Enhancement of the Glass Corrosion in the Presence of Clay Minerals: Testing Experimental Results with an Integrated Glass Dissolution Model

1992 ◽  
Vol 294 ◽  
Author(s):  
Enzo Curti ◽  
N. Godon ◽  
E.Y. Vernaz
Keyword(s):  
Kinetic Equation ◽  
Clay Content ◽  
Distribution Coefficients ◽  
Mineral Surfaces ◽  
Glass Dissolution ◽  
Corrosion Rates ◽  
Glass Corrosion ◽  
Dissolution Model ◽  
Backfill Materials ◽  
Range Of Values

ABSTRACTRecent glass dissolution experiments, conducted at 90°C in the presence of potential backfill materials, indicate remarkably faster glass corrosion in the presence of clay, compared to tests where the glass is leached either alone or with alternative backfill materials. This effect correlates with the clay content in the backfill, and may be attributed to the removal of silica from solution. Sorption, or dissolution with reprecipitation of a silica-rich clay, have been proposed as possible mechanisms for the silica consumption.The results of some experiments have been tested against a glass dissolution model, in which a widely used kinetic equation for glass corrosion is coupled with diffusive silica transport through a single porosity, linearly sorbing medium, which represents the backfilling. Because the glass corrosion rates imposed by the kinetic equation are inversely proportional to the silicic acid concentration of the leachant contacting the glass, the model predicts enhanced glass dissolution if silica is sorbed by the porous medium.The experimental data proved to be consistent with the predicted enhancement of the glass dissolution. Moreover, the model-estimated distribution coefficients for silica sorption (Kd) fall within the range of values extracted from available literature data, thus supporting the hypothesis that the observed high corrosion rates are due to sorption of silica on the clay mineral surfaces.

Diffusion of Radionuclides in Brine-Saturated Backfill Barrier Materials

1982 ◽  
Vol 15 ◽  
Author(s):  
E. J. Nowak
Keyword(s):  
Sodium Titanate ◽  
Distribution Coefficients ◽  
Barrier Materials ◽  
Compacted Bentonite ◽  
Metal Diffusion ◽  
Diffusion Cells ◽  
Linear Sorption ◽  
Backfill Materials ◽  
Cylindrical Diffusion ◽  
Apparent Distribution

ABSTRACTThe diffusion of cesium(I), strontium(II), pertechnetate and europium in brine-saturated backfill materials was measured. Plastic diffusion cells containing cylindrical diffusion columns were used for low density backfill materials. The diffusion of gamma-emitters was followed by a gamma scanning technique. Metal diffusion cells constructed entirely from Hastelloy C-276 were used for the diffusion of pertechnetate in highly compacted bentonite. Apparent distribution coefficients calculated from diffusion data are (a) 0.02 m3 /kg for cesium(I) in 40 wt.% mordenite and 60 wt.% bentonite; (b) 0.04 m3/kg for strontium(II) in 10 wt.% sodium titanate and 90 wt.% bentonite; (c) 0.5 m3/kg for pertechnetate in 70 wt.% charcoal and 30 wt.% bentonite; and (d) 3 m3/kg for europium in 100% bentonite. Backfill effectiveness estimates based on batch sorption measurements were supported by these results;however, the diffusion results for europium did not agree well with a model for diffusion retarded by linear sorption. First measurements of pertechnetate diffusion in highly compacted bentonite suggest that anion exclusion may play a role in reducing mass transport rates of anions in this material. Needs for diffusion measurements that take into account site-specific materials interactions are described.

About U(t) form of pH-dependence of glass corrosion rates at zero surface to volume ratio

2015 ◽  
Vol 1744 ◽  
pp. 153-161 ◽  
Author(s):  
Michael I. Ojovan ◽  
William E. Lee
Keyword(s):  
Nuclear Waste ◽  
Low Temperatures ◽  
Ph Dependence ◽  
Effective Diffusion ◽  
Volume Ratio ◽  
Surface Layers ◽  
Near Surface ◽  
Numerical Examples ◽  
Corrosion Rates ◽  
Glass Corrosion

ABSTRACTThe pH-dependence of glass corrosion rates has a well-known U-shaped form with minima for near-neutral solutions. This paper analyses the change of U-shaped form with time and reveals that the pH dependence evolves even for solutions that have pH not affected by glass corrosion mathematically corresponding to a zero surface to volume ratio. The U(t) dependence is due to changes of concentration profiles of elements in the near-surface layers of glasses in contact with water and is most evident within the initial stages of glass corrosion at relatively low temperatures. Numerical examples are given for the nuclear waste borosilicate glass K-26 which is experimentally characterised by an effective diffusion coefficient of caesium DCs = 4.5 10-12 cm2/day and by a rate of glass hydrolysis in non-saturated groundwater as high as rh = 100 nm/year The changes of U-shaped form need to be accounted when assessing the performance of glasses in contact with water solutions.

