Effect of Surface Layers on the Dissolution of Nuclear Waste Glasses

1993 ◽  
Vol 333 ◽  
Author(s):  
Shi-Ben Xing ◽  
Andrew C. Buechele ◽  
Ian L. Pegg
Keyword(s):  
Surface Layer ◽  
Nuclear Waste ◽  
Glass Composition ◽  
Reaction Rates ◽  
Surface Layers ◽  
Linear Effect ◽  
Glass Dissolution ◽  
Important Challenge ◽  
Saturation Effects ◽  
Glass Powders

ABSTRACTExplanation of the striking non-linear effect of glass composition on the aqueous dissolution represents an important challenge to existing dissolution mechanisms. Surface layers that are formed during glass dissolution may play an important role in this effect. One chemically reactive and one less-reactive nuclear waste glass (leachate concentrations differ by about a factor of 10) were reacted in deionized water. Two types of glass powders were used: Type A powders were pristine glass powders; Type B powders were the glass powders which had been reacted for 120 days to develop the surface layers. Both the solution concentrations and the surface layers were investigated. The experimental observations indicate that: (i) There is a range of glass compositions over which small differences in composition lead to large changes in both reaction rates and surface layer thickness; and (ii) The reaction rate is strongly affected by the formation of the surface layer (the layer appears to be protective) and cannot be explained in terms of saturation effects alone. The findings are contrary to the conclusion of a previous study and serve to highlight the inadequacy of existing dissolution models predicated on an overly simplistic mechanism, especially with regard to glass composition effects.

Electrokinetics, Adsorption and Colloid Study of Simulated Nuclear Waste Glasses Leached in Aqueous Solutions

1984 ◽  
Vol 44 ◽  
Author(s):  
Cheng T. Lee ◽  
D. E. Clark
Keyword(s):  
Surface Layer ◽  
Nuclear Waste ◽  
Glass Surface ◽  
Charged Particles ◽  
Electrostatic Repulsion ◽  
Surface Layers ◽  
Short Term ◽  
Chloride Solutions ◽  
Zeta Potentials ◽  
Glass Surfaces

AbstractZeta potentials of SRL-131-29.8% TOS simulated nuclear waste glasses leached in D.I. water, Al, Ca, Mg, and Zn chloride solutions at 90°C were measured as a function of leaching time. For short term leaching, the adsorption of Ca, Mg, Zn and Al reverses the glass surface potential from negative to positive. Colloids were found to be stable in D.I. water and AICl3 solutions after leaching, presumably due to the electrostatic repulsion between the glass surface and similarly charged particles. Colloids were not found in Mg, Zn or Ca chloride solutions after leaching; instead, a relatively thick metasilicate surface layer was formed on glass surfaces leached in these solutions. The concentration of Si in solution is reduced by the formation of these surface layers.

The effect of phosphate melt cooling rate on phase composition and leach resistance of final waste form

MRS Advances ◽  
2017 ◽  
Vol 3 (20) ◽  
pp. 1085-1091 ◽  
Author(s):  
Konstantin V. Martynov ◽  
Elena V. Zakharova ◽  
Sergey V. Stefanovsky ◽  
Boris F. Myasoedov
Keyword(s):  
Nuclear Waste ◽  
Glass Composition ◽  
Crystalline Material ◽  
Slow Cooling ◽  
Leach Rate ◽  
Glass Dissolution ◽  
Phosphate Phase ◽  
Partial Crystallization ◽  
Melt Cooling ◽  
Melt Solidification

ABSTRACTSlow cooling of phosphate melt at liquid nuclear waste solidification yields glass-crystalline material. Partial crystallization during melt solidification results in elemental partitioning among crystalline phase and glass: Al, Cr, Fe are concentrated in the crystalline phosphate phase while Ca, Ni, La, U enter predominantly in the residual glass. Glass dissolution rate and leach rate of La and U as rare earth and actinide surrogates depends strongly on the glass composition, for example reduction of Al2O3 content in the glass to ∼10-12 wt.% increases leachability by three orders of magnitude as compared to the glass with specified composition (∼18-22 wt.% Al2O3).

Role of Surface Layers in the Leaching Behavior of Glass

1988 ◽  
Vol 125 ◽  
Author(s):  
B.K. Zoitos ◽  
D.E. Clark
Keyword(s):  
Surface Layer ◽  
Nuclear Waste ◽  
Surface Composition ◽  
Analytical Techniques ◽  
Surface Layers ◽  
Leaching Behavior ◽  
Leach Rate ◽  
Layer Analysis ◽  
Nuclear Waste Glass

ABSTRACTResults are presented from a two-year dynamic leach test of nuclear waste glass under conditions designed to simulate those of the Stripa granite repository. Solution and surface analytical techniques were used to assess the glass leach rate as well as surface composition and morphology. Glass leach rates were observed to decrease by a factor of two during the first six months. This effect is attributed to the formation of a protective surface layer. Analysis of this layer shows it to be rich in silicon and iron and depleted in lithium, sodium and boron. It was also found that the layer is subject to dissolution.

