Development of "MOX weighing and Ball-mill blending" based on experience in operation and maintenance of MOX fuel manufacturing equipment

Kawasaki, Kohei; Ono, Takanori; Shibanuma, Kimikazu; Goto, Kenta; Aita, Takahiro; Okamoto, Naritoshi; Shinada, Kenta; Ichige, Hidekazu; Takase, Tatsuya; Osaka, Yuki; et al.

JAEA-Technology 2022-031, 91 Pages, 2023/02

JAEA-Technology-2022-031.pdf:6.57MB

The document for back-end policy opened to the public in 2018 by Japan Atomic Energy Agency (hereafter, JAEA) states the decommissioning of facilities of Nuclear Fuel Cycle Engineering Laboratories and JAEA have started gathering up nuclear fuel material of the facilities into Plutonium Fuel Production Facilities (hereafter, PFPF) in order to put it long-term, stable and safe storage. Because we planned to manufacture scrap assemblies almost same with Monju fuel assembly using unsealed plutonium-uranium mixed-oxide (hereafter, MOX) powder held in PFPF and transfer them to storage facilities as part of this "concentration" task of nuclear fuel material, we obtained permission to change the use of nuclear fuel material in response to the new regulatory Requirements in Japan for that. The amount of plutonium (which is neither sintered pellets nor in a lidded powder-transport container) that could be handled in the pellet-manufacturing process was limited to 50 kg Pu or less in order to decrease the facility risk in this manufacture. Therefore, we developed and installed the "MOX weighing and blending equipment" corresponding with small batch sizes that functioned in a starting process and the equipment would decrease handling amounts of plutonium on its downstream processes. The failure data based on our operation and maintenance experiences of MOX fuel production facilities was reflected in the design of the equipment to further improve reliability and maintainability in this development. The completed equipment started its operation using MOX powder in February 2022 and the design has been validated through this half-a-year operation. This report organizes the knowledge obtained through the development of the equipment, the evaluation of the design based on the half-a-year operation results and the issues in future equipment development.

Development of fireproof sheet on glove box panels

Kawasaki, Kohei; Shinada, Kenta; Okamoto, Naritoshi; Kageyama, Tomio; Eda, Takashi; Okazaki, Hiro; Suzuki, Hiromichi; Yamamoto, Kazuya; Otabe, Jun

JAEA-Technology 2020-025, 80 Pages, 2021/03

JAEA-Technology-2020-025.pdf:3.72MB

Plutonium Fuel Production Facility was built in 1988 for the purpose of mainly producing MOX fuel of the prototype fast breeder reactor MONJU, and large glove boxes were installed for handling unsealed nuclear fuel material remotely. The panels of these glove boxes are made of acrylic, except for those installed after December 2013. For fires inside the glove box, automatic fire extinguishing systems using halides have been introduced since the beginning of construction, but for fires outside the glove box, there have been issues with direct measures for acrylic. Therefore, we have developed a fireproof sheet that mitigates the effect of fire outside the glove box on the panels as much as possible. As a result, fire-retardant sheets have been selected and attached to the glove box panels. We conducted a flammability test of the acrylic plate attached with these fireproof sheets and a usage environment influence test of fireproof sheets, and obtained good results. In addition, we set up a working group in the Plutonium Fuel Development Center in view of reducing external exposure during the work of attaching fireproof sheets, in which we discussed and examined the work procedure, and summarized it in the basic procedure manual.

