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

1997 ◽  
Vol 506 ◽  
Author(s):  
J. Eikenberg ◽  
M. Ruethi ◽  
W.R. Alexander ◽  
B. Frieg ◽  
T. Fierz
Keyword(s):  
High Resolution ◽  
Shear Zone ◽  
Test Site ◽  
Breakthrough Curves ◽  
Laboratory Measurements ◽  
Radionuclide Migration ◽  
Grimsel Test Site ◽  
On Line ◽  
Comprehensive Study

ABSTRACTFull 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.

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

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.

The Assessment of Radionuclide Retardation in Fractured Crystalline Rocks

1997 ◽  
Vol 506 ◽  
Author(s):  
W. Russell Alexander ◽  
Kunio Ota ◽  
Bernhard Frieg ◽  
Ian G. Mckinley
Keyword(s):  
Test Site ◽  
Breakthrough Curves ◽  
Swiss Alps ◽  
Radionuclide Migration ◽  
Sorption Data ◽  
Kd Values ◽  
Long Term Experiment ◽  
Fractured Crystalline Rocks ◽  
Tracer Migration

ABSTRACTThe joint Nagra/PNC Radionuclide Migration Programme has been running for over ten years in Nagra‘s Grimsel Test Site in the central Swiss Alps. The programme is specifically aimed at the further development of conceptual models of radionuclide transport in the geosphere, rigorously testing the applicability of current transport codes to quantify radionuclide migration in situ and assessing how successfully laboratory sorption data (specifically, Kd values) may be extrapolated to in situ conditions to predict radionuclide retardation in the geosphere [1]. A large series of field tracer migration experiments was carried out in a hydrologically well characterised water-bearing, complex fracture (or shear zone), increasing in complexity from simple, nonsorbing fluoresceine (a fluorescent dye), 3H, 3,4He, 82Br and 123I through weakly sorbing 22.24Na,85Sr and 86Rb to a final, long-term experiment with moderately sorbing 134,137Cs. The radionuclides were injected into a dipole flow field where the flowpath length, dipole width or shape and groundwater flow velocity were all varied. After a considerable learning period, generally good fits could be obtained between transport code predictions and subsequent field tracer breakthrough curves, suggesting that the transport codes tested were a reasonable representation of in situ conditions.

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

2014 ◽  
Vol 1665 ◽  
pp. 85-91 ◽  
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.

scholarly journals The seismo-hydro-mechanical behaviour during deep geothermal reservoir stimulations: open questions tackled in a decameter-scale in-situ stimulation experiment

2017 ◽  
Author(s):  
Florian Amann ◽  
Valentin Gischig ◽  
Keith Evans ◽  
Joseph Doetsch ◽  
Reza Jalali ◽  
...  
Keyword(s):  
Rock Mass ◽  
Geothermal Energy ◽  
Numerical Models ◽  
Test Site ◽  
Crystalline Rock ◽  
Coupled Processes ◽  
Small Scale ◽  
Intermediate Scale ◽  
Grimsel Test Site

Abstract. In this contribution we present a review of scientific research results that address seismo-hydro-mechanical coupled processes relevant for the development of a sustainable heat exchanger in low permeability crystalline rock and introduce the design of the In-situ Stimulation and Circulation (ISC) experiment at the Grimsel Test Site dedicated to study such processes under controlled conditions. The review shows that research on reservoir stimulation for deep geothermal energy exploitation has been largely based on laboratory observations, large-scale projects and numerical models. Observations of full-scale reservoir stimulations have yielded important results. However, the limited access to the reservoir and limitations in the control on the experimental conditions during deep reservoir stimulations is insufficient to resolve the details of the hydro-mechanical processes that would enhance process understanding in a way that aids future stimulation design. Small scale laboratory experiments provide a fundamental insights into various processes relevant for enhanced geothermal energy, but suffer from 1) difficulties and uncertainties in upscaling the results to the field-scale and 2) relatively homogeneous material and stress conditions that lead to an over-simplistic fracture flow and/or hydraulic fracture propagation behaviour that is not representative for a heterogeneous reservoir. Thus, there is a need for intermediate-scale hydraulic stimulation experiments with high experimental control that bridge the various scales, and for which access to the target rock mass with a comprehensive monitoring system is possible. Only few intermediate-scale hydro-shearing and hydro-fracturing experiments have recently been performed in a densely instrumented rock mass. No such measurements have been performed on faults in crystalline basement rocks. The In-situ Stimulation and Circulation (ISC) experiment currently performed in a naturally fractured and faulted crystalline rock mass at the Grimsel Test Site (Switzerland) is designed to address open research questions, which could not be investigated in the required detail so far. Two hydraulic injection phases were executed to enhance the permeability of the rock mass: a hydro-shearing phase and then a hydraulic fracturing phase. During the injection phases the rock mass deformation across fractures and within intact rock, the pore pressure distribution and propagation and the micro-seismic response were monitored at a high spatial and temporal resolution.

