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JAEA Reports

Removal of spent fuel sheared powder for decommissioning of Main Plant

Nishino, Saki; Okada, Jumpei; Watanabe, Kazuki; Furuuchi, Yuta; Yokota, Satoru; Yada, Yuji; Kusaka, Shota; Morokado, Shiori; Nakamura, Yoshinobu

JAEA-Technology 2023-011, 39 Pages, 2023/06

JAEA-Technology-2023-011.pdf:2.51MB

Tokai Reprocessing Plant (TRP) which shifted to decommissioning phase in 2014 had nuclear fuel materials such as the spent fuel sheared powder, the diluted plutonium solution and the uranium solution in a part of the reprocessing main equipment because TRP intended to resume reprocessing operations when it suspended the operations in 2007. Therefore, we have planned to remove these nuclear materials in sequence as Flush-out before beginning the decommissioning, and conducted removal of the spent fuel sheared powder as the first stage. The spent fuel sheared powder that had accumulated in the cell of the Main Plant (MP) as a result of the spent fuel shearing process was recovered from the cell floor, the shearing machine and the distributor between April 2016 and April 2017 as part of maintenance. Removing the recovered spent fuel sheared powder was conducted between June 2022 and September 2022. In this work, the recovered powder was dissolved in nitric acid at the dissolver in a small amount in order to remove it safely and early, and the dissolved solution was sent to the highly radioactive waste storage tanks without separating uranium and plutonium. Then, the dissolved solution transfer route was rinsed with nitric acid and water. Although about 15 years had passed since previous process operations, the removing work was successfully completed without any equipment failure because of the organization of a system that combines veterans experienced the operation with young workers, careful equipment inspections, and worker education and training. Removing this powder was conducted after revising the decommissioning project and obtaining approval from the Nuclear Regulation Authority owing to operating a part of process equipment.

JAEA Reports

Controlled release of radioactive krypton gas

Watanabe, Kazuki; Kimura, Norimichi*; Okada, Jumpei; Furuuchi, Yuta; Kuwana, Hideharu*; Otani, Takehisa; Yokota, Satoru; Nakamura, Yoshinobu

JAEA-Technology 2023-010, 29 Pages, 2023/06

JAEA-Technology-2023-010.pdf:3.12MB

The Krypton Recovery Development Facility reached an intended technical target (krypton purity of over 90% and recovery rate of over 90%) by separation and rectification of krypton gas from receiving off-gas produced by the shearing and the dissolution process in the spent fuel reprocessing at the Tokai Reprocessing Plant (TRP) between 1988 and 2001. In addition, the feasibility of the technology was confirmed through immobilization test with ion-implantation in a small test vessel from 2000 to 2002, using a part of recovered krypton gas. As there were no intentions to use the remaining radioactive krypton gas in the krypton storage cylinders, we planned to release this gas by controlling the release amount from the main stack, and conducted it from February 14 to April 26, 2022. In this work, all the radioactive krypton gas in the cylinders (about 7.1$$times$$10$$^{5}$$ GBq) was released at the rate of 50 GBq/min or less lower than the maximum release rate from the main stuck stipulated in safety regulations (3.7$$times$$10$$^{3}$$ GBq/min). Then, the equipment used in the controlled release of radioactive krypton gas and the main process (all systems, including branch pipes connected to the main process) were cleaned with nitrogen gas. Although there were delays due to weather, we were able to complete the controlled release of radioactive krypton gas by the end of April 2022, as originally targeted without any problems such as equipment failure.

Journal Articles

Enhanced $$d$$-$$p$$ hybridization intertwined with anomalous ground state formation in the van der Waals itinerant magnet Fe$$_5$$GeTe$$_2$$

Yamagami, Kohei*; Fujisawa, Yuita*; Pardo-Almanza, M*; Smith, B. R. M.*; Sumida, Kazuki; Takeda, Yukiharu; Okada, Yoshinori*

Physical Review B, 106(4), p.045137_1 - 045137_8, 2022/07

https://doi.org/10.1103/PhysRevB.106.045137
 Times Cited Count：6 Percentile：54.70(Materials Science, Multidisciplinary)

Journal Articles

Evaluation of Tsunami debris impact on Tokai Reprocessing Plant

Nishino, Saki; Tsuboi, Masatoshi; Okada, Jumpei; Saegusa, Yu; Omori, Kazuki; Yasuo, Kiyoshi; Seshimo, Kazuyoshi; Domura, Kazuyuki; Yamamoto, Masahiko

Nihon Hozen Gakkai Dai-17-Kai Gakujutsu Koenkai Yoshishu, p.541 - 548, 2021/07

no abstracts in English

Journal Articles

$$q$$=0 long-range magnetic order in centennialite CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O; A Spin-$$frac{1}{2}$$ perfect kagome antiferromagnet with $$J_{1}$$-$$J_{2}$$-$$J_{d}$$

Iida, Kazuki*; Yoshida, Hiroyuki*; Nakao, Akiko*; Jeschke, H. O.*; Iqbal, Y.*; Nakajima, Kenji; Kawamura, Seiko; Munakata, Koji*; Inamura, Yasuhiro; Murai, Naoki; et al.

