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Hidaka, Akihide
Journal of Radioanalytical and Nuclear Chemistry, 332, p.1607 - 1623, 2023/03
Times Cited Count：0 Percentile：0.01(Chemistry, Analytical)no abstracts in English
Tashiro, Shinsuke; Ono, Takuya; Amano, Yuki; Yoshida, Ryoichiro; Watanabe, Koji*; Abe, Hitoshi
Nuclear Technology, 208(10), p.1553 - 1561, 2022/10
Times Cited Count：1 Percentile：0.01(Nuclear Science & Technology)To contribute to the confinement safety evaluation of the radioactive materials in the Glove box (GB) fire accident, combustion tests with the Polymethyl methacrylate (PMMA) and the Polycarbonate (PC) as typical panel materials for the GB have been conducted with a relatively large scale apparatus. As the important data for evaluating confinement safety, the release ratio and the particle size distribution of the soot generated from the burned materials were obtained. Furthermore, the rise of the differential pressure (
P) of the high efficiency particle air (HEPA) filter by the soot loading was also investigated. As results, the release ratio of the soot from the PC was about seven times as large as the PMMA. In addition, it was found that the behavior of the rise of the P with soot loading could be represented uniformly regardless of kinds of combustion materials by considering effect of the loading volume of the soot particle in the relatively low loading region.
Tashiro, Shinsuke; Uchiyama, Gunzo; Ono, Takuya; Amano, Yuki; Yoshida, Ryoichiro; Abe, Hitoshi
Nuclear Technology, 208(7), p.1205 - 1213, 2022/07
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)A clogging behavior of a high-efficiency particulate air (HEPA) filter at solvent fire accidents for reprocessing facilities has been studied. In this study, the burning rates of 30% tri-butyl phosphate (TBP)/dodecane (DD) mixed solvent and DD solvent and the differential pressure (P) of a high airflow typed HEPA filter applied in the actual facilities in Japan were measured. It was confirmed that the mainly burned was DD at the early stage of the mixed solvent burning and the TBP at the late stage. Furthermore, it was found that the P rapidly rose at the late stage of the mixed solvent burning. The increase of the release ratio of the unburned particulate composition (TBP, its degraded solvent and inorganic phosphorus (P
O
)) was considered to contribute to the rapid rise. The correlating formulas with the P and the mass of the loading particulates, except for the region of the rapid rise of P, could be induced.
Hidaka, Akihide
Nuclear Technology, 208(2), p.318 - 334, 2022/02
Times Cited Count：6 Percentile：64.12(Nuclear Science & Technology)The author previously proposed that the Cs bearing microparticle (Type A) may have been formed by melting and atomization of glass fibers (GF) of the HEPA filter in the SGTS due to flame and blast during the hydrogen explosion in Unit 3. If this hypothesis is correct, the Type A could contain or accompany carbon (C), that ignites spontaneously above 623 K, because of the limited time to be heated up, inclusion of C in the binder applied on the GF surface and closely located charcoal filter. As the previous studies did not focus on C, the present analyses were performed with EPMA whether the Type A contains C. The results showed that the Type A contained C originating from the binder, and non-spherical particles accompanied by the Type A and the film surrounding the Type A contained more C, which is thought to originate from the charcoal filter. These results cannot be explained by the other mechanisms proposed so far, and can be explained consistently by the author proposed hypothesis.
Hidaka, Akihide
Proceedings of 2021 International Congress on Advances in Nuclear Power Plants (ICAPP 2021) (USB Flash Drive), 10 Pages, 2021/10
Author recently proposed that the Type A glassy Cesium-bearing microparticles that were released during the Fukushima accident may have been formed by melting and atomization of glass fibers of the High Efficiency Particulate Air (HEPA) filter in the Stand-by Gas Treatment System (SGTS) line in Unit 3 during the hydrogen explosion. In the present study, the components of the Type A and glass fibers of HEPA filter were examined using EPMA. The results showed that the components of the Type A were almost the same as that of the glass fibers except for Cs, Fe, Sn, which are considered to have been contained in the in-vessel-derived particles. When the glass fiber was irradiated with the electron beam of the Electron Probe Micro Analyzer (EPMA) under vacuum condition, spherical particles of a few micro m size were formed that looked very similar to the Type A. These strongly suggest that the HEPA filter is Si source of the Type A.
