A method for identification of human originated test and maintenance failures

In order to improve the coverage of PRAs (probabilistic risk assessments) and the maintenance planning at nuclear power plants, the Technical Research Centre of Finland has developed a method for identification of possible test-and-maintenance-caused common-cause failures. The method has been tested in analyses of safety-related systems at a nuclear power plant in Olkiluoto, which consists of two 660 MW BWR (boiling water reactor) units. The method is praxis-oriented and provides a simple way to cluster operating and maintenance experience to improve safety. The starting point of the method is to go through a process systematically in group sessions and by using a special form. Identified possible common-cause failures are classified into three categories with respect to the risk they are considered to cause to the installation.<>