Working group of experts on rare events in common mode failure analysis

The scope of the study is mainly concerned with automatic protective systems for nuclear power plant. This is because these are the type of system in which common-mode failure problems are known to occur, the experience is much greater, and requirements have been identified for further studies in this area. However, aircraft and chemical plant systems have also been considered, and this report contains a preliminary analysis of data and information from all three sources. Although the term 'common-mode failure' is commonly used internationally, it has been found necessary for this study to first define the type of system to which they apply, to define the term itself, and to classify the events according to type