O 2 Consumption in a Granitic Environment
- PDF / 1,582,226 Bytes
- 6 Pages / 414 x 635.4 pts Page_size
- 73 Downloads / 197 Views
2 CEA, Cadarache, France 3 Univ. of G6teborg, Dept. of Cell and Molecular Biology, Goteborg, Sweden 4 ANDRA, Chatenay-Malabry, France 5 CNRS, Aix-en-Provence, France 6 JNC, Tono Geoscience Center, Gifu, Japan 7 BGS, Fluid Processes Group, Keyworth, UK
8 University of Sheffield, Dept. of Civil & Structural Engineering, Sheffield, UK 9 University of Bradford, Dept. of Civil & Environmental Engineering, Bradford, UK 1oTerralogica AB, GrAbo, Sweden
ABSTRACT The fate of 02 in a granitic repository has been addressed by an international project: The redox experiment in detailedscale (REA9. The emphasis of the project was on a field experiment involving groundwater in contact with a fracture surface. To this aim a borehole, -20 cm in diameter, was drilled at 380 m depth in the tunnel of the Asp6 Hard Rock Laboratory, Sweden. Injection pulses of molecular oxygen were performed at in situ temperature and pressure. Several microbial and chemical parameters were studied as a function of time: microbial counts, pH, 0 2 -concentration, Eh (redox potential), etc. The field study has been supported by laboratory experiments to determine 02 reaction rates and mechanisms. These laboratory studies have been performed with Asp6 samples (both for inorganic and microbially mediated processes). A replica experiment has also been completed at CEA, France, with the other half of the fracture surface obtained in the drilling procedure of the field experiment. The aim of the replica experiment has been to duplicate as far as possible the conditions of the REX in situ experiment, for example by using groundwater sampled at the REX site in Sweden, shipped in special containers to France. The data that has been collected from the 02 injection pulses in the REX field and replica experiments have been compared with the rates of 02 uptake determined in the laboratory experiments. These data allow an estimate of the life-times for oxygen uptake in fractures in granitoids, which is of consequence for performance assessment calculations. INTRODUCTION Molecular oxygen entrapped in a crystalline rock repository after closure could affect the corrosion of metal canisters. Similarly, future intrusions of oxygen-rich melt waters during a glacial event may affect the integrity of the canisters, as well as the migration of radionuclides. This paper presents results from an international project (The redox experiment in detailed scale: REX) that aimed to study the fate of 02 in the granitic environment of the underground Asp6 Hard Rock Laboratory in South East Sweden. 179 Mat. Res. Soc. Symp. Proc. Vol. 608 © 2000 Materials Research Society
A block scale redox experiment was carried out previously in a fracture zone at 70 m depth in the entrance tunnel to Asp6l,2. In spite of massive surface water input, the fracture zone remained persistently anoxic. The main conclusion from that study was that the increased inflow of relatively organic-rich shallow groundwater instead of adding dissolved oxygen, it added organic compounds that acted as reductants in t
Data Loading...
