patent_number
stringlengths 0
9
| section
stringclasses 4
values | raw_text
stringlengths 0
954k
|
|---|---|---|
047524375 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show a packaging for radioactive materials according to this invention, which comprises a packaging body 1 made of cast iron or cast steel wherein a bottom 20 is united with a shell 2. The open end of the shell 2 is hermetically sealed with the inner lid 10 and the outer lid 11 via a gasket (not shown). At both opposite ends on the surface of the shell 2, trunnions 9 are disposed. Reference numerals 5 and 6 indicate a shock absorbing cover. The packaging body 1 contains a basket 4 for charging of radioactive materials therein to. Within the shell 2, a plural bar-shaped shielding materials 7 are axially positioned in the circumferential direction in such a manner that neutrons can be shielded from radiating in a radial direction from the basket 4 through the shell 2 of the packaging body 1. The shielding materials may be also disposed within the bottom 20 of the shell 2. On the outer surface of the shell 2, a plurality of fins 8 are disposed to dissipate heat from the radioactive materials. These fins may be circumferentially disposed on the packaging body 1. As shown in FIG. 3, an annular arrangement of material 70 can be used as a shielding material instead of the bar-shaped shielding materials. The annular material 70 is circumferentially disposed, so that a more effective shielding effect can be attained thereby enabling the reduction of the thickness of the shell 2. The shielding materials which can be selected include, for example, ceramic material concrete, heavy metals such as uranium and led, organic materials such as resin, plastics and wood, boron nitride, boron carbide, graphite, hydrogenous alloys or the like. The packaging according to this invention is manufactured as follows: A fine powder (diameter: 1-5 .mu.m) of at least one selected from the group consisting of resin, concrete, boron nitride, boron carbide, graphite and hydrogenous alloys is compressed under a high pressure such as for example, about 100 kg/cm.sup.2 and; sintered and/or molded in the desired shape. Alternatively, the fine powder may be solidified at about 2000.degree. C. under 200 kg/cm.sup.2 by the HIP (Hot Isostatic Pressing) method with the formation of a sintered compact of the desired shape and design. The resulting compact of the shielding material is disposed within a mold (not shown) for a packaging body followed by pouring of cast iron or cast steel into the mold, thereby obtaining packaging body 1 in which the compact of the shielding material is buried within the shell 2. When boron nitride, boron carbide, graphite and hydrogenous alloys are used as the shielding material, the thermal conductivity of such material is so excellent that the cast in the mold can be effectively cooled. Especially, when spheroidal graphite cast iron is used as the shell material, rapid cooling of the cast is required and ideally achieved by using the above-mentioned shielding material, thus resulting in a metal having an excellent structure. Moreover, due to excellent thermal conductivity, the resulting packaging body does not require the use of passages for thermal conduct therein. Since the shielding material is cast within the packaging body, it is firmly installed in the packaging body and the packaging is simple in shape and design. Also, the operation for making hollows in the packaging body and charging the shielding material therein can be omitted thereby simplifying the process of manufacturing the packaging. Alternatively, as shown in FIG. 4, a plurality of heat-resistant pipes 3 filled with the shielding material 7 may be axially cast within the shell 2. In the event that organic materials are used as the shielding material, cast iron or cast steel is first cast in a mold for the packaging body, to bury the pipes 3 within the packaging body and then the organic materials are charged into said pipes 3 under pressure. In the event that boron nitride, boron carbide or graphite is used as the shielding material, it is first charged into the pipes 3 and then the pipes 3 are disposed in the mold for the packaging body followed by pouring cast iron or cast steel into the mold. These shielding materials may be charged into the pipes 3 in a fine powder form or a sintered compact form. Instead of utilizing the pipes 3 an annular case 30 may be employed, as shown in FIG. 5, which is circumferentially positioned to thereby attain a better shielding effect and reduce the thickness of the shell 2 as well. As shown in FIG. 6, the fins 80 may be formed in such a manner that the inner plate 31 and the outer plate 32 constituting the case 30 are connected with each other by the fins 80. The fins 80 may be connected to the inner plate 31 and the outer plate 32 by means of welding, thereby preventing the inner plate 31 from shifting from the cast compact, i.e. shell 2. FIG. 7 shows another fin 80 which is formed such that it passes through the shielding material 7 and its end is positioned toward the inside of the inner plate 31, thereby tightly connecting the case 30 to the cast compact. FIG. 8 shows another fin 82 which is formed on the outside of the outer plate 32 and thus the shielding material 7 is circumferentially oriented to thereby attain a complete shielding effect. FIG. 9 shows an annular shielding case, consisting of inner plate 31 and outer plate 32, which is located inside the inner wall of the shell 2. As seen from the above-mentioned various embodiments, the pipes or the case in which the shielding material is to be injected may be positioned at any location within the packaging body. Since the case for the shielding material is cast within the packaging body, it is firmly mounted to the packaging body and the packaging is simple in shape and design. Moreover, the operation of charging the shielding material into the pipes or the case can be performed in parallel with the formation of the mold for the packaging body. It is understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those skilled in the art to which this invention pertains. |
claims | 1. An irradiation target encapsulation assembly, comprising:a container defining a cavity;at least one first irradiation target disposed in the cavity of the container;at least one second irradiation target disposed in the cavity of the container;a positioning structure disposed in the cavity of the container and configured to position the first irradiation target closer to an axial center of the cavity of the container than the second irradiation target; and whereinthe container is sealed,wherein the positioning structure comprises:a central body extending along an axis of the container; anda spacing structure configured to position the central body along the axis of the container. 2. The assembly of claim 1, wherein the first and second irradiation targets do not include nuclear fuel. 3. The assembly of claim 1, whereinthe first irradiation target is a material including at least one of cobalt (Co), chromium (Cr), copper (Cu), erbium (Er), germanium (Ge), gold (Au), holmium (Ho), iridium (Ir), lutetium (Lu), molybdenum (Mo), palladium (Pd), samarium (Sm), thulium (Tm), ytterbium (Yb), and yttrium (Y); andthe second irradiation target is a material including at least one of cobalt (Co), chromium (Cr), copper (Cu), erbium (Er), germanium (Ge), gold (Au), holmium (Ho), iridium (Ir), lutetium (Lu), molybdenum (Mo), palladium (Pd), samarium (Sm), thulium (Tm), ytterbium (Yb), and yttrium (Y). 4. The assembly of claim 1, wherein the first and second irradiation targets are a same material. 5. The assembly of claim 1, wherein the first and second irradiation targets are different materials. 6. The assembly of claim 1, wherein the spacing structure includes a plurality of projections projecting from the central body. 7. The assembly of claim 1, wherein the spacing structure includes one or more members connected to the central body and having a periphery matching an inner periphery of the container. 8. The assembly of claim 1, whereinthe container has a cylindrical shape; andthe central body has a rod shape. 9. The assembly of claim 1, whereinthe second irradiation target is disposed at next to one end of the central body; andthe first irradiation target is disposed between the central body and the container. 10. The assembly of claim 9, wherein a length of the central body is based on the reactor flux profile and a desired specific activity resulting from irradiating the first and second irradiation targets in the flux profile. 11. The assembly of claim 9, wherein a cross sectional area of the central body is based on a desired specific activity resulting from irradiating the first irradiation target. 12. The assembly of claim 1, wherein the central body includes a neutron moderator and/or a neutron multiplier. 13. The assembly of claim 1, wherein the positioning structure has a cross-sectional area that varies along a length thereof to create different sized spaces between the positioning structure and the container for holding the first irradiation target(s). 14. The assembly of claim 1, whereinthe container is a hollow cylinder;the positioning structure includes a rod having fins projecting from the rod;the second irradiation target is disposed at one end of the rod; anda plurality of first irradiation targets are disposed between the rod and the container. 15. The assembly of claim 1, whereinthe container is a hollow cylinder;the positioning structure includes a rod having one or more annular disk attached thereto;the second irradiation target is disposed at one end of the rod; anda plurality of first irradiation targets are disposed between the rod and the container. 16. The assembly of claim 1, whereinthe container is a hollow cylinder;the positioning structure includes a cylindrical member, at least two portions of the cylindrical member have different diameters;the second irradiation target is disposed at one end of the cylindrical member; anda plurality of first irradiation targets are disposed between the cylindrical member and the container. 17. The assembly of claim 1, wherein the container includes a liner, and the liner includes a neutron moderator and/or neutron multiplier. 18. An irradiation target encapsulation assembly, comprising:a container defining a cavity;a first irradiation target disposed in the cavity of the container;a second irradiation target disposed in the cavity of the container;a positioning structure disposed in the cavity of the container and configured to position the second irradiation target closer to an axial periphery of the cavity of the container than the first irradiation target; and whereinthe container is sealed,wherein the positioning structure includes,a central body extending along an axis of the container; anda spacing structure configured to position the central body along the axis of the container. 19. A method for assembling an irradiation target encapsulation assembly, comprising:placing a positioning structure within a container defining a cavity;adding a plurality of first irradiation targets to the cavity of the container, the positioning structure configured to position the first irradiation targets between the positioning structure and the container;adding at least one second irradiation target to the cavity of the container, the positioning structure configured to position the second irradiation target at an end of the position structure; andsealing the container,wherein the positioning structure comprises:a central body extending along an axis of the container; anda spacing structure configured to position the central body along the axis of the container. |
|
055568980 | summary | FIELD OF THE INVENTION This invention relates to novel products for radiation shielding and for containment of nuclear materials such as nuclear waste. More particularly, it relates to gadolinium oxide-containing thermoplastic polymers which provide shielding against low level neutron and gamma radiation (typically up to about 60,000 electron volts), and to various forms in which these polymers may be used, such as a pressed sheet, a fabric-backed sheet or as part of a laminate. Radiation-shielding constructions now employed, such as slab tanks for holding nuclear waste, are made up of laminates made by bonding or sealing a lead sheet between two thermoplastic sheets. In such laminates the edge of the thermoplastic has to be welded to seal the lead. This welding, however, risks exposure to lead fumes at the high temperatures required to seal the plastic. And, when the useful life of such a part is reached, the waste-containing lead must be disposed of in a safe manner. It would thus be highly desirable to find a material that provides the required shielding in a single sheet, which avoids the use of lead, and which eliminates fabrication hazards and disposal problems associated with the use of lead. Applicant is not aware of any prior disclosure of the inventive compositions. STATEMENT OF THE INVENTION A radiation resistant composition comprising a blend of a thermoplastic polymer and from about 1 to about 20 percent by weight of gadolinium oxide, based on the weight of the composition, is provided, the polymer optionally containing other additives such as calcium carbonate. This invention also relates to various forms in which the composition may be employed, such as pressed sheets, fabric-backed pressed sheets, and laminates wherein the radiation resistant composition is sandwiched between two compatible thermoplastic sheets, and to methods of making the same. DETAILED DESCRIPTION OF THE INVENTION It has now been found that incorporation of a small amount of gadolinium oxide into a thermoplastic polymer results in a material which accomplishes the above objectives of providing protection against low level radiation while eliminating the problems associated with the use of lead. The thermoplastic can be chosen to provide the most suitable and cost effective protection. Suitable polymers include, for example, polyethylene (PE), polypropylene (PP), fire resistant polypropylene (FRPP), chlorotrifluoroethylene (CTFE), ethylenechlorotrifluoroethylene (ECTFE), ethylenetrifluoroethylene (ETFE), and preferably, where the polymer is to be used in a corrosive environment requiring chemical resistance, vinylidene fluoride (VDF) polymers. "VDF polymer" refers not only to the homopolymers of VDF but also to the copolymers prepared from at least about 60% by weight of the VDF monomer. Comonomers may include other fluorinated monomers such as hexafluoropropylene ("HFP") and tetrafluoroethylene ("TFE"). Preferred are the homopolymers and the copolymers prepared from VDF and HFP. Minor amounts of other conventional additives, such as calcium carbonate and flame retardants, may also be added. The preferred VDF polymer resins are those having a melt viscosity (according to ASTM D3835) in the range of from about 7 to about 30 Kp (kilopoise) at a shear rate of 100 sec.sup.-1 and a temperature of 232.degree. C. Examples of such polymers include KYNAR grades 2750, 2800, 2850, 2900, and 2950 (copolymers of VDF and HFP) and KYNAR grades 460, 710, 720, 740, and 760 (PVDF homopolymers) which are available from Elf Atochem North America, Inc. of Philadelphia, Pa. The thermoplastic polymer is blended with from about 1 to about 20 weight percent gadolinium oxide, more typically about 5-15%, preferably by mixing both components in powder form. The gadolinium oxide is available in powder form, for example, from Research Chemicals of Phoenix, Ariz. For making a pressed sheet, the powder mix can be compression molded, typically with heated platens or a Carver press using a pressure of about 15,000-25,000 pounds (ram force). Sheet widths of from about one-eighths inch to about six inches are suitable for most low level radiation. Any additive(s) can be blended into the polymer using conventional polymer milling and mixing equipment so as to provide a good dispersion of the additive(s) in the base polymer. When the material to be contained is corrosive, an extra measure of protection can be provided by using a laminate wherein the thermoplastic/gadolinium oxide blend is placed between two sheets of compatible polymer and heat pressed. This multi-laminate sheet can be thermoformed, welded, cut and in general handled in a manner similar to those utilized for plastic sheets. Such a construction will prevent extraction of the gadolinium oxide by the corrosive environment. Fabric-backed sheet can be incorporated on one or both sides to permit bonding of the sheet, for example to the inside of the tank. The fabric will typically be chosen from glass cloth, carbon cloth, or a synthetic cloth such as a polyester. |
062194003 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows an X-ray optical system in an X-ray exposure apparatus, according to a first embodiment of the present invention. Light source 1 such as a charged particle accumulation ring produces X-rays (synchrotron radiation light) which are emitted from a light emission point as a sheet-like beam with thin thickness in the direction (Y-axis direction) perpendicular to the orbit of the charged particle accumulation ring, for example. It is then expanded in the Y-axis direction by means of an expanding mirror 2a. Disposed upstream of this expanding mirror 2a is a collecting mirror 2b which comprises a concaved surface mirror being curbed with respect to X-axis direction. This mirror serves to collect the X-rays in the X-axis direction to enlarge the intensity, and to project the rays to the expanding mirror 2a. Expanded beam L.sub.1 thus collected and expanded by an X-ray illumination system having the expanding mirror 2a and the collecting mirror 2b, is introduced into an exposure chamber through a beryllium window 3, and it irradiates a mask M.sub.1 (original) and then a wafer (substrate) being held by a unshown substrate holding means such as a wafer stage, for example. The beam duct from the light source 1 to the beryllium window 3 of the exposure chamber is controlled to provide therein a ultra-high vacuum ambience to thereby prevent attenuation of X-rays. Also, the the exposure chamber is controlled to provide therein a reduced pressure ambience of helium gas, for example. The expanding mirror 2a comprises a cylindrical mirror having a reflection surface curved into a cylindrical shape. It is suspended within a vacuum chamber, not shown, If the incidence position or incidence angle of X-rays upon the expanding mirror 2a changes due to fluctuation of X-rays, for example, the X-ray intensity distribution of the expanded beam L.sub.1 varies largely. It causes large non-uniformness of intensity within the exposure picture angle, and disables uniform exposure. In consideration of this, an actuator 4a (driving means) for changing the position or attitude of the expanding mirror 2a is provided and, additionally, a beam position detecting device 5a for detecting relative positional deviation of the X-rays relative to the expanding mirror 2a is provided as a unit with the expanding mirror 2a. The output of the beam position detector 5a is applied to a controller 6 to control the actuator 4a. Like the expanding mirror 2a, the collecting mirror 2b is disposed within a vacuum chamber, and it is supported by an actuator 4b (driving means). If the incidence position or incidence angle of X-rays upon the collecting mirror 2b changes due to fluctuation of X-rays, for example, a required collecting power is not produced. It results in large change in X-ray intensity distribution of the expanded beam L.sub.1, and disables uniform exposure. In consideration of this, an actuator 4b (driving means) for changing the position or attitude of the collecting mirror 2b is provided and, additionally, a beam position detecting device 5b for detecting relative positional deviation of the X-rays relative to the collecting mirror 2b is provided as a unit with the collecting mirror 2b. The output of the beam position detector 5b is supplied to the controller 6 to control the actuator 4b. The beam position detector 5a for the expanding mirror 2a and the beam position detector 5b for the collecting mirror 2b have the same structure. They comprise optical axis sensors 11a and 11b (first measuring means), respectively, for detecting X-axis incidence position of X-rays and incidence angles of X-rays with respect to wX and wY directions, and position sensors 12a and 12b (second measuring means), respectively, for detecting Y-axis incidence position of X-rays and incidence angle of X-rays with respect to wZ direction. As shown in FIG. 3A, each of the optical axis sensors 11a and 11b comprises a cylindrical frame member 10a, a pinhole plate 10b fixed to one end thereof, and an X-ray area sensor 10c held at the other end of the frame member 10a. X-rays passing through the pinhole 10b are sensed as a spot upon the X-ray area sensor 10c. If the optical axis of the X-rays tilts, the position of the spot on the X-ray area sensor shifts. The amount of such shift of spot position is measured and, on the basis of the amount of shift and of the distance between the pinhole 10b and the X-ray area sensor 10c, the tilt of the optical axis of X-rays with respect to the wX and wY directions is calculated. Then, on the basis of these data, the incidence position of X-rays with respect to the X-axis direction and incidence angles of X-rays with respect to the wX and wY directions, relative to the expanding mirror 2a and collecting mirror 2b, are determined. As shown in FIG. 3B, each of the position sensor 12a and 12b comprises a supporting member 10d which is integral with the expanding mirror 2a or collecting mirror 2b, and first to third X-ray intensity sensors 10e-10g being supported by the supporting member. The first and second X-ray intensity sensors 10e and 10f are disposed in series along the X-axis direction, and the second and third X-ray intensity sensors 10f and 10g are disposed in series along the Y-axis direction. From the ratio between the outputs of the first and second X-ray intensity sensors 10e and 10f, the incidence angle of the sheet-like X-ray beam about the optical axis (i.e., in the wZ direction) can be detected. Also, by comparing the sum and the difference of and between outputs of the second and third X-ray intensity sensors 10f and 10g, the incidence position of X-rays with respect to the Y-axis direction can be detected. As described above, the expanding mirror 2a and collecting mirror 2b are equipped with beam position detecting devices 5a and 5b, respectively, for detecting incidence positions of X-rays with respect to X-axis and Y-axis directions as well as incidence angles with respect to wX, wY and wZ directions. On the basis of the outputs of these sensors, drive amounts for the actuators 4a and 4b for the expanding mirror 2a and the collecting mirror 2b are controlled. This avoids relative positional deviation of the expanding mirror 2a or collecting mirror 2b with respect to the X-rays impinging thereupon. The X-ray intensity distribution of the expanded beam L.sub.1, being expanded by the expanding mirror 2a in the thickness direction (Y-axis direction) and additionally being collected by the collecting mirror 2b into high intensity, can be maintained constant stably as above and, as a result, uniform and simultaneous exposure can be done in a short time. This provides improved transfer precision of X-ray exposure apparatus as well as significantly enlarged throughput. FIG. 4 shows a modified form of the first embodiment. In this structure, only the collecting mirror 2b is equipped with a beam position detecting device 5b, and the beam position detecting device 5b for the expanding mirror 2a is omitted. As regards the incidence position of the X-rays and tilt, for example, of the X-rays with respect to the expanding mirror 2a, they can be calculated by the controller 6 on the basis of the drive amount of the actuator 4b and the output of the beam position detecting device 5b for the collecting mirror 2b. Particularly, when the actuator 4a for the expanding mirror 2a is arranged to control only the incidence position of X-rays with respect to the Y-axis direction, use of the detected data from the beam position detecting device 5b of the collecting mirror 2b such as described above is effective and preferable in respect to simplification of the structure of the X-ray optical system. FIG. 5 shows an X-ray optical system according to a second embodiment of the present invention. Like the first embodiment, light source 21 such as a charged particle accumulation ring produces X-rays (synchrotron radiation light) which are emitted from a light emission point as a sheet-like beam with thin thickness in the direction (Y-axis direction) perpendicular to the orbit of the charged particle accumulation ring, for example. It is then expanded in the Y-axis direction by means of an expanding mirror 22a. Disposed upstream of this expanding mirror 22a is a collecting mirror 22b which comprises a concaved surface mirror being curbed with respect to X-axis direction. This mirror serves to collect the X-rays in the X-axis direction to enlarge the intensity, and to project the rays to the expanding mirror 22a. Expanded beam L.sub.2 thus collected by the collecting mirror 22b and expanded by the expanding mirror 22a, is introduced into an exposure chamber through a beryllium window 23, and it irradiates a mask M.sub.2 (original) and then a wafer (substrate) being held by a unshown substrate holding means such as a wafer stage, for example. The beam duct from the light source 21 to the beryllium window 23 of the exposure chamber is controlled to provide therein a ultra-high vacuum ambience to thereby prevent attenuation of X-rays. Also, the the exposure chamber is controlled to provide therein a reduced pressure ambience of helium gas, for example. The expanding mirror 22a comprises a cylindrical mirror having a reflection surface curved into a cylindrical shape. It is suspended within a vacuum chamber, not shown, If the incidence position or incidence angle of X-rays upon the expanding mirror 22a changes due to fluctuation of X-rays, for example, the X-ray intensity distribution of the expanded beam L.sub.2 varies largely. It causes large non-uniformness of intensity within the exposure picture angle, and disables uniform exposure. In consideration of this, an actuator 24a (driving means) for changing the position or attitude of the expanding mirror 22a is provided and, additionally, an X-ray intensity distribution sensor 25 which comprises measuring means having at least four X-ray intensity sensors is provided. Also, there is a controller 26 (control means) which serves to detect relative positional deviation of the X-rays relative to the expanding mirror 22a on the basis of the output of the X-ray intensity distribution sensor 25 and to control the actuator 24a. Like the expanding mirror 22a, the collecting mirror 22b is disposed within a vacuum chamber, and it is supported by an actuator 24b (driving means). If the incidence position or incidence angle of X-rays upon the collecting mirror 22b changes due to fluctuation of X-rays, for example, a required collecting power is not produced. It results in large change in X-ray intensity distribution of the expanded beam L.sub.2, and disables uniform exposure. In consideration of this, an actuator 24b (driving means) for changing the position or attitude of the collecting mirror 22b is provided. Additionally, a relative positional deviation of the X-rays with respect to the collecting mirror 22b is detected on the basis of the output of the X-ray intensity distribution sensor 25, and the result is applied to the controller 26 to control the actuator 24b. As shown in an enlarged view of FIG. 6, the X-ray intensity distribution sensor 25 comprises an aperture member 30 which is disposed upstream of a variable aperture member 27 for defining the exposure angle to the expanded beam L.sub.2 to be projected to the mask M.sub.2, and eight X-ray intensity sensors 31a-31h in this embodiment which are disposed at the peripheral edge of the aperture 30a of the aperture member 30. The aperture 30a of the aperture member 30 has a rectangular shape. The X-ray intensity sensors 31a, 31c, 31e and 31g are disposed at four corners of the aperture 30a, respectively, while the remaining X-ray intensity sensors are disposed at middles of sides of the apertures 30a, respectively. It should be noted that, as regards the number of X-ray intensity sensors, a number of at least four may be sufficient. Namely, the number is not limited to eight and, as an example, the X-ray intensity sensors 31b, 31d, 31f and 31h disposed at the sides of the aperture 30a may be omitted. As regards the X-ray intensity distribution of the expanded beam L.sub.2 having been collected by the collecting mirror 22b with respect to the X-axis direction and having been expanded by the expanding mirror 22a in the Y-axis direction, a notable change can be observed particularly at the four sides of the mask M.sub.2 with a change in incidence position or incidence angle thereof with respect to the expanding mirror 22a or the collecting mirror 22b. FIG. 7A shows the result of measurement of the X-ray intensity distribution, measured upon the mask M.sub.2 surface, as the relative position (tilt) of the collecting mirror 22b and the X-rays shifts by +.DELTA.wX. It is seen from this drawing that the X-ray intensity decreases as a whole in inverse direction (negative direction) along the Y axis. Also, local X-ray intensity decreases are observed at the opposite ends in the X-axis direction. FIG. 7B shows measurement data as the relative position (tilt) of the collecting mirror 22b and the X-rays shift by -.DELTA.wX, to the contrary. In this case, the X-ray intensity decreases as a whole in the direction (positive direction) along the Y axis. Also, local X-ray intensity increases are observed at the opposite ends in the X-axis direction. As described above, from the profile of increase/decrease of outputs of the eight X-ray intensity sensors 31a-31h disposed along the peripheral edge of the exposure view angle, relative positional deviation of the X-rays with respect to the collecting mirror 22b or the expanding mirror 22a can be discriminated, specifically as to which of X, Y, wX, wY and Z directions the deviation resides in. More specifically, the outputs of the X-ray intensity sensors 31a-31h are applied to a computing means (not shown) and these outputs are compared with each other in accordance with the following equations: EQU {(Ia+Ic)-(Ie+Ig)}/{(Ia+Ic)+(Ie+Ig)} (1) EQU {(Ia+Ig)-(Ic+Ie)}/{(Ia+Ig)+(Ic+Ie)} (2) EQU {(Ia+Ie)-(Ic+Ig)}/{(Ia+Ie)+(Ic+Ig)} (3) EQU Side ac: (Ia-Ib)/(Ia+Ib), (Ib-Ic)/(Ib+Ic) (4) EQU Side ce: (Ic-Id)/(Ic+Id), (Id-Ie)/(Id+Ie) (5) EQU Side eg: (Ie-If)/(Ie+If), (If-Ig)/(If+Ig) (6) EQU Side ga: (Ig-Ih)/(Ig+Ih), (Ih-Ia)/(Ih+Ia) (7) If for example the collecting mirror 22b shifts by +.DELTA.wX, then: EQU {(Ia+Ic)-(Ie+Ig)}/{(Ia+Ic)+(Ie+Ig)}>0 (1) EQU {(Ia+Ig)-(Ic+Ie)}/{(Ia+Ig)+(Ic+Ie)}=0 (2) EQU {(Ia+Ie)-(Ic+Ig)}/{(Ia+Ie)+(Ic+Ig)}=0 (3) EQU (Ia-Ib)/(Ia+Ib)<0, (Ib-Ic)/(Ib+Ic)>0 (4 ) EQU (Ic-Id)/(Ic+Id)>0, (Id-Ie)/(Id+Ie)>0 (5) EQU (Ie-If)/(Ie+If)<0, (If-Ig)/(If+Ig)>0 (6) EQU (Ig-Ih)/(Ig+Ih)<0, (Ih-Ia)/(Ih+Ia)<0 (7) Using these equations in combination, deviation of X-ray intensity distribution can be discriminated as being a relative positional deviation of the collecting mirror 22b in +.DELTA.wX direction, and appropriate drive amount of the actuator 24b with which all of these equations result in zero (0) is calculated. In this manner, the position or attitude of the collecting mirror 22b is adjusted. As described, the X-ray intensity distribution of the expanded beam L.sub.2, being expanded by the expanding mirror 22a in the thickness direction (Y-axis direction) and additionally being collected by the collecting mirror 22b into high intensity, can be maintained constant stably as above and, as a result, uniform and simultaneous exposure can be done in a short time. This provides improved transfer precision of X-ray exposure apparatus as well as significantly enlarged throughput. Additionally, since the X-ray intensity distribution of the expanded beam L.sub.2 just prior to impingement on the mask M.sub.2 is measured directly, there is a specifically advantageous effect that high precision control which is very effective to provide uniform X-ray intensity distribution upon the wafer surface to be exposed, is assured. Further, as compared with an arrangement wherein the collecting mirror or expanding mirror is equipped with an optical axis sensor or a position sensor, the structure around the mirror can be simplified. FIG. 8 shows a modified form of the second embodiment. In this structure, a position sensor 28 which comprises three X-ray intensity sensors is added to the collecting mirror 22b, by which relative positional deviations of X-rays in the Y-axis direction and in the wZ direction, with respect to the collecting mirror 22b, can be detected. Since the relative positional deviations to be calculated by the X-ray intensity distribution sensor 25 require only three in the X-axis direction, wX direction and wY direction, algorithm of computing means can be simplified. Thus, the processing time can be advantageously reduced. FIG. 9 shows a third embodiment of the present invention, and illustrates an X-ray illumination system having two X-ray mirrors, like the preceding embodiments. In this illumination system, the synchrotron radiation light is collected with respect to the X direction. It is expanded in the Y direction by swinging movement of an X-ray mirror, to illuminate the surface of a mask. Denoted in FIG. 9 at 41 is synchrotron radiation light, and denoted at 42 is a first X-ray mirror. Denoted at 43 is driving means for moving the first mirror to adjust the position or attitude thereof. Denoted at 12b is a position sensor, like that described hereinbefore, which is fixedly mounted on the first mirror to detect the intensity center of the synchrotron radiation light. Denoted at 11b is an optical axis sensor, like that described hereinbefore, which is fixedly mounted on the first mirror to detect the optical axis of synchrotron radiation light. Denoted at 46 is a second X-ray mirror, and denoted at 47 is driving means for moving the second mirror to adjust the position or attitude of it. Denoted at 12a a position sensor, like that described hereinbefore, which is fixedly mounted on the first mirror to detect the intensity center of the synchrotron radiation light. Denoted at 11a is an optical axis sensor, like that described hereinbefore, which is fixedly mounted on the first mirror to detect the optical axis of synchrotron radiation light. Denoted at 50 is control means which serves to control the driving means 43 for the first mirror 42 on the basis of the outputs of the position sensor 12b and the optical axis sensor 11b, and also to control the driving means 47 for the second mirror 46 on the basis of the outputs of the position sensor 12a and the optical axis sensor 11a. Denoted at 3 is a beryllium window (vacuum partition) like that described hereinbefore, which functions as an X-ray extraction window. Denoted at M.sub.1 is an X-ray mask which is demountably mounted on a mask stage, not shown, of an X-ray exposure apparatus, not shown. Denoted at 1 is a light source which in this embodiment comprises a synchrotron radiation ring for accumulating electrons therein and for emitting synchrotron radiation light. While not specifically illustrated in this drawing, the components from the synchrotron ring 1 to the beryllium window are placed inside a vacuum chamber wherein a ultra-high vacuum is kept therein. In the structure described above, the synchrotron radiation light 41 emitted from the synchrotron radiation ring 1 impinges on the first mirror 42. Also, at the same time, the synchrotron radiation light impinges on the position sensor 12b and the optical axis sensor 11b. In response, the intensity center position and the optical axis of the synchrotron radiation light are detected. Thus, a change in synchrotron radiation light with respect to X, Y, wX, wY and wZ directions can be detected. Measured values are applied to the control means 50, whereby drive amounts for the first mirror driving means 43 with respect to these directions are calculated and the position or attitude of the first mirror 42 is controlled. The second mirror 46 also should be controlled into a predetermined position or attitude with respect to the synchrotron radiation light 41. To this end, like the case of the first mirror 42, the outputs of the X-ray position sensor 12a and the X-ray optical axis sensor 11a are applied to the control means 50, whereby drive amounts for the second mirror driving means 47 with respect to various directions are calculated and the position or attitude of the second mirror 46 is controlled. Here, since the center of swinging movement of the second mirror 46 during the scan exposure operation should be controlled to a predetermined position or attitude with respect to the synchrotron radiation light, an unshown swinging motion mechanism is mounted on the driving means 47. Namely, the drive amount of the driving means 47 is a value with which the center of swinging motion of the swinging mechanism is placed at a predetermined position or attitude with respect to the synchrotron radiation light 41. FIG. 10 shows a modified form of the third embodiment of the present invention. In this structure, as regards the second mirror 46, a drive amount for controlling the position or attitude of the second mirror 46 is calculated by the control means 50 on the basis of the output of the synchrotron radiation light optical axis sensor 11b and of the drive amount for controlling the position of the first mirror 42. This structure provides the following advantage: since there is no necessity of provision of an intensity sensor and an optical axis sensor on the second mirror, the structure of the second mirror can be made quite simple. Next, an embodiment of device manufacturing method which uses an X-ray exposure apparatus as described above, will be explained. FIG. 11 is a flow chart of procedure for manufacture of microdevices such as semiconductor chips (e.g. ICs or LSIs), liquid crystal panels, or CCDS, for example. Step 1 is a design process for designing a circuit of a semiconductor device. Step 2 is a process for making a mask on the basis of the circuit pattern design. Step 3 is a process for preparing a wafer by using a material such as silicon. Step 4 is a wafer process which is called a preprocess wherein, by using the so prepared mask and wafer, circuits are practically formed on the wafer through lithography. Step 5 subsequent to this is an assembling step which is called a post-process wherein the wafer having been processed by step 4 is formed into semiconductor chips. This step includes assembling (dicing and bonding) process and packaging (chip sealing) process. Step 6 is an inspection step wherein operation check, durability check and so on for the semiconductor devices provided by step 5, are carried out. With these processes, semiconductor devices are completed and they are shipped (step 7). FIG. 12 is a flow chart showing details of the wafer process. Step 11 is an oxidation process for oxidizing the surface of a wafer. Step 12 is a CVD process for forming an insulating film on the wafer surface. Step 13 is an electrode forming process for forming electrodes upon the wafer by vapor deposition. Step 14 is an ion implanting process for implanting ions to the wafer. Step 15 is a resist process for applying a resist (photosensitive material) to the wafer. Step 16 is an exposure process for printing, by exposure, the circuit pattern of the mask on the wafer through the exposure apparatus described above. Step 17 is a developing process for developing the exposed wafer. Step 18 is an etching process for removing portions other than the developed resist image. Step 19 is a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are superposedly formed on the wafer. With these processes, high density microdevices can be manufactured. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims. |
041860497 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The prior art components which have already been described with reference to FIG. 1 will not be described relative to FIG. 2 and in addition the same reference numerals will be used. FIG. 2 shows in a more explicit manner an autonomous heat transfer module 14 suspended on the upper slab 16 of the reactor by elastic means 15 which permit a limited angular displacement of the assembly about its vertical axis. Autonomous module 14 comprises a primary circuit 17, designated by arrows F for the circulation of the combustible salt which when heated on leaving core 4 penetrates the module via an opening 18 provided in the upper part thereof and then after cooling is forced back by a pump 19 located in the lower part thereof. A secondary salt circuit whose inlets and outlets are designated by reference numeral 20 receives the calories from the combustible salt in the primary circuit and finally transfers them to a not shown water circuit where the steam produced is finally used to operate an also not shown turbine. The lower part of autonomous module 14 has, if necessary, a non-return valve for the molten salt flow, said valve not being shown in FIG. 2. According to the invention, between reactor skirt 5 and main vessel 3 a conical ferrule 21 is provided which by one end is fixed to reactor skirt 5 and whose other end 22 is mounted freely in the immediate vicinity of main vessel 3 in the solidified salt layer 13. According to the invention, the surface of conical ferrule 21 has openings 23 distributed around the core axis, each being surrounded by a planar bearing surface 24 and cooperating in the present embodiment with a spherical bearing surface 25 in the lower part of autonomous module 14. The bearing of spherical bearing surface 25 on planar bearing surface 24 makes it possible to support the weight of module 14, whilst ensuring the relative displacements of the said members relative to one another in accordance with the different thermal operating cycles of the reactor, whilst providing the sealing relative to the pressure of the cold salt delivered by pump 19 at the base of autonomous module 14. In the embodiment of FIG. 2 a delivery pipe 26 directly links the base of module 14 through opening 23 and the lower part of the reactor core via an opening 27 made in wall 5 of the reactor skirt below conical ferrule 21. Pipe 26 is made from the same material as the reactor skirt 5 and ferrule 21, said members being at the same temperature during normal operation of the reactor. This makes it possible to avoid all differential expansion problems encountered in prior art solutions using transverse connections between the base of each exchanger shaft and the base of each pump shaft, said two components being completely separate. A second embodiment of the invention will now be described with reference to FIG. 3. In this embodiment each autonomous heat transfer module 14 provided with its pump 19 is supported, as in the previous embodiment, on a conical ferrule 21 having openings 23 for the passage of the cold salt delivered by the corresponding pump 19. As in the previous embodiment, the cooperation between a spherical bearing surface 25 at the base of module 14 and a planar bearing surface 24 surrounding opening 23 leads to a tightly sealed support and permits the relative movements of module 14 and ferrule 21. In this embodiment the space below ferrule 21 between main vessel 3 and reactor skirt 5 is subject to the pressure of pump 19, whereby the cold salt flows through channels 33 made in carbonaceous mass 7 connecting the outlet of the pumps to openings 29 made in the lower part of skirt 5 to the reactor core and in accordance with arrow F. Channels 33 are obtained by an appropriate shaping of the carbonaceous material in the absence of any metallic element connecting the opening of the pumps to those of the reactor skirt. Thus, the mass of carbonaceous material ensures the filling of space 28, whilst piping the combustible salt between the pumps and openings 29. This space is not tightly sealed and construction joints can exist between the carbonaceous elements and there can be tolerances between said elements and the metallic structures defining space 28. Cracks may also occur in the carbonaceous mass. Therefore the delivery pressure of the pumps can be exerted on the periphery of this space which from then on should be sealed. With regard to vessel 23 and ferrule 21, this sealing is more particularly obtained by the cooperation of a boss 30 and the free end 31, which is preferably slightly tapered, of conical ferrule 21 which moves freely beneath boss 30, the assembly being located in area 13 which is filled by the neutral solid salt crust which is voluntarily maintained against the inner surface of main vessel 3. This arrangement which is essential for the second embodiment of the invention is described in greater detail with reference to FIG. 4. FIG. 4a illustrates the reciprocal arrangement of boss 30 on main vessel 3 and the free end 31 of ferrule 21 when, with the reactor shut down, the different members are at the same ambient temperature, for example about 20.degree. C. The external diameter of ferrule 21 is then below the inner bore of boss 30 providing a given clearance between said members permitting a one piece fitting of the ferrule during assembly. In FIG. 4b the respective position of the different members corresponds to the formation stage of salt crust 13, i.e. when vessel 3 is heated to a temperature of about 300.degree. C. whilst ferrule 21 is at a temperature of about 400.degree. C. Under these conditions boss 30 connected to vessel 3, and on which it is suspended by its upper part, drops slightly relative to the position which it occupied in FIG. 4a, whilst conical ferrule 21 has expanded transversely towards the outside of the reactor by a distance sufficient to bring about a partial covering of said boss by said ferrule measured by the distance j'. Simultaneously, the upward vertical expansion of ferrule 21 causes the engagement of its end 31 beneath boss 30, approaching the latter in the area of solid salt 13. In FIG. 4c which corresponds to the normal operation of the reactor, the main vessel 3 is still at a temperature of 300.degree. C. necessary for maintaining the crust of solid salt 13 against its surface, whilst conical ferrule 21 has reached a temperature of about 560.degree. C., its expansion in both the radial and vertical directions having increased further. Therefore its free end 31 engages beneath boss 30, permitting if necessary the fitting of a piece of graphite 32 located in a groove made in the upper part of end 31 so as to increase the sealing between the latter and boss 30. It should also be noted that the cooperation between end 31 of ferrule 21 and boss 30 of main vessel 3 is beneficial from the thermal standpoint because the tapered portion constitutes a significant impedance for the calories which would otherwise tend to escape directly from the core towards the periphery. Moreover, boss 30 constitutes a mass whose thermal impedance is very low and via which it is possible to evacuate very rapidly the calories from conical ferrule 21 towards the air-conditioning fluid 9 contained between main vessel 3 and outer vessel 8. It is clear that the solidification of salt crust 13 takes place automatically even when occasional cracks occur in said crust, for example during the sliding of the two metal members 30 and 31. In the extreme case where a break in the sealing could occur due to cracks in the crust 13 between boss 30 and end 31 as a result of said two members sliding, e.g. due to a change in the thermal operating cycle, combustible salt could possibly pass through the carbonaceous lining and flow between ferrule 21 and vessel 3. This mixture which would have to pass into the cold area adjacent to the main vessel 3 where the temperature is lower than its melting point would then be rapidly solidified again which would automatically re-establish the sealing. In other words, the device according to the invention permits a certain relative movement between the metal members as a result, for example, of a change in the thermal state of the ferrule, but the sealing is automatically restored by solidification of the liquid salt coming into contact with the cold metal parts. The invention is not limited to the embodiments described and represented hereinbefore, and various modifications can be made thereto without passing beyond the scope of the invention. |
046882421 | summary | BACKGROUND OF THE INVENTION The present invention relates to an X-ray imaging system which irradiates an object with X-rays, and detects X-rays transmitted through the object to obtain transmission X-ray data, thereby forming a visible image based on the transmission X-ray data and, more particularly, to a scattered X-ray elimination technique suitable for a so-called digital radiography apparatus which converts an X-ray image into digital data. In conventional X-ray imaging systems, a detector for detecting X-rays receives direct X-rays transmitted through an object without being scattered, as well as scattered X-rays scattered by the object. The scattered X-rays are a major factor contributing to the degradation of contrast and sharpness of an X-ray image obtained through the detector. For this reason, in X-ray imaging systems, it is very important to eliminate scattered X-rays. In order to eliminate scattered X-rays, a grid is usually used in conventional systems. However, since the grid itself generates scattered X-rays, it cannot perform satisfactory elimination of scattered X-rays. If scattered X-rays can be eliminated, a contrast and sharpness of an X-ray image can be improved, thus providing a good X-ray image. In addition, if an image based on direct X-rays can be obtained, attenuation of the X-rays by the object can be accurately calculated by logarithmic conversion of the image data. Therefore, it is very desirable to eliminate scattered X-rays. Although various studies have been made on the nature of these scattered X-rays, since X-ray scattering involves complicated phenomena, many aspects thereof still remain unsolved. SUMMARY OF THE INVENTION It is an object of the present invention to provide an X-ray imaging system which effectively eliminates scattered X-ray components contained in image data, and which can form an X-ray image of high contrast and sharpness without blurring. In order to achieve the above object of the present invention, there is provided an X-ray imaging system comprising: an X-ray source for emitting X-rays to be radiated on an object; an X-ray image detection section for detecting an X-ray image emitted from the X-ray source and transmitted through the object; an X-ray mask member, having a plurality of X-ray shielding regions distributed in a predetermined pattern, for locally shielding X-rays with the plurality of X-ray shielding regions; a drive unit for moving the X-ray mask member so that the X-ray mask member is inserted or removed with respect to an X-ray radiation field between the X-ray image detection section and the X-ray source and is sequentially positioned at a plurality of predetermined positions in the X-ray radiation field; a storage section for storing X-ray image data; a first calculating section, associated with the storage section, for calculating scattered X-ray intensity distribution data associated with the object, based on a plurality of transmission X-ray data obtained by irradiating the object with X-rays when the X-ray mask member is located at different positions in the X-ray radiation field, and on transmission X-ray data obtained by irradiating the object with X-rays when the X-ray mask member is located outside the X-ray radiation field; a second calculating section, associated with the storage section, for calculating X-ray image data, from which the influence of scattered X-rays is eliminated, in accordance with the scattered X-ray intensity distribution data obtained by the first calculating section and transmission X-ray data obtained by irradiating the object with X-rays when the X-ray mask member is located outside the X-ray radiation field; and an image output unit for outputting the X-ray image data calculated by the second calculating section as a visible image. The present invention provides an X-ray imaging system, which can sufficiently eliminate scattered X-ray components contained in the image data and can form an X-ray image of high contrast and sharpness without blurring. More specifically, in the X-ray imaging system of this invention, a plurality of masked X-ray data, produced by an X-ray mask member displaced to different positions in an X-ray radiation field, are subjected to calculation of scattered X-ray intensity distribution, thus greatly improving calculation precision of the scattered X-ray components contained in the image data. Therefore, the scattered X-ray components contained in the image data can be effectively eliminated. |
abstract | In an operation monitoring apparatus of a nuclear power plant, a first operation console (12) that can be operated by an operator and includes displays (31 to 37), an operation command console (14) that can be operated by a shift supervisor and includes displays (41 to 44) , a transfer device (51) that can display an image displayed on the displays (31 to 37) of the first operation console (12) on the displays (41 to 44) of the operation command console (14), and a switching device (54) that switches an image on the displays (41 to 44) of the operation command console (14) to the image on the displays (31 to 37) of the first operation console transferred by the transfer device (51) are provided. With this configuration, it is possible to improve communications between the supervisor and the operation in operation of the nuclear power plant. |
|
053274725 | description | Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is seen a boiling water reactor having a pressure vessel 231, in which a reactor core is disposed, that has vertically disposed nuclear reactor fuel assemblies 232, as shown in FIGS. 2-7, between which absorber assemblies 242 are disposed that are driven into a space between the fuel assemblies or retracted from the space in order to control the reactor. An outlet 233 for water vapor at the top of the pressure vessel 231 is connected to a steam turbine 234, which drives an electric generator 235. A condenser 236 associated with the steam turbine 234 is connected laterally through a feedwater pump 237 and a feedwater inlet 238 to the top of the pressure vessel 231. This feedwater pump 237 pumps condensed steam from the steam turbine 234 back into the pressure vessel 231 as feedwater. In older boiling water reactors, the pressure vessel 231 also has a coolant outlet 239 below the feedwater inlet 238, laterally of the reactor core having the nuclear fuel assemblies 232. The pressure vessel 231 also has a coolant inlet 241 below the reactor core. A coolant pump 240 connected to the coolant outlet 239 and to the coolant inlet 241 pumps water continuously out of the pressure vessel 231, through the coolant outlet 239 and back into the pressure vessel 231 through the coolant inlet 241, thus assuring a continuous coolant flow through the reactor core and thus longitudinally through the nuclear fuel assemblies 232, beginning at the bottom of the pressure vessel 231. In modern reactors, this pump 240 is disposed in the interior of the pressure vessel. One of the fuel assemblies 232 of FIG. 2 for a boiling water reactor of FIG. 1, has a fuel assembly top, which is not identified by a reference numeral, with a handle 2 on top of a square grid plate. Two or four stay bolts, that are likewise not shown in the drawing, are located on top of this square grid plate. An elongated sheet-metal fuel assembly case, box or jacket 3 made of a zirconium alloy and associated with the fuel assembly rests on these stay bolts with two or four non-illustrated crosswise strips, that are also made of sheet metal that is made of a zirconium alloy, which are mounted on the inside of two or four corners of the upper end the fuel assembly case 3. Each crosswise strip is screwed to the applicable stay bolt. The fuel assembly case 3 is square in cross section and open on both ends. The grid plate itself is provided with a number of flow openings in the longitudinal direction of the fuel assembly 232, through which the coolant flows in the reactor core of the boiling water reactor. This grid plate is at right angles to the longitudinal direction of the fuel assembly 232. The side walls of the fuel assembly case 3 close off the fuel assembly at the sides. The fuel assembly of FIG. 2 is also provided with a base 4, which also has a hidden and non-illustrated square grid plate. This square grid plate also has a number of coolant flow openings in the core of the boiling water reactor, extending longitudinally of the fuel assembly 232. The lower surface or underside of the grid plate of the fuel assembly base 4 is provided with a fitting device 5 that is open toward the grid plate and is inserted into a fitting opening on a so-called lower core grid plate located in the core of the boiling water reactor. On the upper end, the fuel assembly 232 is fixed in a mesh, opening or space of a so-called upper core grid. The fuel assembly 232 of FIG. 2 also has a row of nuclear fuel-filled fuel rods, which are constructed as retaining rods 9, for the top part and bottom part 4 of the fuel assembly 232. These retaining rods 9 are screwed into the grid plate of the fuel assembly base 4 and reach through the grid plate of the fuel assembly top, where they are screwed to the grid plate with a nut located on the top of the grid plate. Other fuel rods 10 filled with nuclear fuel are loosely inserted by their ends into openings in the grid plates of the top and the base 4 of the fuel assembly. Holding-down springs which are constructed as helical springs are mounted on their upper end. These springs are compression springs and each is supported at one end on the fuel rod 10 and at the other end on the lower surface or underside of the grid plate of the fuel assembly top. Finally, the fuel assembly 232 of FIG. 2 has a plurality of square gridlike spacers between the fuel assembly top and the fuel assembly base. The spacers are located in a cross section of the fuel assembly case 3 and are aligned with the square grid plates of the top part and the base part 4. One gridlike spacer 22 can be seen in FIG. 2. The other gridlike spacers are constructed identically to the spacer 22 but are concealed both by the side walls of the fuel assembly case 3 and by the grid plate of the top part and the grid plate of the base part 4 and therefore cannot be seen. The plan view of FIG. 3 is a portion of FIG. 2 showing the coolant outflow end of a gridlike spacer 22, which is made of a nickel-chromium-iron alloy. This coolant outflow side faces toward the top of the fuel assembly 232. The gridlike spacer 22 has two groups of flat, planar ribs 23 and 24, which are located in a cross section of the fuel assembly case 3 and thus on a cross section of the fuel assembly 232. The ribs 23 ("crosswise ribs") of one group and the ribs 24 ("lengthwise ribs") of the other group penetrate one another at right angles. The spacing between two ribs 23 of one group is equal to the spacing between two ribs 24 of the other group. Correspondingly, the ribs 23 and 24 form square meshes 25 of equal area, which are located at points where equidistant lengthwise rows that are parallel to one another ("lines Z") intersect with equidistant crosswise rows ("columns S") that are parallel to one another. One retaining rod 9 or one fuel rod 10 is guided through each square mesh 25. Non-illustrated springs and knobs are located inside the meshes 25 at the ribs 23 and 24, assuring a positive holding connection of the retaining rod 9 or the fuel rod 10 to the gridlike spacers. At an intersection 26 of one rib 23 and one rib 24, the rib 23 has a three-dimensionally curved vane or blade 27 or 28 on each respective side of the rib 24. Each vane tapers in the coolant flow direction. At an adjacent intersection 29, the rib 24 has one of these vanes 27 or 28 on each respective side of the rib 23. These vanes 27 and 28 increase gradually outwardly from the edge of the applicable rib facing toward the intersecting rib. The vanes mounted on the ribs 23 have a curvature about a direction parallel to these ribs 23, while the vanes mounted on the ribs 24 have a curvature about a direction parallel to the ribs 24. In order to form this curvature, two of the vanes 27 and 28 located at an intersection of the ribs 23 and 24 are three-dimensionally curved in different directions. The rib 24, which has the two vanes 27 and 28 of the rib 23 on either side of it at the intersection 26, also has the two vanes 27 and 28 at the intersection 27, which are constructed identically to the other vanes 27 and 28. These vanes 27 and 28 at the rib 24 are curved toward different meshes 25 from those toward which the vanes 27 and 28 on the rib 23 at the intersection 26 are curved. The arrow A indicates the direction in which the side view of a rib with the two vanes 27, 28 appears in FIG. 4. The same is true for the rib 23 with respect to the intersection 29 next to the intersection 26. The four retaining rods 9 or fuel rods 10 immediately surrounding one intersection 26 or 29 define flow subchannels or secondary channels 32, 33 having a center in which the intersection 26 or 29 is located. In the flow subchannels at the intersections of the ribs 23 and 24, coolant flowing through the gridlike spacer shown in FIG. 3 at right angles to the plane of the drawing, from below that plane to above it, is made to swirl, as is represented by arrows 30 and 31, around the center of the flow subchannels. Although there is practically no net flow in the horizontal direction between the various flow subchannels, the two swirling flows of adjacent flow subchannels mix together somewhat at their boundary surfaces, which promotes temperature equalization and reinforces the swirl produced in the adjacent flow subchannel. In the upper part of the fuel assembly, the coolant is in the form of a two-phase mixture of water and steam, and vanes attached there assure that the water is spun against the outer surfaces of the retaining rods 9 and the fuel rods 10, thus counteracting dryout. In the spacer of FIG. 5, dashed lines represent the position of the fuel rods 9 and 10 that define flow subchannels 32 and 33. Four vanes 101, 102, 103, 104 and 101', 102', 103', 104' are respectively provided in each of these flow subchannels. The vanes 101 . . . 104 are disposed rotationally symmetrically about the center line of the flow channel 32, or in other words the line of intersection of a lengthwise rib 110 with a crosswise rib 111, where the two ribs are also joined together by spot welds 105. Reference numerals 106 and 107 indicate knobs on the ribs, against which the fuel rods 9 and 10 are pressed by means of opposed springs 108, 109, in order to define the lateral spacing between the fuel rods. On either side of the spot weld 105, the lengthwise rib 110 carries the vanes 101, 103, which are disposed and bent rotationally symmetrically in the direction of an arrow D, while in the adjacent flow subchannel 33, the crosswise rib 112 intersecting the lengthwise rib 110 includes corresponding vanes 102' and 104', but they are disposed and bent rotationally symmetrically in the opposite direction indicated by an arrow D'. The arrows D and D' therefore indicate the direction of rotation of the swirl in the subchannel. The vanes 102, 104 and 101', 103', respectively, which are mounted in addition to those of FIG. 3, are subordinate to these rotational symmetries, which are each applicable to all of the vanes of one flow subchannel. In the gridlike spacer of FIGS. 6a and 6b the meshes 25 for the retaining rods 9 and the fuel rods 10 are likewise located at intersections of parallel lengthwise rows Z and parallel crosswise rows S that are orthogonal to those lines. The lengthwise rows Z are equidistant from one another, as are the crosswise rows S. The spacing between two crosswise rows is also equal to the spacing between two lengthwise rows. The meshes 25 are formed by hollow-cylindrical sheaths 70 of equal height, which have the same inside and outside cross section. Non-illustrated contact springs and contact knobs for a retaining rod 9 or a fuel rod 10 are located in the sheaths 70. The center of the inside cross section of each sheath 70 is disposed at an intersection of one line Z and one column S. One end of all of the sheaths 70 is located in a cross-sectional plane of the fuel assembly case 3, and the other end of all of the sheaths is located in a cross-sectional plane parallel to that cross-section plane. Adjacent sheaths touch one another along a jacket or mantel line, at which they are welded to one another. Each respective group of four sheaths 70, disposed at the intersections of two adjacent lines Z and two adjacent columns S, form a flow subchannel parallel to these sheaths 70, which is located in the center between these four sheaths 70. Two vanes 72 that are disposed opposite each other along a sheath diameter, are formed at an end of these sheaths 70 facing away from the coolant flow. For each sheath 70, the two vanes 72 are rotationally symmetrical with respect to a longitudinal sheath axis in the center of the sheath. The vanes taper in the coolant outflow direction. The vanes are also each curved three-dimensionally inward, forming a bulge, into one respective flow subchannel. The vanes 72 of the sheaths 70 touching one another are also oppositely rotationally symmetrical with respect to the longitudinal axis in the center of the applicable sheath 70. Two vanes 72 protrude into each flow subchannel and are rotationally symmetrical with respect to a central axis of this flow subchannel that is parallel to the sheaths 70. In this way, in one flow subchannel, the vanes 72 are oppositely rotationally symmetrical to the vanes in every other flow subchannel. Adjacent flow subchannels are located alternatingly, so that one is on an intermediate line UZ parallel to the lines Z and the next is on an intermediate column US parallel to the columns S, and so forth. A coolant flowing from below the plane of the drawing in FIG. 6 to above it, orthogonally to the plane of the drawing, is accordingly provided with a swirl, which is symbolized by respective arrows 73 and 74, in the flow subchannels. Each swirl in one subchannel has a reinforcing effect on the swirl in an adjacent subchannel, and water droplets contained in the coolant are spun outward against the outer surface of the retaining rods 9 or fuel rods 10, as in the case of the gridlike spacer of FIG. 3. The more vanes a subchannel has, and the more its cross section decreases, and the more the pressure loss in the vertical flow increases, yet it is still advantageous to provide four vanes 72, 75, 76, 77 in each flow conduit, having a rotationally symmetrical configuration and shape that produces a spacer as shown in FIG. 7. Once again, the arrow A indicates a view toward a sheath 70 shown in FIG. 8. It can also be seen that by providing indentations 78 in the sheaths, knobs are formed, against which the fuel rods 9, 10 are pressed by springs 79 that engage two adjacent sheaths. An outer rib 80 has contact knobs 81 that rest on side walls 82 of the fuel assembly case, it runs along an outer edge of the spacer and it has tabs 83. Like the vanes in the flow subchannels, the tabs 83 are located on the side of the spacer facing away from the flow, they taper in the flow direction, and are inclined relative to the case wall. Reference numeral 84 indicates the wall of a water tube, which in this case occupies the cross section of 3.times.3 grid meshes and is seated in the center of the fuel assembly. An inner rib 85 with corresponding tabs 86 defines the spacer relative to the water tube 84. FIG. 9 shows a cross section of a portion of a corresponding structure, which is disposed between the water tube 84 and the fuel assembly case having the side wall 82 and serves initially only as a support for the vanes in the flow subchannels. It is therefore initially a mixing grid, but by using suitable spring and knob combinations it can be expanded at any time to make a spacer. A controllable absorber element is indicated at reference numeral 90. Such absorber elements are only located outside the fuel assembly case and are therefore protected by the case walls from any possible horizontal flows of liquid/steam mixture. The spacer of FIGS. 10-12 is square and is likewise made of a nickel-chromium-iron alloy. Two flat, planar outer ribs 323 and 324 can be seen, which are disposed on edge and at right angles to one another and form a rounded portion at the corners of the spacer 22. The spacer 22 also has grid meshes 25, which are located like the squares of a checkerboard at positions disposed in dense lines and in columns at right angles to the lines. One non-illustrated nuclear-fuel-containing retaining rod or fuel rod of the fuel assembly 232 reaches through each of the grid meshes 25. The outer ribs 323 and 324 are at right angles to this fuel assembly, and these outer ribs 323 and 324 face flat toward it. Inside the outer ribs 323 and 324 of the spacer 22 are pairs of mutually aligned main sheaths 327 and 328, which have longitudinal axes that are parallel to one another and to the fuel rods in the spacer 22, like the squares of the same color in a checkerboard at the positions of the grid meshes 25, in lines and in columns at right angles to the lines, in each case leaving one intermediate position open between two occupied positions. The main sheaths 327 and 328 of all of the pairs of main sheaths of the spacer 22 have a cross section with a congruent outer contour, which is a regular octagon. On two sides of this octagon, which are parallel to the same outer rib 323 or 324, the main sheaths 327 and 328 are provided with connecting ribs 329 and 330, which extend over a direction that is parallel to the longitudinal axes of the pairs of the main sheath 327 and 328. At the main sheaths 327 and 328, these connecting ribs 329 and 330 are each formed on to the middle of the side of the regular octagon forming the outer contour of the cross section, and their width equals approximately one-third the length of the side of this rectangular octagon. Two connecting ribs 329 and 330 seated on parallel sides of this octagon are each curved in the same direction in the middle. In other words, one connecting rib 329 is curved outward with respect to the main sheath 327 and 328, and one connecting rib 330 is curved inward with respect to the main sheath 327 and 328. In the middle of the sides of the outer contour of their cross section forming a rectangular octagon, the main sheaths 327 and 328 also have respective rigid knobs 331 and 332 on the applicable main sheath wall. The rigid knob 331 faces inward, if the connecting rib 329 faces outward on the side of the outer contour with respect to the main sheath 327 or 328, and the rigid knob 332 faces outward with respect to the main sheaths 327 or 328 if the connecting rib 330 faces inward with respect to this main sheath 327 or 328. In the spacer, pairs of additional or spacer sheaths 333 and 334, which are aligned with one another, are disposed in the diagonal direction between the main sheaths 327 and 328 and have a cross section that is smaller than the cross section of the main sheaths 327 and 328. The spacer sheaths have a square outer contour, with a length on a side that is equal to the length of the side of the outer contour of the cross section of the main sheaths 327 and 328, forming a regular octagon. These spacer sheaths 333 and 334 are located between the respective main sheaths 327 and 328 and are each formed by two respective spacer sheath parts 433 and 434, each of which is formed on the outer edge of one main sheath 327 or 328, on the side of the outer contour between two sides with the connecting ribs 329 and 330 and the knobs 331 and 332, respectively. Each spacer sheath part 433 and 434 is half of one spacer sheath 333 or 334 of two adjacent main sheaths 327 and 328, respectively. These half spacer sheaths 333 are welded to one another at welding points or locations 439 and 440. The main sheaths 327, together with the spacer sheaths 333 formed onto them, form a first partial grid of the spacer 22, and the main sheaths 328, together with the spacer sheaths 334 welded onto them, form a second partial grid, parallel to the first partial grid. Each of the spacer sheaths 333 and 334 are seated on the outside of these partial grids and form additional sheaths in the flow subchannel that is formed in the respective center between four retaining rods 9 or fuel rods 10. These four retaining rods 9 or fuel rods 10 are each located in meshes 26 of the gridlike spacer, in two adjacent lines and two adjacent columns. As is shown only in FIG. 12 for the sake of clarity, one spacer sheath 333 on the coolant outflow side of the gridlike spacer of FIGS. 4 and 5 has two vanes 172 that curve three-dimensionally inward into the flow subchannel and taper toward one another in the coolant outflow direction. These vanes 172 are located on two opposed coolant outflow edges that are parallel to one another and thus at the coolant outflow ends of the main sheath 327. These vanes are rotationally symmetrical to a central axis of the flow subchannel extending through the intersection points of the diagonals of the cross sections of the spacer sheaths 333. Vanes on spacer sheaths that are immediately adjacent to sides of the main sheaths 327, in sublines and subcolumns defined by these sides in the spacer sheaths 333 shown in FIG. 6, carry vanes on the coolant outflow edges that in contrast are rotationally symmetrical to the vanes on the spacer sheath 333 of FIG. 11. Once again, it is advantageous to supplement each of the pairs of vanes shown in one flow subchannel with a further pair of vanes, that are adapted to the rotational direction in the applicable flow subchannel. The disadvantages entailed by the resultant increased flow resistance can be more than compensated for by the advantages of making the liquid/steam mixture turbulent. |
H00009202 | claims | 1. Method for the removal of radioactive cesium from a vapor stream which comprises: (a) passing an input vapor stream containing radioactive cesium into a bed of silicate glass particles at a temperature of at least about 700.degree. F.; (b) chemically incorporating at least a portion of the radioactive cesium in said silicate glass particles; and (c) withdrawing an output vapor stream containing a reduced content of radioactive cesium from said bed. (a) passing input steam containing radioactive cesium into a bed of silicate glass particles; (b) chemically incorporating at least a portion of the radioactive cesium in said silicate glass particles at a temperature of at least about 700.degree. F.; and (c) withdrawing output steam containing a reduced content of radioactive cesium from said bed. 2. Method according to claim wherein the temperature of the vapor and the bed of silicate glass particles is at least about 800.degree. F. 3. Method according to claim 2 wherein the silicate glass particles comprise borosilicate glass. 4. Method according to claim 3 wherein the glass particles are in the form of spheres. 5. Method according to claim 1 wherein the silicate glass particles comprise borosilicate glass. 6. Method according to claim 5 wherein the glass particles are in the form of spheres. 7. Method according to claim 1 wherein the cesium forms a stable silicate by combining with silica in the glass. 8. Method according to claim 1 wherein said cesium is present in said vapor in a form selected from the group consisting of CsI, CsOH, and mixtures thereof. 9. Method for the removal of radioactive cesium from steam which comprises: 10. Method according to claim 9 wherein the temperature of the steam and the bed of silicate glass particles is at least about 800.degree. F. 11. Method according to claim 10 wherein the silicate glass particles comprise borosilicate glass. 12. Method according to claim 11 wherein the glass particles are in the form of spheres. 13. Method according to claim 9 wherein the silicate glass particles comprise borosilicate glass. 14. Method according to claim 15 wherein the glass particles are in the form of spheres. 15. Method according to claim 9 wherein the cesium forms a stable silicate by combining with silica in the glass. 16. Method according to claim 9 wherein said cesium is present in said steam in a form selected from the group consisting of CsI, CsOH, and mixtures thereof. |
summary | ||
description | Referring to FIG. 3, the basic components of the leaktight closure mechanism of the invention include a three-piece segmented shear ring 30, including pieces 30a, 30b and 30c. It will be understood that a one-piece, spliced shear ring or a two-piece shear ring could also be used. In the illustrated embodiment, the container containment boundary for the canister cylinder 32 is formed by welding the three segments together and welding the resultant shear ring 30 to the canister shell 32 and to the top shield plug assembly including shield plug 34. This is shown in FIG. 4 wherein, as illustrated, shear ring 30 is received in an annular recess 32a in the inner wall of shell 32 and is welded by a weld 31 to shell 32 and by a weld 33 to shield plug 34. As is also shown in FIG. 4, an outer seal plate 36 is welded by respective welds 35 and 37 to the shield plug 34 and the shell 32, respectively. Outer seal plate 36 provides the redundant seal required by 10 C.F.R. xc2xa772. As shown in FIG. 4, the canister 10 also includes canister leak testing components which are located on the circumference of the shield plug 34 and the seal plate 36. The components, which are conventional, include an L-shaped hole 38 connected to a vertical channel 40 in the shield plug 34 which communicates with the interior of the canister 10, a pipe plug 42 disposed in the vertical leg 38a of hole 38 and seal plug 44 which seals off a larger diameter opening 46 which is connected to pipe leg 38a. In addition, outer seal plate 36 includes an outer seal plate boss 48 in which a pipe plug 50 is received and a seal plug 52 for sealing opening 54 in seal plate 36. An intermediate diameter opening 56 is disposed between, and provides communication between, upper opening 54 and the smaller diameter opening in which pipe plug 50 is received. Once the shear ring seal welds 31 and 33 are completed, a leak test adapter 58 of the kind disclosed in U.S. Pat. No. 5,548,992 (Hallett et al) is installed in the shield plug penetration, as shown in FIG. 5. In general, adaptor 58 includes a stem member 58a, which is received in a cylindrical body 58b, operated by handle 58c and sealed by o-rings 58d, and which is used, inter alia, to remove pipe plugs such as plug 42 and thus open a connection to a helium supply or mass spectrometer, indicated at 59, through a branch connector 58e. Reference is made to the Hallett et al patent, which is hereby incorporated by reference, for more details with respect to adaptor 58. The adaptor 58 is used in FIG. 5 to remove the pipe plug 42 (as illustrated), evacuate the canister 10, and reinstall the pipe plug 42 once the canister 10 is filled with helium. Referring to FIG. 6, after these operations are completed, the seal plug 44 is, as illustrated, welded to the shield plug 34. Referring to FIG. 7, in a further step, after the outer seal plate 36 is welded to the shield plug 34 (by weld 35) and to the shell 32 (by weld 37), the leak test adapter 58 is installed in the outer seal plate boss 48, as illustrated. Once the leak test adapter 58 is installed, the adapter 58 is connected to a mass spectrometer (such as that indicated generally at 59 in FIG. 5) which is used to sample the air between the shield plug 34 and the outer seal plate 36. This process is referred to as a helium mass spectrometer envelope leak test and can be used to demonstrate that the inner seal is leak tight (i.e., has leakage rate less than or equal to 1xc3x9710xe2x88x927 std cm3/s. This is an improvement over the current state of the art sniffer test which is limited to demonstrating leaks no greater than about 1xc3x9710xe2x88x925 std cm3/s. Once the inner seal is tested, the void or space between the shield plug 34 and the outer seal plate 36 is filled with helium, the pipe plug 50 is installed, the leak test adapter 58 is removed, and the seal plug 52 is welded to the penetration or opening of the outer seal plate 36. A sniff test is then performed on the outer seal plate 36 to demonstrate a leak rate of no greater than about 1xc3x9710xe2x88x925 std cm3/s. The weld shear ring arrangement of the invention does not require specific alignment of the shield plug 34 and the various weld joints are backed by the shear ring 30, shield plug 34, and canister shell 32. The weld joint geometry can be sized to be structurally adequate, while affording the required clearances needed to install the shear ring 30. Preliminary testing has indicated that preferential weld distortion eliminates these clearances, thereby resulting in metal-to-metal contact between the shield plug 34 and shear ring 30 and between the shear ring 30 and the canister shell 32. This is an improvement over the current state of the art which relies on the closure welds 22 and 24 for lifting. The metal-to-metal contact between the shield plug 34 and shear ring 30 and canister shell 32 results in the shear ring 30 being the load bearing member and the welds 31 and 33 being classified as seal welds. In an alternative embodiment illustrated in FIG. 8, the mating surfaces 30m and 32m between the shear ring 30 and the canister shell 32 are sloped or tapered to ensure metal-to-metal contact between these components prior to welding. To permit lifting with the thick shield plug 34 and to provide a redundant seal, the outer seal plate 36, as indicated above, comprises a ring which is welded, by welds 35 and 37 respectively, to the shield plug 34 and canister shell 32. Lifting with the shield plug 34 (rather than an outer lid 16 which is the state of the art method) is preferred because the plug 34 is very rigid and reduces the bending moment which is applied to the canister shell 32. Lifting is accomplished by attaching safety hoist rings (not shown) or a grapple adapter (not shown) to the shield plug 34 using bolt holes drilled in the outer surface of the plug 34. One such bolt hole, denoted 60, is indicated in FIG. 6. The force required to lift the canister is transmitted from the lift attachments, through the shield plug 34, to the shear ring 30 which contacts or bears on the canister shell 32. Some of the lifting load is transmitted to the seal welds 31 and 33 but the primary load is through the shear ring 30. The shear ring 30 could lift the canister without the two seal welds 31 and 33 and thus, the weld shear ring provides a xe2x80x9cdefense-in-depthxe2x80x9d approach and improved safety for lifting the spent fuel canister. Although the invention has been described above in relation to preferred embodiments thereof, it will be understood by those skilled in the art that variation and modifications can be effected in these preferred embodiments without departing from the scope and spirit of the invention. |
|
050698621 | claims | 1. Apparatus for handling a machine for the simultaneous tensioning of a plurality vertically disposed screwed connecting elements (3) for fastening a cover (1) of a pressurized vessel (2), said apparatus comprising a tensioning module (20) for said connecting elements (3), means (10, 11, 12) for moving said tensioning module (20) in a horizontal plane, and means (15, 22, 24) for moving said tensioning module (20) along a vertical axis of said connecting elements (3), wherein said means for moving said tensioning module (20) in a horizontal plane comprise assembled modular elements forming a rolling track (10) on which travels a train (12) supporting said tensioning module. 2. Handling apparatus according to claim 1, wherein said train (2) comprises a driving carriage (12a) and a driven carriage (12b), said driving and driven carriages each being equipped with a set of guide wheels (13, 14) and being connected to one another by means of a strut (12c). 3. Handling apparatus according to claim 2, wherein said strut (12c) is semicircular. 4. Handling apparatus according to claim 2, wherein said means for moving said tensioning module along said vertical axis consist of a vertical endless screw (15a, 15b) rotatably mounted on each of said driving carriage (12a) and driven carriage (12a, 12b) and a nut (24a, 24b) screwed onto each of said endless screws (15a, 15b), each of said carriages being connected to said tensioning module by means of a bracket (22a, 22b). 5. Handling apparatus according to claim 4, wherein each said endless screw (15a, 15b) is driven in rotation by means of a single motor (27) mounted on said strut (12c) half-way between said driving and driven carriages (12a, 12b) and connected to each of said endless screws (15a, 15b) by means of a control linkage (28). 6. Handling apparatus according to claim 4, wherein each said bracket (22a, 22b) has a first end fixed to said tensioning module (20) and a second end containing an eye (23a, 23b) centered on a corresponding nut (24a, 24b) and bearing on said corresponding nut by means of a thrust ball-bearing (25). 7. Handling apparatus according to claim 4, wherein each said nut (24a, 24b) has an appendage (26a, 26b) with an orifice through which passes a vertical anti-rotation rod (16a, 16b) arranged on each carriage (12a, 12b) parallel to said endless screws (15a, 15b). 8. Handling apparatus according to claim 4, wherein said endless screws (15a, 15b) are arranged in a plane of a center of gravity of said tensioning module (20). |
046631186 | abstract | A flow channel-to-nozzle attachment for a nuclear fuel assembly wherein the flow channel and nozzle are formed of material having different thermal coefficients of expansion, the attachment comprising tapered bars secured to the lower inner ends of the channel which bars are fitted into similarly tapered grooves in the adjacent outer surfaces of the nozzle, the angle of taper being selected such that the tapered bars move more or less deeply into the grooves in the nozzle with temperature changes without bending or stressing the lower end of the channel. |
claims | 1. A scanning device configured for backscatter imaging, the scanning device consisting essentially of:a radiation source, wherein the radiation source emits x-ray radiation; anda stationary shield plate and a single rotary shield body positioned respectively between the radiation source and a subject to be scanned, wherein the stationary shield plate is fixed relative to the radiation source, and the single rotary shield body is rotatable relative to the stationary shield plate; wherein:a ray passing area, permitting radiation beams from the radiation source to pass through the stationary shield plate, is provided on the stationary shield plate; anda ray incidence area and a ray exit area are respectively provided on the rotary shield body, wherein the ray incidence area is formed by a first spiral slit and the ray exit area is formed by a second spiral slit,wherein, during a process of rotating and scanning of the rotary shield body, the ray passing area of the stationary shield plate intersects consecutively with the ray incidence area and the ray exit area of the single rotary shield body to form scanning collimation holes; andwherein the width of each of the first and second spiral slits at their longitudinal ends is narrower than the width of each of the slits at a longitudinally center position, and the scanning collimation holes at both longitudinal ends of each of the first and second spiral slits are formed at an angle relative to the collimation holes at the longitudinal center position of each of the first and second spiral slits. 2. The scanning device configured backscatter imaging according to claim 1, wherein:the ray passing area of the stationary shield plate is a linear slit;the single rotary shield body is a cylinder; andwhen the single rotary shield body rotates at a uniform velocity, the scanning collimation holes consecutively move along the linear slit. 3. The scanning device configured for backscatter imaging according to claim 2, further comprising:a drive unit adapted for driving rotation of the rotary shield body, wherein the single rotary shield body is hollow or a solid cylinder. 4. The scanning device configured for backscatter imaging according to claim 2, wherein:a rotary axis of the single rotary shield body is located on a coplanar plane which is defined in common by the radiation source and the linear slit of the stationary shield plate. 5. The scanning device configured for backscatter imaging according to claim 1, wherein:the stationary shield plate is provided between the radiation source and the rotary shield body. 6. The scanning device configured for backscatter imaging according to claim 5, further comprising:a control unit which controls scanning velocity of the radiation beam by controlling rotary velocity of the single rotary shield body and acquires exit direction of the radiation beam by detecting rotary angle of the rotary shield body. 7. The scanning device configured for backscatter imaging according to claim 6, wherein:by limiting widths of the spiral slits of the single rotary shield body at different positions, shapes of the scanning collimation holes at different positions are controlled such that sectional shape of the radiation beam passing through the scanning collimation holes and irradiating on the subject to be scanned is controlled. 8. A scanning method for backscatter imaging, consisting essentially of:providing a radiation source which emits a radiation beam, wherein the radiation source emits x-ray radiation;providing a stationary shield plate and a single rotary shield body positioned respectively between the radiation source and a subject to be scanned, wherein the stationary shield plate is fixed relative to the radiation source, and the single rotary shield body is rotatable relative to the stationary shield plate; wherein a ray passing area permitting radiation beams from the radiation source to pass through the stationary shield plate is provided on the stationary shield plate, and a ray incidence area and a ray exit area are respectively provided on the rotary shield body, wherein the ray incidence area is formed by a first spiral slit and the ray exit area is formed by a second spiral slit; androtating the single rotary shield body such that the ray passing area of the stationary shield plate intersects consecutively with the ray incidence area and the ray exit area of the single rotary shield body to form scanning collimation holes;wherein the width of each of the first and second spiral slits at their longitudinal ends is narrower than the width of each of the slits at a longitudinally center position, and the scanning collimation holes at both longitudinal ends of each of the first and second spiral slits are formed at an angle relative to the collimation holes at the longitudinal center position of each of the first and second spiral slits. 9. The scanning method for backscatter imaging according to claim 8, wherein:the ray passing area of the stationary shield plate is a linear slit;the single rotary shield body is a cylinder; andwhen the single rotary shield body rotates at a uniform velocity, the scanning collimation holes consecutively move along the linear slit. 10. The scanning method for backscatter imaging according to claim 8, wherein:the stationary shield plate is provided between the radiation source and the rotary shield body. 11. The scanning method for backscatter imaging according to claim 10, further comprising the step of:controlling scanning velocity of the radiation beam by controlling rotary velocity of the rotary shield body, and acquiring exit direction of the radiation beam by detecting rotary angle of the rotary shield body. 12. The scanning method for backscatter imaging according to claim 11, wherein:by limiting widths of the spiral slits of the single rotary shield body at different positions, shapes of the scanning collimation holes at different positions are controlled such that sectional shape of the radiation beam passing through the scanning collimation holes and irradiating on the subject to be scanned is controlled. |
|
claims | 1. A beam transport system for a hadron therapy facility with at least two patient treatment stations, comprising:a main beam transport line into which a hadron beam is injected;a secondary beam transport line branching off from said main beam transport line for delivering said hadron beam into one of said patient treatment stations;a switching electromagnet for deviating said hadron beam from said main beam transport line into said secondary beam transport line, said switching electromagnet comprising an electromagnet coil;an energising circuit associated with said electromagnet coil for energising the latter so as to produce a hadron beam deviation from said main beam transport line into said secondary beam transport line; anda discharge circuit capable of dissipating the electromagnetic energy stored in the switching electromagnet, when the energization of said electromagnet coil is interrupted;wherein said discharge circuit comprises a discharge accelerating circuit capable of generating a voltage opposing the counter electromotive force induced in the electromagnet coil when the energization of said electromagnet coil producing said hadron beam deviation is interrupted, wherein said voltage stays substantially constant or increases as the current induced in the electromagnet coil decreases. 2. The beam transport system as claimed in claim 1, wherein the discharge accelerating function of said discharge accelerating circuit only starts when the current induced in the electromagnet coil drops below a certain value. 3. The beam transport system as claimed in claim 1, wherein said discharge accelerating circuit comprises a power source capable of generating an electromotive force opposing the counter electromotive force induced in the electromagnet coil when the energization of said electromagnet coil is interrupted. 4. The beam transport system as claimed in claim 1, wherein said discharge accelerating circuit comprises a Zener diode, and the breakdown voltage of the Zener diode opposes the counter electromotive force induced in the electromagnet coil when the energization of said electromagnet coil is interrupted. 5. The beam transport system as claimed in claim 4, wherein said discharge accelerating circuit comprises at least two Zener diodes mounted in parallel. 6. The beam transport system as claimed in claim 4, wherein said discharge accelerating circuit comprises at least two Zener diodes mounted in series. 7. The beam transport system as claimed in claim 4, wherein said discharge accelerating circuit further comprises a current sensitive bypass circuit mounted in parallel with said Zener diode, respectively said Zener diodes, said current sensitive bypass circuit bypassing the decay current around said Zener diode, respectively said Zener diodes, until this current drops below a certain value. 8. The beam transport system as claimed in claim 1, wherein said discharge accelerating circuit comprises:a first circuit including a first Zener diode and a first current sensitive bypass circuit mounted in parallel with said first Zener diode, said first current sensitive bypass circuit bypassing the decay current around said Zener diode until this current drops below a certain value I1; anda second circuit mounted in series with said first circuit and including a second Zener diode and a second current sensitive bypass circuit mounted in parallel with said second Zener diode, said second current sensitive bypass circuit bypassing the decay current around said second Zener diode until this decay current drops below a certain value I2<I1. 9. The beam transport system as claimed in claim 4, further comprising a fly-back diode mounted in series with said discharge accelerating circuit. 10. The beam transport system as claimed in claim 1, wherein said discharge accelerating circuit includes:a first branch including a Zener diode;a second branch connected in parallel with said first branch, said second branch including a high-power MOSFET; andan amplifying circuit controlling the gate of the MOSFET so that the breakdown voltage VZD of the Zener diode defines the drain-source voltage VDS of the MOSFET;wherein said discharge accelerating circuit is further designed so that the current flowing through said first branch is small in comparison to the current flowing through said second branch. 11. The beam transport system as claimed in claim 1, wherein:a single power source is associated with several electromagnet coils;a switching device is connected between said power source and said electromagnet coils for selectively disconnecting one electromagnet coil from said power source and connecting another electromagnet coil to said power source; anda discharge accelerating circuit is associated with each of said electromagnet coils. 12. The beam transport system as claimed in claim 1, wherein said power source has a voltage output adjustable between a maximum value and a steady state value; said beam transport system further including a controller setting the voltage of said power source to its maximum value when said power source is newly connected to one of said electromagnet coils and reducing it to its steady state value as soon as the current in said electromagnet coil reaches its steady state value. 13. The beam transport system as claimed in claim 1, wherein said energising circuit and said discharge accelerating circuit are designed so that the time interval required for reducing to zero the decay current induced in the electromagnet coil associated with a first patient treatment station, when its energization is interrupted, is substantially equal to the time interval required for establishing a desired working current in the electromagnet coil associated with a second patient treatment station, when the hadron beam is to be switched from said first patient treatment station into said second treatment station. |
|
059986891 | description | Although the invention is illustrated and described herein as embodied in a method for recycling contaminated metal parts, it is nevertheless not intended to be limited to the details given, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. The method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the preceding description of specific embodiments and the following description of advantages. The method according to the invention brings the advantage of ensuring that a significantly improved degree of decontamination of metal parts is achieved by using a melt decontamination. The shaped metal parts produced from the decontaminated metal melt can then be used without restrictions. |
abstract | The invention relates to the production of radiostrontium. The problem to be solved by the invention is the extraction of radiostrontium from a large pool of liquid metallic rubidium to improve the efficiency of radiostrontium production and simplify the technology. Sorption is carried out directly on the inner surface of the target shell at a temperature of 275 to 350° C., or by means of extraction of radiostrontium from circulating rubidium via sorption on the heated surface of a trap at a temperature of 220 to 350° C., or by means of filtering liquid rubidium through a filtering unit made of a porous material resistant to liquid rubidium metal. |
|
claims | 1. A method comprising:diluting a radioactive isotope in a filler material;mixing the radioactive isotope diluted in the filler material with a radioactive material treatment composition for at least two minutes to form a resulting mixture, the radioactive material treatment composition including mostly salt, and from 0.5 to 15 wt % sorbent, wherein the sorbent comprises a zeolite;during said mixing, sorbing the radioactive isotope with the sorbent;during said mixing, crystallizing the salt to form a matrix of growing salt crystals around the sorbent that comprises the zeolite and the filler, wherein the matrix of salt crystals formed around the sorbent help to encapsulate the radioactive isotope that has been sorbed by the sorbent;after said mixing the radioactive isotope diluted in the filler material with the radioactive material treatment composition, mixing an inorganic binding agent with the resulting mixture for a period of time with a mixer;hardening the inorganic binding agent around the crystallized salt and around the sorbent. 2. The method of claim 1, wherein said diluting comprises:diluting the radioactive isotope in a first portion of the filler material; anddiluting the first portion having the radioactive isotope in a second portion of the filler material, wherein the first portion has one or more selected from a different material and a different average particle size, than the second portion. 3. The method of claim 1, further comprising preparing the filler material including mixing particles of different materials that are capable of participating in interfacial binding reactions with one another. 4. The method of claim 1, wherein said diluting comprises:mixing an indicator chemical with the filler material and the radioactive isotope; andassessing homogeneity of mixing using the indicator chemical. 5. The method of claim 1, further comprising, prior to said sorbing, discarding particles of the filler material that pass through a 100 or smaller mesh. 6. The method of claim 1, further comprising preparing the filler material including adjusting a particle size distribution of the filler material to achieve a fineness modulus in a predetermined range. 7. The method of claim 1, wherein said mixing the radioactive isotope diluted in the filler material with the radioactive material treatment composition comprises mixing for less than 10 minutes using a plough mixer operating at a Froude number ranging from 6 to 8. 8. The method of claim 1, wherein the radioactive material treatment composition comprises at least 75 wt % salt including halide salt and sulfate salt, and wherein said crystallizing the salt comprises forming intergrown and interlocking halide salt crystals and sulfate salt crystals around the sorbent. 9. The method of claim 1, wherein the radioactive material treatment composition comprises at least 75 wt % salt including monovalent cation halide salt and polyvalent cation halide salt, and wherein said crystallizing the salt comprises forming intergrown and interlocking monovalent cation halide salt crystals and polyvalent cation halide salt crystals around the sorbent. 10. A method comprising:mixing a radioactive isotope diluted in a filler material with a radioactive material treatment composition to form a resulting material, the radioactive material treatment composition including mostly salt, and from 0.5 to 15 wt % sorbent, wherein most of the salt comprises one or more selected from sodium chloride, potassium chloride, calcium chloride, and magnesium chloride;mixing the resulting material with one or more inorganic binding agents;diluting the radioactive isotope in a first portion of the filler material; anddiluting the first portion having the radioactive isotope in a second portion of the filler material,wherein the first portion has one or more selected from a different material and a different average particle size, than the second portion. 11. A method comprising:preparing a filler material including mixing particles of different materials that are capable of participating in interfacial binding reactions with one another;mixing a radioactive isotope diluted in the filler material with a radioactive material treatment composition to form a resulting material, the radioactive material treatment composition including mostly salt, and from 0.5 to 15 wt % sorbent, wherein most of the salt comprises one or more selected from sodium chloride, potassium chloride, calcium chloride, and magnesium chloride; andmixing the resulting material with one or more inorganic binding agents. 12. A method comprising:mixing a radioactive isotope diluted in a filler material with a radioactive material treatment composition to form a resulting material the radioactive material treatment composition including mostly salt, and from 0.5 to 15 wt % sorbent, wherein most of the salt comprises one or more selected from sodium chloride, potassium chloride, calcium chloride, and magnesium chloride;mixing the resulting material with one or more inorganic binding agents;prior to said mixing the radioactive isotope diluted in the filler material with the radioactive material treatment composition, mixing the radioactive isotope, the filler material, and an indicator chemical; andassessing homogeneity of mixing using the indicator chemical. 13. A method comprising:mixing a radioactive isotope diluted in a filler material with a radioactive material treatment composition to form a resulting material, the radioactive material treatment composition including mostly salt, and from 0.5 to 15 wt % sorbent, wherein most of the salt comprises one or more selected from sodium chloride, potassium chloride, calcium chloride, and magnesium chloride;mixing the resulting material with one or more inorganic binding agents; anddiscarding particles of the filler material that pass through a 100 or smaller mesh. 14. A method comprising:preparing a filler material including adjusting a particle size distribution of the filler material to achieve a fineness modulus in a predetermined range;mixing a radioactive isotope diluted in the filler material with a radioactive material treatment composition to form a resulting material, the radioactive material treatment composition including mostly salt, and from 0.5 to 15 wt % sorbent, wherein most of the salt comprises one or more selected from sodium chloride, potassium chloride, calcium chloride, and magnesium chloride; andmixing the resulting material with one or more inorganic binding agents. 15. A method comprising:mixing a radioactive isotope diluted in a filler material with a radioactive material treatment composition to form a resulting material, the radioactive material treatment composition including mostly salt, and from 0.5 to 15 wt % sorbent, wherein most of the salt comprises one or more selected from sodium chloride, potassium chloride, calcium chloride, and magnesium chloride, wherein said mixing the radioactive isotope diluted in the filler material with the radioactive material treatment composition comprises mixing for less than 10 minutes using a plough mixer operating at a Froude number ranging from 6 to 8; andmixing the resulting material with one or more inorganic binding agents. 16. A method comprising:mixing a radioactive isotope diluted in a filler material with a radioactive material treatment composition to form a resulting material, the radioactive material treatment composition including mostly salt, and from 0.5 to 15 wt % sorbent, wherein most of the salt comprises one or more selected from sodium chloride, potassium chloride, calcium chloride, and magnesium chloride;mixing the resulting material with one or more inorganic binding agents; andcrystallizing the salt to form a matrix of growing salt crystals around the sorbent and the filler. |
|
summary | ||
summary | ||
