BS IEC 61226:2005 defines a classification method for the information and command functions within nuclear power plants, along with the instrumentation and control (I&C) systems and equipment that facilitate those functions. The classification categorizes these functions based on their importance to safety, which in turn informs the relevant design criteria.
The design criteria serve as benchmarks of quality to ensure that each function meets the necessary standards relative to its significance for plant safety. In this context, the criteria include functionality, reliability, performance, environmental resilience (including seismic considerations), and quality assurance.
This standard applies to all information and command functions, as well as the I&C systems and equipment that support them. The functions, systems, and equipment in question are responsible for providing automated protection, controlling processes (both closed and open loop), and delivering information to operating personnel. They maintain the nuclear power plant (NPP) within safe operating parameters and facilitate automatic or manual actions to prevent or mitigate accidents and minimize radioactive releases to the site or surrounding environment. The I&C functions that fulfill these responsibilities are essential for safeguarding the health and safety of NPP operators and the public.
This standard is aligned with the general principles outlined in the IAEA safety code NS-R-1 and safety guide NS-G-1.3. It establishes a structured approach for applying the guidance from these codes and standards to the I&C systems that perform safety-critical functions in an NPP. It is recommended that this standard be consulted alongside the IAEA guides and IEC 61513 when implementing the requirements of IEC 61508.
