Irradiation target holders and methods of using the same in a nuclear reactor startup source holder position

Abstract

Irradiation target holders are configured to fit in open locations inside of an operating commercial nuclear core. Holders can be placed with ends at vertical bottom and top of the core or any position therebetween to directly expose holders to nuclear fuel reactions. Holders have ends and overall shape that can join with existing reactor structures, while fitting closely with fuel and moderator and being easily removable from the same. Holders are fabricated of any reactor-compatible material that will retain irradiation targets and daughter products. Holders securely retain irradiation targets and daughter products of any shape or phase throughout reactor operation. Holders can be installed during reactor outages and irradiated during operation without risk of movement or interference with operation. After a desired period of operation and irradiation, holders can be harvested from the core independent of other core structures and fuel.

What is claimed is: 
     
         1 . A method of irradiating materials in a commercial nuclear reactor generating heat for use in power production, the method comprising:
 removing a startup source from a startup source location within a core of the nuclear reactor; and   installing a target holder in the startup source location, wherein the target holder includes a same structure as the startup source that directly connect to structures within the core, and wherein the target holder includes an irradiation target that is not a neutron source.   
     
     
         2 . The method of  claim 1 , wherein the installing includes seating the target holder into a core plate in the reactor and into a top guide in the reactor, wherein the core plate and the top guide are at opposite ends of the core. 
     
     
         3 . The method of  claim 2 , wherein the installing further includes seating a fin of the target holder into a fuel casting on the core plate. 
     
     
         4 . The method of  claim 1 , further comprising:
 moving fuel assemblies directly adjacent to the startup source holder in order to expose the startup source holder.   
     
     
         5 . The method of  claim 1 , wherein the removing and the installing are performed with the startup source and the target holder submerged in water in the reactor. 
     
     
         6 . The method of  claim 1 , further comprising:
 sealing the reactor so that the target holder cannot be accessed; and   operating the reactor to generating heat through a fission chain reaction for use in power production.   
     
     
         7 . The method of  claim 1 , wherein the target holder includes a liquid water core that provides moderation to the irradiation target. 
     
     
         8 . The method of  claim 1 , wherein the irradiation target is cobalt-59. 
     
     
         9 . An irradiation target holder for free placement in a nuclear reactor core, the holder comprising:
 a lower end shaped to seat into a non-fuel structure in a nuclear reactor core; and   an irradiation target impermeably sealed within an internal cavity, wherein the irradiation target is non-fissile and not a neutron source.   
     
     
         10 . The target holder of  claim 9 , wherein the non-fuel structure is a core plate at a bottom of the core, wherein the lower end is shaped to seat into a hole for a startup source holder in the core plate, and wherein the holder further comprises:
 an upper end shaped to seat into a top guide at a top of the core, and wherein the internal cavity is positioned between the upper end and the lower end.   
     
     
         11 . The target holder of  claim 10 , further comprising:
 a plurality of fins extending horizontally from the lower end, wherein each of the fins is shaped to fit into a fuel casting above the core plate; and   
       a moderator cavity separated from the internal cavity and containing a neutron moderator, wherein the internal cavity and the moderator cavity extend at least 8 feet vertically.