051924960 | summary | BACKGROUND OF THE INVENTION The present invention relates to a fuel assembly and an upper tie plate thereof, and specially to the fuel assembly and the upper tie plate thereof which are preferable for effective utilization of fissile material and achieving high burnup in boiling water reactors. Improvement of fuel economy is able to achieved by increasing the degree of burnup of the fuel. For increasing the degree of burnup of the fuel, enrichment of uranium 235 in the fuel pellet may be increased. But, increasing of the enrichment without increasing of the moderator to fuel atom number density ratio (H/U ratio) causes hardening of a neutron spectrum. Therefore, an finite multiplication factor of the fuel assembly does not become the maximum value at the enrichment. FIG. 1 illustrates change of the relation between the H/U ratio and the infinite multiplication factor depending on increasing of the enrichment. For obtaining large infinite multiplication factor with a constant enrichment, it is necessary to achieve the most proper H/U ratio corresponding to the enrichment. That is, when the enrichment is increased in order to improve the fuel economy, the most proper H/U ratio is increased, and accordingly it becomes necessary to increase the number of water rods or to increase a horizontal cross sectional area of the water rods. And, when the enrichment is increased, power peaking in radial direction of the fuel assembly is increased and linear power density of fuel rod becomes large, and consequently the fuel rod is exposed to a more severe condition. Further, distribution of voids in axial direction of the reactor core is small at the lower end portion of the reactor core, and is large from the middle to the upper end portion of the reactor core. Therefore, as burning of the fissile material at the upper region of the fuel assembly is retarded, the concentration of uranium 235 becomes higher relatively than that in the other portion. And by effect of the void, fissile plutonium is produced and built up at the upper region of the fuel assembly. According to the reason mentioned above, power peaking becomes high at the upper portion in axial direction of the fuel assembly. As the increasing of the enrichment relates also to the increasing of power peaking in the axial direction, linear power density of the fuel rod becomes large as well, and the fuel rod is exposed to a more severe condition. On the other hand, a flow rate spectral shift operation of a nuclear reactor is currently considered, in which the void fraction is changed greatly by operating the nuclear reactor with smaller flow rate (the flow rate of the coolant which flows through the reactor core) in the reactor core than the designed flow rate value at the beginning of operation cycle and with larger flow rate in the reactor core than the designed flow rate value at the end of the operation cycle, and fissile plutonium is built up and burnt effectively. In performing the flow rate spectral shift operation, as the power peaking in axial direction becomes large, the linear power density of the fuel rod becomes larger and the fuel rod is exposed to a more severe condition. Accordingly, in order to decrease the linear power density of the fuel rod and to be sure to maintain thermal margin, it is necessary to reduce the power load per fuel rod by increasing number of the fuel rods in the fuel assembly by such method as changing the configuration of a fuel rods lattice from 8 lines by 8 rows to 9 lines by 9 rows etc. In view of the two aspects described above, increasing of the number of fuel rods in the fuel assembly by changing the configuration of the fuel rods lattice and increasing of the H/U ratio by increasing of horizontal cross sectional area of the water rod or number of the water rods are a current trend in the fuel assembly for boiling water reactor. For instance, in U.S. Pat. No. 4,781,885, a fuel assembly having a fuel rods lattice of 9 lines by 9 rows is disclosed, in which a large square water rod is installed at the central region which is equivalent to the 9 fuel rods arranged in a square lattice of 3 lines by 3 rows. Further, in JP-A-1-196593 (1989), a fuel assembly having fuel rods in diamond lattice of which bearings to the internal wall of the channel box is 45.degree. is disclosed, in which a cruciform large water rod is installed at the central region which is equivalent to a region for 12 fuel rods. More plutonium is built up generally at the upper region of the fuel assembly as described above, especially in case of the flow rate spectral shift operation, much plutonium are built up. When the quantity of plutonium built up at the upper region of the fuel assembly is increased so much, it becomes difficult to maintain surely the margin of the reactor shut down at cold shut down. The difficulty is caused by increasing of the infinite multiplication factor with disappearance of voids at the upper portion of the reactor core at the cold shut down. In order to solve the problem, in JP-A-64-88292 (1989), a plurality of water rods are installed at least in symmetrical positions to the diagonal line of the fuel assembly and fuel rods having shorter length in axial direction than the other fuel rods (partial fuel rod) are installed at least at the position between the water rods. In the fuel assembly, the void fraction of coolant at the space above the partial fuel rods where the fuel is not located, namely vanishing rods, becomes zero at the cold shut down of the reactor. The portion of the vanishing rod acts as a large water rod with the other water rods at the cold shut down. Therefore, the portion of the vanishing rod has an excessive neutron moderating effect and reversely a large neutron absorbing effect at the cold shut down. As the result, the difference between the infinite multiplication factors during the operation of the reactor and during the cold shut down becomes small, and shut down margin of the reactor is increased. Further, in the case of installing of the partial fuel rods, an additional effect such as reducing of pressure loss at two phase flow portion in the fuel assembly under the reactor operation is brought. As described above, increasing of the H/U ratio by increasing of the number of fuel rods, and further, increasing of horizontal cross sectional area of the water rods or the number of the water rods are the current tendency. Under such trend of the current technical development, a trial is performed which is aimed at high burnup by increasing the enrichment further. Such increment of the enrichment aiming at the increasing of the discharge burnup necessitates further enlarging of the horizontal cross sectional area of the water rods in order to make the H/U ratio the most proper. Nevertheless, as the horizontal cross sectional area of the large water rod is enlarged according to U.S. Pat. No. 4,781,885 and JP-A-1-196593 (1989), the pressure loss of the reactor core is increased by narrowing of the area of the coolant flow path which is formed between the fuel rods. The increasing of the pressure loss of the reactor core is a problem mainly in following points. (1) When the pressure loss of the reactor core is increased, the capacity of the pump has to be increased in order to compensate the increment. If the maximum flow in the reactor core is achieved by the maximum rotation of the pump under the condition without the increment of the pressure loss, the pump is not able to achieve the maximum flow in the reactor core when the pressure loss is increased. (2) Stability is lowered by increasing of the pressure loss. That is, as the pressure loss of the two phase flow in the upper portion of the fuel assembly is larger than the pressure loss of the single phase flow portion, when entering flow to the fuel assembly is increased, the resistance at the two phase flow portion is increased in order to reduce the entering flow. When the entering flow is reduced, the resistance at the two phase flow portion is reduced and the entering flow is increased again. By repeating of the phenomena, vibration of the flow is caused in the fuel assembly, and the stability is lowered. The larger the pressure loss at the two phase flow portion is, the easier the vibration of the flow is caused. On the other hand, the fuel assembly which is described in JP-A-64-88292 (1989) has a problem in aspect of fuel economy because optimization of the H/U ratio is not considered on the fuel assembly. Further, in case of installing partial fuel rods, which has two advantages such as the reduction of pressure loss at two phase flow portion and the secureness of the reactor shut down margin into the fuel assembly for high burnup as described in JP-A-64-88292, fuel inventory is decreased. The reduction of the fuel inventory increases the number of reload fuel assemblies and causes problems such as increment of the number of generated spent fuel assemblies. One of the methods for solving the problem is enlarging the diameter of the fuel rod for keeping the same fuel inventory as before installing of the partial fuel rod. But the method causes another problem of increasing pressure loss which is accompanied with the reduction of flow path area for the coolant. SUMMARY OF THE INVENTION One of the objects of the present invention is to provide a fuel assembly which is able to optimize the H/U ratio without increasing of pressure loss of the reactor core for achieving high burn up, and an upper tie plate thereof. Another object of the present invention is to provide a fuel assembly which enables partial fuel rods to be installed without increasing of the pressure loss of the reactor core and reducing of the fuel inventory. The characteristic of the present invention to achieve the objects described above is in the fuel assembly having: a plurality of fuel rods which are arranged in a lattice, a plurality of first means of water rods each of which has larger first cross sectional area than the area of a unit lattice of the fuel rods which corresponds to the each of the fuel rods described above and is arranged adjacently each other, first coolant flow path which is formed in a portion where is generated as an excessively moderated region in a second cross section when second means of water rods having the second cross section of same area as whole area of interior region of the outermost peripheral of a group of whole unit lattices of the fuel rods, which are occupied substantially by a plurality of the first means of water rods is assumed and also the second means of the water rods is assumed to be arranged in the fuel assembly instead of a plurality of the first means of water rods, and third coolant flow path connecting a plurality of the first means of water rods which are arranged substantially in the interior region in surrounding the first coolant flow path to second coolant flow paths which surround the first coolant flow path and the fuel rods and is located among the first means of water rods. By the present invention, a fuel assembly having a plurality of fuel rods which are arranged in a square lattice and a means of water rods is provided. The fuel assembly is characterized in having a plurality of the fuel rods comprising a plurality of the first fuel rods which are arranged in square lattices of 10 lines by 10 rows except the central region where the fuel rods are able to be arranged in a lattice of 4 lines by 4 rows, four second fuel rods each of which is arranged at each of four corners of the central region respectively, and means of water rods comprising a plurality of the water rods having a large diameter which are arranged adjacently each other in a circle with intervals in the central region, wherein 12 fuel rods are able to be arranged, except four corner portions. And, by the present invention, a fuel assembly having a plurality of fuel rods which are arranged in a square lattice and a means of water rods is provided. The fuel assembly is characterized in having a plurality of the fuel rods comprising a plurality of the first fuel rods which are arranged in a square lattice of 10 lines by 10 rows except the central region where the fuel rods are able to be arranged in a lattice of 4 lines by 4 rows, four second fuel rods each of which has a shorter axial length than the first fuel rod and is arranged at each of four corner portion of the central region respectively, and the means of water rods comprising a plurality of the water rods having a large diameter which are arranged adjacently each other in a circle with intervals in the central region, wherein 12 fuel rods are able to be arranged, except four corner portions. Further, by the present invention, a fuel assembly having a plurality of fuel rods which are arranged in a square lattice and a means of water rods is provided. The fuel assembly is characterized in having a plurality of the fuel rods comprising a plurality of the fuel rods which are arranged in a square lattice of 10 lines by 10 rows except the central region where the fuel rods are able to be arranged in a lattice of 4 lines by 4 rows, four fuel rods each of which is arranged at each of four corner portions of the central region respectively, and the means of water rods comprising a plurality of spectral shift water rods of which internal liquid level are adjustable by control of the coolant flow in the reactor core, which are arranged adjacently each other in a circle with intervals in the central region wherein 12 fuel rods are able to be arranged except four corner portions. Further, by the present invention, a fuel assembly having a plurality of fuel rods which are arranged in a square lattice and a means of water rods is provided. The fuel assembly is characterized in having a plurality of the fuel rods comprising a plurality of the first fuel rods which are arranged in a square lattice of 10 lines by 10 rows except the central region where the fuel rods are able to be arranged in a lattice of 4 lines by 4 rows, and four second fuel rods each of which is arranged at each of four corner portions of the central region respectively, and installing the means of water rods in the central region wherein 12 fuel rods are able to be arranged except four corner portions in surrounding the center of the central region, and forming a coolant flow path which leads to the coolant flow paths which are formed around the fuel rods is formed at the center of the central region. By the present invention, a fuel assembly having a plurality of fuel rods which are arranged in a square lattice and a means of water rods is provided. The fuel assembly is characterized in arranging a plurality of the fuel rods in a square lattice of 9 lines by 9 rows except the central region where the fuel rods are able to be arranged in a lattice of 3 lines by 3 rows, and having the means of water rods comprising four water rods having a large diameter which are arranged adjacently each other in a circle with intervals in the central region. Further, by the present invention, a fuel assembly having a plurality of the fuel rods which are arranged in a square lattice of at least 9 lines by 9 rows and are able to achieve the average discharge burn up of at least 45 GWd/t, and a means of water rod which is arranged at the central region of the square lattice is provided. The fuel assembly is characterized in comprising the means of water rods which have enough cross sectional area of water rods to give sufficient H/U ratio to make the infinite multiplication factor almost be saturated under the core-average void fraction and are so installed as to surround the center of the central region, and forming a coolant flow path which leads to the outer region of the means of water rods at the center of the central region. In order to achieve the objects described above, an upper tie plate comprising a plurality of first bosses each of which has a hole portion wherein upper end of the fuel rods is inserted, a plurality of second bosses each of which has a hole portion wherein upper end of the means of water rod is inserted, and a plurality of ribs each of which connects the bosses described above each other, is provided by the present invention. The upper tie plate is characterized in that the second bosses are installed at the center portion and that second opening which is formed among the four adjacent second bosses is larger than the opening which is formed among the four adjacent first bosses. The inventors found that a fuel assembly having a plurality of fuel rods in a square lattice of 10 lines by 10 rows and a water rod which has a large cross sectional area (for instance, the water rod having such a horizontal cross section as to occupy a region wherein 12 fuel rods are able to be placed as disclosed in JP-A-1-196593 (1989)) has an infinite multiplication factor which is hardly changed even though the H/U ratio is altered around 4.5 by changing of the horizontal cross section of the water rod at the average void fraction of the reactor core in case of aiming at discharge burn up of 55-60 MWd/t and is saturated to the increasing of horizontal cross section of the water rod (refer to line AB in FIG. 2). The saturation of the infinite multiplication factor is revealed to be caused by formation of an excessively moderated region at center of the horizontal cross section of the water rod with increasing of area of the cross section. The present invention is performed based on the finding described above, and the horizontal cross section of the water rod (simply called water rod area hereinafter) is so reduced as to optimize the H/U ratio of the fuel assembly by making the excessively moderated region, which is not contributable to improvement of moderating effect, an exterior region of the water rod, and further by making the region a coolant flow path wherein vapor-liquid two phase flow which leads to coolant path of around the fuel rods. Moreover, the present invention is aimed at reducing pressure loss of the fuel assembly by making the excessively moderated region the coolant flow path as described above. That is, in the present invention, a plurality of the first means of water rods each of which has a larger first horizontal cross section than the area of the fuel unit lattice corresponding to each fuel rod are arranged adjacently each other. Here a second means of water rod which has the second horizontal cross section equivalent to the whole area of the interior region of the outermost periphery of a group of whole fuel unit lattices, which is substantially occupied by the first means of water rods is assumed. The second means of water rod has a large horizontal cross sectional area which generates the excessively moderated region as described above. Therefore, the first coolant flow path is formed at the portion where the excessively moderated region is generated, and a plurality of the first means of water rods are arranged around the first coolant flow path. And the third coolant flow path which connects the first coolant flow path and the second coolant flow path which surrounds the fuel rods is formed among the first means of water rods. For instance, in the fuel assembly having a plurality of fuel rods arranged in a square lattice of 10 lines by 10 rows, a plurality of (for instance, four) water rods having a large diameter are arranged adjacently in a circle with intervals between each other respectively in the central region wherein 12 fuel rods are able to be arranged in a lattice of 4 lines by 4 rows except each of our corner portions (called the central region of 4 lines by 4 rows hereinafter). In case of arranging a plurality of water rods having a large diameter, the sum of the whole horizontal cross sectional area becomes smaller than the case when a large cruciform water rods is arranged in the region of the same area. The reduction of the total horizontal cross sectional area of the water rods is the result of exclusion of excessively moderated region in the saturated region of the infinite multiplication factor to the change of the H/U ratio. But, almost same infinite multiplication factor as the large cruciform water rods is obtained by the arrangement of a plurality of the water rods having a large diameter. The water rod having a large diameter has wider horizontal cross section than the area of a fuel unit lattice (refer to numeral 31 in FIG. 3), and has a larger outer diameter than the arrangement pitch of the fuel rods. On the other hand, by replacing the large cruciform water rods with a plurality of water rods having a large diameter, coolant flow paths are formed in the region of water rods having a large diameter. As the water rods having a large diameter are arranged with intervals between each other, the coolant flow path leads to coolant flow paths around the fuel rods through the intervals. Therefore, such composition as described above reduces pressure loss in comparison with the case in which the large cruciform water rod is arranged. Moreover, voids are flowed easily into the coolant flow path which is surrounded with each of the water rods from the coolant flow path which is formed around the fuel rods because the coolant flow path which is surrounded with a plurality of water rods is far from the fuel rods, which are heaters, and is surrounded with a plurality of water rods having a wider horizontal cross section than the fuel unit lattice, which are not heaters. Accordingly, in the upper region of the fuel assembly where the void fraction is high, void is gathered much to the coolant flow path which is surrounded with water rods, and consequently pressure loss of the fuel assembly is reduced. By the reason described above, the present invention is able to achieve making the fuel high enriched and high burn up, and also is able to optimize the H/U ratio without increasing of the pressure loss. In one of the examples of the present invention, each of four second fuel rods having short axial length is arranged at each of the four corner portions of the central region of 4 lines by 4 rows. In the case, as the coolant flow path which is surrounded with a plurality of the water rods having a large diameter reduces the pressure loss as described above, the increment of the pressure loss by increasing of the diameter of fuel rods is able to be compensated. Therefore, the arrangement of the partial fuel rods maintains certainly the effect of reduction of pressure loss and increment of shut down margin without reducing of the quantity of loaded fuel, and concurrently fuel economy is able to be improved. When a plurality of the water rods having a large diameter are arranged adjacently each other in a circle, there is a possibility to cause fretting by flow vibration of each other of the water rods in the upper region of the fuel assembly where two phase current flows, but, by arrangement of the partial fuel rods, an operation area of a small camera for inspection of the fretting is provided in the upper region of the partial fuel rods 20 and inspection of the water rods can be performed easily during regular inspection. In other example of the present invention, by using spectral shift water rods as the water rods having a large diameter, the fuel economy is further improved by the flow rate spectral shift operation. Further, the inventors found the saturation phenomenon of the infinite multiplication factor by the arrangement of the water rods even in the fuel assembly having a plurality of fuel rods in a square lattice of 9 lines by 9 rows, and by arranging of the four water rods having a large diameter adjacently in a circle in the central region where the fuel rods are able to be arranged in 3 lines by 3 rows, the H/U ratio is optimized and the pressure loss is reduced similarly. |
claims | 1. A chemical control system for a power plant, comprising:at least one flow-type sensor for coolant electrochemical indication, a unit for measurement data processing and transmission, a central computer (CPC), an actuator for injection of hydrogen and chemical reagents, a sampling tube, a first heat exchanger, a first throttling device, and a coolant supply circuit;the at least one flow-type sensor electrically connected to the unit for measurement data processing and transmission with output of the unit being connected to the central computer, the central computer configured to control the actuator for injection of hydrogen and chemical reagents;a hydraulic inlet of the at least one flow-type sensor for coolant electrochemical indication is configured to be connected by the sampling tube to a process circuit of the power plant;a hydraulic output of the at least one flow-type sensor is hydraulically connected in series to the first heat exchanger and the first throttling device with the coolant supply circuit; andwherein the sampling tube is configured to pass a coolant sample to the at least one flow-type sensor for coolant electrochemical indication and the coolant supply circuit comprises tubes and valves configured to reverse a flow of the coolant sample through the first throttling device. 2. The system as defined in claim 1, wherein the at least one flow-type sensor for coolant electrochemical indication is a flow-type sensor of polarization resistance. 3. The system as defined in claim 1, wherein the at least one flow-type sensor for coolant electrochemical indication is a flow-type sensor of electrochemical potential. 4. The system as defined in claim 1, wherein said system comprises a second heat exchanger, a second throttling device, a second unit for measurement data processing and transmission, and at least one additional sensor selected from the group consisting of: a sensor for dissolved oxygen, a sensor for dissolved hydrogen, a sensor for electrical conductivity, and a pH sensor; the at least one additional sensor installed (i) between the second heat exchanger and the second throttling device or (ii) downstream of the second throttling device; and the second heat exchanger being hydraulically connected to the process circuit, and the at least one additional sensor being electrically connected to the second unit for measurement data processing and transmission with output of the second unit being connected to the central computer. 5. The system as defined in claim 1, wherein the process circuit is a primary process circuit of the power plant. |
|
description | This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/JP2005/019778, filed on Oct. 27, 2005, which in turn claims the benefit of Japanese Application No. 2004-319352, filed on Nov. 2, 2004, the disclosures of which Applications are incorporated by reference herein. The present invention relates to a plasma processing method and a plasma processing apparatus. In particular, the invention relates to a method and apparatus for supplying plasma to a surface layer of a sample uniformly. Among known techniques for introducing an impurity into a surface layer of a solid sample is a plasma doping method in which an impurity is ionized and introduced into a solid at low energy (refer to Patent document 1, for example). FIG. 12 shows a general configuration of a plasma processing apparatus which is used for a plasma doping method as a conventional impurity introducing method disclosed in the above-mentioned Patent document 1. As shown in FIG. 12, a sample electrode 43 to be mounted with a sample 42 which is a silicon wafer is provided in a vacuum container 41. A gas supply apparatus 44 for supplying a doping source gas containing a desired element such as B2H6 to the inside of the vacuum container 41 and a pump 45 for reducing the pressure in the vacuum container 41 are provided, whereby the pressure in the vacuum container 41 can be kept at a prescribed value. Microwaves are radiated from a microwave waveguide 46 into the vacuum container 41 via a quartz plate 47 as a dielectric window. The microwaves interact with a DC magnetic field formed by an electromagnet 48, whereby microwave plasma with a magnetic field (electron cyclotron resonance plasma) 49 is formed in the vacuum container 41. A high-frequency power source 51 is connected to the sample electrode 43 via a capacitor 50 so as to enable control of the potential of the sample electrode 43. A gas that is supplied form the gas supply apparatus 44 is introduced into the vacuum container 41 through a gas inlet 52 and exhausted into the pump 45 through an exhaust hole 53. In the above-configured plasma processing apparatus, a doping source gas such as B2H6 that is introduced through the gas inlet 52 is converted into plasma 49 by a plasma generating means consisting of the microwave waveguide 46 and the electromagnet 48 and boron ions in the plasma 49 are supplied to the surface of a sample 42 by means of the high-frequency power source 51. Incidentally, in general, gases containing an impurity that is rendered electrically active when supplied to a sample such as a silicon wafer, such as a doping source gas B2H6, have a problem that they are very dangerous; for example, they are harmful to human bodies or high in reactivity. In plasma doping methods, all substances contained in a doping source gas are introduced into a sample. In the case of a doping source gas B2H6, for example, hydrogen is also introduced into a sample though only boron is an impurity that is effective when introduced into the sample. Introduction of hydrogen into a sample raises a problem that lattice defects occur in the sample in subsequent heat treatment for epitaxial growth, for example. In view of the above, the following method has been proposed (refer to Patent document 2, for example). An impurity solid containing an impurity which is rendered electrically active when introduced into a sample is disposed in a vacuum container. Plasma of a rare gas is generated in the vacuum container and an impurity solid is bombarded with ions of the inert gas, whereby the impurity is separated from the impurity solid and supplied to the sample. FIG. 13 shows a general configuration of a plasma doping apparatus which is used in a plasma doping method as the conventional impurity introducing method disclosed in Patent document 2. As shown in FIG. 13, a sample electrode 43 to be mounted with a sample 42 which is a silicon wafer is provided in a vacuum container 41. A gas supply apparatus 44 for supplying an inert gas to the inside of the vacuum container 41 and a pump 45 for reducing the pressure in the vacuum container 41 are provided, whereby the pressure in the vacuum container 41 can be kept at a prescribed value. Microwaves are radiated from a microwave waveguide 46 into the vacuum container 41 via a quartz plate 47 as a dielectric window. The microwaves interact with a DC magnetic field formed by an electromagnet 48, whereby microwave plasma with a magnetic field (electron cyclotron resonance plasma) 49 is formed in the vacuum container 41. A high-frequency power source 51 is connected to the sample electrode 43 via a capacitor 50, whereby the potential of the sample electrode 43 can be controlled. An impurity solid 54 containing an impurity element such as boron is mounted on a solid holding stage 55, whose potential is controlled by a high-frequency power source 57 connected to it via a capacitor 56. A gas that is supplied form the gas supply apparatus 44 is introduced into the vacuum container 41 through a gas inlet 52 and exhausted into the pump 45 through an exhaust hole 53. In the above-configured plasma doping apparatus, an inert gas such as argon (Ar) introduced through the gas inlet 11 is converted into plasma by a plasma generating means consisting of the microwave waveguide 46 and the electromagnet 48, and part of impurity element atoms that have been expelled from the impurity solid 54 by the bombardment into the plasma are ionized and introduced into a surface layer of a sample 42. Usually, a silicon oxide film as a gate oxide film is formed on the surface of the sample 42. A conductive layer for formation of gate electrodes is formed on the gate oxide film by CVD or the like and then patterned into gate electrode patterns. The sample 42 on which the gate electrodes have been formed in this manner is set in the plasma doping apparatus, and source and drain regions are formed by introducing an impurity by the above-described method in a self-aligned manner using the gate electrodes as a mask. MOS transistors are thus obtained. However, activation processing needs to be performed after the introduction of the impurity by the plasma doping. The activation processing is processing of rendering the crystal in an active state by heating the sample 42 by flash lamp annealing, laser annealing, or the like. A shallow activation layer can be obtained by heating a very thin impurity-introduced layer effectively. To heat a very thin impurity-introduced layer effectively, processing for increasing, before introduction of the impurity, the absorbance, for light emitted from a light source such as a laser or a lamp, of a very thin layer into which to introduce the impurity is performed. This processing, which is called “pre-amorphyzation,” is as follows. In a plasma processing apparatus which is similar in configuration to the above-described plasma doping apparatus, plasma of a He gas, for example, is generated and generated He ions, for example, are caused to be accelerated toward and collide with a substrate by a bias voltage, whereby the crystal structure of a substrate surface layer is destroyed to attain amorphyzation. This technique has already been proposed by the inventors of this application (refer to Non-patent document 1, for example). Patent document 1: U.S. Pat. No. 4,912,065 Patent document 2: JP-A-09-115851 Non-patent document 1: Y. Sasaki et al., “B2H6 Plasma Doping with In-situ He Pre-amorphyzation,” 2004 Symposia on VLSI Technology and Circuits. Incidentally, with the recent miniaturization and the increase in integration density of semiconductor devices, it is necessary to form shallow and very fine impurity-introduced regions. This requires extremely accurate depth and impurity concentration controls. In these circumstances, conventional methods have a problem that it is difficult to form an impurity-introduced layer that is uniform in a sample or, in a current situation that the wafer diameter is increasing, in a wafer surface. This is because of not only difficulty in forming impurity-containing plasma with a uniform distribution in a wafer surface but also a high degree of difficulty in amorphyzing a surface layer of a sample with high accuracy and a uniform depth distribution in the above-described pre-amorphyzation processing. FIG. 10 shows a result of a measurement of the thickness of an amorphous layer produced by amorphyzing a 200-mm-diameter silicon wafer by the conventional plasma doping apparatus of FIG. 12. The x-axis is taken in the top-to-bottom direction in FIG. 12. As seen from FIG. 10, the thickness of the amorphous layer is extremely high in a peripheral portion of the wafer (sample), in particular, in an area within 10 mm of the outer perimeter of the wafer. The thickness of the amorphous layer is a thickness of an amorphous silicon layer of a single crystal silicon wafer measured by an elliptometry method. This phenomenon is not limited to the thickness of an amorphous layer. It has been found that high impurity concentrations likewise occur in an area close to the outer perimeter of a wafer when plasma doping is performed by supplying impurity plasma to the surface of an amorphous layer after formation of the amorphous layer. It is considered that each of the above phenomena occurs because an edge effect causes plasma concentration in a peripheral area of a wafer, whereby energy concentration occurs in the vicinity of the outer perimeter of a wafer and plasma reaches the wafer surface in a state that the plasma concentration is high. The present invention has been made in view of the above circumstances, and an object of the invention is therefore to increase the uniformity of plasma processing. Another object of the invention is to provide an amorphyzing method and apparatus capable of increasing the uniformity of amorphyzation processing. A further object of the invention is to provide an impurity introducing method and apparatus capable of increasing the sample surface uniformity of the impurity introduction amount. A plasma processing method according to the invention is characterized in that plasma is applied to a surface of a sample while being adjusted so that thickness of an ion sheath is made uniform on the surface of the sample. With this constitution, the incidence energy of plasma incident on the sample is made uniform in the entire area including the area corresponding to the portion, close to the outer perimeter, of the sample, which makes it possible to increase the uniformity of the plasma processing. In particular, when it is necessary to perform high-precision processing on very fine regions in amorphyzation processing, doping processing, or the like in which not only the dimensions in the surface but also the depth from the surface needs to be taken into consideration, this method enables not only control of the in-plane uniformity but also control in the three dimensions including the depth. The workings of this constitution will be described below in detail. When a conductor having a potential VP is inserted in plasma having a plasma potential VS, a negative electric field is formed around the conductor if VP<VS. Since ions are attracted and electrons are repelled, a condition (ion concentration)>(electron concentration) is established and a charge layer consisting of only ions is formed. Conversely, if VP>VS, a charge layer consisting of only electrons is formed. This charge layer is called “sheath.” A sheath consisting of electrons is called “electron sheath” and a sheath consisting of ions is called “ion sheath.” On the other hand, when an insulator, instead of a conductor, is inserted in plasma, the number of electrons that come flying per unit time should be equal to that of ions that come flying per unit time because no DC current flows between the insulator and the plasma. However, since in general the speeds of electrons are much higher than those of ions, more electrons reach the surface of the insulator than ions. Therefore, excess electrons on the surface form a negative electric field in the vicinity of the surface and charging progresses until the electron current and the ion current become identical. A negative potential occurring in this manner is called “floating potential.” In this case, an ion sheath is formed on the surface. A sheath voltage drop VSH can be increased (controlled) by applying high-frequency power to the electrode. Since the mobility of electrons is much higher than that of ions, a large electron current flows in if the application voltage is positive whereas a small ion current flows in if the application voltage is negative. Since the electrode (or substrate surface) is in a floating state in a DC sense, a steady state is established when the net current (the DC component of the current) becomes zero. Therefore, the electrode (or substrate surface) is self-biased at a negative potential. In general, the self-bias voltage is represented by VDC (direct-current voltage) and the difference VPP between the instantaneous maximum and minimum values of the high-frequency voltage is represented by VPP (peak-to-peak voltage). If the high-frequency power applied to the electrode is increased, VDC and VPP are increased. For example, in the invention, the capacitance per unit area between a substrate and a pedestal is set a little larger than that between plasma and the pedestal via a dielectric ring, whereby the difference between the ion sheath thickness in the area corresponding to the substrate central portion and that in the area corresponding to the substrate peripheral portion is reduced. The uniformity of pre-amorphyzation processing can be increased by decreasing the difference between the capacitance per unit area between the substrate and the pedestal and the capacitance between the plasma and the pedestal via the dielectric ring in the above manner. With the above constitution, to make physical-phenomenon-dominated processing uniform, an otherwise excessively high ion concentration in the area corresponding to the substrate peripheral portion is reduced or the thickness of an ion sheath in the area corresponding to the substrate peripheral portion is made equal to that in the area corresponding to the other area of the substrate by using a focus ring (or dielectric ring). The plasma processing method according to the invention includes a method for amorphyzing a surface layer of the sample. The amorphyzation which introduces plasma to a prescribed depth from the sample surface and thereby amorphyzes plasma-introduced regions can control the introduction depth of an impurity with high accuracy if performed before or during doping. The plasma processing method according to the invention includes a method for introducing an impurity into a surface layer of the sample. The introduction of an impurity, that is, the doping processing, depends on, in particular, the in-plane distribution in the sample and the energy state of the impurity at that position. Therefore, uniform processing can be attained with high accuracy. The plasma processing method according to the invention includes a method comprising the steps of mounting the sample on a sample electrode disposed in a vacuum container, exhausting the vacuum container while supplying a source gas to inside the vacuum container, and generating plasma in the vacuum container by supplying high-frequency power to a plasma source; and applying plasma to the surface of the sample in a state that a conductor ring having a surface that is approximately the same in height as the surface of the sample is disposed so as to surround an outer perimeter of the sample. Capable of avoiding concentration of plasma on a peripheral portion of the sample, this constitution can attain a uniform in-plane distribution in the surface of the sample. For example, the invention provides an amorphyzing method having the steps of mounting a sample on a sample electrode disposed in a vacuum container, exhausting the vacuum container while supplying a gas to inside the vacuum container by a gas supply apparatus and controlling pressure in the vacuum container at a prescribed value, generating plasma in the vacuum container by supplying high-frequency power to a plasma source; and amorphyzing a surface crystal layer of a sample by supplying a voltage to the sample electrode, characterized in that the amorphyzation is performed in a state that a conductor ring having a surface that is approximately the same in height as the surface of the sample is disposed outside an outer perimeter of the sample. According to this constitution, the distortion of equipotential lines of a sheath layer in the area corresponding to the portion, close to the outer perimeter, of the sample is reduced and the incidence energy of ions incident on the sample is thereby made uniform in the entire area including the area corresponding to the portion, close to the outer perimeter, of the sample. The uniformity of the amorphyzation processing can thus be increased. The plasma processing method according to the invention includes a method in which a distance between the outer perimeter of the sample and an inner perimeter of the conductor ring is in a range of 1 mm to 10 mm. This constitution makes it possible to secure both of a sufficient margin for transport of a substrate and high uniformity of processing. The plasma processing method according to the invention includes a method in which a difference in height between the surface of the sample and a surface of the conductor ring is in a range of 0.001 mm to 1 mm. This constitution makes it possible to attain even higher uniformity of processing. The plasma processing method according to the invention includes a method in which a voltage is applied to a pedestal in a state that the sample electrode has a layered structure in which a first dielectric layer, an electrostatic chuck electrode, a second dielectric layer, and the pedestal are arranged in this order from the side that is closer to the sample, that the first dielectric layer, the electrostatic chuck electrode, and the second dielectric layer project from the pedestal, and that a third dielectric layer is disposed between the conductor ring and the pedestal. This case includes a method in which Ca=1/(d1/∈1+d2/∈2) is larger than or equal to 0.5 times Cb=∈3/d3 and smaller than or equal to 2 times Cb, where ∈1 and d1 are relative permittivity and thickness of the first dielectric layer, ∈2 and d2 are relative permittivity and thickness of the second dielectric layer, and ∈3 and d3 are relative permittivity and thickness of the third dielectric layer. With this constitution, the capacitance between the pedestal and the substrate can be made approximately equal to that between the pedestal and the conductor ring. It is desirable that the two capacitances be approximately identical. If the former is smaller than 0.5 times the latter, an ion sheath is too thick over the surface of the conductor ring and the electric field strength of the sheath in the area corresponding to the edge portion of the sample is lower than in the area corresponding to the central portion of the sample. As a result, the processing rate may become low in the edge portion of the sample. On the other hand, if the former is larger than 2 times the latter, an ion sheath is too thin over the surface of the conductor ring and the electric field strength of the sheath in the area corresponding to the edge portion of the sample is higher than in the area corresponding to the central portion of the sample. As a result, the processing rate may become high in the edge portion of the sample. The constitution that satisfies the above condition makes it possible to satisfy the conditions for uniform processing though the condition may vary a little depending on the permittivity and the thickness of the sample. The plasma processing method according to also includes a method in which a voltage is applied to an electrostatic chuck electrode in a state that the sample electrode has a layered structure in which a first dielectric layer, the electrostatic chuck electrode, a second dielectric layer, and a pedestal are arranged in this order from the side that is closer to the sample, that the first dielectric layer, the electrostatic chuck electrode, and the second dielectric layer project from the pedestal, and that a third dielectric layer is disposed between the conductor ring and the pedestal. This case includes a method in which Cc=∈1/d1 is larger than or equal to 0.5 times Cd=1/{(d2×S2)/(∈2×S1)+d3/∈3} and smaller than or equal to 2 times Cd, where ∈1 and d1 are relative permittivity and thickness of the first dielectric layer, ∈2 and d2 are relative permittivity and thickness of the second dielectric layer, ∈3 and d3 are relative permittivity and thickness of the third dielectric layer, S1 is an area of a surface, exposed to the plasma, of the sample, and S2 is an area of a surface, exposed to the plasma, of the conductor ring. Also with this constitution, the capacitance between the pedestal and the substrate can be made approximately equal to that between the pedestal and the conductor ring. It is desirable that the two capacitances be approximately identical. If the former is smaller than 0.5 times the latter, an ion sheath is too thick over the surface of the conductor ring and the electric field strength of the sheath in the area corresponding to the edge portion of the sample is lower than in the area corresponding to the central portion of the sample. As a result, the processing rate may become low in the edge portion of the sample. On the other hand, if the former is larger than 2 times the latter, an ion sheath is too thin over the surface of the conductor ring and the electric field strength of the sheath in the area corresponding to the edge portion of the sample is higher than in the area corresponding to the central portion of the sample. As a result, the processing rate may become high in the edge portion of the sample. The constitution that satisfies the above condition makes it possible to satisfy the conditions for uniform processing though the condition may vary a little depending on the permittivity and the thickness of the sample. The plasma processing method according to the invention includes a method in which plasma processing is performed in a state that a focus ring having a surface that is higher than the surface of the sample by 1 mm or more is disposed outside an outer perimeter of the sample. According to this constitution, the distortion of equipotential lines of a sheath layer is reduced by concentrating plasma on the focus ring in the area corresponding to the portion, close to the outer perimeter, of the sample and the incidence energy of ions or plasma incident on the sample is thereby made uniform in the entire area including the area corresponding to the portion, close to the outer perimeter, of the sample. The uniformity of the amorphyzation processing can thus be increased. The plasma processing method according to the invention includes a method in which a distance between the outer perimeter of the sample and an inner perimeter of the focus ring is in a range of 1 mm to 10 mm. This constitution makes it possible to secure both of a sufficient margin for transport of a substrate and high uniformity of processing. If the distance is shorter than 1 mm, the transport of a substrate is difficult. If the distance is longer than 10 mm, it is difficult to obtain the effect of reducing the distortion of equipotential lines. The plasma processing method according to the invention includes a method in which a difference in height between the surface of the sample and a surface of the focus ring is in a range of 1 mm to 15 mm. This constitution makes it possible to attain even higher uniformity of processing. The plasma processing method according to includes a method comprising the steps of mounting the sample on a tray disposed in a vacuum container and having a step inside which the sample is mounted, exhausting the vacuum container while supplying a source gas to inside the vacuum container, and generating plasma in the vacuum container by supplying high-frequency power to a plasma source; and applying plasma to the surface of the sample while making an adjustment so that a surface of a portion, outside the recess, of the tray is approximately the same in height as the surface of the sample. According to this constitution, the distortion of equipotential lines of a sheath layer in the area corresponding to the portion, close to the outer perimeter, of the sample is reduced and the incidence energy of ions incident on the sample is thereby made uniform in the entire area including the area corresponding to the portion, close to the outer perimeter, of the sample. The uniformity of the amorphyzation processing can thus be increased. The plasma processing method according to the invention includes a method in which a distance between the outer perimeter of the sample and the step is in a range of 1 mm to 10 mm. This constitution makes it possible to secure both of a sufficient margin for transport of a substrate and high uniformity of processing. The plasma processing method according to the invention includes a method in which a difference in height between the surface of the sample and a surface of the portion, outside the step, of the tray is in a range of 0.001 mm to 1 mm. This constitution makes it possible to attain even higher uniformity of processing. The plasma processing method according to the invention includes a method in which the sample is a silicon wafer and the tray is made of silicon. This constitution can minimize of the substrate pollution. The plasma processing method according to the invention includes a method in which the plasma processing is performed in a state that the tray is pressed against the sample electrode. This constitution enables efficient heat dissipation from the substrate via the sample electrode and thereby makes it possible to control the substrate temperature more precisely. The plasma processing method according to the invention includes a method in which a step of generating plasma and a step in which the plasma generation is suspended and pressure in the vacuum container is set higher than in the step of generating plasma are performed alternately and repeatedly. With this constitution, heat that has been stored in the substrate in the step of generating plasma is allowed to escape to the sample electrode side in the step in which the plasma generation is suspended and the pressure in the vacuum container is set higher than in the step of generating plasma. This in turn makes it possible to control the substrate temperature more precisely. In this case, it is even desirable that the pressure in the vacuum container is in a range of 100 Pa to 1,000 Pa in the step in which the plasma generation is suspended and the pressure in the vacuum container is set higher than in the step of generating plasma. This constitution makes it possible to control the substrate temperature more precisely. The invention provides a plasma processing apparatus having a vacuum container; a sample electrode disposed in the vacuum container and to be mounted with a sample; a gas supply apparatus for supplying a gas to inside the vacuum container; an exhaust apparatus for exhausting the vacuum container; a pressure control device for controlling pressure in the vacuum container; a plasma source; a high-frequency power source for supplying high-frequency power to the plasma source; and a voltage source for applying a voltage to the sample electrode, characterized by comprising an auxiliary member disposed around the sample electrode so that plasma is applied to a surface of a sample while being adjusted so as to have a uniform energy state on the surface of the sample. The plasma processing apparatus according to the invention includes an apparatus in which the plasma is adjusted so as to amorphyze a surface layer of the sample. The plasma processing apparatus according to the invention includes an apparatus in which the plasma is adjusted so as to introduce an impurity into a surface layer of the sample. The plasma processing apparatus according to the invention includes an apparatus in which the sample electrode has a projecting portion to be mounted with the sample, and the auxiliary member is a conductor ring disposed so as to surround an outer perimeter of the sample and to have a surface that is approximately the same in height as the surface of the sample. According to this configuration, the distortion of equipotential lines of a sheath layer in the area corresponding to the portion, close to the outer perimeter, of the sample is reduced and the incidence energy of ions incident on the sample is thereby made uniform in the entire area including the area corresponding to the portion, close to the outer perimeter, of the sample. The uniformity of the amorphyzation processing can thus be increased. The plasma processing apparatus according to the invention includes an apparatus in which a distance between the outer perimeter of the sample and an inner perimeter of the conductor ring is in a range of 2 mm to 11 mm. This configuration makes it possible to secure both of a sufficient margin for transport of a substrate and high uniformity of processing. The plasma processing apparatus according to the invention includes an apparatus in which a difference in height between the surface of the sample and a surface of the conductor ring is in a range of 0.001 mm to 2 mm. This configuration makes it possible to attain even higher uniformity of processing. The plasma processing apparatus according to the invention includes an apparatus in which a voltage is applied to a pedestal in a state that the sample electrode has a layered structure in which a first dielectric layer, an electrostatic chuck electrode, a second dielectric layer, and the pedestal are arranged in this order from the side that is closer to the sample, that the first dielectric layer, the electrostatic chuck electrode, and the second dielectric layer project from the pedestal, and that a third dielectric layer is disposed between the conductor ring and the pedestal. The plasma processing apparatus according to the invention includes an apparatus in which Ca=1/(d1/∈1+d2/∈2) is larger than or equal to 0.5 times Cb=∈3/d3 and smaller than or equal to 2 times Cb, where ∈1 and d1 are relative permittivity and thickness of the first dielectric layer, ∈2 and d2 are relative permittivity and thickness of the second dielectric layer, and ∈3 and d3 are relative permittivity and thickness of the third dielectric layer. This configuration makes it possible to increase the uniformity of processing while controlling the substrate temperature precisely. The plasma processing apparatus according to the invention includes an apparatus in which a voltage is applied to an electrostatic chuck electrode in a state that the sample electrode has a layered structure in which a first dielectric layer, the electrostatic chuck electrode, a second dielectric layer, and a pedestal are arranged in this order from the side that is closer to the sample, that the first dielectric layer, the electrostatic chuck electrode, and the second dielectric layer project from the pedestal, and that a third dielectric layer is disposed between the conductor ring and the pedestal. The plasma processing apparatus according to the invention includes an apparatus in which Cc=∈1/d1 is larger than or equal to 0.5 times Cd=1/{(d2×S2)/(∈2×S1)+d3/∈3} and smaller than or equal to 2 times Cd, where ∈1 and d1 are relative permittivity and thickness of the first dielectric layer, ∈2 and d2 are relative permittivity and thickness of the second dielectric layer, and ∈3 and d3 are relative permittivity and thickness of the third dielectric layer. This configuration makes it possible to increase the uniformity of processing while controlling the substrate temperature precisely. The plasma processing apparatus according to the invention includes an apparatus in which the sample electrode has a projecting portion, and a focus ring is disposed so as to have a surface that is higher than the surface of the projecting portion of the sample electrode by 1 mm or more. According to this configuration, the distortion of equipotential lines of a sheath layer in the area corresponding to the portion, close to the outer perimeter, of the sample is reduced and the incidence energy of plasma or ions incident on the sample is thereby made uniform in the entire area including the area corresponding to the portion, close to the outer perimeter, of the sample. The uniformity of the amorphyzation processing can thus be increased. The plasma processing apparatus according to the invention includes an apparatus in which a distance between the outer perimeter of the sample and an inner perimeter of the focus ring is in a range of 2 mm to 11 mm. This configuration makes it possible to secure both of a sufficient margin for transport of a substrate and high uniformity of processing. The plasma processing apparatus according to the invention includes an apparatus in which a difference in height between the surface of the sample and a surface of the focus ring is in a range of 2 mm to 16 mm. This configuration makes it possible to attain even higher uniformity of processing. As described above, the plasma processing method and the plasma processing apparatus according to the invention can increase the uniformity of processing and thereby realize plasma processing that is high in accuracy and reliability. In particular, they can increase the uniformity of amorphyzation processing in forming an impurity-introduced layer. Furthermore, they make it possible to control, with high accuracy, the amount of a supplied impurity also in plasma doping using impurity plasma. 1: Vacuum container 2: Gas supply apparatus 3: Turbomolecular pump 4: Pressure regulating valve 5: High-frequency power source 6: Sample electrode 7: Dielectric window 8: Coil 9: Wafer 10: High-frequency power source 11: Gas inlet 12: Exhaust hole Embodiments of the present invention will be hereinafter described. Before doing so, the principle of the invention will be described in detail with reference to the drawings. In the plasma processing method according to the invention, plasma is applied to the surface of a sample while being adjusted so that the thickness of an ion sheath is made uniform on the surface of the sample. The workings of this configuration will be described below in detail. As described above, when a conductor having a potential VP is inserted in plasma having a plasma potential VS, a negative electric field is formed around the conductor if VP<VS. Since ions are attracted and electrons are repelled, a condition (ion concentration)>(electron concentration) is established and a charge layer consisting of only ions is formed. Conversely, if VP>VS, a charge layer consisting of only electrons is formed. On the other hand, when an insulator, instead of a conductor, is inserted in plasma, the number of electrons that come flying per unit time should be equal to that of ions that come flying per unit time because no DC current flows between the insulator and the plasma. However, since in general the speeds of electrons are much higher than those of ions, more electrons reach the surface of the insulator than ions. Therefore, excess electrons on the surface form a negative electric field in the vicinity of the surface and charging progresses until the electron current and the ion current become identical. A floating potential (negative potential) occurs in this manner, and in this case an ion sheath is formed on the surface. A sheath voltage drop VSH can be increased (controlled) by applying high-frequency power to the electrode. FIG. 1 shows an exemplary current-voltage characteristic of the electrode (or substrate surface). As seen from FIG. 1, since the mobility of electrons is much higher than that of ions, a large electron current flows in if the application voltage is positive whereas a small ion current flows in if the application voltage is negative. Since the electrode (or substrate surface) is in a floating state in a DC sense, a steady state is established when the net current (the DC component of the current) becomes zero. Therefore, the electrode (or substrate surface) is self-biased at a negative potential. If the high-frequency power applied to the electrode is increased, the self-bias voltage VDC and the difference VPP between the instantaneous maximum and minimum values of the high-frequency voltage are increased. FIG. 2 shows a sheath formed in the vicinity of a substrate in the case where no dielectric ring is provided (corresponds to FIG. 8). Symbol B-1 denotes the boundary between an ion sheath and bulk plasma. A high-frequency voltage is applied to a substrate 9 from a pedestal 16 via a second dielectric layer 15, an electrostatic chuck electrode 14, and a first dielectric layer 13. Therefore, a high-frequency current flows between the substrate 9 and the plasma. On the other hand, a high-frequency current also flows between the pedestal 16 and the plasma via a dielectric ring 19 (in general, the dielectric ring 19 is made of quartz glass having relative permittivity of about 4 and its capacitance per unit area is very small because its thickness is approximately equal to the sum of the thicknesses of the first dielectric layer 13 and the second dielectric layer 15). In general, the first and second dielectric layers for electrostatic absorption are made of ceramics and their relative permittivity is larger than 4 and is typically in a range of 8 to 12. Where the surface of the substrate 9 is the same in height as the surface of the dielectric ring 19, the thickness of the dielectric ring 19 is greater than the sum of the thicknesses of the first dielectric layer 13 and the second dielectric layer 15 by the thickness of the substrate 9. It is understood from the above discussion that the capacitance per unit area between the substrate 9 and the pedestal 16 is larger than that between the plasma and the pedestal 16 via the dielectric ring 19. As a result, the current per unit area flowing between the plasma and the substrate 9 is much larger than that flowing between the plasma and the pedestal via the dielectric ring 19. Therefore, as shown in FIG. 2, the ion sheath has a great thickness and hence causes a large voltage drop in the area corresponding to the portion of the substrate 9 excluding its peripheral portion. It is seen from FIG. 2 that the boundary B-1 between the ion sheath and the bulk plasma is closer in the area corresponding to the peripheral portion of the substrate 9 than in the area corresponding to its central portion. The potential of the substrate 9 in the central portion is the same as in the peripheral portion. It is therefore concluded that the electric field strength in the ion sheath is much higher in the area corresponding to the peripheral portion of the substrate 9 than in the area corresponding to its central portion. We think that this leads to the phenomenon that the energy of ions impinging on the peripheral portion of the substrate 9 is higher than that impinging on its central portion, which in turn produces the result that the pre-amorphyzation processing rate in the peripheral portion of the substrate 9 is higher than in its central portion. In the invention, the difference in ion sheath thickness between the area corresponding to the substrate central portion and the area corresponding to the substrate peripheral portion is made smaller as seen from a boundary C-1 between an ion sheath and bulk plasma shown in FIG. 3. FIG. 3 corresponds to a case that the capacitance per unit area between the substrate 9 and the pedestal 16 is a little larger than that between the plasma and the pedestal 16 via the dielectric ring 19. On the other hand, FIG. 4 corresponds to a case that the capacitance per unit area between the substrate 9 and the pedestal 16 is a little smaller than that between the plasma and the pedestal 16 via the dielectric ring 19. As described above, we empirically found that setting small the difference between the capacitance per unit area between the substrate 9 and the pedestal 16 and that between the plasma and the pedestal 16 via the dielectric ring 19 is important in increasing the uniformity of pre-amorphyzation processing, and also succeeded in proposing a proper model therefor. As described above, the focus ring used in the invention is entirely different in the effect of introduction from that used in the dry etching technology though they have similarities in structure. The pre-amorphyzation processing is performed by causing inert gas ions (having almost no chemical reactivity) in plasma to collide with the substrate surface. The elements constituting the substrate are hardly volatilized and chemical reactions such as etching seldom occur (amorphyzation of a substrate surface layer occurs). The plasma doping processing is performed by causing ions of B, for example, in plasma (which have almost no chemical reactivity with silicon) to collide with the substrate surface. The elements constituting the substrate are hardly volatilized and chemical reactions such as etching seldom occur (B ions remain in the substrate). Each of the above kinds of processing is a physical phenomenon and is not a chemical-reaction-dominated phenomenon such as dry etching. To make such a physical-phenomenon-dominated processing uniform, the invention uses the focus ring (dielectric ring) or the like to decrease an otherwise excessive ion concentration in the area corresponding to the substrate peripheral portion or equalize the thickness of an ion sheath in the area corresponding to the substrate peripheral portion to that in the area corresponding to the other portion of the substrate. As such, the conductor ring, the focus ring, etc. used in the invention are very different in purposes and effects from the focus ring etc. used in the conventional dry etching technology. In contrast, in the dry etching technology, what is called a loading effect occurs and the etching rate tends to be high in the substrate peripheral portion. In the vicinity of the substrate peripheral portion, the concentrations of etching reaction products are lower than in the vicinity of the other portion of the substrate and, as a result, the concentration of the etchant (an etching reaction species as typified by a reactive halogen radical) is higher than in the vicinity of the other portion of the substrate (loading effect). This is the reason why the etching rate is high in the substrate peripheral portion. The focus ring is used conventionally to prevent this phenomenon. When the focus ring is introduced, etching reaction products generated from the substrate peripheral portion are rendered apt to stay in the vicinity of the substrate peripheral portion, whereby the concentrations of the etching reaction products in the vicinity of the substrate peripheral portion become approximately equal to those in the vicinity of the other portion of the substrate. Therefore, the etchant concentration in the vicinity of the substrate peripheral portion become approximately equal to that in the vicinity of the other portion of the substrate, which provides an advantage that and the etching rate distribution is made uniform. As described above, the focus ring used in the dry etching technology is intended to provide a uniform reactive particle concentration distribution to make the chemical-reaction-dominated etching reaction uniform, and hence is entirely different in workings and advantages. A first embodiment of the invention will be described below with reference to FIGS. 5-8. This embodiment is characterized in that amorphyzation processing of applying plasma to regions, into which to introduce an impurity, of a surface layer of a single crystal silicon wafer as a sample before introduction of the impurity is performed in a state that a conductor ring is disposed so as to surround the outer perimeter of the wafer. FIG. 5 is a sectional view of an amorphyzation apparatus used in an amorphyzing method according to the first embodiment of the invention. As shown in FIG. 5, the amorphyzation apparatus is composed of a vacuum container 1, a turbomolecular pump 3 as an exhaust apparatus for exhausting the vacuum container 1, a pressure regulating valve 4 for controlling the pressure in the vacuum container 1, a coil 8 as a plasma source disposed close to a dielectric window 7 which is opposed to a sample electrode 6, a high-frequency power source 5 for supplying high-frequency electric power of 13.56 MHz to the coil 8, and a high-frequency power source 10 as a voltage source for supplying a voltage to the sample electrode 6. Reference numerals 11 and 12 denote a gas inlet and an exhaust hole, respectively. As shown in FIG. 5, a prescribed gas is introduced into the vacuum container 1 from the gas supply apparatus 2 while being exhausted by the turbomolecular pump 3 as the exhaust apparatus. The pressure in the vacuum container 1 can be kept at a prescribed value by the pressure regulating valve 4. High-frequency electric power of 13.56 MHz is supplied from the high-frequency power source 5 to the coil 8 disposed close to the dielectric window 7 which is opposed to the sample electrode 6, whereby induction-coupled plasma can be generated in the vacuum container 1. The high-frequency power source 10 for supplying high-frequency electric power to the sample electrode 6 is provided which functions as a voltage source for controlling the potential of the sample electrode 6 so that the potential of a wafer 9 as a sample becomes negative with respect to that of plasma. A gas that is supplied from the gas supply apparatus 2 is introduced into the vacuum container 1 through the gas inlet 11, and the gas in the vacuum container 1 is exhausted into the pump 3 through the exhaust hole 11. FIG. 6 is an enlarged, detailed sectional view of a part in which the silicon wafer 9 is mounted on the sample electrode 6. As shown in FIG. 6, the sample electrode 6 has a layered structure in which a first dielectric layer 13, an electrostatic chuck electrode 14, a second dielectric layer 15, and a pedestal 16 are arranged in this order from the side that is closer to the silicon wafer 9 as the sample. The first dielectric layer 13, the electrostatic chuck electrode 14, and the second dielectric layer 15 project from the pedestal 16. A third dielectric layer 17 and a conductor ring 18, which have ring shapes, are disposed around the projecting portion. The third dielectric layer 17 is interposed between the conductor ring 18 and the pedestal 16. The conductor ring 18 is disposed outside the outer perimeter of the silicon wafer 9 as the sample, and the surface of the conductor ring 18 is approximately flush with the surface of the silicon wafer 9. A DC voltage is applied to the electrostatic chuck electrode 14, whereby the silicon wafer 9 is absorbed on the surface of the first dielectric layer 13 which is the surface of the projecting portion of the sample electrode 6, whereby the temperature of the silicon wafer 9 can be controlled precisely. Prior to amorphyzation processing, gate electrodes are formed on the surface of a silicon wafer as a sample. More specifically, gate electrode patterns are formed by forming a silicon oxide film as a gate oxide film on the surface of a single crystal silicon wafer, forming a conductive layer for formation of gate electrodes on the silicon oxide film by CVD or the like, and patterning the conductive layer. After the silicon wafer 9 on which the gate electrodes have been formed in the above manner is mounted on the sample electrode 6, a helium gas is supplied at 50 sccm to the inside of the vacuum container 1 through the gas inlet 11 while the vacuum container 1 is exhausted through the exhaust hole 12 and the temperature of the sample electrode 6 is kept at 25° C. The pressure in the vacuum container 1 is kept at 1 Pa by controlling the pressure regulating valve 4. Then, plasma is generated in the vacuum container 1 by supplying high-frequency power of 800 W to the coil 8 as the plasma source and high-frequency power of 200 W is supplied to the pedestal 16 of the sample electrode 6. In this manner, a surface crystal layer of the silicon wafer 9 was rendered amorphous successfully. FIG. 7 shows a result of a measurement of the thickness of an amorphous layer produced by amorphyzing a 200-mm-diameter silicon wafer. The x-axis is taken in the left-to-right direction in FIG. 5 or 6. As seen from FIG. 7, the thickness of the amorphous layer does not have eminent peaks in portions close to the outer perimeter and the uniformity is increased greatly to as high as ±1.59%. When an amorphyzation apparatus having a conventional configuration without a conductor ring was used, the thickness variation of an amorphous layer with respect to the measurement position was ±3.26%. This improvement is considered due to that the distortion of equipotential lines of the sheath layer in the area corresponding to the portion, close to the outer perimeter, of the wafer 9 is reduced and the incidence energy of ions incident on the wafer 9 is thereby made uniform in the entire area including the area corresponding to the portion, close to the outer perimeter, of the wafer 9. The capacitance Ca per unit area between the wafer 9 and the pedestal 16 is given by Ca=1/(d1/∈1+d2/∈2) and the capacitance Cb per unit area between the conductor ring 18 and the pedestal 16 is given by Cb=∈3/d3, where ∈1 and d1 are the relative permittivity and the thickness of the first dielectric layer 13, ∈2 and d2 are the relative permittivity and the thickness of the second dielectric layer 15, and ∈3 and d3 are the relative permittivity and the thickness of the third dielectric layer 17. In the embodiment, the relative permittivities and the thicknesses of the respective electric layers are set so as to establish a relationship Ca=1.2Cb. As in this example, it is desirable that the capacitances Ca and Cb per unit area be set approximately identical. If the capacitances Ca and Cb have a large difference, the high-frequency impedance per unit area corresponding to the larger one of Ca and Cb is small and the current densities (ion currents per unit area) of ion currents flowing into the wafer 9 and the conductor ring 18 have a large difference, which is a factor in lowering the uniformity of amorphyzation processing. In our experiments, high in-plane uniformity was secured when Ca was larger than or equal to 0.5 times Cb and smaller than or equal to 2 times Cb. For comparison, a similar experiment was conducted with a structure that a dielectric ring 19 was disposed around a wafer 9 but no conductor ring is provided (see FIG. 8). As in the conventional example, an amorphous layer was extremely thick in the portion close to the outer perimeter of the wafer and the uniformity was ±3.31%. Although in the embodiment the distance A between the outer perimeter of the wafer 9 and the inner perimeter of the conductor ring 18 is set at 1.5 mm, it is desirable that the distance A be set in a range of 1 mm to 10 mm. If the distance A is shorter than 1 mm, the wafer 9 may run onto the conductor ring 18 due to a transport error occurring in its transport. That is, the distance A being shorter than 1 mm is not preferable because of an insufficient transport margin. If the distance A is longer than 10 mm, an amorphous layer may become extremely thick in the portion, close to the outer perimeter, of the wafer 9. The distance A being longer than 10 mm is thus not preferable. Usually, the diameter (typical length) of the wafer 9 is designed so as to be longer than the diameter (typical length) of the projecting portion of the sample electrode 6 by about 1 mm. Therefore, it is desirable that the distance between the outer perimeter of the projecting portion of the sample electrode 6 and the inner perimeter of the conductor ring 18 be set in a range of 2 mm to 11 mm. Although in the embodiment the difference B in height between the surface of the wafer 9 and the conductor ring 18 is set at 0.3 mm, it is desirable that the difference B be set in a range of 0.001 mm to 1 mm. Setting the difference B at 0.001 mm is difficult in design. If the difference B is larger than 1 mm, an amorphous layer may become extremely thin or thick in the portion, close to the outer perimeter, of the wafer 9. Therefore, the difference B being larger than 1 mm is not preferable. Since the thickness of the wafer 9 is about 1 mm, it is desirable that the difference in height between the surface of the projecting portion of the sample electrode 6 and the surface of the conductor ring 18 be in a range of 0.001 mm to 2 mm. Next, a second embodiment of the invention will be described. This embodiment employs the same amorphyzation apparatus as the first embodiment does except that a high-frequency voltage for controlling the ion energy is applied to the electrostatic chuck electrode 14 rather than the pedestal 16 (see FIG. 8). Also in this case, we confirmed that the uniformity of processing was increased. The capacitance between the electrostatic chuck electrode and the sample is given by (∈1×S1)/d1 and the capacitance between the electrostatic chuck electrode and the conductor ring is given by 1/{d2/(∈2×S1)+d3/(∈3×S2)}, where ∈1 and d1 are the relative permittivity and the thickness of the first dielectric layer, ∈2 and d2 are the relative permittivity and the thickness of the second dielectric layer, ∈3 and d3 are the relative permittivity and the thickness of the third dielectric layer, S1 is the area of the electrostatic chuck electrode, and S2 is the surface area of the conductor ring. Therefore, the ratio between the RF current flowing into the sample and the RF current flowing into the conductor ring is (∈1×S1)/d1:1/{d2/(∈2×S1)+d3/(∈3×S2)}. By dividing the above formulae by S1 and S2, respectively, the ratio between the RF currents per unit area is obtained as ∈1/d1:1/{(d2×S2)/(∈2×S1)+d3/∈3}. In the embodiment, the relative permittivities and the thicknesses of the respective electric layers are set so as to establish a relationship Cc=1.1Cd. If the capacitances Cc and Cd have a large difference, the high-frequency impedance per unit area corresponding to the larger one of Cc and Cd is small and the current densities (ion currents per unit area) of ion currents flowing into the wafer and the conductor ring have a large difference, which is a factor in lowering the uniformity of amorphyzation processing. In our experiments, high in-plane uniformity was secured when Cc was larger than or equal to 0.5 times Cd and smaller than or equal to 2 times Cd. Next, a third embodiment of the invention will be described with reference to FIG. 9. This embodiment employs the same amorphyzation apparatus as the first embodiment does except that the structure of the sample electrode 6 is as shown in a detailed sectional view of FIG. 9. As shown in FIG. 9, the sample electrode 6 has a layered structure in which a first dielectric layer 13, an electrostatic chuck electrode 14, a second dielectric layer 15, and a pedestal 16 are arranged in this order from the side that is closer to a silicon wafer 9 as a sample. The first dielectric layer 13, the electrostatic chuck electrode 14, and the second dielectric layer 15 project from the pedestal 16. A dielectric ring 19 is disposed around the projecting portion, and a focus ring 20 made of a dielectric is disposed on the dielectric ring 19. The distance C between the outer perimeter of the wafer 9 and the inner perimeter of the focus ring is set at 6 mm. The focus ring 20 is disposed outside the outer perimeter of the wafer 9 as the sample, and the surface of the focus ring 20 is higher than the surface of the wafer 9 by 7 mm. That is, the difference D in height between the surface of the wafer 9 as the sample and the surface of the focus ring 20 is equal to 7 mm. A DC voltage is applied to the electrostatic chuck electrode 14 to control the temperature of the wafer precisely by the silicon wafer 9 by causing it to be absorbed on the surface of the first dielectric layer 13 which is the surface of the projecting portion of the sample electrode 6. After a wafer 9 is mounted on the sample electrode 6, a helium gas is supplied at 50 sccm to the inside of the vacuum container 1 through the gas inlet 11 while the vacuum container 1 is exhausted through the exhaust hole 12 and the temperature of the sample electrode 6 is kept at 25° C. The pressure in the vacuum container 1 is kept at 1 Pa by controlling the pressure regulating valve 4. Then, plasma is generated in the vacuum container 1 by supplying high-frequency power of 800 W to the coil 8 as the plasma source and high-frequency power of 200 W is supplied to the pedestal 16 of the sample electrode 6. In this manner, a surface crystal layer of the silicon wafer 9 was rendered amorphous uniformly. The result that the amorphous layer is not extremely thick in the portion, close to the outer perimeter, of the wafer and the uniformity is increased greatly is considered due to that the distortion of equipotential lines of the sheath layer in the area corresponding to the portion, close to the outer perimeter, of the wafer 9 is reduced and the incidence energy of ions incident on the wafer 9 is thereby made uniform in the entire area including the area corresponding to the portion, close to the outer perimeter, of the wafer 9. It is desirable that the distance C between the outer perimeter of the wafer 9 as the sample and the inner perimeter of the focus ring 20 be set in a range of 1 mm to 10 mm. If the distance C is shorter than 1 mm, an amorphous layer may become too thin in the area corresponding to the portion, close to the outer perimeter, of the wafer 9. That is, the distance C being shorter than 1 mm is not preferable. Conversely, if the distance C is longer than 10 mm, an amorphous layer may become extremely thick in the portion, close to the outer perimeter, of the wafer 9. The distance C being longer than 10 mm is thus not preferable. Usually, the diameter (typical length) of the wafer 9 is designed so as to be longer than the diameter (typical length) of the projecting portion of the sample electrode 6 by about 1 mm. Therefore, it is desirable that the distance between the outer perimeter of the projecting portion of the sample electrode 6 and the inner perimeter of the focus ring 20 be set in a range of 2 mm to 11 mm. It is desirable that the difference D in height between the surface of the wafer 9 as the sample and the surface of the focus ring 20 be set in a range of 1 mm to 15 mm. If the difference D is shorter than 1 mm, an amorphous layer may become extremely thick in the portion, close to the outer perimeter, of the wafer 9. That is, the difference D being shorter than 1 mm is not preferable. Conversely, if the difference D is larger than 15 mm, an amorphous layer may become too thin in the portion, close to the outer perimeter, of the wafer 9. Therefore, the difference D being larger than 1 mm is not preferable. Since the thickness of the wafer 9 is about 1 mm, it is desirable that the difference in height between the surface of the projecting portion of the sample electrode 6 and the surface of the focus ring 20 be in a range of 2 mm to 16 mm. Next, a fourth embodiment of the invention will be described with reference to FIG. 10. This embodiment is characterized in that a silicon tray 21 having a recess that conforms to the outward shape of a silicon wafer 9 as a sample is disposed on the sample electrode 6, and that the tray 21 has a ring-shaped surface which is approximately the same in height as the surface of the silicon wafer 9. This embodiment employs the same amorphyzation apparatus as the first embodiment does except that the structure of the sample electrode 6 is as shown in a detailed sectional view of FIG. 10. As shown in FIG. 10, a wafer 9 mounted on the silicon tray 21 is placed on the sample electrode 6. The tray 21 may always be placed on the sample electrode 6. An alternative procedure is that a wafer 9 is mounted on the tray 21 in the air and the tray 21 is then transported to the sample electrode 6. The former procedure is advantageous in that the configuration of the transport system is simple. The latter procedure is advantageous in that it is not necessary to expose the vacuum container 1 to the air in replacing the tray 21 when it is worn. The tray 21 is formed with the step so that a sample occupies an inside space of the tray 21. The surface of the portion, outside the step, of the tray 21 is set approximately the same in height as the surface of a sample. After the tray 21 mounted with a wafer 9 is placed on the sample electrode 6, a helium gas is supplied at 50 sccm to the inside of the vacuum container 1 through the gas inlet 11 while the vacuum container 1 is exhausted through the exhaust hole 12 and the temperature of the sample electrode 6 is kept at 15° C. The pressure in the vacuum container 1 is kept at 1 Pa by controlling the pressure regulating valve 4. Then, plasma is generated in the vacuum container 1 by supplying high-frequency power of 800 W to the coil 8 as the plasma source and high-frequency power of 200 W is supplied to the sample electrode 6. In this manner, a surface crystal layer of the silicon wafer 9 was rendered amorphous uniformly. The result that the amorphous layer is not extremely thick in the portion, close to the outer perimeter, of the wafer and the uniformity is increased is considered due to that the distortion of equipotential lines of the sheath layer in the area corresponding to the portion, close to the outer perimeter, of the wafer 9 is reduced and the incidence energy of ions incident on the wafer 9 is thereby made uniform in the entire area including the area corresponding to the portion, close to the outer perimeter, of the wafer 9. Although in the embodiment the distance E between the outer perimeter of the wafer 9 as the sample and the step is set at 1 mm, it is desirable that the distance E be set in a range of 1 mm to 10 mm. If the distance E is shorter than 1 mm, the wafer 9 may run onto the portion, outside the step, of the tray 21 due to a transport error occurring in its transport. That is, the distance E being shorter than 1 mm is not preferable because of an insufficient transport margin. If the distance E is longer than 10 mm, an amorphous layer may become extremely thick in the portion, close to the outer perimeter, of the wafer 9. The distance E being longer than 10 mm is thus not preferable. Although in the embodiment the difference F in height between the surface of the wafer 9 as the sample and the surface of the portion, outside the step, of the tray 21 is set at 0.4 mm, it is desirable that the difference F be set in a range of 0.001 mm to 1 mm. Setting the difference Fat 0.001 mm is difficult in design. If the difference F is larger than 1 mm, an amorphous layer may become extremely thin or thick in the portion, close to the outer perimeter, of the wafer 9. Therefore, the difference F being larger than 1 mm is not preferable. In the embodiment, the sample is a silicon wafer and the tray is made of silicon. This combination can minimize the substrate pollution. As in a modification shown in FIG. 11, amorphyzation may be performed in a state that the tray 21 is pressed against the sample electrode by a clamp ring 22. This structure increases the heat conduction between the tray 21 and the sample electrode 6 and thereby makes it possible to control the temperature of the wafer 9 more precisely. A manufacturing step of generating plasma and a manufacturing step in which the plasma generation is suspended and the pressure in the vacuum container is set higher than in the step of generating plasma may be executed alternately and repeatedly. With this process, heat that has been stored in a wafer 9 in the step of generating plasma is allowed to escape to the sample electrode 6 side through heat transmission by a gas that flows into the interstices between the wafer 9 and the tray 21 and those between the tray 21 and the sample electrode 6 in the step in which the plasma generation is suspended and the pressure in the vacuum container is set higher than in the step of generating plasma. This in turn makes it possible to control the temperature of the wafer 9 more precisely. In the above case, it is preferable that the pressure in the vacuum container in the step in which the plasma generation is suspended and the pressure in the vacuum container is set higher than in the step of generating plasma be set in a range of 100 Pa to 1,000 Pa. If the pressure is lower than 100 Pa, the effect of allowing heat to escape is small and too much time is taken to lower the temperature of the wafer 9. Conversely, if the pressure is higher than 1,000 Pa, too much time is taken to increase or decrease the pressure. As for the shape of the vacuum container, the type and the manner of disposition of the plasma source, etc. in the application ranges of the invention, only part of various variations have been described in the above-described embodiments of the invention. It goes without saying that various variations other than the above-described ones are possible in applying the invention. For example, the coil 8 may be a planar one. Alternatively, a helicon wave plasma source, a magnetically neutral loop plasma source, or a magnetic field microwave plasma source (electron cyclotron resonance plasma source) may be used. A parallel-plate plasma source may also be used. An inert gas other than helium may be used; that is, a gas of one of neon, argon, krypton, and xenon may be used. These inert gases are advantageous in that adverse effects on a sample are smaller than of other gases. Although the embodiments are directed to the case that the sample is a single crystal silicon wafer, the invention can also be applied to cases of processing samples made of other various materials such as a polysilicon wafer or a compound semiconductor wafer (e.g., GaAs wafer). Capable of increasing the uniformity of amorphyzation processing, the amorphyzing method and apparatus according to the invention can be applied to various uses such as semiconductor impurity doping processes, manufacture of thin-film transistors that are used in liquid crystal devices etc., and surface reforming of various materials. |
|
abstract | A floating nuclear power reactor including one or two nuclear power reactors positioned in a floating vessel such as a barge or the like. Means is disclosed for flooding the containment structure of the nuclear reactor and for flooding the reactor vessels to cool the same. |
|
abstract | In general, systems and methods for identifying anomalous activity are described. For example, systems and methods are described, in which patterns of unusual behavior can be identified by aggregating logged, or sampled, data into cells and annotating each cell with statistically derived measures of how extreme the cell is relative to, for example, historical behavior of corresponding characteristics or relative to, for example, behavior of characteristics from a general population. Cells that have more than a predefined number of such annotations can be identified as anomalous and can be investigated by a user or outright acted upon in an automatic, pre-defined way. |
|
description | This application claims the benefit of U.S. provisional patent application No. 61/183,998, filed Jun. 4, 2009, and U.S. provisional patent application No. 61/184,004, filed Jun. 4, 2009, the contents of which are incorporated herein in their entireties. The subject matter disclosed herein relates to X-ray imaging. More particularly, the subject matter disclosed herein relates to strain matching crystals and horizontally-spaced monochromator and analyzer crystal arrays in diffraction enhanced imaging systems and related methods. X-ray imaging has been used in a variety of fields for imaging objects. For example, X-ray imaging has been used extensively in the medical field for non-destructive testing and X-ray computed tomography (CT). Various other types of technology are also being used for medical imaging. For example, diffraction enhanced imaging (DEI) is an X-ray imaging technique that dramatically extends the capability of conventional X-ray imaging. The DEI technique is an X-ray imaging modality capable of generating contrast from X-ray absorption, X-ray refraction, and ultra-small angle scatter rejection (extinction). In contrast, conventional X-ray imaging techniques measure only X-ray attenuation. The DEI absorption image and peak image shows the same information as a conventional radiograph, except that it is virtually free of scatter degradation. Based on Bragg's law of X-ray diffraction, nλ=2d sin(θ), DEI utilizes the Bragg peak of perfect crystal diffraction to convert angular changes into intensity changes, providing a large change in intensity for a small change in angle. Thus, DEI is well suited to soft-tissue imaging, and very promising for mammography. The use of a silicon analyzer crystal in the path of the X-ray beam generates two additional forms of image contrast, X-ray refraction, and extinction (ultra small angle scatter rejection). DEI utilizes highly collimated X-rays prepared by X-ray diffraction from perfect single-crystal silicon. These collimated X-rays are of single X-ray energy, practically monochromatic, and are used as the beam to image an object. Objects that have very little absorption contrast may have considerable refraction and extinction contrast, thus improving visualization and extending the utility of X-ray imaging. Applications of DEI techniques to biology and materials science have generated significant gains in both contrast and resolution, indicating the potential for use in mainstream medical imaging. An area of medicine where DEI may be particularly effective is in breast imaging for cancer diagnosis, where the diagnostic structures of interest often have low absorption contrast, making them difficult to see. Structures with low absorption contrast, such as the spiculations extending from a malignant mass, have high refraction and ultra-small angle scatter contrast. It is desirable to provide a DEI system with the capability to increase both the sensitivity and specificity of X-ray-based breast imaging. Multiple studies have demonstrated improved image contrast in both medical and industrial applications of DEI. Advantages of DEI systems over conventional X-ray imaging systems in the medical field include a dramatic reduction in patient radiation dose and improved image quality. The dose reduction is due to the ability of DEI systems to function at higher X-ray energies. X-ray absorption is governed by the photoelectric effect, Z2/E3, where Z is the atomic number and E is the photon energy. The core theory of DEI is based on Bragg's law of X-ray diffraction. Bragg's law is defined by the following equation:nλ=2d sin(θ)where λ is the wavelength of the incident X-ray beam, θ is the angle of incidence, d is the distance between the atomic layers in the crystal, and n is an integer. A monoenergetic radiograph contains several components that can affect image contrast and resolution: a coherently scattered component IC, an incoherently scattered component II, and a transmitted component. X-rays passing through an object or medium where there are variations in density can be refracted, resulting in an angular deviation. Specifically, deviations in the X-ray range result from variations in pt along the path of the beam, where ρ is the density and t is the thickness. A fraction of the incident photons may also be diffracted by structures within an object, which are generally on the order of milliradians and referred to as small angle scattering. The sum total of these interactions contributed to the recorded intensity in a radiograph IN, which can be represented by the following equation:IN=IR+ID+IC+II System spatial resolution and contrast will be degraded by the contributions of both coherent and incoherent scatter. Anti-scatter grids are often used in medical imaging to reduce the contribution of scatter, but their performance is limited and use of a grid often requires a higher dose to compensate for the loss in intensity. The DEI technique utilizes a silicon analyzer crystal in the path of the post-object X-ray beam to virtually eliminate the effects of both coherent and incoherent scatter. The narrow angular acceptance window of the silicon analyzer crystal is referred to as its rocking curve, and is on the order of microradians for the X-ray energies used in DEI. The analyzer acts as an exquisitely sensitive angular filter, which can be used to measure both refraction and extinction contrast. Extinction contrast is defined as the loss of intensity from the incident beam due to scattering, which can produce substantial improvements in both contrast and resolution. The Darwin Width (DW) is used to describe reflectivity curves, and is approximately the Full Width at Half Maximum (FWHM) of the reflectivity curve. Points at −½ DW and +½ DW are points on the curve with a steep slope, producing the greatest change in photon intensity per microradian for a particular analyzer reflection and beam energy. Contrast at the peak of the analyzer crystal rocking curve is dominated by X-ray absorption and extinction, resulting in near scatter-free radiographs. Refraction contrast is highest where the slope of the rocking curve is greatest, at the −½ and +½ DW positions. One DEI based image processing technique uses these points to extract the contrast components of refraction and apparent absorption from these image pairs. The following paragraph describes this technique for extracting the contrast components of refraction and apparent absorption from an image pair. When the analyzer crystal is set to an angle representing +/−½ DW for a given reflection and beam energy, the slope of the rocking curve is relatively consistent and can be represented as a two-term Taylor series approximation as represented by the following equation: R ( θ 0 + Δθ Z ) = R ( θ 0 ) + ⅆ R ⅆ θ ( θ 0 ) Δθ Z . If the analyzer crystal is set to the low-angle side of the rocking curve (−½ DW), the resulting image intensity can be represented by the following equation: I L = I R ( R ( θ L ) + ⅆ R ⅆ θ ❘ θ = θ L Δθ Z ) . The recorded intensity for images acquired with the analyzer crystal set to the high-angle position (+½ DW) can be represented by the following equation: I H = I R ( R ( θ H ) + ⅆ R ⅆ θ ( θ H ) Δθ Z ) . These equations can be solved for the changes in intensity due to apparent absorption (IR) and the refraction in angle observed in the z direction (ΔθZ) represented by the following equation: Δθ Z = I H R ( θ L ) - I L R ( θ H ) I L ( ⅆ R ⅆ θ ) ( θ H ) - I H ( ⅆ R ⅆ θ ) ( θ L ) I R = I L ( ⅆ R ⅆ θ ) ( θ H ) - I H ( ⅆ R ⅆ θ ) ( θ L ) R ( θ L ) ( ⅆ R ⅆ θ ) ( θ H ) - R ( θ H ) ( ⅆ R ⅆ θ ) ( θ L ) . These equations can be applied to the high and low angle images on a pixel-by-pixel basis to separate the two contrast elements into what is known as a DEI apparent absorption and refraction image. However, it is important to note that each of the single point rocking curve images used to generate DEI apparent absorption and refraction images is useful. Development of a clinical DEI imager may have significance for women's health and medical imaging in general for the following reasons: (1) DEI has been shown to produce very high contrast for the features that are most important to detection and characterization of breast cancer; (2) the physics of DEI allows for imaging at higher x-ray energies than used with absorption alone; and (3) the ability of DEI to generate contrast without the need of photons to be absorbed dramatically reduces ionization, and thus reduces the absorbed dose. Further, screen-film mammography has been studied extensively for the last 40 years, and because of many large randomized screening trials, it is known to reduce breast cancer mortality by approximately 18-30%. The rate of breast cancer death in the last few years has begun to decline, likely due in part to the widespread use of this imaging test. However, standard screen-film mammography is neither perfectly sensitive nor highly specific. Dense breast tissue and diffuse involvement of the breast with tumor tends to reduce the sensitivity of screening mammography. For women with dense breasts, lesions that develop are difficult to see because their ability to absorb photons is not much greater than the surrounding adipose tissue, generating little contrast for visualization. Approximately 10-20% of breast cancers that are detected by self-examination or physical examination are not visible by screen-film mammography. In addition, when lesions are detected by mammography and biopsy, only 5-40% of lesions prove to be malignant. Furthermore, approximately 30% of breast cancers are visible in retrospect on prior mammograms. Current DEI and DEI imaging processing techniques are based heavily on conventional imaging theory and rely, at least in part, on X-ray absorption for image generation. Thus, objects imaged using these techniques absorb radiation. Such radiation exposure is undesirable in applications for medical imaging given concerns of dose, and this reasoning places considerable engineering limitations that make clinical and industrial translation challenging. Thus, it is desirable to provide DEI and DEI techniques that produce high quality images and that rely less on absorption but produce images with equivalent diagnostic quality and feature visualization. Accordingly, in light of desired improvements associated with DEI and DEI systems, there exists a need for improved DEI and DEI systems and related methods for detecting an image of an object. Strain matching of crystals and horizontally-spaced monochromator and analyzer crystal arrays in DEI systems and related methods are disclosed. For example, a DEI system, including strain matched crystals can comprise an X-ray source configured to generate a first X-ray beam. A first monochromator crystal can be positioned to intercept the first X-ray beam for producing a second X-ray beam. A second monochromator crystal can be positioned to intercept the second X-ray beam to produce a third X-ray beam for transmission through an object. The second monochromator crystal has a thickness selected such that a mechanical strain at and near the face of the first monochromator crystal is the same as a mechanical strain at and near the face of the second monochromator crystal. An analyzer crystal has a thickness selected such that a mechanical strain at and near the face of the first monochromator crystal is the same as a mechanical strain on the analyzer crystal. The analyzer crystal is positioned to intercept transmitted X-ray beams at angles of incidence of the analyzer crystal. An image detector can be configured to detect an image of the object from a beam diffracted from the analyzer crystal. This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. The subject matter of the presently disclosed subject matter is described with specificity to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different steps or elements similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the term “step” may be used herein to connote different aspects of methods employed, the term should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly described. The subject matter described herein discloses strain matching of crystals in DEI systems. According to one aspect, the subject matter described herein can include a DEI system can comprise an X-ray source configured to generate a first X-ray beam. A first monochromator crystal can be positioned to intercept the first X-ray beam for producing a second X-ray beam. A second monochromator crystal can be positioned to intercept the second X-ray beam to produce a third X-ray beam for transmission through an object. The second monochromator crystal has a thickness and width selected such that a mechanical strain on a side of the first monochromator crystal is the same as a mechanical strain on the second monochromator crystal. An analyzer crystal has a thickness and width selected such that a mechanical strain on a side of the first monochromator crystal is the same as a mechanical strain on the analyzer crystal. The analyzer crystal is positioned to intercept transmitted X-ray beams at angles of incidence of the analyzer crystal. An image detector can be configured to detect an image of the object from a beam diffracted from the analyzer crystal. An image processing technique using DEI in accordance with the subject matter described herein can use images acquired at symmetric points of the rocking curve to generate apparent absorption and refraction images of an object. A DEI apparent absorption image is similar to a conventional radiograph image, but exhibits much greater contrast owing to scatter rejection. DEI refraction images can depict the magnitude of small beam deflections caused by large-scale refractive-index features (features of a size at or greater than the system resolution). A DEI extinction image is generated at points on the rocking curve where the primary mechanism of contrast is due to photons that have been scattered by an object on the order of microradians. Another DEI based imaging processing technique is referred to as Multiple Image Radiography (MIR) which uses multiple points on the rocking curve to generate quantitative images representing an object's X-ray absorption, refraction, and ultra-small angle scatter. Systems and methods in accordance with the subject matter described herein can generate images at any point on the analyzer rocking curve, and can thus be used to generate: (1) single image DEI at any analyzer position; (2) DEI apparent absorption and refraction images; and (3) mass density images. The ability to generate the raw image data required for these processes and any other DEI based processing technique are useful for all DEI based processing techniques. In addition, systems and methods described herein are amenable for use in computed tomography, and can provide the raw data for use in any DEI-based computed tomography algorithm. As understood, a small area source may refer to any source capable of generating X-ray beams from a small area in space. For example, an X-ray tube may include multiple small area sources for emitting X-ray beams from multiple points. The small area sources may be within the same X-ray tube source. Alternatively or in addition to being a part of a system as disclosed herein, multiple X-ray tube sources may each provide one or more small area sources and be used together for generating multiple X-ray beams. The subject matter disclosed herein provides an additional advantage of providing spacing between individual DEI crystal optics arrays and improved heat dissipation with the source anode due the power load being delivered to several, separated points, both advancements over a single-source, multiple-beam design. This applies to one beam per small area source (wherein the number of beams equals the number of small area sources) as well as multiple beams per source point (if each source generates n beams, then the beams will number n times the number of small area sources). The subject matter disclosed herein is advantageous over previous DEI systems and methods, because it allows for greater mechanical separation between the individual optical elements, thereby solving the problem of potential mechanical interference between monochromator crystals. By using multiple small area sources as described herein, rather than having a single, very high power source location, the power load can be divided amongst several source locations, thus the heat load to the anode may be distributed over a larger area, which can allow for longer operating times for the tube sources. By spacing out the small area sources, the monochromator crystal sizes, as well as the size of the electromechanical control systems, can be larger as compared to previous systems. In addition, the subject matter disclosed herein can allow for greater distribution of the heating load to the anode for decreasing time between imaging sessions. A DEI system according to one embodiment of the subject matter described herein can include multiple monochromator crystals for rejecting particular X-rays emitted by multiple X-ray small area sources. FIGS. 1-11 are schematic diagrams of different example DEI systems including multiple monochromator crystals and multiple small area sources according to embodiments of the subject matter described herein. The DEI systems are operable to produce images of an object by use of the X-ray beams generated by the multiple small area sources. The DEI systems can include multiple small area sources operable to produce a polychromatic X-ray beam, generally designated XB1. X-ray beams XB1 can include photons having different energies. In one example, the X-ray beams are generated by one or more tungsten X-ray tubes having a small area source from which an X-ray beam is emitted. In another example, a system may include multiple X-ray tube sources that each provide one or more small area sources and may be used together for generating multiple X-ray beams. FIG. 12 is a schematic diagram of X-ray tube XT based on a stationary X-ray tube design according to an embodiment of the subject matter described herein. Referring to FIG. 12, X-ray tube XT includes a cathode C configured to generate an electron beam, generally designated EB. Cathode C is made of tungsten or a tungsten alloy. A high voltage is applied across cathode C and anode A, which creates a high potential difference across a vacuum interior V of X-ray tube XT. A voltage potential can be applied to anode A via an anode connection ANC. X-ray tube XT can include a filament F configured to heat cathode C. Filament F can be connected to a power supply by filament connections FC. Vacuum interior V is defined within X-ray tube housing XTH. Electrons may be thermonically ejected from cathode C by heating cathode C. An electrostatic focusing cup EFC surrounds the point of electron ejection, which helps to focus the electron stream towards anode A. Further, electrons being emitted from cathode C are focused across vacuum interior V to anode A, with the velocity across the gap being determined by the voltage applied across the circuit. Electrons ejected from cathode C can be directed towards and incident upon a tungsten target T of anode A. As a result of the impact of electrons upon target T, X-ray beam XB is generated. X-ray beam XB exits vacuum interior V via an X-ray window XW. X-ray beam XB can include characteristic emission lines and Bremsstrahlung radiation. One example of an X-ray generator is the ISOVOLT TITAN 160 available from GE Inspection Technologies of Ahrensburg, Germany. Other exemplary X-ray tubes include the COMET MXR-160 Series of X-ray tubes, such as the MXR-160HP/20 X-ray tube, which are available from Comet AG of Flamatt, Switzerland. Other exemplary X-ray tubes can include those that use anodes including tungsten, molybdenum, iron, or copper. Other suitable types of targets include a barium hexaboride target and a samarium target. A barium hexaboride target can produce X-rays at about 30 keV. Samarium's Kα1 line is at about 40 keV. In one example, an anode of an x-ray tube can be a rotating anode from which x-ray beams can be emitted. In another example, an anode of an x-ray tube can be a stationary anode from which x-ray beams can be emitted. Referring again to FIG. 1, a DEI system, generally designated 100, includes a number N X-ray tubes XT-1-XT-N, each including at least one small area source S, for generating multiple X-ray beams XB1. An array of collimators (not shown) may be positioned adjacent each small area source S for blocking a portion of each of X-ray beams XB1 that fall outside an angular acceptance window of respective monochromator crystals MC-1-MC-n. System 100 can also include other collimators positioned between small area sources S and monochromator crystals MC-1-MC-n for blocking a portion of X-ray