Scaling Analysis For Passive Containment System Based On Multi Coupled Physical Processes

The passive design concepts were widely used in AP advanced pressurized water reactors.The passive containment system of AP advanced pressurized water reactors is one of the most important passive safety design technology.There are many distinctive physical phenomena from traditional containments.It is urgent to solve many problems,such as how to correctly simulate the important physical phenomena,how to put forward systematic and feasible scaling methodology for subscale test device and how to decide the size of the device.The present essay is focused on AP passive containment system.Scaling analysis based on multi coupled physical processes was carried out,which concentrates on the essence of important physical phenomenon and mechanisms of physical processes of passive containment system.Based on H2 TS methodology,considering of features of passive containment,Sequential Parallel Interdependent Complement(SPIC)scaling method was put forward.Firstly,the containment system was decomposed into hierarchy structures and the top level system was scaled.For the outside cooling of the passive containment,a simplified containment mathematical model was built and numerically solved.Air circulation driven by natural forces for a steady condition along with the coupled thermal-hydraulic phenomena was then obtained and analyzed.Variations of humid air temperature and velocity,water film sub-cooling and heat fluxes along the flow direction were discussed and driving forces were compared to obtain the ranked important phenomena of the PCCS outside cooling.Then,scaling analysis of air circulation was studied and dimensionless numbers were obtained.The relationships between dimensionless numbers were analyzed in detail.The experimental investigation and theoretical analysis were separately carried out for water film flow behavior with evaporations.Making use of the experiment device of passive containment coupled heat transfer in State Nuclear Power Company,the influence of the counter-current air velocity on the water film behavior was studied.Water film thickness,transient wave features and water film average velocity were measured and obtained for different relative humidity and temperature.The effects of counter-current air velocity and test plate angle on the water film thickness were also considered in experimental studies.The correlation of the water film was then obtained.Theoretical analysis was made for falling water flow behavior with evaporations and the influences of the contact angle and water temperature on water coverage were then discussed.The falling water flow with evaporation for AP1000 containment was simulated and local water coverage fraction were obtained for various water flow rates.Finally,based on the above analysis of the falling water evaporation process,the scaling-down for AP1000 containment is deduced and the similarity criteria were obtained,which would be used to improve designs for scaling-down test facility.Current work numerically studied the AP1000 heat removal enhancement due to the partially wetted.FLUENT was used to simulate two-dimension thermal conduction of the containment shell and calculate the local heat fluxes and their distributions.Finally,according to the wetted coverage ranges for AP1000 passive containment,empirical correlations for heat transfer enhancement were concluded.Based on above analysis,scaling analysis of thermal conduction of the containment shell was made and the similarity criteria were obtained.