal plane at an angle of 45.degree.. In this manner, the sector portion of the reactor core fuel assembly 32 illuminated by means of the corresponding light source 28 is able to be visually scanned by means of the particular mirror assembly 36 and the scanned image transmitted to the respective television camera 24. Each camera assembly 24 is of course provided with suitable power and signal cable means 40 whereby the images seen by the camera assemblies 24 as transmitted by the mirror assemblies 36 can be further transmitted to television monitors, not shown in FIG. 1, which may be located at a remote location for viewing by the refueling machine operator or personnel, such as, for example, upon the refueling machine trolley, also not shown. It is to be appreciated that while the mirror assembly 36 shown in FIG. 1 is in fact the particular mirror assembly operatively associated with the particular camera assembly 24 shown in the extreme right portion of FIG. 1, the light source assembly 28 shown in FIG. 1 is not the corresponding light source assembly for the illustrated mirror assembly 36 and the right-most camera assembly 24, but is operatively associated with the camera assembly 24 which is illustrated in the extreme left portion of FIG. 1, its corresponding mirror assembly having been omitted for clarity purposes. Similarly, the light source assembly operatively associated with the illustrated mirror assembly 36 and the right-most camera assembly 24 has also been omitted from FIG. 1 for clarity purposes. It is lastly to be appreciated that while the camera and mirror assemblies 24 and 36, respectively, are co-axially aligned, each respective light source assembly 28 is angularly offset in the circumferential direction so as to properly illuminate the particularly desired sector of the reactor core fuel assembly 32 for scanning by the respective mirror assembly 36. In operation, it will be readily understood that during the performance of a refueling operation, the refueling machine will serve to remove a fuel assembly 32 from the reactor core, and it is desired to scan the entire external surface area of the fuel assembly 32 in order to detect or determine the existence of any damage or defects upon the fuel assembly 32 or its associated grid strap 34. The particular fuel assembly 32 may in fact be one which is to be entirely removed from the reactor core for refueling with fresh or new fuel, or simply one which is being transferred from one section of the reactor core to another section thereof. In either instance, the fuel assembly 32 will have been grasped by means of the refueling machine inner mast or gripper tube, not shown, and its associated gripper mechanisms, also not shown, and hoisted vertically out from the reactor core so as to be retracted within the outer stationary mast 12 of the refueling machine. As the fuel assembly 32 is moved vertically upwardly as denoted by arrow A, successive axial portions of the fuel assembly 32 will be continuously scanned by means of the light-mirror-camera system of the present invention whereby any defects or damage existing upon the external surface of the fuel assembly 32 or grid strap 34 will be able to be viewed by means of the refueling machine operator or personnel upon their television monitors. In view of the fact that the scanning system of the present invention includes four substantially equiangularly spaced, circumferentially arranged scanner assemblies, each capable of viewing a circumferential sector of the fuel assembly 32 of at least 90.degree., the entire circumferential surface area of the fuel assembly is able to be scanned. In lieu of utilizing the camera system of the present invention for its scanning operation, or in addition to the use of such apparatus in such an operational mode, the camera system of the present invention may also be utilized to facilitate the insertion of either a new or transferred fuel assembly 32 into an awaiting spacial location within the reactor core. In accordance with such an operational mode, the mirror assemblies 36 are simply removed and the light assemblies 28 directionally re-oriented so as to project their light beams downwardly for illumination of the reactor core. In this manner, the television cameras 24 can view the illuminated core, and in particular a core space into which the fuel assembly 32 may be inserted when moved in the vertically downward direction as denoted by the arrow B. Referring now to FIGS. 2-4, a second embodiment of the present invention is disclosed, and it is noted that corresponding parts of the system of FIGS. 2-4, relative to those of the system of FIG. 1, are denoted by the same reference characters except that all of the reference characters are in the 100 series. The refueling machine is generally designated by the reference character 100 and is seen to include the outer stationary mast 112 which is suspendingly supported from the refueling machine trolley 150 by means of a support mast 152. The trolley 150 is schematically illustrated as being movable along a suitable track system 154, and atop support mast 152 there is disposed the hoist drive system 156 for the inner mast or gripper tube, not shown, of the refueling machine. In lieu of the camera, light, and mirror assemblies 124, 128, and 136, respectively, being secured to or mounted upon a support sleeve as in the first embodiment of FIG. 1, the various assemblies are mounted upon a support module or framework which is suspendingly supported upon the lower end of the refueling machine outer mast 112 by means of two stainless steel support cables 158, only one of which is shown in FIG. 2. The cables 158 are routed vertically upwardly upon opposite sides of the outer mast 112 so as to pass over a first set of sheaves 160 mounted upon the upper end of mast 112 by suitable support bands 162, and a second set of sheaves 164 mounted upon one end of the bottom deck of trolley 150. The cables 158 then continue upwardly so as to be secured to two hand-operated winches 166 which are mounted atop trolley 150. The power and signal cables 140 for the television cameras 124 are similarly routed upwardly along mast 112 by being intertwined with the support cables 158, and ultimately, cables 140 are operatively connected to the television monitors and video tape recorder apparatus disclosed at 168 upon the refueling machine trolley 150. The basket-type support module or framework upon which the camera, light, and mirror assemblies 124, 128, and 136, respectively, are mounted is seen to include an upper annular ring member 170 circumferentially surrounding the outer mast 112, and a lower annular ring member 172 similarly circumferentially surrounding the outer mast 112, the ring members 170 and 172 being fixedly secured together by means of five substantially vertical, circumferentially spaced struts or columns 174. As best seen in FIG. 3, four of the five struts 174 serve to mount the television cameras 124 thereon by means of suitable brackets 126. It is to be readily appreciated that by means of the relatively easy movement of the basket-type framework along mast 112 as dictated by control of the winches 166 and the support cables 158, the positioning of the framework upon the lower end of mast 112 may be efficiently controlled from the remote location of the operator or personnel trolley 150. Still further, should maintenance, repair, or replacement of any one of the camera, light, or mirror assemblies 124, 128, or 136, respectively, prove to be necessary, the entire framework may be simply removed from the lower end of mast 112 and hoisted vertically upwardly out of the reactor core cavity water without the necessity of dewatering the cavity or lowering the water level thereof. In order to accomplish such an operation in a remote controlled manner, an aligning fixture or workholder 176 is disposed at a position laterally off to one side of the reactor core and at a sufficient depth below the lower end of stationary mast 112 so as to permit the basket-type framework 178 to be lowered relative to mast 112 until the same is freed therefrom. In particular, the trolley 150 would be initially moved along its track 154 until the mast 112 was co-axially aligned with fixture or workholder 176. The winch drives 166 would then be operated so as to lower the framework 178 onto the fixture or workholder 176. The support cables 158 would then be disengaged from the sheaves 160 disposed upon mast 112, and subsequently, the trolley 150 would then be moved back toward the right, as viewed in FIG. 2, toward its initial illustrated position. The winch drives 166 may then be operated so as to vertically lift the basket framework 178 out from the reactor core cavity water in order that the necessary repair, maintenance, or replacement work can be performed. Re-mounting of the framework 178 upon the mast 112 is of course to be performed in a similar but reverse operational mode. As was the case with the first embodiment of the present invention, the mirror assemblies 136 of the second embodiment may also be removed from the framework 178 and the light assemblies 128 directionally re-oriented so as to project their light beams vertically downwardly for illumination of the reactor core in order to facilitate the insertion of a fuel assembly within an awaiting spacial location within the reactor core. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein. |
abstract | An anti-scatter device for suppressing scattered radiation includes a plurality of x-ray absorbing layers. The anti-scatter device further includes a plurality of spacer layers, such that each spacer layer is arranged between any two of the plurality of x-ray absorbing layers in order to hold each of the x-ray absorbing layers in a pre-defined orientation. Furthermore, each of the spacer layers includes a plurality of unsealed voids to reduce the absorption of x-rays incident on at least a portion of each of the spacer layers. |
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046648810 | summary | BACKGROUND OF THE INVENTION The present invention pertains to the fields of zirconium base alloys and their use in water reactor fuel rod cladding. It is especially concerned with zirconium base alloys having properties which minimize the adverse effects of pellet-clad interaction (PCI) in water reactor fuel elements. The use of cladding tubes made entirely of a high zirconium alloy has been the practice in the water reactor industry. Examples of common alloys used are Zircaloy-2, Zircaloy-4 and zirconium-2.5 w/o niobium. These alloys were selected based on their nuclear properties, mechanical properties, and high-temperature aqueous-corrosion resistance. The history of the development of Zircaloy-2 and 4, and the abandonment of Zircaloy-1 and 3 is summarized in: Stanley Kass, "The Development of the Zircaloys," published in ASTM Special Technical Publication No. 368 (1964) pp. 3-27. This article is hereby incorporated by reference. Also of interest with respect to Zircaloy development are U.S. Pat. Nos. 2,772,964; 3,097,094; and 3,148,055. Most commercial chemistry specifications for Zircaloy-2 and 4 conform essentially with the requirements published in ASTM B350-80, (for alloy UNS No. R60802 and R60804, respectively) for example. In addition to these requirements the oxygen content for these alloys is required to be between 900 to 1600 ppm but typically is about 1200.+-.200 ppm. It has been a common practice to manufacture Zircaloy cladding tubes by a fabrication process involving: hot working an ingot to an intermediate size billet, or log; beta solution treating the billet; machining a hollow billet; high temperature alpha extruding the hollow billet to a hollow cylindrical extrusion; and then reducing the extrusion to substantially final size cladding through a number of cold pilger reduction passes, having an alpha recrystallization anneal prior to each pass. The cold worked, substantially final size cladding is then final annealed. This final anneal may be a stress relief anneal, partial recrystallization anneal or full recrystallization anneal. The type of final anneal provided, is selected based on the designer's specification for the mechanical properties of the fuel cladding. One problem that has occurred in the use of fuel rods utilizing the aforementioned cladding has been the observation of cracks emanating from the interior surface of the cladding which is placed under additional stress by contact with thermally expanding oxide fuel pellet fragments. These cracks sometimes propagate through the wall thickness of the cladding destroying the integrity of the fuel rod and thereby allowing coolant into the rod and radioactive fission products to contaminate primary coolant circulating through the reactor core. This cracking phenomena, is generally believed to be caused by the interaction of irradiation hardening, mechanical stress and fission products, producing an environment conducive to crack initiation and propagation in zirconium alloys. Zircaloy fuel cladding tubes having a zirconium layer bonded to their inside surface have been proposed as being resistant to the propagation of cracks initiated at the interface between the fuel pellet and cladding during water reactor operation. Examples of these proposals are provided by U.S. Pat. Nos. 4,372,817; 4,200,492; and 4,390,497. The zirconium liners of the foregoing patents have been selected because of their resistance to PCI crack propagation without consideration of their resistance to aqueous corrosion. If the cladding should breach in the reactor, allowing coolant inside the cladding, it is expected that the aqueous corrosion resistance of the liner will be vastly inferior to that of the high zirconium alloy making up the bulk of the cladding. Under these conditions the liner would be expected to completely oxidize thereby becoming useless, relatively rapidly, while leading to increased hydride formation in the zirconium alloy portion of the cladding, thereby comprising the structural integrity of the zirconium alloy. This degradation of the cladding could lead to gross failure with significantly higher release or uranium and radioactive species to the coolant. The present inventors have proposed the following alloy barrier fuel cladding design which addresses this failing of the aforementioned designs. It is submitted that the following zirconium base alloys will be particularly effective as a barrier to the propagation of PCI related cracks when they are metallurgically bonded in a thin fully recrystallized layer of at least about 0.003 mils in thickness to the inside surface of water reactor fuel cladding tubes composed of conventional zirconium base alloys. These PCI resistant alloys in accordance with the present invention contain: 1. About 0.1 to 0.6 weight percent tin; PA0 2. About 0.07 to 0.24 weight percent iron; PA0 3. About 0.05 to 0.15 weight percent chromium; PA0 4. Up to about 0.05 weight percent nickel. PA0 5. The balance of the alloy consists essentially of zirconium except for incidental impurities including oxygen which is limited to less than about 350 ppm. Within the above composition range it is preferred that the tin content be held to about 0.2 to 0.6 wt. %, and most preferably about 0.3 to 0.5 wt. %. It is also preferred that the total content of incidental impurities be limited to less than about 1500 ppm and more preferably less than 1000 ppm. In addition, it is preferred that the oxygen and nitrogen contents be limited to less than about 250 ppm and about 40 ppm, respectively. More particularly, the alloys shown in Table I are submitted to be particularly well suited for use as fuel element PCI barriers. These Table 1 alloys may, of course, be modified in accordance with aforementioned preferred teachings with respect to tin, oxygen, nitrogen and total incidental impurity content. TABLE I ______________________________________ Preferred Preferred Broad Range Range I Range II Element (wt. percent) (wt. percent) (wt. percent) ______________________________________ Sn 0.1-0.6 0.1-0.6 0.1-0.6 Fe 0.04-0.24 0.18-0.24 0.04-0.20 Cr 0.05-0.15 0.07-0.13 0.05-0.15 Ni .ltoreq.0.05 <0.007 0.03-0.05 Zr Balance* Balance* Balance* O <350 ppm <250 ppm <250 ppm N <40 ppm <40 ppm <40 ppm ______________________________________ *Zirconium constitutes the balance of these alloys with the exception of incidental impurities (including oxygen and nitrogen) which are kept belo about 1500 ppm, total. The preceding and other aspects of the present invention will become more apparent upon review of the drawings in conjunction with the detailed description of the invention which follows below. |
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claims | 1. An X-ray micro-CT system with multiple sources for dynamic and volumetric imaging of small animals. 2. The system of claim 1 , wherein filtered backprojection type reconstruction programs are used that make use of a generalized half-scan weighting scheme, such as what we described above or modified in the same spirit. claim 1 3. The system of claim 2 , wherein dedicated hardware/workstation may be used for accelerated data preprocessing, image reconstruction and/or image visualization. claim 2 4. The system of claim 3 , wherein any interventional procedure may be performed that is guided by the images observed or derived. claim 3 5. The system of claim 4 , wherein advanced data acquisition components and/or systems are integrated for desirable imaging performance. claim 4 6. The system of claim 5 , wherein Internet computing/communication techniques may be applied to enhance the overall utilities of the system. claim 5 7. The system of claim 6 , wherein other relevant physiologic device and measures may be used in any synergic fashion. claim 6 |
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048184705 | description | Referring to FIG. 1, a reactor R is illustrated adjacent a holding pool P. A steam separator S is shown removed from the reactor vessel R and placed within the holding pool. Man M manipulates a shoe S at the end of a long pole 14. Shoe S contains a flat bottom with an upwardly exposed piezoelectric device. As will hereinafter more fully appear, manipulation of pole 14 places the shoe S with the upwardly exposed piezoelectric device at the bottom and immersed end of shroud hold down bolt B. Consequently, an ultrasonic test may be conducted from the bottom immersed radioactive portion of the bolt to and toward the upper end of the bolt in the holding pool P. It will be appreciated that the testing apparatus is flexible; testing of the bolts while the steam separator is in the reactor vessel may as well occur. Referring to FIGS. 2A and 2B, the prior art shroud hold down bolt B can be understood. In pertinent part for the purposes of this application, shroud hold down bolt consists of two elongate members. First, there is an inner tension member 20. Inner tension member 20 is constructed of stainless steel and extends the full length of the bolt. Tension member 20 includes a rectangular lug at the bottom thereof which is roughly rectangular in bottom plan view. (See FIG. 2B.) Lug L at the ends of its rectangular section extends beyond the side edges of the inner tension member 20. The side edges 22, 24 of this rectangular lug engage brackets on the shroud 30 overlying the reactor core. The bolt also includes an outer compression tube or member 26 surrounding tension member 20. Compression member 26 compresses downwardly onto the lower portion of the steam separator at a collar 28. The interaction between the lug L and the collar 28 is easy to understand. Specifically, and when the bolt is tightened lug L moves upwardly to and toward collar 28. Lug L, however, is attached underneath a bracket on the reactor shroud. Collar 28 rides on the lower portion of the steam separator. When the bolt is tightened, the steam separator is pushed down onto the shroud bracket. Consequently, attachment of the steam separator to the shroud occurs. As pertinent to the disclosure herein, collar 28 has a sleeve 40 directly fastened to the collar and extending below the collar to and towards lug L. Sleeve 40 is apertured with a window W. Window W includes a lower notch N. Rod 20 is transpierced with a pin P. Pin P protrudes outwardly from the side of shaft 20 through the window W. It is the action of pin P in moving into and out of notch N which causes lug L to move to and from an unlocked position. Simply stated, a mechanism M effects loosening and tightening of the bolt B utilizing a prior art thread driven apparatus. When mechanism M loosens lug L with respect to collar 28, pin P falls downwardly in window W. This downwardly falling disposition occurs until such time as lug L clears the lower portion of the bracket 30 attached to the shroud of the reactor R. Once lug L has cleared the bracket, rectangular lug L rotates until radial alignment to the steam separator occurs. This rotation of the rectangular lug L into radial alignment also aligns pin P directly over notch N. Further loosening of the bolt continues. This loosening continues until the pin P moves downwardly into and within notch N. Once this occurs, lug L is held in the unlatched position. The importance of such a mechanism can be easily understood. Assuming there are 48 bolts securing a steam separator to a reactor shroud 30, all must be unlatched before any upward removal movement of the steam separator S can occur. If one or two bolts remain secured, the reader will understand the damage to the bolts, steam separator or reactor shroud could well occur in the lifting process. It has been emphasized that sleeve 40 contributes to a latent defect in the rod 20. Specifically. and due to welding and other construction of the rod 20, intergranular stress corrosion cracking has been known to occur underneath sleeve 40. When such cracking occurs, sleeve 40 obscures from view the resultant cracks. Moreover, the pin P co-acting with the window W and the notch N hold and maintain the lug L to the bolt B. Simply stated, even where the bolt B at tension member 20 is cracked through, the defect is latent. It will be understood that lug L is highly radioactive. Referring to FIG. 1, the reader can see that this lug is immediately adjacent the core C of the reactor. Having set forth the problem environment, the solution to the problem can now be set forth with respect to FIGS. 3, 4, and 5. Referring to the perspective view of FIG. 3, shoe S is illustrated. The shoe includes a rectangular block shaped member 50 configured with a rectangular sectioned concavity 52. Just as lug L is rectangular in section (see FIGS. 2A and 2B), cavity 52 within shoe 50 is also rectangular in complementary section. The cavity 52 includes a bottom surface 54. Configured centrally of the bottom surface 54 and upwardly exposed for contact at the bottom of the lug is a piezoelectric device 56. This piezoelectric device is placed within a defined aperture and is suitably connected by wires 58 to instrumentation (not shown). It will be remembered that shoe S is remotely manipulated some 20 feet from the users. Consequently, the shoe is provided on all surfaces adjacent cavity 52 with gathering surfaces G. These gathering surfaces enable the device to conveniently find, slide onto, and fit lug L. Once shoe S is in place over a lug L, a clamp member C at a defined grove 62 mate to tension member 20 immediately overlying rectangular lug L. Clamp member C moves downwardly onto and over shaft 20 at groove 20 until contact with the top of the rectangular lug L occurs. Such downward movement is actuated about shoe shaft 60 by a pneumatic cylinder 70. Such movement traps lug L within the cavity against the piezoelectric device 56. Thereafter, ultrasound testing of the shroud bolt can occur. Referring to FIG. 4, a shoe S is shown adjacent a lug L with a pole 14 manipulating the shoe onto the end of the lug L. Attachment of the pole to the shoe S can be easily understood. The pole 14 includes a shaft 64. Shaft 64 on the pole 14 threads into an L shaped notch on tube 66 filling over pole 14 and attached to shoe S. Consequently, shoe S can be remotely manipulated onto and off of rectangular lug L for the test herein described. Referring to FIG. 5, shoe S is shown clamping lug L onto the piezoeleotric device (hidden from view). Testing of the shroud bolt can occur. |
053274695 | claims | 1. An arrangement for the underwater storage of hazardous waste characterized in that the arrangement includes at least one substantially cylindrical concrete body (1) provided with a single central storage cavity (3) for accommodating and enclosing waste, and a plurality of ballast chambers (4) which are located in the vicinity of and within the cylindrical surface of said body and distributed around the circumference thereof and which can be filled to varying degrees with water and the total volume of which is such as to enable the body to be brought to a water-buoyant state by emptying said ballast chambers. 2. An arrangement according to claim 1, characterized in that the concrete body (1) is provided with a plurality of inner cooling channels (5) which extend substantially in an axial direction in spaced relationship around the circumference of said body and the respective ends of which channels open in the outer surface of the concrete body. 3. An arrangement according to claim 2, characterized in that the cooling channels (5) are located between the ballast chambers (4) and the storage cavity (3). 4. An arrangement according to claim 1, characterized in that the storage cavity (3) has the form of a hollow shaft which is open at one end and which extends axially and centrally in the concrete body (1); said shaft being intended to receive a waste-containing capsule (2) and thereafter to be sealed at its open end. 5. An arrangement according to claim 1, characterized in that the two ends of the concrete body (1) are substantially hemi-spherical in shape. 6. An arrangement according to claim 1, characterized in that the concrete body (1) is provided with a water-jet propulsion unit for movement of the body in water. 7. An arrangement according to claim 6, characterized in that the concrete body (1) is provided with pump means for varying the volume of water in the ballast chambers (4). 8. An arrangement according to claim 7, characterized in that said water-jet propulsion unit and/or said pump means comprise a unit which can be detachably fitted to the concrete body (1). 9. An arrangement according to claim 1, characterized in that the arrangement further comprises a rigid, single-piece coherent concrete structure (6) having a substantially greater cross-sectional area than height and which is intended to rest on a sea bed and includes a large number of mutually adjacent cylindrical storage spaces (9) which are open at least at their upper ends and each of which is formed to receive a concrete body (1) of the aforesaid kind; and in that the walls of the concrete structure (6) contain a plurality of ballast chambers which can be filled to varying degrees with water and which together have a total volume such as to enable the concrete structure (6) to be brought to a buoyant state in water by emptying the ballast chambers. 10. An arrangement according to claim 9, characterized in that the concrete structure (6) has an annular configuration. |
abstract | An upper detector and a lower detector that face at least one side of a fuel assembly, on which neutrons are irradiated in a nuclear reactor, and detect radiation are set at a predetermined interval in an axial direction of the fuel assembly. Distributions of radiation signals are measured by the upper detector and the lower detector while the fuel assembly and the upper detector and the lower detectors are relatively moved along the axial direction of the fuel assembly. Soundness of radiation signals measured by the upper detector and the lower detector is determined in every measurement by comparing radiation signal distributions obtained by measuring the same portion in the axial direction of the fuel assembly in a multiplexed manner with the upper detector and the lower detector. Thereafter, relative burn-up is calculated by utilizing the measured radiation signals to measure a burn-up profile. According to the present invention, it is possible to measure a burn-up profile of the fuel assembly while securing reliability of a measurement result. |
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042382890 | claims | 1. A pressure suppressing arrangement for pressurized fluid-handling apparatus including a nuclear reactor and associated coolant system from which a pressurized expansible fluid may escape comprising: a reactor compartment housing said fluid-handling apparatus; an annular condenser compartment substantially encircling the reactor compartment; means for supporting a quantity of fusible material in a solid state in the condenser compartment, said material having the property of melting at a temperature lower than the condensation temperature of the condensable portions of said escaping expansible fluid; a plurality of door ports in the condenser compartment wall which establish communication between the condenser compartment and the reactor compartment, said ports containing normally closed hinged doors openable in response to a differential pressure between said compartments; said doors and ports being of a size to provide a resistance to flow of the escaping fluid from the reactor compartment into said condenser compartment, said resistance being of one value in that area closest to the fluid handling apparatus, and a lesser value in those areas farther away from said apparatus, so as to more uniformly distribute the energy in said fluid to all sections of the condenser compartment. 2. The combination defined in claim 1, wherein door ports located close to the fluid-handling apparatus have a smaller cross-sectional area than ports located at a greater distance from said apparatus. 3. The combination defined in claim 1, wherein said door ports are of the same size, and flow restricting means secured in selected ports for limiting flow from the reactor compartment through said selected ports into the condenser compartment. 4. The combination defined in claim 3, wherein the flow restricting means comprises baffles of different surface area in adjacent sections of selected door ports the size of said baffles decreasing in surface area from section to section as the sections increase in distance from said fluid handling apparatus. |
description | This application is the National Phase of International Application PCT/EP2011/005856 filed Nov. 21, 2011 which designated the U.S. This application claims priority to German Patent Application No. DE102010054876.6 filed Dec. 17, 2010, which application is incorporated by reference herein. The automatic monitoring methods known from the state of the art consider only those algorithms using which a plurality of signals are processed in an unstructured manner. It is predominantly only statistical methods which are used here to illustrate the correlations between individual components. A method for monitoring of a vehicle is known from EP 2 063 399 A2. Although the overall system is subdivided into sub-systems here, it is not a causality in the system that is considered on the basis of a subdivision of the physical system, instead there is parallel and algorithm-assisted monitoring for each sub-system. It has proved to be a disadvantage in the procedures known from the state of the art that an error causality of the overall system is not taken into account. A further disadvantage of the previously known methods is that they cannot take sufficiently into account the difficulties of real systems, in which for example an error occurs between a physical sensor and the system. Only two states are taken into account here, i.e. complete functioning or complete failure, which in turn leads to erroneous monitoring of the overall system. By contrast, real systems include a plurality of sensors for measuring a parameter of the system, so that the quality of monitoring could be improved by exploiting redundancy. The object underlying the present invention is to provide a method for automatic monitoring of at least one component of a physical system which permits dependable automatic error assessment in a complex system too. It is a particular object to provide solution to the above problems by a combination of features described herein. Further advantageous embodiments will become apparent from the present description. In accordance with the invention, at least one sensor of a component to be monitored emits in this method an electrical signal via a measurement chain, which signal is read and processed and then saved as a file in a data record. Subsequently, the data of the data record is checked (in a first checking step) for errors that might be caused by the preceding data processing. Hence an automatic search takes place for errors which are caused by the data processing of the measurement chain, but not however by the sensor itself, for example. In a subsequent (second) checking step, and in accordance with the invention, the data of the data record is placed in the physical context of the at least one sensor and checked for errors that might result from infringements of the assumptions of the physical and/or system-related factors in the elements of the measurement chain. There is thus an error search in the physical system within the measurement chain. In an (optional and interposed) checking step, the sensors classed as equivalent are, if present in the system to be monitored, compared with one another. This provides further indications of sensors reacting incorrectly. In the following (in a third checking step) the data of the data record is placed in the context of the component itself and checked for errors that might result from infringements of the physical and/or system-related factors of the component. After a search in the first checking step for data processing errors and in the second checking step for errors in the elements of the measurement chain, a search for errors of the component itself therefore takes place in the third checking step. In accordance with the invention, a subdivision of the overall system is therefore made which considers all physical units and their relationships to one another. The present invention can thus be applied to any complex physical system. Following the object-based check, the individually asserted (detected) errors are in accordance with the invention checked against one another in a feedback section. The errors (error messages) are, as a consequence of the check, either rejected or displayed to a human operator of the physical system as an error message with reference to the error source. In accordance with the invention, an overall architecture of the monitoring system is therefore based on the fact that every error has causes and effects. These effects do not necessarily show themselves at the same place as the cause, but can give rise to symptoms in remote and dependent sub-systems. These symptoms can result in additional errors and thus make isolation of the error more difficult. The feedback described above is therefore regarded as an integral part of the monitoring system and of the monitoring method. In accordance with the invention, erroneous units, or data in general within the causal system, are therefore searched for. Dependent and following units thus receive in accordance with the invention only trustworthy information and can take into account the state of upstream units in their own monitoring system, so that the disadvantages resulting from the monitoring systems known from the state of the art are prevented or mitigated in accordance with the invention. Furthermore, the method in accordance with the invention acts as an accelerator for error detection and isolation algorithms, since the major problem involved in monitoring a complex system is subdivided into smaller partial problems. FIG. 1 shows in a schematic and simplified representation a physical system based on a pump. This includes for example a sensor N for the speed, a sensor Pe for the inlet pressure and several sensors Pa for the outlet pressure. The signals of the sensors are converted using an analog/digital converter. This is followed by a quantity conversion, for example in order to convert vibration signals of the sensor N into a speed value, or to convert voltage values of the sensors Pe and Pa into pressure values. This in turn is followed by a data output and saving of the respective data in a file. In the configuration shown in FIG. 1, the sensor Pa represents a sensor arrangement with three sensors that are equivalent to one another. The following represents the model configuration on the basis of FIG. 2: The monitoring system in accordance with the invention, which represents an illustration of the physical system, consists of the following elements: a data reader which receives the data from the emitting system; sensors, i.e. a sensor Pe, a sensor N and three sensors Pa; a sensor arrangement using the three sensors Pa as an input; a component reflecting the pump. Each of the objects is provided with algorithms, which on the one hand make available values derived from the input values and on the other hand check the validity of the input values. In the following an error detection by the data reader is represented on the basis of FIG. 3. In the data reader (see FIG. 2), the values were not yet assigned any context. These are therefore only values as such, which however have in common their processing by the physical data output system. FIG. 3 shows a possible case of error in which the data output system for a moment writes meaningless values into the file. This can be due to various causes, for example a transmission error between a test rig and a hard drive connected via a network. This error can be detected by the abrupt change of all input values, for example. FIG. 3 shows that in a comparison with the preceding input values, it is striking that for a certain period widely different values occur, while subsequently the preceding identical values are present again (the abscissa shows the time axis). Further errors can be erroneous time scales or wide discontinuities. The relevance of detecting this type of error lies in its further use. A following sensor object could adopt these values and from them supply incorrect values for the monitoring algorithms of the then following component. Interruptions in measurement in connection with the sensors are explained on the basis of FIG. 4. Sensors are physical objects whose context is assigned to the model sensors. The context exists in this case in the measurement range, for example. Accordingly, this information can already be used for error detection at the level of the sensor. In respect of the illustration in FIG. 4, the importance of the preceding validation becomes evident in turn. If it was already detected in the data reader object that the values are meaningless, by definition no error can be detected at the sensor. A classification as “erroneous” for wrong reasons is thus not possible. A further example for an actual error of the sensor would be unstable electrical connections, due to which interruptions result. A process of this type is shown by way of example in FIG. 4. The assumption that there is no error in the data output applies of course here too (see symbolically sensor 2). Such errors can be detected for example by very steep and physically unexplainable flanks. In the following the sensor arrangement is explained in detail: If there is redundancy at a physical position (as in the example Pa with respect to three equivalent sensors provided parallel to one another), this can be used for error detection. For example, one of the sensors from the measurement group might supply measured values with incorrect prefixes, without leaving its measurement range to do so. Whether this error is due to an incorrect physical connection of the sensor (incorrect polarity), to the A/D conversion or to a quantity conversion can only be ascertained with difficulty. The crucial point is however to pinpoint the problem as such. The following deals with the component in conjunction with FIG. 5. While sensors are still relatively simple systems, the “component” objects are intended to illustrate complex systems or system groups. Error detection can be very simple here, for example extreme values of a parameter can be fixed in the normal state and defined as error threshold values. These are shown in FIG. 5 as the “upper and lower limit values of the parameter”. These threshold values or limit values usually have to be completely within the measurement range of the recording sensors, permitting simple assignment. This broad approach can be narrowed by a model-based limitation of the normal values for the respective operating state. These models can also be designed to be adaptive, which would appear to be particularly sensible for long-operating systems subject to wear. At this point, the advantages of sequential error detection existing in accordance with the invention become particularly clear. In the course of adaptation, erroneous input values would distort the adapted model. A further example for the approach in accordance with the invention is detection by signatures. A broken-off vane in the pump can, depending on the speed regulation, lead to an increase in the speed with a simultaneous reduction of the pressure Pa. This change can still take place within the model tolerances set forth above if the latter have been selected relatively wide for reasons of robustness. Sequential error detection in accordance with the invention can in turn corroborate the result here. If the sensor arrangement Pa were to detect that only one of the sensors is reacting, it would class its status as erroneous. That would only leave the speed increase, which however might be for deliberate reasons. The decision on this is then the job of the final stage of automatic monitoring (checking, see next section) in accordance with the invention, but initially an error detection would be averted. Further examples for errors to be detected here are parameter drifts or measurement range distortions. In the following, the feedback is described on the basis of FIG. 6. In the automatic monitoring sequence described above, the evaluation of the physically present elements of the monitored system ends in principle. An important aspect here in accordance with the invention is the continuing improvement in the validation of the data away from the data output towards the component, which is enabled by the sequential method of error detection. Hence search algorithms of the subsequent object are based on already validated data. The outcome of this is more trustworthy results. Despite this, it is necessary with regard to the automatic monitoring method in accordance with the invention to re-evaluate all detected errors. If for example there was, within the “component pump” object, monitoring of the frequency pattern in the pressure measurement, this monitoring would ascertain the change in the form of an additional reaction for the frequency of the pump at precisely that sensor actually identified as non-valid by the comparison within the sensor arrangement. The feedback section, represented by the object “checking” (see FIG. 6), is designed to make the decision on whether a subordinate object must be completely distrusted and thus excluded from all considerations. Accordingly, there is conversely the possibility to take changes into account, for example the frequency pattern change for the pump frequency as discussed above, and hence to detect the true error. The feedback section thus forms the central factor for the entire monitoring. All information is collated here and checked on the basis of a suitable set of algorithms. These algorithms take the information and data into account and prioritize them with one another. It is for example possible for an error message to be ignored when “checking” ascertains that this error is only the result of another error. As can be concluded from the above explanations, a dual connection of the algorithms is thus provided in accordance with the invention, i.e. firstly in the sequence of objects and secondly by the overriding “checking”. The result in accordance with the invention is furthermore the possibility to use simpler and clearer algorithms. As a result, on the one hand less computing capacity is needed, and on the other hand the proneness of the algorithms themselves to errors is reduced. In accordance with the invention, there is thus a transition from the physical system to be monitored to the pure monitoring system, and subsequently reference back to the physical system within the monitoring system. It must furthermore be pointed out that the user of the method for automatic monitoring in accordance with the invention is not necessarily the person that operates or directly uses the system to be monitored. The method for automatic monitoring can instead be used for complex systems at a suitable location. There is furthermore the possibility in accordance with the invention that the user or human operator of the physical system interactively cooperates with the computer program implementing the method, for example to change the structures, to react to automatic messages and to extract data generated by the algorithms for a manual analysis. A basic computer program can furthermore offer the possibility of automatically saving the ascertained data for later evaluation and/or use. Furthermore, there is the possibility of saving the results during “checking” while taking into account and evaluating the error messages that have occurred. By doing so, error frequencies and their elimination can be automatically taken into account when errors of this type occur repeatedly. |
