Detailed visualization of radioactive hotspots inside the Unit 1 reactor building of the Fukushima Daiichi Nuclear Power Station using an integrated Radiation Imaging System mounted on a Mecanum wheel robot

Sato, Yuki; Terasaka, Yuta; Oura, Masatoshi*

Journal of Nuclear Science and Technology, 61(7), p.856 - 870, 2024/07

https://doi.org/10.1080/00223131.2023.2282551

A Phoswich alpha/beta detector for monitoring in the site of Fukushima Daiichi Nuclear Power Station

Morishita, Yuki; Takasaki, Koji; Kitayama, Yoshiharu; Tagawa, Akihiro; Shibata, Takuya; Hoshi, Katsuya; Kaneko, Junichi*; Higuchi, Mikio*; Oura, Masatoshi*

Radiation Measurements, 160, p.106896_1 - 106896_10, 2023/01

https://doi.org/10.1016/j.radmeas.2022.106896

This study proposes a newly developed phoswich alpha/beta detector that can discriminate alpha and beta particles emitted from the alpha and beta contaminations in the FDNPS site. The phoswich alpha/beta detector is made up of two layers of scintillators that detect alpha and beta particles. The pulse shape discrimination (PSD) method was used to detect alpha particles in high beta particle and high gamma-ray (comparable to gamma-ray dose rate near the FDNPS reactor building) environments. Due to a 23.3% full width at half maximum (FWHM) energy resolution for alpha particles, the detector can be used to distinguish between nuclear fuel materials such as plutonium and its radon progeny (Po-214). Moreover, the detector could distinguish alpha particles from Cs gamma rays with a dose rate background up to 9.0 mSv/h. It is the first to demonstrate that the developed phoswich detector can be used to discriminate and measure alpha and beta particles of the actual contaminated FDNPS samples.

Acceleration of highly charged GeV Fe ions from a low-Z substrate by intense femtosecond laser

Nishiuchi, Mamiko; Sakaki, Hironao; Esirkepov, T. Z.; Nishio, Katsuhisa; Pikuz, T.*; Faenov, A.*; Skobelev, I. Yu.*; Orlandi, R.; Sako, Hiroyuki; Pirozhkov, A. S.; et al.

Physics of Plasmas, 22(3), p.033107_1 - 033107_8, 2015/03

https://doi.org/10.1063/1.4913434

Almost fully stripped Fe ions accelerated up to 0.9 GeV are demonstrated with a 200 TW femtosecond high-intensity laser irradiating a micron-thick Al foil with Fe impurity on the surface. An energetic low-emittance high-density beam of heavy ions with a large charge-to-mass ratio can be obtained, which is useful for many applications, such as a compact radio isotope source in combination with conventional technology.

Ion-beam irradiation, gene identification, and marker-assisted breeding in the development of low-cadmium rice

Ishikawa, Satoru*; Ishimaru, Yasuhiro*; Igura, Masato*; Kuramata, Masato*; Abe, Tadashi*; Senoura, Takeshi*; Hase, Yoshihiro; Arao, Tomohito*; Nishizawa, Naoko*; Nakanishi, Hiromi*

Proceedings of the National Academy of Sciences of the United States of America, 109(47), p.19166 - 19171, 2012/11

https://doi.org/10.1073/pnas.1211132109

Rice ( L.) is one of major sources of dietary intake of cadmium (Cd) for the human. However, the reliable technique to reduce substantially rice Cd contamination has not been offered so far. Here, we report the ion-beam irradiated rice mutants that do not nearly accumulate Cd in the grains and the mutant gene responsible for the Cd limitation. We found three mutants in which a favorable low-Cd trait is expressed by the different mutations on the same gene (), and the transporter encoded by the mutant gene had a defective function of root Cd influx. The mutants adapted well in the Cd-polluted paddy fields by exhibiting nearly non-detectable Cd concentrations in their grains in accordance with no adverse economic traits. The DNA marker has been developed to breed new cultivars carrying . Our findings would be useful for greatly reducing the Cd level of paddy rice.

Extraction of chromatographic behavior of Rf, Zr, and Hf in HCl solution with styrenedivinylbenzene copolymer resin modified by TOPO (trioctylphosphine oxide)

Toyoshima, Atsushi; Kasamatsu, Yoshitaka*; Tsukada, Kazuaki; Asai, Masato; Ishii, Yasuo; Tome, Hayato*; Nishinaka, Ichiro; Sato, Tetsuya; Nagame, Yuichiro; Schdel, M.; et al.

Journal of Nuclear and Radiochemical Sciences, 11(1), p.7 - 11, 2010/06

https://doi.org/10.14494/jnrs.11.7

The extraction behavior of rutherfordium (Rf) into trioctylphosphine oxide (TOPO) from 2.0 - 7.0 M HCl solution was studied together with that of the homologues Zr and Hf. The extracted yields of Rf, Zr, and Hf increased with an increase of HCl concentration, and the sequence of their extraction was Zr Hf Rf. It is suggested that the stability of the RfCl2(TOPO) complex is lower than that of the corresponding species of the homologues.

