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).

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.

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.

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.

scholarly journals Does Fully Radioactive Glass Behave Differently than Simulated Waste Glass?

1992 ◽  
Vol 294 ◽  
Author(s):  
X. Feng ◽  
J. K. Bates ◽  
C. R. Bradley ◽  
E. C. Buck
Keyword(s):  
Radiation Field ◽  
Nuclear Waste ◽  
Potassium Feldspar ◽  
Waste Glass ◽  
Solution Ph ◽  
Static Tests ◽  
Leach Rate ◽  
Nuclear Waste Glass ◽  
Surface Alteration ◽  
Leach Behavior

ABSTRACTStatic tests at SA/V (ratio of surface area of glass to solution volume) 20,000 m−1 on SRL 200 glass compositions show that, at long test periods, the simulated nuclear waste glass (nonradioactive) leaches faster than the corresponding radioactive glass by a factor of about 40, although comparative tests, done through 560 days, at lower SA/V, 2000 m−1, indicate little difference in the leach behavior of the two types of glasses. The similarity in leach behavior between radioactive and simulated glasses at SAN of 2000 m−1 or lower is also observed for SRL 165/42 and 131/11 compositions. The accelerated glass reaction with the simulated glass 200S is associated with the formation of crystalline phases such as clinoptilolite (or potassium feldspar), and a pH excursion. The radiation field generated by the fully radioactive glass reduces the solution pH. This lower pH, in turn, may retard the onset of increased reaction rate. The radiation field generated by the radioactive glasses does not directly affect the stability of the glass surface alteration layer under those conditions where the radioactive and simulated glasses react at the same rate. These results suggest that the fully radioactive nuclear waste glass 200R may maintain a much lower leach rate than the simulated 200S, if the lower pH in the 200R leachate can be sustained. Meaningful comparison tests between radioactive and simulated nuclear waste glasses should include long-term and high SA/V tests.

Studies of Ancient Glass and Their Application to Nuclear-Waste Management

MRS Bulletin ◽  
2003 ◽  
Vol 28 (7) ◽  
pp. 500-504 ◽  
Author(s):  
Hannelore Römich
Keyword(s):  
Waste Management ◽  
Nuclear Waste ◽  
Laboratory Experiments ◽  
Glass Composition ◽  
Nuclear Waste Management ◽  
High Potassium ◽  
Ancient Glass ◽  
Long Term Behavior ◽  
High Potassium Content

AbstractDuring several hundred years of burial in the soil, glass objects, especially those with the high potassium content of medieval compositions, develop heavily corroded surfaces, showing phenomena such as local pitting, laminated layers, and browning effects. The long-term behavior of glass in the soil or in contact with groundwater is not only of interest to glass scientists with a background in archaeology, but also for those with a special interest in nuclear-waste management. Several attempts have been made to propose the decomposition of ancient glasses as an indicator for the performance of buried nuclear-waste glasses. In spite of differences in glass composition and exposure conditions, the development of alteration or corrosion layers with time is a common concern, as shown in this article. Laboratory experiments, representing a simplified model for real conditions, offer the possibility for systematic investigations.

Structural Thermodynamic Model for the Durability and Viscosity of Nuclear Waste Glasses

1987 ◽  
Vol 112 ◽  
Author(s):  
Xiangdong Feng ◽  
Aaron Barkatt
Keyword(s):  
Nuclear Waste ◽  
Composition Dependence ◽  
Glass Composition ◽  
Chemical Properties ◽  
Test Results ◽  
Structural Rules ◽  
Predominant Factor ◽  
Alkali Oxides ◽  
Bond Strengths ◽  
And Chemical Properties

AbstractA model based upon structural thermodynamic considerations has been proposed for both chemical durability and viscosity of nuclear waste glasses. This model assumes the bond strength between atoms in the glass to be the predominant factor in controlling the composition dependence of physical properties such as viscosity and chemical properties like durability. These characteristic bond strengths in the glass are obtained from known heats of formation of the constituent oxides with a few simple structural rules deduced by distinguishing the structural roles of the various oxides, i.e., separating those components that are clearly “network-formers” (e.g. SiO2, Al2O3, ZrO2) from those that are clearly “network-breakers” (e.g. alkali oxides). This model has been successfully applied to the correlation of glass composition with modified MCC-3 leach test results on nuclear waste glasses measured at various laboratories on one hand and with the viscosities of numerous glasses over a temperature range of 850°C to 1600°C with remarkable accuracy on the other hand.

