Patent Number: 
Section: claims

1. An assembly comprising:a nuclear reactor;a bundle of target assemblies within the reactor, at least one of the target assemblies comprising a housing defining a volume, wherein Np or Am spheres are within the volume;each of the target assemblies within the bundle being defined by a length along one axis, the length being divided into one or more portions, wherein the Np or Am spheres are contained within at least one of the one or more portions; andwherein two target assemblies that are arranged axially to one another have spheres in the upper portion of one and the lower portion of the other. 2. The reactor assembly of claim 1 wherein the target is circular in at least one cross section. 3. The reactor assembly of claim 1 wherein the bundle is an arrangement of target assemblies, the target assemblies being arranged in substantial circles about a center portion of the bundle. 4. The reactor assembly of claim 3 wherein the circles are substantially concentric defining both inner and outer circles. 5. The reactor assembly of claim 4 wherein each of the assemblies in the inner circle house Np or Am spheres. 6. The reactor assembly of claim 4 wherein each of the assemblies in the inner circle is lined with a ceramic material. 7. The reactor assembly of claim 4 wherein each of the assemblies in the inner circle is capped with a ceramic material.