A Technical Safety Review (TSR) mission was carried out by the International Atomic Energy Agency (IAEA) in Kozloduy NPP from 20 to 31 March, which made a review of the probabilistic safety assessment (PSA), level 1 of the plant’s Units 5 and 6.
Being an important analytical tool for risk assessment in support of improvements of the safety in operation of nuclear power plants, the probabilistic safety assessment is periodically updated to account for developments of the analytical methods and tools, as well as plant’s status and performance. The subject of the IAEA’s TSR-PSA mission was the latest update of the PSA, level 1, of Kozloduy NPP Units 5 and 6, that was developed within the period 2020 - 2022. The TSR-PSA mission covered the following areas: internal events, internal fires, internal floods and other internal hazards, seismic and other external hazards relevant for Kozloduy NPP site, and their combinations. The TSR-PSA mission also covered the multi-unit considerations and various modes of operation - full power, low power and shutdown reactor modes.
The goal of the mission was to perform an independent review of the scope, data used, models and approaches applied in the PSA and the quantification of the PSA results against relevant IAEA safety standards and internationally recognised good practices.
The review team comprised six experts from Armenia, Slovakia, Hungary, the Netherlands, Croatia, the USA, and three IAEA officials. The team reviewed the PSA documentation and model, performed walkdowns at the plant site and discussed in detail specific PSA topics that were subject to the TSR review.
The review concluded on 31 March with a final meeting during which the IAEA team of experts presented the mission report with the results of the review. The results of the mission will contribute to further improving and maintaining the high quality of the PSA of Kozloduy NPP Units 5 and 6 and contributing to the safety of the plant.