The Grimsel Test Site – more than 35 years of underground research

Abstract. Nagra and its international partners have been conducting underground research projects at the Grimsel Test Site (GTS, https://www.grimsel.com, last access: 8 November 2021) for more than 35 years. The results have been incorporated directly into modelling, safety and engineering feasibility studies necessary for the siting and construction of deep geological repositories. Various types of experiments are carried out at the GTS, each involving field testing, laboratory studies, design and modelling tasks, thus integrating all scientific aspects. Projects are typically planned over a 5 year period with the option to extend depending on the latest findings from the experiment. In the current 5 year programme (2019–2023) new phases of running in situ experiments using radionuclides were started and include the Long-Term Diffusion experiment (LTD) and the Colloid Formation and Migration project (CFM). A completely new experiment studying the migration of C-14 and I-129 in aged cement (CIM) was also initiated. Other experiments focusing mostly on engineered barrier materials were continued such as the Material Corrosion Test (MaCoTe), which is studying anaerobic corrosion of candidate canister materials in bentonite (Fig. 1). Also, a 1:1 scale experiment studying the high-temperature (>175∘C) effects on bentonite materials (HotBENT project) was started last year. In this paper we provide an overview of the CIM, LTD and MaCoTe projects, including key findings so far. In addition to research, the GTS, as part of the Grimsel Training Centre (GTC), is also used as an education platform for knowledge transfer to the next generation of scientists and engineers in the area of radioactive waste disposal and geosciences.

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Grimsel Test Site - Phase VI: Review of Accomplishments and Next Generation of In-Situ Experiments Under Repository Relevant Boundary Conditions

MRS Proceedings ◽

10.1557/proc-1107-547 ◽

2008 ◽

Vol 1107 ◽

Author(s):

Ingo Blechschmidt ◽

Stratis Vomvoris ◽

Joerg Rueedi ◽

Andrew James Martin

Keyword(s):

Near Field ◽

Planning Horizon ◽

Test Site ◽

Low Ph ◽

Swiss Alps ◽

In Situ Experiments ◽

Grimsel Test Site ◽

And Migration

AbstractThe Grimsel Test Site owned and operated by Nagra is located in the Swiss Alps (www.grimsel.com). The Sixth Phase of investigations was started in 2003 with a ten-year planning horizon. With the investigations and projects of Phase VI the focus has shifted more towards projects assessing perturbation effects of repository implementation and projects evaluating and demonstrating engineering and operational aspects of the repository system. More than 17 international partners participate in the various projects, which form the basic organisational “elements” of Phase VI. Scientific and engineering interaction among the different projects is ensured via an annual meeting and several experimental team meetings throughout the year. On-going projects include: evaluation of full-scale engineered systems under simulated heat production and long-term natural saturation (NF-Pro/FEBEX), gas migration through engineered barrier systems (GMT, finished this year), emplacement of a shotcrete low-pH plug (ESDRED/Module IV), testing and evaluation of standard monitoring techniques (TEM).Numerous in-situ experiments with inactive tracers and radionuclides were successfully carried out over the past few years at the Grimsel Test Site (GTS). For the GTS Phase VI, three major projects have been initiated to simulate the long-term behaviour of contamination plumes in the repository near-field and the surrounding host rock:•The CFM (Colloid Formation and Migration) project, which focuses on colloid generation and migration from a bentonite source doped with radionuclides•The LCS (Long-Term Cement Studies) project, which aims at improving the understanding of low-pH cement interaction effects in water conducting features•The LTD (Long-Term Diffusion) project, which aims at in-situ verification of long-term diffusion concepts for radionuclidesAs Phase VI approaches its mid-term point, what are the next steps planned? The accomplishments assessed to date and the opportunities with the on-going projects as well as new projects – currently under discussion – are presented herein

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Modeling of an in-situ diffusion experiment in granite at the Grimsel Test Site

MRS Proceedings ◽

10.1557/opl.2014.632 ◽

2014 ◽

Vol 1665 ◽

pp. 85-91 ◽

Cited By ~ 2

Author(s):

Josep M. Soler ◽

Jiri Landa ◽

Vaclava Havlova ◽

Yukio Tachi ◽

Takanori Ebina ◽

...