Results of the colloid and radionuclide retention experiment (CRR) at the Grimsel Test Site (GTS), Switzerland – impact of reaction kinetics and speciation on radionuclide migration

2004 ◽  
Vol 92 (9-11) ◽  
Author(s):  
Horst Geckeis ◽  
Thorsten Schäfer ◽  
W. Hauser ◽  
Thomas Rabung ◽  
T. Missana ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Test Site ◽  
Radionuclide Migration ◽  
Migration Behaviour ◽  
Grimsel Test Site

SummaryThe influence of smectite colloids on the migration behaviour of U(VI), Th(IV), Pu(IV), Am(III), Np(V), Sr(II) and Cs(I) is investigated within the Colloid and Radionuclide Retardation experiment (CRR). Two

Site Characterization for Field Radionuclide Migration Studies in Climax Granite

1981 ◽  
Vol 6 ◽  
Author(s):  
Dana Isherwood ◽  
Ellen Raber ◽  
Randolph Stone
Keyword(s):  
Flow Model ◽  
Test Site ◽  
Hydraulic Testing ◽  
Nevada Test Site ◽  
Radionuclide Migration ◽  
Critical Question ◽  
Initial Field ◽  
In Situ Conditions ◽  
Fracture Apertures

ABSTRACTRadionuclide migration experiments in fractured granite at the Climax Stock, Nevada Test Site, are needed to compare field and laboratory measured retardation factors to determine whether laboratory studies accurately reflect in situ conditions. Initial field activities have concentrated on hydrological investigations to determine whether the fractures in Climax granite are suitable for migration experiments. A critical question was whether we could isolate a single vertical fracture between two boreholes and establish flow along that fracture from an upper to a lower borehole. Of the ten fractures tested, one fracture would not take water at pressures up to 200 psig for 24 hours. Several fractures were so permeable they accepted water at a rate which exceeded the pumping capacity of the equipment. Other fractures failed to show a connection between the two boreholes. In two fractures, we were able to establish a circulating system with up to 95 percent of the injected water being recovered. Constant pressure injection tests were conducted. Intrinsic permeabilities of 33 and 75 (μm)2 were estimated using a radial nonsteady flow model. These values correspond to effective fracture apertures of 20 and 30 μm respectively. Concurrent with the hydraulic testing activities is a study of the Climax ground-water chemistry. Our analyses show the natural water to be very different in composition from the granite equilibrated water used in laboratory sorption studies. This paper includes the results of the hydrogeological and geochemical investigations, and describes the overall experimental design plans for the radionuclide migration experiments.

scholarly journals Eighteen years of steel–bentonite interaction in the FEBEX in situ test at the Grimsel Test Site in Switzerland

2019 ◽  
Vol 67 (2) ◽  
pp. 111-131 ◽  
Author(s):  
Jebril Hadi ◽  
Paul Wersin ◽  
Vincent Serneels ◽  
Jean-Marc Greneche
Keyword(s):  
Test Site ◽  
In Situ Test ◽  
Grimsel Test Site
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