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The Excavation Project in the Grimsel Test Site: In Situ High-Resolution Gamma and Alpha Spectrometry of 60Co, 75Se, 113Sn, 152Eu, 235U, and 237Np/233Pa

Published online by Cambridge University Press:  10 February 2011

J. Eikenberg ,
M. Ruethi ,
W.R. Alexander ,
B. Frieg  and
T. Fierz
J. Eikenberg
Affiliation:
PSI (Paul Scherrer Institute), 5232 Villigen-PSI, Switzerland. ([email protected])
M. Ruethi
Affiliation:
PSI (Paul Scherrer Institute), 5232 Villigen-PSI, Switzerland
W.R. Alexander
Affiliation:
GGWW (Rock-Water Interaction Group), Institutes of Geology and of Mineralogy and Petrology, University of Berne, 3012 Berne, Switzerland
B. Frieg
Affiliation:
Nagra (National Cooperative for the Disposal of Radioactive Waste), 5430 Wettingen, Switzerland
T. Fierz
Affiliation:
Solexperts AG, Ifangstrasse 12, 8603 Schwerzenbach, Switzerland
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Abstract

Full excavation of a water-conducting shear zone used for radionuclide migration experiments is part of a comprehensive study to physically determine the sites of in-situ radionuclide retardation. Prior to the excavation, multi-tracer solutions containing strongly sorbing y- and αemitting nuclides were injected into the shear zone and the water extracted was analyzed on-line using in situ, high-resolution y-spectrometry. In addition, water samples were collected to compare quantitatively the on-line data with subsequent laboratory measurements α- and γ- spectrometry) and also to analyze samples with activities below the detection limits of the in-situ analysis. The breakthrough curves indicate that Se had passed through the fracture with a velocity comparable to a conservatively behaving dye (uranine), but very strong retardation of Co. Eu and Sn was observed. The recoveries of these nuclides were found to be in the order of only a few percent when the dipole flow-field was interrupted about one month after radionuclide injection and the fracture was sealed off for excavation. Significant retardation was also obtained for the oxemitters U, Np and Pa. Almost identical breakthrough curves for these actinides were measured, suggesting a similar spatial distribution in the fracture at any given time.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 506: Symposium – Scientific Basis for Nuclear Waste Management XXI , 1997 , 655
Copyright
Copyright © Materials Research Society 1998

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References

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