Overview
ISO 23466:2020 - "Design criteria for the thermal insulation of reactor coolant system main equipments and piping of PWR nuclear power plants" defines basic design requirements and verification principles for thermal insulation applied to the Reactor Coolant System (RCS) of pressurized water reactors (PWR). The standard focuses on two main insulation targets: reactor pressure vessel (RPV) insulation and RCS piping and other equipment insulation, for both metallic and non‑metallic thermal insulation systems.
Key topics and requirements
- Scope and classification
- Applies primarily to PWR nuclear power plants; can be used as reference for other reactor types.
- Distinguishes metallic (reflective foils/sheets, low emissivity) and non‑metallic (fibres, microporous, mattresses) insulation.
- General design procedure
- Integrates reactor safety, material selection, thermal behaviour design/test, and mechanical properties design/test (including seismic and vibration resistance).
- Addresses installation, maintenance, inspection and removal.
- Reactor safety considerations
- Limits on debris generation to avoid adverse effects on ECCS, pit strainers and other safety systems.
- Outer surface temperature limits where personnel access is possible.
- Insulation must not impair other safety functions; nuclear‑safety related insulation may require additional design controls.
- Material selection
- Consider radiation‑induced degradation and service temperature margins.
- Metallic materials: low emissivity metals recommended - austenitic stainless steel preferred; aluminum and galvanized steel permitted if hydrogen production risk is assessed and controlled.
- Non‑metallic materials: porous insulators (fibres, microporous) requiring demonstrated radiation resistance.
- Performance verification
- Thermal behaviour: design calculations and tests to confirm insulating performance and to avoid chimney effects and thermal bridges.
- Mechanical properties: structural strength, seismic restraint, fixation methods and testing.
- Design details and geometry
- Informative annexes provide typical geometries for metallic and non‑metallic insulation and RPV insulation types with safety functions.
Applications and users
ISO 23466:2020 is used by:
- Nuclear plant designers and engineering teams (RCS equipment and RPV design)
- Insulation system manufacturers and suppliers
- Safety and QA engineers, regulatory bodies and inspectors
- Operation & maintenance teams planning installation, inspection and replacement
It helps ensure insulation solutions meet thermal performance, nuclear safety, seismic, and maintainability requirements in PWR plants.
Related standards
- ISO 7345 - Thermal performance of buildings and components (definitions)
- ISO 9229 - Thermal insulation - Vocabulary
Keywords: ISO 23466:2020, thermal insulation, reactor coolant system, RCS, PWR, RPV, metallic insulation, non‑metallic insulation, radiation resistance, seismic design, ECCS, thermal behaviour testing.