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Journal Articles

Modeling of chemical transition of nitrate accompanied with corrosion of carbon steel under alkaline conditions

Honda, Akira; Masuda, Kaoru*; Imakita, Tsuyoshi*; Kato, Osamu*; Nishimura, Tsutomu*

Zairyo To Kankyo, 58(5), p.182 - 189, 2009/05

Interaction between carbon steel and nitrate was modeled using the mixed potential concept. Carbon steel was selected as an example of metal components in the repository of radioactive waste. The nitrate reduction accompanied by the corrosion of carbon steel was modeled as a reaction series such as nitrate - nitrite - ammonia. The sum of the current of the reaction series of nitrate - nitrite - ammonia and that of water reduction was assumed to balance with the corrosion current of carbon steel. The input parameters for this kinetic model were determined by electrochemical measurement and immersion test. The results of the immersion test can be interpreted by the analyses of the model.

Journal Articles

Stable measurement of redox potential of aqueous solution using platinum electrode with continuous polishing tool

Ioka, Seiichiro; Iwatsuki, Teruki; Kato, Osamu*; Imakita, Tsuyoshi*

Bunseki Kagaku, 55(10), p.793 - 797, 2006/10

 Times Cited Count:0 Percentile:0.01(Chemistry, Analytical)

Performance test for redox potential measurement of solution was conducted using continuous polished and untreated Platinum working electrodes in under inert condition. The redox potential measured by polished electrode immediately shows steady value, and approximately coincides with the equilibrium value of redox reaction between HS$$^{-}$$ and S$$_{4}$$$$^{2-}$$. Then the redox potentials would be controlled by the equilibrium of the redox reaction. On the other hand, redox potential measured by untreated electrode was +0.2V higher than that measured by continuous polished electrode. The redox potential measured implies that the SO$$_{4}$$$$^{2-}$$ is dominant species in solution. Disagreement of redox potentials measured by polished and untreated electrodes may be caused by deactivation of platinum electrode of adsorption of sulfuric acid anions.

Journal Articles

Chemical transition of nitrate ions accompanied with corrosion of carbon steel under alkaline conditions

Honda, Akira; Kato, Takashi; Tateishi, Tsuyoshi*; Imakita, Tsuyoshi*; Masuda, Kaoru*; Kato, Osamu*; Nishimura, Tsutomu*

Zairyo To Kankyo, 55(10), p.458 - 465, 2006/10

Migration of radioactive material can be affected by the redox condition and the concentration of ligands in the repository of radioactive waste. It is possible that radioactive waste contains nitrate which can affect the migration behavior of radioactive nuclides by both changing the redox condition of the environment and acting as a ligand. On the other hand, several researchers observed the reduction of nitrate ions in ammonia due to the iron. Ammonia has a potential to ligand for radioactive nuclides. Nitrate can also affect the rate of hydrogen gas evolution accompanied by metal corrosion through changing the rest potential of metal by its oxidizing nature. Carbon steel was, therefore, immersed in an aqueous solution of sodium nitrate in a closed system for observing both the chemical interaction between metal and nitrate, and the effect of nitrate on the hydrogen gas evolution rate. The experimental pH range of the solution was 10.0-13.5 which corresponds to the pH range of pore fluid of cementitious material. The cathodic current density shows a Tafel equation type potential dependency in the aqueous solution containing nitrate or nitrite. In spite of the acceleration of cathodic reaction due to the existence of nitrate, the corrosion rates of carbon steel were not accelerated in the nitrate solutions. This fact suggests that the system is controlled by the anodic reaction. The nitrate reduction accompanied by the corrosion of carbon steel is considered to be a series reaction such as nitrate nitrite ammonia. The nitrate reduction reaction compete with the water reduction reaction within the anodic controlled condition, therefore nitrate strongly reduced the hydrogen evolution rate. The generation rates of ammonia were independent of the concentration of nitrate.

JAEA Reports

A Modeling study for the chemical evolution of nitrate accompanied with the corrosion of carbon steel

Honda, Akira; Masuda, Kaoru*; Kato, Osamu*; Nishimura, Tsutomu*; Tateishi, Tsuyoshi*; Imakita, Tsuyoshi*

