Comprehensive increase in CO release by drying-rewetting cycles among Japanese forests and pastureland soils and exploring predictors of increasing magnitude

Suzuki, Yuri*; Hiradate, Shuntaro*; Koarashi, Jun; Atarashi-Andoh, Mariko; Yomogida, Takumi; Kanda, Yuki*; Nagano, Hirohiko*

Soil (Internet), 11(1), p.35 - 49, 2025/01

https://doi.org/10.5194/soil-11-35-2025

Biofilm formation on excavation damaged zone fractures in deep neogene sedimentary rock

Hirota, Akinari*; Kozuka, Mariko*; Fukuda, Akari*; Miyakawa, Kazuya; Sakuma, Keisuke; Ozaki, Yusuke; Ishii, Eiichi; Suzuki, Yohei*

Microbial Ecology, 87, p.132_1 - 132_15, 2024/10

https://doi.org/10.1007/s00248-024-02451-7

Deep underground galleries are used to access the deep biosphere in addition to mining and other engineering applications such as geological disposal of radioactive wastes. Fracture networks developed in the excavation damaged zone (EDZ) are concerned to accelerate mass transport, where microbial colonization might be possible due to the availability of space and nutrients. In this study, microbial biofilms at EDZ fractures were investigated by drilling from a 350-m deep gallery and subsequent borehole logging at the Horonobe underground research laboratory (URL). By using microscopic and spectroscopic techniques, the dense colonization of microbial cells was demonstrated at the surfaces of the EDZ fractures with high hydraulic conductivities. 16S rRNA gene sequence analysis revealed the dominance of gammaproteobacterial lineages, the cultivated members of which are aerobic methanotrophs. Near-complete Horonobe groundwater genomes affiliated within the methanotrophic lineages were fully equipped with genes involved in aerobic methanotrophy. Although the mediation of aerobic methanotrophy remains to be demonstrated, microbial O production was supported by the presence of genes in the near-complete genomes, such as catalase and superoxide dismutase that produce O from reactive oxygen species and a nitric oxide reductase gene with the substitutions of amino acids in motifs. It is concluded that the EDZ fractures provide energetically favorable subsurface habitats to microorganisms.

Flexible waste management system for the future application of MA P&T technology to the current high-level liquid waste

Fukasawa, Tetsuo*; Suzuki, Akihiro*; Endo, Yoichi*; Inagaki, Yaohiro*; Arima, Tatsumi*; Muroya, Yusa*; Endo, Keita*; Watanabe, Daisuke*; Matsumura, Tatsuro; Ishii, Katsunori; et al.

Journal of Nuclear Science and Technology, 61(3), p.307 - 317, 2024/03

https://doi.org/10.1080/00223131.2023.2226673

A flexible waste management system (FWM) is being developed to apply future MA partitioning and transmutation (P&T) technology to current HLLW. This FWM system will store high-level waste (HLLW) in granular form until MA partitioning and transmutation technology is realized. The feasibility of the main process was essentially confirmed by basic experiments and preliminary thermal analysis for granule production by rotary kiln from simulated HLLW and for temporary storage (50 years) of HLW granules at the HLW storage facility, respectively. The granule production experiments revealed that relatively large particles can be produced by the rotary kiln. The results of the thermal analysis showed that the small diameter canisters could be used to safely store the granules at a higher storage density than vitrified HLW. The effectiveness of the FWM system in terms of potential radiotoxicity and repository area was also evaluated, and it was shown that FWM can reduce these factors and has significant advantages in the disposal of HLW generated in current reprocessing plants. Since LWR fuel is stored for a long period of time in Japan and the operation of a reprocessing plant is expected to start soon, the FWM system is considered to be an effective system for reducing the environmental burden of HLW disposal.

Japan Atomic Energy Agency; Contribution to the decommissioning of the Fukushima Daiichi Nuclear Power Station and the reconstruction of Fukushima Prefecture at the Naraha center for Remote Control technology development

Morimoto, Kyoichi; Ono, Takahiro; Kakutani, Satomi; Yoshida, Moeka; Suzuki, Soichiro

Journal of Robotics and Mechatronics, 36(1), p.125 - 133, 2024/02

https://doi.org/10.20965/jrm.2024.p0125

The Naraha Center for Remote Control Technology Development was established for the purpose of developing and verifying remote control equipment for promoting the decommissioning of the Fukushima Daiichi Nuclear Power Station and the external use of this center was started in 2016. The mission of this center is to contribute to the decommissioning of the Fukushima Daiichi Nuclear Power Station and for the reconstruction of Fukushima Prefecture. In this review, we describe the equipment related to the full-scale mock-up test, the component test for a remote-control device and the virtual reality system in this center. In addition, the case examples for usage of these equipment are introduced.

Validation of the Be ground-state molecular structure using Be()He triple differential reaction cross-section measurements

Li, P. J.*; Beaumel, D.*; Lee, J.*; Assi, M.*; Chen, S.*; Franchoo, S.*; Gibelin, J.*; Hammache, F.*; Harada, T.*; Kanada-En'yo, Yoshiko*; et al.

Physical Review Letters, 131(21), p.212501_1 - 212501_7, 2023/11

https://doi.org/10.1103/PhysRevLett.131.212501

The cluster structure of the neutron-rich isotope Be has been probed via the () reaction. The triple differential cross-section was extracted and compared to distorted-wave impulse approximation reaction calculations performed in a microscopic framework using the Tohsaki-Horiuchi-Schuck-Rpke wave function and the wave function deduced from Antisymmetrized Molecular Dynamics calculations. The remarkable agreement between calculated and measured cross-sections in both shape and magnitude validates the description of the Be ground-state as a rather compact nuclear molecule.

