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Watanabe, So; Takahatake, Yoko; Ogi, Hiromichi*; Osugi, Takeshi; Taniguchi, Takumi; Sato, Junya; Arai, Tsuyoshi*; Kajinami, Akihiko*
Journal of Nuclear Materials, 585, p.154610_1 - 154610_6, 2023/11
Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)Irisawa, Keita; Namiki, Masahiro*; Taniguchi, Takumi; Garcia-Lodeiro, I.*; Kinoshita, Hajime*
Cement and Concrete Research, 156, p.106758_1 - 106758_8, 2022/06
Times Cited Count:9 Percentile:61.08(Construction & Building Technology)Cementation of aqueous radioactive waste contaminated with a significant Sr is challenging, and utilization of calcium aluminate cement (CAC) modified with sodium polyphosphate (CAP) is interesting. The present study investigated solidification and stabilization of Sr
and Cl
ions in CAC and CAP cured in open system at 90
C and in closed system at 20
C. A leaching test showed that Sr
ion could be stabilized more effectively in the CAP than in the CAC. On the other hand, the CAC cured at 20
C had the best stabilization for Cl
ion among the samples. Friedel's salt formed in the CAC may have contributed to the immobilization of Cl
ion. Although the stabilization of Cl
ion by CAP was less effective than CAC, it was significantly improved by the thermal treatment. The results may suggest that Cl
ion in the CAP was incorporated in the poorly crystalline apatite structure.
Kataoka, Noriyuki*; Tanaka, Masashi*; Hosoda, Wataru*; Taniguchi, Takumi*; Fujimori, Shinichi; Wakita, Takanori*; Muraoka, Yuji*; Yokoya, Takashi*
Journal of Physics; Condensed Matter, 33(3), p.035501_1 - 035501_6, 2021/01
Times Cited Count:4 Percentile:24.85(Physics, Condensed Matter)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
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
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 FeO
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
O in the Fe
O
film at room temperature. The results were obtained as follows. It was confirmed that Fe
O
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
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
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
O constant. The constant amount of D
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
O absorbed into the film was analyzed on the basis of Fick's law for diffusion, and diffusion coefficients of D
O were obtained to be 5.1
10
cm
s
and 9.9
10
cm
s
for the films formed for 1.2 and 3.6 ks, respectively. Therefore it was estimated that the diffusion coefficient of the Fe
O
film was in the region from 5.1
10
cm
s
to 9.9
10
cm
s
.
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 Co
-ray. The G(H
) for the phosphate cement decreased with time during dehydration, and was not detected after 7 days. Moreover, the
Co
-ray irradiation during dehydration did not change the crystalline and amorphous phases of the phosphate cement.
Kato, Jun; Nakagawa, Akinori; Taniguchi, Takumi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro
JAEA-Review 2017-015, 173 Pages, 2017/07
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.
Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro; Garca-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 C and in a closed system at 20
C as a reference case. Water contents in both the CAC and the CAP were seen to decrease as curing progressed. For
90
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
C, and a mixture of the orthophosphate hydrate salt and hydroxyapatite, Ca
(PO
)
(OH)
, were formed in the CAP when cured at 90
C. Phosphate products in CAP cured at 120
C appears to consist of a different phosphate phase compared with the CAP cured at 20, 60 and 90
C.
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.
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 DO 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
O for 5184 ks, followed by subjected to TDS to obtain an amount of D
O absorbing into the film. As a result, single-layered film of Fe
O
was formed at 573 and 723 K, and double-layered film of Fe
O
and Fe
O
was formed at 873 K. It was found that an amount of D
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
O was determined as 9.7
10
cm
s
for the Fe
O
film, and 5.5
10
cm
s
to 2.2
10
cm
s
for Fe
O
film.
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:11 Percentile:64.94(Chemistry, Analytical)The At isotope has gathered attention as a promising
-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
Rn-
At generator.
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:15 Percentile:57.38(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 1400-1835C. 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.
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:77.81(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 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.
Taniguchi, Takashi*; Sato, Masashi*; Utsumi, Wataru; Kikegawa, Takumi*; Shimomura, Osamu
Diamond and Related Materials, 6(12), p.1806 - 1815, 1997/12
Times Cited Count:18 Percentile:70.63(Materials Science, Multidisciplinary)no abstracts in English
Taniguchi, Takashi*; Sato, Masashi*; Utsumi, Wataru; Kikegawa, Takumi*; Shimomura, Osamu
Applied Physics Letters, 70(18), p.2392 - 2394, 1997/05
Times Cited Count:25 Percentile:74.39(Physics, Applied)no abstracts in English
Haruna, Takumi*; Miyataki, Yuki*; Hirohata, Yohei*; Taniguchi, Naoki; Tachikawa, Hirokazu*
no journal, ,
no abstracts in English
Taniguchi, Takumi; Irisawa, Keita; Namiki, Masahiro*; Nakazawa, Osamu
no journal, ,
no abstracts in English
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
Irisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu
no journal, ,
no abstracts in English