Hirata, Sakiko*; Kusaka, Ryoji; Meiji, Shogo*; Tamekuni, Seita*; Okudera, Kosuke*; Hamada, Shoken*; Sakamoto, Chihiro*; Honda, Takumi*; Matsushita, Kosuke*; Muramatsu, Satoru*; et al.
Inorganic Chemistry, 62(1), p.474 - 486, 2023/01
Yamashita, Takuya; Honda, Takeshi*; Mizokami, Masato*; Nozaki, Kenichiro*; Suzuki, Hiroyuki*; Pellegrini, M.*; Sakai, Takeshi*; Sato, Ikken; Mizokami, Shinya*
Nuclear Technology, 26 Pages, 2023/00
Yamamura, Sota*; Fujiwara, Kota*; Honda, Kota*; Yoshida, Hiroyuki; Horiguchi, Naoki; Kaneko, Akiko*; Abe, Yutaka*
Physics of Fluids, 34(8), p.082110_1 - 082110_13, 2022/08
Liquid spreading and atomization due to jet impingement in liquid-liquid systems are considered to be crucial for understanding the cooling behavior of high-temperature molten material in a shallow water pool. This phenomenon takes place when a liquid jet enters a pool filled with other immiscible liquid. The jet spreads radially after impinging on the floor while forming a thin liquid film and atomizing droplets. In this paper, we explain the result to quantify the unsteady three-dimensional behavior of the spreading jet by the employment of 3D-LIF measurements and 3-dimensional reconstruction. Under high flow velocity conditions, the phenomena of hydraulic jump and atomization of the liquid film occurred along with the spreading. To evaluate the spreading behavior, a comparison of the jump radius position of the liquid-liquid system as the representative value was made with the one calculated by the existing theory of a gas-liquid system. As the result, the spreading of the liquid film in the liquid-liquid system was suppressed compared with that in the gas-liquid system. Furthermore, the PTV method was successfully used to measure the velocity boundary layer and velocity profile in the liquid film, which are important factors that affect the spreading mechanism of the liquid film. These results revealed that in liquid-liquid systems, shear stress at the liquid-liquid interface causes a decrease in the flow velocity and suppressed the development of the velocity boundary layer. Also, to evaluate the atomization behavior, the number and diameter distribution of the droplets were measured from the acquired 3-dimensional shape data of the jet. As the result, the number of droplets increased with the flow velocity. Based on these results, we concluded that the spreading of the liquid film is affected by such atomization behavior.
Tsubota, Yoichi; Honda, Fumiya; Tokonami, Shinji*; Tamakuma, Yuki*; Nakagawa, Takahiro; Ikeda, Atsushi
Nuclear Instruments and Methods in Physics Research A, 1030, p.166475_1 - 166475_7, 2022/05
In the long-lasting decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), the dismantling of nuclear fuel debris (NFD) remaining in the damaged reactors is an unavoidable but significant issue with many technical difficulties. The dismantling is presumed to involve mechanical cutting, generating significant concentrations of particulates containing -radionuclides (-aerosols) that pose significant health risk upon inhalation. In order to minimize the radiation exposure of workers with -aerosols during the dismantling/decommissioning process at 1F, it is essential to monitor the concentration of -aerosols at the point of initial generation, i.e. inside the primary containment vessels (PCV) of the damaged reactors. Toward this end, an monitoring system for -aerosols ( alpha air monitor: IAAM) was developed and its technical performance was investigated under the conditions expected for the actual environments at 1F. IAAM was confirmed to fulfill four technical requirements: (1) steady operation under high humidity, (2) operation without using filters, (3) capability of measuring a high counting rate of -radiation, and (4) selective measurement of -radiation even under high radiation background with /-rays. IAAM is capable of selectively measuring -aerosols with a concentration of 3.3 10 Bq/cm or higher without saturation under a high humid environment (100%-relative humidity) and under high background with /-radiation (up to 100 mSv/h of -radiation). These results demonstrate promising potential of IAAM to be utilized as a reliable monitoring system for -aerosols during the dismantling of NFD, as well as the whole long-lasting decommissioning of 1F.
