Hydrogen embrittlement and its prevention in 7XXX aluminum alloys with high Zn concentrations

Shimizu, Kazuyuki*; Toda, Hiroyuki*; Fujihara, Hiro*; Yamaguchi, Masatake; Uesugi, Masayuki*; Takeuchi, Akihisa*; Nishijima, Masahiko*; Kamada, Yasuhiro*

Corrosion, 79(8), p.818 - 830, 2023/08

https://doi.org/10.5006/4300

7xxx aluminum alloys are representative high-strength aluminum alloys; however, mechanical property degradation due to hydrogen hinders further strengthening. We propose the dispersion of Mn-based second-phase particles as a novel technique for preventing 7xxx aluminum alloy hydrogen embrittlement. In this study, the deformation and fracture behaviors of high hydrogen 7xxx alloys containing 0.0% Mn and 0.6% Mn are observed in situ using synchrotron radiation X-ray tomography. The obtained macroscopic hydrogen embrittlement is quantitatively analyzed based on hydrogen partitioning in alloys. Adding 0.6% Mn, generating second-phase particles with high hydrogen trapping abilities, significantly suppresses hydrogen-induced quasicleavage fracture.

Reports on research activities and evaluation of advanced computational science in FY2022

Center for Computational Science & e-Systems

JAEA-Evaluation 2023-001, 38 Pages, 2023/07

JAEA-Evaluation-2023-001.pdf:1.04MB

Research on advanced computational science for nuclear applications, based on "the plan to achieve the medium- and long-term goal of the Japan Atomic Energy Agency", has been performed by Center for Computational Science & e-Systems (CCSE), Japan Atomic Energy Agency. CCSE established a committee consisting of external experts and authorities which evaluates and advises toward the future research and development. This report summarizes the results of the R&D performed by CCSE in FY2022 (April 1st, 2022 - March 31st, 2023) and their evaluation by the committee.

Virtualized environment construction work report for electronic approval system

Yamaguchi, Ryo

JAEA-Testing 2023-001, 53 Pages, 2023/05

JAEA-Testing-2023-001.pdf:5.16MB

The electronic approval system, which is one of the common business infrastructures of the Japan Atomic Energy Agency, needed to migrate to a server environment with high scalability and fault tolerance in order to respond to the increased demand for electronic approval due to the COVID-19 pandemic and the future expansion of electronic approval. Therefore, a new virtualized environment with excellent scalability and fault tolerance was constructed as the migration destination server environment. This report describes the procedure for construction a virtualized environment for an electronic approval system, and summarizes the knowledge obtained in the process of construction in a format that even beginners of virtualized environment and server construction can understand.

Parameter optimization for urban wind simulation using ensemble Kalman filter

Onodera, Naoyuki; Idomura, Yasuhiro; Hasegawa, Yuta; Asahi, Yuichi; Inagaki, Atsushi*; Shimose, Kenichi*; Hirano, Kohin*

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 28, 4 Pages, 2023/05

We have developed a multi-scale wind simulation code named CityLBM that can resolve entire cities to detailed streets. CityLBM enables a real time ensemble simulation for several km square area by applying the locally mesh-refined lattice Boltzmann method on GPU supercomputers. On the other hand, real-world wind simulations contain complex boundary conditions that cannot be modeled, so data assimilation techniques are needed to reflect observed data in the simulation. This study proposes an optimization method for ground surface temperature bias based on an ensemble Kalman filter to reproduce wind conditions within urban city blocks. As a verification of CityLBM, an Observing System Simulation Experiment (OSSE) is conducted for the central Tokyo area to estimate boundary conditions from observed near-surface temperature values.

Estimation of temporal variation of tritium inventory discharged from the port of Fukushima Dai-ichi Nuclear Power Plant; Analysis of the temporal variation and comparison with released tritium inventories from Japan and world major nuclear facilities

Machida, Masahiko; Iwata, Ayako; Yamada, Susumu; Otosaka, Shigeyoshi*; Kobayashi, Takuya; Funasaka, Hideyuki*; Morita, Takami*

