Power control of CANDLE reactor by coolant flow rate

CANDLE reactors do not require control rods for burn-up control. Such reactors can achieve the excellent features of previously-considered CANDLE reactors such as constant power shape and reactivity feedback coefficients during the entire operation period at the rated power level. By eliminating control rod use for power level control, the CANDLE reactor can be operated in a load-following mode and its utility will expand dramatically.By numerical calculations, power control by coolant flow rate was studied for the sodium-cooled metallic fuel large CANDLE reactor. The effect of thermal expansion of the core support structure shows considerable contribution toward achieving negative reactivity feedback to improve the power controllability. We employ HT-9 and SUS316 for core support structures. Since the maximum cladding temperature reaches its design constraint, power level cannot be decreased less than its lower limit, which is 66% for HT-9 and 57% for SUS316.