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Akiyama, Daisuke*; Kusaka, Ryoji; Kumagai, Yuta; Nakada, Masami; Watanabe, Masayuki; Okamoto, Yoshihiro; Nagai, Takayuki; Sato, Nobuaki*; Kirishima, Akira*
Journal of Nuclear Materials, 568, p.153847_1 - 153847_10, 2022/09
FeUO, CrUO
, and Fe
Cr
UO
are monouranates containing pentavalent U. Even though these compounds have similar crystal structures, their formation conditions and thermal stability are significantly different. To determine the factors causing the difference in thermal stability between FeUO
and CrUO
, their crystal structures were evaluated in detail. A Raman band was observed at 700 cm
in all the samples. This Raman band was derived from the stretching vibration of the O-U-O axis band, indicating that Fe
Cr
UO
was composed of a uranyl-like structure in its lattice regardless of its "x"' value. M
ssbauer measurements indicated that the Fe in FeUO
and Fe
Cr
UO
were trivalent. Furthermore, Fe
Cr
UO
lost its symmetry around Fe
with increasing electron densities around Fe
, as the abundance of Cr increased. These results suggested no significant structural differences between FeUO
and CrUO
. Thermogravimetric measurements for UO
, FeUO
, and CrUO
showed that the temperature at which FeUO
decomposed under an oxidizing condition (approximately 800
C) was significantly lower than the temperature at which the decomposition of CrUO
started (approximately 1250
C). Based on these results, we concluded that the decomposition of FeUO
was triggered by an ``in-crystal'' redox reaction, i.e., Fe
U
Fe
U
, which would not occur in the CrUO
lattice because Cr
could never be reduced under the investigated condition. Finally, the existence of Cr
in FexCr
UO
effectively suppressed the decomposition of the Fe
Cr
UO
crystal, even at a very low Cr content.
Kirishima, Akira*; Akiyama, Daisuke*; Kumagai, Yuta; Kusaka, Ryoji; Nakada, Masami; Watanabe, Masayuki; Sasaki, Takayuki*; Sato, Nobuaki*
Journal of Nuclear Materials, 567, p.153842_1 - 153842_15, 2022/08
To understand the chemical structure and stability of nuclear fuel debris consisting of UO, Zr, and Stainless Steel (SUS) generated by the Fukushima Daiichi Nuclear Power Plant accident in Japan in 2011, simulated debris of the UO
-SUS-Zr system and other fundamental component systems were synthesized and characterized. The simulated debris were synthesized by heat treatment for 1 to 12 h at 1600
C, in inert (Ar) or oxidative (Ar + 2% O
) atmospheres.
Np and
Am tracers were doped for the leaching tests of these elements and U from the simulated debris. The characterization of the simulated debris was conducted by XRD, SEM-EDX, Raman spectroscopy, and M
ssbauer spectroscopy, which provided the major uranium phase of the UO
-SUS-Zr debris was the solid solution of U
O
(s.s.) with Zr(IV) and Fe(II) regardless of the treatment atmosphere. The long-term immersion test of the simulated debris in pure water and that in seawater revealed the macro scale crystal structure of the simulated debris was chemically very stable in the wet condition for a year or more. Furthermore, the leaching test results showed that the actinide leaching ratios of U, Np, Am from the UO
-SUS-Zr debris were very limited and less than 0.08 % for all the experiments in this study.
Kirishima, Akira*; Terasaki, Mariko*; Miyakawa, Kazuya; Okamoto, Yoshihiro; Akiyama, Daisuke*
Chemosphere, 289, p.133181_1 - 133181_12, 2022/04
no abstracts in English
Kumagai, Yuta; Kusaka, Ryoji; Nakada, Masami; Watanabe, Masayuki; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Sasaki, Takayuki*
Hoshasen Kagaku (Internet), (113), p.61 - 64, 2022/04
The severe accident at TEPCO's Fukushima Daiichi Nuclear Power Station resulted in generation of fuel debris. The fuel debris is in contact with water and the radiolysis of water can accelerate degradation of the debris. The analysis of particles sampled from inside or near the damaged reactors indicates the complicated compositions of the fuel debris. It is challenging to estimate the effect of water radiolysis on such a complicated material. Therefore, in this study, we investigated the potential degradation process by leaching experiments of simulated fuel debris in aqueous HO
solution. The results show that the reaction of H
O
induced uranium dissolution from most of the samples and then formation of uranyl peroxides. In contrast, a sample that had U-Zr oxide solid solution as the major phase exhibited remarkable resistance to H
O
. These findings revealed that the degradation of the simulated debris reflects the reactivity and stability of the uranium phase in the matrices.
