Étude cinétique de la nucléation primaire et de la croissance cristalline au cours de la coprécipitation de solutions solides d’oxalates d’actinides

Abstract : Current concepts for future nuclear systems aim at improving the fuel cycle with the co management of actinides in order to enhance the fuel performance and to reduce the proliferation risk. Actinides coconversion processes play an important role by producing mixed actinides compounds used as starting materials for fuel re-fabrication. Oxalic coprecipitation is one investigated way to synthesize solid solutions of actinides – lanthanides mixed oxalates which have to meet strict standards. The nucleation and growth kinetic laws involve a fundamental crystallization parameter such as the supersaturation. For the precipitation of solid solutions, different theories are developed in the literature, however none have been verified experimentally. A new suitable expression for the supersaturation ratio applicable is presented in order to determine a general model for the expression of nucleation and growth rates. The experimental study of the primary nucleation kinetics is based on a “stopped flow” apparatus which provides a very good micromixing of the reactants. The kinetic laws of solid solutions verify the theory of Volmer and Weber applied to the coprecipitation. The method of calculating the supersaturation developed allows to find the typical behavior of nucleation. The experimental results demonstrate that the coprecipitation of the solid solution is kinetically favored over the precipitation of simple oxalates due to a lower energy barrier for the solid solution. The crystal growth rate is determined from a spectrophotometric monitoring of the reactant concentrations using a seed charge. The crystal growth is controlled by the surface integration with a spiral mechanism.
Document type :
Theses
File URL :
http://docnum.univ-lorraine.fr/prive/DDOC_T_2012_0425_PARMENTIER.pdf
Complete list of metadatas

https://hal.univ-lorraine.fr/tel-02154060
Contributor : Thèses Ul <>
Submitted on : Wednesday, June 12, 2019 - 4:29:28 PM
Last modification on : Thursday, June 13, 2019 - 1:29:49 AM

Identifiers

  • HAL Id : tel-02154060, version 1

Collections

Citation

Delphine Parmentier. Étude cinétique de la nucléation primaire et de la croissance cristalline au cours de la coprécipitation de solutions solides d’oxalates d’actinides. Génie des procédés. Université de Lorraine, 2012. Français. ⟨NNT : 2012LORR0425⟩. ⟨tel-02154060⟩

Share

Metrics

Record views

4