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Yomogida, Takumi; Ouchi, Kazuki; Oka, Toshitaka; Kitatsuji, Yoshihiro; Koma, Yoshikazu; Konno, Katsuhiro*
Scientific Reports (Internet), 12(1), p.7191_1 - 7191_10, 2022/05
Times Cited Count：5 Percentile：50.82(Multidisciplinary Sciences)Particles containing alpha (
) nuclides were identified from sediment in stagnant water at the torus room of the Fukushima Dai-ichi Nuclear Power Station (FDiNPS)'s Unit 2 reactor. Several uranium-bearing particles were identified by SEM observation. These particles contained Zr and other elements which constituted fuel cladding and structural materials. The 
U/
U isotope ratio in the solid fractions that included U particles was consistent with the nuclear fuel in the Unit 2 reactor, which indicated that the U particles had been derived from nuclear fuel. The particles with alpha-emitters detected by alpha track analysis were several tens to several hundred 
m in size. The EDX spectra showed that these particles mainly comprised iron, which indicated Pu, Am, and Cm were adsorbed on the Fe-baring particles. This study clarifies that the major morphologies of U and other -nuclides were differed in the sediment of stagnant water in the torus room of FDiNPS's Unit 2 reactor.
Esaka, Fumitaka; Magara, Masaaki
Mass Spectrometry Letters, 7(2), p.41 - 44, 2016/06
Secondary ion mass spectrometry (SIMS) is a promising tool to measure isotope ratios of individual uranium particles in environmental samples for nuclear safeguards. However, the analysis requires prior identification of a small number of uranium particles that coexist with a large number of other particles without uranium. In the present study, this identification was performed by scanning electron microscopy -energy dispersive X-ray analysis with automated particle search mode. The analytical results for an environmental sample taken at a nuclear facility indicated that the observation of backscattered electron images with 
1000 magnification was appropriate to efficiently identify uranium particles. Lower magnification (less than 500) made it difficult to detect smaller particles of approximately 1 m diameter.
Shirasu, Yoshiro; Minato, Kazuo
Proc. of the Int. Conf. on Future Nuclear Systems (GLOBAL'99)(CD-ROM), 7 Pages, 1999/00
no abstracts in English
;
Journal of Nuclear Materials, 152, p.339 - 342, 1988/00
Times Cited Count：3 Percentile：75(Materials Science, Multidisciplinary)no abstracts in English
;
JAERI-M 84-220, 23 Pages, 1984/12
no abstracts in English
Uyama, Masao*; Hitomi, Takashi*; Iyatomi, Yosuke; Matsui, Hiroya
no journal, ,
no abstracts in English
Iyatomi, Yosuke; Ishibashi, Masayuki; Matsui, Hiroya; Uyama, Masao*; Hitomi, Takashi*
no journal, ,
no abstracts in English
-emitters by SEM-EDX and alpha trackYomogida, Takumi; Ouchi, Kazuki; Oka, Toshitaka; Kitatsuji, Yoshihiro; Koma, Yoshikazu; Konno, Katsuhiro*
no journal, ,
It has been revealed from the analysis results of ICP-MS and -ray spectrometry that the contaminated water at the torus room of Unit 2 reactor contains -nuclides which were derived from nuclear fuels. To investigate the morphology of these -nuclides, we tried to detect particles containing -nuclides by scanning electron microscopy-X-ray detection (SEM-EDX) and the alpha track method. As a result of SEM-EDX observation, several sub-m to several m size particles containing U were identified. These particles contain elements derived from fuel cladding materials such as Zr, suggesting the possibility that these particles are fine fuel debris. The particles containing alpha emitters were identified by alpha-track method. These particles with few hundred m in diameter were mainly composed of iron oxide, which suggest Pu, Am, Cm were attached to the surface of these particles. These results indicated that the forms of U and other -nuclides were different.
-Zr-SS systemAkiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Sasaki, Takayuki*; Watanabe, Masayuki; Kumagai, Yuta; Kusaka, Ryoji
no journal, ,
In the accident at TEPCO's Fukushima Daiichi Nuclear Power Station, it is considered that the molten fuel reacted with zircaloy of the cladding tube and alloys containing iron as the main component, such as stainless steel, at high temperatures to generate fuel debris. For the removal, processing, and disposal of the debris in the future, it will be important to predict the properties of the debris. Therefore, in this study, simulated fuel debris containing Zr or ZrO and the constituent elements of stainless steel was prepared, and structural analysis was performed using XRD and SEM-EDX. We also evaluated the solid phase state after immersing the simulated debris in pure water or seawater.
