A Review of Cs-bearing microparticles in the environment emitted by the Fukushima Dai-ichi Nuclear Power Plant accident

Igarashi, Yasuhito*; Kogure, Toshihiro*; Kuribara, Yuichi; Miura, Hikaru*; Okumura, Taiga*; Satou, Yukihiko; Takahashi, Yoshio*; Yamaguchi, Noriko*

Journal of Environmental Radioactivity, 205-206, p.101 - 118, 2019/09

https://doi.org/10.1016/j.jenvrad.2019.04.011

Scientists face challenge in identifying the radioactive materials which are found as dotted images on various imaging plate (IP) autoradiographic photos of radioactively contaminated materials by the Fukushima Dai-ichi Nuclear Power Plant (F1NPP, or FDNPP) accident, such as air filter, fugitive dust, surface soil, agricultural materials, and water-shed samples. It has been revealed that they are minute particles with distinct morphology and elemental composition with high specific radioactivity, and different from those of the so-called Chernobyl hot particles. Basically, they are glassy particles once molten, composed of Si, O, Fe, Zn etc. with highly concentrated radiocaesium, which can be called as radiocaesium-bearing microparticles (CsMP). At present, CsMP can be classified into two types, Types-A and -B, which are characterized by different specific radioactivity, Cs/Cs ratio, size and morphology, and geographic distribution around F1NPP. Such studies on the CsMP from various aspects have provided valuable information about what happened in the nuclear reactors during the F1NPP accident and fates of the CsMP in the environment. This review first provides a retrospective view on the research history of the CsMP, which is helpful to understand the unique character of the CsMP. Subsequently, more details about the current understanding of the natures of these hot particles, such as origin, morphology, chemical compositions, thermal properties, water-solubility, and secondary migration of CsMP in river and ocean systems are described with future prospects.

Dissolution behaviour of radiocaesium-bearing microparticles released from the Fukushima nuclear plant

Okumura, Taiga*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro*

Scientific Reports (Internet), 9(1), p.3520_1 - 3520_9, 2019/03

https://doi.org/10.1038/s41598-019-40423-x

Radiocesium-bearing microparticles (CsMPs) were released by the FDNPP accident. We conducted dissolution experiments of CsMPs by reaction with pure water absorbing CO from the atmosphere and seawater. The activation energy for the dissolution of CsMPs was estimated to be 67 and 89 kJ/mol, and the dissolution rate at 13C was 0.011 and 0.130 m/y for pure water and seawater, respectively. Probably the faster dissolution rate in seawater than in pure water is mainly owing to the difference in pH. The shapes of CsMPs dissolved in pure water were considerably altered. Tin oxide and iron oxide nanoparticulates were formed on their surfaces. Such features were similar to those observed in a CsMP collected recently in Fukushima Prefecture, indicating that dissolution of CsMPs is also occurring in the environment. In the case of CsMPs dissolved in seawater, a crust of secondary minerals rich in Mg and Fe was formed and the glass matrix became smaller inside the crust.

Constituent elements and their distribution in the radioactive Cs-bearing silicate glass microparticles released from Fukushima Nuclear Plant

Kogure, Toshihiro*; Yamaguchi, Noriko*; Segawa, Hiroyo*; Mukai, Hiroki*; Motai, Satoko*; Akiyama, Kotone*; Mitome, Masanori*; Hara, Toru*; Yaita, Tsuyoshi

Microscopy, 65(5), p.451 - 459, 2016/10

https://doi.org/10.1093/jmicro/dfw030

Digital feedback control for 972 MHz RF system of J-PARC linac

Michizono, Shinichiro*; Fang, Z.*; Matsumoto, Toshihiro*; Yamaguchi, Seiya*; Kobayashi, Tetsuya; Okada, Yoshihito*

Proceedings of 2009 Particle Accelerator Conference (PAC '09) (DVD-ROM), p.2201 - 2203, 2009/05

Upgrade of J-PARC linac has been planed using 972 MHz rf system. The rf eld regulation is required to be less than 1% in amplitude and 1. in phase. The basic digital llrf concept is same as the present 324 MHz llrf system using a compact PCI crate. The main alterations are rf and clock generator (RF&LK), mixer and IQ modulator (IQ&Mixer) and digital llrf algorithm. Since the typical decay time is faster (due to higher operational frequency than present 324 MHz cavity), chopped beam compensation is one of the main concerns. Performance of the digital feedback system using a cavity simulator is summarized.

Developments in the fabrication technology of low density MOX pellets for fast breeder reactor fuel

Asakura, Koichi; Yamaguchi, Toshihiro; Otani, Tetsuo

Journal of Nuclear Materials, 357(1-3), p.126 - 137, 2006/10

https://doi.org/10.1016/j.jnucmat.2006.06.002

The fabrication of low density MOX pellets was studied using some organic compounds as pore formers. The pore former, K3 showed the best performance among five organic compounds in the 7.5 kg-UOX runs, but K3 lost this in 36 kg-MOX run, possibly because plutonium decay heat affected its performance. Comparison of thermal stubilities between K3 and a newly introduced pore former, Avicel, of high softening temperature, showed that K3 lost its spherical particle shape and consequently, its pore forming ability at 70C which was below its reported melting point (84-88C) while Avicel could maintain its spherical particle shape up to 150C. The pore forming performance of Avicel was also comfirmed in the 36 kg-MOX run which is the same scale as for mass production of MOX fuel pellets.

Development of argon cover gas analysis for fast reactors using atmospheric pressure ionization mass spectrometry with collision-indued dissociation

; Ito, Chikara; Arima, Toshihiro*; Yamaguchi, Katsuyuki*

JNC TN9400 2003-009, 25 Pages, 2003/03

JNC-TN9400-2003-009.pdf:0.63MB

The isotopic measurement of krypton in argon is partially obstructed by the isobaric interference in the fast reactor cover gas analysis that is performed using atmospheric pressure ionization mass spectrometry. Collision-induced dissociation is applied to decompose cluster ions and suppress the interference. Cluster ions are accelerated by an electric field in a relatively high-pressure region and are dissociated through multiple collisions with neutral particles. This process is controlled by changing the accelerating voltage in the present study. It is shown that the isobaric interference due to argon dimer ions are suppressed by increasing the accelerating voltage. The isobaric interference could be reduced to 1/60,000 in the most effective condition. It is also found that collision-induced dissociation enhances the detection sensitivity and permits quantitative analysis with a sub-ppt level for the krypton nuclides that are not interfered.

Observation of structure on MOX fuel for fuel failure behaviour study in NSRR

; Yamaguchi, Toshihiro; *

PNC TN8410 87-19, 110 Pages, 1987/01

PNC-TN8410-87-19.pdf:5.79MB

None

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*; Kamimura, Katsuichiro; Kodato, Kazuo; Yamaguchi, Toshihiro; *

PNC TN841 84-23, 190 Pages, 1984/05

PNC-TN841-84-23.pdf:3.76MB

no abstracts in English

None

Konashi, Kenji; Kaneko, Hiromitsu; Nagai, Shuichiro; Tachibana, Toshimichi; Yamaguchi, Toshihiro; *

PNC TN841 82-58, 110 Pages, 1982/10

PNC-TN841-82-58.pdf:1.72MB

no abstracts in English

None

Yamaguchi, Toshihiro; *; Kashima, Sadamitsu; Nagai, Shuichiro; Kaneko, Hiromitsu; *; Uruwashi, Shinichi*

PNC TN841 82-25, 74 Pages, 1982/03

PNC-TN841-82-25.pdf:2.03MB

no abstracts in English