Analysis of representative unprotected accidents for a sub-critical lead-bismuth eutectic reactor using IMPC-transient

For an accelerator driven sub-critical system (ADS), the transient analysis of the sub-critical reactor is very important. It is better to use the 3D neutron transport kinetic model rather than the 0D point reactor kinetic model due to the change of the neutron spatial distribution in some conditions. The code IMPC-transient has been developed to provide an effective system safety analysis tool for Chinese ADS project, in which3D neutron transport kinetics is available. A 10 MW ADS conceptual scheme, in which the target power is 2.5 MW and the reactor power is 7.5 MW, was proposed to test the applicability of IMPC-transient in sub-critical lead-bismuth eutectic (LBE) reactor. The steady state and three accident cases including unprotected loss of flow(ULOF), unprotected beam overpower(UBOP) and unprotected beam-trip(UBT) have been simulated, and the dynamic thermal-hydraulic response was focused on. The results show that IMPC-transient has the function of analyzing the ULOF, UBOP and UBT conditions for the sub-critical LBE reactor, and the 7.5 MW reactor conceptual scheme is feasible under steady state and has remarkable resistance against ULOF, UBOP and UBT.