Yomogida, Takumi; Ouchi, Kazuki; Oka, Toshitaka; Kitatsuji, Yoshihiro; Koma, Yoshikazu; Konno, Katsuhiro*
no journal, ,
As part of the decommissioning work of the Fukushima Daiichi Nuclear Power Plant (1F), disposal of stagnant water existing in the basement of the turbine building is underway. Higher concentrations of alpha nuclides have been detected in the stagnant water in the reactor building than in the downstream buildings. It is necessary to consider technology to effectively remove -nuclides to proceed with the disposal of the stagnant water in the reactor buildings. We focused on particulate -nuclides in the stagnant water in the torus room of Unit 2, and analyzed and investigated their particle size, chemical form, etc to understand morphology of -nuclides. We detected particles containing -nuclides by SEM-EDX and alpha-track detection. The results showed that U is in particle form, ranging from a few hundred nm to a few m. Other -nuclides (Pu, Am, and Cm) were distributed on iron oxide particles.
-emitting nuclides analysis of the stagnant water including sediments in Fukushima Daiichi NPS, 2; Detection of fine particle containing -emitters by SEM-EDX and alpha TrackYomogida, Takumi; Ouchi, Kazuki; Morii, Shiori; Oka, Toshitaka; Kitatsuji, Yoshihiro; Koma, Yoshikazu; Konno, Katsuhiro*
no journal, ,
To investigate the morphology of -nuclides in solid fraction of the stagnant water in the Fukushima Dai-ichi nuclear Power Station's Unit 3 reactor, we tried to detect particles containing -nuclides by scanning electron microscopy-X-ray detection (SEM-EDX) and the alpha track method. As a result of SEM-EDX observation, several sub-m to 10 m size particles containing U were identified. The particles containing alpha emitters were identified by alpha-track method. These particles with few hundred m in diameter were mainly composed of iron.
Yomogida, Takumi
no journal, ,
As one of decommissioning process of Fukushima Dai-ichi Nuclear Power Station, treatment of stagnant water in the reactor building is now in progress. Our group investigated the particle size and chemical form of particulate -nuclides in the stagnant water in the torus room of Unit 2 to understand the morphology of -nuclides for the safe treatment of the stagnant water. The analysis of particles with -nuclides by SEM-EDX and alpha-track detection revealed that U was in the form of particles ranging from several hundred nm to several m, while other -nuclides (Pu, Am, Cm) were distributed on iron oxide particles. The information of morphology of the -nuclides was used in the design of a purification system to remove particles containing -nuclides from the stagnant water.
Endo, Ryo*; Akiyama, Daisuke*; Yomogida, Takumi; Kirishima, Akira*
no journal, ,
In the Fukushima Daiichi Nuclear Power Plant accident, fuel debris were formed by reaction of molten fuel and reactor structural materials. The fuel debris is composed of many elements and crystalline phases. Therefore, it is inevitable to study various solid phase for debris analysis. In this study, we focused on (U, Zr) O solid solution, which is assumed to be formed in the reactor by the reaction of molten nuclear fuel (UO) and oxide of cladding components (ZrO). The morphology of (U, Zr) O solid solution was studied by X-ray diffraction (XRD) in macro-scale analysis, and by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) and micro-Raman spectroscopy (MRS) in micro-scale analysis.
Endo, Ryo*; Akiyama, Daisuke*; Yomogida, Takumi; Okamoto, Yoshihiro; Tanida, Hajime; Kirishima, Akira*
no journal, ,
In the Fukushima Daiichi Nuclear Power Plant accident, fuel debris were formed by the reaction of molten fuel and reactor structural materials. The fuel debris is composed of many elements and crystalline phases. Therefore, it is inevitable to study various solid phases for debris analysis. In this study, we focused on (U,Zr)O solid solution, which is assumed to be formed in the reactor by the reaction of molten nuclear fuel (UO) and oxide of cladding components (ZrO). First, the crystalline phase of (U,Zr)O solid solution in the bulk region were determined by X-ray diffraction. The elemental composition in the micro region was analyzed by scanning electron microscopy-energy dispersive X-ray spectroscopy, and the crystalline phase in the same region was analyzed by micro-Raman spectroscopy. In addition, local elemental and valence analyses of micro regions were performed by -XRD, -XRF, and -XAFS. The U valence determined by XANES spectra was compared to the crystalline phase of (U,Zr)O solid solution. The objective of this study is to develop techniques which determine the chemical state from multiple angles by combining multiple spectroscopic analyses.
