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Asamori, Koichi; Sueoka, Shigeru; Komatsu, Tetsuya; Ogata, Manabu; Uchida, Mao; Nishiyama, Nariaki; Tanaka, Kiriha; Kobayashi, Tomoharu; Mitsuguchi, Takehiro; Murakami, Osamu; et al.
JAEA-Review 2025-035, 29 Pages, 2025/10
JAEA-Review-2025-035.pdf:1.12MB
This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency (JAEA), in fiscal year 2025. The objectives and contents of this research are described in detail based on the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques.
Asamori, Koichi; Sueoka, Shigeru; Kobayashi, Tomoharu; Nishiyama, Nariaki; Tanaka, Kiriha; Murakami, Osamu; Fukuda, Shoma; Ogata, Manabu; Uchida, Mao; Komatsu, Tetsuya; et al.
JAEA-Research 2025-007, 99 Pages, 2025/10
JAEA-Research-2025-007.pdf:12.36MB
This annual report documents the progress of research and development (R&D) in the 3rd fiscal year of the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028) to provide the scientific base for assessing geosphere stability for long-term isolation of high-level radioactive waste. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. The current status of R&D activities with previous scientific and technological progress is summarized.
Itayama, Yui*; Davaasuren, D.*; Ochiai, Shinya*; Minami, Masayo*; Masuki, Yuma*; Yoshimizu, Chikage*; Uchida, Mao; Niwa, Masakazu; Tayasu, Ichiro*; Nagao, Seiya*; et al.
Catena, 258, p.109297_1 - 109297_11, 2025/10
Times Cited Count：0 Percentile：0.00(Geosciences, Multidisciplinary)Niwa, Masakazu; Shimada, Akiomi; Asamori, Koichi; Sueoka, Shigeru; Komatsu, Tetsuya; Nakajima, Toru; Ogata, Manabu; Uchida, Mao; Nishiyama, Nariaki; Tanaka, Kiriha; et al.
JAEA-Review 2024-035, 29 Pages, 2024/09
JAEA-Review-2024-035.pdf:1.24MB
This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency (JAEA), in fiscal year 2024. The objectives and contents of this research are described in detail based on the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques.
Uchida, Mao*; Alzahrani, H.*; Shiono, Mikihito*; Sakai, Takaaki*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 16 Pages, 2022/03
Gas entrainment from cover gas is one of key issues for sodium-cooled fast reactors design to prevent unexpected effects to core reactivity. A vortex model based evaluation method has been developed to evaluate the surface vortex gas core growth at the free surface in the reactor vessel. In this study, water experiments were performed to clarify the prediction accuracy for the vortex gas core growth during the vortex drift motion using a circulating water tunnel with an open flow channel test section. Gas core growth were predicted by applying the evaluation method to the numerical analyses performed in the same geometry of the experiments, and compared with the experimental results. It was observed the gas core growth became large at downstream region where downward velocity became large in experiment. However, the gas core length which were predicted from numerical result showed a discrepancy with the experimental result on the peak position and an overestimation of peak value.
Uchida, Mao*; Sakai, Takaaki*; Ezure, Toshiki; Tanaka, Masaaki
Mechanical Engineering Journal (Internet), 8(4), p.21-00161_1 - 21-00161_11, 2021/08
An evaluation method based on numerical analyses has been developed to predict occurrences gas entrainment phenomena at a free surface in a sodium-cooled fast reactor. In this study, experiments were conducted for gas entrainments due to drifting free surface vortexes observed in a circulating water tunnel geometry. Numerical analyses were also conducted in the same geometry using a computational fluid dynamics (CFD) code. Then, Strouhal numbers of vortex frequency and detailed flow velocity profiles were compared between experimental results and numerical results to clarify the evaluation accuracy of CFD calculation. As the results, the Strouhal numbers of the vortex frequency obtained from numerical analyses showed good agreement with the experimental data.
Matsushita, Kentaro; Fujisaki, Tatsuya*; Ezure, Toshiki; Tanaka, Masaaki; Uchida, Mao*; Sakai, Takaaki*
Keisan Kogaku Koenkai Rombunshu (CD-ROM), 26, 6 Pages, 2021/05
For the gas entrainment vortex at the free surface in sodium-cooled fast reactors, development of the numerical analysis method to evaluate amount of the gas entrainment from the free surface has been developing. In this paper, the automatic creation of analysis meshes which can suppress the calculation cost while maintaining the prediction accuracy of the vortex shape is investigated, and the adaptive mesh refinement (AMR) method is examined to the creation of analysis mesh applying to the unsteady vortex system. The refined mesh based on the criterion evaluated by vorticity, Q-value as second invariant of the velocity and the discriminant for the eigen equation of the velocity gradient tensor is considered, and it found that the AMR method based on Q-value can refine the analysis meshes most efficiently.
