Alteration of Basaltic Glass in Iceland as a Natural Analogue for Nuclear Waste Glasses: Geochemical Modelling with DISSOL

1988 ◽  
Vol 127 ◽  
Author(s):  
J. L. Crovisier ◽  
T. Advocat ◽  
J. C. Petit ◽  
B. Fritz
Keyword(s):  
Computer Code ◽  
Solution Chemistry ◽  
Iron Hydroxides ◽  
Basaltic Glass ◽  
Secondary Products ◽  
Glass Dissolution ◽  
Mineral Phases ◽  
Kinetic Effects ◽  
Good Agreement

ABSTRACTThe long term geochemical consequences of basaltic glass dissolution in fresh water at 0°C have been calculated with the computer code DISSOL. The clay minerals were represented by an ideal solid solution model (CISSFIT) able to describe variations in chemical composition of a clay phase in response to variations of the solution chemistry. The predicted mineral phases were iron hydroxides followed by kaolinite, TOT clays, chabazite and cli-noptilolite. These results are in reasonably good agreement with experimental results and observations of altered subglacial hyaloclastites from Iceland. The formation of secondary products are mainly controlled by thermodynamic constraints. Kinetic effects, such as diffusion in the near glass surface are not important.

Thermokinetic Model of Borosilicate Glass Dissolution: Contextual Affinity

1989 ◽  
Vol 176 ◽  
Author(s):  
T. Advocat ◽  
J.L. Crovisier ◽  
B. Fritz ◽  
E. Vernaz
Keyword(s):  
Experimental Data ◽  
Dissolution Rate ◽  
Rate Equation ◽  
Computer Code ◽  
Solution Chemistry ◽  
Glass Dissolution ◽  
Water Composition ◽  
Silica Activity ◽  
Short And Long Term

ABSTRACTShort and long-term geochemical interactions of R7T7 nuclear glass with water at 100°C were simulated with the DISSOL thermokinetic computer code. Both the dissolved glass quantity and the resulting water composition, saturation states and mineral quantities produced were calculated as a function of time. The rate equation used in the simulation was first proposed by Aagaard and Hegelson: v = k+.S.a(H+)-n(l - e-(A/RT)). It simulates a gradually diminishing dissolution rate as the reaction affinity diminishes. The best agreement with 1-year experimental data was obtained with a reaction affinity calculated from silica activity (Grambow's hypothesis) rather than taking into account the activity of all the glass components as proposed by Jantzen and Plodinec. The concept of residual affinity was introduced by Grambow to express the fact that the glass dissolution rate does not cease. We prefer to replace the term “residual affinity” by “contextual affinity”, which expresses the influence on the dissolution rate of three factors: the solution chemistry, the metastability of SiO2(m), and the possible precipitation of certain aluminosilicates such as zeolites.

Geochemical Simulation of Dissolution of West Valley and Dnpf Glasses in J-13 Water at 90°C

1987 ◽  
Vol 112 ◽  
Author(s):  
Carol J. Bruton
Keyword(s):  
Waste Product ◽  
Computer Code ◽  
Yucca Mountain ◽  
Solution Chemistry ◽  
Complexing Agent ◽  
The West ◽  
Glass Dissolution ◽  
J 13 ◽  
Aqueous Species ◽  
Solution Changes

AbstractDissolution of West Valley and Defense Waste Product Facility (DWPF) glasses in J-13 water at 90°C at the candidate Yucca Mountain, Nevada repository was simulated using the EQ316 computer code package. The objectives of the study were to attempt to predict the concentrations of radionuclides and other glass components in solution resulting from glass dissolution, and to identify potential precipitates that sequester glass components.Modified projected inventories of 10,000 year-old Nest Valley and DNPF SRL-165 frit glasses were used as starting glass compositions. J-13 water was considered to be representative of groundwater at Yucca Mountain. A total of 10 grams of each glass was assumed to dissolve congruently into a kilogram of J-13 water in a closed system. No inhibitions to precipitation, except for crystalline SiO2 polymorphs, were assumed to exist. Radiolysis and materials interactions were not considered.Simulation results predict that radionuclides and other glass components precipitate predominantly in the form of oxides and hydroxides, together with carbonates, silicates and phosphates. Precipitates appear to be effective in limiting the concentrations of radionuclides and other elements in solution. The general compositional trends in precipitates and solution chemistry are the same in the West Valley and DMPF simulations, except for variations arising from differences in glass chemistry.Concentrations of elements released from glass increase until the solution reaches saturation with respect to solids that contain these elements. Elemental concentrations are then predicted to remain constant, increase or decrease depending on: 1) whether the reaction between the dominant aqueous species of the element in solution and its precipitate is pH and/or Eh-dependent; 2) whether the species distribution of the element in solution changes significantly in response to changes in pH, Eh, or other factors; and 3) the competition with other phases for elements required to form the precipitate. pH increases from 7.3 to 9.8 and from 7.2 to 10 in the West Valley and DWPF simulations, respectively. Eh decreases abruptly from about 0.5 to 0.3 volts after dissolution of 3.4 and 5.8 grams of glass in the Nest Valley and DMPF simulations, respectively, because of depletion of dissolved oxygen in solution. Complexing of aqueous species has a significant impact on radionuclide concentrations in solution; predicted concentrations of U in solution, for example, are controlled by the presence or absence of P in solution because H2PO4 is an extremely effective complexing agent for U.

