Migration Behavior of Iron Ion in Compacted Bentonite Under Reducing Condition by using Electromigration.

2002 ◽  
Vol 757 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Seiji Yano ◽  
Xiaobin Xia ◽  
Yoshiro Kikuchi ◽  
Yaohiro Inagaki ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Corrosion Rate ◽  
Initial Period ◽  
Corrosion Products ◽  
High Level Waste ◽  
Migration Behavior ◽  
Iron Ions ◽  
Iron Ion ◽  
Buffer Material ◽  
Reducing Condition

ABSTRACTCarbon steel is one of the candidate overpack materials for high-level waste disposal and is expected to assure complete containment of vitrified waste glass during an initial period of 1000 years in Japan. The lifetime of the carbon steel overpack will depend on its corrosion rate. The corrosion rate of carbon steel is reduced by the presence of buffer material such as bentonite. Buffer material will delay the supply of corrosive materials and discharge of corrosion products through it. Carbon steel overpack will be corroded by consuming oxygen introduced by repository construction after closure of repository and then will keep the reducing environment in the vicinity of repository. The reducing condition will be expected to retard the migration of redox-sensitive radionuclides by lowering their solubilities. Therefore, the diffusion of corrosion products of iron in buffer material is important to discuss the corrosion rate of overpack, properties of buffer material and migration of redox-sensitive radionuclides. Electromigration experiments have been carried out with source of iron ions supplied by anode corrosion of iron coupon. Iron ions migrated as fast as 2mm in 2 or 3 hours under electrical field of 100V/m to the direction of cathode. Because the iron ions displaced exchangeable sodium ions in bentonite at a ratio of 1 to 2 during the electromigration, migrating iron ion could be ferrous ion.

Migration Behavior of Plutonium in Compacted Bentonite Under Reducing Condition Using Electromigration

2006 ◽  
Vol 985 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Yosuke Yamasaki ◽  
Syeda Afsarun Nessa ◽  
Yaohiro Inagaki ◽  
Tatsumi Arima ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Electric Potential ◽  
Initial Period ◽  
High Level Waste ◽  
Diffusion Field ◽  
Migration Behavior ◽  
Ferrous Ions ◽  
Compacted Bentonite ◽  
Buffer Material ◽  
Reducing Condition

AbstractCarbon steel is one of the candidate overpack materials for high-level waste disposal and is expected to assure complete containment of vitrified waste glass during an initial period of 1000 years in Japan. Carbon steel overpack will be corroded by consuming oxygen introduced by repository construction after closure of repository and then will keep the reducing environment in the vicinity of repository. The migration of iron corrosion products through the buffer material will affect migration of redox-sensitive radionuclides. Therefore the authors have carried out electromigration experiments with source of iron ions supplied by anode corrosion of iron coupons attached to compacted bentonite. Authors tried to use plutonium in this experimental configuration to obtain the knowledge of migration behavior of actinides. Authors also used cesium as reference. The concentrations of iron and sodium showed nearly complementary distributions. It is expected that iron ion could migrate as ferrous ion through the interlayer of montmorillonite replacing exchangeable sodium ions in the interlayer. Concentration profiles of plutonium in bentonite grew as time supplying electric potential as long as 168 h. Plutonium migrated from the iron anode toward cathode as deeper than 1 mm of the interior of bentonite even in 48 h, though plutonium could not diffuse 1 mm for 2 years. On the other hand, profiles of cesium seemed to be controlled by ordinary diffusion because of large diffusion coefficient of cesium in bentonite as large as 10$^{-12}$ m$^{2}$/s. Drift of the cesium profile by electric potential gradient could be observed clearly after 240 h at individual experiment for cesium. Apparent dispersion coefficients of plutonium were calculated from the profiles and were as large as 10$^{-13}$ m$^{2}$/s. Since plutonium migration was accelerated by electric potential, plutonium chemical species would have positive charge and were estimated as PuOH$^{2+}$ or PuCl$^{2+}$ by the thermodynamic calculation. Thus this experiment can provide a diffusion field for cations under a reducing condition with ferrous ions in water-saturated bentonite.

