IEC 61513 Overall I&C — general requirements (this standard)
Requirements and recommendations for the overall I&C architecture of a nuclear power plant, the system lifecycle and the safety case. The top of the IEC SC 45A series.
IEC 61513
Nuclear I&C systems important to safety
IEC 61513 is the top-level standard for instrumentation and control (I&C) important to safety in nuclear power plants. It is the nuclear sector application of IEC 61508 functional safety: it sets the general requirements for the overall I&C architecture, then hands off to a family of SC 45A standards that cover categorization, software and hardware. It governs both hard-wired and computer-based systems.
Document structure
IEC 61226 Categorization of functions
Classifies I&C functions important to safety into categories A, B and C by their safety significance — the decision that drives every later requirement.
IEC 60880 Software for Category A functions
Requirements for the software of computer-based systems performing the most safety-significant (Category A) functions — the strictest software regime.
IEC 62138 / IEC 60987 Category B/C software and hardware
IEC 62138 covers software for Category B and C functions; IEC 60987 sets hardware design requirements for computer-based systems. Together they complete the implementation layer.
Key concepts
- The nuclear face of IEC 61508
- IEC 61513 is how the generic functional-safety framework of IEC 61508 is applied to nuclear power plants. It keeps the lifecycle logic but speaks the nuclear vocabulary of categories, defence in depth and licensing.
- Categorization A / B / C
- Per IEC 61226, every I&C function is ranked A (highest safety significance — e.g. reactor trip), B or C. The category fixes how rigorously the implementing system must be designed, qualified and documented.
- Class 1, 2, 3 systems
- Functions of a given category are assigned to systems of a matching safety class. Mixing categories on one system is constrained, because a weaker function must not undermine a stronger one.
- Defence in depth and independence
- Safety rests on independent layers — protection systems separate from control, diversity against common-cause failure, physical and electrical separation. 61513 makes this architecture an explicit requirement, not a hope.
- Hard-wired and computer-based
- I&C important to safety may be conventional hard-wired, computer-based, or a mix. 61513 covers all three, which is why software standards (60880, 62138) sit beneath it.
- The SC 45A series
- 61513 is the apex of a coordinated family — 61226 for categorization, 60880 and 62138 for software, 60987 for hardware, 62645 for cybersecurity — aligned with IAEA safety guidance.
Notes & guidance
The safety backbone of a nuclear plant’s I&C
A nuclear power plant is run, monitored and — when needed — shut down by its instrumentation and control. When that I&C is important to safety, it must meet requirements far beyond ordinary process control. IEC 61513 is the top-level standard that sets those requirements: the overall I&C architecture, the system lifecycle and the safety demonstration for a nuclear plant.
The nuclear face of IEC 61508
IEC 61513 is the nuclear sector application of IEC 61508. It keeps the functional-safety lifecycle — define the functions, allocate them to systems, design, verify, validate — but expresses it in the nuclear language of safety categories, defence in depth and regulatory licensing. It applies whether the I&C is conventional hard-wired equipment, computer-based, or a combination of both.
Categorize, then build to the category
The pivotal step is categorization. Following IEC 61226, every function important to safety is ranked A, B or C by its safety significance — a reactor trip is Category A, a monitoring aid may be C. That category then fixes how rigorously the implementing system must be designed and qualified, and the function is assigned to a system of a matching safety class (1, 2, 3). The principle running through it is independence: protection separated from control, diversity against common-cause failure, physical and electrical separation, so a weaker function can never undermine a stronger one.
Architecture, then the series beneath it
61513 sits at the apex of the coordinated IEC SC 45A family and hands the detail to the standards below it: IEC 61226 for categorization, IEC 60880 for the software of Category A functions, IEC 62138 for Category B and C software, IEC 60987 for hardware, and IEC 62645 for cybersecurity — all aligned with IAEA safety guidance. In practice it also meets IEC 62443 thinking on control-system security, and the plant’s long operating life is managed under ISO 55000 asset management.
Applicable industries
- Nuclear power plant operators and new-build projects
- Reactor I&C and protection-system vendors
- Nuclear safety regulators and technical support organisations
- EPC contractors and qualification laboratories