Background: The 10-MWt TMSR-SF (Thorium-based Molten Salt Reactor-Solid Fuel) uses TRISO (Tri-structural isotropic) fuel and the fluoride salt is taken as a primary coolant. The molten salt could attach at the fuel element when the fuel was discharged from the core

which may consequently affect the reactivity of the spent nuclear fuel storage system. Purpose: This study aims to analyze the effects of the molten salt attached at the fuel element to the criticality safety of the spent nuclear fuel storage system. Methods: First of all

the TRITON (Transport Rigor Implemented with Time-dependent Operation for Neutronic depletion) module in SCALE was employed to calculate the burn-up results of the TRISO fuel in TMSR-SF reactor core

then in the premise of the maximum impregnated amount that the molten salt’s volume is 13.9% of the graphite’s volume

the criticality analysis of the spent nuclear fuel storage system was carried out by using MCNP code. Finally

the effects on the reactivity of spent fuel under conditions of molten salt infiltrated the fuel element and coated on the fuel element were compared separately. Results: Computational results showed that the reactivity in the situation that molten salt infiltrated the fuel element would be 5% greater than the molten salt coated the fuel surfaces

but is still in sub-criticality. The reactivity would be even smaller than that of the fuel elements contained only. Conclusion: Molten salt attached at the fuel element would affect the reactivity of the storage system

but the spent nuclear fuel storage system keeps in sub-criticality

which indicates the spent nuclear fuel storage system for TMSR-SF would remain in safety state. Abstract