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Sujita, Ryota*; Imai, Sahori*; Ouchi, Makoto*; Aoki, Hiroyuki; Terashima, Takaya*
Macromolecules, 56(23), p.9738 - 9749, 2023/12
Times Cited Count：0 Percentile：0(Polymer Science)Shiota, Yuki; Kudo, Junki; Tsuno, Hiromi; Takeuchi, Ryotaro; Ariyoshi, Hideo; Shiohama, Yasutaka; Hamano, Tomoharu; Takagi, Tsuyohiko; Nagaoki, Yoshihiro
JAEA-Technology 2023-002, 87 Pages, 2023/06
JAEA-Technology-2023-002.pdf:8.53MB
In the first stage of Monju decommissioning project, fuel unload work began to be carried out. There are two tasks in this work. One is Fuel Treatment and Storage work that gets rid of sodium on the fuel assemblies unloaded from Ex-Vessel fuel Storage Tank (EVST) and carries it in the storage pool, and the other is Fuel Unloading that the fuel assemblies in the reactor core is replaced with dummy fuels and stored in EVST. Fuel Treatment and Storage work and Fuel Unloading work are performed alternately, and 370 fuel assemblies in the core and 160 fuel assemblies in EVST are all carried to the storage pool. Monju had a large amount of sodium in the reactor vessel and EVST, and there was a residual risk of fuel failure due to the superposition of a large scale sodium fire. Therefore, in the first stage of the Monju decommissioning project, it was decided to take about 5.5 years to remove the residual risk by storing all the fuel rods in the fuel storage pool. There are few Fuel handling system of Sodium Fast Reactor in the world, so the driving record and experience are not enough. So, events that occur even if taken measure are assumed. The following three events apply to this; first, events that are difficult to prevent, events. Second, that are due to lack of experience, and final, events optimization of system is not enough. Plans were taken to suppress these events. This report summarizes the "Monju decommissioning project" work conducted so far in all four campaigns.
Otsuka, Yusuke*; Kanazawa, Naoya*; Hirayama, Motoaki*; Matsui, Akira*; Nomoto, Takuya*; Arita, Ryotaro*; Nakajima, Taro*; Hanashima, Takayasu*; Ukleev, V.*; Aoki, Hiroyuki; et al.
Science Advances (Internet), 7(47), p.eabj0498_1 - eabj0498_9, 2021/11
Times Cited Count：8 Percentile：51.2(Multidisciplinary Sciences)Hirai, Keizo*; Komatsu, Masafumi*; Akama, Akio*; Noguchi, Ryotaro*; Nagakura, Junko*; Ohashi, Shinta*; Saito, Tetsu*; Kawasaki, Tatsuro*; Yazaki, Kenichi*; Ikeda, Shigeto*; et al.
no journal, ,
no abstracts in English
Sugiyama, Issei*; Saito, Masahiro*; Miyata, Noboru*; Hanashima, Takayasu*; Akutsu, Kazuhiro*; Aoki, Yasuhito*; Otsuka, Yuji*; Takeda, Masayasu; Shimizu, Ryota*; Hitosugi, Taro*
no journal, ,
no abstracts in English
Otani, Ryo; Sato, Tetsuya; Aoki, Ryota*; Shirai, Kaori*; Suzuki, Hayato; Tsukada, Kazuaki; Asai, Masato; Ito, Yuta; Nagame, Yuichiro*; Sakama, Minoru*
no journal, ,
The adsorption enthalpy of the Sg dioxydichloride on a quartz surface (
(SgO
Cl)) has been reported to be -98 kJ/mol. The result, however, is still ambiguous because the value was evaluated based on a few experimental points with large statistics errors. To obtain a reliable (SgOCl)) for a discussion of an influence of relativistic effects, a stable gas chemistry apparatus with good reproducibility is mandatory. In this study, we have conducted offline experiments of an isothermal gas chromatography) with short-lived Mo isotopes originated from a 
Cf fission source. We searched for experimental parameters for an on-line experiment. At the presentation, we will present the obtained optimum conditions for gas chromatographic separation of group-6 elements and determined (MoOCl)).
Aoki, Ryota*; Sato, Tetsuya; Otani, Ryo; Suzuki, Hayato; Ito, Yuta; Asai, Masato; Tsukada, Kazuaki; Nagame, Yuichiro*
no journal, ,
To apply a SHEs ion-beam to physical and chemical investigations, we have been developing ion sources that apply to a short-lived single atom. We employed the Electron Beam Generated Plasma (EBGP) method to ionize an element with high ionization energy. The EBGP ion source can ionize an element or a molecule of nuclear reaction products by bombarding an electron beam that accelerated between the cathode and the anode electrode. In this work, we built the EBGP ion source and searched for an optimum condition ionization of a single atom.
