The design of the reactor coolant pump heat shield of Qinshan Nuclear Power Plant in China National Nuclear Power Co., Ltd. is a weakness in the design of the EDF standard 900MW nuclear power plant. When the reactor coolant pump heat shield is broken, and the single failure of the equipment cooling water system valve (RRI219VN (220VN) or RRI225VN (226VN) valve) is considered, it is inevitable that the high-pressure coolant will damage the equipment cooling system (RRI), resulting in a LOCA accident of the containment bypass type. The Unit 3 and Unit 4 of Qinshan Nuclear Power Plant were improved during the construction stage, and the upstream of the heat shield was changed to 2 check valves and the downstream was 2 electric valves. The modification hasn’t been performed in Unit 1 and Unit 2 of Qinshan Nuclear Power Plant. Qinshan Nuclear Power Plant has entrusted the research institute to carry out the plan design, and the on-site verification of the plan was limited by the on-site space and could not be implemented. There are also factors such as a large amount of work to be carried out by the main control room board replacement, and insufficient time for outage implementation. This article makes a safety analysis of this technical modification using PSA method to determine the necessity of the technical modification.

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