[en] The aim of this work is to propose solutions for ultimate wastes management which could be under the form of a mixture of fission products chlorides diluted in the LiCl-KCl eutectics. The idea consists to recover all the fission products (Rb, Cs, Sr, Ba, Y, rare earths) and to study the possibilities of containment inside crystalline matrix(ces). Thus has been retained the direct synthesis of the matrix in the molten salt, or the obtention of a solid precursor which could be used in dry way syntheses. At first is considered the behaviour of rare earths. The study has shown that monazite could be considered to trap all the rare earths and yttrium. The synthesis of this matrix can be made at low temperature (500 C) in molten chloride medium without formation of secondary phases. The second step of this study will consist in specific conditioning of fission products elements inside matrices of different formulations. (O.M.)