Ceramicrete Stabilization of CST Resin: ITP Alternative Phase III Feasibility Study

The Ceramicretetrademark waste form is a magnesium phosphate hydrate, which sets as the result of an acid-base reaction between KH2PO4 and MgO in the presence of water. Based on the results of this feasibility study, this low temperature ceramic waste form is acceptable for stabilization of cesium loaded crystalline silicotitanate (CST) resin. The performance objective of CST stabilization is to convert a friable powdered resin into a monolithic form to improve handling and storage and to reduce the waste mobility. Advantages of this type of the CST-Ceramicretetrademark waste form include: room temperature processing of a fluid slurry, limited off gas, flexible mix designs, rapid setting, no free liquids, temperature tolerant and durable up to at least 90 degrees C. The Ceramicrete/220 waste form can be processed by in-container mixing or by batch mixing. Since a trace amount of free water will be associated with the wet resin in the CST-Ceramicretetrademark waste form, radiolysis of the free water may cause pressurization of the containers. Leaching tests were conducted to evaluate the CST-Ceramicretetrademark waste form performance relative to high-level waste glass. Results were very encouraging given that only one waste loading (50 wt. percent resin) was tested and that the leaching procedures were not fully optimized for a non-glass waste form. In general, the cesium leachability per the PCT test of the CST-Ceramicretetrademark waste was about 2X more than that of the ARM glass and about 200X more than the EA glass. For monolithic samples (MCC-1 test), the CST-Ceramicretetrademark waste form leached 4X to7X more cesium than the ARM glass. (The EA glass is not suited to monolithic leaching.) The CST-Ceramicretetrademark leaching results appear to be independent of curing temperature over the range 24 to 90 degrees C