Modular radioisotope production capsules and related methods

Abstract

Radioisotope production capsules are described. Each capsule generally includes an inner vessel for containing one of a target material and a neutron moderator, an outer vessel surrounding the inner vessel for containing one of the target material and the neutron moderator not contained by the inner vessel, and cladding for isolating the target material from the neutron moderator. One or more modular capsules are disposed on each of a plurality of plug fingers. Each single plug finger loaded with one or more capsules is inserted into a guide thimble of an array of guide thimbles in a fuel assembly.

Description

[Background technology]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 914,661, entitled "MODULAR RADIOISOTOPE PRODUCTION CAPSULES," filed October 14, 2019, the contents of which are incorporated herein by reference.

[0002] 1.Technical Field The present disclosure relates to radioisotopes, and more particularly to devices for capturing radioisotopes during nuclear power generation.

[0003] 2. Description of Background Technology Radioisotopes, or radioisotopes, are used commercially in various industries such as medicine, where gamma rays emitted by radioactive elements are used to detect tumors, in the food industry, where food is sometimes irradiated by exposure to gamma rays to kill certain bacteria, in agriculture, pest control, and in archaeology, where radiocarbon dating uses carbon-14 to determine the age of carbon-containing objects. Radioisotopes are highly unstable and decay easily, emitting radiation in the form of alpha, beta, and gamma rays. Radioisotopes classes are produced as a by-product of the operation of a typical nuclear power plant.

[0004] The production of commercially valuable radioisotopes such as Co-60, Ac-225, and W-188 requires the capture of at least one neutron by a target material placed within a nuclear reactor core. Cobalt-60 (Co-60) produces high-energy gamma rays that can be used, for example, in radiotherapy, sterilization of equipment, and food irradiation. Co-60 is a synthetic radioisotope of cobalt that is artificially produced in nuclear reactors. Intentional industrial production relies on neutron activation of bulk samples of the monoisotopic and mononuclear cobalt isotope Co-59. Actinium-225 (Ac-225) is produced by the decay of thorium-229. Ac-225 can be used in nuclear medicine for the treatment of malignant tumors. Tungsten-188 (W-188) is produced in nuclear reactors by irradiation of tungsten oxide with thermal and high-energy neutrons. W-188 is used to produce rhenium-188 (Re-188), a high-energy, beta-emitting radioisotope that has shown utility for a variety of therapeutic applications in nuclear medicine, oncology, radiology, and cardiology.

[0005] The rate of production of the desired radioisotope depends on the number and energy spectrum of neutrons surrounding the target material (e.g., Co-59, Thorium-229, etc.), as well as the probability that the target material will capture a neutron within the energy range. An example of this phenomenon is revealed by neutron "capture cross section" measurements for Co-59, shown in Figure 1 as a function of neutron energy. The neutron capture cross section is shown to be about 50 barn (b) at 0.025 eV. The neutron capture cross section increases dramatically with a capture resonance present at neutron energies of about 107 eV, which increases to about 7000 b. In U-235 fission, the most likely neutron energy is 0.73 MeV. Ideally, to maximize the rate at which Co-60 is produced, the number of neutrons below 104 eV needs to be maximized. This can be done by simply increasing the number of fissions that occur. This can be accomplished by increasing the amount of U-235 present in the fuel. However, the economic cost of that approach significantly increases the cost of the produced radioisotopes.

[0006] Another method is to increase the amount of 107 eV neutrons surrounding the target material without the need to increase the fission rate. This can be achieved by surrounding the target material with an optimal amount of neutron energy moderating material with high neutron inertness to slow down more neutrons with higher energies that would not normally be captured by the Co-59 target before diffusing out of the area of ​​the target. This effectively increases the number of fission neutrons that are in the desired energy range to maximize neutron capture in the target material. Optimizing the amount and distribution of water surrounding the Co-60 target will allow the average neutron energy spectrum around the target to be controlled to maximize the Co-60 production rate. The same approach can be used to increase the production rate of other desired radioisotopes.

