Neutronics and fuel cycle modeling of a thorium-fueled two-fluid molten salt iso-breeder reactor

Abstract

This paper presents reactor physics modeling to quantify behavior of a thorium-fueled molten salt iso-breeder reactor (MSiBR) system similar to the two-fluid molten salt breeder reactor (MSBR) documented in ORNL-4528. A Python framework was developed to allow for a flexible, fully parameterized modeling strategy for analysis of the fuel cycle and core neutronics. Modeling was performed in Serpent-2 to assess the MSiBR design and performance. The framework can be used for direct evaluation of reactor design parameters such as the fuel and blanket salt fraction, lattice geometry, and reactor core size. A full core model of the MSiBR system is presented. Temperature feedback coefficients of reactivity for the fuel salt, blanket salt, and graphite are calculated. It is observed that the present model demonstrates passive and inherent self-regulation of reactivity. The developed framework is also used to demonstrate a methodology for evaluating two-fluid reactors operating with a thorium fuel cycle. This work is intended to provide a baseline for future research into the development of two-fluid MSR designs.