A new approach is proposed to evaluate the safety of molten-salt reactors (MSRs), using advanced modeling and simulation (M&S) tools. This approach augments the Monitoring and Inspection (M&I) concept for fuel qualification by enabling computation of the change in critical safety parameters as a result of altered thermo-physical fuel properties. This work uses newly developed capabilities in the MOOSE framework to perform the requisite M&S. The neutronics code Griffin, using its neutron

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... n solver, is coupled to the coarse-mesh, multi-dimensional, thermal-hydraulic capabilities of Pronghorn. The resulting new capability enables efficient transient multiphysics simulations of open-pool-type MSR concepts, including delayed neutron precursor advection and beyond design basis events. The proposed approach uses the coupled Griffin/Pronghorn models to perform a sensitivity analysis by perturbing the salt thermophysical properties and evaluating the resulting impact on key safety parameters during an unprotected loss-of-forced-flow accident. In light of the challenges associated with predicting the effect of reactor operations and burnup on bulk salt properties, this work demonstrates how Griffin/ Pronghorn multiphysics simulations may be used to evaluate whether changes in salt properties could potentially lead to unsafe reactor configurations.