2013 Volume 20 Issue 2 Pages 39-52
Performance assessment of geological disposal systems for high-level radioactive waste requires a consideration of long-term systems behaviour. It is possible that the alteration of swelling clay present in bentonite buffers might have an impact on buffer functions. In the present study, iron (as a candidate overpack material)-bentonite (I-B) interactions were evaluated as the main buffer alteration scenario. Existing knowledge on alteration of bentonite during I-B interactions was first reviewed, then the evaluation methodology was developed considering modeling techniques previously used overseas.
A conceptual model for smectite alteration during I-B interactions was produced. The following reactions and processes were selected: 1) release of Fe2+ due to overpack corrosion; 2) diffusion of Fe2+ in compacted bentonite; 3) sorption of Fe2+ on smectite edge and ion exchange in interlayers; 4) dissolution of primary phases and formation of alteration products. Sensitivity analyses were performed to identify the most important factors for the alteration of bentonite by I-B interactions.
