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Furuno, Akiko; Omori, Ryuta*; Tateoka, Hisanori*; Minakawa, Yuya*; Kurihara, Toshiyuki; Yamamoto, Yoichi; Tomita, Yutaka
Pure and Applied Geophysics, 14 Pages, 2024/00
Times Cited Count：0 Percentile：0.00(Geochemistry & Geophysics)The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) Okinawa radionuclide monitoring station (JPP37) is located on a hill facing the East China Sea at the center of the main island of Okinawa. It occasionally detects Cs-137, although no nuclear facilities are located on the island. This study focused on the detection of Cs-137 at JPP37 and examined the ratio of simultaneous detections at nearby stations of the International Monitoring System (IMS) of the CTBTO and the relationship with Asian dust from inland East Asia. The detection of Cs-137 in JPP37 from 2020 to 2023, which motivated this study, was high in spring. Among the nine IMS radionuclide stations in East Asia, the detections in Beijing, Lanzhou, and Ulaanbaatar, Mongolia, were also high in spring. This suggested a high association with the detection of Asian dust in East Asia. Thus, we confirmed the detection of Cs-137 at nine nearby IMS stations when Asian dust was observed at any of the sites in Japan. In addition, we observed that the detection rates were high in Takasaki, Beijing, Lanzhou, and Ulaanbaatar. It can be inferred that the Cs-137 observed mainly in spring at the IMS particulate radionuclide stations in the East Asian region around Japan were likely to pick up the effects of global fallout conveyed by Asian dust. Thereafter, we conducted a preliminary source estimation analysis for Asian dust arrival near Japan. Atmospheric dispersion simulations explained the detection of Cs-137 at nearby IMS particulate radionuclide stations, assuming that Cs-137 was emitted from the desert, the source of the Asian dust.
Nb and 
Ta for chemical studies of element 105, Db, using the GARIS gas-jet systemHuang, M.*; Haba, Hiromitsu*; Murakami, Masashi*; Asai, Masato; Kaji, Daiya*; Kanaya, Jumpei*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Kikutani, Yuki*; Komori, Yukiko*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 304(2), p.845 - 849, 2015/05
Times Cited Count：3 Percentile：23.43(Chemistry, Analytical)A technique to utilize radioisotopes of Nb and Ta was developed for chemical studies of element 105, Db, by coupling a gas-jet transport system to the RIKEN gas-filled recoil ion separator (GARIS). The short-lived Nb and Ta were produced with nuclear reactions using a 
F beam whose energy was the same as that to produce 
Db. Then, they were separated with GARIS and extracted to a chemistry laboratory with the gas-jet transport system. By changing only magnetic field of GARIS and inserting an energy degrader and a shutter for recoil ions, we could deliver the Nb and Ta to a chemistry device for Db without changing other experimental conditions.
Db in the 
Cm(F,5
)Db reaction and decay properties of Db and 
LrHaba, Hiromitsu*; Huang, M.*; Kaji, Daiya*; Kanaya, Jumpei*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Murakami, Masashi*; Ozeki, Kazutaka*; Sakai, Ryutaro*; et al.
Physical Review C, 89(2), p.024618_1 - 024618_11, 2014/02
Times Cited Count：27 Percentile：81.83(Physics, Nuclear)
Sg in the Cm(
Ne,5)Sg reaction and decay properties of two isomeric states in SgHaba, Hiromitsu*; Kaji, Daiya*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Ozeki, Kazutaka*; Sakai, Ryutaro*; Sumita, Takayuki*; Yoneda, Akira*; Kasamatsu, Yoshitaka*; et al.
