Modeling of Solution Renewal with the Kindis Code: Example of R7T7 Glass Dissolution at 90°C

1994 ◽  
Vol 353 ◽  
Author(s):  
T. Advocat ◽  
J. L. Crovisier ◽  
A. Clement ◽  
F. Gerard ◽  
E. Vernaz
Keyword(s):  
Steady State ◽  
Ionic Strength ◽  
Pure Water ◽  
Reaction System ◽  
Dissolution Kinetics ◽  
Glass Mass ◽  
Glass Dissolution ◽  
Geological Repository ◽  
Validity Limit

AbstractThe deep underground environment that would correspond to a geological repository is a system open to fluid flow. It is therefore necessary to investigate the effects of solution renewal on the long-term behavior of glass in contact with water. These effects can now be simulated using the new version of the geochemical Kindis model (thermodynamic and kinetic model).We tested the model at 90°C with an SAIV ratio of 400 m−1 at twelve renewal rates of pure water ranging from 200 to 0 vol% per day. With renewal rates between 200 and 0.065 vol% per day, steady-state conditions were obtained in the reaction system: i.e. the glass corrosion rate remained constant as did the concentrations of the dissolved species in solution (although at different values depending on the renewal rate). The ionic strength never exceeded 1 (the validity limit for the Debye-Huckel law) and long term predictions of the dissolved glass mass, the solution composition and the potential secondary mineral sequence are possible. For simulated renewal rates of less than 0.065 vol% per day (27 vol% per year), the ionic strength rose above 1 (as in a closed system) before steady-state conditions were reached, making it critical to calculate long-term rates; A constant and empirical long-term rate, derived from laboratory measurement, have to be extrapolated. These calculations were based on a first order equation to describe the glass dissolution kinetics. The results obtained with the KINDIS code show discrepancies with some major experimental kinetic data (the long term rate must decrease with the « glass-water » reaction progress, under silica saturation conditions). This clearly indicates that a more refine kinetic relation is needed for the glass matrix.

scholarly journals Chemical durability of vitrified wasteforms: effects of pH and solution composition

2012 ◽  
Vol 76 (8) ◽  
pp. 2919-2930 ◽  
Author(s):  
C. A. Utton ◽  
S. W. Swanton ◽  
J. Schofield ◽  
R. J. Hand ◽  
A. Clacher ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Chemical Durability ◽  
Waste Glass ◽  
High Level Waste ◽  
Solution Composition ◽  
Waste Products ◽  
High Ph ◽  
Glass Dissolution ◽  
Soluble Components

AbstractVitrification is used for the immobilization and conditioning of high-level waste (HLW) arising from the reprocessing of spent nuclear fuel in the UK. Vitrification is also under consideration for the immobilization of certain intermediate-level wastes (ILW), where there may be advantages of volume reduction and removal of uncertainties in long-term waste behaviour, compared to encapsulation in a cement grout. This paper gives an overview of recent work into the chemical durability of UK vitrified wasteforms to inform the technical specification for the disposal facilities for these waste products and the treatment of their long-term behaviour in post-closure performance assessment. This has included: (1) measurements of the initial glass dissolution rates of a simulated HLW Magnox waste glass in a range of groundwater types representative of potential UK host geologies and in simulated high pH near-field porewaters relevant to potential disposal concepts, using Product Consistency Test type-B (PCT-B) at 40°C; and (2) durability testing of three simulant ILW glasses in a saturated calcium hydroxide buffered solution to simulate conditions in cement-based disposal vaults, using PCT-B tests at 50°C.The experimentally defined initial rate of HLW Magnox waste glass dissolution in a range of simulated groundwater compositions appears to be similar regardless of the ionic strength and major element composition of the solution. The release of caesium from HLW Magnox waste glass appears to be sensitive to solution composition. Caesium is selectively retained in the glass compared to other soluble components in the two low ionic strength solutions, but is released at similar rates to other soluble components in the three groundwaters and Ca(OH)2 solution. Whether this change in caesium retention is an ionic strength effect or is related to changes in the nature of the surface alteration layer formed on the glass, has yet to be established. For HLW Magnox waste glass, dissolution is accelerated at high pH in NaOH solution, however, the presence of calcium acts to mitigate the effects of high pH, at least initially. In Ca(OH)2 solution, calcium is found to react with all the glasses studied leading to the formation of calcium-containing alteration products. The initial dissolution behaviour in Ca(OH)2 solution varies with glass composition and in particular appears to be sensitive to the boron content.

