Horonobe Underground Research Laboratory Project Investigation report for the 2024 fiscal year

Nakayama, Masashi; Ishii, Eiichi; Aoyagi, Kazuhei; Hayano, Akira; Murakami, Hiroaki; Ono, Hirokazu; Takeda, Masaki; Fukatsu, Yuta; Mochizuki, Akihito; Ozaki, Yusuke; et al.

JAEA-Review 2025-042, 136 Pages, 2025/12

JAEA-Review-2025-042.pdf:12.95MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant technologies for geological disposal of high-level radioactive waste through investigating the deep geological environment within the host sedimentary rocks at Horonobe-cho in Hokkaido, north Japan. In the fiscal year 2024, we continued R&D on "Study on near-field system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behaviour of sedimentary rock to natural perturbations". These are identified as key R&D on challenges to be tackled in the Horonobe underground research plan for the fiscal year 2020 onwards. Specifically, "full-scale engineered barrier system (EBS) performance experiment" and "solute transport experiment with model testing" were carried out as part of "Study on near-field system performance in geological environment". "Demonstration of engineering feasibility of repository technology" and "evaluation of EBS behaviour over 100C" were addressed for "Demonstration of repository design options". The validation of a method for assessing permeability using the Ductility Index and a method for estimating the state of in-situ ground pressure from hydraulic perturbation tests were investigated as part of the study "Understanding of buffering behaviour of sedimentary rock to natural perturbations". In FY2024, we continued construction of the East Access Shaft and the Ventilation Shaft, and construction of these shafts were completed to a depth of 500 m. After the completion of the East Access Shaft, excavation of the West Access Shaft and 500 m gallery has began. As of the end of FY2024, excavation progress is as follows, the East Access Shaft and the Ventilation Shaft were 500 m depth, the West Access Shaft was 472 m depth, 500 m gallery was 112.9 m, respectively. In the Horonobe International Project (HIP), Management Board and Joint Task Meeting was held at the Horonobe URL in June 2024 to review the progress of construction of galleries and preparations of experiments. Task Meetings to review the implementation plan for in-situ testing and analysis were also held. HIP will be implemented in two phases: Phase 1 (from FY2022 to FY2024) and Phase 2 (from FY2025 to FY2028), the research results of Phase 1 were compiled in FY2024.

Horonobe Underground Research Laboratory Project; Investigation program for the fiscal year 2025

Nakayama, Masashi; Ishii, Eiichi; Hayano, Akira; Aoyagi, Kazuhei; Murakami, Hiroaki; Ono, Hirokazu; Takeda, Masaki; Mochizuki, Akihito; Ozaki, Yusuke; Kimura, Shun; et al.

JAEA-Review 2025-027, 80 Pages, 2025/09

JAEA-Review-2025-027.pdf:6.22MB

The Horonobe Underground Research Laboratory Project is being pursued by the Japan Atomic Energy Agency to enhance the reliability of relevant technologies for geological disposal of high-level radioactive waste through investigating the deep geological environment within the host sedimentary rocks at Horonobe Town in Hokkaido, north Japan. In the fiscal year 2025, we continue R&D on "Study on near-field system performance in geological environment" and "Demonstration of repository design options". These are identified as key R&D challenges to be tackled in the Horonobe underground research plan for the fiscal year 2020 onwards. In the "Study on near-field system performance in geological environment", we continue to obtain data from the full-scale engineered barrier system performance experiment, and work on the specifics of the full-scale engineered barrier system dismantling experiment. As for "Demonstration of repository design options", the investigation, design, and evaluation techniques are to be systemized at various scales, from the tunnel to the pit, by means of an organized set of evaluation methodologies for confinement performance at these respective scales. Preliminary borehole investigations will be conducted within a 500 m gallery, with the objectives of obtaining rock strength and rock permeability data, as well as surveying the extent of the excavation damaged zone surrounding the test tunnel via tomographic analysis. A planning study for the in-situ construction test will be conducted to investigate the construction of backfill material and watertight plugs. The volume of water inflow associated with the excavation of the 500 m gallery will be observed, and its magnitude will be compared with the range of water inflow predicted in the analysis. The test plan to determine the extent of the excavation damaged zone around the pit, which is planned to be constructed in the 500 m gallery, will be studied to determine the in-situ excavation damaged zone. In addition, the investigation and evaluation methods for the amount of water inflow from fractures and the extent of the excavation damaged zone around the pit will be organized. Concerning the construction and maintenance of the subsurface facilities, excavation of the West Access Shaft and the 500 m gallery will continue. It is anticipated that the construction of the facilities will be completed by the end of the fiscal year 2025. In addition, we continue R&D on the following three tasks in the Horonobe International Project; Task A: Solute transport experiment with model testing, Task B: Systematic integration of repository technology options, and Task C: Full-scale engineered barrier system dismantling experiment.

