The Kinetics of Spinel Crystallization from a High-Level Waste Glass

1996 ◽  
Vol 465 ◽  
Author(s):  
J. G. Reynolds ◽  
P. Hrma
Keyword(s):  
Volume Fraction ◽  
Treatment Time ◽  
Waste Glass ◽  
High Level Waste ◽  
Avrami Equation ◽  
Kinetic Coefficients ◽  
High Level Nuclear Waste ◽  
Isothermal Heat Treatments ◽  
High Level ◽  
Kinetics Of

ABSTRACTThe kinetics of spinel crystallization from a molten high-iron simulated high-level nuclear waste glass was studied using isothermal heat treatments. Optical microscopy with image analysis was used to measure volume fraction of spinel as a function of heat treatment time and temperature. The Johnson-Mehl-Avrami equation was fitted to data to determine kinetic coefficients for spinel crystallization. The liquidus temperature and Avrami number are TL = 1337K and n = 1.5.

scholarly journals The initial dissolution rates of simulated UK Magnox–ThORP blend nuclear waste glass as a function of pH, temperature and waste loading

2015 ◽  
Vol 79 (6) ◽  
pp. 1529-1542 ◽  
Author(s):  
N. Cassingham ◽  
C.L. Corkhill ◽  
D.J. Backhouse ◽  
R.J. Hand ◽  
J.V. Ryan ◽  
...  
Keyword(s):  
Dissolution Kinetics ◽  
Intrinsic Rate ◽  
Waste Glass ◽  
High Level Waste ◽  
Dissolution Mechanism ◽  
Dissolution Rates ◽  
Forward Rates ◽  
Glass Dissolution ◽  
High Level ◽  
Kinetics Of

AbstractThe first comprehensive assessment of the dissolution kinetics of simulant Magnox–ThORP blended UK high-level waste glass, obtained by performing a range of single-pass flow-through experiments, is reported here. Inherent forward rates of glass dissolution were determined over a temperature range of 23 to 70°C and an alkaline pH range of 8.0 to 12.0. Linear regression techniques were applied to the TST kinetic rate law to obtain fundamental parameters necessary to model the dissolution kinetics of UK high-level waste glass (the activation energy (Ea), pH power law coefficient (η) and the intrinsic rate constant (k0)), which is of importance to the post-closure safety case for the geological disposal of vitreous products. The activation energies based on B release ranged from 55 ± 3 to 83 ± 9 kJ mol–1, indicating that Magnox–THORP blend glass dissolution has a surface-controlled mechanism, similar to that of other high-level waste simulant glass compositions such as the French SON68 and LAW in the US. Forward dissolution rates, based on Si, B and Na release, suggested that the dissolution mechanism under dilute conditions, and pH and temperature ranges of this study, was not sensitive to composition as defined by HLW-incorporation rate.

Nepheline Crystallization in High-Alumina High-Level Waste Glass

2015 ◽  
Vol 1744 ◽  
pp. 85-91 ◽  
Author(s):  
José Marcial ◽  
John McCloy ◽  
Owen Neill
Keyword(s):  
Nuclear Waste ◽  
Waste Glass ◽  
High Alumina ◽  
High Level Waste ◽  
Interfacial Conditions ◽  
Waste Vitrification ◽  
Cooling Schedules ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Glass Compositions

ABSTRACTThe understanding of the crystallization of aluminosilicate phases in nuclear waste glasses is a major challenge for nuclear waste vitrification. Robust studies on the compositional dependence of nepheline formation have focused on large compositional spaces with hundreds of glass compositions. However, there are clear benefits to obtaining complete descriptions of the conditions under which crystallization occurs for specific glasses, adding to the understanding of nucleation and growth kinetics and interfacial conditions. The focus of this work was the investigation of the microstructure and composition of one simulant high-level nuclear waste glass crystallized under isothermal and continuous cooling schedules. It was observed that conditions of low undercooling, nepheline was the most abundant aluminosilicate phase. Further undercooling led to the formation of additional phases such as calcium phosphate. Nepheline composition was independent of thermal history.