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abstract | An EUV collector mirror for an extreme ultra violet (EUV) radiation source apparatus includes an EUV collector mirror body on which a reflective layer as a reflective surface is disposed, a trajectory correcting device attached to or embedded in the EUV collector mirror body and a trajectory correcting device to adjust the trajectory of metal from the reflective surface of the EUV collector mirror body to an opposite side of the EUV collector mirror body. |
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description | Before describing the preferred embodiments of the present invention, the basic concept will be described. The present invention provides means or steps for moving two points at which the intensity of a sheet synchrotron beam is measured in the thickness direction of the beam. However, it is not necessary to move the two points at an actual measurement time. The measurement of the total intensity of a beam is performed by a radiation detector having a photo-receiving surface capable of receiving the beam in the thickness direction of the beam over the entire range of the beam at one time. Alternatively, the measurement of the total intensity of the beam is performed by detecting the accumulated synchrotron current value. It is also possible to perform a measurement of the total intensity with respect to a beam extracted from a beam line different from the beam line from which the beam whose intensity is measured at two points is extracted. The spacing between the two points is preferably not more than 1.5 times or not less than 2.5 times the size of the beam in the thickness direction, for example, the above-mentioned "sgr". The total intensity is measured in advance in a plurality of conditions in which the accumulated current values are different, measurements are performed for the intensities at two points while the measurement points are moved in the thickness direction, and a correction function is determined in advance on the basis of these measured results. Thus, when actual measurements are to be performed, by using this correction function, it is possible to calculate the position or the size of the beam in the thickness direction on the basis of the measured values of the total intensity and the intensities at two points. The ability to determine the size and the position of the beam in this manner depends on the following principles. If it is assumed that the intensity distribution of the beam follows a Gaussian distribution, the intensity distribution of the beam is determined uniquely if the center position Y0 of the beam, the spread "sgr" of the beam, and the total intensity I0 such that the beam is integrated in the Y direction which is the thickness direction of the beam are determined. Also, if the total intensity I0 such that the beam is integrated in the Y direction of the beam and the intensities at two specific points within the beam are determined, the intensity distribution of the beam is determined uniquely, and furthermore, the center position Y0 of the beam and the spread "sgr" of the beam are also determined. These principles are described with reference to FIGS. 9 and 10. FIG. 9 shows the relationships among the beam profile when the total intensity is constant and the position (Y0) of the beam is varied and the positions of two detectors A and B. As shown in FIG. 9, in a case in which the two detectors A and B are disposed at positions Ya and Yb, which are symmetrical with respect to the beam at a predetermined spacing, if the beam is moved to the side of the detector A, the output of detector A is increased and the output of detector B is decreased. Conversely, if the beam is moved to the side of the detector B as indicated by the broken line, the output of the detector A is decreased and the output of the detector B is increased. In this case, the ratio of the output of the detector A to the output of the detector B is a parameter showing the position of the beam. Also, the larger the spacing between the detectors A and B, the more sharply the ratio of the output of the detector A to the output of the detector B varies with respect to the positional variation of the beam. Therefore, the sensitivity of beam position detection increases as the spacing between the two detectors A and B increases. FIG. 10 shows a variation of a beam profile when the total intensity is constant and the spread ("sgr") of the beam is varied. As shown in FIG. 10, in a case in which the two detectors A and B are disposed symmetrically with respect to the beam at a spacing larger than twice the "sgr" of the beam, if the "sgr" of the beam is increased as indicated by the broken line, both of the outputs of the detectors A and B are increased. Conversely, if the "sgr" of the beam is decreased, both of the outputs of the detectors A and B are decreased. On the other hand, in a case in which detectors Axe2x80x2 and Bxe2x80x2 are disposed at positions Yaxe2x80x2 and Ybxe2x80x2 symmetrical with respect to the beam at a spacing smaller than twice the "sgr" of the beam, if the "sgr" of the beam is increased, both of the outputs of the detectors A and B are decreased. Conversely, if the "sgr" of the beam is decreased, both of the outputs of the detectors Axe2x80x2 and Bxe2x80x2 are increased. In the same manner as described above, the sum of the respective outputs of detectors A and B becomes a parameter indicating the spread of the beam. However, even when the "sgr" of the beam is constant and the intensity of the entire beam is varied, the sum of the outputs of the detectors A and B is varied. That is, even if the sum of the outputs of the detectors A and B varies, no distinction can be made as to whether this is due to the fact that the intensity of the entire beam was varied or whether the "sgr" of the beam was varied. Therefore, the intensity of the entire beam is measured by another means, and the outputs of the detectors A and B are normalized using this value. The sum of the outputs of the detectors A and B which are normalized in this manner allows the spread of the beam to be determined. The method for measuring the intensity of the entire beam is described in detail in the embodiment. Also, in a case in which the two detectors A and B are disposed symmetrically with respect to the beam at a spacing twice the "sgr" of the beam, even if the "sgr" of the beam is varied, the outputs of the detectors A and B do not vary. Therefore, it is not possible to measure the "sgr" of the beam when the spacing between the detectors A and B is twice the "sgr". In order to measure the "sgr" of the beam, it is necessary for the spacing of the detectors to avoid a value close to the "sgr" of the beam. In order to accurately measure the "sgr" of the beam, it is preferable that the spacing of the detectors be not more than 1.5 times the "sgr" of the beam or not less than 2.5 times the "sgr" of the beam. When the spacing between the detectors A and B is increased, the variation increases in the output of the detector when the beam position is varied. That is, when the spacing between the detectors A and B is increased, the sensitivity of beam position detection is improved. Therefore, in order to accurately measure the "sgr" of the beam and the position Y thereof at the same time, preferably, the spacing between the two detectors is larger than two times the "sgr" of the beam, and more preferably, the spacing between the two detectors is larger than 2.5 times the "sgr". Based on these principles, in the present invention, as preparations for measuring the size and the position of the beam, the total intensity of the beam and the intensities at two points are measured while Y scanning is performed under conditions in which the sizes of the beam are different (conditions in which, for example, the accumulated current values are different), and the ratio of these measured values is calculated as a function of Y and "sgr". Specific correction means is described in detail in the embodiment. After the correction is completed, adjustments are made so that the beam enters at approximately the midpoint of the two measurement points, the total intensity I0 and intensities IA and IB at two points are measured, and the value of this ratio is substituted in the correction function determined by the previous correction in order to calculate the thickness "sgr" and the position Y of the beam. This calculation can be performed in a very short time by converting the output of a measurement means into a numerical value by using an analog-digital converter and by processing the information with a computer. FIG. 2 is a block diagram showing the construction of a synchrotron radiation measurement apparatus according to a first embodiment of the present invention. FIG. 1 is a perspective view showing a main portion of the synchrotron radiation measurement apparatus. This apparatus measures the position and the size of a beam by synchrotron radiation by using three photodiodes. As shown in these figures, this apparatus comprises a vacuum container 1 to which a beam 15 by synchrotron radiation is introduced; an aperture plate 5, disposed inside the vacuum container 1, which is provided with two pin holes 2 and one longitudinal slit 4 which is elongated in the Y direction; an X-ray detector, disposed behind this aperture plate 5, which has three photodiodes 7 and 8; a stage/controller 9 for driving this X-ray detector in the Y direction; a rod 10, and a bellows mechanism 11 for mechanically connecting the stage/controller 9 in the air with an X-ray detector in a vacuum by the vacuum container 1 and for maintaining the vacuum; and a detector amplifier/analog-to-digital converter 12 and a calculating unit 13 for inputting the output of the X-ray detector and the amount of stage driving of the stage/controller 9 and for recording this information. The X-ray detector is housed in a shield case 14 made of a metal so that the photodiodes 7 and 8 are prevented from being irradiated by extraneous visible light and photoelectrons. Furthermore, the shield case 14 is placed in the vacuum container 1, and the vacuum container 1 is evacuated to an ultra-high vacuum by an evacuation pump 17. The vacuum container 1 is connected to a synchrotron ring via a gate valve. The aperture plate 5 is provided on the most upstream side of the shield case 14. Also, the aperture plate 5 is made of a copper plate and is cooled by water in order to moderate a temperature increase due to the thermal load of the synchrotron radiation. The diameter of each of pin holes 2 provided in the aperture plate 5 is 0.5 mm, and the Y-direction spacing between the two pin holes 2 is 8 mm. The width of the longitudinal slit 4 is 1 mm, and the length thereof in the Y direction is 20 mm. The spread "sgr" of the synchrotron radiation beam 15 to be measured is approximately 2 mm, and the length of the longitudinal slit 4 has a sufficient size with respect to the spread "sgr" of the beam. Also, the Y-direction spacing of the pin holes 2 is set to be approximately four times as large as "sgr". The shape of the opening of the pin hole 2 may not be circular, and for example, may be rectangular. Also, there is no need for each opening of the pin hole 2 and the longitudinal slit 4 to be provided in a single metallic plate, and three aperture plates having one opening may be combined. On the downstream side of the aperture plate 5, for the purpose of preventing damage by radiation and for blocking visible light contained in the SR beam 15, a filter 16 made of a metallic foil, for example, an aluminum foil having a thickness of several hundreds of xcexcm, is provided. Two photodiodes 7 and one photodiode 8 are provided, downstream of the filter 16, at positions corresponding to the two pin holes 2 and one longitudinal slit 4, respectively. The photodiode 7, provided downstream of the pin hole 2, has a circular photo-receiving surface having a diameter of 5 mm, and the photodiode 8, provided downstream of the longitudinal slit 4, has a rectangular photo-receiving surface of a width having 5 mm and a length of 25 mm, so that the light passing through each aperture of the pin hole 2 and the longitudinal slit 4 enters the photo-receiving surfaces of the photodiodes 7 and 8, respectively. The stage/controller 9 has a Y stage provided outside the vacuum container 1. This Y stage is connected by the rod 10 to the shield case 14 inside the vacuum container 1. The bellows 11 is connected at one end to the rod 10 and is welded at the other end to the chamber 1. This makes it possible for the rod 10 to be driven in the Y direction while maintaining a vacuum. The correction procedure is described below. During correction, it is necessary to measure the output values of the three photodiodes 7 and 8 while performing Y scanning by the Y stage on different beam sizes. Although the beam size cannot be determined beforehand, measurements may be performed by varying another parameter which affects the beam size. For example, the beam size may vary in a manner dependent on the accumulated current value. Therefore, the output values of the three detectors need only be measured while performing Y scanning at different current values. At a particular current value, the outputs of the photodiodes 7 associated with the pin hole 2 are denoted as S1 and S2, and the output of the photodiode 8 for measuring the total intensity associated with the longitudinal slit 4 is denoted as S0. Then, element output ratios R1 and R2 are calculated as a function of Y while Y scanning is performed. Here, R1 and R2 are expressed by the following equations: R1=(SAxe2x88x92SB)/(SA+SB) xe2x80x83R2=(SA+SB)/S0 Next, fitting is performed by Gaussian with the outputs S1 and S2 of the two detectors as a function of Y in order to determine the thickness "sgr" of the beam in the Y direction. Based on the above data processing, R1 and R2 are determined as functions of "sgr" and Y. Y scanning is repeated under conditions in which the current values are different, a table of "sgr", Y, R1, and R2 is stored, and the correction function is determined. For example, scanning is performed at 10 points for every 100 mA from when the accumulated beam current value is 100 mA. In this embodiment, "sgr" and Y are fitted as polynomial equations for R1 and R2. For example, substitution is performed as in the following equation in order to determine each coefficient so that the sum of the squares of the differences with the actually measured "sgr" and Y becomes a minimum. "sgr"=Cs30R1{circumflex over ( )}3+Cs03R2{circumflex over ( )}3+Cs21R1{circumflex over ( )}2R2+Cs12R1R2{circumflex over ( )}2+Cs11R1R2+Cs20R2{circumflex over ( )}1+Cs02R2{circumflex over ( )}2+Cs10R1+Cs10R2+Cs00 Y=Cy30R1{circumflex over ( )}3+Cy03R2{circumflex over ( )}3+Cy21R1{circumflex over ( )}2R2+Cy12R1R2{circumflex over ( )}2+Cy11R1R2+Cy20R1{circumflex over ( )}2+Cy02R2{circumflex over ( )}2+Cy10R1+Cy01R2+Cy00 Since R1 may be a parameter which reflects the ratio of the output S1 to that of S2, correction may similarly be performed by using, for example, a logarithm of the ratio of S1 to S2, R1=log (S1/S2), the ratio of the difference between S1 and S2 to S0, R1=(S1xe2x88x92S2)/S0, and by other means. When the sensitivities of two detectors are different, normalization is performed so that the peak outputs become equal by multiplication by a coefficient. That is, when the maximum value of the output S1 is S1max and the maximum value of the output S2 is S2max, correction may be performed by determining R1 and R2 as detector outputs such that S1/S1max and S2/S2max are each normalized. After the correction is completed, the Y stage is fixed so that the beam enters at nearly the midpoint of the two pin holes 2, and the outputs of the three photodiodes 7 and 8 are measured. R1 and R2 are calculated by the following equations from the measured values of SA, SB, and S0. R1=(SAxe2x88x92SB)/(SA+SB) R2=(SA+SB)/S0 Then, these are substituted in the following correction function which is determined by the previous correction, and the thickness "sgr" and the position Y of the beam are calculated. "sgr"=Cs30R1{circumflex over ( )}3+Cs03R2{circumflex over ( )}3+Cs21R1{circumflex over ( )}2R2+Cs12R1R2{circumflex over ( )}3+Cs11R1R2+Cs20R1{circumflex over ( )}2+Cs02R2{circumflex over ( )}2+Cs10R1+Cs10R2+Cs00 xe2x80x83Y=Cy30R1{circumflex over ( )}3+Cy03R2{circumflex over ( )}3+Cy21R1{circumflex over ( )}2R2+Cy12R1R2{circumflex over ( )}2+Cy11R1R2+Cy20R1{circumflex over ( )}2+Cy02R2{circumflex over ( )}2+Cy10R1+Cy01R2+Cy00 When, however, correction is performed by using R1=log (S1/S2), R1=(S1xe2x88x92S2)/S0, etc., as R1, these parameters are substituted in the function obtained by correction. These calculations can be performed in a very short time by converting the outputs of the photodiodes 7 and 8 into numerical values by using the analog-to-digital converter 12 and by processing the data in a computer 13. According to this measurement method, stage driving is not required during measurement, and the position and the spread of the beam can be determined immediately by calculating the output of a photodiode at a particular time. For this reason, variations over a short time can also be accurately measured. Also, since there is no need to drive the Y stage during measurement, no adverse influence, such as vibration, is exerted on other apparatuses. Furthermore, the power consumption is low, and the service life of the apparatus is long. FIG. 3 is a block diagram showing the construction of a synchrotron radiation measurement apparatus according to a second embodiment of the present invention. FIG. 4 is a perspective view showing a main portion of the synchrotron radiation measurement apparatus. This apparatus measures the position and the size of a beam of synchrotron radiation by using two wires and a total intensity monitor for another beam line. In these figures, reference numeral 18 denotes a metal wire (a total of two) which is a constituent of a detector of synchrotron radiation 15. Reference numeral 9 denotes a stage/controller for driving the metal wire 18 in the Y direction. Reference numeral 19 denotes a total intensity detector provided in the other beam line. Reference numeral 13 denotes a calculating unit for receiving the output of an X-ray detector and the amount of driving of a stage and for storing the data. The other reference numerals which are the same as those of FIGS. 1 and 2 indicate the same elements as those in FIGS. 1 and 2. The metal wire 18 is placed in a vacuum container 1, and the vacuum container 1 is evacuated to an ultra-high vacuum by an evacuation pump 17. The vacuum container 1 is also connected to a synchrotron ring via a gate valve. The two wires 18 are maintained in parallel with the plane of the beam 15 by an insulator 20, such as a ceramic. The insulator 20 is mechanically coupled to a Y stage of the stage/controller 9 outside the vacuum container 1, and is driven in the Y direction. For the wire 18, a tungsten wire, etc., plated with gold, is used. The thickness thereof is, for example, approximately 0.1 to 1 mm. The wire 18 is connected to a bias application circuit of a bias application circuit/current-to-voltage conversion circuit 21 outside the vacuum container 1, so that a voltage of several volts to several hundreds of volts is applied to the vacuum container 1. At this time, when the synchrotron radiation beam 15 is irradiated onto the wire 18, photoelectrons are generated, and since these photoelectrons are moved by an electric field by the applied voltage, electric current is made to flow through the wire 18. In order to detect this electric current, the wire 18 is also connected to a current-to-voltage conversion circuit of the bias application circuit/current-to-voltage conversion circuit 21. The output of the current-to-voltage conversion circuit is made to pass through an analog-to-digital conversion circuit of the detector amplifier/analog-to-digital converter 12 and is input to the calculating unit 13. In this embodiment, a total intensity detector is not provided for the beam line 15 for which measurements are performed, and instead, the output of the total intensity detector 19 provided for another beam line is used. The position and the size of the beam 15 can be measured in a manner similar to the case of the first embodiment. In general, in a synchrotron radiation source, there are cases in which a large number of beam lines are provided, and the positions and the sizes of the beams are measured for a large number of beam lines. In such cases, when the apparatus of this embodiment is used, two detectors are provided for each beam line, and furthermore, a detector for measuring the total intensity is provided for only one beam line. According to this method, it is possible to minimize the number of detectors and to reduce the number of signal processing devices correspondingly. Therefore, it is possible to reduce the cost of the overall system. FIG. 5 is a block diagram showing the construction of a synchrotron radiation measurement apparatus according to a third embodiment of the present invention. FIG. 6 is a perspective view showing a main portion of the synchrotron radiation measurement apparatus. In this apparatus, in order to measure the position and the size of a synchrotron radiation beam, an ion chamber and a synchrotron accumulated current value are used. This apparatus comprises an aperture plate 22 provided with two pin holes, two ion chambers 23 positioned at positions corresponding to these pin holes, a stage/controller 9 for driving the aperture plate 22 in the Y direction, means for measuring the accumulated current value of a synchrotron radiation source 24, a calculating unit 13 for receiving the output of the ion chamber 23, an accumulated current value 28 of the synchrotron radiation source 24, and the amount of driving of the stage of the stage/controller 9 and for storing the data. This measurement apparatus performs measurements of synchrotron radiation in the air. The synchrotron radiation beam 15 which is passed through a beryllium window 26 and then passes through air is shielded by the aperture plate 22 provided with two pin holes, and the X-rays which have passed through the pin holes are measured by the two ion chambers 23. The aperture plate 22 is fixed to the Y stage of the stage/controller 9 and can be driven in the Y direction. The ion chamber 23 is not fixed to the Y stage, but is fixed to the floor surface. The photo-receiving surface of the ion chamber 23 is approximately 20 mm, and even if the aperture plate 22 is moved in the Y direction, the X-rays passing through the pin holes always enter the ion chamber 23. The total intensity of the synchrotron radiation is proportional to the accumulated current value of an electron accumulation ring if the acceleration energy and the intensity of the magnetic field are fixed. In this embodiment, data 28 of the accumulated current value of the electron accumulated ring is used instead of the total intensity by the total intensity detector. The accumulated current value can normally be measured with high accuracy by a current transformer, such as a DCCT. In general, in a synchrotron radiation source, there are cases in which a large number of beam lines are provided, and the positions and the sizes of the beams are measured for a large number of beam lines. In such a case, when the apparatus of this embodiment is used, two detectors are provided for each beam line, and the information of the beam current measured by a current transformer is used in common among a large number of measurement apparatuses, the number of detectors can be minimized, making it possible to reduce the number of signal processing apparatuses correspondingly. Therefore, it is possible to reduce the cost of the overall system. Also, in this embodiment, since the measurement apparatus is in the air, and a vacuum container, an evacuation pump, etc., are not required, the cost of the apparatus can be reduced. Furthermore, in this embodiment, a member driven by a Y stage is only the aperture plate 22 and is of a light weight, and a small stage can be used. Therefore, the cost of the apparatus can be reduced further. FIG. 7 is a block diagram showing the construction of a synchrotron radiation measurement apparatus according to a fourth embodiment of the present invention. FIG. 8 is a perspective view showing a main portion of the synchrotron radiation measurement apparatus. In this apparatus, in order to measure the position and the size of a synchrotron radiation beam, photoelectric effects on four metal plates are used. This apparatus comprises an aperture plate 30 in which a rectangular hole is provided, two metal plates 31 disposed at corresponding positions behind this aperture plate 30, for regulating the range of the synchrotron radiation 15 in the Y direction, which radiation has passed through the aperture plate 30, two metal plates 32 for similarly regulating the range of the synchrotron radiation 15 in the Y direction, a stage/controller 9 for driving the aperture plate 30 and the metal plates 31 and 32 in the Y direction, and a calculating unit 13 for receiving the photoelectric values of the metal plates 31 and 32 and the amount of driving of the stage of the stage/controller 9 and for recording the data. In this embodiment, the synchrotron radiation 15 is irradiated onto a plurality of metal plates 31 and 32, and photoelectrons therefrom are measured. The entire measurement apparatus is housed in the vacuum container 1. The aperture plate 30 is provided most upstream, so that the width of the synchrotron radiation beam 15 in the X direction is controlled. The width of an aperture 33 of the aperture plate 30 in the Y direction is sufficiently larger than the width of the beam, and therefore, the width of the synchrotron radiation beam 15 in the Y direction is not controlled. Behind the aperture 33, two metal plates 31 for regulating the synchrotron radiation beam 15 in the X direction are provided, and furthermore, two metal plates 32 for regulating the synchrotron radiation beam 15 in the Y direction are provided downstream thereof. Since the entire beam 15 in the Y direction is irradiated onto the metal plate 31, photoelectric current therefrom is proportional to the total intensity of the beam 15. Therefore, the metal plate 31 can be used as a total intensity detector. A part of the beam 15 in the Y direction is irradiated onto the metal plate 32. Therefore, photoelectric current from the metal plate 32 can be used as the output of the two detectors located at Y-different positions. According to this embodiment, since the central portion of the beam 15 is not shielded by a detector and is passed through as is, it can be used for other measurements, material processing, and the like. As has thus been described, since the size of a beam in the thickness direction and the position thereof are calculated based on the total intensity of the beam and the intensities at two points, it is possible to determine the size and the position of the beam in a very short time. Therefore, it is possible to accurately measure variations in a short time, which cannot be so determined in conventional technology. Also, it is possible to eliminate the need to drive the stage during measurement, except for the case of correction. For this reason, power consumption can be reduced, and the cost of maintenance can be minimized. Furthermore, since there is no need to drive a stage during measurement except for the case of correction, exertion of adverse influences, such as vibrations, on other apparatuses which use synchrotron radiation can be prevented. In addition, since driving of the stage is limited to the time of correction, the wear on the apparatus, such as the bellows and stage mechanism, can be reduced, and the service life of the apparatus can be substantially extended. FIG. 11 is a diagram of the construction of an embodiment of an X-ray exposure apparatus, including the above-described synchrotron radiation measurement apparatus. Referring to FIG. 11, reference numeral 101 denotes a synchrotron ring which is a light source for emitting synchrotron radiation. Reference numeral 102 denotes a cylindrical mirror for reflecting a sheet-shaped beam 9 from the synchrotron ring 101 in order to form an expanded beam 10. Reference numeral 103 denotes a shutter for controlling the amount of exposure by the expanded beam 10. Reference numeral 104 denotes a mask having an exposure pattern. Reference numeral 105 denotes a wafer in which the pattern of the mask 104 is exposed. Reference numeral 106 denotes a mirror holder for holding the cylindrical mirror 102. Reference numeral 107 denotes a means for driving the mirror holder 106. Reference numeral 108a denotes a first X-ray detector which is mounted in the mirror holder 106. Reference numeral 108b denotes a second X-ray detector which is mounted in the mirror holder 106. Reference numeral 111 denotes a preamplifier for amplifying the outputs of the X-ray detectors 108a and 108b. Reference numeral 112 denotes a mirror controller for controlling the driving of the driving means 107 on the basis of the output of the preamplifier 111. Reference numeral 113 denotes a calculating unit for performing a predetermined calculation on the basis of the output of the preamplifier 111. Reference numeral 114 denotes a shutter controller for controlling the driving of the shutter 103 on the basis of the calculation result of the calculating unit 113. Reference numeral 116 denotes a wafer chuck for holding a wafer 105. Reference numeral 117 denotes a wafer stage for driving the wafer chuck 116. Reference numeral 118 denotes a means for driving the wafer stage 117. Reference numeral 119 denotes an X-ray detector mounted in the wafer stage 117. Reference numeral 120 denotes a preamplifier for amplifying the output of the X-ray detector 119. Reference numeral 121 denotes a calculating unit for performing a predetermined calculation on the basis of the output of the preamplifier 120. Reference numeral 123 denotes a beam monitor for measuring the intensity of the sheet-shaped beam 9 and the intensity distribution. The beam monitor 123 has the construction described above with reference to one of FIGS. 7 and 8. In this construction, the sheet-shaped beam 9 emitted from the synchrotron ring 101 is expanded in the Y direction by the cylindrical mirror 102, and an exposure angle of view on the mask 104 is secured. Since this expanded beam 10 has an intensity distribution in the Y direction, in order that a uniform amount of exposure can be obtained on the mask 104 and wafer 105 by canceling the intensity distribution in the Y direction by the exposure time, the shutter controller 114 controls the driving of the shutter 103 so as to adjust the movement speed of the shutter 103 according to the intensity distribution. For the positional relationship between the cylindrical mirror 102 and the sheet-shaped beam 9, the positions of both of them must be made to coincide with each other with high accuracy, and the cylindrical mirror 102 must be made to follow the sheet-shaped beam 9 in the Y direction according to the vibrations and the deviation of the sheet-shaped beam 9. Therefore, the cylindrical mirror 102 is disposed in the mirror holder 106 so that it can be driven in the Y direction by the driving means 107. The first and second X-ray detectors 108a and 108b mounted in the mirror holder 106 sense beams within a predetermined area in proximity to the upper edge and the lower edge of the sheet-shaped beam 9, respectively. The outputs of the first and second X-ray detectors 108a and 108b are amplified by the preamplifier 111, and the amplified outputs Va and Vb are sent to the preamplifier 111 and the calculating unit 113. The mirror controller 112 compares the amplified outputs Va and Vb of the two X-ray detectors 108a and 108b with each other, and causes the driving means 107 to move the cylindrical mirror 102 so as to control the position thereof on the basis of the comparison result so that the two outputs Va and Vb become equal to each other, thereby causing the sheet-shaped beam 9 and the cylindrical mirror 102 to coincide with each other with high accuracy. Also, the intensity of the synchrotron radiation which enters the mirror 102 and the intensity distribution are measured instantaneously by the beam monitor 123, and the spread of the intensity distribution is determined. The xe2x80x9cspreadxe2x80x9d referred to herein refers to a standard deviation when the intensity distribution of the synchrotron radiation is approximated by a Gaussian distribution. The beam monitor 123 will be described later. Based on the determined intensity and the determined spread of the intensity distribution, the intensity distribution of the synchrotron radiation on the surface of a wafer is determined by a correction method for causing the intensity of the synchrotron radiation which enters the mirror 102 and the spread of the intensity distribution, which are determined in advance, to be related to the intensity distribution of the synchrotron radiation on the wafer surface. This correction method will be described later. The shutter controller 114 calculates the driving time of the shutter 103 on the basis of the intensity distribution of the synchrotron radiation on the wafer surface, and drives the shutter 103 on the basis of the calculated result. That is, the movement speed of the shutter 103 is controlled according to the intensity distribution of the synchrotron radiation on the wafer surface so that the amount of exposure on the wafer 105 becomes uniform. A correction method for causing the intensity of synchrotron radiation which enters the mirror 102 and the spread of the intensity distribution to be related to the intensity distribution of the synchrotron radiation on the wafer surface is described below. Here, a method for determining correction equations is described. Initially, by driving the X-ray detector 108 mounted in the mirror holder 106 in the Y direction, the intensity distribution of the synchrotron radiation which enters the mirror 102 is measured, and the spread of the intensity distribution is determined. That is, while the X-ray detectors 108a and 108b of the mirror holder 106 are driven in the Y direction, the outputs therefrom are amplified by the preamplifier 111, and the outputs Va and Vb thereof are converted into the intensity of the synchrotron radiation and the intensity distribution by the calculating unit 113. The calculating unit 113 further approximates the intensity distribution by an appropriate function, for example, a Gaussian function, in order to determine the spread of the intensity distribution. Also, at the same time, by driving the X-ray detector 119 mounted in the wafer stage in the Y direction, the intensity distribution of the synchrotron radiation on the wafer surface is measured. That is, while the X-ray detector 119 is driven in the Y direction, the output of the X-ray detector 119 is amplified by the preamplifier 120, and an output Vc thereof is converted into the intensity distribution of the synchrotron radiation by the calculating unit 121. By performing this operation by changing the accumulated current value of the synchrotron radiation source, a plurality of pieces of data are taken, and an approximation curve is determined by plotting the intensity of the synchrotron radiation which enters the mirror 102 and the spread of the intensity distribution, and the intensity distribution of the synchrotron radiation on the wafer surface. This approximation curve is approximated by a polynominal equation. Instead of using this polynominal equation, a method may be used in which a table is stored in which the intensity of the synchrotron radiation which enters a mirror and the spread of the intensity distribution are made to correspond to the intensity distribution of the synchrotron radiation on the wafer surface, and compensation is performed by using this table. FIG. 12 is a diagram of the construction of an X-ray exposure apparatus according to another embodiment of the present invention. The construction of this embodiment is the same as that of FIG. 11, except that the beam monitor 123 is not used. When exposure is performed, with respect to the sheet-shaped beam 9, the X-ray detector 108 of the mirror holder 106 is first driven in the Y direction. At this time, the outputs of the first and second X-ray detectors 108a and 108b are amplified by the preamplifier 111, and the amplified outputs Va and Vb thereof are sent to the calculating unit 113. The calculating unit 113 converts the output Va or Vb into the intensity of the synchrotron radiation (sheet-shaped beam 9) and the intensity distribution. The calculating unit 113 further approximates the intensity distribution by an appropriate function, such as a Gaussian function, in order to determine the spread of the intensity distribution. Based on the intensity and the spread of the intensity distribution, the calculating unit 113 further determines the intensity distribution of the synchrotron radiation on the surface of the wafer 105 by a correction method of relating the intensity of the synchrotron radiation which enters the mirror 102 and the spread of the intensity distribution, which are determined in advance, to the intensity distribution of the synchrotron radiation on the surface of the wafer 105. The correction method of relating the intensity of the synchrotron radiation which enters the mirror 102 and the spread of the intensity distribution to the intensity distribution of the synchrotron radiation on the surface of the wafer 105 is the same as that of the first embodiment. Then, the shutter controller 114 calculates the driving time of the shutter 103 on the basis of the intensity distribution of the synchrotron radiation on the surface of the wafer, and drives the shutter 103 on the basis of the calculated result. That is, the movement speed of the shutter 103 is controlled according to the intensity distribution of the synchrotron radiation on the surface of the wafer 105 so that the amount of exposure on the wafer 105 becomes uniform. This embodiment is particularly effective in a case in which, although the intensity distribution of the synchrotron radiation which enters the mirror 102 changes independently of the attenuation of the accumulated current value over time after the incidence of the synchrotron radiation, the cycle of the change is moderate and, there is no variation while, for example, one wafer is exposed. In the construction of FIG. 12, from the time the synchrotron radiation enters until the exposure starts, by driving the X-ray detector 108 of the mirror holder 106 in the Y direction, the intensity of radiation which enters the mirror 102 and the intensity distribution are measured, and the spread of the intensity distribution is determined. Also, at the same time as this, the present accumulated current value is determined in advance. This method for measuring the intensity and the intensity distribution, and for determining the spread of the intensity distribution, is the same as that of the second embodiment. When exposure is performed, the intensity of the synchrotron radiation which enters the mirror 102, and the spread of the intensity distribution are determined from the present accumulated current value. This method will be described later. Based on the present intensity of the synchrotron radiation which enters a mirror and the present intensity distribution, the calculating unit 113 determines the intensity distribution of the synchrotron radiation on the surface of the wafer 105 by a correction method of relating the intensity of the synchrotron radiation which enters a mirror and the spread of the intensity distribution, which are determined in advance, to the intensity distribution of the synchrotron radiation on the surface of the wafer 105. This correction method is the same as those of the first and second embodiments. Then, in a manner similar to the case of the second embodiment, the shutter controller 114 calculates the driving time of the shutter 103 on the basis of the intensity distribution of the synchrotron radiation on the surface of the wafer 105, and drives the shutter 103 on the basis of the calculated result. In practice, since the accumulated current value is proportional to the intensity of the synchrotron radiation which enters the mirror 102, the intensity of the synchrotron radiation is determined, and this is used instead as the accumulated current value. A description is given below of a method for determining a correction equation for relating the accumulated current value of a synchrotron radiation source to the intensity of the synchrotron radiation which enters a mirror and the spread of the intensity distribution. FIG. 13 is a graph showing the intensity distribution of the sheet-shaped beam 9, which is obtained by plotting the outputs Va (y) and Vb (y) of the two X-ray detectors 108a and 108b when the cylindrical mirror 102 is driven in the Y direction by the driving means 107. A curve 41 in the figure indicates Va (y), and a curve 42 indicates Vb (y). These are approximated by a Gaussian distribution, the voltage of the intersection and the area are determined, and the spread of the intensity distribution is determined. The area has a value proportional to the intensity of the synchrotron radiation, and a conversion coefficient is determined in advance from the sensitivity, etc., of the X-ray detector 108. A plurality of pieces of data are, taken by performing these operations by varying the accumulated current value of the synchrotron ring 101, and the voltage of the intersection, the intensity of the synchrotron radiation, and the intensity distribution are plotted. FIG. 14 shows the relationship, which is determined by the above, between the summed signal Va+Vb of the output of the X-ray detector 108, and the intensity of the synchrotron radiation. FIG. 15 shows the relationship, which is determined by the above-described method, between the summed signal Va+Vb of the output of the X-ray detector 108, and the spread of the intensity distribution of the synchrotron radiation. In this manner, the approximated curve and the approximated straight line are determined, and the coefficients therefor are stored in the calculating unit 113. This embodiment is particularly effective in a case in which the intensity distribution of the synchrotron radiation which enters a mirror is determined by a fixed rule with respect to the attenuation of an accumulated current value over time. It is known that SR light before it is reflected by the mirror 102 has a distribution similar to a Gaussian distribution and that the intensity of the center thereof is highest and falls off toward the periphery. It is also known that the SR light has an intensity distribution which is almost symmetrical with respect to the center, and in this case, the intensity distribution of the SR light is determined by the center intensity and the spread thereof. Accordingly, at least two of the total intensity, the center intensity, and the intensity at a position away by a particular distance from the center are measured by a specific method (a method described in the respective embodiments), and the correlation among the measured values and the intensity on the resist surface is determined in advance. The xe2x80x9ctotal intensityxe2x80x9d refers to the intensity such that the entire intensity distribution is integrated, and it can be measured at one time if the detector is sufficiently enlarged with respect to the incident SR light. In addition, before exposure, by measuring the intensity distribution of the SR light before a mirror by a specific method which is the same as the method in which at least two of the total intensity, the center intensity, and the intensity at a position away by a particular distance from the center are measured, the intensity distribution on the resist surface can be corrected. Instead of measuring at least two of the total intensity, the center intensity, and the intensity at a position away by a particular distance from the center, the entire intensity distribution may be determined. FIG. 16 is a flow chart showing a process for manufacturing a micro-device (e.g., a semiconductor chip such as an IC or an LSI, a liquid crystal panel, a CCD (charge-coupled device), a thin film magnetic head, a micro-machine or the like). At step 1 (circuit design), the circuit design of the semiconductor device is effected. At step 2 (the manufacturing of a mask), a mask, as the substrate described in the above embodiments, formed with the designed circuit pattern, is manufactured. On the other hand, at step 3 (the manufacturing of a wafer), a wafer is manufactured by the use of a material such as silicon. Step 4 (wafer process) is called a pre-process, in which by the use of the manufactured mask and wafer, an actual circuit is formed on the wafer by lithography techniques. The next step, step 5 (assembling), is called a post-process, which is a process for making the wafer manufactured at step 4 into a semiconductor chip, and includes steps such as an assembling step (dicing and bonding) and a packaging step (enclosing the chip). At step 6 (inspection), inspections such as an operation confirming test a durability test of the semiconductor device manufactured at step 5 are carried out. Via such steps, the semiconductor device is completed, and it is shipped for delivery (step 7). FIG. 17 is a flowchart showing the detailed steps of the wafer process discussed above with respect to step 4. At step 11 (oxidation), the surface of the wafer is oxidized. At step 12 (chemical vapor depositionxe2x80x94CVD), an insulating film is formed on the surface of the wafer. At step 13 (the forming of an electrode), an electrode is formed on the wafer by vapor deposition. At step 14 (ion implantation), ions are implanted into the wafer. At step 15 (resist-processing), a photo-resist is applied to the wafer. At step 16 (exposure), the circuit pattern of the mask is printed and exposed onto the wafer by the X-ray exposure apparatus. At step 17 (development), the exposed wafer is developed. At step 18 (etching), the portions other than the developed resist image are removed. At step 19 (the peeling-off of the resist), the resist, which has become unnecessary after the etching, is also removed. By repetitively carrying out these steps, circuit patterns are multiplexly formed on the wafer. If the manufacturing method of the present invention is used, it will be possible to manufacture semiconductor devices having a high degree of integration, which have heretofore been difficult to manufacture. Except as otherwise disclosed herein, the various components shown in outline or in block form in the figures are individually well known and their internal construction and operation are not critical either to the making or using of this invention or to a description of the best mode of the invention. While the present invention has been described with respect to what is at present considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention as hereafter claimed. |
