Solubility of Plutonium in MgCl2 and CaCl2 Solutions in Contact with Metallic Iron

The solubility of Pu(IV) hydrous oxide is studied at 22±2 °C under Ar atmosphere in 0.25 and 3.5 M MgCl2 (pHc¿9) and 3.5 M CaCl2 (pHc=11¿12) solutions in contact with iron powder. In alkaline 3.5¿4.0 M CaCl2 ternary Ca-Pu-OH complexes are formed and the solubility of PuO2·xH2O(s) increases from about 10-10 M at pHc=11 to 10-8¿10-7 M at pHc=12, both in the presence and absence of Fe powder. In the presence of iron the aqueous speciation is dominated by Pu(III) at pHc<10 and by Pu(IV) complexes at pHc>10. In the absence of reducing agents the aqueous speciation is dominated by Pu(V), with significant contributions of Pu(IV) complexes at pHc>10. The effect of ternary Ca-Pu(III,IV,V)-OH complexes in alkaline CaCl2 solutions can be described by assuming complex stoichiometries and experimental data from the oxidation state analogs Cm(III)/Nd(III), Th(IV) and Np(V). The ion interaction Pitzer approach is used for model calculations.

ALTMAIER M.;  NECK V.;  LUETZENKIRCHEN J.;  FANGHAENEL Thomas; 

2009-06-04

OLDENBOURG VERLAG

JRC52461

0033-8230,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC52461,   

10.1524/ract.2009.1593,