Isothermal Crystallization Kinetics in Simulated High-Level Nuclear Waste Glass

1996 ◽  
Vol 465 ◽  
Author(s):  
John D. Vienna ◽  
Pavel Hrma ◽  
Donald E. Smith
Keyword(s):  
Crystallization Kinetics ◽  
High Level Waste ◽  
Transformation Kinetic ◽  
Isothermal Crystallization Kinetics ◽  
Isothermal Method ◽  
Glass Crystal ◽  
Temperature Transformation ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Kinetics Of

ABSTRACTCrystallization kinetics of a simulated high-level waste (HLW) glass were measured and modelled. Kinetics of acmite growth in the standard HW39–4 glass were measured using the isothermal method. A time-temperature-transformation (TTT) diagram was generated from these data. Classical glass-crystal transformation kinetic models were empirically applied to the crystallization data. These models adequately describe the kinetics of crystallization in complex HLW glasses (i.e., RSquared = 0.908). An approach to measurement, fitting, and use of TTT diagrams for prediction of crystallinity in a HLW glass canister is proposed.

Nonisothermal kinetics of spinel crystallization in a HLW glass

1999 ◽  
Vol 556 ◽  
Author(s):  
D. G. Casler ◽  
P. Hrma
Keyword(s):  
Cooling Rate ◽  
Empirical Equation ◽  
Volume Fraction ◽  
Kolmogorov Equation ◽  
High Level Waste ◽  
Parameter Study ◽  
Nonisothermal Kinetics ◽  
Dimensionless Numbers ◽  
High Level ◽  
Kinetics Of

AbstractNonisothermal kinetics of spinel crystallization in a high-level waste (HLW) glass was predicted using Mehl-Avrami-Johnson-Kolmogorov equation coefficients from isothermal data. The volume fraction of spinel was determined as a function of time, temperature, and cooling rate. The results were verified experimentally. Also predicted was the spatial distribution of spinel in a HLW glass canister. Finally, a parameter study was performed, and an empirical equation was proposed relating the final spinel volume fraction in glass to dimensionless numbers for cooling rate, phase equilibrium, and crystallization kinetics.

Neptunium Speciation in Humic Acid-rich Clay Water upon Interaction With Radioactive Waste Glass Samples

2002 ◽  
Vol 757 ◽  
Author(s):  
V. Pirlet ◽  
P. Van Iseghem
Keyword(s):  
Humic Substances ◽  
Humic Acids ◽  
Specific Interaction ◽  
Waste Glass ◽  
High Level Waste ◽  
Boom Clay ◽  
Dissolution Tests ◽  
Vis Spectroscopy ◽  
Doped Glasses ◽  
High Level

ABSTRACTOrganic complexes of actinides are known to occur upon interaction of high level waste glass and Boom Clay which is a potential host rock formation for disposal of high level waste in Belgium. The solubility and mobility of 237Np, one of the most critical radionuclides, can be affected by the high dissolved organic carbon content of the Boom Clay porewater through complexation with the humic substances. The influence of humic substances on the Np behaviour is considered through dissolution tests of Np-doped glasses in Boom Clay water and through fundamental study of the specific interaction between Np(IV) and the humic acids using spectroscopic techniques. High Np(IV) concentrations are found in the glass dissolution tests. These concentrations are higher than what we should expect from the solubility of Np(OH)4, the solubility limiting solid phase predicted under the reducing conditions and pH prevailing in Boom Clay. Studying the specific interaction of Np(IV) with humic acids in Boom Clay porewater, high soluble Np concentrations are also measured and two main tetravalent Np-humate species are observed by UV-Vis spectroscopy. The two species are interpreted in terms of mixed hydroxo-humate complexes, Np(OH)xHA with x = 3 or 4. These species are the most likely species that can form according to the pH working conditions. Using thermodynamic simplified approaches, high complexation constants, i.e. log β131 and log β141 respectively equal to 46 and 51.6, are calculated for these species under the Boom Clay conditions.Comparing the spectroscopic results of the dissolution tests with the study of the interaction of Np(IV) with humic substances, we can conclude that the complexation of Np(IV) with the humic acids may occur and increases the solubility of Np(OH)4 upon interaction of a Np-doped glass and the Boom Clay porewater.