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048797367 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to an x-ray examination apparatus, and in particular to such an apparatus having an x-ray image intensifier and an x-ray film changer, with the film changer being mounted so as to be optionally moveable into an exposure position in front of the x-ray image intensifier. 2. Description of the Prior Art An x-ray examination apparatus having an x-ray image intensifier, with an x-ray film changer mounted so as to be optionally introducible into the beam path in front of the x-ray image intensifier for producing x-ray pictures is commercially available from BC Medical Manufacturing Company Limited, and is described in a brochure from that company. In this commercially available apparatus, the x-ray image intensifier has a holder attached thereto, on which the x-ray film changer is mounted so as to be moveable, with the x-ray film changer in the exposure having the same image access as that of the image intensifier. The film changer can be pivoted out of the exposure position by approximately 90.degree. to a standby position. The above commercially available installation is suitable, for example, for conducting angiography examinations. In such an examination, the introduction of a catheter into the patient is tracked using the x-ray image intensifier. When a contrast agent is then injected into the patient via the catheter, x-ray exposures are frequently made, for which purpose the x-ray film changer is brought into the exposure position. After the x-ray exposures have been made, the x-ray film changer is again pivoted back to the standby position. In this known x-ray examination apparatus, the holder for the x-ray film changer is rigidly attached to the image intensifier, so that the film changer has only a single standby position. The brochure of BC Medical Manufacturing Company Limited for this apparatus shows one standby position, at which the x-ray film changer lies at the head side, and behind the image intensifier, as seen by a patient lying on an examination table. This standby position of the x-ray film changer is particularly cumbersome for an anesthesiologist because the patient is difficult to reach proceeding from the head side. A further disadvantage of the standby position of the x-ray film changer is that, given a cranial angling of the x-ray image intensifier, the film changer will press against the stomach or chest of the patient, thereby limiting the available angular displacement. SUMMARY OF THE INVENTION It is an object of the present invention to provide an x-ray examination installation having an x-ray image intensifier and an x-ray film changer optionally moveable from a standby position to an exposure position in front of the x-ray image intensifier, wherein the film changer in the standby position does not impede access to a patient lying on an examination table, and wherein the x-ray image intensifier can be placed in any arbitrary position relative to the patient without being impeded by the film changer in the standby position. The above object is achieved in accordance with the principles of the present invention in an x-ray examination installation wherein the holder for the x-ray film changer is a bearing which at least partically surrounds the x-ray image intensifier, the bearing being disposed in a plane substantially perpendicular to the image axis, and the x-ray film changer being displaceable along this bearing. This permits the x-ray film changer, in its standby position, to be displaced dependent on the desired access to the patient, or dependent on the desired angular position of the x-ray image intensifier. The bearing may be a roller bearing or a smooth bearing. All that is necessary is that the x-ray film changer be easily manually displaceable along the bearing while in its standby position. In one embodiment of the invention, the holder may be a carriage on which the x-ray film changer is displaceable from the exposure position to the standby position. This permits a simple displacement of the film changer between these positions. In a preferred embodiment, the carriage is rigidly connected to the bearing, so that the carriage is also shifted given displacement of the x-ray film changer along the bearing. As a result, the x-ray film changer can always be adjusted into the exposure position as needed, independently of its position in the standby position. Locking means may also be provided along the bearing at selected locations, to lock the film changer at specific locations. |
051397358 | abstract | A reactivity control system includes a reservoir containing a liquid nuclear poison, at least one stationary, hollow control blade extending vertically into a reactor core, and a poison conduit disposed in flow communication between the reservoir and the control blade for channeling the poison between the reservoir and control blade. The level of the poison in the control blade is controlled for selectively varying nuclear reactivity in the core. |
abstract | In one embodiment, the fuel bundle for a liquid metal cooled reactor includes a channel, a nose assembly secured to a lower end of the channel, and a plurality of fuel rods disposed within the channel. At least one of the fuel rods has at least one guard ring surround the fuel rod and spacing the fuel rod from adjacent fuel rods. |
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047769823 | description | DETAILED DESCRIPTION OF THE INVENTION It will be easier to handle the spent fuel after it is taken out of the reactors if it is placed in an acid bath to separate the metal cans of the fuel rods from the fuel. The liquid material is then converted into pellets for direct transfer to a vehicle. The material may also be subjected to a separation process whereafter the different waste products will be stored in separate containers. Another procedure is for the fuel, with the metal cans, to be loaded directly onto the vehicle for transport to the storage place. In an underground storage room 9, blasted out of rock 7, a rail-mounted material handling device approx. 5 meters.times.5 meters in plan and 11 meters in height is arranged to run along a track 6. The material handling device consists of two sections, section 4 arranged to be raised and lowered and equipped with a transfer container for the transfer of spent fuel to and from storage containers, and a section 5 with lifting and carrying arrangements. Section 4 thus functions as a transfer device and section 5 functions as a lifting and carrying device material handling device. The material handling device is designed to fit into lift 8 for moving spent fuel from ground level down to the storage room 9, and to carry and transfer fuel to double-walled containers 1. The double-walled containers the double walls of which are shown diagrammatically as 1A and 1B in FIG. 1, are stacked one on top of the other on a structure 3 which is designed to suit the lifting and carrying section 5. This section can, when required, run under structure 3, lift up one stack of containers, and shift it onto a structure common to both sections for transport from storage room 9. The material of the containers and arrangements for heat removal and cooling comply with accepted engineering practice and are of types approved by the authorities. The containers are provided with safety valve arrangements 2 with three safety locks to prevent radioactive material from escaping during transfer to or from the transfer container of section 4. Transfer is effected either by remote control or manually. The method for heat removal to cool the radioactive material may be chosen according to the practical use the heat is to be put to, such as water heating. The heat can be removed from the space between the inner and outer walls of the containers by a heat exchange medium e.g. air, liquid or gas through inlet-outlet conduits 21 and 22, illustrated diagramatically in FIG. 1 connected to one of the containers 1. When the thermal radiation from the material decreases and there is no longer any need for heat removal or cooling, the material can be transferred into cheaper containers. The material is easily transferred from the double-walled container and moved to another storage place, e.g. after a decision to reprocess it. The containers, which are shown in FIG. 1 as resting on a structure 3 and are adapted to lifting and carrying section 5, may alternatively be cast into concrete. It will be apparent from the foregoing that my invention provides a safe, inexpensive, and practical means of handling and storing spent nuclear fuel. Human contact with the equipment will be negligible. |
summary | ||
claims | 1. A throughput analysis method for a manufacturing line including a plurality of machines, each configured to generate event codes which are input to the throughput analysis, the throughput analysis method comprising:calculating a first throughput value for the plurality of machines based on the input;ranking the plurality of machines and their associated event codes according to their effect on throughput;altering a value of a first event code associated with a first machine to generate an altered first event code for a new event code input;recalculating a second throughput value based on the new event code input; andcomparing the first throughput value with the second throughput value to generate a weight of the first event code on the first throughput value. 2. A method as recited in claim 1 wherein input for the calculating step is derived from:calculating with a mathematical algorithm the mean time to repair for the plurality of machines and from that calculating repair times for the different codes representing breakdowns; andcalculating with a mathematical algorithm mean count between events for the plurality of machines and from that calculating the mean time between failures and mean count between failures. 3. A method as recited in claim 1 wherein calculating a first throughput value, comprises:processing by a discrete event simulation. 4. A method as recited in claim 1 wherein the recalculating step comprises:recalculating with a mathematical algorithm from the mean time to repair for the plurality of machines a new set of event codes and their corresponding repair times; andrecalculating with a mathematical algorithm from the mean count between events for the plurality of machines a new set of event codes and the corresponding number of parts made between events. 5. A method as recited in claim 4 wherein recalculating with the mathematical algorithm, comprises:processing by a discrete event simulation. 6. A method as recited in claim 1 further comprising determining sensitivity, the method further comprising:comparing the first throughput value with the second throughput value to generate a percentage difference in throughput;comparing the difference between the first event code having a repair time and the altered first event code having a repair time to generate the percentage difference in repair time; anddividing the percentage difference in throughput by the percentage difference in repair time to generate the sensitivity. 7. A method as recited in claim 1 wherein altering a value of a first event code comprises:changing a repair time of the first event code. 8. A method as recited in claim 1 wherein altering a value of a first event code comprises:eliminating the first event code. 9. A method as recited in claim 1 wherein altering a value of a first one event code to generate an altered event code further comprises:altering a plurality of event codes values to generate a plurality of altered event code values. 10. A method for evaluating stations of a system for improvability according to predetermined criteria, the method comprising;selecting among the stations, a set of susceptible stations that are affected by at least one selected event;ranking the susceptible stations with respect to a selected event and the predetermined criteria to determine an ordered list of more susceptible stations;altering the selected events to generate a new set of events;reranking the susceptible stations with respect to the selected events comprising the new event to determine a new ordered list of more susceptible stations; anddetermining the most susceptible station based on a comparison criterion of the original ordered list of more susceptible stations and the new ordered list of more susceptible stations. 11. A method as recited in claim 10 wherein determining comprises evaluating with a decision-making tool. 12. The method of claim 11, wherein the decision-making tool comprises a discrete event simulation. 13. The method of claim 10, wherein the comparison criterion comprises cost. 14. The method of claim 10, wherein the comparison criterion comprise maintenance priorities. 15. The method of claim 10, wherein the comparison criterion comprises production throughput. 16. The method of claim 10 wherein a station comprises at least one manufacturing machine. 17. A manufacturing line system comprising a plurality of machines configured to generate event codes as input, the input delivered to a computational subsystem, the system comprising:a calculating module for calculating a first throughput value for the plurality of machines based on the event code input;a ranking module for ranking the plurality of machines and their associated the event codes according to their effect on throughput;an altering module for altering a value of a first event code to generate an altered first event code to generate new event code input;a recalculating module for recalculating the second throughput value based on the new event code input; anda comparing module for comparing the first throughput value with the second throughput value to generate an influence value for the altered event code inputs on the first throughput value. 18. A system as recited in claim 17 wherein the calculating module comprises:a discrete event simulation module. 19. A manufacturing line system as recited in claim 18 wherein the manufacturing line is for the manufacture of motorized vehicles. 20. A system as recited in claim 17 wherein the comparing module comprises:a decision-making tool module. |
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051868873 | claims | 1. An apparatus for inspecting peripheral surfaces of nuclear fuel pellets, comprising: a handling unit for holding a plurality of nuclear fuel pellets in a line and rotating the same on axes thereof; a loading device for loading said nuclear fuel pellets onto said handling unit; an image pick-up device disposed adjacent to said handling unit for picking up image data as to the peripheral surfaces of said nuclear fuel pellets; a judging device operably connected to said image pick-up device for analyzing said image data outputted from said image pick-up device to output judging signals; and a sorting unit operably connected to said judging device for separating defective pellets from non-defective pellets based on said judging signals, said sorting unit including a plurality of sorting members disposed adjacent to said handling unit so as to correspond to said nuclear fuel pellets, respectively, and operating means operably connected to said judging device and said sorting members for operating said sorting members based on said judging signals; wherein: said handling unit includes a first roller having a first predetermined diameter disposed rotatably about an axis thereof and adjacent to said loading device, a second roller having a second predetermined diameter which is comparatively larger than the first predetermined diameter of the first roller disposed adjacent to said first roller so as to be rotatable about an axis parallel to said axis of said first roller, said first roller and said second roller cooperating to define an inspecting position therebetween, said second roller including at least one ejecting groove for receiving and carrying said plurality of nuclear fuel pellets, said ejecting groove being formed in a peripheral surface of said second roller so as to extend axially thereof. a binary conversion means for converting the image data into binary signals based on preset binary levels; a projection data obtaining means operably connected to said binary conversion means for obtaining projection data and storing the same, said projection data being the number of picture elements which are located in a row corresponding to circumferential direction and have one of binary values; a two-dimensional image conversion means for converting the image data from said image pick-up device into two dimensional digital images; a window determining means connected to said projection data obtaining means for determining a window; a gate means for overlaying said window determined in said window determining means, on said two dimensional digital images; and a judging circuit for judging presence of defects on said nuclear fuel pellets based on data outputted from said gate to produce said judging signals. 2. An inspection apparatus according to claim 1, further comprising a drive means operably connected to said first roller and said second roller for rotating said first roller and said second roller in an identical direction at an identical constant peripheral velocity. 3. An inspection apparatus according to claim 1, in which said operating means includes a plurality of actuators mounted so as to correspond to said plurality of sorting members, respectively. 4. An inspection apparatus according to claim 1, in which said image pick-up device includes a light source disposed adjacent to said inspecting position for radiating illuminating light to said plurality of nuclear fuel pellets located at said inspecting position, sensor means for receiving light reflected from said plurality of nuclear fuel pellets and for outputting video signals to said judging device. 5. An inspection apparatus according to claim 1, in which said judging device includes: 6. An inspection apparatus according to claim 1, in which said second roller includes a plurality of said ejecting grooves arranged in circumferentially equally spaced relation to one another. 7. An inspection apparatus according to claim 6, further comprising a guide frame for preventing said pellets received in said ejecting grooves from falling out, said guide frame being disposed adjacent to said second roller so as to cover about half the peripheral surface thereof. 8. An inspection apparatus according to claim 1, wherein said sorting members of said sorting unit comprise pivotable plates, each of said plates being disposed vertically below said second roller, each of said plates being pivotable in response to said judging signals between a first position in which said plate defines a first path for receiving non-defective pellets from said ejecting groove of said second roller and guiding said non-defective pellets to a conveying means, and a second position in which said plate defines a second path for receiving defective pellets from said ejecting groove of said second roller and guiding said defective pellets to a recovery means. |
053316754 | summary | BACKGROUND OF THE INVENTION (1) Field of the Invention The present invention relates to an apparatus and a method for control rod exchange work during the regular inspection of a nuclear power plant using a boiling water reactor (referred to BWR), and more particularly an apparatus and a method for attaching or taking off a control rod (referred to CR), and for easily handling a fuel support piece (referred to FS). (2) Description of the Prior Art Conventionally, the spud coupling is used for connecting a CR and a control rod drive mechanism (referred to CRD) in a BWR. In the CR exchange work, such fittings as described in Japanese Patent Laid-Open No. 103399/1981 were presented. However, in a BWR where the above-mentioned spud coupling is adapted, there is the possibility that the connection between a CR and a CRD is disconnected for some reason during plant operation. If such disconnection takes place during plant operation, normal power control become impossible and it is needed to shut down the plant operation. The bayonet coupling is a way solving the above-mentioned problem of the CR-CRD disconnection. In the work of exchanging a CR to which the bayonet coupling is applied, a coupling socket, namely, a CR must be rotated by a predetermined angle for disconnecting the connection. Then, it is necessary to provide an apparatus for rotating a CR in the work of exchanging a CR to which the bayonet coupling is applied. A method for exchanging a CR to which the bayonet coupling is applied was proposed in Japanese Patent Laid-Open No. 205795/1990. In this method, after a FS is taken out above the upper grid plate by using an exclusive handling equipment for a FS, the CR is grasped by use of a CR handling apparatus attached to a fuel exchange apparatus, disconnected from the CRD by rotation and taken out above the upper grid plate by a subsidiary hoist of a fuel exchange apparatus. In attaching a new CR, the CR is connected to the CRD by using the above-mentioned CR handling apparatus in reverse procedures to the above-mentioned procedures and the FS is attached to a reactor core support plate by using an exclusive handling equipment for a FS. This prior art premises that the FS is taken out by the exclusive handling equipment for a FS. Therefore, in applying the prior art, many steps such as attaching or taking off the exclusive handling equipment for a FS and the CR handling apparatus to or from the subsidiary hoist, winching up or down the exclusive handling equipment for a FS and the control rod handling apparatus into or out of the reactor core and so forth are needed, which brings about much time consuming work. SUMMARY OF THE INVENTION (1) Objects of the Invention The present invention has been achieved in the consideration of the above-described problems, and is aimed at providing an apparatus and a method which can shortening the time for exchanging a CR by disconnecting or coupling a CR and a CRD, and taking out or in a CR and a FS continuously. (2) Method Solving the Problem A CR handling apparatus of the present invention for disconnecting or coupling the CR and the CRD using the bayonet coupling, comprises a member for connection attached to a fuel exchange apparatus, a fixing part having guides to be seated at the top face of an upper grid plate in a reactor vessel and to be supported by the upper grid plate, a CR handling part having a CR grasping instrument, a FS handling part having a FS grasping instrument, a means for vertically moving the FS handling part and a means for rotating the CR handling part, the FS handling part and the means for vertically moving the FS handling part. The first method for disconnecting the CR and the CRD by using the above-mentioned CR handling apparatus, comprises the steps of getting down the CR handling apparatus attached to the fuel exchange apparatus, seating the fixing part at the upper grid plate, lowering the FS handling part, seating the bottom part of the FS handling part at the top face of the FS, positioning the FS handling part, grasping the FS and lifting the FS above the upper grid plate, grasping the CR, rotating the CR handling part grasping the CR and the FS handling part grasping the FS by a predetermined angle, disconnecting the connection between the CR and the CRD, and taking out the CR and the FS from the reactor core. And the first method for coupling the connection between the CR and the CRD by using the above-mentioned CR handling apparatus comprises the steps of the reverse procedures to the above-mentioned first method for disconnecting the connection between the CR and the CRD. And the second method for disconnecting the CR and the CRD by using the above-mentioned CR handling apparatus, comprises the steps of getting down the CR handling apparatus attached to the fuel exchange apparatus, seating the fixing part at the upper grid plate, lowering the FS handling part, seating the bottom part of the FS handling part at the top face of the FS, positioning the FS handling part, grasping the FS and lifting the FS above the top part of the CR, grasping the CR, disconnecting the connection between the CR and the CRD by rotating the CR handling part grasping the CR and the FS handling part grasping the FS by a predetermined angle, lifting the FS handling part by the position right below the upper grid plate, rotating the CR handling part and the FS handling part reversely to the above-mentioned rotation by the predetermined angle, and taking out the CR and the FS from the reactor core. And the second method for coupling the CR and the CRD by using the above-mentioned CR handling apparatus comprises the steps of the reverse procedures to the above-mentioned second method for disconnecting the connection between the CR and the CRD. |
summary | ||
052456455 | description | The invention and its advantages will be described in further detail below with respect to the production of two embodiments of a cladding or casing tube for a fuel rod filled with nuclear fuel such as UO.sub.2, for a nuclear reactor fuel assembly. Referring first to FIG. 1 in particular, there is seen a diagram which shows the relationship between an annealing temperature .phi..sub.A and an annealing time t.sub.A and a resultant geometric mean value X.sub.G.sup.A of the diameter of deposits precipitated out of alloy components after the annealing of a first zirconium alloy Zircaloy-4 (1.2 to 1.7 % by weight tin, 0.18 to 0.24% by weight iron, 0.07 to 0.13% by weight chromium, 0.10 to 0.16% by weight oxygen, up to 120 ppm silicon, with the remainder zirconium and unavoidable contaminants; and the sum in % by weight of iron and chromium: 0.28 to 0.37% by weight) and a second zirconium alloy with the alloy ingredients being 1 to 1.2 % by weight tin, 0.35 to 0.45% by weight iron, 0.2 to 0.3% by weight chromium, 0.1 to 0.18% by weight oxygen, and 80 to 120 ppm silicon, with the remainder zirconium and unavoidable contaminants. In the diagram of FIG. 1, the equation below applies to the geometric mean value X.sub.A.sup.G of the diameters of the precipitates of alloy ingredients i.e. components or alloying elements, in the applicable zirconium alloy: ##EQU1## In the diagram of FIG. 1, the upper scale in the abscissa applies to the first zirconium alloy (Zircaloy-4), and the lower abscissa scale applies to the second zirconium alloy. The above equation was obtained empirically for the two zirconium alloys by determining the geometric mean values of the diameters of precipitated of alloy ingredients in test bodies, in each case involving these two zirconium alloys. These test bodies were first heated to a temperature of 1150.degree. C. and then quenched with water. After this .beta.-quenching, the majority of the alloy ingredients, iron and chrome, have precipitated out in finely-dispersed form. A geometric mean value of the diameters of the precipitates in the test bodies was found to be X.sub.G.sup.A min=20 nm. The various test bodies were then exposed to various annealing temperatures for variously long annealing times. After they had cooled down, the geometric mean values of the diameters of the precipitates were determined for each test body. This geometric mean value became higher, as the annealing temperature became higher or the annealing time for the applicable test body became longer. However, this geometric mean value is limited at the top by the relatively small quantity of the iron and chrome alloy ingredients in the applicable test bodies. This limitation is taken into account for the first zirconium alloy by a constant .DELTA.X.sub.A.sup.G =1000 nm, and for the second zirconium alloy by a constant .DELTA.X.sub.A.sup.G =1260 nm in the above-given equation. In this equation, the following symbols have the following meanings: k.sub.1 =0.47.times.10.sup.-7 per hour, n=0.57; the activation temperature Q/R=18,240K (R=general gas constant) and, T=.phi..sub.A +273 K. The diagram in FIG. 2 shows the relationship between a logarithmic variation .epsilon..sub.D in diameter, a logarithmic variation .epsilon..sub.S in wall thickness, a logarithmic cold work .phi., and a quotient q=.epsilon..sub.S /.epsilon..sub.D when a tube is produced by pilgering. The following equations apply: ##EQU2## The diagram of FIG. 3 shows the relationship between cold-deformation C.sub.W, an annealing temperature .phi..sub.R and an annealing time t.sub.R, and a resultant degree of recrystallization R.sub.x after the annealing of the Zircaloy-4 tube cold-deformed by pilgering. The degree of recrystallization R.sub.x is the proportion in percentage of the crystal structure recrystallized after annealing. The empirically obtained equations below apply to the degree of recrystallization R.sub.x : ##EQU3## where the annealing temperature A=t.sub.R .multidot.exp-Q/RT, with the constant k.sub.2 =8.3.times.10.sup.18 min.sup.-1, and the activation temperature Q/R =40,000K (R=general gas constant), and T=.phi..sub.R +273K (see "Zirconium in the Nuclear Industry"; A.S.T.M. Special Technical Publication 824; 1984; pages 106 through 122). A first solid cylindrical blank or tubular body of Zircaloy-4 has the alloy composition 1.2% by weight tin, 0.24% by weight iron, 0.12% by weight chromium, 0.15% by weight oxygen, 0.01% by weight silicon, and the remainder zirconium with technically unavoidable contaminants, and a second solid cylindrical blank or tubular body has the alloy composition 1.1% by weight tin, 0.4% by weight iron, 0.25% by weight chromium, 0.14% by weight oxygen, 100 ppm silicon and the remainder zirconium with technically unavoidable contaminants. In the case of both of these zirconium alloys, the .alpha. range extends to approximately 810.degree. C., the (.alpha.+.beta.) mixed range extends from approximately 810.degree. to 940.degree. C., and the B range begins at approximately 940.degree. C. The diameter of the blank or tubular body is 600 mm. Both blanks or tubular bodies are heated to a temperature in the .beta. range of 1150.degree. C. At this temperature, each of the two solid cylindrical blanks or tubular bodies is forged into a solid cylindrical starting body having a diameter of 350 mm. Next, the two starting bodies are again heated to a temperature in the .beta. range of 1150.degree. C., until such time as precipitated alloy components have dissolved. Then each starting body is quenched in water at a quenching rate of 35 K/s at the surface of the starting body during temperature passage through the (.alpha.+.beta.) range, in other words through the temperature range from 940.degree. to 810.degree. C. Finally, both starting bodies are left to cool to a temperature of approximately 100.degree. C. on the body surface. Then both starting bodies are annealed at a temperature in the .alpha. range, to form precipitates of the iron and chromium alloy components as secondary phases. The annealing temperature selected is 750.degree. C. for both starting bodies. As can be seen from the diagram of FIG. 1, the associated annealing time for forming the desired precipitates is 5 hours. In the alloy of the first starting body, precipitates of the alloy components iron and chromium form as secondary phases having a geometric mean value of 0.2 .mu.m, and in the alloy of the second starting body they form with a geometric mean value of 0.252 .mu.m. Next, the two starting bodies are hot-forged to a diameter of 150 mm at a temperature of 700.degree. C., which is in the .alpha. range. This hot-forging at 700.degree. C. can also be performed before the development of the precipitates of the alloy components in the starting body. After cooling to room temperature, a continuous hole which is 50 mm in diameter is drilled in the axial direction into each of the two cylindrical forged parts produced, forming a hollow cylinder. The hollow cylinders are reheated to a temperature in the .alpha. range of 700.degree. C. and hot-extruded with a cylinder press. The applicable hollow cylinder is pressed by a cylindrical die with an internal mandrel, producing a tube with an unchanged inside diameter of 50 mm and an outside diameter of 80 mm. Both tubes obtained by extrusion are then placed in a pilgering machine and pilgered in four pilgering steps to a finished tube having an inside diameter of 9.30 mm, an outside diameter of 10.75 mm, and thus a wall thickness of 0.72 mm. A pilgering machine is described in U.S. Pat. No. 4,233,834. In the diagram of FIG. 2, a pilgering path I associated with these four pilgering steps is shown with pilgering steps a from 0 to A, b from A to B, c from B to C, and d from C to D. A logarithmic cold work per pilgering step, for the first three pilgering steps a, b, c, is approximately .phi..sub.a =.phi..sub.b =.phi..sub.c =1.1 each time, which is equivalent to a cold-deformation C.sub.Wa and C.sub.Wb and C.sub.Wc of approximately 67% per pilgering step a or b or c. In the last pilgering step d, the logarithmic cold work .phi..sub.d =1.65, which is equivalent to a cold-deformation C.sub.Wd of 81% as a result of this pilgering step d. The ratio q.sub.a =q.sub.b =q.sub.c for the first three pilgering steps a, b and c, is approximately 1.1 each, and for the fourth and last pilgering step d, q.sub.d =approximately 5.5. Between each two pilgering steps, recrystallization annealing is carried out virtually without secondary recrystallization. The degree of recrystallization R.sub.x is 99%, for example. In the case of this degree of recrystallization, the result is good deformability of the tube for the ensuing pilgering step. Through the use of the diagram of FIG. 3, the annealing parameters A represented by the straight line II can be found for a cold-deformation C.sub.W of 67% and a degree of recrystallization R.sub.x at 99%. The intersections of the straight line II with the annealing isotherms define the annealing temperature .phi..sub.R and the associated annealing time t.sub.R, which are necessary to avoid secondary recrystallization in the recrystallization annealings between the pilgering steps. For instance, an annealing temperature of 590.degree. C. and an annealing time of 100 minutes, in a Zircaloy-4 tube having a cold-deformation of 67%, lead to a degree of recrystallization of 99%. The diagram of FIG. 3 is practically equally applicable to a tube made from the zirconium alloy of the second blank or tubular body. After the last pilgering step, both of the tubes are stress relieved in a final annealing. The result is a degree of recrystallization of at most 10%. In the diagram corresponding to FIG. 3, the maximum annealing parameter A for a cold-deformation of 81% and a degree of recrystallization R.sub.x of a maximum of 10% can be seen. The intersections of the straight line IV with the annealing isotherms define the annealing temperature .phi..sub.R and the associated annealing time t.sub.R for a suitable final annealing. For instance, an annealing temperature of 500.degree. C. and an associated annealing time of 400 minutes leads to the degree of recrystallization R.sub.x =10%. The two finished tubes thus obtained have a texture having the Kearns parameter of 0.63, which is determined substantially by the selection of the ratio q.sub.d for the fourth and last pilgering step d. Moreover, the geometric mean value of the diameter of the alloy components iron and chrome precipitated out of the matrix of the first zirconium alloy as second phases is practically unchanged at 0.2 .mu.m, and in the second zirconium alloy is also practically unchanged at 0.252 .mu.m. A material test sample is taken from each of the finished tubes. Both material samples are annealed for two minutes at a temperature of 660.degree. C. The zirconium alloy of the two test samples is found to have a degree of recrystallization of 99% and the geometric mean value of the grain size of the matrix is 2.8 .mu.m for both zirconium alloys. Both finished tubes are used as nuclear fuel-filled cladding or casing tubes of fuel rods and have such high corrosion resistance that they obtain a service life of 4 years in a pressurized water reactor without becoming damaged, while a service life of only 3 years is obtainable with typical tubes of Zircaloy-4. |
abstract | X-ray detectors for generating digital images are disclosed. An example digital X-ray detector includes: a scintillation screen; a reflector configured to reflect light generated by the scintillation screen; and a digital imaging sensor configured to generate a digital image of the light reflected by the reflector. |
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048470376 | abstract | An apparatus for the inspection of nuclear reactor fuel rods combined in fuel rod clusters with spaces therebetween in a fuel assembly includes test probes each being disposed at a different respective level along the fuel assembly. Fingers are each part of a respective one of the test probes. Ultrasonic test heads are each disposed on a respective one of the fingers. The test heads are inserted into the spaces between the fuel rods, and the insertion position of each of the test probes is corrected independently of the insertion position of the others of the test probes, before insertion of the test probes. |
059466391 | abstract | The method for treating ignitable cutting swarf in accordance with the present invention involves collecting cutting swarf in a casting mold underwater and injecting a binder mixture comprising vinyl ester styrene into the vessel to fill void volume; and form a mixture comprising swarf and vinyl ester styrene; and curing the mixture. The method is especially useful for stabilizing the ignitable characteristics of radioactive zirconium cutting swarf, and can be used to solidify zirconium swarf, or other ignitable finely divided material, underwater. The process could also be performed out of water with other particulate wastes. |
050135228 | claims | 1. A method of determining the chemical composition and content of particulate compounds in a flowing liquid using an analyzing apparatus for the particulate compounds and a sealable container positioned in a microwave oven, the sealable container being made of a material that is permeable to microwaves and containing a filter for the particulate compounds, said method comprising the steps of: (a) withdrawing a batch sample of fixed volume from said flowing liquid and passing said sample into said container, (b) causing said sample to pass through said filter in said container to deposit the particulate compounds in the sample on the filter and provide a permeate, (c) removing the permeate from the container, (d) supplying a fixed amount of solvent for the particulate compounds into the container to contact the particulate compounds on the filter, (e) passing microwaves into the container from the microwave oven to heat the solvent and particulate compounds therein and cause the particulate compounds to dissolve in the solvent, forming a solution, and (f) passing the solution to the analysis apparatus for analysis of the particulate compounds therein. 2. The method of claim 1, wherein during steps (b) and (c) a gas is passed through said container. 3. The method of claim 1, including after step (f) a step of passing cleaning water through said container. 4. The method of claim 1, wherein said solvent is a mixture of hydrochloric acid and thioglycolic acid. 5. The method of claim 1, wherein said filter is made of a fluorinated hydrocarbon polymer. 6. The method of claim 1, wherein said flowing water is the water in a recirculation system of a nuclear reactor. 7. The method of claim 1, including repeating steps (a)-(f) a plurality of times so as to obtain a series of determinations of chemical composition and content of particulate compounds in said flowing liquid over a period of time. |
