The Effect of Groundwater Flow on Release Rate Behavior of Borosilicate Glass

1984 ◽  
Vol 44 ◽  
Author(s):  
M. J. Apted ◽  
R. Adiga
Keyword(s):  
Steady State ◽  
Groundwater Flow ◽  
Dissolution Rate ◽  
Rate Constant ◽  
Flow Rate ◽  
Release Rate ◽  
Borosilicate Glass ◽  
High Flow ◽  
Glass Dissolution ◽  
Dissolution Rate Constant

AbstractA simple open-system model is used to evaluate the effect of groundwater flow on borosilicate glass dissolution. With appropriate assumptions, the mass balance equation is: dc/dt=R-kfc;R=k(ceq-c)where c is the concentration of dissolved species i, t is time, kf is the flushing frequency (i.e., volumetric flow rate divided by fixed pore volume), and R is the normalized rate of dissolution. A first-order dependence of R on departure of c from the equilibrium saturation concentration, Ceq, is also assumed. Results from steady-state (dc/dt = 0; c = css = constant) static and dynamic flow tests on a borosilicate glass at 90°C were used to calculate R and the dissolution rate constant, k, as a function of flow rate. The calculated results of the model are in good agreement with independent measurements.There are three important conclusions. First, even the slowest flow rate used (0.1 ml/hr) corresponds to a high flow rate with respect to the intrinsic dissolution rate of the glass and expected repository flow conditions. Second, previous release models that scale radionuclide release rate directly to solubility concentration may overestimate release at high flow rates. This is because previous models fail to account for the pronounced decrease in steady-state solution concentration at the solid interface with increasing flow rate. Third, increased flow rate accelerates the glass dissolution rate without changing the reaction mechanism. This effect is attributable to constant replenishment of undersaturated solution at the glass surface and an apparent increase in the dissolution rate constant with increasing flow rate.

scholarly journals The Role Of Chemical Reaction In Waste-Form Performance

1987 ◽  
Vol 112 ◽  
Author(s):  
P. L. Chambré ◽  
C. H. Kang ◽  
W. W.-L. Lee ◽  
T. H. Pigford
Keyword(s):  
Mass Transfer ◽  
Steady State ◽  
Dissolution Rate ◽  
Chemical Reaction ◽  
Borosilicate Glass ◽  
Reaction Rate ◽  
Waste Form ◽  
Spent Fuel ◽  
Wide Range ◽  
Chemical Reaction Rate

AbstractThe dissolution rate of waste solids in a geologic repository is a complex function of waste form geometry, chemical reaction rate, exterior flow field, and chemical environment. We present here an analysis to determine the steady-state mass transfer rate, over the entire range of flow conditions relevant to geologic disposal of nuclear waste. The equations for steady-state mass transfer with a chemical-reaction-rate boundary condition are solved by three different mathematical techniques which supplement each other. This theory is illustrated with laboratory leach data for borosilicate-glass and a spherical spent-fuel waste form under typical repository conditions. For borosilicate glass waste in the temperature range of 57°C to 250°C, dissolution rate in a repository is determined for a wide range of chemical reaction rates and for Peclet numbers from zero to well over 100, far beyond any Peclet values expected in a repository. Spent-fuel dissolution in a repository is also investigated, based on the limited leach data now available.

Dissolution Kinetics of a Simple Analogue Nuclear Waste Glass as a Function of Ph, Time and Temperature

1989 ◽  
Vol 176 ◽  
Author(s):  
Kevin G. Knauss ◽  
William L. Bourcier ◽  
Kevin D. McKeegan ◽  
Celia I. Merzbacher ◽  
Son N. Nguyen ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Rate Constant ◽  
Rate Constants ◽  
Dissolution Kinetics ◽  
State Theory ◽  
Alkaline Solutions ◽  
Glass Dissolution ◽  
Constant Ph ◽  
Transport Control ◽  
Dissolution Rate Constants