Mobility of Dicamba, Picloram and 2,4-D in Soil Columns

Weed Science ◽  
1977 ◽  
Vol 25 (2) ◽  
pp. 159-162 ◽  
Author(s):  
R. Grover
Keyword(s):  
Sandy Loam ◽  
Organic Matter Content ◽  
Clay Content ◽  
Distribution Coefficients ◽  
Matter Content ◽  
Soil Columns ◽  
Canadian Prairie ◽  
General Order ◽  
Soil Clay Content ◽  
Acid Herbicides

The movement of dicamba (3,6-dichloro-o-anisic acid), picloram (4-amino-3,5,6-trichloropicolinic acid), and 2,4-D [(2,4-dichlorophenoxy)acetic acid] was studied in five Canadian prairie soils using soil columns. The three acid herbicides showed the following general order of decreasing mobility in the five soils: Asquith sandy loam > Indian Head loam > Regina heavy clay > Weyburn Oxbow loam > Melfort loam, thus indicating an inverse relationship between adsorption and mobility. In general, the distribution coefficients (kd) were comparable to the corresponding Freundlich constants (k) and these were significantly related to the soil organic matter content, to a lesser extent to soil pH, and not correlated with soil clay content. The maximum concentrations of all three herbicides in the column effluents were well below their respective water solubilities and were inversely related to the distribution coefficients. The calculated values for the amounts of precipitation required to leach the three herbicides to a depth of 10 cm showed the following order of mobility: dicamba > picloram > 2,4-D.

Diffusion of Radionuclides in Compacted Bentonite : Results from Combined Glass Dissolution and Migration Tests

1994 ◽  
Vol 353 ◽  
Author(s):  
Masaki Tsukamoto ◽  
T. Ohe ◽  
T. Fujita ◽  
R. HesbÖl ◽  
H-P. Hermansson
Keyword(s):  
Dry Density ◽  
Apparent Diffusion Coefficients ◽  
Glass Dissolution ◽  
Glass Corrosion ◽  
Gas Atmosphere ◽  
Apparent Diffusion ◽  
Calculation Results ◽  
The Difference ◽  
And Migration ◽  
Elemental Mass

AbstractDiffusion experiments of radionuclides in compacted sodium bentonite with a dry density of 1.0 g/cm3 were performed in nitrogen gas atmosphere at 90 °C for 208 d and 375 d. The corrosion experiments of crushed radioactive glass, JSS-A, carried out simultaneously to provide the source of the radionuclides for the diffusion experiments. The normalized elemental mass losses of cesium isotopes and 238Pu were lower than those of boron (ca. 10 g/m2) probably because of the difference of sorption and/or precipitation. The apparent diffusion coefficients of 238Pu, 234U and 125Sb were determined to be 2x 10-14 m2/s, 5x 10-12 m2/s and 2x 10-12 m2/s, respectively. The distribution coefficient of Pu estimated from the diffusion data was of the same order as that from batch sorption experiments. The glass corrosion and the plutonium diffusion were described by the geochemical codes PHREEQE, STRAG4 and GESPER. The calculation results well fitted the observed data.

Effects of Rocks and Backfill Materials on Waste Glass Leaching

1985 ◽  
Vol 50 ◽  
Author(s):  
K. Ishiguro ◽  
N. Sasaki ◽  
H. Kashihara ◽  
M. Yamamoto
Keyword(s):  
Waste Glass ◽  
Distilled Water ◽  
Leach Rate ◽  
Glass Dissolution ◽  
Crushed Granite ◽  
Backfill Materials ◽  
Long Term Experiment ◽  
Static Conditions ◽  
Glass Leaching

AbstractExtensive studies have been made on the interactions between a waste glass and repository materials under static conditions. One of the PNC reference glasses was leached in the solution prepared from water in contact with crushed granite, tuff, diabase and backfill materials such as bentonite and zeolite. The leachant solutions except for some bentonite solutions reduced the glass leach rate compared with that measured in distilled water. The extent of the reduction was a function of silicon concentration in solution. The bentonite solutions enhanced the glass dissolution rate by a factor of 2 to 3 at low bentonite/water ratios but the effect was found to be less important at high bentonite/water ratios and in the long-term experiment. Addition of granite and zeolite to the bentonite solutions decreased the leach rate below the value measured in distilled water.

scholarly journals Dissolution Rates of DWPF Glasses from Long-Term PCT

1996 ◽  
Vol 465 ◽  
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.

Kinetics of the Steel Corrosion in field waters

2008 ◽  
Vol 59 (4) ◽  
Author(s):  
Vasile Dumitrescu ◽  
Maria Moraru ◽  
Ileana Camenita ◽  
Ioan Viorel Branzoi ◽  
Alexandra Schiopescu
Keyword(s):  
Kinetic Equation ◽  
Natural Gas ◽  
Steel Corrosion ◽  
Corrosion Rates ◽  
Experimental Researches ◽  
Kinetics Of ◽  
Dynamics Process

This paper presents the experimental researches regarding the corrosion of some steel materials in field waters attending natural gas. The corrosion rates of tested steels are determined and the results are discussed. It is found that the dynamics process is described by an exponential kinetic equation.

