An Evaluation of solubility limits on maximum uranium concentrations in groundwater

地下水中の最大ウラン溶解度の評価

岩月 輝希  ; Arthur, R. C,*

Iwatsuki, Teruki; Arthur, R. C,*

岐阜県東濃地域において、地下水中におけるウラン溶解度を観察,熱力学解析等に基づいて推測した。その結果、地下水中のウランの溶解度を支配する固相としてアモルファスUOが挙げられた。また、その溶解度は地下水のpH, Eh, 炭酸ガス分圧により大きく異なることが確認された。

Maximum uranium concentrations in groundwaters associated with a uranium ore deposit in Japan appear to be controlled by the solubility of the amorphous hydrous oxide, UO(am). This conclusion is supported by calculated saturation indices for this mineral using geochemical data characterizing the deposit and its surroundings. The conclusion that UO(am) appears to be solubility controlling in a natural system that has evolved over long periods of time supports the assumption adopted in many international studies that the solubility of this phase would limit the aqueous concentrations of U released from a deep geologic repository for nuclear wastes over similar time scales. Natural systems can thus provide a useful framework for testing assumptions and models used in repository safety assessments.