Natural Analogue Studies on Bentonite Buffer for Deep Geological Disposal: A Review; [고준위방사성폐기물 심층처분 벤토나이트 완충재 자연유사 연구: 리뷰]

초록

In deep geological repository for high-level radioactive waste, bentonite buffer materials play a key role in protecting the disposal canister and regulating radionuclide transport. However, there are limitations in determining the alteration of bentonite that may occur over geological time scales based exclusively on short-term laboratory experiments. This study reviews major natural analogue cases and associated alteration mechanisms as important lines of evidence for evaluating the long-term stability of bentonite buffers. The analysis focuses on thermal alteration and interactions with alkaline fluids and saline groundwater conditions relevant to the long-term evolution of engineered barrier systems. The findings indicate that bentonite exposed to maximum temperatures of ~160 °C for approximately 2 million years shows minimal illitization, and, that the structural stability of smectite is largely controlled by potassium availability and diffusional constraints. Furthermore, both alkaline and saline groundwater conditions produce only localized mineralogical changes, whille the crystal structure and swelling capacity of smectite were preserved. Based on the geological and mineralogical characteristics of the Donghae mine in Pohang and the Naah mine in Gyeongju, both designated as domestic natural analogue study sites, this study proposes future research directions to support the safety case of the Korean disposal concept. These findings will provide fundamental information for enhancing the reliability of long-term performance assessment of bentonite buffers. © 2026 The KSEEG.

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