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

This regulatory document is part of the CNSC’s safety analysis series of regulatory documents, which also covers deterministic safety analysis, probabilistic safety assessment and nuclear criticality safety. The full list of regulatory document series is included at the end of this document and can also be found on the CNSC’s website at nuclearsafety.gc.ca/eng/acts-and-regulations/regulatory-documents

Regulatory document 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 longterm radioactive waste management facility, see REGDOC‑2.11.1, Waste Management, Volume III: Safety Case for Long-Term Radioactive Waste Management.

For information on the implementation of regulatory documents and on the graded approach, see REGDOC-3.5.3, Regulatory Fundamentals.

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The words “shall” and "must" are used to express requirements to be satisfied by the licensee or licence applicant. “Should” is used to express guidance or that which is advised. “May” is used to express an option or that which is advised or permissible within the limits of this regulatory document. “Can” is used to express possibility or capability.

Nothing contained in this document is to be construed as relieving any licensee from any other pertinent requirements. It is the licensee’s responsibility to identify and comply with all applicable regulations and licence conditions.

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Introduction

Purpose

This regulatory document 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 provides requirements and guidance for safety analysis of the following Class IB nuclear facilities:

• a plant for the processing, reprocessing or separation of an isotope of uranium, thorium or plutonium
• a plant for the manufacture of a product from uranium, thorium or plutonium
• a plant, other than a Class II nuclear facility as defined in section 1 of the Class II Nuclear Facilities and Prescribed Equipment Regulations, for the processing or use, in a quantity greater than 10¹⁵ Bq per calendar year, of nuclear substances other than uranium, thorium or plutonium
• a facility prescribed by paragraph 19(a) or (b) of the General Nuclear Safety and Control Regulations:
  • a facility for the management, storage or disposal of waste containing radioactive nuclear substances at which the resident inventory of radioactive nuclear substances contained in the waste is 10¹⁵ Bq or more
    note: for the scope of this regulatory document, some examples of these facilities include:
    • any facility for the storage of fissionable material before and after irradiation
    • any facility for associated waste conditioning, effluent treatment and facilities for storage of waste that allow for retrieval of the waste for later disposal
  • a plant for the production of deuterium or deuterium compounds using hydrogen sulphide

For a deep geological repository (DGR), this regulatory document applies for the operational phase, which includes the licensed activities conducted up to the closure of the repository. Some examples of licensed activities in the operational phase include:

• any facility for the handling and packaging of fuel associated with a DGR
• the operational activities at a DGR associated with the handling, packaging and placement of radioactive material in the DGR

• 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 [1].

Note: Given the wide range of Class IB nuclear facilities, a graded approach may be proposed by the applicant or licensee in accordance with REGDOC‑3.5.3, Regulatory Fundamentals [2].

The following provisions of the Nuclear Safety and Control Act (NSCA) and the regulations made under it are relevant to this document:

• NSCA, subsections 24(4) and 24(5) 
• General Nuclear Safety and Control Regulations, paragraph 3(1)(i) 
• Class I Nuclear Facilities Regulations, paragraphs 5(f) and (i); and paragraphs 6(c) and (h); and paragraph 7(f)

Within the CNSC’s safety and control area (SCA) framework, the safety analysis SCA covers maintenance of the safety analysis that supports the overall safety case for the facility.

Safety analysis is a systematic evaluation of the potential hazards associated with the conduct of a proposed activity or facility; it considers the effectiveness of preventive measures and strategies in reducing the effects of such hazards.

A safety analysis program is designed, developed and maintained by the applicant or licensee, and is reviewed by CNSC staff. It is documented in a safety analysis report (SAR). As stated in paragraphs 5(f) and 6(c) of the Class I Nuclear Facilities Regulations:

• “An application for a licence to construct a Class I nuclear facility shall contain the following information... (f) a preliminary safety analysis report demonstrating the adequacy of the design of the nuclear facility;"
• “An application for a licence to operate a Class I nuclear facility shall contain the following information... (c) a final safety analysis report demonstrating the adequacy of the design of the nuclear facility;”

The SAR may reference other safety analysis documentation.

A facility’s SAR forms an important part of the licensing basis for the facility. It is used to:

• establish limits for the safe operation of the facility
• assess proposed changes to the facility

develop and maintain the applicant or licensee’s policies, processes and procedures for the safe conduct of the licensed activities

Guidance

The applicant or licensee should address the concept of defence in depth when developing a safety analysis for a nuclear facility.

Five levels of defence in depth are normally defined for nuclear facilities. Safety analysis plays a major role in demonstrating that levels 1 to 4 have been achieved. The applicability of safety analysis to these levels is as follows:

Level 1      The aim of the first level of defence is to prevent deviations from normal operation, and to prevent failures of structures, systems and components (SSCs) relied upon for safety.

