International Standards central to nuclear NPP safety
Although ensuring a high level of safety for NPPs is a national responsibility, nuclear safety rests on general safety standards and requirements set by the International Atomic Energy Agency (IAEA). The IAEA is the UN agency that works to promote the safe, secure and peaceful use of nuclear technologies.
These IAEA general safety standards and requirements cover many areas, such as the management system or safety assessment for facilities and activities, the decommissioning of facilities or preparedness and response for a nuclear or radiological emergency.
The qualification of "electrical equipment important to safety" is central to the safety of NPPs.
The primary objective of equipment qualification (EQ) is "to demonstrate with reasonable assurance that equipment important to safety can perform its safety function(s) without experiencing common-cause failures before, during, and after [an] applicable DBE [design basis event]."
DBEs are "postulated events used in the design to establish the acceptable performance requirements for the structures, systems, and components."
The IAEA 1998 report on EQ in operational NPPs states that "requirements for implementing EQ in NPPs are prescribed by various international and national standards, codes and guides." The report clearly lists IEC 780 and IEEE-323 in a short catalogue of publications that set EQ requirements.
The new double logo International Standard, IEC/IEEE 60780-323:2016, Nuclear facilities –Electrical equipment important to safety – Qualification, harmonizes in a single publication qualification practices formerly given by IEC 60780:1998 and IEEE Std 323-2003 on initial qualification. This Standard, which was developed by IEC Subcommittee (SC) 45A: Instrumentation, control and electrical systems of nuclear facilities, in cooperation with the Nuclear Power Engineering Committee (NPEC) of the Power & Energy Society (PES) of the IEEE takes into account the need to reassess and extend the qualified life of electrical equipment regarding projects to extend the operating life of nuclear facilities. It also incorporates current practices and lessons learned from the implementation of previous versions of this Standard by the nuclear industry.
IEC/IEEE 60780-323 cancels and replaces IEC 60780:1998 and also supersedes IEEE Std 323-2003.
Is EQ really that important?
Electrical equipment important to safety in nuclear facilities is "equipment that is part of a safety group and/or whose malfunction or failure could lead to undue radiation exposure of the site personnel or members of the public." This equipment includes, among other things:
- electric equipment and systems that are essential to emergency reactor shutdown, containment isolation, reactor core cooling, and containment and reactor heat removal
- electric equipment that is otherwise essential in preventing significant release of radioactive material to the environment
- all electrical equipment needed to ensure emergency energy supply to this equipment in case of a loss of normal power supply
- all electrical equipment needed to ensure ultimate energy supply in case of total loss of on-site power (if selected as design extension condition to be mitigated)
In its 1998 report the IAEA noted that "a common weakness of NPPs built to earlier standards, particularly of the older ones, is a lack of qualification of equipment important to safety". This is particularly important when the service life of NPPs must be extended, during which equipment qualified life must be reassessed and extended.
IEC/IEEE 60780-323 contains the following EQ details:
- scope and object
- terms and definitions
- principles of equipment qualification, including qualification objective, qualified life and condition, qualification elements and documentation
- qualification methods, which include initial qualification, type testing, operating experience, reassessing qualified life (methods, tests and component replacement)
- qualification programme, which gives details of equipment specification (identification, interfaces, qualified life objective, safety functions and service conditions), of the programme plan (ageing, maintenance, etc.) and of its implementation (tests, operating experience and analyses)
Benefits of single Standard outweigh those of several publications
The benefits of bringing together two distinct International Standards for qualification of electrical equipment important to the safety of nuclear facilities into a single publication emerged following discussions between the IEC and IEEE. Seven years were necessary to develop this common Standard with the first technical discussions being held in April 2009 eventually leading to the publication of the International Standard in February 2016.
The cost of the qualification of electrical equipment is very significant for NPP building projects and IEC/IEEE 60780-323 will translate into substantial financial savings for future projects, in particular for exported NPP designs.
Although the general safety standards and requirements for NPPs are set by the IAEA, at national levels nuclear safety is generally supervised by national regulators, such as the Autorité de sûreté nucléaire in France, the Atomic Energy Regulatory Board in India, Rosatom in Russia, or the Nuclear Regulatory Commission in the US.
The advantage of a single International Standards replacing two publications means that in instances when the industry had to ensure equipment qualification met either the IEC or the IEEE Standard in different countries, it now needs only a single Standard to ensure compliance.
Talks have started about a possible endorsement of IEC/IEEE 60780-323 as an EN Standard (European Standard). EN Standards are a means for the uniform implementation of International Standards throughout Western Europe.