CSA N290.16:16 (R2021)

Preface:

This is the first edition of CSA N290.16, Requirements for beyond design basis accidents.

This Standard provides requirements regarding beyond design basis accidents (BDBAs) at water-cooled nuclear reactor facilities. It incorporates work done by operators of Canadian nuclear reactor facilities, the Canadian Nuclear Safety Commission, and the International Atomic Energy Agency to define the requirements for BDBAs, and also reflects guidance from various industry organizations, including the CANDU Owners Group, the Nuclear Energy Institute, and the World Association of Nuclear Operators.

Users of this Standard are reminded that the site selection, design, manufacture, construction, installation, commissioning, operation, and decommissioning of nuclear facilities in Canada are subject to the Nuclear Safety and Control Act and its Regulations. The Canadian Nuclear Safety Commission might impose additional requirements to those specified in this Standard.

The CSA N-Series Standards provide an interlinked set of requirements for the management of nuclear facilities and activities. CSA N286 provides overall direction to management to develop and implement sound management practices and controls, while the other CSA Group nuclear Standards provide technical requirements and guidance that support the management system. This Standard works in harmony with CSA N286 and does not duplicate the generic requirements of CSA N286; however, it might provide more specific direction for those requirements.

Scope:

1.1
This Standard provides requirements and guidance regarding beyond design basis accidents (BDBAs) at existing and new water-cooled reactor facilities with the fundamental objective of protecting the public and environment from the harmful effects of ionizing radiation. This includes
a) determination of the functional DEC requirements for the structures, systems, and components (SSCs) that prevent and mitigate BDBAs, including severe accidents;
Note: This also includes guidance related to reliability, inspections, and operations considerations.
b) development of strategies to mitigate or terminate, or both, BDBAs, including severe accidents; and c) management of BDBAs within and beyond site boundary.

Note: The prevention of long-lived radionuclide releases following a BDBA is the single most important objective for protecting the public and the environment. Thus, a focus on maintaining the barriers to ionizing radioactive releases is essential.

1.2
This Standard also provides guidance on the use of safety analyses (e.g., deterministic safety analysis and probabilistic safety assessment) and operational experience (OPEX).

1.3
This Standard applies to water-cooled reactor facilities. It does not apply to other nuclear facilities.

1.4
This Standard does not specifically address accidents caused by malevolent acts; however, the requirements and guidance in this Standard could provide useful information in developing strategies in this area.
Note: In Canada, malevolent acts are dealt with separately under the CNSC Nuclear Security Regulations.

1.5
This Standard does not provide specific guidance related to the safety classification of SSCs developed and implemented to address DECs (see Clause 0.2) since this is a developing area of industry work. This Standard does provide guidance related to procurement, redundancy, testing, maintenance, and other operational activities for SSCs providing DEC and BDBA mitigation.

1.6
In this Standard, "shall" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; "should" is used to express a recommendation or that which is advised but not required; and "may" is used to express an option or that which is permissible within the limits of the standard. Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements. Annexes are designated normative (mandatory) or informative (nonmandatory) to define their application.

1.7
In this Standard, "shall be considered" or "shall consider" means that the user evaluates the impact and documents any decisions.