2010:42 Using the EPRI Risk-Informed ISI Methodology on Piping Systems in Forsmark 3

In the SSM regulation SSMFS 2008:13, it is stated that the selection of locations for inspection of mechanical components shall be based upon the risk for core damage or the risk of release of radioactive substances. Both qualitative and quantitative measures of the relative risk are allowed to be used. So far only the PWRs in Sweden are using a quantitative procedure to evaluate the risk whereas all the BWRs are using a qualitative risk procedure based upon the so-called damage index and consequence index.

All Nuclear Power Plants in Sweden have a fairly detailed PSA analyses and it is now of interest to find out if such PSA analyses can assist the selection of piping components for inspection also for BWRs. The EPRI-procedure is a semi-quantitative methodology which uses the PSA information together with the assessment of the failure potential from different degradation mechanisms to perform a risk evaluation.

The principal objective of the project is to use the EPRI procedure for risk-informed In-Service Inspection to select piping components for inspection and compare the outcome with the presently used qualitative risk procedure on Forsmark 3.