Design & optimization of two breeding thorium-uranium mixed SCWR fuel assemblies

The rational exploitation of thorium reserves is a promising way to overcome the pressing problems of nuclear fuel shortage, nuclear waste disposal and nuclear proliferation. In this paper, two different kinds of novel conceptual designs of breeding thorium-uranium (Th-U) mixed fuel assemblies in SCWR are proposed. The optimizations of the fuel pin diameter, pitch-to-diameter ratio and enrichment have been carried out, aiming to achieve desired discharge burnup, bigger breeding ratio, and smaller ppf, so as to fulfill the sustainable breeding thorium-uranium cycle. Through the calculations of neutronics and neutronic/thermohydraulic (N-T) coupling, the results indicate that: the introduced two conceptual designs of breeding Th-U mixed fuel assemblies satisfy design rules of SCWR, while have the advantages on ideal breeding performance, less minor actinide generation and reactor safety.