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Defence in Depth Considerations for Inherent Safety Features and Passive Safety Systems in Advanced Reactor Technology Designs

Abstract of a student paper presented at:
The 40th Annual Conference of the Canadian Nuclear Society and the 45th Annual CNS/CNA Student Conference
June 6–9, 2021

Prepared by: Tomas Blanchette, Tiffany Dunbar and Yolande Akl
Canadian Nuclear Safety Commission


Defence in Depth (DiD) is a fundamental safety concept with a central objective to ensure that all safety activities, whether they be organizational, behavioural or equipment related, are subject to layers of overlapping provisions, so that, if a failure should occur, it would be compensated for or corrected without causing public harm. This idea of multiple levels of protection is the central feature of DiD, and they are expected to be implemented during the design and operation of reactor facilities. Advanced reactor technologies are increasingly proposing to incorporate inherent safety features and passive safety systems in their design, with a higher emphasis on earlier levels of DiD and physical barriers. Some considerations include addressing uncertainties with plant operating states, and failure modes due to limited operational experience and research and development. Nevertheless, it is important that fundamental safety objectives are achieved, including a balanced application of DiD.

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