SIST EN IEC 61225:2026

Overview

SIST EN IEC 61225:2026 specifies the requirements for static uninterruptible DC and AC power supply systems (SUPS) in nuclear power plants (NPPs) and, when applicable, in other nuclear facilities. This international standard ensures that SUPS-systems with no rotating parts-deliver continuous, stable low-voltage power essential for the safety, instrumentation, and control functions in nuclear environments. By defining system-level performance and functional requirements for SUPS, the standard supports the reliability and safety of modern nuclear facilities, including new designs such as small modular reactors (SMRs) and plants with passive safety features.

Key Topics

• Definition and Scope: Focuses on the overall performance and functional characteristics required of SUPS used in instrumentation, control, and electrical systems in NPPs.
• Application to Safety-Critical Systems: Emphasizes requirements for supplying continuous power to items important to safety, ensuring operational reliability during normal and abnormal conditions.
• Robustness and Reliability: Requires SUPS to be robust against various electrical disturbances, including voltage fluctuations, faults, and transient events typical in nuclear plant environments.
• System Margins and Protection: Mandates built-in conservatism so equipment ratings and capacities are sufficient to address all operational states and postulated conditions.
• Monitoring, Testing, and Maintenance: Outlines requirements for monitoring SUPS status, electrical protection, ongoing maintenance, and regular testing to uphold system integrity over time.
• Qualification and Ageing Management: Stipulates that equipment must be qualified for use in nuclear applications and designed to address long-term ageing effects.

Applications

SIST EN IEC 61225:2026 is essential for:

• New Nuclear Power Plant Projects: Provides requirements for the design and specification of SUPS in new NPPs, including advanced concepts like SMRs and passive safety systems.
• Facility Modernization and Upgrades: Acts as a reference for the replacement or modernization of existing uninterruptible power supply equipment in operational nuclear facilities.
• SMR and Passive Plant Designs: Includes specific provisions for applying uninterruptible power supply standards to emerging reactor types and passive safety concepts.
• Safety and Regulatory Compliance: Assists plant designers, engineers, and operators in meeting regulatory expectations for electrical reliability and nuclear safety.
• Integrated Safety Systems: Ensures SUPS systems are properly integrated with safety instrumentation, control systems, and facility-wide emergency operations.

Related Standards

To achieve full compliance and integration, SIST EN IEC 61225:2026 should be used in conjunction with:

• IEC 61513: General requirements for instrumentation and control systems important to safety in nuclear power plants.
• IEC 63046: General requirements for electrical power systems of nuclear power plants.
• IEC 60709: Guidance on separation of electrical, control, and instrumentation systems important to safety.
• IEC 62003: Requirements for electromagnetic compatibility testing.
• IEC 62040 series: Standards for uninterruptible power systems.
• IEC/IEEE 60780-323: Qualification of electrical equipment important to safety.
• IEC/IEEE 60980-344: Seismic qualification of equipment important to safety.
• IEC 60146-1-1 and 60146-2: Specifications for semiconductor converters used in power supplies.

Practical Value

Implementing SIST EN IEC 61225:2026 provides:

• Enhanced Nuclear Safety: Reliable SUPS designs reduce the risk of power loss to critical safety systems, ensuring protection of personnel and the public.
• Operational Assurance: Clear requirements enable better planning, validation, and verification activities for SUPS in both design and operational phases.
• Future-Proofing: By emphasizing principles over specific technologies, the standard remains applicable as new SUPS technologies emerge and nuclear power plant designs evolve.
• Regulatory Alignment: Helps facilities demonstrate compliance with international and EU nuclear safety directives and expectations.

By adopting SIST EN IEC 61225:2026, nuclear operators and designers ensure that the backbone power systems of their instrumentation and control architectures maintain the highest standards of reliability, safety, and regulatory compliance.