Key Parameters of Glass Dissolution in Integrated Systems

1990 ◽  
Vol 212 ◽  
Author(s):  
Etienne Y. Vernaz ◽  
Nicole Godon
Keyword(s):  
Nuclear Waste ◽  
Hard Rock ◽  
Pure Water ◽  
Storage Conditions ◽  
Integrated Systems ◽  
Glass Dissolution ◽  
Long Duration ◽  
Geological Repository ◽  
Dissolution Model ◽  
Considerable Work

ABSTRACTLeaching cells were designed to test the alterability of nuclear waste glasses under conditions closely simulating an actual geological repository. This paper summarizes the results of twenty long-duration tests simulating a variety of storage conditions. The effects of the backfilling materials, the canister, glass cracking and crystallization, a activity and the nature of the host rock are discussed. Moreover, an experiment has been in progress for over seven years in a granite medium; after three years the corrosion rate dropped to about 2 × 10−3 g m−2 d−1, and is sustained only by the water renewal due to sampling at regular intervals. These results constitute a valuable data base on R7T7 glass alteration in geological media at 90°C. Glass alteration mechanisms described in pure water appear to be applicable to a hard rock medium. In clay and salt, however, considerable work remains to be done before environmental factors can be taken into account in an overall dissolution model.

Son68 Glass Dissolution Kinetics at High Reaction Progress: Mechanisms Accounting for The Residual Alteration Rate

2006 ◽  
Vol 932 ◽  
Author(s):  
P. Frugier ◽  
S. Gin ◽  
J.E. Lartigue ◽  
E. Deloule
Keyword(s):  
Diffusion Mechanism ◽  
Dissolution Kinetics ◽  
Solution Chemistry ◽  
Behavior Modeling ◽  
Secondary Phases ◽  
Residual Rate ◽  
Glass Dissolution ◽  
Geological Repository ◽  
Element Speciation ◽  
Constituent Elements

ABSTRACTIn a highly confined medium corresponding to geological repository conditions, the alteration rate of the French SON68 inactive nuclear reference glass drops by about four orders of magnitude below the initial rate. However, extended experiments lasting months or years provide evidence of a virtually constant or slowly decreasing residual alteration rate. Although very low, this rate could account for most of the altered glass thickness after 10 000 years. Experiments at high temperatures and especially high glass-surface-area-to-solution-volume ratios were performed to reveal and quantify the predominant mechanisms underlying the residual rate. The authors describe the characterization of the solution chemistry, the crystallized secondary phases, and the amorphous gel observed after alteration of the French SON68 inactive reference glass, and discuss their implications in terms of long-term behavior modeling. A slow diffusion mechanism is identified in the solid, involving alkalis in particular but also boron. This mechanism results in higher concentrations in solution that affect the system chemistry, not only by slightly modifying the pH and element speciation in solution (e.g. silicon), but also by inducing the precipitation of new crystallized secondary phases that can consume glass constituent elements in the same way as simple solution renewal. Diffusion and the precipitation of secondary phases are two mechanisms to be considered to account for the residual rate.

scholarly journals The fate of Si and Fe while nuclear glass alters with steel and clay

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
C. Carriere ◽  
P. Dillmann ◽  
S. Gin ◽  
D. Neff ◽  
L. Gentaz ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Protective Layer ◽  
Glass Dissolution ◽  
A Value ◽  
Waste Forms ◽  
Controlling Mechanism ◽  
Geological Repository ◽  
The Mean ◽  
High Level ◽  
Initial Dissolution Rate

AbstractThe French concept developed to dispose high-level radioactive waste in geological repository relies on glassy waste forms, isolated from the claystone host rock by steel containers. Understanding interactions between glass and surrounding materials is key for assessing the performance of a such system. Here, isotopically tagged SON68 glass, steel and claystone were studied through an integrated mockup conducted at 50 °C for 2.5 years. Post-mortem analyses were performed from nanometric to millimetric scales using TEM, STXM, ToF-SIMS and SEM techniques. The glass alteration layer consisted of a crystallized Fe-rich smectite mineral, close to nontronite, supporting a dissolution/reprecipitation controlling mechanism for glass alteration. The mean glass dissolution rate ranged between 1.6 × 10−2 g m−2 d−1 to 3.0 × 10−2 g m−2 d−1, a value only 3–5 times lower than the initial dissolution rate. Thermodynamic calculations highlighted a competition between nontronite and protective gel, explaining why in the present conditions the formation of a protective layer is prevented.

scholarly journals Novel Surfactant-Free Water Dispersion Technique of TiO2 NPs Using Focused Ultrasound System

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 427
Author(s):  
Seon Ae Hwangbo ◽  
Minjeong Kwak ◽  
Jaeseok Kim ◽  
Tae Geol Lee
Keyword(s):  
Tio2 Nanoparticles ◽  
Focused Ultrasound ◽  
Pure Water ◽  
Free Water ◽  
Dispersion Stability ◽  
Renewable Energy Resources ◽  
Water Dispersion ◽  
Dispersion State ◽  
Dispersion Technique

