A plutonium geochemical database for performance analysis of high-level radioactive waste repositories

A thermodynamic database (TDB) and a sorption database (SDB) for Pu have been developed in the context of the performance analysis for a high-level radioactive waste (HLW) repository in Japan. The TDB for Pu was based on inputs by international experts. The selected thermodynamic data for Fu are based on reliable measurement data and on a thermodynamic model for Pu(IV) and Pu(VI) and by chemical analogy for Pu(III) and Pu(V). The available ion-interaction parameters are also compiled, especially for Fu(IV) and Pu(III). The finally agreed TDB was used to set the necesssary Pu solubility and speciation information fur the: possible repository conditions. The sorption database for Pu was compiled via extensive literature searches. Data relating to reducing conditions were found to be scarce with the exception of some recent studies. K-d selection was carried out differently for the engineered barrier system (by diffusion studies) and for the geosphere (from the batch SDB).