Crystallization of an Yttrium Aluminosilicate Glass for Nuclear Waste Immobilization

2012 ◽  
Vol 1475 ◽  
Author(s):  
Diana Carolina Lago ◽  
Diana Garcés ◽  
Miguel Oscar Prado
Keyword(s):  
Particle Size ◽  
Cross Sections ◽  
Glass Particle ◽  
Aluminosilicate Glass ◽  
Glassy Matrix ◽  
Borosilicate Glasses ◽  
Aluminosilicate Glasses ◽  
Waste Immobilization ◽  
Yttrium Disilicate ◽  
Nuclear Waste Immobilization

ABSTRACTSiO2-Al2O3-Y2O3 glasses exhibit high glass transition temperatures, water corrosion resistance and good mechanical properties. These properties suggest that yttrium aluminosilicate glasses could potentially replace the borosilicate glasses usually used for immobilization of nuclear wastes. At the same time, yttrium can be used to simulate actinides.During waste immobilization, crystallization of the glassy matrix must be avoided or at least controlled, thus, the understanding of glass crystallization kinetics is essential.We found by XRD that the crystalline phases present on heat treatments are yttrium disilicate and sillimanite/mullite. By optical microscopy on polished cross-sections we could only identify highly yttrium enriched crystals which we associate with yttrium disilicate crystals.In this paper we measure the surface density of nucleation sites Ns in as obtained splat cooled pieces obtaining values of about 1.5 · 1011 nucleus · m-2. Crystal growth rate U in the temperature range 1000-1040 oC varies in the range 8-13 μm · h-1. These data are useful for designing sintering or melting thermal paths of YAS glasses in order to control their microstructure. We show the effect of glass particle size on DTA results: crystallization peaks moves towards lower temperatures for smaller particle size, which confirms that mainly surface nucleation is taking place on heating.

Glasses for Nuclear Waste Immobilization. Effect of Lutetium Addition on Yttrium Aluminosilicate Glass Crystallization Kinetics

2019 ◽  
Vol 5 (2) ◽  
Author(s):  
D. C. Lago ◽  
M. B. Bortot ◽  
M. O. Prado
Keyword(s):  
Crystallization Kinetics ◽  
Term Treatment ◽  
Silicate Glasses ◽  
Aluminosilicate Glass ◽  
Radioactive Material ◽  
Glass Crystallization ◽  
Long Term Treatment ◽  
Order Of Magnitude ◽  
Yttrium Disilicate ◽  
Nuclear Waste Immobilization

Glasses have emerged as alternative materials that can be used for long-term treatment and management of radioactive waste. Specifically, glasses can be used as a matrix to immobilize the radioactive material. Within the glass industry, silicate glasses are the most widely used due to their properties and to the large knowledge existent about them. Alkaline free silicate glasses are particularly corrosion resistant. Due to the latter, rare earth aluminosilicate glasses are good candidates for actinides immobilization, especially, yttrium aluminosilicate (YAS) glasses. The crystallization kinetics of YAS glasses on heating has been already studied, and this work is focused on the effect of lutetium addition on the YAS glass crystallization kinetics. The presence of a small amount of lutetium in a YAS glass decreases the surface density of nucleation sites (Ns) by about 1 order of magnitude and significantly decreases the crystal growth rate (U). In this work, it was observed that lutetium additions on the order of 0.2 (wt %) to a YAS glass dramatically decreased Ns, for example, at 1000 °C from 1011 to 109 nuclei/m2. Additionally, U for yttrium disilicate phase decreased from (8.21 ± 0.28) μm/h to (0.54 ± 0.04) μm/h at the same temperature.

