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Journal Articles

Analysis of particles containing alpha-emitters in stagnant water at torus room of Fukushima Dai-ichi Nuclear Power Station's Unit 2 reactor

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 ($$alpha$$) 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 $$^{235}$$U/$$^{238}$$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 $$mu$$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 $$alpha$$-nuclides were differed in the sediment of stagnant water in the torus room of FDiNPS's Unit 2 reactor.

Journal Articles

Technological development of the particle size adjustment of dry recovered powder

Segawa, Tomoomi; Yamamoto, Kazuya; Makino, Takayoshi; Iso, Hidetoshi; Kawaguchi, Koichi; Ishii, Katsunori; Sato, Hisato; Fukasawa, Tomonori*; Fukui, Kunihiro*

Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.738 - 745, 2019/09

In the MOX fuel fabrication process, the dry grinding technology of mixed oxide pellets have been developed for the effective use of nuclear fuel materials. To develop a technology to control the particle size of dry recovered powder, the performance of the buhrstone mill and the collision plate type jet mill were studied using a simulated powder of particle size distribution about 500 $$mu$$m. We found that the particle size can be controlled at the range of about 250 $$mu$$m or less by both by adjusting the clearance between the grinding wheels of the buhrstone mill, and the clearance and elevation angle of the clarification zone of the collision plate type jet mill. And furthermore, the collision plate type jet mill is considered to be suitable for particle size control because the operating parameters of the classifier can be finely adjusted.

Journal Articles

Challenges for enhancing Fukushima environmental resilience, 4; Development of physical and heat treatment methods on aiming at decontamination, volume reduction and reuse of contaminated soil

Yaita, Tsuyoshi; Honda, Mitsunori; Shimoyama, Iwao; Ito, Kenichi*; Mampuku, Yuzo*; Tsuji, Takuya; Matsumura, Daiju

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 59(8), p.483 - 487, 2017/08

no abstracts in English

Journal Articles

Charged nanoparticle formation from humidified gases with and without dilute benzene under electron beam irradiation

Hakoda, Teruyuki; Kim, H.*; Okuyama, Kikuo*; Kojima, Takuji

Journal of Aerosol Science, 34(8), p.977 - 991, 2003/08

 Times Cited Count:15 Percentile:54.91(Engineering, Chemical)

no abstracts in English

Oral presentation

Technological development of the particle size adjustment of recycle powder, 3; Optimization study of collision plate-type jet mill

Segawa, Tomoomi; Yamamoto, Kazuya; Makino, Takayoshi; Iso, Hidetoshi; Sato, Hisato

no journal, , 

The optimizing the centrifugal classifier which influences the classification performance of collision plate-type jet mill was examined for the purpose of the particle size adjustment of recycle powder the MOX pellets. In order to adjust the particle size of recycle powder to 10-250 $$mu$$m, the pulverization test of the simulated raw powder was carried out using the newly prepared components as a parameter. The prospect that the particle size can be adjusted within the range of 10-250 $$mu$$m for recycle powder was obtained by optimizing the parameter of the centrifugal classifier of collision plate-type jet mill.

Oral presentation

Technological development of the particle size adjustment of recycle powder, 4; Pulverization characteristics of collision plate-type jet mill

Makino, Takayoshi; Yamamoto, Kazuya; Segawa, Tomoomi; Kawaguchi, Koichi; Iso, Hidetoshi

no journal, , 

The purpose of this study is to develop technology of the particle size adjustment of dry recovered powder of MOX pellets. Pulverization and classification experiments were conducted using simulated pellets obtained from materials having similar hardness and different density (specific gravity). We report that the results of pulverization and classification experiments in which experimental parameters were the clearance of the centrifugal classifier affecting the classification performance of the collision plate type jet mill.

Oral presentation

Analysis of alpha radionuclide in the contaminated water at the torus room of unit #2 reactor of Fukushima Daiichi NPS, 4; Detection of fine particle containing $$alpha$$-emitters by SEM-EDX and alpha track

Yomogida, 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 $$alpha$$-ray spectrometry that the contaminated water at the torus room of Unit 2 reactor contains $$alpha$$-nuclides which were derived from nuclear fuels. To investigate the morphology of these $$alpha$$-nuclides, we tried to detect particles containing $$alpha$$-nuclides by scanning electron microscopy-X-ray detection (SEM-EDX) and the alpha track method. As a result of SEM-EDX observation, several sub-$$mu$$m to several $$mu$$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 $$mu$$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 $$alpha$$-nuclides were different.

Oral presentation

Detection and analysis of particles containing alpha-emitters in stagnant water at torus room of Fukushima Dai-ichi Nuclear Power Station's Unit 2 reactor

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 $$alpha$$-nuclides to proceed with the disposal of the stagnant water in the reactor buildings. We focused on particulate $$alpha$$-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 $$alpha$$-nuclides. We detected particles containing $$alpha$$-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 $$mu$$m. Other $$alpha$$-nuclides (Pu, Am, and Cm) were distributed on iron oxide particles.

Oral presentation

$$alpha$$-emitting nuclides analysis of the stagnant water including sediments in Fukushima Daiichi NPS, 2; Detection of fine particle containing $$alpha$$-emitters by SEM-EDX and alpha Track

Yomogida, Takumi; Ouchi, Kazuki; Morii, Shiori; Oka, Toshitaka; Kitatsuji, Yoshihiro; Koma, Yoshikazu; Konno, Katsuhiro*

no journal, , 

To investigate the morphology of $$alpha$$-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 $$alpha$$-nuclides by scanning electron microscopy-X-ray detection (SEM-EDX) and the alpha track method. As a result of SEM-EDX observation, several sub-$$mu$$m to 10 $$mu$$m size particles containing U were identified. The particles containing alpha emitters were identified by alpha-track method. These particles with few hundred $$mu$$m in diameter were mainly composed of iron.

Oral presentation

Research on alpha particles in the stagnant water of Fukushima Daiichi Nuclear Power Station

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 $$alpha$$-nuclides in the stagnant water in the torus room of Unit 2 to understand the morphology of $$alpha$$-nuclides for the safe treatment of the stagnant water. The analysis of particles with $$alpha$$-nuclides by SEM-EDX and alpha-track detection revealed that U was in the form of particles ranging from several hundred nm to several $$mu$$m, while other $$alpha$$-nuclides (Pu, Am, Cm) were distributed on iron oxide particles. The information of morphology of the $$alpha$$-nuclides was used in the design of a purification system to remove particles containing $$alpha$$-nuclides from the stagnant water.

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