summary | ||
abstract | The disclosed subject matter is related to a circuit pattern inspection apparatus for detecting a gradual changing of defect expanding over a large area of the semiconductor wafer. In order to detect a gradual changing of a defect related condition expanding over a large area of the semiconductor wafer, comparison is made between dies on a wafer that are separated from each other by a distance of at least one die width. For example, when a value according to a difference between such dies exceeds a pre-determined value, an existence of the gradual changing can be confirmed. |
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051577020 | description | Before explaining at least one embodiment of the invention in detail it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purposes of description and should not be regarded as limiting. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The double crystal monochromator 10 according to the present invention is housed within a vacuum chamber 12. The chamber 12 is mounted on a granite block 14 which is supported by a caster assembly 16, FIGS. 1-4. The top surface 18 of the granite block 14 is inspection grade, being lapped flat within 0.00015 inch. This provides a precision surface on which to gauge the travel of the external linear slide 40 and a precision surface 18 upon which the kinematic mounts 17, 19 for the monochromator 10 and the kinematic mounts 21, 23 for the vacuum chamber 12 are seated. A beam inlet port I3 and a beam outlet port 15 are provided on opposite sides of the chamber 12. The double crystal monochromator 10 as shown in FIG. 5 generally includes an entrance crystal assembly 20, a boomerang assembly 22 and a boomerang carriage 24 which are all mounted on a large platform 26 inside the vacuum chamber 12. The platform 26 is supported by legs 28 that pass through the vacuum chamber wall and are seated on he kinematic mounts 17 and 19 on the granite base block 14. The vacuum integrity of the chamber 12 is maintained by means of a stainless steel bellows 30 which is sealed to the legs 28 and to the vacuum chamber 12. The vacuum chamber 12 is also supported independently on the block 14 by legs 35 seated on kinematic mounts 19 and 21. An exit crystal assembly 32 is mounted in an aluminum box or frame 34 which is supported for linear movement in the vacuum chamber 12 by push rods 36 which are sealed to the vacuum chamber 12 by bellows 38, FIG. 1. The frame 34 is balanced on the rod 36 by a counterweight 37 mounted on a shaft 39 on one side of frame 34. It should be noted that the entrance crystal assembly 20 is mounted for pivotal motion on the platform 26 in the path of the incoming beam "A" through inlet port 13. The exit crystal assembly 32 is mounted for pivotal motion in the frame 34 in the path of the diffracted beam "B" from the entrance crystal assembly 20. The reflective beam "C" from crystal assembly 32 is directed through outlet port 15 The boomerang carriage 24 is mounted for linear motion on the platform 26. The boomerang assembly 22 is mounted for pivotal motion on the boomerang carriage 24 and is operatively connected to simultaneously pivot the entrance crystal assembly 20 and the exit crystal assembly 32 when the frame 34 is moved linearly with respect to the platform 26. In this regard and referring to FIGS. 5A and 5B, a schematic representation is shown of the boomerang assembly 22 and the crystal assemblies 20 and 32 in the first and last positions of the boomerang assembly 22. Referring to FIGS. 5A and 5B the boomerang assembly 22 is represented by the guide blocks 46 and 48 which are mounted to pivot about the axis 42 at the intersection of the guide surfaces 50 and 52, respectively. The intersection of the two surfaces and the axes 42 of rotation do not have to coincide, but the surfaces should be at right angles and the axis of rotation should be half way between the elevation of the two crystal axes. The entrance crystal 165 in assembly 20 is located perpendicular to guide surface 50. The exit crystal 166 in assembly 32 is located parallel to guide surface 52. It should be noted that the crystals 165 and 166 are located in a parallel relation to each other. The entrance beam "A" is diffracted by the entrance crystal 165 to exit crystal 166, beam "B." The diffracted beam "B" is reflected by the exit crystal 166, beam "C" in a parallel relation to beam "A." The pivotal motion of the boomerang assembly 22 is translated to linear motion of the pivot axes of the boomerang assembly 22 and crystal assembly 32 by slider assemblies 264 ad 265 which slide along surfaces 50 and 52 of guide block 46 and 48. The pivot axis of crystal 165 is fixed. The pivot axis of the exit crystal 166 must move in a path parallel to the entrance beam "A" so that the exit beam "C" remains parallel to beam "A." In order to maintain this relationship the pivot axis 42 of the boomerang must move in a path parallel to and equidistant from beams "A" and "C" as more specifically described hereinafter. BOOMERANG ASSEMBLY The boomerang assembly 22, FIGS. 9-11, provides the fixed mechanical relationship between the movements of the crystal assemblies 20 and 32. The boomerang assembly includes a short ceramic block 46 and a long ceramic block 48. Each block 46, 48 includes a flat surface 50, 52 which is straight within 8 microinches. The blocks 46, 48 are supported in a right angular relation by an aluminum framework 54 with the flat surfaces 50, 52 aligned with the axis of revolution of the crystal assemblies 20, 32, respectively. In this regard and referring to FIGS. 9, 10 and 11 the boomerang assembly includes a pair of right angled side plates 58, 60 which are connected at each end by end plates 62. An opening 64 is provided in each of the side plates 58, 60. The ceramic blocks 46, 48 are seated on positioning pucks 66 on one side of the blocks and held in position by spring retainers 68 on the other side of the block as shown in FIG. 9A. Each spring retainer 68 includes a screw 65 and a spring 67 positioned in a hole 69 in screw 65. The ceramic block 46 in the short leg in the boomerang assembly is aligned with dowel pins 70 and 72. The ceramic block 48 in the long leg of the boomerang is aligned with dowel pin 70 at one end and is adjusted by means of an angle adjuster in the form of a flexural hinge 56. The block 48 is adjusted by means of an adjustment screw 74 provided at one end of the hinge 56 and a pin 76 at the other end which is positioned to engage the outer end of block 48. Squareness between the ceramic blocks can be adjusted to less than 1 arc second. The boomerang assembly is counterbalanced by means of a counterweight 78 mounted on the end of a rod 80. As more particularly described herein, each crystal assembly 20, 32 includes a crystal 165, 166 respectively, which is supported to rotate about an axis of rotation that lies on one of the surfaces 50, 52 of the ceramic blocks 46, 48 in the boomerang assembly 22. In this regard the exit crystal 166 is positioned in a parallel relation to the surface 52 of the ceramic block 48. The entrance crystal 165 is positioned in a perpendicular relation to the surface 50 of the ceramic block 46. As the boomerang assembly 22 rotates parallelism is maintained between the crystals 165 and 166 by means of slider assemblies 264 and 265. BOOMERANG CARRIAGE The boomerang carriage 24 as shown in FIGS. 22, 23 and 24 generally includes a mounting plate 82 and a base plate 83 for supporting a pair of bearing support pedestals 84. The base plate 83 is secured to the mounting plate 22 by screws 81. The base plate 83 is secured to the pedestals 84 by screws 85. Each pedestal 84 includes an opening 86 for supporting a boomerang shaft 88 which is mounted on roller bearings 90 in openings 86. The shaft 88 passes through the openings 64 in the boomerang assembly 22. A bearing shoulder ring 92 is inserted into each opening 86 in abutting relation to bearings 90. The rings 92 are secured in each end of the openings 86 by pins 94. The carriage 24 is supported for linear motion in the platform 26 by means of DELTRON.TM. crossed roller ways 96 provided in the edges of the mounting plate 82. In this regard and referring to FIG. 22, the carriage 24 is shown mounted in the platform 26 and supported by the cross roller ways 96. A first roller way guide 98 is secured to the platform by screws 100 along the inside edge of plate 82. A second guide 102 is positioned along the outside edge of plate 82 and is biased into engagement with the bottom of platform 26 by springs 104 mounted on screws 106. The second guide 102 is also biased into engagement with the roller way 96 by means of springs 107 mounted in spring plate 108. Crystal Mount And Adjustment Assembly Each crystal assembly 20 and 32, FIGS. 15-20, includes a base plate 87 and a mounting block 89 which is supported on the base plate 87 by means of a ball mount adjustment screw assembly 91. The ball mount assemblies 91 are located at the exact center of the entrance crystal mounting block 89 and the exit crystal mounting block 121. Each ball mount assembly 91 includes a screw 71 which is screwed through a threaded hole in plate 87. A ball 75 is seated in a depression 77 at the end of the screw 71 and a depression 79 in the bottom of the mounting blocks 89 and 121. A spring 61 is mounted on the screw 71 to hold the screw 7; in a set position in the block with the center of the top surface of the mounting block located at a precise distance from the bottom of the plate 87. Although the entrance crystal assembly 20 is substantially the same as the exit crystal assembly 32, there is a difference in the mounting blocks 89, 121 due to the different operating temperatures of the assemblies 20 and 32. The detailed description of the entrance crystal assembly 20 will be fully described herein. The block 89 is secured to the base plate 87 by two screws 93, 95 which pass through the base plate 87 into the bottom of the mounting block 89. The mounting block 89 is biased by means of springs 97 on screws 93 and 95 into engagement with ball mount assembly 91. In this regard it should be noted that the two screws 93, 95 are aligned with the longitudinal and lateral center lines of the mounting block 89. The ball mount assembly 91 is located at the intersection of the centerlines. The mounting block 89 is balanced on the ball mount assembly 91 by means of yaw, pitch and roll flexure assemblies, as described hereinafter. The mounting block 89 includes a tongue 105 on one end and a tab 107 on one side. The tongue 105 is used to adjust the pitch and yaw of the mounting block 89 and the tab 107 is used to adjust the roll of the mounting block 89. It should be noted that the tongue 105 is located on the end opposite screw 93 and the tab 107 is located on the side opposite screw 95. Referring to FIG. 18 yaw adjustment is made by the compound lever flexural hinge assembly 99 which is secured to the base plate 87 by means of screws 109 in a position to engage the end of tongue 105. The hinge assembly 99 includes a base member 111 having an L-shaped arm 113 connected to member 111 by a flexural hinge 115. A coarse adjustment screw 110 is provided in the arm 113 in a position to engage the side of the tongue 105. A spring 119 is provided between tongue 105 and a vertical leg 112 provided on the other end of the base member 111 to bias the tongue toward screw 110. A cross member 114 is connected to the leg 112 by a flexural hinge 116. A secondary adjustment screw 118 is mounted in the cross member 114 in a position to engage the end of the L-shaped arm 113. The outer end of cross member 114 is connected to the base plate 87 by a primary adjuster screw 120. The cross member 114 is biased upwardly from the base plate 87 by means of a spring 122 mounted on the screw 120. Primary yaw adjustment is made by screw 120 which provides one arc second crystal rotation per 2.5.degree. screw rotation. The secondary adjustment screw 118 provides 0.21.degree. crystal rotation per 360.degree. screw rotation and the coarse adjustment screw 110 provides 0.96.degree. crystal rotation per 360.degree. screw rotation. Referring to FIG. 19 pitch adjustment is provided by the compound lever flexural hinge assembly 101 which is positioned to engage the top of the tongue 105. The flexural hinge assembly 101 includes a base member 122 secured to the plate 87 by screws 124. A first leg 126 is provided on one end of the member 122 and is connected to a cross member 127 by a flexural hinge 128. A coarse adjustment screw 130 is positioned to engage the top of the tongue 105 at the center line of the mounting block 89. A second leg 132 is provided on the other end of the member 122 and is connected to an upper cross member 134 by a flexural hinge 136. A secondary adjustment screw 138 is mounted in cross member 134 in a position to engage the end of the cross member 127. The end of the upper cross member 134 is secured to the base plate 87 by a primary adjustment screw 139 and is biased upward by a spring 140 mounted on screw 139. Primary pitch adjustment is made by screw 139 which provides one arc second crystal rotation per 2.86.degree. screw rotation. Secondary adjustment screw 138 provides 0.12.degree. crystal rotation per 360.degree. screw rotation and coarse adjustment screw 130 provides 0.96.degree. crystal rotation per 360.degree. screw rotation. Roll adjustment is achieved by means of flexural hinge assembly 103, FIG. 20, which is mounted on the side of the mounting block 87 in a position to engage the tab 107. The roll flexural hinge assembly 103 includes a cross or base member 141 secured to the plate 87 by screws 142. A first leg 144 is connected to a cross member 146 by a flexural hinge 148. A coarse adjustment screw 150 is mounted on cross member 146 in a position to engage the tab 107 on the center line of the crystal mounting block 89. A second leg 152 on the other end of base member 141 is connected to an upper cross member 156 by a flexural hinge 158 and includes a secondary adjustment screw 160 which is positioned to engage the end of the first cross member 146. The upper cross member 156 is secured to the base plate 87 by means of a primary adjustment screw 162 and is biased upward by a spring 164. Primary roll adjustment by screw 162 provides one arc second crystal rotation per 5.7.degree. screw rotation. Secondary adjustment screw 160 provides 0.226.degree. crystal rotation per 360.degree. screw rotation. Coarse adjustment screw 150 provides 1.19.degree. crystal rotation per 360.degree. screw rotation. Yaw, pitch and roll adjustment of both crystal assemblies 20, 32 can be made in the vacuum chamber 12 by means of linear rotation gimballed ball ended screw driver 42 mounted on each end of the vacuum chamber 12. CRYSTAL ASSEMBLIES The entrance crystal 165 is mounted on the top of the mounting block 89 and retained thereon by hold down plates 168 secured to each side of the block 89 by bolts 169. Each plate 168 includes a series of lightweight compression springs 170 along each edge to bias the crystal I65 into engagement with the surface of block 89. The spring force can be adjusted by screws 171. The crystal 165 is aligned with a fixed dowel 172 mounted on the top of block 89 and is biased into engagement with the dowel 172 by means of a pair of adjustment guides 176. Each of the guides includes a slot 178 aligned with screws 180 mounted on the top of the block 89. The guides 176 are biased by means of springs 182 mounted on shoulder screws 184 screwed into the block 89. The crystal 165 is corrected for yaw variance by rotating an eccentric washer 174 about screw 175. It should be noted that the exit crystal assembly 32 is basically identical to the entrance crystal assembly 20 with one exception. The mounting block 121 for the exit crystal assembly must be heated while the mounting block 89 for the entrance crystal assembly 20 must be cooled. The mounting block 121, therefore, includes a plurality of openings 123, as shown in FIGS. 34 and 35, an electrical coil 125 is threaded through the openings and electrically connected to a control panel (not shown) for heating the block. Each crystal assembly 20 and 32 is mounted on a corresponding scan assembly 184, FIGS. 6 and 24, and 186, FIGS. 7 and 8. The assemblies 20 and 32 are mounted thereon by means of bayonet pins 188, 190 and 192. It should be noted that the bayonet pin 190 has a flat surface 191 and bayonet pins 188 and 192 have ball shaped surfaces 193. The pins 188, 190 and 192 form a three ball kinematic mount that precisely indexes each crystal assembly with respect to the corresponding scan assembly each time a crystal assembly 20 or 32 is assembled into the respective scan assembly. In this regard the entrance crystal assembly 20 is mounted on the scan assembly 184 which is supported for pivotal movement on support blocks 177 on platform 26. The scan assembly 184 includes a base plate 129 having bearing blocks 131, 133 mounted on each end. The bearing block 131 is mounted on a hollow drive shaft 135 which is pivotally supported by a roller bearing 137 mounted on support block 177. The bearing block 133 is mounted on a roller bearing 139 which is supported by a bearing shaft 143 on support block 177. The roller bearings 137, 139 are axially aligned with each other and with the pivot axis of the surface of crystal 165 in assembly 20. A counterweight 173 is connected to the entrance crystal assembly 20 to counterbalance the weight of the copper radiator 194. In this regard and referring to FIGS. 6 and 24, the counterweight 173 is adjustably mounted on a shaft 175 mounted on one end of an offset bracket 179. The other end is connected to a block 181 on the end of a shaft 183. The shaft 183 is inserted into and secured to a hollow tube 185 which is secured to a plate 187 mounted on the side of mounting block 89. It should be noted that the radiator 194 and counterweight 173 are connected directly to the mounting block 89 independently of the bearings 139 and 137 thus balancing the entrance crystal assembly 20 on plate 129. The entrance crystal assembly 20 is positively located on the base plate 129 by the three bayonet pins 188, 190 and 192 which are aligned within corresponding holes provided in base plate 177. The bayonet pins are locked in the base plate 129 by locating pins which are inserted in holes in the ends of pins 188, 190 and 192. The crystal assemblies 20 and 32 can be quickly and easily removed or replaced in the scan assemblies by merely inserting or removing the pins in the bayonet pins 188, 190 and 192. A counterweight 147 is mounted on the bearing block 133 to balance the weight of the scan assembly 184. The exit crystal assembly 32 is supported in frame 34 by a scan assembly 186, FIGS. 7 and 8, which includes a base plate 149 having a bearing block 151, 153 at each end. A shaft 155 is mounted in bearing block 151 and is supported in the frame 34 by a roller bearing 157. The bearing block 153 is supported for rotary motion on a shaft 159 in frame 34 by a roller bearing 161. The roller bearings 157, 161 are axially aligned with each other and with the axis of rotation of the exit crystal 166 on crystal assembly 32. The exit crystal assembly 32 is positively located on base plate 149 by the bayonet pins 188, 190 and 192 which are aligned in corresponding holes (not shown) in the base plate 149. The bayonet pins are locked into the base plate by locating pins which are inserted into holes in the ends of pins 188, 190 and 192 as described above. A counterweight 167 is mounted on a shaft extension 163 on the shaft 155 to counterbalance the weight of assembly 186. The frame 34 is balanced by a counterweight 37. The exit crystal assembly 32 includes a low voltage ultra high vacuum compatible piezoelectric trimmer 33 which is mounted in series with the exit crystal pitch flexural hinge assembly 101 which is connected to the cross member 134. The trimmer 33 controls pitch rotation of exit crystal 166 relative to the entrance crystal 165 in a range of 40 seconds of arc. The trimmer 33 is also capable of applying dither of up to 2 seconds of arc at frequencies up to 30 Hz. RADIATOR The entrance crystal assembly 20 must be able to transfer heat away from the crystal 165 due to the high temperature experienced by the crystal 165 from the incoming beam "A". This is achieved by forming the block 89 from a solid piece of copper which is cooled by means of a copper radiator 194 connected to a copper manifold 196 which is mounted on one side of the mounting block 89. When placed under ultra high vacuum the optically flat surfaces between the mounting block 89, manifold 196 and copper radiator 194 only contact in three places with a microscopic gap elsewhere that is in the microinch range of spacing. This gap is not really a conductive path but would appear to be a convective path. However, in the absence of a gas while under ultra high vacuum, the main mechanism for heat transfer in the gaps becomes radiation which is much reduced at operating temperatures of 150.degree. C. maximum. To aid in heat transfer therefore the mounting block and manifold surfaces are all lapped flat to a quarter wave optical flatness and are then gold plated to prevent oxidation during handling in the atmosphere. The tapered bore 198 in the copper radiator 94 and the tapered connector 200 on the manifold are also lapped and then gold plated. To further reduce the gap problem between optically flat surfaces, a eutectic alloy of gallium and indium which is liquid at room temperature is wiped onto the surfaces that require heat transfer. The gaps are thereby essentially eliminated. This alloy is vacuum compatible because of its extremely low vapor pressure even in its liquid form. Heat transfer by conduction is thereby assured. The copper radiator 194 is cooled by means of a water cooled heat exchanger 195. It should be noted that the radiator 194 and heat exchanger 195 are independent assemblies. The radiator 194 is mounted on the manifold 196 which is secured to the side of the entrance crystal assembly 20 and, therefore, rotates with assembly 20. The heat exchanger 195 is mounted on a mounting plate 197 which is secured to the wall of the vacuum chamber 12 and matingly engages the radiator 194. The radiator 194 as seen in FIGS. 6 and 28 is formed of solid copper having a base plate 199, five concentric rings 201, 202, 203, 204 and 205 on one side of the base plate and a cylindrical mount 206 on the other side of the base plate. The outer ring 201 has a 1/2.degree. draft on the inner surface. The other rings, 202, 203, 204 and 205 have a 1/2.degree. draft on both sides. The mount 206 is provided with a conical opening 198 and a central bore 209. HEAT EXCHANGER The heat exchanger 195 as shown in FIGS. 28-33 is formed from stainless steel and is mounted on a flange 210 in mounting plate 197 for supporting four thin concentric heat exchanger tubes 212 and a solid heat exchanger tube 214. Each of the concentric tubes 212 is 1/8 inch thick and is formed by an outer cylinder 216 and an inner cylinder 218. The outer cylinder 216, FIG. 33, includes an internal spiral rib 219 which forms a spiral channel 220 that terminates at an outlet channel 222. The inner cylinder 218, FIG. 32, has an outer spiral rib 223 which forms a spiral channel 224 that terminates at an inlet channel 226. The inner cylinder 218 is positioned in the outer cylinder 216 with the spiral rib 219 aligned with the rib 223. The channels 220 and 224 are separated by a cylindrical shim 228 which is positioned between the cylinders 216, 218 in abutting engagement with the ribs 219 and 223. Water enters channel 224 through inlet channel 226 flows through channel 224 to the outer end of the cylinder, crosses over to channel 220 and flows through channel 220 for discharge through outlet channel 222. The center heat exchanger 214 is formed by a solid center post 229 having a spiral channel 230 on the outer surface. A cylindrical sleeve 232 is mounted on the post 229 to enclose the channel 230. Water enters the channel 230 through an inlet 234 at the inner end of the channel 230 and exits through a radial port 236 in tube 214 that is connected to an axially extending outlet port 238 in tube 214. The heat exchanger tubes 212 are supported on the center tube 214 by spacer rings 240 of increasing diameters to accommodate the increasing diameters of the tubes 212. The assembled tubes 212 and 214 are aligned with flange 210 on one side of the mounting plate 197 and retained thereon by means of a water manifold plug 242 which is positioned on a flange 244 on the inside of the mounting plate 197 and sealed thereto by an O-ring seal 246. The center tube 214 is secured to the manifold plug 242 by a stud 247, mounted in solid tube 229 and a hex nut 248. The plug 242 is spaced from the tubes 212 and 214 by a washer 250 which defines a water manifold 252. The manifold is separated by an O-ring 254 positioned in a V-shaped groove 256 in the inner surface of plug 242. The O-ring 254 is seated on the surface of the tube assembly to separate the water manifold 252 into an inlet chamber 252A and an outlet chamber 252B. Water is admitted to the chamber 252A through port 260 and discharged from chamber 252B through port 262. The heat exchanger 195 is mounted on the wall of the vacuum chamber. The radiator 194 is axially aligned with the heat exchanger 195 with one of the heat exchanger tubes 212 positioned in the spaces between the rings 201-202; 202-203; 203-204; and 204-205. The center tube 214 is positioned in ring 205. Since the copper radiator is located in the ultra high vacuum chamber cooling thereof is solely by radiation. Radiation cooling is enhanced by coating the copper radiator and the stainless steel heat exchanger with DAG, a high emissivity black vacuum compatible coating. SLIDER ASSEMBLIES Rotation and translation of each crystal assembly 20 and 32 is achieved by means of slider assemblies 264, 265 as shown in FIG. 10. A left-hand slider assembly 265 is used to rotate the exit crystal assembly 32 as shown in FIG. 10. A right-hand slider assembly 264 is used to rotate the entrance crystal assembly 20. Each of the slider assemblies 264 and 265 is connected to the end of the respective drive shaft 135, 155 for each of the crystal assemblies 20 and 32. Each slider assembly 264, 265 includes an arm 270 having a groove 272 cut laterally across the arm with a V-slot 274 provided at the base of the groove 272. A dowel 278 is placed in the V-slot 274 and a gauge block 280 that is flat, parallel and straight within 1 microinch is supported on the dowel 278 in a slightly spaced relation to the sides of groove 272. A pair of holes 276 are drilled through the arm in a parallel spaced relation beneath the groove 272. An end cap 282 is mounted on each side of the arm and secured thereto by bolts 284. Each end cap includes an arcuate recess 286 which is aligned with the holes 276. A number of 1/8 inch balls 285, AFBMA Grade 3 stainless steel, are fed into the holes 276 and aligned on each side of the recess 286 by guide blocks 288. Balls 285 are placed on each side of the top of the gauge block 280 and aligned on each side by means of tongue 290 which is positioned between the balls 285 on the top of the gauge block. The tongue is secured to the end caps by roll pins 292. A pair of bearing races are formed by the holes 276, arcuate recess 286 and the tongue 290 which allows the bearing balls 285 to roll around the races when the slider assemblies 264, 265 move along the guide surfaces 50, 52. The balls 285 in the portion of the races on the top of the gauge block should extend above the surface of the arm 0.005 inch. It should be noted that the gauge block 280 is balanced on the dowel 278 to provide equal force on both of the rows of balls 285. The sliders 264, 265 are secured to the boomerang assembly 22 by means of ball bearing assemblies 294 which are mounted on the opposite side of the ceramic blocks 46, 48, respectively. Referring to FIGS. 9-1l the ball bearing assemblies 294 are shown secured to the arm 270 by a standoff plate 296. A cantilevered plate 298 is secured to the end of plate 296 and supports the ball bearing assembly 294. In this regard, the bearing assembly 294 includes a flexural hinge 300 which is biased by a spring retainer 68 to bias the roller bearing 304 into engagement with the blocks 46, 48. As shown in FIG. 9, the flexural spring 300 has a diagonal slot 303 which terminates at a hinge 305. The spring retainer 68 biases the bearing 304 into engagement with block 48. CRYSTAL TRANSLATION The boomerang assembly 22 maintains the crystals 165, 166 in a parallel relation as the frame 34 is moved relative to the platform 26. It should be noted that the incoming synchrotron radiation beam "A" impinges on the entrance crystal 165 in assembly 20 with specular light reflected off at the same angle as incident to the crystal surface. X-rays diffracted from the crystal laminar planes which are slightly offset from the crystal surface in order to eliminate reflected specular light output from the crystal surfaces. As the entrance crystal 165 rotates, the apparent laminar plane spacing varies inversely as the sine of the angle of incidence. That is, the X-ray path length, one layer to the next, is changing during scan according to the laminar separation t divided by the sine of the angle of incidence 1=t/sin .theta.. For different path lengths, different X-ray wave lengths are diffracted at the same angle as the angle of incidence. Thus, varying monochromatic X-ray wave lengths exit from the instrument as the crystal 165 is rotated. It should be noted that the diffracted beam "B" from the entrance crystal 165 is double the angle of the crystal with eespect to the beam, the same as if it was a reflected beam. That is because the reflected and diffracted beam exits at the same angle as that of incidence. The sum of the two is 2.theta.. For a 12.degree. crystal position, the diffracted beam is 24.degree., FIG. 5B. For a 72.degree. crystal angle, the diffracted beam is at 144.degree., FIG. 5A. To intercept the beam the exit crystal 166 in assembly 32 must not only be parallel to the first crystal but it must also translate linearally with respect to the axis of rotation of the entrance crystal 165 to a position x=h cot 2.theta. to capture the beam "B" right on the center line of rotation of the exit crystal 166 and reflect the exit beam "C" in a parallel relation to beam "A." As described above, linear translation of the exit crystal 166 is achieved by the boomerang assembly 22 as the boomerang pivots about the axis of the entrance crystal 165. TRANSLATION The entire assembly is driven by means of the external linear slide 40, FIGS. 25 and 26, that directly drives frame 34 for the exit crystal assembly 32. The external slide 40 is supported by cross roller way guides for linear motion with respect to the block 14. The slide 40 is driven by a lead screw which is connected to a stepping motor. A glass linear encoder is used to determine linear position. Encoder resolution is 0.000020 inches per count. The stepping motor is a 200 step per revolution motor with microstepping of 128 microsteps per motor step provided by the stepper motor controller, thus giving 25,000 microsteps per revolution (0.000004 inch linear motion per microstep). The axis of the exit crystal assembly 32 travels in a plane parallel to the path of travel of the external linear slide 40. The linear motion of the crystal assembly 32 forces the slider assembly 265 to pivot the boomerang assembly 22 about the axis of rotation of the entrance crystal assembly 32. The pivotal motion of the boomerang assembly 22 also forces the boomerang carriage 24 to move linearly with respect to the platform 26. As the boomerang assembly 22 pivots, the slider assemblies 264, 265 slide along or translate with respect to the surfaces 50, 52 of the boomerang legs 46, 48. The legs 46 and 48 of the boomerang assembly 22 force the crystal assemblies 20 and 32 to rotate as the slider assemblies 264 and 265 move along the surfaces 50, 52, FIGS. 5A and 5B. Limit switches are provided to control the movement of the external linear slide 40, thus allowing for movement to prescribed locations as desired. All of the bearings used in the movements of the boomerang assembly 22 are sprayed with a monatomic layer of solid tungsten disulfide forming a coating about 20 microinches thick. Since the boomerang assembly is moving in an ultrahigh vacuum of 10.sup.-10 Torr, oils and greases cannot be used. The bearings for the boomerang sliders which require microinch flatness of travel are, therefore, not lubricated. The mechanism has no apparent stick-slip even when running under vacuum and after a 150.degree. bakeout. The system is completely balanced since no torque is considered allowable. As seen in FIG. 6 a counterweight 147 is provided to balance the entrance scan assembly 184. A counterweight 173 is provided on one side of the entrance crystal assembly 20 to balance the radiator 194. A counterweight 78 is provided to balance the boomerang assembly 22. A counterweight 167 is provided to balance the exit scan assembly 186. The frame 34 is balanced by a counterweight 37. TEMPERATURE CONTROL Each crystal mounting block 89, 121 has a through hole 306, FIG. 16, beneath the crystals 165, 166 near its center, where the synchrotron beam impinges as shown in FIGS. 21 and 21A. A thermocouple 117 is mounted in the hole 306. The thermocouple 117 includes a square shanked gold plated copper probe 304 which is positioned in the hole 306 and is biased against the underside of the crystal by means of a spring 308. The probe has a lapped tip that is also wetted with gallium-indium for good heat transfer to sense the crystal temperature. The square shank 304 provides a minimum of contact with the round hole 306 so that the predominant source of heat into the probe is from the crystal itself. A Chromel-Alumel thermocouple 305 is mounted in each probe for the actual temperature measurement. The thermocouple leads 310 are taken out of the vacuum chamber via hermetically sealed feedthrough openings and connected to a temperature controller (not shown) which is of a conventional design. The controller has an electrical power outlet for heating the exit crystal support block 121 to the temperature of the entrance crystal block 89. Radiation heat transfer from the entrance block 89 is dependent upon the difference of the fourth power of absolute temperature between the hot and cold blocks. Therefore, before any significant heat transfer can occur from the entrance crystal mounting block its temperature must rise significantly. For that reason the exit crystal block 121 is heated in order that it can track the temperature rise in the cooled crystal block 89. Heat input to the exit crystal mounting block is by radiation from a resistance wire 125 traveling back and forth through the holes 123 in the support block 121. The wire is insulated by ceramic tubes. Thus, it should be apparent that there has been provided in accordance with the present invention a mechanically actuated double crystal monochromator that fully satisfies the aims and advantages set forth above. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. |
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description | The present invention relates to a protective housing for a radionuclide generator. More particularly, the invention relates to a protective housing that covers and protects the inlet and outlet connections of the radionuclide generator. The use of radionuclides for the diagnosis and treatment of various medical conditions is widespread. In diagnostic procedures it is desirable for a diagnostician to be able to clearly view the tissue of interest, such as, for example, a patient's heart. Some radioactive isotopes have an extremely short half-life. Thus, using them is very desirable in diagnosis since they minimize prolonged radiation exposure to the patient, but provide clear images to the medical diagnostician. In practice, these desirable radioactive isotopes are often provided by a radionuclide nuclear generator, such as Bracco Diagnostic's model Cardiogen 82 (Rubidium RB 82 Generator), model #001500. The radionuclide generators are typically used up to 168 times in a one month time frame. The generator typically includes an inlet connection and an outlet connection. Since the generator may be used up to 168 times the connections often get crushed or kinked. If the inlet or outlet connection becomes damaged, the generator will be rendered unusable. Therefore, it would be desirable to provide a protective cover that prevents the inlet and outlet connections from becoming damaged in combination with the radionuclide generator. In accordance with the present invention, a radionuclide generator assembly is provided. The radionuclide generator assembly includes a radionuclide generator that has a distal end and a protective cover that is removably fixed at the distal end. The protective cover comprises a radioactive resistant polypropylene. In another embodiment of the present invention a cover and radionuclide generator assembly is provided. The radionuclide generator assembly includes a radionuclide generator. The radionuclide generator includes a bucket and a distal end that has a generally flat top surface. The cover includes a protective cover that is removably fixed and positioned over the generally flat top surface. In another embodiment of the present invention a protective cover for a radionuclide generator is provided. The cover provides a housing which covers the inlet and outlet ports of the radionuclide generator and struts for releasably engaging the radionuclide generator. In another embodiment of the present invention a protective cover for a radionuclide generator is provided. The cover includes a generally rectangular housing that has a distal end, a generally flat top surface, a first pair of side portions connected to the top surface, a second pair of side portions connected to the top surface. The cover also includes a semicircular notch that is disposed on each of the pair of first side portions, a bottom surface that is connected to the first and second pairs of side portions and at least two struts that are connected to the bottom surface and project away from the generally flat top surface. In another embodiment the above referenced cover may optionally be combined with a radionuclide generator. The radionuclide generator having an inlet port entering the radionuclide generator from a generally flat top surface, an outlet port exiting the radionuclide generator from a generally flat top surface and a u-shaped handle connected to the bucket. The u-shaped handle having a bottom portion and a semicircular top portion that is designed to be contiguous with the semicircular notch that is disposed on each of the first pair of side portions of the protective cover. The at least two struts may optionally provide a ribbed portion. The ribbed portion of the at least two struts engage the bottom portion of the handle of the bucket such that the engagement prevents the cover from being removed from the handle. The at least two struts may optionally provide four struts and each of the four struts may optionally provide a ribbed portion. In another embodiment of the present invention a combination protective cover and a radionuclide generator assembly is provided. The assembly includes a radionuclide generator that has a bucket and a distal end having two generally flat top surfaces. The two generally flat top surfaces having a first distance D1. The radionuclide generator further includes an inlet port that enters from the generally flat top surface, an outlet port that exits from the generally flat top surface and a handle that is connected to the bucket. The handle provides a bottom portion and a semicircular top portion. The semicircular top portion has a third distance D3. The protective cover is positioned over the inlet and outlet ports, the semicircular top portion of the handle and the generally flat top surface of the distal end. The protective cover provides a generally rectangular housing that has a top portion and a first pair of side portions having corresponding inner surfaces. The first pair of side portions are connected to the top portion and have a second distance D2 that lies between the inner surfaces. The generally rectangular housing also provides a second pair of side portions that are connected to the top portion, a semicircular notch on each of the first pair of side portions and a bottom surface that is connected to the first and second pairs of side portions. The protective cover also provides at least two struts that are connected to the bottom surface. The at least two struts project away from the top portion. The at least two struts have an outer surface and a fourth distance D4 that lies between the outer surfaces. The first distance D1 is about equal to the second distance D2 and the third distance D3 is about equal to the fourth distance D4. The about equal distances D1 and D2 provide an interference fit between the at least two struts and the generally rectangular top surface. The about equal distances D3 and D4 provide an interference fit between the outer surfaces of the struts and the semicircular top portion of the handle. In another embodiment of the present invention a combination protective cover and a radionuclide generator assembly is provided. The assembly includes a radionuclide generator that has a bucket, a distal end having two generally flat top surfaces. The two generally flat top surfaces having a first distance D1. The radionuclide generator further includes an inlet port that enters from the generally flat top surface, an outlet port that exits from the generally flat top surface and a handle that is connected to the bucket. The handle provides a bottom portion and a semicircular top portion. The semicircular top portion has a third distance D3. The protective cover is positioned over the inlet and outlet ports, the semicircular top portion of the handle and the generally flat top surface of the distal end. The protective cover provides a generally rectangular housing that has a top portion and a first pair of side portions having corresponding inner surfaces. The first pair of side portions are connected to the top portion and have a second distance D2 that lies between the inner surfaces. The generally rectangular housing also provides a second pair of side portions that are connected to the top portion, a semicircular notch on each of the first pair of side portions and a bottom surface that is connected to the first and second pairs of side portions. The protective cover also provides at least two struts that are connected to the bottom surface. The at least two struts project away from the top portion and have an outer surface, a rib disposed on the outer surface and a fourth distance D4 lying between the outer surfaces. The first distance D1 is about equal to the second distance D2 and the third distance D3 is about equal to the fourth distance D4. The about equal distances D1 and D2 provide an interference fit between the at least two struts and the generally rectangular top surface. The about equal distances D3 and D4 provide an interference fit between the outer surfaces of the struts and the semicircular top portion of the handle. The ribbed portion of each strut latches and