A STABLE CERAMIC-MATRIX FOR FIXATION OF FISSION-PRODUCTS

A ceramic matrix based on alpha-Al2O3 (corundum) has been developed fo r fixation of radioactive wastes. Transuranium elements are encapsulat ed in a pure alumina matrix whereas fission products that contain cesi um require a mixed matrix consisting of 90 Wt% Al2O3 and 10 Wt% SiO2. The production process utilizes a sol-gel technique supported by seedi ng with alpha-Al2O3 submicron particles. Thus, a good product homogene ity and a relatively low sintering temperature are accomplished. The p roduction process consists of simple and conventional steps: mixing of starting materials and waste, extrusion of the gel, drying, calcinati on and sintering. During heat treatment only negligible volatilization is observed and no corrosive melt must be handled. The waste product shows very low leaching rates. Weight losses of 3 x 10(-7) g cm-2 d-1 have been measured in a Soxhlet apparatus at 97-degrees-C.