Radiation shielding analysis in molten salt reactors

Molten Salt Reactors (MSRs), which offer an innovative approach to nuclear energy technology and stand out due to their various advantages, are one of the potential future options for safe and sustainable nuclear energy. While MSRs are known to operate within the thermal neutron spectrum, certain designs are also capable of functioning in the fast neutron spectrum. In this context, the radiation shielding design in MSRs should be optimized based on variables such as the reactor's fuel cycle, operating temperature, and neutron spectrum. This thesis aims to analyze the proposed layered shielding model and examine radiation damage for a 50 kWth micro-MSR, for which the design has already been established. In the shielding design of the nine-layer micro-reactor, SS316 and B4C were replaced with SS304 and Hastelloy N (HN), respectively. Radiation shielding analyses were performed for both the reactor, as conceptualized in the literature, and the reactor designed using the proposed new materials. To this end, the reactor was modeled and simulated using the Serpent Monte Carlo simulation program in the initial phase. The neutron fluxes produced during the reactor's operation were determined from the simulation results and recorded as inputs for other simulation packages. The interactions of neutrons with the reactor's shielding layers, including secondary radiation, were analyzed using the GEANT4 and FLUKA programs. In addition to neutron analysis, the effectiveness of the shielding design in terms of gamma radiation was evaluated using the GEANT4, FLUKA, and XCOM codes. The results of the calculations demonstrated that SS304 and Hastelloy N provide superior shielding materials for both gamma and neutron radiation compared to SS316 and B4C.