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Journal Articles

Hydrogen gas measurements of phosphate cement irradiated during heat treatment

Irisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu

QST-M-16; QST Takasaki Annual Report 2017, P. 63, 2019/03

no abstracts in English

Journal Articles

Application of phosphate modified CAC for incorporation of simulated secondary aqueous wastes in Fukushima Daiichi NPP, 1; Characterization of solidified cementitious systems with reduced water content

Garcia-Lodeiro, I.*; Lebon, R.*; Machoney, D.*; Zhang, B.*; Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Meguro, Yoshihiro; Kinoshita, Hajime*

Proceedings of 3rd International Symposium on Cement-based Materials for Nuclear Wastes (NUWCEM 2018) (USB Flash Drive), 4 Pages, 2018/11

Journal Articles

Diffusion behavior of D$$_{2}$$O in Fe$$_{3}$$O$$_{4}$$ film on Fe formed in an NaOH solution containing oxidants

Haruna, Takumi*; Miyataki, Yuki*; Hirohata, Yohei*; Shibata, Toshio*; Taniguchi, Naoki; Tachikawa, Hirokazu*

Zairyo To Kankyo, 67(9), p.375 - 380, 2018/09

This research aimed to confirm the formation of Fe$$_{3}$$O$$_{4}$$ film on Fe immersed in aqueous 45 mass% NaOH solution containing some oxidants at the boiling temperature, to recognize the optimum immersion time for the formation of thick and protective film, and to reveal the absorption behavior of D$$_{2}$$O in the Fe$$_{3}$$O$$_{4}$$ film at room temperature. The results were obtained as follows. It was confirmed that Fe$$_{3}$$O$$_{4}$$ film was formed on Fe immersed in the NaOH solution for a time more than 0.6 ks, and the film thickness increased parabolically with an increase in the immersion time. D$$_{2}$$O absorption test was carried out to the films formed in the NaOH solution for immersion times of 1.2 and 3.6 ks. An amount of D$$_{2}$$O absorbed into the film increased with an increase in an absorption time up to 1000 ks, and an absorption time more than 1000 ks made an amount of D$$_{2}$$O constant. The constant amount of D$$_{2}$$O was larger for the film formed on Fe immersed in the NaOH solution for 3.6 ks than that for 1.2 ks. The transient of the amount of D$$_{2}$$O absorbed into the film was analyzed on the basis of Fick's law for diffusion, and diffusion coefficients of D$$_{2}$$O were obtained to be 5.1$$times$$10$$^{-15}$$ cm$$^{2}$$ s$$^{-1}$$ and 9.9$$times$$10$$^{-15}$$ cm$$^{2}$$ s$$^{-1}$$ for the films formed for 1.2 and 3.6 ks, respectively. Therefore it was estimated that the diffusion coefficient of the Fe$$_{3}$$O$$_{4}$$ film was in the region from 5.1$$times$$10$$^{-15}$$ cm$$^{2}$$ s$$^{-1}$$ to 9.9$$times$$10$$^{-15}$$ cm$$^{2}$$ s$$^{-1}$$.

Journal Articles

Characterization of phosphate cement irradiated by $$gamma$$-ray during dehydration

Irisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu

QST-M-8; QST Takasaki Annual Report 2016, P. 63, 2018/03

A solidification technique with minimized water content is being developed using a phosphate cement for safe storage of secondary radioactive wastes in the Fukushima Daiichi Nuclear Power Plant. To understand the applicability of the solidification technique for the actual secondary wastes, phosphate cement during dehydration was irradiated by $$^{60}$$Co $$gamma$$-ray. The G(H$$_{2}$$) for the phosphate cement decreased with time during dehydration, and was not detected after 7 days. Moreover, the $$^{60}$$Co $$gamma$$-ray irradiation during dehydration did not change the crystalline and amorphous phases of the phosphate cement.