Diffusion Behavior of Iron Corrosion Products In Buffer Materials

2002 ◽  
Vol 713 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Seiji Yano ◽  
Xia Xiaobin ◽  
Yaohiro Inagaki ◽  
Tatsumi Arima ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Carbon Steel ◽  
Corrosion Rate ◽  
Apparent Diffusion Coefficient ◽  
Corrosion Products ◽  
High Level Waste ◽  
Diffusion Behavior ◽  
Buffer Material ◽  
Apparent Diffusion ◽  
Reducing Condition

ABSTRACTCarbon steel is one of the candidate overpack materials for high-level waste disposal and is expected to assure complete containment of vitrified waste glass during an initial period of 1000 years in Japan. The lifetime of the carbon steel overpack will depend on its corrosion rate. The corrosion rate of carbon steel is reduced by the presence of buffer material such as bentonite. Buffer material will delay the supply of corrosive materials and discharge of corrosion products through it. Carbon steel overpack will be corroded by consuming oxygen introduced by repository construction after closure of repository and then will keep the reducing environment in the vicinity of repository. The reducing condition will be expected to retard the migration of redox-sensitive radionuclides by lowering their solubilities. Therefore, the diffusion of corrosion products of iron in buffer material is important to discuss the corrosion rate of overpack, migration of redox-sensitive radionuclides and properties of buffer material. The purpose of this paper is to study diffusion behavior of a corrosion product of iron in compacted bentonites under a reducing condition with a carbon steel. The diffusion mechanism of iron in the compacted bentonites were discussed by estimation of iron species in the bentonite pore water. There were two diffusion paths of iron in the compacted bentonites used in this study; the fast path has low capacity of iron, ca. 1wt%, and large apparent diffusion coefficient, ca. 10−12 m2/s and the slow path has high capacity of iron, ca. 10wt%, and small apparent diffusion coefficient, ca. 10−14 m2/s.

Migration Behavior of Plutonium in Compacted Bentonite under Reducing Condition by Using Electromigration

2003 ◽  
Vol 807 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Xiaobin Xia ◽  
Yoshiro Kikuchi ◽  
Yaohiro Inagaki ◽  
Tatsumi Arima ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Initial Period ◽  
Chemical Species ◽  
High Level Waste ◽  
Migration Behavior ◽  
Buffer Material ◽  
Reducing Environment ◽  
High Level ◽  
Corrosion Of Iron ◽  
Reducing Condition

ABSTRACTCarbon steel is one of the candidate overpack materials for high-level waste disposal and is expected to assure complete containment of vitrified waste glass during an initial period of 1000 years in Japan. Carbon steel overpack will be corroded by consuming oxygen introduced by repository construction after closure of repository and then will keep the reducing environment in the vicinity of repository. The reducing condition will be expected to retard the migration of redox-sensitive radionuclides by lowering their solubilities. Therefore, the presence of corrosion products of iron in buffer material is important to discuss the migration behavior of redox-sensitive radionuclides. Plutonium electromigration experiments in bentonite have been carried out with source of iron ions supplied by anode corrosion of iron coupon. Plutonium migrated from the iron anode toward cathode as deep as 1 mm of the interior of bentonite within 24 h. Thus plutonium chemical species would have positive charge and were estimated as PuOH2+ or PuCl2+ by the thermodynamic calculation.

