Reflux Dissolution of Thorium Dioxide in Nitric Acid

• Published in: Hé huàxué yŭ fàngshè huàxué Vol. 47; no. 3; pp. 235 - 241
• Main Authors: Zong-hui LU, Ting YU, Bin LI, Hui HE, Ye ZHANG
• Format: Journal Article
• Language: Chinese
• Published: Editorial Office of Journal of Nuclear and Radiochemistry 01.06.2025
• Subjects: kinetic; reflux dissolution; thorium dioxide
• ISSN: 0253-9950
• DOI: 10.7538/hhx.2025.47.03.0235

This study aims to investigate the reflux dissolution process of thorium dioxide in nitric acid, seeking an alternative to the current fluoride ion-dependent dissolution methods to prevent corrosion of stainless steel dissolvers and subsequent processing issues. By employing a reflux dissolution apparatus and utilizing nitric acid as the solvent, the effects of initial nitric acid concentration, temperature, and initial thorium ion concentration on the dissolution efficiency of thorium dioxide were systematically studied. The experimental results reveal that the apparent activation energy for the dissolution process of thorium dioxide in nitric acid is 41.47 kJ/mol. An increase in initial nitric acid concentration from 9 mol/L to 12 mol/L corresponded with an increased dissolution rate of thorium dioxide, exhibiting an apparent order of about 3. However, a decline in the dissolution rate was observed when the initial nitric acid concentration surpassed 12 mol/L. Additionally, the initial thorium ion concentra