Kinetics of MgO Dissolution and Buffering of Fluids in the Waste Isolation Pilot Plant (Wipp) Repository

MRS Proceedings ◽

10.1557/proc-556-625 ◽

1999 ◽

Vol 556 ◽

Cited By ~ 2

Author(s):

Valerie Monastra ◽

D. E. Grandstaff

Keyword(s):

Dissolution Rate ◽

Surface Area ◽

Pilot Plant ◽

Dissolution Rates ◽

Waste Isolation Pilot Plant ◽

Oxidizing Agents ◽

Reducing Conditions ◽

Kinetics Of ◽

Gas Pressures

AbstractDOE has proposed to add MgO to backfill in the WIPP repository to stabilize pH and reduce gas pressures and spallation. Experiments show that MgO dissolution rates are proportional to surface area, nearly independent of pH, and decrease with increasing dissolved NaCl. The probable repository MgO dissolution rate will be ≤ 10 to 20 μmol m2 min−1. Simulations indicate that MgO dissolution will buffer pH and provide stabilizing cement; however, under highly reducing conditions MgO will not control total gas pressures. Adding oxidizing agents or materials containing oxidized species, for example anhydrite, to the backfill, might control gas pressures.

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The reductive dissolution of synthetic goethite and hematite in dithionite

Clay Minerals ◽

10.1180/claymin.1987.022.3.07 ◽

1987 ◽

Vol 22 (3) ◽

pp. 329-337 ◽

Cited By ~ 83

Author(s):

J. Torrent ◽

U. Schwertmann ◽

V. Barron

Keyword(s):

Specific Surface ◽

Dissolution Rate ◽

Surface Area ◽

Reductive Dissolution ◽

Natural Environments ◽

Dissolution Rates ◽

Aluminium Substitution ◽

Initial Dissolution Rate

AbstractThe reductive dissolution by Na-dithionite of 28 synthetic goethites and 26 hematites having widely different crystal morphologies, specific surfaces and aluminium substitution levels has been investigated. For both minerals the initial dissolution rate per unit of surface area decreased with aluminium substitution. At similar aluminium substitution and specific surface, goethites and hematites showed similar dissolution rates. These results suggest that preferential, reductive dissolution of hematite in some natural environments, such as soils or sediments, might be due to the generally lower aluminium substitution of this mineral compared to goethite.

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Dissolution Rates of DWPF Glasses from Long-Term PCT

MRS Proceedings ◽

10.1557/proc-465-149 ◽

1996 ◽

Vol 465 ◽

Cited By ~ 6

Author(s):

W. L. Ebert ◽

S.-W. Tam

Keyword(s):

Dissolution Rate ◽

Surface Area ◽

Spherical Particles ◽

Dissolution Rates ◽

Glass Dissolution ◽

Dissolution Tests ◽

Dissolution Model ◽

Advanced Stages ◽

Radionuclide Release

ABSTRACTWe have characterized the corrosion behavior of several Defense Waste Processing Facility (DWPF) reference waste glasses by conducting static dissolution tests with crushed glasses. Glass dissolution rates were calculated from measured B concentrations in tests conducted for up to five years. The dissolution rates of all glasses increased significantly after certain alteration phases precipitated. Calculation of the dissolution rates was complicated by the decrease in the available surface area as the glass dissolves. We took the loss of surface area into account by modeling the particles to be spheres, then extracting from the short-term test results the dissolution rate corresponding to a linear decrease in the radius of spherical particles. The measured extent of dissolution in tests conducted for longer times was less than predicted with this linear dissolution model. This indicates that advanced stages of corrosion are affected by another process besides dissolution, which we believe to be associated with a decrease in the precipitation rate of the alteration phases. These results show that the dissolution rate measured soon after the formation of certain alteration phases provides an upper limit for the long-term dissolution rate, and can be used to determine a bounding value for the source term for radionuclide release from waste glasses. The long-term dissolution rates measured in tests at 20,000 m−1 at 90°C in tuff groundwater at pH values near 12 are about 0.2,0.07, and 0.04 g/(m2•d) for the Environmental Assessment glass and glasses made with SRL 131 and SRL 202 frits, respectively.

