Simulation Research Of The Circulating Water System Of Nuclear Power Plant Based On The Security Analysis

In recent years, due to paying more attention to the nuclear safety, it is more and more research on the simulation of nuclear power security. However, it is very few to research the circulating water system of nuclear power units. In this paper, from the perspective of safety, we construct the models of circulating water system and the process of the stopping pump hydraulic transition. Then we simulate the accident conditions of circulating water system of nuclear power units and analyze the simulation results of two models.On the basis of reasonable simplifying assumptions for circulating water system, we applied the process simulation software called APROS to establish the model of circulating water system of 600 mw nuclear power units. After checking the steady state, on the basis of the working conditions THA and TRL, we simulate the working conditions of the auxiliary power loss and the accident stopping pump. For each condition, we respectively set the exhaust flow of steam turbine as 650 kg, 600 kg, 550 kg and 500 kg for simulation experiments. The simulation results show that the time of the pressure of condenser exceeds 12 seconds from the outage value to the atresia side dump value under the working condition of the nuclear power units, which meets the requirement of "condenser available time is bigger than 12 seconds" putting forward by nuclear power institute of China under the conditions of the auxiliary power loss and the accident stopping pump. And on the basis of the results of simulation, we analyze the main influence factors of the pressure of condenser under the two kinds of working conditions and put forward the way how to increase the condenser available time.For the transition analysis of the process of the pump stopping hydraulic, we use the characteristic line method to establish model. And we apply the characteristic line method for the mathematical description of each part of circulating water system. After checking the steady state of the model, under the premise of the circulating water system without any protection measurement of water hammer, the simultaneous stopping pump of two circulating pump is simulated under the condition of considering water column separation and no considering water column separation, respectively. We importantly analyze the results of the pipeline highs, the inlet and the outlet of the condenser. With the simulation results, it can be seen that after stopping the pump the circulating water system without protective measurements, first, the pump reverse speed is close to the forward steady speed value, which can cause the damage of the pump and the motor, then, the condenser outlet can appear the phenomenon of water column separation, after bridge water hammer, which can produce serious damage to the pipeline. According to the analysis of the results, the protection measurement is proposed via setting siphon damage valve to eliminate bridge water hammer.In the paper, the models of circulating water system and accident stopping pump hydraulic transition process based on circulating water system of nuclear power units can correctly simulate the accident conditions, which exists good engineering application value. On the basis of the analysis of simulation results, it has important guiding significance with the improvement measurement of the processing of working condition accident of the circulating water system.