Preferred core conceptual design of pebble bed advanced high temperature reactor

Abstract Key parameters of Pebble Bed Advanced High Temperature Reactor (PB-AHTR) core are studied, and then the preferred core conceptual design is proposed. Both evacuating molten salt and injecting poison into coolant can be used as the auxiliary system of the second shutdown system in PB-AHTR. Compared with injecting poison into coolant, the effect of evacuating molten salt on the core is smaller and more beneficial to the engineering realization. Compared to one-time loading scheme, batch loading scheme can ensure that a small core excess reactivity in whole life-time which is easier to be controlled, but more complex to operation. In one-time loading scheme, the second shutdown system gains enough fast shutdown margins by increasing the number of second control rod, instead of reducing the stack height of core activity. The shutdown margins of both the first shutdown system and the second shutdown system meet the design requirements.