A combined glass dissolution/diffusion experiment in Boom Clay at 30°C

2013 ◽  
Vol 65 ◽  
pp. 72-78
Author(s):  
Marc Aertsens ◽  
Karel Lemmens
Keyword(s):  
Diffusion Experiment ◽  
Boom Clay ◽  
Glass Dissolution

Validation of glass dissolution and Si diffusion parameters with a combined glass dissolution-diffusion experiment in Boom Clay

2006 ◽  
Vol 932 ◽  
Author(s):  
Karel Lemmens ◽  
Marc Aertsens
Keyword(s):  
Diffusion Profile ◽  
Coupled Processes ◽  
Diffusion Experiment ◽  
Boom Clay ◽  
Glass Dissolution ◽  
Diffusion Parameters ◽  
Constant Rate ◽  
Geochemical Reactions ◽  
Glass Silica ◽  
Parameter Values

ABSTRACTExisting knowledge on glass dissolution and silica diffusion in Boom Clay is validated by experiments where both phenomena could be studied simultaneously. SON68 glass coupons, doped with radioactive 32Si, were sandwiched between two cores of fresh humid Boom Clay and heated to 30°C. At the end of the experiment, the system was dismantled, the mass loss of the glass coupon was measured, and the clay core was sliced to determine the diffusion profile of the 32Si dissolved from the glass. These data were completed with analyses of the clay water and surface analyses for analogous tests with undoped glass. The results are interpreted by assuming congruent glass dissolution at a constant rate, with a glass silica saturation concentration between 14 and 20 mg/l, a forward glass dissolution rate (at zero silica concentration) of 0.028 g.m−2day−1, an apparent silica diffusion coefficient in the clay of 1.4 10−12 m2sec−1, and a distribution coefficient for silica on Boom Clay between 0.010 and 0.075 m3kg−1. These parameter values are close to the range found in literature. It was not necessary to consider diffusion through the gel, precipitation or detailed geochemical reactions. The modeling exercise shows that the existing knowledge about the subsystems glass and clay can succesfully be integrated to describe the coupled processes in the whole system.

Measurement of Glass Corrosion in Boom Clay Disposal Conditions: First Results of the Experimental Programme 2000-2003 of SCK•CEN

2003 ◽  
Author(s):  
Karel Lemmens ◽  
Marc Aertsens ◽  
Ve´ra Pirlet ◽  
Norbert Maes ◽  
Hugo Moors ◽  
...  
Keyword(s):  
Low Temperature ◽  
Dissolution Rate ◽  
Near Field ◽  
Glass Frit ◽  
Glass Mass ◽  
Boom Clay ◽  
Glass Dissolution ◽  
Mass Losses ◽  
Dissolution Behaviour ◽  
First Results