Migration Behavior of Ferrous Ions in Compacted Bentonite Under Reducing Conditions Using Electromigration

2004 ◽  
Vol 824 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Xiaobin Xia ◽  
Yoshiro Kikuchi ◽  
Yaohiro Inagaki ◽  
Tatsumi Arima
Keyword(s):  
Carbon Steel ◽  
Corrosion Rate ◽  
Electrical Potential ◽  
Infiltration Rate ◽  
Corrosion Products ◽  
Ferrous Ion ◽  
High Level Waste ◽  
Dry Density ◽  
Compacted Bentonite ◽  
Buffer Material

AbstractCarbon steel is one of the candidate overpack materials for high-level waste disposal and is expected to assure complete containment of vitrified waste glass during an initial period of 1000 years in Japan. The lifetime of the carbon steel overpack will depend on its corrosion rate. The corrosion rate of carbon steel is reduced by the presence of buffer material such as bentonite. Buffer material will delay the supply of corrosive materials and discharge of corrosion products through it. Carbon steeloverpack will be corroded by consuming oxygen introduced by repository construction after closure of repository and then will keep the reducing environment in the vicinity of repository. Therefore, it is important to study the migration of iron corrosion products through the buffer material because it may affect the corrosion rate of overpack, migration of redox-sensitive radionuclides, and the properties of the buffer material. Electromigration experiments have been carried out with source of iron ions supplied byanode corrosion of iron coupon in compacted bentonite. The carbon steel coupon was connected as the working electrode to the potentiostat and was held at a constant applied potential between - 200 to 1000 mV vs. Ag/AgCl electrode for 48 hours. Corrosion currents were 0.5 to 2mA initially and depended on the supplied electrical potential, then decreased to approximately 0.1 mA in a few hours. The final corrosion current was independent of supplied electrical potential. It is expected that iron ion could migrate as ferrous ion through interlayer of montmorillonite replacing exchangeable sodium ions in the interlayer. The rate-determining process of this experimental configuration could be infiltration rate of ferrousioninto bentonite. Infiltration rate of ferrous ion into bentonite was increasing with dry density of bentonite.

Diffusion of Corrosion Products of Iron in Compacted Bentonite.

1992 ◽  
Vol 294 ◽  
Author(s):  
K. Idemitsu ◽  
H. Furuya ◽  
Y. Inagaki
Keyword(s):  
Carbon Steel ◽  
Corrosion Product ◽  
Hydrogen Generation ◽  
Ferric Hydroxide ◽  
Corrosion Products ◽  
Ferrous Ion ◽  
Silica Sand ◽  
High Level Waste ◽  
Buffer Material ◽  
The Difference

ABSTRACTCarbon steel is one of the candidate overpack materials for high-level waste disposal. The corrosion rate of carbon steel is reduced by the presence of buffer materials such as bentonite and seems to be affected by the diffusion of corrosive materials and corrosion products through the buffer material.The apparent diffusivities of corrosion product of iron were measured in some bentonite specimens in contact with carbon steel. The apparent diffusivities of iron were also measured without carbon steel for comparison. The apparent diffusivities of corrosion product were on the order of 10−12 m2/s and showed a tendency to decrease with increasing density of the bentonite specimen. There was no significant effect of silica sand on the apparent diffusivities. The apparent diffusivities of iron in the system without carbon steel were in the range of 10−14 m2/s and showed a tendency to increase with increasing silica sand content. The difference of the diffusivities between corrosion product and iron without carbon steel seems to be due to the difference of diffusing species. The color of the corrosion product was dark-green during contact with bentonite specimens and became red on exposure to air in a few minutes. Gas bubbles were also observed in the corrosion product. This suggests hydrogen generation during corrosion of the carbon steel. Thus the diffusing species seems to be in a reduced state, probably ferrous ion. On the other hand, the diffusing species of iron without carbon steel was probably a ferric hydroxide complex that was negatively charged. This suggests that ferrous ion could diffuse in the surface water adsorbed on bentonite, while ferric complex was excluded.