Keyword(s):

Effective Diffusion ◽

Test Site ◽

Diffusion Experiment ◽

Bulk Rock ◽

Disturbed Zone ◽

Mean Grain Size ◽

Grimsel Test Site ◽

In Situ Diffusion

ABSTRACTMatrix diffusion is a key process for radionuclide retention in crystalline rocks. Within the LTD project (Long-Term Diffusion), an in-situ diffusion experiment in unaltered non-fractured granite was performed at the Grimsel Test Site (www.grimsel.com, Switzerland). The tracers included 3H as HTO, 22Na+, 134Cs+ and 131I- with stable I- as carrier.The dataset (except for 131I- because of complete decay) was analyzed with different diffusion-sorption models by different teams (NAGRA / IDAEA-CSIC, UJV-Rez, JAEA, Univ. Poitiers) using different codes, with the goal of obtaining effective diffusion coefficients (De) and porosity (ϕ) or rock capacity (α) values. A Borehole Disturbed Zone (BDZ), which was observed in the rock profile data for 22Na+ and 134Cs+, had to be taken into account to fit the experimental observations. The extension of the BDZ (1-2 mm) was about the same magnitude as the mean grain size of the quartz and feldspar grains.De and α values for the different tracers in the BDZ are larger than the respective values in the bulk rock. Capacity factors in the bulk rock are largest for Cs+ (strong sorption) and smallest for 3H (no sorption). However, 3H seems to display large α values in the BDZ. This phenomenon will be investigated in more detail in a second test starting in 2013.

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

MRS Proceedings ◽

10.1557/proc-1193-159 ◽

2009 ◽

Vol 1193 ◽

Author(s):

Andrew James Martin ◽

Ingo Blechschmidt

Keyword(s):

Shear Zone ◽

Diffusion Processes ◽

Test Site ◽

Core Material ◽

Laboratory Studies ◽

Grimsel Test Site ◽

And Migration ◽

Colloid Formation

AbstractTwo 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.

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Comparative modeling of an in situ diffusion experiment in granite at the Grimsel Test Site

Journal of Contaminant Hydrology ◽

10.1016/j.jconhyd.2015.06.002 ◽

2015 ◽

Vol 179 ◽

pp. 89-101 ◽

Cited By ~ 29

Author(s):

Josep M. Soler ◽

Jiri Landa ◽

Vaclava Havlova ◽

Yukio Tachi ◽

Takanori Ebina ◽

...

Keyword(s):

Comparative Modeling ◽

Test Site ◽

Diffusion Experiment ◽

Grimsel Test Site ◽

In Situ Diffusion

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Comparison of high‐frequency seismic sources at the Grimsel test site, central Alps, Switzerland

Geophysics ◽

10.1190/1.1444438 ◽

1998 ◽

Vol 63 (4) ◽

pp. 1363-1370 ◽

Cited By ~ 15

Author(s):

Jan Bühnemann ◽

Klaus Holliger

Keyword(s):

