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.

Study of the spin-memory effect with low-energy gamma-rays in Hf(n,)Hf reaction measurement

Kawamura, Shiori*; Endo, Shunsuke; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kimura, Atsushi; Kitaguchi, Masaaki*; Nakamura, Shoji; Okudaira, Takuya*; Rovira Leveroni, G.; Shimizu, Hirohiko*; et al.

EPJ Web of Conferences, 329, p.05002_1 - 05002_3, 2025/06

https://doi.org/10.1051/epjconf/202532905002

no abstracts in English

Neutron capture cross-section measurement at TC-Pn in KUR for holmium among nuclides in decommissioning

Nakamura, Shoji; Endo, Shunsuke; Rovira Leveroni, G.; Kimura, Atsushi; Shibahara, Yuji*

KURNS Progress Report 2024, P. 31, 2025/06

no abstracts in English

Transverse asymmetry of individual rays in the La()La reaction

Okuizumi, Mao*; Auton, C. J.*; Endo, Shunsuke; Fujioka, Hiroyuki*; Hirota, Katsuya*; Ino, Takashi*; Ishizaki, Kohei*; Kimura, Atsushi; Kitaguchi, Masaaki*; Koga, Jun*; et al.

Physical Review C, 111(3), p.034611_1 - 034611_6, 2025/03

https://doi.org/10.1103/PhysRevC.111.034611

Measurements of neutron capture cross-section for nuclides of interest in decommissioning (III); Er(n,)Er and Hf(n,)Hf reactions

Nakamura, Shoji; Shibahara, Yuji*; Endo, Shunsuke; Rovira Leveroni, G.; Kimura, Atsushi

Journal of Nuclear Science and Technology, 14 Pages, 2025/00

https://doi.org/10.1080/00223131.2025.2457589

Variation of electrical resistivity distribution around the opened and backfilled tunnel in the Horonobe Underground Research Laboratory

Ozaki, Yusuke; Aoyagi, Kazuhei; Ono, Hirokazu; Kimura, Shun

Proceedings of 4th International Conference on Coupled Processes in Fractured Geological Media; Observation, Modeling, and Application (CouFrac2024) (Internet), 10 Pages, 2024/11

Electrical resistivity tomography was repeatedly carried out to investigate the changes of the electrical resistivity distribution around 350m Niche No. 2 and No. 4 in the Horonobe Underground Research Laboratory. The electrical resistivity around Niche No. 2 did not change so much after the high resistive zone appeared around the tunnel by the excavation under opened condition during the studied period. Around Niche No. 4, the electrical resistivity was investigated under closed condition by engineered barrier system (EBS) where the EBS and surrounding rocks were disturbed artificially by water injection and heating. Our results could capture the change in the distribution of electrical resistivity due to the artificial disturbances in and around of Niche No. 4. These results would help us to understand the time lapse behavior of excavation damaged zone and re-saturation process in and around the EBS from the construction to the closure.

Circular polarization measurement for individual gamma rays in capture reactions with intense pulsed neutrons

Endo, Shunsuke; Abe, Ryota*; Fujioka, Hiroyuki*; Ino, Takashi*; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kawamura, Shiori*; Kimura, Atsushi; Kitaguchi, Masaaki*; Kobayashi, Ryuju*; et al.

European Physical Journal A, 60(8), p.166_1 - 166_10, 2024/08

https://doi.org/10.1140/epja/s10050-024-01392-6

A Study of evaluation method for buffer material erosion in vertical in-hole emplacement

Kikuchi, Hirohito*; Uda, Toshiaki*; Hayashi, Daisuke*; Emori, Minoru*; Kimura, Shun

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 31(1), p.11 - 20, 2024/06

https://doi.org/10.3327/jnuce.31.1_11

no abstracts in English

Microstructures and hardness of BCC phase iron-based high entropy alloy Fe-Mn-Cr-V-Al-C

Wakai, Eiichi; Noto, Hiroyuki*; Shibayama, Tamaki*; Furuya, Kazuyuki*; Ando, Masami*; Kamada, Takaharu*; Ishida, Taku*; Makimura, Shunsuke*

Materials Characterization, 211, p.113881_1 - 113881_10, 2024/05

https://doi.org/10.1016/j.matchar.2024.113881

The microstructures and mechanical properties of bcc iron-based high entropy alloy (HEA) Fe-20Mn-15Cr-10V-10Al-2.5C (in at%) without Co and Ni elements have been investigated for applications in fields such as accelerator-target system, nuclear reactors and magnetic motors in aircraft and automobiles. This alloy was normalized at 1150C for 2 hr and then water quenched, and it was heated at 800C for 10 min and then water quenched. The alloy had a bcc-phase and vanadium carbides with 2-3 m arranging along grain boundaries, and the Vickers hardness was 520 Hv, harder than pure tungsten. Magnetic domain structure was observed in phase differential contrast method in scanning transmission electron microscope, and the micro-size magnetic domains in grain and sub micro size ones were formed near surface, and it is attractive to the magnetic motor field application. Element distribution in nano scale (20 nm) was observed in matrix, and the presence of crystal lattice disorder in the atomic level region was seen. Very high performance for radiation resistance was confirmed with no irradiation hardening at 300 and 500 C to 1 dpa. It can be speculated that this is due to irradiation-induced nanoscale concentration changes and strain relaxation in the HEA. These properties are very attractive in application of several fields.

Am neutron capture cross section measurement using the NaI(Tl) spectrometer of the ANNRI beamline of J-PARC

Rovira Leveroni, G.; Kimura, Atsushi; Nakamura, Shoji; Endo, Shunsuke; Iwamoto, Osamu; Iwamoto, Nobuyuki; Katabuchi, Tatsuya*; Kodama, Yu*; Nakano, Hideto*; Sato, Yaoki*

Journal of Nuclear Science and Technology, 61(4), p.459 - 477, 2024/04

https://doi.org/10.1080/00223131.2023.2239885