Surface Complexation

1996 ◽  
Author(s):  
Craig M. Bethke
Keyword(s):  
Mass Balance ◽  
Surface Complexation ◽  
Distribution Coefficients ◽  
Mineral Surfaces ◽  
Aluminum Oxides ◽  
Geochemical Model ◽  
Surface Areas ◽  
Dissolved Ions ◽  
Electrical State ◽  
Geochemical Models

An important consideration in constructing certain types of geochemical models, especially those applied to environmental problems, is to account for the sorption of ions from solution onto mineral surfaces. Metal oxides and aluminosilicate minerals, as well as other phases, can sorb electrolytes strongly because of their high reactivities and large surface areas (e.g., Davis and Kent, 1990). When a fluid comes in contact with minerals such as iron or aluminum oxides and zeolites, sorption may significantly diminish the mobility of dissolved components in solution, especially those present in minor amounts. Sorption, for example, may retard the spread of radionuclides near a radioactive waste repository or the migration of contaminants away from a polluting landfill. In acid mine drainages, ferric oxide sorbs heavy metals from surface water, helping limit their downstream movement (see Chapter 23). A geochemical model useful in investigating such cases must provide an accurate assessment of the effects of surface reactions. Many of the sorption theories now in use are too simplistic to be incorporated into a geochemical model intended for general use. To be useful in modeling electrolyte sorption, a theory must account for the electrical charge on the mineral surface and provide for mass balance on the sorbing sites. In addition, an internally consistent and sufficiently broad database of sorption reactions must accompany the theory. The Freundlich and Langmuir theories, which use distribution coefficients Kd to set the ratios of sorbed to dissolved ions, are applied widely in groundwater studies (Domenico and Schwartz, 1990) and used with considerable success to describe sorption of uncharged organic molecules (Adamson, 1976). The models, however, do not account for the electrical state of the surface, which varies sharply with pH, ionic strength, and solution composition. Freundlich theory prescribes no concept of mass balance, so that a surface might be predicted to sorb from solution without limit. Both theories require that distribution coefficients be determined experimentally for individual fluid and rock compositions, and hence both theories lack generality. Ion exchange theory (Stumm and Morgan, 1981; Sposito, 1989) suffers from similar limitations. Surface complexation models, on the other hand, account explicitly for the electrical state of the sorbing surface (e.g., Adamson, 1976; Stumm, 1992).

Experimental investigation on buffer/backfill materials for radioactive waste repository downward facing sorption additivity of cesium, strontium and cobalt with different concentrations

Kerntechnik ◽  
2021 ◽  
Vol 86 (5) ◽  
pp. 375-381
Author(s):  
C.-P. Lee ◽  
Y. Hu ◽  
Y. Sun ◽  
Y. Shi ◽  
N.-C. Tien ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Distribution Coefficients ◽  
Test Method ◽  
Radioactive Waste Disposal ◽  
Batch Test ◽  
Backfill Materials ◽  
Mixing Proportion ◽  
Synthetic Groundwater ◽  
Waste Repository ◽  
Sorption Characteristics

Abstract Buffer/backfill materials for radioactive waste disposal sites consist of pure bentonite or bentonite-rock mixtures. In this study, the batch test method was used to obtain the sorption characteristics of important radionuclides such as Cs, Sr and Co on buffer/backfill materials; i. e., mixing Wyoming MX-80 bentonite or local Taiwanese Zhi-Shin bentonite with possible host rock (argillite and granite) in different proportions (0∼100%). The distribution coefficients (Kd) for Cs, Sr and Co were obtained from the experiments. The distribution coefficient for the bentonite-rock mixtures were found, with more than 50% of mixing proportion of bentonite to argillite or granite, to have very similar values to that of pure bentonite. Furthermore, it was clearly found that the sorption of Cs, Sr and Co to bentonite-rock mixtures is decreased as ionic strength of the liquid phase is increased from 0.001M to 1M for NaCl solutions. According to the experimental results, in synthetic groundwater, it is quite convenient and helpful to assess the distribution coefficients (Kd) of Cs, Sr and Co for buffer/backfill materials using batch sorption experiments with bentonite-rock mixtures of fixed mixing proportions.

The Interaction Between Nuclear Waste Glasses and Clay-II

1989 ◽  
Vol 176 ◽  
Author(s):  
P. Van Iseghem ◽  
K. Berghman ◽  
W. Timmermans
Keyword(s):  
Detection Limit ◽  
Corrosion Rate ◽  
Diffusion Process ◽  
Gamma Irradiation ◽  
Nuclear Waste ◽  
Experimental Conditions ◽  
Glass Dissolution ◽  
Glass Corrosion ◽  
Irradiation Field

ABSTRACTThe interaction between simulated HLW glasses and clay has been investigated, as part of a larger programme to evaluate the performance of vitrified HLW in repository conditions. Experimental conditions were carefully chosen to simulate repository conditions as close as possible. The glass corrosion seems to be controlled by a diffusion process, but there are indications of a (small) final corrosion rate. The leaching of 134Cs, 90Sr, 239Pu and 241Am is characterized by extremely small mobile concentrations leached (for 239pu and 241Am, below detection limit). The presence of a gamma irradiation field does not increase the glass dissolution. The production of radiolythic hydrogen is strongly reduced by the presence of clay.

Sign in / Sign up

Export Citation Format

Share Document