Optimisation of U back-extraction

Few losses and no deposit were observed after the run Lil and Li2. These two experiments were carried out inside the inconel container. The pressure insured by the tightly sealed container prevented the AICI3 volatilisation. 

The weight evolution, the uranium content in the salt phase and the U back extraction efficiency are summarised in Table 6.3.3. The total loss of weight observed after each experiment (that includes both metal and salt phase) is partly due to AICI3 evaporation. It is particularly the case for run Nal where an important volatilisation of AICI3 was observed. The mechanical treatment of the salt after experiment may also explain a part of the total loss of weight. Table 6.3.3 shows that the amount of U in the salt phase, determined by UV-visible spectrophotometry is in perfect agreement with the loss of weight of the metal phase. 

The CaCl2-LiCl (70 to 30 mol%) salt mixture seems to be the best one for the grouped actinide back-extraction studies. However, the use of a perfectly tightly sealed device is absolutely needed to prevent any AICI3 volatilisation. 

3 Extrapolation to the U back-extraction as a function of the AlClj content in the salt 

An extrapolation of the efficiency of U back-extraction as a function of the AICI3 concentration was assessed for the four chloride salts studied using the free Gibbs energy, that is -651.459 kJ/mol for UCI3 

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