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Journal Articles

Unusual redox behavior of ruthenocene confined in the micropores of activated carbon

Itoi, Hiroyuki*; Ninomiya, Takeru*; Hasegawa, Hideyuki*; Maki, Shintaro*; Sakakibara, Akihiro*; Suzuki, Ryutaro*; Kasai, Yuto*; Iwata, Hiroyuki*; Matsumura, Daiju; Owada, Mao*; et al.

Journal of Physical Chemistry C, 124(28), p.15205 - 15215, 2020/07

 Times Cited Count:4 Percentile:61.86(Chemistry, Physical)

Journal Articles

R&D on treatment and disposal of waste resulting from Fukushima Daiichi accident

Wada, Ryutaro*; Yoshinaka, Kazuyuki

Gijutsushi, 28(11), p.4 - 7, 2016/11

AA2016-0292.pdf:0.44MB

It is one of the important subjects for decommissioning to establish the safe and effective waste management. Research and Development programs on the waste management for Fukushima-Daiichi as it differs from normal practices are conducted by IRID. We show the outline of the lecture presented by Mr.Miyamoto, Deputy Director of IRID.

Journal Articles

Thinking about the geologic disposal project of high level radioactive waste (HLW)

Wada, Ryutaro*; Iguchi, Yukihiro

Gijutsushi, 27(4), p.12 - 15, 2015/04

The geological disposal project of high level radioactive waste (HLW) is one of the important problems in the energy policy of Japan. We show the outline of the lecture about the current technologies and activities for the geological disposal project by an invited speakers of Nuclear Waste Management Organization of Japan (NUMO), which is in charge of the project.

Journal Articles

Inter-atomic force constants of Ag$$_{2}$$O from diffuse neutron scattering measurement

Wada, Tamotsu*; Sakuma, Takashi*; Sakai, Ryutaro*; Uehara, Hiroyuki*; Xianglian*; Takahashi, Haruyuki*; Kamishima, Osamu*; Igawa, Naoki; Danilkin, S. A.*

Solid State Ionics, 225, p.18 - 21, 2012/10

 Times Cited Count:6 Percentile:31.07(Chemistry, Physical)

Diffuse neutron scattering measurement on Ag$$_{2}$$O crystals was performed at 8 K and 295 K. The observed diffuse scattering intensities were analyzed by including the correlation effects among thermal displacements of atoms in Ag$$_{2}$$O. Using the values of correlation effects among neighboring atoms and the values of Debye-Waller temperature parameter, force constants among first, second and third nearest neighboring atoms have been evaluated.

Journal Articles

Application of supercritical fluid extraction to metal separation in the field of nuclear technology

Meguro, Yoshihiro; Tomioka, Osamu; Takahashi, Kuniaki; Wada, Ryutaro*; Yamamoto, Seiichi*; Fukuzato, Ryuichi*

Proceedings of 8th International Symposium on Supercritical Fluids (ISSF 2006) (CD-ROM), 6 Pages, 2006/11

A large-scale apparatus having a reaction vessel of ca. 4000 cm$$^3$$ was developed for supercritical CO$$_2$$ leaching. An ultrasonic wave oscillator, stirring device, and piston compressor were equipped to the apparatus to enhance mass transfer rate of substances in supercritical CO$$_2$$. A sea sand sample, an incinerated ash sample, and a porous alumina brick sample, in which uranium oxide was adsorbed, were prepared as simulated samples of radioactive wastes and uranium was tried to remove from these samples to supercritical CO$$_2$$ including nitric acid - tri-n-butyl phosphate complex as a reactant using the apparatus. By several times of the uranium separation, more than 99% of uranium was removed from the sea sand sample and the ash sample. When the mass transfer enhanced system was operated, it was confirmed that separation efficiency of uranium was improved and then 99% of uranium could be removed form the ash sample.

Journal Articles

Removal and recovery of uranium from solid wastes by supercritical carbon dioxide fluid leaching method

Meguro, Yoshihiro; Tomioka, Osamu; Imai, Tomoki*; Fujimoto, Shigeyuki*; Nakashima, Mikio; Yoshida, Zenko; Honda, Tadashi*; Koya, Fumio*; Kitamura, Nobu*; Wada, Ryutaro*; et al.

