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.

Materials Interactions Relating to Long-Term Geologic Disposal of Nuclear Waste Glass

1986 ◽  
Vol 84 ◽  
Author(s):  
Ned E. Bibler ◽  
Carol M. Jantzen
Keyword(s):  
Nuclear Waste ◽  
Review Paper ◽  
Waste Glass ◽  
Waste Form ◽  
Glass Waste ◽  
Waste Package ◽  
Geologic Disposal ◽  
Nuclear Waste Glass ◽  
Backfill Materials

AbstractIn the geologic disposal of nuclear waste glass, the glass will eventually interact with groundwater in the repository system. Interactions can also occur between the glass and other waste package materials that are present. These include the steel canister that holds the glass, the metal overpack over the canister, backfill materials that may be used, and the repository host rock. This review paper systematizes the additional interactions that materials in the waste package will impose on the borosilicate glass waste form-groundwater interactions. The repository geologies reviewed are tuff, salt, basalt, and granite. The interactions emphasized are those appropriate to conditions expected after repository closure, e.g. oxic vs. anoxic conditions. Whenever possible, the effect of radiation from the waste form on the interactions is examined. The interactions are evaluated based on their effect on the release and speciation of various elements including radionuclides from the glass. It is noted when further tests of repository interactions are needed before long-term predictions can be made.

Remaining Uncertainties in Predicting Long-Term Performance of Nuclear Waste Glass From Experiments

1993 ◽  
Vol 333 ◽  
Author(s):  
B. Grambow ◽  
Kernforschungszentrum Karlsruhe
Keyword(s):  
Current Knowledge ◽  
Research Work ◽  
Waste Glass ◽  
Dissolution Mechanism ◽  
Glass Dissolution ◽  
Radionuclide Release ◽  
Long Term Performance ◽  
Term Performance ◽  
Term Maintenance

ABSTRACTThe current knowledge on the glass dissolution mechanism and the representation of glass dissolution concepts within overall repository performance assessment models are briefly summarized and uncertainties related to mechanism, radionuclide chemistry and parameters are discussed. Understanding of the major glass dissolution processes has been significantly increased in recent years. Long-term glass stability is related to the long-term maintenance of silica saturated conditions. The behavior of individual radionuclides in the presence of a dissolving glass has not been sufficiently and results do not yet allow meaningful predictions. Conservative long-term predictions of glass matrix dissolution as upper limit for radionuclide release can be made with sufficient confidence, however these estimations generally result in a situation were the barrier function of the glass is masked by the efficiency of the geologic barrier. Realistic long-term predictions may show that the borosilicate waste glass contributes to overall repository safety to a much larger extent than indicated by overconservatism. Today realistic predictions remain highly uncertain and much more research work is necessary. In particular the long-term rate under silica saturated conditions needs to be understood and the behavior of individual radionuclides in the presence of a dissolving glass deserves more systematic investigations.

Investigations on the Role of Surface Layers in HLW Glass Leaching

1985 ◽  
Vol 50 ◽  
Author(s):  
R. Conradt ◽  
H. Roggendorf ◽  
H. Scholze
Keyword(s):  
Corrosion Test ◽  
Protective Effects ◽  
Reaction Products ◽  
Surface Layers ◽  
Hydrothermal Conditions ◽  
Glass Dissolution ◽  
Salt Brine ◽  
Glass Leaching

AbstractA corrosion test series was performed to clarify the role of reaction product layers on the corrosion of a simulated HLW borosilicate glass in a salt brine under hydrothermal conditions. The layers were unprotective at 200°C. At 120°C, slight protective effects ocurred when the leachant contained dissolved reaction products. The consequence for the long term behaviour between 120 and 200°C is a constant glass dissolution rate.