[0007] One way to achieve a desired shift in the fission neutron energy spectrum around the irradiation target is to vary the amount of neutron energy moderator, such as water, or other material with low neutron capture and high neutron scattering cross section, between the target and the neutrons produced by fission. The hydrogen of the water moderator is very effective at slowing down the high energy neutrons, but does not capture them because it cannot interact with the irradiation target material at all. Adjusting the amount of water surrounding the irradiation target can be achieved in water-cooled and moderated reactor cores by controlling the geometry of the irradiation target. Materials other than water, such as low atomic number metallic materials (e.g., zirconium, nickel, graphite) with small neutron capture cross sections, can also be used to increase neutron capture in the target material.

[0008] Calculations performed by those skilled in the art have shown that the use of pressurized water reactor (PWR) fuel assembly inserts, similar to thimble flow plugs or thermoset absorber rods, containing rod-shaped slugs of Co-59 for the production of Co-60, can be used to produce commercially valuable quantities of Co-60. However, the Ci / cm of the current irradiation target geometry of Co-60 in the irradiated material at the end of the desired irradiation period is 3 and the predicted specific activity (SA) in Ci per unit length is less than required to support economically advantageous production useful in current application practices. Summary of the Invention

[0009] The following summary is provided to facilitate understanding of some of the innovative features unique to the disclosed embodiments and is not intended to be a complete description, A complete understanding of the various aspects of the embodiments can be obtained by taking the specification, claims, abstract and drawings, all of which are taken as a whole.

[0010] Described herein are devices and methods for producing maximum quantities of desired radioisotopes from irradiation targets designed to fit within guide thimbles present in conventional nuclear reactors, such as PWR fuel assemblies, with the intent of benefiting the economics of radioisotope production.

[0011] A radioisotope production capsule used for this purpose may include an inner vessel for containing either the target material or a neutron moderator, an outer vessel surrounding the inner vessel for containing either the target material or the neutron moderator not contained by the inner vessel, and a cladding for isolating the target material from the neutron moderator, which in various aspects may be a coolant such as water.

[0012] In various aspects, the inner vessel is defined by an inner wall of cladding material. In various aspects, the outer vessel is defined between an outer wall of cladding material and an inner wall of cladding material. The capsule may also include a locking member for axially joining adjacent capsules within an insert component of a fuel assembly of a nuclear reactor. The locking member may be mounted on the outer vessel in various aspects. In certain aspects, the locking member may be a quick disconnect locking member.

[0013] The capsule may also include support members for holding the inner vessel in a desired position within the outer vessel. The support members may be struts extending from an outer wall of the cladding material forming the outer vessel to an inner wall of the cladding material defining the inner vessel. The struts are preferably made of a material that expands at temperatures within the reactor to provide a pressure fit for the struts between the outer wall of the outer vessel and the inner wall of the inner vessel, and that contracts when cooled to a temperature below that within the reactor.

[0014] The inner vessel, in various embodiments, is a cylinder and the outer vessel is an annular cylinder concentric with the axis of the inner vessel. In certain embodiments, the inner cylinder holds a neutron moderator and the annular cylinder holds a target material for irradiation. The inner cylinder holds a target material for irradiation and the annular cylinder holds a neutron moderator.

[0015] A method for producing a desired radioisotope is described herein, the method including providing at least one capsule, each capsule having an inner container, an outer container surrounding the inner container, and a cladding material isolating the inner container from the outer container, inserting a target material that produces the desired radioisotope upon irradiation into either the inner container or the outer container, isolating the target material within the capsule by surrounding the target material with a cladding material, inserting a neutron moderator into either the remaining inner container or the outer container not containing the target material, inserting at least one capsule having the inner container and the outer container filled with the target material and the neutron moderator into an insert component of a nuclear fuel assembly, irradiating the target material to form a radioisotope from the target material, and removing the capsule from the insert component.