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Testing of uranium dioxide enriched with 233U under reducing conditions

MRS Proceedings ◽

10.1557/proc-932-76.1 ◽

2006 ◽

Vol 932 ◽

Cited By ~ 4

Author(s):

K. Ollila ◽

V. Oversby

Keyword(s):

Dissolution Rate ◽

Test Duration ◽

Dissolution Rates ◽

Fresh Groundwater ◽

Total Recovery ◽

Test Conditions ◽

Reducing Conditions ◽

Long Duration ◽

Dissolution Tests ◽

Synthetic Groundwater

ABSTRACTExperiments have been conducted to determine an upper limit to the dissolution rate of UO2 under reducing conditions at great depths in granitic bedrock. The aqueous phase was a dilute, synthetic groundwater that simulates fresh groundwater conditions, so-called modified Allard groundwater. Four dissolution tests of long duration were performed. Test duration ranged from 52 to 140 days. Reducing conditions were produced with metallic iron. Average dissolution rates for the UO2 samples under the test conditions were preliminarily calculated based on the total recovery of U at the end of the tests. The dissolution rates ranged from 0.12 to 0.14 ppm/yr for the sum of the total release from the third and fourth cycles of testing (269 days). There was no indication of an effect of alpha radiolysis on the dissolution rate results for UO2 samples with 0, 5, and 10% 233U.

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Dissolution Rate of Flat Plate Limestone in Agitated Sulfuric Acid Solution

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.617.10 ◽

2014 ◽

Vol 617 ◽

pp. 10-13

Author(s):

Daiki Tanaka ◽

Takashi Ito ◽

Shoji Taniguchi ◽

Tadaaki Mizoguchi

Keyword(s):

Sulfuric Acid ◽

Acid Solution ◽

Flat Plate ◽

Dissolution Rate ◽

Surface Area ◽

Acid Concentration ◽

Sulfuric Acid Solution ◽

Chemical Species ◽

Dissolution Rates ◽

Agitated Vessel

In this study, a flat plate limestone of which surface area was accurately defined was dissolved into acid in an agitated vessel. Dissolution rates of limestone were measured under various agitation speeds, temperatures and acid concentrations. As a result, it was found that the rates were controlled by the diffusion of particular chemical species depending on acid concentration.

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Kinetics of UO2 (s) Dissolution in the Presence of Hypochlorite, Chlorite, and Chlorate Solutions

MRS Proceedings ◽

10.1557/proc-1107-599 ◽

2008 ◽

Vol 1107 ◽

Author(s):

Rosa Sureda ◽

Ignasi Casas ◽

Javier Giménez ◽

Joan de Pablo

Keyword(s):

Dissolution Rate ◽

Continuous Flow ◽

Empirical Equation ◽

Uranium Concentration ◽

Experimental Methodology ◽

Dissolution Rates ◽

Experimental Conditions ◽

Flow Through ◽

Kinetics Of ◽

Hypochlorite Anion

AbstractThe influence of hypochlorite, chlorite and chlorate in the UO2 dissolution rate has been studied experimentally using a continuous flow-through reactor. Uranium concentration in each outflow solution was measured as a function of time and dissolution rates were determined once the steady-state was reached. The results obtained show that the influence of the hypochlorite anion concentration on the UO2 dissolution rate can be expressed by the following empirical equationrdiss = 10-8.7±0.1•[ClO-]0.28±0.04The dissolution rates obtained in this work were higher than those previously determined in presence of either oxygen or hydrogen peroxide using the same experimental methodology.In contrast, neither chlorate nor chlorite had any significant effect on the UO2 dissolution rates under the experimental conditions of this work.

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Dissolution kinetics of hydrated calcium aluminates (AFm-Cl) as a function of pH and at room temperature

Mineralogical Magazine ◽

10.1180/minmag.2016.080.161 ◽

2017 ◽

Vol 81 (5) ◽

pp. 1245-1259 ◽

Cited By ~ 5

Author(s):

Nicolas C. M. Marty ◽

Sylvain Grangeon ◽

Catherine Lerouge ◽

Fabienne Warmont ◽

Olivier Rozenbaum ◽

...