Vapour Phase Hydration of Blended Oxide - Magnox Waste Glasses

2003 ◽  
Vol 807 ◽  
Author(s):  
Neil C. Hyatt ◽  
William E. Lee ◽  
Russell J. Hand ◽  
Paul K. Abraitis ◽  
Charlie R. Scales
Keyword(s):  
Glass Matrix ◽  
Alkaline Earth ◽  
Vapour Phase ◽  
Waste Glass ◽  
High Level Waste ◽  
Zirconium Silicate ◽  
Constant Rate ◽  
Surface Alteration ◽  
High Level ◽  
Short Incubation Time

ABSTRACTVapour phase hydration studies of a blended Oxide / Magnox simulant high level waste glass were undertaken at 200°C, over a period of 5 – 25 days. The alteration of this simulant waste glass is characterised by a short incubation time of less than 5 days, leading to the formation of an alteration layer several microns thick. Following the incubation period, the alteration proceeds at a constant rate of 0.15(1)μmd−1. The distribution of key glass matrix (Si, Na) and waste (Cs, Zr, Nd, Mo) elements was found to vary significantly across the alteration layer. Vapour phase hydration leads to formation of surface alteration products, identified as smectite, zirconium silicate and alkaline-earth molybdate phases.

The Use of Repassivation Potential in Predicting The Performance of High-Level Nuclear Waste Container Materials

1994 ◽  
Vol 353 ◽  
Author(s):  
Narasi Sridhar ◽  
Darrell Dunn ◽  
Gustavo Cragnolino
Keyword(s):  
Field Tests ◽  
Localized Corrosion ◽  
High Level Waste ◽  
Repassivation Potential ◽  
Waste Container ◽  
Highly Sensitive ◽  
Plant Equipment ◽  
Robust Parameter ◽  
High Level Nuclear Waste ◽  
High Level

AbstractLocalized corrosion in aqueous environments forms an important bounding condition for the performance assessment of high-level waste (HLW) container materials. A predictive methodology using repassivation potential is examined in this paper. It is shown, based on long-term (continuing for over 11 months) testing of alloy 825, that repassivation potential of deep pits or crevices is a conservative and robust parameter for the prediction of localized corrosion. In contrast, initiation potentials measured by short-term tests are non-conservative and highly sensitive to several surface and environmental factors. Corrosion data from various field tests and plant equipment performance are analyzed in terms of the applicability of repassivation potential. The applicability of repassivation potential for predicting the occurrence of stress corrosion cracking (SCC) and intergranular corrosion in chloride containing environments is also examined.

Materials Interface Interactions Test (MIIT); in-Situ Testing of Simulated Hlw Forms in Salt- Performance of Srs Simulated Waste Glass After up to 5 Years of Burial at the Waste Isolation Pilot Plant (WIPP)

1991 ◽  
Vol 257 ◽  
Author(s):  
G.G. Wicks ◽  
A.R. Lodding ◽  
P.B. Macedo ◽  
D.E. Clark
Keyword(s):  
United States ◽  
Pilot Plant ◽  
Field Tests ◽  
Field Testing ◽  
The United States ◽  
Waste Glass ◽  
Department Of Energy ◽  
High Level Waste ◽  
Waste Isolation Pilot Plant ◽  
High Level

ABSTRACTThe first field tests conducted in the United States involving burial of simulated high-level waste [HLW] forms and package components, were started in July of 1986. The program, called the Materials Interface Interactions Test or MIIT, is the largest cooperative field-testing venture in the international waste management community. Included in the study are over 900 waste form samples comprising 15 different systems supplied by 7 countries. Also included are approximately 300 potential canister or overpack metal samples along with more than 500 geologic and backfill specimens. There are almost 2000 relevant interactions that characterize this effort which is being conducted in the bedded salt site at the Waste Isolation Pilot Plant (WIPP), near Carlsbad, New Mexico. The MIIT program represents a joint endeavor managed by Sandia National Laboratories in Albuquerque, N.M., and Savannah River Laboratory in Aiken, S.C. and sponsored by the U.S. Department of Energy. Also involved in MIIT are participants from various laboratories and universities in France, Germany, Belgium, Canada, Japan, Sweden, the United Kingdom, and the United States. In July of 1991, the experimental portion of the 5-yr. MIIT program was completed. Although only about 5% of all MIIT samples have been assessed thus far, there are already interesting findings that have emerged. The present paper will discuss results obtained for SRS 165/TDS waste glass after burial of 6 mo., 1 yr. and 2 yrs., along with initial analyses of 5 yr. samples.

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