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Studies on radionuclide transport behaviour–The next generation of in-situ experiments at the Grimsel Test Site

Published online by Cambridge University Press:  15 February 2011

Andrew James Martin  and
Ingo Blechschmidt
Andrew James Martin
Affiliation:
Nagra (National Cooperative for the Disposal of Radioactive Waste) 5430 Wettingen, Switzerland
Ingo Blechschmidt
Affiliation:
Nagra (National Cooperative for the Disposal of Radioactive Waste) 5430 Wettingen, Switzerland
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Abstract

Two recent ongoing major projects at the Grimsel Test Site (GTS) (www.grimsel.com) that were initiated to simulate the long-term behaviour of radionuclides in the repository near-field and the surrounding host rock are presented: the Colloid Formation and Migration (CFM) project, which focuses on colloid generation and migration from a bentonite source doped with radionuclides and the Long-Term Diffusion (LTD) project, which aims at in-situ verification and understanding of the processes that control the long-term diffusion of repository-relevant radionuclides. So far, the CFM project has principally involved: development and implementation of a state-of-the-art sealing concept to control hydraulic gradients in a shear zone to imitate repository-relevant conditions; extensive laboratory studies to examine bentonite erosion and colloid formation in a shear zone; and, development of models to estimate colloid formation and migration. The next stage will be to assess the behavior of bentonite colloids generated from a radionuclide spiked bentonite source-term emplaced into the controlled flow field of the shear zone. This will be coupled with further extensive laboratory studies in order to refine and evaluate the colloid models currently used in performance assessments. The LTD project consists of: a monopole diffusion experiment where weakly sorbing and non-sorbing radionuclides (3H, 22Na, 131I, 134Cs) have been circulating and diffusing into undisturbed rock matrix since June 2007; experiments to characterise pore space geometry, including determination of in-situ porosity with 14C doped MMA resin for comparison with laboratory derived data; a study of natural tracers to elucidate evidence of long-term diffusion processes; and, an investigation of the in-situ matrix diffusion paths in core material from earlier GTS experiments. Future experiments will focus on diffusion processes starting from a water-conducting feature under realistic boundary conditions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1193: Scientific Basis for Nuclear Waste Management XXXIII , 2009 , 159
Copyright
Copyright © Materials Research Society 2009

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