VVER long-term operation – A review based on the material studies results from past and ongoing EU-supported research projects

Safe and long-term operation (LTO) of nuclear power plants (NPP) with Water-Water Energetic Reactors (VVER) is essential for several central and eastern European countries to keep their energy supply security. During the last decades, several EU-supported projects in framework projects or Horizon2020 schemes have focused on the material degradation of pressurised water reactors (PWRs), especially VVERs. This paper aims to extract the most important results dominantly from EURATOM projects which support or could limit the long-term operation of this Soviet design of PWRs. The accent is given on ongoing projects such as FRACTESUS, STRUMAT-LTO, APAL, and ENTENTE. Actually, running project DELISA-LTO (2022–2026) comprises not only results from previous research in this area but also incorporates wide material databases coming from nuclear power plant V-1 in Jaslovské Bohunice (Slovakia), which was shut down after 28 years of operation and provides wide-range of original service-aged materials specimens for profound material studies having in mind lifetime extension of VVERs. Consolidated knowledge focused mainly on the reactor pressure vessel (RPV) material studies is summarised and supported by relevant references.