Water Chemistry Control in Secondary System of Nuclear Power Plant

Steam generator (SG) is one of the core equipment of a nuclear power plant(NPP) and also the pressure boundary of primary circuit. The integrity and heat transfer performance of heat transfer tube of SG have a direct impact on the safety and economy performance of NPP. Due to the complex internal structure of SG and low polludant discharge ratio, some corrosive foreign material from feedwater area of secondary circuit are easy to lead to the heat transfer pipe fouling and corrosion beneath the scale or crevice, which will finally affect the safety and reliability of the SG. There are many factors affecting the secondary circuit corrosion, including chemical conditions of fluid, materials of equipment, flow rate of fluid, hydraulic conditions etc. The pH control of the secondary circuit is the key to reduce system corrosion. By analyzing the development history of the alkalizing agent and the selection of the alkalizers, the paper introduces an improvement use of amines in Qinshan NNP. It improves the pH value of the whole secondary circuit to the best level by using the mixed amines, which can effectively mitigate the corrosion of the secondary circuit materials and reduce the corrosion products into SG. Based on the research and application of amine characters and the achievement of mixed amines, it is concluded that the application of mixed amines will be more conducive to the control of secondary circuit corrosions, and will be a stream trend of secondary circuit corrosion protection control in the future.