Data acquisition related to improving operability of ROVs for the retrieval of HASWS stored waste

Tameta, Yuito; Sano, Kyohei; Takano, Yugo*; Yamamoto, Masahiko; Nakazaki, Katsutoshi; Akiyama, Kazuki

JAEA-Technology 2026-004, 27 Pages, 2026/05

JAEA-Technology-2026-004.pdf:3.18MB

At the High Active Solid Waste Storage (HASWS) of Tokai Reprocessing Plant, high active solid waste generated from the reprocessing process is stored. In the wet cell, hull cans containing fuel cladding tubes (hulls) and end pieces are stored, along with used filters and contaminated equipment. It is being considered that utilizes a small underwater remotely operated vehicle (ROV) along with a lifter for recovering and transporting objects from the seafloor for the retrieval of the waste stored in the HASWS. Mock-up tests were conducted in FY2022 and FY2023 to verify the feasibility of retrieving waste using the ROV and the lifter. In this study, to achieve safer and more reliable waste retrieval, improvements were made to each component, including the ROV cable, waste gripping grab, lifting hook, lifter, and ROV monitoring camera, and data were collected to evaluate operational performance. For the ROV cable, attaching a float to the rear section of the ROV cable to reduce its weight facilitated forward-tilt operation and improved the ROV's attitude stability during wire-cutting. For the waste gripping grab, attaching a jig to the tips of the grab of the lifter (grabtype) enhanced the gripping stability of the hull can. For the lifting hook, setting the ring diameter of the lifter (hook-type) to 15 cm shortened the time required for grasping and improved accessibility to the hook. For the lifter, using lifters with modified internal structures enabled fine air-volume adjustment and reduced blockage of air passages, thereby improving the stability of air supply and exhaust. For the ROV monitoring camera, adding a light near the ROV monitoring camera in a dark environment ensured sufficient cell illumination and enhanced cable visibility.

Solidification treatment of simulated decontamination equipment sludge using alkali-activated materials

Matsuzawa, Kazuki*; Yamamoto, Takeshi*; Taniguchi, Takumi; Osugi, Takeshi

Konkurito Kogaku Rombunshu, 36, p.37 - 47, 2025/07

https://doi.org/10.3151/crt.36.37

To dispose the decontamination sludge made from contaminated water in Fukushima Daiichi Nuclear Power Station using alkali-activated materials (AAM), we solidified barium sulfate powder (BS) and potassium hexacyanocobalt(II)-ferrate(II) powder (FCN) with AAM and searched proper compositions corresponding to the standards. At first, we made solidified bodies controlling HO/base ratio, Si/Al molar ratio, and Na/Si molar ratio. When base materials consisted of metakaolin and blast-furnace slag, we found out some proper compositions and two applicable concentrations of solutions to make solidified bodies corresponding to the standards. Secondly, using solutions with the applicable concentrations, we made solidified bodies controlling the amounts of BS, BS+FCN, and HO. The maximum amount of BS+FCN at the proper compositions was larger than that of BS.

Investigation of manganese(II) behavior in molten chlorides at precipitate formation by oxide addition

Yamamoto, Yuri*; Minowa, Kazuki*; Takahatake, Yoko; Watanabe, So; Nakamura, Masahiro; Matsuura, Haruaki*

Electrochemistry (Internet), 92(4), p.043019_1 - 043019_4, 2024/04

https://doi.org/10.5796/electrochemistry.23-69162

In the pyro-reprocessing of spent nuclear fuel, salt bath is normally used in several times, but at final moment, spent salt containing small amount of chloride nuclear fuel material is generated. In terms of managing nuclear fuel materials, it is desirable that the nuclear fuel materials should be recovered from the spent salt. We are proposing methods for recovering nuclear fuel materials using precipitation by oxide addition and distillation for reducing pressure techniques. In this study, we have focused on the behavior of manganese(II), which is one of the radioactivated products. As a result of experiments and thermodynamic simulation, it was found that manganese(II) is likely to be entrained in nuclear fuel materials. Therefore, it is necessary to add a step to separate manganese(II) from nuclear fuel materials.

Sodium-cooled Fast Reactors

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

https://shop.elsevier.com/books/sodium-cooled-fast-reactors/morishita/978-0-12-824076-2

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.

Observation of a Be double-Lambda hypernucleus in the J-PARC E07 experiment

Ekawa, Hiroyuki; Ashikaga, Sakiko; Hasegawa, Shoichi; Hashimoto, Tadashi; Hayakawa, Shuhei; Hosomi, Kenji; Ichikawa, Yudai; Imai, Kenichi; Kimbara, Shinji*; Nanamura, Takuya; et al.

