The highly active fission product solutions arising in reprocessing must be transferred to a product suitable for ultimate disposal. Vitrification has proven to be a suitable method for this purpose. In the French AVM process, the liquid high active waste solution is heated to high temperatures which causes the liquid to evaporate and the resulting granulate is molten at 1,100 ยฐC to glass adding glass frit. This process is used in the French large-scale reprocessing plant La Hague. In the process developed by the Karlsruhe Research Centre, liquid high active waste solution is added directly to the molten glass mass at 1,150 ยฐC. The liquid evaporates and the radioactive solids are homogenously embedded in the molten glass mass. In both processes the molten glass mass is filled into 1.3 m high 150 l steel containers holding about 400 kg glass product. The heat production due to the radioactive decay of the ingredients of such a container amounts to 1.5 to 2 kW.