Sintering Kinetics of an Yttrium Aluminosilicate Glass

2012 ◽  
Vol 1475 ◽  
Author(s):  
Miguel O. Prado ◽  
Diana Lago ◽  
Diego S. Rodriguez
Keyword(s):  
Viscous Flow ◽  
Glass Powder ◽  
Glass Particle ◽  
Aluminosilicate Glass ◽  
Powder Size ◽  
Particle Volume ◽  
Sintering Kinetics ◽  
Nucleation Sites ◽  
Yttrium Disilicate ◽  
Kinetics Of

ABSTRACTYttrium aluminosilicate (YAS) glasses have been proposed as host matrices for the immobilization of radioactive elements. In addition, yttrium has been used to simulate actinides [1]. It is well known that these glasses are resistant to water corrosion and exhibit high Tg and good mechanical properties [2]. As shown in [3], on heating, yttrium disilicate and mullite / sillimanite crystals grow from the pre-existing nucleation sites on the surface, until each glass particle volume is fully crystallized (volume-homogeneous nucleation was not observed), decreasing the glassy surface available for sintering by viscous flow. Sintering takes place simultaneously, by viscous flow but competes with surface crystallization; thus, if thermal treatment is not carefully designed a vitroceramic is obtained. In this paper we study the isothermal sintering kinetics of a YAS glass-powder-size distribution and non-isothermal sintering kinetics at 1, 3, 5, 10 and 15 K/min of two YAS glass-powder-size distributions. From the experimental evidence obtained, and crystallization data from [3], we design a sintering procedure in order to achieve a high-density glass monolith with submicrometric crystalline phases.

Product Models for the Vitrification of West Valley High-Level Wastes

1988 ◽  
Vol 127 ◽  
Author(s):  
I. L. Pegg ◽  
E. E. Saad ◽  
X. Feng ◽  
R. B. Adiga ◽  
W. P. Freeborn ◽  
...  
Keyword(s):  
Process Model ◽  
Process Variations ◽  
Product Performance ◽  
Borosilicate Glasses ◽  
The West ◽  
Product Models ◽  
Waste Immobilization ◽  
High Level Nuclear Waste ◽  
Nuclear Waste Immobilization ◽  
High Level

ABSTRACTProperty models have been developed for the major properties that need to be controlled in the production of borosilicate glasses for West Valley high-level nuclear waste immobilization. The chemical durability is the most important parameter for product performance, while melt viscosity is the most critical parameter in assuring the processability of the glass. Simple models for these properties are described that are based on data from numerous glasses which were prepared with compositions in the region around the West Valley reference glass. A scheme for optimization of the target glass and for predicting the acceptability of glasses resulting from natural process variations is illustrated. This involves integration of the product models with a process model that was described previously. This approach has guided the present placement of the West Valley reference glass.

Role of Sulfate in Structural Modifications of Sodium Barium Borosilicate Glasses Developed for Nuclear Waste Immobilization

2008 ◽  
Vol 91 (12) ◽  
pp. 3903-3907 ◽  
Author(s):  
Raman K. Mishra ◽  
Kumaran V. Sudarsan ◽  
Pranesh Sengupta ◽  
Rajesh K. Vatsa ◽  
Avesh K. Tyagi ◽  
...  
Keyword(s):  
Nuclear Waste ◽  
Borosilicate Glasses ◽  
Structural Modifications ◽  
Waste Immobilization ◽  
Nuclear Waste Immobilization

Molecular Dynamics Simulations of Simplified Sodium Borosilicate Glasses: The Effect of Composition on Structure and Dynamics

2021 ◽  
Author(s):  
Pooja Sahu ◽  
Musharaf Ali ◽  
K. T. Shenoy ◽  
Sadhana Mohan ◽  
Arvind Ananthanarayanan ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Nuclear Waste ◽  
Material Properties ◽  
Borosilicate Glasses ◽  
Structure And Dynamics ◽  
Waste Immobilization ◽  
Nuclear Waste Immobilization ◽  
Dynamics Simulations

Fusion of valuable material properties has lent the acceptance of sodium borosilicate (NBS) glasses for nuclear waste immobilization. In spite of popularity, the mechanisms associated to these properties are yet...

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