Study On Neutronics/Thermal Hydraulics Coupling In Typical Channel Of Subcooled Boiling Flow Under Rolling Condition

Ocean nuclear power plants were a new direction of the development of nuclear energy and become a focus point of current research. As the research background of subcooled boiling flow in the center subchannel of fuel assembly in ocean nuclear power plants under rolling conditions. By the method of the numerical calculation, the simulation and corresponding theoretical analysis about the characteristics of subcooled boiling and nuclear-thermal coupling were given under the rolling conditions in this paper.Based on 3D computational fluid dynamics(CFD) software Fluent?, the thermal hydraulic analysis codes for ocean nuclear power plants under rolling condition were been developed. The mass, momentum and energy transport caused by rolling and phase change were added to the source terms of the equations by the user defined function(UDF), and coupled with nuclear feedback model. The experimental data was used to independent validate each modules of the codes, with satisfactory agreement obtained.The simulated results indicated that the void fraction oscillation caused by rolling motion easily happened in the condition of the void fraction was relative low, rolling motion could not cause the flow oscillation of the outlet, but could cause the pressure drop oscillation of the subchannel. The oscillation amplitude of pressure drop was not influenced by rolling angle and period. The effects of rolling angle and period on the distribution of axial void fraction and relative speed of bubble were showed that the void fraction and speed increased with increasing rolling angle,and decreased with increasing rolling period. Furthermore, the region closing to the bubble departure point was more susceptible to the rolling motion.The actual parameters distribution in steady state was calculated by the codes, and as the initial parameters of rolling condition, the result showed that the trend of the actual power distribution was power decreased with increasing height. Under the same rolling condition, the oscillation amplitude of the void fraction under actual power distribution was greater than that under uniform power distribution. When effect of nuclear feedback was considered, the oscillation amplitude of the void fraction significantly decreased by the effect, and the effect ensured the running stability and security. Compared with the case of static condition, the whole void fraction was higher under rolling condition. As the negative reactivity of the system, the average power of the system was reduced by nuclear feedback effect. The oscillation amplitude of the void fraction in axial height was different, so the variations of power in different height level indicate different tendency.