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Journal Articles

Comparison of airborne and ground-based tools used for radiation measurement in the environment

Ochi, Kotaro; Sasaki, Miyuki; Ishida, Mutsushi*; Sanada, Yukihisa

Progress in Nuclear Science and Technology (Internet), 6, p.103 - 107, 2019/01

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, a large amount of radionuclides was spread out all over the world. In our previous study, we developed the aerial radiation monitoring technique using unmanned helicopter for investigating the dose rate derived deposited radionuclides over wide area. In addition, many monitoring techniques were developed for investigating the local distribution of radionuclides using unmanned aerial vehicle, handheld instrument and car within small area. Distinction of these methods depends on desirable position resolution of dose rate. However, the comparison method of the measurement result between different methods is not established. In this study, we attempted to evaluate the some methods of airborne and ground radiation measurement in same extended farm.

Journal Articles

Estimation of the vertical distribution of radiocesium in soil on the basis of the characteristics of $$gamma$$-ray spectra obtained via aerial radiation monitoring using an unmanned helicopter

Ochi, Kotaro; Sasaki, Miyuki; Ishida, Mutsushi*; Hamamoto, Shoichiro*; Nishimura, Taku*; Sanada, Yukihisa

International Journal of Environmental Research and Public Health, 14(8), p.926_1 - 926_14, 2017/08

 Times Cited Count:4 Percentile:29.51(Environmental Sciences)

After the Fukushima Daiichi Nuclear Power Plant accident, the vertical distribution of radiocesium in soil has been investigated to better understand the behavior of radiocesium in the environment. The typical method used for measuring the vertical distribution of radiocesium is troublesome because it requires collection and measurement of the activity of soil samples. In this study, we established a method of estimating the vertical distribution of radiocesium by focusing on the characteristics of $$gamma$$-ray spectra obtained via aerial radiation monitoring using an unmanned helicopter. In this method, the change in the ratio of direct $$gamma$$ rays to scattered $$gamma$$ rays at various depths in the soil was utilized to quantify the vertical distribution of radiocesium. The results show a positive correlation between the abovementioned and the actual vertical distributions of radiocesium measured in the soil samples.

Journal Articles

Quadrupole and hexadecapole ordering in DyB$$_2$$C$$_2$$; Direct observation with resonant X-ray diffraction

Tanaka, Yoshikazu*; Inami, Toshiya; Lovesey, S. W.*; Knight, K. S.*; Yakhou, F.*; Mannix, D.*; Kokubun, Jun*; Kanazawa, Masayuki*; Ishida, Kotaro*; Nanao, Susumu*; et al.

Physical Review B, 69(2), p.024417_1 - 024417_11, 2004/01

 Times Cited Count:35 Percentile:79.89(Materials Science, Multidisciplinary)

Direct evidence of the spatial ordering of Dy 4$$f$$ quadrupole and hexadecapole moments in DyB$$_2$$C$$_2$$ is demonstrated by resonant X-ray diffraction enhanced by an electric quadrupole event ($$E$$2 resonance) at the Dy L$$_{III}$$ absorption edge. The diffraction data show that the structural phase transition at $$T$$$$_{Q}$$ = 24.7 K is accompanied by a reduction in the symmetry of the Dy site to 2/$$m$$, from 4/$$m$$, and the spatial ordering of the time-even Dy multipoles with A$$_{g}$$ character. Below $$T$$$$_{Q}$$ the crystal structure is described by the space group $$P$$4$$_2$$/$$mnm$$ and Dy ions occupy sites (4$$c$$). The distortion at T$$_{Q}$$ involves the lattice occupied by B and C ions, and it amounts to a buckling of B-C planes that are normal to the two-fold rotation axis of 2/$$m$$. An immediately plausible model of low-energy Dy states correlates data on the specific heat, our X-ray diffraction signals, and magnetic ordering below 15.3 K which has been observed in magnetic neutron diffraction.

Oral presentation

Estimation of depth profile of radiocesium in soil based on characteristics of $$gamma$$-ray spectra obtained by airborne radiation monitoring

Ochi, Kotaro; Sasaki, Miyuki; Ishida, Mutsushi*; Sato, Tomohiko*; Hamamoto, Shoichiro*; Nishimura, Taku*; Sanada, Yukihisa

no journal, , 

A large amount of radiocesium ($$^{134}$$Cs & $$^{137}$$Cs) were released into the atmosphere as a result of 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. To estimate the impact of the accident to the environment, dose rate around FDNPP have been measured by MEXT. Dose rate nearby FDNPP, however, still stay high even though decontamination work was carried out, which means it is necessary to develop an effective decontamination method promptly. Information of depth profile of radiocesium in soil is required to realize it, though, most of measurement methods have trouble due to collection and measurement of soil samples. As we have developed the radiation measurement techniques using unmanned aerial vehicle to measure dose rate distribution over wide areas for years, we attempt to establish the estimation method of depth profile of radiocesium in soil based on characteristics of $$gamma$$-ray spectra obtained by airborne radiation monitoring in this paper.

Oral presentation

Advancement of airborne radiation measurement technology, 2; Estimation of vertical distribution of radiocesium in soil using an unmanned helicopter

Ochi, Kotaro; Sasaki, Miyuki; Ishida, Mutsushi*; Sanada, Yukihisa

no journal, , 

In previous studies, our group have developed the airborne radiation measurement (ARM) technique. We mounted a radiation detector under an unmanned aerial vehicle to evaluate the deposition of Fukushima accident-derived radiocesium over wide area. In this study, we performed ARM with mounting a LaBr$$_{3}$$(Ce) detector under an unmanned helicopter. A rapid and simple estimation of depth profile of radiocesium in soil was developed on the basis of the relationship between spectra obtained via ARM and actual depth profile of radiocesium. Our goal is same to series 1 that we attempt to achieve the advancement of airborne radiation measurement technique.

Oral presentation

Advancement of airborne radiation measurement technology, 1; Aerial radiation monitoring using an unmanned helicopter with a LaBr$$_{3}$$(Ce) detector for estimating radiocesium distribution in soil

Ochi, Kotaro; Malins, A.; Ishida, Mutsushi*; Yamada, Tsutomu*; Nakasone, Takamasa*; Sanada, Yukihisa

no journal, , 

no abstracts in English

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