Hydrolysis of R7T7 Nuclear Waste Glass in Dilute Media: Mechanisms and Rate as a function of Ph

1990 ◽  
Vol 212 ◽  
Author(s):  
T. Advocat ◽  
J. L. Crovisier ◽  
E. Vernaz ◽  
G. Ehret ◽  
H. Charpentier
Keyword(s):  
Nuclear Waste ◽  
Aqueous Media ◽  
Glass Network ◽  
Surface Region ◽  
Waste Glass ◽  
Transition Elements ◽  
Acid Media ◽  
Glass Dissolution ◽  
Nuclear Waste Glass ◽  
Static Conditions

ABSTRACTR7T7 nuclear waste glass dissolution in highly dilute aqueous media under static conditions at 90°C occurs according to two different mechanisms depending on the solution acidity. In acid media (pH 4.8 and 5.5), preferential extraction of glass network modifiers results in the formation of an alkali metal-depleted surface region on which amorphous and crystallized (phosphate) compounds rich in transition elements precipitate. Steady-state dissolution conditions are not reached, as attested by variable normalized SI, B and Na mass losses. Glass dissolution is stoichiometric in basic media (pH 7 to 10): the strong bonds of the silicated network are broken at a rate that increases with the pH: the glass dissolution rate increases by a factor of 15 between pH 7 and 10. Under these conditions, alteration products at the glass/solution interface do not constitute a short-term kinetic barrier against the release of the major glass components.

Waste Glass Leaching: Chemistry and Kinetics

1986 ◽  
Vol 84 ◽  
Author(s):  
Bruce C. Bunker
Keyword(s):  
Release Kinetics ◽  
Glass Structure ◽  
Waste Glass ◽  
Release Rates ◽  
Glass Dissolution ◽  
Surface Alteration ◽  
Order Of Magnitude ◽  
Level Of Understanding ◽  
Radionuclide Release ◽  
Glass Leaching

AbstractNuclear waste glass leaching has been studied extensively during the past ten years. Although much has been learned concerning the kinetics and mechanisms of glass dissolution, it does not appear that accurate predictions can yet be made concerning the release kinetics for specific elements from a given glass as a function of environmental conditions. In order to reliably predict elemental release rates, one needs to know: 1) how a given element is incorporated into the glass structure, 2) how specific sites in the glass react with water, 3) how the composition and reactivity of the leachate influence glass reactivity, 4) how the structure and reactivity of the glass changes in surface alteration layers, and 5) how glass dissolution modifies the chemistry of the leachate. At our current level of understanding, we are only able to make qualitative predictions concerning each of the above factors which allow us to make “order of magnitude” or “upper limit” predictions for radionuclide release rates.

scholarly journals Chemical durability of vitrified wasteforms: effects of pH and solution composition

2012 ◽  
Vol 76 (8) ◽  
pp. 2919-2930 ◽  
Author(s):  
C. A. Utton ◽  
S. W. Swanton ◽  
J. Schofield ◽  
R. J. Hand ◽  
A. Clacher ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Chemical Durability ◽  
Waste Glass ◽  
High Level Waste ◽  
Solution Composition ◽  
Waste Products ◽  
High Ph ◽  
Glass Dissolution ◽  
Soluble Components

AbstractVitrification is used for the immobilization and conditioning of high-level waste (HLW) arising from the reprocessing of spent nuclear fuel in the UK. Vitrification is also under consideration for the immobilization of certain intermediate-level wastes (ILW), where there may be advantages of volume reduction and removal of uncertainties in long-term waste behaviour, compared to encapsulation in a cement grout. This paper gives an overview of recent work into the chemical durability of UK vitrified wasteforms to inform the technical specification for the disposal facilities for these waste products and the treatment of their long-term behaviour in post-closure performance assessment. This has included: (1) measurements of the initial glass dissolution rates of a simulated HLW Magnox waste glass in a range of groundwater types representative of potential UK host geologies and in simulated high pH near-field porewaters relevant to potential disposal concepts, using Product Consistency Test type-B (PCT-B) at 40°C; and (2) durability testing of three simulant ILW glasses in a saturated calcium hydroxide buffered solution to simulate conditions in cement-based disposal vaults, using PCT-B tests at 50°C.The experimentally defined initial rate of HLW Magnox waste glass dissolution in a range of simulated groundwater compositions appears to be similar regardless of the ionic strength and major element composition of the solution. The release of caesium from HLW Magnox waste glass appears to be sensitive to solution composition. Caesium is selectively retained in the glass compared to other soluble components in the two low ionic strength solutions, but is released at similar rates to other soluble components in the three groundwaters and Ca(OH)2 solution. Whether this change in caesium retention is an ionic strength effect or is related to changes in the nature of the surface alteration layer formed on the glass, has yet to be established. For HLW Magnox waste glass, dissolution is accelerated at high pH in NaOH solution, however, the presence of calcium acts to mitigate the effects of high pH, at least initially. In Ca(OH)2 solution, calcium is found to react with all the glasses studied leading to the formation of calcium-containing alteration products. The initial dissolution behaviour in Ca(OH)2 solution varies with glass composition and in particular appears to be sensitive to the boron content.

