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Phase 1 Pre-Licensing Vendor Design Review Executive Summary: Ultra Safe Nuclear Corporation



The Canadian Nuclear Safety Commission (CNSC) is Canada’s nuclear regulator and operates under the authority of the Nuclear Safety and Control Act (NSCA). The CNSC regulates the use of nuclear energy and materials to protect health, safety, security and the environment; to implement Canada’s international commitments on the peaceful use of nuclear energy; and to disseminate scientific, technical, and regulatory information concerning its activities.

A pre-licensing review of a vendor’s reactor design, also referred to as a vendor design review (VDR), is a high-level assessment of a proposed reactor technology. It is an optional service provided by the CNSC when requested by a vendor. This service does not involve the issuance of a licence under the NSCA and is not part of the licensing process. The conclusions of such a review will not bind or otherwise influence decisions made by the Commission.

A VDR is intended to provide early feedback to the vendor as it addresses Canadian regulatory requirements and other expectations in its design. It can allow early identification and resolution of potential regulatory or technical issues in the design process, particularly those that could result in significant changes to the design or safety analysis. The CNSC will require a more detailed review of the design and safety case for a specific application for a licence to construct a nuclear reactor at a specific site. The VDR process enables CNSC staff to:

  • identify challenges associated with the interpretation of requirements
  • develop regulatory positions as needed
  • improve their understanding of implications, challenges, and readiness of new technological approaches

Ultra Safe Nuclear Corporation (USNC) is designing a 15-thermal-megawatt micro modular reactor (MMR), with a net electrical output of approximately 5 megawatts. The MMR concept draws on operational experience from the high-temperature gas-cooled reactors developed by the U.S., Germany, China and Japan.

In May 2016, the CNSC and USNC signed a service agreement for the conduct of a Phase 1 VDR of the MMR. This Phase 1 report outlines the review process followed, the assessment findings and conclusions of that review.

Application of REGDOC-2.5.2 and RD-367 to a high-temperature gas-cooled reactor technology

Regulatory documents REGDOC-2.5.2, Design of Reactor Facilities: Nuclear Power Plants, and RD-367, Design of Small Reactor Facilities, were written to be technology-neutral to the extent practicable. However, these documents contain requirements and guidance that incorporate extensive operating experience from the use of water-cooled reactors. It is recognized that vendors of specific technologies may present alternative approaches and that designs are subject to the safety objectives, high-level safety concepts and safety management principles associated with REGDOC-2.5.2 and/or RD-367. Technical expertise, professional judgement and adequately documented processes are used to ensure that the application of, or departure from, regulatory requirements is done objectively and consistently to achieve the required level of safety.

Phase 1 vendor design review results

Based on the documentation submitted, CNSC staff concluded that:

  • USNC understands and has correctly interpreted the high-level intent of CNSC regulatory requirements pertaining to 19 focus areas under consideration for the scope of Phase 1 VDR
  • USNC has demonstrated its intent to comply with CNSC regulatory requirements and expectations for new reactors, as specified in REGDOC-2.5.2 and/or RD-367. In some cases, due to the unique characteristics of their design, USNC is proposing alternative approaches to meeting CNSC regulatory requirements, in accordance with section 11 of REGDOC-2.5.2. USNC has demonstrated that it intends to adequately justify these approaches. The alternative approaches will be expected to result in an equivalent or superior level of safety.
  • additional work is required by USNC to address the findings raised as part of this review, including the need to establish robust quality-assured processes for design and safety analysis activities

CNSC staff has emphasized that research and development activities will play a significant role in justifying the use of alternative approaches in addition to any relevant operating experience.

Noteworthy clarifications or findings that will require additional follow-up with USNC in a future review are summarized as follows:

  1. Additional information is required to confirm that the management system processes to control design, safety analysis and research and development (R&D) meet the intent of requirements and expectations from applicable regulatory documents and standards. If a decision is made to proceed with a Phase 2 review, USNC is expected to demonstrate that it has established sufficient systematic processes in its management system to support its ongoing development activities.
  2. Contractor partners play a major role in the MMR design. USNC is expected to confirm that:
    1. the interfaces between the various participating organizations in the design, R&D, and safety analysis are adequate
    2. the transfer of design authority is effective, as USNC has indicated that it intends to transfer its design authority to complete the final design to a separate organization. This is to ensure that the overall responsibility for the design process and the requisite knowledge are maintained.
  3. Because of the novelty of some of the MMR design and safety features, additional information is required to confirm:
    • adequacy of the R&D activities to substantiate MMR safety claims and the fuel qualification program, including the role of a first-of-a-kind reactor
    • applicability of the operating experience data from previous high-temperature gas-cooled reactors to the MMR design and safety analyses
    • consistency between the safety functions and the safety classification for the structures, systems and components related to civil structures
    • adequacy of shutdown means, shutdown margins and the guaranteed shutdown state
    • adequacy of the probabilistic risk assessment methodology that USNC has proposed; this methodology uses technology-inclusive metrics, such as source term parameters and radiological doses, to demonstrate that safety goals are met

Notwithstanding the above, these issues are foreseen to be resolvable and will be followed up on in future VDRs.

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