1. Introduction G2 and G3 graphite/gaz reactors were used from 1956 to 1984 in CEA-Marcoule. Reprocessing of their spent fuel were performed in MAR200 (dissolution) and UP1 (liquid/liquid separation) plants. During those operations, deposits (Figure 1) have formed at the bottom of tanks containing fission products. To carry out their dismantling, first of all the sludges have to be removed. To do so, CEA has to collect as much input data as possible to define a scenario. The properties of solid phases constituting the raw waste are key pa-rameters in preparation of the deposit retrieval scenario and the interim storage management. Technical choices such as retrieval tools and filtration process design will depend on the nature, particle size distribution, and mechanical behavior of the sludge and on the radiological inventory. This presentation will focus on the strategy used to collect experimental mesurements on their chemical, thermal and physical properties. A first part will present the context, the transfer from UP1 to hot cells in Atalante facility and the equipments used in the laboratory. This high activity raw materials require a new approach for sample preparation to reduce radiological impact on Atalante apparatus. Several characterizations were performed on adapted samples such as SEM-EDS, EPMA, Raman spectroscopy, XRD, calorimetry, image processing (Figure 2). The second part will focus on the sample preparation strategy and results obtained in the laboratory. To conclude this presentation, a scenario of retrieval to an intermediate storage way will be presented.