Modelling localized water inflow into a region filled with bentonite pellets

Abstract

There is significant international consensus that the appropriate approach for long-term management of radioactive waste is disposal in an underground geological disposal facility. The gaps between waste containers and the host rock may be filled with bentonite, which swells to fill the gaps as it absorbs groundwater. Bentonite is soft, absorbing shear displacements in the host rock, and has low permeability, which restricts groundwater flow and hence corrosion of the waste containers. Many experiments have studied localized inflows of water into a region of bentonite pellets. Upward flow against gravity has often been observed. This study attempted to build understanding of this by modelling one experiment. A systematic approach was adopted in which models of increasing complexity were used, with the parameters at earlier stages used as a guide for later stages. Initially, only water flow was considered. Then water absorption and swelling, which lead to stresses and strains, were addressed. On the basis of the understanding developed, a conceptual model that represents the observed behaviour is proposed. Thematic collection: This article is part of the Sustainable geological disposal and containment of radioactive waste collection available at: https://www.lyellcollection.org/topic/collections/radioactive