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Journal Articles

Guidance for ${it in situ}$ gamma spectrometry intercomparison based on the information obtained through five intercomparisons during the Fukushima mapping project

Mikami, Satoshi; Ishikawa, Daisuke*; Matsuda, Hideo*; Hoshide, Yoshifumi*; Okuda, Naotoshi*; Sakamoto, Ryuichi*; Saito, Kimiaki

Journal of Environmental Radioactivity, 210, p.105938_1 - 105938_7, 2019/12

 Times Cited Count:1 Percentile:10.3(Environmental Sciences)

Five intercomparisons of in situ $$gamma$$ spectrometry by 6-7 participating teams have been conducted between December 2011 and August 2015 at sites in Fukushima prefecture which affected by the fallout of FDNPS accident occurred in March 2011. The evaluated deposition densities agreed within 5-6% in terms of coefficient of variation (CV) for radiocesium ($$^{134}$$Cs and $$^{137}$$Cs), by our best achievement, and the ratio of $$^{134}$$Cs/$$^{137}$$Cs in deposition density agreed within 1-2% in CV, through five intercomparisons. These results guarantee the accuracy of the measurements of the mapping project. Two different methods for intercomparison were conducted: (1) sequential measurements at an identical point; and (2) simultaneous measurements in a narrow area within 3 m radius. In a comparison between the two methods at a site, no significant difference was observed between the results. The standard protocols for the two different intercomparison methods were proposed based on our experience.

Journal Articles

The Deposition densities of radiocesium and the air dose rates in undisturbed fields around the Fukushima Dai-ichi Nuclear Power Plant; Their temporal changes for five years after the accident

Mikami, Satoshi; Tanaka, Hiroyuki*; Matsuda, Hideo*; Sato, Shoji*; Hoshide, Yoshifumi*; Okuda, Naotoshi*; Suzuki, Takeo*; Sakamoto, Ryuichi*; Ando, Masaki; Saito, Kimiaki

Journal of Environmental Radioactivity, 210, p.105941_1 - 105941_12, 2019/12

AA2019-0019.pdf:2.65MB

 Times Cited Count:17 Percentile:84.46(Environmental Sciences)

The deposition densities of radiocesium and the air dose rates were repeatedly measured in a large number of undisturbed fields within the 80km zone that surrounds the Fukushima Dai-ichi Nuclear Power Plant site between 2011 and 2016, and features of their temporal changes were clarified. The average air dose rate excluding background radiation in this zone decreased to about 20% of the initial value during the period from June 2011 to August 2016, which was essentially a result of the radioactive decay of $$^{134}$$Cs with a half-life of 2.06y. The air dose rate reduction was faster than that expected from the decay of radiocesium by a factor of about two, with most of this reduction being attributed to the penetration of radiocesium into the soil. The average deposition densities of $$^{134}$$Cs and $$^{137}$$Cs in fields that were not decontaminated were found to have decreased nearly according to their expected radioactive decay, which indicated that the movement of radiocesium in the horizontal direction was relatively small. The effect of decontamination was apparently observed in the measurements of air dose rates and deposition densities. Nominally, the average air dose rates in the measurement locations were reduced by about 20% by decontamination and other human activities, of which accurate quantitative analysis is and continue to be a challenge.

Journal Articles

In situ $$gamma$$ spectrometry intercomparison in Fukushima, Japan

Mikami, Satoshi; Sato, Shoji*; Hoshide, Yoshifumi*; Sakamoto, Ryuichi*; Okuda, Naotoshi*; Saito, Kimiaki

Hoken Butsuri, 50(3), p.182 - 188, 2015/09

Intercomparison of in situ $$gamma$$ spectrometry was organized at a site contaminated by the radioactive fallout that originated from the Fukushima Dai-ichi Nuclear Power Plant accident. This intercomparison was conducted by eight teams from four different institutions, which have contributed to the government-led project to construct distribution maps of radionuclides deposited on the ground soil. The resultant $$^{134}$$Cs and $$^{137}$$Cs inventories evaluated by the participants agreed within 6% of the coefficient of variation, after correction for inhomogeneous distribution of the air dose rate. The evaluated $$^{40}$$K inventories agreed within 4% of the coefficient of variation. The authors estimated that these results were in good agreement for creating distribution maps of the radionuclide inventory in the ground soil.

