ORALS

SESSION: GlassTuePM2-R10	Durán International Symposium on Sustainable Glass Processing and Applications
Tue. 28 Nov. 2023 / Room: Boardroom
Session Chairs: Stephen Whettingsteel; Urmilla Jokhu-Sowell; Session Monitor: TBA

16:50: [GlassTuePM211] OL
IMMOBILIZATION OF SIMULATED RADIOACTIVE CESIUM VIA ALKALINE ACTIVATION OF WASTE PHARMACEUTICAL GLASS
Diana Lago¹ ; Giulia Tameni² ; Federico Zorzi³ ; Jozef Kraxner⁴ ; Dušan Galusek⁵ ; Enrico Bernardo² ; ¹FunGlass – Centre for Functional and Surface Functionalized Glass - Alexander Dubček University of Trenčín, Trenčín, Slovakia, Slovakia; ²Department of Industrial Engineering, University of Padova, Italy, Padova, Italy; ³Centro di Analisi e Servizi per la Certificazione (CEASC), University of Padova, University of Padova, Italy, Padova, Italy; ⁴FunGlass, Alexander Dubcek University of Trenčín, Trenčín, Slovakia; ⁵FunGlass – Centre for Functional and Surface Functionalized Glass, Alexander Dubček University of Trenčín. Joint Glass Centre of the IIC SAS, TnUAD and FChFT STU., Trenčín, Slovakia, Slovakia;
Paper Id: 470 [Abstract]

Vitrification is a widely used technology for treating high-level radioactive wastes (HLW) [1]. Borosilicate glasses are the matrix internationally selected for the immobilization of HLW. However, the use of this glass is linked to melting at high temperatures or sintering the glass powders loaded with wastes, which poses a risk of evaporation of volatile radioactive elements [2]. An attractive technology that implies the use of boro-aluminosilicate glasses (BASG) to produce materials with interesting properties for the stabilization of contaminants is the alkali activation [3]. Alkali-activated materials (AAMs) are widely recognized as eco-friendly alternatives to conventional high-CO2 binders. Alkali-activation technology also plays an important role in advancing the circular economy by effectively transforming inorganic waste streams into valuable products [4]. One of the promising areas for AAMs is the wastewater treatment. Various works addressed this topic. However, the use of these materials for immobilizing nuclear waste has been investigated less frequently, probably due to the intrinsic complexity of radioactive materials, that include a long half-life, high activity, solubility in water, and high volatility. One of the highly problematic radionuclides is cesium [5]. This work presents a new method of cesium immobilization, using alkali activation of BASG. This sustainable approach involves reused powdered glass from discarded pharmaceutical vials that are treated with a 2.5 M CsOH aqueous solution. The glass powders are suspended in the solution and consolidated at 40°C for 7 days, resulting in condensation reactions at hydrated surface layers. The products from partial glass dissolution combine with Cs+ ions to form a boro-pollucite (CsBSi2O6) solid solution. The immobilization process involves the formation of a stable gel that binds both the residual glass powder and the newly formed crystal phase. The main novelty lies in the use of a very low temperature to incorporate cesium into a framework mineral structure, which is recognized as one of the most promising options for storing radioactive cesium. Additionally, boro-pollucite represents the first example of an insoluble crystalline phase formed through the combination of activation by an alkaline compound (CsOH) and glass dissolution products. Cesium remains immobilized in blocks that can withstand immersion in boiling water. Further stabilization was achieved through the formation of glass matrix viscous flow sintered at temperatures as low as 700°C. The content of cesium remained almost constant before and after sintering. The effectiveness of the immobilization is confirmed by leaching test using the MCC-1 standard.

References:
[1] Jantzen, C. (2011). Development of glass matrices for high level radioactive wastes. In Handbook of advanced radioactive waste conditioning technologies (pp. 230-292). Woodhead Publishing.
[2] Lago, D. (2022). Cesium immobilization in porous silica and 137Cs self-heating simulations. Journal of Nuclear Materials, 565, 153697.
[3] Davidovits, J. (2011). Geopolymer Chemistry and Applications, 3rd Edition. Geopolymer Institute.
[4] Mazzi, A., Sciarrone, M., & Bernardo, E. (2023). Environmental performance of glass foam as insulation material from waste glass with the alkali activation process. Heliyon, 9(8).
[5] Caurant, D. (2007). Glasses, glass-ceramics and ceramics for immobilization of highly radioactive nuclear wastes. Nova Science.