The Improvement And Study On Low Temperature Heat-sink Of North Nuclear Power Plants

With the growing energy crisis and the increasingly prominent environmental issues, nuclear power which is clean, economical and sustainable will become the inevitable energy choice of China’s economic and social development. In the history of China’s nuclear power development, nuclear power plants have been mostly sited in southern coastal areas. But since the Eleventh Five-Year Plan, with the increasing demand for nuclear power plants, nuclear power plant sites began to extend to the northern mid-latitudes area. In the northern winter, the seawater temperature is too low and would affect the safe operation of nuclear power plants. Heat sink system is the medium of releasing waste heat into the nature, which could ensures the safe operation in units normal condition and accident condition. In this article, the design improvements and research progresses of low temperature heat sink system are briefly introduced firstly. Then two improved schemes of heat exchanger bypass and hot water reflux are presented. Finally, this article highlights the new problems and corresponding solutions found in the system construction.For the heat exchanger bypass scheme, this article expounds the rationality and feasibility of design improvements from the aspects of improvement necessity, system layout program, system operating mode and improved control scheme. And the improved control scheme includes the impact of new plate on the running, the impact of sea tide and the analysis of thermal load regulation blind spot.For the hot water reflux scheme, the advantages are demonstrated by comparison with the heat exchanger bypass scheme. And the feasibility is further demonstrated from the aspects of flow rate calculation, stall load analysis, system operation control and some others. Finally, it is analyzed from the impact of improvement on other professions.Take engineering practice for example, a series of new problems and corresponding solutions which were found during the improved system start-up phase are listed. The heat exchanger bypass scheme includes heat exchanger icing problem, ultrasonic fiowmeter display problem and nuclear power fluctuation problem. The hot water reflux scheme includes gas accumulation problem in spare hot water reflux line, pressure interaction problem at the RRI/SEC start and stop moment and the problem that low stall cannot meet safety standards in winter mode.The basic data of different heat exchanger improvements are obtained through this research. The understanding of the heat sink system design and operation,which is used at cold high latitudes area, is enhanced. All these above will provide a fundamental basis for the design and safety assessment of nuclear power plants heat sink at cold high latitudes area.