[0016] The modular radioisotope production capsule described herein allows the neutron energy spectrum to be optimized for target capture cross section and minimum reactor fuel assembly reactivity reduction, with the ability to tailor the total activity contained in the modular envelope. [Brief description of the drawings]

[0017] The features and advantages of the present disclosure can be better understood with reference to the accompanying drawings.

[0018] [Figure 1] This is an image of a graph (BNL-325) of the neutron capture cross section of Co-59 as a function of neutron energy. [Figure 2A] 1 shows an exemplary group of guide thimbles (A). [Figure 2B] 1B shows a schematic top cross-sectional view of the guide thimble when it is positioned within the fuel assembly. [Figure 2C] (C) Schematic illustration of a thimble plug finger and radioisotope production capsule for insertion in a guide thimble. [Figure 3A] FIG. 2 is a schematic top cross-sectional view of an exemplary modular radioisotope production capsule having an outer annular target material arrangement. [Figure 3B] 1 is a schematic cross-sectional side view of an exemplary modular radioisotope production capsule having an outer annular target material arrangement; [Figure 4A] FIG. 2 is a schematic top cross-sectional view of an exemplary modular radioisotope production capsule having a centrally located target material. [Figure 4B] FIG. 2 is a schematic cross-sectional side view of an exemplary modular radioisotope production capsule having a centrally located target material. [Diagram 5] 5 is a schematic illustration of the target material of the capsule shown in FIG. 4 inserted into the moderator-filled core of the capsule of FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0020] Directional expressions used herein, such as, for example, but not limited to, top, bottom, left, right, lower, upper, front, back, and variations thereof, relate to the orientation of the elements as shown in the accompanying drawings and do not limit the scope of the claims, unless expressly stated otherwise.

[0021] In this application, including the claims, unless otherwise stated, all numbers expressing quantities, values, or properties should be understood in all cases to be modified by the term "about". Thus, a number can be read as if it is preceded by the word "about", even if the term "about" is not expressly indicated with the number. Thus, unless indicated to the contrary, any numerical parameter set forth in the following description may vary depending on the desired properties sought to be obtained in the compositions and methods according to the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter set forth in this description should be construed at least in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0022] Any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges between (and including) the recited minimum of 1 and the recited maximum of 10, i.e., all subranges with minimums of 1 or more and maximums of 10 or less.

[0023] 2A and 2B, a nuclear fuel assembly 46 generally includes a number of fuel rods 48 (for clarity, only a few rods are shown around the perimeter, but in use, the rods will occupy most of the fuel assembly space) and a set of guide thimble tubes 30. The guide thimbles 30 are empty tubes provided to hold control rods or in-core instrumentation used within the nuclear reactor (not shown). As shown, each guide thimble 30 includes a neck 38, a midsection 32, and a tapered end 34. Several guide thimbles 30 are suspended from a plate 40, which is itself suspended by hold-down springs 44 from a top core plate 42 of the fuel assembly 46. In the example shown in FIG. 2B, there are 25 guide thimbles 30 in each fuel assembly 46. The number may vary depending on factors such as the size of the reactor.

[0024] 2C illustrates a cross-sectional view of an exemplary thimble plug finger 26 sized to fit within a guide thimble 30. The plug finger 26 includes an outer sheath 36, a cap 28 for closing the open end of the finger 26, and a tapered closed end 24. The plug finger 26 is intended to fit inside the guide thimble 30 such that the outer dimension of the finger 26 is equal to or less than the inside diameter of the guide thimble mid section 30. Either the junction between the mid section 32 and the tip 34, or the mid section 32 and the neck 38, may be open for insertion of the plug finger 26.

[0025] An exemplary radioisotope production capsule 100 (see FIG. 4 ) is shown positioned within the plug finger 26. In the absence of the plug finger 26 inserted into the fuel assembly guide thimble 30 during reactor operation, the guide thimble tubes would be filled with neutron moderator and coolant used in PWRs, such as water, with a flow rate exceeding that of the neutron moderator, which would flow through the fuel rods 48 contained within the fuel assembly 46. The plug finger 26 blocks this flow, resulting in an increase in the flow of neutron moderator and coolant between the fuel rods 48. The inclusion of irradiation target material within the plug finger 26 allows the plug finger 26 to both perform their intended function and produce the desired radioisotopes.