Level structures of Ca cast doubt on a doubly magic Ca

Chen, S.*; Browne, F.*; Doornenbal, P.*; Lee, J.*; Obertelli, A.*; Tsunoda, Yusuke*; Otsuka, Takaharu*; Chazono, Yoshiki*; Hagen, G.*; Holt, J. D.*; et al.

Physics Letters B, 843, p.138025_1 - 138025_7, 2023/08

https://doi.org/10.1016/j.physletb.2023.138025

Gamma decays were observed in Ca and Ca following quasi-free one-proton knockout reactions from Sc. For Ca, a ray transition was measured to be 1456(12) keV, while for Ca an indication for a transition was observed at 1115(34) keV. Both transitions were tentatively assigned as the decays. A shell-model calculation in a wide model space with a marginally modified effective nucleon-nucleon interaction depicts excellent agreement with experiment for level energies, two-neutron separation energies, and reaction cross sections, corroborating the formation of a new nuclear shell above the N = 34 shell. Its constituents, the and orbitals, are almost degenerate. This degeneracy precludes the possibility for a doubly magic Ca and potentially drives the dripline of Ca isotopes to Ca or even beyond.

An Automotive intelligent catalyst that contributes to hydrogen safety for the Decommissioning of Fukushima Daiichi Nuclear Power Station (1FD)

Tanaka, Hirohisa*; Masaki, Sayaka*; Aotani, Takuro*; Inagawa, Kohei*; Iwata, Sogo*; Aida, Tatsuya*; Yamamoto, Tadasuke*; Kita, Tomoaki*; Ono, Hitomi*; Takenaka, Keisuke*; et al.

SAE Technical Paper 2022-01-0534 (Internet), 10 Pages, 2022/03

https://doi.org/10.4271/2022-01-0534

Interim activity status report of "the group for investigation of reasonable safety assurance based on graded approach" (from September, 2019 to September, 2020)

Yonomoto, Taisuke; Nakashima, Hiroshi*; Sono, Hiroki; Kishimoto, Katsumi; Izawa, Kazuhiko; Kinase, Masami; Osa, Akihiko; Ogawa, Kazuhiko; Horiguchi, Hironori; Inoi, Hiroyuki; et al.

JAEA-Review 2020-056, 51 Pages, 2021/03

JAEA-Review-2020-056.pdf:3.26MB

A group named as "The group for investigation of reasonable safety assurance based on graded approach", which consists of about 10 staffs from Sector of Nuclear Science Research, Safety and Nuclear Security Administration Department, departments for management of nuclear facility, Sector of Nuclear Safety Research and Emergency Preparedness, aims to realize effective graded approach (GA) about management of facilities and regulatory compliance of JAEA. The group started its activities in September, 2019 and has had discussions through 10 meetings and email communications. In the meetings, basic ideas of GA, status of compliance with new regulatory standards at each facility, new inspection system, etc were discussed, while individual investigation at each facility were shared among the members. This report is compiled with expectation that it will help promote rational and effective safety management based on GA by sharing contents of the activity widely inside and outside JAEA.

