The Canadian Nuclear Safety Commission (CNSC) has completed a preliminary regulatory design assessment of US-based Clean Core Thorium Energy’s (CCTE’s) novel thoria-urania fuel pellet design – also called Advanced Nuclear Energy for Enriched Life (ANEEL) – for intended use in Candu nuclear reactors.
The proposed intent of the new fuel design is to create an inherently safer and more efficient fuel pellet/bundle that produces a smaller waste footprint and provides enhanced fuel burn-up while maintaining current geometries and operating characteristics for ease of retrofit.
The fuel is made of thorium and high-assay low-enriched uranium (HALEU), developed for use in pressurised heavy water reactors (PHWRs) and Canada deuterium uranium (Candu) reactors. Clean Core says the fuel can offer significantly improved performance with existing proven heavy water reactor systems by leveraging thorium’s inherently superior nuclear, thermal and physical properties. It also retains the same external dimensions and configuration design as in currently used natural uranium (NU) fuel bundles. “Without any significant modifications to the reactor, the replacement of the currently used NU fuel bundles with Clean Core’s ANEEL fuel bundles can reduce life-cycle operating costs and waste volumes, increase safety and accident tolerance, and result in additional proliferation resistance,” the company notes. Clean Core completed initial design studies, and in April, announced the successful conclusion of the Phase 1 Pre-licensing Vendor Design Review (VDR) process with CNSC.
Under the authority of Canada’s Nuclear Safety & Control Act, CNSC, entered into a service agreement with CCTE in March 2023 to conduct a preliminary regulatory design assessment of the fuel design. CNSC staff performed this assessment by modifying the documented approach for a VDR and selecting an applicable subset of focus areas for the assessment.
A preliminary regulatory design assessment is an optional service that the CNSC provides at the request of a vendor. It is a high-level review of the vendor’s proposed technology and corporate structure against Canadian regulatory requirements and guidance. The intention is to provide early feedback to the vendor on matters relating to CNSC regulatory requirements and expectations, which can allow for early identification and resolution of potential regulatory or technical issues in the design and design process, particularly those that could result in significant changes to the design.
The assessment does not involve issuing a licence under the Nuclear Safety & Control Act and is not part of the licensing process. The conclusions of the assessment do not bind or otherwise influence decisions made by the Commission. CNSC says its licensing process for a proposed project would require a more detailed review of the design and safety case for a specific licence application at a specific site.
Through the preliminary regulatory design assessment, CNSC staff were to provide:
- a general assessment of the proposed fuel design and qualification programme to confirm that CCTE would be capable of demonstrating that its programmes pertaining to nuclear fuel design and qualification could meet CNSC expectations, applicable regulatory documents, and applicable Canadian codes and standards;
- regulatory information to CCTE relating to the regulatory process or the requirements associated with the licensing of novel fuel for use in a nuclear power plant facility.
The preliminary regulatory design assessment was conducted over an approximately six-month period. CCTE submitted documents relating to nine applicable focus areas. CCTE also organised familiarisation sessions, responded to requests for additional information, and provided technical clarifications through letters, emails and meetings.
CNSC staff concluded the following:
- CCTE generally understands and has correctly interpreted the high-level intent of the CNSC’s regulatory requirements as applicable to fuel design and qualification.
- Additional work will be required to address the technical clarifications and findings raised within this assessment should the use of this fuel design be pursued in a reactor in Canada.
- The issues documented within this report are foreseen to be resolvable and will need to be followed up on in any future licensee application or review.
- Any changes to the design would be expected to be documented and described in detail for any prospective future review and/or licensee application for use of the fuel design.
CNSC said some of its findings and technical clarifications will require additional follow-up in any future review. The management system is not yet well documented to meet the regulatory requirements, with specific emphasis on the establishment of vendor management. Given the novelty of some of the design and safety features, in future assessments or licensee applications, information will be required to confirm:
- the adequacy of the research and development activities to substantiate the fuel qualification programme;
- the validation and verification of the capability of the software tools to model the reactor and to analyse reactor behaviour under all operating modes.
In several instances, given the unique fuel design characteristics of the ANEEL fuel, CCTE is proposing alternative approaches and methodologies to address the underlying intent of CNSC regulatory requirements. CCTE has indicated that it intends to adequately justify the use of these alternative approaches, and it is expected that it will provide evidence that these alternative approaches will result in an equivalent or superior level of safety in future submissions.