To estimate the lifetime of vitrified high level waste (HLW-glass) in Boom Clay disposal conditions, the dissolution behaviour of waste glass has been studied with experiments performed in surface laboratories and in the HADES underground research facility of SCK·CEN since 1980. We present the main topics and first results of the SCK·CEN programme 2000–2003. This programme focuses on the following items: (1) the diffusion/sorption/precipitation of silica in Boom clay or backfill clay, (2) demonstration of glass dissolution behaviour in realistic test conditions, (3) the effect of presaturation of the clay with silica, and (4) the estimation of near field concentrations of critical isotopes. The experiments have shown so far that Si, released by the glass, is effectively immobilized by Boom Clay, but it can nevertheless diffuse into the clay without immediately precipitating. The dissolution rate of glass SON68 and SM539 is determined in Boom Clay at in situ density and at 30°C (this is the long-term temperature expected near the waste glass packages in a Boom Clay repository). The dissolution rates, based on glass mass losses, are constant during the first year, at ∼ 0.010 g.m−2.day−1 for glass SON68 and ∼ 0.012 g.m−2.day−1 for glass SM539. The addition of glass frit causes a decrease of the glass dissolution rate, both with glass SON68 and SM539, and both in Boom Clay and in FoCa-clay. In FoCa-clay at high density with glass frit, the dissolution rates, based on glass mass losses, after 8 months at 30°C are ∼ 0.001 g.m−2.day−1 (SM539) and ∼0.005 g.m−2.day−1 (SON68). Because the experiments performed in Boom Clay and FoCa-clay with glass frit simulate realistic conditions (high clay density, low temperature), they can be used to estimate the maximum glass dissolution rate in a (Boom) clay repository. The corresponding minimum lifetime of a glass canister, calculated with the SCK·CEN code for lifetime predictions, is of the order of 105 to 106 years, if we neglect the internal glass surface area (due to cracking). In more diluted clay suspensions with glass frit, the glass dissolution rate is 10−4 to 10−5 g.m−2.day−1 or even zero. This would correspond to a lifetime of >>106 years. So far, there is no indication that the addition of glass frit leads to secondary phase formation at low temperature (30–40°C). Leach experiments with doped glasses SON68 and SM539 suggest that the maximum concentrations of most critical radionuclides in near field conditions are lower than the best estimate solubilities used for performance assessment studies in Boom Clay. For Se, relatively high concentrations were measured, though. The research programme for the underground laboratory is not discussed.

The Long-Term Dissolution Behaviour of the Pamela Borosilicate Glass SM527 - Application of SA/V as Accelerating Parameter

1991 ◽  
Vol 257 ◽  
Author(s):  
K. Lemmens ◽  
P. Van Iseghem
Keyword(s):  
Borosilicate Glass ◽  
Water Mixture ◽  
Boom Clay ◽  
Glass Dissolution ◽  
Dissolution Behaviour ◽  
Powdered Glass ◽  
Clay Slurry ◽  
Term Data ◽  
Solution Volume

ABSTRACTThe Al2O3 rich borosilicate glass SM527 was submitted to corrosion tests with glass surface area to solution volume ratios ranging from 10 to 10000 m-1. This latter condition would correspond with a 1000 fold acceleration relative to the reference MCCI condition. Powdered glass was used to reach SANV ratios of 500 m-1 and more. The leaching solutions were either distilled water or referred to Boom clay disposal conditions. The results based on the boron concentration in solution revealed a relatively linear dependence on SA/V.t0.5 in the pure solutions, on the longer term (DW and clay water). Diffusion is suggested to be the process governing the glass dissolution, although other processes should not be excluded. In a clay / clay water mixture (slurry), long term dissolution seems to be limited by saturation. Short term data for boron are largest in the clay slurry, but with time the boron concentrations converge to similar values in the three media considered. The use of SA/V as an accelerating factor is promising, but certainly requires additional research.

Measurement of Glass Corrosion in Boom Clay Disposal Conditions

2001 ◽  
Author(s):  
Karel Lemmens ◽  
Marc Aertsens ◽  
Véra Pirlet ◽  
Hélène Serra ◽  
Elie Valcke ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Kinetic Modeling ◽  
Dissolution Time ◽  
Dissolution Test ◽  
Dissolution Rates ◽  
Boom Clay ◽  
Glass Dissolution ◽  
Dissolution Tests ◽  
Environmental Materials

