Transition cycle analysis of light water-cooled SMR core loaded with MOX (TRU) and FCM (TRU) fueled PWR assemblies

Highlights: • New fuel assemblies using MOX and FCM fuels for deep burning of TRU • Neutronic analysis for transition cycle of the SMR core with the new BA design • Void reactivity decomposition for better understanding of the physics In this study, a light water-cooled small modular reactor (SMR) core loaded with special fuel assemblies composed of mixed oxide (MOX) fuel rods using UO₂-TRUO₂ and fully ceramic micro-encapsulated (FCM) fuel rods using TRUO₂ was suggested and analyzed for transuranic (TRU) transmutation as an alternative option before the commercialization of sodium-cooled fast reactor (SFR). Especially, the FCM rods were loaded with only TRUO₂ for deep burning of TRU. This study performed neutronic analysis of the transition cycle cores with the new fuel assemblies. In addition to the neutronic analysis, detailed analyses on two important issues for the light water-cooled reactor (LWR) core loaded with TRU were performed in fuel assembly level calculation. First, an effective burnable absorber design was searched to mitigate the degradation in effectiveness of the burnable absorber caused by the hardened neutron spectrum. Secondly, a reactivity decomposition analysis was performed for understanding quantitative nuclide-wise and reaction-wise contributions to the void reactivity which is a key safety parameter of TRU-bearing fuel assemblies. The analysis on the TRU mass flow through the transition cycles showed that a high net TRU consumption rate of 14.7% can be achieved at the equilibrium cycle.