[0026] Those skilled in the art will appreciate that a variety of different geometries for the plug fingers 26 and radioisotope production capsules 10, 100 may be used, but using the same geometry as the conventional fuel assembly guide thimble 30 avoids the need to make any modifications to the mechanical design of the fuel assembly. This approach significantly reduces the costs associated with implementing radioisotope production in commercial light water reactor (LWR) designs.

[0027] 3A and 3B illustrate an exemplary embodiment of a modular radioisotope capsule 10 for insertion within a plug finger 26. Each capsule 10 shown includes an inner vessel, such as an inner cylinder 52 defined by an inner cladding 16. The inner cylinder contains a neutron moderator 14, in this embodiment, and a coolant, which in various aspects is water. Surrounding the inner cylinder 52 is an outer vessel, such as an outer annular cylinder 54, defined between the inner cladding 16 and the outer cladding 18. In various aspects, the inner cylinder 52 is positioned such that its axis is concentric with the axis of the outer annular cylinder 54. The annular cylinder 54 holds a target material 12, which in this embodiment is irradiated during a nuclear power cycle. The target material 12 will vary depending on the desired radioisotope to be produced, and an appropriate target material for production of the desired radioisotope may be selected. The target material 12 may be in any suitable form, including, but not limited to, a solid block, powder, pellets, spheres, or liquid. The top and bottom ends of the inner vessel in this embodiment, which holds the neutron moderator and coolant, are open to the plug finger interior, as shown by FIG. 3, by open ends 22. The top and bottom ends of the outer vessel, which holds the target material, are closed by top and bottom extensions of the outer cladding 18 to isolate the target material from the neutron moderator and coolant. In various aspects, two or more modular capsules 10 may be axially stacked within the plug finger 26 and connected to one another by locking rings or pegs 20 or similar mechanisms for joining adjacent capsules 10.

[0028] 4A and 4B illustrate an alternative embodiment of a radioisotope production capsule 100. The capsule 100 includes an inner vessel, such as an inner cylinder 152, which holds the target material 120, and an outer vessel, such as an outer annular cylinder 154, which holds the neutron moderator 140 and coolant in a PWR. An inner cladding 160 surrounds the top, bottom, and sides of the target material and separates the inner cylinder from the annular cylinder. An outer cladding 180 surrounds the sides of the annular cylinder. If the irradiated target material is a solid, the cladding may simply be deposited on the target material. If the target material is a powder, pellets, spheres, or liquid, the cladding forms the walls of the vessel for the target material to isolate it from the neutron moderator and coolant.

[0029] The support member 210 supports the inner cylinder 152 in place within the annular cylinder 154. The support member may be any device suitable for either or both centering and rigidly mechanically supporting the inner cylinder 152 within the annular cylinder 154. For example, the support member 210 may be a finger or post-like structure that extends radially outward from the inner cladding 160 or radially inward from the outer cladding 180 to connect with a mating surface on the opposing cladding surface. Alternatively, the support member 210 may be made of a material that undergoes thermal expansion under typical reactor temperatures to create a press-fit, but shrinks sufficiently upon a drop in the ambient temperature to allow the inner cylinder 152 to be removed from the annular cylinder 154.

[0030] In various embodiments, two or more modular capsules 100 may be axially stacked within the plug finger 26 and connected to one another by locking rings or pegs 200 or similar mechanisms for joining adjacent capsules 100.

[0031] The design of the capsule 10 or 100 described herein for the production of radioisotopes such as Co-60 maximizes gamma radiation emission intensity by maximizing conversion rate. Neutron moderator coolant, which may be water within the inner cylinder 52 or annular cylinder 154, enters and exits the outer sheath 36 of the plug finger 26 through small holes 50 that penetrate the outer sheath 36 and tip 24 of the finger 26 at the top and bottom of the plug finger 26, respectively. (See FIG. 2C.) As explained above, the portion of the capsule 10 / 100 that contains the moderator and coolant is not capped, so that the top and bottom of the capsule in this portion are open to the liquid moderator and coolant environment inside the PWR thimble plug finger 26.

