Analysis of 3H, 36Cl, 133Ba, 134Cs and 22Na from synthetic granitic groundwater: an in situ through diffusion experiment at ONKALO

Radionuclides usually migrate slower than the flowing water due to sorption and matrix diffusion. The performance assessment assumes that retention takes place mostly in the vicinity of the deposition holes. REPRO (REtention Properties of ROck matrix) experiments analyzed the matrix retention properties of the rock matrix under realistic conditions deep in the bedrock in ONKALO underground characterization facility at Olkiluoto, Finland. The objective was to investigate tracer transport in the rock matrix, which was representative to the near-field of the final disposal repository of the spent nuclear fuel, and to demonstrate that the assumptions made in the safety case of the deep geological spent fuel repository were in line with site evidence.REPRO is composed of several supporting laboratory and in-situ experiments which investigate the retention properties under different experimental configurations. The first in-situ experiments were water phase diffusion experiments performed 2012-2013. Through Diffusion Experiment (TDE) studies diffusion and porosity properties of rock matrix in stress field of repository level and sorption properties of nuclides in intact rock circumstances.The TDE experiment has been performed in three parallel drillholes drilled near to each other. Breakthrough of the radioactive tracer is monitored with on-line measurements and samplings along and perpendicular to the foliation. The non-sorbing radioactive isotope traces of HTO and 36Cl, as well as slightly sorbing 22Na and strongly sorbing 133Ba and 134Cs were used. TDE was designed to control advective flow, as it had caused problems in previous in-situ tests.Supporting laboratory studies were performed for drillcore samples sampled from the experimental drillholes. In these laboratory experiments, i.e. porosity, permeability and diffusion coefficients of the drillcores were determined using different methods.The TDE experiment was carried out from 2016 to 2019. A breakthrough was seen in the timeframe predicted by scoping calculations carried out. REPRO has produced data and knowledge to the safety case and the performance assessment. According to the preliminary results, values measured in the laboratory are applicable also in larger scale and in-situ conditions.

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Comparison between in situ and laboratory diffusion studies of HTO and halides in Opalinus Clay from the Mont Terri

Radiochimica Acta ◽

10.1524/ract.92.9.781.54989 ◽

2004 ◽

Vol 92 (9-11) ◽

Cited By ~ 37

Author(s):

Etienne Tevissen ◽

J. M. Soler ◽

P. Montarnal ◽

A. Gautschi ◽

Luc R. Van Loon

Keyword(s):

Tritiated Water ◽

Opalinus Clay ◽

Diffusion Experiment ◽

Diffusion Technique ◽

Diffusion Studies ◽

Through Diffusion ◽

Mont Terri

SummaryA long-term single-borehole diffusion experiment (DI) using tritiated water (HTO) and stable iodide (All HTO results obtained with a through diffusion technique are within the same range as those obtained in the

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Measurement on Diffusion Coefficients and Isotope Fractionation Factors by a Through-Diffusion Experiment

Minerals ◽

10.3390/min11020208 ◽

2021 ◽

Vol 11 (2) ◽

pp. 208

Author(s):

Takuma Hasegawa ◽

Kotaro Nakata ◽

Rhys Gwynne

Keyword(s):

Groundwater Flow ◽

Diffusion Coefficients ◽

Isotope Fractionation ◽

Free Water ◽

Effective Porosity ◽

Diffusion Experiment ◽

Fractionation Factor ◽

Through Diffusion ◽

Geological Formations ◽

Fractionation Factors

For radioactive waste disposal, it is important that local groundwater flow is slow as groundwater flow is the main transport medium for radioactive nuclides in geological formations. When the groundwater flow is very slow, diffusion is the dominant transport mechanism (diffusion-dominant domain). Key pieces of evidence indicating a diffusion-dominant domain are the separation of components and the fractionation of isotopes by diffusion. To prove this, it is necessary to investigate the different diffusion coefficients for each component and the related stable isotope fractionation factors. Thus, in this study, through-diffusion and effective-porosity experiments were conducted on selected artificial materials and natural rocks. We also undertook measurements relating to the isotope fractionation factors of Cl and Br isotopes for natural samples. For natural rock samples, the diffusion coefficients of water isotopes (HDO and H218O) were three to four times higher than those of monovalent anions (Cl−, Br- and NO3−), and the isotope fractionation factor of 37Cl (1.0017–1.0021) was slightly higher than that of free water. It was experimentally confirmed that the isotope fractionation factor of 81Br was approximately 1.0007–1.0010, which is equivalent to that of free water. The enrichment factor of 81Br was almost half that of 37Cl. The effective porosity ratios of HDO and Cl were slightly different, but the difference was not significant compared to the ratio of their diffusion coefficients. As a result, component separation was dominated by diffusion. For artificial samples, the diffusion coefficients and effective porosities of HDO and Cl were almost the same; it was thus difficult to assess the component separation by diffusion. However, isotope fractionation of Cl and Br was confirmed using a through-diffusion experiment. The results show that HDO and Cl separation and isotope fractionation of Cl and Br can be expected in diffusion-dominant domains in geological formations.

