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Kusaka, Ryoji; Kumagai, Yuta; Watanabe, Masayuki; Sasaki, Takayuki*; Akiyama, Daisuke*; Sato, Nobuaki*; Kirishima, Akira*
Journal of Nuclear Science and Technology, 60(5), p.603 - 613, 2023/05
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)Tonna, Ryutaro*; Sasaki, Takayuki*; Kodama, Yuji*; Kobayashi, Taishi*; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Kumagai, Yuta; Kusaka, Ryoji; Watanabe, Masayuki
Nuclear Engineering and Technology, 55(4), p.1300 - 1309, 2023/04
Times Cited Count:0 Percentile:0.02(Nuclear Science & Technology)Simulated debris was synthesized using UO, Zr, and stainless steel and a heat treatment method under inert or oxidizing conditions. The primary U solid phase of the debris synthesized at 1473 K under inert conditions was UO
, whereas a (U,Zr)O
solid solution formed at 1873 K. Under oxidizing conditions, a mixture of U
O
and (Fe,Cr)UO
phases formed at 1473 K whereas a (U,Zr)O
solid solution formed at 1873 K. The leaching behavior of the fission products from the simulated debris was evaluated using two methods: the irradiation method, for which fission products were produced via neutron irradiation, and the doping method, for which trace amounts of non-radioactive elements were doped into the debris. The dissolution behavior of U depended on the properties of the debris and aqueous medium the debris was immersed in. Cs, Sr, and Ba leached out regardless of the primary solid phases. The leaching of high-valence Eu and Ru ions was suppressed, possibly owing to their solid-solution reaction with or incorporation into the uranium compounds of the simulated debris.
McGrady, J.; Kumagai, Yuta; Watanabe, Masayuki; Kirishima, Akira*; Akiyama, Daisuke*; Kimuro, Shingo; Ishidera, Takamitsu
Journal of Nuclear Science and Technology, 9 Pages, 2023/00
Times Cited Count:0 Percentile:0.02(Nuclear Science & Technology)Yomogida, Takumi; Akiyama, Daisuke*; Ouchi, Kazuki; Kumagai, Yuta; Higashi, Kotaro*; Kitatsuji, Yoshihiro; Kirishima, Akira*; Kawamura, Naomi*; Takahashi, Yoshio*
Inorganic Chemistry, 61(50), p.20206 - 20210, 2022/12
Times Cited Count:1 Percentile:27.23(Chemistry, Inorganic & Nuclear)FeUO was studied to clarify the electronic structure of U(V) in a metal monouranate compound. We obtained the peak splitting of HERFD-XANES spectra utilizing high-energy-resolution fluorescence detection-X-ray absorption near edge structure (HERFD-XANES) spectroscopy at the U L
-edge, which is a novel technique in the U(V) compounds. Theoretical calculations revealed that the peak splitting was caused by splitting the 6d orbital of U(V). Such distinctive electronic states are of major interest to researchers and engineers working in various fields, from fundamental physics to the nuclear industry and environmental sciences for actinide elements.
Ikeuchi, Hirotomo; Koyama, Shinichi; Osaka, Masahiko; Takano, Masahide; Nakamura, Satoshi; Onozawa, Atsushi; Sasaki, Shinji; Onishi, Takashi; Maeda, Koji; Kirishima, Akira*; et al.
JAEA-Technology 2022-021, 224 Pages, 2022/10
A set of technology, including acid dissolving, has to be established for the analysis of content of elements/nuclides in the fuel debris samples. In this project, a blind test was performed for the purpose of clarifying the current level of analytical accuracy and establishing the alternative methods in case that the insoluble residue remains. Overall composition of the simulated fuel debris (homogenized powder having a specific composition) were quantitatively determined in the four analytical institutions in Japan by using their own dissolving and analytical techniques. The merit and drawback for each technique were then evaluated, based on which a tentative flow of the analyses of fuel debris was constructed.
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
Times Cited Count:2 Percentile:63.62(Materials Science, Multidisciplinary)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
Times Cited Count:3 Percentile:77.29(Materials Science, Multidisciplinary)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.
Kumagai, Yuta; Kusaka, Ryoji; Nakada, Masami; Watanabe, Masayuki; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Sasaki, Takayuki*
Journal of Nuclear Science and Technology, 59(8), p.961 - 971, 2022/08
Times Cited Count:2 Percentile:63.62(Nuclear Science & Technology)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.
Tachi, Yukio; Saito, Takumi*; Kirishima, Akira*
Nihon Genshiryoku Gakkai-Shi ATOMO, 64(5), p.290 - 295, 2022/05
no abstracts in English
Kirishima, Akira*; Terasaki, Mariko*; Miyakawa, Kazuya; Okamoto, Yoshihiro; Akiyama, Daisuke*
Chemosphere, 289, p.133181_1 - 133181_12, 2022/04
Times Cited Count:1 Percentile:7.55(Environmental Sciences)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.
Sato, Nobuaki*; Kirishima, Akira*; Watanabe, Masayuki; Sasaki, Takayuki*; Uehara, Akihiro*; Takeda, Shino*; Kitatsuji, Yoshihiro; Otobe, Haruyoshi; Kobayashi, Taishi*
The Chemistry of Thorium, Plutonium and MA, 254 Pages, 2022/03
The chemistry of nuclear materials such as Thorium (Part 1) and Plutonium (Part 2) was described in relation from the fundamentals on solid chemistry and solution chemistry to the practicals on the experiment and evaluation method in detail. Minor actinides such as Neptunium, Americium, Curium and Protoactinium, was introduced the basics on the solid and solution chemistry.
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
Times Cited Count:2 Percentile:63.62(Materials Science, Multidisciplinary)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:4 Percentile:43.75(Chemistry, Multidisciplinary)Kusaka, 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:7 Percentile:70.19(Nuclear Science & Technology)Sato, Nobuaki*; Kirishima, Akira*; Watanabe, Masayuki; Sasaki, Takayuki*; Uehara, Akihiro*; Takeda, Shino*
Uran No Kagaku (II); Hoho To Jissen, 143 Pages, 2021/03
This book describes necessary facts when readers would have an opportunity to treat Uranium for experiments. In the content, the method section shows experimental facilities and equipment including method, and the practical section mentions solution and solid state experiments using Uranium and/or radioisotopes.
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
Sato, Nobuaki*; Kirishima, Akira*; Watanabe, Masayuki
Uran No Kagaku (I); Kiso To Oyo, 184 Pages, 2020/06
This particular book deals with fundamental items related with chemistry of Uranium and consists of basic section and practical section. In the basic section, inorganic and radiochemistry of Uranium was described. On the other hand, in the practical section, the process chemistry related with reprocessing of nuclear fuels and "debris" involved with Fukushima Daiichi Power Plant accident were described. This book is intended for use by scientists, engineers and students in the nuclear industry in their education and/or professional practice.