engages the bottom portion of the handle such that the engagement prevents removal of the cover from the radionuclide generator. While the invention includes embodiments in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as exemplary of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. Referring to FIG. 1, there is shown in perspective view a radionuclide generator assembly of the present invention. Radionuclide generator assembly 10 comprises a protective housing or cover 14 of the invention and a radionuclide generator 12. Radionuclide generator 12 includes a distal end 16, a u-shaped handle 18 and a bucket 24 that contains a lead liner (not shown) and a column containing the radionuclide (not shown). For purposes of the description of the radionuclide generator and present invention, the term “distal end” refers to the end closest to the end having the inlet and outlet connections, whereas the term “proximal end” refers to the end furthest from the end having the inlet and outlet connections. The distal end 16 includes generally flat top surfaces 20a and 20b and generally flat side surfaces 22a, 22b, 22c and 22d. Referring now to FIG. 2, there is shown a top plan view of the radionuclide generator 12. A first distance D1 spans across the generally flat top surfaces 20a and 20b of the radionuclide generator 12. Generally flat top surface 20a includes an inlet port 28. Saline (not shown) enters the radionuclide generator 12 through an inlet connector assembly 32a and activates the radionuclide generator to create the desired isotope, such as, for example, rubidium (not shown). Inlet connector assembly 32a enters the radionuclide generator 12 through inlet port 28. Inlet connector assembly 32a is directly connected to the column that is housed within the radionuclide generator 12. Generally flat top surface 20b includes an outlet port 30. The radionuclide exits the radionuclide generator 12 through outlet port 30. Outlet connector assembly 32b exits the radionuclide generator 12 through outlet port 30. Outlet connector assembly 32b is directly connected to the column that is housed within the radionuclide generator 12. It should be recognized by those skilled in the art that the location of the inlet and outlet ports need not be limited to their exact positions as shown in FIG. 2. That is, they may, for example, be reversed so that the inlet port is in the location of the outlet port and the outlet port is in the location of the inlet port. This applies to the inlet and outlet connections as well. Referring now to FIGS. 3-4; there are shown two separate perspective views of the protective cover 14. The protective cover 14 is made from a radioactive resistant material such as polypropylene. One such supplier of the radioactive resistant polypropylene material is Huntsman Polyurethanes. Huntsman Polyurethanes is located at 2190 Executive Hills Boulevard, Auburn Hills, Mich. 48326. Their material designation for the radioactive resistant polypropylene is Huntsman H1200 PP. The protective cover 14 includes a housing 38. In a preferred embodiment the housing 38 is generally rectangular; however, the invention includes housings of any shape or configuration sufficient to cover the inlet 28 and outlet 30 ports and to engage with the radionuclide generator such that the cover will only be removed when desired by the user. In a preferred embodiment, the protective cover engages with the radionuclide generator to provide an interference fit such as that described in more detail below. In the embodiment depicted in FIGS. 3-4, the generally rectangular housing 38 includes a top portion 40 and a first pair of side portions 42a and 42b. The first pair of side portions 42a and 42b have corresponding inner surfaces 44a and 44b. The first pair of side portions 42a and 42b are connected to the top portion 40 at a first pair of intersections 46a and 46b. The generally rectangular housing 38 also includes a second pair of side portions 48a and 48b. The second pair of side portions 48a and 48b are connected to the top portion 40 at a second pair of intersections 50a and 50b. It should be recognized by those skilled in the art that the first pair of intersections 46a and 46b and the second pair of intersections 50a and 50b should not be limited to being a particular radius. Additionally, the intersections may optionally be configured to meet to form a right angle. The first pair of side portions 42a and 42b each include a semicircular notch 52a and 52b that is respectively disposed on each of the first pair of side portions. The protective cover 14 also includes a bottom surface 54 that is connected to the first and second pairs of side portions 42a, 42b, 48a and 48b. The first side portion 42a includes at least two struts 56a and 56a′ that are connected to the bottom surface 54 and semicircular notch 52a. The at least two struts 56a and 56a′ project away from the top portion 40. The at least two struts 56a and 56a′ have outer surfaces 58a and 58a′ respectively. A fourth distance D4 spans across the outer surfaces 58a and 58a′. One embodiment is illustrated in FIGS. 1-5. FIG. 5 shows a side perspective view of the radionuclide assembly 10 of the present invention. The u-shaped handle 18 includes a bottom portion 34 and a semicircular top portion 36. A third distance D3 spans across the semicircular top portion 36 of the handle 18. The protective cover 14 is positioned over the inlet 28 and outlet 30 ports, the semicircular top portion 36 of the u-shaped handle 18 and the generally flat top surfaces 20a and 20b of the distal end 16. The semicircular top portion 36 is designed to be contiguous with the semicircular notches 52a and 52b that are disposed on each of the first pair of side portions 42a and 42b respectively. The third distance D3 is about equal to the fourth distance D4. Since the distances D3 and D4 are about equal, an interference fit is created between the outer surfaces 58a and 58a′ of the cover 14 and the semicircular top portion 36 of the handle 18. The range of the interference fit is about (0.002) mm-(0.005) mm. The interference fit keeps the cover 14 positioned over the radionuclide generator 12 so that the inlet and outlet connector assemblies 32a and 32b are protected from any damage that may occur during handling. In use, the protective cover 14 may be removed by holding the protective cover 14 and lifting it off of the assembly 10. The protective cover 14 is secured to the assembly 10 such that it is held snug enough that the protective cover 14 will not fall off during handling. Referring to FIG. 6, there is shown an alternate embodiment of the protective cover 14. In this embodiment, the protective cover is the same as described above except the second side portion 42b may optionally provide two additional struts 60b and 60b′. The two additional struts 60b and 60b′ are configured the same as struts 56a and 56a′ described above. A second distance D2 lies between struts 56a, 56a′, 60b and 60b′. Since the distances D1 and D2 are about equal, a further interference fit is created between struts 56a, 56a′, 60b and 60b′ of the cover 14 and the generally rectangular top surfaces 20a and 20b of the radionuclide generator 12. The range of the interference fit is about (0.002) mm-(0.005) mm. The engagement prevents removal of the cover 14 from the radionuclide generator 12 unless so desired by a user, such as a diagnostician. Referring to FIG. 7, there is shown an alternate embodiment of the protective cover. Protective cover 114 is identical to the protective cover 14 that was described in connection with FIG. 3 above except that struts 156a and 156a′ have ribs 164a and 164a′ that are disposed on outer surfaces 158a and 158a′. The ribs 164a and 164a′ latch and engage the bottom portion 34 of the handle 18. The engagement further prevents removal of the cover 114 from the radionuclide generator 12 unless so desired by a user. Referring to FIG. 8, there is shown another alternate embodiment of the protective cover. The protective cover 114 in this embodiment is the same as the protective cover disclosed in connection with FIG. 7, except the protective cover 114 may include two additional struts 160b and 160b′ that have two additional corresponding ribs 164b and 164b′. The additional ribs 164b and 164b′ latch and engage the bottom portion 34 of the handle 18. This engagement additionally prevents removal of the protective cover 114 from the radionuclide generator 12 unless so desired by the user. |
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claims | 1. An exposure method using X-rays as an exposure beam, said method comprising: a step of setting, in an optical path, a light blocking member for limiting a view angle of exposure by blocking a portion of the exposure beam; a step of setting in the view angle an X-ray transfer mask having an attenuation area for attenuating the exposure beam at an outer periphery of a pattern to be transferred; a step of setting a view angle of exposure on the mask by positioning the light blocking member such that an inner edge of the attenuation area of the X-ray transfer mask overlaps a penumbra of the exposure beam provided by the light blocking member on the mask; and a step of exposing a photosensitive substrate to the pattern to be transferred, formed on the mask in the view angle, to transfer the pattern onto the substrate. 2. An exposure method using X-rays as an exposure beam, said method comprising: a step of setting, in an optical path, a light blocking member for limiting a view angle of exposure by blocking a portion of the exposure beam; a step of setting in the view angle an X-ray transfer mask having an attenuation area for attenuating the exposure beam at an outer periphery of a pattern to be transferred; a step of setting a view angle of exposure on the mask by positioning the light blocking member such that an inner edge of the attenuation area of the X-ray transfer mask overlaps a penumbra of the exposure beam provided by the light blocking member on the mask; a step of determining whether to expose the substrate with an outer area of the pattern to be transferred; a step of controlling a position of the light blocking plate in accordance with a result of a determination in said determining step; and a step of exposing a photosensitive substrate to the pattern to be transferred, formed on the mask in the view angle, to transfer the pattern onto the substrate. 3. An exposure apparatus using X-rays as an exposure beam, said apparatus comprising: a light blocking plate, disposed at a position optically between an exposure beam source for providing an exposure beam and an X-ray transfer mask, for setting a view angle of exposure; and driving means for positioning said light blocking plate to set a view angle of exposure on the mask such that an inner edge of the attenuation area of the X-ray transfer mask overlaps a penumbra of the exposure beam provided by said light blocking member on the mask. 4. An exposure apparatus using X-rays as an exposure beam, said apparatus comprising: a light blocking plate, disposed in a position optically between an exposure beam source for providing an exposure beam and an X-ray transfer mask, for setting a view angle for exposure; driving means for positioning said light blocking plate to set a view angle of exposure on the mask such that an inner edge of the attenuation area of the X-ray transfer mask overlaps a penumbra of the exposure beam provided by said light blocking member on the mask; exposure area determining means for determining whether to expose the substrate with an outer area of the pattern to be transferred; and control means for controlling a position of said light blocking plate in accordance with a result of a determination by said determining means. 5. A semiconductor device manufacturing method using X-rays as an exposure beam, said method comprising: a step of setting, in an optical path, a light blocking member for limiting a view angle of exposure by blocking a portion of the exposure beam; a step of setting in the view angle an X-ray transfer mask having an attenuation area for attenuating the exposure beam at an outer periphery of a pattern to be transferred; a step of setting a view angle of exposure on the mask by positioning the light blocking member such that an inner edge of the attenuation area of the X-ray transfer mask overlaps a penumbra of the exposure beam provided by the light blocking member on the mask; a step of exposing a photosensitive substrate to the pattern to be transferred formed on the mask in the view angle to transfer the pattern onto the substrate; and a step of developing the photosensitive substrate after said exposing step. 6. An exposure method using X-rays as an exposure beam, said method comprising: a step of setting, in an optical path, a light blocking member for limiting a view angle of exposure by blocking a portion of the exposure beam; a step of setting in the view angle an X-ray transfer mask having an attenuation area for attenuating the exposure beam at an outer periphery of a pattern to be transferred; a step of setting a view angle of exposure on the mask by positioning the light blocking member such that an inner edge of the attenuation area of the X-ray transfer mask overlaps a penumbra of the exposure beam provided by the light blocking member on the mask; a step of determining whether to expose the substrate with an outer area of the pattern to be transferred; a step of controlling a position of the light blocking plate in accordance with a result of a determination in said determining step; a step of exposing a photosensitive substrate to the pattern to be transferred formed on the mask in the view angle to transfer the pattern onto the substrate; and a step of developing the photosensitive substrate after said exposing step. |
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046474218 | summary | BACKGROUND OF THE INVENTION This invention relates to operation control methods for nuclear reactors, and more particularly it is concerned with an operation control method for a nuclear reactor that can have application in a nuclear reactor performing a daily load follow-up operation in which power control is effected by using control rods and liquid poisons. A pressure tube type nuclear reactor comprises a multiplicity of pressure tubes having fuel assemblies therein which are mounted in a calandria tank to extend through a moderator contained therein. A coolant flows through the pressure tubes. Power control of this type pressure tube type nuclear reactor is effected by inserting and withdrawing control rods in the moderator between the pressure tubes in the calandria tank, and adjusting the concentration of a liquid poison incorporated in the moderator in the calandria tank. In recent years, there has been a tendency to adopt a method of operation of a nuclear reactor which aims not only at producing a fixed reactor power for a base load but also at developing a reactor power which may vary depending on a fluctuation in load, by performing a load follow-up operation. The pressure tube type nuclear reactor of the type described hereinabove is not an exception, and research has been conducted into the possibilities of incorporating the load follow-up operation in this type of nuclear reactor. For example, a proposal has been made in Japanese Patent Laid-Open No. 141594/82 to incorporate the load follow-up operation in a pressure tube type nuclear reactor. The document referred to hereinabove shows in FIG. 5 thereof a load follow-up operation control system for a pressure tube type nuclear reactor which is designed to effect control of operation of a nuclear reactor in a manner to cope with demands for electrical power which vary from daytime to nighttime during a day by increasing power in the daytime and reducing it in the nighttime everyday. In a nuclear reactor using control rods and liquid poison concentration adjustments as control means, such as a pressure tube type nuclear reactor and pressurised-water reactor, control is effected to keep the reactor power in the range of allowable powers between an upper limit line and a lower limit line set above and below, respectively, a power fall line or a predetermined power fall rate (or a power rise line or a predetermined power rise rate) in accordance with a fall (or a rise) of the reactor power. Load follow-up operation control of a pressure tube type nuclear reactor will be described. In this control process, a high reactor power achieved in the daytime is reduced to a low power level in the nighttime by increasing the concentration of a liquid poison in the calandria tank. Insertion and withdrawal of the control rod are performed only when the reactor power tends to exceed the upper limit line or lower limit line of the range of allowable powers because they cause great damage to the fuel assemblies by bringing about sudden changes in reactor power. Operation of the control rods has a much higher rate of change in reactor power than adjustments of the concentration of the liquid poison, and has the risk of damaging the fuel assemblies in a high nuclear power range. Thus, one should refrain from operating the control rods as much as possible in the high power range. The load follow-up operation control of the pressure tube type nuclear reactor shown in FIG. 5 of the document referred to hereinabove aims at the reduction of the number of times of operation of the control rods during a load follow-up operation of the reactor. The control is effected by obtaining predicted values of changes with time of the reactivity from changes in the reactor power by using values of the reactor power set beforehand and data for analyzing the dynamic characteristics of the nuclear reactor, splitting the time for effecting power control into time units in accordance with the changing rate of reactivity obtained from the predicted values, and determining optimum values of the quantity of liquid poison to be injected or removed for each time unit, to thereby control the concentration of the liquid poison in the calandria tank to an optimum level at all times. Although this control process has achieved a success in reducing the number of times of operation of the control rods, the control rods are still operated for about 300 times to keep the reactor power to the vicinity of 50% when a load follow-up operation of the reactor is performed while maintaining the reactor power at a 50% level. SUMMARY OF THE INVENTION An object of this invention is to provide a method of operation control for a nuclear reactor enabling load follow-up operation control performed repeatedly to be simplified in process. Another object is to provide a method of operation control for a nuclear reactor capable of reducing the number of times of operation of control means for effecting coarse adjustments of the power of the nuclear reactor. One outstanding characteristic of the invention is that a reactivity introduced by operating control means in a first cycle of a load variation program is obtained, a manipulated variable of second control means for effecting fine adjustments of reactor power in a second cycle of the load variation program which follows the first cycle is obtained based on the reactivity introduced in the first cycle, and control of reactor power is effected by operating the second control means in the second cycle based on the manipulated variable obtained in the first cycle. The outstanding characteristic described hereinabove simplifies the process of effecting load follow-up operation control because power control is effected by operating the second control means in the next following cycle based on the reactivity introduced in the preceding cycle, thereby facilitating load follow-up operation control. Another outstanding characteristic is that a reactivity introduced by operating first control means in a first cycle of a load variation program is obtained, a manipulated variable of second control means for effecting fine adjustments of reactor power in a second cycle of the load variation program which follows the first cycle is obtained based on the reactivity introduced in the first cycle, and control of reactor power is effected by operating the second control means in the second cycle based on the manipulated variable obtained in the first cycle, when a change in the reactivity occurring in the second cycle becomes equal to a change in the reactivity occurring in the first cycle. The outstanding characteristic described hereinabove enables the number of times of operation of the first control means for effecting coarse adjustments of reactor power to be reduced much more than the first mentioned outstanding characteristic. It has been ascertained that, when load follow-up operation of a pressure tube type nuclear reactor is performed, if the load variation program has the same pattern for each and every day of the operation or if the operation is performed in accordance with the same load variation cycle every day, then changes in the reactor core reactivity have substantially the same pattern after the second day of operation. This phenomenon will be described. FIG. 1 shows changes in the reactivity in the reactor core of a pressure tube type nuclear reactor which occur when load follow-up operation is performed by varying the load every day. In this case, the load follow-up operation is performed in accordance with a load variation program 37A having an operation pattern (load variation cycle) in which an electrical power is reduced from 100% to 50% in one hour as indicated by a characteristic 1 (solid line) and kept at a 50% level for eight hours, followed by a rise from 50% to a 100% level in one hour after lapse of the eight hours and holding the electric power at the 100% level for fourteen hours. This operation pattern is repeated every day. Assume that the pressure tube type nuclear reactor has been operated to obtain 100% of electrical power until the load follow-up operation in conformity with the load follow-up operation program 37A is initiated. Then, if the electrical power changes as indicated by the characteristic 1, a thermal power of the nuclear reactor changes from 55% to 100% as indicated by a characteristic 2 (broken line) and the concentration of xenon produced in the reactor core by nuclear fission changes as represented by a characteristic 3 (one-dot-and-dash line). If the electrical power shows the changes represented by the characteristic 1, then the reactor core reactivity changes as indicated by a characteristic 4 (two-dot-and-dash line) under the influences of the changes in the xenon concentration and power coefficient. The reactor core reactivity indicated by the characteristic 4 is such that, except for the first day on which the mode of operation of the nuclear reactor is switched, changes occurring in the reactor core reactivity follow substantially the same pattern every day. This phenomenon occurs also when the pattern of load follow-up operation is switched from one with a range between a high electrical power of 100% and a low electrical power of 50% to one with a range between a high electrical power of 100% and a low electrical power of 70%. Stated differently, when the load follow-up operation is performed in accordance with the latter pattern, changes occurring in the reactor core reactivity follow substantially the same pattern after the second day following the first day of introduction of a change in pattern. The invention is based on the discovery that when load follow-up operation is performed repeatedly in accordance with the same pattern, changes occurring in the reactor core reactivity are substantially equal to each other after the same pattern of operation is repeatedly performed several times. |
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description | The present invention relates generally to ion implantation systems, and more particularly to a system and method for ion dose measurement and compensation in the presence of photoresist outgassing, pressure and ion source fluctuations in a serial ion implanter. In the manufacture of semiconductor devices, ion implantation is used to dope semiconductors with impurities. Ion beam implanters are used to treat silicon wafers with an ion beam, in order to produce n or p type extrinsic material doping or to form passivation layers during fabrication of an integrated circuit. When used for doping semiconductors, the ion beam implanter injects a selected ion species to produce the desired extrinsic material. Implanting ions generated from source materials such as antimony, arsenic or phosphorus results in “n type” extrinsic material wafers, whereas if “p type” extrinsic material wafers are desired, ions generated with source materials such as boron, gallium or indium may be implanted. Typical ion beam implanters include an ion source for generating positively charged ions from ionizable source materials. The generated ions are formed into a beam and directed along a predetermined beam path to an implantation station. The ion beam implanter may include beam forming and shaping structures extending between the ion source and the implantation station. The beam forming and shaping structures maintain the ion beam and bound an elongated interior cavity or passageway through which the beam passes en route to the implantation station. When operating an implanter, this passageway is typically evacuated to reduce the probability of ions being deflected from the predetermined beam path as a result of collisions with air molecules. The mass of an ion relative to the charge thereon (e.g., charge-to-mass ratio) affects the degree to which it is accelerated both axially and transversely by an electrostatic or magnetic field. Therefore, the beam which reaches a desired area of a semiconductor wafer or other target can be made very pure since ions of undesirable molecular weight will be deflected to positions away from the beam and implantation of other than desired materials can be avoided. The process of selectively separating ions of desired and undesired charge-to-mass ratios is known as mass analysis. Mass analyzers typically employ a mass analysis magnet creating a dipole magnetic field to deflect various ions in an ion beam via magnetic deflection in an arcuate passageway which will effectively separate ions of different charge-to-mass ratios. Dosimetry is the measurement of ions implanted in a wafer or other workpiece. In controlling the dosage of implanted ions, closed loop feedback control systems typically are utilized in order to dynamically adjust the implantation to achieve uniformity in the implanted workpiece. Such control systems utilize real-time current monitoring to control the slow scan velocity of an implanter. A Faraday disk or Faraday cup periodically measures the beam current and adjusts the slow scan speed to ensure a constant dose. Frequent measurement allows the dose control system to respond quickly to changes in beam current. The Faraday cup may be stationary, well shielded, and located close to the wafers, making it sensitive to the beam current dosing the wafers. However, Faraday cups measure only the electric current portion of the beam current. Interactions between the ion beam and gases evolved during implant can cause the electric current, a charge flux, to vary even when the particle current, a dopant flux, is constant. To compensate for this effect, the dose controller may read the beam current from the Faraday cup and the pressure from a pressure gauge concurrently. When a pressure compensation factor is specified for an implantation recipe, the measured beam current is modified by software to present a compensated beam current signal to the circuit controlling the slow scan. The amount of compensation (e.g., in the compensated beam current signal) in such a closed loop system may thus be a function of both the current measured at the Faraday cup and the pressure. When properly applied, pressure compensation improves repeatability and uniformity over a wide range of implant pressures. However, the vacuum in an implanter is never perfect. There is always some residual gas in the system. Usually the residual gas poses no problems (in fact, a small amount of residual gas is beneficial for good beam transport and effective charge control). However, at high enough pressure, for example, increased pressure due to photoresist outgassing, charge exchange between the ion beam and the residual gas can cause dosimetry errors. If the shift in dose between implants into bare wafers and implants into photoresist-coated (PR) wafers is unacceptably large, or if the dose uniformity is significantly degraded, then pressure compensation may be employed in order to improve uniformity. Charge exchange reactions between ion beams and residual gas can add or subtract electrons from the ion, changing the ion's charge state from the value desired in the recipe. When the charge exchange reaction is neutralization, a portion of the incident ion flux is neutralized. The result is a reduction in the electrical current while the particle current (including neutrals) remains unchanged. When the charge exchange reaction is electron stripping, a portion of the ion flux loses electrons. The result is an increase in the electrical current while the particle current remains the same. For typical recipes where charge exchange is an issue, the beam often undergoes much more neutralization than stripping. As a result, the beam current measured by the Faraday cup decreases whenever the end station pressure increases. Ions in the beam are neutralized, but they are not deflected or stopped by the residual gas. The dose rate, dopant atoms per area per time, is unchanged by charge exchange after the analyzer magnet. Implanted neutrals contribute to the dose received by the wafer, but are not measured by the Faraday cup. As a result, the wafer may become overdosed. Pressure compensation may thus be employed whenever charge exchange between the ion beam and residual gas in the process chamber has a significant effect on dose. The pressure at which this happens depends on the recipe and the process specifications. For some recipes, compensation is required to meet implanter specification when the pressure due to photoresist outgassing is 5×10−6 torr as measured on the pressure gauge. For most recipes where the pressure due to photoresist outgassing is 2×10−5 torr or higher, compensation may be worth investigating. Such compensation may include measuring the effect of photoresist outgassing by implanting monitor wafers with and without photoresist, and comparing the measured variation to the process specification. The amount of compensation required depends on the pressure, which the dose controller reads from a pressure gauge during the implant. In addition, changes in the ion source output itself may result in some of the beam current variations measured at the dose cups. Dose cup measurements of such ion source changes at the wafer are also subject to the proportion of neutral generation to the electric current measured and outgassing pressure changes as discussed. It is necessary to compensate dose rates for the actual change in ion flux at the wafer which requires the system to differentiate between a change in the current caused by a change in source output and a change caused by charge exchange in the gas in the beam path. Therefore, the use of such dose cup measurements to correct or compensate dose rates may be significantly hampered by these variables. Thus, there is a need for improved systems and methods for obtaining uniform dose rates in ion implanters without the added complications and costs associated with the use of pressure measurements and pressure compensation in the presence of beam current changes from the ion source and outgassing from the wafer. The present invention is directed to a system and method for providing an accurate ion current measurement associated with the dose of a wafer for use in an ion implantation system. In accordance with the present invention, the ion implantation system has a dose cup located near a final energy bend of a scanned or ribbon-like ion beam of a serial implanter. The system comprises an ion implanter having a charged particle source for producing a ribbon-like ion beam. The system further comprises an angular energy filter (AEF) system configured to filter an energy of the ribbon-like ion beam using the final energy bend in the ion beam. The AEF system further comprises the AEF dose cup preferably immediately following the final energy bend of the ion beam to provide an accurate measurement of the ion current of the beam. The AEF system directs the beam along a beam path in a downstream direction toward a target wafer held in an end station. The AEF system is defined by a chamber or AEF chamber wherein the AEF components reside upstream of the process chamber or end station. The end station downstream of the AEF system is defined by a chamber wherein the wafer or workpiece is secured in place for movement relative to the ribbon-like ion beam for implanting ions into the wafer. The AEF system may include pumping that maintains a lower pressure near the AEF than in the end station where the gas is being generated. The AEF system may be separated from the end station chamber by an opening that limits gas flow so as to allow a pressure difference between the AEF chamber and the end station process chamber. The AEF dose cup in one aspect of the present invention is beneficially located up stream of the end station within the AEF system near the final energy bend to mitigate pressure variations due to outgassing from implantation operations on the wafer. Thus, the system provides accurate ion current measurement before such gases can produce substantial quantities of neutral particles in the ion beam, generally without the need for pressure compensation. Such dosimetry measurements may also be used to affect the scan velocity of the wafer to ensure uniform closed loop dose control in the presence of beam current changes from the ion source and outgassing from the wafer. In accordance with one aspect of the present invention, the ion beam may comprise a scanned or a continuous ribbon-like beam. In another aspect of the present invention, the plane of the final energy bend in the ion beam is orthogonal to the plane of the ribbon-like ion beam In accordance with still another aspect of the present invention, the AEF system is located in an AEF chamber region upsteam of the endstation, and the pressure within the AEF chamber is further reduced by a pump, thereby reducing the effect of outgassing and other sources of pressure on the AEF dose cup. Although in one aspect of the invention the AEF dose cup is located near the final energy bend in the AEF chamber and upstream of the end station and no pressure compensation is employed, in another aspect of the present invention, the ion implantation system further comprises pressure compensation to further refine the AEF dose cup measurements. In yet another aspect of the present invention, the AEF dose cup is located in an overscan region in relationship to the wafer or workpiece scanned by the ribbon-like ion beam. In another aspect of the present invention, the readings from a profiler cup at about the plane of the wafer are compared to those of the AEF cup during an implant to deduce the charge exchange rate difference between the two positions, thereby enabling a determination of the number of neutral particles produced over the corresponding path length. Although some ions will become neutral in transit to the wafer in the system of the present invention, the ion current Imeasured measured at the AEF dose cup, will be proportional to the particle current Iimplanted going to the wafer according to: (1) Iimplanted=Imeasured*CP*CCC, where Cp is a factor which corrects for the fraction of beam current which underwent charge exchange to neutrals or higher charge states as defined below, and CCC is a proportionality constant which may be determined during a cup calibration at an initial implant setup for each recipe based on the ratio of current measured at the AEF dose cup relative to the current measured near the plane of the wafer (e.g., as measured by a profile cup at the wafer). (a) In the case where the pressure in the AEF region remains low enough that charge exchange over the short path between the AEF bend and the AEF cup is a small fraction of the actual current, Cp can be assumed to be =1. This is expected to cover most of the recipes of a medium current tool. (b) Alternatively, in the case where pressure in the AEF region is high enough to affect IAEF=Imeasured*CCC enough to require correction, pressure compensation could be used on the AEF cup reading using Cp=exp(K*PAEF) as is done presently on high current tools. In that case K can be determined empirically by plotting the beam current measured in a Faraday cup used for dose control as a function of pressure as the pressure is increased over a range of interest as described in “Two Implant Measurement of Pressure Compensation Factors”, Mike Halling, IEEE Proceedings of 2000 International Conference on Ion Implantation Technology, Alpbach, Austria, (2000) 585. The plot of measured beam current vs pressure can be fit to a function of I0=Imeasured*exp(K*P), where I0 is the current at zero pressure and K is the factor that best fits the data. (c) A third alternative is to use the difference in current between the AEF cup and the cup in the end station to compensate for charge exchange. In this case,Cp=1+((IAEF−IES)/IAEF)*(LAEF/(LES−LAEF))* (PAEF/PES), where IAEF is the current measured by the AEF cup corrected by setup cup calibration IES is the current measured by the End Station cup corrected by setup cup calibration LAEF is nominally the distance from the AEF bend to the AEF cup LES is nominally the distance from the AEF bend to the End Station cup PAEF is the pressure measured in the AEF chamber PES is the pressure measured in the End Station This approach enables the AEF cup current to be corrected for the shorter distance over which charge exchange can affect its reading compared to the End Station cup, which is done by the factor, (LAEF/(LES−LAEF). It also allows for that shorter distance to be corrected for the lower pressure in the AEF region, which is nominally done by the factor, (PAEF/PES). These two factors are applied to the fractional change in beam current between the two cups, (IAEF−IES)/IAEF). This approach may provide a non-empirical pressure compensation. To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the invention. