Intruder configurations in Ne at the transition into the island of inversion; Detailed structure study of Ne

Wang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.

Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08

https://doi.org/10.1016/j.physletb.2023.138038

Detailed -ray spectroscopy of the exotic neon isotope Ne has been performed using the one-neutron removal reaction from Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Hydrogen occupation and hydrogen-induced volume expansion in FeNiD at high conditions

Shito, Chikara*; Kagi, Hiroyuki*; Kakizawa, Sho*; Aoki, Katsutoshi*; Komatsu, Kazuki*; Iizuka, Riko*; Abe, Jun*; Saito, Hiroyuki*; Sano, Asami; Hattori, Takanori

American Mineralogist, 108(4), p.659 - 666, 2023/04

https://doi.org/10.2138/am-2022-8348

The phase relation and crystal structure of FeNiH (D) at high pressures and temperatures up to 12 GPa and 1000 K were clarified by in-situ X-ray and neutron diffraction measurements. Under conditions of the present study, no deuterium atoms occupied tetragonal () sites of face-centered cubic (fcc) FeNiD unlike fcc FeH(D). The deuterium-induced volume expansion per deuterium was determined as 2.45(4) and 3.31(6) for fcc and hcp phases, respectively, which were significantly larger than the corresponding values for FeD. The value slightly increased with increasing temperature. This study suggests that only 10% of nickel in iron drastically changes the behaviors of hydrogen in metal. Assuming that is constant regardless of pressure, the maximum hydrogen content in the Earth's inner core is estimated to be one to two times the amount of hydrogen in the oceans.

Volatilization of BC control rods in Fukushima Daiichi nuclear reactors during meltdown; B-Li isotopic signatures in cesium-rich microparticles

Fueda, Kazuki*; Takami, Ryu*; Minomo, Kenta*; Morooka, Kazuya*; Horie, Kenji*; Takehara, Mami*; Yamasaki, Shinya*; Saito, Takumi*; Shiotsu, Hiroyuki; Onuki, Toshihiko*; et al.

Journal of Hazardous Materials, 428, p.128214_1 - 128214_10, 2022/04

https://doi.org/10.1016/j.jhazmat.2022.128214

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2020

Nakada, Akira; Nakano, Masanao; Kanai, Katsuta; Seya, Natsumi; Nishimura, Shusaku; Nemoto, Masashi; Tobita, Keiji; Futagawa, Kazuo; Yamada, Ryohei; Uchiyama, Rei; et al.

JAEA-Review 2021-062, 163 Pages, 2022/02

JAEA-Review-2021-062.pdf:2.87MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2020 to March 2021. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Co., Inc. (the trade name was changed to Tokyo Electric Power Company Holdings, Inc. on April 1, 2016) in March 2011. Appendices present comprehensive information, such as monitoring programs, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes. In addition, the data which were influenced by the accidental release and exceeded the normal range of fluctuation in the monitoring, were evaluated.

Origin of magnetovolume effect in a cobaltite

Miao, P.*; Tan, Z.*; Lee, S. H.*; Ishikawa, Yoshihisa*; Torii, Shuki*; Yonemura, Masao*; Koda, Akihiro*; Komatsu, Kazuki*; Machida, Shinichi*; Sano, Asami; et al.

Physical Review B, 103(9), p.094302_1 - 094302_18, 2021/03

https://doi.org/10.1103/PhysRevB.103.094302

The layered perovskite PrBaCoO demonstrates a strong negative thermal expansion (NTE) which holds potential for being fabricated into composites with zero thermal expansion. The NTE was found to be intimately associated with the spontaneous magnetic ordering, known as magneto-volume effect (MVE). Here we report with compelling evidences that the continuous-like MVE in PrBaCoO is intrinsically of discontinuous character, originating from an magnetoelectric transition from an antiferromagnetic insulating large-volume (AFILV) phase to a ferromagnetic less-insulating small-volume (FLISV) phase. Furthermore, the magnetoelectric effect (ME) shows high sensitivity to multiple external stimuli such as temperature, carrier doping, hydrostatic pressure, magnetic field etc. In contrast to the well-known ME such as colossal magnetoresistance and multi-ferroic effect which involve symmetry breaking of crystal structure, the ME in the cobaltite is purely isostructural. Our discovery provides a new path way to realizing the ME as well as the NTE, which may find applications in new techniques.

