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Proceedings Paper

Instrumentation of borehole with fiber Bragg grating thermal probes: study of the geothermic behaviour of rocks
Author(s): Veronique Dewynter; S. Rougeault; J. Boussoir; N. Roussel; Pierre Ferdinand; Y. Wileveau
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Paper Abstract

In-situ thermal measurements of argillaceous rocks is required by the ANDRA to evaluate the feasibility and dimensioning of a long-life radioactive waste storage in deep geological underground repository sites. The last large scale experiment called HE-D has started in the middle of 2004 in the Mont Terri Underground Rock Laboratory based in Switzerland to evaluate new kinds of thermal instrumentations and improve the understanding of the thermal conductivity coefficient of the Opalinus clay. A thermal cane equipped with 6 optical Fiber Bragg Grating sensors (FBGs) has been developed by the CEA-List and installed in a 15 m-long borehole surrounding a central heating borehole. The sensitivity and thermal transduction of FBG sensor packaging have been characterized in laboratory before installation. Mechanically, the robustness of FBG packaging has been validated during the introduction in the borehole and the two measurement campaigns respectively four and nine months thereafter. In this paper, we report the results of the FBG temperature measurements in comparison with traditional resistive probes (Pt100) at different stages of the experiment. The temperature accuracy and resolution obtained in the laboratory are better than 0.2°C and 0.1°C respectively. In the borehole, the differences between both kinds of sensors were no more than 0.2°C.

Paper Details

Date Published: 23 May 2005
PDF: 4 pages
Proc. SPIE 5855, 17th International Conference on Optical Fibre Sensors, (23 May 2005); doi: 10.1117/12.623588
Show Author Affiliations
Veronique Dewynter, CEA Saclay (France)
S. Rougeault, CEA Saclay (France)
J. Boussoir, CEA Saclay (France)
N. Roussel, CEA Saclay (France)
Pierre Ferdinand, CEA Saclay (France)
Y. Wileveau, ANDRA (France)

Published in SPIE Proceedings Vol. 5855:
17th International Conference on Optical Fibre Sensors
Marc Voet; Reinhardt Willsch; Wolfgang Ecke; Julian Jones; Brian Culshaw, Editor(s)

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