The objective of the present report is to document a study that was performed on a set of common-cause failure (CCF) events. These events were derived from the International Common-cause Failure Data Exchange (ICDE) database, with the study focusing on events where failures occurred due to modifications in systems, components or procedures. The study is also based on a workshop held during an ICDE Steering Group meeting, where 53 ICDE events were assessed. The report is mainly intended for designers, operators and regulators to improve their understanding in relation to modifications-induced CCF risks and to provide insight into relevant failure mechanisms.
The report evaluates CCF events that occurred as a result of modifications, back-fitting, and/or replacements. However, there were no CCF events identified that were related to modifications resulting from a regulatory back-fit, i.e. relating to new or amended regulatory requirements or regulations.