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Abstract

An essential item for the long-term safety of a high level waste underground repository is the effective backfilling and sealing of access shafts and connection galleries. Any opening created during the repository construction is a potential preferential pathway for water, gas and radionuclide migration and has to be sealed.

The Reseal project aims at demonstrating the sealing of a borehole and shaft with bentonite in plastic clay. This project includes the selection of the sealing material, the development of the seal installation technique, the monitoring of the borehole and the shaft sealing tests, and the modelling of the main processes and phenomena observed during the tests. These demonstration tests are performed in the HADES URL (Mol, Belgium).

The borehole sealing tests consists of the sealing of a 270mm diameter borehole with pre-compacted blocks of Serrata clay and FoCa clay. The excellent agreement between the experimental results and the calculations shows a good understanding of the bentonite host rock interaction and the quality of the independently measured model parameters giving confidence in the predictive capability of the model. In the shaft-sealing test, it is not technically and financially possible to test both materials; here, only FoCa clay is tested.

The material selected to seal the shaft is a mixture of FoCa clay powder and high-density FoCa clay pellets. This material can be applied easily to backfill irregularly shaped volumes and has a low production cost. The effectiveness of the seal should be demonstrated in the coming years. The properties of this material have been investigated through a laboratory characterisation programme. The result of this study shows that after saturation the original heterogeneous mixture has a homogenous density, and that the powder between the pellets does not result in preferential pathways. At saturation and for equal density, pre-compacted samples and pellets/powder have the same hydraulic a

Additional information

Authors: VOLCKAERT G ET AL, SCK-CEN (BE);GENS A ET AL, UPC (ES);VILLAR M.V ET AL, Ciemat (ES);IMBERT C ET AL, CEA (FR)
Bibliographic Reference: EUR: 19612 EN (2000), 273pp, Euro: 42.50
Availability: Available from the European Commission, DG XII Communication Unit, rue de la Loi/Wetstraat 200, B-1049 Bruxelles (BE) Tel: +32-2-2950001 Fax:+32-2-2958220 E-mail:rtd-info@ec.europa.eu
ISBN: ISBN 92-894-0095-1
Record Number: 200012987 / Last updated on: 2000-12-22
Category: PUBLICATION
Original language: en
Available languages: en
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