[0032] The claddings 16 and 18, as well as the claddings 160 and 180, are made from materials that prevent the target material 12 / 120, such as Co-60, from leaching out of the cylinder that holds the target material within the cylinder that holds the neutron moderator.

[0033] The most suitable material will depend on the target material and the desired radioisotope to be produced. Exemplary materials for Co-60 include Ni and Zr. Exemplary materials for Ac-225 and W-188 include Zr and stainless steel. The material for the cladding will depend on factors such as the corrosion resistance of the target material to irradiation of the target material and the need to avoid chemical reactions that cause perforation during cladding.

[0034] The ratio of the thickness of the annular cylinder 54 / 154 to the diameter of the inner cylinder 52 / 152 can be adjusted using commercially available nuclear design tools, such as a software package utilizing the advanced nodal code for reactor core analysis (ANC™), or a similar package sold under the mark PALADIN®, as would be understood by one of ordinary skill in the art to calculate the dimensions necessary to maximize the production rate of the desired radioisotope.

[0035] The maximum value of the outer diameter of the capsule 10 or 100, shown in Figures 3 and 4 as Dm, is equal to the inner diameter (ID) of the plug finger 26, shown in Figure 2C. An example ID of the plug finger 26 is 6.1 mm. The length of the irradiation target material 12 / 120 contained in the capsule 10 / 100 is shown in Figures 3 and 4 as dimension Lt. This length is determined by the needs of the end user of the radioisotope. For example, the irradiation activity of a selected radioisotope required for a particular application can be calculated per unit length of target material in the capsule 10 / 100. For reasons that will be explained in more detail below, the ideal diameter (Ds) of the inner cylinder 152, as shown in Figure 4, or the target material 120 held within the inner cylinder 152, is equal to or less than the diameter (Dc) of the inner cylinder 52, as shown in Figure 3.

[0036] One or more capsules 10 and 100 may be loaded in tandem inside the plug finger 26. FIGS. 3 and 4 show exemplary modular capsules 10 and 100, respectively, which may be spaced apart from one another or stacked together within the internal cavity of the plug finger 26. In various embodiments, a means for mechanically joining adjacent capsule modules 10 or adjacent capsule modules 100 together, such as a locking ring 20 or 200, may be provided, optionally, to minimize the potential for mechanical vibration of the modules causing failure of the outer sheath of the plug finger, for example. An example of the type of connection method is the use of a quarter-turn quick-disconnect design. Numerous examples of quick-disconnect designs are known in the art. Modules 10 or 100 may be joined until the overall length and activity meets the needs of the end user.

[0037] The connected or stacked modules may be spaced apart from one another and separated within fingers 26 to allow the modular capsule 10 or 100 retrieved after irradiation to fit properly inside a shipping container used to transport the irradiated material from the production reactor to a final processing facility. Any suitable means may be used to separate the modular capsules from one another, such as support members 210 that hold the capsules from the sides and mount on the outer vessel rim or on the joining mechanism 20 / 200 (e.g., quick disconnect members on the rim) to axially separate adjacent modules within plug fingers 26, or similar mechanical attachments known to those skilled in the art. A suitable design of the attachment or suspension support will allow the capsule 10 / 100 and target material 12 / 120 to be easily extracted at low temperatures to facilitate removal of the target material from the capsule 10 / 100 at the irradiated material processing facility.

[0038] In practice, one or more capsule 10 modules will be placed in each of the multiple plug fingers 26. Each single plug finger 26 loaded with one or more capsules 10 will be inserted into the middle section 32 of the guide thimble 30. As shown in FIG. 2B, each individual guide thimble 30 in the array of guide thimbles may receive a plug finger 26 that is itself loaded with one or more capsules 10. In various embodiments, only one or a few of the guide thimbles 30 in the array of guide thimbles need be used to accommodate the plug finger 26 and capsule 10. Thus, multiple capsules 10 may be inserted into one or more guide thimbles 30 via the multiple plug fingers 26 and exposed to radiation in a nuclear reactor to produce the desired radioisotopes.

