REGDOC-2.4.4, Safety Analysis for Class IB Nuclear Facilities - Public Consultation

Consultation has concluded

Consultation on REGDOC-2.4.4, Safety Analysis for Class IB Nuclear Facilities is now closed. Thank you to everyone who submitted comments.

REGDOC-2.4.4, Safety Analysis for Class IB Nuclear Facilities sets out requirements and guidance for applicants and licensees to demonstrate the safety of a Class IB nuclear facility, including:

  • a safety analysis program (the managed process that governs conduct of a safety analysis)
  • conduct of a safety analysis (a systematic evaluation of the potential hazards)
  • safety analysis documents, records and reporting

This document is the first version of REGDOC‑2.4.4, Safety Analysis for Class IB Nuclear Facilities.

For additional information on safety analysis for the post-closure phase of a disposal facility, see REGDOC‑2.11.1, Waste Management, Volume III: Safety Case for Disposal of Radioactive Waste.

Consultation on REGDOC-2.4.4, Safety Analysis for Class IB Nuclear Facilities is now closed. Thank you to everyone who submitted comments.

REGDOC-2.4.4, Safety Analysis for Class IB Nuclear Facilities sets out requirements and guidance for applicants and licensees to demonstrate the safety of a Class IB nuclear facility, including:

  • a safety analysis program (the managed process that governs conduct of a safety analysis)
  • conduct of a safety analysis (a systematic evaluation of the potential hazards)
  • safety analysis documents, records and reporting

This document is the first version of REGDOC‑2.4.4, Safety Analysis for Class IB Nuclear Facilities.

For additional information on safety analysis for the post-closure phase of a disposal facility, see REGDOC‑2.11.1, Waste Management, Volume III: Safety Case for Disposal of Radioactive Waste.

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    Requirements

    The applicant or licensee shall derive the OLCs from the safety analysis. The applicant or licensee shall prepare the OLCs before starting operation of the facility.

    Guidance

    OLCs include limiting conditions for safe operation (values, conditions), monitoring systems and associated alarm settings, and surveillance and administrative requirements. The OLCs should set minimum requirements for the availability of staff and equipment. For more information on the availability of staff, see REGDOC‑2.2.5, Minimum Staff Complement [11].

    Where it is not practicable to define precisely the safe limits of all relevant parameters, OLCs should be set to define the limits of the assessment in order to prevent operation in the unanalyzed or unanalyzable conditions.

    Appendix B provides examples of parameters that may be managed through OLCs across the broad range of facilities.

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    Requirements

    The applicant or licensee shall establish explicit criteria for the level of safety to be achieved to demonstrate that the applicant or licensee is making adequate provision for the protection of the environment and the health and safety of persons [3].

    The applicant or licensee shall set limits on the radiological consequences and associated chemical consequences for the workers and the public of direct exposures to radiation or discharges of radionuclides to the environment. These limits shall:

    • be set equal to, or below:
      • the provisions of the Radiation Protection Regulations, when applicable and as far as practicable; otherwise
      • criteria established by national or international standards as triggers for protective measures during radiological or chemical emergencies (for example, for sheltering, evacuation, temporary relocation and permanent resettlement, or distribution of iodine pills)
    • apply to the consequences of operational states and the possible consequences of AOO and DBA at the facility

    For new designs, the applicant or licensee shall consider targets that are below these limits.

    The applicant or licensee shall establish derived acceptance criteria to demonstrate that the barriers to prevent the release of nuclear or hazardous substances are effective; that is, the barriers:

    • avoid the potential for consequential failures resulting from an initiating event
    • maintain SSCs important to safety in a configuration that prevents releases of nuclear or hazardous material to the environment or in the facility
    • prevent development of a severe accident (that is, with effects extending beyond the facility)
    • are consistent with the design requirements for the facility’s SSCs

    For acceptance criteria for nuclear criticality safety, see REGDOC‑2.4.3, Nuclear Criticality Safety [12].

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    Requirements

    The applicant or licensee shall demonstrate that the offsite consequences of a BDBA included in the DEC do not exceed criteria established as a trigger for temporary evacuation, for longterm relocation of the local population, or for both temporary evacuation and longterm relocation in:

    • Health Canada, Canadian Guidelines for Intervention During a Nuclear Emergency [13]
    • IAEA GSR Part 7, Preparedness and Response for a Nuclear or Radiological Emergency [14]

    The applicant or licensee shall include events from BDBA in the DEC. As a minimum, the applicant or licensee shall include the following events in the DEC [6]:

    • an extended loss of AC power (ELAP)
    • PIEs and event sequences, including those that are specific or unique to the facility, that belong to a category of credible abnormal events [6]

    For naturally occurring PIEs (for example, seismic events, flooding and severe weather), when selection of credible abnormal events is not practical, the applicant or licensee shall include in the DEC events that are more severe than considered in analyses of DBA consistent with the guidance of national or international standards (see appendix C)

    The classification shall be based on likelihood, as specified in section 4.4.2.

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    The safety analysis documents describe the methods used in performing analyses, and record the results of each analysis. They support the siting, design, commissioning, operation and decommissioning of a nuclear facility. They demonstrate that any risks to the health and safety of persons are managed and mitigated, and also help to demonstrate that defence in depth has been achieved.