Unconventional supercondnuctivity in the itinerant ferromagnet UGe; Ge-NQR study under pressure

Harada, Atsushi*; Kawasaki, Shinji*; Mukuda, Hidekazu*; Kitaoka, Yoshio*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Ito, Kohei*; Haller, E. E.*; Harima, Hisatomo*

Physica B; Condensed Matter, 378-380, p.963 - 964, 2006/05

https://doi.org/10.1016/j.physb.2006.01.368

The superconducting characteristics on the itinerant ferromagnetic superconductor UGe have been investigated via the Ge-NQR measurements under pressure () near the critical pressure where the first-order transition takes place from the low-temperature () and low- ferromagnetic phase (FM2) to high- and high- one (FM1). The measurements of nuclear spin-lattice relaxation rate have revealed a power-law like behavior as without the coherence peak, whereas at low temperatures, it deviates from the dependence to a -linear like behavior. These results that depend on the pressure are well understood in terms of non-unitary spin-triplet pairing state where the ferromagnetic up-spin band is gapped, but the down-spin band remains gapless at the Fermi level. We will argue an intimate relationship of the onset of SC with FM1 and FM2.

Spin wave and orbital ordering in the C-type antiferromagnetic phase of NdSrMnO

Kajimoto, Ryoichi; Yoshizawa, Hideki*; Kawasaki, Ryuichi*; Noda, Kohei*; Kuwahara, Hideki*

Journal of the Physical Society of Japan, 74(1), p.502 - 503, 2005/01

https://doi.org/10.1143/JPSJ.74.502

The spin wave dispersion relation of the C-type antiferromagnetic structure in NdSrMnO was determined by neutron scattering. The spin exchange interactions show a large anisotropy, which evidences the d orbital ordering along the axis. The exchange interaction along the direction is fairly large and similar to the value in the ferromagnetic metallic phase, suggesting there is finite hopping of charges along the orbital chains.

Improvement of fireproof performance by sealing the fire-retardant sheet on glove box panels, 1; Influence of burning on glove box panels

Kawasaki, Kohei; Shinada, Kenta; Makino, Takayoshi; Okamoto, Naritoshi

no journal, , 

no abstracts in English

Contamination in the controlled area at the Plutonium Fuel Fabrication Facility in Nuclear Fuel Cycle Engineering Laboratories, 1; Brief overview of the event

Isozaki, Kohei; Tamura, Ken; Yoshida, Tadayoshi; Nakagawa, Takahiro; Kawasaki, Takashi; Momose, Takumaro

no journal, , 

no abstracts in English

Contamination in the controlled area at the Plutonium Fuel Fabrication Facility in Nuclear Fuel Cycle Engineering Laboratories, 3; Improvement of manuals for body radioactive decontamination

Yoshida, Tadayoshi; Isozaki, Kohei; Tamura, Ken; Nakagawa, Takahiro; Kawasaki, Takashi; Momose, Takumaro

no journal, , 

no abstracts in English

Improving the efficiency of vehicle screening during a nuclear emergency using portable radiation portal monitors, 1; Time and manpower savings expected from simultaneous screening of tires and wiper area

Kawasaki, Kohei*; Hiraoka, Hirokazu; Ezaki, Iwao*; Kameda, Shuji*; Kimura, Masanori; Saito, Shota

no journal, , 

In the current contamination screening plan, the vehicle's tires are measured using a portable radiation portal monitor, while wiper area is measured by an inspector using a survey meter. These two measurements confirm that contamination levels are below the screening thresholds. However, if both areas could be screened simultaneously using the portal monitor, it would improve the efficiency of the screening process. In this study, the degree of efficiency that can be expected from simultaneous screening by the portal monitor was verified through simulated screening using actual vehicles. The results showed that this screening method can contribute to a 9.4 second time reduction, from an average of 29.5 seconds to 20.1 seconds per vehicle, and a reduction of two inspectors per lane.

Influence of -ray irradiation on mechanical strength of polycarbonate material

Kawasaki, Kohei

no journal, , 

no abstracts in English

Development of MOX weighting and blending equipment on Plutonium Fuel Production Facility

Kawasaki, Kohei; Shinada, Kenta; Okamoto, Naritoshi; Ono, Takanori; Shibanuma, Kimikazu; Goto, Kenta

no journal, , 

Plutonium Fuel Production Facility of JAEA plans to produce waste packages with stable sealed state by processing MOX powder into pellet. Therefore, we have developed Weighting and blending equipment with improved reliability and maintainability based on experience of operation and maintenance the fast reactor MOX fuel.