PSA of no-load operation - findings about the optimization of plant operating strategies

The practice of plant operation under outage conditions has proved to work in a large number of successful plant outages, and optimization measures have led to excellent results benefitting plant operation. Within the level-2 probabilistic safety analysis (PSA) project, the Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) conducted a study to this effect of no-load operation (NLO) of the Neckar II (GKN II) nuclear power plant as the reference plant. The plant operator performed an analysis based on the PSA of GRS for the other unit on site, GKN I. Know-how was permanently exchanged among the participants, including information about specific knowledge of technical devices and technical process sequences. Sequences of steps in the period of time particularly relevant to safety in the first mid-loop operation were considered in detail in the NLPSA. The analysis resulted in measures which greatly contribute to a major reduction of the frequency of systems damage states as originally indicated. These measures mainly related to the administrative sector. There was no need for any new technical systems, and the effectiveness of existing installations was increased systematically by a closed concept. In this way, the safety level of the plant in the status examined was raised considerably at little overall expense. (orig.)