Uchida, Mao*; Hirakawa, Moe*; Sano, Aaru*; Inoue, Keisuke*; Sakai, Takaaki*; Ezure, Toshiki; Tanaka, Masaaki
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 7 Pages, 2020/08
Numerical analysis using CFD code for rectangular open channel experiments has been carried out to development an evaluation method for gas entrainment phenomena at free surface of a sodium-cooled fast reactor. From the point of validation of the evaluation method, Strouhal number of vortex frequency and velocity distributions obtained from the numerical analyses were compared with experimental results. As the results, the Strouhal number of the vortex frequency behind the plate obstacle and the velocity distributions reasonably agreed with experimental results.
collisions at 
= 200 GeVAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07
Times Cited Count：35 Percentile：75.74(Astronomy & Astrophysics)We report on the event structure and double helicity asymmetry (
) of jet production in longitudinally polarized collisions at = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured = -0.0014 
0.0037 at the lowest 
bin and -0.0181 0.0282 at the highest bin. The measured is compared with the predictions that assume various 
distributions.
collisions at = 200 and 62.4 GeVAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06
Times Cited Count：197 Percentile：99.35(Physics, Nuclear)Transverse momentum distributions and yields for 
, and 
in collisions at = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different collisions. We also present the scaling properties such as 
and 
scaling and discuss the mechanism of the particle production in collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.
and Au+Au collisions at 
= 200 GeVAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.
Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04
Times Cited Count：9 Percentile：50.62(Physics, Nuclear)Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to collisions.
+ collisions at = 200 GeV and scaling properties of hadron productionAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03
Times Cited Count：188 Percentile：98.33(Astronomy & Astrophysics)The PHENIX experiment at RHIC has measured the invariant differential cross section for production of 
, 
, 
and 
mesons in collisions at = 200 GeV. The spectral shapes of all hadron transverse momentum distributions are well described by a Tsallis distribution functional form with only two parameters, 
and 
, determining the high 
and characterizing the low regions for the spectra, respectively. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.
Uchida, Mao; Nishiyama, Nariaki; Ogata, Manabu; Komatsu, Tetsuya; Tsukahara, Yuzuko; Ishihara, Takanori; Kawamura, Makoto; Nakanishi, Toshimichi*; Terada, Tatsuya*; Hosoya, Takashi*
no journal, ,
no abstracts in English
Uchida, Mao*; Hirakawa, Moe*; Inoue, Keisuke*; Sano, Aaru*; Sakai, Takaaki*; Ezure, Toshiki; Tanaka, Masaaki
no journal, ,
Visualization measurements using a high-speed camera and numerical analyses were carried out for gas entrainment phenomenon due to free surface drifting vortices in an open rectangular channel. The applicability of gas core length based on numerical analyses was confirmed for drifting vortices in the open channel through the comparison with experimental results.
Uchida, Mao; Nishiyama, Nariaki; Ogata, Manabu; Komatsu, Tetsuya; Tsukahara, Yuzuko; Ishihara, Takanori; Kawamura, Makoto; Nakanishi, Toshimichi*; Terada, Tatsuya*; Hosoya, Takashi*
no journal, ,
no abstracts in English
Terada, Tatsuya*; Nishiyama, Nariaki; Komatsu, Tetsuya; Uchida, Mao; Ogata, Manabu; Ishihara, Takanori; Kawamura, Makoto; Nakanishi, Toshimichi*
no journal, ,
no abstracts in English
Ogata, Manabu; Nishiyama, Nariaki; Matsushi, Yuki*; Uchida, Mao; Komatsu, Tetsuya; Sueoka, Shigeru
no journal, ,
Optically stimulated luminescence (OSL) dating of feldspar is one of the most promising methods for determining the emergence ages of Middle-Late Pleistocene marine terraces on account of the following reasons: (1) feldspar is ubiquitous in Quaternary sediments; (2) the applicable dating range extends from several thousand to several hundred thousand years; and (3) the OSL signal is reset during sediment transport and exposure to sunlight, and is therefore capable of constraining burial (depositional) ages. Previous studies have demonstrated the application of feldspar OSL dating to Japanese marine terraces by cross-checking with the known tephrochronological framework. However, there are still few examples, and thus the accumulation of the case studies is required to improve the reliability. In this presentation, we will present the results of feldspar OSL dating of MIS 5c marine terrace sediments in Suzu, Noto Peninsula.
Ogata, Manabu; Tsukahara, Yuzuko; Nishiyama, Nariaki; Komatsu, Tetsuya; Uchida, Mao; Kawamura, Makoto; Ishihara, Takanori; Nakanishi, Toshimichi*
no journal, ,
Terrace to terrace (TT) method is mainly used for estimating uplift rate on mountain areas of Japan on 10
-year time scale. However, this method cannot be applied to the area with poor distribution of fluvial terraces. In such area, the method based on the emergence ages of the fluvial landform, e.g., an abandoned river valley around a cutoff spur, and the relative elevation between old and present reiver bed is expected instead of TT method. This method calculates the river-incision rate by dividing the relative elevation by the emergence age. The river-incision rate is equal to the uplift rate if the river is at equilibrium (graded stream). We are investigating the fluvial landform in the Oi River basin for verifying this method. In this presentation, we will present the incision and uplift rate estimated by feldspar OSL dating results.
Sueoka, Shigeru; Komatsu, Tetsuya; Ogata, Manabu; Fukuda, Shoma; Nakajima, Toru; Nishiyama, Nariaki; Tsukahara, Yuzuko; Uchida, Mao; Kawamura, Makoto
no journal, ,
no abstracts in English
Uchida, Mao; Ogata, Manabu; Komatsu, Tetsuya; Nishiyama, Nariaki; Nara, Fumiko; Kida, Fukuka; Ogita, Yasuhiro; Nakanishi, Toshimichi*
no journal, ,
no abstracts in English
