Abstract:

Reinforced concrete containment structures are critical to nuclear safety and durability, and the long-term integrity of embedded steel reinforcement (rebar) is a major factor influencing service life. The ARC-100 sodium-cooled fast reactor is an emerging small modular reactor (SMR) concept proposed for deployment at the Point Lepreau site in New Brunswick, Canada, with a target operation date of the early to mid-2030s. However, because this Sodium-cooled SMR is still in the feasibility assessment phase, durability planning must rely on evidence-informed assessments and underpinned degradation mechanism of various intended materials under anticipated exposure conditions. This study provides a mechanism-based review of degradation pathways relevant to ARC-100 containment concrete, along with an evaluation of the implications for rebar corrosion, through a review of published data from operating nuclear facilities and from research studies. The review is organized by specific degradation mechanisms and follows a structured framework that includes: (i) ARC-100 design-relevant exposure conditions, (ii) concrete deterioration processes that modify transport properties and pore solution chemistry, and (iii) resulting effects on steel passivity, corrosion initiation, and localized corrosion susceptibility. Key mechanisms assessed include irradiation-related concrete aging, sulfate attack associated with below-grade soil environments, chloride ingress, carbonation, freeze–thaw damage under Canadian climatic conditions, and secondary processes such as leaching and thermal cycling. For each mechanism, available experimental findings, inspection observations, and monitoring approaches from existing nuclear reactor facilities are synthesized to understand plausible degradation pathways applicable to ARC-100-type structures. By combining mechanistic understanding with service-based evidence, this review provides a structured assessment of the fundamental durability challenges that may govern rebar corrosion in ARC-100 containment concrete. This study identifies key uncertainties associated with degradation mechanisms and proposes targeted research and monitoring priorities to support long-term durability management for ARC-100 and future SMR deployments in Canada.

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Mr. Joshua Atiba