ABSTRACTWe have measured the dissolution rate of a simple five-component borosilicate glass (Na2O, CaO, Al2O3, B2O3, SiO2) using a flow-through system. The experiments were designed to measure the dissolution rate constant over the interval pH 1 through pH 13 at 3 temperatures (25°, 50° and 70°C). Dilute buffers were used to maintain a constant pH. Analyses of solutions and solid surfaces provided information that is used to develop a kinetic model for glass dissolution.Under all conditions we eventually observed linear dissolution kinetics. In strongly acidic solutions (pH 1 to pH 3) all components but Si were released in their stoichiometric proportions and a thick, Si-rich gel was formed. In mildly acidic to neutral solutions the gel was thinner and was both Si- and Al-rich, while the other components were released to solution in stoichiometric proportions. In mildly to strongly alkaline solutions all components were released to solution in stoichiometric proportions. By varying the flow rate at each pH we demonstrated a lack of transport control of the dissolution rate.The dissolution rates were found to be lowest at near-neutral pH and to increase at both low and high pH. A rate equation based on transition-state theory (TST) was used to calculate dissolution rate constants and reaction order with respect to pH over two pH intervals at each temperature. At 250C between pH 1 and pH 7 based on the Si release rate the log rate constant for glass dissolution (g glass/m20d) was −0.77 and the order with respect to pH was −0.48. Between pH 7 and pH 13 the log rate constant for glass dissolution was −8.1 and the order with respect to pH was +0.51. The measured simple glass dissolution rate constants compare very well with constants estimated by fitting the same TST equation to experimental results obtained for SRL-165 glass and to dissolution rate estimates made for synthetic basaltic glasses.

Failure Analysis on a Flowmeter

2009 ◽  
Vol 409 ◽  
pp. 65-71
Author(s):  
Jakob Kuebler
Keyword(s):  
Failure Analysis ◽  
Flow Rate ◽  
Borosilicate Glass ◽  
Life Time ◽  
High Flow ◽  
High Flow Rate ◽  
Surface Areas ◽  
Final Failure ◽  
Longitudinal Cracks

A measuring cone made of borosilicate glass mounted in a flowmeter failed after a life¬time of only a few months. Therefore, a failure analysis was conducted which revealed that the reason for failure was a too high flow rate. The high flow rate made the float touch the upper float stop. When contacting the stop, the float started to rotate in an unstable manner and as a result was hitting and grinding along the inner cone wall which resulted in cracks, micro-chipped surface areas and grinding marks. One of the longitudinal cracks then grew subcritically till final failure occurred.

scholarly journals A Kinetic Model for Borosilicate Glass Dissolution Based on the Dissolution Affinity of a Surface Alteration Layer

1989 ◽  
Vol 176 ◽  
Author(s):  
William L. Bourcier ◽  
Dennis W. Peiffer ◽  
Kevin G. Knauss ◽  
Kevin D. McKeegan ◽  
David K. Smith
Keyword(s):  
Kinetic Model ◽  
Dissolution Rate ◽  
Borosilicate Glass ◽  
Geochemical Modeling ◽  
Secondary Phases ◽  
Dissolution Rates ◽  
Ion Concentrations ◽  
Glass Dissolution ◽  
Gel Layer ◽  
Amorphous Surface

ABSTRACTA kinetic model for the dissolution of borosilicate glass, incorporated into the EQ3/6 geochemical modeling code, is used to predict the dissolution rate of a nuclear waste glass. In the model, the glass dissolution rate is controlled by the rate of dissolution of an alkalidepleted amorphous surface (gel) layer. Assuming that the gel layer dissolution affinity controls glass dissolution rates is similar to the silica saturation concept of Grambow [1] except that our model predicts that all components concentrated in the surface layer, not just silica, affect glass dissolution rates. The good agreement between predicted and observed elemental dissolution rates suggests that the dissolution rate of the gel layer limits the overall rate of glass dissolution. The model predicts that the long-term rate of glass dissolution will depend mainly on ion concentrations in solution, and therefore on the secondary phases which precipitate and control ion concentrations.

The Prediction of the Dissolution Rate Constant by Mixing Rules: The Study of Acetaminophen Batches

2008 ◽  
Vol 34 (5) ◽  
pp. 522-535 ◽  
Author(s):  
Tu Lee ◽  
Hung Ju Hou ◽  
Hsiang Yu Hsieh ◽  
Yan Chan Su ◽  
Yeh Wen Wang ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Rate Constant ◽  
Mixing Rules ◽  
Dissolution Rate Constant

Theory of Copper-Electrolyte Slimes Decoppering in the Presence of Hydrogen Peroxide

2019 ◽  
Vol 946 ◽  
pp. 585-590
Author(s):  
V.G. Lobanov ◽  
K.D. Naumov ◽  
A.A. Korolev
Keyword(s):  
Hydrogen Peroxide ◽  
Dissolution Rate ◽  
Rate Constant ◽  
Chemical Transformations ◽  
Composition Effect ◽  
Rotating Disc ◽  
Copper Dissolution ◽  
Copper Leaching ◽  
Copper Electrolyte ◽  
Dissolution Rate Constant

The problem of copper leaching from copper-electrolyte slimes is discussed. To intensify the long and costly process, it is proposed to use a leaching system containing sulfuric acid and hydrogen peroxide as an oxidizing agent. The chemical transformations possible variants at the treatment of slime under the specified conditions and the thermodynamic parameters of the predicted reactions are considered. Solution composition effect on the copper dissolution rate at room temperature was studied in the presence of hydrogen peroxide using the rotating disc technique. It is found that dissolution rate constant at using hydrogen peroxide slightly inferior to dissolution rate constant under autoclaved conditions in an oxygen atmosphere.