Physical Review B, 101(22), p.220408_1 - 220408_6, 2020/06

https://doi.org/10.1103/PhysRevB.101.220408
 Times Cited Count：26 Percentile：79.28(Materials Science, Multidisciplinary)

Crystal and magnetic structures of the mineral centennialite CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O are investigated by means of synchrotron X-ray diffraction and neutron diffraction measurements complemented by density functional theory (DFT) and pseudofermion functional renormalization group (PFFRG) calculations. In CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O, Cu$$^{2+}$$ ions form a geometrically perfect kagome network with antiferromagnetic $$J_{1}$$. No intersite disorder between Cu$$^{2+}$$ and Ca$$^{2+}$$ ions is detected. CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O enters a magnetic long-range ordered state below $$T_{rm N}$$ = 7.2 K, and the $$q$$=0 magnetic structure with negative vector spin chirality is obtained. The ordered moment at 0.3 K is suppressed to 0.58(2)$$mu$$B. Our DFT calculations indicate the presence of antiferromagnetic $$J_{2}$$ and ferromagnetic $$J_{d}$$ superexchange couplings of a strength which places the system at the crossroads of three magnetic orders (at the classical level) and a spin-$$frac{1}{2}$$ PFFRG analysis shows a dominance of $$q$$=0 type magnetic correlations, consistent with and indicating proximity to the observed $$q$$=0 spin structure. The results suggest that this material is located close to a quantum critical point and is a good realization of a $$J_{1}$$-$$J_{2}$$-$$J_{d}$$ kagome antiferromagnet.

Journal Articles

Experimental and theoretical studies on oxidation of Cu-Au alloy surfaces; Effect of bulk Au concentration

Okada, Michio*; Tsuda, Yasutaka*; Oka, Kohei*; Kojima, Kazuki*; Di$~n$o, W. A.*; Yoshigoe, Akitaka; Kasai, Hideaki*

Scientific Reports (Internet), 6, p.31101_1 - 31101_8, 2016/08

https://doi.org/10.1038/srep31101
 Times Cited Count：32 Percentile：74.01(Multidisciplinary Sciences)

We report results of our experimental and theoretical studies on the oxidation of Cu-Au alloy surfaces, viz., Cu$$_{3}$$Au(111), CuAu(111), and Au$$_{3}$$Cu(111), using hyperthermal O$$_{2}$$ molecular beam (HOMB). We observed strong Au segregation to the top layer of the corresponding clean (111) surfaces. This forms a protective layer that hinders further oxidation into the bulk. The higher the concentration of Au in the protective layer formed, the higher the protective efficacy. As a result, of the three Cu-Au surfaces studied, Au$$_{3}$$Cu(111) is the most stable against dissociative adsorption of O$$_{2}$$, even with HOMB. We also found that this protective property breaks down for oxidations occurring at temperatures above 300 K.

JAEA Reports

Geological survey and initial stress measurement test consernig of "The crustal deformation study in the active fault zone"

Takemura, Tomoyuki*; Shingu, Kazuki*; Sakogaichi, Kaoru*; Nishikawa, Yuji*; Okada, Yoichi*; Nakajima, Toshihide*; Yamashita, Mitsugu*

JNC TJ7420 2005-035, 152 Pages, 1998/03

JNC-TJ7420-2005-035.pdf:27.16MB

The active fault survey tunnel that crossed the Mozumi-Sukenobu fault (MSF) is located at the Kamioka mine, northern Gifu prefecture, Central Japan. The comprehensive study of the active fault, such as the study of the earthquake mechanism and the development of the new initial stress measurement method is done by using this tunnel. One of the purposes of this investigation is to define the three-dimensional distribution of the MSF by geological survey, on the basis of the seismic and geophysical studies on this fault. The other purpose is to develop the new initial stress measurement method.