Migration Behaviour of Ferrous Ion in Compacted Bentonite Under Reducing Conditions Controlled With Potentiostat

2008 ◽  
Vol 1107 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Syeda Afsarun Nessa ◽  
Shigeru Yamazaki ◽  
Hirotomo Ikeuchi ◽  
Yaohiro Inagaki ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Dispersion Coefficient ◽  
Corrosion Products ◽  
Ferrous Ion ◽  
Iron Ions ◽  
Ferrous Ions ◽  
Iron Corrosion ◽  
Compacted Bentonite ◽  
Migration Behaviour ◽  
Buffer Material

AbstractCarbon steel overpack is corroded by consuming oxygen introduced by repository construction after closure of the repository and then maintains the reducing environment in the vicinity of the repository. The migration of iron corrosion products through the buffer material will affect the migration of redox-sensitive radionuclides. Therefore, it is important to study the migration of iron corrosion products through the buffer material because it may affect the corrosion rate of overpack, and migration of redox-sensitive radionuclides. Electromigration experiments have been conducted with the source of iron ions supplied by anode corrosion of the iron coupon in compacted bentonite. The carbon steel coupon was connected as the working electrode to the potentiostat and was held at a constant supplied potential between - 650 to +300 mV vs. Ag/AgCl electrode for up to 168 hours. The amount of iron penetrated into a bentonite specimen was in good agreement with the calculated value from the corrosion current under the assumption that iron is dissolved as ferrous ions. A model using dispersion and electromigration could explain the measured iron profiles in the bentonite specimens. The fitted value of electromigration velocity depended on the potential supplied. On the other hand the fitted value of the dispersion coefficient did not depend on the potential supplied but a constant. This constant dispersion coefficient could be due to the much larger diffusion coefficient of ferrous ion in bentonite compared with the effect of mechanical dispersion. The experimental configurations used in this study are applicable to the examination of the migration behaviour of cations with the source of iron ions under a reducing condition controlled with a potentiostat.

Migration Behaviour of Lanthanides in Compacted Bentonite with Iron Corrosion Product Using Electrochemical Method

2012 ◽  
Vol 1475 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Daisuke Akiyama ◽  
Yoshihiko Matsuki ◽  
Yusuke Irie ◽  
Yaohiro Inagaki ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Dispersion Coefficient ◽  
Reference Electrode ◽  
High Level Waste ◽  
Dry Density ◽  
Migration Behavior ◽  
Iron Corrosion ◽  
Compacted Bentonite ◽  
Steel Coupon ◽  
Best Fit

ABSTRACTAfter 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(NO3)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-fit 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 μm2/s.

The Relation between Corrosion Rate and Corrosion Products from Low Carbon Steel

2000 ◽  
Vol 220 (1) ◽  
pp. 351-356 ◽  
Author(s):  
A.L. Morales ◽  
D. Cartagena ◽  
J.L. Rendón ◽  
A. Valencia
Keyword(s):  
Carbon Steel ◽  
Corrosion Rate ◽  
Low Carbon Steel ◽  
Corrosion Products ◽  
Low Carbon

Dissolution Behavior of Waste Glass Under Reducing Condition

1993 ◽  
Vol 333 ◽  
Author(s):  
Tsuyoshi Imakita ◽  
Kaoru Sasakawa ◽  
Fumio Matsuda ◽  
Ryutaro Wada
Keyword(s):  
Carbon Steel ◽  
Corrosion Rate ◽  
Redox Potential ◽  
Corrosion Test ◽  
Waste Glass ◽  
Dissolution Behavior ◽  
Leaching Behavior ◽  
Reducing Conditions ◽  
Reducing Condition

ABSTRACTA corrosion test of a model waste glass was carried out with and without carbon steel, and the leaching behavior of the glass was studied under reducing condition in a glove box purged with N2. The redox potential and pH were monitored, and the concentration of Fe, Na, Si, and Mo in the leachates were measured to understand the leaching behavior of the glass. The redox potential of the leachates obtained in the corrosion test coexisting with carbon steel under reducing conditions showed initially that it was based on an Fe0/Fe2+ redox potential, and gradually it increased to that based on Fe2+/Fe3+ one. The corrosion rate of the glass under oxidizing conditions was ten times greater than that obtained with carbon steel, and that under reducing condition with carbon steel was negligible small.

Sign in / Sign up

Export Citation Format

Share Document