Proceedings of International Waste Management Symposium 2004 (WM '04) (CD-ROM), 8 Pages, 2004/03

Supercritical CO$$_{2}$$ fluid leaching (SFL) method using supercritical CO$$_{2}$$ fluid containing a complex of HNO$$_{3}$$ - tri-n-butyl phosphate (TBP) was applied to removal of uranium from radioactive solid wastes. Sea sands, incineration ashes and porous alumina bricks were employed as matrixes of simulated solid wastes. Real radioactive incineration ash wastes and firebrick wastes were also subjected to the SFL treatment. It was found that uranium could be efficiently removed from both of the simulated wastes and real wastes by the SFL method. The removal efficiency of uranium from the real waste was lower than that from the corresponding artificial waste. About 1 g and 35 mg of uranium were recovered from 10 g of the real ash waste and 37 g of the real firebrick waste, respectively.

JAEA Reports

Study on Long-Term Corrosion Behavior of High Corrosion Resistant Metal Overpack under Reducing Condition

Wada, Ryutaro*; Nishimura, Tsutomu*; Nakanishi, Tomoaki*; Nakayama, Takenori*; Sakashita, Shinji*; Fujiwara, Kazuo*; Tateishi, Tsuyoshi*

JNC TJ8400 2005-001, 224 Pages, 2004/02

JNC-TJ8400-2005-001.pdf:16.23MB

For repository container material of high-level radioactive waste, titanium and nickel-base alloys have been investigated as high corrosion resistance metal. In this study, the effects of environmental and material factors on hydrogen absorption of titanium were investigated experimentally. As for nickel-base allys, previous studies on corrosion behavior were serched.

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

Journal Articles

Recovery of alkali salt by supercritical fluid leaching method using carbon dioxide

Watanabe, Takeshi*; Tsushima, Satoru*; Yamamoto, Ichiro*; Tomioka, Osamu; Meguro, Yoshihiro; Nakashima, Mikio; Wada, Ryutaro*; Nagase, Yoshiyuki*; Fukuzato, Ryuichi*

Proceedings of 2nd International Symposium on Supercritical Fluid Technology for Energy and Environment Applications (Super Green 2003), p.363 - 366, 2004/00

Recovery of salts by supercritical fluid leaching (SFL) method using carbon dioxide was experimentally studied. It was confirmed that LiCl was recovered with a mixed fluid of carbon dioxide and methanol, and KCl and SrCl$$_2$$ were recovered with a mixed fluid of carbon dioxide, methanol and crown ether. The influence of crown ether for KCl and SrCl$$_2$$ extraction were found to increase in the order of 15-crown-5 (15C5) $$<$$ 18-crown-6 (18C6) $$<$$ dicychlohexyl-18-crown-6 (DC18C6). It is expected that other salts can be recovered selectively with a mixed fluid of carbon dioxide, methanol and suitable crown ether.

Journal Articles

Development of radioactive waste treatment by Supercritical Fluid Leaching (SFL) method

Nagase, Yoshiyuki*; Masuda, Kaoru*; Wada, Ryutaro*; Yamamoto, Ichiro*; Tomioka, Osamu; Meguro, Yoshihiro; Fukuzato, Ryuichi*

Proceedings of 2nd International Symposium on Supercritical Fluid Technology for Energy and Environment Applications (Super Green 2003), p.254 - 257, 2004/00

no abstracts in English

JAEA Reports

Study on Hydrogen Absorption of Titanium Overpack

Wada, Ryutaro*; Nishimura, Tsutomu*; Nakanishi, Tomoaki*; Fujiwara, Kazuo*; Inoue, Takao*; Tateishi, Tsuyoshi*; Masugata, Tsuyoshi*

JNC TJ8400 2003-092, 246 Pages, 2003/02

JNC-TJ8400-2003-092.pdf:35.08MB

Titanium is being studied for the high-level radioactive waste package material. Titanium has good corrosion resistance, however there is the possibility of hydrogen embrittlement with absorption of hydrogen in reducing condition. Experimental studies were performed to evaluate the hydrogen absorption behaviors of titanium in reducing condition. The failure model of the titanium overpack was also examined from the viewpoint of fracture mechanism in order to evaluate the fracture behavior of the titanium overpack caused by the hydrogen absorption. (1) Scratch test was conducted in reduce condition. The surface films on the titanium specimen were analyzed to examine the changes of the existing films and the growth phenomena of the regenerated films on the titanium specimen. (2)The long-term reaction test of the titanium specimen using the glass-seal ampoules maintaining reducing condition was conducted and analyses of the hydrogen gas generation and absorption quantitative as well as the generated film evaluation were performed. (3) Under reducing condition, the electrochemical acceleration tests of the titanium specimen were conducted. The effect of acceleration rate on the hydrogen absorption and surface film was evaluated, and the prediction as to the hydrogen absorption behavior at a natural state was also made. (4) The prediction of the maximum residual stress and the evaluation of crack growth of the titanium overpack based on the previous studies were performed. Feasibility of the modeling of fracture phenomenon with existing analysis technique was examined and the items to be developed were also discussed.

