CSA N290.6:25

Preface This is the fourth 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 2016, 2009, and 1982. Major changes to this edition include a) updated definitions for alignment with CSA common definitions and CNSC REGDOC-3.6; b) incorporated requirements and guidance from internationally accepted Standards for increased alignment; c) clarified the application of the Standard to new builds; d) included more technology neutral language; e) reordered clause structure for alignment with N290A TC table of contents template; and f) added clause titles at all levels for the purposes of accessibility. 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 requirements of CSA N286; however, it might provide more specific direction for 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 nuclear power plants (NPP) and NPP facility irradiated fuel storage. 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, or municipal authorities. This Standard should not be considered as a replacement for the requirements contained in the Nuclear Safety and Control Act and its Regulations or in other legislation, standards, or guides. This Standard was prepared by the Subcommittee on Requirements for Monitoring and Display of Nuclear Power Plant Safety Functions in the Event of an Accident, under the jurisdiction of the Technical Committee on Reactor Control Systems, Safety Systems, and Instrumentation for Nuclear Power Plants and the Strategic Steering Committee on Nuclear Standards, and has been formally approved by the Technical Committee. Scope 1.1 Inclusions This Standard provides requirements for the design and qualification of components for the monitoring and display of NPPs and NPP facility irradiated fuel storage safety functions in the event of a design basis accident (DBA) or a design extension condition (DEC) during the operational phase of the facility lifecycle. Notes: 1) This Standard applies only to the functions of plant systems, including safety systems and process control systems, associated with monitoring in the event of an accident; other monitoring functions are beyond the scope of this Standard. 2) 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. 3) General requirements and guidance regarding DECs [as a subset of beyond design basis accidents (BDBAs)] are covered in CSA N290.16. 4) The operational phase of the facility lifecycle would include the period of time wherein the reactor is capable of operations, generally from the end of commissioning with fuel loaded, through to the end of operations with fuel unloaded prior to decommissioning. 1.2 New and existing NPPs 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) For existing NPPs, the application should address the information in this Standard to the extent practicable. Any alternative approaches selected or mitigating measures applied should be identified. 3) This Standard may provide guidance for nuclear facilities other than NPPs, using a graded approach. 1.3 Application This Standard applies to components and systems that enable NPP staff, in the event of an accident, to a) monitor and display the plant safety functions for diagnosing that an accident, including severe accident, is occurring or has occurred; 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 and display plant conditions for the purposes of accident management to continuously address the state of safety functions; 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 and display parameters for the initiation of on-site and off-site emergency management to confirm the effectiveness of the accident management actions. Notes: 1) 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. 2) If the emergency planning basis, as defined in CSA N1600, does not require off-site emergency management actions, any functions associated with monitoring off-site parameters may be excluded where justified. 1.4 Terminology 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.