Structural Characterisations of Rare Earth-Rich Glasses for Nuclear Waste Immobilisation

2003 ◽  
Vol 807 ◽  
Author(s):  
I. Bardez ◽  
D. Caurant ◽  
F. Ribot ◽  
P. Loiseau ◽  
J. L. Dussossoy ◽  
...  
Keyword(s):  
Rare Earth ◽  
Nuclear Waste ◽  
Glass Composition ◽  
Optical Absorption Spectroscopy ◽  
X Ray ◽  
Liquid Wastes ◽  
X Ray Absorption ◽  
Glassy Matrices ◽  
Characterisation Methods ◽  
The Rare Earth

ABSTRACTNew glassy matrices, able to incorporate new highly concentrated radioactive liquid wastes (HLW), are being studied. Investigations were performed on rare earth-rich glasses, known as very durable matrices. The selected basic glass composition was (wt. %): 51.0 SiO2 – 8.5 B2O3–12.2 Na2O – 4.3 Al2O3 – 4.8 CaO – 3.2 ZrO2 – 16.0 Nd2O3. To determine both the environment around the rare earth in this glass and its evolution according to its concentration (1.3 – 30 wt. % Nd2O3), EXAFS (Extended X-Ray Absorption Fine Structure) spectroscopy at the LIII-edge of neodymium and optical absorption spectroscopy were used. By coupling these two characterisation methods, several hypotheses are proposed about the nature of the rare earth neighbouring in the glass.

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.

The Interaction of Na-Al-P-Glass (Cs, Sr-Bearing) with Water at Elevated Temperatures (70–250°C)

1994 ◽  
Vol 353 ◽  
Author(s):  
Alexander P. Mukhamet-Galeyev ◽  
Larisa O. Magazina ◽  
Konstantin A. Levin ◽  
Nikolay D. Samotoin ◽  
Alexander V. Zotov ◽  
...  
Keyword(s):  
Nuclear Waste ◽  
Elevated Temperatures ◽  
Solid Phase ◽  
Geochemical Behavior ◽  
Slowing Down ◽  
Glass Dissolution ◽  
Detailed Composition ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Glass Leaching

At present Na-Al-P-glass is used in Russia as matrix for high level nuclear waste which include a sufficient portion of 90Sr and 137Cs isotopes. It has been known that this type of glass is characterized by relatively poor hydrothermal stability above 120°C (Krilova et al., 1990 [1], Balukova et al., 1987 [2]). Although careful studies were devoted to the glass, some questions of geochemical behavior of Sr and Cs in the limits of the nearest repository environment have remained undecided. For example, these have been left uncertain: the mechanism of the glass leaching, phenomena limiting the glass dissolution, the detailed composition of newly formed phases, temperature dependence of the glass solubility. The main purpose of the present experimental investigation was to detect factors controlling Sr and Cs concentrations of aquous solutions and to study the possibility of new solid phase formation as a factor slowing down migration of Cs and Sr in water satureted circumstance.

Effect of Surface Finish on Nuclear Glass Dissolution Rate

1991 ◽  
Vol 257 ◽  
Author(s):  
J.L. Dussossoy ◽  
C. Dubois ◽  
E. Vernaz ◽  
A. Chambaudet
Keyword(s):  
Dissolution Rate ◽  
Surface Finish ◽  
Surface Defects ◽  
Initial Period ◽  
Three Dimensional ◽  
Diamond Powder ◽  
Actual Surface ◽  
Leach Rate ◽  
Glass Dissolution ◽  
The Mean

ABSTRACTThe influence of the surface finish on nuclear glass dissolution was investigated. Seven different surface finishes were tested: a specimen as cut, three specimens polished with 220, 600 and 4000 mesh SiC paper and one with 1 μm diamond powder, a flame-polished specimen and a thermal rupture specimen.The initial glass corrosion rates were measured after 7 and 28 days of Soxhlet leaching at 100°C. The surface finish of each glass coupon was also assessed by three-dimensional analysis before and after leaching for 28 days. Leaching solution analyses showed that the mean apparent leach rate for the first 7 days was highly dependent on the surface finish: the measured rates ranged from 3.8·g.m-2d-1 for the as-cut specimen to 1.3 g·m-2d-1 for the flamepolished specimen. The differences in the leach rates diminished considerably after 28 days of leaching: the mean rate measured between 7 and 28 days for the as-cut and polished specimens was identical (1.7 g·m-2d-1), but was still lower for the remaining two specimens. Three-dimensional surface analysis showed that leaching revealed surface defects (superficial microcracks) produced by cutting or polishing. These effects were less perceptible on the flame-polished or thermally ruptured specimens. The actual surface area of the cut and polished specimens exceeded the apparent geometrical area.In another experiment, the leach rates measured for as-cut specimens and flamepolished specimens were measured over periods of five months or more using a thermogravity balance placed above the Soxhlet device. The experiment confirmed the existence of an initial period during which the dissolution rate for the as-cut specimen was much higher than the mean corrosion rate.

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