Research On Flow Charateristics Of Wire-wrapped Rod Bundles Fuel Assemblies In Fast Reactor

Sodium cooled fast reactor which provides economic and stable energy,and has higher utilization rate of uranium and higher security coefficent,is one of the fourth generation advanced nuclear power technology in the world.Fluid mechanics research of reactor premary circuit focus on the structure design of fuel assemblies in the fast reactor,which is related to core flow distribution and coolant pump parameters.The function and location of assemblies in the reactor lead to a significant difference requirement of coolant flow.Before the core flow distribution experiment,the hydraulic experiment of single fuel assembly should be carried out to verify the rationality of fuel assembly structure and provide experimental basis for reactor core design.The calculation of the resistance coefficient of wire wrapped rod bundle in the empirical formula is usually related to the structural parameters of the assembly,and it performance great uncertainty for different assemblies.Compared with others,Fuel assemblies in Chinese fast reactor are unique and have diefferent charateristics.On the other hand,much numerical simulation has been done,and experimental data are mostly kept secret.Among them,it studied the flow resistance characteristics of single fuel assembly in this paper,and the result would be applied to the experimental design of core flow distribution and monomer experiment apparatus.Core flow distribution experiment is one of the most important experients of fast reactor,and it requires a large number of fuel assembies.However,fuel rods are expensive and have trouble in producing.Considering from the economic and process cycle,there is a design scheme that using the test assembly instead,which keep the flow property and simplify the constructure.For this purpose,the feasibility of fuel assembly replacement scheme and structural parameters of the test assembly are confirmed through experiments,which has a certain engineering application value.In this paper,the flow characteristics of demonstration fast reactor with wire wrapped rod bundle are studied by theoretical calculation,hydraulic experiment and numerical simulation.Based on the empirical formulas,the fewer-rod assemblies with different rod bundle length were designed.According to the experimental data,the applicability of the three empirical formulas is compared.The local pressure drop of assembly except rod bundle is calculated by numerical simulation.At first,this paper verifies the accuracy of different empirical formulas in predicting the pressure loss coefficient of Chinese fast reactor fuel assembly and gives the error reference value.Secondly,the structural parameters of the fewer-rod assembly that can be substituted for the experiment are determined,which proves the feasibility of fuel assembly replacement scheme.Finally,the flowing property of complex component in fuel assembly was determined by the numerical simulation.Compared with experimental results of simulated assembly,results show that drag coefficient along the axial distribution is uneven and assess the fuel components resistance pressure drop of function structure,which has certain reference value on numerical simulation of simplified model selection.This study provides reference and experimental basis for the design and engineering application of fast reactor.