CSA N290.6-16 (2021)

Preface

This is the third edition of CSA N290.6, Requirements for monitoring and display of nuclear power plant safety functions in the event of an accident. It supersedes the previous editions, published in 2009 and 1982.

Major changes to this edition include new requirements, guidance, and recommendations for design extension condition monitoring as a subset of beyond design basis accidents. The scope of this standard has been broadened to include requirements for monitoring of irradiated fuel bays under design extension conditions.

Consistent with industry initiatives to further classify and subdivide the beyond design basis accident regime, the informative annex on severe accidents in the 2009 edition has been incorporated into the body of the standard to the extent it is applicable to accident monitoring for design extension conditions. Other requirements for beyond design basis accidents are addressed in the CSA N290.16 standard.

The CSA N-Series Standards provide an interlinked set of requirements for the management of nuclear facilities and activities. The CSA N286 Standard provides overall direction to management to develop and implement sound management practices and controls while the other CSA nuclear Standards provide specific 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 can provide more specific direction for meeting those requirements.

This Standard provides requirements and recommendations for the design and qualification of those components specifically involved in the monitoring and display of safety functions for a nuclear reactor. The monitoring and display of nuclear power plant variables following an accident are important safety functions; appropriate operator actions following such an event rely on the availability of essential information.

Users of this Standard are reminded that additional and site-specific requirements might be specified by federal, provincial/territorial, or municipal authorities. This Standard should not be considered a replacement for the requirements contained in any

a) applicable federal/territorial, or provincial statute, including the Nuclear Safety and Control Act; or

b) regulation, license, or permit issued pursuant to an applicable statute.

Scope

1.1
This Standard provides requirements for the design and qualification of components for the monitoring and display of nuclear power plants (NPP) and irradiated fuel bay safety functions in the event of a design basis accident (DBA) or a design extension condition (DEC).

Note: The requirements for a DBA and those for a DEC might differ. Where requirements differ for a DBA and a DEC, the difference is explicitly stated.

1.2
This Standard applies to existing NPPs and new NPPs.

Notes:

1) The requirements for new plants and existing plants might differ. Where requirements differ for new plants and existing plants, the difference is explicitly stated.

2) This Standard may provide guidance for nuclear facilities other than NPPs, using a graded approach.

1.3
This Standard addresses the specific requirements for the monitoring and display of safety functions under DECs.

Note: Requirements and guidance regarding DECs [as a subset of beyond design basis accidents (BDBAs)] are covered in CSA N290.16.

1.4
This Standard applies to components and systems that enable NPP staff, in the event of an accident, to

a) monitor the plant safety functions;

Note: The purpose of monitoring the plant safety functions is to guide operator actions that might be required as a part of the accident response.

b) monitor plant conditions for the purposes of accident management; and

Note: Accident management refers to specific actions taken within the NPP during the evolution of an accident to prevent escalation, mitigate consequences, and to achieve a long-term controlled stable state. Accident management actions are the responsibility of the plant operator. Refer to CNSC REGDOC-2.3.2 for further clarification.

c) monitor parameters for the initiation of on-site and off-site emergency management.

Note: Emergency management in this context refers to the overall coordinated response to, mitigation of, and recovery from a nuclear emergency. Emergency management is not concerned with the specific actions taken within the NPP to manage the accident (i.e., accident management as described above). Emergency management actions can be the responsibility of the operating organization or other jurisdictions (e.g., operator emergency response organizations, government bodies, emergency workers). Refer to CSA N1600 for guidance on nuclear emergency categorization and notification.

1.5
This Standard applies only to the functions associated with monitoring in the event of an accident; other monitoring functions are beyond the scope of this Standard.

Plant systems, including safety systems and process control systems, can provide functions associated with monitoring in the event of an accident as a part of the design.

Note: The design of monitoring capability for process and safety systems are covered in other CSA N290 Standards.

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 (non-mandatory) 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.

Note: Examples can include no action, operating procedures, design features.