LEU Fuel Fabrication and Liability Disposition at Chalk River Laboratories and the Nuclear Criticality Safety Regulatory Framework in Canada

Technical paper presented at:
IAEA Workshop on Operational Aspects of Manufacturing High Assay Low Enriched Uranium Advanced Fuels
August 17-21, 2026

Prepared by:
Shawna Miller and Richard McNamara
Canadian Nuclear Laboratories
Ruxandra Dranga and Vladimir Khotylev
Canadian Nuclear Safety Commission

History of Fuel Fabrication

Fuel fabrication has been part of the work at Chalk River Laboratories since the early days of the site. This began in an active machine shop that evolved into an HEU production facility to support operations of the NRU reactor. Over the years, several international non-proliferation initiatives came into effect, ultimately necessitating an alternative to HEU-based fuel. These initiatives required the development of a production process at CRL that would allow the manufacture of fuel and targets from the next lowest grade of commercially available enriched uranium: LEU.

Manufacturing of HALEU Fuel

With this shift, new facilities were temporary established to demonstrate the use of production equipment to fabricate LEU, and eventually a permanent facility was established, known as the Nuclear Fuel Fabrication Facility (NFFF). Commissioning of this facility was completed in 1993.

This facility produced LEU Uranium Silicide fuel (19.75% enrichment) dispersed in Aluminum (U₃Si-Al) primarily for the NRU reactor from 1993 to 2018.

The fabrication process for this fuel was comprised of the following steps:

• Receiving LEU metal into the facility, casting with silicide, and heat treating,
• LEU chipping and crushing,
• Washing and drying of LEU chips,
• Pulverizing, weighing, blending with aluminum, and compacting,
• LEU core extrusion, drawing, straightening, gamma scanning, washing and vacuum drying,
• LEU core cladding (in aluminum), eddy current scanning, welding and x-ray,
• Final assembly into LEU fuel rods.

In addition, experimental LEU plates were produced in this facility but were never moved into production.

These processes generated scrap comprised of excess material generated during processing activities. This included: flashing and slag, powders, material adhered to machine parts that was later chipped away, cuttings and core pieces, finished and unfinished items that did not meet quality assurance (QA) requirements and could not be re-introduced into fabrication activities, and samples in plastic.

Fresh Fuel Scrap Disposition Project

Because of the nature of the excess material, it requires a high security storage location. This type of storage is more costly to maintain and is limited at CRL. Additionally, this material was not all efficiently packaged when first sent to storage.

In 2019 an opportunity was recognized to repatriate this material for the purpose of recovery into an oxide. A comparison was made between the cost of physically processing, repackaging, and shipping this material, to treating this material as waste within Canada, and repatriation was a more viable and permanent solution. Additionally, establishing a facility at CRL to perform recovery operations was not feasible due to the relatively small amount of material in storage.

CNL embarked on a partnership to physically process the material to a form acceptable to the recovery facility. The NFFF was available for use at the time, and operations staff who previously performed the fabrication activities were still available to work. This opportunity was very valuable to the project as the operations staff had a deep knowledge of the material and the required handling of it.

The fabrication facility had ceased production in 2018 but remained a licensed facility while clean out activities ensued. There were challenges in bringing the facility back online to perform the work for the repatriation project. Setting up operations included reviewing and updating existing facility documentation including the criticality safety document for the facility, acquiring new equipment, writing new procedures and work control documents, and testing new processes. Locating detailed records for the material proved challenging as it consisted of many years of scrap which had been moved in and out of the facility.

Material was brought into the facility in batches, removed from old containers and/or cladding, documented (through tracking and photographs), broken apart (if required), and consolidated and repackaged. During these activities there were often items whose physical description didn’t match what was in the cans when opened and the project had to develop new procedures and processes throughout the operational period.

Transportation Package

The final step for the project will be to transfer the liability to the country of origin, and to do this a new transportation package is being certified in Canada. When determining an appropriate package for transport of this material CNL assessed previously used packages that could hold this material type. The ES3100 was commonly used at the site but has a small primary containment vessel which would require the project to use many packages and complete many shipments. It was recognized that the 9979 Type AF package, designed by Savannah River National Laboratory, would be suitable, and the team began working with SRNL to amend the content envelope to accommodate larger quantities of HALEU. In tandem, CNL sought out certification of this package in Canada on the current content envelope and will resubmit for an updated certificate once the amendment is completed.

Regulatory Framework for Nuclear Criticality Safety in Canada

Canada’s REGDOC-2.4.3, Nuclear Criticality Safety provides a risk-informed and graded approach to nuclear criticality safety, ensuring that Canada is ready to support advanced fuel manufacturing, including HALEU operations. The framework is built on proven criticality safety principles such as application of the double contingency principle, rigorous validation and verification of the nuclear criticality safety analysis, and demonstration that subcriticality is maintained under all normal and credible abnormal conditions. These principles are similar or comparable with international requirements and provisions for nuclear criticality safety.

Regulatory requirements are graded according to the quantity and risk significance of fissionable materials, ensuring safety while providing flexibility to accommodate evolving advanced fuel technologies and manufacturing processes.

The regulatory requirements from REGDOC-2.4.3 have been and continue to be implemented at Canadian Nuclear Laboratories to ensure the criticality safety of all activities involving fissionable materials, including fuel fabrication and handling, disposition of fresh fuel scrap material, and transportation of HALEU material. Implementation of the nuclear criticality safety requirements highlights the importance of a robust process to systematically look at the proposed operations to define normal conditions and determine event and event sequences that fall within the credible abnormal conditions range.