Safety Performance of a Large Scale Sodium Cooled Fast Reactor in Unprotected Transient Overpower Scenarios

Design options of large scale sodium cooled fast reactors are being studied intensively in China, and China Fast Reactor 1000 (CFR-1000) is one of the options. An unprotected transient overpower (UTOP) scenario analysis is carried out during the concept design phase of CFR-1000, aiming at estimating the safety performances of the core during the transient and providing feedbacks for the design. Reactivity insertion scenarios are simulated with different reactivity insertion rates. Safety aspects of core design are evaluated based on the simulation and analyses, including the design of reactivity feedbacks, the design of control rod as well as safety margin of fuel and cladding. The UTOP scenario analysis provides insights of CFR-1000 core design in safety aspect, and valuable information on safety design is given for future China fast reactor design.