American approval and publication
The American Nuclear Society has reported that ANSI/ANS-54.8-2025, Liquid Metal Fire Protection in LMR Plants, received approval from the American National Standards Institute on 2 September.
It said the new edition replaces ANS-54.8-1988, which was withdrawn more than three decades ago.
The society explained that the Advanced Reactor Codes and Standards Collaborative identified demand for an updated version through an industry survey.
According to the group, the reissued standard provides guidelines for the performance of fire detection, alarm, suppression, control, and structural protection systems in liquid metal reactor facilities.
It added that the publication is now available for purchase.
Purpose of the standard
The American Nuclear Society stated that the updated standard sets out minimum design requirements for preventing, detecting, and suppressing liquid metal fires and mitigating their consequences.
It explained that liquid sodium and NaK mixtures are widely used in primary, intermediate, and auxiliary heat transport systems in liquid metal reactor designs.
It noted that both sodium and NaK react easily with oxygen, water, and other compounds, requiring special precautions in design, construction, testing, and maintenance.
The organisation reported that the requirements aim to protect the health and safety of both the public and plant staff while also minimising potential economic loss in the event of a sodium or NaK leak.
It confirmed that the standard is not a total plant fire protection code and does not override other applicable standards.
Scope and application
The society said the new edition applies specifically to plant protection and operating features designed to prevent or reduce the effects of sodium or NaK spill accidents in nuclear plants.
It added that it does not cover sodium–water reactions within steam generator boundaries and is not applicable to liquid metals other than sodium or NaK.
The group confirmed that the standard allows the use of new protection methods, provided sufficient technical data can show equivalent safety and reliability.
It reported that this flexibility supports innovation while maintaining the required safety thresholds.
The organisation advised that the scope is limited to areas where no other applicable fire protection standards exist.
Background to the revision
According to the American Nuclear Society, the Advanced Reactor Codes and Standards Collaborative was created in 2022 to address needs related to advanced reactor design.
The society explained that the collaborative includes standards development organisations, reactor designers, regulators, and stakeholders working on a roadmap for future codes.
It added that survey responses from this group highlighted the absence of an up-to-date liquid metal fire protection standard.
The society reported that the ANS Standards Board subsequently authorised work to reissue ANS-54.8 with only minor changes to the 1988 version.
It said the aim was to restore the standard quickly due to its continued use despite being withdrawn.
Process and timeline
The American Nuclear Society stated that the reissue process began on 12 June 2024 with a Project Initiation Notification Systems form submitted to ANSI.
It explained that ANSI approval of the new edition was finalised in September 2025, just over 15 months later.
The society noted that most standards require six years or longer for development and approval.
It commented that the accelerated timeline represented a rapid pace in comparison to typical practice.
The group confirmed that the ANS-54.8 Working Group was responsible for the effort.
Industry context
The society said liquid metal reactor projects in the United States and internationally continue to advance, making the availability of current fire protection requirements important for developers and regulators.
It reported that sodium and NaK systems remain integral to many liquid metal reactor designs.
It added that without updated guidance, stakeholders were referencing the withdrawn 1988 edition.
The organisation stated that the new version closes this gap by re-establishing applicable requirements.
It explained that the update was considered necessary by both regulators and industry to support ongoing advanced reactor programmes.
Relevance for fire and safety professionals
The American Nuclear Society’s standard provides specific requirements for fire detection, suppression, and structural protection in liquid metal reactor facilities.
It offers defined procedures for managing sodium and NaK spill hazards that are unique to liquid metal systems.
Fire safety professionals can reference the standard to understand how fire protection requirements are applied in nuclear reactor environments.
The standard also shows how industry-led collaborations can accelerate the creation of safety documents in response to stakeholder needs.
New standard released for liquid metal fire protection: Summary
ANSI/ANS-54.8-2025 was approved by the American National Standards Institute on 2 September.
The American Nuclear Society reported the publication of the new standard.
The standard replaces the withdrawn ANS-54.8-1988.
The Advanced Reactor Codes and Standards Collaborative identified the need for reissue through an industry survey.
The standard sets requirements for preventing, detecting, and suppressing sodium and NaK fires in liquid metal reactor facilities.
It covers fire detection, alarm, suppression, control, and structural protection systems.
It does not apply to sodium–water reactions in steam generators or other liquid metals.
The reissue was initiated on 12 June 2024 with ANSI approval achieved in September 2025.
The approval was completed in 15 months compared with the six years typical for standards.
The ANS-54.8 Working Group managed the revision process.
The new edition provides updated guidance for advanced reactor developers, regulators, and fire safety professionals.