Chemical and technological aspects of the vitrification of high level radioactive wastes

The problems of transforming highly radioactive fission-product solutions from reprocessed fuel elements into a form suitable for final deposit are described. As storage in liquid form cannot be considered as optimum, a solidification is intended. Criteria are given for the selection of suitable final products. Accordingly, the vitrification, i.e. the incorporation of the fission products in glass, is generally suggested as the best method. The development as well as various vitrification processes are described. Chemical and technological problems affiliated to the vitrification and manufacture of monolithic glass blocks are pointed out. An alternative process aiming at the solidification of the fission-product solutions into glass beads as a first step and the embedding of these into a metal matrix as a second step presents various advantages compared to other processes. (orig.)