Selection of near field parameters for the Dessel near surface repository: Project near surface disposal of category A waste at Dessel

This report is a part of the documentation to support the safety assessment (SA) of the near surface disposal of category A waste at Dessel, Belgium. The aim of the report is to provide traceable scientific justification for all material parameters of the near field model (installation model) used in the safety assessment. The parameter values are established for the cementitious near field and earth cover through literature review, experiments from studies on cementitious materials specific for the Dessel repository and supplementary numerical modelling studies. The parameters specific to cementitious barriers include degree of saturation, hydraulic conductivity, diffusion coefficient, dispersivity, porosity, bulk density, distribution coefficient and effective solubility. Also included in this report are the infiltration rate for the earth cover, which is a hydraulic boundary condition required in the installation model and supplementary information on unsaturated hydraulic properties of the earth cover (Annex 1). Chapter 2 sets out a general strategy for the data selection and processing of the material parameters applicable to cementitious Systems, Structures and Components (SSCs) (concrete, mortar and embankment) and the earth cover. For all the parameters, salient conceptual and theoretical aspects are briefly discussed. Careful attention has been paid to the selection criteria for the cementitious SSCs based on knowledge of composition, water to cement ratio (W/C) and measurement techniques. Where possible, distinction has been made between cement paste, mortar and concrete. Where appropriate, methodology for upscaling from laboratory to repository scale of some of the parameters has been discussed and values presented, including extrapolation in time.