beams XB1 that falls outside an angular acceptance window of the monochromator crystals MC-1-MC-n. The collimators can define a slit or hole through which a portion of X-ray beams XB1 can pass to monochromator crystals MC-1-MC-n. Further, the collimators can be made of any suitable material for blocking X-ray beams such as lead. The monochromator crystals MC-1-MC-n can be configured to select a predetermined energy of a portion of X-ray beams XB1 incident thereon. In one example, a monochromator crystal is a silicon [333] monochromator crystal adapted to reject the majority of photons of its respective X-ray beams that do not have a desired energy. For the case of a tungsten X-ray tube, there can be a range of beam energies that are reflected by the silicon monochromator crystal. In this case, the characteristic emission lines of the X-ray beams are 59.13 keV (Kα1) and 57.983 (Kα2), and the bremsstrahlung radiation that falls within the narrow angular acceptance window of the monochromator crystal. The brightness of the bremsstrahlung radiation is several orders of magnitude less than the two Kα emission lines. An X-ray beam may be scattered by its respective monochromator crystal in several different directions. Another array of collimators (not shown) may be positioned between the monochromator crystals MC-1-MC-n and the object O for blocking a portion of the X-ray beam that falls outside an angular acceptance window of its corresponding analyzer crystal, one of analyzer crystals AC-1-AC-n. Each collimator can define a slit or hole through which a portion of one of the X-ray beams can pass towards its analyzer crystal for interception by the analyzer crystal. The analyzer crystals AC-1-AC-n can be rotated for measuring the amount of radiation traveling in a particular direction. The angular reflectivity function of the crystal system is called the intrinsic rocking curve, and this property is used to generate image refraction contrast. If an X-ray photon is deviated towards the peak of the rocking curve, its reflectivity, and thus intensity will increase. If an object feature causes a photon to be deflected down the rocking curve, or away from the peak reflectivity position, it will cause a reduction in intensity. A sample or object O can be imaged in air or immersed in a coupling medium, such as water. The use of a coupling medium can be used to reduce the index gradient between the air and the object O to be imaged, thus allowing the incident X-rays to pass into the object without experiencing significant refraction at the air-object interface. This is not necessary for most objects, but it is an application of the DEI method and can be used to improve the internal contrast of an object. In one example, a monochromator crystal is a symmetric crystal which is narrow in one dimension. A symmetric crystal's lattice planes (the atomic layers that contribute to diffracting the X-ray beam) are parallel to the surface of the crystal. A symmetric crystal preserves the vertical height of the corresponding X-ray source in the incoming beam. In comparison, an asymmetric crystal modifies the divergence and size of the incoming beam. In this example of a monochromator crystal being a symmetric crystal, two-dimensional imaging of large imaging fields (e.g., imaging fields of about 25 cm by 20 cm) can be achieved by scanning a sample object and a detector using a symmetric crystal. One exemplary advantage of a symmetric crystal over an asymmetric crystal is that the asymmetric crystal requires a large monochromator crystal to prepare the imaging beam (e.g., selecting and collimating X-rays), imposing a severe limitation on the perfection of the large crystal. Further, the size of an asymmetric crystal increases with increasing X-ray beam energy, thus making it impractical for X-rays of about 59.13 keV. In contrast, for example, a symmetric monochromator crystal used in accordance with the subject matter described herein can utilize 59.13 keV X-rays with a modest sized crystal of about 30 mm in length. An advantage, over single-beam DEI, of the system and methods disclosed herein, with multiple sources, is that this scan range can be greatly reduced, because of much better spatial coverage of the beams (i.e. if you have a required 25 cm scan range, and 10 beams, then the object will only have to be scanned through a range of 2.5 cm). Referring again to FIG. 1, the object O can be positioned in the path of X-ray beams XB2 (the X-ray beams resulting for the interaction of X-ray beams XB1 with the monochromator crystals MC-1-MC-n) by, for example, a scanning stage (not shown) for imaging of the object O. The object O can be scanned in a direction D, which is approximately perpendicular to the direction of X-ray beams XB2. During scanning of the object O, X-ray beams XB2 can pass through object O and can be analyzed by analyzer crystals AC-1-AC-n, which can be silicon crystals that match monochromator crystals MC-1-MC-n. X-ray beams XB2 incident on analyzer crystals AC-1-AC-n can each diffract (resulting in diffraction X-ray beams, generally designated DXB) for interception by a digital detector (or image plate) DD. Digital detector DD can detect the diffracted X-ray beams DXB and generate electrical signals representative of the intercepted X-ray beams DXB. The electrical signals can be communicated to a computer C for image analysis and display to an operator. The computer C can be configured to generate an absorption image, an image showing refraction effects, and an image depicting ultra-small-angle scattering, the types of which are described in more detail below. The monochromator crystals can propagate their respective x-ray beams as a horizontally-divergent (FIG. 4) and partially vertically divergent (see FIG. 3) fan beam. The fan beam can be collimated with one or more collimators to shield against undesired X-rays, resulting in clear DEI images and low subject dose. In contrast to a two-dimensional beam, a fan beam can be more readily controlled for the shielding of undesired X-rays. Referring now to FIGS. 2 and 3, the DEI system 100 is shown in different operation modes. For clarity, the X-ray beam generated by only one small area source S is shown. Characteristic emission lines Kα1 K1 and Kα2 K2 of the X-ray beam are generated by small area source S. Emission lines Kα1 K1 and Kα2 K2 originate from the same small area source S. As stated above, monochromator crystal MC rejects the majority of photons of the X-ray beam that do not have the desired energy. In this case, emission lines Kα1 K1 and Kα2 K2 and bremsstrahlung radiation pass monochromator crystal MC and are redirected towards an analyzer crystal AC as shown. Collimator C2 is positioned in a path of emission lines Kα1 K1 and Kα2 K2. Collimator C2 defines an adjustable slit through which emission lines can be selectively passed towards analyzer crystal AC. In the first operational mode shown in FIG. 2, the slit is adjusted for an aperture of the vertical size of the X-ray source at a distance of about 400 mm from the small area source S, and positioned such that emission line Kα1 K1 passes collimator C2 and Kα2 K2 is blocked. Thus, collimator C2 removes all X-rays except for the X-rays from emission line Kα1 K1 and a very narrow range of bremsstrahlung radiation. In this mode, the beam is not vertically divergent and thus the object O and detector DD are scanned at the same scanning speed, in opposite directions. This mode yields a maximum possible out-of-plane resolution (the direction of DEI's contrast), but at the cost of removing a portion of the X-rays from the X-ray beam, thereby necessitating increased exposure time. The virtual small area source for the object O is designated VPS. Referring now to FIG. 3, in the second operational mode, emission lines Kα1 K1 and Kα2 K2 and the bremsstrahlung radiation at nearby energies are passed through the collimator C2. The slit of collimator C2 is adjusted for an aperture of about 2.0 mm at a distance of about 400 mm from the small area source S and positioned such that emission lines Kα1 K1 and Kα2 K2 and the bremsstrahlung radiation passes collimator C2. In this mode, the beam divergence is taken into account. In order to avoid image blurring, the object O and detector DD can be scanned at the same angular speed. The relative scanning speeds of detector DD and the sample stage on which the object O is placed can be determined by the source-to-object distance and the source-to-detector distance (where the distances are taken along the beam path). The beam divergence in this mode can lead to lower resolution out-of-plane, but this mode has the advantage of passing more X-rays and thus allows for a faster exposure time. The virtual small area source for detector DD is designated VPS. Circle portions CP1 and CP2 are centered at the virtual source points for the object O and detector DD, respectively. Further, in one embodiment of using the second mode, the Bremsstrahlung radiation at x-ray energies that are different from the K alpha lines can be captured. Thus, in this embodiment, the system is tunable in x-ray energy and is not limited to the characteristic emission energies. This functionality can be achieved by changing the incident angle of the monochromator crystal and the analyzer crystal. In one example, this functionality can be achieved by changing the incident angle to 11.4 degrees, following the Bragg's law, and replacing the Copper filter with an Aluminum filter. In this example, imaging can occur at 30 keV x-ray energy. X-ray energies lower than the Tungsten emission line energies can be utilized for relatively thin objects. In one example, the copper filter can be configured to remove about 19 keV bremsstrahlung radiation for reducing or eliminating unwanted crystal reflections and harmonics. Images have the potential to be degraded without this filtering. FIG. 4 is a top schematic view illustrating the DEI system 100 of FIG. 1 according to an embodiment of the subject matter described herein. For clarity, the X-ray beam XB generated by only one small area source S of an X-ray tube is shown. Referring to FIG. 4, X-ray beam XB are generated by a source of X-ray tube XT. Collimators C1 and C2 block the horizontal spread of the portion of X-ray beam XB to define the angular spread of the X-ray beam XB and its horizontal size at the object O position. The portion of X-ray beam XB that passes through collimators C1 and C2 is the X-ray beam portion that passes through slits in the collimators. The angle θ may be about 17° or any other suitable angle. The DEI system 100 can include right and left post-analyzer crystal sodium iodide detectors D1 and D2, respectively, and right and left post-monochromator crystal sodium iodide detectors D3 and D4, respectively. Detectors D3 and D4 are used to ensure alignment of the monochromator crystals (MC) and detectors D1 and D2 are used to ensure analyzer crystal (AC) alignment. These detectors are used to measure the intensity of the diffracted X-ray beam being emitted from the monochromator crystal MC, or the analyzer AC. For system alignment, detectors D1 and D2 are placed in the post analyzer crystal AC X-ray beam XB. If the analyzer crystal is not tuned to the desired angle, the intensity measured by the detectors D1 and D2 will show this and the system can be adjusted. The same is true for the detectors in the post-monochromator crystal MC X-ray beam XB. In addition, detectors D1-D4 can be used to measure X-ray beam XB in real time and adjust the analyzer crystal, D1 and D2, chi (angle as measured about the axis along the X-ray beam path) or monochromator crystal chi, D3 and D4. The use of these detectors to set, measure, and adjust the analyzer crystal AC and monochromator crystal MC can be important for successful DEI image acquisition. Referring now to FIG. 5, another example DEI system 500 for detecting an image of the object O according to an embodiment of the subject matter disclosed herein is shown. The DEI system 500 is similar to DEI system 100 shown in FIG. 1 except that DEI system 500 includes a second set of monochromator crystals MC2-1-MC2-n positioned downstream from a first set of monochromator crystals MC1-1-MC1-n. Referring now to FIG. 6, another example DEI system 600 for detecting an image of the object O according to an embodiment of the subject matter disclosed herein is shown. DEI system 600 is similar to DEI system 100 shown in FIG. 1 except that, rather than the use of multiple X-ray tubes XT-1-XT-n, system 600 includes a single X-ray tube XT having multiple source points SP-1-SP-n, each capable of functioning as a small area source. Therefore, X-ray tube XT can produce a plurality of X-ray beams, generally designated XB1. The system 600 may also include a collimator array CA positioned near the X-ray tube XT. Referring now to FIG. 7, another example DEI system 700 for detecting an image of the object O according to an embodiment of the subject matter disclosed herein is shown. DEI system 700 is similar to DEI system 500 shown in FIG. 5 and DEI system 600 shown in FIG. 6. Similar to system 500 shown in FIG. 5, system 700 includes monochromator crystals MC1-1-MC1-n and MC2-1-MC2-n. Further, similar to system 600 shown in FIG. 6, system 700 includes a single X-ray tube XT having multiple source points SP-1-SP-n, each capable of functioning as a small area source for producing X-ray beams XB1. Referring now to FIG. 8, another example DEI system 800 for detecting an image of the object O according to an embodiment of the subject matter disclosed herein is shown. DEI system 800 is similar to DEI system 600 shown in FIG. 6 except that the source points SP-1-SP-n of system 800 each emit an X-ray beam XB that fans out toward sets of monochromator crystals MC-1-MC-n. For example, source points SP-1 and SP-n emit fanning X-ray beams, generally designated XB1-1 and XB1-n, respectively, directed to the sets of monochromator crystals MC-1 and MC-n, respectively. In turn, X-ray beam sets XB2-1-XB2-n, originating from the monochromator crystals, are directed towards the analyzer crystal sets AC-1-AC-n. System 800 includes a plurality of digital detectors DD-1-DD-n each configured to receive respective, diffracted X-ray beams DXB-1-DXB-n from the analyzer crystal sets AC-1-AC-n. Computer C is operable to receive electrical signals from the digital detectors DD-1-DD-n for generating an image of the object O. Referring now to FIG. 9, another example DEI system 900 for detecting an image of the object O according to an embodiment of the subject matter disclosed herein is shown. DEI system 900 is similar to DEI system 800 shown in FIG. 8 except that system 900 includes monochromator crystals MC1-1-MC1-n and MC2-1-MC2-n similar to DEI system 500 shown in FIG. 5. Referring now to FIG. 10, another example DEI system 1000 for detecting an image of the object O according to an embodiment of the subject matter disclosed herein is shown. DEI system 1000 is similar to DEI system 800 shown in FIG. 8 except that system 1000 includes X-ray tubes XT-1-XT-n similar to the DEI system 500 shown in FIG. 5. Referring now to FIG. 11, another example DEI system 1100 for detecting an image of the object O according to an embodiment of the subject matter disclosed herein is shown. DEI system 1100 is similar to DEI system 900 shown in FIG. 9 except that the source points originate from different X-ray tubes XT-1-XT-n similar to the DEI system 500 shown in FIG. 5. The monochromator and analyzer crystals can strain under their own weight, which result in changes in the lattice spacing of the crystals. Because the reflection energy and angle are dependent upon the lattice spacing of the crystal, variations in the lattice spacing of the crystals can lead to misaligned, or even unalignable optics. The surfaces of the crystals may be strain-matched so that any X-ray from a diverging X-ray beam “sees” the same crystal lattice spacing at each reflection. This can be accomplished by varying the crystal cross-section as a function of the beam size on the optics. In their simplest form, equations for prefect crystal diffraction require constant lattice spacing. Practically, crystal strains, causing variations in lattice spacing, are unavoidable. The strain can be from thermal variations within the crystal or from mechanical loads on the crystal. While the thermal variations can be mitigated through strict temperature controls, mechanical strains are unavoidable. Because of the extremely fine angular and energy sensitivity of perfect crystal optics, variations in the lattice spacing on the order of 0.005% can lead to intensity variations in the DEI system on the order of 50%. The subject matter disclosed herein solves this problem by allowing for strain along the crystal face, but vary the vertical and horizontal cross-section of the crystals to match that strain along any beam within the system. With an x-ray tube-based DEI system such as system 500 shown in FIG. 5, the beam is divergent along the horizontal direction. For example, FIG. 13 shows a top view of a DEI system with divergent X-ray beams emitting from an X-ray tube XT. Referring to FIG. 13, in order to have each of the diverging beams (e.g. beam ABC or beam DEF) see a constant lattice spacing along each of the crystal faces, then the vertical and horizontal cross-section of each crystal must be varied. This can be achieved by scaling the crystals' vertical and horizontal cross-sections with the beam size on the crystal. For example, if the horizontal beam size is 2 cm on the first monochromator crystal MC1, 4 cm on the second monochromator crystal MC2, and 8 cm on the analyzer crystal AC, and the first monochromator crystal MC1 has a height of 0.5 cm, then the second monochromator crystal MC2 may have a height of 1 cm, and the analyzer crystal AC should have a height of 2 cm. In this example, the ratio between the beam size along one dimension and the crystal size along the same dimension remains constant. It should be noted that the crystals and X-ray beam shown in FIG. 13 are not to scale. FIG. 14 shows cross-sectional views of each of the crystals MC1, MC2, and AC. FIG. 15 is a flow chart illustrating an exemplary process for imaging an object by use of a DEI system, such as the DEI system shown in FIGS. 13 and 14, according to an embodiment of the subject matter described herein. Referring to FIG. 15, in step 1500, a first X-ray beam is generated. For example, X-ray tube XT shown in FIG. 13 can generate an X-ray beam. At step 1502, a monochromator crystal may be positioned to intercept the first X-ray beam such that a second X-ray beam is produced. For example, one or more the monochromator crystals (such as monochromator crystals MC1 and MC2 shown in FIG. 13) can be positioned to intercept the X-ray beam generated by an X-ray tube XT. At step 1504, an object (such as object O shown in FIG. 13) is positioned in a path of the second X-ray beam for transmission of the second X-ray beam through the object and for emitting from the object a transmission X-ray beam. An analyzer crystal can be positioned to intercept the transmission X-ray beam at angles of incidence of the analyzer crystal (step 1506). For example, the analyzer crystal AC can be positioned to intercept the beams transmitted through the object O. At step 1508, a detector may detect an image of the object from one or more beams diffracted from the analyzer crystal. In order to have a clinically useful, general purpose DEI system, it is desirable to provide a field of view for imaging that is about 36 cm by 43 cm, or greater. A concern of providing field of view on this scale is that a crystal of this width will have surface straining sufficient to cause it to be virtually impossible to fully align the system across the full width of the beam. Additionally, there is a concern that it could be cost-prohibitive to use x-ray optics of this size. Through the use of arrays of vertically-offset, horizontal x-ray beams, a horizontally large x-ray beam can be created using horizontally small monochromator and analyzer crystals for solving these and other issues. In their simplest form, equations for prefect crystal diffraction require a constant lattice spacing. In reality though, crystal strains, causing variations in lattice spacing, are unavoidable. The strain can be from thermal variations within the crystal or from mechanical loads on the crystal. Because of the extremely fine angular and energy sensitivity of perfect crystal optics, variations in the lattice spacing on the order of 0.005% can lead to intensity variations in the DEI system on the order of 50%. There are common techniques practiced within the synchrotron research community to minimize the strain gradients along the face of perfect crystal optics, including making strain cuts along the edges of crystals and placing the mechanical support outside of the strain cuts. Though this technique works for smaller crystals, it is not clear to what extent the strain can be reduced along the crystal face when crystals as large as 40 cm are being implemented. FIGS. 16 and 17 illustrate different views of an exemplary DEI system for solving the above-described difficulties. In this example, the horizontally large crystals in other DEI systems are replaced with a horizontal array of smaller crystals. Referring to FIGS. 16 and 17, the DEI system includes a horizontal array of monochromator crystals MC1T1 and MC2T1, monochromator crystal MC1B1, monochromator crystals MC2T1 and MC2B1, and analyzer crystals ACT1 and ACB1. Gaps or spacings are provided between the arrays of crystals along a substantially horizontal direction HD. In order to overcome this, the adjacent crystals in the horizontal array will be vertically offset from one another. Monochromator crystals MC1T1 and MC2T1 (indicated by diagonal markings) are positioned above monochromator crystals MC1B1 and MC2B1, respectively. An X-ray beam XB emitted by X-ray tube XT can be intercepted by top surfaces of monochromator crystals MC1T1, and MC1B1. The top surfaces of these monochromator crystals can overlap one another in the direction HD such that there is no spacings of crystal surface in the direction HD. The intercepted X-ray beam XB can then be redirected by monochromator crystals MC1T1 and MC1B1 to respective monochromator crystals MC2B1 and MC2T1. Reference indicia WB and WT indicate the widths of the bottom crystal and the top crystal, respectively. Similar to monochromator crystals MC1T1 and MC1B1, monochromator crystals MC2B1 and MC2T1 and the other monochromator crystals aligned in the direction HD can be spaced apart such that there is no spacings of crystal surface in the direction HD. The monochromator crystals MC2B1 and MC2T1 can redirect the X-ray beam XB for transmission through an object O. The detector can detect an image of the object from beams diffracted from the analyzer crystals as described in further detail herein. FIG. 18 is a flow chart of an exemplary process for imaging an object by use of a DEI system, such as the DEI system shown in FIGS. 16 and 17, according to an embodiment of the subject matter described herein. Referring to FIG. 18, at step 1800, first and second X-ray beams are generated. For example, X-ray tube XT, shown in FIG. 17, can produce X-ray beams. At step 1802, first monochromator crystals are provided that are spaced apart substantially along a first direction. Further, at step 1802, the first monochromator crystals are positioned to intercept the first X-ray beam on surfaces of the first monochromator crystals for producing a third X-ray beam. For example, referring to FIG. 17, monochromator crystals MC1T1 can be provided for intercepting an X-ray beam from X-ray tube XT and for generating another X-ray beam. At step 1804, second monochromator crystals are provided that are spaced apart substantially along the first direction. Further, at step 1804, the second monochromator crystals are positioned to intercept the second X-ray beam on surfaces of the second monochromator crystals for producing a fourth X-ray beam. For example, referring to FIG. 17, monochromator crystals MC1B1 can be provided for intercepting an X-ray beam from X-ray tube XT and for generating another X-ray beam. At step 1806, third monochromator crystals are provided that are spaced apart substantially along the first direction. Further, at step 1806, the third monochromator crystals are positioned to intercept the third X-ray beam on surfaces of the third monochromator crystals to produce a fifth X-ray beam for transmission through an object. For example, monochromator crystals MC2T1 can be positioned to intercept the X-ray beam from monochromator crystals MC1T1 to produce another X-ray beam. At step 1808, fourth monochromator crystals are provided that are spaced apart substantially along the first direction. Further, at step 1808, the fourth monochromator crystals are positioned to intercept the fourth X-ray beam on surfaces of the fourth monochromator crystals to produce a sixth X-ray beam for transmission through the object. For example, monochromator crystals MC2B1 can be positioned to intercept the X-ray beam from monochromator crystals MC1B1 to produce another X-ray beam. At step 1810, analyzer crystals are provided and positioned to intercept the fifth and sixth X-ray beams at angles of incidence of the analyzer crystals. For example, analyzer crystals ACT1 and ACB1 shown in FIG. 17 can be positioned to intercept X-ray beams from monochromator crystals MC2T1 and MC2B1, respectively. At step 1812, an image of the object is detected from beams diffracted from the analyzer crystals. For example, detector DD can detect the image of object O from the beams diffracted from analyzer crystals MC2T1 and MC2B1. FIG. 19 is a side view of analyzer crystal AC of any one of the DEI systems shown in FIGS. 1-11, 16, and 17 according to an embodiment of the subject matter described herein. Referring to FIG. 19, the diffraction of characteristic emission lines Kα1 and Kα2 from the surface of analyzer crystal AC are shown. The accommodation of more than one x-ray energy can result in improved X-ray flux. In another embodiment, a DEI system in accordance with the subject matter described herein can include a mismatch crystal design for rejecting particular X-rays emitted by an X-ray tube. In this design, the Kα2 emission line of the X-ray beam can be eliminated at the monochromator. A collimator can be positioned for blocking a portion of an X-ray beam that fall outside an angular acceptance window of a first monochromator crystal, such as, for example, one of monochromator crystals MC1-1-MC1-n. The unblocked portion of the X-ray beam can intercept the first monochromator crystal, which refracts the unblocked portion in a direction for intercept by a second monochromator crystal, such as, for example, one of monochromator crystals MC2-1-MC2-n. The first monochromator crystal can be tuned to a particular angle using Bragg's Law to select a very narrow range of photon energies for resulting in a diffracted monochromatic beam directed towards the second monochromator crystal. Because of the divergence of the X-ray beam from a source point, the first monochromator crystal can diffract a range of energies which can include the characteristic emission lines Kα1 and Kα2 and bremsstrahlung radiation at nearby energies. A function of the second monochromator crystal is to redirect the beam to a direction parallel to the incident beam and aligned with the analyzer crystal. When tuning the system for a particular energy, the first monochromator crystal is aligned first, and then the second crystal is tuned to find the position of the beam. With the second monochromator crystal aligned, the analyzer crystal is scanned to find the position of the beam on the crystal. Rocking the crystal to find the beam position is analogous to scanning a radio dial to find a particular station, generating a sharp rise in intensity when the angular position of the analyzer is in perfect alignment with the second monochromator crystal. Once the analyzer crystal is aligned, the system is tuned and ready for use. The first and second monochromator crystals, respectively, can be configured in a mismatch crystal design for rejecting particular X-ray beams emitted by a source point, such as a source point of an X-ray tube. The monochromator crystals can be used to eliminate the Kα2 emission line of the X-ray beam, which can be achieved by utilizing the angular acceptance versus energy for different crystals. In one example, the monochromator crystals can be germanium [333] and silicon [333] monochromator crystals, respectively. In another example of detecting the image of the object, a first angle image of object O can be detected from a first diffracted beam emitted from an analyzer crystal positioned at a first angular position. The first angle image of an object can be detected at a low rocking curve angle setting of the analyzer crystal. Further, a second angle image of the object can be detected from a second diffracted beam emitted from the analyzer crystal positioned at a second angular position. The second angle image of the object can be detected at a high rocking curve angle setting of the analyzer crystal. The first and second angle images can be combined by a computer to derive a refraction image. Further, the computer can derive a mass density image of the object from the refraction image. The mass density image can be presented to a user via a display of the computer. Monochromator and analyzer crystals in accordance with embodiments of the subject matter described herein may be scaled in one or more directions. Particularly, the crystals may be manipulated to deform or bow two-dimensionally or three-dimensionally. FIG. 20 is a perspective view of a crystal 2000 being supported at a plurality of points for three-dimensional bowing in accordance with an embodiment of the subject matter described herein. Referring to FIG. 20, the crystal 2000 rests on ball bearings 2002, 2004, and 2006, which correspond to support tips 2008, 2010, and 2012, respectively, on support structures 2014, 2016, and 2018, respectively. The crystal 2000 is supported at a few points such that there will be bowing of the crystal 2000 relative to the support points. Thickness of the crystal may be varied to adjust bowing. The systems and methods in accordance with the subject matter described herein can be applied to a variety of medical applications. As set forth above, the systems and methods described herein can be applied for breast imaging. Further, for example, the systems and methods described herein can be applied to cartilage imaging, neuroimaging, cardiac imaging, vascular imaging (with and without contrast), pulmonary (lung) imaging, bone imaging, genitourinary imaging, gastrointestinal imaging, soft tissue imaging in general, hematopoietic system imaging, and endocrine system imaging. In addition to image time and dose, a major advancement of using higher energy X-rays is the thickness of the object that can be imaged. For applications such as breast imaging, the system described allows for imaging full thickness breast tissue with a clinically realistic imaging time. The same can be said for other regions of the body, such as the head, neck, extremities, abdomen, and pelvis. Without the limitations of X-ray absorption, utilization of DEI with higher energy X-rays dramatically increases the penetration ability of X-rays. For soft tissue, only a small portion of the X-ray photons incident on the object are absorbed, which greatly increases efficiency of emitted photons from the X-ray tube reaching the detector. With respect to pulmonary imaging, DEI techniques as described herein can produce excellent contrast in the lungs and can be used heavily for diagnosing pulmonary conditions such as pneumonia. Fluid collections in the lungs generate a marked density gradient that could be detected easily with DEI. The density gradient, characteristics of the surrounding tissue, and geometric differences between normal lung tissue and tissue with a tumor can be large, producing good contrast. Further, DEI techniques described herein can be applied to lung cancer screening and diagnosis. With respect to bone imaging, DEI techniques as described herein can produce an excellent image of bone in general. High refraction and extinction contrast of DEI can be especially useful for visualizing fractures and lesions within the bone. Further, the systems and methods in accordance with the subject matter described herein can be applied to a variety of inspection and industrial applications. For example, the systems and methods can be applied for meat inspection, such as poultry inspection. For example, the systems and methods can be used for viewing sharp bones, feathers, and other low contrast objects in meats that required screening and/or removal. The systems and methods described herein can be applied for such screening. The systems and methods described herein can also be applied for manufacture inspection. For example, the systems and methods can be used for inspecting welds, such as in aircraft production. DEI techniques as described herein can be used to inspect key structural parts that undergo heavy wear and tear, such as jet turbine blades. Further, for example, the systems and methods described herein can be used for inspecting circuit boards and other electronics. In another example, the systems and methods described herein can be used for tire inspection, such as the inspection of steel belts and tread integrity. Further, the systems and methods in accordance with the subject matter described herein can be used for security screening purposes. For example, the systems and methods can be used for screening at airports and seaports. DEI techniques as described herein can be used for screening for plastic and low absorption contrast objects, such as plastic knives, composite guns difficult to detect with conventional X-ray, and plastic explosives. For imaging larger objects, such is for airport baggage inspection, the distance between the X-ray tube and detector can be increased to allow beam divergence. A larger analyzer crystal would be necessary to accommodate a larger fan beam. The device described provides a mechanism that can be translated into a computed tomography imaging system, or DEI-CT. A DEI-CT system, resembling a third generation conventional computed tomography system, would use the same apparatus but modified for rotation around a central point. Alternatively, the system could remain stationary and the object, sample, or patient could be rotated in the beam. A DEI-CT system of this design would produce images representing X-ray absorption, refraction, and ultra-small angle scatter rejection (extinction), but they would be resolved in three dimensions. The various techniques described herein may be implemented with hardware or software or, where appropriate, with a combination of both. Thus, the methods and apparatus of the disclosed embodiments, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other machine-readable storage medium, wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the presently disclosed subject matter. In the case of program code execution on programmable computers, the computer will generally include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device and at least one output device. One or more programs are preferably implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the program(s) can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations. The described methods and apparatus may also be embodied in the form of program code that is transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via any other form of transmission, wherein, when the program code is received and loaded into and executed by a machine, such as an EPROM, a gate array, a programmable logic device (PLD), a client computer, a video recorder or the like, the machine becomes an apparatus for practicing the presently disclosed subject matter. When implemented on a general-purpose processor, the program code combines with the processor to provide a unique apparatus that operates to perform the processing of the presently disclosed subject matter. While the embodiments have been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function without deviating therefrom. Therefore, the disclosed embodiments should not be limited to any single embodiment, but rather should be construed in breadth and scope in accordance with the appended claims. |
|
summary | ||
summary | ||
description | The present invention relates to an advanced non-toxic Red Mud based Nano gel type material for functional radiation shielding materials and a process thereof. The applications of diagnostic “X” ray radiation are well known in medical sciences. However, there is an always need to overcome the health hazards due to radiations by utilizing appropriate radiation shielding materials. The conventional shielding materials are made using a) lead which is toxic and otherwise also possess many other important applications e.g. lead acid battery, b) barite which is relatively costly and contains deleterious impurities and c) hematite ore useful for making iron metal. All the three conventional shielding materials namely lead, barite and hematite ore are non-replinshable commodities. Further, the conventional shielding materials possess limited functionality. In view of above, there is an urgent need to develop advanced radiation shielding materials possessing additional functionality e.g. a) fire resistance, b) heat resistance, c) mold ability and flexibility to the developed material by, employing appropriate novel matrixes for the fabrication of lead, barium and hematite ore free advanced radiation shielding material utilizing red mud based “Nano” gel type material. The so far known conventional and advanced shielding materials developed till date, utilizes lead, barium and hematite ore based compounds as raw materials and depend on involvement of cumbersome and energy intensive process. Further the use of conventional matrixes limits the functionality aspects which are otherwise very much necessary to face the challenges of new millennium. Conventional polymeric matrixes used in making shielding material are not durable and therefore are prone to health hazard over the years. In view of above there is an urgent need to develop advanced non-toxic Lead, Barium and Hematite ore free, red mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes. The novel matrixes used are 1) Advanced Geopolymer matrix, 2) Advanced geo polymeric matrix, 3) Advanced putty and cement matrix, 4) Advance phosphatic material based matrix, 5) Apart from these novel matrixes the material is also compatible with conventional matrixes, however with the limited functionality as against novel matrixes. To this end a novel process for making advanced Lead, Barium and Hematite ore free, “Nano” gel, based non-toxic, functional radiation shielding materials has been developed utilizing industrial waste red mud generated in large quantity all over the world in Aluminum producing industries. The developed process is highly energy efficient and environment friendly. The novel process involves the appropriate physico-chemical consolidation and or densification of red mud using advanced or conventional matrix helps in obtaining functional radiation shielding material. Red mud is an industrial Waste generated in aluminum industry containing 8-10% silica, 28-31% iron oxide, 20-24% alumina, 19-21% titanium oxide, 6-7% sodium oxide and 4-5% calcium oxide. The novel process involves simultaneous and synergistic chemical reactions of various mineralogical and chemical compounds like hematite, anatse, rutile, gibbsite and cancraite of red mud with complementary various chemical compounds present in citrus fruit wastes (namely orange peel waste, lemon peel waste etc.) like cellulose, hemicellulose, pectin and especially citric acid to form nano gel material to obtain the fine “tailored shielding powder” useful for making functional radiation shielding materials using various appropriate matrixes. The genus Citrus comprises of about 140 genera and 1,300 species and belongs to the Rutaceae or Rue family, and majorly includes Some important fruits like Citrus sinensis (Orange), Citrus paradisi (Grapefruit), Citrus limon (Lemon), Citrus reticulata (tangerine), Citrus grandis (shaddock), Citrus aurantium (sour orange), Citrus medica (Citron), and Citrus aurantifolia (lime). Citrus are well known as one of the world's major fruit crops that are produced in many countries with tropical or subtropical climate. Brazil, USA, Japan, China, Mexico, Pakistan, and countries of the Mediterranean region, are the major Citrus producers. Worldwide, Citrus production is estimated to be at levels as high as 105 million metric tons (MMT) per annum, Brazil being the largest producer with contribution of 19.2 MMT followed by the United States. Further, the citrus peel waste is generates from the processing of citrus fruit, constituting cellulose, hemicellulose, pectin and especially citric acid. The citrus peel waste is highly biodegradable, produced worldwide and therefore its disposal has become major environmental concern. Further apart from achieving technological and functional characteristics in the developed “Advanced non-toxic Lead, Barium and hematite ore free, functional radiation shielding materials, “the process is simple, highly energy efficient, environmental friendly and is also highly cost effective and therefore enabling wide spread utilization of developed material for broad application spectrum ranging from diagnostic radiation installations such as diagnostic X-ray room to CT scanner room etc. Reference may be made to article “Development of high performance gel type radiation shielding material using polymer resin by Naotero Odano etal. In Progress in nuclear science and technology vol. 4 (2014) pp. 639-642, wherein new gel type shielding material mainly consist of conventional resin, lead powder and boron compound was developed. The drawback of the process is use of toxic lead for the preparation of gel type radiation shielding material. Reference may be made to patent, Radiation shielding material and method of making same by Rosensweig Alan and Tashlick Irving, U.S. Pat. No. 3,437,602 wherein Radiation shielding material have been developed using hematite ore. The drawback of the process leads to the formation of in-homogeneous radiation shielding matrix. Reference may be made to patent, low temperature process for making radiaopac materials utilizing industrial/agricultural waste as raw material by S.S Amritphale et al., wherein low temperature process for making radiaopac materials have been disclosed. The drawback of the process is making shielding material by a) sintering in the temperature range of 900-1300° C. and b) need of barium based compounds. Further, from the hitherto reported prior art it is clear that “Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes has not been pursued at all. From the hitherto reported prior art and based on the drawbacks of the known process, the various issues that need to be addressed and problems to be solved for making highly value Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials and also ensuring total utilization of red mud are summarized here as under:— 1) The use of toxic lead for the preparation of gel type shielding materials. 2) The need of use of conventional hematite and barite for making shielding materials. 3) The need of high temperature sintering in the temperature range of 900-1300° C. for making shielding materials. The main object of the present invention is to provide Advanced non-toxic Lead, barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes and the process there of. The use of developed “Nano” gel, based non-toxic, functional radiation shielding materials” lies in the areas of radiation shielding applications e.g. diagnostic radiation installations such as diagnostic X-ray and CT scanner room etc., which obviates the drawbacks of the hitherto known prior art as detailed above. Another object of the present invention is involving simultaneous and synergistic chemical reactions of various mineralogical and chemical compounds hematite, anatse, rutile, gibbsite and cancraite of red mud with complementary various chemical compounds present in orange peel waste namely cellulose, hemicellulose, pectin and especially citric acid to form nano gel material to obtain the fine “tailored shielding powder”. Another object of the present invention is to provide a novel process involving simultaneous and synergistic chemical reactions of various mineralogical and chemical compounds of Red mud with various constituents of novel matrixes enabling homogeneous radiation shielding matrix with desired functionality. Another object of the present invention is to provide advanced functional radiation shielding materials which are devoid of conventionally use toxic lead, barium compound and hematite ore. Still another object of the present invention is to obtain desired homogeneous shielding matrix by chemically designed and mineralogical formulated compositions using various complementary precursors present in red mud and various constituents of novel matrixes. Still another object of the present invention is a novel approach of making functional shielding material utilizing novel matrixes. The novel matrixes involved are 1) Advanced Geopolymer matrix, 2) Advanced geo polymeric matrix, 3) Advanced putty and cement matrix, 4) Advance phosphatic material based matrix, 5)—Apart from these novel matrixes the material is also compatible with conventional matrixes, however with the limited functionality as against novel matrixes. Yet another object of the present invention is enabling the development of simple, highly energy efficient, environmental friendly and highly cost effective process enabling wide spread utilization of developed material for broad application spectrum ranging from diagnostic radiation installations such as diagnostic X-ray room to CT scanner room etc. Yet another object of the present invention is simple as it involves only physico-chemical and mechanical processing of red mud with novel matrix and obviates the need of sintering of red mud at high temperature using various additives like barium sulphate and carbon source etc. Yet another object of the present invention is independent of use of conventional pure polymeric, ceramic or cementations matrixes. Yet another object of the present invention is development of functional shielding materials possessing a) heat resistance, b) fire resistance, c) flexibility and moldability aspects. Yet another object of the present invention is to solve the disposal problem of red mud and citrus peel waste and to save the environment all over the world. The main field of the present invention essentially involves, Development of Advanced non-toxic Lead, barium and hematite ore free, red mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes and the process there of. Conventionally the basic raw material required for making conventional shielding material involves use of either lead or barium or hematite ore and various appropriate combinations all the three depending on the respective application spectra. Further, the lead being toxic in nature, barite being costly and associate with deleterious material and hematite ore being an important source of making iron metal, thus there is an urgent need to develop radiation shielding material which are free of Lead, Barium and hematite ore. Further the advancement of technology and material, there is an urgent need to develop advanced functional shielding materials. To this end a novel process for making Advanced Lead, Barium and hematite ore free, “Nano” gel, based non-toxic, functional radiation shielding materials have been developed utilizing industrial waste Red Mud generated in large quantity all over the world in Aluminum producing industries. The developed process is highly energy efficient and environment friendly. The novel process involves the appropriate physico-chemical consolidation and or densification of red mud using advanced or conventional matrix helps in obtaining functional radiation shielding material. A novel process involving simultaneous and synergistic chemical reactions of various mineralogical and chemical compounds hematite, anatse, rutile, gibbsite and cancraite of red mud with complementary various chemical compounds present in citrus peel waste namely cellulose, hemicellulose, pectin and especially citric acid to form nano gel material to obtain the fine “tailored shielding powder”. The citrus peel waste is generates from the processing of citrus fruit, constituting cellulose, hemicellulose, pectin and especially citric acid. The citrus peel waste is highly biodegradable, produced worldwide and therefore its disposal has become major environmental concern. The chemical reaction among “tailored shielding powder” and various constituents of novel matrixes enables homogeneous radiation shielding matrix with desired functionality in the developed functional shielding materials. Further, Novel process essentially involves a novel process for making Advanced non-toxic Lead, barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes. The novelty of the process of the present invention essentially lies in that: 1) The novel process involves simultaneous and synergistic chemical reactions of various mineralogical and chemical compounds hematite, anatse, rutile, gibbsite and cancraite of red mud with complementary various chemical compounds present in citrus peel waste namely cellulose, hemicellulose, pectin and especially citric acid to form nano gel material to obtain the fine “tailored shielding powder”.2) The novel process involves the tailored shielding powder so obtained having multi shielding phases due to presence of multi elemental Fe, FeO, Fe2O3, TiO2, Ti, Al(OH), SiO2.3) The novel process involves simultaneous and synergistic chemical reactions of various mineralogical and chemical compounds of Red mud with various constituents of novel matrixes enabling homogeneous radiation shielding matrix with desired functionality.4) The novel process involves advanced functional radiation shielding material which is devoid of conventionally use toxic lead, barium compound and hematite ore.5) To obtain desired homogeneous shielding matrix by chemically designed and mineralogical formulated compositions using various complementary precursors present in red mud and various constituents of novel matrixes.6) To enables a novel approach of making functional shielding material utilizing novel matrixes. The novel matrixes involved are 1—Advanced Geopolymer matrix 2—Advanced geo polymeric polymeric matrix 3—Advanced putty and cement matrix 4—Advance phosphatic material based matrix 6—Apart from these novel matrixes the material is also compatible with conventional matrixes, however with the limited functionality as against novel matrixes.7) The novel process developed is simple, highly energy efficient, environmental friendly and is also highly cost effective enabling wide spread utilization of developed material for broad application spectrum ranging from diagnostic radiation installations such as diagnostic X-ray room to CT scanner room etc.8) The developed s novel process is simple as it involves only physico-chemical and mechanical processing of red mud with novel matrix and obviates the need of sintering of red mud at high temperature using various additives like barium sulphate and carbon source etc.9) Another novel aspect of the present invention is independent of use of conventional pure polymeric, ceramic or cementations matrixes.10) Another novel and non-obvious inventive aspect in present invention is development of functional shielding materials possessing a) heat resistance, b) fire resistance, c) flexibility and moldability aspects etc.To overcome the drawbacks of the hitherto to known processes, the present novel process involves—1) The novel process involves simultaneous and synergistic chemical reactions of various mineralogical and chemical compounds hematite, anatse, rutile, gibbsite and cancraite of red mud with complementary various chemical compounds present in citrus peel waste namely cellulose, hemicellulose, pectin and especially citric acid to form nano gel material to obtain the fine “tailored shielding powder”.2) The novel process involves the tailored shielding powder so obtained having multi shielding phases due to presence of multi elemental Fe, FeO, Fe2O3, TiO2, Ti, Al(OH), SiO2.3) The novel process involves simultaneous and synergistic chemical reactions of various mineralogical and chemical compounds of red mud with various constituents of novel matrixes enabling homogeneous radiation shielding matrix with desired functionality.4) The novel process involves advanced functional radiation shielding material which is obviates the use of conventionally use toxic lead, barium compound and hematite ore.5) The novel process involves obtaining desired homogeneous shielding matrix by chemically designed and mineralogical formulated compositions using various complementary precursors present in red mud and various constituents of novel matrixes.6) The novel process enables a novel approach of making functional shielding material utilizing novel matrixes. The novel matrixes involved are 1) Advanced geopolymer matrix, 2) Advanced geo polymeric polymeric matrix, 3) Advanced putty and cement matrix, 4) Advance phosphatic material based matrix, 5) Apart from these novel matrixes the material is also compatible with conventional matrixes, however with the limited functionality as against novel matrixes.7) The novel process enables development of is simple, highly energy efficient, environmental friendly and is highly cost effective process enabling wide spread utilization of developed material for broad application spectrum ranging from diagnostic radiation installations such as diagnostic X-ray room to CT scanner room etc.8) The novel process is simple as it involves only physico-chemical and mechanical processing of Red mud with novel matrix and obviates the need of reduction of red mud at high temperature using various additives like barium sulphate etc and thus making the process highly energy efficient for the development of advance radiation shielding material.9) Another novel aspect of the present invention is independent of use of conventional pure polymeric, ceramic or cementations matrixes.10) Another novel aspect in present invention is development of functional shielding materials possessing a) heat resistance, b) fire resistance, c) flexibility and moldability aspects. In conclusion, the novel process of the present invention enables for making “Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes and the process there of”. The use of developed “advanced non-toxic radiation shielding material” lies in the areas of radiation shielding applications e.g. diagnostic radiation installations such as diagnostic X-ray and CT scanner room etc. Accordingly the present invention provides, Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes and the process there of which comprises digesting 100 g-600 g of Red mud with 80-300 g of crushed citrus peel waste, in the temperature range of 30° C.-90° C. for a period of 2-6 hours and the digested nano gel material so obtained was further dried in an air oven for duration of 2-3 hours in the temperature range of 100° C.-110° C., which was then grinded to obtain the fine “tailored shielding powder” which was further blended with either of the novel matrixes like:— a) “Advanced geopolymer matrix” for obtaining heat resistance properties in the shielding material by taking 100 g-600 g of tailored shielding powder and mixing it with ground powder of 10 g-60 g fly ash, 2 g-8 g sodium hydroxide and 1 g-4 g sodium silicate and 4 ml-16 ml of water and the material so obtained was compacted in the form of tiles of dimension 10 cm×10 cm×5 mm at a compaction pressure of 100-200 kg/cm2 b) “Advanced geopolymeric-polymeric matrix” for obtaining flexible and moldable properties by taking 100 g-600 g of tailored shielding powder and mixing it firstly with ground powder of 1 g-6 g fly ash, 1 g-2 g sodium hydroxide and 0.5 g-1 g sodium silicate and 4 ml-10 ml of water and followed by blending with 150 g to 650 g of Silicone rubber or 150 g to 650 g of PDMS and curing the material in the mold of desired dimension in the temperature range of 30 to 60 degree centigrade for a period ranging from 24 hours to 30 minutes for obtaining the advanced flexible and moldable shielding material,c) Advance putty matrix based material for plastering the X-ray room by taking 100 g-600 g of tailored shielding powder and blending it with 20 g to 60 g of conventional putty and applying on wall by adapting conventional practices,d) Advance cement matrix based material for plastering the X-ray room by taking 100 g-600 g of tailored shielding powder and blending it with 10 g to 50 g of conventional cement and applying on wall by adapting conventional practices,e) Advance phosphatic matrix based material for plastering the X-ray room by taking 100 g-600 g of tailored shielding powder and blending it with 10 ml to 50 ml of conventional orthophosphoric acid or sodium hexametaphosphate and applying on wall by adapting conventional practices, andf) also the appropriate physico-chemical consolidation and or densification of red mud by using unique gravity fractionalization of red mud or digested red mud, advanced or conventional matrix helps in obtaining functional radiation shielding material. A novel process which comprises digesting of 100 g-600 g of Red mud with 80 g-300 g of crushed citrus peel waste, in the temperature range of 30° C.-90° C. for a period of 2-6 hours to obtain digested nano gel material. A novel process which comprises further drying of digested nano gel material so obtained in an air oven for duration of 2-3 hours in the temperature range of 100° C.-110° C. A novel process in which the above dried nano gel material was then grinded to obtain the fine “tailored shielding powder” for making functional shielding materials using advanced and conventional matrixes. A novel process in which for obtaining heat resistance properties in the shielding material using “Advanced geo polymer matrix” by taking 100 g-600 g of tailored shielding powder and mixing it with ground powder of 10 g-60 g fly ash, 2 g-8 g sodium hydroxide and 1 g-4 g sodium silicate and 4 ml-16 ml of water and the material so obtained was compacted in the form of tiles of dimension 10 cm×10 cm×5 mm at a compaction pressure of 100-200 kg/cm2. A novel process in which for obtaining flexible and moldable properties in the in the shielding material using “Advance geopolymeric-polymeric matrix” by taking 100 g-600 g of tailored shielding powder and mixing it firstly with ground powder of 1 g-6 g fly ash, 1 g-2 g sodium hydroxide and 0.5 g-1 g sodium silicate and 4 ml-10 ml of water and followed by blending with 150 g to 650 g of Silicone rubber or 150 g to 650 g of PDMS and curing the material in the mold of desired dimension in the temperature range of 30 to 60 degree centigrade for a period ranging from 24 hours to 30 minutes for obtaining the advanced flexible and moldable shielding material. A novel process in which Advance putty matrix based shielding material for plastering the X-ray room by taking 100 g-600 g of tailored shielding powder and blending it with 20 g to 60 g of conventional putty and applying on wall by adapting conventional practices. A novel process in which Advance cement matrix based shielding material for plastering the X-ray room is developed by taking 100 g-600 g of tailored shielding powder and blending it with 10 g to 50 g of Conventional cement and applying on wall by adapting conventional practices. A novel process in which Advance phosphatic matrix based shielding material for plastering the X-ray room is developed by taking 100 g-600 g of tailored shielding powder and blending it with 10 ml to 50 ml of conventional ortho phosphoric acid or sodium hexametaphosphate and applying on wall by adapting conventional practices. A novel process in which the appropriate physico-chemical consolidation and or densification of red mud using advanced or conventional matrix helps in obtaining functional radiation shielding material. The novel and non-obvious inventive step in the present invention involves simultaneous and synergistic chemical reactions of various mineralogical and chemical compounds hematite, anatse, rutile, gibbsite and cancraite of red mud with complementary various chemical compounds present in orange peel waste namely cellulose, hemicellulose, pectin and especially citric acid to form nano gel material to obtain the fine “tailored shielding powder”. The novel and non-obvious inventive step in the present invention is the tailored shielding powder so obtained and is having multi shielding phases due to presence of multi elemental Fe, FeO, Fe2O3, TiO2, Ti, Al(OH), SiO2. The novel and non-obvious inventive step in the present invention is the tailored shielding powder so obtained is possesses particle ranging from micron to nano size. The novel and non-obvious inventive step in the present invention is chemical reaction among “tailored shielding powder” and various constituents of novel matrixes enabling homogeneous radiation shielding matrix with desired functionality. The other novel and non-obvious inventive aspect in present invention is to provide advanced functional radiation shielding materials which are devoid of conventionally used toxic lead, barium compound and hematite ore. The other novel and non-obvious inventive step in present invention is to obtain desired homogeneous shielding matrix by chemically designed and mineralogical formulated compositions using various complementary precursors present in red mud and various constituents of novel matrixes. The other novel and non-obvious inventive aspect in present invention is the novel approach of making functional shielding material utilizing novel matrixes. The novel matrixes involved are 1—Advanced Geopolymer matrix, 2—Advanced geo polymeric polymeric matrix, 3—Advanced putty and cement matrix, 4—Advance phosphatic material based matrix, 5—Apart from these novel matrixes the material is also compatible with conventional matrixes, however with the limited functionality as against novel matrixes. The other novel and non-obvious inventive aspect in present invention is the development of simple, highly energy efficient, environmental friendly and the cost effective process enabling wide spread utilization of developed material for broad application spectrum ranging from diagnostic radiation installations such as diagnostic X-ray room to CT scanner room etc. The other novel and non-obvious inventive aspect in present invention simple as it involves only physico-chemical and mechanical processing of red mud with novel matrix and obviates the need of sintering of red mud at high temperature using various additives like barium sulphate and carbon source etc. The other novel and non-obvious inventive aspect in present invention is independent of use of conventional pure polymeric, ceramic or cementations matrixes. The other novel and non-obvious inventive aspect in present invention is development of functional shielding materials possessing a) heat resistance, b) Fire resistance, c) flexibility and moldability aspects. Accordingly, present invention provides an advanced non-toxic Red Mud based functional radiation shielding materials which comprises; a) 55.6 wt %-66.7 wt % of Red mud; b) 44.4 wt %-33.3 wt % of crushed citrus peel waste. In an embodiment, an advanced non-toxic Red Mud based functional radiation shielding materials (85.47 wt %-87.20 wt %) further comprises fly ash in the range of 8.54 wt %-8.72 wt %, sodium hydroxide in the range of 1.70 wt %-1.16 wt %, sodium silicate in the range of 0.85 wt %-0.581 wt % and water in the range of 3.41 wt %-2.32 wt % to obtain Heat resistant properties of the shielding material. In further embodiment an advanced non-toxic Red Mud based functional radiation shielding materials is further comprises Silicone rubber in the range of 58.47 wt %-51.22 wt % or poly di-methyl siloxane (PDMS) in the range of 58.47 wt %-51.22 wt % to obtain flexible and moldable properties of the shielding material. In yet another embodiment, an advanced non-toxic Red Mud based functional radiation shielding materials (83.4 wt %-90.90 wt %) further comprises either putty in the range of 16.6 wt %-9.10 wt % of or cement in the range of 9.1 wt %-7.7 wt % or ortho phosphoric acid in the range of 9.1 wt %-7.7 wt % of or sodium hexametaphosphate in the range of 9.1 wt %-7.7 wt % for plastering the room for X-ray shielding. In yet another embodiment, a process for manufacturing of an advanced non-toxic Red Mud based functional radiation shielding materials comprises; a. digesting 55.6 wt %-66.7 wt % of Red mud with 44.4 wt %-33.3 wt % of crushed citrus peel waste, in the temperature range of 30° C.-90° C. for a period of 2-6 hours to form a nano gel material; b. the said nano gel is dried in an air oven for the duration of 2-3 hours in the temperature range of 100° C.-110° C. and grinded to make “tailored shielding powder”; c. the said tailored shielding powder is mixed with ground powder of 8.54 wt %-8.72 wt % of fly ash, 1.70 wt %-1.16 wt % of sodium hydroxide, 0.85 wt %-0.581 wt % of sodium silicate and 3.41 wt %-2.32 wt % of water to obtain Advanced geo polymer matrix. d. the said tailored shielding powder is optionally mixed with 0.39 wt %-0.472 wt % of fly ash, 0.39 wt %-0.157 wt % of sodium hydroxide, 0.2 wt %-0.07 wt % of sodium silicate and 1.55 wt %-0.788 wt % of water and followed by blending with 58.47 wt %-51.22 wt % of Silicone rubber or 58.47 wt %-51.22 wt % of PDMS to obtain ‘Advance geopolymeric-polymeric matrix’. In yet another embodiment a process for manufacturing of an advanced non-toxic Red Mud based functional radiation shielding materials wherein an Advanced geo polymer matrix so obtained is compacted in the form of tiles of dimension 10 cm×10 cm×5 mm at a compaction pressure of 100-200 kg/cm2. In yet another embodiment, a process for manufacturing of an advanced non-toxic Red Mud based functional radiation shielding materials wherein Advance geopolymeric-polymeric matrix is cured in the mold of desired dimension in the temperature range of 30 to 60 degree centigrade for a period ranging from 24 hours to 30 minutes for obtaining the advanced flexible and moldable shielding material. In yet another embodiment, a process for manufacturing of an advanced non-toxic Red Mud based functional radiation shielding materials wherein Advance putty matrix is made for plastering the X-ray room by taking tailored shielding powder and blending it with conventional putty. In yet another embodiment, a process for manufacturing of an advanced non-toxic Red Mud based functional radiation shielding materials wherein advance cement matrix is made for plastering the X-ray room by taking of tailored shielding powder and blending it with of Conventional cement. In yet another embodiment, a process for manufacturing of an advanced non-toxic Red Mud based functional radiation shielding materials wherein Advance phosphatic matrix is made for plastering the X-ray room by taking tailored shielding powder and blending it with conventional ortho phosphoric acid or sodium hexametaphosphate. The following examples are given by way of illustration of the working of the invention in actual practice and therefore should not be construed to limit the scope of the present invention in any way. For making ““Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like “Advanced geo polymer matrix” for obtaining heat resistance properties in the shielding material, comprises of digesting 100 g of Red mud with 80 g of crushed orange peel waste, in the temperature of 30° C. for a period of 2 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 2 hours at the temperature of 100° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 100 g of tailored shielding powder was then mixed with 10 g fly ash, 2 g sodium hydroxide, 1 g sodium silicate and 4 ml of water, the material so obtained was compacted in the form of tiles of dimension 10 cm×10 cm×5 mm at a compaction pressure of 100 kg/cm2. The X-ray radiation shielding attenuation properties of developed sample having thickness 5 mm were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp X-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X ray and the % attenuation was found to be 80. The density of the tile is found to be 2.68 g/cm3. The impact strength of the sample was found to be 0.026 kgfm·cm−1 and water absorption in the range of 18.0%. For making Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like “Advanced geo polymer matrix” for obtaining heat resistance properties in the shielding material, comprises of digesting 600 g of Red mud with 300 g of crushed orange peel waste, in the temperature of 90° C. for a period of 6 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 2 hours at the temperature of 110° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 600 g of tailored shielding powder was then mixed with 60 g fly ash, 8 g sodium hydroxide, 4 g sodium silicate and 4 ml of water. The material so obtained was compacted in the form of tiles of dimension 10 cm×10 cm×5 mm at a compaction pressure of 200 kg/cm2. The X-ray radiation shielding attenuation properties of developed sample having thickness 5 mm were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp X-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X-ray and the % attenuation was found to be 85. The density of the tile is found to be 2.88 g/cm3. The impact strength of the sample was found to be 0.029 kgfm·cm−1 and water absorption in the range of 17.0%. For making Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like “Advanced geo polymer polymer matrix” for obtaining for obtaining flexible and moldable properties in the shielding material, comprises of digesting 100 g of Red mud with 80 g of crushed orange peel waste, in the temperature of 30° C. for a period of 2 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 2 hours at the temperature of 100° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 100 g of tailored shielding powder was then mixed with 100 g of tailored shielding powder and mixing it firstly with ground powder of 1 g fly ash, 1 g sodium hydroxide and 0.5 g sodium silicate and 4 ml of water and followed by blending with 150 g of Silicone rubber or 150 g of PDMS and curing the material in the mold of dimension 15 cm×15 cm×5 mm at the temperature of 30 degree centigrade for a period for 30 minutes for obtaining the advanced flexible and moldable shielding material. The X-ray radiation shielding attenuation properties of developed sample having thickness 5 mm were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp X-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X-ray and the % attenuation was found to be 83. The density of the material was found to be 2.66 g/cm3. For making Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like “Advanced geo polymer polymer matrix” for obtaining for obtaining flexible and moldable properties in the shielding material, comprises of digesting 600 g of Red mud with 300 g of crushed orange peel waste, in the temperature of 90° C. for a period of 6 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 2 hours at the temperature of 100° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 600 g of tailored shielding powder was then mixed with 6 g fly ash, 2 g sodium hydroxide and 1 g sodium silicate and 10 ml of water and followed by blending with 650 g of PDMS and curing the material in the mold of dimension 15 cm×15 cm 5 mm dimension at the temperature of 60 degree centigrade for a period of 30 minutes for obtaining the advanced flexible and moldable shielding material. The X-ray radiation shielding attenuation properties of developed sample having thickness 5 mm were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp X-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X ray and the % attenuation was found to be 88. The density of the material was found to be 2.99 g/cm3. For making “Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like Advance putty matrix for plastering the X-ray room, comprises of digesting 100 g of Red mud with 80 g of crushed orange peel waste, in the temperature of 30° C. for a period of 2 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 2 hours at the temperature of 100° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 100 g tailored shielding powder was blended with 20 g of conventional putty and applying on wall by adapting conventional practices. The X-ray radiation shielding attenuation properties of developed sample were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp x-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X ray and the % attenuation was found to be 84. For making “Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like Advance putty matrix for plastering the X-ray room, comprises of digesting 600 g of Red mud with 300 g of crushed orange peel waste, in the temperature of 90° C. for a period of 6 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 2 hours at the temperature of 100° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 600 g tailored shielding powder was blended with 60 g of conventional putty and applying on wall by adapting conventional practices. The X-ray radiation shielding attenuation properties of developed sample were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp X-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X ray and the % attenuation was found to be 89. For making Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like cement matrix based material for plastering the X-ray room, comprises of digesting 100 g of Red mud with 80 g of crushed orange peel waste, in the temperature of 30° C. for a period of 2 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 2 hours at the temperature of 100° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 100 g tailored shielding powder was blended with 10 g of conventional cement and applying on wall by adapting conventional practices. The X-ray radiation shielding attenuation properties of developed sample were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp X-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X ray and the % attenuation was found to be 84. For making “Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like cement matrix based material for plastering the X-ray room, comprises of digesting 600 g of Red mud with 300 g of crushed orange peel waste, in the temperature of 90° C. for a period of 6 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 3 hours at the temperature of 110° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 100 g tailored shielding powder was blended with 50 g of conventional cement and applying on wall by adapting conventional practices. The X-ray radiation shielding attenuation properties of developed sample were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp X-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X ray and the % attenuation was found to be 88. For making “Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like advance phosphatic matrix based material for plastering the X-ray room, comprises of digesting 100 g of red mud with 80 g of crushed citrus peel waste, in the temperature of 30° C. for a period of 2 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 2 hours at the temperature of 100° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 100 g tailored shielding powder was blended with 10 ml of conventional ortho phosphoric acid and applying on wall by adapting conventional practices. The X-ray radiation shielding attenuation properties of developed sample were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp X-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X ray and the % attenuation was found to be 86. For making “Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like “Advanced geo polymer matrix” for obtaining heat resistance properties in the shielding material, comprises of digesting 100 g of Red mud with 50 g of crushed lemon peel waste, in the temperature of 30° C. for a period of 1 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 2 hours at the temperature of 100° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 100 g of tailored shielding powder was then mixed with 10 g fly ash, 2 g sodium hydroxide, 1 g sodium silicate and 4 ml of water. The material so obtained was compacted in the form of tiles of dimension 10 cm×10 cm×5 mm at a compaction pressure of 100 kg/cm2. The X-ray radiation shielding attenuation properties of developed sample having thickness 5 mm were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp X-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X ray and the % attenuation was found to be 90. The density of the tile is found to be 2.88 g/cm3. The impact strength of the sample was found to be 0.029 kgfm·cm−1 and water absorption in the range of 16.0%. For making Advanced non-toxic Lead, Barium and hematite ore free, Red Mud based “Nano” gel type material useful for making, functional radiation shielding materials utilizing appropriate novel matrixes like “Advanced geo polymer matrix” for obtaining heat resistance properties in the shielding material, comprises of digesting 500 g of Red mud with 300 g of crushed grapefruit peel waste, in the temperature of 90° C. for a period of 8 hours. The digested nano gel material so obtained was further dried in an air oven for duration of 2 hours at the temperature of 110° C. and which was then grinded to obtain the fine “tailored shielding powder”. Further, 600 g of tailored shielding powder was then mixed with 60 g fly ash, 8 g sodium hydroxide, 4 g sodium silicate and 4 ml of water. The material so obtained was compacted in the form of tiles of dimension 10 cm×10 cm×5 mm at a compaction pressure of 200 kg/cm2. The X-ray radiation shielding attenuation properties of developed sample having thickness 5 mm were studied using Nomex multimeter from PTW. The X-ray machine used for testing is DX 525—a 500 mA, 125 Kvp X-ray machine of Wipro GE make. The evaluation was done at 100 Kvp of X-ray and the % attenuation was found to be 78. The density of the tile is found to be 2.58 g/cm3. The impact strength of the sample was found to be 0.023 kgfm·cm−1 and water absorption in the range of 19.0%. The Main Advantages of the Present Invention are: The developed novel process for making involves “ADVANCED NON-TOXIC LEAD, BARIUM AND HEMATITE ORE FREE, RED MUD BASED “NANO” GEL TYPE MATERIAL USEFUL FOR MAKING, FUNCTIONAL RADIATION SHIELDING MATERIALS UTILIZING APPROPRIATE NOVEL MATRIXES AND THE PROCESS THERE OF”, is advantageous due to the following reasons:— a) The advantage of the developed novel process is to ensure total utilization of two industrial waste red mud and citrus fruit peel waste for making highly value added material. b) The advantage of the novel process is it's highly energy efficient process as the novel process involves reaction of red mud with citrus peel waste at the temperature of 30 to 80° C. of as it does not involves sintering of red mud based compound in the range of the temperature 900-1300° C.c) The advantage of the novel process involves designing of raw materials and processing parameters, enabling synergistic and simultaneous chemical reactions among the various reactants which enable to obtain micron to nano tailored shielding precursor for obtaining non-toxic radiation shielding material.d) The developed shielding precursor is compatible with in advanced as well as all the conventional shielding matrixes.e) Other advantage of the developed novel process is to convert a red waste material in to a highly value added advanced non-toxic radiation shielding materials possessing homogeneous radiation shielding matrix.f) Other advantage of the developed novel process is to ensure total utilization of two industrial waste red mud and citrus peel waste for making highly value added material.g) Other advantage of the developed novel process is to utilize and save the cost of costly chemicals inherently present in red mud and orange peel waste otherwise required for making advanced non-toxic radiation shielding materials.h) Other advantage of the developed novel process is to solve the disposal problem of both the waste and to save the environment all over the world and thus the process is environment friendly.i) Materials helps in obtaining homogeneous radiation shielding material which is one of the important characteristic of shielding materials which lacks to certain extend in conventional shielding materials. |
|
056152450 | abstract | A monochromator for radiant X-rays is composed of a first crystal which has a first surface of incidence having a concave letter V-shaped groove and cooling means for flowing a cooling material behind the first surface of incidence along the letter V-shaped groove, and a second crystal which has a second surface of incidence having a letter V-shaped convex. A parallel pencil of X-rays which impinges on the first surface of incidence elongates to a half-ellipse on the first surface of incidence and reflects in parallel therefrom to the second surface of incidence. Then, a pencil of emissive X-rays having the same size as the initial parallel pencil of X-rays exits the second surface of incidence to become useful light. The monochromator for radiant X-rays which has a high cooling efficiency, is easy to adjust, provides a pencil of emissive X-rays stably and highly accurately. The monochromator is easy to use and economical, and allows easy maintenance. |
description | The present application claims the benefit of U.S. Provisional Patent Application No. 60/859,748, entitled “High-Resolution, Low-Distortion and High-Efficiency Optical Coupling In Detection System Of Electron Beam Apparatus”, filed Nov. 17, 2006, by inventors David Walker, Salam Harb, Vassil Spasov, David Stites, Izzy Lewis, and Marian Mankos, the disclosure of which is hereby incorporated by reference. 1. Field of the Invention The present invention relates to apparatus and methods for inspection or review of substrates, such as, for example, semiconductor wafers and masks. 2. Description of the Background Art Emission electron microscopes include low energy emission microscopes (LEEM), photo-electron emission microscopes (PEEM), and secondary electron emission microscopes (SEEM). LEEM imaging systems detect electrons reflecting or mirroring off of the surface of a flat substrate. PEEM imaging systems detect photoelectrons emitted from a surface of a substrate. SEEM imaging systems detect secondary electrons emitted from a surface of a substrate It is desirable to improve emission electron microscope systems, including those utilized for the automated inspection or review of substrate surfaces. More particularly, it is desirable to improve pixel alignment and image resolution in emission electron microscope systems. One embodiment relates to an apparatus for inspecting a substrate using charged particles. The apparatus includes an illumination subsystem, an objective subsystem, a projection subsystem, and a beam separator interconnecting those subsystems. The apparatus further includes a detection system which includes a scintillating screen, a detector array, and an optical coupling apparatus positioned therebetween. The optical coupling apparatus includes both refractive and reflective elements. Other embodiments and features are also disclosed. FIG. 1 is a schematic diagram depicting an apparatus 100 for inspecting a substrate using charged particles in accordance with an embodiment of the invention. The apparatus 100 includes illumination electron-optics 102, objective electron-optics 104, projection electron-optics 106, and a beam separator 108. The beam separator 108 is coupled to and interconnects the illumination electron-optics 102, the objective electron-optics 104, and the projection electron-optics 106. For simplicity, the electron-optics may be referred to as simply “optics,” though they operate on electrons. The illumination optics 102 is configured to receive and collimate charged particles from a charged-particle source. In a preferred embodiment, the charged particles comprise electrons, and the source comprises an electron gun 110. In a preferred embodiment, the illumination optics 102 comprises an arrangement of magnetic and/or electrostatic lenses configured to focus the charged particles from the source so as to generate an incident charged-particle beam. The specific details of the arrangement of lenses depend on specific parameters of the apparatus and may be determined by one of skill in the pertinent art. The beam separator 108 is configured to receive the incident beam from the illumination optics 102 and to bend or deflect the incident beam by 90 degrees into the objective optics 104. In a preferred embodiment, the beam separator 108 comprises a magnetic prism array including a central magnetic section, an inner magnetic section outside the central section, and an outer magnetic section outside the inner section. One specific embodiment of the beam separator 108 is disclosed in U.S. Pat. No. 6,878,937, entitled “Prism array for electron beam inspection and defect review,” by inventor Marian Mankos. The objective optics 104 is configured to receive the incident beam from the beam separator 108 and to decelerate and focus the incident beam onto the substrate 112. The incident beam onto the substrate 108 causes reflection and/or emission of a scattered beam of charged particles. The scattered beam comprises a two-dimensional image of the illuminated area of the substrate 112. The objective optics 104 is further configured to re-accelerate the scattered beam and to refocus the two-dimensional image of the substrate area. In a preferred embodiment, the objective optics 104 comprises an arrangement of magnetic and/or electrostatic lenses configured to focus and decelerate the incident beam to the substrate 112 and to retrieve and re-accelerate the scattered beam from the substrate 112. In one implementation, to accomplish the deceleration and re-acceleration, the substrate may be maintained at a negative high voltage potential close to that of the incident beam source while the objective optics 104 is at ground potential. In an alternative arrangement, the substrate (and source) may be at ground potential and the objective optics (and other components) at a high voltage. Further specific details of the arrangement of lenses depend on specific parameters of the apparatus and may be determined by one of skill in the pertinent art. The beam separator 108 is configured to receive the scattered beam from the objective optics 104 and to bend the scattered beam towards the projection optics 106. The projection optics 106 is configured to receive the scattered beam from the beam separator 108 and to magnify and project the scattered beam onto a detection system 116. Direct Detection of Electrons by Detector Array In one implementation (not illustrated), the detection system 116 may include charged-coupled device (CCD) array in the vacuum environment of the apparatus 100 so as to directly receive the projected electrons. Unfortunately, such an implementation has problems with radiation damage to the CCD array. Also, the sensor gain in converting incident electrons to electrons in the well is very large. This limits the amount of beam current, and thus limits the speed of the detection system. Detection Using Scintillating Screen and Detector Array To avoid such problems, in accordance with an embodiment of the invention, the detection system 116 may include a phosphorescent or scintillating screen 118. The screen 118 generates a light-based or optical image of the projected electrons. The optical image may then be transferred to a camera (not depicted in FIG. 1) or detector (sensor) array 120 (shown in FIG. 1). Preferably, the detector array may be a charge-coupled device (CCD) array which is part of a time-delay integration (TDI) detection system. Coupling the Scintillating Screen to the Detector Array The optical image generated from the projected electrons by the scintillating screen 118 needs to be transferred to the detector array 120 by some type of coupling apparatus 202. FIG. 2 is a high-level diagram illustrating a detection system 116 including an optical coupling apparatus (relay optics) 202 for coupling a scintillating screen 118 to a detector array 120. One type of optical coupling apparatus 202 that may be used is bonded fiber optics. This requires large, expensive fiber optics and would involve the difficult task of aligning the fiber optics to the TDI (CCD) pixels. In addition, the optical fibers typically degrade the image resolution. Another type of optical coupling apparatus 202 that may be used is a refractive optical system which may include multiple refractive optical elements. Such a refractive optical system would be complex to manufacture with many refractive elements if high resolution and low distortion are to be achieved. Furthermore, such a refractive optical system has the disadvantage of typically achieving only a relatively low numerical aperture (NA). Optical Coupling Apparatus with Both Refractive and Reflective Elements In accordance with an embodiment of the invention, the optical coupling apparatus 202 includes both refractive and reflective elements. One embodiment of such a refractive/reflective (catadioptric) optical coupling apparatus is described further below in relation to FIGS. 3 and 4. FIG. 3 is a side (cross-sectional) view and FIG. 4 is a three-dimensional (perspective) view of an apparatus 202 for optically coupling a scintillating screen 118 to a detector array 120 in accordance with an embodiment of the invention. The scintillating screen 118 may be positioned at one end of an electrically conductive tube (not depicted) which is insulated from electrical ground. The tube may be used as a Faraday cup for calibration purposes. While the scintillating screen 118 is in a vacuum environment so as to receive the projected electrons, a transparent window and vacuum seal (not depicted) may be used to separate the vacuum environment from the optical coupling apparatus 202. The scintillating screen 118 may be, for example, a YAG (yttrium aluminum garnet) scintillator, and the detector array 120 may be, for example, a CCD array which is part of a time-delay integration (TDI) detection system. The YAG scintillator may be, for example, one millimeter thick, and may be coated with ITO (indium tin oxide) or aluminum on its front side (facing the projection optics 106). An ITO layer provides conductivity so that the YAG does not build up electrical charge. An aluminum layer provides conductivity and also increases the light collection efficiency by reflecting the light towards the optical coupling apparatus (relay optics) 202. In accordance with an embodiment of the invention, the optical coupling apparatus 202 includes both refractive and reflective elements. As shown, the refractive elements may include a first prism 302, a first lens 304, a second lens 306, a third lens 308, and a second prism 312. The lenses and prisms may be constructed of different types of glass. The reflective elements may include a mirror 310. In addition, the back surface of the prisms 302 and 312 may also serve as reflective elements. The illustrated embodiment provides 1× (one times) magnification and achieves an advantageously compact design by folding the light with the reflective elements such that the light is passed twice through each refractive element. Light rays are shown in FIG. 3 from three points originating on the screen 118. The light rays are shown as they pass through the first prism 302 and then a first time through each of the three lenses (304, 306, and 308). The light rays are reflected by the mirror (310) such that they pass a second time (in reverse order) through each of the three lenses (308, 306, and 304). The light rays then pass through the second prism 312 such that they are focused onto three corresponding points on the detector array 120. The refractive/reflective optical coupling apparatus described above in relation to FIGS. 3 and 4 provides at least the following advantages. (i) It provides a high-resolution image of the light from the scintillating screen 118 onto the detector array 120. The coupling apparatus described herein may be implemented to achieve a resolution of eight microns or less. (ii) It further achieves sufficiently small distortion so as to prevent blurring of the image on the detector array 120; in other words, the image on the detector array 120 is sharp. The coupling apparatus described herein may be implemented to achieve a distortion of less than 0.1%. (iii) Additionally, it provides a high numerical aperture which is required for high light collection efficiency to allow high-speed inspection. The coupling apparatus described herein may be implemented to achieve a numerical aperture of 0.4 or more. Continuous data collection during inspection of a semiconductor wafer or other substrate may be achieved by synchronizing the stage velocity and the clocking of the TDI detection system. An optional feature that may be implemented is an intensity adjustment aperture. Such an aperture may be positioned, for example, in front of the mirror 310 of the optical coupling apparatus. The size of the opening of the aperture may then be controllably adjusted. The larger the opening, the greater the intensity detected at the detector array 120. The smaller the opening, the less the intensity detected at the detector array 120. Due to the design of the optical coupling apparatus, the intensity change would be applied uniformly or relatively uniformly across the detector array. Such an intensity adjusting aperture would not provide uniform intensity changes if fiber optic coupling were used, for example. FIG. 5 is a through focus spot diagram based on the optical coupling apparatus using refractive and reflective elements in accordance with an embodiment of the invention. The through focus spot diagram shows a simulated surface image at the CCD array. As seen from FIG. 5, the optical coupling apparatus couples the scintillating screen 118 to the detector array 120 with a low distortion. The above-described diagrams are not necessarily to scale and are intended be illustrative and not limiting to a particular implementation. The above-described invention may be used in an automatic inspection or review system and applied to the inspection or review of optical or X-ray masks and similar substrates in a production environment. In the above description, numerous specific details are given to provide a thorough understanding of embodiments of the invention. However, the above description of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed. One skilled in the relevant art will recognize that the invention can be practiced without one or more of the specific details, or with other methods, components, etc. In other instances, well-known structures or operations are not shown or described in detail to avoid obscuring aspects of the invention. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the invention is to be determined by the following claims, which are to be construed in accordance with established doctrines of claim interpretation. |
|
041982720 | summary | BACKGROUND OF THE INVENTION This invention relates to fuel sub-assemblies for liquid metal cooled fast breeder nuclear reactors. A fuel assembly for a liquid metal cooled fast breeder nuclear reactor comprises a bundle of spaced fuel pins within a tubular wrapper or sleeve through which liquid metal coolant can be flowed in heat exchange with the fuel pins. The wrapper is extended at one end by a tubular neutron shield of massive steel and the other end, hereinafter referred to as the lower end, has a spike extension whereby the sub-assembly can be located by plugging into a support structure and arranged with other sub-assemblies to upstand in side-by-side array to form a fuel assembly. Hitherto, it has been proposed, see for example U.S. Pat. No. 3,383,287, to arrange the fuel assembly of a liquid metal cooled fast breeder nuclear reactor in a plurality of groups of sub-assemblies and for the sub-assemblies of each group to be biassed inwardly towards the centre of the group so that the sub-assemblies of the group lean on each other or on a central support member. Whilst such a system has the advantage of elimination of vibrational movement of the sub-assemblies due to coolant flow it is now recommended that the fuel assembly of a liquid metal cooled fast breeder nuclear reactor should be restrained as a whole from the periphery, that is, the fuel sub-assemblies of the fuel assembly should be centripetally urged together in parallel vertical array. For a fuel assembly of this kind some provision should be made to allow lateral displacement of the wrappers of the sub-assemblies relative to the spike extension in order to relieve stresses throughout the fuel assembly. Accordingly it is an object of the present invention to provide a construction of fuel sub-assembly which has sufficient flexibility to enable some lateral movement of the wrapper relative to the spike extension. SUMMARY OF THE INVENTION According to the present invention in a fuel sub-assembly for a liquid metal cooled fast breeder nuclear reactor comprising a bundle of spaced fuel pins within a tubular wrapper having a spike extension for plugging into fuel assembly support structure the wrapper is pivotally connected to the spike extension. The invention also resides in a liquid metal cooled fast breeder nuclear reactor having a fuel assembly comprising a plurality of closely packed fuel sub-assemblies upstanding in side-by-side array on a support structure and wherein each sub-assembly comprises a bundle of spaced fuel pins within a tubular wrapper having a spike extension for plugging into the support structure and wherein the wrapper is pivotally connected to the spike extension. The invention provides that lateral displacement of individual fuel pin containing wrappers to accommodate dimensional changes within the fuel assembly is effected by movement of each wrapper relative to its spike extension. The spike extension of a fuel sub-assembly may conveniently comprise a sleeve providing axially spaced spigot surfaces for engaging vertically spaced sockets in a fuel assembly support structure the wrapper being tied to the sleeve by a resilient tie member extending through the sleeve and having ends encastered, that is fixed to the wrapper and the sleeve. In a preferred construcion of fuel sub-assembly the end of the tubular wrapper which is connected to the sleeve is arranged to enclose an end region of the sleeve with annular clearance therebetween and the sleeve carries resilient split rings for sealing against liquid metal coolant flow between the wrapper and the sleeve. |
summary | ||
summary | ||
abstract | A method for preparing a specimen for application of microanalysis thereto includes forming an initial conductive layer over a defined area of interest on a semiconductor substrate, the initial conductive layer formed through an electron beam deposition process. A volume of substrate material surrounding the area of interest is removed, thereby forming the specimen, including said area of interest and said initial conductive layer over the area of interest. The specimen is then removed from the bulk substrate material. |
|
050323482 | claims | 1. A stowage rack for dry transport of nuclear fuel elements of elongated shape, comprising a plurality of elongated, parallel, adjacent prismatic cells having walls fulfilling the functions of mechanical strength, thermal conductivity and neutron absorption, and formed from first and second sets of materials, said first set of materials being selected from the group consisting of steel, aluminum, copper, magnesium and alloys thereof, said first set of materials provided in the form of elongated sections stacked in successive layers, each said layer lying in a plane perpendicular to the axis of said cells, the sections of a particular layer being equidistant and oriented in the same direction according to the direction of the axis of the cells to form cell walls of predetermined thickness, the sections of two successive layers being oriented in different directions, said second set of materials containing at least one neutron absorber selected from the group consisting of B, Gd, Hf, Cd, In and Li, and said second set of materials provided in the form of elongated sections which are arranged within the thickness of the cell walls, parallel or perpendicular to the axis of the cells, wherein said materials forming said walls are formed of identical bent sections having edges parallel with each other and parallel with the axis of the cells. said first set of materials being selected from the group consisting of steel, aluminum, copper, magnesium and alloys thereof, and said second set of materials containing at least one neutron absorber selected from the group consisting of B, Gd, Hf, Cd, In and Li, said first and second sets of materials being provided in elongated sections of substantially identical shape, which are stacked in a series of layers, each layer lying in a plane perpendicular to the axis of the cells, the sections of a particular layer being equidistant and oriented in the same direction according to the direction of the axis of the cells to form cell walls, the sections of two successive layers being oriented in different directions, said first and second sets of materials forming said walls being formed of identical bent sections having edges parallel with each other and parallel with the axis of the cells. said first set of materials being selected from the group consisting of steel, aluminum, copper, magnesium and alloys thereof, said first set of materials provided in the form of elongated sections stacked in successive layers, each said layer lying in a plane perpendicular to the axis of said cells, the sections of a particular layer being equidistant and oriented in the same direction according to the direction of the axis of the cells to form cell walls of predetermined thickness, the sections of two successive layers being oriented in different directions, said second set of materials containing at least one neutron absorber selected from the group consisting of B, Gd, Hf, Cd, In and Li, and said second set of materials provided in the form of elongated sections which are arranged within the thickness of the cell walls, parallel or perpendicular to the axis of the cells, wherein said first set of materials forming said walls is in the form of elongated, extruded flat bars containing tubular receptacle adapted to receive said second set of materials in rod or wire form. 2. A stowage rack for dry transport of nuclear fuel elements of elongated shape, comprising a plurality of elongated, parallel, adjacent, prismatic cells having walls fulfilling the functions of mechanical strength, thermal conductivity and neutron absorption, and formed of first and second sets of materials, 3. A stowage rack for dry transport of nuclear fuel elements of elongated shape, comprising a plurality of elongated, parallel, adjacent prismatic cells having walls fulfilling the functions of mechanical strength, thermal conductivity and neuron absorption, and formed from first and second sets of materials, 4. The rack of claims 1, 2 or 3, wherein said first and second set of materials forming said walls are rigidly connected together by joining means to maintain the rigidity and cohesion of the stack. 5. The rack of claim 4, wherein said joining means are pins or tie rods. 6. The rack of claims 1, 2 or 3, wherein said first and second sets of materials forming said walls are provided with positioning notches which interact to maintain the cohesion, rigidity and compactness of the stack. 7. The rack of claims 1 or 3, wherein said first set of materials forming said walls is in the form of elements including openings to house said second set of materials in the form of rods or wires, parallel with the axis of the cells. 8. The rack of claims 1 or 3, wherein said second set of materials is in the form of a wire of aluminum-boron master alloy. 9. The rack of claims 1, 2 or 3, wherein at least one section of said second set of materials comprises a plurality of abutted subsections. 10. The rack of claim 2, wherein a layer of materials of said first set is stacked alternately with a layer of substantially identically shaped materials of said second set. |
044477333 | abstract | A package for radioactive material which comprises a radiation-absorbing vessel having a plug-type inner cover sealingly engaging this vessel and an outer security cover overlying the massive plug-type cover and defining a clearance therewith in which gas can be monitored to detect failure of the seal, this safety cover being sealed to the vessel so that the latter chamber is sealed from the atmosphere. According to the invention, this chamber is sealed with gas at a superatmospheric pressure which is also above the pressure within the vessel and the pressure of the chamber is monitored, a drop in pressure signaling a breach either of the seal between the plug-type cover and the interior of the vessel or between the safety cover and the vessel. |