Journal Articles

The Air dose rate around the Fukushima Dai-ichi Nuclear Power Plant; Its spatial characteristics and temporal changes until December 2012

Mikami, Satoshi; Maeyama, Takeshi*; Hoshide, Yoshifumi*; Sakamoto, Ryuichi*; Sato, Shoji*; Okuda, Naotoshi*; Sato, Tetsuro*; Takemiya, Hiroshi; Saito, Kimiaki

Journal of Environmental Radioactivity, 139, p.250 - 259, 2015/01

 Times Cited Count:43 Percentile:86.58(Environmental Sciences)

Journal Articles

Spatial distributions of radionuclides deposited onto ground soil around the Fukushima Dai-ichi Nuclear Power Plant and their temporal change until December 2012

Mikami, Satoshi; Maeyama, Takeshi*; Hoshide, Yoshifumi*; Sakamoto, Ryuichi*; Sato, Shoji*; Okuda, Naotoshi*; Demongeot, S.*; Gurriaran, R.*; Uwamino, Yoshitomo*; Kato, Hiroaki*; et al.

Journal of Environmental Radioactivity, 139, p.320 - 343, 2015/01

 Times Cited Count:70 Percentile:94.06(Environmental Sciences)

Journal Articles

Perpendicular magnetic anisotropy with enhanced orbital moments of Fe adatoms on a topological surface of Bi$$_2$$Se$$_3$$

Ye, M.*; Kuroda, Kenta*; Takeda, Yukiharu; Saito, Yuji; Okamoto, Kazuaki*; Zhu, S.-Y.*; Shirai, Kaito*; Miyamoto, Koji*; Arita, Masashi*; Nakatake, Masashi*; et al.

Journal of Physics; Condensed Matter, 25(23), p.232201_1 - 232201_5, 2013/06

 Times Cited Count:11 Percentile:50.94(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Quasiparticle interference on the surface of Bi$$_{2}$$Se$$_{3}$$ induced by cobalt adatom in the absence of ferromagnetic ordering

Ye. M.*; Eremeev, S. V.*; Kuroda, Kenta*; Krasovskii, E. E.*; Chulkov, E. V.*; Takeda, Yukiharu; Saito, Yuji; Okamoto, Kazuaki*; Zhu, S. Y.*; Miyamoto, Koji*; et al.

Physical Review B, 85(20), p.205317_1 - 205317_5, 2012/05

 Times Cited Count:54 Percentile:90.06(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Electronic structure of heavy fermion uranium compounds studied by core-level photoelectron spectroscopy

Fujimori, Shinichi; Okochi, Takuo*; Kawasaki, Ikuto; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; et al.

Journal of the Physical Society of Japan, 81(1), p.014703_1 - 014703_9, 2012/01

 Times Cited Count:35 Percentile:83.28(Physics, Multidisciplinary)

High-energy-resolution core-level and valence-band photoelectron spectroscopic studies were performed for the heavy Fermion uranium compounds UGe$$_2$$, UCoGe, URhGe, URu$$_2$$Si$$_2$$, UNi$$_2$$Al$$_3$$, UPd$$_2$$Al$$_3$$, and UPt$$_3$$ as well as typical localized and itinerant uranium compounds to understand the relationship between the uranium valence state and their core-level spectral line shapes. The core-level spectra of UGe$$_2$$, UCoGe, URhGe, URu$$_2$$Si$$_2$$, and UNi$$_2$$Al$$_3$$ are rather similar to those of itinerant compounds, suggesting that U 5$$f$$ electrons in these compounds are well hybridized with ligand states. On the other hand, the core-level spectra of UPd$$_2$$Al$$_3$$ and UPt$$_3$$ show considerably different spectral line shapes from those of the itinerant compounds, suggesting that U 5$$f$$ electrons in UPd$$_2$$Al$$_3$$ and UPt$$_3$$ are less hybridized with ligand states, leading to the correlated nature of U 5$$f$$ electrons in these compounds.