Aoki, Ryota; Sato, Tetsuya; Uchibaba, Yuta; Miyachi, Yuta*; Gong, G.; Natori, Hina*; Ito, Yuta; Asai, Masato; Tsukada, Kazuaki; Nagame, Yuichiro*
no journal, ,
In order to apply the ion beams of superheavy elements with atomic number over 100 to physics and chemistry research, we constructed an EBGP (Electron Beam Generated Plasma) ion source as an ion source applicable to short-lived single atoms. The EBGP ion source was installed in the JAEA-ISOL (Isotope Separator On-Line), and ion beam generation in various ionization conditions has been conducted with several noble gases. As a result, we confirmed the ion source worked in a stable condition, and an ion beam was successfully generated.
Uchibaba, Yuta; Ito, Yuta; Sato, Tetsuya; Aoki, Ryota; Asai, Masato; Gong, G.; Miyachi, Yuta*; Nagame, Yuichiro*; Natori, Hina*; Tsukada, Kazuaki
no journal, ,
In anticipation of precise mass measurement of superheavy nuclei with an atomic number of 104 or more, we are developing an ion trap for the purpose of improving the accuracy of mass determination by prior identification of ions to be measured by decay spectroscopy and correlation with decay information. In order to capture radiation from trapped unstable nuclear ions at a large solid angle, we have developed a vane electrode type ion trap using a thin plate-like vane electrode. As an indication of performance, the trap lifetime and accumulated charge were evaluated in comparison with a circular electrode type ion trap.
Sato, Tetsuya; Aoki, Ryota; Miyachi, Yuta*; Asai, Masato; Ito, Yuta; Uchibaba, Yuta; Gong, G.; Natori, Hina*; Tsukada, Kazuaki; Nagame, Yuichiro*
no journal, ,
We have been developing an EBGP (Electron Beam Generated Plasma) ion source1 coupled to the gas-jet transport system to produce SHE ion beams for rapid chemical experiments. The EBGP ion source ionizes atoms and molecules by electron impact and is expected to produce ion beams of various elements. We have succeeded to produce ion-beams of several noble gases using the present ion source, and it has been found that the beam intensities increase with increasing atomic number. We report on the ionization of various short-lived nuclides produced in spontaneous fission of Cf.
Es targetAsai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Ito, Yuta; Nishio, Katsuhisa; Makii, Hiroyuki; Hirose, Kentaro; Orlandi, R.; Suzaki, Fumi; Aoki, Ryota; et al.
no journal, ,
Fission of neutron-rich heavy-actinide nuclei exhibits extremely characteristic fission-fragment mass distributions which differ significantly from those of typical actinide nuclei. In the present study, we have succeeded in producing those neutron-rich heavy-actinide nuclei with multinucleon transfer reactions using an extremely rare and short-lived Es target bombarded with heavy-ion beam from the JAEA Tandem Accelerator. The products were mass-separated with an on-line isotope separator (ISOL), and spontaneous fission of 
Fm, 
Fm, 
Md, Lr was observed. Fission-fragment mass distributions and total kinetic energy distributions were obtained precisely, which provides us with important information to clarify the characteristic fission mechanism observed in this nuclear region.
MdAsai, Masato; Ishibashi, Yuichi*; Tsukada, Kazuaki; Sato, Tetsuya; Aoki, Ryota*; Ito, Yuta; Uchibaba, Yuta*; Orlandi, R.; Gong, G.-M.*; Suzaki, Fumi; et al.
no journal, ,
Measurement of mass and total kinetic energy (TKE) distribution for the spontaneous fission (SF) of Md has been performed to clarify the fission mechanism in the neutron-rich fermium region. Md nuclei were produced with the Es target and 
O beam, and mass-separated with an on-line isotope separator (ISOL). We discuss the mechanism of fission observed in the SF of Md on the basis of the observed mass-TKE distribution.
Ra
ions for decay-recoil-correlated spectroscopyUchibaba, Yuta; Ito, Yuta; Sato, Tetsuya; Aoki, Ryota; Asai, Masato; Gong, G.; Tsukada, Kazuaki; Natori, Hina; Miyachi, Yuta; Nagame, Yuichiro*
no journal, ,
We have developed a Paul trap with an advanced electrode structure that allows for the detection of radiation and decay recoils over a large solid angle, aiming to perform identifications of radioactive ions by decay spectroscopy and precision mass spectroscopy combined with decay correlation. In order to measure the correlation between radiations and decay recoils from ions stored in the trap, we tested the performance of a semiconductor detector in the vicinity of radio-frequency electrodes and demonstrated in-trap decay measurements using Ra ions.
Ra ions for decay-recoil-correlated spectroscopyUchibaba, Yuta; Ito, Yuta; Sato, Tetsuya; Aoki, Ryota; Asai, Masato; Gong, G.; Tsukada, Kazuaki; Natori, Hina; Miyachi, Yuta; Nagame, Yuichiro*
no journal, ,
We have developed a Paul trap with an advanced electrode structure that allows for the detection of radiation and decay recoils over a large solid angle, aiming to perform identifications of radioactive ions by decay spectroscopy and precision mass spectroscopy combined with decay correlation. In order to measure the correlation between radiations and decay recoils from ions stored in the trap, we tested the performance of a semiconductor detector in the vicinity of radio-frequency electrodes and demonstrated in-trap decay measurements using Ra ions.
