Development And Application Of Neutronics And Thermal-hydraulics Coupling Model For Nuclear-powered Propulsion Reactor Under Strong Transient Conditions

With the development of propulsion technology,human beings are eager to explore the universe more frequently.However,chemical propulsion technology has been an important constraint for humans to do space activities.Nuclear-powered propulsion technology provides the possibility to break through the restriction.The working fluid is heated to a very high temperature in the core reactor of nuclear-powered propulsion device.Then Nozzle accelerates to remove working fluid to generate thrust.As nuclear reactors have the advantages of high-power density and long working time,nuclear-powered propulsion devices have an irreplaceable advantage when spacecraft performing tasks which last long time.In the paper,the nuclear-powered propulsion reactor is taken as the research object.Firstly,based on numerical simulation,the turbulent heat transfer characteristics of high-temperature in the typical flow channel of the nuclear-powered propulsion reactor were explored.By comparing with experimental results,the heat transfer characteristics of the air in the circular channel under the condition of high heat flux were evaluated.The comparison of the simulated results and the experimental results verifies the accuracy of the numerical simulation method.Based on the verified numerical simulation method,the heat transfer characteristics of high-temperature air under non-uniform heating conditions were studied which could provide support for the subsequent neutronics and thermal-hydraulics coupling simulation.Secondly,based on the Monte Carlo code Open MC,the core of a typical nuclear-powered propulsion reactor was modeled and analyzed in the paper.And the physics parameters such as power distribution at different temperatures and delayed neutron share were obtained.Based on the point reactor model,how power of reactor changing with time under strong transient conditions with the introduction of reactivity was analyzed.Finally,to solve the issue that it costs a lot of computing resources when performing three-dimensional transient simulation of the core by traditional CFD.The paper proposes an improved numerical model to consider the heat transfer process between the fuel region and the coolant region,which could reduce a lot of time spent on the three-dimensional transient simulation.Based on the newly developed numerical model,the paper realizes the coupling calculation of the three-dimensional CFD method and the point reactor model and carries out the three-dimensional transient neutronics and thermal-hydraulics coupling analysis of the whole core.The thermal-hydraulics characteristics of the reactor under strong transient conditions were explored.The coupling results show that although heat release power of the core will increase instantaneously when a large amount of reactivity is introduced into the reactor,the temperature of the core will not increase instantaneously due to the heat capacity of the core and the cooling effect of the coolant.The numerical research results in the paper have certain reference and guidance significance for the design and manufacture of nuclear-powered propulsion reactors and the analysis of the characteristics of nuclear-powered propulsion reactors during the startup process.