Metalophysical Problems of WWER Reactor Vessel Welding Joints Reliability

Abstract

The prospects and possibilities of replacing the capacities of nuclear power units of Ukrainian nuclear power plants, which are currently almost completely depleting their operational life, as well as the possibility of extending the guaranteed service life are analyzed and generalized. Based on the study of reactor construction trends and proposals on the world market, a basic promising modern model of a high-capacity 3+ AP1000 nuclear water reactor manufactured by Westinghouse El. Corp. was selected and recommended as a basic promising for use in Ukraine. The results of new studies on the dynamics of strength loss of reactor steels of WWER reactors and their welding joints under the action of radiation are considered. The main attention is paid to the presence and processes of migration and segregation in the crystal structure of reactor steels of harmful impurities, in particular phosphorus and nickel. It is concluded that there are significant advantages of new foreign metallurgical technologies, the use of which in vessel steels provides reliability and increased guaranteed life of safe operation of PWR reactors, in particular, AP1000 type made in the USA. The urgent problems of commissioning additional shunting capacities in the National Unified Energy System of Ukraine were assessed and the conclusion was made that they can be solved by improving the shunting characteristics of existing high-capacity nuclear power units and (mainly) by accelerating construction and commissioning of small modular reactors with high shunting characteristics, in particular the SMR-160 model manufactured by SMR LLC (USA).