Application of PSA techniques for evaluation of proposed changes to DG maintenance at Kozloduy-3 NPP

This presentation is a brief overview of a study done by Risk Engineering Ltd for EP-2 Directorate of the Kozloduy NPP Branch of the National Electric Company of Bulgaria. The complete report is contained in REL document NRI/D-06, May 1992 (in Bulgarian). The PSA techniques has been applied for evaluation of the impact on CDF of the additional maintenance of DG electrical systems and components, proposed by the personnel of the Electrical Dept. of Kozloduy-3 NPP. The proposal included a request to the regulatory body to allow the proposed maintenance to be performed once per month on each DG train without starting-up of other trains, which should normally be done for all on-line maintenance of the safety systems according to an action statement in the plant Technical Specifications. The study had to be done without an existing PSA. The study includes discussion on the applicable accident sequences and analysis of the relevant safety functions, including restoration for the existing as well as for the proposed maintenance practices on a yearly-averaged basis. The comparative character of the study allows the use of generic data, but the available plant statistics has also been used, and sensitivity calculations has been done for the key modelling parameters. (author). 3 tabs