Komuro, Michiyasu; Kanazawa, Hiroyuki; Kokusen, Junya; Shimizu, Osamu; Honda, Junichi; Harada, Katsuya; Otobe, Haruyoshi; Nakada, Masami; Inagawa, Jun
JAEA-Technology 2021-042, 197 Pages, 2022/03
Plutonium Research Building No.1 was constructed in 1960 for the purpose of establishing plutonium handling technology and studying its basic physical properties. Radiochemical research, physicochemical research and analytical chemistry regarding solutions and solid plutonium compounds had been doing for the research program in Japan Atomic Energy Agency (JAEA). In 1964, the laboratory building was expanded and started the researching plutonium-uranium mixed fuel and reprocessing of plutonium-based fuel, playing an advanced role in plutonium-related research in Japan. Since then, the research target has been expanded to include transplutonium elements, and it has functioned as a basic research facility for actinides. The laboratory is constructed by concrete structure and it has the second floor, equipped with 15 glove boxes and 4 chemical hoods. Plutonium Research Building No.1 was decided as one of the facilities to be decommissioned by Japan Atomic Energy Agency Reform Plan in September 2014. So far, the contamination survey of the radioactive materials in the controlled area, the decontamination of glove boxes, and the consideration of the equipment dismantling procedure have been performed as planned. The radioisotope and nuclear fuel materials used in the facility have been transfer to the other facilities in JAEA. The decommissioning of the facility is proceeding with the goal of completing by decommissioning the radiation controlled area in 2026. In this report, the details of the decommissioning plan and the past achievements are reported with the several data.
Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Haga, Yoshinori; Tokiwa, Yoshifumi; Opletal, P.; Fujibayashi, Hiroyuki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; et al.
Journal of the Physical Society of Japan, 91(2), p.023707_1 - 023707_5, 2022/02
Te NMR experiments in field () applied along the easy magnetization axis (the -axis) revealed slow electronic dynamics developing in the paramagnetic state of UTe. The observed slow fluctuations are concerned with a successive growth of long-range electronic correlations below 3040 K, where the spin susceptibility along the hard magnetization axis (the -axis) shows a broad maximum. The experiments also imply that tiny amounts of disorder or defects locally disturb the long-range electronic correlations and develop an inhomogeneous electronic state at low temperatures, leading to a low temperature upturn observed in the bulk-susceptibility in . We suggest that UTe would be located on the paramagnetic side near an electronic phase boundary, where either the magnetic or Fermi-surface instability would be the origin of the characteristic fluctuations.
Oda, Chie; Kawama, Daisuke*; Shimizu, Hiroyuki*; Benbow, S. J.*; Hirano, Fumio; Takayama, Yusuke; Takase, Hiroyasu*; Mihara, Morihiro; Honda, Akira
Journal of Advanced Concrete Technology, 19(10), p.1075 - 1087, 2021/10
Concrete in a transuranic (TRU) waste repository is considered a suitable material to ensure safety, provide structural integrity and retard radionuclide migration after the waste containers fail. In the current study, coupling between chemical, mass-transport and mechanical, so-called non-linear processes that control concrete degradation and crack development were investigated by coupled numerical models. Application of such coupled numerical models allows identification of the dominant non-linear processes that will control long-term concrete degradation and crack development in a TRU waste repository.
Fujimoto, Nozomu*; Fukuda, Kodai*; Honda, Yuki*; Tochio, Daisuke; Ho, H. Q.; Nagasumi, Satoru; Ishii, Toshiaki; Hamamoto, Shimpei; Nakano, Yumi*; Ishitsuka, Etsuo
JAEA-Technology 2021-008, 23 Pages, 2021/06
The effect of mesh division around the burnable poison rod on the burnup calculation of the HTTR core was investigated using the SRAC code system. As a result, the mesh division inside the burnable poison rod does not have a large effect on the burnup calculation, and the effective multiplication factor is closer to the measured value than the conventional calculation by dividing the graphite region around the burnable poison rod into a mesh. It became clear that the mesh division of the graphite region around the burnable poison rod is important for more appropriately evaluating the burnup behavior of the HTTR core..
