Studies on use of reflector material and its position within FBR core for reducing U232 content of U produced in ThO2 radial blankets

Presence of U232 in U233 bred in thorium blanket of fast reactor is a major concern in fuel reprocessing. The former's daughter products being hard gamma emitter and the isotope itself having substantial half life, its presence beyond 10 ppm makes fuel recycle complicated and expensive. In this study possibility of decreasing U232 production in a typical FBR blanket by means of spectrum modification is examined. SS, depleted B4C, SiC, Mo and W regions were introduced between core and radial blanket and evolution of isotopes were studied to arrive at an optimal configuration that satisfies requirements of breeding U233 and lowering U232concentration. SS, B4C, SiC, Mo and W are known to be high temperature material with appropriate stability in harsh fast reactor environment. Study has shown that introducing two SS reflector rows can achieve the required low value of U232concentration without greatly compromising the U233production.