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Calcul des conductivites thermiques de ces composes de l'uranium a partir de leurs diffusivites thermiques mesurees entre 750 et 1500°K

An investigation was undertaken to determine the activation energy of iodine diffusion in graphite and the mechanism of diffusion and formation of the iodide. The heating curve of deposited iodide was found to have a peak at 530 deg C, while a diffusion peak occurred at 750 deg C, with an activation energy of 47 kcal/mole. The results are compared with diffusion of xenon and annealing of graphite irradiated with fast neutrons. (D.L.C.)

Uranium tetraiodide is oxidized to triuranium octoxide through three intermediates, which are deposited on silica powder heated to temperatures of about 400, 300 and 200°C respectively. The intermediates are produced by the action of oxygen contained in small amounts in a helium stream (1/100–1/10000 atm.) on uranium tetraiodide. The intermediates are considered to be compounds consisting of uranium, iodine and oxygen. Chemical analysis, the measurement of the melting point and X-ray analysis show that the compound deposited at the temperature of 400°C is uranium triiodide, while the compounds deposited at 300 and 200°C are both uranium tetraiodides. Three hypotheses have been formulated to interpret the above phenomenon, in which the reaction of uranium iodides with iodine has been studied.