[0039] Alternatively, one or more capsule 100 modules would be placed on each of the multiple plug fingers 26. Each single plug finger 26 loaded with one or more capsules 100 would be inserted into the middle section 32 of the guide thimble 30. As shown in FIG. 2B, each individual guide thimble 30 in the array of guide thimbles may receive a plug finger 26 that is itself loaded with one or more capsules 100. In various embodiments, only one or a few of the guide thimbles 30 in the array of guide thimbles need be used to accommodate the plug finger 26 and capsule 100. Thus, multiple capsules 100 may be inserted into one or more guide thimbles 30 via multiple plug fingers 26 and exposed to radiation in a nuclear reactor to produce the desired radioisotope.

[0040] In a third alternative approach, modules of one or more capsules 10 are placed in one or more single plug fingers 26, and modules of one or more capsules 100 are placed in one or more different single plug fingers 26. The plug fingers 26 loaded with one or more capsules 10 and the plug fingers 26 loaded with one or more capsules 100 would be inserted into the intermediate sections 32 of different guide thimbles 30. As shown in FIG. 2B, each individual guide thimble 30 in the array of guide thimbles may receive a plug finger 26 that is itself loaded with one or more capsules 10 or one or more capsules 100. In various embodiments, only one or a few of the guide thimbles 30 in the array of guide thimbles need be used to accommodate a plug finger 26 with a capsule 10 or 100.

[0041] After irradiation, the capsule 10 / 100 and plug finger 26 must be removed from the guide thimble 30. The guide thimble will be withdrawn from the fuel assembly 46 by known means. The middle section 34 of the withdrawn guide thimble 30 may be opened, for example, by removing either or both of the tip 34 and neck 38. The plug finger or fingers 26 will be removed from the guide thimble 30 and the capsules 10 and 100 will be removed from the plug finger 26 and transported to a radioisotope production facility. In one embodiment, the capsule 10 / 100 may be retrieved from the plug finger 26 by cutting the finger 26 to an appropriate length to fit into a shipping container. Upon arrival at the production facility, the irradiated target material will be removed from the capsule and the desired radioisotopes will be separated from the irradiated material by known techniques.

[0042] FIG. 5 illustrates an exemplary method that can be used to increase the activity housed in the module shown in FIG. 3. The method involves irradiating (e.g., simultaneously or sequentially) modules such as those shown in FIG. 3 and FIG. 4 in the same reactor or in different reactor cores. Once the desired level of radioisotopes reaches the desired activity level and is transported to a processing facility, the linked modules of capsules 10 or 100 can be decoupled to produce individual modules. The contents of the cylinder 152, for example the contents of capsule 100 housed in the module shown in FIG. 4, are pushed out of the center of the module and into the cylinder 52 of the module of capsule 10 shown in FIG. 3. The diameter of the inner cylinder 152 in this procedure will be smaller than the diameter of the inner cylinder 52. The material received in the cylinder 52 will be prevented from passing completely through the bottom of the cylinder 52 by the rim around the bottom of the cylinder 52 and the locking ring 20. This will increase the net activity per unit length of the modules of the irradiation capsule 10 in the annular cylinder 54 to essentially the sum of the activities of both capsules 10 and 100. This approach can be used to build tubular irradiation sources with user-defined axial source intensity distributions that may be required to maximize the end user's desired radiation dose distribution.

[0043] Although capsules 10 and 100 have been described as having an inner cylinder and an annular outer cylinder, other shapes may be used, both housed within a capsule that may be inserted into an insert component for a nuclear fuel assembly such that radiation from the reactor may be absorbed by the target material to produce the desired radioisotopes, a cylinder fits best into an existing fuel assembly insert component, but the described concept of a container containing target material for irradiation adjacent to (e.g., either surrounded by or positioned within) a container of neutron moderator is not limited to a cylinder and may vary depending on the geometry of the reactor component.