Journal of Nuclear Science and Technology, 60(3), p.258 - 276, 2023/03

https://doi.org/10.1080/00223131.2022.2093800

We estimate monthly discharge inventory of tritium from the port of Fukushima Dai-ichi Nuclear Power Plant (1F) from Jun. 2013 to Mar. 2020 using the Voronoi tessellation scheme, following the tritium monitoring results inside the port started in Jun. 2013. As for the missing period from the first month of 1F accident, Apr. 2011 to May 2013, we calculate the tritium discharge inventory by utilizing the concentration ratio of tritium to Cs in stagnant contaminant water during the initial direct run-off period until Jun. 2011 and the discharge inventory correlation between tritium and Cs for the next-unknown continuous-discharge period from Jul. 2011 to May 2013. From all the estimated results over 9 years, we find that the monthly discharge inventory sharply dropped immediately after closing the seaside impermeable wall in Oct. 2015 and consequently coincided well with the sum of input inventories of drainage water and subdrain etc. purified water into the port. By comparing the above estimated results with those in the normal operation period before the accident, we point out that the discharge inventory from 1F port after the accident is not so large. Even the estimation value for the accident year 2011 is found to be comparable to the maximum of operating pressurized water reactors releasing relatively large inventories in the order. At the national level, the total domestic release inventory in Japan significantly decreased after the accident owing to the operational shutdown of most plants. Furthermore, the total Japanese discharge inventory including 1F are found to be minor compared with those of nuclear reprocessing plants and heavy-water reactors on a worldwide level. From the above results, we suggest that various scenarios can be openly discussed regarding the management of tritium stored inside 1F with the help of the present estimated data and its comparison with the past discharge inventory as well as those of other nuclear facilities.

Machine learning molecular dynamics simulations for evaluation of high-temperature properties of nuclear fuel materials

Kobayashi, Keita; Nakamura, Hiroki; Itakura, Mitsuhiro; Machida, Masahiko; Okumura, Masahiko

Materia, 62(3), p.175 - 181, 2023/03

https://doi.org/10.2320/materia.62.175

no abstracts in English

High-sensitive XANES analysis at Ce L-edge for Ce in bauxites using transition-edge sensors; Implications for Ti-rich geological samples

Li, W.*; Yamada, Shinya*; Hashimoto, Tadashi; Okumura, Takuma*; Hayakawa, Ryota*; Nitta, Kiyofumi*; Sekizawa, Oki*; Suga, Hiroki*; Uruga, Tomoya*; Ichinohe, Yuto*; et al.

Analytica Chimica Acta, 1240, p.340755_1 - 340755_9, 2023/02

https://doi.org/10.1016/j.aca.2022.340755

no abstracts in English

VR extension of client server type particle-based volume visualization application

Kawamura, Takuma; Sakamoto, Naohisa*; Osaki, Tsukasa*

Journal of Advanced Simulation in Science and Engineering (Internet), 10(1), p.31 - 39, 2023/02

https://doi.org/10.15748/jasse.10.31

Visualization of large fluid computation results at remote locations by VR, especially using volume rendering, is one of the key challenges in the visualization field. The remote visualization application CS-PBVR is capable of interactive volume rendering of large-scale data in remote locations. In this study, the image generation of CS-PBVR was extended for head-mounted displays to develop a remote VR visualization application, VR-PBVR. We also developed a function that allows manipulation of visualization data by gesture control with both hands in VR space. We applied VR-PBVR to remote volume data and confirmed that it can visualize the data at interactive frame rates.

A New data conversion method for mixed precision Krylov solvers with FP16/BF16 Jacobi preconditioners

Ina, Takuya; Idomura, Yasuhiro; Imamura, Toshiyuki*; Onodera, Naoyuki

Proceedings of International Conference on High Performance Computing in Asia-Pacific Region (HPC Asia 2023) (Internet), p.29 - 34, 2023/02

https://doi.org/10.1145/3578178.3578222

Mixed precision Krylov solvers with the Jacobi preconditioner often show significant convergence degradation when the Jacobi preconditioner is computed in low precision such as FP16 and BF16. It is found that this convergence degradation is attributed to loss of diagonal dominance due to roundoff errors in data conversion. To resolve this issue, we propose a new data conversion method, which is designed to keep diagonal dominance of the original matrix data. The proposed method is tested by computing the Poisson equation using the conjugate gradient method, the general minimum residual method, and the biconjugate gradient stabilized method with the FP16/BF16 Jacobi preconditioner on NVIDIA V100 GPUs. Here, the new data conversion is implemented by switching the round-nearest, round-up, round-down, and round-towards-zero intrinsics in CUDA, and is called once before the main iteration. Therefore, the cost of the new data conversion is negligible. When the coefficients of matrix is continuously changed by scaling the linear system, the conventional data conversion based on the round-nearest intrinsic shows periodic changes of the convergence property depending on the difference of the roundoff errors between diagonal and off-diagonal coefficients. Here, the period and magnitude of the convergence degradation depend on the bit length of significand. On the other hand, the proposed data conversion method is shown to fully avoid the convergence degradation, and robust mixed precision computing is enabled for the Jacobi preconditioner without extra overheads.

LASSO reconstruction scheme to predict radioactive source distributions inside reactor building rooms; Practical applications

Machida, Masahiko; Shi, W.*; Yamada, Susumu; Miyamura, Hiroko; Yoshida, Toru*; Hasegawa, Yukihiro*; Okamoto, Koji; Aoki, Yuto; Ito, Rintaro; Yamaguchi, Takashi; et al.

Proceedings of Waste Management Symposia 2023 (WM2023) (Internet), 11 Pages, 2023/02