Experience Obtained and Lessons Learnt from the Transition of Ukrainian NPPs to Long-Term Operation

Nuclear energy is a strategic Ukrainian industry that produces more than 50% of electricity at present. Over the last decade during the operation of Ukrainian NPPs, the set of technical matters have been found and corresponding tasks shall be decided with engaging of scientific potential of the country. One of such matter is a safety justification of NPP components and structures for the period that is bigger than an initial design one and that is defined as transition from design operation to the long-term operation (LTO). From the end of 2010 to the beginning of 2020, the State Nuclear Regulatory Inspectorate of Ukraine granted 11 licenses for 11 power units based on positive results of the state assessment and review of Periodic Safety Review Reports considering mandatory safety review each ten years. These results became possible due to the coordinated, conscientious and longstanding work of thousands of highly qualified nuclear experts, which led to the fact that Ukraine now has a unique experience in preparation for a transition of various types of WWER-1000 and WWER-440 reactors to LTO. The summarized results and lessons learnt from the practice of transition to LTO are presented in this paper. (author)