Kumagai, Yuta; Kusaka, Ryoji; Nakada, Masami; Watanabe, Masayuki; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Sasaki, Takayuki*
Journal of Nuclear Science and Technology, 11 Pages, 2022/03
We investigated potential degradation of fuel debris caused by HO
, which is the oxidant of major impact from water radiolysis. We performed leaching experiments on different kinds of simulated debris comprising U, Fe, Cr, Ni, and Zr in an aqueous H
O
solution. Chemical analysis of the leaching solution showed that U dissolution was induced by H
O
. Raman analysis after the leaching revealed that uranyl peroxides were formed on the surface of the simulated debris. These results demonstrate that uranyl peroxides are possible alteration products of fuel debris from H
O
reaction. However, the sample in which the main uranium-containing phase was a U-Zr oxide solid solution showed much less uranium dissolution and no Raman signal of uranyl peroxides. Comparison of these results indicates that formation of an oxide solid solution of Zr with UO
improves the stability of fuel debris against H
O
reaction.
Uehara, Akihiro*; Akiyama, Daisuke*; Ikeda, Atsushi; Numako, Chiya*; Terada, Yasuko*; Nitta, Kiyofumi*; Ina, Toshiaki*; Takeda-Homma, Shino*; Kirishima, Akira*; Sato, Nobuaki*
Journal of Nuclear Materials, 559, p.153422_1 - 153422_11, 2022/02
Wada, Yuki*; Matsumoto, Takahiro*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; Furuta, Yoshihiro*; Yonetoku, Daisuke*; Sawano, Tatsuya*; Okada, Go*; Nanto, Hidehito*; et al.
Physical Review Research (Internet), 3(4), p.043117_1 - 043117_31, 2021/12
Nagai, Takayuki; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Okamoto, Yoshihiro
2020-Nendo "Busshitsu, Debaisu Ryoiki Kyodo Kenkyu Kyoten" Oyobi "Hito, Kankyo To Busshitsu O Tsunagu Inobeshion Soshutsu Dainamikku, Araiansu" Kenkyu Seika, Katsudo Hokokusho (CD-ROM), 1 Pages, 2021/11
no abstracts in English
Koyama, Shinichi; Nakagiri, Toshio; Osaka, Masahiko; Yoshida, Hiroyuki; Kurata, Masaki; Ikeuchi, Hirotomo; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Takano, Masahide; et al.
Hairo, Osensui Taisaku jigyo jimukyoku Homu Peji (Internet), 144 Pages, 2021/08
JAEA performed the subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))" in 2020JFY. This presentation summarized briefly the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning and Contaminated Water Management.
McGrady, J.; Kumagai, Yuta; Watanabe, Masayuki; Kirishima, Akira*; Akiyama, Daisuke*; Kitamura, Akira; Kimuro, Shingo
RSC Advances (Internet), 11(46), p.28940 - 28948, 2021/08
Times Cited Count:0Kusaka, Ryoji; Kumagai, Yuta; Yomogida, Takumi; Takano, Masahide; Watanabe, Masayuki; Sasaki, Takayuki*; Akiyama, Daisuke*; Sato, Nobuaki*; Kirishima, Akira*
Journal of Nuclear Science and Technology, 58(6), p.629 - 634, 2021/06
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)Nagai, Takayuki; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Okamoto, Yoshihiro
2019-Nendo "Busshitsu, Debaisu Ryoiki Kyodo Kenkyu Kyoten" Oyobi "Hito, Kankyo To Busshitsu O Tsunagu Inobeshion Soshutsu Dainamikku, Araiansu" Kenkyu Seika, Katsudo Hokokusho (CD-ROM), P. 20191107_1, 2020/11
no abstracts in English
Haba, Hiromitsu*; Fan, F.*; Kaji, Daiya*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Komori, Yukiko*; Kondo, Narumi*; Kudo, Hisaaki*; Morimoto, Koji*; Morita, Kosuke*; et al.
Physical Review C, 102(2), p.024625_1 - 024625_12, 2020/08
Times Cited Count:2 Percentile:57.67(Physics, Nuclear)Nagashima, Mariko*; Armbruster, T.*; Akasaka, Masahide*; Sano, Asami; Nishio-Hamane, Daisuke*; Malsy, A.*; Imaoka, Teruyoshi*; Nakashima, Kazuo*
Physics and Chemistry of Minerals, 47(6), p.29_1 - 29_18, 2020/06
Times Cited Count:1 Percentile:27.06(Materials Science, Multidisciplinary)Three non-metamict chevkinite-subgroup minerals, from Cape Ashizuri, Japan, Tangir Valley, Diamar District, Pakistan and Haramosh Mts., Skardu district, Pakistan, were studied by crystal chemical techniques. Powder X-ray diffraction and transmission electron microscopic observations confirmed well crystalline samples. Electron-microprobe analyses indicated the general composition known for chevkinite-(Ce). Site scattering values determined by single-crystal X-ray structure refinements suggested assignment of subordinate Nb to the octahedral M3 and M4 sites, minor Th to M1 for the Ashizuri sample and minor Mg to M1 for both samples from Pakistan. Neutron time-of-flight powder diffraction studies were applied to determine the Ti/Fe distribution among octahedral sites for all samples and Mossbauer spectroscopy served for the Fe valence assignment at the four octahedral sites. The dominant iron valence at M1 of the Haramosh sample is ferric whereas for samples Nos. 1 and 2 iron is ferrous.