JAEA Reports

The Catalog of solidification and volume reduction technologies for the treatment of radioactive waste generated by the decommissioning of Fukushima Daiichi Nuclear Power Station

Kato, Jun; Nakagawa, Akinori; Taniguchi, Takumi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro

JAEA-Review 2017-015, 173 Pages, 2017/07

JAEA-Review-2017-015.pdf:6.67MB

Various radioactive wastes have been generated at the Fukushima Daiichi Nuclear Power Station (1F). To dispose of the wastes underground, it is necessary to make a suitable waste package by the volume reduction and solidification of the wastes. To plan the future decommissioning of 1F, it is also necessary to estimate feasibility of existing treatment technology for those wastes. Therefore the document survey has been performed about volume reduction and solidification technologies that have domestic or foreign experiences of practical treatment for radioactive wastes to assist selection of suitable treatment of the wastes. This report shows the arranged results. The 1F wastes are classified into two groups, homogeneous particulate and liquid wastes and heterogeneous solid wastes. The needful items for the feasibility study such as a technology name, a fundamental principle, treatment efficiency, and characteristic of solidified waste are summarized in each group.

Journal Articles

Heat treatment of phosphate-modified cementitious matrices for safe storage of secondary radioactive aqueous wastes in Fukushima Daiichi Nuclear Power Plant

Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro; Garc$'i$a-Lodeiro, I.*; Osugi, Takeshi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro; Kinoshita, Hajime*

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 6 Pages, 2017/04

A solidification technique with minimized water content is being developed using phosphate cements for the safe storage of secondary radioactive wastes in the Fukushima Daiichi Nuclear Power Plant. Conventional cement systems become solidified via hydration reactions, and need a certain water content. Phosphate cement systems, however, become solidified via an acid-base reaction, and so they only require water mainly for reasons of workability. A reduced water content of phosphate cement systems is beneficial for the immobilization of the radioactive wastes from mitigating the potential to generate hydrogen gas by the radiolysis of water by radioactive wastes. The current study investigated the water content and mineralogy of calcium aluminate cement (CAC) and phosphate-modified CAC (CAP) cured in open systems at 60, 90 and 120 $$^{circ}$$C and in a closed system at 20 $$^{circ}$$C as a reference case. Water contents in both the CAC and the CAP were seen to decrease as curing progressed. For $$geq$$ 90 $$^{circ}$$C, the CAP contained less water than CAC. Free water in CAC converted to structural water by heat treatment, but this was not the case for CAP. An orthophosphate hydrate salt, a precursor phase of hydroxyapatite, was found in CAP when cured at 20 and 60 $$^{circ}$$C, and a mixture of the orthophosphate hydrate salt and hydroxyapatite, Ca$$_{10}$$(PO$$_{4}$$)$$_{6}$$(OH)$$_{2}$$, were formed in the CAP when cured at 90 $$^{circ}$$C. Phosphate products in CAP cured at 120 $$^{circ}$$C appears to consist of a different phosphate phase compared with the CAP cured at 20, 60 and 90 $$^{circ}$$C.

Journal Articles

Report on the weekend basic course for Division of Nuclear Fuel Cycle and Environment in fiscal year 2015

Taniguchi, Takumi; Abe, Tomohisa

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 23(1), p.73 - 74, 2016/06

The weekend basic course for Division of Nuclear Fuel Cycle and Environment was held on November 7 (Sat) and 8 (Sun) on 2015 at Tohoku University Aobayama Campus in Sendai City. Twenty-eight people from universities and companies attended the course, and seven lectures and group discussions were held. I will report the outline of this course and the contents of the group discussion.

Journal Articles

Diffusion behavior of D$$_{2}$$O in the film on Fe oxidized at high temperature in air

Haruna, Takumi*; Yamamoto, Tatsuya*; Miyairi, Yoji*; Shibata, Toshio*; Taniguchi, Naoki; Sakamaki, Keiko; Tachikawa, Hirokazu*

Zairyo To Kankyo, 64(5), p.201 - 206, 2015/05

Diffusion coefficients of D$$_{2}$$O in the films was determined in order to estimate corrosion rate of carbon steel for the overpack in ground water. Fe plates were heated to form oxide films. The films were characterized with XRD and SEM. After that, the specimen was contacted with D$$_{2}$$O for 5184 ks, followed by subjected to TDS to obtain an amount of D$$_{2}$$O absorbing into the film. As a result, single-layered film of Fe$$_{3}$$O$$_{4}$$ was formed at 573 and 723 K, and double-layered film of Fe$$_{2}$$O$$_{3}$$ and Fe$$_{3}$$O$$_{4}$$ was formed at 873 K. It was found that an amount of D$$_{2}$$O in the film correlated linearly with a square root of the absorption period, and that the amount was steady for a long period. From the results and Fick's second law, diffusion coefficients of D$$_{2}$$O was determined as 9.7$$times$$10$$^{-13}$$ cm$$^{2.}$$s$$^{-1}$$ for the Fe$$_{3}$$O$$_{4}$$ film, and 5.5$$times$$10$$^{-13}$$ cm$$^{2.}$$s$$^{-1}$$ to 2.2$$times$$10$$^{-12}$$ cm$$^{2.}$$s$$^{-1}$$ for Fe$$_{2}$$O$$_{3}$$ film.

