Quantitative characterization of steel corrosion products and bentonite alteration in a 21-year experiment

Ishiwata, Tobimaru*; Kikuchi, Ryosuke*; Kawakita, Ryohei  ; Anraku, Sohtaro ; Mitsui, Seiichiro 

The engineered barrier system (EBS) in the geological disposal of high-level radioactive waste includes the iron- or steel-based overpack and a compacted bentonite buffer. Over long timescales, interactions between iron and bentonite may alter the barrier's performance. To ensure the long-term stability of the EBS, it is essential to quantitatively evaluate these interactions, providing fundamental data for predictive modelling. In this study, we performed a quantitative micro-scale analysis of mineralogical alterations and their spatial distributions across the steel-bentonite interface after 21 years of contact under controlled conditions, thereby providing a reliable basis for validating the observed alterations and supporting predictive modelling.