A small long-cycle PWR core design concept using fully ceramic micro-encapsulated (FCM) and UO2-ThO2 fuels for burning of TRU

In this paper, a new small pressurized water reactor (PWR) core design concept using fully ceramic micro-encapsulated (FCM) particle fuels and UO2-ThO2 fuels was studied for effective burning of transuranics from a view point of core neutronics. The core of this concept rate is 100 MWe. The core designs use the current PWR-proven technologies except for a mixed use of the FCM and UO2-ThO2 fuel pins of low-enriched uranium. The significant burning of TRU is achieved with tri-isotropic particle fuels of FCM fuel pins, and the ThO2-UO2 fuel pins are employed to achieve long-cycle length of approximate to 4 EFPYs (effective full-power year). Also, the effects of several candidate materials for reflector are analyzed in terms of core neutronics because the small core size leads to high sensitivity of reflector material on the cycle length. The final cores having 10 w/o SS303 and 90 w/o graphite reflector are shown to have high TRU burning rates of 33%-35% in FCM pins and significant net burning rates of 24%-25% in the total core with negative reactivity coefficients, low power peaking factors, and sufficient shutdown margins of control rods.