A periodic safety review (PSR) is a comprehensive assessment of safety that is normally carried out at defined intervals as prescribed in the license. Plant ageing, configuration changes, modifications to procedures, significant events, operating experience, and other safety reviews occur over the life­time of a plant and the PSR is a systematic way of assessing the cumulative effects of any changes to plant safety. In addition, a PSR takes into account advances in safety standards since the time of construction or the previous review. The safety of future operation of the plant can be evaluated from the PSR.

The scope of the PSR includes an assessment of plant design and opera­tion against the current safety standards and practices. Therefore, the PSR is a tool for securing a high level of safety throughout the NPP’s operating lifetime, taking into account changes in the plant and the evolution of safety knowledge. The PSR does not replace the routine safety reviews of nuclear power plant operation, which are the primary means of safety verification throughout the plant operating cycle. The IAEA provides recommenda­tions and guidance on how to conduct the PSR (IAEA, 2003e).

From experience, the IAEA recommends that a PSR should be first undertaken about 10 years after the start of plant operation and that sub­sequent PSRs should be done every 10 years. The 10-year period is based on the expected developments in safety standards from both experience and ongoing R&D, and from the expected rate of the changes that could affect the plant. The PSR covers all aspects of operations, including manage­ment structures, reporting systems, staff experience and competence, plant configuration, safety culture, knowledge management, ageing effects on the SSCs, radiological protection, emergency planning, and operating experi­ence, to mention just a few. Owing to its comprehensive scope, the PSR provides reassurance to both the licensee and the regulator that the licens­ing basis for the NPP is still valid.

The licensee has prime responsibility for performing the PSR. The start­ing point is agreement between the licensee and RB on the scope, schedule, and requirements for the review. Owing to the broad scope of the assess­ment, a PSR is a complex task that could take up to a maximum of three years to complete. Therefore, the IAEA has broken down the review into five subject areas with 14 safety factors to ensure that the review is com­prehensive (IAEA, 2003e). These cover the plant (plant design, actual con­ditions of the SSCs, equipment qualification, ageing), safety analysis (deterministic safety analysis, probabilistic safety analysis, hazards analysis), performance and feedback from experience (safety performance, use of experience from other plants and research findings), management (organi­zation and administration, procedures, the human factor, emergency plan­ning) and environment (radiological impact on the environment). Each of these factors is reviewed and assessed against current safety standards and practices. In addition, IAEA (2003e) recommends a global assessment to integrate the results of the review of the safety factors.

Where necessary, corrective actions are determined and implementation plans are enacted. Since these actions lead to safety improvements, an objective is to complete as many of the actions as possible within the time frame of the PSR. The end point of the PSR is regulatory approval of the integrated programme to address any outstanding safety issues. Any safety gaps that cannot be reasonably addressed would require further assessment of the risk and justification to allow the plant to continue operation.

The PSR is a major undertaking that involves considerable planning and preparation. To initiate the review, the licensee establishes a dedicated project management team, develops guidance documentation laying out the scope and methodologies, defines the documents to be produced and their formats, develops a QA plan, prepares the review plan and budget, and secures approvals. The plan is then executed with many activities carried out in parallel, including, to a reasonable extent, the amelioration of issues as they are identified. This is followed by execution of an integrated plan to implement corrective actions and/or safety improvements. Further details are contained in IAEA (2003e) and recent experience in IAEA Member States is detailed in IAEA (2010b).