Reactivity Impact of Updated ³⁵Cl Nuclear Data on the Molten Chloride Reactor Experiment

The Molten Chloride Reactor Experiment (MCRE) will be built and operated as part of an Advanced Reactor Demonstration Project Risk Reduction Award. This fast spectrum, chloride salt–fueled molten salt reactor is sensitive to chlorine nuclear data. Recent experimental measurements of the ³⁵Cl (n,p) cross section disagree with ³⁵Cl nuclear data evaluations outside the bounds of the nuclear data uncertainty covariance matrices. To address this challenge, Los Alamos National Laboratory has been charged with measuring the ³⁵Cl (n,p) cross section at the Los Alamos Neutron Science Center and generating an updated ³⁵Cl nuclear data evaluation integrating recent cross-section measurements. This paper evaluates the reactivity impact of using the updated ³⁵Cl evaluation on the MCRE application compared to publicly available evaluations (ENDF/B up to VIII.0 and JENDL-5).