ABSTRACT
In the design of engineered barrier systems of a waste landfill or a deep geological repository, modelling of the integrated performance of all the involved components is required. Currently, a number of numerical codes and analytical methods are available. We have seen in previous chapters that the evolution of the microstructure of clay seals that function as buffer systems depends on a number of factors, such as access to water and temperature. Maturation processes involving microstructural reorganization and water saturation can be described by fairly accurate conceptual and simple theoretical models. The record shows that modelling of the evolution of liners of landfill wastes and water saturation of clay seals in underground repositories can be reasonably performed for isothermal and geometrically simple 1D conditions. However, for the most critical and real practical cases of clay isolation of heat-producing high level nuclear waste (HLW), the phenomena and issues of coupled processes have yet to be fully addressed. The physical models for these coupled processes have been described in the earlier portion of this book. The record shows that existing theoretical models that include coupled thermal-hydraulic-chemicalbiological (THMCB) processes have yet to meet the requirements and strict tests for verification and validation.