056404344 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Firstly, referring to FIG. 1 which is a diagrammatic view of a miniaturized nuclear reactor 10 utilizing improved fuel channel pressure tube 14 structural members. The entire miniaturized nuclear reactor 10 is composed of a moderator tank having a moderator inlet and a moderator outlet. The fluid contained within the moderator is circulated throughout the moderator tank by the moderator pump and is cooled in the moderator cooler. An additional coolant system to extract heat from and cool the fuel pressure channel tubes through a coolant duct system is composed of a coolant inlet, coolant outlet having a coolant gas fan. The coolant passes through a heat exchanger which has its own closed heat extraction system utilizing a feed water pump to circulate fluid throughout. The heat exchanger extracts the heat from the coolant utilizing the energy to propel a turbine which generates electricity from a generator. Within the heat exchanger system a condenser is positioned. The heat extracted from this system can heat apartment buildings and/or office buildings and/or green houses as well as generate electricity. Secondly, referring to FIG. 2 which is a end perspective view of a miniaturized nuclear reactor 10 utilizing improved fuel channel pressure tube 14 structural member. The calandria tubes 12 are contained within the moderator 20. The miniaturized nuclear reactor 10 has exterior reactor walls 42 with a matrix of interior partitioning walls: the reactor wall interior horizontal 44 and the reactor wall interior vertical 46. Although in the drawing there only shows four moderator 20 compartments, there may be lesser or more moderator compartments 20 by utilizing additional reactor wall interior horizontal 44 and reactor wall interior vertical 46. The calandria tubes 12 are supported within the moderator 20 on the bottom by horizontal interior support pad 22 which is integrally positioned approximately mid-distance within and extending lengthwise throughout the reactor wall interior horizontal 44. The calandria tubes are supported within the moderator 20 on an inner side by a vertical support pad 24 which is integrally positioned approximately mid-distance within and extending lengthwise throughout the reactor wall interior vertical 46. The calandria tubes are supported within the moderator 20 on an angular inner side by a angular support pad 28 which is integrally positioned within extending lengthwise throughout the corner formed between throughout top and bottom of the reactor walls 42. Within the calandria tube 12, a fuel channel pressure tube support 18 is positioned at the bottom upon which the fuel channel pressure tube 14 rests. At a bottom position within the fuel channel pressure tube 14, a fuel bundle support pad 16 is situated upon which rests the fuel bundle 26. Now referring to FIG. 2A which is a front view of the a miniaturized nuclear reactor 10 utilizing improved pressure tube 14 structural members. The calandria tubes 12 are contained within the moderator 20. The miniaturized nuclear reactor 10 has exterior reactor walls 42 with a matrix of interior partitioning walls: the reactor wall interior horizontal 44 and the reactor wall interior vertical 46. Although in the drawing there only shows four moderator 20 compartments, there may be lesser or more moderator compartments 20 by utilizing additional reactor wall interior horizontal 44 and reactor wall interior vertical 46. The calandria tubes 12 are supported within the moderator 20 on the bottom by horizontal interior support pad 22 which is integrally positioned approximately mid-distance within and extending lengthwise throughout the reactor wall interior horizontal 44. The calandria tubes are supported within the moderator 20 on an inner side by a vertical support pad 24 which is integrally positioned approximately mid-distance within and extending lengthwise throughout the reactor wall interior vertical 46. The calandria tubes 14 are supported within the moderator 20 on an angular inner side by a angular support pad 28 which is integrally positioned within extending lengthwise throughout the corner formed between throughout top and bottom of the reactor walls 42. Now referring to FIG. 2B which is an enlarged perspective view of a horizontal interior support pad 22 positioned on reactor wall interior horizontal 44. By resting atop of the horizontal interior support pad 22 on the horizontal interior support pad concave 22D, it holds an upper calandria tube 12 in place as well as holding a lower calandria tube 12 in place at its top by positioning in the upper convex surface of the calandria tube into the horizontal interior support pad concave 22D. The horizontal interior support pad 22 is positioned approximately mid-distance and extends throughout in an interspersed lengthwise fashion of the reactor wall interior horizontal 44. The horizontal interior support pad 22 comprises: horizontal interior support pad proximal end 22A; horizontal interior support pad distal end 22B; horizontal interior support pad groove 22C; and horizontal interior support pad concave 22D. The horizontal interior support pad proximal end 22A is flat and abuts an inner segment of the reactor wall interior horizontal 44. There are two horizontal interior support pad distal ends 22B forming a horizontal interior support pad groove 22C therebetween. Referring to FIG. 2C which is an enlarged front view of an angular support pad 28 affixed to a reactor wall 42. The calandria tubes are supported within the moderator 20 on an angular inner side by a angular support pad 28 which is integrally positioned within extending lengthwise throughout the corner formed between throughout top and bottom of the reactor walls 42. The angular support pad 28 comprises: angular support pad top member 28A and angular support pad bottom member 28B. The angular support pad top member 28A abuts the calandria tube 12 and the angular support pad bottom member 28B is securely affixed within the corner formed between throughout top and bottom of the reactor walls 42. Referring now to FIG. 2D which is an enlarged front view of a vertical support pad 24 positioned in the reactor wall interior vertical 46. By resting on a side of the a vertical support pad 24 on the vertical support pad concave 24D, it holds left calandria tube 12 in place as well as holding a right calandria tube 12 in place at its top by positioning in the upper convex surface of the calandria tube 12 into the vertical support pad concave 24D located on both sides of the vertical support pad 24. The vertical support pad 24 is positioned approximately mid-distance and extends throughout in an interspersed lengthwise fashion of the reactor wall interior vertical 46. The vertical support pad 24 comprises: a vertical support pad proximal end 24A; vertical support pad distal end 24B; and vertical support pad groove 24C. The vertical support pad proximal end 24A is flat and abuts an inner segment of the reactor wall interior vertical 46. There are vertical support pad distal end 24B forming a horizontal interior support pad groove 22C therebetween. The horizontal interior support pad groove 22C wraps around an exterior segment of the reactor wall interior vertical 46. Now referring to FIG. 3 is an enlarged front view of a horizontal exterior support pad 30 affixed upon the bottom interior surface of the reactor wall 42. The horizontal exterior support pad 30 comprises: a horizontal exterior support pad end 30A; a horizontal exterior support pad fastener 30; and a horizontal exterior support pad concave 30C. The calandria tube 12 rests atop of the horizontal exterior support pad 30 within the horizontal exterior support pad concave 30C. The horizontal exterior support pad 30 extends at an approximate mid-position throughout in a lengthwise configuration throughout the moderator 20. Now referring to FIG. 2E is an enlarged front upper left view of a miniaturized nuclear reactor 10 utilizing improved pressure tube 14 structural member, the fuel bundle 40 rests atop of the fuel bundle support pad 16 which rests upon the fuel channel pressure tube 14 which in turn rests atop of the fuel channel pressure tube support pad 18 which rests atop of the calandria tube 12 which rests atop of the calandria support pad 12. The fuel bundle support pad 16 forming a bridge-like support upon which the fuel bundle 40 rests comprises a pair of fuel bundle support pad spacers 16A which are positioned at distal ends of a fuel bundle support pad strap 16B. The fuel channel pressure tube support pad 18 comprises: fuel channel pressure tube pad vertical spacer 18A; fuel channel pressure tube pad end 18B and fuel channel pressure tube pad horizontal spacer 18C. The fuel channel pressure tube pad end 18B is positioned at an obtuse angle to the fuel channel pressure tube pad vertical spacer 18A in order to conform m the interior curvature of the calandria tube 12. The fuel channel pressure tube support pad 18 may extend throughout the length of the calandria tube 12. Referring now to FIG. 4 which is a front view of a second embodiment fuel channel pressure tube 114 exhibiting a plurality of second fuel channel pressure tube compartments 114A arranged around the exterior periphery of the second fuel channel pressure tube 114. The second embodiment second embodiment fuel channel pressure tubes 114 are inserted within the second calandria tube 112. The plurality of second fuel channel pressure tube compartments 114A interlock into the opposingly configured second calandria tube compartments 112A which are positioned about an interior periphery of the second calandria tube 112. Referring to FIG. 4A which is a front view of a second calandria tube 12. There are second calandria tube compartments 12A positioned about an interior periphery of the second calandria tube 12 in and throughout which the second fuel channel pressure tube compartments 14A slide within. Now referring to FIG. 5 and FIG. 5A which are a perspective view and a cross-sectional view of a second fuel channel pressure tube support pad 113 comprising: second fuel channel pressure tube support pad end 113A; second fuel channel pressure tube support pad spacer 113B; second fuel channel pressure tube support pad concave 113C; second fuel channel pressure tube support pad convex 113D; and second fuel channel pressure tube support pad groove 113E. The second fuel channel pressure tube support pad 113 functions to support the fuel channel pressure tube 14 and extends full length and attach to the calandria tube 12 at each end. It is important that the pads are affixed in place. The second fuel channel pressure tube support pad concave 113C and the second fuel channel pressure tube support pad convex 113D have a second fuel channel pressure tube support pad spacer which functions as a spacer therebetween forming second fuel channel pressure tube support pad openings 113F. The second fuel channel pressure tube support pad 113 is interspersed throughout its length with The second fuel channel pressure tube support pad grooves 113E. The second fuel channel pressure tube support pad groove 113E and the second fuel channel pressure tube support pad openings 113F function for circulation of fluid. Referring now to FIG. 6 and FIG. 6A which is a perspective view of an assembled and unassembled, respectively, of a fuel bundle 40 comprising: first fuel bundle proximal end plate 40AA; first fuel bundle proximal end plate fuel element end fastener 40AAA; first fuel bundle proximal end plate port 40AAB; first fuel bundle proximal end plate indent 40AAC; first fuel bundle proximal end plate opening 40AAD; second fuel bundle distal end plate 40BA; second fuel bundle distal end plate fuel element end fastener 40BAA; second fuel bundle distal end plate port 40BAB; second fuel bundle distal end plate indent 40BAC; second fuel bundle distal end plate opening 40BAD; fuel element 40C; fuel bundle support 40D; fuel bundle support proximal end 40DA; fuel bundle support proximal end spacer 40DB; fuel bundle support distal end 40DC; fuel bundle support distal end spacer 40DD; fuel bundle support spacer tube 40DE; and fuel bundle support rod 40DF. The second fuel bundle distal end plate 40BA has a plurality of second fuel bundle distal end plate fuel element end fastener 40BAA which affix a second distal end of fuel elements 40C. The second fuel bundle distal end plate 40BA has a plurality of second fuel bundle distal end plate port 40BAB interspersed throughout and between the second fuel bundle distal end plate fuel element end fasteners 40BAA. The second fuel bundle distal end plate indent 40BAC functions to accept the fuel bundle support nut 40DG therein. The second fuel bundle distal end plate opening 40BAD accepts the fuel bundle support distal end 40DC therethrough. The fuel bundle support 40D has a fuel bundle support proximal end 40DA which passes through first fuel bundle proximal end plate opening 40AAD being secured by fuel bundle support nut 40DG. The fuel bundle support proximal end spacer 40DB functions to form a space between the fuel bundle support 40D and the first fuel bundle proximal end plate 40AA. The fuel bundle support distal end 40DC passes through second fuel bundle proximal end plate opening 40BAD being secured by fuel bundle support nut 40DG. The fuel bundle support distal end spacer 40DD functions to form a space between the fuel bundle support 40D and the second fuel bundle proximal end plate 40BA. Now referring to FIG. 6B which is a perspective view of a first fuel bundle end plate 40AA. Observe the plurality of first fuel bundle proximal end plate ports 40AAB interspersed throughout which function to increase circulation of fluid throughout the fuel bundle 40. The first fuel bundle proximal end plate indent 40AAC is positioned on an exterior of the first fuel bundle proximal end plate opening 40AAD. The first fuel bundle proximal end plate indent 40AAC functions to accept the fuel bundle support nut 40DG therein. The first fuel bundle proximal end plate opening 40AAD accepts the fuel bundle support distal end 40DC therethrough. Referring to FIG. 6C which is a perspective view of a fuel bundle support 40D. The fuel bundle support 40D is composed of a fuel bundle support spacer tube 40DE surrounding and encasing a fuel bundle support rod 40DF. The function of this configuration is to increase strength, heating and cooling characteristics. Referring to FIG. 6D which is a cross-sectional view of a first fuel bundle end plate 40AA. Notice how the first fuel bundle proximal end plate 40AA comprises a plurality of first fuel bundle proximal end plate fuel element end fasteners 40AAA which affix to a first distal end of a fuel element 40C. The first fuel bundle proximal end plate 40AA has multiple first fuel bundle proximal end plate ports 40AAB throughout which function to increase circulation of fluid throughout the fuel bundle 40. The first fuel bundle proximal end plate indent 40AAC is positioned on an exterior of the first fuel bundle proximal end plate opening 40AAD. The first fuel bundle proximal end plate indent 40AAC functions to accept the fuel bundle support nut 40DG therein. The first fuel bundle proximal end plate opening 40AAD accepts the fuel bundle support distal end 40DC therethrough. Referring to FIG. 6E which is a cross-sectional view of a second fuel bundle end plate 40BA. The second fuel bundle distal end plate 40BA has a plurality of second fuel bundle distal end plate fuel element end fastener 40BAA which affix a second distal end of fuel elements 40C. The second fuel bundle distal end plate indent 40BAG functions to accept the fuel bundle support nut 40DG therein. The second fuel bundle distal end plate opening 40BAD accepts the fuel bundle support distal end 40DC therethrough. Referring now to FIG. 7 which is a cross-sectional view of a fuel channel pressure tube 14 having fuel channel pressure tube coating 14A; fuel channel pressure tube lining 14B; and fuel channel pressure tube cladding 14C which function to resist abrasion and increase inherent overall strength of the fuel channel pressure tube 14. Referring to FIG. 8 which is a cross-sectional view of a calandria tube having coating, lining and cladding of the surfaces having calandria tube coating 12A; calandria tube lining 12B; and calandria tube cladding 12C which function to resist abrasion and increase inherent overall strength of the calandria tube 12. Referring to FIG. 9 is a cross-sectional view of a horizontal interior support pad 22 having horizontal interior support pad coating 22E, horizontal interior support pad lining 22F and horizontal interior support pad cladding 22G of the surfaces. Lastly, referring to FIG. 10 which is a cross-sectional view of a refueling of a miniaturized reactor 10. The fuel channel pressure tube 14 has a joint connection at the end walls of the reactor for refilling. The joint connection is comprised of a joiner 48 having joiner thread 48A which screws into closure ring thread 50A being affixed to closure ring 50. The closure ring 50 is affixed to service tube 52 which is connected to the fluids which circulate through the reactor 10. It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the type described above. While the invention has been illustrated and described as embodied in a structural member for nuclear reactor pressure tubes, it is not intended to be limited to the details shown, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention. What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims. |
048759457 | claims | 1. Process for cleaning an exhaust gas from a fusion reactor of exhaust gas components containing heavy hydrogen, the heavy hydrogen components of the exhaust gas being (i) at last one elemental heavy hydrogen isotope selected from deuterium and tritium and (ii) impurities containing the heavy hydrogen isotope deuterium and/or tritium in chemically bound form, the impurities being at least hydrocarbon and water vapor, the exhaust gas further containing carbon monoxide as an impurity, wherein the heavy hydrogen is released from its chemically bound form, and the released heavy hydrogen and the at least one elemental heavy hydrogen isotope (i) are separated from the exhaust gas and returned into the fuel cycle, comprising: (a) bringing the exhaust gas into a palladium/silver permeator operating at a temperature below 450.degree. C. to decompose into its elements any ammonia in the exhaust gas and to separate the exhaust gas into a first stream containing a major fraction of the elemental heavy hydrogen (i) and elemental heavy hydrogen formed by any decomposition of ammonia and a residual gas stream containing the impurities, (b) adding carbon monoxide to the residual gas stream if the carbon monoxide/water ratio is less than 1.5 to bring the carbon monoxide/water ratio in the residual gas stream to .gtoreq.1.5, (c) reacting the water vapor in the residual gas stream with the carbon monoxide at a carbon monoxide/water ratio of .gtoreq.1.5 at 150.degree. to 200.degree. C. on a CuO/Cr.sub.2 O.sub.3 /ZnO catalyst to produce quantitatively hydrogen and carbon dioxide, (d) passing the resulting gas stream from step (c) either into a palladium/silver permeator containing a nickel/aluminum oxide-bulk catalyst or into a nickel catalyst bed followed by a palladium/silver permeator in order to split up the hydrocarbon into its elements and to separate the hydrogen in its elemental form from the remaining gas to form a decontaminated residual gas stream which does not contain any hydrogen and a hydrogen gas stream which contains elemental hydrogen, and (e) combining the hydrogen gas stream containing elemental hydrogen separated in step (d) with the first stream containing the major fraction of hydrogen separated in step (a). 2. Process according to claim 1, wherein the decontaminated residual gas stream which does not contain any hydrogen is released into the atmosphere. 3. Process according to claim 1, wherein the decontaminated residual gas stream which does not contain any hydrogen is recycled into the CuO/Cr.sub.2 O.sub.3 /ZnO catalyst in step (c). |
summary | ||
abstract | A jet pump diffuser weld repair device includes a lower ring section and an upper ring section respectively sized to fit around a circumference of the diffuser on opposite sides of the weld to be repaired. The lower and upper ring sections are provided with a plurality of aligned gripper slots. A corresponding plurality of grippers are fit into the gripper slots, where at least one of the gripper slots and the grippers defines cam surfaces shaped to drive the grippers radially inward as lower and upper ring sections are drawn toward each other. A plurality of connector bolts are secured between the lower ring section and the upper ring section. Tightening of the connector bolts draws the lower and upper ring sections toward each other. |
|
abstract | A method and apparatus is presented for using a pressure control system to monitor a plasma processing system. By monitoring variations in the state of the pressure control system, a fault condition, an erroneous fault condition, or a service condition can be detected. For example, the service condition can include monitoring the accumulation of residue between successive preventative maintenance events. |
|
claims | 1. A method of installing a remote seal, the method comprising:inserting a first part of a capillary connection through an opening in a wall, the first part of the capillary connection comprising an outer sleeve, an inner sleeve and an inner capillary, where the outer sleeve extends around the inner sleeve and the inner sleeve extends around the inner capillary such that the inner capillary is separated from the inner sleeve along an entirety of a section of the inner sleeve that is within the outer sleeve and is sealed to the inner sleeve at a capillary fitting;connecting the capillary fitting to a receiver in a second part of the capillary connection;connecting the second part of the capillary connection to a remote seal on the same side of the wall as the capillary fitting;connecting the first part the capillary connection to a pressure transmitter on an opposite side of the wall from the capillary fitting;filling the capillary connection from the remote seal to the pressure transmitter with a fill fluid to form a filled system to thereby communicate a pressure applied to the remote seal to the pressure transmitter;testing the filled system's ability to communicate a pressure applied to the remote seal to the pressure transmitter; andsecuring the capillary connection to the wall after testing the filled system. 2. The method of claim 1 wherein securing the capillary connection to the wall comprises welding the outer sleeve of the capillary connection to the wall. 3. The method of claim 1 wherein securing the capillary connection to the wall comprises using a compression fitting. 4. The method of claim 1 wherein the space prevents the fill fluid from being damaged when the capillary connection is secured to the wall. 5. An apparatus comprising:a remote process seal connected to a process conduit on a first side of a containment shell;a connector mounted through and secured to the containment shell, the connector carrying a fill fluid fluidically connected to the remote seal, the connector comprising:a receiver;a first capillary extending from the remote process seal to the receiver;a wall mount secured to the containment shell and having a capillary fitting that is received by and welded to the receiver on the first side of the containment shell; anda second capillary that passes through the wall mount and the containment shell from the capillary fitting to the second side of the containment shell, wherein an exterior surface of the second capillary contacts an interior surface the capillary fitting at a sealing section; anda pressure transmitter fluidically connected to the second capillary of the connector on the second side of the containment shell to thereby receive a process pressure applied to the remote seal. 6. The apparatus of claim 5 wherein the wall mount comprises an outer sleeve, and a space surrounding the second capillary between the second capillary and the outer sleeve. 7. The apparatus of claim 6 wherein the connector further comprises an internal tapered section that tapers the space before the sealing section of the capillary fitting. 8. The apparatus of claim 6 wherein the connector is secured to the containment shell by being welded to the containment shell. |
|
043483569 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing a nuclear reactor vessel 10--which houses a nuclear reactor core (not shown)--is provided with an outwardly extending support ring 11 at the top thereof. The support ring 11 and other outward portions of the reactor system are shown generally covered by thermal insulation 11a such as alumina-silica type. The containment structure 12 for the reactor includes an integral support ledge 13 extending inwardly therefrom into reactor vessel cavity 14. Cavity 14 in addition to reactor vessel 10 can also contain the primary heat exchanger and primary liquid metal coolant loop in a liquid-metal-cooled reactor system. Reactor vessel 10 typically includes double walls (not shown) in a liquid-metal-cooled fast breeder reactor system, which makes ordinary support arrangements integral with coolant nozzles difficult or impractical to employ. Interposed between support ring 11 and support ledge 13 is a box ring 15 which is shown resting on a top plate 16 of the support ledge 13. Although the box ring 15 carries the weight of support ring 11 and thus that of reactor vessel 10, it also defines an annular space 15a to limit heat flow between the reactor and its containment. Support ring 11 is fastened to support ledge 13 by holddown studs 17 (see FIG. 3) which extend through box ring 15 and ledge 13. The studs, at the top, are provided with nuts 18 enclosed within seal caps 19 which in cooperation with suitable gaskets seal the stud hole leakage path. The containment structure 12 and integral ledge 13 are illustrated as being of concrete and ledge 13 is shown with a metal top plate 16, however, it will be clear that other suitable materials and arrangements can be used. For instance, the complete thickness of ledge 13 may be of suitably strong steel or other metal securely and integrally fastened into the containment structure. Similarly studs 17 are shown as preferable extending through the support ring 11 and the support ledge 13, but other appropriate arrangements involving suitably anchored studs might also be devised to meet various design conditions. Upper and lower radial keys 25 and 26 (see FIG. 3) respectively transmit horizontal seismic loads from the reactor vessel through the box ring 15 to the support ledge 13. Mating keyways 27 and 28 respectively are machined in the bottom of the reactor vessel support ring and in the top plate of the support ledge. Upper and lower keys 25 and 26 are fastened to the box ring 15 by screws 29 and 30 respectively. Tapered wedges 25a and 26a provide metal to metal fit between the upper and lower keys 25 and 26 respectively and their associated keyways 27 and 28. Located between box ring 15 and reactor vessel 10 is a shield ring 20 (FIG. 4) tied to top plate 16 of support ledge 13 by bolts 21. The shield ring is a generally non-loaded member of suitable material such as concrete surrounded by thermal insulation 20a. A flat ring of crushable sealing material 20b seals between the insulation 20a and the reactor vessel support ring 11. A cooling gas header 22 separated from the reactor head access area 23 by seal collar 24 surrounds support ring 11 and box ring 15. Seal collar 24 is a ring of metal plate with angular cross section having a horizontal flange over the a portion of the support ring 11 and a vertical flange engaging the containment 12. The seal collar 24 is bolted to the top of reactor vessel support ring 11 by studs 17 and is generally covered on both sides by thermal insulation 11a. The seal collar 24 in combination with seal caps 19 also provide a seal between the reactor cavity 14 which is under an inert gas cover and the head access area 23 which normally has an air atmosphere. The inert gas may be nitrogen or air with most of the oxygen removed. The seal collar 24 is sealed at its horizontal flange edge to the reactor vessel support ring 11 by a seal 24a of such as graphite-type material in tape form. At the edge of its vertical flange it is bolted and sealed to the containment structure 12 by a suitable arrangement such as bolts 35 holddown clampblock 37 and a suitable seal 39 as shown. One or more supply headers (not shown) bring cooling gas across the floor of the head access area 23 to cooling header 22. Nitrogen or other inert gas from cooling gas header 22 flows through slots 31 (FIG. 3) in lower radial keys 26, and in gaps 31a left between the bottom of the box ring and the top of the support ledge. This gas flow limits the heat flow from the reactor vessel through the box ring support to the concrete support ledge so that its temperature remains below specified limits. The gas then flows in keyways 28 (FIG. 4) under shield ring 20 and then downward past steel shield ring 32 and insulation 33 on the inside diameter of the support ledge 13. The gas then flows radially outwardly between the bottom of the support ledge and shield collar 41 into reactor vessel cavity 14. Thus, the support ledge is cooled without having cooling headers and lines installed in its structure. In one particular application box ring 15 is a ring about 322" outside diameter, about 8" thick, and about 15" deep with a box type cross-section defining an annular space 15a. The top and bottom of the box are about 3" thick low alloy steel. The relatively thin (about 1" thick) inside and outside cylindrical side walls shown in the box cross-sections are Inconel 600 which has relatively low thermal conductivity. The box structure with its annular space 15a limits the heat flow from the reactor vessel to the support ledge to within acceptable limits. It is thus seen that the present invention provides a reactor support system that is particularly well suited for supporting loop type, liquid-metal-cooled reactors. The support includes a sealing arrangement for containing an inert cover gas within the reactor containment providing additional security against undesirable reactions between reactive alkali metal coolants such as sodium or sodium-potassium alloy with the air atmosphere of the head access area. The support system also effectively transmits horizontal seismic loads between the vessel and the supporting structure. An annular box ring arrangement limits the flow of heat from the high temperature, liquid-metal-cooled reactor to the supporting structure of the containment. Although the present invention has been described in terms of specific embodiments, it will be clear that variations in structure, materials and methods will occur to those skilled in the art within the scope of the following claims. |
abstract | An ultrasonic reactor water level measuring device and an evaluation method are provided and prevent a reduction in the measurement accuracy of a water level that is in a wide measurement range. The ultrasonic reactor water level measuring device includes an upper tube extending from a gas phase portion in a reactor, a lower tube extending from a liquid phase portion in the reactor, measurement tubes connected to each other and arranged at multiple stages between the upper tube and the lower tube, and units for generating and receiving ultrasonic waves, the units being arranged at bottom portions of the measurement tubes. The ultrasonic reactor water level measuring device measures levels of water within the measurement tubes and calculates a water level within the reactor from the sum of the measured water levels, the sum excluding an overlapped part of the measurement tubes. |
|
051436531 | summary | The present invention relates to a process for the immobilization of radioactive ion exchange resins (IER) by means of an hydraulic binder. The radioactive IER to be treated originate essentially from nuclear reactors in which they are used for purifying the water of the different circuits of the reactor, and in some cases, for purifying the water of pools used for storing irradiated fuel elements. In particular, in pressurized-water reactors or PWR, anionic IER are placed in the primary circuit of which the water contains boric acid acting as a moderator. The anionic IER can then serve as "boron lungs" to keep up the required boron concentration inside the circuit. Nuclear power station operators consider that the waste IER can contain, in borates form, up to the equivalent of 1000 g of boric acid per kg of dry IER. Besides borates, these IER (cationic, anionic, mixed bed) can contain lithium, ammonium, iron, cobalt, chromium, nickel and cesium cations and hydroxide, sulphate, phosphate, silicate, fluoride, chloride, and bicarbonate anions. Some IER are also used in installations for reprocessing irradiated fuel elements, for purifying the water of storage pools and for treating liquids. The IER are placed in columns or cartridges. At the moment, they are regenerated on the spot before immobilization. Then, they essentially contain H.sup.+, OH.sup.- and non-eluted active metallic cations. To prevent dissemination of radioactive substances in the environment, it is sought to immobilize the wastes containing such substances, in a matrix capable of resisting mechanical, chemical or other agents liable to damage it during storage of said wastes. One way of doing this consists in mixing said wastes with an hydraulic binder which, by setting and subsequently hardening, confers a certain mechanical resistance to the mixture and a certain resistance against chemical attacks. The values of such mechanical and chemical resistances which the immobilized waste (also called final product or coated product) should reach, in order to be stored with all the safety guarantees required for man and environment, are fixed by the nuclear safety standards. Said standards are set by the national authorities and can consequently vary from one country to another. French safety standards concerning wastes immobilized in an hydraulic binder are among the strictest: few countries have succeeded in reaching such standards with wastes containing IER. For example, in France, since 1982, the concreting of IER has been discontinued because the methods used do not give final products meeting the safety requirements. Indeed, the treatment of IER with an hydraulic binder raises two essential problems which do not arise with other types of nuclear wastes. The first problem is that of ion exchange between the IER and the medium containing the hydraulic binder. The ions of the medium which have a greater affinity for the IER than the affinity which the ions contained in these IER have for them, settle on the IER in the place of the ions which they used to contain, which latter have been salted out into the medium. There is fixation of ions and simultaneously salting-out of other ions. As a result, the medium loses ions from the hydraulic binder (Ca.sup.++ and SO.sub.4 =essentially) but, on the other hand, gains ions originating from the nuclear installations (active metallic cations, phosphates, sulphates . . . H.sup.+, OH.sup.- and borates). The loss of binder ions, and in particular Ca.sup.++ and SO.sub.4.sup.--, alters the setting (delay, uncontrollability, incomplete setting). Moreover, the ions brought by the IER and salted out into the medium can interfere with the setting or hardening or they can affect the stability in time of the immobilized wastes. Zn.sup.++ has a setting- retardant or inhibitor action; PA0 Mg.sup.++ can interchange with Ca.sup.++ of the calcium hydrates, after setting, and therefore modify the stability in time of the product; PA0 .sup.H+ the binder hydration reactions occur in basic medium, a reductin of the pH to acid values retards, if not inhibits the setting; PA0 the phosphates also have an inhibiting effect on the setting. PA0 1) the volume of the coated product to be stored on a long-term basis must be as reduced as possible in order to minimize the costs of storage installations; PA0 2) the immobilization process must be technologically implementable with relatively simple, reliable and quick-acting means. PA0 to fix the ions of the eluant solution on the IER, said ions contributing to helping the immobilization by hydraulic binder; PA0 to place the IER ions in solution, some of which ions hinder the immobilization by hydraulic binder; PA0 to induce precipitation in the solution of said hindering ions in the form of solids which are non-soluble in the conditions of immobilization by hydraulic binder. PA0 the elution is efficient (effective precipitation and fixation); PA0 there is no need to add water in order to obtain the E/C and F ratios; PA0 the weight of the final coated product is not disproportionate; PA0 the volume of solution is not too large, and the elution and treatment with the binder can be carried out in the same apparatus. PA0 adequate elution and precipitation so that the retardant effect on the setting of borates is no longer felt; PA0 industrial requirements : shortest contact time possible in order to produce the largest possible amount of coated products per day. PA0 In France: PA0 in the U.S.A.: Portland blast furnace cement, 25-65% slag PA0 in West Germany: Eisenportland cement>40% slag PA0 in Japan: Blast furnace cement type C, 60-70% slag The ions which, by far, create the greatest problems are the borates. Their effect is known on hydraulic binders, and depending on their concentration in the medium, they either retard or inhibit the setting, whether they are in free form or associated with certain ions such as lithium to form Li.sub.2 B.sub.4 O.sub.7. Ionic exchanges can continue after the setting, particularly during lixiviation tests, between the lixiviating medium and the IER rendered accessible in the coated product through various causes (permeable matrix, bad homogeneity, high porosity, . . . ). The released ions can generate reactions which are harmful to the coated product, this is, for example, the case with sulphates. The second type of difficulty which is met when treating IER is specifically due to water migration from the IER toward the medium containing the hydraulic binder. The IER release a fraction of their water according to the equilibrium principle between the water of the IER and the water of the medium. The binder hydration reactions being exothermic, water continues to be lost throughout the setting. On completion of the setting, the partly dehydrated particles of IER can, if the final product is placed in contact with water, regain some water. This is the wellknown phenomenon of swelling and cracking of immersed coated products after setting and even after hardening: the swelling due to the regain of water causes cracking of the material and can result in a complete disintegration of the matter. Industrial solutions must be found to these two categories of problems, in which solutions: French Patent FR-A-75 33 518 proposes to adjoin additives whose function is to prevent the water from penetrating into the particles of IER. Such additive substances form a protection layer around the IER particle. They are organic compounds (organic ester, polyvinyl propionate), or mineral compounds (alkaline silicate). But there is no certainty that any borate ions contained in the IER will not be able to penetrate into the aqueous medium. What is more, this method is not really advantageous because it is expensive and difficult to work. In order to limit the transfer of water between the IER and the binder during setting, another patent, FR-A-80 21 524 recommends to use blast furnace slag cement in specific conditions and to saturate the IER with water. Set conditions: cement-mixing water/cement (by weight)=0.20 to 0.40, and proportions of incorporation=dry resin/coated product (by weight) .ltoreq.15% for a powdered IER and .ltoreq.25% for particled IER. It should be specified that the cement-mixing water is the water added to the water-saturated IER to ensure the setting of the cement. This process does not allow for any possibility of ion exchanges occurring between the cement and the IER. Such a process is not applicable to borate-containing IER: the salted-out borate-containing ions inhibit the setting of the cement in the aforesaid conditions. Moreover, the solidification by hydraulic binder of borate-containing effluents is known from Patent FR-A-85 04 222 which describes a process in which, before adding the cement, the borate-containing effluents are treated with lime in order to precipitate the calcium borates of predetermined structure in specific conditions. A solution was then essential for treating the borate-containing IER, consisting in eluting them in order to extract the borate-containing ions therefrom and to replace them in solution, then in separating the IER from the eluting solution, in rinsing in order to remove as much as possible the traces of borates, and finally in concreting the IER on one side and the borate-containing effluents on the other, according to the processes described hereinabove. Elution of the radioactive IER has already been used before solidification for bituminization or polymerization of a thermosetting resin. In patent FR-A-76 24 624, the eluting solution is a solution of sodium hydroxide, aqueous ammonia, lime, aluminium chloride, sodium acetate, sodium citrate or sodium oxalate, or else an amine. The obtained IER are decanted or de-watered, then they are mixed with the thermosetting resin of which the polymerization is induced. This type of treatment causes the elimination from the cationic IER of the H.sup.+ ions, which ions have an action on the cross-linking accelerating agent added to the thermosetting resin: H.sup.+ ions are extracted from the IER, then placed in solution and separated from said IER. In patent EP-157 683, elution is achieved with a solution of Ca.sup.++, Be.sup.++ or Sr.sup.++ (nitrate, formiate or acetate anions), the IER are separated from the eluant solution, rinsed, placed in suspension in water and bituminized. The object of the pre-treatment is to replace the H.sup.+, Na.sup.+, OH.sup.-, Cl.sup.- ions from the IER with the ions from the eluant solution, which latter are more voluminous and modify the tri-dimensional structure of the IER in such a way as to prevent the water from penetrating in the bituminous coated products immersed in the lixiviation medium. In this way, the risks of swelling are extremely reduced. According to the aforesaid IER treatment processes using an elution in order to eliminate the unwanted ions from the IER--which ions are a hindrance either because of their action on the solidifying medium or because of their ability to induce a regain of water by the IER--said IER are separated from the eluant solution before being immobilized. It is an object of the present invention to propose a process, applicable on an industrial scale, for treating any IER containing borates, in a single operation, on the same site, and at the same time, with a view to obtaining coated products which meet the standards of safety imposed in the country. Such process includes a step of pre-treatment by elution followed by a solidifying step by the setting of the hydraulic binder, the elution conditions making it possible to unexpectedly obtain a solidifiable medium such as can be obtained with an hydraulic binder, although containing different ions, such as borates in particular. More specifically, the object of the present invention is to propose a process for immobilizing, by using an hydraulic binder, radioactive ion exchange resins (IER) which may contain borates in a quantity which can reach up to the equivalent of 1000 g of H.sub.3 BO.sub.3 per kg of dry IER, wherein the IER are decanted, then placed in contact, for 3 hours or more, with an eluant solution of 100 to 300 g/l Ca(NO.sub.3).sub.2 in the proportion of 1 to 2 l/kg of decanted IER, an hydraulic binder of low hydration heat being added to the medium of pH.gtoreq.9, so that the ratio: water from the eluant solution/binder (by weight) is between 0.3 and 0.5 and the rate of incorporation F'=dry IER/coated product (by weight) is between 3 and 10%. It should be noted that F' differs from F in that F is equal to ##EQU1## wherein 10%.ltoreq.F.ltoreq.25% as compared with F' which is 3%.ltoreq.F'.ltoreq.10%. The ion exchange resins issued from nuclear installations (i.e. cationic, anionic or in mixed bed) are collected, stored and then sent to the treatment unit. Therefore, generally, nothing is known with precision before the treatment, of their composition, of their nature and of the quantity of ions that they contain. In any case, it is not easy to give a precise range of values for the borates content, since condensed molecules may have formed and settled. A high content is estimated at 1000 g eq. H.sub.3 BO.sub.3 so that an average content would be 500 g eq. H.sub.3 BO.sub.3. The stored IER are in suspension form. According to the process of the invention, the IER to be treated are first left to decant, and the supernatant is removed (by pumping, etc . . . ). The resulting water-saturated IER (called 100% decanted IER) are then weighed. The weight of 100% decanted IER introduced for treatment will serve as a reference to calculate the quantities of material to be added thereafter. The object of placing the IER in contact with the eluant solution is: The precipitation is combined with the elution, which considerably improves the efficiency of the elution: as the eluted ions precipitate and their concentration in the solution reduces, the balance between the borates in the IER and the borates in solution is shifted. The selected eluant solution is an aqueous solution of calcium nitrate which induces the precipitation of calcium borates. The favorable effect of the precipitation on the elution permits a fast contact time : less than 3 hours, and preferably 1 hour. Said contact time has been determined, together with the quantity equivalents-gms of -g cation or anion, and the quantity of water, both quantities being brought by the eluant solution per kg of IER, from numerous tests carried out by the Applicant. Indeed, it was not possible to select process values, without knowing either the composition, or the theoretical exchange capacity of the starting IER, or their borates content. Moreover, the volume of eluant solution introduced for said elution has a direct effect on the next treatment step with the hydraulic binder, the whole volume being kept for that treatment. Indeed, the ratio of the water of the eluant solution (by weight) to the binder (by weight) has to be kept within strict limits. As a result, the weight of added binder is dependent on the volume of the eluant solution, the weight of the coated product (binder+eluant solution+IER) being likewise dependent on said volume. Yet, it is not possible to increase the weight of the coated product inconsiderately without creating handling and storage problems. It was therefore important to choose the concentration and volume of the eluant solution so that: Simultaneously, the contact time had to be determined in such a way as to meet the conditions of the process: The experiments conducted by the Applicant show that the optimum is reached with an aqueous solution of Ca(NO.sub.3).sub.2 containing 100 to 300 g/l of calcium nitrate in the proportion of 1 to 2 l/kg of 100% decanted IER and a contact time of 3 hours maximum. It is obvious that the contact time and the quantity of ions introduced are dependent on the borates content, which, in general, is not known. The preferred values correspond to coated (i.e. "final") products which are in conformity with the French standards of safety: eluant solution concentration=about 200 g/l; 100% decanted IER=about 1 l/kg; contact time: 1 hour. The operator is free to choose other values within the ranges allowed by the standards applied in his country: with less strict standards, the operator may, advantageously, reduce the contact time. It is true that the elution is more important with a longer contact time, and then the unwanted ions are blocked in the solution by precipitation. To increase elution efficiency, lime (preferably in solid form in order not to have to add any water) is advantageously added to the eluant solution, in the proportion of 200 g/kg of 100% decanted IER. Elution therefore takes place according to a discontinuous process in one single step: the eluant solution is added, under stirring, to the 100% decanted IER. Advantageously, the decanting, elution and treatment by the hydraulic binder are conducted in the same apparatus (mingler-mixer). It is an important feature of the process to treat the totality of the mixture obtained after the elution step. Indeed, as illustrated in the prior art, when there is elution on the IER, there is after a separation of the IER from the solution. The low hydration heat hydraulic binder is therefore added under stirring to the mixture obtained as abovedescribed, the medium having a pH at least equal to 9. Preferably, the binder is a slag cement which, when hard, presents the added characteristic of having a poor porosity and a poor permeability. Slag cements contain variable rates of clinker (the clinker being responsible for the exothermicity of the hydration reaction), by way of example: cement: CLK>80% slag, <3% additives PA1 HFC 40 to 75% slag, <3% additives PA1 CLC 20 to 45% slag, <3% additives, 20-45% ashes. Among the aforesaid cements, those with a high proportion of slag (>60%) are preferred. In France, the choice will go to the CLK type. Other additives, such as fillers, plasticizers, . . . can be introduced with the hydraulic binder. The basis of the final matrix in which the IER are immobilized is the hydraulic binder, but said matrix can include other elements in lesser proportions. The added quantity of binder is such that the ratio: water of eluant solution/weight of binder ranges between 0.3 and 0.5 and is preferably 0.4 for a rate of incorporation of IER F'=weight of dry IER/weight of the coated product ranging between 3 and 10%. The weight of the coated product will be equal to the sum of the weight of the eluent solution plus the weight of the decanted IER, plus that of the binder, wherein F' is equal to |
description | The present invention relates to a device for the dry handling of nuclear fuel assemblies. The invention also relates to the unloading of nuclear fuel assemblies stored in slots in a cask, as well as the dry loading of nuclear fuel assemblies in the slots of a cask. The nuclear fuel assemblies are formed by assembling rods with a small diameter relative to their length. These rods, of which there are 200 to 300 per assembly, are formed by sheaths filled with nuclear fuel pellets, for example MOX. These assemblies have a rectangular section of several tens of centimeters per side and measure several meters long. Each nuclear reactor must be stopped periodically to replace some of the spent fuel assemblies with new fuel assemblies. The new fuel assemblies are generally made in a pellet manufacturing plant and must be transported to the nuclear plants, where they will be placed in a storage facility before being transferred into the reactors. The transport of these assemblies between the production plant and the nuclear power plant is done using a cask that includes slots in each of which a new fuel assembly is placed. Upon arrival at the nuclear power plant, the new fuel assemblies are unloaded from the cask and brought into the storage facility made up of a storage pool, situated near the core of the reactor and in most cases at a level higher than the arrival level of the casks of the assemblies. The first method for checking the reactivity of a fuel element is its geometry. The handling of a fuel assembly must therefore meet high reliability criteria and in particular show that the consequences of a fall of an assembly are acceptable and do not cause critical accidents or serious environmental consequences. To date, when the fuel assemblies are transferred from a cask, that cask is moved and brought close to the pool and each assembly is removed from the cask and placed in a pool. This lifting operation of the cask close to the pool then makes it possible to limit the potential fall height of the assembly. The transfer is done either underwater or dry. In the case of an underwater transfer, the cask is removed from the transport vehicle by suitable lifting means, for example such as a handling crane, and brought into a pool, or an unloading station, attached the storage pool. The related pool is then filled with water, then each fuel assembly is removed from its slot using lifting means and placed in the storage pool. The movement of the fuel assemblies is done underwater, thereby providing suitable biological protection for the operators. This underwater fuel transfer nevertheless has a drawback, since it is next necessary to decontaminate the cask, and that decontamination operation exposes operators to doses of reactivity. In the case of a dry transfer, as for example described in FR 2 260 169, the cask is removed from the transport vehicle by a lifting carriage supported by a bridge crane, then deposited in an area designed for storage thereof. Next, the fuel assembly is removed from the transport carriage and hoisted in an armored handling container suspended from the lifting carriage and then transported in the pool. Lifting means, for example such as a winch and a gripping handle fastened to the free end of a chain of the winch, make it possible to hoist the fuel assembly inside the handling container. The fuel assembly is also transferred into an inspection area before being placed in the pool. All of these operations are time-consuming and require human interventions that risk subjecting operators to critical doses. Furthermore, it is necessary each time to be able to hoist the cask to the level of the storage pool, which involves constraints on the installation of the receiving building and fall risks for the cask during these operations. Furthermore, the handling container described in the dry unloading device mentioned above does not, however, have every safety guarantee in the event the fuel assembly falls due to the fact that it does not include closing elements at its base, but rather only means for gripping the fuel assembly in the container. To that end, handling containers or transfer baskets are known that include closing elements at the base and primarily used to unload spent fuel assemblies from a storage area to store them in containers intended to be transported to another location. The closing element is in particular formed by a sliding or pivoting door actuated remotely. This solution is complex to implement due to the fact that it requires an entire mechanism for actuating the sliding or pivoting door. An object of the invention is to provide a device for the dry handling of fuel assemblies that avoids these drawbacks, is easy to implement, and is adaptable on new or existing installations, while having all of the safety guarantees inherent to the handling of nuclear fuel assemblies. A device for the dry handling of nuclear fuel assemblies is provided. The device includes a transfer basket which can be connected to lifting means and having an inner member for gripping the fuel assembly to be transferred on the one hand, supported by a lifting mechanism built into the basket, and a bottom provided with valves pivoting between an open position for the passage of the fuel assembly to be transferred and a closed position of the basket, on the other hand, and an indexing table which can be placed on a cask and including means for positioning the basket on a slot of said cask and orienting the gripping member supported by said basket relative to said fuel assembly. of the invention may include one or more of the following features: the basket comprises an upper portion including a double attachment system with a hook for a handling assembly, a body containing the built-in lifting mechanism bearing the gripping member and a lower portion formed by the bottom provided with said valves, the bottom of the basket includes a central opening for the passage of the gripping member and the fuel assembly in the open position of the valves, each valve is placed above the bottom and is associated with at least one movement element between said open and closed positions, said at least one movement element is formed by at least one pin sliding in the bottom and including a first end situated below the bottom and a second end bearing against the corresponding valve, the valves have mutually complementary shapes to cover the central opening in the closed position of said valves, each valve is formed by a triangular plate whereof the base is hingedly mounted on the bottom, the lifting mechanism built into the basket comprises a carriage movable by sliding of the basket in the body by means of a handling assembly, the device includes, between the indexing table and the cask, an adaptor part whereof the inner surface has a profile conjugated to the peripheral edge of the cask and the outer face of which is adapted to the standard dimensions of the indexing table, the indexing table comprises a peripheral support piece placed on the adaptor piece, a first stopper rotating inside the support piece, a second stopper rotating inside the first rotating stopper, and a third stopper rotating on the second stopper and forming a carrier for receiving the basket, the second and third stoppers communicating with the inside of the cask by an opening, the axis of the first stopper corresponds to the axis of the cask, the axis of the third stopper corresponds to the axis of the most extreme slot in the cask, and the axis of the second stopper is situated at an equal distance from the axes of the other two stoppers, the bottom of the third stopper includes, around the opening, a bearing rim for the first end of each movement element, and the second stopper includes, below the third stopper, a sleeve including an axial passage communicating with the openings of those stoppers, the axial passage determining an inspection area of the fuel assembly to be transferred and being provided with display and lighting means. The description that follows will be provided as an example in the context of a use of the handling device to unload new fuel assemblies from a cask. The new fuel assemblies are transported between a manufacturing plant and a nuclear power plant by a road or rail vehicle in an armored cask 1, diagrammatically shown in FIG. 1. The transport cask 1 includes slots 2, in each of which new fuel assembly 3 is placed (shown in FIG. 3). In the nuclear power plant, the new fuel assemblies 3 are brought toward the packaging and storage installations and stored in a storage pool 4 (FIG. 12). To transfer the new fuel assemblies 3 from the cask 1 to the storage pool 4, said cask 1 is brought into a building 5 that includes a bridge crane 6 (FIG. 12) and in which the pool 4 is arranged. The transfer of each fuel assembly 3 is done using a dry unloading device shown in FIG. 2. This unloading device is made up of two primary elements, i.e.: a transfer basket 20 that can be connected to a lifter, for example the bridge crane 6, and an indexing table 50 that can be placed on the cask 1. The transfer basket 20 will now be described in reference to FIGS. 3 to 7. The basket 20 comprises an upper portion 21 for attaching to the bridge crane 6 including a hook 8 connected by chains or cables 7 to the bridge crane 6, a body 22 forming a sheath for receiving the fuel assembly 3 during the transfer thereof, and a lower portion 23 including a bottom 24 that will be described later. The upper portion 21 comprises a double attachment system made up of a member 25 for fastening on the hook 8 and claws 26 for fastening on the support 9 of that hook 8. The body 22 of the basket 20 is inwardly provided with a built-in lifting mechanism 27 bearing a gripping member 28 for the fuel assembly 3. As shown in FIG. 7, the built-in lifting mechanism 27 comprises a carriage 29 bearing the gripping member formed for example by a grab 28 of a known type, the carriage 29 being guided and moved by sliding in the body 22 by a handling assembly for example comprising a winch 30 provided with chains 31 cooperating with pulleys 32 supported by the carriage 29. As shown in FIGS. 3 and 7, the assembly of the lifting mechanism 27, i.e., the carriage 29, the winch 30, the chains 31 and the pulleys 32, is built into the body 22 of the basket 20, which prevents any communication with the outside of said basket. The lifting mechanism 27 is dedicated to lifting and lowering the fuel assembly 3 to be transferred and is distinct from the bridge crane 6 generally used for handling heavier objects. The lifting mechanism 27 built in the basket for example has a lifting capacity of approximately 1 ton whereas the bridge crane 6 has a lifting capacity of approximately 20 tons. The mechanism 27 therefore has much greater precision than the bridge crane. As appears in FIGS. 4 to 6, the bottom 24 of the lower portion 23 of the basket 20 is provided with valves 35 pivoting between an open position (FIG. 6) for the passage of the fuel assembly 3 to be transferred and a closed position (FIG. 5) of the body 22 of the basket 20. This bottom 24 has a central opening 34 for the passage of the gripping member 28 and the fuel assembly 3 when the valves 35 are in the open position, as shown in FIG. 6. In the example embodiment illustrated in FIGS. 4 to 6, each valve 35 is placed above the bottom 24 and associated with at least one movement element 36 between the open and closed positions. Each movement element is formed by a pin 36 sliding in the bottom 24 and including a first end 36a situated below the bottom 24 and a second end 36b bearing against the corresponding valve 35. As more particularly shown in FIGS. 4 to 6, the valves 35 have a complementary shape to cover the central opening 34 in the closed position of said valves 35 and each valve 35 is formed by a triangular plate 37 whereof the base 37a is hingedly mounted by means of an axle 37b on the bottom 24 of the basket 20. The valves 35 close automatically by gravitational return to work under the effect of a torsion spring arranged on the shaft 37b of each plate 37. It will be noted that the example embodiment illustrated in the figures is only one example among others of an automatic closing system of the basket using valves. The valves may have a different shape, for example rectangular. There may be two or more of them. They do not necessarily have complementary shapes, they may also be arranged so as to be superimposed on one another when they close or so as not to join perfectly with each other. However, the valves must rest directly or by means of an intermediate piece on a surface of the basket, for example on the bottom 24, to ensure reaction of the load in case of an assembly falls in the basket. Likewise, the movement elements of the valves may have a shape other than the pins 36 and they may be more or less numerous. The pins may in particular be connected to each other on the side of their first end 36a so as only to form a single piece. The transfer basket 20 provides the fuel assembly 3, during transport thereof, with mechanical protection against lateral impacts and makes it possible to withstand the potential fall of the fuel assembly and limit the possible fall height when the base of the basket 20 is closed by the valves 35. This basket 20 also makes it possible to orient the grab 28, as will be described later. The indexing table 50 will now be described in reference to FIG. 8 in particular. The purpose of this indexing table 50 is to adapt to the different casks and position the basket 20 directly across from the slot 2 corresponding to the fuel assembly 3 to be transferred, to support that basket 20 during the lifting operations of the fuel assembly 3, and to allow inspection of that fuel assembly 3 when it leaves the casks 1. To that end, an adaptor piece 51 is inserted between the indexing table 50 and the casks 1, and said adaptor piece 51 has an interface having a profile conjugated with the peripheral edge of the cask and an outer face adapted to the standard dimensions of the indexing table 50. In the example embodiment shown in FIG. 8, this adaptor piece 51 has a transverse section in the shape of an inverted U. The sealing between the adaptor piece 51 and the peripheral edge of the cask is for example ensured by two O-rings or by any other suitable member. The correct positioning of the basket 20 across from the proper slot 2 containing the fuel assembly 3 to be transferred is done by the indexing table 50, which includes: a first stopper 55 rotating inside a support piece 52, a second supper 56 rotating inside a first stopper 55, and a third stopper 57 rotating on the second stopper 56. The support piece 52 provides the interface with the adaptor piece 51 and is therefore stationary relative to the cask 1. The stoppers 55, 56 and 57 may for example be supported by ball bearings guided by rails, for example made from steel, or any other suitable system of a known type, ensuring proper positioning of the basket 20 and also ensuring reaction of the weight of the assembly formed by the basket 20 with the built-in lifting mechanism and also the fuel assembly 3 to be transferred. The sealing between each stopper is ensured by a set of two O-rings or by any other suitable sealing member. Thus, as shown in FIG. 9, the axis A of the first stopper 55 corresponds to the axis of the cask 1, the axis C of the third stopper 57 corresponds to the axis of the outermost slot 2 in the cask 1, and the axis B of the second stopper 56 is situated at an equal distance between the axes A and C of the other two stoppers 55 and 57. In this way, the basket 20 can be placed in all of the positions of the slots 2 of the cask 1. The second stopper 56 communicates with the inside of the cask 1 by an opening 60 and the third stopper 57 communicates with the inside of the cask 1 by an opening 61, the openings 60 and 61 being coaxial. As shown in FIG. 8, the third stopper 57 forms a carrier for receiving the basket 20 and includes conical steps in its upper portion, making it possible to guide the basket 20 during its positioning in the third stopper 57. When the basket 20 is alongside the third stopper 57, that basket 20 is rotatably connected with the third stopper 57, either by its own weight, or by a temporary connecting device of a known type. The rotation of the third stopper 57 makes it possible to rotate the basket 20 by an angle of approximately 45° so that the grab 28 is properly aligned with the fuel assembly 3 to be transferred. To allow opening of the valves 35, the bottom of the third stopper 57 includes, around the opening 61, a bearing rim 62 for the first end 36a of each pin 36. The basket 20 is provided with a set of O-rings in the lower portion to maintain the confinement of the cask 1. As shown in FIG. 8, the second stopper 56 includes, below the third stopper 57, a sleeve 65 including an axial passage 66 communicating with the openings 60 and 61 of those stoppers 56 and 57, respectively. The axial passage 66 determines an inspection area of the fuel assembly 3 to be transferred and that area is equipped with a display 80, such as cameras and lighting 82, for example which are schematically shown. Several cameras can be installed at a same level. The rotation of the second stopper 56 makes it possible to view the periphery of the fuel assembly 3 during its transfer. The new fuel assemblies 3 are unloaded as follows. The cask 1 containing the new fuel assemblies 3 is brought by its own transport vehicle into the building 5 of the nuclear power plant. The operators proceed to prepare the cask 1 and the fuel assemblies 3 for unloading. First, the adaptor piece 51 adapted to the cask 1 is placed thereon and the assembly of the indexing table 50 including the support piece 52 and the stoppers 55, 56 and 57, respectively, is placed on the adaptor piece 51, as shown in FIG. 10. The stoppers 55 and 56 are rotated to place the openings 60 and 61 in the axis of the slot 2 containing the fuel assembly 3 to be transferred. Then, the basket 20 is brought by the bridge crane 6 above the third stopper 57, as shown in FIGS. 10 and 11. During the movement of the basket 20, the valves 35 are in the closed position and the end 36a of the pins 36 protrude below the bottom 24 of the basket 20. This basket 20 is gradually lowered into the third stopper 57 so as to bring the ends 36a of the pins 36 into contact with the bearing rim 62 formed around the opening 61 of that third stopper 57. The end 36a of the pins 36 come into contact with the bearing rim 62 and the pins 36 with the valves 35, as shown in FIGS. 6 and 8, so as to put the inside of the basket 20 in communication with the slot 2 containing the fuel assembly 3 to be transferred. The third stopper 57 is rotated to pivot the basket 20 and thereby orient the grab 28 in the appropriate position to grasp the fuel assembly 3. This fuel assembly 3 is gripped by the grab 28 and gradually lifted by the chains 31 driven by the winch 30. In the event the fuel assembly falls into the cask 1, the static confinement is provided by the indexing table 50 and the basket 20. The lifting chains 31 are suitable for handling fuel assemblies and have a high level of reliability and are in particular equipped with overload and excess speed detectors. During its passage in the area 66 delimited by the sleeve 65, the fuel assembly 3 undergoes a visual inspection, which avoids the need to transport that fuel assembly 3 into a specific inspection room. The fuel assembly 3 is gradually brought to the inside of the basket 20 and once it is placed therein, the lifting means of the bridge crane 6 lift the basket 20, which moves away from the bottom 62 of the third stopper 57. Once the basket 20 moves away from that bottom 62, the valves 35 close, thereby ensuring confinement of the fuel assembly 3 in the basket 20. This basket 20 provides protection against any lateral impacts and limits the height of a potential fall of the fuel assembly 3 when the latter is in said basket, as shown in FIG. 12. The basket 20 containing the fuel assembly 3 is horizontally movable by the bridge crane 6 and brought toward the packaging and storage installations for new assemblies, then into the storage pool 4. As shown in FIGS. 12 and 13, this pool 4 is equipped with a carrier 70 for receiving the lower portion of the basket 20 that includes, identically to the third stopper 57, a bearing surface for the end 36a of the pistons 36 so as to allow opening of the valves 35 when the basket 20 is placed in the carrier 70. The bottom of this carrier 70 is also provided with an opening to allow the passage of the fuel assembly 3 to be deposited in the pool 4. This fuel assembly 3 is gradually lowered into the pool 4 using the grab 28, the chains 31 and the winch 30 of the basket 20. The new fuel assembly 3 is then deposited in the storage pool 4. The device for the dry handling of new fuel assemblies makes it possible to limit the risks of defect or deterioration of those assemblies by using, dedicated handling equipment offering mechanical protection during handling on the one hand, and by not needing to lift the cask under any circumstances on the other hand. The reliability of the lifting is further increased by having a transport basket handled by a crane whereof the maximum load is much larger than the weight of the cask and having a redundant attachment between the basket and the crane. The handling device according to the invention also has the advantage of limiting the consequences of any fall of the fuel assembly either by limiting the height of the possible falls, or by providing additional static confinement in certain parts of the unloading steps. The basket also protects the fuel assembly against the lateral impacts that may occur during the handling phase. The device according to the invention may of course also adapt to a new installation as well as an existing installation, given that it involves little or no modification to the existing material and makes it possible to limit the dose rates for operators due to the fact that the unloading is done dry, which avoids having to decontaminate the cask and limits the needs for human intervention. Although the device for the dry handling of nuclear fuel assemblies described above is particularly well suited to unloading new fuels containing MOX, it may advantageously also be used to handle spent fuel, in particular when spent fuel assemblies must be transported into fuel re-treatment plants using a cask. |
|
abstract | Noise map for CT images have been estimated by generalizing the prior art even-and-odd views approach. One example is to estimate a noise map from images reconstructed from three sets of independent views. A second example is to estimate a noise map from images reconstructed by using two sets of correlated views. A third example is to estimate a noise map from noise map from two images reconstructed from two sets of independent views while the number of views in each set is unequal. Physical phantom data were employed to validate our proposed noise map estimation methods. In comparison to the existing method, our alternative methods yield reasonably accurate noise map estimation. |
|
052710467 | description | Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is seen a pipeline 2 which is introduced into a vessel 1 through a connection piece or pipe 3 and is joined to it by welding. The vessel 1 is surrounded by a biological shield 4 and a thermal insulation 5. At the entry point of the pipeline 2, the biological shield 4 has an opening 6, which is typically rectangular in shape. As can be seen in FIGS. 1 and 2, a manipulator 7 includes two trolleys 8, 9 that are movable circumferentially around the connection piece 2, and a jointed-shank arm 10 which pivots like scissors. This jointed-shank arm 10 has two shanks 11, 12, which are each supported at one end in a respective hinged support 13, 14 disposed on the trolleys 8, 9, with the hinged support being constructed as a cardan joint or ball and socket joint. The other ends of the shanks 11, 12 are joined together by a crown hinge 15. A support 16 with a test head 17 is disposed on the crown hinge 15. The crown hinge 15 advantageously includes one toothed ring segment 11a, 12a on the end of each respective one of the shanks 11, 12. The toothed ring segments 11a, 12a mesh with one another. Center points of the toothed ring segments 11a, 12a are each supported in a respective pivot pin 16a, 16b. The pivot pins are mounted on the support 16. As a result, the support 16, upon a change in the angle between the two shanks 11, 12 and a resultant radial motion of the crown hinge 15, is always aligned in the axis between the shanks 11, 12 bisecting that angle. In other words, it maintains its same angular position. The trolleys 8, 9 have the shape of a segment of a circle and are movable along an annular rail 26 circumferentially of the pipe 2. The trolleys 8, 9 are supported on the annular rail 26 by means of pairs of rollers 27a, 27b and are each driven by a respective electric motor 18, 19 with position encoders 20, 21. The motors 18 and 19 each act through a respective pinion 28a (28b) on a common circular rack 29. A respective base plate 30a, 30b is disposed on each of the trolleys 8, 9, and a respective guide rail 31a, 31b is clamped thereon parallel to the axis of the connection piece 3 by means of a respective clamping device 31c, 31d. The jointed-shank arm 10 can be introduced on the guide rails. The guide rails 31a, 31b also serve to fix a distance between the hinged supports 13, 14 and a wall of the vessel 1. The hinged supports 13 and 14 of the jointed-shank arm are each connected through a respective web 13a, 14a to a shoe, 32a, 32b, which is guided adjustably in the axial direction of the pipe 2 in a dovetail-like recess of the respective guide rail 31a, 31b. A locking device 33a, 33b serves to fix the position. One spring means 22, 23 is disposed between each of the shoes or carriages 32a, 32b and a respective one of the shanks 11, 12, in order to press the test head 17 or a tool against the wall region to be tested. The spring means 22, 23 may preferably be constructed as pneumatic or hydraulic cylinders. As FIG. 3 shows, a pivot pin 34 is disposed on the web 13a and a bracket 35 is rotatably supported on the pivot pin 34. An eyelet 36 is disposed on the bracket 35 for rotatably retaining the spring means 22. A pivot pin 37 on which the shank 11 is supported, is also secured to the bracket 35. The configuration forms a cardan joint. At least one angle encoder 24 and/or 25 for detecting the inclination of at least one of the shanks 11 or 12 relative to a reference plane, is provided on the hinged supports 13, 14. The motors 18, 19, the associated position encoders 20, 21 and the angle encoders 24, 25 are connected to a control device 34' containing an arithmetic unit 35', for the trolleys 8, 9. The crown hinge 15 is moved radially into a predetermined position by varying the position of at least one of the trolleys 8, 9, by means of the control device 34' acting upon the drive motors 18, 19. By moving both of the trolleys 8, 9 simultaneously and in the same direction, the test head 17 or a tool can be moved along a curve having a center which is located in the axis of the connection piece 3. Through the use of a different coordinated control of the drive motors 18, 19, an arbitrary testing path can be established in the radial direction and in the circumferential direction of the connection piece. For removal (tool changing, test head changing), the two trolleys 8, 9 are moved far enough apart that the jointed-shank arm 10 rests almost on the connection piece 3 (in the position shown in dashed lines in FIG. 2). The spring means 22, 23 are then relaxed, or the pneumatic or hydraulic cylinders are retracted, so that the test head 17 no longer rests on the vessel wall and the jointed-shank arm 10, after release of the clamping device 31c, 31d, with the guide rails 31a, 31b, is removed from the opening 6. |
claims | 1. A confinement matrix for the storage or incineration of at least one long-life radioactive element, comprising:at least one crystalline boron compound of a rhombohedral structure comprising said at least one long-life radioactive element. 2. The matrix according to claim 1, wherein said at least one long-life radioactive element is inserted in the crystalline network of the boron compound. 3. The matrix according to claim 1, wherein said at least one long-life radioactive element is dispersed in oxide form in the rhombohedral structured boron compound. 4. The matrix according to claim 3, wherein the boron compound is B3Si. 5. The matrix according to claim 3, wherein the boron compound is B6O. 6. The matrix according to claim 3, wherein the boron compound is B4C. 7. The matrix according to claim 1 for the incineration of at least one radioactive element, wherein the boron of the boron compound is enriched with 11B. 8. A method for preparing a confinement matrix for at least one long life radioactive element, comprising:mixing a powder of said at least one long-life radioactive element or a powder of at least one compound of said at least one long-life element with a boron powder or a boron precursor, to obtain a powder mixture, andthen producing a hot reaction of the powder mixture at a temperature of 800 to 1500° C. and sintering the powders obtained;thereby obtaining said confinement matrix which comprises at least one crystalline compound of a rhombohedral structure in the crystalline network into which said at least one long-life radioactive element is inserted. 9. The method according to claim 8, wherein the powder mixture also comprises one or more additives selected from the group consisting of metals, catalysts, metal oxides, and the adjuvants required to form the matrix or improve its properties. 10. The method according to claim 8, wherein the boron precursor is selected from the group consisting of B2O3, H3BO3, B3Si, B6O and B4C. 11. The method according to claim 8, wherein the powders of the mixture are powders of boron, a metal oxide and at least one radioactive element,wherein the powders are first reacted at a temperature of 1000 to 1500° C., under an inert gas stream, andwherein the sintering is then carried out at a temperature of 1200 to 1800° C., at a pressure of 30 to 200 MPa. 12. A method for preparing a confinement matrix for at least one long-life radioactive element, comprising:mixing a powder of said at least one long-life radioactive element or a powder of at least one compound of said at least one long-life element with a boron powder or a boron precursor, to obtain a powder mixture; andthen a hot reaction and sintering are performed at the same time by reactive sintering at a temperature of 1000 to 1800° C., at a pressure of 30 to 200 MPa;thereby obtaining said confinement matrix which comprises at least one crystalline compound of a rhombohedral structure in the crystalline network into which said at least one long-life radioactive element is inserted. 13. The method according to claim 9, wherein the powders of the mixture are powders of boron, a metal oxide and at least one radioactive element, andwherein the reactive sintering is performed at a temperature of 1300 to 1400° C., at a pressure of 30 to 200 MPa. 14. A method for preparing a confinement matrix in the form of a composite material, comprising:dispersing at least one long-life radioactive element in a crystalline boron compound of a rhombohedral structure by a method comprising:mixing of a powder of the crystalline boron compound having said rhombohedral structure with a powder of the radioactive element or a compound of said element selected from the group consisting of oxides, to obtain a mixture; andpressurised sintering of the mixture at a temperature of 1000 to 1800° C., and at a pressure of 30 to 200 MPa. 15. The method according to claim 14, wherein the boron compound is B4C, B6O or B3Si. |
|
claims | 1. A container for the storage and transport of nuclear fuel elements comprising a plurality of elongate compartments for receiving the nuclear fuel elements, the compartments being defined by a first set of plates having a common plane intersecting with a second set of plates, the first set of plates extending perpendicularly with respect to the second set of plates to define compartments having a rectangular cross section, wherein the plates include an interlocking joint, the interlocking joint comprising at least one projection provided on one plate of one set and a recess formed in the other plate of the same set, and wherein a retaining portion is provided in the recess for engagement by the projection so as to interlock the plates to prevent separation of the plates by relative movement in their common plane. 2. A container according to claim 1 , wherein the plates in the first set are interconnected by an interlocking joint comprising a plurality of projections spaced along a longitudinal edge of one of the plates and a plurality of recesses spaced along a longitudinal edge of the other plate. claim 1 3. A container according to claim 2 , wherein the projection comprises a first portion extending forwardly from the longitudinal edge of the said one of the plates and an arm portion extending laterally from an end of the first portion, and wherein the arm portion engages with the retaining portion in the recess. claim 2 4. A container according to claim 3 , wherein an arm portion extends from each side of the first portion, the recess having two retaining portions, each of which is engaged by an arm portion. claim 3 5. A container according to claim 4 , wherein the first portion and each arm portion may define a substantially T-shaped projection and wherein the recess is correspondingly substantially T-shaped. claim 4 6. A container according to claim 5 , wherein each arm portion may be formed by a deflectable tab extending rearwardly and outwardly from an end of the first portion, the tabs being deflected inwardly as the projection is pushed into the recess, the tabs tending to resume their undeflected positions when the projection is located in the recess. claim 5 7. A container according to claim 6 , wherein the recess has a first passage region extending into an enlarged region, the junction of the first passage region and the enlarged region defining the retaining portion. claim 6 8. A container according to claim 6 , wherein at an intersection of the first and second set of plates the recess is in a plate of the second set. claim 6 9. A container according to claim 1 , wherein at an intersection of the first and second set of plates at least one tenon projects from each of the mutually facing longitudinal edges of the plates of the second set, the tenons extending into a slot provided in the plate of the first set. claim 1 10. A container according to claim 9 , wherein a tenon projects from each of the mutually facing longitudinal edges of the plates of the second set, the tenons being received by the same slot. claim 9 11. A container according to claim 9 , wherein the tenons on each of the longitudinal edges are provided with interengaging latch portions. claim 9 12. A container according to claim 1 , wherein the recess has a first passage region extending into an enlarged region, and wherein a junction of the first passage region and the enlarged region defines the retaining portion. claim 1 13. A container according to claim 12 , wherein at an intersection of the first and second set of plates the recess is in a plate of the second set. claim 12 14. A container according to claim 2 , wherein at an intersection of the first and second set of plates at least one tenon projects from each of the mutually facing longitudinal edges of the plates of the second set, the tenons extending into a slot provided in the plate of the first set. claim 2 15. A container according to claim 14 , wherein a tenon projects from each of the mutually facing longitudinal edges of the plates of the second set, the tenons being received by the same slot. claim 14 16. A container according to claim 14 , wherein the tenons on each of the longitudinal edges are provided with interengaging latch portions. claim 14 17. A container according to claim 15 , wherein the tenons on each of the longitudinal edges are provided with interengaging latch portions. claim 15 18. A container according to claim 3 , wherein at an intersection of the first and second set of plates at least one tenon projects from each of the mutually facing longitudinal edges of the plates of the second set, the tenons extending into a slot provided in the plate of the first set. claim 3 19. A container according to claim 18 , wherein a tenon projects from each of the mutually facing longitudinal edges of the plates of the second set, the tenons being received by the same slot. claim 18 20. A container according to claim 18 , wherein the tenons on each of the longitudinal edges are provided with interengaging latch portions. claim 18 21. A container according to claim 19 , wherein the tenons on each of the longitudinal edges are provided with interengaging latch portions. claim 19 22. A container according to claim 4 , wherein at an intersection of the first and second set of plates at least one tenon projects from each of the mutually facing longitudinal edges of the plates of the second set, the tenons extending into a slot provided in the plate of the first set. claim 4 23. A container according to claim 22 , wherein a tenon projects from each of the mutually facing longitudinal edges of the plates of the second set, the tenons being received by the same slot. claim 22 24. A container according to claim 22 , wherein the tenons on each of the longitudinal edges are provided with interengaging latch portions. claim 22 25. A container according to claim 23 , wherein the tenons on each of the longitudinal edges are provided with interengaging latch portions. claim 23 26. A container according to claim 5 , wherein at an intersection of the first and second set of plates at least one tenon projects from each of the mutually facing longitudinal edges of the plates of the second set, the tenons extending into a slot provided in the plate of the first set. claim 5 27. A container according to claim 26 , wherein a tenon projects from each of the mutually facing longitudinal edges of the plates of the second set, the tenons being received by the same slot. claim 26 28. A container according to claim 26 , wherein the tenons on each of the longitudinal edges are provided with interengaging latch portions. claim 26 29. A container according to claim 27 , wherein the tenons on each of the longitudinal edges are provided with interengaging latch portions. claim 27 30. A container according to claim 10 , wherein the tenons on each of the longitudinal edges are provided with interengaging latch portions. claim 10 |
|
claims | 1. A radiation protection panel to protect a living body against space radiation, the radiation protection panel comprising:a radiation attenuation layer comprising a plurality of shielding elements; andeach of said shielding elements comprising an individual radiation attenuating characteristics;wherein the individual radiation attenuating characteristic is at least one of a thickness or a density of the shielding element that is substantially inversely related to radiation attenuation levels of tissue present between each of said plurality of shielding elements and the underlying organ of the living body; andeach said shielding element being a geometric shape; anda flexible material connecting the plurality of shielding elements;wherein the panel comprises flexibility greater than an individual shielding element,wherein the plurality of the shielding elements includes a plurality of longitudinal members that are attached to the flexible material, the plurality of longitudinal members result in varying radiation attenuating characteristics across a surface of the radiation protection layer, and each longitudinal member extends further in a direction perpendicular to a plane of the flexible material than it does in a direction parallel to the plane of the flexible material. 2. The radiation protection panel of claim 1, comprising a wearable garment. 3. The radiation protection panel of claim 1, the shielding element wherein the geometric shape comprises any three-dimensional form arising from the three-dimensional extrusion of a two-dimensional repeating, adjacent, tessellated pattern such as squares, rectangles, hexagons, triangles, pentagons or any combination of regular or irregular shapes using one or multiple geometrical shapes in a single pattern. 4. The radiation protection panel of claim 1, the shielding element comprises a friction minimizing material. 5. The radiation protection panel of claim 1, whereinthe shielding element comprises an outer solid material shell defining an internal cavity;one of the radiation attenuating characteristics of the shielding element is determined by the composition of the outer solid material shell of the shielding element; andanother of the radiation attenuating characteristics of the shielding element is determined by the composition of the internal cavity of the shielding element. 6. The radiation protection panel of claim 1, comprising:a vertical axis;wherein the shielding element has a thickness defined along the vertical axis;wherein one of the radiation attenuating characteristics of the shielding element is the thickness of the shielding element; andwherein the thickness of the shielding element is varied to vary the radiation attenuation of the shielding element. 7. The radiation protection panel of claim 6, wherein each subset of the plurality of the shielding element having the same thickness is marked enabling the identification of the shielding element having the same thickness. 8. The radiation protection panel of claim 6, wherein the thickness of the shielding element is oriented perpendicular to a tissue. 9. The radiation protection panel of claim 8, comprisesat least two light-weight radiation protection panels; andwherein the at least two light-weight radiation protection panels partially overlap;wherein the thickness of the at least two are varied to maintain the relationship between radiation attenuation levels of the shielding element and the radiation attenuation tolerance of the tissue protected by the plurality of shielding element. 10. The radiation protection panel of claim 9, comprising:the at least two light-weight radiation protection panels comprise a wearable garment. 11. The radiation protection panel of claim 1, wherein the plurality of longitudinal members have uniform heights, resulting in a uniform thickness of the radiation protection layer. 12. The radiation protection panel of claim 1, wherein the plurality of longitudinal members have non-uniform heights, resulting in a varying thickness of the radiation protection layer. 13. The radiation protection panel of claim 1, wherein the longitudinal members are slidable against each other. 14. The radiation protection panel of claim 1, wherein the longitudinal members are attached to the flexible material on both sides using heat welding. 15. The radiation protection panel of claim 1, wherein the plurality of longitudinal members includes a first layer of longitudinal members, and a second layer of longitudinal members staggered on top of the first layer of longitudinal members. 16. The radiation protection panel of claim 15, wherein the first layer of longitudinal members has a uniform thickness. 17. The radiation protection panel of claim 15, wherein the second layer of longitudinal members has a non-uniform thickness, and includes longitudinal members of non-uniform heights that correspond to varying radiation attenuating characteristics. 18. The radiation protection panel of claim 15, wherein the first layer of longitudinal members includes a first radiation attenuating material, and the second layer of longitudinal members include a second radiation attenuating material different from the first radiation attenuating material. 19. The radiation protection panel of claim 1, wherein the plurality of longitudinal members are attached to the flexible material by a plurality of snap buttons. 20. The radiation protection panel of claim 19, wherein each snap button includes a ring and a pin for holding the flexible material. 21. The radiation protection panel of claim 19, wherein the snap buttons include a material more flexible than the flexible material. 22. The radiation protection panel of claim 1, wherein the plurality of longitudinal members include a plurality of poles. |
|
description | The present application is a continuation of U.S. patent application Ser. No. 13/323,743, filed Dec. 12, 2011, which is a continuation of U.S. patent application Ser. No. 11/054,898, filed Feb. 10, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 10/803,620, filed Mar. 18, 2004, and granted as U.S. Pat. No. 7,068,748, the entireties of which are hereby incorporated by reference. The present invention related generally to the field of storing spent nuclear fuel, and specifically to systems and methods for storing spent nuclear fuel in ventilated vertical modules. In the operation of nuclear reactors, it is customary to remove fuel assemblies after their energy has been depleted down to a predetermined level. Upon removal, this spent nuclear fuel is still highly radioactive and produces considerable heat, requiring that great care be taken in its packaging, transporting, and storing. In order to protect the environment from radiation exposure, spent nuclear fuel is first placed in a canister. The loaded canister is then transported and stored in large cylindrical containers called casks. A transfer cask is used to transport spent nuclear fuel from location to location while a storage cask is used to store spent nuclear fuel for a determined period of time. In a typical nuclear power plant, an open empty canister is first placed in an open transfer cask. The transfer cask and empty canister are then submerged in a pool of water. Spent nuclear fuel is loaded into the canister while the canister and transfer cask remain submerged in the pool of water. Once fully loaded with spent nuclear fuel, a lid typically placed atop the canister while in the pool. The transfer cask and canister are then removed from the pool of water, the lid of the canister is welded thereon and a lid is installed on the transfer cask. The canister is then properly dewatered and filled with inert gas. The transfer cask (which is holding the loaded canister) is then transported to a location where a storage cask is located. The loaded canister is then transferred from the transfer cask to the storage cask for long term storage. During transfer from the transfer cask to the storage cask, it is imperative that the loaded canister is not exposed to the environment. One type of storage cask is a ventilated vertical overpack “VVO”). A VVO is a massive structure made principally from steel and concrete and is used to store a canister loaded with spent nuclear fuel. VVOs stand above ground and are typically cylindrical in shape and extremely heavy, weighing over 150 tons and often having a height greater than 16 feet. VVOs typically have a flat bottom, a cylindrical body having a cavity to receive a canister of spent nuclear fuel, and a removable top lid. In using a VVO to store spent nuclear fuel, a canister loaded with spent nuclear fuel is placed in the cavity of the cylindrical body of the VVO. Because the spent nuclear fuel is still producing a considerable amount of heat when it is placed in the VVO for storage, it is necessary that this heat energy have a means to escape from the VVO cavity. This heat energy is removed from the outside surface of the canister by ventilating, the VVO cavity. In ventilating the VVO cavity, cool air enters the VVO chamber through bottom ventilation ducts, flows upward past the loaded canister, and exits the VVO at an elevated temperature through top ventilation ducts. The bottom and top ventilation ducts of existing VVOs are located circumferentially near the bottom and top of the VVOs cylindrical body respectively, as illustrated in FIG. 1. While it is necessary that the VVO cavity be vented so that heat can escape from the canister, it is also imperative that the VVO provide adequate radiation shielding and that the spent nuclear fuel not be directly exposed to the external environment. The inlet duct located near the bottom of the overpack is a particularly vulnerable source of radiation exposure to security and surveillance personnel who, in order to monitor the loaded overpacks, must place themselves in close vicinity of the ducts for short durations. Additionally, when a canister loaded with spent nuclear fuel is transferred from a transfer cask to a storage VVO, the transfer cask is stacked atop the storage VVO so that the canister can be lowered into the storage VVO's cavity. Most casks are very large structures and can weigh up to 250,000 lbs. and have a height of 16 ft. or more. Stacking a transfer cask atop a storage VVO/cask requires a lot of space, a large overhead crane, and possibly a restraint system for stabilization. Often, such space is not available inside a nuclear power plant. Finally, above ground storage VVOs stand at least 16 feet above around, thus, presenting a sizable target of attack to a terrorist. FIG. 1 illustrates a traditional prior art VVO 2. Prior art VVO 2 comprises flat bottom 17, cylindrical body 12, and lid 14. Lid 14 is secured to cylindrical body 12 by bolts 18. Bolts 18 serve to restrain separation of lid 13 from body 12 if prior art VVO 2 were to tip over. Cylindrical body 12 has top ventilation ducts 15 and bottom ventilation ducts 16. Top ventilation ducts 15 are located at or near the top of cylindrical body 12 while bottom ventilation ducts 16 are located at or near the bottom of cylindrical body 12. Both bottom ventilation ducts 16 and top ventilation ducts 15 are located around the circumference of the cylindrical body 12. The entirety of prior an VVO 2 is positioned above grade. It is an object of the present invention to provide a system and method for storing spent nuclear fuel that reduces the height of the stack assembly when a transfer cask is stacked atop a storage VVO. It is another object of the present invention to provide a system and method for storing spent nuclear fuel that requires less vertical space. Yet another object of the present invention is to provide a system and method for storing spent nuclear fuel that utilizes the radiation shielding properties of the subgrade during storage while providing adequate ventilation of the spent nuclear fuel. A further object of the present invention is to provide a system and method for storing spent nuclear fuel that provides the same or greater level of operational safeguards that are available inside a fully certified nuclear power plant structure. A still further object of the present invention is to provide a system and method for storing, spent nuclear fuel that decreases the dangers presented by earthquakes and other catastrophic events and virtually eliminates the potential damage from a World Trade Center or Pentagon type of attack on the stored canister. It is also an object of the present invention to provide a system and method for storing spent nuclear fuel that allows an ergonomic transfer of the spent nuclear fuel from a transfer cask to a storage VVO. Another object of the present invention is to provide a system and method for storing spent nuclear fuel below grade. Yet another object of the present invention is to provide a system and method of storing spent nuclear fuel that reduces the amount of radiation emitted to the environment. Still another object of the present invention is to provide a system and method of storing spent nuclear fuel that affords adequate heat removal capabilities from a stored canister during flood conditions, including “smart flood” conditions. These and other objects are met by the present invention which in one aspect is a method of storing spent nuclear fuel comprising: providing a below grade hole; providing a system comprising a shell forming a cavity for receiving, a canister of spent nuclear fuel, at least a portion of the shell positioned below grade, and at least one inlet ventilation duct extending from an inlet to an outlet at or near a bottom of the cavity, the inlet ventilation duct connected to the shell; positioning, the apparatus in the hole so that the inlet of the inlet ventilation duct is above grade and the outlet of the inlet ventilation duct into the cavity is below grade; filling the hole with engineered fill; and lowering; a spent fuel canister into the cavity. In another aspect, the invention is a method of storing spent nuclear fuel comprising: providing a system comprising a structure forming a cavity for receiving and storing a spent nuclear fuel canister, the cavity having a top, a bottom, and a bottom surface, at least one inlet ventilation duct forming a passageway from an ambient air inlet to an outlet at or near the bottom of the cavity, and at least one outlet ventilation duct forming a passageway from at or near the top of the cavity to ambient air; lowering a canister loaded with spent nuclear fuel into the cavity until a bottom surface of the canister is lower than a top of the outlet of the at least one inlet ventilation duct; and supporting the canister in the cavity in a position where the bottom surface of the canister is lower than the top of the outlet of the at least one inlet ventilation duct. In yet another aspect, the invention is a method of storing spent nuclear fuel comprising: providing a system comprising a body having a cavity for receiving and storing a spent fuel canister, a major portion of the body positioned below grade, and the body having at least one inlet ventilation duct extending from an above grade inlet to a below grade outlet in the cavity; lowering the spent fuel canister into the cavity so that a major portion of the canister is below grade; and placing a lid atop the body so as to enclose the cavity, the lid having at least one outlet ventilation duct for allowing heated air to exit the cavity; wherein ventilation of the canister is provided by cold air entering the cavity through the inlet ventilation duct in the body, the cold air being heated within the cavity by the spent nuclear fuel, and warm air exiting the cavity through the outlet ventilation duct in the lid. In even yet another aspect, the invention is a method of storing spent nuclear fuel having a low level heat load comprising: providing a system comprising a structure forming a cavity for receiving a canister of spent nuclear fuel, at least a portion of the cavity being positioned below grade, and at least one ventilation duct forming a passageway from at or near the top of the cavity to an ambient atmosphere, wherein the cavity is hermetically sealed to ingress of below grade fluids; lowering a canister of low heat spent nuclear fuel into the cavity until at least a major portion of the canister is below grade; and supporting the canister in the cavity. Referring to FIGS. 2 and 3, underground VVO 20 is illustrated according to a first embodiment of the present invention. Underground VVO 20 is a vertical, ventilated dry spent fuel storage system that is fully compatible with 100 ton and 125 ton transfer casks for spent fuel canister transfer operations. Underground VVO 20 can be modified/designed to be compatible with any size or style transfer cask. Underground VVO 20 is designed to accept spent fuel canisters for storage at an Independent Spent Fuel Storage Installation “ISFSI”) in lieu of above ground overpacks (such as prior art VVO 2 in FIG. 1). All spent fuel canister types engineered for storage in free-standing and anchored overpack models can be stored in underground VVO 20. As used herein the term “canister” broadly includes any spent fuel containment apparatus, including, without limitation, multi-purpose canisters and thermally conductive casks. For example, in some areas of the world, spent fuel is transferred and stored in metal casks having a honeycomb grid-work/basket built directly into the metal cask. Such casks and similar containment apparatus qualify as canisters, as that term is used herein, and can be used in conjunction with underground VVO 20 as discussed below. Underground VVO 20 comprises body 21, base 22, and removable lid 41. Body 21 is constructed of concrete, but can be constructed of other suitable materials. Body 21 is rectangular in shape but can be any shape, such as for example, cylindrical, conical, spherical, semi-spherical, triangular, or irregular in shape. A portion of body 21 is positioned below grade so that only top portion 24 protrudes above grade level 23. Preferably, at least a major portion of the height of body 21 is positioned below grade. The exact height which top portion 24 of body 21 extends above ground level 23 can be varied greatly and will depend on a multitude of design considerations, such as canister dimensions, radioactivity levels of the spent fuel to be stored, ISFSI space limitations, geographic location considering susceptibility to missile-type and ground attacks, geographic location considering frequency of and susceptibility to natural disasters (such as earthquakes, floods, tornadoes, hurricanes, tsunamis, etc.), environmental conditions (such as temperature, precipitation levels), and/or ground water levels. Preferably, top portion 24 of body 21 is less than approximately 42 inches above ground level 23, and most preferably approximately 6 to 36 inches above ground level 23. In some embodiments, it may even be preferable that the entire height of body 21 be below grade (illustrated in FIGS. 8D and 8E). As will be discussed in more detail below, when the entire height of body is below grade, only the top surface of the body will be exposed to the ambient air above grade. Referring still to FIGS. 2 and 3, body 21 forms cylindrical cavity 26 therein (best shown in FIG. 3). While cavity 26 is cylindrical in shape, cavity 26 is not limited to any specific size, shape, and/or depth and can be designed to receive and store almost any shape of canister without departing from the spirit of the invention. While not necessary to practice the invention, it is preferred that the horizontal cross-sectional size and shape of cavity 26 be designed to generally correspond to the horizontal cross-sectional size and shape of the canister-type that is to be used in conjunction with that particular underground VVO. More specifically, it is desirable that the size and shape of cavity be designed so that when a spent fuel canister (such as canister 70) is positioned in cavity 26 for storage, a small clearance exists between the outer side walls of the canister and the side walls of cavity 26. Designing cavity 26 so that a small clearance is formed between the side walls of the stored canister and the side walls of cavity 26 limits the degree the canister can move within the cavity during a catastrophic event, thereby minimizing damage to the canister and the cavity walls and prohibiting the canister from tipping over within the cavity. This small clearance also facilitates flow of the heated air during spent nuclear fuel cooling. The exact size of the clearance can be controlled/designed to achieve the desired fluid flow dynamics and beat transfer capabilities for any given situation. In some embodiments, for example, the clearance may be 1 to 3 inches. A small clearance also reduces radiation streaming. Two inlet ventilation ducts 25 are provided in body 21 for providing inlet ventilation to the bottom of cavity 26. Inlet ventilation ducts 25 are elongated substantially S-shaped passageways extending from above grade inlets 27 to below grade outlets 28. Above grade inlets 27 are located on opposing side walls of top portion 24 of body 21 and open to the ambient air above ground level 23. As use herein, the terms ambient air, ambient atmosphere, or outside atmosphere, refer to the atmosphere/air external, to the underground VVO, and include the natural outside environment and spaces within buildings, tents, caves, tunnels, or other man-made or natural enclosures. Below grade outlets 28 open into cavity 26 at or near its bottom at a position below the ground level 23. Thus, inlet ventilation ducts 25 provide a passageway for the inlet of ambient air to the bottom of cavity 26, despite the bottom of cavity 26 being well below grade. Vent screens 31 (FIG. 3) are provided to cover above grade inlets 27 so that objects and other debris can not enter and block the passageways of inlet ventilation ducts 25. As a result of the elongated S-shape of inlet ventilation ducts 25, above grade inlets 27 cease to be a location of elevated dose rate that is common in free-standing above ground VVOs. While below grade outlets 28 are illustrated as being opening near the bottom of the walls of cavity 26, below grade outlets 28 can be located in the floor of cavity 26 is desired. This can be accomplished by appropriately reshaping inlet ventilation ducts 25 and forming an opening through bottom plate 38 and into cavity 26. In such an embodiment, base 22 can be considered part of the body 21 through which the inlet ventilation ducts 25 extend. Above grade inlets 27 are located in the side walls of body 21 at an elevation of about 10 inches above ground level 23. However, the elevation of above grade inlets 27 is not limiting of the present invention. The inlets 27 can be located at any desired elevation above the ground level, including level/flush therewith, as shown in FIGS. 8D and 8E. Elevating above grade inlets 27 substantially above the ground level 23 helps reduce the likelihood that rain or flood water will enter the cavity 26. It is noted that for IFSI's in flood zones, floodwater can possibly rise more than a foot above ground level and, thus, enter cavity 26 via inlet ventilation ducts 25. However, as discussed below with respect to FIG. 6, underground VVO 20 is specifically designed to deal with the worst flood conditions in a safe and effective manner. While above grade inlets 27 are preferably located in the side walls of body 21, the above grade inlets are not limited to such a location and, if desired, can be located anywhere on the body, including for example in the top surface (or any other surface) of the body. Further examples of possible locations for above grade inlets 27 on body 21 are illustrated in FIGS. 8A-8E. Referring still to FIGS. 2 and 3, inlet ventilation ducts 25 have a rectangular cross-sectional area of about 6 inches by 40 inches. However, any cross-sectional shape and/or size can be used, such as for example, round, elliptical, triangular, hexagonal, octagonal, etc. Additionally, while the shape of inlet ventilation ducts 25 is an elongated substantially S-shaped passageway, a multitude of shapes can be used that still achieve acceptable dose rates at the above grade inlets 27. For example, rather than an elongated S-shape, the inlet ventilation duct can extend from the above grade inlet to the below grade outlet in a zig-zag shape, a tilted linear shape, a general L-shape, or any angular, linear, or curved combination. The exact shape, size, and cross-sectional configuration of the inlet ventilation duct is a matter of design preference and will be dictated by such factors, such as thickness of the body of the VVO, radioactivity level of the spent fuel being stored in the cavity, temperature of the spent fuel canister, desired fluid flow dynamics through the ducts, and placement of the above grade inlet vents on the body (i.e., whether the above grade inlet vents/opening are located on the side walls of the body, its top surface, or some other surface of the body). Further examples of possible shapes for inlet ventilation ducts 25 are illustrated in FIGS. 8A-8E. Inlet ventilation ducts 25 are preferably formed by a low carbon steel liner. However, inlet ventilation ducts 25 can be made of any material or can be mere passageways formed into concrete body 21 without a lining. As best illustrated in FIG. 3, cavity 26 is formed by thick steel shell 34 and bottom plate 38. Shell 34, bottom plate 38, and inlet ventilation ducts 25 are preferably made of a metal, such as steel, preferably low carbon steel, but can be made of other materials, such as stainless steel, aluminum, aluminum-alloys, plastics, and the like. Inlet ventilation ducts 25 are seal joined to shell 34 and bottom plate 38 to form an integral/unitary structure 100 (shown in isolation in FIG. 9) that is hermetically sealed to the ingress of below grade water and other fluids. In the case of weldable metals, this seal joining may comprise welding or the use of gaskets. Thus, the only way water or other fluids can enter cavity 26 is through above grade inlets 27 or outlet ventilation ducts 42 in lid 41. As will be discussed below with respect to FIGS. 9-15, the integral structure itself is an invention and can be used to store spent nuclear fuel without the use of body 21. An appropriate preservative, such as a coal tar epoxy or the like, is applied to the exposed surfaces of shell 34, bottom plate 38, and inlet ventilation ducts 25 in order to ensure sealing, to decrease decay of the materials, and to protect against fire. A suitable coal tar epoxy is produced by Carboline Company out of St. Louis, Mo. under the tradename Bitumastic 300M. In some embodiments of the underground VVO of the present invention, a bottom plate will not be used. Concrete body 21 surrounds shell 34 and inlet, ventilation ducts 25. Body 21 provides non-structural protection for shell 34 and inlet ventilation ducts 25. Insulation 37 is provided at the interface between shell 34 and concrete body 21 and at the interface between inlet ventilation ducts 25 and concrete body 21. Insulation 37 is provided to prevent excessive transmission of heat decay from spent fuel canister 70 to concrete body 21, thus maintaining the bulk temperature of the concrete within FSAR limits. Insulating shell 34 and inlet ventilation ducts 25 from concrete body 21 also serves to minimize the heat-up of the incoming cooling air before it enters cavity 26. Suitable forms of insulation include, without limitation, blankets of alumina-silica fire clay (Kaowool Blanket), oxides of alimuna and silica (Kaowool S