Experiences in using PRA as an operational tool

The Probabilistic Risk Assessment (PRA) of Koeberg Nuclear Power Station has been used for a number of years to support operation decision making. The principle aim of this risk assessment of Koeberg is to determine the probability of a severe accident under varying operating conditions. This plant model is used by ourselves and our licensing authority to assess nuclear safety issues. Through this process, considerable practical experience has been gained in using a “living” PRA to improve plant safety and performance. This paper presents some of the insights obtained in using reliability engineering in such a dynamic way and demonstrates that by developing and using the “living” PRA considerable safety and financial gains can be obtained. These insights mainly concern the prerequisites required before optimal use of a “living” PRA can be made. Other insights concern how PRA results are best presented and interpreted. Finally, examples are presented of occurrences when PRA was used to aid operating decisions.