Progress of Theoretical and Experimental Physics (Internet), 2019(2), p.021D02_1 - 021D02_11, 2019/02

https://doi.org/10.1093/ptep/pty149

Research and development roadmap for reactor physics 2017; Future of reactor physics projected by next generations

Yamamoto, Akio*; Chiba, Go*; Kirimura, Kazuki*; Miki, Yosuke*; Yokoyama, Kenji

Nihon Genshiryoku Gakkai-Shi ATOMO, 60(4), p.241 - 245, 2018/04

no abstracts in English

Flexible heat-flow sensing sheets based on the longitudinal spin Seebeck effect using one-dimensional spin-current conducting films

Kirihara, Akihiro*; Kondo, Koichi*; Ishida, Masahiko*; Ihara, Kazuki*; Iwasaki, Yuma*; Someya, Hiroko*; Matsuba, Asuka*; Uchida, Kenichi*; Saito, Eiji; Yamamoto, Naoharu*; et al.

Scientific Reports (Internet), 6, p.23114_1 - 23114_7, 2016/03

https://doi.org/10.1038/srep23114

Heat-flow sensing is expected to be an important technological component of smart thermal management in the future. Conventionally, the thermoelectric (TE) conversion technique, which is based on the Seebeck effect, has been used to measure a heat flow by converting the flow into electric voltage. However, for ubiquitous heat-flow visualization, thin and flexible sensors with extremely low thermal resistance are highly desired. Recently, another type of TE effect, the longitudinal spin Seebeck effect (LSSE), has aroused great interest because the LSSE potentially offers favourable features for TE applications such as simple thin-film device structures. Here we demonstrate an LSSE-based flexible TE sheet that is especially suitable for a heat-flow sensing application. This TE sheet contained a NiZnFeO film which was formed on a flexible plastic sheet using a spray-coating method known as ferrite plating. The experimental results suggest that the ferrite-plated film, which has a columnar crystal structure aligned perpendicular to the film plane, functions as a unique one-dimensional spin- current conductor suitable for bendable LSSE-based sensors. This newly developed thin TE sheet may be attached to differently shaped heat sources without obstructing an innate heat flux, paving the way to versatile heat-flow measurements and management.

Fabrication and evaluation of light-emitting SiO substrates implanted with Ge ions

Shinagawa, Teruyoshi*; Umenyi, A. V.*; Kikuchi, Shusuke*; Aiba, Mizuki*; Inada, Kazuki*; Miura, Kenta*; Hanaizumi, Osamu*; Yamamoto, Shunya; Kawaguchi, Kazuhiro; Yoshikawa, Masahito

no journal, , 

Light emission between ultraviolet and blue from SiO substrates implanted with Ge ions in comparatively shallow depth (100 nm) has been reported. In this paper, we report the photoluminescence (PL) properties of SiO substrates implanted with Ge ions deeper than previous works (200 nm depth) in order to enlarge the spot size of the photonic crystals waveguides. Ge ions were implanted into an SiO substrate with 350 keV, and the implantation amount was 110 ions/cm. PL peaks around a wavelength of 400 nm were observed. Stronger PL peaks were measured after annealing (900 C), which confirmed an effect of improving the emission intensity by the annealing process. Though Ge ions were implanted more deeply than the earlier reported depth, similar results were confirmed. The expectation for a new light-emitting waveguide device that combines Ge-ion-implanted SiO substrates with photonic crystal characteristics has risen.

Fabrication and evaluation of light-emitting SiO substrate co-implanted with Si and C ions

Kikuchi, Shusuke*; Umenyi, A. V.*; Inada, Kazuki*; Kawashima, Akihiro*; Noguchi, Katsuya*; Sasaki, Tomoyuki*; Miura, Kenta*; Hanaizumi, Osamu*; Yamamoto, Shunya; Kawaguchi, Kazuhiro; et al.

no journal, , 

Light emission around a wavelength () of 500 nm from SiO substrates implanted with Si and C ions and annealed at 1100C has been reported. In this report, we investigated photoluminescence (PL) properties of SiO substrates implanted with Si and C ions and annealed at the lower temperature of 700C. PL peaks by Si-ion implantation were observed around = 650 nm, and PL peaks by C-ion implantation were observed around = 450 nm from SiO substrates annealed at 700C. The PL peak wavelength became shorter by increasing the ratio of C to Si ions. Consequently, it was confirmed that it is possible to control the emission wavelength by the ratio of C to Si ions. Our samples showed typical light-emission though the annealing temperature was lower than the temperature reported by other groups.

Research and development on preceding processing methods for contaminated water management waste at Fukushima Daiichi Nuclear Power Station, 33; Effect of storage condition on alteration behavior of solidified body

Sato, Junya; Taniguchi, Takumi; Matsuzawa, Kazuki*; Kikuchi, Michio*; Yamamoto, Takeshi*; Kakuda, Ayaka; Sone, Tomoyuki; Osugi, Takeshi; Kuroki, Ryoichiro

no journal, , 

no abstracts in English