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other aspects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. The present invention will now be described with reference to the drawings wherein like reference numerals are used to refer to like elements throughout. The invention provides a system and method for providing an accurate ion current measurement associated with the dose of a wafer for use in an ion implantation system. Such use may include dosimetry measurements, data recordings, and feedback to the system for closed loop control of, for example, the velocity of a wafer slow scan motion drive. Dose control in the presence of high pressures in the process chamber, particularly due to photo-resist outgassing, requires a means of determining the effective implant beam current when some fraction of the beam ions have become neutralized on their path to the wafer. Traditionally this has been accomplished by measuring the pressure in the beam path and correcting the current measured at the wafer in the end station by estimating the fraction that has become neutral based on the pressure and known or empirically determined charge exchange probability. These measurement and estimation techniques are cumbersome, may be expensive, and may introduce additional inaccuracies to the final dose determination, particularly in association with beam current changes from the ion source and outgassing from the wafer. The ion implantation system of the present invention combines a final energy filter having a final energy bend and a scanned or ribbon-like beam to provide a new beginning point for the ion beam. That is, beginning from the final energy bend, the ion beam is substantially without neutrals in the ion beam that is directed toward the wafer. In accordance with one aspect of the invention, a Faraday dose cup is provided immediately after a final energy bend that is orthogonal to the plane of the ribbon-like beam. In this way, ion current is measured before there is significant opportunity to create neutrals in the path directed toward the wafer. Thus, cup current measurement near the final energy bend eliminates the need for pressure compensation of the measured current in a significant portion of implant conditions. By contrast, dose cups located in the end station or chamber region suffer the substantial deleterious effects of photo-resist outgassing. Referring now to the drawings, FIGS. 1 and 2 illustrates an ion beam implantation system shown generally at 100, in which the various aspects of the present invention may be implemented. The system 100 includes an ion implanter 102 for providing ions that form a scanned or ribbon-like ion beam 104 that traverses a beam path through an angular energy filter (AEF) system 110 using a final energy bend to filter and redirect the ions of a final energy ion beam 114 for implantation into a workpiece or wafer 118 at end station 120. In the present invention, the terms wafer and workpiece will be used interchangeably. The AEF system 110 comprises a pair of deflection plates 122 that electrostatically (or alternately magnetically) bend charged ions of the scanned or ribbon-like ion beam 104 to produce the resultant ion beam 114 at a selective final energy. Suppression electrodes 124 of the AEF system 110, terminate the potential field of a positive charged deflection plate so electrons are not pulled from the end station 120. The AEF system 110 further comprises an AEF dose cup 128 immediately following the final energy bend of the ion beam to accurately measure the ion current. The final energy bend of the AEF system further serves to direct the energy filtered beam 114 along a beam path in a downstream direction toward the target wafer 118 held by an electrostatic clamp 130 in end station 120. FIG. 3 illustrates a diagram 300 of several system components and a region scanned by the ion beam of the implantation system of FIGS. 1 and 2 as viewed from the energy filtered ion beam 114. The ribbon-like ion beam 114 impacts the wafer 118, held to, for example, a translating disk-shaped electrostatic clamp 130 within the end station 120 or another such implantation chamber. Although a translating clamp 130 is disclosed, it should also be appreciated that the present invention is equally applicable to several types of clamp motions, including rotation, translation, and that of a “serial” ion beam implanter, that is, one in which the ion beam 114 is directed to scan over the surface of a stationary workpiece 118. The translating “slow scan” or “y” motion 330 of the wafer 118, together with the “x” width of the scanned or ribbon-like ion beam 114 provides a larger scanned region 310, which encompasses the entire wafer 118. The area not used or scanned by the wafer is termed an overscan region 320 which may be useful for dose measurements. In accordance with the present invention, immediately after the final energy bend, the ribbon-like ion beam 114 also impacts the AEF dose cup 128 of FIG. 2 enroute to the wafer 118. FIG. 3 illustrates that AEF dose cup 128 makes use of the overscan region 320, and thus does not interfere with the beam striking the workpiece. Unlike conventional systems that have the dose cup at, near, or beyond the wafer, the ion implantation system 100 of the present invention provides the AEF dose cup 128 of the AEF system 110 within an AEF chamber, well upstream of the end station or implantation chamber, thereby mitigating the outgassing and ion exchange issues discussed. In addition, by having the dose cup 128 immediately after the final energy bend, neutral ions have been removed from the beam and very little neutralization of the beam has yet to occur, thereby making the measured electric current an extremely accurate approximation of the implant current. Although AEF dose cup 128 is illustrated on the right side of the ion beam overscan region 320 in this example, it should also be appreciated that in the present invention either left or right sides of the ion beam overscan may be utilized for placement of the AEF dose cup 128, such as dose cup alternate position 128a. FIG. 4 illustrates selected final energy filter components of an exemplary ion beam implantation system 400 in accordance with the present invention. An implanter (e.g., 102 of FIGS. 1 and 2) may be used to provide a scanned or ribbon-like ion beam 104. Ion beam 104 enters an angular energy filter AEF system 110, wherein the beam is bent (deflected) between deflection plates 122 that may, for example, comprise a positive potential plate 122a (e.g., +25 kV) and a negative potential plate 122b (e.g., −25 kV). Ion beam 104 then passes through suppression electrodes 124 for termination of the positive potential deflection plate 122a and energy absorption of the neutral portion of the beam. The ion current within ion beam 104 is then measured by the AEF dose cup 128 within the AEF system 110 immediately after the energy bend at plates 122 before being directed downstream toward an end station 120. The AEF dose cup 128 measures the ion current associated with final energy of beam 104 before the beam traverses a significant distance of the beam path toward the workpiece and suffers an ever increasing rate of ion exchange. Thus, a more accurate dose measurement may be obtained relative to that of typical measurements made at or about the vicinity of the wafer. As AEF dose cup 128 measures the ion current in the overscan region (e.g., 320 FIG. 3), either left or right sides of the ion beam overscan (or both) may be utilized for placement of the dose cup 128, such as dose cup alternate position 128a. Ion beam implantation system 400 further comprises components within the end station 120 defined by an implantation chamber wall. Energy filter slits 440 further define the height and therefore the energy band of acceptable ions within the ion beam 114 directed toward the wafer 118. A profiler or profiler dose cup 442 at or near the plane of the wafer may be used at implant set-up and for calibration of the system 400. FIGS. 5A and 5B schematically illustrate top plan and right side views, respectively, of an ion beam path and several possible dose cup locations for monitoring ion current during implant using an ion beam implantation system 500 in accordance with the present invention. System 500 generates a scanned or ribbon-like ion beam 502 from an ion source, wherein the ions of the beam, in one example, are uniformly shaped and accelerated by a P-Lens and acceleration tube 503 to a more energetic state or a less energetic state. Ion beam 502 then enters an angular energy filter system 504 configured to filter an energy of the beam 502. For example, a generally positively charged ion beam 502 is bent (e.g., about nominal bend axis 505) by deflection plates 506 toward the negative deflection plate and away from the positive deflection plate by an angle (e.g., a 15° angle) corresponding to the final energy state and direction desired. Although a 15° deflection angle is illustrated and discussed herein, it should also be appreciated that any such angle and corresponding energy may be used in accordance with the present invention. After the ion beam has been bent by the deflection plates 506, the beam 502 then passes through suppression electrodes 507 for termination of the positive potential deflection plate (e.g., 122a) and energy absorption of the neutral portion of the beam 502. The ion current within ion beam 502 is then measured by AEF dose cup 508 within the AEF system 504 immediately after being directed in a downstream direction toward an end station 510. The AEF dose cup 508 measures the ion current associated with final energy of beam 502 before the beam traverses a significant distance of the beam path toward the workpiece 512. Following the AEF system 504, the ion beam 502 leaves the AEF system 504 in the AEF chamber section and traverses the beam path downstream entering the end station 510. In the evacuated implantation chamber of the end station 510, the ion beam enters an electron flood assembly (EF) 514 that controls the electron charge on the wafer 512. EF 514 may also optionally, comprise one or more associated dose cups 516, which may be used to monitor overscan current in the end station. Ion beam 502 then impacts the wafer 512, a profiler dose cup 518 for measuring the flux across the wafer 512, and finally a tune flag 520 used to measure the unscanned or scanned beam current while beam optics is being adjusted to the desired value prior to implant. During setup, just prior to start of implant, current measured in dose cups 508 and 516 are compared to the flux measured by the profile cup 518 as it passes across the scanned beam near the plane of the wafer. Since implant has not yet begun, there is relatively little correction at this time for charge exchange differences between these cups, but the differences in location may result in small differences in current due to flux variations and beam transport differences between the positions of the dose cups and the position of the wafer. The factor Ccc=IP-cup/IAEF in equation (1) measured during cup calibration corrects for these effects. A similar factor Ccc′=IP-cup/IES is used to calibrate the end station cup 516. This correction ensures that currents measured at the dose cups 508 or 516 are scaled appropriately to represent the current at the wafer and useable for accurate dose control in the absence of large pressure changes. During implant as charged ions traverse the ion beam path 502, they suffer charge exchange collisions with stray gas molecules. Although the effect is minimized in the present invention, some fraction of the ions are neutralized and will not be counted by dose cups 508 or 516. Therefore, the measured ion beam current may not completely reflect the actual dopant flux at the wafer 512. However, one of the methods, a, b, or c described above, can be applied to the AEF dose cup reading during implant to correct for the charge exchange effects on the beam current. In order to minimize the effect of outgassing at the wafer, the AEF dose cup 508 is located as far as possible from the end station in a part of the system such as the AEF chamber that has a much better vacuum. Still, the fraction of ions made neutral after the bend that contribute to the implanted dose may be accounted for, for example, using the proportionality constant CP to obtain the actual implanted dose level. For example, for most implants, the lower pressure rise in the AEF and shorter distance for charge exchange may keep the effects of charge exchange in the AEF dose cup small enough that they can be ignored and Cp=1 gives adequate dose control. On the other hand, if experience shows that some implants result in a higher level of outgassing such that the pressure in the AEF region is high enough to significantly affect the AEF dose cup reading, this condition can be corrected using either of the two methods of deriving Cp as shown above in (b) and (c). This conclusion may be determined in one of several ways: 1) The dose accumulated in a photo-resist covered wafer may be approximately 1% or more different from a bare wafer implanted by the same recipe. Or, there may be non-uniformity in the dose of a photo-resist covered wafer due to more outgassing which occurs as the beam sweeps across the middle of the wafer compared to the ends of the slow scan where it spends less time on the wafer. 2) A significant change in the reading of the AEF cup current correlated with a change in the AEF pressure during implant would indicate that the current reading is affected by charge exchange rather than source output changes. 3) A large change in the End Station dose cup 516 correlated with a smaller change in the AEF dose cup reading is consistent with charge exchange in this path to the wafer. FIG. 6 illustrates another exemplary ion beam implantation system 600 in accordance with the present invention. System 600 further illustrates the path of an ion beam 602 through the system 600 having an angular energy filter system 604 located in a region of an AEF chamber 607 upsteam of the endstation 610 residing within an implantation process chamber 612. The atmosphere within the end station 610 may be isolated from that of the AEF chamber 607 by a vacuum isolation valve 614. During operations, the pressure within one or both of these chambers may be reduced by a vacuum or cryogenic pump, for example, vacuum pump 620 and two cryogenic pumps 622. In one implementation of the present invention, the pressure within the AEF chamber region 607, may be reduced below the pressure of the end station 610, thereby reducing the effect of outgassing and other sources of pressure on the AEF dose cup. Similar to the previously described systems, system 600 generates a scanned or ribbon-like ion beam 602 from an ion source, wherein the ions are either accelerated or decelerated as desired by acceleration tube 626. Ion beam 602 then enters an angular energy filter system 604 configured to filter an energy of the beam 602. For example, a generally positively charged ion beam 602 is bent by deflection plates 630 away from the positive deflection plate 630a and toward the negative deflection plate 630b by an angle (e.g., a 15° angle) corresponding to the final energy state and direction desired. The ions within ion beam 602 having the desired energy are now deflected in a desired beam path trajectory thru suppression electrodes 632 and to an AEF dose cup 634 of the AEF system 604 located near the AEF bend. The energy of undeflected neutral particles may be absorbed by a neutral beam trap 636 following the suppression electrodes. The AEF dose cup 634 may be located just behind this neutral beam dump. Over-energetic ions are filtered out (trapped) by high energy contaminate dump 638, while under-energetic ions are filtered out by low energy contaminant dump 640 (shown two places). The resultant ion beam 602 having the desired energy, together with a proportion of neutral particles formed in ion exchanges after the final energy bend, then impacts a wafer 642, held by wafer support structure 644 within the implantation process chamber 612 of the end station 610. The wafer support structure 644 may be utilized to impart rotary and/or translational motion to the wafer relative to the scanned or ribbon-like ion beam 602. During a production run, that is, when semiconductor wafer workpieces 642 are being impinged upon by the ion beam 602 and thereby being implanted with ions, the ion beam 602 travels through an evacuated path from the ion source (not shown) to the implantation chamber 612, which is also evacuated. The ion beam 602 strikes the wafer workpiece 642 as it rotates and/or translates (e.g., 330 of FIG. 3). In accordance with one aspect of the present invention, the ion dosage received by the workpiece 642 may be determined (at least partially) by the velocity of translation of the support structure 644 under closed-loop control of control electronics (not shown) as provided by feedback from measurements of the AEF dose cup 634. FIG. 7 illustrates an exemplary AEF system 704 suitable for use in the ion beam implantation systems of FIGS. 1–6 in accordance with the present invention. AEF system 704 has a mounting 705 which may be mounted on either the right or left hand side of the AEF chamber wall 707. AEF system 704 comprises deflection plates 730 that typically utilize a high voltage potential (e.g., +/−25 kV) on positive and negative deflection plates, 730a and 730b, respectively, to deflect a positively charged ion beam 702 as shown. In the present implementation, ion beam 702 is bent about 15° in a downward direction relative to a horizontal beam path, passing through suppression electrodes 732 to an AEF dose cup 734 before continuing downstream to the end station and the wafer workpiece. Similar to the other components of the AEF system 704, the AEF dose cup 734 may also be affixed to mounting 705 or may be mounted to the side or rear wall of the AEF chamber 707. A goal of the present invention is to locate the AEF dose cup 734 as near as possible to final energy bend within the AEF system 704, given consideration for other factors such as maintaining uniform deflection fields within the AEF. Accordingly, the purpose of this location is to provide the ions the shortest possible path for ion exchange before the dose measurement is made, and to mount the dose cup 734 in a location that will achieve the best possible vacuum to minimize ion exchange collisions. In addition, it is intended to place the AEF dose cup 734 as far as possible from the wafer, which is a major source of pressure due to photoresist outgassing, thereby minimizing such ion exchange collision opportunities that negatively impact dosimetry. AEF system 704 further comprises another set of suppression electrodes 740 used to suppress electrons from moving from the AEF region toward the acceleration tube. Thus, in the systems described in the present invention, a dose cup is located near the AEF final energy bend to measure those ions that remain charged long enough to complete the bend in the beam path to the wafer, but before traversing much of that path length. In that way, the current as such a cup becomes proportional to the current going to the wafer and would suffer substantially less charge exchange than the dose cups previously used for that purpose in the end station. The proportionality constant CP may be determined by one of two disclosed methods to compensate for pressure changes that are large enough to require corrections. Then, during implant, CP and the AEF dose measurement may be used to determine the actual implanted dose proportional to the AEF dose measurement, as shown in equations (1) above. Thus, as indicated above, other dose cups such as those shown at 516 of FIG. 5A may be unnecessary. The effect of photoresist outgassing on the AEF dose cup may be further reduced by locating a pump at the AEF chamber (e.g., 607, 707) in order to keep the pressure within the AEF chamber lower than that of the process chamber 612. Thus, a dose cup located at a final energy bend of a scanned or ribbon-like ion beam may be used for accurate dosimetry measurements or for closed loop dose control. Such control may be used to affect scan velocity to ensure uniform dose in the presence of beam current changes from the ion source output, for example, or in the presence of outgassing from the wafer. Although the invention has been shown and described with respect to a certain applications and implementations, it will be appreciated that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, systems, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure, which performs the function in the herein illustrated exemplary implementations of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms “includes”, “including”, “has”, “having”, and variants thereof are used in either the detailed description or the claims, these terms are intended to be inclusive in a manner similar to the term “comprising”. |
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abstract | A subject is imaged for treatment of the subject such as an eye to be inspected, while irradiating a charged particle beam on the eye, so that an aim position of a charged particle beam for treatment can be determined. |
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053295625 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, an embodiment for accomplishing the first means of the present invention will be explained with reference to the accompanying drawings. As shown in FIG. 1, a pressure vessel 1 inside a reactor is supported at its jaw 3 by a concrete base 2. When this pressure vessel 2 is to be dismantled, a grouting material 4 is pressure-fed via an opening bored in the jaw 3 or between the jaw 3 and the concrete base 2. The grouting material uses cement and a mortar paste as a base material and contains a suitable amount of admixtures for making a packing operation smooth and for improving fluidity. A grouting material of a non-shrinkable type is used. Besides the grouting material, a synthetic resin such as an epoxy resin and a suitable material such as cement can be used as materials for fixing installation, pipings, etc, inside the reactor. An opening 6 is also bored in the upper part of the pressure vessel 1 and a similar grouting material 5 is packed through this opening 6. As a result, the inside and outer periphery of the pressure vessel and the inside of the concrete base, inclusive of various instruments such as the pipings, are all integrated and solidified after the solidification of the grouting material. When the grouting material 5 is packed, a vibrator may be used so that the grouting material 5 can be reliably packed even into narrow spaces of the pressure vessel 1. To horizontally cut the structure 7 inside the reactor which is thus integrated by the grouting material, a first endless wire saw 12 is passed around a first guide pulley 10 and a first driving pulley 11 which are fixed to a wall 8 so that their vertical positions can be freely adjusted, as shown in FIGS. 2 and 3. The first driving pulley 11 is fixed to a first driving device 13 which is equipped therein with a driving motor, and the height of this first driving device 13 is adjustable. The first driving pulley 11 is fixed to the first driving device 13 in such a manner as to be movable in a direction of the structure to be cut, and when its fixing position is adjusted, the tension of the first wire saw 12 can be kept substantially constant. A pull side 14 of the first wire saw 12 is hooked to the structure 7 inside the reactor and its feed side 15 is directly set over the first guide pulley 10 through guide rollers 16, 16. A second wire saw 17 is disposed at the back with respect to the cutting direction of the first wire saw 12 and is passed around a second guide pulley 18 and a second driving pulley 19. The second driving pulley 19 is fixed to a second driving device 20 equipped therein with a driving motor and the height of this second driving device 20 is adjustable. The second driving pulley 19 is fixed to the second driving device 20 in such a manner as to be capable of moving in the direction of the structure to be cut, and the tension of the second wire saw 17 can be kept substantially constant. A pull side 21 of the second wire saw 17 is put into a cutting groove formed by the first wire saw in the structure 7 inside the reactor, and its feed side 22 is directly set over the second guide pulley 17 through guide rollers 23, 23 that are fixed to the structure inside the reactor. According to the construction described above, the structure 7 inside the reactor is gradually cut integrally with the metal members, concrete members and the grouting material which is packed, by the pull side 14 of the first wire saw 17. In order to integrally cut the concrete materials, inclusive of the austenitic stainless steel, constituting the pressure vessel, it is suitable to use, as the wire saw, a diamond sintered cutting edge obtained by connecting beads formed by sintering diamond grains with powder of cobalt, bronze, etc, a diamond electrodeposition cutting edge obtained by connecting beads formed by electro-depositing diamond onto an alloy of steel in a nickel solution, or a wire-like wire saw obtained by electrodeposition diamond grains to a steel wire. Among them, the diamond electrodeposition cutting edge and the wire-like wire saw involve the problem that since the diamond layer exists only on the surface of the alloy, the wire saw must be replaced by another as soon as the diamond layer on the surface is worn out, and hence, the replacement of the wire saw must be carried out very frequently. If the diamond sintered cutting edge is used, in contrast, a new cutting edge appears one after another as the surface is worn out, so that cuttability is high and the frequency of the replacement of the wire saw drops. However, when the diamond sintered cutting edge is used, the diameter of the wire saw becomes smaller due to the wear at the time of cutting and when the wire saw must be replaced in the middle of cutting, a new wire saw having an initial diameter cannot be fitted easily into the cutting portion. Therefore, cutting is effected by the second wire saw 17 immediately after cutting by the first wire saw 12, as shown in FIG. 2. As a result, the first wire saw 12 as a preceding cutting edge forms the cutting groove 25 and the second wire saw 17 defines a cutting width adjustment portion 26 as shown in FIG. 4 so that a new wire saw having the initial diameter can be fitted into the cutting groove by the cutting width adjustment portion 26. Accordingly, when the first wire saw 12 as the preceding cutting edge is worn out, the second wire saw 17 plays the role of the receding first wire and forms a new cutting edge, and the new wire saw inserted at the back of the second wire saw 17 functions as the second wire saw for the cutting width adjustment. In this way, the reactor structure is cut horizontally and when this cutting is carried out starting with the upper part of the structure inside the reactor with predetermined intervals, the structure inside the reactor is finely cut in the horizontal direction. As a horizontal cutting apparatus for the structure of the reactor, a truck 29 that runs on right and left rails 27, 28 as shown in FIG. 5, for example, can also be used. A driving motor 32 is fixed to a first frame 30 of this truck 29, and a first wire saw 34 set over a driving pulley 33 of the driving motor 32 is then passed sequentially around guide pullies 35, 36, 37, 38, 39, 40 that are supported by the truck 29, so as to constitute a first wire saw driving portion 41. A second wire saw driving portion 42 having a construction similar to that of the first wire saw driving portion 41 is disposed immediately at the back of the first wire saw driving portion 41. The first wire saw 34 is used as the preceding cutting edge and the second wire saw 43, as the cutting width adjustment cutting edge. When the horizontal plane of the wire saw driving device and the cutting horizontal plane are different, a driving device 48 supporting the driving pulley 47 is disposed on the truck 46 on the foundation surface 45 as shown in FIG. 6, the wire saw 50 set over the driving pulley 47 is guided to the cutting horizontal direction by the guide pullies 51, 52, and the wire saw 50 is disposed to be driven inside the horizontal plane by the vertical pulley 53 and horizontal guide pulley 54 that are fixed to the structure 7 inside the reactor. The truck 46 moves back in such a manner as to keep a predetermined tension in accordance with the cutting condition. Cutting on an arbitrary horizontal plane becomes possible by fixing a guide pulley unit 55 comprising the vertical guide pulley 53 and the horizontal guide pulley 54 described above onto an arbitrary horizontal plane. When the structure inside the reactor is cut vertically, on the other hand, a gate-shaped frame 60 is disposed movably on rails 61, 62 in such a manner as to encompass the structure 7 inside the reactor as shown in FIG. 7. The wire saws are passed around pullies 65, 66 of pulley units 65, 66 that are disposed on support poles 63, 64 of the gate-shaped frame 60 in such a manner as to be movable in the vertical direction, and while the wire saw 68 is being driven by a motor 67, cutting is carried out in the vertical direction by lowering the pulley units 65, 66 in accordance with the cutting condition. Cutting in the vertical direction can be made by the use of the following arrangement. A driving pulley 73 is supported on a truck 72 disposed movably on a rail 71 of a base 70 as shown in FIG. 8, and a driving device 74 equipped therein with a motor is provided. Then, the wire saw 69 set over the driving pulley 73 is passed around guide pullies 78, 79 disposed at upper and lower portions of a wall 77 through the guide pullies 75, 75, 76. When the wire saw 69 is placed over the top of the structure 7 inside the reactor and is driven, the structure 7 inside the reactor is cut in the vertical direction and when the truck 72 is moved back in accordance with this cutting operation, the wire saw can make cutting always with a predetermined tension. The cutting operation described above is preferably carried out remotely in consideration of adverse influences of radioactivity on the human body. In this instance, video cameras 80 are disposed around the structure 7 inside the reactor to be cut as shown in FIG. 9, and the image of the structure 7 is monitored by a video monitor 82 disposed inside a remote control room 81. An operator operates an operation panel 83 and controls the operation of the driving device 83. Incidentally, FIG. 9 shows an example where cutting is carried out by a single wire saw when cutting the structure 7 inside the reactor in the horizontal direction. Wedges may be driven into the cutting groove in order to prevent the fall by gravity of the structure inside the reactor due to the expansion of the cutting groove during the cutting operation. After the cutting operations are carried out in both the horizontal and vertical directions as described above, the structure 7 inside the reactor is cut into a large number of blocks as shown in FIG. 10. In each of the blocks, the appliances that particularly emit radioactivity are sealed by the grouting material. Therefore, the emission of radioactivity of each block is small, and the blocks are transported to the site of disposal by suitable transportation means, and are stored or processed. An embodiment for accomplishing the second object of the present invention will be explained with reference to the drawings. As shown in FIG. 11, the pressure vessel 101 inside the nuclear reactor is supported at its jaw 103 by the concrete base 102 and to dismantle the reactor, a cement grouting material or a synthetic resin material 104 is pressure-fed through openings formed at the jaw 103 or from between the jaw 103 and the concrete base 102. The cement grouting material comprises a cement and a mortar paste as the base material and a suitable amount of an admixture for accomplishing smooth packing and improving fluidity. A non-shrinkable material is suitable as this admixture. Various synthetic resins, such as a polyester resin, a polyether resin, a polyacrylonitrile resin, a polyamide resin, a vinyl chloride resin, an epoxy resin, a melamine resin, a polyurethane resin, can be used as the synthetic resin material. An inorganic material consisting of calcium aluminate and calcium silicate as the principal components can also be employed. An opening 106 is formed at the upper part of the pressure vessel 101, and a similar grouting material 105 or synthetic resin material is also packed through this opening 106. Furthermore, a framework is set up around the outer periphery of the upper part of the pressure vessel 101 and the concrete material is packed into the inside and solidified so as to form an outer peripheral concrete portion 109. As a result, after the cement grouting material or the synthetic resin material and the concrete material are solidified, the inside of the pressure vessel 101 and its outer periphery and the inside of the concrete base 102, inclusive of various appliances such as pipings, are all integrated and solidified by the cement grouting material or the synthetic resin material, and their outer periphery is covered with the concrete portion and the concrete base. When the reactor internal structure 107, which is thus integrated by the cement grouting material or the synthetic resin material and the concrete, is cut in the horizontal direction, an endless wire saw 112 is passed around a guide pulley 110 and a driving pulley 111 that are so fixed on a wall 108 as to be capable of adjusting their vertical positions as shown in FIGS. 12 and 13. The driving pulley 111 is fixed to a driving device 113 with a built-in driving motor, and the driving device 113 is fixed in such a manner that its height is adjustable. The driving pulley 111 is fixed to the driving device 113 so that it can be move freely in the cutting direction of the material. Accordingly, when its fixed position is adjusted, the tension of the wire saw 112 can be kept substantially constant. A pull side 114 of the wire saw 112 is hooked on the reactor internal structure 107 while its feed side 115 is hooked directly on the guide pulley 110 through guide rollers 116, 116. The wire saw 112 cuts integrally the concrete materials such as the austenitic stainless steel constituting the pressure vessel and to this end, diamond sintered beads or electrodeposition beads formed by baking diamond grains with powder such as cobalt bronze are used. When the sintered beads are used in the present invention particularly for cutting the main body of the nuclear reactor made of the stainless steel, the concrete material is provided to the outer periphery of the main body of the reactor and for this reason, even when the surface of the cutting edge becomes flattened and its sharpness drops, the corners of the surface of the cutting edge which becomes flattened is cut away when the wire saw passes through the concrete material layer and cuts into the concrete material, so that a suitable cutting edge can be formed. In this way, the concrete material on the outer periphery of the reactor main body plays the role of the grinding stone for the sintered beads of the wire saw. When the horizontal plane of the driving device of the wire saw is different from that of the cut portion, a driving device 121 supporting a driving pulley 120 is disposed on a truck 118 on the surface of a foundation 117, a wire saw 122 passed around the driving pulley 120 is guided in a cutting horizontal direction by guide pulleys 123, 124, and the wire saw 122 is disposed drivably inside the horizontal plane by a vertical guide pulley 125 and a horizontal guide pulley 126 that are fixed to the reactor internal structure 107, etc, as shown in FIG. 14. The truck 118 moves back in accordance with the cutting state so that the wire saw can maintain a predetermined tension. Cutting on an arbitrary horizontal plane becomes possible by fixing a pulley unit 127 consisting of the vertical guide pulley 125 and the horizontal pulley 126 to an arbitrary horizontal plane. A wedge may be implanted appropriately into the cut groove. On the other hand, when the reactor internal structure is cut in the vertical direction, a gate-shaped frame 130 is movably disposed on rails 131, 132 in such a fashion as to surround the reactor internal structure 107 as shown in FIG. 15. A wire saw 138 is wound on each pulley of pulley units 135, 136 so disposed on support poles 133, 134 of the gate-shaped frame 130 as to be movable in the vertical direction, and while the wire saw 138 is being driven by a motor 137, the pulley units 135, 136 are lowered in match with the cutting state so as to carry out cutting in the vertical direction. The top of the reactor main body is substantially spherical. Therefore, even when an operator attempts to start cutting of an arbitrary vertical section, it is very difficult to cut the section because the wire saw slips on the spherical surface. In accordance with the present invention, however, since the concrete material is provided to the outer periphery of the reactor main body, the concrete material can be easily cut when the wire saw is set to an arbitrary vertical section and then the cutting operation is started. When the wire saw reaches the reactor main body as cutting proceeds, the cut groove of the concrete material functions as a guide groove and the wire saw can cut the spherical surface of the reactor main body without slipping on the spherical surface. When the cutting operation is carried out in both the horizontal and vertical directions as described above, the reactor internal structure 107 is cut into a large number of blocks as shown in FIG. 16. Since the appliances and the like emitting radioactivity are sealed by the concrete material and the grouting material in these blocks, emission of radioactivity of each of the blocks is less. Therefore, the blocks are transported to the site of disposal by suitable conveyor means, and are preserved or processed there. A new nuclear reactor can be set up at the site after removal of the old reactor. When it is desired to shorten the time required for cutting and dismantling, and the cutting time or in other words, the execution time, due to the term of works, the overall term of works can be reduced to a half by plasma-cutting the metallic portions at the outer part of the reactor after the grouting material or the synthetic resin material is packed into the reactor, and then cutting the inside of the reactor with a wire saw. The plasma-cutting method in such a case can use an oxidizing plasma such as oxygen plasma and air plasma, nitrogen plasma (inclusive of a water jet system which jets water to an operation gas), and a plasma consisting mainly of argon such as an argon-nitrogen plasma and an argon-hydrogen plasma. The first object of the present invention is accomplished as described above. In other words, various internal and external members of the structure inside the reactor are all integrated and solidified by the grouting material, and each appliance does not move at the time of cutting, so that the cutting operation can be carried out stably. Since fragments and pieces do not scatter at the time of cutting of each appliance, contamination by radioactivity can be reduced. Since the appliances in the blocks are covered with the grouting material at the time of cutting, radioactivity emitted from each block is reduced and transportation of the blocks becomes safer. The cutting operation can be carried out smoothly by the use of the wire saw having the diamond grains on the surface. Since the preceding cutting edge and the cutting groove width adjustment cutting edge are used for the cutting operation, the cutting groove width which becomes smaller with the wear of the preceding cutting edge can be kept at a predetermined width by the cutting groove width adjustment cutting edge that follows. Accordingly, a new cutting edge can be inserted easily into the cutting groove and the cutting operation becomes smooth. When the second object of the invention is accomplished in the way as described above, the wire saw first cuts the concrete material at the start of cutting of the structure. Therefore, the cutting operation can be started smoothly and the cut section becomes stable. As the cutting operation proceeds and the wire saw reaches the metal surface of the reactor main body, the cut groove of the concrete serves as the guide groove for the wire saw, so that the wire saw does not slip along the curved surface on the metal surface but can stably cut a predetermined position. Even when the surface of the sintered material of the wire saw is worn out and flattened and its sharpness drops during cutting of the metallic reactor main body, the corners of the flattened cutting surface are cut off and the concrete material plays the role of the grinding stone when the wire saw cuts the metal surface of the reactor main body, which is equipped with the concrete material layer around the outer periphery of the metal surface, through the concrete layer. Accordingly, the wire saw can always maintain a stable cutting edge surface and can maintain also stable cuttability for a long period. |
054835631 | summary | BACKGROUND OF THE INVENTION Fabrication of the seamless tubing with multi-layered metals provides superior corrosion, strength, or performance properties over that offered by tubing with only a one layer composition. The demand for high performance nuclear fuel cladding material is increasing due to higher nuclear fuel burn-ups and longer component lifetime requirements. Generally, the extrusion billet is assembled with multiple metallic cylinders of different alloys to produce a thin inside or outside layer. Typical products include a zirconium alloy outside layer on a zirconium alloy base material called duplex, a zirconium inside layer with a zirconium alloy base called barrier, or a zirconium layer between two zirconium alloy layers called triplex. The process involves machining the zirconium or zirconium alloy components into base and liner assemblies. The components are typically cleaned to remove foreign debris like dirt and oil by pickling in baths of hydrofluoric and nitric acids before assembling into billet components. The annular opening at each end of the component is sealed by electron beam welding the end joints in vacuum. The welded billet is preheated between 550.degree.-750.degree. C. and extruded into a seamless tube. The extrusion cycle metallurgically bonds the dissimilar metals by temperature and pressure. The stringent quality requirements of the nuclear industry require inspection by ultrasonic techniques for bondline defects. The sensitivity of the ultrasonic test typically detects defects larger than 125 .mu.m in transverse width. The metallurgical bond between the two metallic layers is influenced by the extrusion cycle and component cleaning process prior to billet assembly. The short extrusion cycle may not adequately bond the two or more metallic layers especially if contamination exists in the annulus of the billet. Thus, U.S. Pat. No. 4,977,034 proposed to heal the bondline defects by hot isostatic pressing instead of eliminating the cause of defects. The contamination is typically of a zirconium-fluoride species that remains chemically bonded to the cleaned component after the hydrofluoric acid pickling. During the extrusion cycle, regions of the bondzone with a high concentration of fluoride-rich residue form voids where the dissimilar metals fail to bond. Small bondline voids may not be detected with ultrasonic inspection but can be revealed by destructive testing. Bondline defects can be detrimental to the fuel cladding's performance since a large void can create discontinuities in the heat transfer efficiency and cause a localized increase in the corrosion rate for the duplex type tubing. The present invention provides a process to improve the bond integrity between the metallic layers by cleaning the cylindrical components by ice blasting. |
abstract | A method and system for generating flashes on a substrate. The method includes receiving one or more figures of a pattern to be printed on the substrate and decomposing each figure into at least four substantially rectangular shapes. The four substantially rectangular shapes are separated by at least one horizontal boundary and at least one vertical boundary. The method further includes generating a flash for each substantially rectangular shape such that each edge of each figure is an image of the same aperture. |
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054250722 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of treating a surface, and more particularly a surface contaminated with radionuclides. 2. Discussion of the Prior Art In the nuclear industry, surfaces of objects including mechanical components and constructional features may become contaminated with radionuclides such as cobalt-60, caesium-137 or strontium-90, or radioactive compounds such as PuO.sub.2 or UO.sub.2. Current practices for treating these surfaces include the use of chemical reagents, and abrasive jets. However, the contaminating radionuclides may penetrate deeply into the surface portion of the components or features and may present difficulties in being removed by these known surface treatments. A number of alternative surface treatments have been tried by others. One such treatment is described in European patent specification number EP 91646 A1 which discloses a method of removing a radioactive metal oxide from the surface of a radioactive component by means of a laser beam directed at the surface. In UK patent specification number GB 2242060 A a concrete surface contaminated with tritium is treated by irradiating the surface with microwaves in order to vaporise water from the surface thereby removing tritium. German patent specification number DE 3500750 A discloses a method for removing radioactively contaminated surface layers of concrete from a reinforced concrete structure by inductively heating the reinforcing bars within the structure. In a further method, described in Japanese patent specification number JP 3002595 A, a radioactively contaminated concrete surface is removed by irradiating the surface with microwave radiation. In all of these alternative treatments radioactive contamination is removed from a surface or else the contaminated surface is itself removed. Because of the nature of these treatments, the contamination becomes airborne thus necessitating downstream processing and leading to further complications and expense. SUMMARY OF THE INVENTION According to the present invention there is provided a method of treating a surface contaminated with radionuclides, the method comprising passing a local area of intense heat across the surface so as to fix or seal the radionuclides therein. As stated previously, the aforementioned alternative treatments are used to remove contamination from a surface or to remove a surface layer containing contamination. None of these aforementioned treatments provide a method which achieves fixing or sealing of the contamination to a surface as is provided by the present invention. The present invention allows simpler and cheaper treatment. Desirably, in the present invention, the intense heat has an energy level of at least 150 W/cm.sup.2. Preferably, the intense heat is applied by a laser source, or from a laser source through a fibre optic cable. The local area of intense heat may be passed, eg in an x-y raster fashion across the surface by moving the object defining the surface and/or by moving a source of the intense heat. A relatively large treatment area may be achieved by overlapping movement of the object and/or the source of the intense heat. The contaminated surface may comprise a layer applied to an object, for example a paint, or a plastics coating such as an epoxy layer. At least one layer of a coating material may be applied before or after the application of the intense heat to fix and seal the radionuclides on or in the object by melting the coating material and forming a bond of the coating material to a substrate, or by forming a fused layer comprising the coating material and said substrate material. Examples of coating materials include glass, metal, ceramics, pozzolana and chamotte, or a mixture thereof. A further application of intense heat may be necessary to bond the coating to the surface. In another application of the invention to a metal surface, the local area of intense heat causes local melting of the metal at the surface which subsequently solidifies as the local area of intense heat passes across the surface. The melting and re-solidification at the surface fixes the radionuclides in the metal and may repair local faults at the surface such as porosity or cracks. |