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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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In situ nuclear-glass corrosion under geological repository conditions

npj Materials Degradation ◽

10.1038/s41529-019-0100-7 ◽

2019 ◽

Vol 3 (1) ◽

Cited By ~ 3

Author(s):

Mathieu Debure ◽

Yannick Linard ◽

Christelle Martin ◽

Francis Claret

Keyword(s):

Pure Water ◽

Secondary Phase ◽

Predictive Modelling ◽

Diffusion Experiment ◽

Secondary Phases ◽

Glass Corrosion ◽

Geological Repository ◽

High Level ◽

Rock Supports

Abstract Silicate glasses are durable materials but laboratory experiments reveal that elements that derive from their environment may induce high corrosion rates and reduce their capacity to confine high-level radioactive waste. This study investigates nuclear-glass corrosion in geological media using an in situ diffusion experiment and multi-component diffusion modelling. The model highlights that the pH imposed by the Callovo–Oxfordian (COx) claystone host rock supports secondary-phase precipitation and increases glass corrosion compared with pure water. Elements from the COx rock (mainly Mg and Fe) form secondary phases with Si provided by the glass, which delay the establishment of a passivating interface. The presence of elements (Mg and Fe) that sustain glass alteration does not prevent a significant decrease in the glass-alteration rate, mainly due to the limited species transport that drives system reactivity. These improvements in the understanding of glass corrosion in its environment provide further insights for predictive modelling over larger timescales and space.

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Effect of density-driven flow on the through-diffusion experiment

Journal of Contaminant Hydrology ◽

10.1016/j.jconhyd.2009.02.006 ◽

2009 ◽

Vol 106 (3-4) ◽

pp. 166-172 ◽

Cited By ~ 10

Author(s):

Yusuke Kirino ◽

Tadashi Yokoyama ◽

Tetsuro Hirono ◽

Takashi Nakajima ◽

Satoru Nakashima

Keyword(s):

Diffusion Experiment ◽

Density Driven Flow ◽

Through Diffusion

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A fully 3-D anisotropic numerical model of the DI-B in situ diffusion experiment in the Opalinus clay formation

Physics and Chemistry of the Earth Parts A/B/C ◽

10.1016/j.pce.2006.04.017 ◽

2006 ◽

Vol 31 (10-14) ◽

pp. 531-540 ◽

Cited By ~ 30

Author(s):

J. Samper ◽

C. Yang ◽

A. Naves ◽

A. Yllera ◽

A. Hernández ◽

...

Keyword(s):

Numerical Model ◽

Opalinus Clay ◽

Diffusion Experiment ◽

In Situ Diffusion ◽

Clay Formation

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In-Situ Diffusion Experiment In Sparsely Fractured Granite

MRS Proceedings ◽

10.1557/proc-824-cc7.4 ◽

2004 ◽

Vol 824 ◽

Cited By ~ 1

Author(s):

Peter Vilks ◽

Neil H. Miller ◽

Mark Jensen

Keyword(s):

Field Experiments ◽

Effective Diffusion ◽

Rock Properties ◽

Experimental Program ◽

Diffusion Experiment ◽

Stress Regime ◽

In Situ Experiments ◽

In Situ Diffusion ◽

Conservative Values

AbstractThe in-situ diffusion experiment was conducted at AECL's Underground Research Laboratory (URL) to improve the understanding of diffusive solute transport in sparsely fractured or intact granitic rock (SFR). The experimental program used a comparative series of laboratory and in-situ field experiments to evaluate the ability of laboratory measurements to estimate in-situ rock properties and to explore issues surrounding the influence of stress relaxation, rock texture, porosity, pore geometry, and anisotropy on derived effective diffusion coefficients (De). In-situ experiments yielded iodide Debetween 1.4 × 10−13 and 1.1 × 10−12 m2/s. Unlike laboratory results, the in-situ De estimates did not exhibit correlation with sample depth or varied stress regime. Laboratory-derived measurements of De, porosity and permeability were found to systematically increase for samples removed from greater depths and higher stress regimes. Laboratory-derived iodide De values consistently trended higher than in-situ values by a factor of 1 to 15, except on the shallowest 240-m Level (σ1 ≍ 30 MPa) where differences were negligible. Laboratory-derived estimates of permeability were consistently higher than in-situ derived values by a factor of 2 to 100. This experimental program provides evidence that laboratory steady-state diffusion experiments are most likely to yield conservative values of De for simulation of diffusive mass transport in SFR.

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