JNC TN8400 2005-023, 40 Pages, 2005/09

JNC-TN8400-2005-023.pdf:1.15MB

Uranium and Plutonium are planed to be recovered from spent fuel by the reprocessing in Japan. PUREX method is internationally dominant among the commercial reprocessing plants. PUREX method has been also employed in Japan. The low level liquid waste from PUREX process would contain NO3- as forms of soluble salts, if the special process for decomposing NO3- were not adopted. The nitrate is possibly brought within the repository for TRU waste. The specie of NO3- is an oxidizing agent which can be reduced to NO2- and NH3/NH4+ by the coexistence of reducing materials such as metals.In order to estimate the safety of the repository for TRU waste, the impacts of nitrate on the disposal system for TRU waste have to be estimated. Especially, NH3 can elevate the solubility and reduce Rd value through the formation of ammine complexes. The quantitative information of chemical evolution of nitrate is necessary for evaluating the impact of nitrate and the chemical species arising from nitrate on the safety of the repository of TRU waste. The evolution of chemical form of NO3- by the reducing reaction accompanied with metal corrosion was experimentally examined. The reduction of NO3- was considered to be a serial reaction, that is, NO3- - NO2- - NH3. The rate equations of cathodic reactions (water reduction and reduction of nitrate and nitrite) were experimentally determined through the electrochemical measurements. The rate equation of metal dissolution (anodic reaction) which must be balanced to the cathodic reactions in charge transfer is determined from the results of immersion tests without nitrate. The combination of the rate equations forms an assessment model of chemical evolution of NO3-. The model provided the interpretation of the results of immersion tests with nitrate.

JAEA Reports

Research on Changes of Nitrate by Interactions with Metals under the Wastes Disposal Environment Containing TRU Nuclide (2) -Summary Report-

Wada, Ryutaro*; Nishimura, Tsutomu*; Masuda, Kaoru*; Fujiwara, Kazuo*; Imakita, Tsuyoshi*; Tateishi, Tsuyoshi*

JNC TJ8400 2004-017, 71 Pages, 2004/02

JNC-TJ8400-2004-017.pdf:3.42MB

Research on changes of nitrate by interactions with metals under the wastes disposal environment containing TRU nuclide

JAEA Reports

Research on Changes of Nitrate by Interactions with Metals under the Wastes Disposal Environment Containing TRU Nuclide (2)

Wada, Ryutaro*; Nishimura, Tsutomu*; Masuda, Kaoru*; Fujiwara, Kazuo*; Imakita, Tsuyoshi*; Tateishi, Tsuyoshi*

JNC TJ8400 2004-016, 194 Pages, 2004/02

JNC-TJ8400-2004-016.pdf:12.45MB

Research on Changes of Nitrate by Chemical Interactions with Metals under the wastes Disposal Environment Contaioning TRU Nucride

JAEA Reports

Research on changes of nitrate interactions with metals under the wastes disposal environment containing TRU nuclide (Summary report)

Wada, Ryutaro*; Nishimura, Tsutomu*; Masuda, Kaoru*; Fujiwara, Kazuo*; Imakita, Tsuyoshi*; Tateishi, Tsuyoshi*

JNC TJ8400 2003-080, 153 Pages, 2003/02

JNC-TJ8400-2003-080.pdf:2.63MB

There exists the waste including a nitrate ion as a salt in the TRU waste materials. This nitrate ion can be transferred to the nitrite ion and/or ammonia by reducing materials such as metals in the waste disposal environment, and has the possibility to affect on the disposal environment and nuclide transfer parameters.Therefore, electrochemical tests were conducted to evaluate the reaction rate parameters of the nitrate ion and metals under the low oxygen environment. The long-term reaction test using the glass-seal vessel was also conducted to grasp precisely the nitrate ion transition reaction rate and the gas generation rate caused by the reaction of metal and the nitrate ion coexist solution. (1) Reaction rate constants under various environments were obtained performing the potentiostatic holding tests with the parameters of the solution pH, temperature, and the nitrate and nitrite ion concentrations. The formula of the nitrate ion transition reaction rate was also examined based on these obtained data. (2) Conducting the immersion tests under the environment of the low oxygen and high-pH rainfall underground water site, the long-term reaction rate data were obtained on the reaction products (ammonia, hydrogen gas etc.) of metals (carbon steel, stainless steel and zircaloy etc.) with nitrate ion. The tests under the same conditions as in the past were also conducted to evaluate the test accuracy and error range of the long-term reaction test with the glass-seal vessels.

