Research On Subchannel Analysis Method Of Lead-based Fast Reactor Fuel Assembly With Wire Spacers For CiADS

Accelerator Driven System is recognized as an effective way to dispose of nuclear waste in the world.The subcritical reactor of the China Initiative Accelerator Driven subcritical System(CiADS)uses the liquid lead-bismuth eutectic(LBE)cooled fast neutron reactor,and the fuel assemblies are closed.In the design scheme of CiADS,the rod bundles are arranged in a triangular grid,and the fuel rods are positioned by wire spacers.The presence of wire can not only increase the transverse mixing in the bundles,but also decrease the hot spot factor and hot channel factor.LBE has better heat transfer ability and a high boiling point,which also does not react with water and air.Because of the complexity of the heat transfer phenomenon of leadbismuth coolant flow,the accurate calculation of coolant and cladding temperature of leadbismuth cooling fuel assembly with wire spacers is important for thermal hydraulic analysis of liquid metal cooled fast reactor fuel assembly,and is also the necessary part to ensure the safety of reactor.Therefore,it is essential to conduct sub-channel analysis for CiADS fuel assembly design parameters.In this paper,the CiADS lead-bismuth cooled fast reactor fuel assembly design scheme is taken as the research object,and a subchannel analysis code for lead-bismuth fast reactor wirewrapped fuel assembly is independently developed.The lumped parameter method is used to solve the conservation equation,and the applicability of liquid lead-bismuth in the friction resistance models,turbulent mixing models and heat transfer models of rod bundle fuel assembly is analyzed.Then the flow and heat transfer are compared and verified with the large eddy simulation results,THEADES lead-bismuth rod bundle experiment,and KYLIN-II leadbismuth rod bundle experiment,respectively.The results prove that the accuracy of the subchannel code in the calculation of flow and temperature,and the relative calculation error is within 10%.The subchannel analysis code can complete the thermal-hydraulic calculation of liquid lead-bismuth cooled wire-wrapped fuel assembly,which provides support for the design and thermal-hydraulic analysis of lead-bismuth fast reactor.Finally,the model of CiADS lead-bismuth fast reactor wire-wrapped fuel assembly is analyzed by using the subchannel analysis code under steady-state condition.According to the design scheme of CiADS lead-bismuth fast reactor,the axial temperature and mass flow distribution of coolant,the axial and radial temperature distribution of fuel rods,the hottest channel and the hottest rod are calculated.In addition,the sensitivity analysis of pitch to diameter is one of the key parameters in thermal-hydraulic and rod bundles of different sizes are also calculated.The calculation results show that the outlet temperature of the coolant,the maximum temperature of cladding and the fuel are all within the limits of the design values.The heat transfer performance and economy are the best when the rod diameter ratio between1.133 and 1.145.When the minimum scaling rod bundle is recommended to be 37 rods,the calculation result is the closest to the original size.