Design chemistry implementation experience during the power unit start-up and commissioning

The article covers the results of the design chemistry implementation during the commissioning of the innovative Unit 1 at the Novovoronezh NPP II equipped with a VVER-1200 reactor. The design chemistry is composed of the requirements for the primary and secondary coolant quality, recirculating coolant water (including essential service water), solutions used in safety systems as well as the requirements for technological tools maintaining their quality. Water chemistry setup operations play a significant role at all the stages of commissioning and low power testing. An analysis is made of essential system reactivation and cleansing stages, preliminary treatment technologies, primary and secondary circuit chemical water treatment, and radioactive water treatment. Some design advantages are highlighted, such as the use of reverse osmosis as one of the stages of water treatment and high-pressure filters on the bypass blowdown cleanup system. Consideration is given to some problematic issues that arose in the course of the start-up operations during the equipment depreservation, radioactive drain water treatment and in the recycling water supply system. The authors also analyze the design flaws and issues that may arise during long-lasting operation and the ways to solve them: (1) to provide a reference technology and equipment for processing radioactive drain water; (2) to exclude flushing with chlorinated hydrocarbons from the technology for depreserving the TG internal surfaces; (3) to apply water treatment with inhibitors providing calcium transport with a value close to 100% to the circulating water supply system with a cooling tower or provide liming of all additional water for southern NPPs to minimize the carbonate index.