Feasibility study on LEU-based molten salt and metal reactor for ultramicro miniaturization

Abstract

As a means of maintaining inherent safety features of Molten Salt Reactor (MSR) whilst miniaturizing its size concerning LEU-based MSR, a concept of Molten Salt and Metal Reactor (MSMR) is proposed and investigated in this paper. Unlike the conventional MSRs which exploit molten salt as both fuel and coolant, the MSMR utilizes liquid metal of a uranium alloy and molten salt as its fuel and coolant, respectively. The usage of compacted nuclear fuel renders MSMR to achieve criticality even for the ultra-micro reactor size and results in a higher conversion ratio which enhances the possibility of attaining long-life operation without online reprocessing. In addition, the reduction of initial heavy metal mass implies reduced construction cost that enhances the potential for commercialization. The configuration of the reactor core and enrichment of the uranium fuel are both optimized in order to minimize the reactivity swing while maintaining the feasibility of the long-life operation alongside a drum-type control device for managing the excess reactivity during operation. The calculations are conducted with Monte-Carlo Serpent 2 code with ENDF/B-VII.1 library.