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Document History of REGDOC-2.4.3, Nuclear Criticality Safety

View [HTML version of REGDOC-2.4.3, Version 1.1] [PDF version of REGDOC-2.4.3, Version 1.1 | 148 pages, 2.2 MB]


REGDOC-2.4.3, Nuclear Criticality Safety, sets out requirements for nuclear criticality safety and provide guidance on how those requirements may be met. It provides information for preventing criticality accidents in the handling, storage, processing and transportation of fissionable materials and the long-term management of nuclear waste.

This document clarifies the minimum physical constraints and limits on fissionable materials to ensure nuclear criticality safety during the construction, operation, decommissioning or abandonment of the licensed facility. It applies to operations with fissionable materials outside nuclear reactors, except for the assembly of these materials under controlled conditions (such as in critical experiments).

This regulatory document is part of the CNSC’s safety analysis series of regulatory documents, which also covers deterministic and probabilistic safety analysis and probabilistic safety assessment.

Key principles and elements used in developing this document are consistent with national and international standards. Some sections of this document are extracted from the specified standards from the American National Standards Institute, with permission of the publisher, the American Nuclear Society. Where necessary, the text has been adapted to make it applicable to Canada’s international obligations to the International Atomic Energy Agency (IAEA) and consistent with the CNSC’s regulatory requirements.

This document supersedes:

Note: A "tracked changes" version of draft REGDOC-2.4.3, Nuclear Criticality Safety, which indicates where updates and amendments were made, is available upon request to

Version 1.1 includes administrative updates so that references to the IAEA’s SSR-6, Regulations for the Safe Transport of Radioactive Material, reflect the 2018 edition.


September 2020: Published

Document Milestone Dates Links
Previous consultation as draft REGDOC-2.4.3, Nuclear Criticality Safety July 11, 2017 to September 14, 2017

View the July 11, 2017 news release

View the consultation version of draft REGDOC-2.4.3

(Draft REGDOC-2.4.3 HTML) (Draft REGDOC-2.4.3 PDF)

Invitation to provide feedback on comments received October 6 to October 30, 2017

View the comments received:

Feedback received October 31, 2017 No feedback was received
Approved by the Commission December 2018 View comments table
Publication February 2019 View HTML version of REGDOC-2.4.3

View PDF version of REGDOC-2.4.3

Publication of version 1.1 September 2020 View the HTML version of REGDOC-2.4.3, Version 1.1

View the PDF version of REGDOC-2.4.3, Version 1.1 | 148 pages, 2.2 MB

Contact information

For questions and information related to REGDOC-2.4.3, Nuclear Criticality Safety, please contact:

Directorate of Assessment and Analysis

Canadian Nuclear Safety Commission
280 Slater St
PO Box 1046 Stn B
Ottawa ON  K1P 5S9

Telephone: 1-800-668-5284 (Canada only)
Fax: 613-995-5086

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