Utilization of gamma ray irradiation at the WASTEF Facility

Sano, Naruto; Yamashita, Naoki; Watanabe, Masaya; Tsukada, Manabu*; Hoshino, Kazutoyo*; Hirai, Koki; Ikegami, Yuta*; Tashiro, Shinsuke; Yoshida, Ryoichiro; Hatakeyama, Yuichi; et al.

JAEA-Technology 2023-029, 36 Pages, 2024/03

JAEA-Technology-2023-029.pdf:2.47MB

At the Waste Safety Testing Facility (WASTEF), the gamma ray irradiation device "Gamma Cell 220" was relocated from the 4th research building of the Nuclear Science Research Institute in FY2019, and the use of gamma ray irradiation has begun. Initially, Fuel Cycle Safety Research Group, Fuel Cycle Safety Research Division, Nuclear Safety Research Center, Sector of Nuclear Safety Research and Emergency Preparedness, the owner of this device, conducted the tests as the main user, but since 2022, other users, including those outside the organization, have started using it. The gamma ray irradiation device "Gamma Cell 220" is manufactured by Nordion International Inc. in Canada. Since it was purchased in 1989, the built-in 60Co radiation source has been updated once, and safety research related to nuclear fuel cycles, etc. It is still used for this purpose to this day. This report summarizes the equipment overview of the gamma ray irradiation device "Gamma Cell 220", its permits and licenses at WASTEF, usage status, maintenance and inspection, and future prospects.

Stable hydrogen and oxygen isotope analyses of geological samples using a thermal conversion elemental analyzer-isotope ratio mass spectrometer at Tono Geoscience Center

Yamamoto, Yusuke*; Watanabe, Takahiro; Niwa, Masakazu; Shimada, Koji

JAEA-Testing 2023-003, 67 Pages, 2024/02

JAEA-Testing-2023-003.pdf:4.63MB

A long-term geosphere stability for geological disposal is evaluated by the past geological environmental changes and modern conditions. Stable hydrogen and oxygen isotope ratios (D, O) of geological samples are useful information to estimate the past environmental changes and modern conditions. Recently, the thermal conversion elemental analyzer and isotope ratio mass spectrometer (TC-EA/IRMS) were installed in the Tono Geoscience Center for D and O measurements of geological samples. In this study, we reported analytical methods of D and O using international standard reference materials. In addition, evaluation tests of uncertainty by repeated analyses of the standards were performed using the TC-EA/IRMS. Furthermore, the D and O analyses by the TC- EA/IRMS were also applied to fault rock samples.

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.

Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal year 2022

Niwa, Masakazu; Shimada, Koji; Sueoka, Shigeru; Ishihara, Takanori; Ogawa, Hiroki; Hakoiwa, Hiroaki; Watanabe, Tsuyoshi; Nishiyama, Nariaki; Yokoyama, Tatsunori; Ogata, Manabu; et al.

JAEA-Research 2023-005, 78 Pages, 2023/10

JAEA-Research-2023-005.pdf:6.51MB

This annual report documents the progress of research and development (R&D) in the 1st fiscal year of the Japan Atomic Energy Agency 4th Medium- and Long-term Plan (fiscal years 2022-2028) to provide the scientific base for assessing geosphere stability for long-term isolation of high-level radioactive waste. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. The current status of R&D activities with previous scientific and technological progress is summarized.

Incommensurate nature of the antiferromagnetic order in GdCu

Kaneko, Koji; Tabata, Chihiro; Hagihara, Masato; Yamauchi, Hiroki; Kubota, Masato; Osakabe, Toyotaka; Onuki, Yoshichika*

Journal of the Physical Society of Japan, 92(8), p.085001_1 - 085001_2, 2023/08

https://doi.org/10.7566/JPSJ.92.085001

Investigation of the electronic structure of the MgZnY alloy using X-ray photoelectron spectroscopy

Miyazaki, Hidetoshi*; Akatsuka, Tatsuyoshi*; Kimura, Koji*; Egusa, Daisuke*; Sato, Yohei*; Itakura, Mitsuhiro; Takagi, Yasumasa*; Yasui, Akira*; Ozawa, Kenichi*; Mase, Kazuhiko*; et al.

Materials Transactions, 64(6), p.1194 - 1198, 2023/06

https://doi.org/10.2320/matertrans.MT-MD2022019

We investigated the electronic structure of the MgZnY alloy using hard and soft X-ray photoemission spectroscopy and electronic band structure calculations to understand the mechanism of the phase stability of this material. Electronic structure of the MgZnY alloy showed a semi-metallic electronic structure with a pseudo-gap at the Fermi level. The observed electronic structure of the MgZnY alloy suggests that the presence of a pseudogap structure is responsible for phase stability.

Pressure-modulated magnetism and negative thermal expansion in the HoFe intermetallic compound

Cao, Y.*; Zhou, H.*; Khmelevskyi, S.*; Lin, K.*; Avdeev, M.*; Wang, C.-W.*; Wang, B.*; Hu, F.*; Kato, Kenichi*; Hattori, Takanori; et al.

Chemistry of Materials, 35(8), p.3249 - 3255, 2023/04

https://doi.org/10.1021/acs.chemmater.3c00158

Hydrostatic and chemical pressure are efficient stimuli to alter the crystal structure and are commonly used for tuning electronic and magnetic properties in materials science. However, chemical pressure is difficult to quantify and a clear correspondence between these two types of pressure is still lacking. Here, we study intermetallic candidates for a permanent magnet with a negative thermal expansion (NTE). Based on in situ synchrotron X-ray diffraction, negative chemical pressure is revealed in HoFe on Al doping and quantitatively evaluated by using temperature and pressure dependence of unit cell volume. A combination of magnetization and neutron diffraction measurements also allowed one to compare the effect of chemical pressure on magnetic ordering with that of hydrostatic pressure. Intriguingly, pressure can be used to control suppression and enhancement of NTE. Electronic structure calculations indicate that pressure affected the top of the majority band with respect to the Fermi level, which has implications for the magnetic stability, which in turn plays a critical role in modulating magnetism and NTE. This work presents a good example of understanding the effect of pressure and utilizing it to control properties of functional materials.

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.

Study of hierarchical deformation mechanism in LPSO-type magnesium alloys using diffraction method

Shiro, Ayumi*; Shobu, Takahisa; Hagihara, Koji*; Watanabe, Masashi*

SPring-8/SACLA Riyo Kenkyu Seikashu (Internet), 10(5), p.438 - 446, 2022/10

https://doi.org/10.18957/rr.10.5.438

no abstracts in English

Magnetic orderings from spin-orbit coupled electrons on kagome lattice

Watanabe, Jin*; Araki, Yasufumi; Kobayashi, Koji*; Ozawa, Akihiro*; Nomura, Kentaro*

Journal of the Physical Society of Japan, 91(8), p.083702_1 - 083702_5, 2022/08

https://doi.org/10.7566/JPSJ.91.083702

We investigate magnetic orderings on kagome lattice numerically from the tight-binding Hamiltonian of electrons, governed by the filling factor and spin-orbit coupling (SOC) of electrons. We find that even a simple kagome lattice model can host both ferromagnetic and noncollinear antiferromagnetic orderings depending on the electron filling, reflecting gap structures in the Dirac and flat bands characteristic to the kagome lattice. Kane-Mele- or Rashba-type SOC tends to stabilize noncollinear orderings, such a magnetic spirals and 120-degree antiferromagnetic orderings, due to the effective Dzyaloshinskii-Moriya interaction from SOC. The obtained phase structure helps qualitative understanding of magnetic orderings in various kagome-layered materials with Weyl or Dirac electrons.