Re-establishing pathways for HT9 fuel cladding production and examining fuel cycle options for sodium fast reactors
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Date
2025-08
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University of New Brunswick
Abstract
The ARC-100 sodium fast reactor (SFR) developed by ARC Clean Technology Canada is currently in the pre-licensing stage with the Canadian Nuclear Safety Commission (CNSC). The commercial demonstration unit (CDU) of the ARC reactor is expected to be deployed at NB Power’s Point Lepreau site in the early 2030s; availability of fuel supply and fuel qualification are major considerations for its economic and licensing basis. Recent sanctions imposed on the Russian state have constrained the global nuclear fuel supply chain, resulting in the only commercial supplier of High-Assay Low-Enriched Uranium (HALEU) fuel becoming unavailable. Furthermore, the fuel cladding material of choice, HT9, has not been produced in commercial quantities in several decades. Thus, re-establishing the production pathway for cladding tubes is a critical fuel qualification activity for the ARC project.
An experimental thermomechanical treatment (TMT) process for HT9 plate material has been developed. The microstructure and mechanical properties were optimized to provide a balance between void swelling resistance and fracture toughness, two attributes which dictate the service life of fuel cladding in sodium fast reactors. The microstructure and mechanical properties were confirmed to be consistent with the historical material, allowing the extensive experience of HT9’s performance as fuel cladding gained in previous test reactors to be leveraged.
A neutronics model was developed to evaluate the feasibility of transitioning the ARC reactor to a lower enrichment fuel, the supply of which is available in a timeline complementary to the deployment of the ARC commercial demonstration unit. The model demonstrated that there was sufficient excess reactivity to retain the desired 20-year fuel cycle, though the reactivity continued to increase throughout the cycle. To maintain adequate safety margins in transient events, a limit was imposed on the excess reactivity.
A fuel management scheme was devised, consisting of periodic shuffling and withdrawal of fuel assemblies during scheduled plant outages, which kept the excess reactivity below the imposed limit. As an added benefit, shuffling assemblies maintained the fast neutron irradiation damage in the fuel cladding within the operational experience envelope, which provides strong justification for the licensing readiness of the ARC fuel design.