Sol–gel synthesis of iodosodalite precursors and subsequent consolidation with a glass binder made from oxides and sol–gel routes

Radioiodine accumulates in aqueous solutions and off-gas streams during nuclear fuel reprocessing. In addition, radioiodine is highly mobile in geological environments. Most of the radioiodine can be captured during fuel reprocessing in off-gas streams using solid sorbents and scrubbing solutions. Once iodine is captured, it must be stored in a durable form for eventual disposal. Iodosodalite has been investigated as a waste form for radioiodine, however these synthesis processes often result in mixed products and iodine volatilization during consolidation. This paper proposes a novel approach to synthesizing iodosodalite utilizing a sol–gel method followed by heat treatment. This method was chosen to lower processing temperatures and improve product yield. Preliminary experiments conducted to determine the viability of this synthesis method are presented. In addition, consolidation of sol–gel derived iodosodalite with a glass binder was explored using three different methods: (1) incorporating the glass binder during gel preparation using alkoxide precursors; (2) separately preparing the glass binder using a sol–gel method; and (3) separately preparing the glass binder using a melt-quench technique. Glass-bonded iodosodalite was successfully synthesized using these novel sol–gel-based approaches. Highlights Iodosodalite precursors were produced with sol–gel approaches purely from alkoxides and NaI. For B2, the NaBSi 3 O 8 glass binder was added during the sol–gel process to produce the base gel. For B3, the NaBSi 3 O 8 glass binder was added in as alkoxides during the initial gel synthesis. For B4, NaBSi 3 O 8 glass binders were introduced as melt-quenched or sol–gel-derived additives. Similar iodosodalite yields for samples with melt-quench and sol–gel-derived glass binders (B4).