046510095 | summary | BACKGROUND OF THE INVENTION The present invention relates to a contact exposure apparatus wherein a member is exposed to a pattern of another member while they are in close-contact with each other, more particularly, the apparatus wherein a difference between vacuum pressure to one of the members and to the other is utilized. Conventionally, the apparatus of this type is often used with a so-called mask aligner. FIG. 1 shows an example of such an apparatus, wherein an expansible and closed space or chamber 6 is formed between the two members which, in this case, a mask 1 and a wafer 3. The space is evacuated so that the mask 1 is bent or curved toward the wafer 3 by the atmospheric pressure exerted to the backside of the mask 1 to bring them into close-contact with each other. Since however, the gases existing in the space between the mask 1 and the wafer 3 is quickly evacuated to a high vacuum required for the desired close-contact from the atmospheric pressure, the conventional apparatus involves the following drawbacks. Firstly, the close-contact therebetween is degraded. In the prior art apparatus, the entire surfaces of the mask 1 and the wafer 3 start contacting substantially simultaneously at all points. Then, the gases in the middle of the wafer 3 can not escape, tending to be captured there. This tendency is remarkable, particularly when the wafer 3 is processed after it has been subjected to some of many semiconductor manufacturing process steps resulting in deteriorated flatness of its surface. The gases thus captured degrade the close contact. When this occurs, the light can diffract in the fine space between the mask 1 and the wafer 3 created by the captured gases, which results in poor resolution. Thus, in the contact type exposure apparatus, the poor close-contact directly leads to poor pattern exposure. In order to vent the captured gases, the conventional apparatus is operated in such a manner that the pattern exposure operation is carried out with a delay of time after they are contacted. This, however, has been a cause of preventing the increase of throughput, that is, the number of wafers processed per unit time. The second drawback is an increase in a pitch error. In the above described apparatus, when the mask 1 and the wafer 3 are to be contacted to each other, they are supported with a proper space therebetween, and thereafter, the closed space 6 formed therebetween is evacuated so as to allow the atmospheric pressure exerted to the backside of the mask 1 to curve the mask 1 toward the wafer 3, thus bringing them into close-contact with each other. In doing this, the initial setting of the gap or clearance between the mask 1 and the wafer 3 has a significant influence to the closeness of the contact. More particularly, when the gap is small, the amount of curve of the mask 1 is small so that the closeness in the marginal areas is better and that the so-called pitch error is smaller. The pitch error is an error in which the mask pattern is projected slightly out of alignment with the position where it is to be projected, because the pattern of the mask 1 is expanded due to the curve of the mask 1. On the contrary, as explained hereinbefore, the closeness in the central area is rather poor because of the fine gaps created. When, on the other hand, the amount of the gap is large, as shown in FIG. 2, the mask 1 is greatly curved, so that the contact between the mask 1 and wafer 3 starts at the central area, and the contacted area extends gradually toward marginal areas with the increase of the vacuum. Therefore, the occurrence of the captured gases in the neighborhood of the center of the mask 1 and the wafer 3 is mitigated, and therefore, the closeness of contact in the central area is increased. However, since the mask 1 is significantly curved toward the wafer 3, the pitch error is larger in this case. Therefore, in the prior art apparatus, when the gap is increased in order to provide a better closeness of contact between the two members, such as the mask 1 and the wafer 3, a larger pitch error results; whereas if the gap is reduced in an attempt to decrease the pitch error, the poor closeness of contact results. Thus, it involves contradictory drawbacks. SUMMARY OF THE INVENTION Accordingly, it is a principal object of the present invention to provide a contact alignment apparatus wherein a good state of close contact is accomplished between two members. In order to achieve this object, the present invention provides and apparatus wherein the space formed between the two members is evacuated without contacting them with each other, only then the two members are brought into contact. These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. |
054105749 | claims | 1. An internal component of a fusion reactor in which an internal structure assembly is housed in a toric vacuum vessel in an arrangement along a circumferential direction thereof and in which a high-temperature plasma in which hydrogen and hydrogen isotopes are maintained in a plasma state is confined in a toric internal space device in the internal structure assembly, said internal component comprising: a cooling structure formed in the internal structure assembly, said cooling structure including an inner wall member in which a flow channel for the cooling fluid is formed and an outer wall member surrounding said inner wall member with a gap formed therebetween wherein said flow channel formed in said cooling structure for the cooling fluid extracts heat caused by the plasma and a nuclear reaction; and a leak detection mechanism which communicates with the gap and detects leakage of the cooling fluid into said gap between the inner and outer wall members. a cooling structure having inner and outer walls formed in the internal structure assembly; a flow channel formed in said cooling structure for cooling fluid for extracting heat caused by the plasma and a nuclear reaction, and gas and liquid circulating systems; wherein a gap is formed between the walls of the cooling structure and the gas and liquid circulation systems are communicated with the gap, said circulation systems including a mechanism which measures a change of a state of pressure and water content in a gas and a liquid existing in said gap so as to detect a leak of the gas and a cooling liquid flowing through the cooling structure. a cooling structure having inner and outer walls formed in the internal structure assembly; a flow channel formed in said cooling structure for a cooling fluid for extracting heat caused by the plasma and a nuclear reaction, and a pressure detecting mechanism wherein a gap is formed between the walls of the cooling structure and the pressure detection mechanism communicates with the gap so as to detect a leak of the cooling structure of a gas existing in said gap. a cooling structure having inner and outer walls formed in the internal structure assembly; and a flow channel formed in said cooling structure for a cooling fluid which extracts heat caused by the plasma and a nuclear reaction, wherein a detector for detecting a gas is provided at an exhaust port communicating with the internal space of the toric vacuum vessel so as to detect a leak of the gas out of the cooling structure through an internal space of the vacuum vessel. a cooling structure having inner and outer walls formed in the internal structure assembly; and a flow channel formed in said cooling structure for a cooling fluid for extracting heat caused by the plasma and a nuclear reaction, wherein a plurality of exhaust ports communicating with the internal space of the toric vacuum vessel are arranged in a circumferential direction of the vacuum vessel and detectors for detecting a gas are respectively provided at the exhaust ports to detect a place through which the gas leaks out of the cooling structure. 2. An internal component of a fusion reactor according to claim 1, which comprises a hydrogen processor wherein a gap is formed between the walls and said hydrogen processor so as to separate and store hydrogen and hydrogen isotopes entering said cooling structure. 3. An internal component of a fusion reactor according to claim 2, which comprises a gas circulation system in which a gas circulates and for which said hydrogen processor is provided, wherein an internal space of said hydrogen processor is partitioned into a processed gas chamber forming a part of the gas circulation system and a processing chamber storing hydrogen and hydrogen isotopes by a hydrogen permeable membrane permeable to hydrogen and hydrogen isotopes. 4. An internal component of a fusion reactor according to claim 3, wherein said hydrogen processor oxidizes at least one of hydrogen and hydrogen isotopes separated by the hydrogen permeable membrane. 5. An internal apparatus of a fusion reactor according to claim 3, which comprises a hydrogen getter which is located in the processing chamber of said hydrogen processor wherein separated hydrogen and hydrogen isotopes are absorbed and stored by the hydrogen getter. 6. An internal component of a fusion reactor in which an internal structure assembly is housed in a toric vacuum vessel in an arrangement along a circumferential direction thereof and in which a high-temperature plasma in which hydrogen and hydrogen isotopes are maintained in a plasma state is confined in a toric internal space defined in the internal structure assembly, said internal component comprising: 7. An internal component of a fusion reactor according to claim 6, wherein the change of the state includes the temperature in the gas to detect a leak of the gas. 8. An internal component of a fusion reactor in which an internal structure assembly is housed in a toric vacuum vessel in an arrangement along a circumferential direction thereof and in which a high-temperature plasma in which hydrogen and hydrogen isotopes are maintained in a plasma state is confined in a toric internal space defined in the internal structure assembly, said internal component comprising: 9. An internal component of a fusion reactor in which an internal structure assembly is housed in a toric vacuum vessel in an arrangement along a circumferential direction thereof and in which a high-temperature plasma in which hydrogen and hydrogen isotopes are maintained in a plasma state is confined in a toric internal space defined in the internal structure assembly, said internal component comprising: 10. An internal component of a fusion reactor in which an internal structure assembly is housed in a toric vacuum vessel in an arrangement along a circumferential direction thereof and in which a high-temperature plasma in which hydrogen and hydrogen isotopes are maintained in a plasma state is confined in a toric internal space defined in the internal structure assembly, said internal component comprising: 11. An internal component of a fusion reactor according to claim 1, wherein a gap is formed between the multiple walls of the cooling structure and metallic wires having a high heat conductivity are provided in the gap. 12. An internal component of a fusion reactor according to claim 11, wherein said metallic wires are formed of the same material as that of the cooling structure. 13. An internal component of a fusion reactor according to claim 11, wherein said metallic wires are formed of a material having a heat conductivity higher than that of a material forming the cooling structure. 14. An internal component of a fusion reactor according to claim 1, wherein said walls are closely fitted to each other with partial gaps formed between the walls as grooves through which a fluid is caused to flow. 15. An internal component of a fusion reactor according to claim 1, wherein said structure has at least a portion formed of one of a hydrogen storage material and an alloy thereof. 16. An internal component of a fusion reactor according to claim 1, wherein said structure has a thickness which is reduced at a side facing the high-temperature plasma. 17. An internal component of a fusion reactor according to claim 1, wherein said internal structure assembly comprises a plurality of outboard blanket assemblies each having a surface facing the plasma, a plurality of inboard blanket assemblies each having a surface facing the plasma and a plurality of diverter assemblies each having a surface facing the plasma, said outboard blanket assemblies and said inboard blanket assemblies and said diverter assemblies being arranged along a circumferential direction of the toric vacuum vessel and wherein each of said outboard blanket assemblies and said inboard blanket assemblies and said diverter assemblies is provided with the cooling structure formed on the surface thereof facing the plasma. 18. An internal component of a fusion reactor according to claim 17, wherein a gap is formed between the walls and a hydrogen processor capable of communicating with the gap is provided to separate and store hydrogen and hydrogen isotopes entering said cooling structure. 19. An internal component of a fusion reactor according to claim 18, wherein said hydrogen processor is provided for a gas circulation system in which a gas circulates, an internal space of said hydrogen processor is partitioned into a processed gas chamber forming a part of the gas circulation system and a processing chamber for storing hydrogen and hydrogen isotopes by a hydrogen permeable membrane which is permeable to hydrogen and hydrogen isotopes. 20. An internal component of a fusion reactor according to claim 19, wherein said hydrogen processor oxidizes at least one of hydrogen and hydrogen isotopes separated by the hydrogen permeable membrane. 21. An internal apparatus of a fusion reactor according to claim 19, which comprises a hydrogen getter accommodated in the processing chamber of said hydrogen processor wherein separated hydrogen and hydrogen isotopes are absorbed and stored by the hydrogen getter. 22. An internal apparatus of a fusion reactor according to claim 17, wherein a gap is formed between the walls and gas and liquid circulation systems are communicated with the gap, said circulation systems including a mechanism which measures a change of a state of pressure and water content in a gas and a liquid existing in said gap to detect a leak of the gas and a cooling liquid flowing through the cooling structure. 23. An internal component of a fusion reactor according to claim 17, wherein a gap is formed between the walls of the cooling structure and a pressure detection mechanism, which communicates with the gap, is provided to detect a leak out of the cooling structure of a gas existing in the gap. 24. An internal component of a fusion reactor according to claim 17, wherein a detector for detecting a gas is provided at an exhaust port communicating with the internal space of the toric vacuum vessel to detect a leak of the gas out of said cooling structure through an internal space of the vacuum vessel. 25. An internal component of a fusion reactor according to claim 17, wherein a plurality of exhaust ports communicating with the internal space of the toric vacuum vessel are arranged in a circumferential direction of the vacuum vessel and detectors for detecting a gas are respectively provided at said exhaust ports to detect a place through which the gas leaks out of the cooling structure. 26. An internal component of a fusion reactor according to claim 17, wherein a gap is formed between the walls of said cooling structure and wherein metallic wires having a high heat conductivity are provided in said gap. 27. An internal component of a fusion reactor according to claim 26, wherein said metallic wires are formed of a same material as that of the cooling structure. 28. An internal component of a fusion reactor according to claim 26, wherein said metallic wires are formed of a material having a heat conductivity higher than that of a material forming the cooling structure. 29. An internal component of a fusion reactor according to claim 17, wherein said walls are closely fitted to each other with partial gaps formed between the walls so as to form grooves through which a fluid is caused to flow. 30. An internal component of a fusion reactor according to claim 18, wherein said structure has at least a portion formed of one of a hydrogen storage material and an alloy thereof. 31. An internal component of a fusion reactor according to claim 17, wherein said structure has a thickness which is reduced at a side facing the high-temperature plasma. 32. An internal component of a fusion reactor according to claim 17, wherein said structure has a rectangular shape in cross section. 33. An internal component of a fusion reactor according to claim 17, wherein said structure has a circular shape in cross section. 34. An internal component of a fusion reactor according to claim 17, wherein the circular structure comprises inner and outer pipe members between which a circular gap is formed. 35. An internal component of a fusion reactor according to claim 17, wherein the cooling structure is integrally formed with the surface, facing the plasma, of each of the outboard blanket assemblies, inboard blanket assemblies and diverter assemblies. 36. An internal component of a fusion reactor according to claim 17, wherein the cooling structure is separately formed from the surface, facing the plasma, of each of the outboard blanket assemblies, inboard blanket assemblies and diverter assemblies and the cooling structure is secured to the surface thereof. |
summary | ||
claims | 1. A scintillator having a columnar crystal structure vapor-deposited on a substrate,wherein each column of the crystal structure contains:an alkali halide metal compound as a host material;an activator agent for forming a trap level in a band gap of the crystal structure so as to improve luminous efficiency of the host material, wherein the activator agent is at least one element selected from the group consisting of thallium (Tl), europium (Eu), and indium (In); anda compound of a precious metal, which is a metal having a lower ionization tendency than hydrogen (H), as an additive that is different from the activator agent and that has a lower melting point than the host material, wherein the precious metal is at least one element selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os), copper (Cu), and mercury (Hg). 2. The scintillator according to claim 1, wherein the additive is not contained as a granular or powdery impurity in the crystal structure. 3. The scintillator according to claim 1, wherein the host material is at least one selected from the group consisting of cesium iodide (CsI), sodium iodide (NaI), and potassium iodide (KI). 4. The scintillator according to claim 1, wherein the host material is cesium iodide (CsI), the activator agent is thallium (Tl), and the precious metal is at least one element selected from the group consisting of gold (Au), silver (Ag), and copper (Cu). 5. The scintillator according to claim 1, wherein the host material is cesium iodide (CsI), the activator agent is thallium (Tl), and the additive is a copper compound at a content of 10 ppm to 30 ppm, andwherein when X-ray diffraction is performed for a powder of the scintillator obtained by dissolving the scintillator in water and then vaporizing and drying, at least one selected from the group consisting of CuI, Cs3Cu2I5, and CsCu2I3 is detected as the copper compound. 6. A radiation detection apparatus comprising:a scintillator defined in claim 1; anda sensor unit in which a plurality of photoelectric conversion elements are arrayed. 7. A scintillator having a columnar crystal structure vapor-deposited on a substrate,wherein each column of the crystal structure contains:an alkali halide metal compound as a host material;an activator agent for forming a trap level in a band gap of the crystal structure so as to improve luminous efficiency of the host material, wherein the activator agent is at least one element selected from the group consisting of thallium (Tl), europium (Eu), and indium (In); anda compound of a precious metal, which is a metal having a lower ionization tendency than hydrogen (H), as an additive that is different from the activator agent and that has a lower melting point than the host material, at a concentration at which luminance of scintillation light is maintained, wherein the precious metal is at least one element selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os), copper (Cu), and mercury (Hg). 8. A method of forming a scintillator, the method comprising:preparing a substrate; andforming a scintillator having a columnar crystal structure by vapor-depositing an alkali halide metal compound, an activator agent, and a precious metal, which is a metal having a lower ionization tendency than hydrogen (H), on the substrate,wherein each column of the crystal structure contains:the alkali halide metal compound as a host material;the activator agent for forming a trap level in a band gap of the crystal structure so as to improve luminous efficiency of the host material, wherein the activator agent is at least one element selected from the group consisting of thallium (Tl), europium (Eu), and indium (In); anda compound of the precious metal as an additive having a lower melting point than the host material, where the additive is different from the activator agent, wherein the precious metal is at least one element selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os), copper (Cu), and mercury (Hg). |
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claims | 1. A nuclear fuel bundle comprising:an upper tie plate;a lower tie plate;at least one full-length fuel rod extending between the upper tie plate and the lower tie plate;at least one partial length fuel rod extending from the lower tie plate towards the upper tie plate;a fuel assembly component mounted on the at least one partial length fuel rod, the fuel assembly component including,a cylindrical device having first and second ends, the first end having a mounting assembly including a locking assembly attaching the cylindrical device to one of the at least one partial length fuel rods; andthe nuclear fuel bundle being in a nuclear reactor,wherein the cylindrical device is one of a hollow tube with solid walls and a solid rod, the hollow tube not including any material in the tube. 2. The nuclear fuel bundle of claim 1, wherein the fuel assembly component is configured to collect in-service material performance data. 3. The nuclear fuel bundle of claim 1, wherein the fuel assembly component is configured to test fuel materials. 4. The fuel assembly component of claim 1, wherein the cylindrical device is a fuel rod tube. 5. The nuclear fuel bundle of claim 4, wherein the fuel rod tube is an unfueled section of fuel rod cladding. 6. The nuclear fuel bundle of claim 1, further including:at least one of an end cap, an endplug, and a partial length fuel rod endplug attached to the second end of the cylindrical device. 7. The nuclear fuel bundle of claim 6, wherein the fuel assembly component is pressurized. 8. The nuclear fuel bundle of claim 1, wherein the fuel assembly component has the same outer diameter as the partial length fuel rod. 9. The nuclear fuel bundle of claim 6, wherein the second end of the cylindrical device is a partial length fuel rod endplug. 10. The nuclear fuel bundle of claim 1, wherein the locking assembly includes a locking spring recess and a locking spring. 11. The nuclear fuel bundle of claim 1, wherein the mounting assembly includes a bayonet female endplug. |
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description | The present invention relates to a beam intensity converting film and a method of producing a beam intensity converting film. Accelerators such as a cyclotron, which produce various charged particle beams, are required to carry out size adjustment of charged particle beams and control of beam intensity within a wide range. For satisfying such requirements, a beam intensity converting film having an opening, such as a scraper to reduce the size of a charged particle beam or an attenuator to attenuate the intensity of a charged particle beam, is used. For example Patent Literature 1 discloses an attenuator constituted by a metal mesh, which serves as a moderator for slow positron generation. The metal mesh is composed of tungsten. Patent Literature 2 discloses a self-supporting multilayer film that includes both: non-diamond-like carbon such as carbon in the form of graphite or amorphous carbon; and diamond-like carbon. Furthermore, as a material constituting a beam intensity converting film, titanium and the like are known in addition to the foregoing tungsten. [Patent Literature 1] Japanese Patent Application Publication, Tokukai, No. 2005-326299 [Patent Literature 2] Published Japanese Translation of PCT International Application, Tokuhyo, No. 2009-530493 However, the conventional techniques as described above have the following issues: (1) durability of an intensity converting film against charged particle beams is low; and (2) some means is needed to reduce the extent of radioactivation, due to a charged particle beam, of the intensity converting film and apparatuses near the film. Generally, as a beam intensity converting film, a film made of a metal such as titanium or tungsten is often used from the viewpoint of durability and heat resistance, or a carbon material is often used from the viewpoint that the carbon materials do not easily become radioactive. The term “becomes radioactive (radioactivation)” as used herein means not only that an intensity converting film itself becomes radioactive but also that an apparatus near the beam intensity converting film becomes radioactive due to a reflected beam from the beam intensity converting film. The beam intensity converting film and apparatuses near the beam intensity converting film, which have become highly radioactive, cannot be handled by humans. Therefore, it is necessary to stop the accelerator and replace the beam intensity converting film before the intensity converting film becomes too radioactive. This leads to a substantial decrease in operating time of the accelerator. Furthermore, beam intensity converting films (such as attenuator and scraper) in an accelerator are required to be highly durable against temperature rise resulting from beam irradiation. For example, the required durability of the attenuator varies depending on location and/or open area ratio, and the replacement frequency of the beam intensity converting film of the attenuator also varies. For example, an attenuator composed of amorphous carbon and having an open area ratio of 50% becomes damaged in a very short period of time by uranium beam irradiation, and thus the converting film needs to be replaced very frequently. The increased replacement frequency leads to a substantial decrease in operating time of the accelerator. Such an issue concerning the durability of an intensity converting film against charged particle beams is a major issue particularly in a case where the beam intensity converting film is composed of a carbon material such as that disclosed in Patent Literature 2. That is, the greatest issue that the beam intensity converting film composed of carbon faces is about its durability. The present invention was made in view of the above issues, and an object thereof is to obtain a beam intensity converting film that is capable of reducing the extent of radioactivation, that is composed of carbon, and that is sufficiently durable against charged particle beams, and a method of producing a beam intensity converting film. A beam intensity converting film of one aspect of the present invention is a beam intensity converting film having an opening that allows passage of a charged particle beam, the beam intensity converting film including one or more graphite films placed such that a surface thereof intersects a beam axis of the charged particle beam, wherein the one or more graphite films each have a thickness of 1 μm or greater, and wherein, in the one or more graphite films, a thermal conductivity in a surface direction is equal to or greater than 20 times a thermal conductivity in a thickness direction. A beam intensity converting film of another aspect of the present invention is a beam intensity converting film having an opening that allows passage of a charged particle beam, the beam intensity converting film including one or more graphite films placed such that a surface thereof intersects a beam axis of the charged particle beam, wherein the one or more graphite films each have a thickness of 1 μm or greater, and wherein, in the one or more graphite films, an electric conductivity in a surface direction is equal to or greater than 100 times an electric conductivity in a thickness direction. A method of producing a beam intensity converting film of still another aspect of the present invention is a method of producing a beam intensity converting film having an opening that allows passage of a charged particle beam, the beam intensity converting film including one or more graphite films, the method including a step of preparing the one or more graphite films by firing one or more polymeric films. An aspect of the present invention provides the following effect: it is possible to provide a beam intensity converting film that is sufficiently durable against charged particle beams and that is capable of reducing the extent of radioactivation. As described earlier, a carbon material such as amorphous carbon, which is said to become radioactive only to a relatively small extent, has been sometimes used as a beam intensity converting film having an opening that allows passage of a charged particle beam, conventionally. However, a beam intensity converting film prepared using amorphous carbon as a raw material is far from satisfactory in terms of durability. When a charged particle beam is incident on a beam intensity converting film, the beam intensity converting film experiences a very large heat load. For example, a beam intensity converting film composed of amorphous carbon and having an open area ratio of 50% is damaged almost instantly upon irradiation with a high-energy uranium beam. In addition, amorphous carbon films have low mechanical strength, and therefore require some arrangement such as combining an amorphous carbon film with a diamond-like carbon (DLC) film or the like to from a multilayer film in order to serve as self-supporting films. In a preparation example of such a multilayer film, as disclosed in Patent Literature 2, the following complicated processes are necessary: (i) a water-soluble release layer is formed on a polished substrate; (ii) an amorphous carbon layer is deposited; (iii) a DLC layer is deposited, (iv) an amorphous carbon layer is deposited, (v) the multilayer film is removed from the substrate in water; (vi) the multilayer film is dried, and the like. Under such circumstances, the inventors worked hard in an attempt to develop a beam intensity converting film that has excellent self-supporting property and excellent mechanical strength despite being made of carbon and that is highly durable to withstand the above-mentioned heat load. As a result, the inventors succeeded in developing a beam intensity converting film that has excellent self-supporting property and excellent mechanical strength, that is sufficiently durable against heat load, and that is capable of reducing the extent of radioactivation, by employing graphite having specific properties and a specific thickness. First of all, given the fact that an intensity converting film for an accelerator is mainly used in vacuum, the inventors arrived at the present invention by employing graphite that has high crystallinity and high orientation in order that: the graphite can have high heat resistant characteristics at temperatures equal to and above 3000° C. in vacuum; and the thermal conductivity characteristics in a surface direction of the intensity converting film or the electric conductivity characteristics in the surface direction of the intensity converting film can have at least a certain degree of anisotropy. Furthermore, the inventors found that is possible to achieve sufficient shielding property against charged particle beams and sufficient mechanical property by employing the above graphite film having physical property values of thermal conductivity and electric conductivity falling within certain ranges and having a thickness falling within a certain range. On the basis of this finding, the inventors accomplished the present invention. The extent of radioactivation of a beam intensity converting film and the extent of beam reflection by the intensity converting film are related to a material (element) from which the beam intensity converting film is made. For example, use of carbon (atomic number: 12), which is a light element, reduces the extent of radioactivation of the beam converting film itself and the extent of charged particle beam reflection, as compared to titanium (atomic number: 22) and tungsten (atomic number: 74). Furthermore, the inventors conducted a study and obtained a new finding that the extent of charged particle beam reflection is also related to the temperature of the beam intensity converting film, and that a higher temperature of the beam intensity converting film cause a greater extent of charged particle beam reflection. That is, a beam intensity converting film increases in temperature in response to charged particle beam irradiation, and this temperature rise causes the beam intensity converting film to reflect the charged particle beam to a greater extent. On the other hand, it is inferred that, if it is possible to prevent or reduce the temperature rise of the beam intensity converting film, it will be possible to reduce charged particle beam reflection. That is, the inventors made a new finding that a graphite film of the present invention can reduce the extent to which apparatuses near the graphite film become radioactive, as compared not only to metal films such as conventionally used titanium and tungsten but also to amorphous carbon films. As described earlier, the effect “a graphite intensity converting film of the present invention, which consists only of elemental carbon, is superior to metal films such as titanium and tungsten in terms of reducing radioactivation” is an effect brought about by the constituent element of the film, and thus is a predictable effect. The graphite film of the present invention, however, is capable of reducing the extent to which apparatuses near the graphite film become radioactive, even when compared to amorphous carbon films. This effect is brought about by the earlier-mentioned finding that the extent of charged particle beam reflection by a beam intensity converting film is dependent on temperature rise of the film. That is, this effect is brought about by the totally new finding that, if it is possible to keep the temperature of a beam intensity converting film low, it will be possible to reduce the reflection of a charged particle beam from the intensity converting film. The graphite film of the present invention is characterized in that it is not only superior in thermal conductivity and thus in thermal diffusion performance to amorphous carbon films, but also dissipates much heat through a radiation mechanism, and therefore the temperature of the graphite film itself does not rise easily. Accordingly, it is possible to reduce the charged particle beam reflection and to reduce the extent to which apparatuses near the graphite film become radioactive. The technical idea of the present invention based on the above finding is not the one that is predictable from conventional findings, but the one that has been accomplished by the inventors themselves. In a case where the intensity of a charged particle beam such as an ion beam is to be controlled at a desired intensity, it is preferable that the thickness of a graphite film required to shield against the beam, and an opening that allows passage of the beam, are precisely controlled depending on the intensity of the charged particle beam. According to the present invention, it is possible to prepare a graphite film of any thickness, and the graphite film has excellent mechanical strength and thus it is easy to form the opening by precision machining using a laser or the like. The present invention thus provides a very superior method. The beam intensity converting film herein may be any beam intensity converting film, provided that the beam intensity converting film has an opening which allows passage of a charged particle beam and that the intensity is different between an incident charged particle beam and an outgoing charged particle beam. Such a beam converting film is, for example, an attenuator to attenuate the energy of a charged particle beam, a scraper to adjust the beam size of a charged particle beam, or the like. The following description will discuss one embodiment of the present invention in detail. FIG. 1 schematically illustrates an attenuator (beam intensity converting film) 1 in accordance with Embodiment 1. (a) of FIG. 1 is a cross-sectional view, and (b) of FIG. 1 is a front view showing the surface from which a charged particle beam travels outward. As illustrated in (a) of FIG. 1, the attenuator 1 in accordance with Embodiment 1 has openings 1a that allow passage of a charged particle beam X. The attenuator 1 is a film that serves to attenuate the intensity of the charged particle beam X incident thereon, and is placed such that its surface intersects the optical axis of the charged particle beam X. The attenuator 1 is constituted by one or more graphite films, each of which has a thickness of 1 μm or greater. In the attenuator 1, portion, where no openings 1a exist, of the attenuator 1 serves to shield against the charged particle beam X. Therefore, the attenuator 1 needs to be thick to an extent that charged particles do not penetrate through the attenuator 1. The thickness of a graphite film required to totally shield against charged particles differs depending on the intensity of the charged particle beam X. In a case of a high-intensity beam, the thickness of a graphite film required to totally shield against the beam is large, whereas, in a case of a low-intensity beam, the thickness of a graphite film required to totally shield against the beam is small. In a case of a charged particle beam X with a relatively low intensity of about 1 MeV, such a beam can be significantly shielded against by a graphite film equal to or greater than 1 μm in thickness. The charged particle beam X, after emitted from a charged particle beam source (not illustrated), is incident on the attenuator 1. The charged particle beam X passes through an opening 1a in the attenuator 1, but is shielded against by the portion of the attenuator 1 where no openings 1a exist. As such, a charged particle beam X's component that has passed through the opening 1a travels outward from the attenuator 1. In this way, the intensity of the charged particle beam X is attenuated by the attenuator 1. It should be noted that, although the charged particle beam X is non-uniform in intensity for a while after passage through the opening of the attenuator 1, the uneven distribution will become uniform afterwards and provide a desirably attenuated beam intensity. The extent of attenuation of the charged particle beam X through the attenuator 1 depends on the open area ratio (the ratio of the area of opening(s) 1a to the area of a surface of the attenuator 1) of the attenuator 1. The open area ratio of the attenuator 1 can therefore be selected appropriately depending on a desired intensity of the charged particle beam X. Given the strength and the like of a graphite film constituting the attenuator 1, the open area ratio of the attenuator 1 can be selected from the range of from 1% to 80%. As illustrated in (b) of FIG. 1, the openings 1a of the attenuator 1 are in the form of slits (in the form of blinds). The openings 1a need only be configured such that the openings 1a pass through the attenuator 1 from the surface on which the charged particle beam X is incident to the surface from which the charged particle beam X travels outward, and are not limited to the configuration as illustrated in (b) of FIG. 1. The openings 1a may be, for example, through-holes like punched holes or may be in the form of a mesh structure. An opening may be constituted with the use of a plurality of attenuators. For example, in a case where a plurality of attenuators 1 each having openings 1a as illustrated in FIG. 1 are used, the open area ratio can be adjusted by changing the relative positions of the attenuators 1. The following discusses an example in which two attenuators 1 each having openings 1a in the form of slits are used. The attenuators 1 in this example each have an open area ratio of 50%, and are arranged such that openings 1a of one attenuator 1 and openings 1a of the other attenuator 1 are coincident with each other. In this case, by rotating the two attenuators 1 relative to each other and thereby changing the angle between each opening 1a of one attenuator 1 and its corresponding opening 1a of the other attenuator 1, it is possible to adjust the open area ratio. When the two attenuators 1 are arranged such that their openings 1a are at a right angle to each other, the open area ratio is 25%. Therefore, in a case where two attenuators 1 having openings 1a coincident with each other are used, the open area ratio can be adjusted within the range of from 25% to 50% by rotating the two attenuators 1 relative to each other. Alternatively, in a case where two attenuators 1 are adjusted such that their openings 1a do not overlap each other, that is, in a case where two attenuators 1 are adjusted such that each opening 1a of one attenuator 1 overlaps the portion where no openings 1a exist (shielding portion) of the other attenuator 1, the open area ratio is 0%. By rotating the two attenuators 1 relative to each other, it is possible to adjust the open area ratio within the range of from 0% to 25%. (Graphite Film Constituting Attenuator 1) A graphite film constituting the attenuator 1 needs to be thick to an extent that the charged particle beam X is shielded against by the portion, where no openings exist, of the graphite film constituting the attenuator 1 and that charged particles do not penetrate through that portion. A graphite film greater than 1 μm in thickness is capable of significantly shielding against a low-energy charged particle beam X. On the other hand, in order to totally shield against a higher-energy charged particle beam, the graphite film needs to be thicker. In such a case, it is effective to use a method of preparing a thicker film by: stacking a plurality of graphite films for use in Embodiment 1; and, for example, heating the stack under pressure. In general, it is extremely difficult to prepare a thick graphite film that is highly oriented and that has high crystallinity such as those for use in Embodiment 1. However, by stacking a plurality of graphite films for use in Embodiment 1 together, possible to prepare an attenuator that is highly oriented, that has high crystallinity, and that is equal to or greater than 100 μm in thickness. A graphite film in Embodiment 1 is characterized in that it has high crystallinity and is highly oriented, and that the basal (net) planes of graphite constituting the graphite film are parallel to a surface of the graphite film. Such an orientation can be evaluated on the basis of a thermal conductivity of the graphite film. A graphite film in Embodiment 1 is characterized in that the thermal conductivity in a surface direction is equal to or greater than 20 times the thermal conductivity in the thickness direction. Other configurations of the graphite film are not particularly limited, provided that the thermal conductivity in the surface direction is greater than 20 times the thermal conductivity in the thickness direction. A graphite film constituting the attenuator 1 is equal to or greater than 1 μm in thickness, and the orientation of the graphite can be evaluated also on the basis of an electric conductivity of the graphite film. A graphite film in Embodiment 1 is characterized in that the electric conductivity in the surface direction is equal to or greater than 100 times the thermal conductivity in an electrical direction. Other configurations of the graphite film are not particularly limited, provided that the electric conductivity in the surface direction is greater than 100 times the thermal conductivity in an electrical direction. It should be