Wallner, A.*; Froehlich, M. B.*; Hotchkis, M. A. C.*; Kinoshita, N.*; Paul, M.*; Martschini, M.*; Pavetich, S.*; Tims, S. G.*; Kivel, N.*; Schumann, D.*; et al.
Science, 372(6543), p.742 - 745, 2021/05
Half of the chemical elements heavier than iron are produced by the rapid neutron capture process (r-process). The sites and yields of this process are disputed, with candidates including some types of supernovae (SNe) and mergers of neutron stars. We search for two isotopic signatures in a sample of Pacific Ocean crust-iron-60 (Fe) (half-life, 2.6 million years), which is predominantly produced in massive stars and ejected in supernova explosions, and Pu (half-life, 80.6 million years), which is produced solely in r-process events. We detect two distinct influxes of Fe to Earth in the last 10 million years and accompanying lower quantities of Pu. The Pu/Fe influx ratios are similar for both events. The Pu influx is lower than expected if SNe dominate r-process nucleosynthesis, which implies some contribution from other sources.
Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Aihara, Jun; Ueta, Shohei; Honda, Masaki*; Mizuta, Naoki; Goto, Minoru; Tachibana, Yukio; Okamoto, Koji*
Journal of Nuclear Science and Technology, 58(1), p.107 - 116, 2021/01
The concept of a Pu-burner high temperature gas-cooled reactor (HTGR) has been proposed for purpose of more safely reducing amount of recovered Pu. This concept employs coated fuel particles (CFPs) with ZrC coated PuO-YSZ kernel and with tristructural (TRISO) coating for very high Pu burn-up and high nuclear proliferation resistance. In this report, we investigate the microstructure of the region that includes the surface of an as-fabricated CeO-YSZ kernel simulating PuO-YSZ kernel. We found both Zr-rich grains and Ce-rich grains to be densely distributed in that region including surface of CeO-YSZ kernel. On the other hand, it has been reported that there was a porous region near surface of the CeO-YSZ kernel of Batch I. This finding confirms that Ce-rich grains near surface of CeO-YSZ kernels coated with ZrC layers have been corroded during the deposition of the ZrC layer, whereas the Zr-rich grains were hardly affected.
Sasa, Kimikazu*; Honda, Maki; Hosoya, Seiji*; Takahashi, Tsutomu*; Takano, Kenta*; Ochiai, Yuta*; Sakaguchi, Aya*; Kurita, Saori*; Satou, Yukihiko; Sueki, Keisuke*
Journal of Nuclear Science and Technology, 58(1), p.72 - 79, 2021/01
Kokusen, Junya; Akasaka, Shingo*; Shimizu, Osamu; Kanazawa, Hiroyuki; Honda, Junichi; Harada, Katsuya; Okamoto, Hisato
JAEA-Technology 2020-011, 70 Pages, 2020/10
The Uranium Enrichment Laboratory in the Japan Atomic Energy Agency (JAEA) was constructed in 1972 for the purpose of uranium enrichment research. The smoke emitting accident on 1989 and the fire accident on 1997 had been happened in this facility. The research on uranium enrichment was completed in JFY1998. The decommissioning work was started including the transfer of the nuclear fuel material to the other facility in JFY2012. The decommissioning work was completed in JFY2019 which are consisting of removing the hood, dismantlement of wall and ceiling with contamination caused by fire accident. The releasing the controlled area was performed after the confirmation of any contamination is not remained in the target area. The radioactive waste was generated while decommissioning, burnable and non-flammable are 1.7t and 69.5t respectively. The Laboratory will be used as a general facility for cold experiments.
Okudaira, Takuya; Oku, Takayuki; Ino, Takashi*; Hayashida, Hirotoshi*; Kira, Hiroshi*; Sakai, Kenji; Hiroi, Kosuke; Takahashi, Shingo*; Aizawa, Kazuya; Endo, Hitoshi*; et al.