Katsumata, Tetsuhiro*; Suzuki, Ryo*; Sato, Naoto*; Suzuki, Shumpei*; Nakashima, Mamoru*; Inaguma, Yoshiyuki*; Mori, Daisuke*; Aimi, Akihisa*; Yoneda, Yasuhiro
Journal of Solid State Chemistry, 279, p.120919_1 - 120919_8, 2019/11
Times Cited Count:5 Percentile:55.42(Chemistry, Inorganic & Nuclear)Wada, Yuki*; Enoto, Teruaki*; Nakamura, Yoshitaka*; Furuta, Yoshihiro; Yuasa, Takayuki*; Nakazawa, Kazuhiro*; Morimoto, Takeshi*; Sato, Mitsuteru*; Matsumoto, Takahiro*; Yonetoku, Daisuke*; et al.
Communications Physics (Internet), 2(1), p.67_1 - 67_9, 2019/06
Times Cited Count:18 Percentile:89.5(Physics, Multidisciplinary)Kimuro, Shingo; Kirishima, Akira*; Kitatsuji, Yoshihiro; Miyakawa, Kazuya; Akiyama, Daisuke*; Sato, Nobuaki*
Journal of Chemical Thermodynamics, 132, p.352 - 362, 2019/05
Times Cited Count:6 Percentile:53.99(Thermodynamics)A combination of potentiometry and calorimetry was used for the determination of the thermodynamic quantities of complexation of generic and groundwater humic acid (HA), which was isolated from deep groundwater at Horonobe, Hokkaido, Japan, with copper (II) ions and uranyl (VI) ions. The apparent complexation constant of Horonobe HA was independent of the pH, whereas that of generic HA was dependent on the pH. This observation indicates that the polyelectrolyte effect of Horonobe HA is negligible because of its small molecular size. In addition, the effect of the heterogeneity of Horonobe HA was not significant. Moreover, the complexation enthalpy of Horonobe HA was consistent with that of homogeneous poly(acrylic acid), which means the complexation of Horonobe HA was not affected by the functional group heterogeneity. Consequently, the characteristic complexation mechanism of Horonobe HA was revealed based on the determined thermodynamic quantities.
Tojo, Masayuki*; Kanazawa, Toru*; Nakashima, Kazuo*; Iwamoto, Tatsuya*; Kobayashi, Kensuke*; Goto, Daisuke*; Nemoto, Yoshiyuki; Kaji, Yoshiyuki
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 13 Pages, 2019/05
In this study, fuel loading effects in BWR spent fuel rack accidents are widely investigated using three-dimensional analysis methods from both nuclear and thermal hydraulics viewpoints, including: (a) Decay heat of spent fuel after discharge, (b) The maximum temperature of spent fuel cladding in the spent fuel rack depending on heat transfer phenomena, and (c) Criticality of the spent fuel rack after collapsing of the fuel due to a severe accidents in the BWR spent fuel pool (SFP).
Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Beerwerth, R.*; Kaneya, Yusuke*; Makii, Hiroyuki; Mitsukai, Akina*; Nagame, Yuichiro; Osa, Akihiko; Toyoshima, Atsushi; et al.
Journal of the American Chemical Society, 140(44), p.14609 - 14613, 2018/11
Times Cited Count:16 Percentile:70.21(Chemistry, Multidisciplinary)The first ionization potential (IP) yields information on valence electronic structure of an atom. IP
values of heavy actinides beyond einsteinium (Es, Z = 99), however, have not been determined experimentally so far due to the difficulty in obtaining these elements on scales of more than one atom at a time. Recently, we successfully measured IP
of lawrencium (Lr, Z = 103) using a surface ionization method. The result suggests that Lr has a loosely-bound electron in the outermost orbital. In contrast to Lr, nobelium (No, Z = 102) is expected to have the highest IP
among the actinide elements owing to its full-filled 5f and the 7s orbitals. In the present study, we have successfully determined IP
values of No as well as fermium (Fm, Z = 100) and mendelevium (Md, Z = 101) using the surface ionization method. The obtained results indicate that the IP
value of heavy actinoids would increase monotonically with filling electrons up in the 5f orbital like heavy lanthanoids.
Kimuro, Shingo*; Kirishima, Akira*; Nagao, Seiya*; Saito, Takumi*; Amano, Yuki; Miyakawa, Kazuya; Akiyama, Daisuke*; Sato, Nobuaki*
Journal of Nuclear Science and Technology, 55(5), p.503 - 515, 2018/05
Times Cited Count:3 Percentile:45.99(Nuclear Science & Technology)no abstracts in English