Patent Number: 
Section: 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.