Secondary Phase Formation and the Microstructural Evolution of Surface Layers During Vapor Phase Alteration of the French Son68 Nuclear Waste Glass at 200 °C

1995 ◽  
Vol 412 ◽  
Author(s):  
W. L. Gong ◽  
R. C. Ewing ◽  
L. M. Wang ◽  
E. Vernaz ◽  
J. K. Bates ◽  
...  
Keyword(s):  
Surface Layer ◽  
Nuclear Waste ◽  
Vapor Phase ◽  
Rare Earths ◽  
Waste Glass ◽  
Transition Elements ◽  
Surface Layers ◽  
Crystalline Phases ◽  
Developed Surface ◽  
Nuclear Waste Glass

AbstractThe SON68 inactive “R7T7” composition is the French reference glass for the LWR nuclear waste glass. Vapor phase alteration was used to accelerate the reaction progress of glass corrosion and to develop the characteristic suite of secondary, alteration phases. Extensive solid-state characterization (AEM/SEM/HRTEM) was completed on six inactive R7T7 waste glasses which were altered in the presence of saturated water vapor (200 °C) for 91, 241, 908, 1000, 1013, and 1021 days. The AEM samples were examined in cross-section (lattice-fringe imaging, microdiffraction, and quantitative thin-film EDS analysis). The glass monoliths were invariably covered with a thin altered rind. The layer became thicker with time: 0.5μm for 22 days; 4 μm for 91 days; 6 μm for 241 days; 10 μm for 908 days; 26 μm for 1013 days; and <35μm for 1021 days. The composite alteration layer of the SON68 samples is at least four time less thick than that of the SRL 131 glass composition.Six distinctive zones, based on phase chemistry and microstructure, were distinguished within the well-developed surface layers. Numerous crystalline phases such as analcime, tobermorite, apatite, and weeksite were identified on the surfaces of the reacted glasses as precipitates. Two crystalline phases, Ag2TeO3 and (Ca,Sr)Mo3O9(OH)2, were found within the inner zones of surface layers, and they must have nucleated in situ, indicating that Ag, Te, Sr, and Mo can be retained within the surface layer. The majority of the surface layer volume is composed of two morphologically and chemically different structures: one consists of well-crystallized fibrous smectite aggregates occurring along with cavities, the A-domain; and the other consists of poorlycrystallized regions containing needle-like smectite (montmorillonite) crystallites, a silica-rich amorphous matrix, and possibly ZrO2 particles, the B-domain. The retention of rare-earths and Zr mostly occurred within B-domains and that of transition elements, such as Zn, Cr, Ni, and Mn, in A-domains. The recrystallization of poorly-crystallized B-domains into well-crystallized Adomains may influence the long-term behavior of rare-earths, Zr, and transition elements. The mechanism of surface layer formation during vapor phase alteration is discussed based on the cross-sectional AEM studies of surface layers of the SON68 waste glasses.

scholarly journals Forty years of durability assessment of nuclear waste glass by standard methods

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Clare L. Thorpe ◽  
James J. Neeway ◽  
Carolyn I. Pearce ◽  
Russell J. Hand ◽  
Adam J. Fisher ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Nuclear Waste ◽  
Glass Composition ◽  
Radioactive Waste Disposal ◽  
Experimental Conditions ◽  
Standard Methods ◽  
Glass Dissolution ◽  
Nuclear Waste Glass ◽  
Safety Case ◽  
Durability Assessment

AbstractStandard methods to assess the durability of vitrified radioactive waste were first developed in the 1980’s and, over the last 40 years, have evolved to yield a range of responses depending on experimental conditions and glass composition. Mechanistic understanding of glass dissolution has progressed in parallel, enhancing our interpretation of the data acquired. With the implementation of subsurface disposal for vitrified radioactive waste drawing closer, it is timely to review the available standard methodologies and reflect upon their relative advantages, limitations, and how the data obtained can be interpreted to support the post-closure safety case for radioactive waste disposal.

