[en] The objective of the work presented in this paper is to develop an advanced technology for the conversion of the highly radiactive liquid wastes from fuel reprocessing into solid products of properties ensuring the safe isolation of the contained radionuclides from the biosphere. In pursuing this objective, the chemical and technical investigations led to the development of a process, called MINERVA, which was demonstrated in cold laboratory scale tests to be applicable not only to the solidification of various types of liquid high-level waste but also to all kinds of liquid aqueous medium-level and organic wastes generated in a Purex reprocessing plant. The Minerva process is carried out in two main operation steps: the solidification of the different waste solutions, either individually or mixed, to mineral-like granular phosphate compounds at about 500 deg C using a stirred-bed reactor; and the conditioning of the granulates according to their chemical composition and generated specific heat into either a monlithic phosphate glass-ceramic block by using the in-can melting technique, or by incorporating them into a metal matrix. (author)