Titanium dioxide (TiO2) nanoparticles are used in a wide variety of products, such as renewable energy resources, cosmetics, foods, packaging materials, and inks. However, large quantities of surfactants are used to prepare waterborne TiO2 nanoparticles with long-term dispersion stability, and very few studies have investigated the development of pure water dispersion technology without the use of surfactants and synthetic auxiliaries. This study investigated the use of focused ultrasound to prepare surfactant-free waterborne TiO2 nanoparticles to determine the optimal conditions for dispersion of TiO2 nanoparticles in water. Under 395–400 kHz and 100–105 W conditions, 1 wt% TiO2 colloids were prepared. Even in the absence of a surfactant, in the water dispersion state, the nanoparticles were dispersed with a particle size distribution of ≤100 nm and did not re-agglomerate for up to 30 days, demonstrating their excellent dispersion stability.

scholarly journals Long-term repopulating hematopoietic stem cells and “side population” in human steady state peripheral blood

2013 ◽  
Vol 11 (1) ◽  
pp. 625-633 ◽  
Author(s):  
Philippe Brunet de la Grange ◽  
Marija Vlaski ◽  
Pascale Duchez ◽  
Jean Chevaleyre ◽  
Veronique Lapostolle ◽  
...  
Keyword(s):  
Stem Cells ◽  
Steady State ◽  
Hematopoietic Stem Cells ◽  
Peripheral Blood ◽  
Side Population ◽  
Hematopoietic Stem

scholarly journals Development of a Water Matrix Certified Reference Material for Volatile Organic Compounds Analysis in Water

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4370
Author(s):  
Liping Fang ◽  
Linyan Huang ◽  
Gang Yang ◽  
Yang Jiang ◽  
Haiping Liu ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Reference Material ◽  
Organic Compounds ◽  
Certified Reference Material ◽  
Pure Water ◽  
Term Stability ◽  
Long Term Stability ◽  
Water Matrix ◽  
Volatile Organic

Water matrix certified reference material (MCRM) of volatile organic compounds (VOCs) is used to provide quality assurance and quality control (QA/QC) during the analysis of VOCs in water. In this research, a water MCRM of 28 VOCs was developed using a “reconstitution” approach by adding VOCs spiking, methanol solution into pure water immediately prior to analysis. The VOCs spiking solution was prepared gravimetrically by dividing 28 VOCs into seven groups, then based on ISO Guide 35, using gas chromatography-mass spectrometry (GC-MS) to investigate the homogeneity and long-term stability. The studies of homogeneity and long-term stability indicated that the batch of VOCs spiking solution was homogeneous and stable at room temperature for at least 15 months. Moreover, the water MCRM of 28 VOCs was certified by a network of nine competent laboratories, and the certified values and expanded uncertainties of 28 VOCs ranged from 6.2 to 17 μg/L and 0.5 to 5.3 μg/L, respectively.

scholarly journals Bone Regeneration by Novel Bioactive Glasses Containing Strontium and/or Magnesium: A Preliminary In-Vivo Study

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2223 ◽  
Author(s):  
Devis Bellucci ◽  
Valeria Cannillo ◽  
Alexandre Anesi ◽  
Roberta Salvatori ◽  
Luigi Chiarini ◽  
...  
Keyword(s):  
Statistical Significance ◽  
Formation Processes ◽  
Complete Dissolution ◽  
In Vitro Bioactivity ◽  
Bioactive Glasses ◽  
Beneficial Effects ◽  
Glass Dissolution

In this work, a set of novel bioactive glasses have been tested in vivo in an animal model. The new compositions, characterized by an exceptional thermal stability and high in vitro bioactivity, contain strontium and/or magnesium, whose biological benefits are well documented in the literature. To simulate a long-term implant and to study the effect of the complete dissolution of glasses, samples were implanted in the mid-shaft of rabbits’ femur and analyzed 60 days after the surgery; such samples were in undersized powder form. The statistical significance with respect to the type of bioactive glass was analyzed by Kruskal–Wallis test. The results show high levels of bone remodeling, several new bone formations containing granules of calcium phosphate (sometimes with amounts of strontium and/or magnesium), and the absence of adverse effects on bone processes due to the almost complete glass dissolution. In vivo results confirming the cell culture outcomes of a previous study highlighted that these novel bioglasses had osteostimulative effect without adverse skeletal reaction, thus indicating possible beneficial effects on bone formation processes. The presence of strontium in the glasses seems to be particularly interesting.

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