Hidaka, Akihide
Nihon Genshiryoku Gakkai-Shi ATOMO
, 63(9), p.679 - 680, 2021/09
no abstracts in English
Hidaka, Akihide
Journal of Nuclear Science and Technology, 56(9-10), p.831 - 841, 2019/09
Times Cited Count：12 Percentile：79.53(Nuclear Science & Technology)The insoluble Cs particles (Type A) were firstly observed in Tsukuba-city on the morning of March 15. The particles have been considered to be generated in RPV of Unit 2 by evaporation/condensation based on the measured 
Cs/
Cs ratio and the core temperatures of each unit. However, the Type A particles with smaller diameter than the Type B particles of Unit 1 origin, are covered by almost pure silicate glass and have a trace of the quenching. This indicates that the particles could have been generated due to the melting of the HEPA filter in SGTS by the fire of H detonation at Unit 3, and atomization followed by quenching of the molten materials by air blast of the explosion. Although the particles were mostly dispersed to the sea because of the wind direction, some of them deposited onto the lower elevation of R/B at Unit 3, could have been subsequently re-suspended and released into the environment, by the steam flow in the R/B caused by restart of the Unit 3 core cooling water injection at 2:30 of March 15.
Ono, Takuya; Watanabe, Koji; Tashiro, Shinsuke; Amano, Yuki; Abe, Hitoshi
Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 7 Pages, 2017/07
After the Fukushima-Daiichi accident, countermeasures against the severe accident are newly required as regulatory items for nuclear facilities. Organic solvent fire in cell was defined as one of the accidents in the fuel reprocessing plant. When the solvent burns, aerosols including soot are released. The substances clog HEPA filters in the ventilation system and their breakthrough may happen because of differential pressure rising. Moreover, the fire can also release volatile radioactive gaseous species, which can pass through HEPA filters. These phenomena are important for evaluation of confinement capability of the facility and public exposure. We have investigated, in relating to the clogging behavior, release behavior of aerosols as well as of volatile materials from burnt solvent. In the presentation, we will report experimental data and evaluation results obtained from recent research.
Tsukamoto, Michio; Takada, Junichi; Koike, Tadao; Watanabe, Koji*; Miyata, Teijiro*; Nishio, Gunji*; Murata, Mikio*; Uchiyama, Gunzo
JAERI-Tech 2001-031, 47 Pages, 2001/03
JAERI-Tech-2001-031.pdf:2.75MB
no abstracts in English
Murata, Mikio; Takada, Junichi; Tsukamoto, Michio
KURRI-KR-30, p.5 - 11, 1998/00
no abstracts in English
; ; Ikezawa, Yoshio
Hoken Butsuri, 32(2), p.185 - 191, 1997/00
no abstracts in English
Takada, Junichi; Suzuki, Motoe; Tsukamoto, Michio; Koike, Tadao; *
JAERI-Tech 96-054, 237 Pages, 1996/12
no abstracts in English
Takada, Junichi; Suzuki, Motoe; Tsukamoto, Michio; Koike, Tadao; Nishio, Gunji
JAERI-Tech 95-024, 339 Pages, 1995/03
no abstracts in English
Ikezawa, Yoshio
Saikin No Kenkyu Shisetsu, 0, p.304 - 311, 1995/00
no abstracts in English
Abe, Hitoshi; Nishio, Gunji; Naito, Yoshitaka
JAERI-M 93-220, 107 Pages, 1993/11
no abstracts in English
Ikezawa, Yoshio
Kurin Tekunoroji, 3(4), p.41 - 45, 1993/04
no abstracts in English
Nishio, Gunji; Suzuki, Motoe; Takada, Junichi; Koike, Tadao; Tsukamoto, Michio
JAERI-M 93-019, 209 Pages, 1993/02
no abstracts in English
Hashimoto, Kazuichiro; Nishio, Gunji; Soda, Kunihisa
Nuclear Technology, 101, p.218 - 226, 1993/02
Times Cited Count：7 Percentile：60.37(Nuclear Science & Technology)no abstracts in English
Suzuki, Motoe; Nishio, Gunji; Takada, Junichi; Tsukamoto, Michio; Koike, Tadao
JAERI 1328, 90 Pages, 1993/01
no abstracts in English