[0044] The modular capsule 10 / 100 design and associated methods allow for the maximum amount of desired radioisotope production with minimal disruption in fuel assembly power distribution and minimal detrimental fuel assembly enrichment effects. The methods and capsule designs described herein allow for the desired radioisotope to be produced within existing fuel assemblies using existing guide thimble insertion designs.

[0045] The modular radioisotope production capsule 10 / 100 described herein allows the neutron energy spectrum to be optimized for target capture cross section and minimum reactor fuel assembly reactivity reduction, with the ability to tailor the total activity contained in the modular envelope.

[0046] Although the modular capsules 10 / 100 are described as being inserted into guide thimbles 30, they may additionally or alternatively be installed into other existing fuel assembly inserts, such as wet annular combustible absorber assemblies. The modular capsule 10 / 100 design offers radioisotope product suppliers a significant increase in product flexibility with respect to irradiation source activity levels and the distribution of activity levels within the irradiation source assembly.

[0047] Various aspects of the subject matter described herein are illustrated in the following examples.

[0048] Example 1 - A radioisotope production capsule comprising an inner vessel for containing one of a target material and a neutron moderator, an outer vessel surrounding the inner vessel for containing one of the target material and the neutron moderator not contained by the inner vessel, and a cladding for isolating the target material from the neutron moderator.

[0049] Example 2 - The capsule of example 1, wherein the inner container is defined by an inner wall of a cladding material.

[0050] Example 3 - The capsule of example 1 or 2, wherein an outer container is defined between an outer wall of a cladding material and the inner wall of the cladding material.

[0051] Example 4 - A capsule according to any of Examples 1-3, further comprising a locking member for axially joining adjacent capsules.

[0052] Example 5 - The capsule of example 4, wherein the locking member is mounted on the outer container.

[0053] Example 6 - The capsule of example 4 or 5, wherein the locking member is a quick disconnect locking member.

[0054] Example 7 - The capsule of any of Examples 1-6, further comprising a support member for holding the inner container in a desired position within the outer container.

[0055] Example 8 - The capsule of example 7, wherein the support member is a post extending from an outer wall of the cladding material forming the outer container to an inner wall of the cladding material defining the inner container.

[0056] Example 9 - The capsule of Example 7 or 8, wherein the struts are made from a material that expands at temperatures within the reactor to provide a press fit for the struts between the outer wall of the outer vessel and the inner wall of the inner vessel, and that contracts when cooled to a temperature below that within the reactor.

[0057] Example 10 - A capsule according to any of Examples 7-9, wherein the desired location of the inner container is axially centrally located within the outer container.

[0058] Example 11 - A capsule according to any of Examples 1-10, wherein the inner container is a cylinder and the outer container is an annular cylinder concentric with the axis of the inner container.

[0059] Example 12 - A capsule as described in example 11, wherein the inner cylinder holds a neutron moderator and the annular cylinder holds a target material for irradiation.

[0060] Example 13 - A capsule as described in example 11, wherein the inner cylinder holds the target material for irradiation and the annular cylinder holds a neutron moderator.

[0061] Example 14 - A method for producing a desired radioisotope, comprising: providing at least one capsule, each capsule having an inner container, an outer container surrounding the inner container, and a cladding material isolating the inner container from the outer container; inserting a target material that produces the desired radioisotope upon irradiation into either the inner container or the outer container; surrounding the target material with cladding material to isolate the target material within the capsule; inserting a neutron moderator into either the remaining inner container or the outer container into which the target material is not inserted; inserting at least one capsule having the inner and outer containers filled with the target material and neutron moderator into an insert component of a nuclear fuel assembly; irradiating the target material to form a radioisotope in the target material; and removing the capsule from the insert component.

[0062] Example 15 - The method of example 14, further comprising removing the irradiated target material from the capsule and separating the desired radioisotope from the irradiated material.