Physical Review C, 85(2), p.024611_1 - 024611_11, 2012/02
Times Cited Count：56 Percentile：91.18(Physics, Nuclear)Two isomeric states in Sg, i.e, Sg
and Sg
were produced in the Cm(Ne,5) reaction. Decay properties of Sg
were investigated with a rotating-wheel apparatus for 
and spontaneous fission (SF) spectrometry under low background condition attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. Based on genetically correlated - (-) and -SF decay chains, 18 and 24 events were assigned to Sg and Sg, respectively. The half-life and -particle energy of Sg were measured to be 
s and 
MeV, respectively, and those of Sg were 
s and 
MeV.
Takamatsu, Kuniyoshi; Sawa, Kazuhiro; Kunitomi, Kazuhiko; Hino, Ryutaro; Ogawa, Masuro; Komori, Yoshihiro; Nakazawa, Toshio*; Iyoku, Tatsuo; Fujimoto, Nozomu; Nishihara, Tetsuo; et al.
Nihon Genshiryoku Gakkai Wabun Rombunshi, 10(4), p.290 - 300, 2011/12
A high temperature (950
C) continuous operation has been performed for 50 days on the HTTR from January to March in 2010, and the potential to supply stable heat of high temperature for hydrogen production for a long time was demonstrated for the first time in the world. This successful operation could establish technological basis of HTGRs and show potential of nuclear energy as heat source for innovative thermo-chemical-based hydrogen production, emitting greenhouse gases on a "low-carbon path" for the first time in the world.
113 produced by the 
Bi(
Zn,n)113 reactionMorimoto, Koji*; Morita, Kosuke*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.
no journal, ,
We performed the experiment to synthesize an isotope of the element 113 produced by a Bi(Zn,n)113 reaction using a gas-filled recoil ion separator (GARIS) at RIKEN. Two decay chains were observed, and assigned to those originating from an isotope 113. Both chains were connected into the previously known decays of 
Bh and Db via previously unknown decays of 113, 
Rg, and 
Mt. Although the Bh was known nuclide, a number of atoms reported so far was limited. In order to study more precise decay property of the Bh, we performed the direct production of Bh by the Cm(
Na,5n)Bh reaction. In this experiment, the Bh was clearly identified from the correlation of the nuclide, Db. The obtained decay properties of Bh and Db are consistent with those observed in the 113 chain, which provided further confirmation of the discovery of 113.
Furuno, Akiko; Kijima, Yuichi; Yamamoto, Yoichi; Omori, Ryuta*; Tateoka, Hisanori*; Minakawa, Yuya*; Tomita, Yutaka
no journal, ,
JAEA cooperates in all aspects of work related to radionuclides in the detection of nuclear tests conducted under the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Radionuclide monitoring stations are deployed all over the world in case radionuclides produced by nuclear tests are released into the atmosphere, and we are operating two of these stations in Japan (Takasaki City, Gunma Prefecture and Onna Village, Okinawa Prefecture). In this report, we introduce our observation method and outline of recent observation results.
Kasugai, Atsushi; Sakamoto, Keishi; Takahashi, Koji; Kajiwara, Ken; Ikeda, Yukiharu; Komori, Shinji; Kobayashi, Noriyuki; Kariya, Tsuyoshi*; Minami, Ryutaro*; Mitsunaka, Yoshika*
no journal, ,
no abstracts in English
Furuno, Akiko; Omori, Ryuta*; Tateoka, Hisanori*; Minakawa, Yuya*; Kurihara, Toshiyuki; Yamamoto, Yoichi; Tomita, Yutaka
no journal, ,
Our team manages the Okinawa and Takasaki stations, which are part of the International Monitoring Stations (IMS) network for airborne radionuclides operated by CTBTO. The Okinawa station occasionally detects Cs-137. Since there are no nuclear facilities on the main island of Okinawa, where the Okinawa station is located, it is highly likely that it has arrived from a distant source. Cs-137 is mainly detected in Okinawa from winter to spring, so in this study, we hypothesize that the Cs-137 detected in Okinawa is related to the Asian dust, and we will check the Cs-137 detection status at IMS observation stations in East Asian countries and conduct preliminary verification using the atmospheric dispersion model FLEXPART.
