Project Portugal 2030

Summary

The main objective of this proposal is exploring the potential processing routes for the immobilization of fluoride salts produced from MSRs into oxide glasses and glass-ceramics. A MSR salt waste has typical composition of 65LiF–29BeF2–5ZrF4–1UF4 (mol.%) (Davis et al., 2023; Mcmurray et al., 2021; Riley et al., 2019; Sun et al., 2019) . Since this composition is highly dangerous to use in laboratory experiments, a simulated salt waste with composition 65LiF–29CaF2–5ZrF4–1NdF3 (mol.%) will be used in the present proposal. Therefore, several objectives can be itemized: Objective 1: exploration of potential processing pathways for the immobilization of fluoride salt wastes using borosilicate-based glass compositions in the system Na2O–CaO–Al2O3–B2O3–SiO2 (mol.%). It will be important to consider the fluoride-solubility in borosilicate glasses, which depends on the molar ratio of ormers to modifiers. Glasses will be synthesized by melt-quench technique. The goal is to optimize the glass compositions and the processing parameters in order attain the highest waste loadings while maintaining the melting temperatures as low has possible (=1200°C). This will be a novel approach to use glass compositions to incorporate wastes generated by MSRs. - Objective 2: Evaluate the feasibility of synthesis of compositions similar to those obtained in objective 1 by incorporating glass cullet, which is mainly constituted by soda-lime glass typically containing SiO2, Na2O, CaO and Al2O3 oxides. This approach will allow to increase the total incorporation of wastes by including the glass cullet. This approach could allow the recycling of some glass cullet that is typical more difficult to recycle in common glass industry such as windowpanes or coloured glass containers (e.g. green or brown bottles) or even Cathode-ray tube glasses, which would add some of the principal oxides of the glass compositions in the system Na2O–CaO–Al2O3–B2O3–SiO2. - Objective 3: preparation of glass-ceramic materials from compositions obtained according to objective 1. The goal is to obtain materials with enhanced chemical and mechanical durability through controlled partial crystallization of the selected glass compositions aiming at obtaining materials with enhanced resistance to degradation. - Objective 4: preparation of monolithic glass and GC samples containing the mobilized fluoride salt wastes for chemical durability assessment in order to establish the composition-structure-chemical durability correlations. The proposed objectives constitute a step forward in the scientific knowledge regarding the immobilization of MSR wastes and represent an opportunity to European scientific community establish a position in a research field that is presently dominated by U.S. and Russian Federation. The results expected from the present proposal pretend to shed some light in the correlations composition-structure-properties of MSR waste-containing borosilicate glasses.