Deep geological repositories - A review of design concepts, near-field evolution, and their implications for nuclear...

Effective nuclear waste disposal is crucial for strengthening public confidence in nuclear energy as a cornerstone of sustainable, large-scale, carbon-neutral energy generation. Deep geological repositories (DGRs) provide the most viable long-term solution, employing a multi-barrier isolation system that inhibits radionuclide release and migration through a combination of engineered and natural barriers. While extensive research has focused on radionuclide transport mechanisms and the influence of geochemical interactions within host rock formations, a comprehensive understanding of the near-field environment, its physicochemical evolution, and its implications for repository design and nuclear waste management decisions remains underexplored. This review critically examines DGR concepts, near-field components, and processes, with a particular focus on canister-bentonite interactions, corrosion evolution, bentonite self-sealing mechanisms, and hydrogen gas generation. A critical assessment of experimental, numerical, and full-scale studies, highlights the complexities of coupled thermal, hydraulic, mechanical, and chemical (THMC) processes that govern repository evolution. Key challenges include scaling laboratory findings to field-scale repository conditions, integrating microbial and radiation-driven interactions, and refining long-term predictive models for corrosion and radionuclide migration. Addressing these gaps is critical for advancing repository safety assessments, optimizing engineered barrier systems, and ensuring the long-term stability of nuclear waste disposal strategies. These insights are expected to contribute to the ongoing development of robust and globally implementable waste management solutions, reinforcing nuclear energy's role in climate change mitigation and the transition to a net-zero carbon economy.