A New Insight into the Nature of the Leached Layers Formed on Basaltic Glasses in Relation to the Choice of Constraints for Long Term Modelling

1988 ◽  
Vol 127 ◽  
Author(s):  
J. L. Crovisier ◽  
H. Atassi ◽  
V. Daux ◽  
J. Honnorez ◽  
J. C. Petit ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Basaltic Glass ◽  
Chemical Gradient ◽  
Glass Dissolution ◽  
Clayey Material ◽  
Congruent Dissolution ◽  
Ph Increase ◽  
Significant Chemical ◽  
Insight Into

ABSTRACTExperimental basaltic glass dissolution in fresh water is compared with analyses made on subglacial hyaloclastites from Iceland. The dissolution is initially selective and remains selective if the solution is renewed, whereas it becomes apparently congruent in non-renewed conditions. The congruent dissolution is ascribed to a pH increase (up to 7.0–7.5) which is hampered in the former conditions. The palagonite hydrated layer on the Icelandic basaltic glasses is made up of amorphous to crystallized clay-like materials. The chemical composition of palagonite is close to that of the intergranular clayey material, thus, it is inferred that in most cases no significant chemical gradient exists in the solution between the reaction zone, namely the glass/palagonite interface, and the intergranular solution. We conclude that the dissolution of basaltic glass under subglacial conditions is controlled by thermodynamics and that kinetic constraints, such as the diffusion of species through the altered layers, do not play a major role.

Investigations on the filtration of natural aquatic suspensions supported by dosing small amounts of Fe(III)-salts (βFe ≤ 0.1 mg.L-1): mode of action and basic design criteria

2002 ◽  
Vol 2 (2) ◽  
pp. 91-98
Author(s):  
R. Winzenbacher ◽  
R. Schick ◽  
H.-H. Stabel ◽  
M. Jekel
Keyword(s):  
Large Scale ◽  
Suspended Solids ◽  
Iron Hydroxides ◽  
Essential Step ◽  
Iron Salts ◽  
Alkaline Earths ◽  
Co Precipitation ◽  
Solid Liquid ◽  
Solid Liquid Separation

Improved removal of particles during the treatment of natural aquatic suspensions has been achieved by pre-ozonation and the addition of small quantities of iron salts (βFe ≤ 0.1 mg.L-1; “Fe(III)-assisted filtration”) followed by rapid filtration. As shown by investigations on a large-scale installation at Lake Constance Water Supply, this procedure reliably reduces suspended solids by at least 2-3 powers of ten in long-term use. However, the high efficacy of Fe(III)-assisted filtration cannot be explained on the basis of known coagulation mechanisms (like adsorption-charge neutralization, co-precipitation). Instead, the essential step was found to be the conditioning of the filter medium by coating it with colloids containing Fe(OH)3, and this “Fe coating” process occurs only in the presence of alkaline earths (especially Ca2+). According to further experiments, the enhanced solid-liquid separation was ultimately traced to chemical interactions such as the formation of calcium-organic association structures between the iron hydroxides and other solids. For design of Fe(III)-assisted filtration steps, finally, a βCa/DOC ratio above 40 mg.mg-1 and pre-oxidation with ozone dosages not exceeding 2 mg O3/mg DOC was recommended.

