Preliminary Study On Physics-thermal Coupling Technology Of Integrated Reactor Under Rolling Condition

The development of marine strategy requires more efficient and safer ship reactors to provide power,and the integrated natural circulation small reactors are valued for their high inherent safety.However,under complex ocean conditions,the position of the nuclear power plant changes when it receives the action of sea,wave and surge,which seriously affects the natural circulation of the reactor.In this paper,SNCLFR-10,a natural circulation pool type lead-cooled fast reactor with good natural circulation capability,is simulated,and a physical-thermal coupling program suitable for integrated ship reactor is developed.The influence of oscillating conditions on the reactivity of natural cyclic flow and the influence of physical-thermal coupling on the calculation are studied.In this paper,the physics-thermal coupling method is studied by using the large commercial computational fluid dynamics program ANSYS FLUENT program,point reactor neutron dynamics method and fuel rod transient heat conduction model.The coupling method is internal coupling,and FLUENT software is used as the main calculation program.The compiled point reactor neutron dynamics calculation model and fuel rod transient heat conductionmodel are invoked through the UDF interface to realize the physical parameter calculation and fuel rod transient heat conduction calculation functions that FLUENT does not have.The program was verified by a typical UTOP transient event,indicating that the coupled program developed can be used for reactor safety analysis.Under marine conditions,nuclear power plants move relative to the ground.The study uses a non-inertial system for analysis,and the additional inertial forces and gravity generated by the ocean action cause the fluid to move.The UDF function of FLUENT software is used to mount additional inertial forces on momentum source terms for iterative calculation,which enables FLUENT to study the influence of typical Marine conditions such as swing conditions on natural circulation flow characteristics.The calculation of swing condition is compared by using physical-thermodynamic coupling program and without considering physical-thermodynamic coupling.It is found that the average mass flow rate of the system decreases under rolling condition.Meanwhile,the amplitude of mass flow increases with the decrease of swing period and decreases with the decrease of swing amplitude.In the physical-thermodynamic coupling calculation,the actual power is lower than the rated power,thus affecting the temperature change of the core outlet and the influence on the mass flow rate of the system is negligible.