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Challenges in PSA regulatory expectations for nuclear power plants in Canada

An abstract of a technical presentation presented at:
Technical Meeting on Probabilistic Safety Assessment for New Nuclear Power Plants’ Design
Vienna, Austria (IAEA Headquarters)
October 1–5, 2012

Prepared by:
Guna Renganathan and Raducu Gheorghe
Technical Specialists
Probabilistic Safety Assessment and Reliability Division
Canadian Nuclear Safety Commission
Ottawa, Ontario, Canada


The paper briefly describes the existing international and Canadian practices and guidance in the areas considered for regulatory review of probabilistic safety assessment (PSA). Moreover, the paper presents the situation where the lack of information was experienced, how the situation was handled and the type of information expected from the international community. This paper also highlights the international activities in progress for a better understanding of some of the cases considered in the discussion.

In Canada, the PSAs are being developed to demonstrate compliance with the safety goals, to identify plant vulnerabilities, for operation management, risk informed decision making, configuration management, testing and maintenance planning and optimization, safety upgrading programmes, and cost impact assessment. Post Fukushima event review, provided additional insights in the treatment of external events. 

The Canadian NPPs are pressurised heavy water reactors (PHWR). However, vendors have submitted pressurised water reactor (PWR) designs for review by the Canadian regulator, Canadian Nuclear Safety Commission (CNSC). Review of PSAs for operating, refurbished plants and new reactors revealed the need of new regulatory requirements and guidance. For instance, passive safety systems and computer based control systems are part of the new designs, digital instrumentation and control is part of upgrades, refurbishment and in new NPP designs for many systems. The gaps in regulatory requirements and international guidance in such areas requires reliance on expert judgement. There are also gaps in guidance relating to human action modelling associated with digital I&C, treatment of software and hardware failure in the PSA models and their quantification, as well as the scope and treatment of external events.

To obtain a copy of the abstract's document, contact the CNSC. When contacting the CNSC, please provide the title and date of the abstract.

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