The article presents the methods used for the Periodic Safety Review (PSR) of unit 5 at Kozloduy NPP. It is based on the Bulgarian Nuclear Regulatory Agency (BgNRA) requirements and the IAEA Specific Safety Guide SSG-25 – Periodic Safety Review for NPPs (2013). The role, requirements, objectives, scope, approach, stages and activities, and resources for the PSR are briefly described. The key points are that (1) the PSR should assess future safety at the nuclear power unit/plant at least until the next PSR and, where appropriate, up to the end of planned operation; (2) the PSR is complementary to the routine and specific safety reviews and does not replaced them; (3) the level of compliance with current safety requirements towards higher conservatism are point out; (4) all safety aspects (fourteen Safety Factors – SF) of NPP operation and all equipment (SSCs) on site are covered; (5) four stages with the main activities for the PSR are defined and performed. It is point out that the success of the PSR is based on the NPP staff team work, the cooperation and approval of PSR activities by the Bulgarian Regulator (BgNRA), and cooperation with external organizations in some areas with proved experience.
Keywords: Periodic Safety Review (PSR), Safety Factor (SF), NPP lifetime extension, NPP licence renewal.