ISO 12749-5:2018

Overview

ISO 12749-5:2018 - "Nuclear energy, nuclear technologies, and radiological protection - Vocabulary - Part 5: Nuclear reactors" is an international vocabulary that defines core terms and concepts used across the field of nuclear reactors. The standard collects terms, definitions, notes and examples for reactor-related concepts at a broad, non‑quantitative level. It is intended to promote clear communication and a common understanding among engineers, regulators, researchers and other stakeholders working with nuclear reactors.

Key characteristics:

• Provides minimum essential information for each nuclear reactor concept.
• Excludes quantitative data (no numerical specifications or performance limits).
• Organizes entries in a conceptual (preferred-term) order and includes systematic and alphabetical indexes.
• Includes an informative Annex A (methodology) and a bibliography.

Key topics

ISO 12749-5:2018 covers foundational nuclear reactor vocabulary, including but not limited to:

• Nuclear fission (spontaneous and induced) and fission energy
• Prompt and delayed fission neutrons and fission radiation
• Fission products, fast and thermal neutrons
• Fissile and fertile nuclides
• Nuclear chain reaction, controlled chain reaction, and nuclear criticality
• Effective neutron multiplication factor (keff) and reactivity (ρ)
• Poison (neutron absorbers), neutron multiplicative configuration, and reactor kinetics
• Notes and examples to clarify ambiguous or widely misunderstood terms

The standard draws on established sources (ISO/TC 85 materials, IAEA, IEC) and documents terminological consensus from subject‑matter experts.

Applications

ISO 12749-5:2018 is practical for any activity that requires precise, unambiguous terminology related to nuclear reactors:

• Technical documentation, procedures and operating manuals
• Regulatory guidance, licensing documents and safety cases
• Standards development and cross‑organization coordination
• Training materials, textbooks and translator/reference glossaries
• Communication between multidisciplinary teams (design, operations, safety, procurement)

Because the vocabulary excludes quantitative specifications, it is complementary to technical standards that set numerical requirements.

Who should use it

• Nuclear engineers and reactor physicists
• Regulatory bodies and safety analysts
• Standards writers and technical editors
• Educators, trainers and translators working in nuclear technology
• Project managers and procurement specialists who need consistent terminology

Related standards

• Part of the ISO 12749 series (vocabulary for nuclear energy and radiological protection)
• Cross-references to ISO/TC 85 publications and IAEA terminology resources are included in the bibliography

Using ISO 12749-5:2018 helps reduce ambiguity, improve documentation quality, and ensure consistent use of core nuclear reactor terms across international projects and regulatory frameworks.