Abstract To estimate the life-time of vitrified high level waste (HLW-glass) in geological disposal conditions in Boom Clay, the dissolution behaviour of waste glass has been studied in experiments in surface laboratories and in the HADES underground research facility of SCK•CEN since the 1980’s. The programme consists mainly of dissolution tests. The purpose of these tests is to understand the basic glass dissolution mechanisms, and to demonstrate realistic long-term dissolution rates. The main experimental variables are glass composition, environmental materials, temperature, and test duration. The studied glasses are the COGEMA glass R7T7, and the PAMELA glasses with SM539, SM527 and SM513 glass frit. The environmental materials comprise Boom Clay, metallic corrosion products and engineered barrier materials. Dissolution tests have been performed at temperatures from 40 to 190°C, for test durations from days to several years. The tests are performed with inactive glasses, which can be doped with radionuclides of interest. Because of the importance of silica sorption by the environmental materials, the dissolution test programme was extended with silica diffusion- and sorption tests in Boom Clay and FoCa clay. The interpretation of the experimental results is supported by geochemical and kinetic modeling. In the area of kinetic modeling, both analytical and Monte Carlo codes are applied. The dissolution tests have demonstrated that, although the presence of Boom Clay initially increases the glass dissolution rate, the long-term dissolution rate decreases for diluted clay / clay water slurries. This decrease has not yet been demonstrated for the R7T7 glass in compact Boom Clay, but is expected to occur here also on the long term. The dissolution rate decreases faster after sufficient addition of glass powder to the medium. This was tested in experiments with the R7T7 glass at relatively high clay concentration (2000 g of humid Boom Clay per liter clay water, this is about half the solid/liquid ratio of compact Boom Clay), at 40 and 90°C. Linear interpolation of the long-term mass losses resulted in dissolution rates of ∼ 0.01 g.m−2.day−1. The statistical uncertainties on the dissolution test results did not allow to demonstrate smaller rates. The minimum statistically significant dissolution rate depends on the test conditions. Therefore, the present SCK•CEN programme includes dissolution tests at long-term near-field conditions (this is at 30°C, with compact Boom Clay and FoCa clay), which are considered more representee for the long-term situation. In view of the uncertainties on the experimental long-term dissolution rates and on the long-term dissolution mechanisms, rates smaller than 0.01 g.m−2.day1 (about 1 μ/year) should not be used as best estimate in the present performance assessment studies for disposal in Boom Clay. A constant dissolution rate of 0.01 g.m−2.day−1 would correspond to a dissolution time for a R7T7 glass package of approximately 150 000 years. The minimum dissolution time is of the order of 104 years.

scholarly journals Modeling cesium migration through Opalinus clay: a benchmark for single- and multi-species sorption-diffusion models

2021 ◽  
Author(s):  
Jesús F. Águila ◽  
Vanessa Montoya ◽  
Javier Samper ◽  
Luis Montenegro ◽  
Georg Kosakowski ◽  
...  
Keyword(s):  
Time Discretization ◽  
Single Species ◽  
Opalinus Clay ◽  
Sorption Behavior ◽  
Diffusion Experiment ◽  
Modeling Tools ◽  
Cesium Sorption ◽  
Code Performance ◽  
Good Agreement

AbstractSophisticated modeling of the migration of sorbing radionuclides in compacted claystones is needed for supporting the safety analysis of deep geological repositories for radioactive waste, which requires robust modeling tools/codes. Here, a benchmark related to a long term laboratory scale diffusion experiment of cesium, a moderately sorbing radionuclide, through Opalinus clay is presented. The benchmark was performed with the following codes: CORE2DV5, Flotran, COMSOL Multiphysics, OpenGeoSys-GEM, MCOTAC and PHREEQC v.3. The migration setup was solved with two different conceptual models, i) a single-species model by using a look-up table for a cesium sorption isotherm and ii) a multi-species diffusion model including a complex mechanistic cesium sorption model. The calculations were performed for three different cesium boundary concentrations (10−3, 10−5, 10−7 mol / L) to investigate the models/codes capabilities taking into account the nonlinear sorption behavior of cesium. Generally, good agreement for both single- and multi-species benchmark concepts could be achieved, however, some discrepancies have been identified, especially near the boundaries, where code specific spatial (and time) discretization had to be improved to achieve better agreement at the expense of longer computation times. In addition, the benchmark exercise yielded useful information on code performance, setup options, input and output data management, and post processing options. Finally, the comparison of single-species and multi-species model concepts showed that the single-species approach yielded generally earlier breakthrough, because this approach accounts neither for cation exchange of Cs+ with K+ and Na+, nor K+ and Na+ diffusion in the pore water.

