Experimental visualization of water/ice phase distribution at cold start for practical-sized polymer electrolyte fuel cells

Higuchi, Yuki*; Yoshimune, Wataru*; Kato, Satoru*; Hibi, Shogo*; Setoyama, Daigo*; Isegawa, Kazuhisa*; Matsumoto, Yoshihiro*; Hayashida, Hirotoshi*; Nozaki, Hiroshi*; Harada, Masashi*; et al.

Communications Engineering (Internet), 3, p.33_1 - 33_7, 2024/02

https://doi.org/10.1038/s44172-024-00176-6

Neutron scattering study of antiferromagnet UPtAl

Ota, Kyugo*; Matsumoto, Yuji*; Watabe, Yuki*; Kaneko, Koji; Tabata, Chihiro; Haga, Yoshinori

New Physics; Sae Mulli, 73(12), p.1170 - 1173, 2023/12

https://doi.org/10.3938/NPSM.73.1170

We have performed the neutron scattering study of antiferromagnet UPtAl with the honeycomb lattice to determine the magnetic structure. UPtAl exhibits two phase transitions at = 9 K and = 26 K. In phase I at , the magnetic reflections described by a propagation vector = (1/3, 0, 0) were observed. In phase II at , magnetic reflections of = (1/3, 0, 0) and = (1/2, 0, 0) were observed and the magnetic reflection intensity of = (1/3, 0, 0) is weak but finite. The hysteresis in the temperature dependent intensities is observed across the phase transition at , suggesting that the transition at is of first order.

Synthesis, crystal structure, local structure, and magnetic properties of polycrystalline and single-crystalline CePtAl

Ota, Kyugo*; Watabe, Yuki*; Haga, Yoshinori; Iesari, F.*; Okajima, Toshihiko*; Matsumoto, Yuji*

Symmetry (Internet), 15(8), p.1488_1 - 1488_13, 2023/07

https://doi.org/10.3390/sym15081488

Current status of decommissioning and waste management at the Ningyo-Toge Environmental Engineering Center

Ohashi, Yusuke; Shimaike, Masamitsu; Matsumoto, Takashi; Takahashi, Nobuo; Yokoyama, Kaoru; Morimoto, Yasuyuki

Nuclear Technology, 209(5), p.777 - 786, 2023/05

https://doi.org/10.1080/00295450.2022.2145136

At the Ningyo-Toge Center, technical development related to uranium refining conversion and enrichment has been completed, and decommissioning of these facilities has begun. The error between the quantity of dismantled materials estimated from the facility design drawings and the actual quantity of dismantled materials was minimal when averaging over the entire Uranium Refining and Conversion Plant and Uranium Enrichment Engineering Facility, which results indicated that the preliminary estimate of the quantity of dismantled materials for decommissioning was reasonable. Most of the dismantled materials, which have no contamination history and are properly managed were able to be carried out to recyclers as non-radioactive waste (NR). In addition, the possibility of evaluating the uranium concentration of clearance level in dismantled objects was confirmed through gamma-ray measurement tests using mock-up waste.

Materials science and fuel technologies of uranium and plutonium mixed oxide

Kato, Masato; Machida, Masahiko; Hirooka, Shun; Nakamichi, Shinya; Ikusawa, Yoshihisa; Nakamura, Hiroki; Kobayashi, Keita; Ozawa, Takayuki; Maeda, Koji; Sasaki, Shinji; et al.

Materials Science and Fuel Technologies of Uranium and Plutonium mixed Oxide, 171 Pages, 2022/10

https://doi.org/10.1201/9781003298205

Innovative and advanced nuclear reactors using plutonium fuel has been developed in each country. In order to develop a new nuclear fuel, irradiation tests are indispensable, and it is necessary to demonstrate the performance and safety of nuclear fuels. If we can develop a technology that accurately simulates irradiation behavior as a technology that complements the irradiation test, the cost, time, and labor involved in nuclear fuel research and development will be greatly reduced. And safety and reliability can be significantly improved through simulation of nuclear fuel irradiation behavior. In order to evaluate the performance of nuclear fuel, it is necessary to know the physical and chemical properties of the fuel at high temperatures. And it is indispensable to develop a behavior model that describes various phenomena that occur during irradiation. In previous research and development, empirical methods with fitting parameters have been used in many parts of model development. However, empirical techniques can give very different results in areas where there is no data. Therefore, the purpose of this study is to construct a scientific descriptive model that can extrapolate the basic characteristics of fuel to the composition and temperature, and to develop an irradiation behavior analysis code to which the model is applied.

Temporal variability of Cs concentrations in coastal sediments off Fukushima

Suzuki, Shotaro*; Amano, Yosuke*; Enomoto, Masahiro*; Matsumoto, Akira*; Morioka, Yoshiaki*; Sakuma, Kazuyuki; Tsuruta, Tadahiko; Kaeriyama, Hideki*; Miura, Hikaru*; Tsumune, Daisuke*; et al.

