Ageing management improvement of primary sea water system in Qinshan nuclear power plant for operating license extension

摘要

Primary Sea Water System(PSWS)of Qinshan Nuclear Power Plant(QNPP)was designed to supply sea water as the cooling water for heat exchangers of component cooling water system and emergency diesel generator(EDG)cooling water system.The main ageing mechanism of PSWS components with the environment of sea water includes corrosion,erosion,bio-fouling,aggressive chemical attack and sediment deposition,which would induce blocking,protective liner failure,corrosion perforation,reduction of heat transfer capability and jeopardize the safety and economical operation of plant.In order to reduce the risk of ageing degradation in PSWS during the period of extended operating,this paper identifies the potential ageing degradation mode for PSWS components in QNPP,analyzes the insufficiency of the previous management measure,and investigated the coping strategy for each ageing degradation.Finally,the ageing management improvements of PSWS are provided that include biocide treatment,system flow testing,disassembling inspection for critical equipment and heat transfer capability motoring for safety important heat exchanger.These improvements have been applied in QNPP and proved effective in managing the ageing degradation of PSWS.