TY - GEN
T1 - Migration behaviour of lanthanides in compacted bentonite with iron corrosion product using electrochemical method
AU - Idemitsu, Kazuya
AU - Akiyama, Daisuke
AU - Matsuki, Yoshihiko
AU - Irie, Yusuke
AU - Inagaki, Yaohiro
AU - Arima, Tatsumi
PY - 2012
Y1 - 2012
N2 - After the closure of a high-level waste repository, corrosion of the carbon steel overpack will occur. The corrosion products can then migrate into bentonite and affect the migration behavior of radionuclides in bentonite. Therefore, electrochemical experiments, with Fe2+ supplied by anodic corrosion of carbon steel, were carried out to study trivalent lanthanides in compacted bentonite. The interface between a carbon steel coupon and bentonite (dry density, 1.5 Mg/m3) was spiked with a tracer solution containing Nd(NO3)3, Eu(NO3)3, Dy(NO 3)3, and Er(NO3)3. The carbon steel coupon was connected as the working electrode to a potentiostat and held at a constant potential between -550 and 0 mV (vs. Ag/AgCl reference electrode) for 7 days. A model using dispersion and electromigration could explain the measured profiles in the bentonite specimens. The best-fit electromigration velocity was related to the applied electric potential and was 1.0-3.8 nm/s for Nd, Eu, Dy, and Er ions. For these lanthanides, the best-tit dispersion coefficient was also related to the applied potential and was 0.8-1.6 μm2/s, and the dispersion length was calculated as 0.2 mm from the linear relationship between the dispersion coefficient and electromigration velocity. Finally, the apparent diffusion coefficient for these lanthanides was estimated as 0.6-0.9 μm 2/s.
AB - After the closure of a high-level waste repository, corrosion of the carbon steel overpack will occur. The corrosion products can then migrate into bentonite and affect the migration behavior of radionuclides in bentonite. Therefore, electrochemical experiments, with Fe2+ supplied by anodic corrosion of carbon steel, were carried out to study trivalent lanthanides in compacted bentonite. The interface between a carbon steel coupon and bentonite (dry density, 1.5 Mg/m3) was spiked with a tracer solution containing Nd(NO3)3, Eu(NO3)3, Dy(NO 3)3, and Er(NO3)3. The carbon steel coupon was connected as the working electrode to a potentiostat and held at a constant potential between -550 and 0 mV (vs. Ag/AgCl reference electrode) for 7 days. A model using dispersion and electromigration could explain the measured profiles in the bentonite specimens. The best-fit electromigration velocity was related to the applied electric potential and was 1.0-3.8 nm/s for Nd, Eu, Dy, and Er ions. For these lanthanides, the best-tit dispersion coefficient was also related to the applied potential and was 0.8-1.6 μm2/s, and the dispersion length was calculated as 0.2 mm from the linear relationship between the dispersion coefficient and electromigration velocity. Finally, the apparent diffusion coefficient for these lanthanides was estimated as 0.6-0.9 μm 2/s.
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U2 - 10.1557/opl.2012.641
DO - 10.1557/opl.2012.641
M3 - Conference contribution
AN - SCOPUS:84875508770
SN - 9781605114521
T3 - Materials Research Society Symposium Proceedings
SP - 611
EP - 616
BT - Scientific Basis for Nuclear Waste Management XXXV
T2 - 2012 MRS Spring Meeting
Y2 - 9 April 2012 through 13 April 2012
ER -