Passive Systems Reliability for New and Advanced Reactors in Canada: Learning Lessons and Setting Expectations

Abstract of the technical paper/presentation presented at:

Passive Systems Performance and Reliability Workshop

30 March - 1 April 2026

Prepared by:

Katherine Gromek, Tomas Blanchette, Abderrazzaq Bounagui

Canadian Nuclear Safety Commission (CNSC)

Abstract:

In preparation for the deployment of the next generation of nuclear power plants in Canada, the Canadian Nuclear Safety Commission (CNSC) comprehensively evaluated and updated the licensing requirements and regulations to learn from past successes and industry experience. Passive system reliability has become one of the focus areas due to wide deployment of passive safety systems in advanced reactor designs. The CNSC has established a flexible regulatory framework, outlined in the CNSC regulatory document REGDOC-3.5.3. Technical safety objectives and design requirements for new reactors are defined in the CNSC REGDOC-2.5.2.

The CNSC is currently engaged in licensing activities in support of BWRX-300 SMR reactor deployment in Canada, the Darlington New Nuclear Project (DNNP), which is the first commercial application of the BWRX-300 SMR. The practical application of the Canadian regulatory framework to passive safety systems during the licensing review of the BWRX-300 SMR reactor revealed that passive systems requirements may need some additional guidance.

The focus of this paper is on the evolution of the Canadian regulatory requirements and expectations for passive safety system design, reliability, and incorporation within the safety analysis to support licensing and future operations. Input is taken from the industry experience and lessons learned during the CNSC staff’s ongoing review of the BWRX-300 design, in particular the Isolation Condenser System (ICS). ICS is a passive system that removes decay heat and controls pressure in the reactor, a first of a kind application in Canada. The system is designed with a high degree of independence, diversity, and redundancy in the actuation function.

This paper will discuss the lessons learned from the BWRX-300 project with respect to various aspects of passive system reliability assessment such as elements of the passive reliability model, relevant failure modes and phenomenological challenges, key parameters and performance acceptance criteria under different accident conditions including design basis accidents (DBA) and beyond design basis accidents (BDBA), treatment of uncertainties in passive reliability modeling, and integration of the ICS passive reliability representation into the overall safety analysis. Application of best industry practices in passive system reliability assessment and use of the respective safety standards, codes, and guidance is also addressed.

To obtain a copy of the abstract’s document, please contact us at cnsc.info.ccsn@cnsc-ccsn.gc.ca  or call 613-995-5894 or 1-800-668-5284 (in Canada). When contacting us, please provide the title and date of the abstract.