Blanket), alumina-silica-zirconia fiber (Cerablanket), and alumina-silica-chromia (Cerachrome Blanket). Insulating, inlet ventilation ducts 25 from the heat load of spent fuel in cavity 26 is very important in facilitating and maintaining adequate ventilation/cooling of the spent fuel. The insulating process can be achieved in a variety of ways, none of which are limiting of the present invention. For example, in addition to adding, an insulating material to the exterior of the shell 34 and inlet ventilation ducts 25, it is also possible to insulate inlet ventilation ducts 25 by providing a gap in concrete body 21 between cavity 26 and inlet ventilation ducts 25. The gap may be filled with an inert gas or air if desired. Moreover, irrespective of the means used to provide the insulating effect, the insulating means is not limited to being positioned on the outside surfaces of shell 34 or inlet ventilation ducts 25 but can be positioned anywhere between cavity 26 and inlet ventilation ducts 25. Body 21, along with the integral steel unit formed by bottom plate 38, shell 34, and ventilation ducts 25, are placed atop base 22. Base 22 is a reinforced concrete slab designed to satisfy the load combinations of recognized industry standards, such as, without limitation, ACI-349. Base 22 is rectangular in shape but can take on any shape necessary to support body 21, such as round, elliptical, triangular, hexagonal, octagonal, irregularly shaped, etc. While using a base is preferable to achieve adequate load supporting requirements, situations can arise where using such a base may be unnecessary. Referring back to FIG. 2, underground VVO 20 has a removable ventilated lid 41. Lid 41 is positioned atop body 21, thereby substantially enclosing cavity 26 so that radiation does not escape through the top of cavity 26 when canister 70 is positioned in cavity 26. When lid 41 is placed atop body 21 and spent fuel canister 70 is positioned in cavity 26, outlet air plenum 36 is formed between the top surface of canister 70 and lid 41. Outlet air plenum 36 is preferably a minimum of 3 inches in height, but can be any desired height. The exact height will be dictated by design considerations such as desired fluid flow dynamics, canister height, VVO height, the depth of the cavity, canister heat load, etc. Lid 41 has four outlet ventilation ducts 42. Outlet ventilation ducts 42 form a passageway from the top of cavity 26 (specifically from outlet air plenum 36) to the ambient air so that heated air can escape from cavity 26. Outlet ventilation ducts 42 are horizontal passageways that extend through side wall 30 of lid 41. However, the outlet ventilation ducts can be any shape or orientation, such as vertical, L-shaped, S-shaped, angular, curved, etc. Because outlet ventilation ducts 42 are located within lid 41 itself, the total height of body 21 is minimized. Lid 41 comprises a roof 35 made of concrete. Roof 35 provides radiation shielding so that radiation does not escape from the top of cavity 26. Side wall 30 of lid 41 is an annular ring. Outlet air plenum 36 helps facilitate the removal of heated air via outlet ventilation ducts 42. In order to minimize the heated air exiting outlet ventilation ducts 42 from being siphoned back into inlet ventilation ducts 25, outlet ventilation ducts 42 are azimuthally and circumferentially separated from inlet ventilation ducts 25. Ventilated lid 41 also comprises shear ring 47. When lid 41 is placed atop body 21, shear ring 47 protrudes into cavity 26, thus, providing enormous shear resistance against lateral forces from earthquakes, impactive missiles, or other projectiles. Lid 41 is secured to body 21 with bolts (not shown) that extend therethrough. While not illustrated, it is preferable that duct photon attenuators be inserted into all of inlet ventilation ducts 25 and/or outlet ventilation ducts 42 of underground VVO 20, irrespective of shape and/or size. A suitable duct photon attenuator is described in U.S. Pat. No. 6,519,307, Bongrazio, the teachings of which are incorporated herein by reference. Referring now to FIG. 4, an embodiment of a lid 50 that can be used in underground VVO 20 is illustrated. Lid 50 contains similar design aspects as lid 41 and is illustrated to more fully disclose the aforementioned lid design aspects. Lid 50 has four horizontal outlet ventilation ducts 51 in side wall 52. Shear ring 54 is provided on the bottom of lid 50 to fit into cavity 26. Bolts 18 are used to secure lid 50 to tapped holes in the top of body 21. While the outlet ventilation ducts are illustrated as being located within the lid 50 of underground VVO 20, the present invention is not so limited. For example, outlet ventilation ducts can be located in the body of the underground VVO at a location above grade. This concept is illustrated if FIGS. 8A-8E. If the outlet ventilation ducts are located in the body of the underground VVO, the openings of the outlet ventilation ducts to the ambient air can be located in the body's side walls, on its top surface, or in an other surface. Similar to when the outlet ventilation ducts are located in the lid, the outlet ventilation ducts can take on a variety of shapes and/or configurations when located in the body of the underground VVO itself. As with the inlet ventilation ducts, the outlet ventilation ducts are preferably formed by a low carbon steel liner, but can be made of any material or can be mere passageways formed into concrete body 21 or lid 41 without a lining. In all embodiments of the present invention which have both inlet and outlet ventilation ducts, it is preferred that the outlet ventilation duct openings be azimuthally and circumferentially separated, from the inlets of the inlet ventilation ducts to minimize interaction between inlet and outlet air streams. There is no limitation on the shape and style of lid used in conjunction with underground VVO 20. Referring back to FIG. 2, soil 29 surrounds body 21 for almost the entirety of its height. When spent fuel canister 70 is positioned in cavity 26, at least a major portion, if not the entirety, of canister 79 is below grade. Preferably, the entire height of canister 70 is below grade in order to take full advantage of the shielding, effect of the soil 29. Thus, soil 29 provides a degree of radiation shielding for spent fuel stored in underground VVO 20 that can not be achieved in above-ground overpacks. Underground VVO 20 is unobtrusive in appearance and there is no danger of underground VVO 20 tipping over. Additionally, underground VVO 20 does not have to contend with soil-structure interaction effects that magnify the free-field acceleration and potentially challenge the stability of an above ground free-standing overpack. Referring to FIG. 6, area VI-VI of FIG. 2 is illustrated in detail. FIG. 6 illustrates design aspects that are important to ensure that underground VVO 20 can successfully withstand flood conditions without adverse impact. Support blocks 32 are provided on the bottom surface (formed by plate 38) of cavity 26 so that canister 70 can be placed thereon. Support blocks 32 are circumferentially spaced from one another (shown in FIG. 7). When canister 70 is loaded into cavity 26 for storage, the bottom surface 71 of canister 70 rests on support blocks 32, forming an inlet air plenum 33 between the bottom surface 71 of the canister 70 and the bottom surface/floor of cavity 26. Support blocks 32 are made of low carbon steel and are preferably welded to the bottom surface of the cavity 26. Other suitable materials of construction include, without limitation, reinforced-concrete, stainless steel, and other metal alloys. Support blocks 32 also serve an energy/impact absorbing function. Support blocks 32 are preferably of a honeycomb grid style, such as those manufactured by Hexcel Corp., out of California, U.S. Support blocks 32 are specifically designed so that bottom surface 71 of canister 70 is lower than top 74 of below grade outlets 28 (FIG. 2) of inlet ventilation ducts 25. Preferably, support blocks 32 are designed so that bottom surface 71 of canister 70 is about 2 to 6 inches below top 74 of below grade outlets 28. However, any desired height differential can be achieved through proper design. By supporting canister 70 in cavity 26 so that its bottom surface 71 is lower than top 74 of below grade outlets 28, underground VVO 20 will provide adequate cooling to canister 70 under even the most adverse flood condition, which is colloquially referred to as a “smart flood.” A “smart flood” is one that floods the VVO so that the water level is just high enough to block airflow though the inlet ventilation ducts 25 completely. In other words, the water level is just even with top 74 of the below grade outlets 28. However, underground VVO 20 can adequately deal with the “smart flood” condition because the bottom surface 71 of the canister 70 is situated at a height that is below top 74 of below grade outlets 28. As a result, if a “smart flood” was to occur, the bottom of the canister 70 will be in contact with (i.e. submerged in) the water. Because the heat removal efficacy of water is over 100 times that of air, a wet bottom is all that is needed to effectively remove heat and keep the canister 70 cool. The deeper the submergence of canister 70 in the water, the cooler canister 70 and its contained fuel will remain. As the water in cavity 26 is heated by the bottom of canister 70, the water evaporates, rises through cavity 26 via annular space 60, and exits cavity 26 via the outlet ventilation ducts. Thus, the canister cooling action changes from ventilation air-cooling to evaporative water cooling. In one embodiment, below grade outlets 28 of inlet ventilation ducts 25 will be 8 inches high by 40 inches wide and inlet air plenum 33 is 6 inches high. This provides a height differential of 2 inches. It should be noted that the height differential design aspect of underground VVO 20 that is detailed in FIG. 6 can also be incorporated into free-standing above ground casks and VVOs to deal with “smart flood” conditions, independent of the other features of underground VVO 20. Thus, this concept is an independent inventive aspect of the present application. When incorporated into above ground VVOs, the inlet ventilation duets should be designed so that radiation can not escape to the surrounding environment front the inlet ventilation ducts. This is a threat because the canister will be below the inlet duct's opening, into the storage cavity. In this embodiment, the inlet ventilation ducts will be shaped so that a line of sight does not exist to the canister in the storage cavity from the ambient air. For example, the inlet ventilation ducts can comprise a portion that is L-shaped, angled, S-shaped, or curved. Moreover, while the height differential design aspect of FIG. 6 is achieved using support blocks 32, it is also possible to practice this aspect of the invention without support blocks 32. In such embodiments, canister 70 will be positioned in cavity 26 and rest directly on the floor of cavity 26. However, the use of support blocks 32 is desirable because of the creation of air inlet plenum 33 and because the use of support blocks 32 helps prohibit debris and dirt from getting trapped at the bottom of cavity 26. Referring now to FIGS. 8A-8E, examples of alternative configurations of the outlet ventilation ducts and the inlet ventilation ducts in an underground VVO according to the present invention are schematically illustrated. Much of the detail, and some structure, has been omitted in FIGS. 8A-8E for simplicity with the understanding that any or all of the details discussed above with respect to underground VVO 20 can be incorporated therein. Like numbers are used to identify like parts with the exception of alphabetical suffixes being used for each embodiment. It should be noted that in addition to the configurations of the inlet ventilation ducts and the outlet ventilation ducts illustrated in FIGS. 8A-8E, a multitude of other configurations, combinations, and modifications can be incorporated into the present invention. Some of these details are discussed above. Additionally, the outlet ventilation duct configurations of any of the illustrated embodiments can be combined with any of the illustrated inlet ventilation duct configurations, and vice versa. In all embodiments of the present invention, it is desirable that the heated air exiting the outlet ventilation ducts 42 be prohibited from being siphoned back into the inlet ventilation ducts 25 (i.e., keeping the warm outlet air stream from mixing with the cool inlet air stream). This can be accomplished by in a number of ways, including: (1) the positioning/placement of the inlets 27 on the underground VVO 20 with respect to the outlets of the outlet ventilation ducts 42; providing a plate 98 or other structure that segregates the air streams (as exemplified in FIGS. 8A and 8C-8E); and/or (3) extending the inlet ventilation ducts 25 to a position away from the outlet ventilation ducts 42. As a result of the heat emanating from canister 70, cool air from the ambient is siphoned into inlet ventilation ducts 25 and into the bottom of cavity 26. This cool air is then warmed by the heat from the spent fuel in canister 70, rises in cavity 26 via annular space 60 (FIG. 6) around canister 70, and then exits cavity 26 as heated air via outlet ventilation ducts 42 in lid 41. Referring now to FIG. 5, ISFIs can be designed to employ any number of underground VVOs 20 for integral structures 100) and can be expanded in number easily to meet growing needs. Although underground VVOs 20 are closely spaced, the design permits any cavity to be independently accessed by cask crawler 90 with ease. The subterranean configuration of underground VVOs 20 greatly reduce the height of the stack structures created during loading/transfer procedures where transfer cask 80 is positioned atop underground VVO 20. An embodiment of a method of using underground VVO 20 to store spent nuclear fuel canister 70 will now be discussed in relation to FIGS. 2-5. Upon being removed from a spent fuel pool and treated for dry storage, spent fuel canister 70 is positioned in transfer cask 80. Transfer cask is 80 is carried by cask crawler 90 to a desired underground VVO 20 for storage. While a cask crawler is illustrated, any suitable means of transporting transfer cask 80 to a position above underground VVO 20 can be used. For example, any suitable type of load-handling device, such as without limitation, a gantry crane, overhead crane, or other crane device can be used. In preparing the desired underground VVO 20 to receive canister 70, lid 41 is removed from body 21 so that cavity 26 is open. Cask crawler 90 positions transfer cask 80 atop underground VVO 20. After transfer cask is properly secured to the top of underground VVO 20, a bottom plate of transfer cask 80 is removed. If necessary, a suitable mating device can be used to secure the connection of transfer cask 80 to underground VVO 20 and to remove the bottom plate of transfer cask 80 to an unobtrusive position. Such mating, devices are well known in the art and are often used in canister transfer procedures. Canister 70 is then lowered by cask crawler 90 from transfer cask 80 into cavity 26 of underground VVO 20 until the bottom surface of canister 70 contacts and rests atop support blocks 32, as described above. When resting on support blocks 32, a major portion of the canister's height is below grade. Most preferably, the entirety of canister 70 is below grade when in its storage position. Once canister 70 is positioned and resting in cavity 26, lid 41 is placed over cavity 26, substantially enclosing cavity 26. Lid 41 is oriented atop body 21 so that shear ring 47 protrudes into cavity 26 and outlet ventilation ducts 42 are azimuthally and circumferentially separated from inlet ventilation ducts 25 on body 21. Lid 41 is then secured to body 21 with bolts. As a result of the heat emanating from canister 70, cool air from the ambient is siphoned into inlet ventilation ducts 25 and into the bottom of cavity 26. This cool air is then warmed by the heat from the spent fuel in canister 70, rises in cavity 26 via annular space 60 (FIG. 6) around canister 70, and then exits cavity 26 as heated air via outlet ventilation ducts 42 in lid 41. Referring now to FIG. 9, an integral structure 100 for storing spent nuclear fuel is illustrated according to an embodiment of the invention. Integral structure 100 is essentially a combination of shell 34, inlet ventilation ducts 25, and bottom plate 38 of underground VVO 20 without the concrete body. Integral shell 100 can be used to store canisters of spent nuclear fuel without the addition of the concrete body. Therefore, some embodiments of the present invention will be the integral structure 100 itself. Shell 34, bottom plate 38, and inlet ventilation ducts 25 are preferably formed of a metal, such as low carbon steel. Other suitable materials include, without limitation, stainless steel, aluminum, aluminum-alloys, plastics, and the like. Inlet ventilation ducts 25, bottom plate 38, and shell 34 are seal welded at all junctures to form a unitary structure that is hermetically sealed to the ingress water and other fluids. The only way water or other fluids can enter cavity 26 is through inlets 27 or top opening 101 of shell 34. The height of shell 34 is designed so that a canister of spent fuel can be positioned within cavity 26 so as not to protrude from top opening 101. There is no limitation on the height to which shell 34 can be constructed. The exact height of shell 34 will be dictated by the height of the spent fuel canister to be stored therein, the desired depth (below grade) at which the canister is to be stored, whether the outlet ventilation ducts are in the lid or integrated into the shell 34, and/or the desired height of the outlet air plenum that is to exist during canister storage. FIGS. 10-13 illustrate a process of using integral structure 100 to store a spent fuel canister at a below grade position at an ISFSI, or other location, according to one embodiment of the present invention. It should be noted that the any of the design and/or structural details discussed above with respect to underground VVO 20 can be incorporated into integral structure 100, such as, for example, the use of vent screens, variable configurations of the inlet and outlet ducts, clearances, the use of an insulation, etc. However, in order to avoid redundancy, a discussion of these details will be omitted with the understanding that any or all of the details of underground VVO 20 are (or can be) incorporated into the storing methods and apparatus of integral structure 100, and vice versa. Referring to FIG. 10, a hole 200 is first dug, into the ground 210 at a desired position within the ISFSI and at a desired depth. Once hole 200 is dug, and its bottom properly leveled, base 22 is placed at the bottom of hole 200. Base 22 is a reinforced concrete slab designed to satisfy the load combinations of recognized industry standards, such as ACI-349. However, in some embodiments, depending on the load to be supported and/or the ground characteristics, the use of a base may be unnecessary. Once base 22 is properly positioned in hole 200, integral structure 100 is lowered into the hole 200 in a vertical orientation until it rests atop base 22. Bottom plate 38 of integral structure 100 contacts and rests atop the top surface of base 22. If desired, the bottom plate 38 can be bolted or otherwise secured to the base 22 at this point to prohibit future movement of the integral structure 100 with respect to the base 22. Referring to FIG. 11, once integral structure 100 is resting atop base 22 in the vertical orientation, soil supply pipe 300 is moved into position above hole 200. Soil 301 is delivered into hole 200 exterior of integral structure 100, thereby filling hole 200 with soil 301 and burying, a portion, of the integral structure 100. While soil 301 is exemplified to fill hole 200, any suitable engineered fill can be used that meets environmental and shielding requirements. Other suitable engineered fills include, without limitation, gravel, crushed rock, concrete, sand, and the like. Moreover, the desired engineered fill can be supplied to the hole by any means feasible, including manually, dumping, and the like. Referring to FIG. 12, soil 301 is supplied to hole 200 until soil 301 surrounds integral structure 100 and fills hole 200 to a level where soil 301 is approximately equal to ground level 212. Soil 301 is in direct contact with the exterior surfaces of integral structure 100 that are below grade. When hole 200 is filled with soil 301, inlets 27 of inlet ventilation ducts 25 are above grade. Shell 34 also protrudes from soil 301 so that opening 101 is slightly above grade. Therefore, because integral structure 100 is hermetically sealed at all junctures, below grade liquids and soil can not enter into cavity 26 or inlet ventilation ducts 25. Support blocks 32 are provided at the bottom of cavity 26 for supporting a stored spent fuel canister. Referring to FIG. 13, once hole 200 is adequately filled with soil 301, a canister 70 of spent fuel 70 is loaded into cavity 26 of integral structure 100. The canister loading sequence is discussed in greater detail above with respect to FIG. 5. Canister 70 is lowered into cavity 26 until it rests on support blocks 32. As discussed above with respect to FIG. 6, support blocks 32 and outlets 28 of integral structure 100 are specially designed to deal with “smart flood” conditions. Canister 70 rests on support blocks 32, forming an inlet air plenum 33 between the bottom of canister 70 and the floor of cavity 26 (which in this case is bottom plate 38). When canister 70 is supported on support blocks 32, the entire height of canister 70 is below ground level 212. This maximizes use of the ground's radiation shielding capabilities. The depth at which canister 70 is below ground level 212 can be varied by increasing or decreasing the depth of hole 200. Once canister 70 is supported in cavity 26, lid 41 is placed atop shell 34, thereby closing opening 101 and prohibiting radiation from escaping upwards from cavity 26. Outlet air plenum 36 is formed between the bottom surface of lid 41 and the top of canister 70. Lid 41 comprises outlet ventilation ducts 42. Outlet ventilation ducts 42 form passageways from outlet air plenum 36, through lid 41, to the ambient air above ground level 212. Outlet ventilation ducts 42 do not have to be provided in lid 41, but can be formed as part of the integral structure 100 if desired. This will be discussed in greater detail below with respect to FIG. 14. Referring still to FIG. 13, when integral structure 100 is used to store spent nuclear fuel canister 70, the radiation shielding effect of the sub-grade is utilized while adequately facilitating cooling of canister 70. The cooling of canister 70 is facilitated by cool air entering inlet ventilation ducts 25 via above grade inlets 27. The cool air travels through inlet ventilation ducts 25 until it enters cavity 26 at or near inlet air plenum 33 via below grade outlets 28. Once the cool air is within cavity 26 it is warmed by the heat emanating from canister 70. As the air is warmed, it travels upward along the outer surface of canister 70 via annular space 60 until the air enters outlet air plenum 36. As the air travels upward through annular space 60 it continues to remove heat from canister 70. The warmed air then exits cavity 26 via outlet ventilation ducts 42 and enters the ambient air. This natural convective cooling flow repeats continuously until the canister 70 is adequately cooled. Referring now to FIG. 14, an alternative embodiment of an integral structure 200 is illustrated. Integral structure 200 is used to store a spent fuel canister in manner similar to that of integral structure 100 discussed above. While much of the structure is identical to that of integral structure 100, integral structure 200 further comprises outlet ventilation ducts 42 seal welded directly to shell 34. The outlet ventilation ducts 42 can be formed out of any of the materials discussed above with respect to the inlet ventilation ducts 25. As a result of the outlet ventilation ducts 42 being part of integral structure 200, lid 41 can be free of such ducts. The cooling process of canister 70 remains the same. FIG. 15 illustrates an integral structure 300 according to another aspect of the present invention. Integral structure 300 is similar in many respect to that of integral structures 100 and 200 in its design and functioning. However, integral structure 300 is specifically designed to store canisters 70 holding low heat spent fuel. When a canister 70 is giving off low heat, for example in the magnitude of 2-3 kW, it is not necessary to supply inlet ventilation ducts to supply cool air to cavity 26. Therefore, the inlet ventilation ducts are omitted from integral structure 300. Integral structure 300 comprises only outlet ventilation ducts 42, which act as both an inlet for the cooler air and an outlet for the warmer air. While outlet ventilation ducts 42 of integral structure 300 are seal welded to shell 34, it is possible for the outlet ventilation ducts to be located in the lid 41 if desired. Moreover, the concept of eliminating the inlet ventilation ducts for low heat load canister storage can be applied to any of the underground or above ground VVO embodiments illustrated in this application, specifically including underground VVO 20 and it derivatives. While the invention has been described and illustrated in sufficient detail that those skilled in this art can readily make and use it, various alternatives, modifications, and improvements should become readily apparent without departing from the spirit and scope of the invention. Specifically, it is possible for the entire underground VVO and/or integral structure of the present invention to be below grade, so long as the inlet ventilation ducts and/or outlet ventilation ducts open to the ambient air above grade. This facilitates very deep storage of spent fuel canisters. |
|
046577262 | description | DETAILED DESCRIPTION OF THE INVENTION In the following description, like reference characters designate like or corresponding parts throughout the several views. Also, in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like, are words of convenience and are not to be construed as limiting terms. IN GENERAL Referring now to the drawings, and particularly to FIG. 1, there is shown an elevational view of a conventional fuel assembly, represented in vertically foreshortened form and being generally designated by the numeral 10. Fuel assembly 10 is the type used in a PWR (Pressurized Water Reactor) and basically comprises a lower end structure or bottom nozzle 12 for supporting the assembly on the lower core plate (not shown) in the core region of a reactor (not shown); a number of longitudinally extending guide tubes or thimbles 14 projecting upwardly from the bottom nozzle 12; a plurality of transverse grids 16 axially spaced along the guide thimbles 14; an organized array of elongated fuel rods 18 transversely spaced and supported by the grids 16; an instrumentation tube 20 located in the center of the assembly; and an upper end structure or top nozzle, generally designated by the numeral 22, attached to the upper ends of the guide thimbles 14 to form an integral assembly capable of being conventionally handled without damaging the assembly components. The top nozzle 22 includes a transversely extending adapter plate 24 having upstanding sidewalls 26 (the front wall being partially broken away) secured to the perpherial edges thereof in defining an enclosure or housing. An annular flange 28 is secured to the top of the sidewalls 26. Suitably clamped to the annular flange 28 are leaf springs (not shown) which cooperate with the upper core plate (not shown) in a conventional manner to prevent hydraulic lifting of the fuel assembly caused by upward coolant flow, while allowing for changes in fuel assembly length due to core induced thermal expansion and the like. Disposed within the opening defined by the annular flange 28 is the moderator control apparatus of the present invention, being designated generally by the numeral 30, which will be described in detail shortly hereafter. In that fuel assembly 10 does not form a part of the present invention, but is merely for illustrational purposes in representing the operative environment for use of the moderator control apparatus 30, a further description thereof will not be given. For a more detailed description of fuel assembly 10, reference should be made to the pending patent application of John M. Shallenberger et al, entitled "Nuclear Reactor Fuel Assembly With A Removable Top Nozzle"; filed Aug. 27, 1984; and assigned U.S. Ser. No. 644,758, a continuation-in-part of Ser. No. 537,775, filed Sept. 30, 1983 and now abandoned. MODERATOR CONTROL APPARATUS The moderator control apparatus 30 will now be discussed in further detail with particular reference to FIGS. 2, 3, and 4. As best seen in FIG. 2, the apparatus 30 includes a plurality of hollow elongated displacer rods 32 adapted to be inserted into respective ones of the guide thimbles 14 of the fuel assembly 10 for displacement of a predetermined volume of the moderator/coolant associated with the fuel rods 18. The displaced volume of the moderator/coolant decreases the H/U (hydrogen/uranium) ratio from a given normal level. The displacer rods 32 are interconnected by a manifold, generally designated by the numeral 34, located on the top of fuel assembly 10 and being disposed within the top nozzle and resting on the adapter plate 24 (see FIG. 1). In the preferred embodiment, the manifold 34 is in the form of a central hub 36 defining a central opening 38 (see FIGS. 3 and 4) and includes a plurality of, radially extending, hollow tube-like vanes 40 interconnecting the upper ends of the displacer rods 32 to the central hub 36. The hub 36 is provided with a number of radial bores or inlet ports 42 corresponding to the number of vanes 40. The inward end of the vanes are suitably secured to the hub such that the inlet ports 42 serve as unitary channel extensions of the vanes (best seen in FIG. 2), the arrangement being such that the inlet ports are circumferentially spaced about and adjacent the central opening 38 defined by the hub 36 (see FIGS. 3 and 4). It is preferred that each inlet port be disposed diametrically opposite another inlet port (the purpose for which being clearly understood from below). Each of the vanes 40 have at least one exit port 44 defined therein, some of the vanes have one such exit port whereas adjacent vanes have two exit ports. The number of exit ports 44 corresponds to the number and strategic location of the displacer rods 32. Although not specifically shown, it is preferred that the rods be threadably connected with the vanes 40 to facilitate assembly and dismantling, however, other suitable connections could equally be used. As can be appreciated, the connections are such that the inlet ports 42 are in fluid flow communication with the exit ports 44 of a respective vane 40, whereas, the exit ports 44 are in fluid flow communication with the respective displacer rods 32. Before continuing, it should be pointed out that the specific above-described manifold structure with its central hub and radially extending vanes is only illustrative of one possible type configuration and construction used, it being understood that other smaller structures and arrangements are equally applicale in keeping within the principles of the present invention. Again referring to FIG. 2, the control apparatus 30 further includes valves means operably associated with the manifold inlet ports 42 for controlling the flow and non-flow of the coolant into the displacer rods 32. More particularly, when the inlet ports are in closed position the flow of coolant therethrough is prohibited, whereas, in an opened position, coolant flows through the inlet ports 42, along through the vanes 40, and then out through the exit ports 44 and into the displacer rods 32. Thus, by opening the inlet ports, the original displacement of the coolant is removed as the rods are filled with coolant in thereby increasing or returning the H/U ratio back to its normal given level (shifting of the energy spectrum). In the preferred embodiment, the valve means takes on the form of a rotatable hollow stem 46 which is operable to open and close all of the inlet ports 42 in a predetermined sequential manner, however, as can be appreciated, a separate valve may be associated with each of the inlet ports. The valve stem 46 is circular with its lower section being provided with at least one, and preferably two diametrically opposite, flow aperatures or orifices 48. Still referring to FIG. 2, the valve stem 46 is mounted such that the lower end of the stem rests on an integral annular lip 50 of hub 36, whereas, a circumferential groove, on the stem at an axial location above the orifices 48, engages an annular flange 52, integrally formed on the hub 36 above the lower lip 50. The mounting arrangement permits rotation of the stem on the manifold, and more specifically, the rotation of the lower section of the stem 46 within the central opening 38. The dimension of the lower section of stem 46 is such that its exterior wall surface snugly abuts the inlet ports 42 and manifold 34 in sealing off the inlet ports so as to prevent the flow of coolant therethrough. Flow of coolant through the inlet ports 42, and thus into the displacer rods 32, only occurs when the valve stem 46 has been rotated to a point such that the orifices 48 are aligned with the inlet ports 42, as illustrated in FIG. 4. The valving is such that only two inlet ports (and the maximum of four displacer rods) are open to the flow of coolant therethrough at any one time, thereby insuring safety against accidental release or large change of reactivity during any single occurrence or transient. Further, such valving system provides an operator with increased flexibility to relieve unexpected power tilts during an operating cycle. Slidably mounted on the valve stem 48 is a perforated hold down plate 54 which compresses spring 56 as the upper core plate (not shown) is lowered down unto the assembly. Spring 56 is coiled about the valve stem 46 and is interposed between the hold down plate 54 and the central hub 36. This conventional arrangement prevents the control apparatus 30 from being ejected off the fuel assembly 10 by the forces of the upwardly flowing coolant. As best seen in FIG. 2, supported on plate 54 is a motor 58, battery 60, and transmitter/receiver 62 which diagramatically represent conventional means for rotating the valve stem 46 to cause the inlet ports 42 to open and close as described above. The motor 58 drives sprocket 64 which meshes with circular ring gear 66 that is attached to valve stem 46. From an external location, an operator sends a signal (electromagnetic, radio, or microwave) to the transmitter/receiver 60 which in turn actuates the motor 58, causing the valve stem to rotate. In the alternative, the motor 58 can be actuated by an incore buttom 68 which is accessible via the instrumentation tube 20 that is located within the center of fuel assembly 10. In that the displacement of the coolant in the guide thimbles 14 may not be sufficient to insure a negative moderator temperature coefficient and that selective displacement of the coolant may be insufficient for power shaping control, the invention further contemplates the use of a burnable poison. More specifically, each of the displacer rods 32 are filled with a burnable poison gas, preferably the gas is He.sup.3. The gas is released as the inlet ports 42 are opened to permit the flow of the coolant into the displacer rods 32. Due to the specific valving arrangement discussed above, the gas can only be released from two inlet ports (maximum of four displacer rods) at any one time, thus alleviating many safety problems. In order that the control apparatus 30 may be reused after completion of a cycle, in the preferred embodiment, each of the displacer rods 32 are provided with a refill valve 70, located at the lower end of the rod. In addition to the inherent cost savings in being able to reuse the rods 32 rather than discarding them, the refill valves 70 provide for last minute power distribution adjustment. Since the rods can be refilled on-site, the specific poison loading can be delayed until the time when the apparatus is placed on a fuel assembly. It is thought that the moderator control apparatus of the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in form, construction and arrangement thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore being merely a preferred or exemplary embodiment thereof. |
summary | ||
summary | ||
summary | ||
040244202 | claims | 1. A deep diode atomic battery comprising: a body of single crystal semiconductor material having a preferred crystallographic structure, a vertical axis, first and second major opposed surfaces, a peripheral side surface, a selected resistivity and a first type conductivity; at least one of the major opposed surfaces having a preferred planar orientation which is one selected from (111), (110) and (100); a plurality of regions of second and opposite type conductivity and a selected resistivity disposed in the body; each region having a preferred crystallographic orientation and extending substantially parallel to a preferred axis of the crystallographic structure between, and terminating in, the two major opposed surfaces and having two opposed end surfaces; one of the two end surfaces of each region is coextensive with one of the major surfaces; the other end surface of each region is coextensive with the other one of the major opposed surfaces; the material of each of the second regions being of recrystallized semiconductor material of the body having solid solubility of a dopant material therein to impart the second type conductivity and selective level of resistivity thereto; the dopant material being substantially uniformly distributed throughout the second region, its solid solubility and its concentration being determined by a selected temperature range at which it was distributed within the region when migrated therethrough; a P-N junction formed by the contiguous surfaces of the materials of each region and the body; means for electrically connecting the first regions into a first internal electrical circuit arrangement; means for electrically connecting the second regions into a second internal electrical circuit arrangement; means for disposing a radioactive source within the body in a predetermined relationship with the first and second regions. the distance from any P-N junction at any point in a region of first type conductivity is less than approximately one diffusion length of a minority carrier in the region of first type conductivity. the distance from any P-N junction at any point in a region of second type conductivity is less than approximately one diffusion length of a minority carrier in the region of second type conductivity. each P-N junction is substantially perpendicular to the two major opposed surfaces and substantially parallel to each other. the first and second regions form a parallel planar lamellar array. the preferred planar orientation is (111). the preferred planar orientation is (111), and the second regions are oriented in a preferred wire direction which is one selected from the group consisting of (110), (101) and (011). the preferred planar orientation is (111), and the second regions are oriented in a preferred wire direction which is one selected from the group consisting of (112), (121) and (211). the P-N junctions formed by the contiguous surfaces of each pair of first and second regions of opposite type conductivity define a parallel columnar array. each second region has a triangular cross-section and the three sides of the region are parallel to the (112) plane, the (121) plane and the (211) plane, respectively. the preferred planar orientation is (100); each second region has a square cross-section and two pairs of sides, the sides of each pair being parallel to each other, and each side of one pair lies in, or is parallel to the (011) crystallographic plane and each side of the other pair lies in, or is parallel to, the (011). the preferred planar orientation is (110); each second region has a diamond-like cross-section, and two pairs of sides, the sides of each pair being parallel to each other, and each side of one pair lies in, or is parallel to, the (001) crystallographic plane and each side of the other pair lies in, or is parallel to, the (111) crystallographic plane. each second region has a hexagonal cross-section and three pairs of sides parallel to the (112), the (121) and the (211) crystallographic planes, respectively. means for disposing a radioactive source within the semiconductor body includes walls defining an aperature extending entirely between, and terminating in, the two major opposed surfaces of the body and substantially aligned with the vertical axis and centered with respect to the peripheral side surface of the semiconductor body. the means for disposing a radioactive source within the semiconductor body includes a deep buried layer of radioactive material located substantially midway between the two major opposed surfaces and centered with respect to the peripheral side surfaces of the semiconductor body. the means for disposing a radioactive source within the semiconductor body includes a third region having a preferred crystallographic orientation and an vertical axis substantially aligned with the vertical axis of the body and extending between, and terminating in, the two major opposed surfaces, the material of third region being recrystallized semiconductor material of the body having solid solubility of at least a radioactive material therein, at least the radioactive material being substantially uniformly distributed throughout the third region, its solid solubility and its concentration being determined by a selected temperature range at which it was distributed within the region when migrated therethrough. the means for disposing a radioactive source within the semiconductor body includes a symmetric array of apertures substantially midway between the two major opposed surfaces of the semiconductor body. the means for disposing a radioactive source within the semiconductor body includes a symmetric array of deep buried layers of radioactive material located substantially midway between the two major opposed surfaces of the semiconductor body. the means for disposing a radioactive source within the semiconductor body includes the neutron activation of the semiconductor material of the semiconductor body. the radioactive source is a gamma emitter. the radioactive source is an x-ray emitter. the radioactive source is a Beta emitter the radioactive source is a Beta emitter. the radioactive source is a Beta emitter. the energy of the radioactive emissions is less than the radiation damage threshold of the semiconductor material. the rate of decrease in minority carrier lifetime from radiation damage arising from radioactive emissions in the semiconductor body is less than the rate of decay of the radioactive source. means for electrically connecting the battery into an external electric circuit. means for electrically connecting the battery into an external electrical circuit. the first internal electrical circuit arrangement includes a plurality of first electrical contacts, each first electrical contact being affixed to, and in an electrically conductive relationship with, only one first region, and the second internal electrical circuit arrangement includes a plurality of second electrical contacts, each second electrical contact being affixed to, and in an electrically conductive relationship with, only one second region. at least one radial electrical isolation planar region of second type conductivity extending between and terminating in the two opposed major surfaces; dividing the body symmetrically into a plurality of equal radial sectors each containing a plurality of first and second type conductivity regions. the first internal circuit arrangement includes electrically connecting together in parallel circuit arrangement all regions of first type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a first series circuit arrangement, and the second internal circuit arrangement includes electrically connecting together in a parallel circuit arrangement all regions of second type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a second series circuit arrangement. at least one radial electrical isolation planar region of second type conductivity extending between, and terminating in the two opposed major surfaces; dividing the body symmetrically into a plurality of equal radial sectors each containing a plurality of first and second type conductivity regions. the first internal circuit arrangement includes electrically connecting together in parallel circuit arrangement all regions of first type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a first series circuit arrangement, and the second internal circuit arrangement includes electrically connecting together in a parallel circuit arrangement all regions of second type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a second series circuit arrangement. at least one electrical isolation planar region the second type conductivity disposed in the body and extending between, and terminating in, the two opposed major surfaces; dividing the body symmetrically into a plurality of equal cross-sectional area sectors. the first internal circuit arrangement includes electrically connecting together in parallel circuit arrangement all regions of first type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a first series circuit arrangement, and the second internal circuit arrangement includes electrically connecting together in a parallel circuit arrangement all regions of second type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a second series circuit arrangement. at least one electrical isolation planar region of second type conductivity disposed in the body and extending between, and terminating in, the two opposed major surfaces; dividing the body symmetrically into a plurality of equal sectors. the first internal circuit arrangement includes electrically connecting together in parallel circuit arrangement all regions of first type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a first series circuit arrangement, and the second internal circuit arrangement includes electrically connecting together in a parallel circuit arrangement all regions of second type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a second series circuit arrangement. at least one electrical isolation planar region of second type conductivity disposed in the body and extending between, and terminating in, the two opposed major surfaces; dividing the body symmetrically into a plurality of equal sectors. the first internal circuit arrangement includes electrically connecting together in parallel circuit arrangement all regions of first type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangemens in a first series circuit arrangement, and the second internal circuit arrangement includes electrically connecting together in a parallel circuit arrangement all regions of second type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a second series circuit arrangements. at least one electrical isolation planar region of second type conductivity disposed in the body and extending between, and terminating in, the two opposed major surfaces; dividing the body symmetrically into a plurality of equal sectors. the first internal circuit arrangement includes electrically connecting together in parallel circuit arrangement all regions of first type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a first series circuit arrangement, and the second internal circuit arrangement includes electrically connecting together in a parallel circuit arrangement all regions of second type conductivity in each of the plurality of radial sectors and electrically connecting all the parallel circuit arrangements in a second series circuit arrangement. the semiconductor material is silicon, the conductivity of the first regions is N-type, and the conductivity of the second regions is P-type. each of the second regions has aluminum as a dopant impurity therein, the concentration of which is the solid solubility of aluminum in silicon at the migration processing temperature. the semiconductor material is gallium arsenide. the semiconductor material is germanium. 2. The deep diode atomic battery of claim 1 wherein: 3. The deep diode atomic battery of claim 2 wherein: 4. The deep diode atomic battery of claim 1 wherein: 5. The deep diode atomic battery of claim 4 wherein 6. The deep diode atomic battery of claim 5 wherein: 7. The deep diode atomic battery of claim 5 wherein: 8. The deep diode atomic battery of claim 5 wherein: 9. The deep diode atomic battery of claim 5 in which the two major opposed surfaces of the semiconductor body are parallel to a single (100) crystallographic plane and in which the planar P-N junctions are parallel to a single crystallographic plane selected from the group consisting of the (011) and the (011) crystallographic planes. 10. The deep diode atomic battery of claim 5 in which the two major opposed surfaces of the semiconductor body are parallel to a single (110) crystallographic plane and in which the planar P-N junctions are parallel to the (001) crystallographic plane. 11. The deep diode atomic battery of claim 4 wherein 12. The deep diode atomic battery of claim 6 wherein 13. The deep diode atomic battery of claim 1 wherein 14. The deep diode atomic battery of claim 11 wherein 15. The deep diode atomic battery of claim 6 wherein 16. The deep diode atomic battery of claim 1 wherein 17. The deep diode atomic battery of claim 1 wherein 18. The deep diode atomic battery of claim 1 wherein 19. The deep diode atomic battery of claim 1 wherein 20. The deep diode atomic battery of claim 1 wherein 21. The deep diode atomic battery of claim 1 wherein 22. The deep diode atomic battery of claim 1 wherein 23. The deep diode atomic battery of claim 1 wherein 24. The deep diode atomic battery of claim 18 wherein 25. The deep diode atomic battery of claim 19 wherein 26. The deep diode atomic battery of claim 20 wherein 27. The deep diode atomic battery of claim 1 wherein 28. The deep diode atomic battery of claim 1 wherein 29. The deep diode atomic battery of claim 22 and including 30. The deep diode atomic battery of claim 23 and including 31. The deep diode atomic battery of claim 1 and wherein 32. The deep diode atomic battery of claim 16 and including 33. The deep diode atomic battery of claim 32 wherein 34. The deep diode atomic battery of claim 17 wherein 35. The deep diode atomic battery of claim 34 wherein 36. The deep diode atomic battery of claim 18 and including 37. The deep diode atomic battery of claim 36 and including 38. The deep diode atomic battery of claim 19 wherein 39. The deep diode atomic battery of claim 38 wherein 40. The deep diode atomic battery of claim 20 and including 41. The deep diode atomic battery of claim 40 wherein 42. The deep diode atomic battery of claim 21 and including 43. The deep diode atomic battery of claim 42 wherein 44. The deep diode atomic battery of claim 1 wherein 45. The deep diode atomic battery of claim 44 wherein 46. The deep diode atomic battery of claim 1 wherein 47. The deep diode atomic battery of claim 1 wherein |
047387998 | abstract | A cartridge for the permanent storage and disposal of radioactive particulate waste composed of a liquid impervious casing enclosing a waste storage region provided with a ferromagnetic matrix made of steel wool, together with inlet and outlet conduits suitably associated with the waste storage region to enable a liquid containing such waste material to be conducted through the matrix while the particulate waste is adhered thereto under the influence of a magnetic field and the remaining liquid filtrate is expelled from the cartridge, and to then permit an encapsulating material, such as a resin-catalyst mixture, to be introduced into the waste storage region to completely fill that region. The cartridge is temporarily connected into a system including remotely controllable valves and conduits for permitting the liquid containing waste material to be introduced into the cartridge while the liquid component thereof is removed to a storage container, and the encapsulating material to be then introduced into the waste storage region, followed by direct insertion of the cartridge into a drum which can be subsequently sealed and permanently stored, all of this occurring in a fully mechanized and remote manner which does not require the exposure of any operating personnel to significant radiation dose. |
description | This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0141608 filed on Nov. 20, 2013, the disclosure of which is incorporated herein by reference in its entirety. 1. Field The present disclosure relates to a control rod drive mechanism built in a nuclear reactor, which is configured with a coil housing substituting for a latch housing of a latch assembly, to miniaturize the control rod drive mechanism built in the nuclear reactor and thus to secure a sufficient fluid passage of a reactor coolant as well as to enhance space efficiency, and also configured to improve an operating load carrying path of the latch assembly so that the coil housing supports only the weight of a coil, a load of the reactor coolant and a load applied to the coil. 2. Discussion of Related Art In a control rod drive mechanism built in a nuclear reactor, the Westinghouse Electric Corporation has proposed a configuration using a coil used at a high temperature, which is disclosed in U.S. Patent Application Publication No. 2012/0148007 A1. Here, a drive rod housing is formed of a non-magnetic material to have the same configuration as the housing of the control rod drive mechanism of an existing commercial nuclear reactor, and applied to a design thereof. However, in spite of the above-mentioned improvement, the control rod drive mechanism built in the nuclear reactor, in which the housing of the control rod drive mechanism or the housing of the latch assembly does not serve as a pressure vessel, also has a housing in which a concept and size are similar to those the housing of the control rod drive mechanism applied to a current commercial nuclear reactor, and thus space efficiency of the control rod drive mechanism and the nuclear reactor is degraded. Further, in a configuration in which the housing of the latch assembly is formed of one magnetic material or non-magnetic material and installed to extend in a lengthwise direction of the latch assembly, it is impossible to optimize formation of a magnetic field and thus to maximally generate a lifting force. Also, in the current nuclear reactor, two kinds of methods, i.e., a method of controlling an insertion level of the control rod into the core and a controlling method by injection of a boric acid solution, are used to control reactivity of a reactor core, and thus the control rod need not be inserted into all nuclear fuel. However, since a large amount of radioactive waste is discharged in the method of controlling the reactivity of the reactor core using the boric acid solution, a nuclear reactor having the boron-free core which controls the reactivity using only the control rod drive mechanism is being developed. To this end, the control rod should be installed and controlled at most of the nuclear fuel. However, since a size of the current control rod drive mechanism is larger than or the same as a size of a single nuclear fuel, it is impossible to install more control rod drive mechanisms at the current commercial nuclear reactor, and thus it is necessary to reduce the size of the control rod drive mechanism. Further, in the control rod drive mechanism built in the nuclear reactor, a driving force generating mechanism (particularly, an electromagnet) should be cooled by the reactor coolant, and thus to secure a fluid passage of the reactor coolant flowing around the control rod drive mechanism, it is urgently required to develop a device which may realize miniaturization of the control rod drive mechanism. An aspect of the present invention is directed to a control rod drive mechanism built in a nuclear reactor, which is configured with a coil housing substituting for a latch housing of a latch assembly, to miniaturize the control rod drive mechanism built in the nuclear reactor and thus to secure a sufficient fluid passage of a reactor coolant as well as to enhance space efficiency. Also, another aspect of the present invention is directed to a control rod drive mechanism built in a nuclear reactor, which is configured to improve an operating load carrying path of the latch assembly so that the coil housing substituting for the latch housing supports only the weight of a coil, a load of the reactor coolant and a load applied to the coil. Also, a further aspect of the present invention is directed to a control rod drive mechanism built in a nuclear reactor, in which a magnetic material and a non-magnetic material are alternately arranged at the coil housing to prevent leakage of a magnetic field, and thus efficiency of a magnetic force generated at the coil is enhanced. According to an aspect of the present invention, there is provided a control rod drive mechanism including a guide member disposed in a nuclear reactor to receiving a drive shaft; a latch assembly disposed in the guide member to enable the drive shaft to be withdrawn and inserted; a supporting member connected to the guide member to cover the drive shaft and to support the latch assembly; and a plurality of coil housings spaced apart and installed outside of the guide member to cover the latch assembly, and each having a coil built therein. Each of the coil housings may include an internal member exposed toward an inner side of the guide member, and an external member connected to the internal member to be exposed toward an outer side of the guide member and to form a receiving space for the coil. The internal member of the coil housing may be configured of a non-magnetic material and a magnetic material that are alternately arranged. [Detailed Description of Main Elements]M: magnetic materialNM: non-magnetic material1: internal structure of a2: drive shaftnuclear reactor3: extension shaft4: shaft tooth10: reactor head100: guide member110: upper guide130: lower guide150: middle guide170: connecting part200: latch assembly210: latch220: lifting stator230: moving latch stator240: moving latch plunger250: stationary latch stator260: stationary latch plunger270: latch housing270M: magnetic material of latch housing270NM: non-magnetic material of latch housing300: supporting member310: guide window400: coil housing410: coil430: internal member of coil housing430M: magnetic material of internal member of coil housing430NM: non-magnetic material of internal member of coil housing450: external member of coil housing Hereinafter, a control rod drive mechanism built in a nuclear reactor according to embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Referring to FIG. 3, generally, in a control rod drive mechanism of a commercial nuclear reactor, a latch assembly housing 20 (receiving a plurality of stators 31, 32 and 34 and plungers 33 and 35), an upper housing 21 and a lower housing 22 are installed at a nozzle 11 of the control rod drive mechanism, which passes through a reactor head 10, to form part of a reactor coolant pressure boundary, a coil assembly 36 including a coil housing 37 having a built-in coil is provided, a magnetic field is generated to operate a latch assembly, and thus vertical movement of a control rod and extension shaft assembly 30 is induced. In such a structure, when the housing or the nozzle of the control rod drive mechanism is damaged, there may be a risk of accidents such as a loss of coolant or a control rod ejection. If a control rod drive mechanism built in a nuclear reactor is applied, since the nozzle of the control rod drive mechanism is removed and the housing of the control rod drive mechanism does not form the reactor coolant pressure boundary, the control rod ejection accident can be fundamentally prevented to enhance safety of the nuclear power plant, the plurality of control rods may be installed so as to realize a boron-free core and thus to minimize related equipment, a passing-through design of a reactor vessel may be simplified, and an amount of radioactive waste may be reduced. The control rod drive mechanism built in the nuclear reactor according to an embodiment of the present invention illustrated in FIG. 1 includes a guide member 100 which is disposed in a nuclear reactor to receive a drive shaft 2, a supporting member 300 which is connected with the guide member 100 to support a latch assembly 200, and coil housings which are spaced apart and installed outside of the guide member 100 to cover the latch assembly, and each having a coil 410 built therein. The drive shaft 2 serves to insert or withdraw a control rod assembly disposed at a reactor core into/from the reactor core by the control rod drive mechanism according to an embodiment of the present invention. An extension shaft 3 is connected to a lower portion of each drive shaft 2 to form a control rod and extension shaft assembly, and the control rod connected to the control rod and extension shaft assembly is withdrawn from or inserted into the reactor core by vertical movement of the drive shaft to control the number of neutrons in the reactor core and thus to control an output of the reactor core. The control rod drive mechanism for this has the guide member 100 connected to an internal structure 1 of a nuclear reactor, and the drive shaft 2 is disposed in the guide member 100. The guide member 100 includes an upper guide 110 which is fixed to the internal structure 1 of the upper reactor, a lower guide 130 which is fixed to the internal structure 1 of the lower reactor, and a plurality of middle guides 150 which are disposed between the upper guide 110 and the upper guide 130 and connected with the plurality of coil housings 400 to be spaced from each other. The latch assembly 200 according to an embodiment of the present invention is disposed in the guide member 100 and provided around the drive shaft 2, and includes a lifting stator 220, a moving latching stator 230, a moving latch plunger 240 connected with a latch 210, a stationary latch stator 250, and a stationary latch plunger 260 connected with the latch 210. In this case, when a current is applied to the coil 410, a magnetic field is generated, and the plunger is moved toward the stator by a mutual attractive force between the stators formed of the magnetic materials and the plungers, such that the latch 210 is engaged with the drive shaft or the latch engaged with the shaft moves up or down. At this time, a plurality of shaft teeth 4 are formed on an outer circumferential surface of the drive shaft 2, and the latch 210 located between the shaft teeth 4 is moved up or down the drive shaft 2 through vertical movement thereof. When the drive shaft 2 moves up, the extension shaft 3 also moves up so that the control rod is withdrawn from the reactor core, and thus the output of the reactor core may be increased. Alternatively, when the drive shaft 2 moves down, the extension shaft 3 also moves down so that the control rod is inserted into the reactor core, and thus the output of the reactor core may be reduced. In addition, the supporting member 300 according to an embodiment of the present invention is formed to cover the drive shaft 2 and to support the latch assembly 200. The supporting member 300 is formed in a cylindrical shape, an upper end thereof is coupled and fixed to the upper guide 110 of the guide member 100, and a lower end thereof is coupled and fixed to the lower guide 130 of the guide member 100. A guide window 310 for the latch 210 is formed in the supporting member 300 to provide a moving space of the latch 210 when the latch 210 moves vertically. In particular, the supporting member 300 transmits a load acting on the latch 210 of the latch assembly 200 to the internal structure 1 of the nuclear reactor and thus improves an operating load carrying path. In the control rod drive mechanism according to an embodiment of the present invention, the coil housing 400 has the coil 410 built therein, and forms the magnetic field when the current is applied, and thus operates the latch assembly 200. Firstly, the plurality of coil housings 400 are fixed to each connecting part 170 disposed between the upper guide 110 of the guide member 100 and the middle guide 150, between the middle guides 150, and between the middle guide 150 and the lower guide 130 to be spaced, and disposed to be spaced vertically. In this case, each coil housing 400 is coupled to the connecting part 170 and then fixed and coupled to the guide member 100. Each coil housing 400 disposed at each connecting part 170 of the guide member 100 includes an internal member 430 which is exposed toward an inner side of the guide member 100, and an external member 450 which is connected to the internal member 430 to be exposed toward an outer side of the guide member 100 and to form a receiving space for the coil 410. That is, each coil housing 400 has a rectangular cross-sectional shape, such that the internal member 430 forms part of an inner surface of the guide member 100 and the external member 450 forms part of an outer surface of the guide member 100, and thus substitutes for a latch housing supporting the existing latch assembly 200. As described in the background, in the case of a control rod drive mechanism installed at an outer side of the nuclear reactor, the latch housing forms part of a reactor coolant pressure boundary, and the nozzle or the housing of the control rod drive mechanism is damaged, and thus there is a risk of accidents such as loss of coolant or a control rod ejection. To this end, in the case of the control rod drive mechanism built in the nuclear reactor, the latch housing does not form the reactor coolant pressure boundary, and thus the above-mentioned problem may be solved. However, although the latch housing does not form the reactor coolant pressure boundary, the latch housing is used as it is. When the boron-free core is applied, it is necessary for the control rod drive mechanism built in the nuclear reactor to be installed at most of the nuclear fuel in the nuclear reactor to control the output of the reactor core. In this case, since a size of the control rod drive mechanism which is currently used is larger than or the same as that of a single nuclear fuel, it is necessary to install more control rod drive mechanisms at a current commercial nuclear reactor, and thus it is necessary to reduce the size of the control rod drive mechanism. Further, in the control rod drive mechanism built in the nuclear reactor, reactor coolant should flow to cool heat generated from a driving force generating mechanism (particularly, an electromagnet). In this case, to sufficiently secure a fluid passage of the reactor coolant flowing around the control rod drive mechanism, it is necessary to minimize the control rod drive mechanism. Therefore, the coil housings 400 according to an embodiment of the present invention are integrally formed with the guide member 100 to reduce the size of the control rod drive mechanism and thereby to realize the miniaturization thereof. Also, through this, it is possible to secure the sufficient fluid passage for the reactor coolant and thus to enhance cooling efficiency. Furthermore, the supporting member 300 supports the operating load of the latch 210, and transmits the operating load to the internal structure 1 of the nuclear reactor, and thus the operating load of the latch 210 is not transmitted to the coil housing 400. Therefore, the coil housing 400 supports only the weight of the coil, the load of the reactor coolant and the load applied to the coil, and thus may enhance structural stability. In the coil housing 400 according to an embodiment of the present invention, part of the internal member 430 may be formed of a non-magnetic material NM, and the external member 450 and portions of the internal member 430 other than the non-magnetic material NM, may be formed of a magnetic material M, so that the magnetic force is transmitted through the latch assembly 200 with no leakage. That is, the non-magnetic material NM is disposed at a middle portion of the internal member 430, and the magnetic material M is disposed at portions connected with the middle portion of the internal member 430 and arranged vertically, and the entire external member 450 connected with the portions. Therefore, the non-magnetic material NM and the magnetic material M are alternately arranged in a vertical direction of the control rod drive mechanism to prevent the leakage of the magnetic field, and the attractive force generated between the stator of the latch assembly 200 and the plunger may be maximized, and thus the driving force of the latch 210 may be optimized. Further, in the case of the control rod drive mechanism built in the nuclear reactor, which is operated at a high temperature, the magnetic field generated from the coil 410 is formed to be smaller than that formed at a room temperature. Since the non-magnetic material NM and the magnetic material M are alternately arranged at the coil housings 400, magnetic force transmission efficiency may be increased, and thus operating reliability of the control rod drive mechanism may be ensured. As illustrated in FIG. 2, in another modified example of the present invention, an existing latch housing 270 may be used as it is, and the latch housings 270 may be welded and connected to each other, such that the non-magnetic material NM and the magnetic material M are alternately arranged. The latch housings 270 located at upper and lower ends are fixed and coupled to the upper guide 110 and the lower guide 130 so as to prevent the leakage of the magnetic field, and the attractive force generated between the stator of the latch assembly and the plunger may be maximized. Although the supporting member 300 is not illustrated in FIG. 2, unlike FIG. 1, the supporting member 300 may be added in other modified examples according to an embodiment of the present invention. At this time, the supporting member 300 transmits the load acting on the latch 210 of the latch assembly 200 to the internal structure 1 of the nuclear reactor, and thus the operating load carrying path may be improved. The control rod drive mechanism built in the nuclear reactor according to an embodiment of the present invention can be miniaturized so that the control rod is enabled to be installed at most of the nuclear fuel of the nuclear core, and also can secure the fluid passage so that the reactor coolant flows around the control rod drive mechanism. Further, according to an embodiment of the present invention the coil housing can substitute for the latch housing so as to improve the operating load carrying path, thereby enhancing the durability of the apparatus. Furthermore, the magnetic material and the non-magnetic material are alternately arranged at the coil housing to prevent leakage of a magnetic field, and thus the efficiency of the magnetic force generated at the coil is enhanced. 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 cover all such modifications provided they come within the scope of the appended claims and their equivalents. |
|
039768880 | summary | BACKGROUND OF THE INVENTION The present invention relates to high energy neutron sources, particularly sources of about 14 MeV neutrons for simulating radiation exposures that may be encountered within controlled thermonuclear reactor (CTR) devices. Several areas of research have been identified as requiring neutron sources capable of providing large fluxes and fluences of 14 MeV neutrons. Applicants' recent report, "Fission Fragment Driven (d + t) Neutron Irradiation Source for CTR Materials Damage Irradiations", Aerojet Nuclear Co., ANCR-1134 (1974) lists a number of these applications respecting the testing of materials. This report is hereby expressly incorporated by reference. Those applications to which the present invention are thought to be particularly applicable include: Cross Sections and Related Nuclear Data The measurement of reaction cross sections, particularly for activation cross sections of reactions for which the target is scarce and/or the product has a long half life, and for the (n, .sup.4 He), (nn', .sup.4 He) etc. reactions by which helium is produced. PA0 Measurement Description PA0 Measurement Description PA0 Source Description PA0 Measurement Description Source Description Energy Range: 2-14 MeV PA1 Intensity: 10.sup.5 -10.sup.8 n/sec PA1 Geometry: point source, beam flux PA1 Radiation effect on hydrogen, deuterium and tritium permeabilities in vacuum wall and structural materials. PA1 Radiolysis of molten salt coolants and/or breeding blanket. PA1 Radiation decomposition of LiD, LiT, shielding and structural materials (e.g. borated water, organic materials for seals, etc.). PA1 Radiation effect in trapping efficiencies in diverter materials. PA1 Energy Range: keV -- 14 MeV PA1 Intensity: 10.sup.9 -10.sup.10 n/cm.sup.2 -sec PA1 Fluence: 10.sup.18 n/cm.sup.2 PA1 Geometry: beam flux, in-core irradiation PA1 Vacuum wall erosion PA1 Plasma contamination PA1 Energy Range: keV - 14 MeV PA1 Intensity (at sample surface): >10.sup.12 n/cm.sup.2 -sec PA1 Fluence (yield 0.1 monolayer): 3 .times. 10.sup.17 n/cm.sup.2 PA1 High Fluence Effects: 10.sup.20 -10.sup.21 n/cm.sup.2 PA1 Geometry: point source, beam flux PA1 Neutron fluence effects on physical and mechanical properties: creep strength, and loss of ductility in vacuum wall and structural material at temperatures in range of 500.degree.-1000.degree.C. PA1 Synergistic effect of high gas generation and point defect production rates in a high flux of high energy neutrons on void formation at temperatures in the range of 500.degree.-1000.degree.C. PA1 Establish correlation between heavy-ion bombardment effects and neutron radiation effects at several energies (discrete or integral) in the range of 2-14 MeV. PA1 Transmutation effects on physical and mechanical properties of structural materials. Radiolysis in Materials Source Description Surface Physics Sputtering PA2 Radiation blistering by reaction products: (n, He), (n,p), etc. PA2 Particle desorption by direct neutron and reaction product interactions. PA2 Photo-decomposition of surface compounds by neutron-induced energetic photons and reaction products. PA2 Radiation damage in surface layers. PA2 Multiple backscattering PA2 Secondary particle emission PA2 Secondary electron emission (electron sheath formation). Material Radiation Damage ______________________________________ Source Description Energy Range: keV - 14 MeV Intensity (long term): >10.sup.15 n/cm.sup.2 -sec High Fluence: 10.sup.23 -10.sup.24 n/cm.sup.2 Intensity (correlation 10.sup.13 -10.sup.14 n/cm.sup.2 -sec experiments): Minimum Fluence: 10.sup.20 n/cm.sup.2 Geometry: point source, beam flux in-core irradi- ation ______________________________________ From such studies predictions as to material swelling, transmutation of elements, void formation, changes in superconducting properties and various other materials' characteristics are to be obtained. For the studies relating to materials radiation damage extremely high neutron fluxes (up to 3 .times. 10.sup.12, 14 MeV n/cm.sup.2 -sec) and fluences (10.sup.20, 14 MeV n/cm.sup.2) may be required. Many facilities existing at present or presently proposed have various limitations either to these flux levels, to the required neutron energy or in that they are not conveniently available for materials testing. Table I below includes a partial list of existing neutron source facilities. A more comprehensive list is included within applicants' recent report ANCR-1134, (1974), cited above. TABLE I ______________________________________ NEUTRON SOURCE FACILITIES A. Nuclear Reactors Experimental Breeder Reactor EBR-II (ANL) ______________________________________ Fast neutron flux facility; in-core irradiaton capability. Neutron Flux Data: Radial Position (n/cm.sup.2 -sec) Energy Range Core Center Edge of Core ______________________________________ >3.7 MeV 0.08 .times. 10.sup.15 0.04 .times. 10.sup.15 1.35 MeV-3.7 MeV 0.45 .times. 10.sup.15 0.20 .times. 10.sup.15 100 keV-1.35 MeV 1.70 .times. 10.sup.15 1.18 .times. 10.sup.15 1-100 keV 0.45 .times. 10.sup.15 0.33 .times. 10.sup.15 <1 keV Total 2.68 .times. 10.sup.15 1.75 .times. 10.sup.15 High Flux Isotope Reactor HFIR (ORNL) ______________________________________ Thermal neutron flux facility; in-core irradiation capability. Neutron Flux data: Radial Position (n/cm.sup.2 -sec) Energy Range Central Region Fuel Region ______________________________________ >1.35 MeV 5.21 .times. 10.sup.14 111 keV-1.35 MeV 6.80 .times. 10.sup.14 9 keV-111 keV 3.18 .times. 10.sup.14 0.4 eV-9 keV 1.06 .times. 10.sup.15 Nonthermal (max) 4.0 .times. 10.sup.15 Thermal 2.8 .times. 1.sup.15 ______________________________________ TABLE I ______________________________________ NEUTRON SOURCE FACILITIES B. Accelerator and Target Systems Los Alamos Meson Physics Facility LAMPF (LASL) High-current proton accelerator. Beam Energy, MeV 800 Ion Current (average), mA 1 Cycle Time, pps 120 Pulse Width (.THETA..sub.p), .mu.sec 500 Protons/sec 6 .times. 10.sup.15 Target Uranium Copper Neutron Source Intensity, n/sec 2 .times. 10.sup.17 7 .times. 10.sup.16 Neutron Flux (Target Cavity), n/cm.sup.2 -sec .about. 10.sup.14 <10.sup.14 Energy Spectra Mean, MeV 2 4 Rotating Neutron Target System (LLL) 500-kV Insulated Core Transformer System. Beam Energy (Deuteron), keV 400 Current, mA 8 Target T Rotational Speed, rpm 1100 Neutron Source Intensity (Initial), n/sec 2 .times. 10.sup.12 Flux (1/2 cm from target), n/cm.sup.2 -sec .about. 10.sup.12 Target Half-life, mAh .about. 700 Neutron Energy, MeV 13-15 ______________________________________ One concept which offers immediate promise in producing an intense flux of 14 MeV neutrons is that of a thermal neutron converter. For this purpose materials such as LiOH--D.sub.2 O salts or LiD within converter plates have been suggested for installation within high flux, thermal neutron, reactor systems. The approximately 14 MeV neutrons of these concepts are produced by the following reactions: EQU .sup.6 Li + n thermal .fwdarw. t + .sup.4 He and EQU t + d .fwdarw. .sup.n 14 MeV + .sup.4 He Unfortunately only up to about 10.sup..sup.-4 neutrons of 14 MeV energy per thermal neutrons are produced by these reactions based on the interaction rate as represented by the cross section of the (d + t) reaction. SUMMARY OF THE INVENTION Therefore in view of the limitations of prior neutron source systems, it is an object of the present invention to provide an improved neutron source and method for producing approximately 14 MeV neutrons. It is a further object to provide a method of producing approximately 14 MeV neutrons from a thermal neutron source in which the rate of conversion is more than 10.sup..sup.-4 MeV neutrons per thermal neutron. It is a further object to provide a materials testing device that can be used to expose a sample material to a high flux of about 14 Mev neutrons produced from thermal neutron flux. In accordance with the present invention, fissionable material such as U.sup.235 is contacted with a deuterium - tritium gas mixture in the presence of a thermal neutron flux. As a result the following reactions occur to produce an intense flux of about 14 MeV neutrons: EQU .sup.235 U + n.sub.thermal .fwdarw. 2 fission fragments + 2.3 n.sub.fast EQU 2 fission fragments + (d or t) .fwdarw. (d or t).sub. 100 KeV EQU (d or t).sub. 100 KeV + (t or d) .fwdarw. 3.5 .times. 10.sup..sup.-4 (n.sub.14 MeV + .sup.4 He) A materials testing device employing these reactions includes a plurality of foils containing fissionable material enclosed within a vessel also containing a sample of the material to be tested. The vessel is filled with a mixture of deuterium - tritium gas and exposed to a thermal neutron flux. A coolant system utilizing the circulation of the deuterium - tritium gas mixture is included to remove the heat generated by the reactions. |
description | This application is a continuation-in-part of U.S. patent application Ser. No. 15/167,617 filed May 27, 2016, which is: a continuation-in-part of U.S. patent application Ser. No. 15/152,479 filed May 11, 2016, which: is a continuation-in-part of U.S. patent application Ser. No. 14/216,788 filed Mar. 17, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 13/087,096 filed Apr. 14, 2011, which claims benefit of U.S. provisional patent application No. 61/324,776 filed Apr. 16, 2010; and is a continuation-in-part of U.S. patent application Ser. No. 13/788,890 filed Mar. 7, 2013; is a continuation-in-part of U.S. patent application Ser. No. 14/952,817 filed Nov. 25, 2015, which is a continuation-in-part of U.S. patent application Ser. No. 14/293,861 filed Jun. 2, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 12/985,039 filed Jan. 5, 2011, which claims the benefit of U.S. provisional patent application No. 61/324,776, filed Apr. 16, 2010; is a continuation-in-part of U.S. patent application Ser. No. 14/860,577 filed Sep. 21, 2015, which is a continuation of U.S. patent application Ser. No. 14/223,289 filed Mar. 24, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 14/216,788 filed Mar. 17, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 12/985,039 filed Jan. 5, 2011, which claims the benefit of U.S. provisional patent application No. 61/324,776, filed Apr. 16, 2010; and is a continuation-in-part U.S. patent application Ser. No. 15/073,471 filed Mar. 17, 2016, which claims benefit of U.S. provisional patent application No. 62/304,839 filed Mar. 7, 2016, is a continuation-in-part of U.S. patent application Ser. No. 14/860,577 filed Sep. 21, 2015, which is a continuation of U.S. patent application Ser. No. 14/223,289 filed Mar. 24, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 14/216,788 filed Mar. 17, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 13/572,542 filed Aug. 10, 2012, which is a continuation-in-part of U.S. patent application Ser. No. 12/425,683 filed Apr. 17, 2009, which claims the benefit of U.S. provisional patent application No. 61/055,395 filed May 22, 2008, now U.S. Pat. No. 7,939,809 B2; all of which are incorporated herein in their entirety by this reference thereto. Field of the Invention The invention relates generally to imaging and/or treatment of solid cancers. More particularly, the invention relates to control of a charged particle beam state using a patient specific beam control insert proximate an exit nozzle of a beam transport line of a charged particle cancer treatment system. Discussion of the Prior Art Cancer Treatment Proton therapy works by aiming energetic ionizing particles, such as protons accelerated with a particle accelerator, onto a target tumor. These particles damage the DNA of cells, ultimately causing their death. Cancerous cells, because of their high rate of division and their reduced ability to repair damaged DNA, are particularly vulnerable to attack on their DNA. Patents related to the current invention are summarized here. Proton Beam Therapy System F. Cole, et. al. of Loma Linda University Medical Center “Multi-Station Proton Beam Therapy System”, U.S. Pat. No. 4,870,287 (Sep. 26, 1989) describe a proton beam therapy system for selectively generating and transporting proton beams from a single proton source and accelerator to a selected treatment room of a plurality of patient treatment rooms. Imaging P. Adamee, et. al. “Charged Particle Beam Apparatus and Method for Operating the Same”, U.S. Pat. No. 7,274,018 (Sep. 25, 2007) and P. Adamee, et. al. “Charged Particle Beam Apparatus and Method for Operating the Same”, U.S. Pat. No. 7,045,781 (May 16, 2006) describe a charged particle beam apparatus configured for serial and/or parallel imaging of an object. K. Hiramoto, et. al. “Ion Beam Therapy System and its Couch Positioning System”, U.S. Pat. No. 7,193,227 (Mar. 20, 2007) describe an ion beam therapy system having an X-ray imaging system moving in conjunction with a rotating gantry. C. Maurer, et. al. “Apparatus and Method for Registration of Images to Physical Space Using a Weighted Combination of Points and Surfaces”, U.S. Pat. No. 6,560,354 (May 6, 2003) described a process of X-ray computed tomography registered to physical measurements taken on the patient's body, where different body parts are given different weights. Weights are used in an iterative registration process to determine a rigid body transformation process, where the transformation function is used to assist surgical or stereotactic procedures. M. Blair, et. al. “Proton Beam Digital Imaging System”, U.S. Pat. No. 5,825,845 (Oct. 20, 1998) describe a proton beam digital imaging system having an X-ray source that is movable into a treatment beam line that can produce an X-ray beam through a region of the body. By comparison of the relative positions of the center of the beam in the patient orientation image and the isocentre in the master prescription image with respect to selected monuments, the amount and direction of movement of the patient to make the best beam center correspond to the target isocentre is determined. S. Nishihara, et. al. “Therapeutic Apparatus”, U.S. Pat. No. 5,039,867 (Aug. 13, 1991) describe a method and apparatus for positioning a therapeutic beam in which a first distance is determined on the basis of a first image, a second distance is determined on the basis of a second image, and the patient is moved to a therapy beam irradiation position on the basis of the first and second distances. Problem There exists in the art of charged particle irradiation therapy a need to know and/or control position, direction, energy, intensity, and/or cross-sectional area or shape of the charged particle beam relative to a uniquely shaped tumor in a uniquely shaped patient. The invention comprises a patient specific beam control tray assembly installed proximate an exit nozzle of a positively charged particle cancer treatment beam and safety features thereof. Elements and steps in the figures are illustrated for simplicity and clarity and have not necessarily been rendered according to any particular sequence. For example, steps that are performed concurrently or in different order are illustrated in the figures to help improve understanding of embodiments of the present invention. The invention relates generally to a patient specific beam control assembly removably insertable into a charged particle beam path for controlling beam state. In one embodiment, a patient specific tray insert is inserted into a tray frame to form a beam control tray assembly, the beam control tray assembly is inserted into a slot of a tray receiver assembly, and the tray assembly is positioned relative to a gantry nozzle. Optionally, multiple tray inserts, each used to control a beam state parameter, are inserted into slots of the tray receiver assembly. The beam control tray assembling includes an identifier, such as an electromechanical identifier, of the particular insert type, which is communicated to a main controller, such as via the tray receiver assembly. Optionally and preferably, a hand control pendant is used in loading and/or positioning the tray receiver assembly. In another embodiment, a gantry positions both: (1) a section of a beam transport system, such as a terminal section, used to transport and direct positively charged particles to a tumor and (2) at least one imaging system. In one case, the imaging system is orientated on a same axis as the positively charged particle, such as at a different time through rotation of the gantry. In another case, the imaging system uses at least two crossing beamlines, each beamline coupled to a respective detector, to yield multiple views of the patient. In another case, one or more imaging subsystem yields a two-dimensional image of the patient, such as for position confirmation and/or as part of a set of images used to develop a three-dimensional image of the patient. In still another embodiment, multiple linked control stations are used to control position of elements of a beam transport system, nozzle, and/or patient specific beam shaping element relative to a dynamically controlled patient position and/or an imaging surface, element, or system. In yet another embodiment, a tomography system is optionally used in combination with a charged particle cancer therapy system. Optionally and preferably, a common injector, accelerator, and beam transport system is used for both charged particle based tomographic imaging and charged particle cancer therapy. In one case, an output nozzle of the beam transport system is positioned with a gantry system while the gantry system and/or a patient support maintains a scintillation plate of the tomography system on the opposite side of the patient from the output nozzle. In another example, a charged particle state determination system, of a cancer therapy system or tomographic imaging system, uses one or more coated layers in conjunction with a scintillation detector or a tomographic imaging system at time of tumor and surrounding tissue sample mapping and/or at time of tumor treatment, such as to determine an input vector of the charged particle beam into a patient and/or an output vector of the charged particle beam from the patient. In another example, the charged particle tomography apparatus is used in combination with a charged particle cancer therapy system. For example, tomographic imaging of a cancerous tumor is performed using charged particles generated with an injector, accelerator, and guided with a delivery system. The cancer therapy system uses the same injector, accelerator, and guided delivery system in delivering charged particles to the cancerous tumor. For example, the tomography apparatus and cancer therapy system use a common raster beam method and apparatus for treatment of solid cancers. More particularly, the invention comprises a multi-axis and/or multi-field raster beam charged particle accelerator used in: (1) tomography and (2) cancer therapy. Optionally, the system independently controls patient translation position, patient rotation position, two-dimensional beam trajectory, delivered radiation beam energy, delivered radiation beam intensity, beam velocity, timing of charged particle delivery, and/or distribution of radiation striking healthy tissue. The system operates in conjunction with a negative ion beam source, synchrotron, patient positioning, imaging, and/or targeting method and apparatus to deliver an effective and uniform dose of radiation to a tumor while distributing radiation striking healthy tissue. In another embodiment, a treatment delivery control system (TDCS) or main controller is used to control multiple aspects of the cancer therapy system, including one or more of: an imaging system, such as a CT or PET; a positioner, such as a couch or patient interface module; an injector or injection system; a radio-frequency quadrupole system; a ring accelerator or synchrotron; an extraction system; an irradiation plan; and a display system. The TDCS is preferably a control system for automated cancer therapy once the patient is positioned. The TDCS integrates output of one or more of the below described cancer therapy system elements with inputs of one or more of the below described cancer therapy system elements. More generally, the TDCS controls or manages input and/or output of imaging, an irradiation plan, and charged particle delivery. In yet another embodiment, one or more trays are inserted into the positively charged particle beam path, such as at or near the exit port of a gantry nozzle in close proximity to the patient. Each tray holds an insert, such as a patient specific insert for controlling the energy, focus depth, and/or shape of the charged particle beam. Examples of inserts include a range shifter, a compensator, an aperture, a ridge filter, and a blank. Optionally and preferably, each tray communicates a held and positioned insert to a main controller of the charged particle cancer therapy system. The trays optionally hold one or more of the imaging sheets configured to emit light upon transmission of the charged particle beam through a corresponding localized position of the one or more imaging sheets. Charged Particle Beam Therapy Throughout this document, a charged particle beam therapy system, such as a proton beam, hydrogen ion beam, or carbon ion beam, is described. Herein, the charged particle beam therapy system is described using a proton beam. However, the aspects taught and described in terms of a proton beam are not intended to be limiting to that of a proton beam and are illustrative of a charged particle beam system, a positively charged beam system, and/or a multiply charged particle beam system, such as C4+ or C6+. Any of the techniques described herein are equally applicable to any charged particle beam system. Referring now to FIG. 1A, a charged particle beam system 100 is illustrated. The charged particle beam preferably comprises a number of subsystems including any of: a main controller 110; an injection system 120; a synchrotron 130 that typically includes: (1) an accelerator system 132 and (2) an internal or connected extraction system 134; a beam transport system 135; a scanning/targeting/delivery system 140; a patient interface module 150; a display system 160; and/or an imaging system 170. An exemplary method of use of the charged particle beam system 100 is provided. The main controller 110 controls one or more of the subsystems to accurately and precisely deliver protons to a tumor of a patient. For example, the main controller 110 obtains an image, such as a portion of a body and/or of a tumor, from the imaging system 170. The main controller 110 also obtains position and/or timing information from the patient interface module 150. The main controller 110 optionally controls the injection system 120 to inject a proton into a synchrotron 130. The synchrotron typically contains at least an accelerator system 132 and an extraction system 134. The main controller 110 preferably controls the proton beam within the accelerator system, such as by controlling speed, trajectory, and timing of the proton beam. The main controller then controls extraction of a proton beam from the accelerator through the extraction system 134. For example, the controller controls timing, energy, and/or intensity of the extracted beam. The controller 110 also preferably controls targeting of the proton beam through the scanning/targeting/delivery system 140 to the patient interface module 150. One or more components of the patient interface module 150, such as translational and rotational position of the patient, are preferably controlled by the main controller 110. Further, display elements of the display system 160 are preferably controlled via the main controller 110. Displays, such as display screens, are typically provided to one or more operators and/or to one or more patients. In one embodiment, the main controller 110 times the delivery of the proton beam from all systems, such that protons are delivered in an optimal therapeutic manner to the tumor of the patient. Herein, the main controller 110 refers to a single system controlling the charged particle beam system 100, to a single controller controlling a plurality of subsystems controlling the charged particle beam system 100, or to a plurality of individual controllers controlling one or more sub-systems of the charged particle beam system 100. Referring now to FIG. 13A, a first example of an integrated cancer treatment-imaging system 1300 is illustrated. In this example, the charged particle beam system 100 is illustrated with a treatment beam 269 directed to the tumor 720 of the patient 730 along the z-axis. Also illustrated is a set of imaging sources 1310, imaging system elements, and/or paths therefrom and a set of detectors 1320 corresponding to a respective element of the set of imaging sources 1310. Herein, the set of imaging sources 1310 are referred to as sources, but are optionally any point or element of the beam train prior to the tumor or a center point about which the gantry rotates. Hence, a given imaging source is optionally a dispersion element used to for cone beam. As illustrated, a first imaging source 1312 yields a first beam path 1332 and a second imaging source 1314 yields a second beam path 1334, where each path passes at least into the tumor 720 and optionally and preferably to a first detector array 1322 and a second detector array 1324, respectively, of the set of detectors 1320. Herein, the first beam path 1332 and the second beam path 1334 are illustrated as forming a ninety degree angle, which yields complementary images of the tumor 720 and/or the patient 730. However, the formed angle is optionally any angle from ten to three hundred fifty degrees. Herein, for clarity of presentation, the first beam path 1332 and the second beam path 1334 are illustrated as single lines, which optionally is an expanding, uniform diameter, or focusing beam. Herein, the first beam path 1332 and the second beam path 1334 are illustrated in transmission mode with their respective sources and detectors on opposite sides of the patient 730. However, a beam path from a source to a detector is optionally a scattered path and/or a diffuse reflectance path. Optionally, one or more detectors of the set of detectors 1320 are a single detector element, a line of detector elements, or preferably a two-dimensional detector array. Use of two two-dimensional detector arrays is referred to herein as a two-dimensional-two-dimensional imaging system or a 2D-2D imaging system. Still referring to FIG. 13A, the first imaging source 1312 and the second imaging source 1314 are illustrated at a first position and a second position, respectively. Each of the first imaging source 1312 and the second imaging source 1322 optionally: (1) maintain a fixed position; (2) provide the first beam path 1332 and the second beam path 1334, respectively, through the gantry 960, such as through a set of one or more holes or slits; (3) provide the first beam path 1332 and the second beam path 1334, respectively, off axis to a plane of movement of the nozzle system 760; (4) move with the gantry 960 as the gantry 960 rotates about at least a first axis; and/or (5) represent a narrow cross-diameter section of an expanding cone beam path. Still referring to FIG. 13A, the set of detectors 1320 are illustrated as coupling with respective elements of the set of sources 1310. Each member of the set of detectors 1320 optionally and preferably co-moves/and/or co-rotates with a respective member of the set of sources 1310. Thus, if the first imaging source 1312 is statically positioned, then the first detector 1322 is optionally and preferably statically positioned. Similarly, to facilitate imaging, if the first imaging source 1312 moves along a first arc as the gantry 960 moves, then the first detector 1322 optionally and preferably moves along the first arc or a second arc as the gantry 960 moves, where relative positions of the first imaging source 1312 on the first arc, a point that the gantry 960 moves about, and relative positions of the first detector 1322 along the second arc are constant. To facilitate the process, the detectors are optionally mechanically linked, such as with a first mechanical support 1342 to the gantry 960 in a manner that when the gantry 960 moves, the gantry moves both the source and the corresponding detector. Optionally, the source moves and a series of detectors, such as along the second arc, capture a set of images. Still referring to FIG. 13A, optionally and preferably, elements of the set of sources 1310 combined with elements of the set of detectors 1320 are used to collect a series of responses, such as one source and one detector yielding a detected intensity and preferably a set of detected intensities to form an image. For instance, the first imaging source 1312, such as a first X-ray source or first cone beam X-ray source, and the first detector 1322, such as an X-ray film, digital X-ray detector, or two-dimensional detector, yield a first X-ray image of the patient at a first time and a second X-ray image of the patient at a second time, such as to confirm a maintained location of a tumor or after movement of the gantry 760 or rotation of the patient 730. A set of n images using the first imaging source 1312 and the first detector 1322 collected as a function of movement of the gantry 760 and/or as a function of movement and/or rotation of the patient 730 are optionally and preferably combined to yield a three-dimensional image of the patient 730, such as a three-dimensional X-ray image of the patient 730, where n is a positive integer, such as greater than 1, 2, 3, 4, 5, 10, 15, 25, 50, or 100. The set of n images is optionally gathered as described in combination with images gathered using the second imaging source 1314, such as a second X-ray source or second cone beam X-ray source, and the second detector 1324, such as a second X-ray detector, where the use of two, or multiple, source/detector combinations are combined to yield images where the patient 730 has not moved between images as the two, or the multiple, images are optionally and preferably collected at the same time, such as with a difference in time of less than 0.01, 0.1, 1, or 5 seconds. Longer time differences are optionally used. Preferably the n two-dimensional images are collected as a function of rotation of the gantry 960 about the tumor and/or the patient and/or as a function of rotation of the patient 730 and the two-dimensional images of the X-ray cone beam are mathematically combined to form a three-dimensional image of the tumor 720 and/or the patient 730. Optionally, the first X-ray source and/or the second X-ray source is the source of X-rays that are divergent forming a cone through the tumor. A set of images collected as a function of rotation of the divergent X-ray cone around the tumor with a two-dimensional detector that detects the divergent X-rays transmitted through the tumor is used to form a three-dimensional X-ray of the tumor and of a portion of the patient, such as in X-ray computed tomography. Still referring to FIG. 13A, use of two imaging sources and two detectors set at ninety degrees to one another allows the gantry 960 or the patient 730 to rotate through half an angle required using only one imaging source and detector combination. A third imaging source/detector combination allows the three imaging source/detector combination to be set at sixty degree intervals allowing the imaging time to be cut to that of one-third that gantry 960 or patient 730 rotation required using a single imaging source-detector combination. Generally, n source-detector combinations reduces the time and/or the rotation requirements to 1/n. Further reduction is possible if the patient 730 and the gantry 960 rotate in opposite directions. Generally, the used of multiple source-detector combination of a given technology allow for a gantry that need not rotate through as large of an angle, with dramatic engineering benefits. Still referring to FIG. 13A, the set of sources 1310 and set of detectors 1320 optionally use more than one imaging technology. For example, a first imaging technology uses X-rays, a second used fluoroscopy, a third detects fluorescence, a fourth uses cone beam computed tomography or cone beam CT, and a fifth uses other electromagnetic waves. Optionally, the set of sources 1310 and the set of detectors 1320 use two or more sources and/or two or more detectors of a given imaging technology, such as described supra with two X-ray sources to n X-ray sources. Still referring to FIG. 13A, use of one or more of the set of sources 1310 and use of one or more of the set of detectors 1320 is optionally coupled with use of the positively charged particle tomography system described supra. As illustrated in FIG. 13A, the positively charged particle tomography system uses a second mechanical support 1343 to co-rotate the scintillation plate 710 with the gantry 960, as well as to co-rotate an optional sheet, such as the first sheet 760 and/or the fourth sheet 790. Referring now to FIG. 1B, an example of a charged particle cancer therapy system 100 is provided. A main controller receives input from one, two, three, or four of a respiration monitoring and/or controlling controller 180, a beam controller 185, a rotation controller 147, and/or a timing to a time period in a respiration cycle controller 148. The beam controller 185 preferably includes one or more or a beam energy controller 182, the beam intensity controller 340, a beam velocity controller 186, and/or a horizontal/vertical beam positioning controller 188. The main controller 110 controls any element of the injection system 120; the synchrotron 130; the scanning/targeting/delivery system 140; the patient interface module 150; the display system 160; and/or the imaging system 170. For example, the respiration monitoring/controlling controller 180 controls any element or method associated with the respiration of the patient; the beam controller 185 controls any of the elements controlling acceleration and/or extraction of the charged particle beam; the rotation controller 147 controls any element associated with rotation of the patient 830 or gantry; and the timing to a period in respiration cycle controller 148 controls any aspects affecting delivery time of the charged particle beam to the patient. As a further example, the beam controller 185 optionally controls any magnetic and/or electric field about any magnet in the charged particle cancer therapy system 100. One or more beam state sensors 190 sense position, direction, intensity, and/or energy of the charged particles at one or more positions in the charged particle beam path. A tomography system 700, described infra, is optionally used to monitor intensity and/or position of the charged particle beam. Referring now to FIG. 2, an illustrative exemplary embodiment of one version of the charged particle beam system 100 is provided. The number, position, and described type of components is illustrative and non-limiting in nature. In the illustrated embodiment, the injection system 120 or ion source or charged particle beam source generates protons. The injection system 120 optionally includes one or more of: a negative ion beam source, an ion beam focusing lens, and a tandem accelerator. The protons are delivered into a vacuum tube that runs into, through, and out of the synchrotron. The generated protons are delivered along an initial path 262. Focusing magnets 230, such as quadrupole magnets or injection quadrupole magnets, are used to focus the proton beam path. A quadrupole magnet is a focusing magnet. An injector bending magnet 232 bends the proton beam toward a plane of the synchrotron 130. The focused protons having an initial energy are introduced into an injector magnet 240, which is preferably an injection Lamberson magnet. Typically, the initial beam path 262 is along an axis off of, such as above, a circulating plane of the synchrotron 130. The injector bending magnet 232 and injector magnet 240 combine to move the protons into the synchrotron 130. Main bending magnets, dipole magnets, turning magnets, or circulating magnets 250 are used to turn the protons along a circulating beam path 264. A dipole magnet is a bending magnet. The main bending magnets 250 bend the initial beam path 262 into a circulating beam path 264. In this example, the main bending magnets 250 or circulating magnets are represented as four sets of four magnets to maintain the circulating beam path 264 into a stable circulating beam path. However, any number of magnets or sets of magnets are optionally used to move the protons around a single orbit in the circulation process. The protons pass through an accelerator 270. The accelerator accelerates the protons in the circulating beam path 264. As the protons are accelerated, the fields applied by the magnets are increased. Particularly, the speed of the protons achieved by the accelerator 270 are synchronized with magnetic fields of the main bending magnets 250 or circulating magnets to maintain stable circulation of the protons about a central point or region 280 of the synchrotron. At separate points in time the accelerator 270/main bending magnet 250 combination is used to accelerate and/or decelerate the circulating protons while maintaining the protons in the circulating path or orbit. An extraction element of an inflector/deflector system is used in combination with a Lamberson extraction magnet 292 to remove protons from their circulating beam path 264 within the synchrotron 130. One example of a deflector component is a Lamberson magnet. Typically the deflector moves the protons from the circulating plane to an axis off of the circulating plane, such as above the circulating plane. Extracted protons are preferably directed and/or focused using an extraction bending magnet 237 and extraction focusing magnets 235, such as quadrupole magnets along a positively charged particle beam transport path 268 in a beam transport system 135, such as a beam path or proton beam path, into the scanning/targeting/delivery system 140. Two components of a scanning system 140 or targeting system typically include a first axis control 142, such as a vertical control, and a second axis control 144, such as a horizontal control. In one embodiment, the first axis control 142 allows for about 100 mm of vertical or y-axis scanning of the proton beam 268 and the second axis control 144 allows for about 700 mm of horizontal or x-axis scanning of the proton beam 268. A nozzle system 146 is used for imaging the proton beam, for defining shape of the proton beam, and/or as a vacuum barrier between the low pressure beam path of the synchrotron and the atmosphere. Protons are delivered with control to the patient interface module 150 and to a tumor of a patient. All of the above listed elements are optional and may be used in various permutations and combinations. Proton Beam Extraction Referring now to FIG. 3, both: (1) an exemplary proton beam extraction system 300 from the synchrotron 130 and (2) a charged particle beam intensity control system 305 are illustrated. For clarity, FIG. 3 removes elements represented in FIG. 2, such as the turning magnets, which allows for greater clarity of presentation of the proton beam path as a function of time. Generally, protons are extracted from the synchrotron 130 by slowing the protons. As described, supra, the protons were initially accelerated in a circulating path, which is maintained