Overview
IEC 63435:2025 - Nuclear facilities - Human machine interfaces - Operator support systems (OSS) defines the characteristics, lifecycle principles and human factors engineering (HFE) requirements for operator support systems used in nuclear facilities. The standard specifies human factors guidelines and verification and validation (V&V) requirements for OSS design. It is applicable to new nuclear facilities whose conceptual design begins after publication, and can also guide OSS upgrades or retrofits in existing plants.
Keywords: IEC 63435:2025, operator support systems, OSS, human machine interfaces, HMI, human factors engineering, V&V, nuclear facilities, control room
Key topics and technical requirements
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Concept and role of OSS
Defines OSS purpose, capabilities and interfaces with control room HMI and plant systems to support situation assessment and decision making.
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OSS lifecycle and project organization
Establishes lifecycle stages (analysis, design, verification, validation, deployment) and responsibilities for vendors, utilities and licensors.
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Human Factors Engineering (HFE) programme
Requires HFE-based design processes, including user-centered design, training integration and ergonomics considerations.
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Analysis inputs to design
Mandatory analyses include needs & constraints assessment, functional analysis and allocation, task analysis, human reliability analysis and operator time-response analysis.
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System and functional design
Specifies fundamental OSS functions (monitoring, diagnosis, decision support), human factors guidelines for displays and controls, user control of interaction, modes of operation, collaboration and communication support.
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Safety, performance and maintainability
Addresses safety classification, dependability, accuracy, response time expectations, loss-of-OSS implications and maintainability/location considerations.
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Verification & validation (V&V)
Outlines stages: task support verification, design verification, preliminary validation and integrated system validation to demonstrate OSS effectiveness and operator performance.
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Illustrative applications (Annex A)
Examples include intelligent alarm handling, computer-based procedures, reactor core monitoring, fault diagnosis and maintenance support.
Practical applications and users
IEC 63435:2025 is intended for:
- Nuclear facility designers, vendors and system integrators
- Plant utilities and operators (control room staff)
- Maintenance engineers and emergency response teams
- Regulatory bodies, safety assessors and licensors
Use cases: designing new OSS for nuclear power plants, upgrading HMI and decision-support tools, developing V&V programs, and ensuring OSS meets human factors and safety requirements.
Related standards
IEC 63435:2025 supplements IEC 60964 (control room design, data acquisition and alarm systems) and aligns with other SC 45A HMI/HFE standards. It should be used alongside applicable IAEA, ISO and national nuclear safety guidance when implementing OSS.