In many countries periodic safety reviews are required to be carried out by the plant operator as a condition for his site licence. The primary objective of most PSRs is to undertake a detailed and comprehensive review of the safety of the plant, taking into account operational safety, the possible deleterious effects of ageing, and also advances in safety standards since the original construction or time of the last review.

Periodic safety reviews are usually complementary to the normal regulatory reviews that are carried out, e. g. between fuel cycles and do not affect them. PSRs have developed

for a number of reasons. Public confidence has diminished and regulatory requirements have become more stringent over the past decade or so driving a demand for higher standards of safety not only in new plants, but also in currently operating plants. Perhaps rather more importantly though, experience has shown that there are positive benefits from PSRs to both safety and performance and they are supported by both operators and regulators.

A list of safety issues identified for PSRs is given in Table 3.8 together with a frame­work for review that was endorsed by the 1991 IAEA Safety Conference (Goodison, 1997).

A review of experience of PSRs has been published in CEC Working Group (1990) and Goodison (1997). It concludes that PSR practices show considerable commonalties. This is particularly so within the EC due to similarities in regulatory regimes within the EC countries. At the top level, the procedure is broadly similar. There is agreement of the scope between the licensee and the regulator. The licensee undertakes the review, implements the modifications and reports to the regulator. The procedure is then followed by review by the regulator and the identification of any further modifications. Finally agreement is reached between the licensee and the regulator on how to fulfil the agreed programme.

The differences in PSR practices depend mainly on the methodology, the standards and scope that are adopted. These differences might relate to the standards for radiological protection or on the level of redundancy and diversity of the safety systems. The criteria for PSAs are also not universally agreed. There are also differences in the periodicity requirements for PSR reviews.

The potential benefits of PSAs include improved safety via the implementation of modifications to an improved safety level (closer to that of a modern plant), including the

Table 3.8. Safety issues to be addressed in PSRs

Safety issues Recommended procedures for assessing each issue

1-5

Assess each issue with current methods to determine the safety status Compare the safety status with current standards Identify shortfalls

Assess the safety significance of any

shortfalls and carry out remedial measures Implement practicable modifications and assess safety significance of remaining shortfalls Repeat for each issue

Gain indication of safety level compared with modern plant and identify shortfalls from current safety standards and best practices Improve plant routine operations including optimisation of maintenance, test and inspection techniques and improve plant availability Identify strengths and weaknesses of personnel

Gain improved understanding of plant safe working life and life-limiting causes Improve regulator confidence in the continued safe running of the plant, improve the licensee’s confidence for future planning and investment and improve national public and international confidence

Goodison (1997).

identification of short-falls in present practices and improved confidence (in the regulator, operator, public, etc.) (Table 3.9).

The first comprehensive review of the plant is usually the most demanding. Subsequent reviews would be expected to be quicker (and cheaper). Initial PSRs, of very old plants may require extensive modification or possibly result in closure. For future plants, initial PSRs might be expected to be less onerous.