Nuclear Criticality Safety Standards: Overview of the areas covered by the ANSI/ANS-8 and the ISO/WG8 series

The International Organisation for Standardization (ISO) and the American National Standards Institute (ANSI) are similar organizations that develop and publish standards that cover a very large scope of applications. Both organizations have nuclear energy and technologies standards; established by experts of the Technical Committee 85 (TC 85) for ISO and the American National Society (ANS) for ANSI. Among them, a series of standards is dedicated to Nuclear Criticality Safety (NCS) practices: the Working Group 8 series for ISO and ANS-8 series for ANSI. Currently, ANSI/ANS has a set of 18 published NCS standards, where ISO/WG8 has 11 published NCS Standards (and other in progress). Some of them are very close in their scope: ANSI/ANS-8.1 and ISO 1709:2018 related to principles of criticality safety in operations with fissionable materials, ANSI/ ANS-8.3-2022 and ISO 7753:2022 related to criticality accident alarm systems, ANSI/ ANS-8.23-2019 and ISO 11320:2011 related to emergency preparedness and response or ANSI/ANS-8.20-2025 and ISO 23133:2021 related to Nuclear Criticality Safety training…Others only exist in one or the other institution: ANSI/ANS-8.14-2004 and 21 related to the use soluble and fixed of neutron absorbers, ANSI/ANS-8.22-1997 related to the moderators limits and controls, ISO 21391:2019 related to subcritical geometry dimensions, ISO 27467:2009 related to the analysis of a postulated accident or ISO 22946:2020 related to solid waste… In addition, the ISO Working Group has developed internal documents to track the positions taken by the group (e.g. applicability of a standard to transportation) as well as documents to ease the development of future standards (e.g. the two column guidance which compare the definition of safety principles in the French guides and US standards). This paper will present an overview of the similarities and differences between the Nuclear Criticality Safety standards corpus of ANSI/ANS and ISO/TC85/SC5/G8.