Glass - Back to the Future!



Presenting Author:
Marek Liška
<marek.liska@tnuni.sk>

article posted 21 April 2016


Marek Liška is a full professor at the A. Dubcek University of Trencín. Deputy head of the VILA Glass Centre.






Thermodynamic model and viscosity of glasses for Chrompik vitrification

Marek Liška1, Mária Chromcíková1, Magdaléna Teplanová1, Jan Machácek2
1Vitrum Laugaricio – Joint Glass Center of IIC SAS, TnUAD, and FChPT STU, Študentská 2, Trencín, SK-91150, Slovakia
2 University of Chemistry and Technology, Technická 5, Prague, CZ-166 28, Czech Republic


The present contribution deals with the structure and viscosity of boro-alumino-silicate glasses used for vitrification of the chrompic radioactive waste. Chrompic is a mixture of potassium chromate and potassium dichromate obtained during cooling of fuel elements after their removal from reactor A1 of NPP Jaslovské Bohunice [1,2]. The temperature-composition dependence of dynamic viscosity of glass forming melts with chemical composition close to the contemporary used glass for chrompic vitrification was studied. The chemical composition of 7-components studied glasses can be characterized (in weight %) as: (3.5 ± 3.5) % Li2O·(9.0 ± 5.0) % Na2O·(14.5 ± 3.5) % B2O3·(5.5 ± 5.5) % Al2O3·(5.5 ± 5.5) % TiO2·(4.5 ± 4.5) % Fe2O3·(57.5 ± 5.5) % SiO2. Thermodynamic model of Shakhmatkin and Vedishcheva [3] was constructed for each studied glass composition at Tg temperature. Within the model the glasses were considered as an ideal solution of 55 components with the stoichiometry given by the composition of stable crystalline phases of the studied 7-component oxide system. The components with negligible equilibrium molar amounts found in all studied glasses were not considered in the model. Such way only 14 components were retained. The temperature dependence of viscosity was measured in the range (102 - 1012) dPa.s using the falling ball and/or the rotational viscosimetry for high temperature viscosity and thermomechanical analysis measurement of the rate of isothermal axial deformation of axially loaded prismatic sample for the low temperature viscosity. The temperature dependence of viscosity was described by the Vogel Fulcher Tammann empirical equation and by the Adam and Gibbs configuration entropy viscosity equation. The compositional dependence of parameters of considered viscosity equations was described by multilinear forms (retaining only the statistically significant terms) of equilibrium molar amounts obtained from the thermodynamic model.

Temperature dependence of the glass contemporary used for Chromik vitrification:


References
1. http://www.javys.sk/sk/jadrove-zariadenia/technologie-spracovania-a-upravy-rao/vitrifikacna-linka (2013).
2. M.I. Ojovan, W.E. Lee: An introduction to nuclear waste immobilization. Elsevier, Oxford 2005.
3. N.M Vedishcheva, B.A. Shakhmatkin, C.A. Wright, J. Non-Cryst. Solids. 345–346 (2004) 39–44.

Acknowledgements
This work was supported by the Slovak Grant Agency for Science under the grant VEGA 2/0088/16 & 1/0386/16.