with a plurality of main bending magnets 250. The circulating path is referred to herein as an original central beamline 264. The protons repeatedly cycle around a central point in the synchrotron 280. The proton path traverses through a radio frequency (RF) cavity system 310. To initiate extraction, an RF field is applied across a first blade 312 and a second blade 314, in the RF cavity system 310. The first blade 312 and second blade 314 are referred to herein as a first pair of blades. In the proton extraction process, an RF voltage is applied across the first pair of blades, where the first blade 312 of the first pair of blades is on one side of the circulating proton beam path 264 and the second blade 314 of the first pair of blades is on an opposite side of the circulating proton beam path 264. The applied RF field applies energy to the circulating charged-particle beam. The applied RF field alters the orbiting or circulating beam path slightly of the protons from the original central beamline 264 to an altered circulating beam path 265. Upon a second pass of the protons through the RF cavity system, the RF field further moves the protons off of the original proton beamline 264. For example, if the original beamline is considered as a circular path, then the altered beamline is slightly elliptical. The frequency of the applied RF field is timed to apply outward or inward movement to a given band of protons circulating in the synchrotron accelerator. Orbits of the protons are slightly more off axis compared to the original circulating beam path 264. Successive passes of the protons through the RF cavity system are forced further and further from the original central beamline 264 by altering the direction and/or intensity of the RF field with each successive pass of the proton beam through the RF field. Timing of application of the RF field and/or frequency of the RF field is related to the circulating charged particles circulation pathlength in the synchrotron 130 and the velocity of the charged particles so that the applied RF field has a period, with a peak-to-peak time period, equal to a period of time of beam circulation in the synchrotron 130 about the center 280 or an integer multiple of the time period of beam circulation about the center 280 of the synchrotron 130. Alternatively, the time period of beam circulation about the center 280 of the synchrotron 130 is an integer multiple of the RF period time. The RF period is optionally used to calculated the velocity of the charged particles, which relates directly to the energy of the circulating charged particles. The RF voltage is frequency modulated at a frequency about equal to the period of one proton cycling around the synchrotron for one revolution or at a frequency than is an integral multiplier of the period of one proton cycling about the synchrotron. The applied RF frequency modulated voltage excites a betatron oscillation. For example, the oscillation is a sine wave motion of the protons. The process of timing the RF field to a given proton beam within the RF cavity system is repeated thousands of times with each successive pass of the protons being moved approximately one micrometer further off of the original central beamline 264. For clarity, the approximately 1000 changing beam paths with each successive path of a given band of protons through the RF field are illustrated as the altered beam path 265. The RF time period is process is known, thus energy of the charged particles at time of hitting the extraction material or material 330, described infra, is known. With a sufficient sine wave betatron amplitude, the altered circulating beam path 265 touches and/or traverses a material 330, such as a foil or a sheet of foil. The foil is preferably a lightweight material, such as beryllium, a lithium hydride, a carbon sheet, or a material having low nuclear charge components. Herein, a material of low nuclear charge is a material composed of atoms consisting essentially of atoms having six or fewer protons. The foil is preferably about 10 to 150 microns thick, is more preferably about 30 to 100 microns thick, and is still more preferably about 40 to 60 microns thick. In one example, the foil is beryllium with a thickness of about 50 microns. When the protons traverse through the foil, energy of the protons is lost and the speed of the protons is reduced. Typically, a current is also generated, described infra. Protons moving at the slower speed travel in the synchrotron with a reduced radius of curvature 266 compared to either the original central beamline 264 or the altered circulating path 265. The reduced radius of curvature 266 path is also referred to herein as a path having a smaller diameter of trajectory or a path having protons with reduced energy. The reduced radius of curvature 266 is typically about two millimeters less than a radius of curvature of the last pass of the protons along the altered proton beam path 265. The thickness of the material 330 is optionally adjusted to create a change in the radius of curvature, such as about ½, 1, 2, 3, or 4 mm less than the last pass of the protons 265 or original radius of curvature 264. The reduction in velocity of the charged particles transmitting through the material 330 is calculable, such as by using the pathlength of the betatron oscillating charged particle beam through the material 330 and/or using the density of the material 330. Protons moving with the smaller radius of curvature travel between a second pair of blades. In one case, the second pair of blades is physically distinct and/or is separated from the first pair of blades. In a second case, one of the first pair of blades is also a member of the second pair of blades. For example, the second pair of blades is the second blade 314 and a third blade 316 in the RF cavity system 310. A high voltage DC signal, such as about 1 to 5 kV, is then applied across the second pair of blades, which directs the protons out of the synchrotron through an extraction magnet 292, such as a Lamberson extraction magnet, into a transport path 268. Control of acceleration of the charged particle beam path in the synchrotron with the accelerator and/or applied fields of the turning magnets in combination with the above described extraction system allows for control of the intensity of the extracted proton beam, where intensity is a proton flux per unit time or the number of protons extracted as a function of time. For example, when a current is measured beyond a threshold, the RF field modulation in the RF cavity system is terminated or reinitiated to establish a subsequent cycle of proton beam extraction. This process is repeated to yield many cycles of proton beam extraction from the synchrotron accelerator. In another embodiment, instead of moving the charged particles to the material 330, the material 330 is mechanically moved to the circulating charged particles. Particularly, the material 330 is mechanically or electromechanically translated into the path of the circulating charged particles to induce the extraction process, described supra. In this case, the velocity or energy of the circulating charged particle beam is calculable using the pathlength of the beam path about the center 280 of the synchrotron 130 and from the force applied by the bending magnets 250. In either case, because the extraction system does not depend on any change in magnetic field properties, it allows the synchrotron to continue to operate in acceleration or deceleration mode during the extraction process. Stated differently, the extraction process does not interfere with synchrotron acceleration. In stark contrast, traditional extraction systems introduce a new magnetic field, such as via a hexapole, during the extraction process. More particularly, traditional synchrotrons have a magnet, such as a hexapole magnet, that is off during an acceleration stage. During the extraction phase, the hexapole magnetic field is introduced to the circulating path of the synchrotron. The introduction of the magnetic field necessitates two distinct modes, an acceleration mode and an extraction mode, which are mutually exclusive in time. The herein described system allows for acceleration and/or deceleration of the proton during the extraction step and tumor treatment without the use of a newly introduced magnetic field, such as by a hexapole magnet. Charged Particle Beam Intensity Control Control of applied field, such as a radio-frequency (RF) field, frequency and magnitude in the RF cavity system 310 allows for intensity control of the extracted proton beam, where intensity is extracted proton flux per unit time or the number of protons extracted as a function of time. Still referring FIG. 3, the intensity control system 305 is further described. In this example, an intensity control feedback loop is added to the extraction system, described supra. When protons in the proton beam hit the material 330 electrons are given off from the material 330 resulting in a current. The resulting current is converted to a voltage and is used as part of an ion beam intensity monitoring system or as part of an ion beam feedback loop for controlling beam intensity. The voltage is optionally measured and sent to the main controller 110 or to an intensity controller subsystem 340, which is preferably in communication or under the direction of the main controller 110. More particularly, when protons in the charged particle beam path pass through the material 330, some of the protons lose a small fraction of their energy, such as about one-tenth of a percent, which results in a secondary electron. That is, protons in the charged particle beam push some electrons when passing through material 330 giving the electrons enough energy to cause secondary emission. The resulting electron flow results in a current or signal that is proportional to the number of protons going through the target or extraction material 330. The resulting current is preferably converted to voltage and amplified. The resulting signal is referred to as a measured intensity signal. The amplified signal or measured intensity signal resulting from the protons passing through the material 330 is optionally used in monitoring the intensity of the extracted protons and is preferably used in controlling the intensity of the extracted protons. For example, the measured intensity signal is compared to a goal signal, which is predetermined in an irradiation of the tumor plan. The difference between the measured intensity signal and the planned for goal signal is calculated. The difference is used as a control to the RF generator. Hence, the measured flow of current resulting from the protons passing through the material 330 is used as a control in the RF generator to increase or decrease the number of protons undergoing betatron oscillation and striking the material 330. Hence, the voltage determined off of the material 330 is used as a measure of the orbital path and is used as a feedback control to control the RF cavity system. In one example, the intensity controller subsystem 340 preferably additionally receives input from: (1) a detector 350, which provides a reading of the actual intensity of the proton beam and/or (2) an irradiation plan 360. The irradiation plan provides the desired intensity of the proton beam for each x, y, energy, and/or rotational position of the patient/tumor as a function of time. Thus, the intensity controller 340 receives the desired intensity from the irradiation plan 350, the actual intensity from the detector 350 and/or a measure of intensity from the material 330, and adjusts the amplitude and/or the duration of application of the applied radio-frequency field in the RF cavity system 310 to yield an intensity of the proton beam that matches the desired intensity from the irradiation plan 360. As described, supra, the protons striking the material 330 is a step in the extraction of the protons from the synchrotron 130. Hence, the measured intensity signal is used to change the number of protons per unit time being extracted, which is referred to as intensity of the proton beam. The intensity of the proton beam is thus under algorithm control. Further, the intensity of the proton beam is controlled separately from the velocity of the protons in the synchrotron 130. Hence, intensity of the protons extracted and the energy of the protons extracted are independently variable. Still further, the intensity of the extracted protons is controllably variable while scanning the charged particles beam in the tumor from one voxel to an adjacent voxel as a separate hexapole and separated time period from acceleration and/or treatment is not required, as described supra. For example, protons initially move at an equilibrium trajectory in the synchrotron 130. An RF field is used to excite or move the protons into a betatron oscillation. In one case, the frequency of the protons orbit is about 10 MHz. In one example, in about one millisecond or after about 10,000 orbits, the first protons hit an outer edge of the target material 130. The specific frequency is dependent upon the period of the orbit. Upon hitting the material 130, the protons push electrons through the foil to produce a current. The current is converted to voltage and amplified to yield a measured intensity signal. The measured intensity signal is used as a feedback input to control the applied RF magnitude or RF field. An energy beam sensor, described infra, is optionally used as a feedback control to the RF field frequency or RF field of the RF field extraction system 310 to dynamically control, modify, and/or alter the delivered charge particle beam energy, such as in a continuous pencil beam scanning system operating to treat tumor voxels without alternating between an extraction phase and a treatment phase. Preferably, the measured intensity signal is compared to a target signal and a measure of the difference between the measured intensity signal and target signal is used to adjust the applied RF field in the RF cavity system 310 in the extraction system to control the intensity of the protons in the extraction step. Stated again, the signal resulting from the protons striking and/or passing through the material 130 is used as an input in RF field modulation. An increase in the magnitude of the RF modulation results in protons hitting the foil or material 130 sooner. By increasing the RF, more protons are pushed into the foil, which results in an increased intensity, or more protons per unit time, of protons extracted from the synchrotron 130. In another example, a detector 350 external to the synchrotron 130 is used to determine the flux of protons extracted from the synchrotron and a signal from the external detector is used to alter the RF field, RF intensity, RF amplitude, and/or RF modulation in the RF cavity system 310. Here the external detector generates an external signal, which is used in a manner similar to the measured intensity signal, described in the preceding paragraphs. Preferably, an algorithm or irradiation plan 360 is used as an input to the intensity controller 340, which controls the RF field modulation by directing the RF signal in the betatron oscillation generation in the RF cavity system 310. The irradiation plan 360 preferably includes the desired intensity of the charged particle beam as a function of time and/or energy of the charged particle beam as a function of time, for each patient rotation position, and/or for each x-, y-position of the charged particle beam. In yet another example, when a current from material 330 resulting from protons passing through or hitting material is measured beyond a threshold, the RF field modulation in the RF cavity system is terminated or reinitiated to establish a subsequent cycle of proton beam extraction. This process is repeated to yield many cycles of proton beam extraction from the synchrotron accelerator. In still yet another embodiment, intensity modulation of the extracted proton beam is controlled by the main controller 110. The main controller 110 optionally and/or additionally controls timing of extraction of the charged particle beam and energy of the extracted proton beam. The benefits of the system include a multi-dimensional scanning system. Particularly, the system allows independence in: (1) energy of the protons extracted and (2) intensity of the protons extracted. That is, energy of the protons extracted is controlled by an energy control system and an intensity control system controls the intensity of the extracted protons. The energy control system and intensity control system are optionally independently controlled. Preferably, the main controller 110 controls the energy control system and the main controller 110 simultaneously controls the intensity control system to yield an extracted proton beam with controlled energy and controlled intensity where the controlled energy and controlled intensity are independently variable and/or continually available as a separate extraction phase and acceleration phase are not required, as described supra. Thus the irradiation spot hitting the tumor is under independent control of: time; energy; intensity; x-axis position, where the x-axis represents horizontal movement of the proton beam relative to the patient, and y-axis position, where the y-axis represents vertical movement of the proton beam relative to the patient. In addition, the patient is optionally independently translated and/or rotated relative to a translational axis of the proton beam at the same time. Beam Transport The beam transport system 135 is used to move the charged particles from the accelerator to the patient, such as via a nozzle in a gantry, described infra. Charged Particle Energy The beam transport system 135 optionally includes means for determining an energy of the charged particles in the charged particle beam. For example, an energy of the charged particle beam is determined via calculation, such as via equation 1, using knowledge of a magnet geometry and applied magnetic field to determine mass and/or energy. Referring now to equation 1, for a known magnet geometry, charge, q, and magnetic field, B, the Larmor radius, ρL, or magnet bend radius is defined as: ρ L = v ⊥ Ω c = 2 E m q B ( eq . 1 ) where: ν⊥ is the ion velocity perpendicular to the magnetic field, Ωc is the cyclotron frequency, q is the charge of the ion, B is the magnetic field, m is the mass of the charge particle, and E is the charged particle energy. Solving for the charged particle energy yields equation 2. E = ( ρ L q B ) 2 2 m ( eq . 2 ) Thus, an energy of the charged particle in the charged particle beam in the beam transport system 135 is calculable from the know magnet geometry, known or measured magnetic field, charged particle mass, charged particle charge, and the known magnet bend radius, which is proportional to and/or equivalent to the Larmor radius. Nozzle After extraction from the synchrotron 130 and transport of the charged particle beam along the proton beam path 268 in the beam transport system 135, the charged particle beam exits through the nozzle system 146. In one example, the nozzle system includes a nozzle foil covering an end of the nozzle system 146 or a cross-sectional area within the nozzle system forming a vacuum seal. The nozzle system includes a nozzle that expands in x/y-cross-sectional area along the z-axis of the proton beam path 268 to allow the proton beam 268 to be scanned along the x-axis and y-axis by the vertical control element and horizontal control element, respectively. The nozzle foil is preferably mechanically supported by the outer edges of an exit port of the nozzle 146. An example of a nozzle foil is a sheet of about 0.1 inch thick aluminum foil. Generally, the nozzle foil separates atmosphere pressures on the patient side of the nozzle foil from the low pressure region, such as about 10−5 to 10−7 torr region, on the synchrotron 130 side of the nozzle foil. The low pressure region is maintained to reduce scattering of the circulating charged particle beam in the synchrotron. Herein, the exit foil of the nozzle is optionally the first sheet 760 of the charged particle beam state determination system 750, described infra. Charged Particle Control Referring now to FIG. 4A, FIG. 4B, FIG. 5, FIG. 6A, and FIG. 6B, a charged particle beam control system is described where one or more patient specific beam control assemblies are removably inserted into the charged particle beam path proximate the nozzle of the charged particle cancer therapy system 100, where the patient specific beam control assemblies adjust the beam energy, diameter, cross-sectional shape, focal point, and/or beam state of the charged particle beam to properly couple energy of the charged particle beam to the individual's specific tumor. Beam Control Tray Referring now to FIG. 4A and FIG. 4B, a beam control tray assembly 400 is illustrated in a top view and side view, respectively. The beam control tray assembly 400 optionally comprises any of a tray frame 410, a tray aperture 412, a tray handle 420, a tray connector/communicator 430, and means for holding a patient specific tray insert 510, described infra. Generally, the beam control tray assembly 400 is used to: (1) hold the patient specific tray insert 510 in a rigid location relative to the beam control tray 400, (2) electronically identify the held patient specific tray insert 510 to the main controller 110, and (3) removably insert the patient specific tray insert 510 into an accurate and precise fixed location relative to the charged particle beam, such as the proton beam path 268 at the nozzle of the charged particle cancer therapy system 100. For clarity of presentation and without loss of generality, the means for holding the patient specific tray insert 510 in the tray frame 410 of the beam control tray assembly 400 is illustrated as a set of recessed set screws 415. However, the means for holding the patient specific tray insert 510 relative to the rest of the beam control tray assembly 400 is optionally any mechanical and/or electromechanical positioning element, such as a latch, clamp, fastener, clip, slide, strap, or the like. Generally, the means for holding the patient specific tray insert 510 in the beam control tray 400 fixes the tray insert and tray frame relative to one another even when rotated along and/or around multiple axes, such as when attached to a charged particle cancer therapy system 100 dynamic gantry nozzle 610 or gantry nozzle, which is an optional element of the nozzle system 146, that moves in three-dimensional space relative to a fixed point in the beamline, proton beam path 268, and/or a given patient position. As illustrated in FIG. 4A and FIG. 4B, the recessed set screws 415 fix the patient specific tray insert 510 into the aperture 412 of the tray frame 410. The tray frame 410 is illustrated as circumferentially surrounding the patient specific tray insert 510, which aids in structural stability of the beam control tray assembly 400. However, generally the tray frame 410 is of any geometry that forms a stable beam control tray assembly 400. Still referring to FIG. 4A and now referring to FIG. 5 and FIG. 6A, the optional tray handle 420 is used to manually insert/retract the beam control tray assembly 400 into a receiving element of the gantry nozzle or dynamic gantry nozzle 610. While the beam control tray assembly 400 is optionally inserted into the charged particle beam path 268 at any point after extraction from the synchrotron 130, the beam control tray assembly 400 is preferably inserted into the positively charged particle beam proximate the dynamic gantry nozzle 610 as control of the beam shape is preferably done with little space for the beam shape to defocus before striking the tumor. Optionally, insertion and/or retraction of the beam control tray assembly 400 is semi-automated, such as in a manner of a digital-video disk player receiving a digital-video disk, with a selected auto load and/or a selected auto unload feature. Patient Specific Tray Insert Referring again to FIG. 5, a system of assembling trays 500 is described. The beam control tray assembly 400 optionally and preferably has interchangeable patient specific tray inserts 510, such as a range shifter insert 511, a patient specific ridge filter insert 512, an aperture insert 513, a compensator insert 514, or a blank insert 515. As described, supra, any of the range shifter insert 511, the patient specific ridge filter insert 512, the aperture insert 513, the compensator insert 514, or the blank insert 515 after insertion into the tray frame 410 are inserted as the beam control tray assembly 400 into the positively charged particle beam path 268, such as proximate the dynamic gantry nozzle 610. Still referring to FIG. 5, the patient specific tray inserts 510 are further described. The patient specific tray inserts comprise a combination of any of: (1) a standardized beam control insert and (2) a patient specific beam control insert. For example, the range shifter insert or 511 or compensator insert 514 used to control the depth of penetration of the charged particle beam into the patient is optionally: (a) a standard thickness of a beam slowing material, such as a first thickness of Lucite, an acrylic, a clear plastic, and/or a thermoplastic material, (b) one member of a set of members of varying thicknesses and/or densities where each member of the set of members slows the charged particles in the beam path by a known amount, or (c) is a material with a density and thickness designed to slow the charged particles by a customized amount for the individual patient being treated, based on the depth of the individual's tumor in the tissue, the thickness of intervening tissue, and/or the density of intervening bone/tissue. Similarly, the ridge filter insert 512 used to change the focal point or shape of the beam as a function of depth is optionally: (1) selected from a set of ridge filters where different members of the set of ridge filters yield different focal depths or (2) customized for treatment of the individual's tumor based on position of the tumor in the tissue of the individual. Similarly, the aperture insert is: (1) optionally selected from a set of aperture shapes or (2) is a customized individual aperture insert 513 designed for the specific shape of the individual's tumor. The blank insert 515 is an open slot, but serves the purpose of identifying slot occupancy, as described infra. Slot Occupancy/Identification Referring again to FIG. 4A, FIG. 4B, and FIG. 5, occupancy and identification of the particular patient specific tray insert 510 into the beam control tray assembly 400 is described. Generally, the beam control tray assembly 400 optionally contains means for identifying, to the main controller 110 and/or a treatment delivery control system described infra, the specific patient tray insert 510 and its location in the charged particle beam path 268. First, the particular tray insert is optionally labeled and/or communicated to the beam control tray assembly 400 or directly to the main controller 110. Second, the beam control tray assembly 400 optionally communicates the tray type and/or tray insert to the main controller 110. In various embodiments, communication of the particular tray insert to the main controller 110 is performed: (1) directly from the tray insert, (2) from the tray insert 510 to the tray assembly 400 and subsequently to the main controller 110, and/or (3) directly from the tray assembly 400. Generally, communication is performed wirelessly and/or via an established electromechanical link. Identification is optionally performed using a radio-frequency identification label, use of a barcode, or the like, and/or via operator input. Examples are provided to further clarify identification of the patient specific tray insert 510 in a given beam control tray assembly 400 to the main controller. In a first example, one or more of the patient specific tray inserts 510, such as the range shifter insert 511, the patient specific ridge filter insert 512, the aperture insert 513, the compensator insert 514, or the blank insert 515 include an identifier 520 and/or and a first electromechanical identifier plug 530. The identifier 520 is optionally a label, a radio-frequency identification tag, a barcode, a 2-dimensional bar-code, a matrix-code, or the like. The first electromechanical identifier plug 530 optionally includes memory programmed with the particular patient specific tray insert information and a connector used to communicate the information to the beam control tray assembly 400 and/or to the main controller 110. As illustrated in FIG. 5, the first electromechanical identifier plug 530 affixed to the patient specific tray insert 510 plugs into a second electromechanical identifier plug, such as the tray connector/communicator 430, of the beam control tray assembly 400, which is described infra. In a second example, the beam control tray assembly 400 uses the second electromechanical identifier plug to send occupancy, position, and/or identification information related to the type of tray insert or the patient specific tray insert 510 associated with the beam control tray assembly to the main controller 110. For example, a first tray assembly is configured with a first tray insert and a second tray assembly is configured with a second tray insert. The first tray assembly sends information to the main controller 110 that the first tray assembly holds the first tray insert, such as a range shifter, and the second tray assembly sends information to the main controller 110 that the second tray assembly holds the second tray insert, such as an aperture. The second electromechanical identifier plug optionally contains programmable memory for the operator to input the specific tray insert type, a selection switch for the operator to select the tray insert type, and/or an electromechanical connection to the main controller. The second electromechanical identifier plug associated with the beam control tray assembly 400 is optionally used without use of the first electromechanical identifier plug 530 associated with the tray insert 510. In a third example, one type of tray connector/communicator 430 is used for each type of patient specific tray insert 510. For example, a first connector/communicator type is used for holding a range shifter insert 511, while a second, third, fourth, and fifth connector/communicator type is used for trays respectively holding a patient specific ridge filter insert 512, an aperture insert 513, a compensator insert 514, or a blank insert 515. In one case, the tray communicates tray type with the main controller. In a second case, the tray communicates patient specific tray insert information with the main controller, such as an aperture identifier custom built for the individual patient being treated. Tray Insertion/Coupling Referring now to FIG. 6A and FIG. 6B a beam control insertion process 600 is described. The beam control insertion process 600 comprises: (1) insertion of the beam control tray assembly 400 and the associated patient specific tray insert 510 into the charged particle beam path 268 and/or dynamic gantry nozzle 610, such as into a tray assembly receiver 620 and (2) an optional partial or total retraction of beam of the tray assembly receiver 620 into the dynamic gantry nozzle 610. Referring now to FIG. 6A, insertion of one or more of the beam control tray assemblies 400 and the associated patient specific tray inserts 510 into the dynamic gantry nozzle 610 is further described. In FIG. 6A, three beam control tray assemblies, of a possible n tray assemblies, are illustrated, a first tray assembly 402, a second tray assembly 404, and a third tray assembly 406, where n is a positive integer of 1, 2, 3, 4, 5 or more. As illustrated, the first tray assembly 402 slides into a first receiving slot 403, the second tray assembly 404 slides into a second receiving slot 405, and the third tray assembly 406 slides into a third receiving slot 407. Generally, any tray optionally inserts into any slot or tray types are limited to particular slots through use of a mechanical, physical, positional, and/or steric constraints, such as a first tray type configured for a first insert type having a first size and a second tray type configured for a second insert type having a second distinct size at least ten percent different from the first size. Still referring to FIG. 6A, identification of individual tray inserts inserted into individual receiving slots is further described. As illustrated, sliding the first tray assembly 402 into the first receiving slot 403 connects the associated electromechanical connector/communicator 430 of the first tray assembly 402 to a first receptor 626. The electromechanical connector/communicator 430 of the first tray assembly communicates tray insert information of the first beam control tray assembly to the main controller 110 via the first receptor 626. Similarly, sliding the second tray assembly 404 into the second receiving slot 405 connects the associated electromechanical connector/communicator 430 of the second tray assembly 404 into a second receptor 627, which links communication of the associated electromechanical connector/communicator 430 with the main controller 110 via the second receptor 627, while a third receptor 628 connects to the electromechanical connected placed into the third slot 407. The non-wireless/direct connection is preferred due to the high radiation levels within the treatment room and the high shielding of the treatment room, which both hinder wireless communication. The connection of the communicator and the receptor is optionally of any configuration and/or orientation. Tray Receiver Assembly Retraction Referring again to FIG. 6A and FIG. 6B, retraction of the tray receiver assembly 620 relative to a nozzle end 612 of the dynamic gantry nozzle 610 is described. The tray receiver assembly 620 comprises a framework to hold one or more of the beam control tray assemblies 400 in one or more slots, such as through use of a first tray receiver assembly side 622 through which the beam control tray assemblies 400 are inserted and/or through use of a second tray receiver assembly side 624 used as a backstop, as illustrated holding the plugin receptors configured to receive associated tray connector/communicators 430, such as the first, second, and third receptors 626, 627, 628. Optionally, the tray receiver assembly 620 retracts partially or completely into the dynamic gantry nozzle 610 using a retraction mechanism 660 configured to alternatingly retract and extend the tray receiver assembly 620 relative to a nozzle end 612 of the gantry nozzle 610, such as along a first retraction track 662 and a second retraction track 664 using one or more motors and computer control. Optionally the tray receiver assembly 620 is partially or fully retracted when moving the gantry, nozzle, and/or gantry nozzle 610 to avoid physical constraints of movement, such as potential collision with another object in the patient treatment room. For clarity of presentation and without loss of generality, several examples of loading patient specific tray inserts into tray assemblies with subsequent insertion into an positively charged particle beam path proximate a gantry nozzle 610 are provided. In a first example, a single beam control tray assembly 400 is used to control the charged particle beam 268 in the charged particle cancer therapy system 100. In this example, a patient specific range shifter insert 511, which is custom fabricated for a patient, is loaded into a patient specific tray insert 510 to form a first tray assembly 402, where the first tray assembly 402 is loaded into the third receptor 628, which is fully retracted into the gantry nozzle 610. In a second example, two beam control assemblies 400 are used to control the charged particle beam 268 in the charged particle cancer therapy system 100. In this example, a patient specific ridge filter 512 is loaded into a first tray assembly 402, which is loaded into the second receptor 627 and a patient specific aperture 513 is loaded into a second tray assembly 404, which is loaded into the first receptor 626 and the two associated tray connector/communicators 430 using the first receptor 626 and second receptor 627 communicate to the main controller 110 the patient specific tray inserts 510. The tray receiver assembly 620 is subsequently retracted one slot so that the patient specific ridge filter 512 and the patient specific aperture reside outside of and at the nozzle end 612 of the gantry nozzle 610. In a third example, three beam control tray assemblies 400 are used, such as a range shifter 511 in a first tray inserted into the first receiving slot 403, a compensator in a second tray inserted into the second receiving slot 405, and an aperture in a third tray inserted into the third receiving slot 407. Generally, any patient specific tray insert 510 is inserted into a tray frame 410 to form a beam control tray assembly 400 inserted into any slot of the tray receiver assembly 620 and the tray assembly is not retracted or retracted any distance into the gantry nozzle 610. Tomography/Beam State In one embodiment, the charged particle tomography apparatus is used to image a tumor in a patient. As current beam position determination/verification is used in both tomography and cancer therapy treatment, for clarity of presentation and without limitation beam state determination is also addressed in this section. However, beam state determination is optionally used separately and without tomography. In another example, the charged particle tomography apparatus is used in combination with a charged particle cancer therapy system using common elements. For example, tomographic imaging of a cancerous tumor is performed using charged particles generated with an injector, accelerator, and guided with a delivery system that are part of the cancer therapy system, described supra. In various examples, the tomography imaging system is optionally simultaneously operational with a charged particle cancer therapy system using common elements, allows tomographic imaging with rotation of the patient, is operational on a patient in an upright, semi-upright, and/or horizontal position, is simultaneously operational with X-ray imaging, and/or allows use of adaptive charged particle cancer therapy. Further, the common tomography and cancer therapy apparatus elements are optionally operational in a multi-axis and/or multi-field raster beam mode. In conventional medical X-ray tomography, a sectional image through a body is made by moving one or both of an X-ray source and the X-ray film in opposite directions during the exposure. By modifying the direction and extent of the movement, operators can select different focal planes, which contain the structures of interest. More modern variations of tomography involve gathering projection data from multiple directions by moving the X-ray source and feeding the data into a tomographic reconstruction software algorithm processed by a computer. Herein, in stark contrast to known methods, the radiation source is a charged particle, such as a proton ion beam or a carbon ion beam. A proton beam is used herein to describe the tomography system, but the description applies to a heavier ion beam, such as a carbon ion beam. Further, in stark contrast to known techniques, herein the radiation source is preferably stationary while the patient is rotated. Referring now to FIG. 7, an example of a tomography apparatus is described and an example of a beam state determination is described. In this example, the tomography system 700 uses elements in common with the charged particle beam system 100, including elements of one or more of the injection system 120, accelerator 130, targeting/delivery system 140, patient interface module 150, display system 160, and/or imaging system 170, such as the X-ray imaging system. One or more scintillation plates, such as a scintillating plastic, are used to measure energy, intensity, and/or position of the charged particle beam. For instance, a scintillation plate 710 is positioned behind the patient 730 relative to the targeting/delivery system 140 elements, which is optionally used to measure intensity and/or position of the charged particle beam after transmitting through the patient. Optionally, a second scintillation plate or a charged particle induced photon emitting sheet, described infra, is positioned prior to the patient 730 relative to the targeting/delivery system 140 elements, which is optionally used to measure incident intensity and/or position of the charged particle beam prior to transmitting through the patient. The charged particle beam system 100 as described has proven operation at up to and including 330 MeV, which is sufficient to send protons through the body and into contact with the scintillation material. Particularly, 250 MeV to 330 MeV are used to pass the beam through a standard sized patient with a standard sized pathlength, such as through the chest. The intensity or count of protons hitting the plate as a function of position is used to create an image. The velocity or energy of the proton hitting the scintillation plate is also used in creation of an image of the tumor 720 and/or an image of the patient 730. The patient 730 is rotated about the y-axis and a new image is collected. Preferably, a new image is collected with about every one degree of rotation of the patient resulting in about 360 images that are combined into a tomogram using tomographic reconstruction software. The tomographic reconstruction software uses overlapping rotationally varied images in the reconstruction. Optionally, a new image is collected at about every 2, 3, 4, 5, 10, 15, 30, or 45 degrees of rotation of the patient. In one embodiment, a tomogram or an individual tomogram section image is collected at about the same time as cancer therapy occurs using the charged particle beam system 100. For example, a tomogram is collected and cancer therapy is subsequently performed: without the patient moving from the positioning systems, such as in a semi-vertical partial immobilization system, a sitting partial immobilization system, or the a laying position. In a second example, an individual tomogram slice is collected using a first cycle of the accelerator 130 and using a following cycle of the accelerator 130, the tumor 720 is irradiated, such as within about 1, 2, 5, 10, 15 or 30 seconds. In a third case, about 2, 3, 4, or 5 tomogram slices are collected using 1, 2, 3, 4, or more rotation positions of the patient 730 within about 5, 10, 15, 30, or 60 seconds of subsequent tumor irradiation therapy. In another embodiment, the independent control of the tomographic imaging process and X-ray collection process allows simultaneous single and/or multi-field collection of X-ray images and tomographic images easing interpretation of multiple images. Indeed, the X-ray and tomographic images are optionally overlaid to from a hybrid X-ray/proton beam tomographic image as the patient 730 is optionally in the same position for each image. In still another embodiment, the tomogram is collected with the patient 730 in the about the same position as when the patient's tumor is treated using subsequent irradiation therapy. For some tumors, the patient being positioned in the same upright or semi-upright position allows the tumor 720 to be separated from surrounding organs or tissue of the patient 730 better than in a laying position. Positioning of the scintillation plate 710 behind the patient 730 allows the tomographic imaging to occur while the patient is in the same upright or semi-upright position. The use of common elements in the tomographic imaging and in the charged particle cancer therapy allows benefits of the cancer therapy, described supra, to optionally be used with the tomographic imaging, such as proton beam x-axis control, proton beam y-axis control, control of proton beam energy, control of proton beam intensity, timing control of beam delivery to the patient, rotation control of the patient, and control of patient translation all in a raster beam mode of proton energy delivery. The use of a single proton or cation beamline for both imaging and treatment facilitates eases patient setup, reduces alignment uncertainties, reduces beam state uncertainties, and eases quality assurance. In yet still another embodiment, initially a three-dimensional tomographic proton based reference image is collected, such as with hundreds of individual rotation images of the tumor 720 and patient 730. Subsequently, just prior to proton treatment of the cancer, just a few 2-dimensional control tomographic images of the patient are collected, such as with a stationary patient or at just a few rotation positions, such as an image straight on to the patient, with the patient rotated about 45 degrees each way, and/or the patient rotated about 90 degrees each way about the y-axis. The individual control images are compared with the 3-dimensional reference image. An adaptive proton therapy is subsequently performed where: (1) the proton cancer therapy is not used for a given position based on the differences between the 3-dimensional reference image and one or more of the 2-dimensional control images and/or (2) the proton cancer therapy is modified in real time based on the differences between the 3-dimensional reference image and one or more of the 2-dimensional control images. Charged Particle State Determination/Verification/Photonic Monitoring Still referring to FIG. 7, the tomography system 700 is optionally used with a charged particle beam state determination system 750, optionally used as a charged particle verification system. The charged particle state determination system 750 optionally measures, determines, and/or verifies one of more of: (1) position of the charged particle beam, (2) direction of the charged particle beam, (3) intensity of the charged particle beam, (4) energy of the charged particle beam, and (5) a history of the charged particle beam. For clarity of presentation and without loss of generality, a description of the charged particle beam state determination system 750 is described and illustrated separately in FIG. 8 and FIG. 9A; however, as described herein elements of the charged particle beam state determination system 750 are optionally and preferably integrated into the nozzle system 146 and/or the tomography system 700 of the charged particle treatment system 100. More particularly, any element of the charged particle beam state determination system 750 is integrated into the nozzle system 146, the dynamic gantry nozzle 610, and/or tomography system 700, such as a surface of the scintillation plate 710 or a surface of a scintillation detector, plate, or system. The nozzle system 146 or the dynamic gantry nozzle 610 provides an outlet of the charged particle beam from the vacuum tube initiating at the injection system 120 and passing through the synchrotron 130 and beam transport system 135. Any plate, sheet, fluorophore, or detector of the charged particle beam state determination system is optionally integrated into the nozzle system 146. For example, an exit foil of the nozzle 610 is optionally a first sheet 760 of the charged particle beam state determination system 750 and a first coating 762 is optionally coated onto the exit foil, as illustrated in FIG. 7. Similarly, optionally a surface of the scintillation plate 710 is a support surface for a fourth coating 792, as illustrated in FIG. 7. The charged particle beam state determination system 750 is further described, infra. Referring now to FIG. 7, FIG. 8, and FIG. 9A, four sheets, a first sheet 760, a second sheet 770, a third sheet 780, and a fourth sheet 790 are used to illustrated detection sheets and/or photon emitting sheets upon transmittance of a charged particle beam. Each sheet is optionally coated with a photon emitter, such as a fluorophore, such as the first sheet 760 is optionally coated with a first coating 762. Without loss of generality and for clarity of presentation, the four sheets are each illustrated as units, where the light emitting layer is not illustrated. Thus, for example, the second sheet 770 optionally refers to a support sheet, a light emitting sheet, and/or a support sheet coated by a light emitting element. The four sheets are representative of n sheets, where n is a positive integer. Referring now to FIG. 7 and FIG. 8, the charged particle beam state verification system 750 is a system that allows for monitoring of the actual charged particle beam position in real-time without destruction of the charged particle beam. The charged particle beam state verification system 750 preferably includes a first position element or first beam verification layer, which is also referred to herein as a coating, luminescent, fluorescent, phosphorescent, radiance, or viewing layer. The first position element optionally and preferably includes a coating or thin layer substantially in contact with a sheet, such as an inside surface of the nozzle foil, where the inside surface is on the synchrotron side of the nozzle foil. Less preferably, the verification layer or coating layer is substantially in contact with an outer surface of the nozzle foil, where the outer surface is on the patient treatment side of the nozzle foil. Preferably, the nozzle foil provides a substrate surface for coating by the coating layer. Optionally, a binding layer is located between the coating layer and the nozzle foil, substrate, or support sheet. Optionally, the position element is placed anywhere in the charged particle beam path. Optionally, more than one position element on more than one sheet, respectively, is used in the charged particle beam path and is used to determine a state property of the charged particle beam, as described infra. Still referring to FIG. 7 and FIG. 8, the coating, referred to as a fluorophore, yields a measurable spectroscopic response, spatially viewable by a detector or camera, as a result of transmission by the proton beam. The coating is preferably a phosphor, but is optionally any material that is viewable or imaged by a detector where the material changes spectroscopically as a result of the charged particle beam hitting or transmitting through the coating or coating layer. A detector or camera views secondary photons emitted from the coating layer and determines a position of a treatment beam 269, which is also referred to as a current position of the charged particle beam or final treatment vector of the charged particle beam, by the spectroscopic differences resulting from protons and/or charged particle beam passing through the coating layer. For example, the camera views a surface of the coating surface as the proton beam or positively charged cation beam is being scanned by the first axis control 142, vertical control, and the second axis control 144, horizontal control, beam position control elements during treatment of the tumor 720. The camera views the current position of the charged particle beam or treatment beam 269 as measured by spectroscopic response. The coating layer is preferably a phosphor or luminescent material that glows and/or emits photons for a short period of time, such as less than 5 seconds for a 50% intensity, as a result of excitation by the charged particle beam. The detector observes the temperature change and/or observe photons emitted from the charged particle beam traversed spot. Optionally, a plurality of cameras or detectors are used, where each detector views all or a portion of the coating layer. For example, two detectors are used where a first detector views a first half of the coating layer and the second detector views a second half of the coating layer. Preferably, at least a portion of the detector is mounted into the nozzle system to view the proton beam position after passing through the first axis and second axis controllers 142, 144. Preferably, the coating layer is positioned in the proton beam path 268 in a position prior to the protons striking the patient 730. Referring now to FIG. 1 and FIG. 7, the main controller 110, connected to the camera or detector output, optionally and preferably compares the final proton beam position or position of the treatment beam 269 with the planned proton beam position and/or a calibration reference to determine if the actual proton beam position or position of the treatment beam 269 is within tolerance. The charged particle beam state determination system 750 preferably is used in one or more phases, such as a calibration phase, a mapping phase, a beam position verification phase, a treatment phase, and a treatment plan modification phase. The calibration phase is used to correlate, as a function of x-, y-position of the glowing response the actual x-, y-position of the proton beam at the patient interface. During the treatment phase, the charged particle beam position is monitored and compared to the calibration and/or treatment plan to verify accurate proton delivery to the tumor 720 and/or as a charged particle beam shutoff safety indicator. Referring now to FIG. 10, the position verification system 172 and/or the treatment delivery control system 112, upon determination of a tumor shift, an unpredicted tumor distortion upon treatment, and/or a treatment anomaly optionally generates and or provides a recommended treatment change 1070. The treatment change 1070 is optionally sent out while the patient 730 is still in the treatment position, such as to a proximate physician or over the internet to a remote physician, for physician approval 1072, receipt of which allows continuation of the now modified and approved treatment plan. Referring now to FIG. 13B, a second example of the integrated cancer treatment-imaging system 1300 is illustrated using greater than three imagers. Still referring to FIG. 13B, two pairs of imaging systems are illustrated. Particularly, the first and second imaging source 1312, 1314 coupled to the first and second detectors 1322, 1324 are as described supra. For clarity of presentation and without loss of generality, the first and second imaging systems are referred to as a first X-ray imaging system and a second X-ray imaging system. The second pair of imaging systems uses a third imaging source 1316 coupled to a third detector 1326 and a fourth imaging source 1318 coupled to a fourth detector 1328 in a manner similar to the first and second imaging systems described in the previous example. Here, the second pair of imaging systems optionally and preferably uses a second imaging technology, such as fluoroscopy. Optionally, the second pair of imaging systems is a single unit, such as the third imaging source 1318 couple to the third detector 1328, and not a pair of units. Optionally, one or more of the set of imaging sources 1310 are statically positioned while one of more of the set of imaging sources 1310 co-rotate with the gantry 960. Pairs of imaging sources/detector optionally have common and distinct distances, such as a first distance, d1, such as for a first source-detector pair and a second distance, d2, such as for a second source-detector or second source-detector pair. As illustrated, the tomography detector or the scintillation plate 710 is at a third distance, d3. The distinct differences allow the source-detector elements to rotate on a separate rotation system at a rate different from rotation of the gantry 960, which allows collection of a full three-dimensional image while tumor treatment is proceeding with the positively charged particles. For clarity of presentation, referring now to FIG. 13C, any of the beams or beam paths described herein is optionally a cone beam 1390 as illustrated. The patient support 152 is an mechanical and/or electromechanical device used to position, rotate, and/or constrain any portion of the tumor 720 and/or the patient 730 relative to any axis. Still yet another embodiment includes any combination and/or permutation of any of the elements described herein. Herein, any number, such as 1, 2, 3, 4, 5, is optionally more than the number, less than the number, or within 1, 2, 5, 10, 20, or 50 percent of the number. The particular implementations shown and described are illustrative of the invention and its best mode and are not intended to otherwise limit the scope of the present invention in any way. Indeed, for the sake of brevity, conventional manufacturing, connection, preparation, and other functional aspects of the system may not be described in detail. Furthermore, the connecting lines shown in the various figures are intended to represent exemplary functional relationships and/or physical couplings between the various elements. Many alternative or additional functional relationships or physical connections may be present in a practical system. In the foregoing description, the invention has been described with reference to specific exemplary embodiments; however, it will be appreciated that various modifications and changes may be made without departing from the scope of the present invention as set forth herein. The description and figures are to be regarded in an illustrative manner, rather than a restrictive one and all such modifications are intended to be included within the scope of the present invention. Accordingly, the scope of the invention should be determined by the generic embodiments described herein and their legal equivalents rather than by merely the specific examples described above. For example, the steps recited in any method or process embodiment may be executed in any order and are not limited to the explicit order presented in the specific examples. Additionally, the components and/or elements recited in any apparatus embodiment may be assembled or otherwise operationally configured in a variety of permutations to produce substantially the same result as the present invention and are accordingly not limited to the specific configuration recited in the specific examples. Benefits, other advantages and solutions to problems have been described above with regard to particular embodiments; however, any benefit, advantage, solution to problems or any element that may cause any particular benefit, advantage or solution to occur or to become more pronounced are not to be construed as critical, required or essential features or components. As used herein, the terms “comprises”, “comprising”, or any variation thereof, are intended to reference a non-exclusive inclusion, such that a process, method, article, composition or apparatus that comprises a list of elements does not include only those elements recited, but may also include other elements not expressly listed or inherent to such process, method, article, composition or apparatus. Other combinations and/or modifications of the above-described structures, arrangements, applications, proportions, elements, materials or components used in the practice of the present invention, in addition to those not specifically recited, may be varied or otherwise particularly adapted to specific environments, manufacturing specifications, design parameters or other operating requirements without departing from the general principles of the same. Although the invention has been described herein with reference to certain preferred embodiments, one skilled in the art will readily appreciate that other applications may be substituted for those set forth herein without departing from the spirit and scope of the present invention. Accordingly, the invention should only be limited by the Claims included below. In a fourth example, the gantry comprises at least two imaging devices, where each imaging device moves with rotation of the gantry and where the two imaging devices view the patient 730 along two axes forming an angle of ninety degrees, in the range of eighty-five to ninety-five degrees, and/or in the range of seventy-five to one hundred five degrees. Pendant Referring still to FIG. 12A and referring now to FIG. 12B, a pendant system 1250, such as a system using the external pendant 1216 and/or internal pendent 1218 is described. In a first case, the external pendant 1216 and internal pendant 1218 have identical controls. In a second case, controls and/or functions of the external pendant 1216 intersect with controls and/or function of the internal pendant 1218. Particular processes and functions of the internal pendant 1218 are provided below, without loss of generality, to facilitate description of the external and internal pendants 1216, 1218. The internal pendant 1218 optionally comprises any number of input buttons, screens, tabs, switches, or the like. The pendant system 1250 is further described, infra. |
|
052241440 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, an imaging system which uses a flying spot scanner in accordance with the teachings of the prior art is illustrated. The system uses penetrating radiation such as x-rays to inspect object for contraband, and is operative to display relevant information on monitor 13. Referring to the figure in greater detail, an x-ray source 14 is seen to provide a generally conical beam of x-rays 15, which are collimated into a fan beam 16 by fixed slit 19 in absorber plate 17. The fan beam is incident upon the rotating chopper wheel 18 formed with an array of peripheral radial slits, such as 21, for intercepting the fan beam to produce a pencil beam. The pencil beam 23 scans object 11 and radiation sensitive detector 25 from top to bottom as chopper wheel 18 rotates in the direction of arrow 24. The scanning pencil beam 23 is also known as a flying spot. The detector 25 provides an image signal output on line 26, which is transmitted to video storage and display unit 13 to produce the desired image 12 as conveyor 27 carries object 11 in the direction of arrow 28 across the vertical scanning lines. The geometry and timing of the system is arranged so that each slit 21 causes a new pencil beam or flying spot to strike the top of detector 25 just after the previous pencil beam has swept past the bottom of the detector. That is to say, the height of fan beam 16 corresponds substantially to the separation between adjacent ones of slits 21 at substantially the maximum radial distance from the edge of disc 18 where the slits intercept fan beam 16. While FIG. 1 shows the elements that provide the flying spot source in exploded form to better illustrate the principles of the invention, the elements 14, 17 and 18 are preferably housed relatively close together in an enclosure that shields radiation, so that the only significant radiant energy that escapes is in pencil beam 23. As object 11 moves past the line being scanned, it differentially attenuates the x-rays in pencil beam 23 incident upon detector 25 so that the electrical signal provided on output line 26 is amplitude modulated in proportion to the instantaneous x-ray flux incident upon it. This signal thus corresponds to a vertical line image of the transmissivity of parcel 11 and is analogous to one scan line of a television video signal. As parcel moves horizontally past the line being scanned, sequential pencil beams intercept slightly displaced regions of parcel 11 so that the corresponding electrical signals from detector 25 may be appropriately displayed line-by-line to produce a two dimensional image of object 11 in x-rays analogous to the display of a picture on a television monitor as formed by line-by-line images. The output of detector 25 may thus be processed in accordance with the same storage and display techniques used in conventional video systems to store and display single raster images. Referring to FIG. 2, it is seen in greater detail how the pencil beam 23 is formed. In this figure, slit 30 is a projection of the fixed slit of the stationary absorber plate, which is made of a high Z material such as lead. Further, in the embodiment shown in FIG. 2, chopper wheel 31 is comprised of an annular disk or doughnut shaped insert 32 of a high Z material such as lead, which is inserted in- aluminum wheel 34. The-lead doughnut has a plurality of radially oriented slits 36 disposed therein. As the wheel rotates, a radially oriented slit 36 passes over the projection of the radiation passing through fixed slit 30, thus forming the pencil beam. It follows from this that the length of the radial slits is dependent on the required scan length of the pencil beam. Thus, it is seen that as the wheel rotates from point A to point B in FIG. 2, half the length of the fixed slit 30 is covered, and near point A, the pencil beam is formed by the fixed slit and the outside area of the radial slit, while near point B it is the fixed slit and the inside area of the radial slit which forms the beam. The fact that the radial slits must be of a certain minimum length to accomplish proper scanning has led to a problem in the system of the prior art. This is because, as may be seen by referring to FIG. 2, the length of the-radial slits dictates the width d of the lead annular or doughnut, which in turn, at least in part, controls how heavy the lead annular is. It has been found that with the system of the prior art, the lead annular is so heavy, that at the rotation speeds which are necessary for certain applications, it beaks apart. Additionally, a powerful motor is required to rotate the heavy chopper wheel at such speeds. Referring to an illustrative example, in a planned design, a 380 KV x-ray source is used, and to sufficiently absorb the x-rays from such a source, the required thickness of the lead doughnut is about 2 inches (approx. 5 cm), while the required radius R of the wheel to the outer edge of the lead is about 20 inches (approx. 50 cm). The width of the lead doughnut d, in FIG. 2, is given by: EQU d=R(1-cos .pi./n) where n=the number of radial slits. In this design, n=4, so that d=50(1-cos 45.degree.)=14.6 cm. In this case, the width of a typical radial slit (and fixed slit) opening is 4 mm. The weight of the lead doughnut which is necessary to achieve these dimensions is about 510 lbs (approx. 230 Kg.). Referring to FIG. 3, a detailed view of a portion of a flying spot scanner in accordance with an embodiment of the present invention is shown. In accordance with this embodiment, is seen that fixed slit 40 in the stationary absorber plate is arcuate rather than straight. A ring 42 of high Z material is provided in a wheel of aluminum or other material 44, as in the prior art, but it is noted that the length of radial slits 46 may be made much shorter than in the case of the prior art. This is because the fixed slit and the doughnut of high Z material are functionally coincide with each other, and as the wheel rotates, the length of the radial slit continuously overlies the projected radiation which passes through the fixed slit. The result of the modification shown in FIG. 3 is that the required slit length is only 2 cm as opposed to 14.6 cm. With a slit width of 4 mm in both the rotating wheel and the fixed absorber plate, the weight of the lead ring is only about 36 Kg (80 lbs.), or about less than 1/6 of the weight of the lead doughnut which was in the prior art embodiment. The lower weight provided by the present invention is much more manageable, and permits rotation of the scanning wheel at high speeds without structural problems developing. Additionally, it permits a less powerful motor to be used to effect rotation. It should be noted that in the preferred embodiment of FIG. 3, the radius of the fixed slit 40 is such that as the chopper wheel rotates, the high Z insert 42 and slits 46 follow exactly the curve of the radiation passing through the fixed slit. In this regard, it is noted in FIG. 3, that high Z insert 42 and the projection of fixed slit 40 are drawn as being coincident with each other. However, it should be appreciated that the projection of slit 40 may be in the shape of a curve of larger radius than is illustrated. In this case, the slits 46 would not exactly follow the curve of the fixed slit as they rotate; however, in this case, the radial slits may still be made smaller than when the fixed slit is a straight line, although not so small as is illustrated in FIG. 3. Referring to FIG. 4, an inspection system which incorporates the present invention is shown. In this figure, x-ray source 50 produces conical beam 60, which is fed through arcuate slit 62 in absorber plate 64 to produce an arcuately shaped fan beam 66, which is incident on chopper wheel 68. Chopper wheel 68 has lead ring 70 therein, which contains radial slits 72. As the wheel 68, is rotated, flying spot scanning in arcuate lines is accomplished. Object 74 is transported on conveyor 76 past the scanning beam. Transmission detector 78 is provided, which it is noted is also arcuately shaped, so that the scanning pencil beam which is transmitted through the object 74 is incident on the detector over the length of the scan line. Additionally, backscatter detectors 79 may also provided, and if the particular system calls for them, forward scatter detectors may be provided as well. The outputs of detectors 78 and 79 are digitized, and are divided into pixels, each of which corresponds to an elementary unit of frontal area of the object which is scanned. The pixels are stored and/or displayed, and in the specific system of FIG. 4, which is shown only for the purposes of illustration, separate images of transmitted and scattered image information are provided in displays 80 and 82. Since the scanning which is provided is in arcuate lines, there must be some provision made for addressing a utilization means such as a memory or a display in such manner that an accurate representation of the desired image is obtained. In accordance with the invention, this is accomplished by addressing the utilization means so that an arcuate scan line of the object being scanned is defined in the utilization device by an arcuate line of pixels. Referring to FIG. 5, a utilization means such as a memory device 90 is depicted in schematic form. Each storage location in the memory is given a number, and for purposes of illustration the memory is considered to have 500 rows and 500 columns, resulting in 250 K storage locations. The pixels corresponding to certain, spaced apart scan lines of the object are illustrated in FIG. 5, and are seen to define respective arcuate lines of pixels in the memory. If this memory were to be read out in conventional raster fashion to a display, a proper image of the object information would result. The addressing of the memory with image information is explained with reference to FIG. 6, which shows a block diagram of the components which may accomplish the addressing function. Referring to this figure, detection means 100 is a detector of radiant energy such as a transmission or scatter detector, or some combination thereof, which detects the radiation after it interacts with the object which is being inspected. The signal which is outputted by detection means 100 will in general have a varying magnitude, as determined by the atomic number, density, and thickness of the part of the object which is being instantaneously scanned. This magnitude is digitized in analog to digital converter 102. As mentioned above, the detected signal is divided into pixels, each of which corresponds to an elementary frontal area of the object being scanned. This may be accomplished by clock 104, and scan counter 106, which are shown in FIG. 6. Clock 104 is arranged to count up to the number of pixels which are determined to be in a single scan line, and then reset itself. The number value of the signal appearing on clock output line 110 is thus indicative of the position of the instantaneous pixel being scanned within a scan line. Scan counter 106 is arranged to count to the number of pixels in a scan line, and then reset itself, while incrementing the number value of the signal on output line 114. Thus, the signals on lines 110 and 114 taken together are representative of the instantaneous pixel number which is being scanned at any time. These signals are inputted to look up table 116. For each pixel number, look up table 116 has a corresponding memory address stored. These memory addresses are determined after consideration of the precise shape and dimensions of the arcuate scanning path which is effected by the scanner shown in FIGS. 3 and 4, as well as the number of pixels into which each scan line is divided. For example, referring to FIG. 5, as an example, the first pixel which is scanned may be inputted to memory address No. 150, the second pixel may be inputted to address No. 610, the third may be inputted to address No. 1070, and so forth. As the object is scanned, each successive scan line is defined in the memory by an arcuate line of pixels which corresponds in shape to the original scanning line. Thus, referring again to FIG. 6, the magnitude value of each pixel occurs on line 118 at the output of analog to digital converter 102, and the address in the memory 90 to which it is routed is determined by the address signal on line 120, at the output of look up table 116. After the memory has been loaded in the manner shown in FIGS. 5 and 6, it is a simple matter to read the contents out to a display in conventional row by row fashion to produce a proper display of the required image information. Of course, it is also within the scope of the invention to read each scan line into the memory in conventional vertical or horizontal line by line fashion, and to perform the "straightening" of the image information when the contents of the memory are read out to a display, or to not use a memory at all, but rather to directly address a display with "straightened" image information, e.g., in the same manner as memory 90 is addressed in FIG. 6. There thus has been disclosed a method and apparatus for providing image information with a flying spot scanner of reduced mass. While the invention has been illustrated by illustrative and preferred embodiments, variations will be apparent to those skilled in the art. For example, flying spot scanners which produce curved scanning lines which are not arcuate may be provided. It therefore should be understood that the invention is to be construed as embracing each and every novel feature and combination of novel features present in or possessed by the method and apparatus disclosed herein, and should be limited only by the claims appended hereto. |
047284838 | description | DETAILED DESCRIPTION OF THE INVENTION In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like, are words of convenience and are not to be construed as limiting terms. IN GENERAL Referring now to the drawings, and particularly to FIG. 1, there is shown an elevational view of a fuel assembly, represented in vertically foreshortened form and being generally designated by the numeral 10. The fuel assembly 10 is the type used in a pressurized water reactor (PWR) and basically includes a lower end structure or bottom nozzle 12 for supporting the assembly on the lower core plate (not shown) in the core region of a reactor (not shown), and a number of longitudinally extending guide tubes or thimbles 14 which project upwardly from the bottom nozzle 12. The assembly 10 further includes a plurality of transverse grids 16 axially spaced along the guide thimbles 14 and an organized array of elongated fuel rods 18 transversely spaced and supported by the grids 16. Also, the assembly 10 has an instrumentation tube 20 located in the center thereof and an upper end structure or top nozzle 22 attached to the upper ends of the guide thimbles 14. With such an arrangement of parts, the fuel assembly 10 forms an integral unit capable of being conventionally handled without damaging the assembly parts. As mentioned above, the fuel rods 18 in the array thereof in the assembly 10 are held in closely spaced relationship with one another by the grids 16 spaced along the fuel assembly length. Each fuel rod 18 contains nuclear fuel pellets 24 and is closed at its opposite ends by upper and lower end plugs 26,28 so as to hermetically seal the rod. Commonly, a plenum spring 30 is disposed between the upper end plug 26 and the pellets 24 to maintain the pellets in a tight, stacked relationship within the rod 18. The fuel pellets 24 composed of fissile material are responsible for creating the reactive power of the PWR. A liquid moderator/coolant such as water, or water containing boron, is pumped upwardly through the guide thimbles 14 and along the fuel rods 18 of the fuel assembly 10 in order to extract heat generated therein for the production of useful work. APPARATUS FOR INTEGRATED FUEL ASSEMBLY INSPECTION SYSTEM At the completion of manufacture of the fuel assembly 10, an inspection of the fuel assembly 10 is performed to determine whether it meets the rigorous dimensional standards required to place it in a tight operating position with other fuel assemblies in a reactor core. In FIGS. 2 to 7, there is shown an apparatus, generally designated by the numeral 32 and comprising the preferred embodiment of the present invention, which is utilized in an integrated and automated system for inspecting the dimensional integrity of the fuel assembly 10 in terms of its envelope and length and the spacing between its fuel rods 18. All inspection procedures are carried out with the fuel assembly 10 placed on the single apparatus 32, thus eliminating the necessity of being moved from station to station to complete the various measurements of the inspection, as was the case previously. Referring to FIGS. 2 and 3, in addition to various measurement components to be described hereafter, the fuel assembly inspection apparatus 32 basically includes a support platform or base 34, an elongated fixture 36, top and bottom carriages 38,40 and a pedestal 42. The fixture 36 is mounted in a stationary upright position upon the base 34. Both top and bottom carriages 38,40 are mounted on, and extend in cantilever fashion forwardly and outwardly from, common, parallel vertical rails or tracks 44 fixed on the front side of the fixture 36 for movement vertically therealong away from and toward one another and the base 34. The pedestal 42 is stationarily mounted on the base 34 adjacent to, but spaced in front of, the fixture 36 and aligned with the top carriage 38 for supporting therebetween and along the fixture 36 the nuclear fuel assembly 10 (seen in phantom outline form) to be inspected. Movement of the top carriage 38 is generally confined to along a limited upper extent of the fixture 36 which only occurs during placement of the fuel assembly 10 on the apparatus 32, whereas the bottom carriage 40 is more extensively moved between the pedestal 42 and the top carriage 38 during performance of the measurement operations by the apparatus 32. The top and bottom carriages 38,40 are selectively driven along the fixture 36 by d.c. stepping motors 46,48 mounted thereon and drivingly coupled to a gear track 50 fixed along the right side of the fixture, as seen in FIGS. 2 and 3. Also, as clearly depicted in FIGS. 4 to 6, the bottom carriage 40 has central opening 52 sized to receive the fuel assembly 10 therethrough when supported between the upper carriage 38 and lower pedestal 2. In such manner, the bottom carriage 40 surrounds all sides of the fuel assembly 10 and travels therealong as it moves along the fixture 36. The several different measurements performed heretofore at different or separate stations are now performed at a common, integrated station defined by the inspection apparatus 32. Components are disposed on the apparatus 32 for measuring the envelope and length of the fuel assembly 10 and channel spacing between the fuel rods 18 of the fuel assembly. Also, the apparatus 32 includes self-calibration components for continuously monitoring the fixture 36 for any out-of-straightness for adjusting the envelope measurement to compensate for such condition of the fixture. The inspection procedure is initiated by placing the fuel assembly 10 into the fixture 36, i.e. by placing its bottom nozzle 12 on the pedestal 42 and then lowering the top carriage 38 onto the top nozzle 22 to hold the fuel assembly stationary. Then, the bottom carriage 40 is moved along the length of the fuel assembly 10 taking measurements at the bottom nozzle 12, the grids 16, midspans and the top nozzle 22 of the fuel assembly. A computer (not shown) is responsible for stepping motor control, data acquisition, and issuing a comprehensive report upon completion of the fuel assembly inspection. In particular, as seen in FIGS. 5 to 7, components on the bottom carriage 40 for measuring fuel assembly envelope, when the bottom carriage is moved to and stationed at selected axial positions along the fuel assembly 10, include a plurality of sets of single-axis positioning tables 54, proximity sensors 56, feed screws 58 and d.c. stepping drive motors 60. Each set is disposed on one of four sides of bottom carriage 40 encompassing the central opening 52 thereof and adjacent to one of four sides of the fuel assembly 10. In each set, the feed screw 58 is rotatable mounted on the table 54 and coupled with the sensor 56 and motor 60 such that upon rotation of the screw 58 by the motor 60, the sensor 56 is moved linearly along the respective fuel assembly side. Preferably, each motor 60 accurately moves the respective sensor 56 across the side to record a distance measurement at three locations. The sensors 56 are stationed in a "home" position while the bottom carriage 40 travels up along the fuel assembly 10. Once the bottom carriage 40 is positioned at a grid, each sensor 56 sequentially sweeps across its respective side and then returns to its home position. The proximity sensors 56 are, preferably, conventional off-the-shelf devices, for instance ELECTRO-MIKE sensors designated as model #PA115-03, of the type using non-contact sensing, having high accuracy and a linear response, capable of integrating measurement over an area, and having sufficient range of distance measurement. Their principle of operation is based on eddy currents. The sensor produces an inductive field which will generate eddy currents in any metal target within its range. These eddy currents change the state of the field which can be translated into a signal output that is proportional to the distance from sensor to target. As seen in FIGS. 2 and 4, self-calibration components disposed on the top and bottom carriages 38,40 for continuously monitoring out-of-straightness of the fixture 36 and facilitating correction of the envelope measurement, as the bottom carriage 40 travels up the fuel assembly 10, include a pair of X-Y axes lasers 62 and a pair of Z-Y axes photodetectors 64 (only one of each pair is shown). The two lasers 62 are mounted on to the top carriage 38 and the two photodetectors 64 are mounted on the bottom carriage 40. Each laser beam is a straight line reference used to excite each photodetector 64. The photodetector output indicates a deflection of the bottom carriage 40 in the left/right and the back/front direction. Two laser/photodetector pairs are required to measure both translational and rotational motion of the bottom carriage 40. As the bottom carriage 40 travels up along the fuel assembly 10, the computer will adjust the envelope measurement for any fixture error measured at each grid. A linear photodetector which can be used to track the motion of the bottom carriage 40 is the United Detector Technology model UDT SC/25 with its compatible amplifier model UDT 301B-AC. The straight line reference can be obtained by using a low power Helium-Neon laser, such as one manufactured by Uniphase, being designated as model 1103P. Turning now to FIGS. 4 and 5, components disposed on the bottom carriage 40 for measuring channel spacing between fuel rods 18 of the fuel assembly 10 include a single-axis positioning platform 66 located on each of a pair of adjacent sides of the fuel assembly 10, probe housings 68 mounted on the respective platforms 66 for movement along the sides of the fuel assembly 10, and motive means in the form of d.c. stepping motors 70 to drive the platforms 66. Each probe housing 68 contains a probe 69 mounted in a track and motive means in the form of d.c. stepping motors 71 to drive probe 69 in and out of probe housing 68. Preferably, the probes 69 are of the capacitive type, such as HITEC capacitive probes. Once the bottom carriage 40 is positioned at one of the selected axial positions along the fuel assembly and after the motors 70 are operated to move the probe housings 68 to specified channel locations along the fuel assembly sides, the probes 69 are then actuated for taking channel spacing measurements. In particular, the probes 69 are moved in between the fuel rods 18 by stepping motors 71 until the end of the probe 69 extends through the opposite side of the fuel assembly 10. The channel spacing measurement is taken while stepping motor 71 retracts the probe back through the fuel assembly 10. The signal produced by the probe 69 is processed by electronic circuitry not shown. As seen in FIG. 2, components disposed on the bottom carriage 40 and the fixture 36 for measuring fuel assembly length, starting with movement of the bottom carriage 40 at the bottom nozzle 12 of the fuel assembly 10 and finishing at the top nozzle 22 thereof, includes four photoswitches 72 and the combination of a laser 74 and two linear photodetectors 76. One photoswitch 72 is mounted on each side of the bottom carriage 40 adjacent each side of the fuel assembly 10 and operable to detect a leading edge of the respective bottom and top nozzle 12,22. Also, the laser 74 and linear photodetectors 76 form a linear scale. The position of the bottom carriage 40 is measured using the two linear photodetectors 76 mounted on the fixture 36, one near the bottom nozzle 12 and the other near the top nozzle 22. The locations of these photodetectors are precisely known so that a laser beam traveling from the laser 74 on the bottom carriage 40 can be used to accurately measure the position of the bottom carriage. As the bottom carriage 40 travels up the fuel assembly 10, the photoswitches 72 will detect the edge of the respective nozzle. When an edge is detected, the position of the carriage is recorded. Once the positions of the bottom and top nozzles are determined, an assembly length can be derived by computer. The main principle of the length measurement is to accurately determine the position of the bottom carriage 40 as it travels across the bottom and top nozzles 12,22. The edge detectors or photoswitches will signal when the bottom carriage is in position and the linear scale mounted on the fixture 36 will convert the position into an actual length. The photoswitches 72 are non-contact devices which have both a light source and a photodetector. A device called a SCAN-A-MATIC sensor can be used. The linear scale could either be optical, as described above, or magnetic. The magnetic scale is constructed with small evenly spaced lines of magnetic material. A magnetic switch located on the bottom carriage would count the lines as the bottom carriage travels along the assembly. The location of the linear scales on the fixture must be precisely measured to assure an accurate assembly length measurement. It is thought that the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, constuction and arrangement thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof. |
summary | ||
059206020 | description | The figures show sections of a storage facility for radioactive waste formed in a mountain, particularly heat-generating waste, such as spent fuel elements. The storage facility comprises a transport gallery 10, beneath which runs a storage gallery 12. The transport gallery 10 having in cross-section the geometry of a semi-ellipse or semi-oval has a concrete floor 14 on the one hand covering the storage gallery 12 of rectangular section and on the other hand having openings 18 closable via covers 16 and giving access to the storage gallery 12, in order to introduce or remove radioactive waste in the manner described in the following. The storage gallery 12 itself has a concrete floor 20 and is protected against earthquakes by side struts 22. The opening is are also closable by concrete covers 16. To ensure safe fitting of the cover 6 into the opening 18 and to shield it from the storage gallery 12, the cover 16 has all all-round flange, not however shown in detail, that can be set down on a step of the opening 18, also not shown in detail. As FIGS. 2 to 4 make clear, the lateral extent of the transport gallery 10 is greater than that of the storage gallery 12. The width of the transport gallery 10 is preferably two to three times that of the storage gallery 12. The advantage of this is that rock thrusts are diverted well away, thereby creating a long-term and strong cavern as the storage gallery 12 that requires no further expansion. To remove the cover 16 from an opening 18 or to close it, a movable carriage 24 with a holding device 26 for the cover 16 is provided. The carriage 24 moves on rails 28, 30 that are arranged on both sides of the openings 18 arranged in a row along the transport gallery 10. A conveying container 32 is also movable on the rails 28 and 30 in order to pick up waste for interim storage from a transport container 34, move it inside the transport gallery 10 and then set it down in the storage gallery 12 via one of the openings 18, and vice versa. The waste itself is in an inner container 36 of the transport container 34, which can have a conventional design, i.e. closable with a single or double cover, for example, which is howsoever not shown in FIG. 1. In order to remove the inner container 36 together with the waste from the transport container 34, the latter is initially moved into a cell 38 which is shielded over its circumference by concrete walls 40. On the top the cell 38 has an opening 42 which can be traversed by the converting container 32 in order to pick up the inner container 36. To that end, the conveying container 32 is picked up by a conveying carriage 44 such as a caterpillar unit in order on the one hand to be raised/lowered and on the other hand to be moved along the floor 14. The conveying container 32 is closable at the bottom by means of a plate 46 movable parallel to the floor 14 of the transport gallery 10 and extending from a frame 48 that is part of the conveying container 32 and that can be picked up by the conveying carriage 44. Furthermore, a conveying unit 50 extends inside the conveying container 32 in order to remove the inner container from the transport container 34 and to place it inside the storage gallery 12 via one of the openings 18 and vice versa. In order to place an inner container 36 with waste for interim storage inside the storage gallery 12, the caterpillar unit 44 and hence the conveying container 32 are first moved to a required opening 18 in the floor 14 of the transport gallery 10. Then the cover 16 is lifted using the carriage 24 and moved laterally to the opening 18, in order to permit alignment of the conveying container 32 with the opening 18 and lowering of the inner container 36, as is made clear in FIG. 3. Once the inner container 36 has been set down on the floor 20 of the storage gallery 12 and the conveying container 32 has been moved clear of the opening 18, the latter is closed using the cover, as shown in FIG. 4. The cover 16 is designed as a shielding cover, so that the storage area is separated from the transport gallery 10 in respect of the effects of radiation. The conveying container 32 can then once again be moved to the cell 38 using the caterpillar unit 44 in order to pick up a further inner container. It is also possible to remove and transfer inner containers 36 from the storage gallery 12. The same measures are taken when the inner container 36 is to be removed from the interim storage facility and transferred to a final storage facility. It may only be necessary here to provide the inner container 36 with corrosion protection before it is placed in final storage. The fact that only inner containers 36 are placed inside the storage gallery 12 and are accessible from above means that the storage gallery can be designed fairly narrow. One advantage of this is that favorable air flows result when ventilation ducts lead upwards out of the storage gallery 12 and have a good cooling effect on the waste. Furthermore, the storage gallery 12 can be sealed at the end by filtering devices. The width of the transport gallery 10 should be about 2 to 3 times that of the storage gallery 12, in order to divert rock thrusts away from the storage gallery 12. |
047131993 | summary | The invention concerns a depository, particularly a dry depository, for radioactive waste and spent fuel cells comprising a concrete storage block having cooling channels for circulation of air to remove residual heat from the stored waste. In the storing of such materials, particularly temporary storage of spontaneously-heating radioactive materials, care must be taken to prevent the release of radioactive substances due to overheating. Depositories for the dry storage of spontaneously-heating radioactive materials have been disclosed in which the storage material is packed in containers and the containers are inserted into vertical tubular shafts, whose floor consists of the grid of a storage rack. The storage rack is made of steel and is located in a shielded storage cell. The depository has several storage cells. The cooling of the containers heated by residual heat is provided by natural convection. For this purpose, an annular gap is left between container and storage shaft. Atmospheric air as cooling air enters through an air supply opening under the storage rack, picks up heat while passing through the annular gap and flows through an exhaust opening to the environment. The space underneath the storage rack serves as an air supply chamber for the stabilizing and uniform distribution of the cooling air in the storage shafts. The space above the storage rack serves as a used air chamber. The cooling air is fed from the outside via air supply openings in the air supply shafts. The air supply openings are above ground and lead at an angle upward into the air supply shafts. The air supply openings and also the exhaust openings are so made and equipped that rain, dust, etc., are prevented from entering. In these known depositories the disadvantages are the relatively big constructional expense and the associated high costs. It is also a known practice to use monolithic concrete blocks with cast vertical channels instead of the storage rack and shafts of steel, for accommodating the radioactive materials. Because of the temperature differences and variations that occur, there is the danger of damage to the concrete block, since there is no compensation for thermal tensions. The construction of the known depository is relatively expensive. Dismantling is possible only with great expense. The object of the present invention is to provide an improved and safer concrete depository having a storage block composed of concrete blocks with vertical channels therethrough, the blocks being piled up in adjacent rows with the channels aligned. The present fuel cells are disposed within the channels with an annular space surrounding them for cooling air. The embodiment of the invention actually provides for a structure on the modular construction principle. The individual small concrete block units are easily and cheaply produced. They are easily installable for the building of the storage blocks and correspondingly easily removable. The storage block can be built up by sections. The embodiment of the invention leads to an improved and more efficient natural cooling of the material stored in the channels. The cooling air flows upward in the channels of the concrete block as in a chimney. A blower is not necessary. The natural draft is sufficient and provides an inherently safe cooling system. The construction with individually-combined concrete blocks avoids harmful thermal tensions in the storage block as a whole. The depository of the invention is thus inherently safe in this respect, also. In one form of the invention the blocks rest on ribs projecting above the concrete floor or base, and the spaces between the ribs provide conduits which communicate with the vertical channels in the blocks for air circulation. In another form of the invention, the metal storage containers for the radioactive waste and spent fuel cells have radial ribs along their length to conduct heat to the cooling air passing through the vertical channels. An increase in seismic security is achieved by bracing the stacked individual concrete blocks against the base plate and bracing the containers against blocks. The metal storage containers may be suspended within the channels of the concrete blocks with the use of supports resting on the top of the stack. This has the advantage that the longer part of the storage container beneath the support can expand freely and unhindered downwardly without any harmful forces being exerted on any structural part. By providing air filters in the air inlet openings, dust, micro-organisms, etc., are prevented from getting into the depository. In a preferred form of the invention the individual blocks have on their tops and bottoms mating centering elements to facilitate the stacking and arrangement of the concrete blocks. A sealing sleeve is provided for sealing off from the environment the upper part of the storage and cooling channels or the opening in the concrete ceiling. The sleeve can accommodate itself to thermal movements of the portion of the storage container extending into the opening in the concrete ceiling. Preferably the upper end of the storage container is enlarged and has an annular shoulder which rests on a cooperating ledge in the opening through the ceiling. A shielding plug fits in the enlargement. In order to secure the optimum protection against the penetration of water, especially ground water, into the depository, a water sensing means is provided to monitor the presence of water and actuate a pump. Water is thereby prevented from getting into the space underneath the storage blocks and into the storage and cooling channels and interfering with or interrupting the natural draft cooling. The invention will now be explained in more detail with reference to the attached drawings. |
abstract | A method and apparatus for inserting or removing a string of tubulars from a subsea borehole. The apparatus includes a first, lower, gripping mechanism locatable subsea in the vicinity of the subsea borehole. The first gripping mechanism is capable of gripping a portion of the string of tubulars. The apparatus further includes a second, upper, gripping mechanism locatable subsea in the vicinity of the subsea borehole, the second gripping mechanism being capable of-gripping a portion of the sting of tubulars. The first and second gripping mechanisms are moveable with respect to one another. The apparatus further includes a movement mechanism which, when actuated, moves one of the first and second gripping mechanisms with respect to the other of the first and second gripping mechanisms, such that the string of tubulars is inserted into or removed from the subsea borehole. |
|
claims | 1. A computer-implemented method comprising:receiving scenario test data representative of a plurality of different scenarios for a system, wherein each scenario is characterized by a set of observable parameters for the system;filtering the plurality of different test scenarios to identify a sub-set of scenarios from the plurality of different scenarios having similar behavior characteristics;providing the sub-set of scenarios to a trained neural network to identify one or more sub-set of scenarios, wherein:the trained neural network is one of: a convolutional neural network and a modular neural network,the modular neural network utilizes a modular topology formed by smaller network nodes each utilizing different techniques to perform filtering the plurality of different test scenarios to identify a sub-set of scenarios from the plurality of different scenarios having similar behavior characteristics,the techniques used in the modular topology comprises two or more of: highly-clustered non-regular (HCNR) topology, repeated blocks topology, multi-architectural topology,the repeated blocks topology further comprises a multi-path node, a modular node, a sequential node and a recursive node,the one or more identified sub-set of scenarios correspond to one or more anomaly scenarios from the sub-set of scenarios that is most likely to lead to an undesirable outcome associated with an emergency causing event; andtaking corrective actions to mitigate or to prevent occurrence of the undesirable outcome according to the identified one or more sub-set scenarios. 2. The computer-implemented method of claim 1, further comprising training a neural network based on scenario training data comprising a plurality of different training scenarios for the system. 3. The computer-implemented method of claim 1, wherein the user input comprises a number of convolution layers, a number of pooling layers, an output layer, an input layer, and a number of fully connected layers. 4. The computer-implemented method of claim 3, wherein the convolutional neural network comprises six convolutional layers, three max pooling layers, and three fully connected layers. 5. The computer-implemented method of claim 1, further comprising:training the neural network based on scenario training data comprising a plurality of training scenarios, the trained neural network corresponding to a trained neural network; andwherein the providing comprises providing the sub-set of scenarios to the neural network for classification of the sub-set of scenarios. 6. The computer-implemented method of claim 5, wherein the classification comprises one of classifying the one or more sub-set of scenarios as one of having (i) a total effective dose equivalent (TEDE) less than or equal to 10 rem, and (ii) a TEDE greater than 10 rem. 7. The computer-implemented method of claim 6, wherein the one or more sub-set of scenarios classified as having the TEDE greater than 10 rem correspond to the one or more scenarios that is most likely to lead to the undesirable outcome. 8. The computer-implemented method of claim 7, further comprising:generating display data characterizing the one or more sub-set of scenarios classified as having the TEDE greater than 10 rem; anddisplaying the display data on a display to provide a human a visualization of the one or more sub-set of scenarios classified as having the TEDE greater than 10 rem. 9. The computer-implemented method of claim 7, further comprising generating a real-time emergency plan based on the one or more sub-set of scenarios classified as having the TEDE greater than 10 rem. 10. The computer-implemented method of claim 1, wherein the undesirable outcome is a release of ionizing radiation. 11. The computer-implement method of claim 10, wherein the emergency causing event is a radiological causing event. 12. The computer-implemented method of claim 1, wherein the system is a given system at a nuclear facility. 13. The computer-implemented method of claim 1, wherein the filtering comprises applying a clustering processing to the plurality of different scenarios to identify the sub-set of scenarios from the plurality of the different scenarios. 14. The computer-implemented method of claim 13, wherein the applying comprises applying a mean shift methodology (MSM) to the plurality of different scenarios to identify a cluster of scenarios, wherein one or more cluster of scenarios corresponds to the sub-set of scenarios from the plurality of the different scenarios. 15. The computer-implemented method of claim 14, wherein the sub-set of scenarios is assigned to a given bin of a plurality of bins, wherein the plurality of bins comprises a first bin corresponding to a total effective does equivalent (TEDE) that is greater than 10 rem and a second bin corresponding to a TEDE less than or equal to 10 rem. 16. The computer-implemented method of claim 1, wherein the scenario test data is provided by an Analysis of Dynamic Accident Progression Trees (ADAPT) system. 17. The computer-implemented method of claim 1, wherein each test scenario is represented by a matrix, n×m, wherein n is a number of the set of observable parameters and m is a given number of time divisions over a plurality of simulations of a system model for the system. 18. The computer-implemented method of claim 1, wherein the modular neural network comprises an aggregate network formed by a plurality of specialized blocks for processing micro tasks, wherein the aggregate network having an architecture of a shallow block depth at a front portion, and increases depth in the block as a flow of the scenario test data increases towards a back portion, wherein each block having a different kernel size at a same level for capturing features with different data sizes in the scenario test data. 19. The computer-implemented method of claim 18, wherein the kernels are selected from one of: a convolution kernel, a transpose convolution kernel. 20. The computer-implemented method of claim 18, wherein processing channels increases in each block. 21. A computer-implemented method comprising:receiving scenario test data representative of a plurality of different scenarios for a system, wherein each scenario is characterized by a set of observable parameters for the system;filtering the plurality of different test scenarios to identify a sub-set of scenarios from the plurality of different scenarios having similar behavior characteristics;providing the sub-set of scenarios to a trained neural network to identify one or more sub-set of scenarios, wherein the trained neural network is one of: a convolutional neural network and a modular neural network and the one or more identified sub-set of scenarios correspond to one or more anomaly scenarios from the sub-set of scenarios that is most likely to lead to an undesirable outcome associated with an emergency causing event;training the neural network based on scenario training data comprising a plurality of training scenarios, the trained neural network corresponding to a trained neural network, wherein the providing comprises providing the sub-set of scenarios to the neural network for classification of the sub-set of scenarios, and the classification comprises one of classifying the one or more sub-set of scenarios as one of having (i) a total effective dose equivalent (TEDE) less than or equal to 10 rem, and (ii) a TEDE greater than 10 rem; andtaking corrective actions to mitigate or to prevent occurrence of the undesirable outcome according to the identified one or more sub-set scenarios. 22. A computer-implemented method comprising:receiving scenario test data representative of a plurality of different scenarios for a system, wherein each scenario is characterized by a set of observable parameters for the system;filtering the plurality of different test scenarios to identify a sub-set of scenarios from the plurality of different scenarios having similar behavior characteristics, wherein each test scenario is represented by a matrix, n×m, wherein n is a number of the set of observable parameters and m is a given number of time divisions over a plurality of simulations of a system model for the system;providing the sub-set of scenarios to a trained neural network to identify one or more sub-set of scenarios, wherein the one or more identified sub-set of scenarios correspond to one or more anomaly scenarios from the sub-set of scenarios that is most likely to lead to an undesirable outcome associated with an emergency causing event; andtaking corrective actions to mitigate or to prevent occurrence of the undesirable outcome according to the identified one or more sub-set scenarios. |
|
abstract | Apparatus and methods are described for use with an X-ray system including an X-ray anti-scatter grid that includes at least a first layer of elongate radiopaque septa arranged such that longitudinal axes of each the septa belonging to the first layer are disposed along a first direction, in parallel to each other. Spaces between the septa are filled with air, and a rigid frame supports the septa. Two or more slotted plates are coupled to the rigid frame, each of the slotted plates defining a plurality of slots, each of the septa passing through a respective pair of slots defined by a pair of the slotted plates disposed on opposite sides of the frame from each other, such that the orientation of each of the septa with respect to the frame is determined by the orientation of the corresponding pair of slots with respect to the frame. |
|
044328923 | description | The following example explains in more detail the advantages of the process of the invention. DETAILED DESCRIPTION Example A tritium containing body made of titanium was surrounded on all sides with aluminum powder in the pressing mold. The mold was clad beforehand with an aluminum jacket. Thereupon, the slug was compressed with a force of 6 Mp/cm.sup.2 ; subsequently, the aluminum jacket was tightly sealed in a further processing step. This type of enclosed titanium body compared to a piece of substantially the same type but not enclosed emitted only a negligibly small amount of tritium. By including the slug in a stainless steel tube closed on one side which was closed after the filling, the emission could not be measured (because it was so small). The entire disclosure of German priority application No. P 3018745.2 is hereby incorporated by reference. |
