Two updated standards on criticality safety published

ANSI/ANS-8.20-2025, Nuclear Criticality Safety Training for Fissionable Material Operations Outside Reactors, provides a framework for the training of personnel associated with fissionable material operations outside reactors where criticality safety measures are needed to prevent hazards that could arise from the presence of enough fissionable material.

This is the first revision of the ANS-8.20 standard, which was first developed after a need was identified in the 1980s by the Training Work Group of the Department of Energy Nuclear Criticality Technology and Safety Project.

The ANS Standards Committee’s ANS-8.20 Working Group, which prepared this standard, is composed of members from across the DOE and its contractors, the U.S. Nuclear Regulatory Commission and its licensees, private nuclear industry entities, academia, and international organizations.

This standard does not apply to the training and qualification of NCS engineers who are responsible for developing the analyses, controls, and safety documentation required for the safe handling of fissionable materials. Management is required to establish a program for that training under ANSI/ANS-8.19-2014 (R2024), Administrative Practices for Nuclear Criticality Safety. Guidance for establishing that program may be obtained from the second of the two recently published standards, ANSI/ANS-8.26-2024, Nuclear Criticality Safety Engineer Training and Qualification Program.

ANSI/ANS-8.26-2024 presents a flexible array of competencies for use by management to develop tailored training and qualification (T&Q) programs applicable to site-specific job functions, facilities, and operations. This standard stresses the necessity of integrating standard training subjects with operational experience in order to qualify as an NCS engineer.

Key elements of an effective training program that can enable NCS engineers to become effective advocates in fostering sound nuclear safety practices include the following:

Understanding the impact of controlled parameters on the multiplication of a defined system.

Effectively predicting the reactivity of a system or process.

Learning lessons from previous criticality accidents.

Practical experience with parameters that affect the neutron multiplication of fissionable material systems.

ANSI/ANS-8.26-2024 does not specify how to develop or execute these T&Q programs; it provides only the elements that should be included in the programs. It is not intended that these programs lead to any professional engineer certification, only that they create a common basis for NCS engineer qualification across the diverse organizations that rely on these specialists. Standard criteria for establishing scopes, functions, and levels of competence for safety professionals are available in ANSI/ASSE Z590.2-2003 (R2012), Criteria for Establishing the Scope and Functions of the Professional Safety Position.

ANSI/ANS-8.26-2024 is a revision of ANS-8.26-2007 (withdrawn). The 2024 edition adds an appendix providing examples of NCS engineer training program content. ANSI/ANS-8.26-2024 presents the elements of a T&Q program for several categories of NCS engineers. The standard does not include guidance on how these elements are to be incorporated into site-specific T&Q programs, but it does require that such programs be established. The appendix presents examples of content that should typically be included in T&Q programs, depending on the activities of specific sites, presented according to the corresponding areas of Sec. 6 of the standard. Management should use this appendix only as a basis for establishing or maintaining their T&Q program, not as an all-inclusive template.

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