Nuclear Instruments and Methods in Physics Research A, 977, p.164301_1 - 164301_8, 2020/10
Yamashita, Takuya; Sato, Ikken; Honda, Takeshi*; Nozaki, Kenichiro*; Suzuki, Hiroyuki*; Pellegrini, M.*; Sakai, Takeshi*; Mizokami, Shinya*
Nuclear Technology, 206(10), p.1517 - 1537, 2020/10
Benbow, S. J.*; Kawama, Daisuke*; Takase, Hiroyasu*; Shimizu, Hiroyuki*; Oda, Chie; Hirano, Fumio; Takayama, Yusuke; Mihara, Morihiro; Honda, Akira
Crystals (Internet), 10(9), p.767_1 - 767_33, 2020/09
Details are presented of the development of a coupled modeling simulator for assessing the evolution in the near-field of a geological repository for radioactive waste disposal where concrete is used as a backfill. The simulator uses OpenMI, a standard for exchanging data between simulation software programs at run-time, to form a coupled chemical-mechanical-hydrogeological model of the system. The approach combines a tunnel scale stress analysis finite element model, a discrete element model for accurately modeling the patterns of emerging cracks in the concrete, and a finite element and finite volume model of the chemical processes and alteration in the porous matrix and cracks in the concrete, to produce a fully coupled model of the system. Combining existing detailed simulation software in this way with OpenMI has the benefit of not relying on simplifications that might be necessary to combine all of the modeled processes in a single piece of software.
Ho, H. Q.; Honda, Yuki*; Hamamoto, Shimpei; Ishii, Toshiaki; Takada, Shoji; Fujimoto, Nozomu*; Ishitsuka, Etsuo
Journal of Nuclear Engineering and Radiation Science, 6(2), p.021902_1 - 021902_6, 2020/04
Ueta, Shohei; Mizuta, Naoki; Fukaya, Yuji; Goto, Minoru; Tachibana, Yukio; Honda, Masaki*; Saiki, Yohei*; Takahashi, Masashi*; Ohira, Koichi*; Nakano, Masaaki*; et al.
Nuclear Engineering and Design, 357, p.110419_1 - 110419_10, 2020/02
The concept of a plutonium (Pu) burner HTGR is proposed to incarnate highly-effective Pu utilization by its inherent safety features. The security and safety fuel (3S-TRISO fuel) employs the coated fuel particle with a fuel kernel made of plutonium dioxide (PuO) and yttria stabilized zirconia (YSZ) as an inert matrix. This paper presents feasibility study of Pu burner HTGR and R&D on the 3S-TRISO fuel.
Aihara, Jun; Yasuda, Atsushi*; Ueta, Shohei; Ogawa, Hiroaki; Honda, Masaki*; Ohira, Koichi*; Tachibana, Yukio
Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(4), p.237 - 245, 2019/12
Development of fabrication and inspection technologies of oxidation resistant fuel element for improvement of safety of high temperature gas-cooled reactors (HTGRs) in severe oxidation accident was carried out. Simulated coated fuel particles (CFPs), alumina particles, were over-coated with mixed powder of Si, C and small amount of resin to form over-coated particles, and over-coated particles were molded and hot-pressed to sinter simulated oxidation resistant fuel elements with SiC/C mixed matrix. Simulated oxidation resistant fuel elements with matrix whose Si/C mole ratio is 1.00 were fabricated. Failure fraction of CFPs in fuel elements is one of very important inspection subjects of HTGR fuel. It is essential that CFPs are extracted from fuel elements without additional failure. Development of method for extraction of CFPs was carried out. Desolation of SiC by KOH method or pressurized acidolysis method should be applied to extraction of CFPs.
Honda, Ryotaro*; Hasegawa, Shoichi; Hayakawa, Shuhei; Hosomi, Kenji; Imai, Kenichi; Ichikawa, Yudai; Nanamura, Takuya; Naruki, Megumi; Sako, Hiroyuki; Sato, Susumu; et al.
JPS Conference Proceedings (Internet), 26, p.023014_1 - 023014_4, 2019/11