Coupled thermal-hydraulics and neutron-physics analysis of SCWR with mixed spectrum core

The new SCWR conceptual design (SCWR-M) is proposed on the basis of a mixed spectrum core consisting of a thermal spectrum zone and a fast spectrum zone. This new core design is considered to be the hybrid of the existing thermal SCWR and fast SCWR cores. It combines the merits of both thermal and fast SCWR cores, at the same time minimizes their shortcomings. For the thermal zone, the difficulties in the mechanical design and the maximum cladding temperature can be reduced as far as possible by the co-current flow mode; and for the fast zone, a sufficiently large negative coolant void reactivity coefficient and breeding ratio can be achieved by the multi-layer arrangement of fuel rods.The performance, including the burn-up behavior, of the proposed core is investigated with 3-D coupled neutron-physical and thermal-hydraulic calculations. During the coupling procedure, the thermal-hydraulic behavior is analyzed using a sub-channel analysis code and the neutron-physical performance is computed with a 3-D diffusion code. The results obtained so far have shown that the mixed spectrum SCWR concept (SCWR-M) is feasible and promising.