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Genre/Form: | Thèses et écrits académiques |
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Material Type: | Thesis/dissertation |
Document Type: | Book |
All Authors / Contributors: |
Bénédicte Arab-Chapelet; Francis Abraham; Université Lille 1 - Sciences et technologies (Villeneuve-d'Ascq / 1970-2017). |
OCLC Number: | 982736180 |
Notes: | N° d'ordre (Lille 1) : 3693. Résumé en français et en anglais. |
Description: | 1 vol. (179 p.) : ill. en noir et en coul. ; 30 cm. |
Responsibility: | par Bénédicte Chapelet-Arab ; [sous la direction de Francis Abraham]. |
Abstract:
At the end of the nuclear fuel reprocessing, co-conversion by oxalic co-precipitation is one of the routes investigated to immobilize actinides in a solid compound before their subsequent recycling. The development of this process requires a good knowledge of the structure of the co-precipitated compounds. The structural resolution by single crystal X-ray diffraction of U(IV)-Ln(III) oxalates, where lanthanides simulate the actinides behaviour, led to elucidate three solid solutions characterized by an unexpected U(IV)-Ln(III) mixed site and to the constitution of a structural database decisive for the identification of actinides co-precipitated compounds. In addition, the thorough investigation of these mixed oxalates has allowed (i) to specify the solid solution domains; (ii) to underline the quantitative transfer of actinides initially in solution to the co-precipitated solid, without modification of their oxidation state; (iii) to clarify the role of monovalent cations taking part in the deficit charge compensation in the structure. Finally, these original results were extended to the An(IV)-An(III) mixtures and mixed oxalates exhibiting structures similar to those obtained for the U(IV)-Ln(III) co-precipitates, were synthesised. The existence of An(IV)-An(III) mixed site within a compound oxalate is totally original and at the basis of the original properties of the co-precipitate. Then, actinides co-precipitation allows to elaborate particularly homogeneous solid compounds with desired composition which can be advantageously used as starting materials for mixed oxides synthesis.
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