The objectives of this work package are to
- derive the degree of disorder (homogeneity or heterogeneity) that results from specific bentonite applications such as the ANDRA tunnel plug, the Nagra disposal cell and the KBS-3 deposition tunnel backfill based on experimental evidence and numerical simulations
- integrate a term of property variability in the safety assessment of the nearfield and
- formulate requirements in respect to the emplacement density of bentonite that includes property variability and that allows to fulfil specific safety functions.
Description of work
Since the safety relevant performance of the bentonite is mainly defined by its chemical, mineralogical, and physical properties comprehensive sets of requirements regarding the chemical, mineralogical and physical, characteristics of bentonite have been developed by the different waste management organizations for their concepts. In most cases these requirements assume a bentonite density as boundary conditions for the requirement to be fulfilled.
In the frame of WP1 the needs of safety assessment regarding the evaluation of non-homogeneous backfill properties are addressed. In particular, in how far non-homogeneous material property distributions comply with safety requirements. The outcome of the this work package is planned to be a (hydro)-mechanical assessment of the case studies, given a range of uncertainties in the boundary conditions based on empirical and numerical evidence that, based on a probabilistic approach, would ultimately result in a set of requirements under consideration of the host rock and the repository design. For this work package three case studies were defined: the ANDRA tunnel plug, the Nagra disposal cell and the KBS-3 deposition tunnel backfill.
Based on the outcome of the assessment cases and the evaluation method and uncertainties, the end user will formulate design specific requirements that can be used for the safety case in a final workshop.