JAEA Reports

Investigation of the Hydraulic Properties around the Active Fault in the Crustal Deformation Zone

Takemura, Tomoyuki*; Shingu, Kazuki*; Takahashi, Eiichiro*; Okada, Yoichi*; Takebe, Akimitsu*; Nakajima, Toshihide*; Inoue, Toshio*

JNC TJ7420 2005-033, 128 Pages, 1998/03

JNC-TJ7420-2005-033.pdf:51.98MB

The active fault survey tunnel that crossed the Mozumi-Sukenobu fault (a member of the Atotsugawa fault system) is located at the Kamioka mine, northern Gifu prefecture, Central Japan. The comprehensive study of the active fault is done by using this tunnel. The purpose of this investigation is to define the hydrological characteristics of the Mozumi-Sukenobu fault crush zones. The permeability of the crush zones is measured by the Lugeon test and the simple injection test.

Oral presentation

Flush-out for Tokai Reprocessing Plant decommissioning, 2; Dissolution of the spent fuel sheared powder

Watanabe, Kazuki; Okada, Jumpei; Yokota, Satoru; Oyama, Daisuke; Yamada, Takashi; Yatabe, Hitoshi; Horie, Koji; Uchida, Naoki

no journal, , 

no abstracts in English

Oral presentation

Flush-out for Tokai Reprocessing Plant decommissioning, 1; Preparation for removal of the Spent Fuel Sheared Powder

Yokota, Satoru; Okada, Jumpei; Watanabe, Kazuki; Yatabe, Hitoshi; Yamada, Takashi; Horie, Koji; Furuuchi, Yuta; Uchida, Naoki

no journal, , 

no abstracts in English

Oral presentation

Fission dynamics using six-dimensional Langevin equation with Cassini shape parameterization

Okada, Kazuki; Nishio, Katsuhisa; Wada, Takahiro*; Carjan, N.*

no journal, , 

no abstracts in English

Oral presentation

Dynamical approach to fission using six-dimensional Cassini shape parameterization

Okada, Kazuki; Nishio, Katsuhisa

no journal, , 

Oral presentation

Study of fission dynamics using six-dimensional Langevin equation

Okada, Kazuki; Nishio, Katsuhisa

no journal, , 

no abstracts in English

Oral presentation

Rationalization of maintenance at the Krypton Recovery Development Facility by adding nitrogen replacement equipment and removing liquid nitrogen storage tank

Furuuchi, Yuta; Okada, Jumpei; Kimura, Norimichi*; Watanabe, Kazuki; Hayashi, Yoshitsugu*; Hirayama, Yusuke*; Tashiro, Yoshiyuki*; Uchida, Naoki

no journal, , 

At Krypton Recovery Development Facility in Tokai Reprocessing Plant (TRP), the nitrogen gas, which was supplied from the liquid nitrogen tank, was used instead of compressed air to manage the enclosure function of the facility during the compressor was broken. It was necessary to remove the liquid nitrogen tank possible because it had the possibility of being tsunami debris which affect significant impact on the other TRP facility. Before the tank removal, the automatic switching function was attached to the air compressors as nitrogen replacement equipment. This function switches the starting and stopping the compressors, opening and closing valves after detection of equipment failure. When attaching this function, additional equipment was minimized by utilizing existing equipment. Then, the liquid nitrogen tank was dismantled after transporting outside TRP. These works eliminated the cost of purchasing liquid nitrogen and inspections of the equipment.

Oral presentation

Research and development on preceding processing methods for contaminated water management waste at Fukushima Daiichi Nuclear Power Station, 44; Investigation of solidification range for simulated sludge containing ferrocyanide

Taniguchi, Takumi; Kuramochi, Ryo*; Sakamoto, Ryo*; Osawa, Norihisa*; Kaneda, Yoshihisa*; Matsuzawa, Kazuki*; Yamamoto, Takeshi*; Kuroki, Ryoichiro; Okada, Takashi; Yoshida, Yukihiko; et al.

no journal, , 

no abstracts in English

Oral presentation

Study of fission modes in $$^{258}$$Md with six-dimensional Langevin equation

Okada, Kazuki; Nishio, Katsuhisa; Wada, Takahiro*; Carjan, N.*

no journal, , 

Oral presentation

None

Nishio, Katsuhisa; Iwamoto, Osamu; Makii, Hiroyuki; Hirose, Kentaro; Orlandi, R.; Suzaki, Fumi; Smallcombe, J.; Okada, Kazuki; Asai, Masato; Tsukada, Kazuaki

no journal, , 

no abstracts in English

Oral presentation

Finite element analysis of stress relaxation behavior on shot peening

Kitamura, Yoshisato*; Okada, Takashi*; Ikushima, Kazuki*; Shibahara, Masakazu*; Nishikawa, Satoru*; Akita, Koichi

no journal, , 

no abstracts in English

18 (Records 1-18 displayed on this page)
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