Standards Development

Scope

This international Standard establishes requirements associated with the defense of Electrical, Instrumentation and Control (E, I&C) systems against Common Cause Failure (CCF) in nuclear facilities.  It sets out requirements for:Plant analysis; Analysis and defence against CCF from hazards; Analysis and defence against CCF from systematic faults; and Documentation of the defences against CCF to allow their adequacy to be judged.This standard does not provide detailed design requirements for defence of systems against CCF; this falls to standards from IEC SC45A WG11 and IEC SC45A WG3 respectively.The requirements for determining the adequacy of the provisions to defend against CCF are also outside the scope of this standard.  This is due to the differences in national approaches to CCF; some countries treat CCF as a Design Basis Accident requirement (DBA), others as a Design Extension Condition (DEC) and some as a deterministic requirement, and also because of the dependence on the type of facility and the plant specific details.This standard follows the general principles given in IAEA safety requirement SSR-2/1 and IAEA safety guides SSG-34 and SSG-39  for E, I&C systems, and it defines a structured method of applying the guidance contained in those codes and standards to the E, I&C and that perform functions important to safety in a NPP. This standard should be read in association with these IAEA guides and IEC 63046 and 61513 in implementing the requirements of basic safety publication IEC 61508.Clause 5 of the standard addresses the overall approach to CCF and its analysis.Clause 6 of this standard addresses the approach to the facility and system analysis that are to be undertaken for provision of defence against CCF from Hazards.Clause 7 of this standard addresses the approach to the facility and system analysis that are to be undertaken for provision of defence against CCF from fault propagation.  This includes between divisions of the same system and systems of different lines of defence.Clause 8 of this standard addresses the approach to the defence against CCF of from systematic faults through production excellence and use of diversity...