JAEA Reports

Research on Changes of Nitrate Interactions with Metals under the Wastes Disposal Environment Containing TRU Nuclide

Wada, Ryutaro*; Nishimura, Tsutomu*; Masuda, Kaoru*; Fujiwara, Kazuo*; Imakita, Tsuyoshi*; Tateishi, Tsuyoshi*

JNC TJ8400 2003-079, 252 Pages, 2003/02

JNC-TJ8400-2003-079.pdf:11.19MB

There exists the waste including a nitrate ion as a salt in the TRU waste materials. This nitrate ion can be transferred to the nitrite ion and/or ammonia by reducing materials such as metals in the waste disposal environment, and has the possibility to affect on the disposal environment and nuclide transfer parameters. Therefore, electrochemical tests were conducted to evaluate the reaction rate parameters of the nitrate ion and metals under the low oxygen environment. The long-term reaction test using the glass-seal vessel was also conducted to grasp precisely the nitrate ion transition reaction rate and the gas generation rate caused by the reaction of metal and the nitrate ion coexist solution. (1)}Reaction rate constants under various environments were obtained performing the potentiostatic holding tests with the parameters of the solution pH, temperature, and the nitrate and nitrite ion concentrations. The formula of the nitrate ion transition reaction rate was also examined based on these obtained data. (2) Conducting the immersion tests under the environment of the low oxygen and high-pH rainfall underground water site, the long-term reaction rate data were obtained on the reaction products (ammonia, hydrogen gas etc.) of metals (carbon steel, stainless steel and zircaloy etc.) with nitrate ion. The tests under the same conditions as in the past were also conducted to evaluate the test accuracy and error range of the long-term reaction test with the glass-seal vessels.

JAEA Reports

Research on the Transformation of Nitrate Due to its Chemical Interaction with Metals in TRU Waste Disposal Environmen (Summary Report)

Wada, Ryutaro*; Nishimura, Tsutomu*; Masuda, Kaoru*; Fujiwara, Kazuo*; Imakita, Tsuyoshi*; Tateishi, Tsuyoshi*

JNC TJ8400 2003-077, 156 Pages, 2002/02

JNC-TJ8400-2003-077.pdf:3.63MB

Some TRU wastes contain nitrate ions as salt.The nitrate ions might transform into NO2- and NH3, etc. in the disposal site environment because of reducing agent such as metals, possibly changing disposal site environment or affecting nuclide migration parameters.Therefore, we investigated of chemical interaction between NO3- and metals in a low oxygen environment that corresponds to the disposal site environment.

JAEA Reports

Research on the Transformation of Nitrate Due to its Chemical Interaction with Metals in TRU Waste Disposal Environment

Wada, Ryutaro*; Nishimura, Tsutomu*; Masuda, Kaoru*; Fujiwara, Kazuo*; Imakita, Tsuyoshi*; Tateishi, Tsuyoshi*

JNC TJ8400 2003-076, 300 Pages, 2002/02

JNC-TJ8400-2003-076.pdf:17.65MB

Some TRU wastes contain nitrate ions as salt.The nitrate ions might transform into NO2- and NH3, etc. in the disposal site environment because of reducing agent such as metals, possibly changing disposal site environment or affecting nuclide migration parameters. Therefore, we investigated of chemical interaction between NO3- and metals in a low oxygen environment that corresponds to the disposal site environment.

Oral presentation

New methodology of redox potential measurement in solution

Ioka, Seiichiro; Iwatsuki, Teruki; Kato, Osamu*; Imakita, Tsuyoshi*

no journal, , 

no abstracts in English

Oral presentation

Issue on oxidation-reduction potential measurement of groundwater using platinum electrode; Materials on the platinum electrode surface

Ioka, Seiichiro; Iwatsuki, Teruki; Mizuno, Takashi; Kato, Osamu*; Imakita, Tsuyoshi*

no journal, , 

no abstracts in English

Oral presentation

Study on the relationship between organic complexiation and water pressure

Iwatsuki, Teruki; Yoshida, Haruo; Kato, Osamu*; Imakita, Tsuyoshi*; Kurimoto, Noritaka*; Hama, Katsuhiro

no journal, , 

no abstracts in English

Oral presentation

Pressure dependency of complexiation constant between trace element and organics

Iwatsuki, Teruki; Hama, Katsuhiro; Imakita, Tsuyoshi*; Kurimoto, Noritaka*; Yoshida, Haruo*; Kato, Osamu*

no journal, , 

Batch experiments on complexiation reaction between Fe ion and organics were conducted to estimate pressure dependency of reaction constant. The results show that the ratio of metal-organic complex increases with pressure. The reaction constants estimated range from 5.3$$times$$10$$^{5}$$ to 1.2$$times$$10$$^{6}$$.

Oral presentation

Development of a beam monitor for high intensity positive ion beams using negative ion beam injection

Shinto, Katsuhiro; Wada, Motoi*; Imakita, Shinsuke*; Kaneko, Osamu*; Tsumori, Katsuyoshi*

no journal, , 

no abstracts in English

15 (Records 1-15 displayed on this page)
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