description | This application is a national stage application, filed under 35 U.S.C. §371, of International Application No. PCT/SE2011/050586, filed May 10, 2011, which claims priority to Swedish Patent Application No. 1050519-6, filed May 25, 2010, both of which are hereby incorporated by reference in their entirety. The present invention relates to fuel assemblies for pressurized water reactors according to the presently pending claims . The present invention also relates to a guide thimble device according to the presently pending claims and to use of the guide thimble device in a fuel assembly. U.S. Pat. No. 4,631,168 discloses a fuel assembly for nuclear pressurized water reactors comprising a number of elongated fuel elements or rods and guide thimbles held together by spacers spaced along the assembly length and attached to the guide thimbles. The top and bottom nozzles extend slightly above and below the ends of the fuel rods on opposite ends and are secured to the guide thimbles. The top nozzle is removable and includes a passageway extending through the top nozzle and an annular groove formed in said passageway. A guide thimble device includes a guide thimble and an elongated sleeve configured for attaching the guide thimble to the top nozzle. The sleeve has slots in the upper end portion of said sleeve. Each slot extends downwardly from a top end of said sleeve, wherein the upper end portion of the sleeve includes shoulders or bulges. The bulges seat in the annular grooves comprised in the passageway in the top nozzle, when the sleeve is in an expanded locked position within said passageway. Each bulge has two ends and extends between two of the slots. Each bulge has a circumferential bulge profile. The top nozzle is connected to the fuel assembly in a removable manner. This is necessary for several reasons, for example, to have access to the fuel rods when these need to be replaced. The fuel assemblies are transported in and out of the reactor by lifting the fuel assembly by the top nozzle. This means that the attachment structure that connects the top nozzle with the guide thimbles needs to be strong enough to hold the weight of the fuel assembly. Apart from the mechanical attachment function, the guide thimbles also serve to house absorbent or control rods used for controlling the chain reaction at any time. These control rods are inserted into the guide thimble through the top nozzle, which has passages for this purpose. The control rods are inserted into the guide thimble with force and as rapidly as possible. Again, it is important that the attachment structure is strong enough to withstand these forces. U.S. Pat. No. 4,617,171 describes a fuel assembly wherein the bulge on the sleeve of the guide thimble has different profiles. The bulge described may for example have a rectangular profile (FIG. 3), with attachment threads (FIG. 4) or a biconical profile (FIG. 5). All bulges described in the prior art extend from slot to slot in a circumferential manner. Object of the present invention is to improve the attachment of the guide thimble device in a top nozzle of a fuel assembly. This object is achieved by the guide thimble device initially defined and which is characterized in that at least one end of the bulge extends to a position at a distance from the respective slot. One effect of this novel profile of the bulge is that the guide thimble device can withstand a higher axial load before the bulge begins to straighten. This increases the strength of the attachment of the guide thimble to the top nozzle. An advantage with the improved design is that by letting the cylindrical part of the sleeve pass by on at least one side of the bulge, the material in this area must exceed the yield point in tension, before the bulges can start to straighten. Thereby, the bulge can withstand a higher load. In the existing design of the bulges, the bulges may start to straighten before the yield point has been reached. As explained above, this results in improved security at the nuclear reactor plant. The improved bulges can be used in existing attachment structures without having to redesign the other parts in the joint. In the prior art different profiles of the bulge have been described to improve said attachment. All bulges described extend from slot to slot in a circumferential manner. No hints are given that the strength of the attachment can be improved with a bulge consisting of two ends and whereby at least one end of the bulge extends to a position at a distance from the respective slot. The present invention further relates to the guide thimble device initially defined and which is characterized in that at least one end of the bulge extends to a position at a distance from the respective slot. The present invention also relates to use of the guide thimble device in a fuel assembly. In one embodiment of the invention the bulge has an end portion at the respective end, wherein the end portion has a curved shape in a longitudinal section and in a transversal section along the bulge. Such a curvature will further improve the strength of the sleeve, and increase the resistance to deformation of the bulge and the sleeve. Thus the attachment of the sleeve in the passageway of the top nozzle is further enhanced. In one embodiment of the invention, both ends of the bulge extend to a position at a distance from the respective slot. In another embodiment, one end of the bulge extends to a position at a distance from the respective slot. In another embodiment of the invention, the bulges are provided so that there is one bulge between each pair of adjacent slots. In one embodiment of the invention, the bulges are provided circumferentially after each other. In one embodiment of the invention, the sleeve has a wall thickness seen in a radial direction with respect to the longitudinal direction. The distance between the end of the bulge and the slot may be important for the axial strength of the material. In one embodiment of the invention, the distance is equally long, or at least equally long, as the wall thickness of the sleeve. In another embodiment, the distance is two or three times longer than the wall thickness of the sleeve, or even longer. The wall thickness of the sleeve may also be important for the axial strength of the material. In one embodiment of the invention, the wall thickness is in the range of from 0.20 to 0.50 mm. The sleeve may be divided into several slots. In one embodiment of the invention, the sleeve has 3, 4, 5 or 6 slots. The profile of the bulges may vary. In one embodiment of the invention, the bulge has a cylindrical profile seen in a longitudinal section. FIG. 1 shows a fuel assembly 1 for a nuclear pressurized water reactor. The fuel assembly 1 comprises a number of elongated fuel rods 2 and guide thimbles, or guide tubes, 3 held together by spacers 4 spaced along the fuel assembly 1 length and attached to the guide thimbles 3. Top and bottom nozzles 5 and 6 extend slightly above and below the ends of the fuel rods 2 on opposite ends and are secured to the guide thimbles 3. The top nozzle 5 includes a transversely extending adapter plate 7 having upstanding sidewalls 8. Within the opening defined by the sidewalls 8 is a conventional rod cluster control assembly (not shown) introducible for vertically moving the control rods in the guide thimbles 3. FIGS. 2 and 3 show a part of a guide thimble device 9 present in the top nozzle 5. The top nozzle 5 includes a plurality of passageways extending through the adapter plate 7 of the top nozzle 5. An annular groove 10 is formed in each passageway. The guide thimble device 9 comprises a guide thimble 3 and an elongated sleeve 11 provided at an upper end of the guide thimble 3. The elongated sleeve 11 is cylindrical and has slots 12 in the upper end portion of the sleeve 11. The slots 12 extend downwardly from a top end of the sleeve 11. Bulges 13 are provided between the slots 12 positioned at distance d from the slot 12. The bulges 13 project outwardly from the cylindrical sleeve 11. Thanks to the distance d, there is a cylindrically shaped area 14 located between the end of the bulge 13 and the slot 12. A locking member 15 is introduced into the sleeve 11 from above the top nozzle 5. The sleeve 11 included in the guide thimble 3 may be an integrated part of the guide thimble 3. The sleeve 11 may also be a separated part of the guide thimble 3 attached thereto by any means, for instance by plastic deformation as indicated in FIG. 2. In the embodiment disclosed, both ends of the bulge 13 extend, as mentioned above, to a position at a distance d from the respective slot 12. It may also be possible to let only one end of the bulge 13 extend to a position at a distance d from the respective slot 12. As can be partly seen in FIG. 3, each the bulge 13 has an end portion at the respective end of the bulge 13. The end portions defining or including the respective end has a curved shape seen in a radial direction. Moreover, each of the end portions has a curved shape in a longitudinal section and in a transversal section along the bulge. The bulges 13 are provided so that there is one bulge 13 between each pair of adjacent slots 12. The bulges 13 may alternatively be provided so that there are two bulges 13 between each pair of adjacent slots 12 or even so that there are three bulges 13 between each pair of adjacent slots 12. This may be understood with further reference to FIGS. 4A-7B. Furthermore, the bulges 13 are provided circumferentially after each other. Alternatively, the neighbouring bulges 13 are not provided circumferentially but at different distances from the top end of the sleeve 11. This may be understood with further reference to FIGS. 4A-7B. The sleeve 11 has a wall thickness seen in a radial direction with respect to the longitudinal direction. The wall thickness is in the range of from 0.20 to 0.50 mm. The wall thickness may be in the range of from 0.25 to 0.40 mm, or in the range of from 0.30 to 0.35 mm. Alternatively, the wall thickness ranges from 0.20 to 0.35 mm, from 0.20 to 0.40 mm, or from 0.30 to 0.40 mm. The distance d mentioned above is equally long or is at least equally long as the wall thickness of the sleeve 11. The distance d may also be two times longer than the wall thickness of the sleeve 11. Alternatively, the distance d is three times longer than the wall thickness of the sleeve 11. Otherwise, the distance d ranges between one to five times the wall thickness of the sleeve 11. As mentioned above, the sleeve 11 may comprise or be divided into several slots 12. In the embodiment disclosed the sleeve 11 has four slots 12. Alternatively, the sleeve 11 may have three slots 12 or the sleeve 11 may have five slots 12 or more. These three, four, or five slot configurations may be understood with further reference to FIGS. 4A-7B, respectively. The bulge 13, at least between the end portions, may have a cylindrical profile seen in a longitudinal section. Alternatively, the bulge 13 may have any suitable outwardly projecting profile such as a rectangular or a biconical profile. The present invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims. |
|
claims | 1. A nondestructive method for determining a defective cladding of a nuclear fuel rod from the presence of a liquid in the fuel rod, comprising the steps of:(a) providing a tube to be inspected, wherein the tube comprises an outer surface and an internal surface;(b) arranging a wave emitter close to a side of the tube to be inspected for discharging an inspection wave obliquely incident to a first position on the outer surface by a predefined tilt angle and subsequently progressing to come into contact with the internal surface at a second position thereon;(c) arranging a receiving device at another side of the tube with respect to the wave emitter for receiving the inspection wave passing through the tube;(d) making an evaluation to determine whether the passing-through inspection wave can only be detected by the receiving device while the same is being arranged at a specific position at another side of the tube with respect to the wave emitter; if so, it represents that there is no liquid existed inside the tube under the level indicated by the second position;(e) making an evaluation to determine whether the passing-through inspection wave can be detected by the receiving device while the same is being arranged at two different positions both at another side of the tube with respect to the wave emitter; if so, it represents that there is liquid existed inside the tube at the level indicated by the second position. 2. The method as recited in claim 1, wherein the wave emitter is connected to a driving mechanism for driving the wave emitter to move up and down along the tube. 3. The method as recited in claim 2, wherein the level of liquid accumulated in the tube is detected by moving the wave emitter up and down along the tube while repeating the step (b) to step (e). 4. The method as recited in claim 1, wherein the tube is substantially a Zircaloy cladding tube. 5. The method as recited in claim 1, wherein the inspection wave is substantially an ultrasonic wave. 6. The method as recited in claim 1, wherein the inspection wave is substantially a light wave. 7. The method as recited in claim 6, wherein the tube is made of a transparent material. 8. The method as recited in claim 1, wherein the receiving device comprises at least a receiver. 9. The method as recited in claim 8, wherein the receiving device can be moved up-and-down and back-and-forth the tube for receiving the inspection waves discharging from different positions of the outer surface of the tube. 10. The method as recited in claim 1, wherein the receiving device comprises a plurality of receivers. 11. The method as recited in claim 1, wherein the receiving device is substantially a stationary device capable of receiving the inspection waves discharging from different positions of the outer surface of the tube by a plurality of receivers disposed at different areas of the receiving device. |
|
055747590 | summary | BACKGROUND OF THE INVENTION Field of the Invention The invention relates to a method for dismantling bulky parts of pressure-vessel fittings of a nuclear plant and for storing the dismantled parts. Such a method is known from Published European Patent Application 0 500 404 A1. In that method, fittings are inserted in a dismantling container which is disposed in a water tank. The fittings are dismantled into predeterminable sizes and introduced into a receiving container that is likewise disposed in the water tank through the use of a dismantling manipulator which can be fixed relative to the dismantling container. Each detached portion must be transported to the receiving container through the use of a lifting appliance, which results in transport distances that are too long and therefore time-consuming. Pressure vessels of nuclear plants are equipped with so-called pressure-vessel fittings for the purpose of receiving fuel assemblies. One bulky part of the fittings is, for example, the core container which fills a large proportion of the pressure-vessel interior, so that when the activated and contaminated core container is exchanged, very large and, due to the shielding requirements, very heavy transport containers, are required for transporting that bulky part. In order to ensure that smaller transport containers can be used, it is necessary to dismantle the bulky parts through the use of known dismantling devices. SUMMARY OF THE INVENTION: It is accordingly an object of the invention to provide a method for dismantling bulky parts of pressure-vessel fittings of a nuclear plant and for receiving the dismantled parts, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods of this general type and which preserves short transport distances while ensuring a radiation-proof handling and reception of the bulky parts before and after their dismantling. With the foregoing and other objects in view there is provided, in accordance with the invention, a method for dismantling bulky parts of pressure-vessel fittings of a nuclear plant and for storing the dismantled parts, which comprises setting down a dismantling container for pressure-vessel fittings in a water tank; inserting the pressure-vessel fittings into the dismantling container; introducing a receiving container for the dismantled parts into the dismantling container; fixing a dismantling manipulator relative to the dismantling container; separating the pressure-vessel fittings into predeterminable smaller-size parts; introducing the smaller-size parts into the receiving container; removing the receiving container from the dismantling container; and transferring the parts disposed within the receiving container, within the nuclear plant, into a transport container. Thus, the pressure-vessel fittings to be dismantled are inserted into the dismantling container. The dismantling device is fixed in the immediate vicinity of the dismantling container or to the dismantling container itself. The receiving container for the dismantling products is disposed within the dismantling container, so that short distances have to be covered from dismantling to storage. As soon as the receiving container is filled with dismantled portions, it is inserted into a transport container. The proposed measures ensure intermediately storable or, if required, ultimately storable conditioning as early as within the nuclear plant, with the dismantling and storage operations taking place in a very confined space. In accordance with another mode of the invention, there is provided a method which comprises setting down a bottom part of the dismantling container in the water tank; inserting the pressure-vessel fittings to be dismantled into the bottom part; and pushing a casing part of the dismantling container over the pressure-vessel fittings like a sleeve, and releasably connecting the casing part to the bottom part. In accordance with a further mode of the invention, there is provided a method which comprises introducing the receiving container into a shielding container within the water tank and transferring the receiving container from the shielding container into the transport container outside the water tank. In accordance with an added mode of the invention, there is provided a method which comprises inserting the shielding container together with the receiving container disposed in it, into the transport container. In accordance with a concomitant mode of the invention, there is provided a method which comprises bringing the shielding container and the transport container into position axially-parallel one above the other, removing at least one of a bottom and a cover of the mutually adjacent containers, and passing the receiving container from the shielding container into the transport container with a lifting appliance. Thus, to guarantee a sufficient water covering, a dismantling container being formed of a bottom part and a casing part is used, with the components to be dismantled being moved in from the side before the casing part is pushed over the component in a sleeve-like manner. Radiation-proof handling is also served by the measure calling for the filled receiving container to be introduced into a shielding container as early as within the dismantling container. The receiving container can then be transferred from the shielding container into a transport container outside the water tank. It is also possible to use the shielding container directly, thereby making it possible to employ a thin-walled and therefore light-weight transport container. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a method for dismantling bulky parts of pressure-vessel fittings of a nuclear plant and for receiving the dismantled parts, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. |
claims | 1. A method for shielding medical personnel from radiation emitted by a radiation source during a radiologic procedure performed on a patient supported by a table, comprising:positioning a radiation-shielding barrier between the medical personnel and the radiation source, and adjacent the table such that a portion of the table extends through an opening in the radiation-shielding barrier;covering at least a portion of the patient with a first flexible sterile drape; covering the opening in the radiation-shielding barrier and at least a portion of the first flexible sterile drape with a flexible radiation-resistive drape; andcovering at least a portion of the flexible radiation-resistive drape with a second flexible sterile drape. 2. The method of claim 1, wherein the first and second flexible sterile drapes are disposable. 3. The method of claim 1, wherein the flexible radiation-resistive drape is reusable. 4. The method of claim 1, wherein the first and second flexible sterile drapes are connected. 5. The method of claim 1, wherein the first and second flexible sterile drapes are connected such that a pocket is formed between the first and second flexible sterile drapes. 6. The method of claim 5, wherein the flexible radiation-resistive drape is inserted in the pocket formed between the first and second flexible sterile drapes. 7. The method of claim 1, wherein the first and second flexible sterile drapes comprise a single sheet folded over on top of itself. 8. The method of claim 1, further comprising: attaching at least one of the first and second flexible sterile drapes and the flexible radiation-resistive drape to the radiation-shielding barrier. 9. The method of claim 8, wherein said attaching at least one of the first and second flexible drapes and the flexible radiation-resistive drape to the radiation barrier uses a fastener selected from a group of fasteners consisting of a hook and loop fastener, a Velcro fastener, a screw fastener, a snap fastener, and an adhesive. 10. The method of claim 1, wherein the first and second flexible sterile drape and the flexible radiation-resistive drape generally extend between at least a lower portion to a middle portion of the patient. 11. The method of claim 1, wherein the radiation barrier comprises a patient aperture hoop of adjustable size, through which a portion of the table extends. 12. A system for shielding medical personnel from radiation emitted by a radiation source during a radiologic procedure performed on a patient, comprising:a table for supporting a patient during a radiologic procedure;an upper shield adjacent and above the table such that a portion of the table extends through an opening in the upper shield; a lower shield extending below the table;a linking mechanism between the upper and lower shield; wherein the lower shield and the upper shield overlap such that radiation does not leak between the two; andthe linking mechanism attaches the upper shield to the lower shield such that both the upper shield and lower shield can be moved independent of one another within a range of motion without opening a gap between the two through which radiation can leak. 13. The system of claim 12, wherein the linking mechanism comprises: an arm attached at one end to a top portion of a post of the lower shield and is moveably attached via a bearing at the other end of the arm to a track along the bottom of the upper shield. 14. The system of claim 12, further comprising: a flexible radiation-resistive interconnect drape to at least partially cover the opening in the upper shield; and at least one unidirectional chain arranged along the underside of the interconnect drape arranged such that when the upper shield is moved with respect to the table, the interconnect drape maintains the radiation barrier, and the unidirectional chain is flexible when the chain is extended in a first direction and supportive when extended in a second direction. 15. The system of claim 12, further comprising: a first flexible sterile drape covering at least a portion of the patient; a flexible radiation-resistive drape covering the opening in the upper shield and at least a portion of the first flexible sterile drape; and a second flexible sterile drape covering at least a portion of the flexible radiation-resistive drape. |
|
050826026 | summary | BACKGROUND OF THE INVENTION This invention relates to a process for regenerating a spent extraction solvent containing anions and cations used in e.g. nuclear power plants by separating and removing these ions from the extraction solvent and an apparatus used therefor. This invention is particularly suitable for separating and removing ions contained in an organic solvent for reprocessing in large amounts. Heretofore, an extraction solvent was regenerated by cleaning the extraction solvent with an alkaline cleaning agent such as sodium carbonate, triethanolamine, etc. by using a liquid-liquid extraction apparatus such as a mixer-settler, etc. (e.g. U.S. Pat. No. 4,059,671). But such a cleaning agent has problems in that it easily precipitates metal ions contained in the deteriorated solvent, the resulting precipitate is collected at an interface of the solvent and the cleaning agent thus interfering with the removal action of captured impurities and making the separation of the solvent and the cleaning agent worse. SUMMARY OF THE INVENTION It is an object of this invention to provide a process and an apparatus for regenerating a spent reprocessing extraction solvent without causing interference with cleaning operation accompanied by production of a precipitate in an alkaline circumstance. This invention provides a process for regenerating a spent organic solvent containing anions and cations by separating and removing these ions from the organic solvent which comprises: forming one or more alkaline aqueous solution phases for capturing anions via a first hydrophobic porous membrane and forming one or more acidic aqueous solution phases for capturing cations in the organic solvent containing cations via a second hydrophobic porous membrane and anions, capturing the cations by the acidic aqueous solution phases and the anions by the alkaline aqueous solution phases simultaneously through the first and second hydrophobic porous membranes, and collecting the acidic aqueous solution phases for removing the cations therefrom and collecting the alkaline aqueous solution phases for removing the anions therefrom. This invention also provides an apparatus used for such a process. |
claims | 1. Ion implantation apparatus having an evacuated housing and, contained in said housing, a) a holder for holding a substrate for implantation; b) a source of positive ions for implanting in said substrate; c) a beam of said ions being formed which is directed at said substrate; d) an electron flood source to supply low energy electrons to the beam in front of said substrate for neutralizing positive charge build up on said substrate; e) a magnetic filter located adjacent to said substrate holder between said substrate holder and said electron flood source providing a magnetic field extending across the beam immediately in front of said substrate, said field having a strength selected to deflect out of the region containing the beam secondary electrons emitted from the substrate with energies above 15 eV, but to allow lower energy electrons including those supplied by said flood source to diffuse across said field without being deflected out of said beam region; and f) a conductive element located out of said beam region to be impacted by and absorb said deflected secondary electrons; said magnetic filter being located substantially at a substrate end of the conductive element. 2. Apparatus as claimed in claim 1 , wherein said magnetic filter provides said magnetic field with a field strength selected to deflect secondary electrons with energies above 5 eV to impact said conductive element. claim 1 3. Apparatus as claimed in claim 1 , wherein said magnetic filter includes a pair of opposite magnetic poles located on opposite sides of said beam region. claim 1 4. Apparatus as claimed in claim 1 , wherein said conductive element comprises a conductive tube surrounding said beam in front of said substrate holder. claim 1 5. Apparatus as claimed in claim 4 , wherein said electron flood source is located to supply said low energy electrons into said conductive tube. claim 4 6. A method of implanting ions in a substrate comprising, holding the substrate in an evacuated housing; directing a beam of desired positive ions at the substrate for implanting therein; flooding the beam in front of the substrate with low energy electrons from an electron flood source to neutralize positive charge build up on the substrate; applying a magnetic filtering field extending across the beam immediately in front of said substrate between the substrate and the electron flood source, said field having a strength selected to deflect out of the region containing the ion beam secondary electrons emitted from the substrate with energies above 15 eV but to allow lower energy electrons, including those from the flood source, to diffuse across said magnetic filtering field without being deflected out of said beam region, and absorbing said secondary electrons deflected by said magnetic filtering field on a conductive element located out of said beam region. 7. A method of implanting as claimed in claim 6 , wherein the field strength of the magnetic filtering field is selected to deflect said secondary electrons with energies above 5 eV out of said region for absorbing on said conductive element. claim 6 8. A method of implanting as claimed in claim 6 , wherein said magnetic filtering field is a dipole field. claim 6 9. A method of implanting as claimed in claim 6 , wherein the low energy electrons from said flood source are contained around the ion beam region by a conductive tube surrounding the beam in front of the substrate, and said deflected secondary electrons are absorbed on said tube. claim 6 10. A method of preventing negative charge build up on a substrate being implanted with positive ions comprising absorbing higher energy secondary electrons emitted from the substrate at a located proximate said substrate, said higher energy secondary electrons being those emitted with energies above a predetermined value, whereby the population density of said higher energy secondary electrons immediately in front of said substrate is reduced. 11. A method as claimed in claim 10 , wherein said higher energy secondary electrons are absorbed by deflecting them with a magnetic field extending across the surface of the substrate being implanted to impact and be absorbed on a conductive element. claim 10 12. A method as claimed in claim 11 , wherein a beam of positive ions is directed at the substrate and said magnetic field extends across said beam to deflect said higher energy secondary electrons to be absorbed on said conductive element located out of the beam region. claim 11 13. A method as claimed in claim 11 , including the step of flooding the region in front of said magnetic field across the substrate with low energy electrons having energies below said predetermined value, whereby said low energy electrons diffuse through said magnetic field and are absorbed on the substrate to prevent positive charge build up thereon. claim 11 |
|
060751762 | abstract | A method of immobilizing mixed low-level waste is provided which uses low cost materials and has a relatively long hardening period. The method includes: forming a mixture of iron oxide powders having ratios, in mass %, of FeO:Fe.sub.2 O.sub.3 :Fe.sub.3 O.sub.4 equal to 25-40:40-10:35-50, or weighing a definite amount of magnetite powder. Metallurgical cinder can also be used as the source of iron oxides. A solution of the orthophosphoric acid, or a solution of the orthophosphoric acid and ferric oxide, is formed and a powder phase of low-level waste and the mixture of iron oxide powders or cinder (or magnetite powder) is also formed. The acid solution is mixed with the powder phase to form a slurry with the ratio of components (mass %) of waste:iron oxide powders or magnetite:acid solution=30-60:15-10:55-30. The slurry is blended to form a homogeneous mixture which is cured at room temperature to form the final product. |
description | This is a divisional application of Ser. No. 12/586,779, issued as U.S. Pat. No. 8,357,316 on Jan. 22, 2013, being entitled Gamma Radiation Source by the same inventors. NA NA NA 1. Field of the Invention The present invention relates generally to radiation testing and medical treatment, and, in particular, relates to radiation testing and the medical treatment using gamma radiation sources, and, in greater particularity, relates to radiation testing and medical treatment using 75Selenium. 2. Description of the Prior Art The use of radioactive sources in present technology is an important feature as compared to x-rays, for example, in that radioactive sources can be tailored to specific uses. These sources may emit particle and/or wave radiation of varying energies in the spectrum and further have half-lives from mere seconds to years. Since some of these elements are extremely reactive, processing these sources into useable products is a critical and complex task to protect users and minimize manufacturing costs. U.S. Pat. No. 6,875,377 describes the specific problem of combining 75Selenium with an acceptable metal source: “In the past, 75Selenium sources have been made by encapsulating elemental 74Selenium target material inside a welded metal target capsule. This is irradiated in a high flux reactor to convert some of the 74Selenium to 75Selenium. Typically, target capsules are made of low-activating metals, such as aluminum, titanium, vanadium and their alloys. Other expensive metals and alloys are also possible. The use of these metals ensures that impurity gamma rays arising from the activation of the target capsule are minimized. The 75Selenium is typically located within a cylindrical cavity inside the target capsule in the form of a pressed pellet or cast bead. To achieve good performance in radiography applications it is necessary for the focal spot size to be as small as possible and the activity to be as high as possible. This is achieved by irradiating in a very high neutron flux and by using very highly isotopically enriched 74Selenium target material, typically >95% enrichment. After the irradiation, the activated target capsule is welded into one or more outer metal capsules to provide a leak-free source, which is free from external radioactive contamination. Elemental selenium is chemically and physically volatile. It melts at 220° C. and boils at 680° C. It reacts with many metals, which might be suitable as low-activating capsule materials at temperatures above about 400° C.; this includes titanium, vanadium and aluminum and their alloys. Selenium may react explosively with aluminum. This means that careful choice of target capsule material is required and the temperature of the target capsule during irradiation must be kept below about 400° C. to prevent the selenium reacting with, and corroding the target capsule wall. If this occurred, it would increase the focal spot size, distort the focal spot shape and reduce the wall thickness and strength of the target capsule.” A solution is offered in U.S. Pat. No. 6,875,377 which is incorporated by reference: “An embodiment of the present invention is to provide a source having a selenium target composition, which overcomes or ameliorates one or more of the problems associated with the use of elemental selenium, specifically the problems of achieving a thermally stable, non-volatile, non-reactive, high density, stable selenium target which nevertheless contains a very high density of selenium, comparable with the elemental form of the material. The invention provides; in one of its aspects, a gamma radiation source comprising 75Selenium or a precursor thereof, wherein the selenium is provided in the form of one or more thermally stable compounds, alloys, or mixed metal phases with one or more metals (hereinafter referred to as acceptable metals or an acceptable metal) the neutron irradiation of which does not produce products capable of sustained emission of radiation which would unacceptably interfere with the gamma radiation of 75Selenium.” A definition of what is an “acceptable” metal is also provided in U.S. Pat. No. 6,875,377: “Thus, for example, an acceptable metal, such as vanadium or rhodium, is activated but has no interfering gamma radiation. Molybdenum produces molybdenum-99 that does have interfering gamma radiation, but is very short lived and is therefore also an acceptable metal. Again, Thorium produces palladium-233 [appears to be an error in that thorium produces protactinium-233] having a 27 day half life, but the gamma radiation of palladium-233 is 300-340 keV which is very similar to selenium-75 and therefore acceptable.” The above U.S. Patent lists “acceptable metals”: “Preferably, the said acceptable metal or metals is from the group comprising vanadium, molybdenum, rhodium, niobium, thorium, titanium, nickel, lead, bismuth, platinum, palladium [see not above], aluminum, or mixtures thereof. More preferably, the said acceptable metal or metals comprises one or a mixture of vanadium or molybdenum or rhodium.” Accordingly, there is an established need for radiation sources that would complement present sources that would provide additional benefits. The present invention is directed at a gamma radiation source having one or more zones of complementary radiation. The present invention has a primary source of radiation contained within a primary radiation zone. A supplemental radiation source may be contained within a supplemental radiation zone that is centered on or about the primary radiation zone. A complementary radiation source is contained either in a lower radiation zone or an upper radiation zone. It should further be understood that during manufacturing of the gamma radiation source components may be irradiated separately before being combined so that subsequent radiation peaks may be adjusted in relative frequency. It should be further understood that the components may be of natural isotopic composition or of isotopically modified composition (enriched or depleted in certain isotopes) so that the subsequent radiation peaks may also be adjusted in relative frequency. In the present invention, a gamma radiation source comprises 75Selenium or a precursor thereof, wherein the 75Selenium is provided in the form of one or more thermally stable compounds, alloys or mixtures with one or more nonmetals, the neutron irradiation of which does not produce products capable of sustained emission of radiation which would unacceptably interfere with the gamma radiation of 75Selenium. A further gamma radiation source comprises 75Selenium or a precursor thereof, wherein the 75Selenium is provided in the form of one or more thermally stable compounds, alloys or mixtures with one or more metals or nonmetals, the neutron irradiation of which does produce products capable of sustained emission of radiation which would acceptably complement the gamma radiation of 75Selenium. An embodiment of the present invention is to provide a gamma radiation source having an adjustable radiation pattern for use in industry, research and medicine. It is another embodiment of the present invention to provide a gamma radiation source having supplemental and/or complementary radiation components. It is another embodiment of the present invention to provide one or more components being of natural isotopic composition or of isotopically modified composition (enriched or depleted in certain isotopes) so that the subsequent radiation peaks may also be adjusted in relative frequency. It is a further embodiment of the present invention to provide a gamma radiation source based upon 75Selenium. It is still a further embodiment of the present invention to provide a gamma radiation source having one or more nonmetal radiation components therein. It is still a further embodiment of the present invention to provide a gamma radiation source based upon 75Selenium and having one or more nonmetal radiation components therein. It is yet a further embodiment of the present invention to provide a gamma radiation source having one or more metallic and/or nonmetallic components therein. It is yet a further embodiment of the present invention to provide a gamma radiation source based upon 75Selenium having one or more metallic and/or nonmetallic components therein. These and other embodiments, features, and advantages of the present invention will become more readily apparent from the attached drawings and the detailed description of the preferred embodiments, which follow. Like reference numerals refer to like parts throughout the several views of the drawings. The present invention is directed at a gamma radiation source based upon 75Selenium and one or more other gamma radiation sources or components combined into a single source having a unique gamma radiation spectrum. Turning to the drawings, wherein like components are designated by like reference numerals throughout the various figures, attention is initially directed to FIG. 1 which illustrates an energy graph of different radiation source patterns/zones according to the present invention. As best shown in FIG. 1, a primary source of radiation is essentially contained within a primary radiation zone 100. A supplemental radiation source is contained within a supplemental radiation zone 102 that is centered on or about the primary radiation zone 100. A complementary radiation source is contained either in a lower radiation zone 104 or an upper radiation zone 106. Supplemental means that it adds to the primary radiation, and complementary means it is additional radiation but not necessarily within the primary radiation zone 100. Although zones are shown in FIG. 1, it should be understood that peaks at different energies may fall outside that zone, but substantially all of the radiation falls within that zone as will be understood from the following discussion and figures. It should further be understood that during manufacturing of the gamma radiation source components of such may be irradiated separately before being combined so that subsequent radiation peaks may be adjusted in relative frequency. It should be further understood that the components may be of natural isotopic composition or of isotopically modified composition (enriched or depleted in certain isotopes) so that the subsequent radiation peaks may also be adjusted in relative frequency. Nonmetallic Compounds There exist a number of nonmetals, the neutron irradiation of which does not produce products capable of sustained emission of radiation which would unacceptably interfere with the gamma radiation of 75Selenium, FIG. 2A, that can be combined with Selenium to form a thermally-stable compound or mixture. Silicon Diselenide (SiSe2) One example is the chemical compound Silicon Diselenide (SiSe2). Silicon is a nonmetal, sometimes referred to as a metalloid (an element with properties intermediate between those of a metal and nonmetal). Silicon diselenide is a compound with a melting temperature of 960° C. (Ref: M. Arai, D. L. Price, S. Susman, K. J. Volin, and U. Walter, Network dynamics of chalcogenide glasses. II. Silicon diselenide, Phys. Rev. B 37, 4240-4245 (1988). Bletskan, in (D. I. Bletskan, PHASE EQUILIBRIUM IN THE BINARY SYSTEMS AIVBVI, Part. I. The systems Silicon-Chalcogen, Journal of Ovonic Research Vol. 1, No. 5, October 2005, p. 47-52) describes the process for manufacturing SiSe2. A more complete description is provided by Johnson et al (R. W. Johnson, S. Susman, J. McMillan, and K. J. Volln, PREPARATION AND CHARACTERIZATION OF SixSe I x GLASSES AND DETERMINATION OF THE EQUILIBRIUM PHASE DIAGRAM, Mat. Res. Bull., Vol. 21, pp. 41-47, 1986). Natural (non-enriched) silicon can be used because neutron irradiation of natural silicon does not produce products capable of sustained emission of radiation. The longest-lived activation product is 31Silicon. Silicon with a half-life of only 2.6 hours. The use of isotopically-enriched or isotopically depleted Silicon would also be acceptable. Germanium Selenide There exist two selenides of Germanium (another nonmetal metalloid): GeSe that melts at 670° C. and GeSe2, which melts at 740° C. (L. Ross and M. Bourgon, The germanium-selenium phase diagram, Canadian Journal of Chemistry, Vol. 47, pp 2555-2559, 1969). There are only two isotopes of Germanium that are capable of sustained emission. 68Germanium has a half-life of 275 days, but is not produced by the neutron irradiation of any of the stable Germanium isotopes. 71Germanium, which is produced by the neutron irradiation of 70Germanium has a half-life of 11.4 days. The radiation outputs of 70Germanium are photons of 11 keV, which would be very heavily shielded by any source encapsulation. Therefore natural (non-enriched) Germanium could be used for this compound. Other nonmetals may be similarly employed. Metallic and Nonmetallic Compounds There exist a number of metals and nonmetals, the neutron irradiation of which does produce products capable of sustained emission of radiation which would acceptably complement the gamma radiation of 75Selenium, that can be combined with selenium to form a thermally-stable compound or mixture. For an element to be practical in this regard, the “sustained emission” needs to be “sustained” for a period of time similar to that of 75Selenium. For purposes of this invention, the half-life of the other isotope or component should be between 25% and 300% of the half-life of 75Selenium (120 days). Therefore, isotopes with half-lives between 30 and 360 days are acceptable. Additionally, in order for the emitted radiation to be complementary to that of 75Selenium, it must have appreciable emission outside the range of energies of 75Selenium. 75Selenium principally emits photons between 120 and 401 keV. See FIG. 2A. Thulium Selenide (TmSe) Kaldis and Fritzler (Kaldis E and Fritzler B, A3 Solid State Chemistry of New Semiconductors with Valance Instabilities: TmSe1-xTex and Tm1-xEuxSe, J. Phys. Colloques 41 (1980) C5-135-05-142) describe a process for synthesizing TmSe that can be used in the present invention. Thulium Selenide can also be synthesized by the method described by Matsumura et al. (Takeshi Matsumura, Shintaro Nakamura, Terutaka Goto, Hiroshi Amitsuka, Kazuyuki Matsuhira, Toshiro Sakakibara and Takashi Suzuki, Low Temperature Properties of the Magnetic Semiconductor TmTe, J. Phys. Soc. Jpn. 67 (1998) pp. 612-621). Another description is provided by Grain in U.S. Pat. No. 4,575,464. The melting temperature of TmSe is ˜2300° C. Thulium, when exposed to neutron irradiation, transmutes into 170Thulium. This isotope has a half-life of 128 days and emits photons of 48, 49, 51, 52, 55, 57, 59, 60, 78 and 84 keV, see FIG. 2B, which are substantially lower than the photons of 75Selenium. These lower-energy photons are very complementary to those of 75Selenium. For example, these would improve the contrast sensitivity of 75Selenium in the radiographic process. Additionally, 170Thulium decays by beta emission, and the beta produces bremsstrahlung within the source material itself. In one typical configuration, the average energy of this bremsstrahlung was 74 keV, which is also very complementary. See FIG. 2C which shows that the radiation source of TmSe being located in the lower radiation zone 104 as compared to the primary source of 75Selenium being in the primary zone of 100. Iridium Selenides There are three identified selenides of Iridium: Ir2Se3, IrSe2 and IrSe3. These are prepared by the reaction of Selenium with Iridium Trichloride. Iridium, when exposed to neutron irradiation, transmutes into 192Iridium. This isotope has a half-life of 74 days and principally emits photons of ˜300, 468, and ˜600 keV. See FIG. 2D. Although the ˜300 keV photons are within the range of those of 75Selenium, the other photon emissions are well above those of 75Selenium. These higher energy photons would be very complementary to those of 75Selenium. For example, these higher energy photons would extend the useful thickness range in the radiographic process. See FIG. 2E that shows the Iridium source radiation being in the upper radiation zone 106. The Iridium may be of natural isotopic composition or of isotopically modified composition (enriched or depleted in certain isotopes) so that the subsequent radiation peaks may also be adjusted in relative frequency. Tungsten Diselenide (WSe2) Tungsten selenide (tungsten diselenide) is commercially available and used as a photovoltaic material in solar cells and other light-to-energy projects, in chemical vapor deposition, sputtering targets, thin-film coatings, and other high-temperature coating and lubricating applications. It has a density of 9.32 mg/mm3. It is reported to have good thermal stability and a high melting point (˜1200° C.). Irradiation of natural tungsten will produce 185Tungsten (t1/2: 75 days; a pure beta emitter), 188Tungsten (t1/2: 69 days; a beta emitter with very little gamma; accompanied by its daughter 188Rhenium in equilibrium with many high energy gammas from 478 keV to 932 keV, and a small amount of 181Tungsten (t1/2: 121 days; with 56-67 keV x-rays). In an alternative composition, the emission of low energy 181Tungsten gammas could be enhanced by using some level of enriched 180Tungsten. Zinc Selenide (ZnSe) Zinc selenide (ZnSe), is an intrinsic semiconductor with a melting temperature of >1500° C. Natural Zinc is comprised of approximately 48.9% 64Zinc, 27.8% of 66Zinc, 4.1% of 67Zinc and 18.6% of 68Zinc and 0.6% of 70Zinc. When irradiated by neutron flux, 64Zinc is transmuted to radioactive 65 Zinc which emits high energy gamma rays (1115 keV) and has a half-life of 245 days. These photon emissions are well above those of 75Selenium. These higher energy photons would be very complementary to those of 75Selenium. The isotopic composition of Zinc-64 can be enriched up to as high as 99% or depleted to as low as 1% in order to adjust the relative frequency of the radiation peaks. See FIGS. 2A, 2F and 2G. For example, these higher energy photons would extend the useful thickness range in the radiographic process. Samarium Selenide (Sm2Se3, CuSm3Se6, CuSm3Se4): Samarium Selenide has a density of 7.33 mg/mm3 and is stable up to at least 1100° C. The only long-lived radionuclide is 145Sm with a half-life of 340 days and X-rays from 38-44 keV and a 61 keV gamma. Tantalum Selenide (TaSe, TaSe2) Tantalum selenide (Tantalum diselenide) has a density in the range of 8.5 to 10.2 mg/mm3. It is reported to have good thermal stability up to ˜900° C.). Tantalum-182 has a half-life of 115 days and emits a large number of gamma rays between 1100 keV and 1300 keV. Other Rare Earth Selenides: Several other rare earth elements (Cerium, Gadolinium, and Ytterbium) form chemically acceptable compounds with Selenium with varying degrees of suitability among the radiological properties. Other Nonmetallic Selenides: Antimony Selenide (Sb2Se3) Antimony Selenide (Sb2Se3) (Antimony is another nonmetal metalloid) melts at 617° C. The isotope 124Antimony, with a half-life of 60.4 days, adds to the spectrum of 75Selenium a variety of high-energy photons (603 keV, 644 keV, 720 keV, 967 keV, 1.048 MeV, 1.31 MeV, 1.37 MeV, 1.45 MeV, 1.692 MeV, and 2.088 MeV). The above compounds may be irradiated by neutron bombardment or may be separately irradiated before being combined and thus the radiation spectrum of the compound so formed may be adjusted in relative frequency as would be known by one skilled in the art knowing of the present invention. The forming of the above stable compound, alloy, or mixture after irradiation into pellets, beads, etc., would require appropriate shielding and handling. For example, a gamma radiation source 300, FIG. 3, has a cylindrical pellet 302 inserted into a tubular container 304 that may be used in brachytherapy. Clearly other source shapes are possible. Since many modifications, variations, and changes in detail can be made to the described embodiments of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents. |
|
description | The present application hereby claims priority under 35 U.S.C. §119 to German patent application number DE 10 2011 103 851.9 filed May 26, 2011, the entire contents of which are hereby incorporated herein by reference. At least one embodiment of the invention generally relates to a grid module of a scattered-radiation grid, to a scattered-radiation grid including a number of grid modules with grid webs arranged next to one another, especially for use in conjunction with a CT detector, to a CT detector and to a CT system with such a detector. Scattered-radiation grids—more precisely scattered-radiation collimators embodied in a grid shape—for CT detectors are generally known and are used in almost every CT system currently employed in practice. Such scattered-radiation grids are of importance in particular in dual-source CT systems with two emitter/detector systems offset at an angle to each other on the gantry, since the amount of scattered radiation from an emitter system operated in parallel and offset at an angle is especially high. In relation to a scattered-radiation grid of modular construction the reader is referred to German publication DE 10 2008 030 893 A1 for example. One problem with such modular scattered-radiation grids with a number of grid modules arranged next to one another however lies in the fact that artifacts occur in the area of the joint between two grid modules in the projections recorded therewith, which have a negative effect on the image quality of a tomographic image dataset reconstructed from such projections or generate visible artifacts in the tomographic image respectively. An embodiment of the invention is directed to a modular scattered-radiation grid in which projection artifacts are largely suppressed. Advantageous developments of the invention are the subject matter of subordinate claims. In accordance with this basic idea, the inventors in at least one embodiment propose improving a grid module for a scattered-radiation grid consisting of a number of grid modules arranged next to one another, each equipped with a plurality of grid webs, such that on at least one edge side of the grid module, a grid web running there along the at least one edge side is embodied at least partly perforated at a plurality of sections. A detector of a CT system with a modular-construction inventive scattered-radiation grid and also a CT system with such a detector is additionally proposed as part of an embodiment of the invention. Various example embodiments will now be described more fully with reference to the accompanying drawings in which only some example embodiments are shown. Specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. The present invention, however, may be embodied in many alternate forms and should not be construed as limited to only the example embodiments set forth herein. Accordingly, while example embodiments of the invention are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments of the present invention to the particular forms disclosed. On the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the invention. Like numbers refer to like elements throughout the description of the figures. Before discussing example embodiments in more detail, it is noted that some example embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations as sequential processes, many of the operations may be performed in parallel, concurrently or simultaneously. In addition, the order of operations may be re-arranged. The processes may be terminated when their operations are completed, but may also have additional steps not included in the figure. The processes may correspond to methods, functions, procedures, subroutines, subprograms, etc. Methods discussed below, some of which are illustrated by the flow charts, may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks will be stored in a machine or computer readable medium such as a storage medium or non-transitory computer readable medium. A processor(s) will perform the necessary tasks. Specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments of the present invention. This invention may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments of the present invention. As used herein, the term “and/or,” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being “connected,” or “coupled,” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected,” or “directly coupled,” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between,” versus “directly between;” “adjacent,” versus “directly adjacent,” etc.). The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments of the invention. As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the terms “and/or” and “at least one of” include any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Portions of the example embodiments and corresponding detailed description may be presented in terms of software, or algorithms and symbolic representations of operation on data bits within a computer memory. These descriptions and representations are the ones by which those of ordinary skill in the art effectively convey the substance of their work to others of ordinary skill in the art. An algorithm, as the term is used here, and as it is used generally, is conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of optical, electrical, or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. In the following description, illustrative embodiments may be described with reference to acts and symbolic representations of operations (e.g., in the form of flowcharts) that may be implemented as program modules or functional processes include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types and may be implemented using existing hardware at existing network elements. Such existing hardware may include one or more Central Processing Units (CPUs), digital signal processors (DSPs), application-specific-integrated-circuits, field programmable gate arrays (FPGAs) computers or the like. Note also that the software implemented aspects of the example embodiments may be typically encoded on some form of program storage medium or implemented over some type of transmission medium. The program storage medium (e.g., non-transitory storage medium) may be magnetic (e.g., a floppy disk or a hard drive) or optical (e.g., a compact disk read only memory, or “CD ROM”), and may be read only or random access. Similarly, the transmission medium may be twisted wire pairs, coaxial cable, optical fiber, or some other suitable transmission medium known to the art. The example embodiments not limited by these aspects of any given implementation. It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise, or as is apparent from the discussion, terms such as “processing” or “computing” or “calculating” or “determining” of “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device/hardware, that manipulates and transforms data represented as physical, electronic quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper”, and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, term such as “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein are interpreted accordingly. Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, it should be understood that these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present invention. The inventors have recognized that the artifacts in the, area of the joints of grid modules of a modular-design scattered-radiation grid essentially arise as a result of a wall thickening of the grid webs occurring in these joint areas because of the doubled walls in these areas and, through this, scattered radiation arriving from the side—in relation to the other, non-doubled grid webs—being more heavily suppressed. Basically, although a greater suppression of scattered radiation would be advantageous, an increased scattered radiation suppression only locally at specific points generates undesired artifacts. In order to avoid this excessive suppression, it would basically be possible to halve the wall thicknesses of the webs of the grids at the joints of the grid modules, so that ultimately, at the joint between two webs, the same, i.e. single, web thickness occurs as at all other webs of the scattered-radiation grid. However such a measure would greatly increase the production costs. To solve this problem, the inventors in at least one embodiment thus propose to provide the grid webs abutting each other and thus forming thicker grid webs with a plurality of breakthoughs, so that overall the material occupancy of the adjoining grid webs available for shielding against scattered radiation is reduced and thereby the increased shielding of the scattered radiation through the construction-related strengthening of the overall web thickness is simply compensated for by the material reduction in the grid webs. Since with this the sum of the non-shielded scattered radiation again corresponds to the value without thickening of the grid web, the artifacts which arise through a disproportionately high scattered radiation shielding at the joints of two grid modules are avoided by this measure. Use is also made of the fact that a reduced material occupancy of the web of a scattered-radiation grid increasingly lets scattered radiation pass through to the detector module lying underneath. The reduction of the material occupancy can occur within the meaning of the invention by cutouts or breakthroughs being created in the lateral grid webs of the grid module. Through this measure the disproportionate shielding of scattered radiation by doubled webs at the joints can be compensated for such that the detector elements at the joints of the grid modules are also shielded with the same effectiveness as detector elements disposed centrally in relation to the grid module. Since the basic assumption is to be made that the shielding effect of a thickened grid web not only relates to the detector element in the immediate vicinity or in the adjacent row or column of detector elements, but also to detector pixels of the next and next-but-one row or column lying towards the middle of the grid module, the attenuation affect extending to these rows or columns can thus be compensated for in an improved embodiment likewise by an, albeit smaller, reduction of the material occupancy of the next grid web and if necessary the grid web lying further inwards in the grid module. For this breakthroughs must merely—inwards with decreasing overall surface, be inserted into the grid webs, which reduce the occupancy density of the grid webs. In accordance with this basic idea, the inventors in at least one embodiment propose improving a grid module for a scattered-radiation grid consisting of a number of grid modules arranged next to one another, each equipped with a plurality of grid webs, such that on at least one edge side of the grid module, a grid web running there along the at least one edge side is embodied at least partly perforated at a plurality of sections. Advantageously the at least partly perforated sections and non-perforated sections can alternate in such cases. In addition the grid module can be embodied so that it has at least two grid webs with breakthroughs opposite one another and on an edge side. Such grid modules can be predominantly arranged in a single row to form a scattered radiation grid alongside one another such that only the grid webs of two modules provided with breakthroughs lie next to one another. It is also useful for the breakthroughs, seen in the longitudinal direction of the webs, to be disposed at the same distances from one another. In an embodiment in such cases exclusively one breakthrough can be arranged at least one longitudinal position of the at least one grid web in each case. In other words a plurality of breakthroughs is distributed over the length of the grid web, with exclusively one single breakthrough being disposed at each longitudinal position of the breakthroughs. The side surface of the edge side grid web thus takes on a strip pattern with a plurality of strips consisting of breakthroughs which run from top to bottom, i.e. at right angles to the longitudinal direction of the grid web. As an alternative to this, a number of breakthroughs can be arranged in each case at least one longitudinal position of the at least one grid web along the web height. For example a checkerboard-like pattern of breakthroughs and intact material or also a strip pattern of a number of strips running in the longitudinal direction of the grid web can arise. It is also advantageous for the breakthroughs on at least two opposing grid webs to the disposed in such a way and embodied in relation to their size such that all breakthroughs of a grid web lie opposite a breakthrough-free surface of the other edge-side grid web in each case. The breakthroughs of two grid webs of the same module lying opposite each other on the edge side are arranged offset. This is especially advantageous because, with grid modules arranged in this way next to one another, the grid webs adjoining one another of two modules the breakthroughs are arranged offset to one another so that, relative to a lateral projection the material occupancy essentially corresponds to a single web and thus the scattered radiation absorbing effect of only a single grid web is generated. Furthermore, in relation to the height of the at least one edge-side grid web, the number of breakthroughs can be embodied equal to the number of breakthrough-free surfaces. For subsequent assembly of a number of grid modules into a complete scattered-radiation grid it is also especially useful, at the minimum and/or maximum height of the at least one edge-side grid web, for a continuous area without breakthroughs to be embodied over the entire length of the grid web. This uninterrupted area prevents the grid modules catching on each other, which could possibly lead to damage to the exposed webs. In order to compensate for the effect of undesirably increased scattered radiation shielding in the edge area of the grid modules, it can also be useful, for grid webs adjacent to the grid webs disposed on the edge side, i.e. grid webs further inwards in the grid module, to have lateral breakthroughs. Since the effect of the excessive scattered radiation shielding in the edge area reduces from the edge inwards, the number and/or overall surface of the breakthroughs in the grid webs should also likewise reduce accordingly from the grid webs of the edge area of the grid module to the center of the grid module. The proposed grid modules can have grid webs both exclusively parallel in one direction and also crossing each other, preferably crossing each other at right angles. To avoid possible mechanical damage to the grid module at least one inventively embodied edge-side grid web can additionally be provided from the outside with a plastic film. This produces a less sensitive unbroken outer side which during assembly has less of the tendency to catch on other grid modules. In addition to the grid modules embodied in accordance with an embodiment of the invention a scattered-radiation grid for an x-ray detector of a CT system is proposed with a plurality of detector elements disposed in rows and columns over its surface, comprising: At least two grid modules disposed next to one another, With each grid module possessing a number of grid webs arranged next to one another with irradiation zones lying between them, and At least one edge-side web of a grid module being adjacent and running in parallel to the at least one other edge-side web of another grid module with no irradiation zone disposed between them. An improvement of at least one embodiment in this case lies in the fact that the grid webs running adjacent to one another and without an irradiation zone lying between them each have a plurality of lateral breakthroughs. In this case the lateral breakthroughs of adjacent edge-side grid webs can be arranged such that the breakthroughs of one grid web are covered in each case by the other grid web adjacent to the edge side. Furthermore the breakthroughs can be dimensioned as regards their number and distribution such that through the breakthroughs the increased scattered radiation reduction as a result of the double grid webs present is compensated for in the edge area of the grid modules. Apart from that the previously described grid modules can advantageously be used. A detector of a CT system with a modular-construction inventive scattered-radiation grid and also a CT system with such a detector is additionally proposed as part of an embodiment of the invention. FIG. 1 shows a schematic diagram of an inventive CT system 1. The CT system 1 has a first emitter/detector system with an x-ray tube 2 and a detector 3 lying opposite it and a second emitter/detector system disposed offset at an angle on the gantry not shown explicitly here, with a second x-ray tube 4 with a detector 5 opposite it. The gantry is located in a gantry housing 6 and rotates the emitter/detector systems during the scanning around a system axis 9. The patient 7 to be examined is located on a movable examination table 8, which is either pushed continuously or sequentially along the system axis 9 through the scanning field located in the gantry housing 6, with the attenuation of the x-ray radiation emitted by the x-ray tubes being measured by the detectors. The operation of the CT system 1 is controlled with the aid of a control and processing system 10, which features computer programs Prg1 through Prgn which execute the control routines necessary for operation, carry out data editing and also perform the reconstruction of image datasets. The two emitter/detector systems of an embodiment feature inventive modular-construction scattered-radiation grids which screen out the scattered radiation occurring during operation and, as exclusively as possible are intended to let the radiation emitted directly from the x-ray tubes of the respective emitter/detector system, after its attenuation by the patient, strike the detector elements of the detector. Because of the simultaneous operation of the two x-ray tubes 2 and 4 it is particularly necessary to screen out scattered radiation occurring during the operation of the tubes 2 and 4. Scattered radiation grids can especially be used for this purpose, which have webs crossing one another, as are shown in the subsequent figures. It is however also pointed out that scattered-radiation grids with webs running exclusively in parallel fall within the scope of the invention. An example of a detector 3 constructed from a plurality of detector elements D disposed next to one another like a checkerboard, with a scattered-radiation grid G lying above them comprising a plurality of webs S, is shown in longitudinal section in FIG. 2. FIG. 3 shows a known grid module GM with a number of grid webs S crossing each other at right angles in a 3D view obliquely from above. To avoid possible confusion of terms, in FIG. 4, which shows an individual grid web S in a 3D view, the length l, the height h and the depth d are entered in the diagram. FIG. 5 shows four grid modules GM disposed next to one another in an overhead view, with the webs S of grid modules GM doubling at the joint line L and thus adding to each other in relation to their overall effective depth. These grid modules GM are shown again in FIG. 6 in a view from the side. Here too it can be recognized that the overall depth of the web material—which at all points has the same wall width, i.e. depth—doubles at the joint line L, by which scattered incident radiation is increasingly absorbed. Thus the detector elements adjacent to such doubled grid webs are heavily shielded from scattered radiation and this produces artifacts in the recorded projections and thus also image artifacts in reconstructed tomographic representations. To avoid this excessive scattered-radiation reduction and the image artifacts associated therewith, by explicit introduction of gaps or breakthroughs in the outer walls, the wall thickness and thus the absorption capability of an immediately adjacent pair of grid webs can be reduced and preferably bought to the same level as that of the other centrally-arranged grid webs. In the first of the variants shown in FIG. 7-four identical grid modules GM are shown—breakthroughs O are only created or parts of walls are removed here in the φ direction of the detector module. In the z-direction the grid webs S remain at their full thickness. Overall this produces a serpentine outer wall on the grid module. At two corners in each case a freestanding end of grid web is produced. This could however also be omitted since the respective next module possesses a wall there. As a supplement an optional plastic foil F is shown on one side of the serpentine outer wall of the grid module GM, which allows a simpler assembly of the scattered-radiation grid. FIG. 8 shows a side view of the grid module GM from FIG. 7, with, at a number of longitudinal positions of the grid web to be seen on the outside, the breakthroughs O passing from the top to the bottom can be seen in the outer grid web. Overall the serpentine outer wall of the grid module GM is produced in this way. In the upper and lower area of the grid web end-to-end bars B can be seen, which during assembly of a number of grid modules GM, ensure that these do not hook into each other and thereby damage each other. FIG. 9 shows a supplementary 3D view of such a grid module GM, with—for technical reasons—the upper and lower end-to-end bars B not been shown however. A second variant of an embodiment of an inventive grid module GM is shown in FIG. 10. The structure is similar to the grid modules shown in FIG. 7-9, however the adaptation is carried out here both for the φ-outer wall and for the z-outer wall, i.e. respective outer grid web pairs lying opposite one another. Thus the entire lateral outer side of such a grid module GM has a serpentine-shaped surface structure. At the points highlighted by the dashed-line circles, however, structures are also produced in such cases (thick foot) that are mechanically sensitive, but are less susceptible however than the individual free walls occurring in the first variant (see dashed-line ellipses in FIG. 7). FIG. 11 once again shows a side view of the grid module GM from FIG. 10, with end-to-end bars “B” also being recognizable here in the upper part and lower area of the grid web to be seen, which on assembly of a number of grid modules GM, ensure that these do not hook into each other and thus damage each other. FIG. 12 once again shows a supplementary 3D view of such a grid module GM, with—for technical reasons—the upper and lower end-to-end bars B not being shown. A third variant of an embodiment of the inventive grid module GM is shown in FIGS. 13 and 14, with cutouts being made here in the outer grid webs S like a checkerboard, which are arranged offset on the respective opposing edge-side grid web. Overall the effect of these—except for the upper and lower bars present if necessary—on assembly of these grid modules GM into a complete scattered-radiation grid, is not to cause any increased shielding of the scattered radiation even at the joint lines L (seen in three dimensions: joint surface)—in relation to the remaining grid webs. In addition mechanically oversensitive parts are avoided with such an embodiment. Such a grid module can be manufactured with known technology since the currently possible minimum wall thickness of around 80 μm does not need to be exceeded. The necessary precision of manufacturing and the positioning is not influenced. Such a grid module no longer possesses smooth outer walls. Therefore it is likely to have to be handled with a little more care than previous grid modules with smooth outer walls. If such interrupted outer walls prove to be a problem to handle, a thin, slightly absorbent plastic film could be glued on as an addition. Overall an embodiment of the invention proposes a grid module of a scattered-radiation grid, a scattered-radiation grid comprising a number of grid modules arranged next to one another with a plurality of webs, especially for use in conjunction with a CT detector, a CT detector with a modular scattered-radiation grid and a CT system with such a detector, with inventively, at the joint surfaces of the grid modules the webs located there being provided with breakthroughs to compensate for disproportionate reduction in scattered radiation. Although the invention has been illustrated and described in greater detail by the preferred exemplary embodiment, the invention is not restricted by the disclosed examples and other variants can be derived herefrom by the person skilled in the art, without departing from the scope of protection of the invention. The patent claims filed with the application are formulation proposals without prejudice for obtaining more extensive patent protection. The applicant reserves the right to claim even further combinations of features previously disclosed only in the description and/or drawings. The example embodiment or each example embodiment should not be understood as a restriction of the invention. Rather, numerous variations and modifications are possible in the context of the present disclosure, in particular those variants and combinations which can be inferred by the person skilled in the art with regard to achieving the object for example by combination or modification of individual features or elements or method steps that are described in connection with the general or specific part of the description and are contained in the claims and/or the drawings, and, by way of combinable features, lead to a new subject matter or to new method steps or sequences of method steps, including insofar as they concern production, testing and operating methods. References back that are used in dependent claims indicate the further embodiment of the subject matter of the main claim by way of the features of the respective dependent claim; they should not be understood as dispensing with obtaining independent protection of the subject matter for the combinations of features in the referred-back dependent claims. Furthermore, with regard to interpreting the claims, where a feature is concretized in more specific detail in a subordinate claim, it should be assumed that such a restriction is not present in the respective preceding claims. Since the subject matter of the dependent claims in relation to the prior art on the priority date may form separate and independent inventions, the applicant reserves the right to make them the subject matter of independent claims or divisional declarations. They may furthermore also contain independent inventions which have a configuration that is independent of the subject matters of the preceding dependent claims. Further, elements and/or features of different example embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims. Still further, any one of the above-described and other example features of the present invention may be embodied in the form of an apparatus, method, system, computer program, tangible computer readable medium and tangible computer program product. For example, of the aforementioned methods may be embodied in the form of a system or device, including, but not limited to, any of the structure for performing the methodology illustrated in the drawings. Even further, any of the aforementioned methods may be embodied in the form of a program. The program may be stored on a tangible computer readable medium and is adapted to perform any one of the aforementioned methods when run on a computer device (a device including a processor). Thus, the tangible storage medium or tangible computer readable medium, is adapted to store information and is adapted to interact with a data processing facility or computer device to execute the program of any of the above mentioned embodiments and/or to perform the method of any of the above mentioned embodiments. The tangible computer readable medium or tangible storage medium may be a built-in medium installed inside a computer device main body or a removable tangible medium arranged so that it can be separated from the computer device main body. Examples of the built-in tangible medium include, but are not limited to, rewriteable non-volatile memories, such as ROMs and flash memories, and hard disks. Examples of the removable tangible medium include, but are not limited to, optical storage media such as CD-ROMs and DVDs; magneto-optical storage media, such as MOs; magnetism storage media, including but not limited to floppy disks (trademark), cassette tapes, and removable hard disks; media with a built-in rewriteable non-volatile memory, including but not limited to memory cards; and media with a built-in ROM, including but not limited to ROM cassettes; etc. Furthermore, various information regarding stored images, for example, property information, may be stored in any other form, or it may be provided in other ways. Example embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. |
|
050698613 | claims | 1. Apparatus for the remote unscrewing and extraction of a fastening screw of an element of a fuel assembly (1) of a nuclear reactor, the head of which is damaged, the screw being engaged by means of its head part (16b) in a bore (18) of a first piece (8) of the assembly (1) and by means of its threaded body (16a) in an internally threaded bore passing through a second piece (10), this apparatus comprising a C-shaped frame (34) having two branches (35, 36) substantially parallel to one another and a joining part (37) between the two branches (35) and (36), an extraction screw (40, 40', 40") engaged in an internally threaded hole passing through one branch of the frame (34) and having one end (50) forming a punch directed towards the inside of the frame (34), and a bearing and centring piece (51), the diameter of which is smaller than the diameter of the internally threaded bore of the second piece (10) and which is fastened to the second branch (36) of the frame (34) and is directed towards the inside of the frame in the axial direction of the extraction screw (40, 40', 40"), characterized in that it also possesses: a pole (32) to the end of which the C-shaped frame (34) is fastened, a ring (47) for centring the extraction screw (40) relative to the screw to be extracted (16), arranged round the extraction screw (40) over a smooth part (45) of this screw located between its threaded part and its end part (50) forming the punch, and a means (43) for the remote actuation of the extraction screw (40, 40', 40") by screwing or unscrewing. 2. Apparatus according to claim 1, characterized in that the centring ring (47) has a diameter corresponding to the diameter of the bore (18), the centring of the extraction screw (40) relative to the screw to be extracted (16) being obtained by means of the bore (18). 3. Apparatus according to claim 2, characterized in that the centring ring (45) is fastened to the extraction screw (40) adjustably in the axial direction. 4. Apparatus according to claim 1, characterized in that the centring ring (55, 62) has an inside diameter slightly larger than the diameter of the screw (16) to be extracted in its damage part, and in that a spring pushing axially towards the end (50', 50") of the screw (40', 40") is fastened to the screw and bears on the ring (55, 62). 5. Apparatus according to claim 4, characterized in that the smooth part (60) of the screw, round which the centring ring (62) is fastened, has a diameter larger than the running diameter of the screw (40") and possesses a bearing shoulder (61), on which a corresponding shoulder (63) of the centring and positioning ring (62) comes to rest. 6. Apparatus according to claim 1, characterized in that the extraction screw (40, 40', 40"), at its end opposite the punch (50), has an engagement profile (41) for the remote engagement of a screwdriver and a widened insertion part (42) for the guidance of the screwdriver in the direction of the profile (41). 7. Apparatus according to claim 1, characterized in that the screw (16) to be extracted is a fastening screw for springs (7, 27) retaining a fuel assembly (1) of a pressurized-water nuclear reactor, the first piece consisting of a flange (8), under which one end of the springs (7, 27) is engaged, and the second piece (10) consisting of a frame of the upper connector (5) of the fuel assembly (1), and in that the frame (34) is fastened to the end of the pole in such a way that its joining part (37) is in the extension of the pole (32), making it possible to carry out the unscrewing of the fastening screw (16) from the upper platform of a fuel-assembly deactivation pool. 8. Apparatus according to claim 1, for when the screw to be extracted is in a horizontal or inclined position, characterized in that the frame (34) is connected to the pole (32) in a corresponding position, and in that the means for the remote actuation of the extraction screw possesses means for adaptation and inclination in order to reach the engagement profile of the extraction screw (40). |
description | The present patent application claims priority to the provisional Application with the Ser. No. 60/965,910 that was filed on Aug. 23, 2007 all the contents thereof being herewith incorporated by reference. (a) Field of the Invention The present invention relates to a high-resolution, modular gamma or X-ray camera based on a scintillator and an image intensifier having a strong optical gain that are optically coupled to a solid state detector. (b) Brief Description of the Related Art In the field of single photon emission computed tomography (SPECT) and molecular imaging, gamma-ray detectors with high spatial resolution are used. Currently, the high-resolution requirement for such systems can be satisfied by using a gamma-ray detector based on high-speed and low-noise charge coupled devices (CCD). Such detectors yield a spatial resolution that is sufficient to satisfy the high-resolution measurement requirements. In these detectors, a scintillation flash is observed as a cluster of signal spread over multiple pixels of the CCD. A few varieties of such detectors exist and each requires the use of a low-noise, high-quantum-efficiency CCD to observe the scintillation events. Such detectors typically consist of thin scintillators optically coupled to an expensive Electron-Multiplying CCD imager (EMCCD) where charge gain is applied within the CCD pixels. A fiber-optic taper that increases the field of view can be used to increase the active imaging area but at the expense of light intensity, thus making cluster detection difficult as well as imposing a limitation of the usable thickness of the scintillation crystal for gamma-ray detection. Another system utilizes a scintillator attached to an electrostatic demagnifying tube (DM) which provides slight gain and an increase in the active imaging area, but light loss in the system requires coupling to an EMCCD via a fiber-optic taper to compensate for the losses. Another CCD-based gamma-ray detector is capable of imaging individual gamma-ray interactions using a high-efficiency optical configuration and a low-noise, high-quantum efficiency, cooled CCD imagers. Substantial disadvantages of this system are that it only works with relatively thin scintillators that are less sensitive, and the CCD used for the detection must be configured to use long readout time for reduced noise which greatly reduces the frame rate capability of the system. Despite all of the above mentioned improvements in the field of gamma-ray detection as discussed above, there is a strong need for increased sensitivity and read-out frequency of the measured scintillations to detect gamma-ray sources for many different applications, such as small-animal SPECT and molecular imaging. Advances in systems are therefore strongly desired requiring high-resolution, high-speed, and highly-sensitive gamma-ray detectors, without substantially increasing the costs of such a system. One aspect of the present invention provides a gamma-ray detection device. Preferably, the gamma-ray detection device includes a scintillator configured to convert the gamma-rays into optical radiation, an optical image intensifier configured to intensify the optical radiation to generate intensified optical radiation, and an optical coupling system configured to guide the intensified optical radiation. In addition, the gamma-ray detection device preferably further includes a solid state detector configured to detect the intensified optical radiation to generate an interaction image representing an energy emission of the gamma ray. According to another aspect of the present invention, a method of estimating the horizontal position, the vertical position, the depth, and the energy of an interaction of the gamma ray in a scintillator is provided. The method preferably includes the steps of absorbing a gamma ray in a scintillator to convert gamma-ray energy into optical photons to produce an optical image on a rear surface of the scintillator, intensifying the optical image to produce an intensified image, projecting the intensified image onto an image sensor, and capturing the intensified image and converting the intensified image into a digital data image. In addition, the method preferably further includes the step of processing the digital data image by a maximum-likelihood estimation to estimate the horizontal position, the vertical position, the depth, and the energy of the interaction of the gamma-ray in the scintillator. According to yet another aspect of the present invention, a system for capturing tomographic imaging data is provided. The system preferably includes a plurality of aperture plates arranged around an inspection area, the plates having at least one pinhole. In addition, the system preferably includes a plurality of gamma-ray detection devices that are arranged around the inspection area so that a plurality of respective optical axes of the plurality of gamma-ray detection devices intersect with the inspection area, the plurality of aperture plates arranged between the detection devices and the inspection area. In addition, in the system preferably each of the plurality of gamma-ray detection devices is arranged at a different angle of orientation towards the inspection area. According to still another aspect of the present invention, a gamma-ray detection apparatus is provided. The detection apparatus preferably includes a scintillator configured to convert gamma rays into optical radiation, a first optical image intensifier configured to intensify optical radiation from a first portion of a rear surface of the scintillator to generate first intensified optical radiation, and a second optical image intensifier configured to intensify optical radiation from a second portion of the rear surface of the scintillator to generate second intensified optical radiation. Moreover, the apparatus preferably also includes a first and second optical coupling system configured to guide the first and second intensified optical radiation, respectively; and a first and second solid state detector configured to detect the first and second intensified optical radiation to generate a first and second interaction image, respectively, representing a gamma-ray energy emission. The summary of the invention is neither intended nor should it be construed as being representative of the full extent and scope of the present invention, which additional aspects will become more readily apparent from the detailed description, particularly when taken together with the appended drawings. Herein, identical reference numerals are used, where possible, to designate identical elements that are common to the figures. The images in the drawings are simplified for illustrative purposes and are not depicted to scale. In accordance with the present invention, a gamma camera is schematically illustrated in FIG. 1, and is referred to throughout by reference numeral 10. First, a scintillator 20 is arranged that can convert the gamma rays or X rays from a corresponding source into optical radiation, such as visible light, to form a light emitting pattern or image on a rear surface of scintillator 20. Scintillator 20 is coupled to an image intensifier 30 that can amplify light emitted by scintillator 20. An interface between scintillator 20 and image intensifier 30 is arranged to minimize light loss and distortion between these two elements. After the image intensifier 30, an optical system 40 is arranged, for example an objective lens that can either magnify or minify an image formed by the amplified light. The image formed by the optical system 40 is then focused on an image sensor of a detector 50 that is connected to the optical system 40. The detector 50 is configured to read out a measurement image that measures the light emitting pattern produced by the scintillator, and further data and image processing can be performed on the measurement image. Gamma camera 10 can be used for various applications, such as molecular imaging with radiotracers, for example small-animal SPECT imaging. A gamma-ray microscope can be designed based on the gamma camera 10. In addition, the present invention is also useful for non-tomographic imaging of isotopes. It can provide a very high resolution compared to conventional systems. With respect to FIG. 2, a cross-sectional schematic view of a gamma camera 10 is shown. Along a propagation path or optical axis 12, the scintillator 20 arranged in the front end is used to absorb gamma rays or X rays from an emitting source 72 and can convert the absorbed rays into wavelengths readable by optical sensors, such as CCD or CMOS image sensors. In the variant shown, source 72 is a mouse that was injected with a tumor-seeking radioactive tracer. In the remaining portions of the description we will refer to gamma rays, but X rays can also be detected and processed by the gamma camera 10, and an X-ray camera is therefore a variant of the present invention. At a back surface 24 of the scintillator plate 22, a light emitting pattern is generated that produces light in the visible spectrum, produced by the crystals of the scintillator. The light emitting pattern typically produces light in the wavelengths between 300 nm and 1000 nm. The gamma rays may exit from a pinhole 73 of an aperture plate 74. An aperture plate 74 having multiple pinholes producing overlapping images can also be used. Plate 74 is arranged between scintillator 20 and gamma-ray source 72 to form an image of the radioactive source distribution producing the gamma rays. By way of an example, pinhole 73 may have a diameter between 100 μm and 1000 μm in an aperture plate 74 having a thickness of 1 mm made of lead, in the case that high-energy gamma rays are used. In a variant, the aperture plate 74 may be made of a thin sheet of platinum have a thickness between 25 μm and 50 μm sufficient to block low-energy gamma-rays (30 keV). Small pinholes provide a large field of view because of the small thickness of the platinum, and they can be used to provide high resolution imaging with high gamma-ray collection efficiency. The scintillator 20 can be a columnar or structured scintillator, a polycrystalline screen of the type used in X-ray detectors, or a monolithic single crystal. A scintillation screen can also be used. The scintillator can also be made of elements of segmented crystals. Many different materials can be used for manufacturing the scintillator, the non-exclusive list includes columnar cesium iodide (Thallium) CsI(Tl), CsI(Na), NaI(Tl), LaBr3(Ce), gadolinium oxysulfide (Gd2O2S), also known as Gadox. The scintillator absorbs the rays at a certain interaction depth. A scintillation event has a duration of about 100 ns to 1 μs, depending on plate 22. In case gamma rays of higher energies have to be detected, the thickness of the scintillator plate 22 in a direction to the propagation path 12 is chosen relative thick. For example, the CsI(Tl) columnar scintillators preferably have a thickness between 100 μm and 3 mm, depending on the gamma-ray energy. More preferably, for such columnar scintillator the thickness is in a range between 2 mm and 3 mm for energies 140 keV photons from 99mTc. In the case Gd2O2S scintillators are used, they preferably have a thickness between 50 μm and 100 μm. Other types of scintillators can also be used that can convert rays of a photon energy of a range of 20 keV to 1 MeV into optical radiation, such as visible light. Other types of rays can be converted to photons, such as α and β rays. With such plate thicknesses, gamma-ray energies of up to several hundred keV can be detected. For example, it is possible to use energies of 511 keV that are available from the isotope fluorine-18. Further improvements in scintillator material technology and manufacturing techniques will allow the production of even thicker scintillator plates 22 that could be used for detectors that could absorb even higher gamma-ray energies. After the scintillator 20, an optical coupler 26 and an image intensifier 30 are arranged so that the scintillator image generated on back surface 24 of plate 22 can be guided by an optical coupler 26 to enter a front surface 31 of the image intensifier 30. The optical coupler can be a fiber optic taper that can have a magnification or a minification ratio. In such configuration, rear surface 24 of plate 22 is in direct contact with the front surface of the fiber optical taper, and a back surface of the taper can be in direct contact with the front surface 31 of light intensifier 30. In an alternative, optical coupler 26 is made of a fiber-optic faceplate or a thin window. For example, the optical coupler 26 can also be a lens with a high numerical aperture NA, in the range of 0.5 to 1. In another variant, the back surface 24 of the scintillator plate 22 and the front surface 31 of the image intensifier 30 are directly coupled to each other without the use of optical coupler 26. The main goal of the optical interface between the scintillator 20 and the image intensifier 30, that is formed by either coupler 26, direct contact, high-efficiency lens coupling, or a combination thereof, is to minimize the light loss of the light emitted from the back surface 24 of the scintillator before entering intensifier 30. The configuration where the light exiting the scintillator 20 is immediately amplified by a light intensifier 30 is an important feature of the invention, because it provides a strongly amplified light or optical radiation from the scintillation event, that allows accurate estimation of a horizontal position, a vertical position, and a depth of interaction, and photon energy of the interaction of gamma ray source, based on the light emitting pattern captured as a cluster. In addition, it allows for the use of an inexpensive CCD/CMOS detector to capture scintillation events capable of running at rapid frame rates. The scintillator image is amplified with image intensifier 30 by a luminous gain in a range between 104 and 107. The image intensifier includes a photocathode 32 at the light entrance side, having a front surface 31, made, for example, of at least one of Bialkali Antimonide, Multialkali Antimonide (for example S20), Multialkali Antimonide (for example S25), Gallium-Arsenic-Phosphorus (GaAsP), or Gallium Arsenide (GaAs), depending on the required luminous gain, resolution, and spectral matching requirements of the photocathode 32 and the scintillator 20. Other types of image intensifiers can also be used. After the photocathode 32, a micro-channel plate 34 (MCP) is arranged. In a variant, dual or multi-stack MCPs may be used to further intensify the luminous gain. For example, it is possible that a two-stage or two-stack image intensifier 30 is used, having two MCPs in series to add additional amplification. A fluorescent screen 38 at the exit of the image intensifier 30 produces an amplified, fluorescent image 76. A high voltage source 36 provides for the required electrical fields for the image intensifier 30. The rear face of image intensifier 30 can be configured for interconnection to standard optical lenses, such as C-mount, CS-mount, F-mount, K-mount lenses, etc. with various focal lengths. An exemplary image intensifier 30 that can be used is a military surplus AN/PVS-4 image intensifier having a single stage micro-channel plate, having 25 mm input and output active diameters, an S25 photocathode, and a fluorescent screen 38 made of P-43 phosphor. After intensifier 30, the amplified image enters optical system 40 that is connected to intensifier 30. The optical system 40 can be made of multiple lenses 44 in a casing 42 that can magnify or minify the amplified image to project a measurement image onto an image sensor 52 of detector 50. The strong optical gain from the image intensifier 30 allows a flexible and customizable optical system 40 for various application requirements. For example, the optical system 40 can be freely chosen for the particular application, and due to large optical gain by intensifier 30, it is not necessary to use an optical coupling with very low light loss and/or low distortion. For example, a special configuration having different magnification or minification of the optical system 40 of the amplified image may be required. As an example, a first 50 mm lens and a second 400 mm lens from the manufacturer Nikon is used that are mounted in series, having a magnification of 1:8 so that small, inexpensive CMOS image sensors can be used. As another example, two 50 mm F/1.2 Nikkor lenses can be mounted face-to-face that can provide for a 1:1 magnification. The optical detector 50 is arranged such that the focal plane of the image exiting the optical system 40 is projected on an image sensor 52 of the detector 50. After the scintillation event with the light emitting pattern is amplified via the image intensifier 30, a reduction of image intensity by the optical system 40 results, but the remaining image impinging on image sensor 52 is still strong enough that the noise and light loss of optical system 40 will not substantially affect the image capturing process and the measurements on the captured image. Therefore the image sensor 52 used by detector 50 need not to be very light sensitive. Standard CCD imaging sensors will be sufficient to generate an image that can be used for various measurements. Other types of solid state imagers such as CMOS imagers, thin-film imagers, etc. can also be used. In addition, with the gamma camera 10, no cooling of the image sensor 52 is needed that would substantially increase the costs of camera 10. The image sensor 52 of detector 50 is coupled to driver unit 54 that is configured to read out the images that are captured by the image sensor 52. For example, all the CCD drivers, clock signal generators, supply and reference voltage generators, analog-to-digital converters, timing signal generators, memory buffers, etc. can be part of the driver unit 54. Driver unit 54 itself can be coupled to a processing unit 56 that can perform data and image processing on the images that are captured by the image sensor 52. The processing unit 56 includes a processor and memory that is configured to store computer-readable instructions that are able to perform various data processing, visualization and communication functions, when the instructions are executed on a processor. The memory can be volatile or FLASH memory, or a combination thereof. In addition, processing unit 56 may also include hardware-coded image processing chips, field-programmable gate arrays (FPGA), or complex programmable logic devices (CPLD) that can perform data processing such as image processing, feature extraction, statistical algorithms, and calibration algorithms, etc. For example, unit 56 may perform image filtering such as median filtering, image calibration, background image sensor noise calibration, statistical image analysis, center-of-gravity calculations, estimation, look-up table generation and management, etc. In addition, the detector 50 may include an interface 58 that can communicate with an external device 59 or deliver images for visualization to an external screen. For example, raw image data or pre-processed image data can be transmitted to a personal computer or a specialized graphics computer for further processing, calibration, visualization, storage, and archiving. External device 59 may include a data reader 57, for example a Universal Serial Bus interface or a CD-ROM drive, and a computer-readable medium 55, for example a CD-ROM, DVD-ROM, USB flash drive, floppy disk, etc. can be read, written and erased by data reader 57, and a program stored on the medium 55 having computer-readable instructions can be transferred and executed on external device or unit 56. Tests have shown the surprising results that by applying a strong optical gain at the beginning of the camera 10 just after the conversion of gamma-rays into light, instead of applying a substantial charge gain by using sophisticated image sensors 52 in the last stage of camera 10, the system is much less limited by light loss and allows great flexibility in the design of camera 10. Because of the strong luminous amplification by the image intensifier 30 of camera 10, and the efficient optical coupling of the scintillator 20 to the image intensifier 30, the light losses of the optical system 40 and the detector 50 are no longer significant comparing to the resulting intensified image. Therefore the design emphasis of the image sensor 52 can be put on relatively low-cost sensors that allows a high read-out speed, instead of having to use low-noise and highly sensitivity imagers, that may also require additional cooling, which can be very expensive. In the variant shown, a Point Grey Research™ Flea 2 was used, having a resolution of 696×516 pixels, with 9.3 μm square pixels to facilitate measurements and capable of operation at 200 fps or 350 fps with 2×2 binning. In another variant, a SBIG Inc. STL-1001E camera was used having a KODAK™ image sensor KAF-1001E CCD with 1 k to 1 k pixels, and with square pixels with a size of 24.6 μm. Of course other image sensors of different technologies may be used, with other pixel sizes, pixel technologies and resolutions. This combination of the use of the light intensifiers and low-cost detection units has lead to surprising and unexpected results allowing wide range of applications for different radiation energies. For example, the gamma camera 10 according to the invention leads to a substantial reduction of costs for detector 50 and image sensor 52 that are used to capture and measure scintillator events on the plate 22. In addition, lower-cost optical systems 40 can be used to couple the output screen 38 of the image intensifier 30 to a detector 50, allowing further cost reduction. Test results with a gamma camera 10 show that an intrinsic resolution to detect pinholes on plate 74 by the detector 50 is approximately 70 μm, an unexpected result in light of the available background art systems that use high-speed and low-noise imaging detectors. By choosing a different pinhole magnification, the resolution of gamma-ray projection images can be increased. The high-intrinsic resolution of the detector allows camera 10 to function as a gamma-ray microscope with the use of micro-coded apertures. Planar reconstructions have been achieved yielding an estimated reconstruction resolution to approximately 30 μm. In addition, the camera 10 is also designed to operate over a wide range of gamma-ray energies based on the scintillator plate thickness and light amplification. It has been demonstrated that the gamma camera 10 is capable of measuring radiation from isotopes used in small animal SPECT such as 125I having approximately 30 keV gamma-rays, 99 mTc with 140 keV gamma-rays, and 111In with both low energy X-rays (24-26 keV) and high energy gamma-rays (171 and 245 keV), and such results were unexpected in light of the existing solutions. Moreover, gamma camera 10 according to the present invention also proposes an attractive, inexpensive modular design for the camera that can be used for high-resolution, multiple-pinhole applications such as molecular imaging and nuclear imaging, and the potential to be used as detectors in clinical SPECT imagers. Another advantage of the configuration of camera 10 is the ability to use ultra high-speed cameras with less sensitivity. The use of high frame rates permits the detection of high flux of gamma-rays without overlap of the clusters of pixels that are associated with different gamma rays. Thereby more information can be gathered and the detection resolution, precision and sampling frequency can be improved. The proposed gamma camera 10 has therefore a much higher count-rate capability for photons than cameras based on EMCCD sensor. An additional aspect of the present invention is the processing unit 56, and the methods of processing the image data that is captured by the gamma camera 10 that can be performed by such processing unit 56. As discussed above, the methods of processing the image data can also be performed on external device such as a processing system 59, such as a personal computer, a parallel supercomputing processing system, dedicated graphics processing system, etc., or the processing unit 56 can also be a separate unit located outside of camera 10, but in communication with the camera 10. Special estimation techniques and combined with data processing algorithms that can be performed in real time can be implemented. The gamma camera 10 is particularly suited for high energies of gamma-ray sources, because thicker scintillator plates 22 can be used, that absorb much higher energies, but also blurring of the light emitting pattern on the back surface 24 of plate 22 can be caused, thereby reducing a detector resolution depending on the depth of interaction. However, by the use of special estimation and processing algorithms with camera 10, it is possible to precisely calculate an effective horizontal position, a vertical position, and an energy of interaction of a gamma-ray inside a scintillator plate 22, as well as the depth of interaction (DOI) based on a light emitting pattern captured as image data in form of a cluster. By calculating or estimating the DOI, these effects of scintillator plate 22 can be compensated for. For example, as illustrated in FIG. 3, gamma-rays pass through a pinhole 73 of a plate 74 after being emitted by source 72, the rays may not progress perpendicularly from the aperture plate 74, but progress from pinhole 73 in different directions. These rays will impact and interact with the scintillator plate 22. In addition, the depth D, of the scintillator material allows that the rays will be absorbed at different depths 84, 85, mostly depending on the energy intensity of the gamma-ray, but also depending on the impact angle, and the material impurities and inconsistencies of plate 22. This penetration depth of the rays is called the Z-axis position or depth of interaction (DOI) of the gamma-rays. The scintillator 22 can be considered to be made of homogeneous material with an attenuation coefficient μ which depends on the photon energy and the material. A fraction 1-(1/e) of the gamma photons, where e is equal to 2.718, are absorbed in a distance of 1/μ. At normal incidence, this distance is also approximately the range of the depths of interaction, but at oblique incidence the range of DOI is less than the absorption distance. DOI effects are observed in the clusters of imaging data from the image sensor 52 showing variability in the light intensity of the captured image, spatial variance, and kurtosis (peakedness), and other features, based upon gamma-ray DOI within the crystals of the scintillator plate 22. In the case a columnar scintillator is used, scintillation light is partially guided towards the rear surface 24 of the scintillator plate 22, the light output varies as a function of the interaction depth. In other types of scintillators, for example scintillation screens made of Gadox and other X-ray phosphors, the light is scattered rather than guided, and for monolithic single crystals there is light spread during propagation from depth of interaction to the intensifier 30. For example, ray 85 that is absorbed at a deeper location than ray 84 will produce a brighter and less blurred light emitting pattern 37 on the back surface of the scintillator plate 22. The combined effect of the variable interaction depth and variable angle of impact of the gamma rays exiting from a pinhole 73 will produce such light emitting pattern 37 on the back surface 24 of the scintillator 20. Information of the light emitting pattern 37 that is projected onto the intensifier 30 can be subjected to calculation and estimation techniques to estimate the DOI, after capturing by sensor 52 as a cluster. Accordingly, by using