In recent years, the operational events that the water intake of heat trap was blocked by marine life in nuclear power plants have occurred repeatedly. Since 2000, there have been more than 200 shutdown events of biological (foreign body) blockage resulting in failure of cooling water system in the United States, the United Kingdom, Sweden, Arabia, India, Israel, Japan, South Korea and China. It has caused major safety risks and brought huge economic losses and has attracted wide attention from various governments, related industries and research institutions. It can be seen that water intake blockage event is a safety problem for all kinds of power plants to face. This paper introduces the typical design of water intake and analyses the potential effects of a large number of marine life into the heat trap water intake from the perspective of circulating water system (CRF) jump pump and essential service water system (SEC) loss of function. Based on the characteristics of the high frequency of such operation events and they may cause major safety risks, the reactor shutdown response time in different conditions is simulated. When a large number of marine organisms flood into the water intake of heat trap, the response of the operator on the potential impact of the unit condition and the operational response plan are analyzed. The impact of the unplanned changes in operating status caused by the blockage of the water intake is explained. Ultimately, based on the analysis as described above, suggestions on the design improvement of the heat trap water intake and seawater filtration system in the nuclear power plant are presented. At the same time, suggestions are put forward on the supervision analysis, dynamic monitoring of the surrounding environment of the water intake, establishing a rapid decision-making mechanism, improving the cold source emergency response plan and increasing the operation control strategy.

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