Detailed Processes of Surface Layer Formation in Borosilicate Waste Glass Dissolution

1984 ◽  
Vol 44 ◽  
Author(s):  
John F. Flintoff ◽  
Alan B. Harker
Keyword(s):  
Chemical Structure ◽  
Development Process ◽  
Waste Glass ◽  
Surface Layers ◽  
Glass Dissolution ◽  
Surface Spectroscopy ◽  
Local Saturation ◽  
Saturation Effects ◽  
Layer Development ◽  
Surface Layer Formation

AbstractThe morphology and chemical structure of surface layers formed during the aqueous leaching of the SRP-type borosilicate waste glass in simulated ground waters have been studied by SEM/EDXS, XRD, and surface spectroscopy. Comparison of layers formed in deionized, silicate, and brine waters shows the processes of both corrosion and precipitation to be highly localized. The corrosion process proceeds on the glass surface preferentially at points of stress and inhomogeneity. Crystalline and noncrystalline precipitates form in well-defined regions within the surface layers indicating the layer development process to be dominated by species migration and local saturation effects.

scholarly journals Prediction of Glass Durability as a Function of Environmental Conditions

1988 ◽  
Vol 125 ◽  
Author(s):  
C. M. Jantzen
Keyword(s):  
Nuclear Waste ◽  
Environmental Conditions ◽  
Glass Composition ◽  
Oxidation Potential ◽  
Natural Environments ◽  
Matrix Elements ◽  
Hydration Free Energy ◽  
Solution Ph ◽  
Pourbaix Diagrams ◽  
Glass Dissolution

ABSTRACTA thermodynamic model of glass durability has been applied to natural, ancient, and nuclear waste glasses. The durabilities of over 150 different natural and man-made glasses, including actual ancient Roman and Islamic glasses (Jalame ca. 350 A. D., Nishapur 10-11th century A. D., and Gorgon 9-11th century A.D.), have been compared. Glass durability has been shown to be a function of the thermodynamic hydration free energy, δGhvd, which can be calculated from glass composition and solution pH. Using this approach the durability of the most durable nuclear waste glasses examined was ˜106 years by comparison with the durability of the natural basalts of ˜106 years. The least durable waste glass formulations were comparable in durability to the most durable simulated medieval window glasses of ˜103 years. In this manner, the durability of nuclear waste glasses has been interpolated to be ˜106 years and no less than 103 years.Hydration thermodynamics have been shown to be applicable to the dissolution of glass in various natural environments. Groundwater-glass interactions relative to geologic disposal of nuclear waste, hydration rind dating of obsidians, and/or other archeological studies can be modeled, e.g. the relative durabilities of six simulated medieval window glasses have been correctly predicted for both laboratory (one month) and burial (5 year) experiments.The effects of solution pH on glass dissolution has been determined experimentally for the 150 different glasses and can be predicted theoretically by hydration thermodynamics. The effects of solution redox (oxidation potential expressed as Eh) on dissolution of glass matrix elements such as Si and B have been shown to be minimal. The combined effects of solution pH and Eh have been described and unified by construction of thermodynamically calculated Pourbaix (pH-Eh) diagrams for glass dissolution. The Pourbaix diagrams have been quantified to describe glass dissolution as a function of environmental conditions by use of the data derived from hydration thermodynamics.

ABUNDANCE ANOMALIES PRODUCED BY NUCLEAR REACTIONS IN STELLAR SURFACE LAYERS: I. NUCLEAR-REACTION RATES

1967 ◽  
Vol 45 (10) ◽  
pp. 3275-3296 ◽  
Author(s):  
P. J. Brancazio ◽  
A. Gilbert ◽  
A. G. W. Cameron
Keyword(s):  
Statistical Theory ◽  
Nuclear Reaction ◽  
Cross Sections ◽  
Nuclear Reactions ◽  
Level Density ◽  
Preliminary Investigation ◽  
Computer Time ◽  
Reaction Rates ◽  
Reaction Cross ◽  
Surface Layers

A preliminary investigation of the effects on abundances in stellar surfaces of extensive nuclear bombardment required the calculation of more than 105 nuclear-reaction cross sections. It was necessary to develop simplified methods for using the statistical theory of nuclear reactions to make these calculations in order that the computer time should not be prohibitive. These methods are described here and the results are compared with experiment. The accuracy of the calculations is, in general, about as good as, or somewhat better than, that obtained in previous applications of the statistical theory, probably because the use of an accurate level density formula outweighed the crudity of other approximations.

Stresses in the Surface Layer and Hydrogen Absorption and Diffusion in Cavitation Condition

2014 ◽  
Vol 225 ◽  
pp. 131-138
Author(s):  
Jarosław Chmiel ◽  
Jolanta Baranowska ◽  
Roman Jędrzejewski ◽  
Arkadiusz Rzeczycki
Keyword(s):  
Surface Layer ◽  
Stress State ◽  
Hydrogen Absorption ◽  
Surface Layers ◽  
Fem Modeling ◽  
And Diffusion

Cavitation attack in liquids generated a various states of stresses in surface layers of metals. Differences in stress state effects on hydrogen absorption activated by the cavitation implosion. Results of XRD investigation and FEM modeling shows on inhomogenity of process.

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.

Sign in / Sign up

Export Citation Format

Share Document