Study on solubility of cesium iodide and cesium molybdate in water at around room temperature

Some of the Cs inside the Fukushima Daiichi Nuclear Power Station would be deposited in chemical forms such as CsI and Cs₂MoO₄. Since Cs compounds are generally water-soluble, it is predicted that the migration of Cs through the aqueous phase occurs in the long term. Knowledge of the solubility in water is required as basic data for such migration behavior evaluation. Therefore, this study was conducted to investigate the dissolution properties of CsI and Cs₂MoO₄ in water at 20℃ and 25℃. The solubilities of CsI at 25℃ calculated using thermodynamic data and the Pitzer ion interaction model were in good agreement with the literature value. It was found that the literature value of CsI at around room temperature is highly reliable. The experimental value of CsI at 20℃ obtained by the OECD test guideline 105 flask method (test guideline) was also in good agreement with the literature value. The measured solubility of Cs₂MoO₄ was 256.8±12.7 (g/100 g H₂O) at 20℃ using the test guideline. This measured solubility of Cs₂MoO₄ was found to be comparable to those of other alkaline molybdates and considered to be more reliable than the literature value. (author)