Preliminary Stability Evaluation for Core subassembly of Liquid Metal Cooled Fast Reactor with Vertical Seismic Exciting

摘要

Liquid Metal Cooled Fast Reactor (LMFR) is an advanced type of nuclear reactor where the primary coolant is liquid metal. Two typical LMFR, Sodium cooled Fast Reactor (SFR) and Lead cooled Fast Reactor (LFR) are selected as the prior scheme of the GEN IV nuclear power system due to its inherent safety features and economic features. Common configuration of LMFR is designed as pool type, and fuel assembly is supported by core support structure at the footing. The fuel assembly is weak constrained in the vertical direction to reserve the space for refuelling, either pressured on the roof or fixed on the upper header. Reactor safety under seismic exciting is design basis, especially for core subassembly. In this paper preliminary stability evaluation for fuel assembly of LMFR with vertical seismic exciting is performed, taking typical SFR and LFR configuration into consideration. The behaviour of fuel assembly with free-standing under vertical seismic loading was discovered and investigated via analytical method. With relationship between siding term and resistance term, the analytical formulation is constructed in non-dimensional form. The typical reactors were taken for examples, the results show that SFR has lower requirement for core subassembly density than LFR, and may be impossible to simplify the seismic requirement for LFR with free standing design, which will provide a certain theoretical support for seismic design of LFR core assembly.