[0063] All patents, patent applications, publications, or other disclosure materials mentioned herein are incorporated herein by reference in their entirety, as if each individual reference were expressly incorporated by reference. All documents and any materials, or portions thereof, mentioned as being incorporated herein by reference are incorporated herein, unless the incorporated materials contradict existing definitions, descriptions, or other disclosure materials set forth in this disclosure. Thus, to the extent necessary, the disclosure set forth herein supersedes any conflicting materials incorporated herein by reference, and the disclosure expressly set forth in this application takes precedence.

[0064] The present invention has been described with reference to various exemplary and illustrative embodiments. The embodiments described herein are understood to provide illustrative features of various details of various embodiments of the disclosed invention. Thus, unless otherwise indicated, it should be understood that, to the extent possible, one or more features, elements, components, ingredients, materials, structures, modules and / or aspects of the disclosed embodiments can be combined, separated, substituted and / or rearranged with one or more other features, elements, components, ingredients, materials, structures, modules and / or aspects of the disclosed embodiments without departing from the scope of the disclosed invention. Thus, one skilled in the art will recognize that various substitutions, modifications or combinations are possible in any of the exemplary embodiments without departing from the scope of the invention. Moreover, one skilled in the art will recognize, upon review of this specification, or be able to ascertain using no more than routine experimentation, many equivalents to the various embodiments of the invention described herein. Thus, the present invention is limited by the claims, and not by the description of the various embodiments.

Claims

1. 1. A radioisotope production capsule comprising: an inner vessel for containing one of a target material and a neutron moderator; an outer vessel surrounding the inner vessel for containing either the target material or the neutron moderator not contained by the inner vessel; a cladding for isolating the target material from the neutron moderator; a locking member for axially joining adjacent capsules; A radioisotope production capsule comprising:

2. The capsule of claim 1 , wherein the inner container is defined by an inner wall of a cladding material.

3. The capsule of claim 2 , wherein the outer container is defined between an outer wall of the cladding material and the inner wall of the cladding material.

4. The capsule according to claim 1 , wherein the locking member is mounted on the outer container.

5. The capsule of claim 1 , wherein the locking member is a quick disconnect locking member.

6. 6. The capsule of claim 1, further comprising a support member for holding the inner container in a desired position within the outer container.

7. The capsule of claim 6 , wherein the support members are struts extending from an outer wall of a cladding material forming the outer container to an inner wall of a cladding material defining the inner container.

8. 8. The capsule of claim 7, wherein the struts are made from a material that expands at a temperature in a nuclear reactor to provide a press fit for the struts between the outer wall of the outer vessel and the inner wall of the inner vessel, and that contracts when cooled to a temperature below the temperature in a nuclear reactor.

9. 9. The capsule of claim 6, wherein the desired location of the inner container is axially centrally located within the outer container.

10. 10. The capsule of claim 1, wherein the inner container is a cylinder and the outer container is an annular cylinder concentric with the axis of the inner container.

11. The capsule of claim 10 , wherein the cylinder holds the neutron moderator and the annular cylinder holds the target material for irradiation.

12. The capsule of claim 10 , wherein the cylinder holds the target material for irradiation and the annular cylinder holds the neutron moderator.

13. 1. A method for producing a desired radioisotope, comprising: providing at least one capsule, each capsule having an inner container, an outer container surrounding the inner container, a cladding material isolating the inner container from the outer container, and a locking member for axially joining adjacent capsules; inserting a target material into either the inner container or the outer container that will produce the desired radioisotope upon irradiation; surrounding the target material with the cladding material to isolate the target material within the capsule; inserting a neutron moderator into either the remaining inner vessel or the outer vessel in which the target material is not inserted; Inserting at least one capsule having an inner container and an outer container filled with a target material and a neutron moderator into an insert component of a nuclear fuel assembly; irradiating the target material to form the radioisotope in the target material; Removing the capsule from the insertion component; A method comprising:

14. 14. The method of claim 13, further comprising removing the irradiated target material from the capsule and separating the desired radioisotope from the irradiated material.

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