Science of the Total Environment, 831, p.154670_1 - 154670_15, 2022/07

https://doi.org/10.1016/j.scitotenv.2022.154670

Catalog of gamma-ray glows during four winter seasons in Japan

Wada, Yuki*; Matsumoto, Takahiro*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; Furuta, Yoshihiro*; Yonetoku, Daisuke*; Sawano, Tatsuya*; Okada, Go*; Nanto, Hidehito*; et al.

Physical Review Research (Internet), 3(4), p.043117_1 - 043117_31, 2021/12

https://doi.org/10.1103/PhysRevResearch.3.043117

Development of evaluation framework for ex-vessel core coolability

Matsumoto, Toshinori; Iwasawa, Yuzuru; Sugiyama, Tomoyuki

Proceedings of Reactor core and Containment Cooling Systems, Long-term management and reliability (RCCS 2021) (Internet), 8 Pages, 2021/10

A methodological framework is being developed in JAEA for evaluating debris coolability at ex-vessel during the severe accident (SA) of BWR under the wet cavity strategy. The probability of ex-vessel debris coolability under the wet cavity strategy is analyzed to demonstrate the evaluation approach. Probabilistic distribution of the melt conditions ejected from the RPV was obtained as the result of the iterative analyses with MELCOR code. Five uncertainty parameters relating with the core degradation and transfer process were chosen. Parameter sets were generated by Latin hypercube sampling (LHS). JASMINE code plays the physical model to predict the mass fraction of agglomerated debris and melt pool spreading on the floor. Fifty-nine input parameter set for JASMINE code were generated by LHS again using the probabilistic distribution of melt condition determined from the results of MELCOR analyses. The depth of the water pool was set as 0.5, 1.0 and 2.0 m. The accumulated debris height was compared with the criterion to judge the debris coolability. As the result, the success probability of debris cooling was obtained through the sequence of calculations.

Pulsed neutron imaging for differentiation of ice and liquid water towards fuel cell vehicle applications

Higuchi, Yuki*; Setoyama, Daigo*; Isegawa, Kazuhisa; Tsuchikawa, Yusuke; Matsumoto, Yoshihiro*; Parker, J. D.*; Shinohara, Takenao; Nagai, Yasutaka*

Physical Chemistry Chemical Physics, 23(2), p.1062 - 1071, 2021/01

https://doi.org/10.1039/D0CP03887C

This study is the first report on liquid water and ice imaging conducted at a pulsed spallation neutron source facility. Neutron imaging can be utilised to visualise the water distribution inside polymer electrolyte fuel cells (PEFCs). Particularly, energy-resolved neutron imaging is a methodology capable of distinguishing between liquid water and ice, and is effective for investigating ice formation in PEFCs operating in a subfreezing environment. The distinction principle is based on the fact that the cross sections of liquid water and ice differ from each other at low neutron energies. In order to quantitatively observe transient freezing and thawing phenomena in a multiphase mixture (gas/liquid/solid) within real PEFCs with high spatial resolution, a pulsed neutron beam with both high intensity and wide energy range is most appropriate. In the validation study of the present work, we used water sealed in narrow capillary tubes to simulate the flow channels of a PEFC, and a pulsed neutron beam was applied to distinguish ice, liquid water and super-cooled water, and to clarify freezing and thawing phenomena of the water within the capillary tubes. Moreover, we have enabled the observation of liquid water/ice distributions in a large field of view (300 mm 300 mm) by manufacturing a sub-zero environment chamber that can be cooled down to -30C, as a step towards visualisation of full-size fuel cells.

The Analysis for Ex-Vessel debris coolability of BWR

Matsumoto, Toshinori; Iwasawa, Yuzuru; Ajima, Kohei*; Sugiyama, Tomoyuki

Proceedings of Asian Symposium on Risk Assessment and Management 2020 (ASRAM 2020) (Internet), 10 Pages, 2020/11

The probability of ex-vessel debris coolability under the wet cavity strategy is analyzed. The first step is the uncertainty analyses by severe accident analysis code MELCOR to obtain the melt condition. Five uncertain parameters which are relating with the core degradation and transfer process were chosen. Input parameter sets were generated by LHS. The analyses were conducted and the conditions of the melt were obtained. The second step is the analyses for the behavior of melt under the water by JASMINE code. The probabilistic distribution of parameters are determined from the results of MELCOR analyses. Fifty-nine parameter sets were generated by LHS. The depth of water pool is set to be 0.5, 1.0 and 2.0 m. Debris height were compared with the criterion to judge the debris coolability. As the result, the success probability of debris cooling was obtained through the sequence of calculations. The technical difficulties of this evaluation method are also discussed.