Abstract

Crystalline rocks are being considered as potential host rocks for the construction of deep geological repositories (DGR) for radioactive waste in a number of European countries including the Czech Republic. Advection is considered as a main process within such a type of test. Tracer tests, using various substances, are used for a number of different purposes; however, they are generally employed particularly for the characterisation of flow systems. A system consisting of a flow field intersecting a water bearing fracture was first identified at the Josef Underground Laboratory, whereupon two boreholes were drilled and fitted with instrumentation so as to determine and characterise an ideal location for the potential injection of a radioactive tracer into the fractured rock massif. A number of methods were employed in order to describe the rock system and the hydraulic flow field in detail prior to tracer injection. This was followed by the conducting of safety calculations aimed at providing a description of any potentially hazardous impacts on humans and the biosphere as required by the site licensing procedure.

1. Introduction

Crystalline rocks are being considered as potential host rocks for the construction of deep geological repositories (DGR) for radioactive waste in a number of European countries including the Czech Republic. The main transport mechanism in crystalline rocks consists of advection; however, migration processes from fractures through fracture coatings into unaltered rock will also have to be studied. The conceptual model is based on the presumption that non-advective migration is driven by diffusion into both altered mineral layers and the undisturbed rock matrix adjacent to water-bearing fissures. The diffusion process depends on a large number of factors: molecule size and charge, sorption, effective porosity, pore construction, tortuosity and groundwater composition.

It is intended that radionuclide migration in fractured crystalline rock environments will be studied using different scale rock samples and in-situ testing as part of the PAMIRE project (TA04020986).

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