Study on Hydrolysis and Complexation Reactions of Transuranium Elements III

Moriyama, Hirotake*

In support of the safety assessment of geologic disposal of high level radioactive wastes, solubility measurement of U(IV) in alkaline solution was performed. The solubility of U(IV) was observed to increase in alkaline solution, and the hydrolysis constants betaand betawere obtained. Reported thermodynamic data of solubility products, hydrolysis constants and complexation constants were also compared and discussed. It was found that uncertainty of the reported betavalues of tetravalent actinide ions is still large. The betavalues were estimated by using a hard sphere model extended to 8 coordination, showing that such large uncertainty is due to the effect of colloid formation.