Overview
IEC TR 63335:2021 is a Technical Report from the International Electrotechnical Commission (IEC) that identifies specific features of light water Small Modular Reactors (SMRs) relevant to instrumentation and control (I&C), control rooms and electrical power systems. The report highlights issues not yet fully addressed by existing IEC SC 45A standards and proposes orientations and roadmaps for working groups to consider when revising standards or proposing new work items. As a Technical Report, IEC TR 63335 is informative (non‑normative) and complements the IEC SC 45A standard series.
Key topics and technical focus
IEC TR 63335 maps SMR characteristics to standardization needs rather than issuing prescriptive requirements. Major technical topics covered include:
- SMR-specific design features: passive safety features, integrated and modular designs, staged construction, and consideration of emerging technologies.
- Operational concepts: mutualised operation (shared support facilities or multi‑unit sites), remote monitoring and support centres, and optimised maintenance strategies.
- I&C and control room implications: system architectures, sensor and measurement techniques, functional and safety fundamentals, human‑machine interface and control room design.
- Electrical power systems: architectures for supply, redundancy and interaction with I&C systems at SMR sites.
- Safety and cross‑disciplinary topics: safety justification frameworks, ageing management, defence against common‑cause failure, electromagnetic compatibility (EMC), cybersecurity and coordination with IAEA guidance.
- Working group roadmaps: recommendations to SC 45A WGAs (e.g., WGA2 sensors, WGA3 I&C architecture, WGA5 radiation monitoring, WGA7 safety fundamentals, WGA8 control rooms, WGA11 electrical power systems).
Practical applications and who uses it
IEC TR 63335 is valuable for stakeholders preparing or applying standards for SMRs:
- Standards developers and IEC SC 45A working groups - use the report as a roadmap to prioritize new or revised standards for SMR needs.
- Nuclear designers and vendors - identify I&C, control room and electrical system considerations unique to light water SMR designs (modularity, integrated systems, multi‑unit sites).
- Regulators and licensing bodies - understand where existing IEC guidance may need adaptation for SMR licensing and safety justification.
- Plant owners/operators and engineering firms - plan instrumentation, control, maintenance and remote‑support strategies compatible with international standards.
- I&C, control room and electrical engineers - align system architectures and qualification strategies with evolving IEC guidance.
Related standards and context
IEC TR 63335 is part of the IEC SC 45A framework and complements second‑level normative standards such as IEC 61513 (I&C systems for NPPs) and IEC 63046 (electrical power systems for NPPs). It also aligns with IAEA safety and security guidance (e.g., SSR‑2/1, SSG‑30, SSG‑34, SSG‑39) when addressing SMR‑specific considerations.
Keywords: IEC TR 63335, SMR standards, small modular reactors, instrumentation and control, control rooms, electrical power systems, IEC SC 45A, light water SMR, nuclear standards.