WGRisk Survey on Reliability of Passive Systems (RoPS)

In March 1999, VTT Automation distributed a questionnaire concerning reliability of passive system (RoPS). Especially, the idea was to map methods developed for passive systems based on thermal hydraulics. The goal was to support developing Finnish national licensing practice and rule generating. In September 1999, the OECD/NEA/CSNI/PWG5 decided to extend the survey to a pre-study for a potential new task force. At the same time, more time was given to the member countries to reply to the questionnaire. This was due to the fact that very few replies had been obtained in due time. In December 1999, the CSNI asked the PWG5 to prepare forming a task force on the topic. Preconditions for such a working group will be discussed under the conclusions about the replies. The questionnaire included four questions as follows: - Have you developed or are you currently developing approaches for passive system reliability / availability / safety assessment (from reliability engineering point of view)? - The same question as 1) for licensing practices? - If so, can you send us articles or reports related to your work? Maybe there is a chance for cooperation. - If you do not know directly about the topic, do you know somebody who is carrying out active work on the area? Can you send us references or contact information? 20 replies were obtained from together 12 countries and from the IAEA. In four replies, methods for passive system reliability assessment were developed. Apart from this, physical barrier reliability was discussed in six replies, and some replies discussed physical and structural uncertainty more generally. A table including shortened versions of the replies is presented. References given in the replies are included in the reference list with some other sources of information