Neutronic Analysis on Homogeneous Mixing Burnable Poison in PWR Loaded with FCM Fuel

Aiming to apply the fully ceramic microencapsulated (FCM) fuel in small module pressurized water reactor （PWR）, neutronic design and analysis on burnable poisons were carried out. The homogeneous mixing burnable poisons embedded in silicon carbide (SiC) matrix, such as Gd₂O₃, Er₂O₃, Sm₂O₃, Eu₂O₃, Dy₂O₃ and HfO₂, were studied via comparing the initial reactivity worth of the burnable absorber, the rate of burnup and the residual negative reactivity worth. The tristructural isotropic (TRISO) particle kernel in the concept FCM fuel design was up to 800 μm, thus the random geometry capability was developed in RMC code to treat the significant selfshielding effect. It is found that Er₂O₃ is excellent in integrated neutronics performance, thus can be used as burnable poison for FCM fuel loaded PWR. Gd₂O₃ and Eu₂O₃ are identified as candidate burnable poisons for further study. Sm₂O₃, HfO₂ and Dy₂O₃ are not capable for burnable poison.