Conceptual design of a small modular natural circulation lead cooled fast reactor SNCLFR-100

•SNCLFR-100, a small modular reactor proposed by USTC, is with passive cooling feature to both normal and abnormal conditions.•LFR-SIN, a code for analyzing the steady state thermal-hydraulic performance of the reactor, was developed.•LFR-DIS, a code for calculating the mass flow distribution characteristics in the core, was developed.•LFR-SUB, a code for evaluating sub−channel T/H features in an assembly, was developed.•Fluent/PK was developed to analyze the major accident scenarios including UTOP and ULOHS in the reactor.

SNCLFR-100, a 100 MWth lead-cooled small modular reactor with a passive cooling feature to both normal and abnormal operations, was proposed by University of Science and Technology of China (USTC). The reactor is well suited as a remote power source because of its compact size, as well as because it has a refueling interval of 10 years without assembly reconfiguration. The reactor is a typical pool-type fast reactor with an array of heterogeneous square fuel assemblies loaded with MOX fuels. In this paper, the overall design and neutronics features were illustrated and evaluated. The steady state thermal-hydraulic performance, mass flow distribution characteristics and sub-channel T/H features were analyzed and discussed. Two major accident scenarios including unprotected overpower transient (UTOP) and unprotected loss of heat sink transient (ULOHS) were selected for a first evaluation of its dynamic behavior. The results show that the safety criteria are satisfied and reactor is tolerant to the UTOP and ULOHS transients. This implies that the conceptual design of SNCLFR-100 is acceptable and the reactor has excellent inherent safety characteristics.