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.

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.

Study on the β1→α+β2 Transformation Kinetics of Ti-6Al-4V Alloy by DSC

2014 ◽  
Vol 508 ◽  
pp. 110-113
Author(s):  
Rong Hua Zhang ◽  
Biao Wu ◽  
Xiao Ping Zheng
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Phase Transformation ◽  
Cooling Rate ◽  
Volume Fraction ◽  
Avrami Exponent ◽  
Transformation Kinetics ◽  
Cooling Process ◽  
Scanning Calorimetry ◽  
Kinetics Of

The temperature and duration of β1→α+β2 transformation of Ti-6Al-4V alloy in cooling process were measured by differential scanning calorimetry, and transformation activation energy and Avrami exponent of β1→α+β2 were also calculated. The results show that the cooling rate is in the range of 在5～20°C/min, the transformation temperature and the transformation duration β1→α+β2 transformation of Ti-6Al-4V alloy decreased with the increasing cooling rate, its transformation activation energy decreased with the increasing phase transformation volume fraction, and Avrami exponent was between 1 and 2 at 660°C.

Long Term Crystallization Behavior of Glasses at Temperatures T < Tg

1988 ◽  
Vol 127 ◽  
Author(s):  
A. D. Stalios ◽  
R. De Batist ◽  
P. Van Iseghem
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Mathematical Expression ◽  
Time Limit ◽  
Minimum Time ◽  
High Level Waste ◽  
System A ◽  
Time Period ◽  
The Times ◽  
High Level

ABSTRACTBoulos et al. [1], derived a mathematical expression predicting the minimum time needed for a glassy system to experience fractional crystallization, not exceeding a few volume percent at temperatures lower than the glass transition temperature, T. The range of applicability of this expression is extended to include crystallization processes governed by either homogeneous or heterogeneous nucleation and by diffusion controlled one-, two-, and three-dimensional crystal growth. This study demonstrates that the Boulos et al. expression is fairly independent of the nucleation, growth habit and dimensionality of the crystallization process. Moreover, the inherent theoretical as well as experimental limitations of the technique are reviewed and discussed.The calculation for evaluating this minimum time limit has been applied for an alkali ferrisilicate alpha-waste reference glass. It is found that, for this system, a barely observable crystallized volume fraction (less than 5 % vol) will be reached at 25°C only after storage for more than 10 years. This time period is certainly beyond the times to be considered for evaluations of geological disposal. In addition some preliminary calculations of the minimum time limit for two types of borosilicate high level waste glass forms (HLW) are presented. These indicate safe time limits of the order of 10–100 years at 450°C, suggesting that crystallization effects cannot be ignored if the assumptions made in the calculations are valid.

Estimating the Alteration Kinetics of the French Vitrified High-Level Waste Package in a Geologic Repository

1998 ◽  
Vol 123 (1) ◽  
pp. 67-81 ◽  
Author(s):  
Patrick Jollivet ◽  
Michèle Nicolas ◽  
Etienne Vernaz
Keyword(s):  
High Level Waste ◽  
Geologic Repository ◽  
Waste Package ◽  
High Level ◽  
Kinetics Of

scholarly journals Mechanisms and Kinetics of Organic Aging and Characterization of Intermediates in High-Level Waste

2002 ◽  
Author(s):  
Donald M Camaioni ◽  
S Tom Autrey ◽  
Michel Dupuis ◽  
Wendy Shaw
Keyword(s):  
High Level Waste ◽  
High Level ◽  
Kinetics Of

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.

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