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Co inventory in the core of the Fukushima Daiichi Nuclear Power Plant; Contribution of fuel deposits to the reactor core inventoryUchida, Shunsuke*; Kino, Chiaki*; Karasawa, Hidetoshi; Takahatake, Yoko; Koma, Yoshikazu
Journal of Nuclear Science and Technology, 62(9), p.863 - 879, 2025/09
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Evaluation of radioactive nuclide behavior on and after the accident is important for the estimating radioactive nuclide composition in the wastes. The reactor core inventories have been obtained from the ORIGEN2 analysis, but the inventory of activation products is determined by the amount of their parent nuclides which are impurities contained in the structural materials. The ORIGEN2 does not treat fuel deposits including the impurities. Estimation of the initial Co-60 inventory in accurate is needed on the evaluation of some kinds of radioactive nuclide amount, since it is possible Co-60 is standard in the scaling factor. In this study, contribution of fuel deposits to the reactor core inventory was estimated by comparing the amount of Co-60 and Ni-63 calculated by the amounts of deposition by the microlayer-evaporation and drying-out model (MEDO model) and the result of the ORIGEN2 analysis, and then the method of estimating the reactor core inventory was proposed.
Aihara, Haruka; Hinai, Hiroshi; Shibata, Atsuhiro; Tomita, Sayuri*; Koma, Yoshikazu
Progress in Nuclear Science and Technology (Internet), 8, p.324 - 328, 2025/09
Pu and Am contained in the contaminated water at Fukushima Daiichi Nuclear Power Station is concerned to contaminate inside the buildings concrete. To understand or estimate the state of contamination, investigation on contamination mechanisms have become quite important. Therefore, the distribution ratio of Pu and Am to cement paste and aggregates was obtained by experiments. Cement paste and aggregate were immersed in Pu and Am solution to obtain distribution ratio. Those of Pu and Am to cement paste was high values, suggesting that they have sorbed and accumulated in the building concrete.
Katsumura, Kosuke*; Takagi, Junichi*; Miyahara, Naoya*; Uchida, Shunsuke*; Koma, Yoshikazu; Karasawa, Hidetoshi; Miwa, Shuhei; Satou, Yukihiko; Nagai, Haruyasu; Kurata, Masaki; et al.
Nihon Genshiryoku Gakkai-Shi ATOMO
, 67(2), p.128 - 132, 2025/02
no abstracts in English
Yomogida, Takumi; Ouchi, Kazuki; Morii, Shiori; Oka, Toshitaka; Kitatsuji, Yoshihiro; Koma, Yoshikazu; Konno, Katsuhiro*
Scientific Reports (Internet), 14, p.14945_1 - 14945_11, 2024/06
Times Cited Count：4 Percentile：41.36(Multidisciplinary Sciences)Particles containing alpha (
) nuclides were identified from sediment in stagnant water in the Unit 3 reactor building of the Fukushima Daiichi Nuclear Power Station (FDiNPS). We analyzed different concentrations of alpha nuclides samples collected at two sampling sites, torus room and Main steam isolation valve (MSIV) room. Most of the -nuclides in the stagnant water samples of the torus room and the MSIV room were present in particle fractions larger than 10 
m. We detected uranium-bearing particles in m-size by scanning electron microscopy-energy dispersive X-Ray (SEM-EDX) observation. Other short lived -nuclides were detected by alpha track detection. The -nuclide-containing particles with several tens to several hundred m in size were mainly comprised iron (Fe) by SEM-EDX analysis. This study clarifies that the morphologies of U and other -nuclides in the sediment of stagnant water in the FDiNPS's Unit 3 reactor building.
Warashina, Tomoro*; Sato, Asako*; Hinai, Hiroshi; Shaikhutdinov, N.*; Shagimardanova, E.*; Mori, Hiroshi*; Tamaki, Satoshi*; Saito, Motofumi*; Sanada, Yukihisa; Sasaki, Yoshito; et al.
Applied and Environmental Microbiology, 90(4), p.e02113-23_1 - e02113-23_23, 2024/04
Times Cited Count：2 Percentile：13.04(Biotechnology & Applied Microbiology)Yamada, Kazuo*; Hokora, Hideyuki*; Maruyama, Ippei*; Aihara, Haruka; Tomita, Sayuri*; Tojo, Yasumasa*; Shibuya, Kazutoshi*; Hosokawa, Yoshifumi*; Igarashi, Go*; Koma, Yoshikazu
Proceedings of Waste Management Symposia 2024 (WM2024) (Internet), 7 Pages, 2024/03
Katsumura, Kosuke*; Takagi, Junichi*; Hosomi, Kenji*; Miyahara, Naoya*; Koma, Yoshikazu; Imoto, Jumpei; Karasawa, Hidetoshi; Miwa, Shuhei; Shiotsu, Hiroyuki; Hidaka, Akihide*; et al.