High Frequency ◽

Shear Zones ◽

Test Site ◽

Radioactive Waste Disposal ◽

Swiss Alps ◽

P Wave ◽

Seismic Sources ◽

Rock Body ◽

Grimsel Test Site ◽

Explosive Charges

In August 1995, various high‐frequency seismic sources were tested at the Grimsel Test Site (GTS), located inside a crystalline rock body in the central Swiss Alps. These source tests were designed to facilitate future tomographic studies of potential radioactive waste disposal sites. The principal objective was to identify borehole and tunnel seismic sources capable of generating powerful high‐frequency signals such that frequencies up to 1000 Hz can be observed over distances of 1000 m in crystalline or consolidated sedimentary rocks. Seismic sources were situated in water‐filled boreholes (sparker, two piezoelectric sources, explosives) and at or near the tunnel wall (accelerated weight drop, minivibrator, bolt gun, buffalo gun, explosives). To evaluate and compare the source characteristics, the direct P-wave generated by the various seismic sources was investigated for the decay of its S/N and dominant frequency with offset and for the maximum distance at which first arrivals could be picked. Of the seismic sources tested, small explosive charges (5–100 g) had the most favorable S/N and frequency characteristics. At GTS, the target distance (∼1000 m) was reached with explosive charges of 50 g or more. None of the sources tested was capable of generating signals that sustained frequencies of 1000 Hz over distances in excess of 100 to 200 m. The unusually strong attenuation implied by this observation is likely due to the fact that the rocks at GTS underwent brittle deformation during the Alpine orogeny and therefore contain numerous fractures and shear zones.

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Multiactinide Analysis with Accelerator Mass Spectrometry for Ultratrace Determination in Small Samples: Application to an in Situ Radionuclide Tracer Test within the Colloid Formation and Migration Experiment at the Grimsel Test Site (Switzerland)

Analytical Chemistry ◽

10.1021/acs.analchem.7b01359 ◽

2017 ◽

Vol 89 (13) ◽

pp. 7182-7189 ◽

Cited By ~ 3

Author(s):

Francesca Quinto ◽

Ingo Blechschmidt ◽

Carmen Garcia Perez ◽

Horst Geckeis ◽

Frank Geyer ◽

...

Keyword(s):

Mass Spectrometry ◽

Test Site ◽

Tracer Test ◽

Small Samples ◽

Grimsel Test Site ◽

Radionuclide Tracer ◽

Migration Experiment ◽

And Migration ◽

Colloid Formation

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Grimsel Test Site — Phase VI: Review of Accomplishments and Next Steps

11th International Conference on Environmental Remediation and Radioactive Waste Management, Parts A and B ◽

10.1115/icem2007-7239 ◽

2007 ◽

Cited By ~ 1

Author(s):

Stratis Vomvoris ◽

Wolfgang Kickmaier

Keyword(s):

Ad Hoc ◽

Field Testing ◽

Planning Horizon ◽

Test Site ◽

Swiss Alps ◽

Tracer Transport ◽

Geophysical Investigation ◽

Grimsel Test Site

The Grimsel Test Site owned and operated by Nagra is located in the Swiss Alps (www.grimsel.com). The sixth Phase of investigations was started in 2003 with a ten-year planning horizon. With the investigations and projects of Phase VI the focus is shifted more towards projects assessing perturbation effects of repository implementation and projects evaluating and demonstrating engineering and operational aspects of the repository system. More than 17 international partners participate in the various projects, which form the basic organisational ‘elements’ of Phase VI, each one further structured in field-testing, laboratory studies, design and modelling tasks, as appropriate. Each project phase is planned with a duration of 3 to 5 years, to facilitate all practical and administrative aspects, ensuring flexibility for updating the overall plan with the recent findings. Scientific and engineering interaction among the different projects is ensured via the annual international meeting and ad-hoc meetings, as appropriate. As Phase VI approaches its mid-term point, a review of the accomplishments to date is performed to provide a sound basis for the detailed planning of the next steps. The accomplishments to date are described and assessed below; the opportunities with the on-going projects as well as new projects – currently under discussion – are also presented and discussed. The on-going projects include: studies of the long-term diffusion with emphasis on the processes in the rock matrix (LTD); colloid studies under in-situ generation conditions and migration velocities closer to velocities expected in an actual repository site (CFM); studies of the long-term cement interactions with natural systems (LCS); evaluation of full-scale engineered systems under simulated heat production and long-term natural saturation (NF-Pro/FEBEX); gas migration through engineered barrier systems (GMT); emplacement of shotcrete low-pH plug (ESDRED/Module IV); test and evaluation of monitoring systems (TEM). In addition, various shorter term projects assessing, for example, new geophysical investigation tools, wireless transmission, testing new tools and training for in-situ tracer transport studies have been performed and/or are planned for the near future.

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