Corrosion of Radioactive, Crushed Waste Glass

1988 ◽  
Vol 127 ◽  
Author(s):  
Inga-Kari Björner ◽  
H. Christensen ◽  
H. P. Hermansson ◽  
M Tsukamoto ◽  
L Werme
Keyword(s):  
Reaction Time ◽  
Radioactive Waste ◽  
Release Rate ◽  
Waste Glass ◽  
Leach Rate ◽  
Order Of Magnitude ◽  
Presence And Absence

ABSTRACTThe corrosion experiments of crushed, radioactive waste glass at Studsvik within phase V of the JSS Project are described. The experiments were performed with high S/V ratios (1100 and 4000 m−1) which resulted in silica saturation already after the shortest reaction time studied (91 d).Thee long term leach rate of the soluble elements is about 10−3 g.m d−1, both in the presence and absence of bentonite. In the presence of bentonite + magnetite the leach rate is higher, about 0.007 g.m1.d−2. The release rate to the solution of Cs is one order of magnitude lower and that of Pu-238 + Am-241 three orders of magnitude lower than the release rate of the soluble elements Mo and B. Most of the Pu-238 and Am-241 fraction, found in the solution, is present as colloids.

Obtaining Solubility Constants to Describe the Incongruent Dissolution of SON68 Waste Glass by an Equilibrium Ideal Solid Solution Model Approach

2006 ◽  
Vol 932 ◽  
Author(s):  
Diederik Jacques ◽  
Karel Lemmens
Keyword(s):  
Solid Solution ◽  
Solid Phase ◽  
Water System ◽  
Waste Glass ◽  
High Level Waste ◽  
Distilled Water ◽  
Incongruent Dissolution ◽  
Glass Dissolution ◽  
High Level ◽  
End Members

ABSTRACTOne of the waste forms resulting from the Belgian programme for nuclear energy is the R7T7 high level waste glass, simulated by the SON68 glass. When exposed to distilled water or synthetic interstitial clay water, SON68 glass dissolves incongruently, releasing some elements (B, Li, Na) faster to the solution than others (Si, Al, Ca). The objective of this study is to describe the composition of the leachate in contact with inactive SON68 glass by assuming congruent glass dissolution followed by the precipitation of a secondary solid phase represented as an ideal solid solution in equilibrium with the leachate. Experimental SON68 dissolution data in distilled water was available at three temperatures. The solubility of the different end members in the solid solution is optimized using the available data for each temperature. The temperature dependence of the different end members was then obtained by Van 't Hoff equation. The calibrated model can describe the composition of the leachate and the altered glass phase during glass dissolution at different temperatures. The model, calibrated for the distilled water system, could successfully describe the composition of the leachate during glass dissolution experiments in a synthetic clay water system.

An overview of simple basic equations used in HLW glass dissolution modeling: consequences for long term leaching and element profiles

2006 ◽  
Vol 932 ◽  
Author(s):  
Marc Aertsens
Keyword(s):  
Experimental Data ◽  
Analytical Solution ◽  
Water Solution ◽  
Numerical Code ◽  
Leach Rate ◽  
Glass Dissolution ◽  
Basic Assumptions ◽  
Basic Equations ◽  
The Relationship

ABSTRACTOver the last decades, several models describing glass dissolution have been published. Starting from the basic equations in their simplest form, the relationships between models are evaluated to address the following questions: 'What is the relationship between their basic assumptions?, What is the resulting long term leach rate? and, Which element profiles do they allow one to predict?' Although not part of it, this paper could complement the European project GLAMOR, where two models describing the dissolution of glass in a water solution, the r(t) and the GM models, are used by several groups to fit the same sets of experimental data. In this paper, other models are considered as well and all models are compared with each other.From comparison with the Boksay model, which uses the same equations, a simplification is suggested for the GM model concerning the water diffusion in the glass. The use of the numerical code developed to solve part of it, can mostly be avoided by using the analytical solution of the Boksay model.

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