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Safety Objectives Proposed for CANDU Fuel in Design Extension Conditions

Abstract of the technical paper/presentation presented at:

TopFuel 2018
September 30 – October 4, 2018
Prague, Czech Republic

Prepared by:
Ho Chun Suk and Michel Couture
Canadian Nuclear Safety Commission


To enhance accident protection beyond those considered in the design basis of the plant, and to reflect lessons learned from the Fukushima Daiichi accident, the Canadian Nuclear Safety Commission (CNSC) introduced the term "design extension conditions" (DECs) with the 2014 issue of regulatory document REGDOC-2.5.2, Design of Reactor Facilities: Nuclear Power Plants, and participated to the development of CSA Group document, CSA N290.16-16, Requirements for beyond design basis accidents, published in 2016. Although much work has already been done in Canada towards addressing DECs for CANDU reactors, the set of fuel safety criteria that should be used for DECs remains to be formulated. As a first step towards that goal, this paper proposes a set of fuel-related safety objectives that ought to be met for CANDU-specific DECs.

The paper begins with a review of the various definitions of DECs and how DECs fit within the concept of defence in depth. This review is followed by a brief overview of the requirements and guidance for DECs provided by CNSC REGDOC-2.5.2 and CSA N290.16-16. A brief review of CANDU fuel behaviour in severe accidents and design-basis accidents is then provided, based on which certain fuel-related safety objectives for DECs are proposed.

The views expressed in this paper are those of the authors and do not necessarily reflect those of CNSC, or any part thereof.

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