Regulatory framework and insights from fire PSA of Canadian nuclear power plants

An abstract of the technical paper presented at:
OECD/NEA International Workshop on Fire PRA
Garching, Germany
April 28–30, 2014

Prepared by: U. Menon
Canadian Nuclear Safety Commission
Ottawa, Ontario, Canada

Abstract

Recognizing that the Probabilistic Safety Assessment (PSA) is a useful tool for the safety of Nuclear Power Plants, the Canadian Nuclear Safety Commission (CNSC) has incorporated PSA in the regulatory framework. The regulatory document S-294 "Probabilistic Safety Assessment (PSA) for Nuclear Power Plants" was issued by the CNSC in 2005. This regulatory document is currently being amended to add recommendations from CNSC's Fukushima Task Force Report. The amended regulatory document will be published as REGDOC 2.4.2 -"Probabilistic Safety Assessment (PSA) for Nuclear Power Plants".

As per S-294, the Canadian utilities are required to perform both internal and external event analyses for all operational states. The PSA results are used to identify weaknesses in the overall plant design for defence-in-depth, and to evaluate the benefits of plant modifications for improving operations and safety. PSA is also used in evaluating the operating procedures, and it is an important input for accident management. In addition to other techniques, PSA is used as input to an Integrated Safety Review in support of plant life extension and plant refurbishment projects.

For example, Fire PSA using probabilistic models analyses the internal fire events at various plant locations and evaluates the safety of the Nuclear Power Plant (NPP). It accounts for the various detection and suppression methods, and assesses the effects on, and damage to the equipment and cables that are required to maintain the plant in a safe state. It can provide the contribution of fire events to the overall plant risk.

This paper presents some of the results and insights gained from the regulatory review of a Fire PSA conducted at a Canadian NPP as part of a refurbishment project. It also touches upon the current methodologies by Canadian utilities to conduct the Fire PSA as part of compliance with the regulatory standard S-294 and re-licensing activities.