Patent Number: 
Section: claims

1. An irradiation target retention system comprising:at least one irradiation target retention device,dimensioned and shaped to fit within a nuclear fuel rod such that a central axis of the at least one irradiation target retention device is parallel to a longitudinal axis of the fuel rod in which the at least one irradiation target retention device is dimensioned and shaped to fit,fabricated of a material configured to substantially maintain its physical and neutronic properties when exposed to the neutron flux in the operating nuclear reactor, andindividually defining each of a plurality of bores, each of the bores being defined with a bottom in the irradiation target retention device in a direction of the central axis of the irradiation target retention device such that the bores do not pass entirely through the irradiation target retention device in the direction of the central axis of the irradiation target retention device, each of the bores being offset from the central axis of the irradiation target retention device; andat least one irradiation target contained in the irradiation target retention device by one of the bores, the irradiation target configured to substantially convert to a radioisotope when exposed to a neutron flux in an operating nuclear reactor. 2. The system of claim 1, wherein the at least one irradiation target retention device includes a cap configured to attach to an end of the irradiation target retention device having the at least one bore, the attaching of the cap and the device configured so as to retain the irradiation target within the at least one bore. 3. The system of claim 1, wherein the irradiation target is at least one of Iridium-191 and Cobalt-59. 4. The system of claim 1, a central axis for each of the bores is placed at an equal radial distance from the central axis of the irradiation target retention device. 5. The system of claim 4, wherein the at least one irradiation target retention device further defines at least one hole passing entirely through the irradiation target retention device, a central axis for the hole being located at the equal radial distance from the central axis of the irradiation target retention device. 6. The system of claim 5, wherein the at least one irradiation target retention device includes a keyed slit positioned about the central axis of the irradiation target retention device and passing through the irradiation target retention device, the keyed slit having a unique orientation with respect to the at least one hole. 7. The system of claim 1, wherein the irradiation target retention device is fabricated from at least one of a zirconium alloy, stainless steel, aluminum, nickel alloy, and Inconel. 8. A nuclear fuel assembly comprising:an upper tie plate;a lower tie plate; anda plurality of fuel rods extending between the upper tie plate and lower tie plate, at least one fuel rod including at least one irradiation target retention device including,a plurality of irradiation targets contained within a bore defined by the irradiation target retention device, the bore being offset from a central axis of the irradiation target retention device by a distance, the bore being defined with a bottom in the irradiation target retention device in a direction of the central axis of the irradiation target retention device such that the bore does not pass entirely through the irradiation target retention device in the direction of the central axis of the irradiation target retention device, the irradiation targets configured to substantially convert to a radioisotope when exposed to a neutron flux in an operating nuclear reactor,the irradiation target retention device including a hole passing entirely through the irradiation target retention device, a central axis of the hole being offset from the central axis of the irradiation target retention device by the distance,the irradiation target retention device dimensioned to fit within the at least one fuel rod, andthe irradiation target retention device fabricated of a material configured to substantially maintain its physical and neutronic properties when exposed to the neutron flux in the operating nuclear reactor. 9. The nuclear fuel assembly of claim 8, wherein the irradiation targets include at least one of Iridium-191 and Cobalt-59. 10. The nuclear fuel assembly of claim 8, wherein the at least one fuel rod includes a plurality of irradiation target retention devices axially stacked within the at least one fuel rod. 11. The nuclear fuel assembly of claim 10, wherein the at least one fuel rod further includes a spring configured to compress the axially stacked plurality of irradiation targets within the at least one fuel rod with a force such that the irradiation target is sealed in the at least one bore. 12. The nuclear fuel assembly of claim 10, wherein the irradiation target retention device individually defines each of a plurality of bores and a central axis of each of the bores is placed at the equal radial distance from the central axis of the irradiation target retention device. 13. The nuclear fuel assembly of claim 8, wherein the irradiation target retention device further includes a keyed slit positioned about the central axis of the irradiation target retention device and passing through the irradiation target retention device, the keyed slit having a unique orientation with respect to the at least one hole. 14. The nuclear fuel assembly of claim 8, wherein the irradiation target retention device is fabricated from at least one of a zirconium alloy, stainless steel, aluminum, a nickel alloy, and Inconel. 15. The nuclear fuel assembly of claim 8, wherein the at least one irradiation target retention device includes a cap configured to attach to an end of the irradiation target retention device having the at least one bore, the attaching of the cap and the device configured so as to retain the irradiation target within the at least one bore. 16. The system of claim 1, wherein the material does not substantially interfere with the neutron flux. 17. The nuclear fuel assembly of claim 8, wherein the material does not substantially interfere with the neutron flux.