PSA Lessons Learned from Viewpoint of the ETSON TSOs

The ETSON PSA Expert Group has recently carried out investigations on the insights and lessons learned from probabilistic risk analyses (PRA1) the Technical Safety Organizations (TSOs) have either conducted or reviewed. One observation of the ETSON PSA Expert Group is that even if the completeness of PSA increases progressively, some real events might not yet be adequately represented in PSA models, although these are regularly improved to incorporate operating experience. Quality and use of PSA have significantly increased over time. PSA is indispensable for present safety culture and some outstanding achievements of PSA have been identified. Nevertheless, the relevance of PSA in decision making varies between member countries and organizations. The paper provides some exemplary insights from PSA applications in ETSON member countries and reviews by member TSOs, not only in the frame of regular, full scope PSA but also by specific assessments required in case of findings or in supporting deterministic assessment for plant modifications. Benefits and limitations of PSA from TSO viewpoint are briefly summarized. (author)