Level 2      The aim of the second level of defence is to detect, intercept and control deviations from normal operation in order to prevent abnormal operational occurrences (AOOs) from escalating to accident conditions, and to return the facility to a state of normal operation.

Level 3      The aim of the third level of defence is to minimize the onsite consequences of accidents by providing inherent safety features, fail‑safe design, additional equipment and mitigating procedures. The most important objective for this level is to prevent releases of radioactive material and associated hazardous material or radiation levels that require offsite protective actions.

Level 4      The aim of the fourth level of defence is to mitigate the consequences of accidents that result from failure of the third level of defence in depth. The most important objective for this level is to ensure that the confinement function is maintained, thus ensuring that radioactive releases are kept as low as reasonably achievable.

Level 5      The aim of the fifth level of defence is to mitigate the radiological consequences and associated chemical consequences of releases or radiation levels that may result from accidents by means of adequately equipped emergency response facilities, emergency plans, and emergency procedures for onsite and offsite emergency response.

For more information on defence in depth, see:

• REGDOC‑3.5.3, Regulatory Fundamentals [2]
• IAEA SSR‑4, Safety of Nuclear Fuel Cycle Facilities [3]

The objectives of a safety analysis are to:

• state the safety goals, objectives and acceptance criteria (the safety requirements) that the facility is designed to meet
• demonstrate that the safety goals, objectives and acceptance criteria are met
• derive or confirm operational limits and conditions (OLCs) that are consistent with the design and safety requirements of the facility
• identify the systems important to safety [4] (that is, the SSCs that are relied upon for the safety of the facility)
• provide data for use in establishing and validating operating and emergency procedures and guidelines

Requirements

The applicant or licensee shall maintain adequate capability to perform or procure safety analysis to:

• resolve technical issues that arise over the life of the nuclear facility
• ensure the safety analysis requirements are met (whether the safety analysis has been developed by the applicant or licensee or procured from a third party)

The applicant or licensee shall establish a process to assess and update the safety analysis to ensure that the safety analysis reflects:

• current configuration (for existing facilities)
• current operating limits and conditions (for existing facilities)
• operating experience, including experience from similar facilities
• results from experimental research, improved theoretical understanding or new modelling capabilities to assess potential effects on the conclusions of safety analyses
• human factors considerations to ensure that credible estimates of human performance are used in the analysis

The applicant or licensee shall systematically review the safety analysis results to ensure they remain valid and continue to meet the safety goals, objectives and acceptance criteria.

The applicant or licensee shall develop, implement, conduct and maintain a safety analysis program for the nuclear facility.

In support of the program, the applicant or licensee shall establish one or more internal safety committees to advise management of the organization on safety issues related to the commissioning, operation and modification of the facility. The applicant or licensee shall ensure that the members of the committees include the necessary breadth of knowledge and experience to provide appropriate advice. The members shall, to the extent necessary, be independent of the operations management raising the safety matter. For more information, see IAEA SSR‑4, Safety of Nuclear Fuel Cycle Facilities [3].

A safety analysis program should include the following elements:

• activities to plan, execute, verify and document safety analyses
• activities to identify and act upon relevant research and experience
• activities to train analysts and preserve knowledge
• interfaces with other programs as necessary to ensure that:
• safety analysis is initiated when needed
• the results of the safety analysis are used appropriately
• descriptions of the applicant or licensee’s safety, health and environmental policies (for more information, refer to IAEA SSR‑4, Safety of Nuclear Fuel Cycle Facilities [3])

Requirements

Essential elements of a safety analysis program are the statements made by the applicant or licensee about the applicant or licensee’s safety, health and environmental policies [3]. The applicant or licensee shall provide these statements in the licence application as a declaration of the organization’s objectives and the public commitment of corporate management. To put these statements into effect, the applicant or licensee shall also specify and put in place organizational structures, standards and management arrangements capable of meeting the organization’s objectives and public commitments.

The applicant or licensee shall demonstrate that the safety analysis program is governed by the applicant or licensee’s management system and is consistent with the applicable requirements of CSA N286‑12, Management System Requirements for Nuclear Facilities [5].

Guidance

The CNSC accepts that the applicant or licensee’s safety analysis program may not map exactly onto the CNSC’s requirements and expectations for this area. However, the applicant or licensee should be able to demonstrate how all the requirements and expectations are addressed by various programs under the overall management system.

Requirements

The applicant or licensee shall perform a safety analysis for normal operation, and for internal and external events that deviate from normal operation and belong to a category of credible abnormal events [6].