OPTIMIZATION OF HETEROGENEOUS FUEL DESIGNS FOR UTILIZATION OF THORIUM IN PWRS TO ENHANCE PROLIFERATION RESISTANCE AND REDUCE

This paper summarizes the first stage of a project aimed at reducing the proliferation potential and spent fuel storage/disposal requirements of commercial power reactors through use of thorium in pressurized water reactors (PWRs) without recycling or separating the bred 233U. The project is carried out within the framework of the US Department of Energy Nuclear Energy Research Initiative (NERI). Two heterogeneous thorium implementation options are explored: 1) the Seed-Blanket Unit (SBU)/Radkowsky Thorium Fuel (RTF) concept which employs a combined, seed-blanket unit that is a one-for-one replacement for a conventional PWR fuel assembly; and 2) the whole assembly seed and blanket (WASB), where each seed or blanket unit occupies one full-size PWR assembly and the assemblies are arranged in the core approximately in a checkerboard array. The objectives are to identify heterogeneous core design and fuel management strategies which maximize the benefits. Both approaches are intended to be retrofittable into existing PWRs with minimum changes to existing systems/hardware, to be competitive economically, and to have comparable environmental, safety and health characteristics to those of existing PWRs (i.e., within the current ?safety envelope?). To date, it appears that reductions of 30% in spent fuel volume and 60% to 70% in plutonium production appear possible.