Integral molten salt reactor temperature sensitivities using Serpent target motion sampling

Abstract

The Molten Salt Reactor (MSR) concept has attracted several start-up companies due to the potential for reducing waste generation, realizing passive safety features, and seizing on the opportunity for cost effective economics. Terrestrial Energy, Inc (TEI), for example, has designed and is seeking regulator licensing for an Integral MSR (IMSR) design that contains all primary system components within a single reactor vessel containment. This study uses sensitivity analysis capabilities unique to Monte-Carlo particle transport code Serpent to determine and evaluate fuel salt Doppler and density temperature coefficients of reactivity for an IMSR over a range of normal or casualty temperature ranges. This study contrasts the temperature coefficients of three candidate molten salt fuels (FLiBe, FLiNaK, and NaF-RbF). The unique advantages and access to insightful neutron physics using Serpent code sensitivity methods are highlighted. An evaluation of the total reactor temperature coefficient and in particular the fuel salt temperature coefficients will show that an IMSR design can be self-limiting from a design basis accident perspective.