ICDE Topical Report: Collection and Analysis of Multi-Unit Common-Cause Failure Events

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This report presents a study performed on a set of common-cause failure (CCF) events within the International Common-cause Failure Data Exchange (ICDE) Project. The topic was multi-unit CCF events.

The main objective of this topical report was to study CCF events that occurred at multiple units at the same site. The report is mainly intended for designers, operators and regulators to improve their understanding of multi-unit CCF events and to provide insight into the relevant failure mechanisms.

The analyses in this report on multi-unit CCF events were carried out according to the updated version of the general coding guidelines of the ICDE provided during phase seven. The updated version of general coding guidelines includes modified definitions to the terms “event cause” and “CCF root cause”.

The observed multi-unit events were classified as internal factors (shared design or organisational factor), external factors (physical, external or environmental connection), or fleet CCF events (same or similar events occurring at multiple sites). The analysis included an assessment of the event parameters: event cause, coupling factor, detection method, corrective action, CCF root cause and multi-unit event severity.