Keyword(s):

Dissolution Rate ◽

Room Temperature ◽

Dissolution Kinetics ◽

Dissolution Rates ◽

Ph Values ◽

Surface Areas ◽

Calcium Aluminates ◽

Waste Repositories ◽

Kinetics Of ◽

Hydrated Calcium

AbstractThe determination of reliable weathering/dissolution rates for cement phases is of fundamental importance for the modelling of the temporal evolution of both radioactive waste repositories and CO2 geological storage sites (e.g. waste matrix, plug in boreholes). Here, the dissolution kinetics of AFm-Cl (hydrated calcium aluminates containing interlayer Cl) has been studied using flow-through experiments conducted at pH values ranging from 9.2 to 13. Mineralogical (XRD) and chemical (EPMA, TEM) analyses have been performed to determine the evolution of the phases during the dissolution experiments. For pH values between 10 and 13, the dissolution of AFm-Cl is congruent (i.e. Ca/Al ratios close to 2 both for solids and outlet concentrations). In contrast, the precipitation of amorphous Al-phases and possibly amorphous mixed Al/Ca phases is observed at pH 9.2, leading to Ca/Al ratios in the outlet solutions higher than those of the initial solid. Therefore, at pH 9.2, even if Cl–/OH– exchange occurs, estimation of dissolution rate from released Cl appears to be the best proxy. Dissolution rates were normalized to the final specific surface areas (ranging from 6.1 to 35.4 m2 g−1). Dissolution rate appears to be pH-independent and therefore the far-from-equilibrium dissolution rate at room temperature is expressed as: logR(mol m–2 s–1) = –9.23 ± 0.18

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Aqueous dissolution kinetics of pyrochlore, zirconolite and brannerite at 25, 50, and 75 °C

Radiochimica Acta ◽

10.1524/ract.2000.88.9-11.539 ◽

2000 ◽

Vol 88 (9-11) ◽

Cited By ~ 33

Author(s):

S. K. Roberts ◽

W.L. Bourcier ◽

H.F. Shaw

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Dissolution Rate ◽

Dissolution Kinetics ◽

Kcal Mole ◽

Dissolution Rates ◽

Flow Through ◽

Kinetics Of ◽

Total Dissolution ◽

Calculated Average

We measured the rates of dissolution of pyrochlore, zirconolite, and brannerite in pH-buffered solutions of pH 2, 4, 6, 8, 10, and 12 at temperatures of 25, 50, and 75 °C in flow-through reactors. The dissolution rates for all phases show a minimum near pH 8. Zirconolite dissolves the slowest of the three phases, with a slightly higher rate for pyrochlore and a much higher dissolution rate for brannerite. Brannerite dissolves as much has 30 times faster than zirconolite. The rates increase with temperature, but the magnitude of the increase varies with pH. The calculated average apparent activation energy for dissolution is 6±3 kcal/mole. Dissolution is non-stoichiometric at all pHs. Ti and Hf are released most slowly, and are often below detection limits (1 ppb for Ti, 0.2 ppb for Hf). Releases of Ca, U, Gd, and Ce appear to be stoichiometric below pH 8. At pH 8 and above only U is measurable in solution. Dissolution rates are slow under all conditions, and commonly in the range of 1-100 nm total dissolution/year (between 10

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Bibliography of reports by U.S. Geological Survey personnel on studies of underground nuclear test sites and on waste management studies at the Nevada Test Site and the Waste Isolation Pilot Plant Site, New Mexico, January 1 to December 31, 1982

Open-File Report ◽

10.3133/ofr8423 ◽

1984 ◽

Author(s):

V.M. Glanzman

Keyword(s):

New Mexico ◽

Waste Management ◽

Pilot Plant ◽

Test Site ◽

Nuclear Test ◽

Geological Survey ◽

Nevada Test Site ◽

Waste Isolation Pilot Plant ◽

Plant Site

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The Reactivity of Different Active Forms of Sodium Carbonate with Respect to Sulfur Dioxide

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19922302 ◽

1992 ◽

Vol 57 (11) ◽

pp. 2302-2308

Author(s):

Karel Mocek ◽

Erich Lippert ◽

Emerich Erdös

Keyword(s):

Thermal Decomposition ◽

Liquid Phase ◽

Sulfur Dioxide ◽

Specific Surface ◽

Surface Area ◽

Sodium Carbonate ◽

Room Temperature ◽

Active Form ◽

The Other ◽

Kinetics Of

The kinetics of the reaction of solid sodium carbonate with sulfur dioxide depends on the microstructure of the solid, which in turn is affected by the way and conditions of its preparation. The active form, analogous to that obtained by thermal decomposition of NaHCO3, emerges from the dehydration of Na2CO3 . 10 H2O in a vacuum or its weathering in air at room temperature. The two active forms are porous and have approximately the same specific surface area. Partial hydration of the active Na2CO3 in air at room temperature followed by thermal dehydration does not bring about a significant decrease in reactivity. On the other hand, if the preparation of anhydrous Na2CO3 involves, partly or completely, the liquid phase, the reactivity of the product is substantially lower.

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