Grimsel Test Site - The Next Decades
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Grimsel Test Site - The Next Decades Stratis Vomvoris, Wolfgang Kickmaier and Ian G. McKinley Nagra, Hardstrasse 73, CH-5430 Wettingen, Switzerland
ABSTRACT The Grimsel Test Site, which has been in operation since 1984, is known in the radioactive waste management community for the scope and quality of the experiments and projects performed over the last two decades. This paper will overview Nagra's commitments and the current plans for future activities in association with Grimsel, which are being developed considering time scales of the order of a decade or more. INTRODUCTION The Grimsel Test Site (GTS), was constructed in 1983 in the Swiss Alps, 450 m below the Juchlistock mountain. Operated by Nagra, Grimsel is not considered for waste disposal, rather it is dedicated to applied research related to waste disposal issues. The main tunnel system, is approximately 1 km long and was extended in 1995, with the construction of the full-scale Engineered Barrier Experiment tunnel, and in 1998, with the construction of the Gas Migration Test access drift, cavern and silo. An overview on the GTS facilities and the experimental programme is presented in the GTS homepage www.grimsel.com. Since the mid-1980s the experiments have focused both on the geosphere and rock characterisation aspects, as well as on the engineered barrier system (EBS). Large-scale, long term demonstrations of EBS are gaining an increasingly important share in the GTS activities. In addition, the controlled zone at GTS allows the unique ability to perform in-situ experiments with radionuclides, including isotopes of uranium, neptunium, americium and plutonium. OVERVIEW OF ACCOMPLISHMENTS TO DATE The ongoing Phase V-Program of Grimsel was initiated in 1997 in co-operation with 19 partners from 10 different countries and the European Community (Table I). An overview of the existing programme can be found in [1] and more details for the Gas Migration Test are described in a separate paper in this volume [2]. An experiment briefly described below is the Colloid and Radionuclide Retardation project (CRR) as an example which illustrates the possibilities of insitu radioisotope testing at GTS. The concept of the CRR experiment [3] focuses on the neartunnel geosphere; the colloid input side corresponds to the interface between the bentonite buffer and the granite. A first radionuclide cocktail containing 131I, 85 Sr, 243Am, 238/242Pu, 232Th, 237Np and 238U dissolved in Grimsel groundwater was injected into a dipole flow field of 2.2 m length which was established in a water conducting shear zone. It was subsequently followed by a second injection of the same radionuclide cocktail in the same flow field, but this time together with bentonite colloids. The breakthrough of radionuclides and bentonite colloids was monitored online at the site and was also confirmed by an extensive off-site laboratory analysis of samples. The findings of the CRR experiment can be summarised as follows:
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Table I: GTS Phase V experimental programs and partners GTS
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