captured image data information from sensor 52 where a cluster represents a light emitting pattern 37, a four-dimensional parameter set including the effective horizontal position, vertical position, depth, and energy of an interaction of a gamma-ray can be calculated. This data can be represented by four different values as a interaction parameter set including X, Y, Z and E. However, it is also possible to first calculate features from the raw image data of the clusters, and then calculate the interaction parameter set from these features. For example, the raw image data of the clusters can be reduced to features such as a sum of all pixel amplitudes of pixels forming the cluster, spatial variance, location of the cluster, kurtosis representing how “peaked” a cluster is, etc. Moreover, the precision of the calculation of the interaction parameter set can be improved by using advanced statistical estimation methods, such as the use of a maximum likelihood estimation technique to estimate the parameter set from either the raw image data of the clusters, the features of the cluster, or both. The following description with respect to FIGS. 4A, 4B, 4C, 4D, 5, and 6, includes information related to the captured image data of detector 50 including clusters 92 representing light emitting patterns 37 and their relationship to the interaction parameter set. FIG. 4A represents an unprocessed captured image of the gamma camera and FIGS. 4B, 4C and 4D represent a series of processed image of the camera after performing image processing such as filtering by the processing unit 56. When gamma camera 10 captures images from rear face 24 of plate 22, the captured image 96 includes a series of clusters 92 and noise that is scattered throughout the unprocessed image 90. In order to improve the precision of the calculated or estimated interaction parameter set X, Y, Z, and E, the unprocessed image 90 can be subjected to various steps of filtering to obtain a processed image 96, thereby substantially removing the noise 93. Continuous regions of pixels form clusters 92 that represent gamma-ray interactions, and these cluster includes information that can be processed to extract an interaction parameter set X, Y, Z, and E for a particular interaction event. Several of such clusters 92 are shown in FIG. 4A, each representing a gamma-ray that traversed a pinhole and absorbed by plate 22. First, the unprocessed image 90 can be subjected to a noise removal filter, for example a median filter resulting in a filtered image shown in FIG. 4B. Other filter algorithms can also be used, such as low-pass filters, fixed pattern noise removal filters eliminating noise introduced by image sensor 52 of detector 50, calibration algorithms compensating optical distortions from the optical system 40 and intensifier 30, etc. Next, the image of FIG. 4B can be subjected to clipping with a thresholding algorithm to generate a processed image 96, and a component labeling algorithm may identify the clusters, as shown in FIG. 4C. Based on the processed image 96, the parameter set X, Y, Z, and E can be calculated or estimated in a next step, where the location of the interaction in X and Y direction is obtained as shown in FIG. 4D. Each calculated or estimated interaction position is shown in its X-Y position with a small dot. FIG. 5 depicts an exemplary diagram showing a method of calculating or estimating the interaction parameter set X, Y, Z, and E, according to another aspect of the present invention. In a first step S10, a gamma-ray interacts in the scintillator plate 22 and produces a light emitting pattern 37 on the back surface 24. Next, in step S20 the pattern 37 is directly amplified or intensified by intensifier 30. In step S30, the intensified light is projected to an active surface of image sensor 52 by an optical coupling system such as a lens, and the image is then captured by the image sensor 52 and converted to digital image data in step S40 for further processing. In a first pre-processing step S50, the digital image data is subjected to filtering and noise removal as described with reference to FIGS. 4A and 4B. Other pre-processing steps can be performed, such as compensation of distortions. Thereafter, in optional step S60 regions of interest (ROI) are identified that include clusters 92 representing light emitting patterns 37, as explained with respect to FIG. 4C. This step is also referred to as frame-parsing. It is also possible that first the ROI are identified with clusters 92 with step S60, and then the filtering step S50 is performed, depending on the quality of the unprocessed captured image. In case the captured image has too many clusters, and therefore identification of ROI would not be beneficial, it is possible to perform full frame processing to directly proceed to step S80. To identify such ROI of the images captured by detector 50, a search algorithm can be implemented by processing unit 56 that searches the captured image and detects ROIs that include clusters 92, to avoid that data of an entire image frame is subjected to such calculations or estimations. In an example of such search algorithm, first a step including a coarse search can be performed over the entire image in a grid of reduced resolution, by using a log-likelihood algorithm to detect presence or absence of a cluster 92. In another step, locations having the highest likelihood above a certain threshold are selected, and a new local search can be performed with a higher resolution to find the exact positions of the clusters. In another step, based on the location information, a ROI can be defined that will include the cluster 92. Preferably, ROIs with a size ranging from 3×3 to 15×15 pixels can be further processed, allowing a substantial increase in processing speed comparing to an implementation where the entire image is processed. Of course other types of searches or detection algorithms can also be performed to detect the clusters 92 of an image. It is also possible to use an image sensor 52 that allows the read-out of only a partial frame or a plurality of partial frames, without having to read out the entire image having a full resolution. Such image sensor readout method could be combined with the search methods to detect the cluster location. Once the location of a cluster is detected by a coarse search, for example by using the sub-sampling or pixel binning capabilities of a sensor, partial images including clusters could therefore be read-out at a substantial increased speed, by using the windowing function of the sensor. In an example, the reading out of four ROIs with a pixel area of 32 to 32 pixels from an image sensor with 1024 to 1024 resolution results in a potential speed-up of the read-out process by a factor 256. In a next optional step S70, the raw image data of the ROIs including the clusters can be reduced by being subjected to feature extraction algorithms, where different features of a cluster 92 may be extracted. The features may include calculation of the sum of all pixels in the cluster, the centroid of clusters, spatial variance, kurtosis, circle-symmetry of a cluster, etc. These features can be calculated from each captured image, and need not to be based on statistical properties. For example, in step S70, it could be possible to implement an algorithm to eliminate two gamma-ray interaction events that occurred in close proximity to each other, thereby producing overlapping clusters, that would be detected as a single cluster. By calculating a features that represents a degree of circular symmetry (eccentricity) of the cluster, overlapping multiple clusters could be eliminated, because a single cluster would have a higher degree of circular-symmetry. In step S80, the parameter set including the position and the energy of a gamma ray interaction is calculated, for example by using the sum of pixels to calculate the energy of the interaction, and the location of the centroids to calculate the interaction position. It is also possible to use a maximum-likelihood estimation using 2D spatial Gaussians fits to find the X, Y interaction location. Moreover, special techniques to estimate the parameters can be used, as further described below. These parameters representing the interaction position and energy can either directly be calculated from the image data from the ROIs of step S60, or from the image features of the optional step S70, thereby using a reduced data set. Other factors that may influence the calculation of the parameter set may be the configuration and hardware parameters of the image sensor 52. The parameters of the image sensor can be pixel delay time constants, integration time, frame rate, shuttering methods, etc. In step S90, further processing can be applied to the parameter set, such as calculation of visualization data with three-dimensional graphics processing, storage, analysis, data communication, etc. An example of processing that can be performed in step S50 is a removal of distortions introduced by intensifier 30. Intensifier 30 can introduce artifacts to an intensified image. While some of these can be compensated for, others can be used as parameters to design the camera 10 and the operation conditions. Artifacts that may be introduced are lag, vignetting effects, pincushion distortion, and the S distortion, depending on what type of intensifier 30 is used. The lag of an intensifier 30 is the persistence of luminescence that acts like a low-pass filter on the light emitted from back face of intensifier 30, and can be expressed as a time constant. This time constant may limit the precision of the calculation of the interaction position and energy, and can also limit the frame rate that is usable. The time constant may also increase with the lifetime of the camera 10. Vignetting is an effect that causes a fall-off in brightness at the periphery of an intensified image, is caused by the concentrated collection of light at the center of the image intensifier 30 around the optical axis 12 compared with the light at a periphery. Therefore it is possible that intensifier 30 has a better resolution, increased brightness, and less distortion around the optical axis. The intensifier 30 may also cause geometric distortions such as the pincushion distortion and the S distortion. Pincushion distortion is a geometric, nonlinear magnification across the image, where a magnification difference at the periphery of an intensified image and can be caused by intensifier 30 and the optical system 40. The S distortion of the intensified image is caused when electrons inside intensifier 30 move in paths along designated lines of flux. External electromagnetic sources affect electron paths at the perimeter of intensifier 30 more so than those nearer the optical axis 12. This characteristic causes the exiting intensified image to distort with an S shape. Intensifiers with larger diameters are more sensitive to the electromagnetic fields and thereby show increased S distortion. The processing unit 56 or external device 59 can be configured to store calibration data and algorithms to compensate for the artifacts that are introduced by intensifier 30, to further increase a detection precision of camera 10. In particular, the geometric distortions, and the distortions of image intensities such as the vignetting can be compensated. Based on the optical information included in a cluster 92 that represents a light emitting pattern 37, processing unit 56 can estimate an interaction parameter set X, Y, Z, and E. Each cluster 92 corresponds to one interaction event at a certain time instant that is captured by a readout frame from image sensor 52. Such estimation techniques yield higher accuracy of the interaction parameters comparing with the use of a centroid and the sum of pixels to calculate the position and energy of the interaction. For further explanation FIG. 6 is presented showing more detail of the image clusters that can be generated by thee different gamma-rays γ1, γ2, and γ3 of different energies. The Z-coordinate relates to the depth of interaction (DOI), and the Z-axis is parallel to an optical axis 12 of the gamma camera 10. The X and Y coordinates refer to a Cartesian coordinate system of the planar surface of the image sensor 52, representing a horizontal and a vertical position. It can be seen that the gamma-ray γ3 that interacts at a deeper DOI in the columnar scintillator statistically produce a stronger light cluster signal with less variance of the pixels in X and Y direction, while the gamma-ray γ1, that interacts at a shallower DOI in the scintillator produces a weaker light cluster signal of less light intensity, it also has more variance in an X and Y direction. The respective light intensity profiles for the clusters 92 (γ1), 92 (γ2) and 92 (γ3) are also represented, and show the decreasing intensity and increasing variance with for decreasing DOI values. This information included in a cluster can be subjected to statistical analysis, to extract highly precise information to estimate parameter sets X, Y, Z, and E. Therefore, according to another aspect of the present invention, the captured image data representing a cluster can be subjected to a maximum-likelihood estimation (MLE) algorithm that will produce an interaction parameter set X, Y, Z, and E for an effective interaction. This processing can be part of step S80. Although more processing is required comparing to a simple centroid calculation, the use of an MLE according to this aspect of the invention will provide increased resolution of the interaction parameter set X, Y, Z, and E. The result of the MLE estimation are the values of Z, Y, Z and E that maximize the probability of the data conditional on X, Y, Z and E for the observed data in each cluster. A likelihood function is a conditional probability of the data given a set of parameters, denoted generally as Prob(data | parameters), where the data are a set of experimental values and the parameters are the unknown quantities to be estimated. In our case, the data are either the pixel values in a captured cluster 92 or a set of features derived from the cluster 92. The unknown parameters are the X, Y, Z and E for the scintillation event that produced the cluster. Maximum-likelihood estimation then chooses the X, Y, Z and E that maximizes prob(data | X, Y, z, E) for the data values that are actually observed for the cluster. The proposed MLE also needs calibration data, that can be stored and pre-processed by the processing unit 56 or external device 59. For this purpose, a series of calibration measurements with a calibration aperture sheet with several pinholes or with a collimated beam can be taken that will be used for the MLE algorithm. The calibration data can be made specific to every single camera and could take several inconsistencies into account from the entire optical path, such as missing pixels, optical distortions, inhomogenities of the light intensifier 30, etc. The calibration data could therefore incorporate information compensating optical distortions introduced by intensifier 30 and optical system 40, and therefore no other optical calibration algorithms would be required. When generating calibration data for the MLE algorithm, a mean cluster template set can be generated for each depth of interaction in the plate 22, for a range of different gamma-ray intensity energies. In addition, multiple mean cluster templates can be generated for various X and Y positions of the interaction event in the plate 22. This may particularly be interesting to compensate for non-homogeneities in X and Y direction of different scintillator plates 22, and can be a camera-specific calibration. For the same energy, position, and depth of interaction, many samples of clusters can be stored and a mean cluster value can be generated. To generate such data, a set of features from image date from a cluster 92, including a sum of all pixels included in the cluster, spatial variance of the cluster, and kurtosis can be assigned by a table to a particular interaction parameter set X, Y, Z, and E for an effective interaction. The table can be stored in each camera 10 and can be used as a look-up table to speed up processing of data. Therefore, by calculating a set of features from cluster 92, it is possible to directly obtain the interaction parameters by the use of the look-up table. As an example for calibration data that can be used for the MLE, FIGS. 7A to 7B represent a series of measurements performed by the gamma camera 10 at different time instants with a beam formed by a collimated gamma ray source. In these measurements, clusters 92 were generated on a plate 22, and the clusters are captured by sensor 52 are represented as a sum signal and the cluster pixel variance that are spread out in X and Y direction is represented as a function of the DOI in plate 22. From FIG. 7A is can be seen that with increased DOI, the signal intensity statistically increases, but there is still a strong variance of different possible signal intensities. As shown in FIG. 7B the pixel variance of a cluster decreases linearly with increased DOI, but again there is a strong variance in the obtained measurements. The representations of FIGS. 7A and 7B further support the use of statistical algorithms based on calibration data that can improve the precision when calculating an interaction parameter set X, Y, Z, and E, to reduce the effects of data spread over time. FIGS. 7C, 7D, and 7E schematically represent different features that can be extracted from the image data of a cluster 92. FIG. 7C represents the kurtosis of clusters, as a function of the depth of interaction in plate 22. With increased depth of interaction, the kurtosis value increases from about −1.05 to −0.6 linearly. FIG. 7D depicts the spatial variance of clusters 92 as a function of the spatial variance. Decreasing spatial variance signifies a deeper interaction depth. FIG. 7E shows the cluster sum signal as a function of the depth of interaction, showing an increasing sum signal for deeper interaction depths. In other words, if a gamma-ray interactions at a deeper depth closer to the rear surface 24 of scintillator plate 22, the clusters 92 appear brighter, but become statistically smaller in diameter. FIG. 8 depicts a three-dimensional representation of a series of three-dimensional estimations of interaction positions of individual gamma rays forming a beam through the scintillator from a collimated gamma-ray source. The collimated beam was incident to the scintillator plate 22 at an angle, and therefore samples of various penetration depths within the crystal of the plate 22 are generated. The Z-axis represents a depth of interaction of the gamma-ray, and the X and Y axis represent the horizontal and vertical positions of the interaction on the plate 22. Because the angle of arrival of the collimated beam and the energy is known, a mean cluster template, dependent on depth of interaction within the scintillator, is generated from many interactions and serves as calibration data. Preferably, 10,000 to 100,000 gamma-ray interactions from the collimated beam are taken for calibration purposes, from the same energy level. Thereafter, a given cluster generated by a particular gamma-ray interaction is identified and the mean cluster template is used to find the maximum-likelihood thee-dimensional position and energy estimate for interaction. The data processing of clusters 92 to extract the interaction parameter sets may require substantial processing power, especially if real-time processing for three-dimensional visualization is required. Such processing can be performed in the processing unit 56 or an external processing device 59. For example, steps S50 and S60 including the pre-processing with calibration, filtering and ROI detection can be performed in the processing unit 56, while steps S70, S80 and S90 requiring higher processing performance, including MLE and three-dimensional reconstruction can be performed in the external processing device 59. Memory of the processing unit 56 or external device 59 can be used to store extensive calibration data for a camera 10, and to create look-up tables that can increase the computing performance when performing an estimation. Another embodiment of the present invention is shown in FIG. 9, where multiple gamma cameras 110a, 110b, etc. are exposed to an inspection area 272 where a gamma-ray source is arranged, to form a system for capturing three dimensional imaging data that can be used for tomography. The inspection area is thereby viewed from different angles, which allows three-dimensional measurements from the inspection area. In the variant shown, a multitude of gamma cameras 110a, 110b, etc, are arranged concentrically around the inspection area, and the angles of the optical axes between each gamma camera are substantially the same. The optical axes of each camera 110a, 110b, etc. are arranged such that they intersect with the inspection area that is arranged in the center. For each gamma camera 110a, 110b, etc, a pinhole 273a, 273b is arranged with a respective aperture plate 274. The aperture plate 274 is arranged concentrically around the inspection area. A distance between a front surface of the gamma camera 110a, 110b and the corresponding aperture plate 274 is in a range between 2 mm to 200 mm. A processing unit 160 can be connected to the gamma cameras 110a, 110b, etc. and can process the image information that has been collected from all the gamma cameras, for example to perform three-dimensional imaging and displaying results thereof. In another embodiment as shown in FIG. 10, a cross-sectional diagrammatic view of a gamma camera system 200 is provided, where a scintillator plate 222 having a large surface is inspected by multiple detectors 250a, 250b, 250c, in a tiling configuration. The rear surface 234 of the plate 222 can have a size of 15 cm to 15 cm, but even bigger plates for clinical purposes could be used. For purposes of clarity, only three detectors 250a, 250b, 250c are shown in a vertical direction, but any number of detectors are also possible, for example the same number of detectors in horizontal direction, thereby having a total of nine detectors inspecting one scintillator plate 222. The rear surface 224 of scintillator plate 222 has different areas or portions that can be inspected by multiple detectors 250a, 250b, 250c. In the configuration shown fiber optical tapers 226a, 226b, 226c are in direct contact with surface 224 and guide optical radiation from surface 224 to image intensifiers 230a, 230b, 230c, respectively. In another variant, other types of optical elements can be used instead of tapers 226a, 226b, 226c, for example lenses with prism assemblies, or lenslet arrays for the particular configuration of tiling. With such lenses or lenslet arrays, it is possible to have overlapping inspection areas of back surface 224, to avoid loss of information at an interface of two inspection areas. The light intensifiers 230a, 230b, and 230c are connected to respective optical coupling systems, 240a, 240b, 240c, for example C-mount lenses. In turn, the optical coupling systems 240a, 240b, and 240c are connected to detectors 250a, 250b, 250c that can read the optic radiation emitted from the rear surface 224 of scintillator plate. The detectors 250a, 250b, 250c may be connected to a processing unit 260 that allows processing of the information gathered by detectors 250a, 250b, 250c, and can display results to a user. Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. For example, throughout the description gamma rays have been described that are interacting with scintillator plates. However, the same principles can also apply and be used for X-rays that are absorbed by a scintillator plate made of a suitable material, for example Csl(TI) or higher-Z bismuth germanate (BGO). In addition, many other types of devices can be used for the image intensifier 30. |
|
summary | ||
abstract | A phase-contrast x-ray imaging device is particularly suited for the medical field. The device includes an x-ray source for generating an x-radiation field and an x-ray detector having a one-dimensional or two-dimensional arrangement of pixels. A phase-contrast differential amplifier is positioned between the x-ray source and the x-ray detector. The phase-contrast differential amplifier amplifies spatial phase differences in the x-radiation field during operation. |
|
040574652 | claims | 1. An auxiliary heat removal system for use in a gas-cooled nuclear reactor system to remove residual heat retained in the reactor core after reactor shutdown comprising: a first recycling flow loop for conducting gaseous primary cooling fluid heated by said reactor core, said first flow loop including said reactor core, a gas turbine, a first heat exchanging means, and a compression means connected in series therein, and first conduit means for transporting said primary fluid from said core to said gas turbine, said first heat exchanging means, and said compression means in series, and for returning said primary fluid to said reactor core; a second flow loop for conducting a second cooling fluid, said second flow loop including a fluid pump, second conduit means for transporting said second fluid from said fluid pump to said first heat exchanging means, and means for removing heat from said second cooling fluid, said second fluid being in thermal communication with said primary fluid in said first heat exchanging means; said fluid pump and said compression means being mechanically coupled to, and driven by, said gas turbine; and starter means for initiating operation of said gas turbine, said starter means being responsive to preselected conditions of said nuclear reactor system and comprising: a pneumatic starter; a container of starter fluid in fluid communication with said starter, said starter fluid being pressurized within said container, and; a starter valve disposed in the flow path between said pneumatic starter and said container, said starter valve controlling the flow of said starter fluid from said container to said pneumatic starter. extracting means for diverting a portion of said primary fluid exiting from said compression means to said container of starter fluid, and; a starter-fluid pump mechanically coupled to, and driven by, said gas turbine, said starter fluid pump pumping said primary fluid through said extracting means. said fluid pump is mechanically coupled to said gearbox, said gas turbine driving said fluid pump through said gearbox. said means for removing heat from said second fluid comprises: a liquid-to-air secondary heat exchanger through which said second fluid flows; circulating means for forcing air flow over said heat exchanger; and a liquid turbine in fluid communication with said second fluid, said second fluid passing through said liquid turbine before entering said heat exchanger, said liquid turbine being interconnected to said circulating means such that said liquid turbine drives said circulating means. said first heat exchanging means comprises a gas-to-air primary heat exchanger; and, said second fluid is rejected to the atmosphere after said second fluid has received heat from said primary fluid. said first heat exchanging means comprises; a supply of water; third conduit means for transporting said water from said supply of water to said fluid pump, and from said first heat exchanging means to said supply of water; and rejecting said second fluid to said supply of water after said second fluid has received heat from said primary coolant. a first recycling flow loop for conducting gaseous primary cooling fluid heated by said reactor core, said first flow loop including said reactor core, a gas turbine, a first heat exchanging means, and a compression means connected in series therein, and first conduit means for transporting said primary fluid from said core to said gas turbine, said first heat exchanging means, and said compression means in series, and for returning said primary fluid to said reactor core; a second flow loop for conducting a second cooling fluid, said second flow loop including a fluid pump, second conduit means for transporting said second fluid from said fluid pump to said first heat exchanging means, and means for removing heat from said second fluid, said second fluid being in thermal communication with said primary fluid in said first heat exchanging means; said fluid pump and said compression means being mechanically coupled to, and driven by, said gas turbine; starter means for initiating operation of said gas turbine, said starter means being responsive to preselected conditions of said nuclear reactor system; and a plurality of temperature-dependent flow controllers parallelly installed in said first conduit means between said core and said gas turbine, said flow controllers regulating the quantity of said primary fluid being supplied to said gas turbine. said flow controllers regulating the quantity of said primary fluid being supplied to said gas turbine such that increases in the temperature of said primary fluid increase the quantity of said primary fluid being supplied to said gas turbine. said means for removing heat from said second fluid comprises: a liquid-to-air secondary heat exchanger through which said second fluid flows; circulating means for forcing air flow over said heat exchanger; and a liquid turbine in fluid communication with said second fluid, said second fluid passing through said liquid turbine before entering said heat exchanger, said liquid turbine being interconnected to said circulating means such that said liquid turbine drives said circulating means. a first recycling flow loop for conducting gaseous primary cooling fluid heated by said reactor core, said first flow loop including said reactor core, a gas turbine, a first heat exchanging means, and a compression means connected in series therein, and first conduit means for transporting said primary fluid from said core to said gas turbine, said first heat exchaning means, and said compression means in series, and for returning said primary fluid to said reactor core; a second flow loop for conducting a second cooling fluid, said second flow loop including a fluid pump, second conduit means for transporting said second fluid from said fluid pump to said first heat exchanging means, and means for removing heat from said second cooling fluid, said second fluid being in thermal communication with said primary fluid in said first heat exchanging means; said fluid pump and said compression means being mechanically coupled to, and driven by, said gas turbine; starter means for initiating operation of said gas turbine, said starter means being responsive to preselected conditions of said nuclear reactor system; a supporting turbine connected in parallel with said gas turbine, said supporting turbine being of the gaseous-powered variety, said primary fluid flowing through said supporting turbine, said supporting turbine being driven by said, primary fluid said supporting turbine being larger than said gas turbine, said supporting turbine requiring higher primary fluid temperatures for operation than said gas turbine, whereby as said primary fluid temperature decreases, said supporting turbine ceases operating prior to said gas turbine ceasing operating; and supporting turbine starting means for initiating operation of said supporting turbine. said means for removing heat from said second fluid comprises: a liquid-to-air secondary heat exchanger through which said second fluid flows; circulating means for forcing air flow over said heat exchanger; and a liquid turbine in fluid communication with said second fluid, said second fluid passing through said liquid turbine before entering said heat exchanger, said liquid turbine being interconnected to said circulating means such that said liquid turbine drives said circulating means. 2. The system according to claim 1 wherein said starter means comprises: 3. The system according to claim 1 wherein said starter valve is responsive to the temperature of said primary fluid and said nuclear core such that, upon attainment of a predetermined temperature, said starter valve permits said starter fluid to flow from said container to said pneumatic starter. 4. The system according to claim 1 wherein a power take-off gearbox is mechanically coupled to said gas turbine; and 5. The system according to claim 1 wherein said second fluid is a liquid, and 6. The system according to claim 5 wherein said second fluid is water. 7. The system according to claim 1 wherein said second fluid is air; 8. The system according to claim 1 wherein said second fluid is water; 9. An auxiliary heat removal system for use in a gas-cooled nuclear reactor system to remove residual heat retained in the reactor core after reactor shutdown comprising: 10. The system according to claim 4 wherein said flow controllers are dependent upon the temperature of said primary fluid; and 11. The system according to claim 10 wherein said flow controllers are temperature-dependent valves. 12. The system according to claim 9 wherein said second fluid is a liquid, and 13. An auxiliary heat removal system for use in a gas-cooled nuclear reactor system to remove residual heat retained in the reactor core after reactor shutdown, comprising: 14. The system according to claim 13 wherein said supporting turbine is mechanically coupled to, and drives said compression and said fluid pump. 15. The system according to claim 13 wherein said means for starting operation of said supporting turbine comprises said gas turbine providing the starting force for said supporting turbine. 16. The system according to claim 13 wherein said second fluid is a liquid, and |
claims | 1. A method of manufacturing a container comprising:the upsetting step of placing a pressurizing platform into a ring-shaped die having a first opening at a first end of the ring shaped die and a second opening at the second end of the ring shaped die, the second opening being smaller than the first opening, and putting a metal billet into a mold composed of the die and the pressurizing platform from the first end of the die so as to pressurize the metal billet by means of a boring punch; andthe metal billet drawing step of supporting the die by means of a drum-shaped spacer and pushing the metal billet by means of the boring punch. 2. A method of manufacturing a container comprising:the upsetting preparation step of stacking a plurality of ring-shaped dies formed with an opening on its inner end portion and stacking a plurality of pressurizing platforms respectively in the dies and putting a metal billet into a mold composed of the die and the pressurizing platform;the upsetting step of pressurizing the metal billet from above the mold using a boring punch to be operated by a pressing machine;the receding step of allowing the boring punch and the whole metal billet including and the upper die to recede;the drawing preparation step of removing the used pressurizing platform and placing a drum-shaped spacer onto the next die and placing the receded whole metal billet including the die onto the spacer;the drawing step of pushing the metal billet by means of the boring punch and drawing the metal billet by means of the die; andthe repeating step of repeating the above-mentioned steps on the next pressurizing platform and die using a spacer of a length according to deformation of the metal billet. |
|
abstract | A method and apparatus for correcting aberrations using a Ronchigram. A STEM apparatus has first calculation means for taking autocorrelation of minute regions on a Ronchigram of an amorphous specimen, detection device for detecting aberrations in the beam formed from local angular regions on an aperture plane from the autocorrelation or from Fourier analysis of the autocorrelation, second calculation device for calculating the aberrations based on the results of the detection, and control device for controlling operation for correcting the aberrations based on results of calculations performed by the second calculation device. |
|
050874128 | claims | 1. A nuclear reactor including a reactor vessel having a core barrel inside the reactor vessel, fuel elements and safety rods inside the core barrel, a fuel element housing thimble surrounding each fuel element and defining a gap therebetween, and a primary coolant flow path that includes flow through the fuel element housing thimble gaps, wherein the improvement comprises: a. means for circulating a liquid moderator through the core barrel around the fuel element housing thimbles; b. said primary coolant being at a cooler temperature than said liquid moderator when entering said fuel element housing thimble gaps; and c. fins on the fuel element housing thimbles for conducting heat from the liquid moderator to the primary coolant flowing through said fuel element housing thimble gaps. a. means for circulating a liquid moderator through the core barrel around the fuel element housing thimbles, b. said primary coolant being at a cooler temperature than said liquid moderator when entering said fuel element housing thimble gaps; and c. finds on the fuel element housing thimbles for conducting heat from the liquid moderator to the primary gas coolant flowing through said fuel element housing thimble gaps. 2. The nuclear reactor of claim 1, wherein the primary coolant is a gas. 3. The nuclear reactor of claim 1, wherein said means for circulating a liquid moderator comprises pumps and fill and drain nozzles on the reactor vessel. 4. A gas cooled nuclear reactor including a reactor vessel having a core barrel inside the reactor vessel, fuel elements and safety rods inside the core barrel, a fuel element housing thimble surrounding each fuel element and defining a gap therebetween, and a primary coolant flow path that includes flow through the fuel element housing thimble gaps, wherein the improvement comprises: 5. The nuclear reactor of claim 4, further comprising a supplemental heat exchanger external to the reactor in fluid communication with the liquid moderator and primary coolant of the reactor for conducting heat from the liquid moderator to the primary coolant. |
summary | ||
abstract | A flexure carriage assembly (24) has a carriage (25) formed of a substantially rigid material. The carriage has four elongate columns (32A, 32B, 32C, 32D) arranged spaced apart and parallel to one another. Each of the elongate columns has first and second ends. The flexure carriage (25) has four first cross members disposed between adjacent pairs of elongate columns and arranged to interconnect the first ends. The flexure carriage also includes four second cross members (38A–D) arranged between adjacent pairs of elongate columns and arranged to interconnect the bottom ends. The elongate columns and first and second cross members define a three-dimensional rectangular structure. The flexure carriage also has disposed centrally between the four elongate columns a translating section (29) spaced equidistant between the first and second ends of the columns. A plurality of flexures (50) are disposed between the translating element and elongate columns and between the elongate columns and first and second cross members in order to permit precise movement of the translating section (20) in a plane according to applied forces against edges of the translating section. A pair of piezoelectric assemblies (26) are connected to the translating section. One applies force to the translating section in a first linear path and the other applies force to the translating section in a second linear path perpendicular path. |
|
summary | ||
summary | ||
054992761 | claims | 1. A method of minor actinide nuclides incineration by adding neptunium of minor actinide nuclides separated from spent fuel to reactor core fuel of a fast reactor and adding americium of the separated minor actinide nuclides and rare earth elements to either or both of radial and axial blankets of the fast reactor for nuclear reaction. 2. A method of minor actinide nuclides incineration by adding neptunium of minor actinide nuclides separated from spent fuel to reactor core fuel of a fast reactor and adding americium of the separated minor actinide nuclides and rare earth elements to either or both of radial and axial shields of the fast reactor for nuclear reaction. 3. The method as claimed in claim 1 wherein curium is added together with americium and rare earth elements. 4. The method as claimed in claim 2 wherein curium is added together with americium and rare earth elements. 5. The method as claimed in claim 1 wherein neptunium is added in an amount of 2% to 5% by weight based on weight of fuel and wherein the rare earth elements are added in an amount of 50% by weight or less based on the weight of the fuel. 6. The method as claimed in claim 2 wherein neptunium is added in an amount of 2% to 5% by weight based on weight of fuel and wherein the rare earth elements are added in an amount of 50% by weight or less based on the weight of the fuel. 7. The method as claimed in claim 3 wherein neptunium is added in an amount of 2% to 5% by weight based on weight of fuel and wherein the rare earth elements are added in an amount of 50% by weight or less based on the weight of the fuel. 8. The method as claimed in claim 4 wherein neptunium is added in an amount of 2% to 5% by weight based on weight of fuel and wherein the rare earth elements are added in an amount of 50% by weight or less based on the weight of the fuel. 9. The method as claimed in any of claims 1-8 wherein minor actinide nuclides separated by a separation method provided by combining a Purex process and a Truex process are used as the minor actinide nuclides to be added. 10. A method for an efficient nuclear reaction of americium and curium in a mixture of americium, curium, and rare earth elements, said method comprising the steps of adding neptunium to reactor core fuel of a fast reactor and placing said mixture on the periphery of the reactor core fuel to which said neptunium is added for causing a nuclear reaction to occur, whereby an efficient nuclear reaction can be caused to occur for americium and curium in said mixture for efficiently making said elements in said mixture incinerate. 11. The method as claimed in claim 10 wherein neptunium is added to the reactor core fuel in an amount of 2% to 5% by weight based on weight of the reactor core fuel and wherein a percentage of the rare earth elements in the mixture of americium, curium, and rare earth elements is 50% or less. 12. The method as claimed in claim 10 wherein the mixture of americium, curium, and rare earth elements is stored in either or both of radial and axial blankets, thereby placing said mixture on the periphery of the reactor core fuel. 13. The method as claimed in claim 12 wherein neptunium is added to the reactor core fuel in an amount of 2% to 5% by weight based on weight of the reactor core fuel and wherein a percentage of the rare earth elements in the mixture of americium, curium, and rare earth elements is 50% or less. 14. A method of making americium and curium incinerate, comprising the steps of: (1) separating neptunium from spent nuclear fuel; (2) separating americium and curium from spent nuclear fuel; (3) placing said separated americium and curium on the periphery of said separated neptunium in a fast reactor core; and (4) causing neptunium to initiate a nuclear reaction for causing an efficient nuclear reaction to occur for said americium and curium separated from the spent nuclear fuel. 15. The method as claimed in claim 14 wherein a Purex process is used to separate neptunium from the spent nuclear fuel and a Truex process is used to separate americium and curium from the spent nuclear fuel. 16. The method as claimed in claim 14 wherein said separated americium and curium are stored in either or both of radial and axial blankets, thereby placing said elements on the periphery of the reactor core fuel. 17. The method as claimed in claim 15 wherein said separated americium and curium are stored in either or both of radial and axial blankets, thereby placing said elements on the periphery of the reactor core fuel. |
description | FIG. 1 is a schematic diagram of a nuclear reactor 10 in accordance with an embodiment of the present invention. Reactor 10 includes a reactor pressure vessel 12 located inside a containment vessel 14. A reactor core 16 is located inside reactor pressure vessel 12. Containment vessel 14 includes a drywell 18, which houses reactor pressure vessel 12, and an enclosed wetwell 20. A suppression pool 22 is located inside wetwell 20. A cooling condenser pool of water 24 is located outside containment vessel 14. A plurality (two shown) of containment cooling condensers 26 are submerged in cooling pool 24. Condenser 26 includes an inlet line 28 in fluid communication with drywell 18. Steam and noncondesible gases flow from drywell 18 through inlet line 28 to an upper drum 30 of condenser 26 and then into a condensing section 32 where the steam is condensed and collected in a lower drum 34. A condensate drain line 36 extends from lower drum 34 of condenser 26 to a condensate drain tank 38. An injection line 39 extends from condensate drain tank 38 to pressure vessel 12 and condensate drains to pressure vessel 12 through injection line 39. Drain line 36 includes a U-pipe loop seal or water trap 40 to restrict the backflow of steam and noncondensible gases from flowing backward through condensate drain line 36 and into condenser 26. A noncondensible gas vent line 42 extends from lower drum 34 to wetwell 20. An outlet end 44 of vent line 42 is submerged in suppression pool 22. A drywell gas recirculation subsystem 46 prevents the buildup of noncondesible gases in wetwell 20. Drywell gas recirculation subsystem 46 includes a suction line 48 connected to and in fluid communication with noncondensible gas vent line 42 at a location downstream of condenser 26 and above outlet end 44 of vent line 42, one or more blowers 50 (one shown) connected to suction line 48, at least one valve 52 (two shown), and a discharge line 54. Discharge line 54 includes a first end 56 and a second end 58. First end 56 of discharge line 54 is connected to blower 50 and second end 58 is open to drywell 18. Valves 52 can be any suitable valves, for example, pyrotechic-type squib valves. Blower 50 circulates the drywell atmosphere through condensers 26 by forced circulation. Particularly, the noncondensible gases circulate from condensing section 32 of condenser 26 through vent line 42 through suction line 48 and are returned to drywell 18, instead of discharging in wetwell 20. Drywell gas recirculation subsystem 46, once actuated, remains as a closed loop extension of containment vessel 14. Locked open maintenance block valves 60 are located outboard of containment vessel 14 on suction line 48 and discharge line 54. Block valves 60 permit servicing of any component of subsystem 46 without the need for drywell entry. FIG. 2 is a schematic diagram of another embodiment of a containment cooling system 62 shown in FIG. 1. In this embodiment drywell gas recirculation subsystem 46 is located entirely inside containment vessel 14. As described above, containment cooling system 62 includes containment vessel 14 having a drywell 18 and a wetwell 20. Cooling condenser 26 is submerged in cooling pool 24 located outside containment 14. Condenser 26 includes inlet line 28 in fluid communication with drywell 18 and connected to upper drum 30, condensing section 32, and lower drum 34. Noncondensible gas vent line 42 extends from lower drum 34 of condenser 26 to wetwell 20 with outlet end 44 of vent line 42 submerged in suppression pool 22. Condensate drain line 36 extends from lower drum 34 of condenser 26 to condensate drain tank 38, and includes U-pipe loop seal 40. The height of loop seal 40 is defined as HLOOP. Condensate drain tank 38 includes a pool of water 64, and condensate drain line 36 enters condensate drain tank 38 above the surface of pool 64. Drywell gas recirculation subsystem 46 includes suction line 48 connected to and in fluid communication with noncondensible gas vent line 42, blower 50 connected to suction line 48, squib valve 52, and discharge line 54. FIG. 3 is a schematic diagram of a straight pipe loop seal 66 of containment cooling system 62 in accordance with another embodiment of the present invention. In this embodiment, condensate drain line 36 is vertically submerged into drain tank 38 a distance HSUB below the surface of drain tank pool of water 64. The advantage of this arrangement is that the static head for the flow passing through drain line 36 is biased depending on the flow direction. Defining the cross-sectional area of drain line 36 and drain tank 38 as APIPE and ATANK respectively, and a forward flow direction as the flow of condensate and noncondensible gases from condenser 26 through drain line 36, into drain tank 38, and to drywell 18. For forward flow, the pressure inside drain line 36 needs to be greater than the pressure in drywell 18 to push down the water level inside drain line 36 to an outlet end 68 of drain line 36. The water level in drain tank 38 rises due to the incoming water volume from drain line 36. The submergence of drain line outlet end 68 becomes HSUB*(1+APIPE/(ATANKxe2x88x92APIPE)). This is the static head difference between the pressure in drain line 36 and the pressure in drywell 18 for the forward flow to occur. For an embodiment with (APIPE/ATANK) greater than greater than 1, or for an embodiment where the water level in drain tank 38 is controlled by the location of injection line 39, the static head for the forward flow is ≅HSUB. The backward flow direction is defined as the flow from drywell 18, through drain tank 38 into drain line 36. For backward flow to occur, the pressure in drywell 18 has to be sufficiently greater than the pressure in drain line 36 to push down the water level inside tank 38 to drain line exit elevation. In this situation, the water level inside drain line 36 rises due to incoming water volume from drain tank 38. The length of the water column inside drain line 36 is HSUB*ATANK/APIPE. This is the static head difference between the pressure in drywell 18 and the pressure in drain line 36 for backward flow to occur. By using the appropriate area ratio between drain tank 38 and drain line 36, the backward flow static head in straight pipe loop seal 66 (shown in FIG. 3) is HSUB*ATANK/APIPE, which can be greater than that in U-pipe loop seal 40 (shown in FIG. 2) of 2*HLOOP. For the same area ratio, the forward flow static head in straight pipe loop seal 66 is HSUB, which can be a fraction of HLOOP in U-pipe loop seal 40 due to the area multiplication factor. Therefore, the advantage of straight pipe loop seal 66 shown in FIG. 3 is a lower static head for forward flow. FIG. 4 is a schematic diagram a portion of containment cooling system 62 that includes a blower 70 in condenser drain line 36 in accordance with another embodiment of the present invention. Blower 70 enhances the flow through condenser 26 and recirculates noncondensible gases back to drywell 18 through condensate drain tank 38. Blower 70 is connected to condensate drain line 36 at a location between lower drum 34 of condenser 26 (shown in FIG. 2) and drain tank pool of water 64. As explained above, the head requirement of blower 70 is less in a drain line 36 that is connected to drain tank 38 with a straight pipe loop seal 66 than a drain line 36 that is connected to drain tank 38 with a U-tube loop seal 40. In alternate embodiments, containment system 62 includes more than one blower 70 in drain line 36. FIG. 5 is a schematic diagram of a portion of containment cooling system 62 that includes three condensate drain lines 36 extending into drain tank 38 in accordance with another embodiment of the present invention. Each condensate drain line 36 includes a blower 70. FIG. 6 is a schematic diagram of a portion of containment cooling system 62 that includes a jet pump 72 in condensate drain line 36 in accordance with another embodiment of the present invention. Jet pump 72 includes a suction line 74, a pump 76 coupled to and in flow communication with suction line 74, a discharge line 78 extending from pump 76 to a jet pump nozzle 80 located inside drain line 36, and a venturi 82 located in drain line 36. Jet pump nozzle 80 is positioned upstream from venturi 82 in drain line 36. An end 84 of suction line 74 is positioned in condensate drain tank pool of water 64. Jet pump suction line 74 takes water from drain tank 38 which is circulated by pump 76 through discharge line 78, and injected into venturi 82 in drain line 36 via jet pump nozzle 80 at high velocity. Low pressure is created in venturi 82 by the high jet velocity of the water. The mixture of condensate and noncondensible gases are drawn through venturi 82 and discharged into drain tank 38. The condensate is collected in drain tank 38 and the noncondensible gases are discharged back to drywell 18. As explained above, the head requirement of jet pump 72 is less in a drain line 36 that is connected to drain tank 38 with a straight pipe loop seal 66 than a drain line 36 that is connected to drain tank 38 with a U-tube loop seal 40. In alternate embodiments, drain line 36 includes more than one jet pump 72. FIG. 7 is a schematic diagram a portion of containment cooling system 62 that includes three condensate drain lines 36 extending into drain tank 38 in accordance with another embodiment of the present invention. Each condensate drain line 36 includes a jet pump 72. FIG. 8 is a schematic diagram a portion of a containment cooling system 62 showing three condensate drain lines 36 extending into drain tank 38. A jet pump 72 is located in one drain line 36, a blower 70 is located in a second drain line 36, and a gravity driven suction pump 86 is located in a third drain line 36 in accordance with another embodiment of the present invention. Gravity driven suction pump 86 includes a suction line 88 extending from lower drum 34 of condenser 26 into venturi section 82 of drain line 36. Gravity driven suction pumps are described in greater detail in U.S. Pat. No. 6,097,778. The above described nuclear reactor containment cooling system 62 enhances flow through condenser 26 as compared to known passive containment cooling systems. Also, the above described containment cooling system 62 effectively redistributes the noncondensible gases between drywell 18 and wetwell 20. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims. |
|
047909609 | description | DETAILED DESCRIPTION OF THE INVENTION It has been found in accordance with the present invention that the acid stability of the precipitation agent molecule and of the resulting precipitate which has low solubility is increased by the introduction of electron-attracting substituents in the phenyl rings of the molecule which prevents to a large extent that positive charges stabilize on the phenyl rings and thus initiate the decomposition of the molecule. The electron-attracting substituents protect the phenyl rings from electrophilic attacks. The synthesis for the precipitation agents, usable for the process according to the present invention can occur, e.g., according to the following scheme: Preparation of Sodium Tetrakis(2,4-difluorophenyl)borate: ##STR1## In the above process, 2,4-difluorobromobenzole (a) in a di-ethyl-ether solution is transformed at -78.degree. C. into a phenyllithium derivative (B) with n-butyllithium (n-BuLi). Into the thus obtained phenyllithium derivative (B) solution, a BCl.sub.3 solution in hexane is dripped. After warming up to room temperature, hydrolization is done, the ether pulled off over water, the aqueous phase (now containing derivative (c)) mixed with some active carbon, filtered and mixed with an aqueous trimethylamine solution. The resulting trimethylammonium salt (D) is recrystallised from methanol/water and dried. With sodium hydride it is transformed into the corresponding alkaline salt (E), which, as needed, can then be recrystallized from chloroform/acetone. The compound lithiumtetrakis(2,3,5,6-tetrafluorophenyl)borate was produced in the same manner by employing lithium hydride instead of sodium hydride. The lithiumtetrakis(pentafluorophenyl)borate production has been taken from A. G. Massey, A. J. Park: J. Organometal. Chem., 2 (1964), pages 245 to 250. The products were analyzed with the aid of IR, NMR and elementary analysis. In order to present the salts in pure form, the "detour" through trimethylammonium salts is needed. However, for precipitation reactions, the aqueous solution of the precipitation reagents (containing derivatives according to derivatives "C" respectively) is already sufficient, the concentrations of which can be simply determined by quantitative precipitation with trimethylamine. The solubilities of the corresponding Cs salts in pure water (298.degree. K.) are given below: Sodium tetrakis(2,4-difluorophenyl)borate: 2.0.10.sup.-4 mol/l PA1 Lithium tetrakis(2,3,5,6-tetrafluorophenyl)borate: 3.7.10.sup.-4 mol/l PA1 Lithium tetrakis(pentafluorophenyl)borate: 2.4.10.sup.-4 mol/l PA1 (1) Sodiumtetrakis(2,4-difluorophenyl)borate PA1 (2) Lithiumtetrakis(2,3,5,6-tetrafluorophenyl)borate PA1 (3) Lithiumtetrakis(pentafluorophenyl)borate The solubilities were determined by means of radiometry. All reagents from precipitates with Cs.sup.+ which have a low solubility, but not with potassium. Coprecipitation of potassium appears in lithium tetrakis(2,3,5,6-tetrafluorophenyl)borate but only with a K.sup.+ to Cs.sup.+ ratio of .gtoreq.100, and appears with sodiumtetrakis(2,4-difluorophenyl)borate and lithiumtetrakis(pentafluorophenyl)borate only at K.sup.+ to Cs.sup.+ ratio of >100. Cs.sup.+ precipitates which have a low solubility also form with sodium tetrakis(4-fluorophenyl)borate, sodium tetrakis(3,4-difluorophenyl)borate, and with lithiumtetrakis(2,4,6-trifluorophenyl)borate, with the precipitate of the first two compounds being formed in neutral and in alkaline media in a very good selectivity, and the precipitate of the third compound also being formed in acid media up to 3 molar acid, but for this compound coprecipitation with K.sup.+ occurs from the ratio of K.sup.+ :Cs.sup.+ as 1 up to higher K.sup.+ /Cs.sup.+ ratios. The following examples are given by way of illustration to further explain the principles of the invention. These examples are merely illustrative and are not to be understood as limiting the scope and underlying principles of the invention in any way. All percentages referred to herein are by weight unless otherwise indicated. EXAMPLE 1 (Cs.sup.+ Precipitation from a Simulated MAW) A simulated MAW solution was prepared having the composition shown in Table 1. TABLE 1 ______________________________________ Sample Composition of the Simulated MAW Solution Element Used as Concentration (Mol/l) ______________________________________ Na NaNO.sub.3 3.53 Al Al(NO.sub.3).sub.3 9H.sub.2 O 8.52 .multidot. 10.sup.-3 Ca Ca(NO.sub.3).sub.2 4H.sub.2 O 3.68 .multidot. 10.sup.-2 Cr Cr(NO.sub.3).sub.3 9H.sub.2 O 1.54 .multidot. 10.sup.-3 Cu Cu(NO.sub.3).sub.3 3H.sub.2 O 2.36 .multidot. 10.sup.-3 Fe Fe(NO.sub.3).sub.3 9H.sub.2 O 6.80 .multidot. 10.sup.-3 K KNO.sub.3 2.50 .multidot. 10.sup.-3 Mg Mg(NO.sub.3).sub.2 6H.sub.2 O 3.09 .multidot. 10.sup.-2 Mn Mn(NO.sub.3).sub.2 4H.sub.2 O 1.46 .multidot. 10.sup.-3 Mo Na.sub.2 MoO.sub.4 2H.sub.2 O 3.96 .multidot. 10.sup.-3 Ni Ni(NO.sub.3).sub.2 6H.sub.2 O 1.36 .multidot. 10.sup.-3 Ru Ru(NO.sub.3).sub.3 (NO)8.8% ig 7.50 .multidot. 10.sup.-4 Zn Zn(NO.sub.3).sub.2 4H.sub.2 O 2.29 .multidot. 10.sup.-3 TBP 7.51 .multidot. 10.sup.- 4 DBP 9.51 .multidot. 10.sup.-4 HNO.sub.3 1.0 ______________________________________ The simulated MAW was mixed with inactive Cs.sup.+. Two different solutions were prepared, one with a Cs.sup.+ concentration 1.0.multidot.10.sup.-3 and the second with a Cs.sup.+ concentration of 1.0.multidot.10.sup.-2 mol/l. The solutions were doped with Cs-137, and this doping was independent of the inactive Cs.sup.+ concentration, to provide an activity of 1 .mu.Ci/ml. In each case, the precipitation agent was added in a threefold amount of the stoichiometric amount with respect to the Cs.sup.+ concentration, whereby it was of no importance if it was added as solution or solid matter. Samples were taken after about 24 hours, they were filtered, the activity of the filtrate measured and the Cs.sup.+ concentration then calculated through calibration. The results are shown in Tables 2 to 4. The following compounds were used as precipitation agents: TABLE 2 ______________________________________ Cs.sup.+ Precipitation with Compound (1) Remaining Cs.sup.+ Concentration in the Initial Inactive Solution After Cs.sup.+ Concentration Temperature Stripping of Precipitate [mol/l] [.degree.K.] [mol/l] ______________________________________ 1.0 .multidot. 10.sup.-3 293 6.0 .multidot. 10.sup.-5 1.0 .multidot. 10.sup.-3 277 3.7 .multidot. 10.sup.-5 1.0 .multidot. 10.sup.-3 260 1.6 .multidot. 10.sup.-5 1.0 .multidot. 10.sup.-2 293 5.6 .multidot. 10.sup.-5 1.0 .multidot. 10.sup.-2 277 3.5 .multidot. 10.sup.-5 1.0 .multidot. 10.sup.-2 260 1.3 .multidot. 10.sup.-5 ______________________________________ TABLE 3 ______________________________________ Cs.sup.+ Precipitation with Compound (2) Remaining Cs.sup.+ Concentration in the Initial Inactive Solution After Cs.sup.+ Concentration Temperature Stripping of Precipitate [mol/l] [.degree.K.] [mol/l] ______________________________________ 1.0 .multidot. 10.sup.-3 293 3.0 .multidot. 10.sup.-4 1.0 .multidot. 10.sup.-3 277 1.9 .multidot. 10.sup.-4 1.0 .multidot. 10.sup.-2 293 3.0 .multidot. 10.sup.-4 1.0 .multidot. 10.sup.-2 277 1.8 .multidot. 10.sup.-4 ______________________________________ TABLE 4 ______________________________________ Cs.sup.+ Precipitation with Compound (3) Remaining Cs.sup.+ Concentration in the Initial Inactive Solution After Cs.sup.+ Concentration Temperature Stripping of Precipitate [mol/l] [.degree.K.] [mol/l] ______________________________________ 1.0 .multidot. 10.sup.-3 293 1.8 .multidot. 10.sup.-4 1.0 .multidot. 10.sup.-3 277 6.8 .multidot. 10.sup.-5 1.0 .multidot. 10.sup.-2 293 1.6 .multidot. 10.sup.-4 1.0 .multidot. 10.sup.-2 277 5.4 .multidot. 10.sup.-5 ______________________________________ EXAMPLE 2 (Cs.sup.+ Precipitation from 5M-Nitric Acid) The same procedure was employed as described in Example 1, except that only Compounds (1) and (3) were tested as precipitation agents, and the acid molarity of the aqueous solution used was chosen in such a manner that in this context it simulated a HAW concentrate (HAW=high radioactive aqueous waste). To prepare the aqueous solution, 5 molar HNO.sub.3 was mixed with inactive Cs.sup.+ to provide a Cs.sup.+ concentration of 1.0.multidot.10.sup.-2 mol/l. The solution was doped with Cs-137 to provide an activity of 1 .mu. Ci/ml. The precipitation agent was added in a threefold amount of the stoichiometric amount with respect to the Cs.sup.+ concentration. After 24 hours, samples were taken, they were filtered, the activity of the filtrate measured and the Cs.sup.+ concentration calculated via calibration. The results are shown in Tables 5 and 6. TABLE 5 ______________________________________ Cs.sup.+ Precipitation with Compound (1): Remaining Cs.sup.+ Concentration in the Initial Inactive Solution After Cs.sup.+ Concentration Temperature Stripping of Precipitate [mol/l] [.degree.K.] [mol/l] ______________________________________ 1.0 .multidot. 10.sup.-2 293 2.6 .multidot. 10.sup.-5 1.0 .multidot. 10.sup.-2 273 1.8 .multidot. 10.sup.-5 1.0 .multidot. 10.sup.-2 260 1.5 .multidot. 10.sup.-5 ______________________________________ TABLE 6 ______________________________________ Cs.sup.+ Precipitation with Compound (3): Remaining Cs.sup.+ Concentration in the Initial Inactive Solution After Cs.sup.+ Concentration Temperature Stripping of Precipitate [mol/l] [.degree.K.] [mol/l] ______________________________________ 1.0 .multidot. 10.sup.-2 313 1.6 .multidot. 10.sup.-3 1.0 .multidot. 10.sup.-2 298 8.4 .multidot. 10.sup.-4 1.0 .multidot. 10.sup.-2 273 6.9 .multidot. 10.sup.-4 1.0 .multidot. 10.sup.-2 260 6.4 .multidot. 10.sup.-4 ______________________________________ Sodium tetrakis(2,4-difluorophenyl)borate (Compound 1) is acid stable to 6M-HNO.sub.3 and at temperatures up to 293.degree. K. Under conditions as they are prevalent in radioactive waste solutions, the Cs salt has the lowest solubility of the compounds examined. The remaining Cs.sup.+ concentration in MAW-simulate or in 5M nitric acid, depending on temperature (239.degree. to 293.degree. K.), are between 1.0.multidot.10.sup.-5 and 8.0.multidot.10.sup.-5 mol/l. (With Kalignost such a solubility determination cannot be done, as the decomposition of the compound occurs too fast under the test conditions). The lowest Cs.sup.+ concentration to be reached by precipitation is determined by the solubility of the corresponding Cs.sup.+ salts. EXAMPLE 3 (Cs.sup.+ Precipitation from Simulated HAW) A simulated HAW solution was prepared having the composition shown in Table 7. The simulated solution was 5 molar in HNO.sub.3 and contained the largest amount of elements in the form of nitrate salts. TABLE 7 ______________________________________ Concentration in the Simulated Element Aqueous solution (g/l) ______________________________________ Ag 0.03 Ba 2.65 Cd 0.14 Ce 3.70 Cr 0.57 Cs 3.54 Eu 0.28 Fe 2.19 Gd 0.25 La 1.90 Mn 0.06 Mo 5.24 Nd 6.16 Pd 2.01 Pr 1.78 Rb 0.49 Rh 0.57 Ru 2.13 Sb 0.009 Se 0.08 Si 0.04 Sm 1.35 Sn 0.06 Sr 1.15 Tc 2.26 Te 0.74 Y 0.66 Zr 5.27 Rest 0.03 Active Compound 4.55 (Am, Cm, Np, Pu, U) Impurities 0.63 ______________________________________ The solution was doped with Cs-137 to provide an activity of 1 .mu.Ci/ml. The precipitation was done as described in Example 2, but only with Compound (3). The result is shown in Table 8: TABLE 8 ______________________________________ Precipitation with Compound (3) Remaining Cs.sup.+ Concentration in the Initial Inactive Solution After Cs.sup.+ Concentration Temperature Stripping of Precipitate [mol/l] [.degree.K.] [mol/l] ______________________________________ 2.68 .multidot. 10.sup.-2 298 7.2 .multidot. 10.sup.-4 2.68 .multidot. 10.sup.-2 283 6.2 .multidot. 10.sup.-4 2.68 .multidot. 10.sup.-2 273 5.9 .multidot. 10.sup.-4 ______________________________________ EXAMPLE 4 (Effectiveness) It is now possible to obtain by precipitation, for example with Compound (1), high decontamination for Cs-137 in various ways and manners as follows: (1) Adjusting the MAW solution to an inactive Cs.sup.+ concentration of 1.0.multidot.10.sup.-3 mol/l. Precipitation at a temperature of 293.degree. K. with Compound (1) in a threefold amount of the stoichiometric amount with respect to the Cs.sup.+ concentration and stripping the precipitate (by filtration or centrifugation) supplies a decontamination factor (DF) of 17. The resulting Cs+ concentration of about 6.0.multidot.10.sup.-5 mol/l is again adjusted to 1.0.multidot.10.sup.-3 mol/l, again precipitated and the whole process repeated as often as desired. With four cycles it is thus possible to attain, without much material investment, a DF for the active Cs of about 80,000 (precipitation temperature 293.degree. K. in each case). (2) Adjusting the MAW solution to an inactive Cs.sup.+ concentration of 1.0.multidot.10.sup.-2 mol/l, and then following the same procedure as in (1) above. The first precipitation results in a DF of 170, after the next cycle, a DF of 29,000 etc. (Precipitation temperature in each case 293.degree. K.). (3) The same procedure is employed as in (1), except that the precipitation temperature is 277.degree. K. The first precipitation produces a DF of 26, after the fourth precipitation the DF is higher than 400,000. (4) The same procedure is employed as in (2), except that the precipitation temperature is 277.degree. K. The first precipitation supplies a DF of 280, the second precipitation already a DF of more than 78,000. (5) The same procedure is employed as in (1), except that the precipitation temperature is 260.degree. K. The first precipitation supplies a DF of 62, after the third precipitation the DF is >230,000. (6) The same procedure is employed as in (2), except that the precipitation temperature is 260.degree. K. The first precipitation supplies a DF of 770, the second precipitation already a DF of >590,000. (7) Adjusting a 5M HNO.sub.3 to an inactive Cs.sup.+ concentration of 10.sup.-2 mol/l. The process otherwise is the same as in (1). The first precipitation supplies a DF of 384, the second precipitation already a DF of 148,000. The precipitation temperature in each case was 293.degree. K. (8) The same procedure is employed as in (7), except that the precipitation temperature is 260.degree. K. The first precipitation supplies a DF of 667, the second precipitation already a DF of 444,000. EXAMPLE 5 (Separation of the Cs precipitate from Compound (3) by Liquid Extraction from an Aqueous Solution) Water was mixed with inactive Cs.sup.+ to provide a Cs.sup.+ concentration of 1.0.multidot.10.sup.-3 mol/l. The solution was doped with Cs-137, as in the previous examples. The precipitating agent was added in a double amount of the stoichiometric amount with respect to the Cs.sup.+ concentration. After 24 hours, samples were taken and subjected to different precipitation separation methods, namely, filtration on the one hand, and extraction on the other, in order to compare the effectiveness of the different precipitation separation methods. In the filtration separation method, the precipitates were filtered off and the residual Cs.sup.+ concentration in the filtrate solution of the samples determined. This Cs.sup.+ concentration in the filtrate solutions amounted to 6.5.multidot.10.sup.-5 mol/l. In the extraction separation method, the solutions containing the precipitates were extracted using various organic solvents, and the residual Cs.sup.+ concentrations in the aqueous phases were measured. The results are shown in Table 9. TABLE 9 ______________________________________ Extraction from the Aqueous Solution Residual Cs.sup.+ Concentration in the Solution Extraction Agent after Extraction (mol/l) ______________________________________ Chloroform 6.2 .multidot. 10.sup.-5 Diethyl ether/ligroine 6.6 .multidot. 10.sup.-5 (b.p. 40-60.degree. C.) 2:1 (vol./vol/) 4-methyl-2-pentanone 6.6 .multidot. 10.sup.-6 (5% by volume in chloroform) 4-methyl-2-pentanone 6.9 .multidot. 10.sup.-6 (5% by volume in toluol) ______________________________________ EXAMPLE 6 (Separation of the Cs.sup.+ precipitates from Compound (3) by means of Liquid Extraction from a Simulated HAW.) Execution of the experiments and the comparison of the separation methods occurred as described in Example 5, except that the precipitant was in this case added in a threefold amount of the stoichiometric amount with respct to the Cs.sup.+ concentration. The residual Cs.sup.+ after filtration of the samples amounted to 7.2.multidot.10.sup.-4 Mol/l. The result of the extractions are shown in Table 10. TABLE 10 ______________________________________ Extraction from Simulated HAW Simulate: Residual Cs.sup.+ Concentration in the Solution Extraction Agent after Extraction (mol/l) ______________________________________ Chloroform 7.1 .multidot. 10.sup.-4 Diethyl ether/ligroine 6.3 .multidot. 10.sup.-4 (b.p. 40-60.degree. C.) 2:1 (vol./vol/) 4-methyl-2-pentanone 6.2 .multidot. 10.sup.-5 (5% by volume in chloroform) 4-methyl-2-pentanone 6.4 .multidot. 10.sup.-5 (5% by volume in toluol) ______________________________________ Other organic solvents may also be used as extraction agents, however, they were not investigated for effectiveness. It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims. |
claims | 1. A system for managing irradiation targets and instrumentation access to a nuclear reactor, the system comprising:a penetration pathway connecting an origin point outside an access barrier of the nuclear reactor to an instrumentation tube extending into the nuclear reactor inside the access barrier, wherein the penetration pathway is traversable by at least one irradiation target and the instrumentation to the instrumentation tube, wherein the penetration pathway includes,one of at least one instrumentation path and at least one irradiation target path distinct from the instrumentation path, andat least one shared path; anda selector inside the access barrier, wherein the selector is configured to connect only one of the instrumentation path and the irradiation target path to the shared path so as to form the penetration pathway. 2. The system of claim 1, wherein,the irradiation target path connects to an irradiation target loading/offloading system, andthe instrumentation path connects to a TIP system. 3. The system of claim 1, wherein the selector is positioned at a pedestal of the nuclear reactor. 4. The system of claim 3, wherein the shared path connects the selector to the instrumentation tube and extends entirely within the pedestal, and wherein the irradiation target path and the instrumentation path extend entirely outside of the pedestal. 5. The system of claim 1, wherein the shared path connects the selector to multiple instrumentation tubes. 6. The system of claim 1, wherein the access barrier is a nuclear reactor containment building. 7. The system of claim 1, further comprising:at least one irradiation target moveable within the irradiation target path and the shared path. 8. The system of claim 7, wherein,the at least one irradiation target are a plurality of irradiation targets, andthe plurality of irradiation targets are spherical. 9. The system of claim 8, wherein,the irradiation target path and the shared path are tubing continuously connecting an irradiation target loading/offloading system and the instrumentation tube via the selector, andthe tubing is sized to permit the plurality of irradiation targets to roll in the tubing. 10. The system of claim 1, wherein the selector includes,a first selection path configured to connect to only the instrumentation path, anda second selection path distinct from the first selection path and configured to connect to only the irradiation target path. 11. The system of claim 10, wherein the selector further includes a moveable block containing the first and the second selection paths, and wherein only one of the first and the second selection paths connects to the shared path based on a position of the moveable block. 12. The system of claim 11, wherein selector further includes at least one motor and a piston connecting the moveable block to the motor, and wherein the motor is configured to rotate so as to move the moveable block to the position. 13. The system of claim 11, wherein the selector further includes an exterior frame configured to block at least one of the first and the second selection paths that is not connected to the shared path. 14. A system for managing irradiation targets and instrumentation, the system comprising:a nuclear reactor including an instrumentation tube; anda means for delivering instrumentation and irradiation targets from outside an access barrier of the nuclear reactor into the instrumentation tube and vice versa, wherein the means includes at least one selector inside of a containment building of the nuclear reactor, wherein the selector is configured to selectively provide access within the access barrier to the irradiation targets and the instrumentation. 15. The system of claim 1, further comprising:an irradiation target reservoir outside the access barrier connected to the origin point; anda harvesting container outside the access barrier connected to the origin point, wherein the harvesting container and the irradiation target reservoir connect to the origin point through separate paths from each other. 16. The system of claim 15, further comprising:a loading junction at the origin point, wherein the loading junction is configured to connect only one of the irradiation target reservoir and the harvesting container to the penetration pathway at any given time. 17. The system of claim 16, further comprising:a retaining flange on the penetration pathway below the instrumentation tube and inside the selector, wherein the retaining flange is configured to hold irradiation targets in the instrumentation tube while the penetration pathway is not filled with irradiation targets. 18. The system of claim 1, further comprising:a plurality of irradiation targets that are unjoined from one another and are moveable in the penetration pathway independent of each other. 19. The system of claim 14, wherein the irradiation targets are not connected and are free to individually roll in the means for delivering instrumentation and irradiation targets. |
|
061782181 | description | DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, a schematic view illustrating an embodiment of the present invention is shown. A neutron source 12 capable of providing neutrons shown. Preferably the neutrons provided from the neutron source 12 have an energy of up to 14 Mev. The neutron source can be a neutron generator or accelerator, such as a MF Physics A-320 probe detector by MF Physics Corporation, which is a variation on the basic A-320 design and is useful in applications where an extremely rugged, highly portable "probe" configured system is required. Alternatively, the neutron source of the present invention could be an isotopic source, such as .sup.252 Cf. Neutrons from the neutron source are directed toward the metal test specimen 14. The metals capable of being tested using the present invention include: steel, aluminum, copper, and alloys thereof. For example, neutron activation of the copper component of many such alloys, including Alcoa 6061/T6 aircraft aluminum which contains 0.25% copper, will produce a positron emitter disposed within the metal. The .sup.63 Cu (n, gamma) reaction produces .sup.64 Cu, a positron emitter having a 12 hour half life. Also, the .sup.63 Cu (n, 2n) reaction produces .sup.62 Cu, a positron emitter having a 9.7 minute half life. Neutron activation of copper in the alloy produces sufficient positrons for fatigue measurements of parts made from aluminum alloys containing at least one tenth of a percent of copper. Other elements found in some aluminum alloys include zinc, which may be also neutron activated to serve as a positron source. Positrons from these neutron activated alloy constituents have been found to be suitable for determining the strength loss from fatigue of components built from aluminum alloys and steel. Further, positrons from these neutron activated alloy constituents permit fatigue measurements to be made at far greater depths within aluminum alloy parts than are possible with external positron sources. Therefore a significant advantage of the present invention is the ability to perform bulk analysis of a metal specimen (e.g., at a depth of up to 3.5 inches in steel) using positron annihilation, rather than being limited to surface analysis (e.g. at a depth of approximately one tenth of an inch) as is achieved by conventional positron annihilation techniques. Exposure of the aluminum alloy to a neutron flux of 1,000,000 neutrons per square centimeter per second for ten minutes has been observed to provide ample activation for measurement of fatigue and related defects in the aluminum alloy. This exposure will not cause measurable neutron embrittlement because measureable embrittlement does not occur until the alloy is subjected to a cumulative flux of 10.sup.15 neutrons per square centimeter. Therefore, use of the present invention on aircraft components can be performed in-situ and will not cause damage to the aircraft. Another neutron activated positron source formed within a metal test specimen is .sup.58 Co, which is formed by in situ neutron capture from .sup.59 Co within the metal. It has been observed that there are sufficient .sup.58 Co produced positrons present during refueling shutdowns at nuclear power plants. The .sup.58 Co is produced during normal operation of a nuclear power plant and is deposited on the primary coolant system surfaces and fixed in the approximately 0.1 micron corrosion layer. The .sup.58 Co is also embedded throughout the reactor pressure vessel wall adjacent to the reactor. Three characteristics of positrons and the radiation that they emit upon annihilation with electrons make the positron annihilation method of the present invention useful for detecting the presence and size of microscopic flaws in metals. First, the positive electrical charge cause positrons to be repelled by protons. This characteristic accounts for the positron's attraction to dislocations, vacant lattice sites, vacancy clusters, cavities and other open volumes (voids) in the metal, where the density of atomic nuclei is lower. Thus, a small increase in the number or size of the microscopic defects in a sample results in a large increase in the proportion of annihilation events occurring in the defects. Second, annihilation radiation is sensitive to the momentum distribution of the electrons with which positron annihilate. Defects contain a higher ratio of free electrons to core electrons than perfect metal. This phenomenon can be explained by the tendency of free (conduction electron) to spill over into the defect more than core electrons. Core electrons have a much higher linear momentum than do free electrons. Thus, gamma rays from annihilation events involving free electrons are more likely to approximate the energy (511 keV) and direction (180 degrees) typical of gamma rays produced by events involving positrons and electrons at rest. These characteristics make it possible to detect the presence of defects from the energy spectrum of the gamma ray emissions and from the spectrum of angles of deviation from 180 degrees. Third, because the density of electrons is lower in defects than in perfect metal, the mean lifetime of thermalized positrons trapped in defects is longer than those diffusing in perfect metal. Thus, measurement of positron lifetimes cans also be used to indicate the presence of defects in the metal. As shown in FIG. 1, the gamma rays 20 resulting from the positron annihilation are emitted from the metal specimen 16 and collimated through a variable slit collimator 22 and detected by a high purity germanium detector 24. Preferably the detector 24 is shielded from the neutron source 12 by a neutron shield 26. The collimator design required for these measurements is a variable slit collimator that allows the area of the metal being measured to be controlled so that the detector can be focused on specific areas such as a weld. The detector shielding configuration is shown schematically in FIG. 1. Interchangeable tungsten collimators with varying slit widths (nominally 1 inch long by either 1/8 inch and 5/8 inch wide) and a solid plug, are used with the shield/detector assembly for data acquisition. The detector/shield assembly is fixed in place at each measurement location with a specially designed strapping device that allows the detector to be attached to piping at any location. The collimator used was selected to achieve count rates that produced analyzer dead times less than 20%. The tungsten shield and the solid collimator plug provided at least two tenth-value layers for 1.3 MeV .sup.60 Co gamma rays. Background photopeak contributions from the solid collimator plug measurements are subtracted from those obtained with the open collimator. The measurement system components are specifically chosen to minimize rate effects on the detector and maximize resolution. In addition, a pulser system is used on the analyzer to provide assurance that the measurements are being performed without rate-dependent effects on peak shape. The detector used was an ORTEC Gamma X detector with a Canberra Inspector multichannel analyzer system being used to perform measurements on samples where the positron source was place near the surface of the metal. The detector has a tungsten backshield to prevent a gamma-ray leakage into the detector. The detector was a 59% detector with a 1.95 keV Full Width and Half Max (FWHM) for .sup.60 Co at 1332 keV. Numerous detectors were evaluated to obtain one with the required stability in variable radiation fields and the necessary resolution for performing these measurements. An example of an analysis system used in the present invention is a Canberra Inspector that had been specially modified so that pulse injection with subsequent removal to confirm that the spectrum was obtained in a stable environment and that gain shifts did not occur during data acquisition. The system had the following features: (a) pulser calibration can remain accurate for months, (b) automatic monitoring of the channel positions, shape of the pulser peaks for gain and zero shifts, extraneous noise, and (c) automatic correction for dead time and random summing. This system was temperature stable over the range 0.degree. to 100.degree. C. with a drift of less than 0.5 keV. Variation in the stability as a function of count rate is less than 3% over the range up to 135,000 counts per second. Referring now to FIG. 2, the method of the present invention is illustrated in schematic form. The data are in the form of gamma ray counts versus gamma ray energy. A parameter S, called a line-shape parameter, is used to measure the gamma spectrum width. The line-shape parameter is equal to the ratio of the number of counts in Region A to the total number of counts under the curve. The value of S increase as the number of defects within the specimen increases. The section of the gamma ray spectrum within 10 keV on each side of the 511 keV positron annihilation peak is extracted from the spectrum for analysis. This is referred to in this application as the "width" of the 511 keV peak. This section of the spectrum is integrated to determine the total number of counts in the spectrum and then is normalized to a predetermined integral quantity (nominally 10M counts). The centroid of the peak is then mathematically adjusted to a previously determined energy within 0.1 keV of the 511 keV peak. The channel contents of the channels above the adjusted centroid channel are then extracted from the spectrum section and the FWHM is calculated for the portion of the peak above the 511 keV energy. This is referred to in this application as the "high momentum structure" of the 511 keV peak. This provides an initial assessment of the peak shape and Doppler broadening of the peak when compared with standard peak shapes as defined by standard FWHM for the detector being used. The section of the spectrum above 511 keV channel is then compared on a channel by channel basis with reference spectra with know fatigue or embrittle levels. Then two spectral sections are identified that most closely bound the measured spectrum, interpolation is performed on the channel contents to determine the exact fatigue of embrittlement level by determining the average difference between the two fatigue levels and calculating the average fatigue based on interpolation of the values. A statistical uncertainty is then calculated by summing the differences in the channel contents between the measure spectrum section and the reference spectrum that is closest to the measured spectrum. The average uncertainty in the difference between the two spectral sections is calculated. This is necessary because the actual shape of the peak may vary based on temperature and other effects that may affect the shape of the peak. These uncertainties are reflected in the uncertainty associated with the fatigue measurement being performed. The fatigue or embrittlement level with an uncertainty associated that reflects how closely the measured spectrum reflects that section of the reference spectrum can then be reported and/or displayed by computer. The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments described explain the principles of the invention and practical application and enable others skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto. |
description | 1. Field of the Invention The present invention relates to a top nozzle having on-off hold-down springs for a nuclear fuel assembly used in a nuclear reactor, thereby preventing the uplifting of the nuclear fuel assembly, and more particularly, to a top nozzle having on-off hold-down springs for a nuclear fuel assembly that has a two-stage elastic section such that a pushing force against the axial movement of the nuclear fuel assembly under normal conditions is optimized and at the same time a suppressing force against a drastic uplifting force of the nuclear fuel assembly under transient conditions is strengthened. 2. Background of the Related Art A nuclear reactor is a device that artificially controls the chain reaction of the nuclear fission of fissile materials, thereby achieving a variety of use purposes such as the generation of heat, the production of radioisotopes and plutonium, the formation of radiation fields, or the like. Generally, enriched uranium that is obtained by raising a ratio of uranium-235 to a range between 2% and 5% is used in a light water nuclear reactor. The uranium is molded to a cylindrical pellet having a weight of 5 g and is processed to a nuclear fuel used in the nuclear reactor. Numerous pellets are piled up to form hundreds of pellet bundles and then put into a cladding tube made of Zircaloy being at a vacuum state. After that, a spring and a helium gas are put thereinto, and a top end closure stopper is welded thereon, thereby making a fuel rod. The fuel rod is finally surrounded by a nuclear fuel assembly and then burnt up within the nuclear reactor through nuclear reaction. The nuclear fuel assembly and the parts therein are shown in FIG. 1. FIG. 1 is a schematic view showing a general nuclear fuel assembly. Referring to FIG. 1, the nuclear fuel assembly includes a skeleton comprised of a top nozzle 4, a bottom nozzle 5, guide thimbles 3, and a plurality of spacer grids 2, and a plurality of fuel rods 1 inserted longitudinally into an organized array by the spacer grids 2 spaced along the length thereof in such a manner as to be supported by means of springs (which are not shown) and dimples (which are not shown) disposed within the spacer grids 2. So as to prevent the formation of the scratches on the fuel rods 1 and the generation of the damage on the springs within the spacer grids 2 upon assembling the nuclear fuel assembly, thereafter, the fuel rods 1 have a locker applied thereon and are then inserted longitudinally into the skeleton of the nuclear fuel assembly. Next, the top and bottom nozzles are secured to the opposite ends of the nuclear fuel assembly, thereby finishing the assembling procedure of the nuclear fuel assembly. Then, after the locker of the finished assembly is removed, the distances between the fuel rods 1, the distortion of the nuclear fuel assembly, the total length thereof, and the dimension thereof are checked out, thereby finishing the manufacturing procedure of the nuclear fuel assembly. Next, an explanation on the structure of the top nozzle 4 will be given with reference to FIG. 2, wherein the top nozzle 4 has a hold-down plate 20, a plurality of outer hold-down springs 30, a plurality of outer guide-tubular sleeves 40, a flow plate 10, and a center guide-tubular sleeve 50. Each of the outer guide-tubular sleeves 40 of the top nozzle 4 is connected at the lower portion thereof to each guide thimble 3 (see FIG. 1) of the skeleton and connected at the upper portion thereof to each insertion tube 6 in the reactor, thereby firmly fixing the nuclear fuel assembly in the reactor and ensuring the structural stability during the burn-up of the nuclear fuel. In more detail, the nuclear fuel assembly receives a hydraulic uplift force generated by the coolant flow during the reactor operation, such that it is floated or vibrated. Further, the thermal expansion due to the temperature rising, the irradiation growth of the nuclear fuel guide thimbles due to the neutron irradiation for a long period of time, and the variation of the axial direction length by creeps are generated in the nuclear fuel assembly. Therefore, the mechanical and structural stability of the nuclear fuel assembly against the axial direction movements and the length variations thereof should be ensured, which is achieved by the top nozzle 4, specifically the outer hold-down springs 30 of the top nozzle 4. In accordance with the designed shapes of the nuclear fuel assembly, there are provided several kinds of hold-down springs. Such the hold-down coil springs as shown in FIG. 2 are adopted in standard nuclear fuel assemblies generally used in Korea. Since the hold-down coil springs have a feature of operating only in an elastic section thereof, they should be designed to satisfy the elastic limits thereof. The hold-down coil springs in the nuclear reactor ensure their elastic section under generally expected operation conditions, that is, under normal conditions, and if the uplift force is generated within the elastic section, the hold-down coil springs have to have a minimum elastic coefficient capable of gently absorbing the generated uplift force, thereby preventing the fuel rods from being bent or distorted due to the deviation of the nuclear fuel assembly from its original position. On the other hand, under transient conditions, that is, if a drastic uplift force is generated, the hold-down coil springs should have a predetermined elastic coefficient such that they are not compressed below their close contact height (at which the springs are not pressed anymore since no space between the coils of the springs exists). In the conventional top nozzle having the hold-down coil springs, if the elastic coefficients of the springs are much lowered, the fuel rods are not sufficiently protected due to the limitation to the close contact height under the transient conditions, and contrarily, if the elastic coefficients of the springs are much raised, the springs are not elastically moved relative to the uplift force of the nuclear fuel assembly, thereby causing the fuel rods to be bent or damaged. Therefore, it is difficult to provide the springs having the elastic coefficient satisfying that the above-mentioned conditions. Therefore, there is a need for the development of the top nozzle having the springs providing a minimum hold-down force requested under normal operation conditions and at the same time easily satisfying the limitation to the close contact height and the allowable stress reference. Accordingly, the present invention has been made in view of the above-mentioned problems occurring in the prior art, and it is an object of the present invention to provide a top nozzle having on-off hold-down springs for a nuclear fuel assembly that is capable of preventing the nuclear fuel assembly from being bent by the generation of the excessive hold-down force under normal conditions. It is another object of the present invention to provide a top nozzle having on-off hold-down springs for a nuclear fuel assembly that is capable of providing a separate elastic force under transient conditions, in addition to the elastic forces of the springs operating under normal conditions. To accomplish the above objects, according to the present invention, there is provided a top nozzle having on-off hold-down springs for a nuclear fuel assembly, the top nozzle being connected to guide thimbles and an instrumentation tube of the nuclear fuel assembly at the lower end portion thereof and to insertion tubes of a reactor at the upper end portion thereof, thereby fixing the nuclear fuel assembly to the reactor, the top nozzle including: a hold-down plate having a center hole formed at the center thereof and a plurality of outer holes formed along the outer edge thereof, the plurality of outer holes being spaced apart by a given distance from the center hole thereof and having a given center angle; a flow plate having a center hole formed at the center thereof and a plurality of outer holes formed along the outer edge thereof, the plurality of outer holes being spaced apart by a given distance from the center hole thereof and having a given center angle, such that the distance between each outer hole and the center hole of the flow plate is the same as between each outer hole and the center hole of the hold-down plate; a plurality of outer guide-tubular sleeves each adapted to be inserted from the upper portion of each outer hole of the hold-down plate, passed through each outer hole of the flow plate, and connected to each guide thimble of the nuclear fuel assembly, each of the outer guide-tubular sleeves having a hold-down plate-locking part disposed at the top end thereof, the hold-down plate-locking part having a larger diameter than the diameter of each outer hole of the hold-down plate; a plurality of outer hold-down springs each disposed around the outer periphery of each outer guide-tubular sleeve between the hold-down plate and the flow plate, the outer hold-down spring being supported by the outer guide-tubular sleeve and providing a given elastic force between the hold-down plate and the flow plate; a center hold-down plate having a through-hole formed longitudinally therethrough; a center guide-tubular sleeve adapted to be inserted from the upper portion of the center hold-down plate and fastened to the center hole of the flow plate; and a center hold-down spring disposed around the outer periphery of the center guide-tubular sleeve between the center hold-down plate and the flow plate, the center hold-down spring being supported by the center guide-tubular sleeve and providing a given elastic force between the center hold-down plate and the flow plate. Therefore, the top nozzle of the present invention can lower the elastic coefficients of the springs operating under normal conditions more than those of existing coil springs, thereby providing an optimal hold-down force against the nuclear fuel assembly, and further, can provide an appropriate hold-down force in response to the variation of the length of the nuclear fuel assembly, thereby stably fixing the position of the nuclear fuel assembly and further preventing the nuclear fuel assembly from being bent. Additionally, the top nozzle of the present invention can provide a relatively strong hold-down force when compared with the conventional top nozzles, thereby ensuring the mechanical and structural stability of the nuclear fuel assembly. Hereinafter, an explanation on a top nozzle having on-off hold-down springs for a nuclear fuel assembly according to the present invention will be given with reference to the attached drawings. In the following description, it is to be understood that such terms as “top”, “bottom”, “left”, “right”, and the like are words of convenience, based upon the states shown in the drawings, and are not to be construed as limiting terms. Referring to FIG. 3a, the top nozzle for the nuclear fuel assembly according to the present invention basically includes a hold-down plate 20, a flow plate 10, a plurality of outer guide-tubular sleeves 40, a plurality of outer hold-down springs 30, a center hold-down plate 52, a center guide-tubular sleeve 50, and a center hold-down spring 53. An explanation on the hold-down plate 20 will be given with reference to FIG. 3b. The hold-down plate 20 has a center hole 22 formed at the center thereof and four outer holes 21 formed along the outer edge thereof, the four outer holes 21 being spaced apart by a given distance from the center hole 22 and having a center angle θ of 90°. The flow plate 10 has a center hole 12 formed at the center thereof and four outer holes 11 formed along the outer edge thereof, the four outer holes 11 being spaced apart by a given distance from the center hole 12 and having a center angle θ of 90°. At this time, the distance between each outer hole 11 and the center hole 12 on the flow plate 10 is the same as between each outer hole 21 and the center hole 22 of the hold-down plate 20. Referring to FIG. 3b, the outer guide-tubular sleeves 40 are described. Each outer guide-tubular sleeve 40 is extended to a predetermined length longitudinally. At the top end of each outer guide-tubular sleeve 40 is provided a hold-down plate-locking part 41 having a larger outer diameter than the inner diameter of each outer hole 21 of the hold-down plate 20. The outer guide-tubular sleeve 40 is inserted from the upper portion of each outer hole 21 of the hold-down plate 20 and is then passed through each outer hole 11 of the flow plate 10. After that, the outer guide-tubular sleeve 40 is connected to a guide thimble (which is not shown) of the nuclear fuel assembly. An explanation on the outer hold-down spring 30 will be given with reference to FIG. 3b. The outer hold-down spring 30 is formed of a hold-down coil spring and is disposed around the outer periphery of each outer guide-tubular sleeve 40 between the hold-down plate 20 and the flow plate 10. The hold-down spring 30 is supported by the outer guide-tubular sleeve 40 and provides a given elastic force between the hold-down plate 20 and the flow plate 10, if the flow plate 10 is lifted up. An explanation on the center hold-down plate 52 will be given with reference to FIG. 3b. The center hold-down plate 52 has a through-hole 54 formed longitudinally therethrough. At this time, the center hold-down plate 52 should have the larger outer diameter than the inner diameter of the center hole 22 of the hold-down plate 20. Referring to FIG. 3b, the center guide-tubular sleeve 50 is described. The center guide-tubular sleeve 50 is extended to a predetermined length longitudinally. At this time, the longitudinal length of the center guide-tubular sleeve 50 is shorter than that of the outer guide-tubular sleeve 40 and the difference between the lengths of the two sleeves causes an outer spring operation section. The center guide-tubular sleeve 50 is inserted from the upper portion of the center hold-down plate 52 and is fastened to the center hole 12 of the flow plate 10. At the top end of the center guide-tubular sleeve 50 is provided a center hold-down plate-locking part 51 having a smaller diameter than the diameter of the center hole 22 of the hold-down plate 20 and a larger diameter than the diameter of the through-hole 54 of the center hold-down plate 52. Next, an explanation on the center hold-down spring 53 will be given with reference to FIG. 3b. The center hold-down spring 53 is formed of a hold-down coil spring and is disposed around the outer periphery of the center guide-tubular sleeve 50 between the center hold-down plate 52 and the flow plate 10. The center hold-down spring 53 is supported by the center guide-tubular sleeve 50 and provides a given elastic force between the center hold-down plate 52 and the flow plate 10. Hereinafter, an explanation on the operations and effects of the top nozzle for the nuclear fuel assembly will be given. Referring to FIG. 3a, each of the outer guide-tubular sleeves 40 is coupled to the insertion tube 6, in the same manner as shown in FIG. 2, such that the nuclear fuel assembly is connected to the upper structure of the reactor, and the lower end of each outer guide-tubular sleeve 40 passed through the flow plate 10 is coupled to the guide thimble (not shown) of the skeleton, such that the skeleton and the fuel rods are fixed to the reactor. Since each outer guide-tubular sleeve 40 is formed of a hollow cylinder, a control rod (which is not shown in the drawings) is passed through the insertion tube 6 (see FIG. 2) and the outer guide-tubular sleeve 40 and is then inserted into the guide thimble connected to the lower end of the outer guide-tubular sleeve 40. In case where the nuclear fuel assembly is fixedly disposed in the reactor, the operations of the outer hold-down springs 30 and the center hold-down spring 53 will be described in detail. The hold-down plate 20 functions to support the outer hold-down springs 30, together with the flow plate 10. Further, the flow plate 10 functions to transmit the axial direction force applied to the nuclear fuel assembly by the hydraulic uplift force during the operation of the reactor to the outer hold-down springs 30. At this time, the outer hold-down springs 30 provide a hold-down force through the elastic force against the axial direction vibration of the nuclear fuel assembly. So as to explain the operations of the outer hold-down springs 30 and the center hold-down spring 53, it is assumed that the hydraulic uplift force is slowly increased. First, if the flow plate 10 is lifted up along the axial direction thereof by the hydraulic uplift force, the outer hold-down springs 30 start to be contracted. The section from the starting point where the outer hold-down springs 30 are contracted to the abutting point where the top end of the center hold-down plate 52 abuts against the lower end of the hold-down plate 20 is called an outer hold-down spring operation section. Referring to FIG. 4, that is, the section that reaches the on/off point along the displacement axis of the springs becomes the outer hold-down spring operation section. After that, if the uplift force is much increased, the center hold-down plate 52 is pressed against the lower end of the hold-down plate 20, such that the center hold-down spring 53 starts to be contracted. The section from the contraction of the center hold-down spring 53 to the contraction of the springs to a maximum contraction length is called an outer hold-down spring and center hold-down spring operation section. As shown in FIG. 4, that is, the section that is ranged over the on/off point along the displacement axis of the springs becomes the outer hold-down spring and center hold-down spring operation section. At this time, the elasticity of the outer hold-down springs 30 and the center hold-down spring 53 is added all, thereby providing the increased hold-down force. As shown in FIG. 4, that is, the four outer hold-down springs 30 are operated in the outer hold-down spring operation section, such that the size of the elasticity of the springs per the unit length of the displacement is not relatively large. However, the five springs are operated in the outer hold-down spring and center hold-down spring operation section, such that the size of the elasticity of the springs per the unit length of the displacement is relatively large. The existing top nozzle having the hold-down springs of a single kind and the top nozzle having the hold-down springs according to the present invention are compared with each other, as shown in FIG. 5, when they are really applied upon the operation of the reactor. The cross-hatched section of the graph in FIG. 5 indicates generally expected spring displacement, that is, normal operation conditions. Under the normal operation conditions, the springs adopted in the present invention show smoother spring characteristics than the existing springs. If the nuclear fuel assembly is lifted up due to the drastic hydraulic raising, the operation conditions of the reactor reach the transient conditions. In this case, the existing springs still show constant inclination characteristics. However, the springs of the present invention show increased inclination characteristics and the spring features having a relatively strong hold-down force, since the five springs are operated together under the transient conditions. Consequently, the springs adopted in the present invention have a relatively lower hold-down force than the existing springs, under the normal conditions, such that they can not give much load to the nuclear fuel assembly, and they have more increased hold-down force than the existing single kind of springs, under the transient conditions, such that they can appropriately protect the nuclear fuel assembly. While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention. |
|
048448621 | claims | 1. A spacing grid assembly for a nuclear fuel assembly, comprising: a plurality of plates disposed in two directions at least for defining cells having a predetermined mutual spacing and formed with windows distributed at even intervals corresponding to the mutual spacing of said cells, and a plurality of hairpin springs each consisting of a metal strip bent to form two mutually confronting legs welded together through said windows, wherein the cross-section of one of said legs of each of said hairpin springs in a direction perpendicular to said legs of the respective one of the hairpin springs has a U shape in a zone bearing on the other leg of the hairpin spring through a respective one of said windows and said U has a width slightly greater than the width of the other leg in the same zone so as to receive said other leg. 2. The spring as claimed in claim 1, wherein the U has a lateral size which corresponds to the width of the windows to be received therein. 3. The spacing grid as claimed in claim 1, wherein said springs are of a material retaining resiliency after irradiation and said plates are of an alloy having a low neutron capture cross-section as compared with said material. 4. The spacing grid as claimed in claim 1, wherein said other leg has a locally decreased width in said zone, so that the lateral size of the U corresponds to that of the remainder of the spring. 5. A hairpin spring for use in holding a fuel rod in position in a fuel assembly grid, consisting of an elongated metal strip having a 180.degree. bend to form two mutually confronting legs each having a zone of limited extent in the direction of elongation which bears on a mating zone of the other, said zones being arranged to be welded together locally and wherein one of said legs only has a U shape in its said zone and said U shape has a width slightly greater than the width of the other leg in the respective zone so as to receive said other leg in flat contact abutment. 6. The spring as claimed in claim 5, wherein the U has a widening shape for self-centering of the other leg. 7. A hairpin spring for use in holding a fuel rod in position in a fuel assembly grid, consisting of a metal strip bent to form two mutually confronting legs arranged to be welded together locally, wherein one of said legs has two lateral appendices bent substantially at 90.degree. which impart to said one of the legs a U shape, at least in a zone which bears on the other leg and said U shape has a width slightly greater than the width of the other leg in the same zone so as to receive said other leg. 8. The spring as claimed in claim 7, wherein the appendices of the U close up slightly so that the other leg can snap therebetween. 9. The spring as claimed in claim 7, wherein said other leg has portions for progressive merging of a current part and the portion of reduced width retained by the U. |
abstract | An Ag film as a light-reflecting film is formed on one surface of an a-C substrate of a scintillator panel. The entire surface of the Ag film is covered with an SiN film for protecting the Ag film. A scintillator having a columnar structure, which converts an incident radiation into visible light, is formed on the surface of the SiN film. The scintillator is covered with a polyparaxylylene film together with the substrate. |
Subsets and Splits
No saved queries yet
Save your SQL queries to embed, download, and access them later. Queries will appear here once saved.