암석학/지구화학/표면동위원소분석․
10월 26일(목)2006 대한지질학회 추계학술발표회 초록집 • • 105
An experimental study of the geochemical behavior of radionuclides
Ju-Young Lee1,*․Je-Hun Jang2․Ho-Wan Chang1
1School of Earth and Environmental Sciences, Seoul National University, Korea, jylee123@snu.ac.kr
2Penn State Institutes of the Environment, Pennsylvania State University, U.S.A
The purpose of this study is to evaluate the leachability of radionuclides from ura- nium(U)-containing black slate under simulated low-/intermediate-level radioactive waste repository environments. The U-containing black slate was defined as a natural analogue to the consolidated radioactive wastes aged under the reducing conditions. It has (i) high car- bon concentration, (ii) enrichment of various isotopes of radioactive elements. Current de- sign concepts for low-/intermediate-level radioactive waste repositories in Korea involve un- derground emplacement of cementitious casings along the coastal area. In the long-term perspective, seawater can intrude into the low-/intermediate-level radioactive waste facility, which could result in the saline water of higher alkalinity from the dissolution of cement casings.
We focused on the leachability of various radionuclides from U-containing black slate in the carbonated water of high pH. The experiments were conducted using batch reactors at ambient conditions (25˚C, 1atm). Ionic strength was adjusted to 0.01M (pH 6, 7, and 8), 0.1M (pH 9 and 9.5) and 0.2M (pH 10) respectively using NaCl. For some experiments, the black slate depleted in Fe-oxide was used to account for the sorption of various radionuclides onto Fe-oxide. The results show that the leaching of uranium increased slightly when 3% FeO in black graphite slate was removed. The leaching concentration of other elements (e.g., Sr, Ni, and Co) increased at pH 6, 7, and 8 as a function of reaction time, but decreased over pH 9. Oppositely, the leaching of uranium was noticeable at pH higher than 9 in 0.1M of ionic strength, and the final concentration of uranium indicated the theoretical equilibrium at pH 9.
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