Application of a Graded Approach to Safety Standards of Research Reactors and Subcritical Assemblies

Abstract of the presentation to be delivered at:
Expert Mission on the Use of a Graded Approach in the Application of Safety Standards to a Subcritical Assembly Project
Sidi Thabet, Tunisia
May 2–6, 2016

Prepared by:
N. Mesmous and J. E. Kowalski
Canadian Nuclear Safety Commission


Most nuclear research facilities, including critical and subcritical research reactors, have a small potential to pose a hazard to the public compared to power reactors. Considering the different types of research facilities and their associated uses, safety assessment should be commensurate with the potential hazard, ensuring that the design and operation of each facility lead to adequate safety and defence in depth. All important factors affecting the overall nuclear facility safety, inherent safety features, the amount of fissile and fissionable materials, and the source terms are to be taken into account.

The Canadian Nuclear Safety Commission (CNSC) has developed a regulatory framework for licensing small reactor facilities, including research reactors, that permits a graded approach for safety assessment, allowing safety requirements to be implemented so that the level of assessment is proportional to the potential hazards posed by the nuclear research facility. In applying a graded approach, the level of assessment, verification, documentation and actions necessary to comply with safety requirements and criteria are commensurate with particular characteristics of the facility or activity, as well as the magnitude of any hazards involved.

The scope of presentation will cover the following topics:

  • the Canadian regulatory framework for licensing small reactors
  • factors to be considered in a graded approach
  • the use of graded approach for safety assessments of research reactors
  • examples of a graded approach used in safety assessment of subcritical assemblies

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