Anthropologic Relationships among Prehistoric Northeastern Amerindians

1980 ◽  
Vol 1 (2) ◽  
pp. 145-159
Author(s):  
Edward F. Harris ◽  
Nicholas F. Bellantoni
Keyword(s):  
New York ◽  
Gene Flow ◽  
Material Culture ◽  
New England ◽  
Cultural Barriers ◽  
Group Differences ◽  
Phenetic Analysis ◽  
Trade Relationships ◽  
Good Agreement

Archaeologically defined inter-group differences in the Northeast subarea ate assessed with a phenetic analysis of published craniometric information. Spatial distinctions in the material culture are in good agreement with those defined by the cranial metrics. The fundamental dichotomy, between the Ontario Iroquois and the eastern grouping of New York and New England, suggests a long-term dissociation between these two groups relative to their ecologic adaptations, trade relationships, trait-list associations, and natural and cultural barriers to gene flow.

scholarly journals Semi-Analytical Solution to Assess CO2 Leakage in the Subsurface through Abandoned Wells

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2452
Author(s):  
Tian Qiao ◽  
Hussein Hoteit ◽  
Marwan Fahs
Keyword(s):  
Analytical Solution ◽  
Storage Site ◽  
Co2 Leakage ◽  
Transient Pressure ◽  
Flow Paths ◽  
Abandoned Wells ◽  
Diffusivity Equation ◽  
Carbon Dioxide Co2 ◽  
Good Agreement

Geological carbon storage is an effective method capable of reducing carbon dioxide (CO2) emissions at significant scales. Subsurface reservoirs with sealing caprocks can provide long-term containment for the injected fluid. Nevertheless, CO2 leakage is a major concern. The presence of abandoned wells penetrating the reservoir caprock may cause leakage flow-paths for CO2 to the overburden. Assessment of time-varying leaky wells is a need. In this paper, we propose a new semi-analytical approach based on pressure-transient analysis to model the behavior of CO2 leakage and corresponding pressure distribution within the storage site and the overburden. Current methods assume instantaneous leakage of CO2 occurring with injection, which is not realistic. In this work, we employ the superposition in time and space to solve the diffusivity equation in 2D radial flow to approximate the transient pressure in the reservoirs. Fluid and rock compressibilities are taken into consideration, which allow calculating the breakthrough time and the leakage rate of CO2 to the overburden accurately. We use numerical simulations to verify the proposed time-dependent semi-analytical solution. The results show good agreement in both pressure and leakage rates. Sensitivity analysis is then conducted to assess different CO2 leakage scenarios to the overburden. The developed semi-analytical solution provides a new simple and practical approach to assess the potential of CO2 leakage outside the storage site. This approach is an alternative to numerical methods when detailed simulations are not feasible. Furthermore, the proposed solution can also be used to verify numerical codes, which often exhibit numerical artifacts.

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.

scholarly journals The key role of contact time in elucidating the mechanisms of enhanced decontamination by Fe0/MnO2/sand systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Viet Cao ◽  
Ghinwa Alyoussef ◽  
Nadège Gatcha-Bandjun ◽  
Willis Gwenzi ◽  
Chicgoua Noubactep
Keyword(s):  
Contact Time ◽  
Diffusive Transport ◽  
Iron Hydroxides ◽  
Iron Corrosion ◽  
Short Term ◽  
Batch Studies ◽  
Water Decontamination ◽  
Co Precipitation

AbstractMetallic iron (Fe0) has shown outstanding performances for water decontamination and its efficiency has been improved by the presence of sand (Fe0/sand) and manganese oxide (Fe0/MnOx). In this study, a ternary Fe0/MnOx/sand system is characterized for its discoloration efficiency of methylene blue (MB) in quiescent batch studies for 7, 18, 25 and 47 days. The objective was to understand the fundamental mechanisms of water treatment in Fe0/H2O systems using MB as an operational tracer of reactivity. The premise was that, in the short term, both MnO2 and sand delay MB discoloration by avoiding the availability of free iron corrosion products (FeCPs). Results clearly demonstrate no monotonous increase in MB discoloration with increasing contact time. As a rule, the extent of MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the vessels (test-tubes). The presence of MnOx and sand enabled the long-term generation of iron hydroxides for MB discoloration by adsorption and co-precipitation. Results clearly reveal the complexity of the Fe0/MnOx/sand system, while establishing that both MnOx and sand improve the efficiency of Fe0/H2O systems in the long-term. This study establishes the mechanisms of the promotion of water decontamination by amending Fe0-based systems with reactive MnOx.

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