Abstract
Solubility of a radionuclide is important for defining the release source term of a radioactive waste in the safety and performance assessments of a radioactive waste repository. When the pH and redox potential of the KURT groundwater were changed by an electrical method, the concentrations of uranium and thorium released from <TEX>$UO_2$</TEX>(cr) and <TEX>$ThO_2$</TEX>(cr) at alkali pH(8.1 <TEX>${\sim}$</TEX> 11.4) and reducing potential (Eh < -0.2 V) conditions were less than <TEX>$10^{-7}mole/L$</TEX>. Unexpectedly, the concentration of tetravalent thorium is slightly higher than that of uranium at pH = 8.1 and Eh= -0.2 V conditions, and this difference may be due to the formation of hydroxide-carbonate complex ions. When <TEX>$UO_2$</TEX>(s) and <TEX>$UO_2$</TEX>(am, hyd.), and <TEX>$ThO_2$</TEX>(s) and <TEX>$Th(OH)_4(am)$</TEX> were assumed as solubility limiting solid phases, the concentrations of uranium and thorium in the KURT groundwater calculated by the PHREEQC code were comparable to the experimental results. The dominating aqueous species of uranium and thorium were presumed as <TEX>$UO_2(CO_3)_3^{4-}$</TEX> and <TEX>$Th(OH)_3CO_3^-$</TEX> at pH = 8.1 <TEX>${\sim}$</TEX> 9.8, and <TEX>$UO_2(OH)_3^-$</TEX> and <TEX>$Th(OH)_4(aq)$</TEX> at pH = 11.4.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