Nihon Genshiryoku Gakkai-Shi ATOMO, 65(11), p.674 - 679, 2023/11
no abstracts in English
Yamada, Kazuo*; Tojo, Yasumasa*; Aihara, Haruka; Tomita, Sayuri*; Hokora, Hideyuki*; Shibuya, Kazutoshi*; Koma, Yoshikazu; Igarashi, Go*; Hosokawa, Yoshifumi*; Maruyama, Ippei*
Proceedings of Waste Management Symposia 2023 (WM2023) (Internet), 12 Pages, 2023/02
Strand, P.*; Jefferies, N.*; Koma, Yoshikazu; Plyer, J.*
Journal of Radiological Protection, 42(2), p.020501_1 - 020501_16, 2022/06
Times Cited Count：2 Percentile：21.09(Environmental Sciences)Yomogida, Takumi; Ouchi, Kazuki; Oka, Toshitaka; Kitatsuji, Yoshihiro; Koma, Yoshikazu; Konno, Katsuhiro*
Scientific Reports (Internet), 12(1), p.7191_1 - 7191_10, 2022/05
Times Cited Count：12 Percentile：54.67(Multidisciplinary Sciences)Particles containing alpha () nuclides were identified from sediment in stagnant water at the torus room of the Fukushima Dai-ichi Nuclear Power Station (FDiNPS)'s Unit 2 reactor. Several uranium-bearing particles were identified by SEM observation. These particles contained Zr and other elements which constituted fuel cladding and structural materials. The 
U/
U isotope ratio in the solid fractions that included U particles was consistent with the nuclear fuel in the Unit 2 reactor, which indicated that the U particles had been derived from nuclear fuel. The particles with alpha-emitters detected by alpha track analysis were several tens to several hundred m in size. The EDX spectra showed that these particles mainly comprised iron, which indicated Pu, Am, and Cm were adsorbed on the Fe-baring particles. This study clarifies that the major morphologies of U and other -nuclides were differed in the sediment of stagnant water in the torus room of FDiNPS's Unit 2 reactor.
Grambow, B.; Nitta, Ayako; Shibata, Atsuhiro; Koma, Yoshikazu; Utsunomiya, Satoshi*; Takami, Ryu*; Fueda, Kazuki*; Onuki, Toshihiko*; Jegou, C.*; Laffolley, H.*; et al.
Journal of Nuclear Science and Technology, 59(1), p.1 - 24, 2022/01
Times Cited Count：39 Percentile：75.74(Nuclear Science & Technology)Pyke, C. K.*; Hiller, P. J.*; Koma, Yoshikazu; Oki, Keiichi
Nuclear Engineering and Technology, 54(1), p.414 - 422, 2022/01
Times Cited Count：4 Percentile：41.78(Nuclear Science & Technology)Igarashi, Go*; Haga, Kazuko*; Yamada, Kazuo*; Aihara, Haruka; Shibata, Atsuhiro; Koma, Yoshikazu; Maruyama, Ippei*
Journal of Advanced Concrete Technology, 19(9), p.950 - 976, 2021/09
Times Cited Count：7 Percentile：27.94(Construction & Building Technology)Sugiyama, Daisuke*; Nakabayashi, Ryo*; Tanaka, Shingo*; Koma, Yoshikazu; Takahatake, Yoko
Journal of Nuclear Science and Technology, 58(4), p.493 - 506, 2021/04
Times Cited Count：3 Percentile：24.98(Nuclear Science & Technology)Yamada, Kazuo*; Maruyama, Ippei*; Haga, Kazuko*; Igarashi, Go*; Aihara, Haruka; Tomita, Sayuri*; Kiran, R.*; Osawa, Norihisa*; Shibata, Atsuhiro; Shibuya, Kazutoshi*; et al.
Proceedings of International Waste Management Symposia 2021 (WM2021) (CD-ROM), 10 Pages, 2021/03
Yin, X.; Zhang, L.*; Harigai, Miki*; Wang, X.*; Ning, S.*; Nakase, Masahiko*; Koma, Yoshikazu; Inaba, Yusuke*; Takeshita, Kenji*
Water Research, 177, p.115804_1 - 115804_10, 2020/06
Times Cited Count：26 Percentile：74.07(Engineering, Environmental)Yin, X.; Zhang, L.*; Meng, C.*; Inaba, Yusuke*; Wang, X.*; Nitta, Ayako; Koma, Yoshikazu; Takeshita, Kenji*
Journal of Hazardous Materials, 387, p.121677_1 - 121677_10, 2020/04
Times Cited Count：15 Percentile：42.05(Engineering, Environmental)Koma, Yoshikazu
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 26(2), p.133 - 136, 2019/12
At Fukushima Daiichi Nuclear Power Station, radioactive waste has been generated due to progress of decommissioning. This review outlines analysis of the waste at the site for R&D concerning waste management technologies.
Koma, Yoshikazu; Niibori, Yuichi*
Nihon Kikai Gakkai-Shi, 122(1211), p.21 - 23, 2019/10
International Topical Workshop on Fukushima Decommissioning Research was held in March 2019 by the Japan Society of Mechanical Engineers and the Atomic Energy Society of Japan. Result of track for waste management technologies among 5 tracks is outlined.
Sugiyama, Daisuke*; Nakabayashi, Ryo*; Koma, Yoshikazu; Takahatake, Yoko; Tsukamoto, Masaki*
Journal of Nuclear Science and Technology, 56(9-10), p.881 - 890, 2019/09
Times Cited Count：5 Percentile：36.76(Nuclear Science & Technology)
