First isolation and analysis of caesium-bearing microparticles from marine samples in the Pacific coastal area near Fukushima Prefecture

Miura, Hikaru*; Ishimaru, Takashi*; Ito, Yukari*; Kuribara, Yuichi; Otosaka, Shigeyoshi*; Sakaguchi, Aya*; Misumi, Kazuhiro*; Tsumune, Daisuke*; Kubo, Atsushi*; Higaki, Shogo*; et al.

Scientific Reports (Internet), 11, p.5664_1 - 5664_11, 2021/03

https://doi.org/10.1038/s41598-021-85085-w

For the first time, we isolated and investigated seven CsMPs (radioactive caesium-bearing microparticles) from marine particulate matter and sediment. From the elemental composition, the Cs/Cs activity ratio, and the Cs activity per unit volume results, we inferred that the five CsMPs collected from particulate matter were emitted from Unit 2 of the FDNPP, whereas the two CsMPs collected from marine sediment were possibly emitted from Unit 3. The presence of CsMPs can cause overestimation of the solid-water distribution coefficient of Cs in marine sediments and particulate matter and a high apparent radiocaesium concentration factor for marine biota. CsMPs emitted from Unit 2, which were collected from the estuary of a river that flowed through a highly contaminated area, may have been deposited on land and then transported by the river. By contrast, CsMPs emitted from Unit 3 were possibly transported eastward by the wind and deposited directly onto the ocean surface.

Difference in the solid-water distributions of radiocesium in rivers in Fukushima and Chernobyl

Takahashi, Yoshio*; Sakaguchi, Aya*; Fan, Q.*; Tanaka, Kazuya; Miura, Hikaru*; Kurihara, Yuichi*

Behavior of Radionuclides in the Environment I; Function of Particles in Aquatic System, p.115 - 150, 2020/00

https://doi.org/10.1007/978-981-15-0679-6

Discovery of radiocesium-bearing microparticles in river water and their influence on the solid-water distribution coefficient () of radiocesium in the Kuchibuto River in Fukushima

Miura, Hikaru*; Kurihara, Yuichi*; Sakaguchi, Aya*; Tanaka, Kazuya; Yamaguchi, Noriko*; Higaki, Shogo*; Takahashi, Yoshio*

Geochemical Journal, 52(2), p.145 - 154, 2018/00

https://doi.org/10.2343/geochemj.2.0517

Solid-water distribution coefficient () of radiocesium in rivers is apparently increased due to the possible presence of highly radioactive radiocesium-bearing microparticles (CsMPs) in the solid phase. In this study, we evaluated the contribution of CsMPs to apparent Kd values. The ratio of the radioactivity of the separated CsMPs to the total radiocesium on fluvial suspended particles ranged from 0 to 46%. This means that the existence of CsMPs in fluvial suspended partcles did not change apparent Kd values in order magnitude.

Observation of a pressure-induced As-As hybridization associated with a change in the electronic state of Fe in the tetragonal phase of EuFeAs

Kobayashi, Hisao*; Ikeda, Shugo*; Sakaguchi, Yui*; Yoda, Yoshitaka*; Nakamura, Hiroki; Machida, Masahiko

Journal of Physics; Condensed Matter, 25(2), p.022201_1 - 022201_6, 2013/01

https://doi.org/10.1088/0953-8984/25/2/022201

The electronic and vibrational properties of EuFeAs in the tetragonal phase between 0 and 5 GPa have been investigated using Fe Mssbauer spectroscopy and Fe nuclear resonance inelastic scattering, respectively. We find a discontinuous increase of the center shift around 2.3 GPa, reflecting a change of the electronic state of Fe, and above 2.5 GPa a softening of the optical phonon modes associated with an increase of the relative volume of the FeAs tetrahedron in the unit cell. Our findings reveal that an effective As-As hybridization along the c axis appears at approximately 2.3 GPa in the tetragonal phase of EuFeAs, along with a change in the electronic state of Fe, causing bulk superconductivity to appear at a low temperature. Consequently, the change in the electronic state of the Fe atom and the effective As-As hybridization play key roles in the pressure-induced superconductivity in the tetragonal phase of AFeAs.

Analysis of hydrogen content and distribution in hydrogen storage alloys using neutron radiography

Sakaguchi, Hiroki*; Hatakeyama, Keisuke*; Satake, Yuichi*; Fujine, Shigenori*; Yoneda, Kenji*; Kanda, Keiji*; Matsubayashi, Masahito; Esaka, Takao*

Kashika Joho Gakkai-Shi, 20(suppl.1), p.373 - 374, 2000/07

no abstracts in English

Discovering U particle with Zr from Type-B particle emitted from Unit 1 of FDNPP using synchrotron radiation X-ray analyses

Miura, Hikaru*; Kuribara, Yuichi; Yamamoto, Masayoshi*; Sakaguchi, Aya*; Higaki, Shogo*; Takahashi, Yoshio*

no journal, , 

A synchrotron radiation X-ray analysis was performed on radioactive particles released into the environment due to the Fukushima Dai-ichi Nuclear Power Plant accident, uranium particles (4 valence and 6 valence) with a size of several microns were present in the particles from the Unit 1. Since these uranium particles also contain zirconium, which is considered to be derived from the fuel cladding, it was presumed that the eutectic mixture of the fuel in the reactor and its cladding was incorporated into the radioactive particulates and released into the environment.

Study on pretreatment methods of seawater for determination of ultra-trace radionuclide Cs

Tajima, Taiyo*; Asai, Shiho*; Saito, Kyoichi*; Seko, Noriaki*; Hoshina, Hiroyuki*; Horita, Takuma; Yamasaki, Shinya*; Takaku, Yuichi*; Sueki, Keisuke*; Sakaguchi, Aya*

no journal, , 

Cs is a radionuclide introduced into the environment by human nuclear activities. The use of Cs as an oceanic circulation tracer and the need for monitoring around nuclear facilities require the establishment of a measurement method for this nuclide. In this study, the appropriate adsorption and desorption conditions of Cs in seawater using the insoluble cobalt ferrocyanide-impregnated adsorbent synthesized by graft polymerisation were investigated. A chemical separation method of Cs for mass spectrometry was also investigated.

Isomer spectroscopy using actinide targets

Sugiyama, Koichi*; Go, Shintaro*; Tomimatsu, Taro*; Kai, Tamito*; Nagae, Daisuke*; Ishibashi, Yuichi*; Matsunaga, Sotaro*; Nagata, Yuto*; Nishibata, Hiroki*; Washiyama, Kohei*; et al.

no journal, , 

We have successfully performed in-beam gamma-ray spectroscopy using the isomer-scope technique to study excited-state structure of neutron-rich heavy-actinide nuclei. The neutron-rich heavy-actinide nuclei were produced in the multinucleon-transfer reactions with a Cm target and O projectiles accelerated with the JAEA tandem accelerator. Projectile-like scattered particles were detected with Si E-E telescopes placed at the backward angle, and target-like scattered particles of isomers were caught by an annular aluminum plate placed at about 60-mm downstream from the target. Four Ge detectors and 4 LaBr detectors were placed at the periphery of the aluminum plate, and detected gamma rays from the isomers. Gamma rays emitted from the actinide isomers were successfully observed with a good sensitivity owing to the tungsten shield placed between the target and the detectors.