Journal Articles

Extraction of astatine isotopes for development of radiopharmaceuticals using a $$^{211}$$Rn-$$^{211}$$At generator

Maeda, Eita*; Yokoyama, Akihiko*; Taniguchi, Takumi*; Washiyama, Koshin*; Nishinaka, Ichiro

Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1465 - 1468, 2015/02

 Times Cited Count:7 Percentile:38.07(Chemistry, Analytical)

The $$^{211}$$At isotope has gathered attention as a promising $$alpha$$-emitter for radionuclide therapy. We report the dependence of the distribution ratio of astatine on the concentration of HCl, and on the polarity of the organic solvent. The results will be useful for development of the $$^{211}$$Rn-$$^{211}$$At generator.

Journal Articles

${it In situ}$ X-ray diffraction of graphite-diamond transformation using various catalysts under high pressures and high temperatures

Utsumi, Wataru; Okada, Taku; Taniguchi, Takashi*; Funakoshi, Kenichi*; Kikegawa, Takumi*; Hamaya, Nozomu; Shimomura, Osamu

Journal of Physics; Condensed Matter, 16(14), p.S1017 - S1026, 2004/04

 Times Cited Count:12 Percentile:46.05(Physics, Condensed Matter)

The graphite-diamond transformation was investigated using in-situ time-resolved X-ray diffraction experiments with a MgO dissolved aqueous fluid as the diamond forming catalyst under conditions of 6.6-8.8 GPa and 1400-1835$$^{circ}$$C. Experiments were conducted using a 180-ton DIA-type cubic-anvil apparatus installed on the beamline BL14B1 at SPring-8, a third-generation synchrotron radiation facility in Japan. By analyzing the kinetic data using the JMAK rate equation, it was clarified that altering the pressure-temperature conditions drastically changes the nucleation and growth process of diamond.

Journal Articles

Accelerator R&D for JT-60U and ITER NB systems

Inoue, Takashi; Hanada, Masaya; Iga, Takashi*; Imai, Tsuyoshi; Kashiwagi, Mieko; Kawai, Mikito; Morishita, Takatoshi; Taniguchi, Masaki; Umeda, Naotaka; Watanabe, Kazuhiro; et al.

Fusion Engineering and Design, 66-68, p.597 - 602, 2003/09

 Times Cited Count:21 Percentile:18.81(Nuclear Science & Technology)

The neutral beam (NB) injection has been one of the most promising methods for plasma heating and current drive in tokamak fusion devices. JAERI has developed high energy electrostatic accelerators for the NB systems in JT-60U and ITER. Recent progress on this R&D are as follows: 1) In the JT-60U NB system, some of the beams has been deflected due to distorted electric field in the accelerator, resulting in an excess heat load on the NB port. By correcting the electric field, a continuous injection of H$$^{0}$$ beam was succeeded for 10 s with the NB power of 2.6 MW at 355 keV. 2) To increase the beam energy, a metal structure called stress ring was designed. The ring reduces electric field concentration at the triple junction point (interface between metal and dielectric insulator inside vacuum). Initial test of the accelerators with the stress rings has shown higher voltage hold off performance in both accelerators for JT-60U and ITER R&D than that without rings.