Work robot (for valves opening/closing) operation manual

Chiba, Yusuke; Nishiyama, Yutaka; Tsubaki, Hirohiko; Iwai, Masaki; Ono, Hayato*; Hayasaka, Toshiro*

JAEA-Testing 2020-006, 24 Pages, 2021/02

JAEA-Testing-2020-006.pdf:3.35MB

Maintenance and Operation Section for Remote Control Equipment in Naraha Center for Remote Control Technology Development was the main part of the nuclear emergency response team of JAEA in full-scale operation starts on the 1st of April, 2020. In this section, we need to develop equipment for a JAEA nuclear emergency. To support full- scale operation, we have created a work robot for opening and closing doors, a work robot for opening and closing valves, and a reconnaissance robot for measuring radiation dose. This report describes how to operate a work robot (opening and closing valves).

Quasifree neutron knockout reaction reveals a small -Orbital component in the Borromean nucleus B

Yang, Z. H.*; Kubota, Yuki*; Corsi, A.*; Yoshida, Kazuki; Sun, X.-X.*; Li, J. G.*; Kimura, Masaaki*; Michel, N.*; Ogata, Kazuyuki*; Yuan, C. X.*; et al.

Physical Review Letters, 126(8), p.082501_1 - 082501_8, 2021/02

AA2020-0819.pdf:1.29MB

https://doi.org/10.1103/PhysRevLett.126.082501

A quasifree (,) experiment was performed to study the structure of the Borromean nucleus B, which had long been considered to have a neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for and orbitals, and a surprisingly small percentage of 9(2)% was determined for . Our finding of such a small component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in B. The present work gives the smallest - or -orbital component among known nuclei exhibiting halo features and implies that the dominant occupation of or orbitals is not a prerequisite for the occurrence of a neutron halo.

Insight into Kondo screening in the intermediate-valence compound SmOsSb uncovered by soft X-ray magnetic circular dichroism

Saito, Yuji; Fujiwara, Hidenori*; Yasui, Akira*; Kadono, Toshiharu*; Sugawara, Hitoshi*; Kikuchi, Daisuke*; Sato, Hideyuki*; Suga, Shigemasa*; Yamasaki, Atsushi*; Sekiyama, Akira*; et al.

Physical Review B, 102(16), p.165152_1 - 165152_8, 2020/10

https://doi.org/10.1103/PhysRevB.102.165152

Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone

Hirahara, Toru*; Otrokov, M. M.*; Sasaki, Taisuke*; Sumida, Kazuki*; Tomohiro, Yuta*; Kusaka, Shotaro*; Okuyama, Yuma*; Ichinokura, Satoru*; Kobayashi, Masaki*; Takeda, Yukiharu; et al.

Nature Communications (Internet), 11, p.4821_1 - 4821_8, 2020/09

https://doi.org/10.1038/s41467-020-18645-9

Spallation and fragmentation cross sections for 168 MeV/nucleon Xe ions on proton, deuteron, and carbon targets

Sun, X. H.*; Wang, H.*; Otsu, Hideaki*; Sakurai, Hiroyoshi*; Ahn, D. S.*; Aikawa, Masayuki*; Fukuda, Naoki*; Isobe, Tadaaki*; Kawakami, Shunsuke*; Koyama, Shumpei*; et al.

Physical Review C, 101(6), p.064623_1 - 064623_12, 2020/06

https://doi.org/10.1103/PhysRevC.101.064623

The spallation and fragmentation reactions of Xe induced by proton, deuteron and carbon at 168 MeV/nucleon were studied at RIKEN Radioactive Isotope Beam Factory via the inverse kinematics technique. The cross sections of the lighter products are larger in the carbon-induced reactions due to the higher total kinetic energy of carbon. The energy dependence was investigated by comparing the newly obtained data with previous results obtained at higher reaction energies. The experimental data were compared with the results of SPACS, EPAX, PHITS and DEURACS calculations. These data serve as benchmarks for the model calculations.