Prioritizing Diverse Observations or Issues from Safety Reviews at Nuclear Power Plants According to Possible Safety Impacts

Abstract

Being a facility with potential for radioactive release, any nuclear power plant (NPP) is, over its operating life time, permanently subject to numerous safety reviews with different scopes and objectives. The reviews may be initiated and implemented by various stakeholders, including regulators, utilities or industry. Some of them are, by their nature, general and extensive in terms of different safety areas or safety attributes which are covered. An example of such a review is a Periodic Safety Review (PSR) which is promoted by the International Atomic Energy Agency (IAEA) and a number of national safety authorities in Europe and worldwide. The others may, depending on the objective, be targeted at particular safety area (e.g., ageing management or equipment qualification or safety analyses). Both of the mentioned cases (single general review or multiple targeted reviews over a time period) can generate an inventory of observations (“findings”) or “issues” which need to be addressed but may be very different in their nature and implications, as well as in benefits or resources associated with their resolutions. For some issues a resolution may be straightforward. For others, it may require a feasibility study and identification of options for possible resolution. Also, in some cases the resolution is simply a “must” (e.g., discrepancy from licensing basis) while in some other cases it may be a matter of balance (e.g., effectiveness of maintenance program). Furthermore, while some of the issues may be directly related to operational safety (e.g., non-compliance with single failure criterion or aging-related degradation of safety features), for some others the link to operational safety may not be explicit (e.g., comparison of safety bases against the newly emerging methodologies or issues observed with regard to so called “soft factors”).

The paper discusses types of different observations or issues which may come from general or targeted safety reviews and outlines some basic principles for their comparison and prioritizing with regard to possible safety impacts, which is many times needed for the purpose of developing an action plan for safety improvements.