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

Extralong test study on carbon steel overpack

Wada, Ryutaro*; *; Nishimura, Tsutomu*; Fujiwara, Kazuo*; Tateishi, Tsuyoshi*

JNC TJ8400 2003-007, 86 Pages, 2003/02

JNC-TJ8400-2003-007.pdf:2.18MB

The overpack for the high-level radioactive waste disposal is expected to maintain the long-term integrity and the corrosion behavior model of the overpack has been developed so far. To verify the adequacy and conservatism of the model, in this study, measurements of hydrogen absorption regarding hydrogen embrittlement of carbon steel, one of the candidate materials, were carried out in the compacted bentonite coexistence environment. The definite research programs to be performed in the future were also established for the important subjects as the extralong tests: (1)The hydrogen penetration-measuring device was designed to measure the penetrated hydrogen caused by the corrosion of carbon steel in the buffer material (compacted bentonite). (2)Out of generated hydrogen by the corrosion of carbon steel in the buffer material, the penetrated hydrogen volumes into carbon steel were measured. (3) Research programs on the four laboratory test themes and the three site test themes were established as the extralong test themes to be performed in the future.

Journal Articles

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.

JAEA Reports

Study on hydrogen embrittlement property of titanium for nuclear fuel waste container

Wada, Ryutaro*; *; Fujiwara, Kazuo*; *; Tateishi, Tsuyoshi*; Masugata, Tsuyoshi*

JNC TJ8400 2002-002, 71 Pages, 2002/02

JNC-TJ8400-2002-002.pdf:20.8MB

In geologic disposal system of high-level radioactive waste, confinement by waste container must be assured over a thousand years. Titanium is one of the candidate materials, so it is important to clarify hydrogen embrittlement property under geological environment for the container lifetime prediction. The purpose of this study is to investigate hydrogen embrittlement behavior of titanium under reducing condition. Hydrogen was absorbed into titanium test pieces by electrochemical method, and tensile bending and impact tests were performed for mechanical property research. Under 1000ppm concentration of hydrogen, while distinct degradation of mechanical properties by hydrogen embrittlement occurred on dynamic stress, micro cracks induced by hydride were observed in fracture, but distinct degradation of mechanical properties by hydrogen embrittlement did not occur on static stress. Under low oxygen circumstances, corrosion rates of titanium were estimated 10$$^{-2}$$ micrometer/year by hydrogen absorption method, on the contrary to 10$$^{-4}$$ micrometer/year by gas evolution method. These results indicated hydrogen generated by corrosion of titanium under reducing condition, is almost absorbed into material. Carbon steel is regarded as reinforcement of the titanium nuclear fuel waste container. Magnetite, corrosion product of carbon steel, is considered to accelerate corrosion rate. Contribution of hydrogen evolution reaction to its acceleration is estimated to ca.60%.

JAEA Reports

Research on a super-long-term test of overpack materials in geological disposal environment

Wada, Ryutaro*; *; Nishimura, Tsutomu*; *; *; *; Fujiwara, Kazuo*

JNC TJ8400 2002-001, 71 Pages, 2002/02

JNC-TJ8400-2002-001.pdf:4.34MB

The overpack is expected to have long-term soundness, and corrosion behavior models of the overpack have been constructed. To verify validity and maintainability of the models, this study conducted a research on a super-long-term test of overpack materials for several decades. (1)We designed a testing device that would allow long-term monitoring of the corrosion behavior of carbon steel, an overpack candidate material, and the condition in the buffer material in an environment corresponding to the environment immediately after disposal. (2)We examined and prototyped a test container that would allow long-term immersion tests of carbon steel without maintenance operations such as solution exchange. (3)We proposed super-long-term tests (about 20 years) that would contribute to future geological disposal projects and safety rules. (4)We investigated a method for managing and preserving the records of the super-long-term test for the test period (20 years).

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