Parametric study of thermal molten salt reactor neutronics criticality behavior

The molten salt reactor (MSR) research and development has attracted more attention recently. Various concepts of MSR designs have been proposed, and related researches regarding MSR materials technologies, neutronics behavior, thermal-hydraulic behavior and the reactor safety have been reported. The MSR neutronics criticality behavior has significant effect in the MSR research aspect. It is important to conduct the comprehensive and systematic investigation of thermal MSR neutronics criticality behavior. In this work, the molten salt reactor type that molten salt dissolves the fuel materials is investigated. Therefore, the evaluations of different thermal MSR neutronics criticality behavior are conducted in this work. By far, various molten salt fuel types have been proposed by different research institutes based on different considerations. Consequently, the evaluation on neutronics characteristics of different molten salt fuel types and the parametric study of neutronics behavior are taken into account. Furthermore, some molten salt fuels contain the lithium element with the isotope Li-6, which has a large thermal neutron absorption cross section. The evaluation of different Li-6 concentration effects is also considered in this work. In addition to the fuel and moderators effect, other parameters such as the volume and geometry effects are also studied. Lastly, the operation temperature on the neutronics behavior is also investigated. The corresponding parameters such as multiplication factor, neutron spectrum, and temperature coefficient are evaluated. In this work, instead of the simulation of whole reactor core, the simulation of a thermal MSR fuel unit is conducted. This work provides a more complete and comprehensive evaluation approach for various parametric effect on MSR neutronics criticality behavior and offers reference for the MSR criticality design.