Analysis of abnormal operation of condenser water chamber evacuation system in nuclear power plants

Abstract

During the operation of a nuclear power plant, there was no level indication in some of the condenser outlet water chamber, the level of the vacuum control tank upstream of the water chamber evacuation pump was rising frequently and unintentionally. To find out the causes of the above phenomena, a phenomenological analysis was first carried out. The cause analysis is then carried out in conjunction with the internal pressure of the condenser, the calculation of the air volume inside the condenser water chamber, and the flow pattern of the medium inside the water chamber evacuation pipeline. The final analysis concludes that a low junction point between the inlet water chamber's evacuation pipeline and the outlet can lead to the formation of an airlock at the top of the condenser's outlet water chamber. When there is a leak in the evacuation pipeline of the condenser's outlet water chamber, the increased air intake, in conjunction with gas-liquid two-phase flow, causes the liquid level in the vacuum control tank to rise unexpectedly and frequently. Thus, the factor of higher pressure at the inlet water chamber evacuation point and the influence of gas-liquid two-phase flow pattern should be taken into account when designing the evacuation pipeline.