Database Development of Chemical Thermodynamics of Protactinium for Performance Assessment of HLW Geological Disposal System

Shibutani, Tomoki; Shibutani, Sanae; Yui, Mikazu

In the performance analysis of geological disposal system of high-level radioactive waste (HLW), solubilities of radioactive elements are estimated by thermodynamic calculation. The reliable thermodynamic database (TDB) is needed for solubility estimation. In this report, thermodynamic data for protactinium solid and aqueous species for performance assessment were selected. For the refinement of previous PNC in house thermodynamic database (PNC-TDB), existing literatures data were surveyed and reliable thermodynamic data were selected under consideration of the scientific defensibility and the consistency with the whole PNC-TDB. The estimated solubility using refined PNC-TDB was higher than measured value. We have confirmed the refined data-set of Pa to be conservative for solubility estimation of performance assessment.