Concept and future design development of a sodium cooled super-safe, small and simple reactor

Concept of 4S (Super-Safe, Small and Simple) reactor has possibility of core design with integrity against all ATWS, non-proliferation and simple maintenance/operation. The 4S type reactors employ a reactivity control system with an annular reflector and driving mechanism. There is no moving part inside the reactor vessel except the reflector which moves very slowly at 1∼2 mm per month. Long-life of 4S reactor core is attained by changing axial power distribution with burn-up controlled by the moving reflector, and by using metallic fuel with the high conversion ratio. The long-life reactor core is envisioned to improve nuclear proliferation resistance. Critical assembly experiment of 4S reactor core is expected to verify the reactor core characteristics. (author)