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Contenu archivé le 2022-12-05

A large scale in situ demonstration test for repository sealing in an argillaceous host rock

Objectif



For the long term performance of an HLW repository, lt lS essential to backflll and/or seal the shafts and galleries so that they cannot act as preferential pathways for the m1gratlon of water, gas or radionuclides. Therefore, we will demonstrate the feasibility of an in situ seallng on a representative scale. Since about 10 years the use of highly compacted bentonite and hydraulic cements for sealing and backfill has been studled on laboratory and ln sltu scale. In granite (STRIPA project), large scale sealing tests have been performed successfully. In clay, only relatlvely small scale experiments have been performed (BACCHUS experlments) in the framework of the development of thermo-hydro-mechanical models. They were essentially related to the study of the near field and its associated temperature effects.
The objectlves of the proposed project are:
- to demonstrate the feasibility of the backfilling and sealing of a shaft on a large scale (1.4 m diameter shaft) in the HADES underground research facility - to demonstrate the effectiveness of the sealing of a borehole - to demonstrate the resistance of the seal against gas and water pressure - to demonstrate that a low permeability shaft seal can avoid preferential migration of water and gas even through the excavation damaged zone of the host clay formation
- to validate models for the calculation of gas and water transfer through the sealing system, takink into account geomechanical effects.
The project simulates the sealing of a shaft that will be situated outside the radiatlon and heat field of an HLW or spent fuel repository. The functioning of a sealing material will be demonstrated. The main sealing material option is a mixture of high density bentonite pellets with bentonite powder. This sealing material will be optimized to obtain the best balance between saturation time, swelling pressure and hydraulic conductivity. The possibility of the use of precompacted clay blocks is also considered as a reserve option.
The transfer of water and gas will be studied. Geomechanical effects will be included for the understanding of the fluid transfer and the design of the experiment. To study the influence of the in situ stress conditions around a gallery on the transfer of water and gas, a preliminary small scale in situ test will be done.
In this project a procedure for the production and installation of a shaft seal will be developed. The transport and geomechanical parameters of the candidate sealing materials in saturated and unsaturated conditions will be measured. These parameters with the results of the small scale borehole sealing experiment, will allow for the calibration and further development of hydro-mechanical codes.
The sealing system for the 1.4 m diameter shaft ln the HADES underground research facility will be designed to allow the validation of the hydro-mechanical codes. Water and gas injection experiments will be done on this sealing system to prove its performance.

Appel à propositions

Data not available

Régime de financement

CSC - Cost-sharing contracts

Coordinateur

BELGIAN NUCLEAR RESEARCH CENTRE
Contribution de l’UE
Aucune donnée
Adresse
200,Boeretang 200
2400 MOL
Belgique

Voir sur la carte

Coût total
Aucune donnée

Participants (5)