Investigating the pore-water chemistry effects on the volume change behaviour of Boom clay

International audienceThe Essen site has been chosen as an alternative site for nuclear waste disposal in Belgium. The soil formation involved at this site is the same as at Mol site: Boom clay. However, owing to its geographical situation closer to the sea, Boom clay at Essen presents a pore water salinity 4-5 times higher than Boom clay at Mol. This study aims at studying the effects of pore water salinity on the hydro-mechanical behaviour of Boom clay. Specific oedometer cells were used allowing "flushing" the pore water in soil specimen by synthetic pore water or distilled water. The synthetic pore water used was prepared with the chemistry as that for the site water: 5.037 g/L for core Ess83 and 5.578 g/L for core Ess96. Mechanical loading was then carried out on the soil specimen after flushing. The results show that water salinity effect on the liquid limit is negligible. The saturation or pore water replacement under the in situ stress of 2.4 MPa does not induce significant volume change. For Ess83, hydro-mechanical behaviour was found to be slightly influenced by the water salinity; on the contrary, no obvious effect was identified on the hydro-mechanical behaviour of Ess96. This can be attributed to the higher smectite content in Ess83 than in Ess96

RESEAL II: a large-scale in situ demonstration for repository sealing in an argillaceous host rock: phase II

Final ReportPreprin

Towards 3-D petrography: application of microfocus computer tomography in geological science

Microfocus computer tomography (mu CT) is a non-destructive technique for imaging internal features within an opaque object. Among the most important recent improvements of mu CT is its resolution of about 10 mum in three dimensions, which is much better than that obtainable with medical CT. The advantage of mu CT versus classical light microscopy is that three-dimensional petrographical information becomes available. The results from two complementary microfocus instruments are presented. The two instruments can accept different object sizes, ranging from a few millimetres to several centimetres in diameter. As a consequence, downscaling of petrographical features is possible both from medical CT to mu CT and within mu CT research. Apart from the possibilities of visualisation. attention is paid to the quantitative measurements that can be obtained from mu CT research which enables petrographical data to be linked to petrophysical data. (C) 2001 Elsevier Science Ltd. All rights reserved.status: publishe

Low-grade metamorphic slates, a potential host-rock for high-level and/or long-lived radioactive waste disposal

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The use of µCT and ESEM in the study of the osmosis-induced water uptake by eurobitum bituminized radioactive waste

Laboratory water uptake tests are performed at the Belgian Nuclear Research Centre SCKCEN to obtain insight into the hydromechanical behavior of Eurobitum bituminized radioactive waste under geological disposal conditions. Small nonradioactive and radioactive Eurobitum samples are hydrated in restricted swelling conditions (i.e., nearly constant volume conditions and constant stress conditions). Microfocus X-ray computer tomography (µCT) proves to be a very suitable technique to follow up the ingress of water in the samples. µCT analyses demonstrate that, under the studied hydration conditions, the water uptake by Eurobitum samples is a diffusion controlled process. A characterization of the partially leached samples with environmental scanning electron microscopy (ESEM) shows that the hydration of salt crystals and the subsequent dilution of the salt solution result in an increase in pore size that is limited to a few tens of µm in restricted swelling conditions. The µCT and ESEM analyses allow improvement in the understanding of water uptake by Eurobitum in restricted swelling conditions. In this article we discuss the µCT and ESEM analyses of nonradioactive Eurobitum samples that were hydrated for 2 to 4 years at a constant stress of 1, 22, 33, and 44 bar or in nearly constant volume conditions.status: publishe

Clay in natural and engineered barriers for radioactive waste confinement

International audienc

RESEAL II: a large-scale in situ demonstration for repository sealing in an argillaceous host rock: phase II

Final Repor