A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media - Archive ouverte HAL Access content directly
Journal Articles EPJ N - Nuclear Sciences & Technologies Year : 2018

A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media

(1) , (1) , (1) , (2)
1
2

Abstract

Dissolution is a milestone of the head-end of hydrometallurgical processes, as the stabilization rates of the chemical elements determine the process performance and holdup. This study aims at better understanding the chemical and physico-chemical phenomena of uranium dioxide dissolution reactions in nitric acid media in the Purex process, which separates the reusable materials and the final wastes of the spent nuclear fuels. It has been documented that the attack of sintering-manufactured uranium dioxide solids occurs through preferential attack sites, which leads to the development of cracks in the solids. Optical microscopy observations show that in some cases, the development of these cracks leads to the solid cleavage. It is shown here that the dissolution of the detached fragments is much slower than the process of the complete cleavage of the solid, and occurs with no disturbing phenomena, like gas bubbling. This fact has motivated the measurement of dissolution kinetics using optical microscopy and image processing. By further discriminating between external resistance and chemical reaction, the " true " chemical kinetics of the reaction have been measured, and the highly autocatalytic nature of the reaction confirmed. Based on these results, the constants of the chemical reactions kinetic laws have also been evaluated.
Fichier principal
Vignette du fichier
epjn160032.pdf (2.23 Mo) Télécharger le fichier
Origin : Publication funded by an institution

Dates and versions

cea-01724047 , version 1 (06-03-2018)

Licence

Attribution - CC BY 4.0

Identifiers

Cite

Philippe Marc, Alastair Magnaldo, Jérémy Godard, Éric Schaer. A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media. EPJ N - Nuclear Sciences & Technologies, 2018, 4 (2), pp.1-13. ⟨10.1051/epjn/2017026⟩. ⟨cea-01724047⟩
81 View
95 Download

Altmetric

Share

Gmail Facebook Twitter LinkedIn More