Neutronic Performance and Safety Analysis of FeCrAl-Coated SiC Reflector in a Boron-Free SMR using LEU+ Fuel

This study investigates the neutronic performance and safety characteristics of applying a FeCrAl-coated Silicon Carbide (SiC) reflector to soluble-boron-free (SBF) Small Modular Reactor (SMR) utilizing 7 wt% LEU+ fuel. Conventional stainless steel (SS304) reflectors in small cores suffer from high neutron absorption, degrading neutron economy. Using the STREAM/RAST-K code system with equilibrium cycle restart calculations, this study compares SS304 and FeCrAl-coated SiC reflectors. Results demonstrate that the SiC reflector softens the peripheral neutron spectrum, enhancing the albedo effect. This improvement in neutron economy extends the cycle length by 25 EFPD (approximately 2.6%). Furthermore, the enhanced fission rate in peripheral assemblies flattens the radial power distribution under both unrodded and rodded conditions. This effect compensates for the 3-D power peaking induced by deeper control rod insertion, maintaining the power peaking factor ( F q ) comparable to the reference case. The impact on the shutdown margin (SDM) is negligible (-55 pcm), and the value remains significantly higher than the regulatory requirement (6,933 pcm > 1,000 pcm). These findings suggest that the FeCrAl-coated SiC reflector is a viable candidate for enhancing the economics of advanced SBF SMRs while preserving safety margins.