scholarly journals Dissolution of simplified nuclear waste glass and formation of secondary phases

2021 ◽  
Vol 1 ◽  
pp. 143-144
Author(s):  
Felix Brandt ◽  
Martina Klinkenberg ◽  
Sébastien Caes ◽  
Jenna Poonoosamy ◽  
Wouter Van Renterghem ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Nuclear Waste ◽  
Borosilicate Glass ◽  
Glass Surface ◽  
Cementitious Materials ◽  
Solution Chemistry ◽  
Secondary Phases ◽  
Release Rates ◽  
Glass Dissolution ◽  
Safety Assessments

Abstract. Immobilization of high-level and intermediate-level nuclear wastes by vitrification in borosilicate glass is a well-established process. There is a consensus between the waste management agencies of many countries and many experts that vitrified nuclear waste should be disposed of in a deep geological waste repository and therefore its long-term behavior needs to be taken into account in safety assessments. In contact with water, borosilicate glass is metastable and dissolves. In static dissolution experiments, often a surface alteration layer (SAL) forms on the dissolving glass, and later sometimes secondary phases form. Based on boron or lithium release rates, commonly three stages of glass dissolution are defined as a function of the reaction progress: (I) initial dissolution, described by a congruent glass dissolution at the highest rate, (II) residual dissolution, characterized by a glass dissolution rate several orders of magnitude lower than the initial one, and (III) resumption of glass alteration with initial rates. Microscopically, the formation of a complex SAL has been identified as a prerequisite for the slower dissolution kinetics of stage II. Stage III is typically observed under specific conditions, i.e., high temperature and/or high pH driven by the uptake of Si and Al into secondary phases. Different glass dissolution models explaining the mechanisms of the SAL formation and rate-limiting steps have been proposed and are still under debate. In this article different aspects of glass dissolution from recent studies in the literature and our own work are discussed with a focus on the microscopic aspects of SAL formation, secondary phase formation and the resumption of glass dissolution. Most of the experiments in the literature were performed under near-neutral pH conditions and at 90 ∘C, following standard procedures, to understand the fundamental mechanisms of glass dissolution. The example of interaction of glass and cementitious materials as discussed here is relevant for safety assessments because most international concepts include cement e.g., as lining, for plugs, or as part of the general construction of the repository. The aim of the investigations presented in this paper was to study the combined effect of hyperalkaline conditions and very high surface area/volume ratios (SA/V=264000m-1) on the dissolution of international simplified glass (ISG) and the formation of secondary phases at 70 ∘C in a synthetic young cement water containing Ca (YCWCa). The new results show that the SA/V ratio is a key parameter for the dissolution rate and for the formation of the altered glass surface and secondary phases. A comparison with similar studies in the literature shows that especially on the microscopic and nanoscale, different SA/V ratios lead to different features on the dissolving glass surface, even though the SA-normalized element release rates appear similar. Zeolite and Ca-silicate-hydrate phases (CSH) were identified and play a key role for the evolution of the solution chemistry. A kinetic dissolution model coupled with precipitation of secondary phases can be applied to relate the amount of dissolved glass to the evolution of the solution's pH.

Mechanisms and Kinetics of Silica-Rich Binary Na2O-SiO2 Glass Corrosion in 100°C Water at pH=7

2007 ◽  
Vol 336-338 ◽  
pp. 1823-1826 ◽  
Author(s):  
K.G. Nickel ◽  
S. Merkel
Keyword(s):  
Dissolution Rate ◽  
Rate Constant ◽  
Edge Length ◽  
Sio2 Content ◽  
Shrinking Core Model ◽  
Water Interaction ◽  
Glass Corrosion ◽  
Shrinking Core ◽  
Dissolution Rate Constant ◽  
Kinetics Of

Sodium-rich glasses of the system Na2O-SiO2 are well known to be easily soluble in water. This is not true for silica-rich compositions. We have manufactured quenched glasses with silica contents between 65 and 80 wt.% SiO2 and followed the water interaction at 100°C by measuring mass and sample dimensions in intervals. Comparing the path of edge length, mass and volume to a general shrinking core model for cuboids we conclude that only compositions between 65 and 70 wt% SiO2 can be described well by a simple dissolution process. The logarithm of the dissolution rate constant varies linearly with the SiO2 content. At higher silica contents the mechanism changes towards leaching of sodium. We propose changing glass structures to be responsible for the change in mechanism.

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