Experimental evidence for the existence of a second partially-ordered phase of ice VI

Yamane, Ryo*; Komatsu, Kazuki*; Gochi, Jun*; Uwatoko, Yoshiya*; Machida, Shinichi*; Hattori, Takanori; Ito, Hayate*; Kagi, Hiroyuki*

Nature Communications (Internet), 12, p.1129_1 - 1129_6, 2021/02

https://doi.org/10.1038/s41467-021-21351-9

Ice exhibits extraordinary structural variety in its polymorphic structures. The existence of a new form of diversity in ice polymorphism has recently been debated in both experimental and theoretical studies, questioning whether hydrogen-disordered ice can transform into multiple hydrogen-ordered phases, contrary to the known one-to-one correspondence between disordered ice and its ordered phase. Here we report a new high-pressure phase, ice XIX, which is a second hydrogen-ordered phase of ice VI. This is the first discovery to demonstrate that disordered ice undergoes different manners of hydrogen ordering. Such multiplicity can appear in all disordered ice, and it widely provides a new research approach to deepen our knowledge, for example of the crucial issues of ice: the centrosymmetry of hydrogen-ordered configurations and potentially induced (anti-)ferroelectricity. Ultimately, this research opens up the possibility of completing the phase diagram of ice.

Neutron diffraction study of hydrogen site occupancy in FeSi at 14.7 GPa and 800 K

Mori, Yuichiro*; Kagi, Hiroyuki*; Kakizawa, Sho*; Komatsu, Kazuki*; Shito, Chikara*; Iizuka, Riko*; Aoki, Katsutoshi*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; et al.

Journal of Mineralogical and Petrological Sciences, 116(6), p.309 - 313, 2021/00

https://doi.org/10.2465/jmps.210825

The Earth's core is believed to contain some light elements because it is 10% less dense than pure Fe under the corresponding pressure and temperature conditions. Hydrogen, a promising candidate among light elements, has phase relations and physical properties that have been investigated mainly for the Fe-H system. This study specifically examined an Fe-Si-H system using in-situ neutron diffraction experiments to investigate the site occupancy of deuterium of hcp-FezSi hydride at 14.7 GPa and 800 K. Results of Rietveld refinement indicate hcp-FeSi hydride as having deuterium (D) occupancy of 0.24(2) exclusively at the interstitial octahedral site in the hcp lattice. The effect on the site occupancy of D by addition of 2.6 wt% Si into Fe (FeSi) was negligible compared to results obtained from an earlier study of an Fe-D system (Machida et al., 2019).

Unveiling spin-dependent unoccupied electronic states of CoMnGe (Ga) film via Ge (Ga) absorption spectroscopy

Yoshikawa, Tomoki*; Antonov, V. N.*; Kono, Takashi*; Kakoki, Masaaki*; Sumida, Kazuki; Miyamoto, Koji*; Takeda, Yukiharu; Saito, Yuji; Goto, Kazuki*; Sakuraba, Yuya*; et al.

Physical Review B, 102(6), p.064428_1 - 064428_7, 2020/08

https://doi.org/10.1103/PhysRevB.102.064428

Element-specific density of states of CoMnGe revealed by resonant photoelectron spectroscopy

Kono, Takashi*; Kakoki, Masaaki*; Yoshikawa, Tomoki*; Wang, X.*; Sumida, Kazuki*; Miyamoto, Koji*; Muro, Takayuki*; Takeda, Yukiharu; Saito, Yuji; Goto, Kazuki*; et al.

Physical Review B, 100(16), p.165120_1 - 165120_6, 2019/10

https://doi.org/10.1103/PhysRevB.100.165120

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2019-002, 235 Pages, 2019/08

JAEA-Research-2019-002.pdf:21.04MB

The accident of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to 1F), Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, JAEA has been conducting Long-term Environmental Dynamics Research concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.