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    Guidance

    The safety analysis documents and records provide information on the safety analysis, as follows:

    • demonstrate that the safety goals, objectives and acceptance criteria are met
    • assist in deriving or confirming operational limits and conditions that are consistent with the design and safety requirements of the facility
    • assist in establishing and validating operating and emergency procedures and guidelines

    The scope of safety analysis documents and records covers internal and external events that could lead to a release of nuclear or hazardous substances, to a criticality accident, or to an accidental exposure to high radiation fields.

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    Requirements

    The applicant or licensee shall report the safety analysis results in sufficient detail to permit review by CNSC staff.

    The applicant or licensee shall ensure that the content of the safety analysis documents and records for a facility includes, as a minimum, the SAR and the OLCs (or equivalent) [3].

    The SAR shall contain a representative summary of the safety analysis documents and records. The SAR shall:

    • describe the site characteristics
    • identify nuclear and hazardous substances and their locations
    • identify applicable acceptance criteria for offsite consequences to the public of pertinent accidents (some examples are radiological, nuclear criticality, fire and chemical accidents, including explosions)
    • identify SSCs that prevent or mitigate release of nuclear or hazardous substances, or prevent accidental exposure to high radiation fields (to the extent appropriate for the facility, in accordance with a graded approach)
    • classify SSCs in accordance with their importance to safety
    • identify operating and emergency procedures and actions that prevent or mitigate release of nuclear or hazardous substances
    • identify the safety analysis assumptions (some examples are boundary conditions, facility configuration, and time for operator actions); many of these assumptions may be documented in the operational limits and conditions
    • identify credible initiating events that may affect the applicant or licensee’s control of nuclear or hazardous substances, including:
      • internal events (for example, component failures, human error, fire or flood)
      • external events (for example, earthquake, fire, flood or extreme weather)
    • group together all initiating events that have similar characteristics and identify bounding events for analysis
    • provide the results of the analysis of the consequences of the analyzed events
    • as appropriate, include uncertainty and sensitivity analysis results
    • compare the results to acceptance criteria
    • provide results and conclusions
    • be independently reviewed as per the management system of the applicant or licensee

    Guidance

    The applicant or licensee may incorporate information by reference. For example, many of the safety analysis assumptions may be documented in the applicant or licensee’s operational limits and conditions and may be incorporated into the SAR by reference.

    Risks to the environment are considered in the applicant or licensee’s environmental risk assessment (ERA) for the facility, and therefore are not considered in the SAR.

    For a sample structure and content for a SAR, see appendix A.

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    Requirements

    The applicant or licensee shall describe the facility’s behaviour following a PIE and compare it to the analysis acceptance criteria.

    Guidance

    For DBAs, the applicant or licensee should describe each event in the SAR as follows:

    • the timing of the main events, including:
      • the initial event and any subsequent failures
      • times at which mitigating equipment is actuated
      • times of operator actions
      • time at which a safe longterm stable state is achieved
    • graphical presentation of key parameters as functions of time during the event (the parameters should be selected so that a full understanding of the event’s progression can be obtained within the context of the acceptance criterion being considered)
    • comparison with acceptance criteria
    • the event’s conclusion
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    The SAR and other safety analysis documents and records are updated periodically throughout the lifecycle of the facility. The period for SAR updates is stated in each facility’s licence conditions handbook (LCH). Five years is the recommended period, but different periods may be set; for example, based on the overall safety impact of the facility or on significant changes to the facility.

    Requirements

    The applicant or licensee shall perform an ongoing site evaluation. If the ongoing site evaluation identifies new information about the site characteristics (that is, changing the results of the identification and classification of PIEs), then safety precautions (such as engineering controls and emergency arrangements) may need to be reviewed and revised.

    Guidance

    The process for updates should meet the requirements of the safety analysis program and should include:

    • identification of sections to be revised due to:
      • changes to initiating events
      • changes to the facility equipment or procedures
      • extension of the facility operating life
      • changes to regulatory requirements
      • new knowledge from research or operating experience
      • aging of SSCs
    • performance of analysis
    • independent review
    • documents and records in the SAR

    Items of safety analysis may be performed at various times, for a variety of reasons. Normal practice is that any updated safety analysis performed in mid-cycle is included with the next scheduled update of the SAR.

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    Guidance

    The safety analysis tools should be validated and verified. For more information, see:

    • REGDOC‑3.5.3, Regulatory Fundamentals [2]
    • CSA Group N286, Management System Requirements for Nuclear Facilities [5]
    • CSA Group N292.0, General Principles for the Management of Radioactive Waste and Irradiated Fuel [15]
    • CSA Group N292.1, Wet Storage of Irradiated Fuel and Other Radioactive Materials [6]
    • CSA Group N292.2, Interim Dry Storage of Irradiated Fuel [16]
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    Guidance

    The applicant or licensee can propose a graded approach to the application of this regulatory document, if they provide adequate justification.

    Some examples of elements of the safety analysis that may be considered using the graded approach include:

    • frequency boundaries for facility states (AOO, DBA, and DEC)
    • rigour of validation and verification of safety analysis tools
    • rigour of uncertainty evaluation
    • extent of sensitivity studies
    • quantity and quality of supporting evidence for analysis

    For more information on the graded approach, see REGDOC‑3.5.3, Regulatory Fundamentals [2].