noted that, since the measurement of electric conductivity is very easy as compared to thermal conductivity, measuring electric conductivity characteristics is a very effective method in managing the performance of a graphite film. The open area ratio of a graphite film(s) constituting the attenuator 1 is 1% to 80%. Provided that the open area ratio falls within this range, the shape of the opening(s) and the method of making the opening(s) are not particularly limited. Furthermore, a graphite film constituting the attenuator 1 preferably has a thermal conductivity in the surface direction of 1000 W/(m·K) or greater, from the viewpoint of high heat dissipation performance, high durability, and excellent mechanical strength. Such a graphite film is preferred, because such a graphite film has high strength and high thermal conductivity. The term “thickness” as used herein means a dimension of the attenuator 1 along the direction in which the charged particle beam X passes through the attenuator 1. A graphite film constituting the attenuator 1 preferably has an electric conductivity in the surface direction of 12000 S/cm or greater, from the viewpoint of high quality, high durability, and excellent mechanical strength. The attenuator 1 in the accelerator is replaced at various time intervals depending on the open area ratio, location, and/or the like. In a case where the attenuator 1 and an apparatus near the attenuator 1 have become radioactive at the time of replacement of the attenuator 1, a worker is at a risk of exposure to radiation. Furthermore, in a case where these members become radioactive, disposal of these members as radioactive waste, for example, will be a problem. If the quantity of heat generated in the attenuator 1 is large during usage of the attenuator 1, the generated heat causes an increase in extent of radioactivation, and not only the attenuator 1 but also members near the attenuator 1 become radioactive. Therefore, preventing heat generation during the emission of a charged particle beam X by employing an attenuator 1 having a high heat dissipation performance is very important in order not only to merely increase the lifetime of the attenuator 1 but also to prevent radioactivation of apparatuses near the attenuator 1. (Method of Producing Graphite Film) A method of producing a graphite film in accordance with Embodiment 1 is not particularly limited, and is, for example, a method of preparing a graphite film by treating a polymeric film with heat. Specifically, a method of producing a graphite film of one example of Embodiment 1 includes a carbonizing step including carbonizing an aromatic polyimide film and a graphitizing step including graphitizing the carbonized aromatic polyimide film. <Carbonizing Step> The carbonizing step involves carrying out carbonization by preheating an aromatic polyimide film, which is a starting material, under reduced pressure or in nitrogen gas. The heat treatment temperature for carbonization is preferably 500° C. or above, more preferably at 600° C. or above, most preferably 700° C. or above. During the carbonization, a pressure may be applied to the film along the thickness direction of the film or a tensile force may be applied to the film along a direction parallel to the surface of the film to the extent that the film is not damaged, in order to prevent wrinkles from forming in the starting polymeric film. <Graphitizing Step> In the graphitizing step, graphitization may be carried out after removing the carbonized polyimide film from a furnace and then transferring it to a graphitization furnace, or carbonization and graphitization may be carried out continuously. The graphitization is carried out under reduced pressure or in an inert gas. Suitable inert gases are argon and helium. The treatment may be carried out until the heat treatment temperature (firing temperature) reaches 2400° C. or above, preferably 2600° C. or above, more preferably 2800° C. or above, most preferably 3000° C. or above. In the graphitizing step, a pressure may be applied along the thickness direction of the film, and/or a tensile force may be applied to the film along a direction parallel to the surface of the film. According to the above method, it is possible to obtain a graphite film that has a good graphite crystal structure and that is highly thermally conductive and highly electrically conductive. A polymeric film for use in Embodiment 1 is not particularly limited, provided that it can be converted, by carbonization, graphitization, or a combination of carbonization and graphitization, into a graphite film whose anisotropies in thermal conductivity and electric conductivity between the surface and thickness directions fall within the foregoing ranges. The polymeric film is, for example, a polymeric film of at least one polymer selected from aromatic polyimides, aromatic polyamides, polyoxadiazoles, polybenzothiazoles, polybenzobisthiazoles, polybenzoxazoles, polybenzobisoxasoles, polyparaphenylene vinylenes, polybenzimidazoles, polybenzobisimidazoles, and polybenzothiazoles. A particularly preferable raw material film for the graphite film of Embodiment 1 is an aromatic polyimide film. (Thermal Conductivity in Surface Direction of Graphite Film) In a graphite film for use in Embodiment 1, the anisotropy in thermal conductivity between surface and thickness directions is equal to or greater than 20 times, more preferably equal to or greater than 30 times, most preferably equal to or greater than 50 times. The term “anisotropy in thermal conductivity between surface and thickness directions” as used herein refers to the ratio of thermal conductivity in the surface direction to thermal conductivity in the thickness direction (that is, thermal conductivity in surface direction/thermal conductivity in thickness direction). In regard to specific values of the thermal conductivity in the surface direction, the thermal conductivity in the surface direction is equal to or greater than 1000 W/(m·K), preferably equal to or greater than 1200 W/(m·K), more preferably equal to of greater than 1400 W/(m·K), even more preferably equal to or greater than 1600 W/(m·K). A graphite film having a thermal conductivity in the surface direction of 1000 W/(m·K) or greater provides a graphite film having a better heat dissipation performance. A graphite film having a thermal conductivity in the surface direction of 1000 W/(m·K) or greater means that the thermal conductivity of this graphite film is equal to or greater than 2.5 to 4 times that of a metal material (for example, copper, aluminum). The thermal conductivity in the surface direction of a graphite film is calculated using the following equation (1):A=α×d×Cp (1) where A represents the thermal conductivity in the surface direction of the graphite film, α represents the thermal diffusivity in the surface direction of the graphite film, d represents the density of the graphite film, and Cp represents the specific heat capacity of the graphite film. The density, the thermal diffusivity, and the specific heat capacity in the surface direction of the graphite film are obtained in the following manner. The density of a graphite film is measured in the following manner: a sample measuring 100 mm×100 mm cut from the graphite film is measured for weight and thickness; and the measured value of the weight is divided by the value of volume (calculated from 100 mm×100 mm×thickness). The specific heat capacity of a graphite film was measured with the use of a differential scanning calorimeter DSC220CU, which is a thermal analysis system manufactured by SII NanoTechnology Inc., in the condition in which temperature was raised from 20° C. to 260° C. at 10° C./min. The thermal conductivity in the thickness direction of the graphite film can be calculated in the same manner as described above using the foregoing equation (1), except that α in the equation is the thermal diffusivity in the thickness direction of the graphite film. The thermal diffusivity in the surface direction of the graphite film was measured with the use of a commercially-available thermal diffusivity measuring instrument using a light alternating-current method (for example, “LaserPIT” available from ULVAC RIKO, Inc.). For example, a sample measuring 4 mm×40 mm cut from the graphite film was measured in an atmosphere of 20° C. at a laser frequency of 10 Hz. The thermal diffusivity in the thickness direction of the graphite film is determined by a pulse heating method using a laser. In this method, a laser is shined on one surface of the film and thereby the film is heated, and thereafter a temperature response (temperature change) at the opposite surface of the film is measured. Then, half-time (t1/2) of time (t) taken for the temperature to reach a certain temperature is calculated using the following equation (2): α = d 2 τ 0 = 0.1388 × d 2 t 1 / 2 ( 2 ) where α represents thermal diffusivity, to represents the period of thermal diffusion, d represents the thickness of a sample, t1/2 represents half-time, and 0.1388 is the apparatus constant of the apparatus used. (Thickness of Graphite Film) The thickness of a graphite film in accordance with Embodiment 1 is 1 μm or greater, more preferably 2 μm or greater and 1 mm or less, particularly preferably 3 μm or greater and 500 μm or less. A graphite film having such a thickness is preferred, because the attenuator 1 increases in temperature to a lesser extent even upon irradiation with a charged particle beam and, as a result, apparatuses near the attenuator 1 do not easily become radioactive. It is difficult, by a polymer firing method, to prepare a graphite film that has physical properties falling within the ranges of Embodiment 1 and that has a thickness equal to or greater than 50 μm. In such a case, a plurality of graphite films may be pressed together. It is also effective to prepare a thick graphite film by press-bonding the graphite films. For example, for preparing a graphite film having a thickness of 200 μm, four graphite films each having a thickness of 50 μm may be pressed together or press-bonded together. By pressing or press-bonding ten graphite films together, it is possible to prepare a graphite film having a thickness of 500 μm. The thickness of a graphite film is measured in the following manner: thicknesses at any ten locations of a sample measuring 50 mm×50 mm cut from the graphite film are measured in a thermostatic chamber at 25° C. with the use of a thickness gage (HEIDENHAIN-CERTO, manufactured by HEIDENHAIN); and the mean of the thicknesses is used as the thickness of the graphite film. (Electric Conductivity in Surface Direction of Graphite Film) The electric conductivity in the surface direction of a graphite film in Embodiment 1 is not particularly limited, and is preferably 12000 S/cm or greater, preferably 14000 S/cm or greater, more preferably 16000 S/cm or greater, most preferably 18000 S/cm or greater. Furthermore, the graphite film preferably has anisotropy (orientation) such that the electric conductivity in the surface direction of the graphite film is equal to or greater than 100 times the electric conductivity in the thickness direction of the graphite film. The electrical conductivity of a graphite film is measured by applying a constant current in a four-point probe method (for example, by using Loresta-GP, manufactured by Mitsubishi Chemical Analytech Co., Ltd.) (Density of Graphite Film) The density of a graphite film in Embodiment 1 is not particularly limited, and is preferably 1.70 g/cm3 or greater, preferably 1.80 g/cm3 or greater more preferably 1.90 g/cm3 or greater, more preferably 2.00 g/cm3 or greater. A graphite film having a density of 1.60 g/cm3 or greater is preferred, because such a graphite film has an excellent self-supporting property and excellent mechanical strength properties. Furthermore, since a graphite film having a greater density has a higher possibility of interacting with a charged particle beam, a graphite film having a high density is highly effective as an attenuator. In addition, a graphite film having a high density has little gap between its constituent graphite layers, and therefore such a graphite film tends to have a high thermal conductivity. In a case where a graphite film has a low density, such a graphite film has a poor efficiency in decelerating a charged particle beam, and, in addition, the graphite film also has a decreased thermal conductivity due to the effects of air layers bet n the constituent graphite layers. This is therefore not preferred. It is also inferred that, in the air layers (hollow portions), thermal conductivity is poor and thus heat is likely to be trapped in these portions, or that the air layers in the hollow portions expand due to temperature increase caused by heat. Therefore, a graphite film having a low density easily deteriorates and/or is damaged. Furthermore, in a case where a graphite film has a high density, a charged particle beam is less likely to be scattered when passing through the graphite film. Therefore, in the case of a graphite film having a high density, a charged particle beam is less likely to be scattered even in a case where such graphite films are stacked together. In view of these matters, the graphite film preferably has a high density. Specifically, the density is preferably 1.70 g/cm3 or greater, preferably 1.80 g/cm3 or greater, more preferably 1.80 g/cm3 or greater, more preferably 1.90 g/cm3 or greater, more preferably 2.00 g/cm3 or greater, more preferably 2.10 g/cm3 or greater. In regard to the upper limit of the density of the graphite film, the density of the graphite film is 2.26 g/cm3 (theoretical value) or less, and may be 2.24 g/cm3 or less. The density of a graphite film is measured in the following manner: a sample measuring 100 mm×100 mm cut from the graphite film is measured for weight and thickness; and the measured value of the weight is divided by the value of volume (calculated from 100 mm×100 mm×thickness). (Formation of Opening) A graphite film constituting the beam intensity converting film of Embodiment 1 preferably has an open area ratio in the range of from 1% to 80%. The open area ratio is not limited to a particular value, provided that the open area ratio falls within the above preferred range. The open area ratio is more preferably in the range of from 2% to 70%, even more preferably in the range of from 5% to 60%, most preferably in the range of from 10% to 50%. A method of forming an opening is not particularly limited, and machining using a laser or the like, mechanical machining, or the like may be used depending on need. In particular, in graphite made of carbon, it is possible to form an opening that is in a desired shape and that provides a desired open area ratio, by laser machining. Machining using a laser is carried out preferably in air. When laser machining is carried out in air, carbon dissipates as carbon dioxide gas and an opening can be easily formed. A laser for use in machining is not particularly limited, provided that machining of graphite can be achieved. The shape of the opening is not particularly limited as well. The shape of the opening can be freely selected from the foregoing blind shape, hole shape, mesh form, and the like. (Mechanical Strength of Graphite Film) A graphite film in Embodiment 1 is superior also in terms of mechanical strength. A graphite film of one embodiment of the present invention is used as a self supporting film, but can be attached to a metal frame or can be sandwiched between two metal frames. One method to evaluate a graphite film having a thickness in the range of from 1 μm to 50 μm, within which the mechanical strength is an issue, is a folding endurance test. The number of times a graphite film having a thickness within the above range is folded in an MIT folding endurance test may be preferably 100 or more, more preferably 200 or more, even more preferably 500 or more, particularly preferably 1000 or more. The MIT folding endurance test for a graphite film is carried out in the following manner. Three test pieces each measuring 1.5×10 cm are removed from the graphite film. The test is carried out with the use of an MIT crease-flex fatigue resistance tester Model D manufactured by Toyo Seiki Seisaku-sho, Ltd. under the conditions in which test load is 100 gf (0.98 N), speed is 90 times/min., and radius of curvature R of folding clamp is 2 mm. The graphite film is folded to an angle of 135° in either direction in an atmosphere of 23° C., and the number of times the graphite film is folded before the graphite film is severed is counted. In the configuration illustrated in FIG. 1, the attenuator 1 is constituted by a single graphite film. Note, however, that the attenuator 1 may be constituted by a plurality of graphite films. The attenuator 1 may be a stack of graphite films so as to have a thickness that is durable against a higher-energy charged particle beam X. Such a stack can be prepared by laminating, by a method such as press bonding, a plurality of graphite films each having a thickness of from 1 μm to 50 μm produced through the foregoing method. This provides an attenuator 1 that is equal to or greater than 50 μm in thickness and that has excellent characteristics such as excellent thermal conductivity in the surface direction. The thickness of the beam intensity converting film constituted by such a stack is not particularly limited. In order to prepare a beam intensity converting film equal to or greater than 100 μm in thickness, employing a multilayer structure is usually very effective. In a case where the attenuator 1 is constituted by a plurality of graphite films, the graphite films in an accelerator may be provided separately from each other. In this case, the graphite films are configured such that their open area ratios correspond to respective desired energy intensities of charged particle beams X. The positions of the respective graphite films can be appropriately determined according to the type of experiment using a charged particle beam(s) X or the configuration of the accelerator. For example, the graphite films may be positioned such that they all intersect the same beam axis of the charged particle beam X, or may be positioned such that the graphite films intersect a respective plurality of beam axes of charged particle beams X in one-to-one correspondence. The following description will discusses another embodiment of the present invention with reference to FIG. 2. For convenience, members having functions identical to those described in Embodiment 1 are assigned identical referential numerals and their descriptions are omitted here. A beam intensity converting film in accordance with Embodiment 2 is different from that of Embodiment 1 in that the beam intensity converting film in accordance with Embodiment 2 is a scraper. FIG. 2 is a cross-sectional view schematically illustrating a configuration of a scraper 2 serving as a beam intensity converting film in accordance with Embodiment 2. As illustrated in FIG. 2, the scraper 2 (beam intensity converting film) in accordance with Embodiment 2 has an opening 2a. The scraper 2 is a film that serves to reduce the beam size of an incident charged particle beam X, and is placed such that a surface thereof intersects the optical axis of the charged particle beam X. The scraper 2 is constituted by one or more graphite films, each of which is equal to or greater than 1 μm in thickness. The charged particle beam X, after emitted from a charged particle beam source (not illustrated), is incident on the scraper 2. The charged particle beam X passes through the central portion of the scraper 2 where the opening 2a exists, but is shielded against by the peripheral portion of the scraper 2 where no opening 2a exists. As such, only a charged particle beam X's component incident on the central portion of the scraper 2 where the opening 2a exits passes through and travels outward from the scraper 2. On the other hand, a charged particle beam X's component of relatively low energy, which is incident on the peripheral portion of the scraper 2 where no opening 2a exists, is shielded against b the scraper 2. Thus, the charged particle beam X's peripheral component, which has a relatively low energy, is removed by the scraper 2, and this provides a charged particle beam X of a smaller size with uniform intensity. (Energy of Charged Particle Beam in Embodiments 1 and 2) A charged particle beam, which is incident on a beam intensity converting film (attenuator 1, scraper 2, or the like) constituted by a graphite film(s), partially passes through an opening of the beam intensity converting film and is partially shielded against by the portion where no openings exist. The energy of a charged particle beam X, which is to be shielded against by a beam intensity converting film, differs depending on the accelerator. The collision stopping power (energy loss) of a target material (in this case, the beam intensity converting film) for a charged particle is represented by the following Bethe equation (equation (3)): S col = - 4 π e 4 z 2 N mv 2 Z [ ln 2 mv 2 I ( 1 - β 2 ) - β 2 ] ( 3 ) where e represents elementary charge of electron, m represents mass of electron, v represents velocity of electron, z represents nuclear charge of incident particle, Z represents the atomic number of the target material, N represents the number of atoms per unit volume of the target material, I represents the mean excitation potential of the target material, and β represents v/c where c is the speed of light. FIG. 3 is a graph showing the relationship between the stopping power based on the Bethe equation (equation (3)) and kinetic energy of particle. As illustrated in FIG. 3, the collision stopping power (energy loss) of a target material for a charged particle increases from A (kinetic energy of particle is low) to B and reaches maximum at B. Then, the stopping power decreases from B to C in proportion to I/v2, and reaches minimum at C. Then, the stopping power gradually increases from C to D, where logarithms of the Bethe equation (equation (3)) are effective. The charged particle beam X received by a beam intensity converting film (attenuator 1, scraper 2, or the like) in Embodiments 1 and 2 is, in many cases, a charged particle beam falling within the energy range of from A to C, which is a relatively low energy range. However, the fact that the beam intensity converting film is used in a relatively low energy range does not mean that the intensity converting film does not require high durability. The energy of the charged particle beam X at B is on the order of MeV (for example, 1 MeV), and the energy of the charged particle beam X at C is on the order of GeV (for example, 3 GeV). The stopping power of the target material at B is about 100 times as high as the stopping power of the target material at C. This means that the energy of charged particles is converted into heat and effectively lost within the target material. Therefore, an intensity converting film for use in the energy range of from B to C, which is for use in one embodiment of the present invention, is required to be highly durable. The number of charged particles differs depending on each accelerator, and therefore the stopping power is not the only factor that determines the durability necessary for the intensity converting film. However, in the energy range of 1 to 100 MeV, which is the major application of the intensity converting film in Embodiments 1 and 2, the intensity converting film is undoubtedly required to be highly durable. Under such severe conditions, the foregoing graphite films constituting the beam intensity converting films of Embodiments 1 and 2 can satisfy the above requirement, provided that the graphite films have physical properties and thickness falling within the foregoing ranges. The present invention not limited to the embodiments, but can be altered by a skilled person in the art within the scope of the claims. The present invention also encompasses, in its technical scope, any embodiment derived by combining technical means disclosed in differing embodiments. Further, it is possible to form a new technical feature by combining the technical means disclosed in the respective embodiments. [Recap] A beam intensity converting film in accordance with one embodiment of the present invention is a beam intensity converting film having an opening that allows passage of a charged particle beam, the beam intensity converting film including one or more graphite films placed such that a surface thereof intersects a beam axis of the charged particle beam, wherein the one or more graphite films each have a thickness of 1 μm or greater, and wherein, in the one or more graphite films, a thermal conductivity in a surface direction is equal to or greater than 20 times a thermal conductivity in a thickness direction. According to the above configuration, each of the graphite films is equal to or greater than 1 μm in thickness, and thus has a sufficient shielding ability against charged beams, mechanical strength sufficient for actual use, and sufficient durability. Furthermore, according to the above arrangement, the one or more graphite films have the following characteristic: the thermal conductivity in the surface direction of a graphite film is equal to or greater than 20 times the thermal conductivity in the thickness direction of the graphite film. This characteristic is one of the indicators for the degree of orientation, and indicates that the one or more graphite films in the beam intensity converting film in accordance with one embodiment of the present invention are highly oriented. A graphite film having such a configuration is basically made only of carbon, and therefore the extent of radioactivation of the film itself can be reduced. Furthermore, since heat generated by beam irradiation is smoothly diffused in the surface direction and thereby the temperature rise of the intensity converting film is prevented, the durability of the intensity converting film improves. In addition, preventing or reducing temperature rise also makes it possible to reduce the extent of radioactivation of apparatuses near the intensity converting film, as described later. Furthermore, the foregoing characteristic concerning thermal conductivity (anisotropy in thermal conductivity) also indicates that the graphite film has a high crystallinity. A graphite film in accordance with one embodiment of the present invention can therefore have high heat resistance. Graphite with high crystallinity has an excellent heat resistance at temperatures equal to and above 3000° C. in vacuum, and thus has a superior durability against charged particle beams to conventional intensity converting films made of titanium. A beam intensity converting film in accordance with one embodiment of the present invention is a beam intensity converting film having an opening that allows passage of a charged particle beam, the beam intensity converting film including one or more graphite films placed such that a surface thereof intersects a beam axis of the charged particle beam, wherein the one or more graphite films each have a thickness of 1 μm or greater, and wherein, in the one or more graphite films, an electric conductivity in a surface direction is equal to or greater than 100 times an electric conductivity in a thickness direction. According to the above configuration, the one or more graphite films have the following characteristic: the electric conductivity in the surface direction of a graphite film is equal to or greater than 100 times the electric conductivity in the thickness direction of the graphite film. This characteristic is one of the indicators for the degree of orientation, and indicates that the one or more graphite films in the beam intensity converting film in accordance with one embodiment of the present invention have high crystallinity and are highly oriented. Thus, the above configuration makes it possible to provide a beam intensity converting film that is made of carbon, that is sufficiently durable against charged particle beams, and that can reduce the extent of radioactivation. Furthermore, since the measurement of electric conductivity is very easy as compared to thermal conductivity, measuring electric conductivity characteristics is a very effective method in managing the performance of a graphite film. Such an anisotropy in electric conductivity is also an indicator that indicates that the graphite film has high crystallinity. As such, the graphite film can have high heat resistance. The beam intensity converting film in accordance with one embodiment of the present invention is preferably arranged such that, in each of the one or more graphite films, the thermal conductivity in the surface direction is 1000 W/(m·K) or greater. Such a high thermal conductivity in the surface direction reduces the temperature rise of the film, and this achieves a reduction in extent to which apparatuses near the intensity converting film become radioactive due to beam reflection by the intensity converting film, for the reasons described later. The beam intensity converting film in accordance with one embodiment of the present invention is preferably arranged such that, in the one or more graphite films, the electric conductivity in the surface direction is 12000 S/cm or greater. Since the measurement of electric conductivity is very easy as compared to thermal conductivity, measuring electric conductivity characteristics is a very effective method in managing the performance of a graphite film. The beam intensity converting film in accordance with one embodiment of the present invention is preferably arranged such that the one or more graphite films have an open area ratio of 1 to 80%. The beam intensity converting film in accordance with one embodiment of the present invention may be arranged such that the one or ore graphite films are two or more graphite films, and that the beam intensity converting film includes a stack of the two or more graphite films. As a graphite film becomes thicker, the shielding ability and durability of the intensity converting film against charged particle beam irradiation improve. Furthermore, the above stack, which is a stack of two or more graphite films of the present invention, may be prepared by press-bonding by a hot press method or the like method. This makes it possible to prepare an intensity converting film having a desired thickness. The thickness of a beam intensity converting film constituted by such a stack is not particularly limited, but employing such a multilayer structure is usually very effective in order to prepare a beam intensity converting film equal to or greater than 100 μm in thickness. The beam intensity converting film in accordance with one embodiment of the present invention is preferably arranged such the one or more graphite films have a density of 1.70 g/cm3 or greater and 2.26 g/cm3 or less. A method of producing a beam intensity converting film in accordance with one embodiment of the present invention is a method of producing a beam intensity converting film having an opening that allows passage of a charged particle beam, the beam intensity converting film including one or more graphite films, the method including a step of preparing the one or more graphite films by firing one or more polymeric films. According to the above arrangement, it is possible to provide a method of producing a beam intensity converting film that has sufficient shielding ability and sufficient durability against charged particle beams and that can reduce the extent of radioactivation. The present invention can be used in the fields in which an accelerator is used. 1 Attenuator (beam intensity converting film) 1a Opening 2 Scraper (beam intensity converting film) 2a Opening |
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061047724 | abstract | A method and an apparatus introduce a self-propelled in-pipe manipulator into the interior of a pipeline. A hollow body receives the in-pipe manipulator, is open at least at one end surface and is positioned at an opening of the pipeline, from where the in-pipe manipulator can drive on its own into the pipeline. |
summary | ||
abstract | Techniques disclosed herein include systems and methods for tracking, visualizing and understanding energy or utilities usage of one or many buildings. The system links building characteristics with energy or utilities use thereby enabling users to view energy or utilities usage and cost information at the portfolio, development, building, or meter levels. This technique allows for easy comparison among and between buildings in a portfolio, group, or common ownership. The system provides for quick creation of custom reports to compare buildings across portfolios. These custom reports further enable users to compare energy/utilities use of buildings within a given account relative to energy/utilities use of similar buildings in a larger database, thus providing meaningful performance benchmarking based on real data. |
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039829944 | claims | 1. A cellular fuel element grid structure comprising, a first plurality of generally parallel apertured fuel element grid plates having protruding bosses formed thereon, a further plurality of apertured fuel element grid plates having protruding bosses formed thereon, said further plurality of plates interlocking with and being generally perpendicular to said first plate plurality to form common corners at said respective apertures in order to establish rows of aligned slits, a plurality of bars lodged within said slits, stubs formed on said bars, said stubs and said adjoining bar portions each having combined lengths that are greater than the widths of said respective slits to enable said stubs selectively to bridge across said slits and engage an adjoining portion of said grid plates and thereby to temporarily deflect said plates. 2. A method for inserting into and withdrawing nuclear fuel rods from a fuel element grid structure comprising the steps of inserting a bar having protruding stubs into the fuel element grid structure, turning said bar in a direction that enables said stubs to engage respective portions of the grid structure, and applying a lengthwise force to said bar in order to press said protruding stubs against the respective portions of the fuel element grid structure to deflect the structure and enable the fuel rods to be inserted into and withdrawn from the grid structure. |
claims | 1. A method for managing a wind turbine, the method comprising:receiving operational information (130) on operational characteristics of a wind turbine (102);analyzing the operational information (130) based on a set of rules (240), the set of rules being configurable;determining that advanced operational information (130) of the wind turbine (102) is required based upon analyzing the operational information (130), wherein the advanced operational information (130) comprises a history of the operational information (130) in the recent past, the advanced operational information (130) comprising sensor data of the wind turbine (102) up to, and after a trip caused by a fault of the wind turbine;receiving the advanced operational information (130) of the wind turbine when the advanced operational information (130) of the wind turbine (102) is required;analyzing the advanced operational information (130) based on the set of rules;determining whether the fault of the wind turbine (102) is resettable based on at least one of the operational information (130) and the advanced operational information (130); andresetting the wind turbine (102) when the fault of the wind turbine is resettable. 2. The method of claim 1, wherein the operational information (130) comprises information on at least one of wind speed, wind speed profile, temperature of wind turbine (102) components, voltage, current, converter, generator, rotor speed sensors, tower vibrations, hardware units of the wind turbine (102), and/or a grid event, and wherein the analyzing comprises further processing the operational information (130). 3. The method of claim 1, wherein the analyzing comprises referring to the set of rules (240) with respect to the operational information (130) of the wind turbine (102), the set of rules (240) comprising threshold values for the operational characteristics of the wind turbine (102) and derivatives of the operational characteristics of the wind turbine (102), and wherein the set of rules (240) comprises threshold values for at least one of wind speed, wind speed profile, temperature of the wind turbine (102) components, voltage levels, current levels, converter faults, generator faults, rotor speed sensors faults, tower vibrations, faults in the hardware units of the wind turbine (102), and a grid event. 4. The method of claim 1, wherein the set of rules (240) are further configured based on the operational characteristics (130) of the wind turbine (102) and fault analysis of the wind turbine (102). 5. A wind turbine management system, comprising:a wind turbine (102) operable to generate electricity using wind energy, the wind turbine (102) comprising operational characteristics related to the operation of the wind turbine (102);a control server (220) comprising a wind turbine management module (224) configured to implement the steps of:receiving operational information (130) on operational characteristics of a wind turbine (102);analyzing the operational information (130) based on a set of rules (240), the set of rules being configurable;determining that advanced operational information (130) of the wind turbine (102) is required based upon analyzing the operational information (130), wherein the advanced operational information (130) comprises a history of the operational information (130) in the recent past, the advanced operational information (130) comprising sensor data of the wind turbine (102) up to, and after a trip caused by a fault of the wind turbine (102);receiving the advanced operational information (130) of the wind turbine (102) when the advanced operational information (130) of the wind turbine (102) is required;analyzing the advanced operational information (130) based on the set of rules;determining whether the fault of the wind turbine (102) is resettable based on at least one of the operational information (130) and the advanced operational information (130); anda network (250),wherein the wind turbine (102) is communicably coupled to the management module (224) via the network (250), and wherein a rule configuration module is accessible via the network (250). 6. The system of claim 5, wherein the operational information (130) comprises information on at least one of wind speed, wind speed profile, temperature of wind turbine (102) components, voltage, current, converter, generator, rotor speed sensors, tower vibrations, hardware units of the wind turbine (102), a grid event, or combinations thereof. 7. The system of claim 5, wherein the control server (220) further comprises a rules engine (226) for configuring the rules (240) based on the operational characteristics of the wind turbine (102) and based on a fault analysis of the wind turbine (102). 8. The system of claim 5, wherein the management module (224) is configured to reset the wind turbine (102) if the fault of the wind turbine (102) is resettable. 9. The system of claim 5, wherein the wind turbine (102) further comprises:a controller (104) configured to receive and process the operational information (130) of the wind turbine (102), the controller (104) further configured to control the operation of the wind turbine (102);an interface computer (106) configured to receive the operational information (130) of the wind turbine (102) from the controller (104), and send the operational information (130) of the wind turbine (102) to be communicated over the network (250), the interface computer (106) configured to receive instructions for operating the wind turbine (102), and send the instructions for operating the wind turbine (102) to the controller (104); anda farm server (120) operably coupled to the interface computer (106) and to the network (250), the farm server (120) configured to receive operational information (130), and/or store operational information (130), of the wind turbine (102), the farm server (120) configured to receive the operating instructions (130) for the wind turbine (102) from the control server (220) over the network (250), and further communicate the operating instructions to the interface computer (106). |
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047737999 | claims | 1. Sampling apparatus for taking up a longitudinal section of a tube in a nuclear fuel assembly comprising a skeleton having two end-pieces, a plurality of tubes fixed to and connecting the end-pieces and grids distributed between the end-pieces along the tubes and comprising a bundle of fuel elements retained by the grids between the end-pieces, including a power tool having: frame means including a sleeve provided with means for releasable connection of said sleeve with an end-piece of a nuclear fuel assembly, in alignment with a tube of said fuel assembly; a spindle arranged in said sleeve for rotation about and movement along a longitudinal axis of said sleeve, a cutter having means for releasable driving connection to said spindle at a distal end of said spindle, of such size as to cut out an opening in said end-piece upon rotation of said spindle of sufficient cross-section for passage of a section of said tube; and a sampling unit having a stationary part provided with means for fixed connection to said frame, a drive tube mounted in said stationary part for rotation about said axis of the sleeve and provided with connection means for non-rotatable axially slidable connection with the spindle in substitution for the cutter, and a shank mounted in the tube for rotation about an axis offset with respect to said longitudinal axis, carrying a radially directed cutting element and whose angular position in the tube about said axis is adjustable, and an adjustment shaft in said tube and axially displaceable with said spindle, connected to said shank via means which convert axial movement of said shaft into rotation of said shank. comprising a power tool having: stationary frame means including a sleeve and support means connectable to said sleeve and provided with a tubular guide for abutment with an upper end-piece of a nuclear fuel assembly and alignment of said sleeve and tubular guide with a tube of said fuel assembly; a spindle arranged in said sleeve for rotation about a longitudinal axis of said sleeve by a motor and manually movable along said longitudinal axis of said sleeve; a drive tube mounted in said tubular guide for rotation about said axis and connected against axial movement relative to said tubular guide; connecting means for providing a non-rotatable axially free connection between the spindle and drive tube; a shank mounted in said drive tube for rotation about an axis offset with respect to said longitudinal axis and carrying a radially directed cutter element; an axially directed shaft fast with said spindle and projecting into said drive tube; means interconnecting said shaft and shank for converting downward movement of said spindle and shaft into rotation of said shank about said offset axis in a direction increasing the amount of radial projection of said cutter element from said longitudinal axis; and abutment means for limiting downward movement of said shaft and spindle with respect to said drive tube. a flange on said drive tube, and an abutment ring threadedly received on a tubular part which belongs to said connecting means and is fast with said spindle. 2. Sampling apparatus for taking up a longitudinal section of a tube in a nuclear fuel assembly comprising a skeleton having two end pieces, and a plurality of tubes fixed to and connecting the end-pieces, 3. Sampling apparatus according to claim 2, wherein said abutment means comprises |
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