[en] The most imprtant step in treating high level radioactive waste is the generation of a solid and stable product out of the radioactive solution arising from reprocessing. This involves a reduction of the volume of the solution by approximately a factor of 10, which means that a 1,000 MWe reactor will only produce a total of 2.0-2.5 m³ of solidified waste a year. Temporary storage facilities in Europe presently only hold small amounts, i.e., approximately 100 m³, of fission product concentrates from reprocessing of light water reactor fuel and another 2,000 m³ from fuels of gas cooled reactors. Three solidification techniques are presently pursued in the Federal Republic, two of them use borosilicate glass blocks, the other one phosphate glass. The purpose of the development work now going on is the contruction of a waste solidification plant for the planned KEWA reprocessing plant with an annual capacity of 1,500 te. (orig.)