• Jacques, Diederik
• Perko, Janez
• Seetharam, Suresh

Abstract

This paper presents a novel approach for the development of a comprehensive data base of time-dependent hydraulic and transport parameters for concrete engineered barriers and the multi-layer cover of the future Dessel near surface repository for short-lived low-level waste. The parameter derivation is based on integration of selective data obtained through an extensive literature review, data from experimental studies on cementitious materials specific for the Dessel repository and numerical modelling using physically based models of water and mass transport. Best estimate parameter values for assessment calculations are derived, together with source and expert range and their probability density function. We further discuss a numerical method for upscaling laboratory derived parameter values to the repository scale; the resulting large-scale effective parameters are commensurate with numerical grids used in models for radionuclide migration. To accommodate different levels of conservatism in the various assessment calculations defined by ONDRAF/NIRAS, several sets of parameter values have been derived based on assumptions that introduce different degrees of conservatism. For pertinent parameters, the time evolution of such properties due to the long-term concrete degradation is also addressed. The implementation of the novel approach is demonstrated by considering the pore water diffusion coefficient as an example.

Topics

• density
• impedance spectroscopy
• pore
• surface