Adsorption of Db and its homologues Nb and Ta, and the pseudo-homologue Pa on anion-exchange resin in HF solution

Tsukada, Kazuaki; Haba, Hiromitsu*; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko*; Kasamatsu, Yoshitaka; Nishinaka, Ichiro; Ichikawa, Shinichi; Yasuda, Kenichiro; Miyamoto, Yutaka; et al.

Radiochimica Acta, 97(2), p.83 - 89, 2009/02

https://doi.org/10.1524/ract.2009.1577

Anion-exchange chromatography of element 105, dubnium (Db), produced in the Cm(F, 5n)Db reaction is investigated together with the homologues Nb and Ta, and the pseudo-homologue Pa in 13.9 M hydrofluoric acid (HF) solution. The distribution coefficient (K) of Db on an anion-exchange resin is successfully determined by running cycles of the 1702 chromatographic column separations. The result clearly indicates that the adsorption of Db on the resin is significantly different from that of the homologues and that the adsorption of anionic fluoro complexes of these elements decreases in the sequence of Ta Nb Db Pa.

Fluoride complexation of element 104, rutherfordium (Rf), investigated by cation-exchange chromatography

Ishii, Yasuo; Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Tome, Hayato; Nishinaka, Ichiro; Nagame, Yuichiro; Miyashita, Sunao*; Mori, Tomotaka*; Suganuma, Hideo*; et al.

Chemistry Letters, 37(3), p.288 - 289, 2008/03

https://doi.org/10.1246/cl.2008.288

We have investigated cation-exchange behavior of Rf together with the lighter homologues of the group-4 elements Zr and Hf, and the tetravalent pseudo-homologue Th, in HF/HNO solution using Automated Ion exchange separation apparatus coupled with the Detection system for Alpha spectroscopy (AIDA). The values of Zr, Hf, Th and Rf in HF/0.1 M HNO were decreased with increasing the concentration of the fluoride ion [F], indicating the formation of the fluoride complexes. The sequence of the fluoride complexation strength is Zr Hf Rf Th.

Development of sodium disposal technology; Experiment of sodium compound solidification process

Matsumoto, Toshiyuki; Oura, Masato*; Yato, Yasuo*

JAEA-Research 2007-049, 73 Pages, 2007/07

JAEA-Research-2007-049.pdf:40.32MB

A large amount of sodium containing radioactive waste will come up at the time of final shutdown/ decommission of FBR plant. The radioactive waste is managed as solid state material in a closed can in Japan. As for the sodium, there is no established method to convert the radioactive sodium to solid waste. Further, the sodium is highly reactive. Thus, it is recommended to convert the sodium to a stable substance before the solidification process. One of the stabilizing methods is conversion of sodium into sodium hydroxide solution. These stabilization and solidification processes should be safe, economical, and efficient. In order to develop such sodium disposal technology, nonradioactive sodium was used and a basic experiment was performed. Waste-fluid Slag Solidification method was employed as the solidification process of sodium hydroxide solution. Experimental parameters were mixing ratio of the sodium hydroxide and the slag solidification material, temperature and concentration of the sodium hydroxide. The best parameters were obtained to achieve the maximum filling ratio of the sodium hydroxide under a condition of enough high compressive strength of the solidified waste. In a beaker level test, the solidified waste was kept in a long term and it was shown that there was no change of appearance, density, and also the compressive strength was kept at a target value. In a real scale test, homogeneous profiles of the density and the compressive strength were obtained. The compressive strength was higher than the target value. It was shown that the Waste-fluid Slag Solidification method can be applied to the solidification process of the sodium hydroxide solution, which was produced by the stabilization process.

Extraction behavior of rutherfordium into tributylphosphate from hydrochloric acid

Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Ishii, Yasuo; Tome, Hayato; Sato, Tetsuya; Nishinaka, Ichiro; Ichikawa, Takatoshi; Ichikawa, Shinichi; et al.

Radiochimica Acta, 95(1), p.1 - 6, 2007/01

https://doi.org/10.1524/ract.2007.95.1.1

no abstracts in English

Experimental identification of spin-parities and single-particle configurations in No and its -decay daughter Fm

Asai, Masato; Tsukada, Kazuaki; Sakama, Minoru*; Ichikawa, Shinichi; Ishii, Tetsuro; Nagame, Yuichiro; Nishinaka, Ichiro; Akiyama, Kazuhiko; Osa, Akihiko; Oura, Yasuji*; et al.

Physical Review Letters, 95(10), p.102502_1 - 102502_4, 2005/09

https://doi.org/10.1103/PhysRevLett.95.102502

Excited states in Fm fed by the decay of No have been established through - and -electron coincidence spectroscopy using a gas-jet transport system and an on-line isotope separator. The spin-parity of the 124.1 keV level in Fm has been identified on the basis of the measured internal conversion coefficients. The configuration has been assigned to the ground state of No as well as to the 124.1 keV level. It was found that the ground state configuration of No is different from that of lighter isotones.