Journal Articles

In-situ X-ray observation of phase transformation of rhombohedral boron nitride under static high pressure and high temperature

Taniguchi, Takashi*; Sato, Masashi*; Utsumi, Wataru; Kikegawa, Takumi*; Shimomura, Osamu

Diamond and Related Materials, 6(12), p.1806 - 1815, 1997/12

 Times Cited Count:17 Percentile:30.41

no abstracts in English

Journal Articles

Effect of nonhydrostaticity on the pressure induced phase transformation of rhombohedral boron nitride

Taniguchi, Takashi*; Sato, Masashi*; Utsumi, Wataru; Kikegawa, Takumi*; Shimomura, Osamu

Applied Physics Letters, 70(18), p.2392 - 2394, 1997/05

 Times Cited Count:24 Percentile:26.01(Physics, Applied)

no abstracts in English

Oral presentation

Nuclear and radiochemical study of production and utilization of radioactive astatine isotopes in the Li+$$^{nat}$$Pb reaction; Aim at the new cancer medical treatment by $$alpha$$-emitting radioisotopes

Nishinaka, Ichiro; Makii, Hiroyuki; Toyoshima, Atsushi; Yokoyama, Akihiko*; Washiyama, Koshin*; Amano, Ryohei*; Maeda, Eita*; Yamada, Norihiro*; Taniguchi, Takumi*; Watanabe, Shigeki; et al.

no journal, , 

no abstracts in English

Oral presentation

Production and utilization of astatine radioisotopes using $$^{7}$$Li ion beams

Nishinaka, Ichiro; Yokoyama, Akihiko*; Washiyama, Koshin*; Amano, Ryohei*; Maeda, Eita*; Taniguchi, Takumi*; Murakami, Kento*; Watanabe, Shigeki; Suzuki, Hiroyuki; Ishioka, Noriko; et al.

no journal, , 

In general, an $$alpha$$-emitter $$^{211}$$At which is a prospective candidate for utilization in targeted alpha radiotherapy is produced through the $$^{209}$$Bi($$^{4}$$He, 2n)$$^{211}$$At reaction. In contrast, our project is focusing on the production in the $$^{209}$$Bi($$^{7}$$Li, 5n)$$^{211}$$Rn reaction. This enables us to supply $$^{211}$$At in a $$^{211}$$Rn/$$^{211}$$At generator system. The daughter $$^{211}$$At (7.2 h half-life) is extracted from the parent $$^{211}$$Rn (14h), expanding time-frame for transportation and use of $$^{211}$$At. To use astatine and iodine radioisotopes in our project, the excitation functions of $$^{209}$$Bi($$^{7}$$Li, xn)$$^{216-x}$$Rn, $$^{nat}$$Pb($$^{7}$$Li, xn)$$^{nat-x}$$At and $$^{nat}$$Sn($$^{7}$$Li, xn)$$^{nat-x}$$I reactions have been measured. In addition to that, separation techniques have been developed. We report not only on the production and separation of astatine and iodine radioisotopes in the reactions but also on the utilization of those radioisotopes.

Oral presentation

Development of $$^{211}$$Rn/$$^{211}$$At generator for targeted alpha therapy

Washiyama, Koshin*; Maeda, Eita*; Yokoyama, Akihiko*; Nishinaka, Ichiro; Taniguchi, Takumi*; Yamada, Norihiro*; Makii, Hiroyuki; Toyoshima, Atsushi; Amano, Ryohei*

no journal, , 

A $$^{211}$$Rn/$$^{211}$$At generator for targeted alpha therapy has been developed.

Oral presentation

Development of solidification techniques with minimised water content for secondary radioactive aqueous wastes in Fukushima, 1; Synthesis and evaluation of simulated wastes

Taniguchi, Takumi; Irisawa, Keita; Ito, Yuzuru; Namiki, Masahiro; Osugi, Takeshi; Abe, Tomohisa; Sato, Junya; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro; et al.

no journal, , 

no abstracts in English

Oral presentation

Diffusion behavior of heavy water in magnetite film formed on iron in basic solution

Haruna, Takumi*; Miyataki, Yuki*; Hirohata, Yohei*; Taniguchi, Naoki; Tachikawa, Hirokazu*

no journal, , 

no abstracts in English

Oral presentation

Development of solidification techniques with minimised water content for secondary radioactive aqueous wastes in Fukushima, 5; Leaching rate of Sr$$^{2+}$$ and Cl$$^{-}$$

Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro*; Garc$'i$a-Lodeiro, I.*; Osugi, Takeshi; Nakazawa, Osamu; Kinoshita, Hajime*

no journal, , 

no abstracts in English

Oral presentation

Influence of $$^{60}$$Co $$gamma$$-ray on characteristics of phosphate cements synthesized during dehydration

Irisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu

no journal, , 

no abstracts in English

31 (Records 1-20 displayed on this page)