Acquisition of saltwater infiltration behavior data in unsaturated compacted bentonite

Sato, Hisashi*; Takayama, Yusuke; Suzuki, Hideaki*; Sato, Daisuke*

JAEA-Data/Code 2023-010, 47 Pages, 2023/09

JAEA-Data-Code-2023-010.pdf:1.45MB

When a high-level radioactive waste repository is constructed in a coastal area, it is necessary to fully evaluate the impact of seawater-based groundwater on engineered barriers, including buffer materials. In this report, one-dimensional saltwater infiltration tests were conducted to obtain data to understand the impact of seawater-based groundwater on the migration phenomena of water and solutes in the buffer material during the transient period. As a result, it was confirmed that the infiltration rate increased as the NaCl concentration in the infiltration solution increased. And it was confirmed that the water content ratio distribution changed as the NaCl concentration in the infiltration solution increased. As a result of analysis of the chloride ion concentration of the post-test specimens confirmed that chloride ion enrichment was occurred with infiltration. As a result of verifying the mechanism by which chloride ion enrichment occurs, it was confirmed that the phenomenon of chloride ion enrichment due to infiltration depends on the initial water content ratio.

Assessment of the infiltration behaviour of buffer material in seawater-type groundwater environments using a coupled THMC analysis model (Contract research)

Suzuki, Hideaki*; Takayama, Yusuke; Sato, Hisashi*; Watahiki, Takanori*; Sato, Daisuke*

JAEA-Research 2022-013, 41 Pages, 2023/03

JAEA-Research-2022-013.pdf:3.99MB

It is anticipated that the coupled thermal-hydraulic-mechanical and chemical (THMC) processes will occur, involving an interactive process with radioactive decay heat arising from the vitrified waste, infiltration of groundwater from the host rock into the buffer material, swelling pressure of buffer material due to its saturation and chemical reaction between bentonite and pore-water in the near-field of a geological disposal system for high-level radioactive waste repository. In order to evaluate these phenomena in the near-field, the THMC model has been developed. In this study, For the purpose of evaluating the near-field infiltration behavior in seawater-type groundwater environment, a hydraulic model was set in which the permeability of the buffer material change depending on the salt concentration in the pore-water. In order to evaluate the drying phenomenon of the buffer material due to waste heat, a temperature gradient water transfer model was set in consideration of the dependence of temperature and pore-water saturation. The THMC analysis of the in-situ experiment of engineered barrier system (EBS) experiment at the Horonobe Underground Research Laboratory was carried out. The validity of the model was then checked through comparison with measured data.

Mechanical properties of pure tungsten and tantalum irradiated by protons and neutrons at the Swiss spallation-neutron source

Saito, Shigeru; Suzuki, Kazuhiro; Obata, Hiroki; Dai, Y.*

Nuclear Materials and Energy (Internet), 34, p.101338_1 - 101338_9, 2023/03

https://doi.org/10.1016/j.nme.2022.101338

In this study, a post-irradiation examination of pure tungsten (W) and tantalum (Ta) specimens irradiated at the Swiss Spallation-Neutron Source is conducted. W is used as a potential candidate for a solid spallation-target material owing to its favorable properties. However, W also suffers from several disadvantages such as poor corrosion resistance to water coolant and irradiation embrittlement. To improve these properties, cladding technologies using Ta for W alloys have been developed. In the present study, we investigated the irradiation effects on two tungsten materials, poly-crystal W (W-Poly) and single-crystal W (W-Sin), along with pure polycrystalline Ta. The tensile-test results revealed that W-Poly exhibited almost no ductility after irradiation of 10.2-35.0 dpa. W-Sin was irradiated up to 10.2 dpa and demonstrated 6% of total elongation (TE). With regard to Ta, TE decreased based on the increase in irradiation, reaching almost zero at doses of more than 10.3 dpa.

Radiation exposure and oxidative stress status of wild Japanese macaques in the ex-evacuation zone of the Fukushima Daiichi Nuclear Power Plant accident

Ishikawa, Ryoya*; Suzuki, Masatoshi*; Kino, Yasushi*; Endo, Satoru*; Nakajima, Hiroo*; Oka, Toshitaka; Takahashi, Atsushi*; Shimizu, Yoshinaka*; Suzuki, Toshihiko*; Shinoda, Hisashi*; et al.

KEK Proceedings 2022-2, p.61 - 66, 2022/11

The balance between oxidative stress and antioxidant activity, which is a defense mechanism against oxidative stress, was investigated in the liver and bladder of wild Japanese macaques captured in Fukushima Prefecture. No significant induction of oxidative stress by exposure to environmental radionuclides after the Fukushima nuclear accident was observed, suggesting that the stress defense mechanism of the organism is activated in some organs.

Temporal variability of Cs concentrations in coastal sediments off Fukushima

Suzuki, Shotaro*; Amano, Yosuke*; Enomoto, Masahiro*; Matsumoto, Akira*; Morioka, Yoshiaki*; Sakuma, Kazuyuki; Tsuruta, Tadahiko; Kaeriyama, Hideki*; Miura, Hikaru*; Tsumune, Daisuke*; et al.

Science of the Total Environment, 831, p.154670_1 - 154670_15, 2022/07

https://doi.org/10.1016/j.scitotenv.2022.154670