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Miyamoto, Yutaka; Suzuki, Daisuke; Tomita, Ryohei; Tomita, Jumpei; Yasuda, Kenichiro
Isotope News, (786), p.22 - 25, 2023/04
no abstracts in English
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：57.04(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.
Iguchi, Kazunari
Nihon Shashin Gakkai-Shi, 68(1), p.56 - 59, 2005/02
In order to detect undeclared activities of nuclear facilities, Japan Atomic Energy Research Institute (JAERI) has developed analytical methods for safeguards environmental samples. As for particle analysis of safeguards environmental sample analysis which can determine isotope ratios of nuclear materials for individual particles, secondary ion mass spectrometry (SIMS) is known as a powerful method. However, it is difficult to analyze particles having diameter below 1 m due to its detection limit. To overcome the problem, JAERI is developing an analytical method using fission track (FT) technique. The outline of the method is described in this report.
Lee, C. G.; Iguchi, Kazunari; Inagawa, Jun; Suzuki, Daisuke; Esaka, Fumitaka; Magara, Masaaki; Sakurai, Satoshi; Watanabe, Kazuo; Usuda, Shigekazu
Dai-26-Kai Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Nenji Taikai Rombunshu, p.171 - 178, 2005/00
Particle analysis by FT-TIMS method is effective for safeguards environmental samples because the isotope ratios of sub-micrometer particles can be determined. The FT-TIMS method developed by the authors, in which the particles are confined in the detector, has merits such as high detection efficiency and the possibility as a screening method for uranium particles according to their enrichment by controlling the etching time. However, it was found that a part of uranium particles contained in a detector may dissolve during the etching process of the detector. In order to overcome the problem, we are developing a novel sample preparing method in which the FT detector and the particle layer are separated. In the conventional FT sample of separated type, the detection process of particles of interest is time-consuming and complicated due to the discrepancy in position between tracks and particles. In contrast, the discrepancy was solved by fixing a part of a detector and a particle layer in our method, which improved the detection efficiency of particles containing fissile materials.
Yomogida, Takumi; Esaka, Fumitaka; Magara, Masaaki
no journal, ,
In this study, we developed a micro-Raman spectroscopy technique combined with alpha track-detection to identify chemical forms of uranium particles. U
O
and UO
particles were used as samples. Films containing uranium-bearing particles were exposed to alpha track detectors (TNF-1) for a few months. The location of uranium particles in the films were identified by observing alpha tracks which caused by spontaneous fission of uranium. The characteristic Raman bands which derive from UO and UO structures were observed in the Raman spectra of uranium particles.
-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.
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.
Yasuda, Kenichiro; Suzuki, Daisuke; Miyamoto, Yutaka; Usami, Hidehiko*
no journal, ,
In safeguards environmental sample analysis, isotopic composition analysis of particles containing nuclear materials is an important technique for detecting undeclared activities at nuclear facilities. The alpha track and the fission track method are often used to detect the position of particles containing nuclear materials, but it has been difficult to use both methods on a sample because the track detector was deformed by the chemical etching. In this study, the alpha track and fission track methods were successfully applied to individual particles by correcting their positions by marking the track detector with a laser. Therefore, it was possible to classify differences in the amount and composition of nuclear material contained in the particles, and it is expected that the particles will be recovered efficiently.
Yasuda, Kenichiro; Suzuki, Daisuke; Tomita, Jumpei; Tomita, Ryohei; Miyamoto, Yutaka
no journal, ,
The safeguards environmental sample analysis by the IAEA requires the development of efficient methods for measuring isotope ratios of ultra-trace amounts of plutonium and uranium particles. We have applied fission track and alpha track techniques to identify of discrimination between plutonium and uranium particles and have successfully measured isotope ratios of the particles using a continuous heating method with a thermal ionization mass spectrometer (TIMS). This method made it possible to find particles containing plutonium and uranium and measure them simultaneously by the TIMS without a chemical separation.
-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.
