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Onishi, Takashi; Koyama, Shinichi*; Yokoyama, Keisuke; Morishita, Kazuki; Watanabe, Masashi; Maeda, Shigetaka; Yano, Yasuhide; Oki, Shigeo
Nuclear Engineering and Design, 432, p.113755_1 - 113755_17, 2025/02
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Ikeuchi, Hirotomo; Sasaki, Shinji; Onishi, Takashi; Nakayoshi, Akira; Arai, Yoichi; Sato, Takumi; Ohgi, Hiroshi; Sekio, Yoshihiro; Yamaguchi, Yukako; Morishita, Kazuki; et al.
JAEA-Data/Code 2023-005, 418 Pages, 2023/12
JAEA-Data-Code-2023-005-01.pdf:24.59MBJAEA-Data-Code-2023-005-02.pdf:32.18MB
For safe and steady decommissioning of Tokyo Electric Power Company Holdings' Fukushima Daiichi Nuclear Power Station (1F), information concerning composition and physical/chemical properties of fuel debris generated in the reactors should be estimated and provided to other projects conducting the decommissioning work including the retrieval of fuel debris and the subsequent storage. For this purpose, in FY2021, samples of contaminants (the wiped smear samples and the deposits) obtained through the internal investigation of the 1F Unit 2 were analyzed to clarify the components and to characterize the micro-particles containing uranium originated from fuel (U-bearing particles) in detail. This report summarized the results of analyses performed in FY2021, including the microscopic analysis by SEM and TEM, radiation analysis, and elemental analysis by ICP-MS, as a database for evaluating the main features of each sample and the probable formation mechanism of the U-bearing particles.
Sato, Takumi; Otobe, Haruyoshi; Morishita, Kazuki; Marufuji, Takato; Ishikawa, Takashi; Fujishima, Tadatsune; Nakano, Tomoyuki
JAEA-Technology 2023-016, 41 Pages, 2023/09
JAEA-Technology-2023-016.pdf:2.74MB
This report summarizes the results of the stabilization treatments of post-experiment nuclear materials in Plutonium Fuel Research Facility (PFRF) from August 2018 to March 2021. Based on the management standards for nuclear materials enacted after the contamination accident that occurred at PFRF on June 6, 2017, the post-experiment nuclear materials containing plutonium (Pu): samples mixed with organic substances that cause an increase in internal pressure due to radiolysis (including X-ray diffraction samples mixed with epoxy resin and plutonium powder which caused contamination accidents), carbides and nitrides samples which is reactive in air, and chloride samples which may cause corrosion of storage containers, were selected as targets of the stabilization. The samples containing organic materials, carbides and nitrides were heated in an air flow at 650 
C and 950 C for 2 hours respectively to remove organic materials and convert uranium (U) and Pu into oxides. U and Pu chlorides in LiCl-KCl eutectic melt were reduced and extracted into liquid Cd metal by a reaction with lithium (Li) -cadmium (Cd) alloy and converted to U-Pu-Cd alloy at 500 C or higher. All of the samples were stabilized and stored at PFRF. We hope that the contents of this report will be utilized to consider methods for stabilizing post experiment nuclear materials at other nuclear fuel material usage facilities.
Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Morishita, Kazuki; Sato, Takumi; Onishi, Takashi; Seki, Takayuki*; Sekine, Shinichi*; Okitsu, Yuichi*
JAEA-Technology 2021-024, 27 Pages, 2021/10
JAEA-Technology-2021-024.pdf:2.41MB
In the case of Plutonium (Pu)-bearing organic materials, organic materials are decomposed by alpha rays emitted mainly from Pu to generate hydrogen gas and other substances. Therefore, to safely store Pu-bearing organic materials for an extended period of time, organic materials must be eliminated. In addition, carbide and nitride fuels must be converted into oxides for safe storage in order to prevent the exothermal reaction of these fuels with oxygen/moisture in air. A survey of the literature on the stabilization treatment of Pu-bearing organic materials confirmed that organic materials can be decomposed and removed by heating at 950 C (1223.15 K) or greater in air. Furthermore, based on the calculated thermodynamic parameters of oxidation reaction of carbide and nitride fuels in air, it was estimated that these fuels would be oxidized in air at 950 C because the equilibrium oxygen partial pressure in the oxidation reaction at 950 C was lower than 2.1
10
Pa (oxygen partial pressure in air). Therefore, it was decided to stabilize Pu-bearing organic materials by heating at 950 C in air to remove the organic materials and oxidize the carbide and nitride fuels. As a mock-up test to remove the organic materials, thin sheets of epoxy resin were heated in air. The changes in appearance and weight before and after heating in air showed that organic materials can be removed. After the mock-up test, Pu-bearing organic materials were also stabilized by heating in the similar condition.
crystalsAbe, Kenichiro*; Miyoshi, Yoshihiro*; Ashida, Atsushi*; Wakita, Kazuki*; Oshima, Takeshi; Morishita, Norio; Kamiya, Tomihiro; Watase, Seiji*; Izaki, Masanobu*
Japanese Journal of Applied Physics, 44(1B), p.718 - 721, 2005/01
Times Cited Count：1 Percentile：4.62(Physics, Applied)no abstracts in English
Sato, Takumi; Morishita, Kazuki; Otobe, Haruyoshi; Fujishima, Tadatsune; Nakano, Tomoyuki
no journal, ,
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Morishita, Kazuki; Onishi, Takashi; Maeda, Koji; Mizokami, Masato*; Ito, Kenichi*; Mizokami, Shinya*
no journal, ,
no abstracts in English
Onishi, Takashi; Morishita, Kazuki; Watanabe, Masashi; Yokoyama, Keisuke; Kato, Masato
no journal, ,
no abstracts in English
Sasaki, Shinji; Maeda, Koji; Morishita, Kazuki; Onishi, Takashi; Sato, Ikken; Mizokami, Masato*; Mizokami, Shinya*
no journal, ,
no abstracts in English
Morishita, Kazuki; Onishi, Takashi; Maeda, Koji; Mizokami, Masato*; Ito, Kenichi*; Mizokami, Shinya*
no journal, ,
Samples, collected from the operating floor of the reactor building of Fukushima Daiichi Unit 2, were immersed in deionized water and nitric acid. Immersed solutions were analyzed by gamma-ray spectrometry and ICP-MS. Analyses suggest small amount of Fe, Mn and Cu derived from structural materials of nuclear reactor, and Te, Cs and U derived from spent fuels.
Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Morishita, Kazuki; Kato, Masato
no journal, ,
no abstracts in English
crystalsMurakami, Go*; Abe, Kenichiro*; Ashida, Atsushi*; Wakita, Kazuki*; Watase, Seiji*; Izaki, Masanobu*; Oshima, Takeshi; Morishita, Norio; Ito, Hisayoshi
no journal, ,
no abstracts in English
Morishita, Kazuki; Onishi, Takashi; Maeda, Koji; Mizokami, Masato*; Ito, Kenichi*; Mizokami, Shinya*
no journal, ,
no abstracts in English
