Effects of Solid Reflectors for Water-Cooled Small Modular Reactor Core Design using FCM Fuels

Recently, many countries including USA have launched projects to develop the accident tolerant fuels (ATF) which can cope with the accidents such as LOCA (Loss of Coolant Accident). Recently, we have designed water-cooled small modular reactors using FCM fuels with uranium-nitride (UN) kernels and with Er₂O₃ burnable poison admixed with SiC matrix. The objective of this work is to increase cycle length of the previous designed PWR small modular reactor by employing two solid radial reflectors in order to improve the fuel economy by increasing fuel burnup and then to analyze the detailed performances of the new cores having solid reflectors. In this work, the effects of the solid reflectors (SS304 and graphite-based reflectors) on performances of the small modular reactor core loaded FCM fuels having UN kernels are analyzed by designing and analyzing the reload cores. From the study, it was concluded that the SS304 and graphited reflectors are very effective to increase the cycle length and discharge burnup by reducing radial neutron leakage. In particular, the graphite-based reflector extended the first cycle and the fifth cycle (almost equilibrium cycle) by 102 and 32 EFPDs, respectively without the considerable degradation of the performance parameters.