Unravelling the dissolution mechanism of polyphosphate glasses by 31P NMR spectroscopy: ligand competition and reactivity of intermediate complexes

2021 ◽  
Author(s):  
Dahiana Andrea Avila Salazar ◽  
Peter Bellstedt ◽  
Atsuhiro Miura ◽  
Yuki Oi ◽  
Toshihiro Kasuga ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Solid State ◽  
Nmr Spectroscopy ◽  
Biomedical Applications ◽  
Structural Changes ◽  
31P Nmr ◽  
Dissolution Mechanism ◽  
31P Nmr Spectroscopy ◽  
Glass Dissolution ◽  
Polyphosphate Glasses

Phosphate glass dissolution can be tailored via compositional and subsequent structural changes, which is of interest for biomedical applications such as therapeutic ion delivery. Here, solid-state 31P nuclear magnetic resonance...

scholarly journals Processing of novel food reveals payoff and rank-biased social learning in a wild primate

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Charlotte Canteloup ◽  
Mabia B. Cera ◽  
Brendan J. Barrett ◽  
Erica van de Waal
Keyword(s):  
Social Learning ◽  
Learning Strategies ◽  
Individual Learning ◽  
Diffusion Experiment ◽  
Vervet Monkeys ◽  
Dynamic Learning ◽  
Novel Food ◽  
Bias Attention ◽  
Higher Rank ◽  
Learning From Others

AbstractSocial learning—learning from others—is the basis for behavioural traditions. Different social learning strategies (SLS), where individuals biasedly learn behaviours based on their content or who demonstrates them, may increase an individual’s fitness and generate behavioural traditions. While SLS have been mostly studied in isolation, their interaction and the interplay between individual and social learning is less understood. We performed a field-based open diffusion experiment in a wild primate. We provided two groups of vervet monkeys with a novel food, unshelled peanuts, and documented how three different peanut opening techniques spread within the groups. We analysed data using hierarchical Bayesian dynamic learning models that explore the integration of multiple SLS with individual learning. We (1) report evidence of social learning compared to strictly individual learning, (2) show that vervets preferentially socially learn the technique that yields the highest observed payoff and (3) also bias attention toward individuals of higher rank. This shows that behavioural preferences can arise when individuals integrate social information about the efficiency of a behaviour alongside cues related to the rank of a demonstrator. When these preferences converge to the same behaviour in a group, they may result in stable behavioural traditions.

scholarly journals The fate of Si and Fe while nuclear glass alters with steel and clay

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
C. Carriere ◽  
P. Dillmann ◽  
S. Gin ◽  
D. Neff ◽  
L. Gentaz ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Protective Layer ◽  
Glass Dissolution ◽  
A Value ◽  
Waste Forms ◽  
Controlling Mechanism ◽  
Geological Repository ◽  
The Mean ◽  
High Level ◽  
Initial Dissolution Rate

AbstractThe French concept developed to dispose high-level radioactive waste in geological repository relies on glassy waste forms, isolated from the claystone host rock by steel containers. Understanding interactions between glass and surrounding materials is key for assessing the performance of a such system. Here, isotopically tagged SON68 glass, steel and claystone were studied through an integrated mockup conducted at 50 °C for 2.5 years. Post-mortem analyses were performed from nanometric to millimetric scales using TEM, STXM, ToF-SIMS and SEM techniques. The glass alteration layer consisted of a crystallized Fe-rich smectite mineral, close to nontronite, supporting a dissolution/reprecipitation controlling mechanism for glass alteration. The mean glass dissolution rate ranged between 1.6 × 10−2 g m−2 d−1 to 3.0 × 10−2 g m−2 d−1, a value only 3–5 times lower than the initial dissolution rate. Thermodynamic calculations highlighted a competition between nontronite and protective gel, explaining why in the present conditions the formation of a protective layer is prevented.

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

Minerals ◽  
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.

Sign in / Sign up

Export Citation Format

Share Document