Journal Articles

Soft X-ray synchrotron radiation photoemission study on uranium compounds

Fujimori, Shinichi; Terai, Kota; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Muramatsu, Yasuji; Fujimori, Atsushi; Yamagami, Hiroshi*; Ikeda, Shugo; Matsuda, Tatsuma; et al.

Physica B; Condensed Matter, 378-380, p.995 - 996, 2006/05

 Times Cited Count:2 Percentile:13.35(Physics, Condensed Matter)

Recently, photoemission experiments in soft X-ray region have attracted much attention due to their high sensitivities for bulk electronic structures of strongly correlated electron system. We have carried out the high-resolution photoemission experiments on some uranium compounds using soft X-ray synchrotron radiation from SPring-8 to understand their electronic structures. Bulk- and U 5$$f$$-sensitive band structure and Fermi surface were obtained for itinerant U 5$$f$$ compounds UFeGa$$_5$$ and USb$$_2$$, and they are compared with the results of the band structure calculations treating U 5$$f$$ states as being itinerant. In addition, we show the results of photoemission study on some heavy fermion compounds such as UPd$$_2$$Al$$_3$$ and UNi$$_2$$Al$$_3$$. The temperature dependences of the U 5$$f$$ electronic structure of UPd$$_2$$Al$$_3$$ will be also reported.

Journal Articles

Itinerant U 5$$f$$ band states in the layered compound UFeGa$$_5$$ observed by soft X-ray angle-resolved photoemission spectroscopy

Fujimori, Shinichi; Terai, Kota; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Muramatsu, Yasuji; Fujimori, Atsushi; Yamagami, Hiroshi*; Tokiwa, Yoshifumi*; Ikeda, Shugo; et al.

Physical Review B, 73(12), p.125109_1 - 125109_6, 2006/03

 Times Cited Count:20 Percentile:66.26(Materials Science, Multidisciplinary)

We have performed angle-resolved photoemission spectroscopy (ARPES) experiments on paramagnetic UFeGa$$_5$$ using soft X-ray synchrotron radiation ($$hnu$$=500 eV) and derived the bulk- and U 5$$f$$-sensitive electronic structure of UFeGa$$_5$$. Although the agreement between the experimental band strucure and the LDA calculation treating U 5$$f$$ electrons as beeing itinerant is qualitative, the morphology of the Fermi surface is well explained by the calculation. This result claims that the importance of the electron correlation effect even for the itinerant U 5$$f$$ compound.

Journal Articles

Submersible compact reactor SCR for under-sea research vessel

Odano, Naoteru; Kusunoki, Tsuyoshi; Yoritsune, Tsutomu; Fukuhara, Yoshifumi*; Saito, Kazuo*; Takahashi, Teruo*; Ishida, Toshihisa

Proceedings of International Workshop on Utilization of Nuclear Power in Oceans (N'ocean 2000), p.164 - 169, 2000/02

no abstracts in English

Oral presentation

Photoemission studies on heavy fermion superconductors

Fujimori, Shinichi; Saito, Yuji; Okane, Tetsuo; Yamagami, Hiroshi; Fujimori, Atsushi*; Shimada, Kenya*; Namatame, Hirofumi*; Taniguchi, Masaki*; Aoki, Dai*; Ikeda, Shugo*; et al.

no journal, , 

no abstracts in English

Oral presentation

Evaluation of the electron distribution function for detached plasma in JT-60U

Uehara, Kazuya; Asakura, Nobuyuki; Sadamoto, Yoshiro*; Kawashima, Hisato; Kubo, Hirotaka; Nakano, Tomohide; Takenaga, Hidenobu; Fujimoto, Kayoko; Amemiya, Hiroshi*; Saito, Yoshifumi*

no journal, , 

The temperature and energy of electrons are important issues when energy and particle fluxes to the divertor are evaluated. To do this, we have analyzed the electron energy distribution function by differentiating the probe current with respect to the probe voltage numerically, where probe current has been measured in the divertor plasma of JT-60U. We have evaluated the electron temperature and the shape of the distribution function when the X point MARFE and the plasma detachment are formed.

Oral presentation

Effect of test conditions on radiation degradation of space solar cells

Saito, Masashi*; Imaizumi, Mitsuru*; Oshima, Takeshi; Ito, Yoshifumi*

no journal, , 

no abstracts in English

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