Iterative methods with mixed-precision preconditioning for ill-conditioned linear systems in multiphase CFD simulations

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

Proceedings of 12th Workshop on Latest Advances in Scalable Algorithms for Large-Scale Systems ScalA21) (Internet), 8 Pages, 2021/11

https://doi.org/10.1109/ScalA54577.2021.00006

A new mixed-precision preconditioner based on the iterative refinement (IR) method is developed for preconditioned conjugate gradient (P-CG) and multigrid preconditioned conjugate gradient (MGCG) solvers in a multi-phase thermal-hydraulic CFD code JUPITER. In the IR preconditioner, all data is stored in FP16 to reduce memory access, while all computation is performed in FP32. The hybrid FP16/32 implementation keeps the similar convergence property as FP32, while the computational performance is close to FP16. The developed solvers are optimized on Fugaku (A64FX), and applied to ill-conditioned matrices in JUPITER. The P-CG and MGCG solvers with the new IR preconditioner show excellent strong scaling up to 8,000 nodes, and at 8,000 nodes, they are respectively accelerated up to 4.86 and 2.39 from the conventional ones on Oakforest-PACS (KNL).

Enhancing emergency response in the field based on analysis of workload distribution at Fukushima Daiichi Nuclear Power Station

Yoshizawa, Atsufumi*; Oba, Kyoko; Kitamura, Masaharu*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(2), p.55 - 68, 2019/06

https://doi.org/10.3327/taesj.J18.041

This study aims to improve the potential of an emergency response by analyzing the workload management during the accident at the Emergency Response Center (ERC) of TEPCO's Fukushima Daiichi Nuclear Power Plant. Specifically, the research focused on the response of the ERC during the time between the discontinuation of Unit 3 core water injection and its recovery. It identified the different types of workload at the ERC had and how they had been managed based on the record of a TV conference. It also deduced the casual factors of the responses, supplementing the interview record of the director of ERC at the time by applying workload management analysis. On the basis of these findings, lessons to enhance the potential of the on-site emergency response have been obtained for ERC and outside organizations.

Proceedings of the Final ISTC/STCU Technical Review Committee Meeting of Fukushima Initiative "On the environmental assessment for long term monitoring and remediation in and around Fukushima" November 5-6, 2015, Tokyo, Japan

ISTC/STCU Fukushima Initiative Technical Review Committee; Fukushima Initiative Technical Review Committee

JAEA-Conf 2016-003, 107 Pages, 2016/07

JAEA-Conf-2016-003.pdf:5.87MB

The final ISTC/STCU Technical Review Committee Meeting "On the environmental assessment for long term monitoring and remediation in and around Fukushima" was held in Hitotsubashi University Hall, Tokyo, on November 5-6, 2015. This report consists of summary reports of Fukushima Initiative projects, which were presented at the meeting. As regarding to the sections those which will be published elsewhere, only their executive summaries are included.

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2014 - March 31, 2015)

Nuclear Emergency Assistance and Training Center

JAEA-Review 2016-005, 55 Pages, 2016/05

JAEA-Review-2016-005.pdf:3.61MB

The Japan Atomic Energy Agency, JAEA, is a designated public institution under the Disaster Countermeasures Basic Act and under the Armed Attack Situations Response Act. Based on these Acts, the JAEA has the responsibility of providing technical support to the national government and/or local governments in case of nuclear and/or radiological incidents. In order to fulfill the tasks as the designated public institution, the JAEA has established the Emergency Action Plan and the Civil Protection Action Plan. In case of a nuclear/radiological emergency, the Nuclear Emergency Assistance and Training Center (NEAT) dispatches specialists of JAEA, supplies the national government and local governments with emergency equipment and materials, and gives them technical advice and information. In normal time, NEAT provides various exercises and training courses concerning nuclear preparedness and response to emergency responders including the national and local government officers, in addition to the JAEA staff members. The NEAT also researches nuclear emergency preparedness and response, and cooperates with international organizations on the above research theme. In the FY2014, the NEAT accomplished the following tasks: (1) Technical support activities as a designated public institution in cooperation with the national and local governments, (2) Human resource development, exercise and training of nuclear emergency responders for the national and local governments, (3) Researches on nuclear emergency preparedness and response, and release to the public as useful information, (4) Technical contributions to Asian countries on nuclear emergency preparedness and response in collaboration with the international organizations.

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2013 - March 31, 2014)

Sato, Takeshi; Muto, Shigeo; Akiyama, Kiyomitsu; Aoki, Kazufumi; Okamoto, Akiko; Kawakami, Takeshi; Kume, Nobuhide; Nakanishi, Chika; Koie, Masahiro; Kawamata, Hiroyuki; et al.

JAEA-Review 2014-048, 69 Pages, 2015/02

JAEA-Review-2014-048.pdf:13.91MB

JAEA was assigned as a designated public institution under the Disaster Countermeasures Basic Act and under the Armed Attack Situations Response Act. Based on these Acts, the JAEA has the responsibility of providing technical support to the national government and/or local governments in case of disaster responses or response in the event of a military attack, etc. In order to fulfill the tasks, the JAEA has established the Emergency Action Plan and the Civil Protection Action Plan. In case of a nuclear emergency, NEAT dispatches specialists of JAEA, supplies the national government and local governments with emergency equipment and materials, and gives technical advice and information. In normal time, NEAT provides various exercises and training courses concerning nuclear disaster prevention to those personnel taking an active part in emergency response institutions of the national and local governments, police, fire fighters, self-defense forces, etc. in addition to the JAEA itself. The NEAT also researches nuclear disaster preparedness and response, and cooperates with international organizations. In the FY2013, the NEAT accomplished the following tasks: (1) Technical support activities as a designated public institution in cooperation with the national and local governments, etc. (2) Human resource development, exercise and training of nuclear emergency response personnel for the national and local governments, etc. (3) Researches on nuclear disaster preparedness and response, and sending useful information (4) International contributions to Asian countries on nuclear disaster preparedness and response in collaboration with the international organizations

High-precision measurement of the wavelength of a nickel-like silver X-ray laser

Hasegawa, Noboru; Kawachi, Tetsuya; Utsumi, Takayuki*; Sasaki, Akira; Tanaka, Momoko; Kado, Masataka; Sukegawa, Kota*; Lu, P.; Kishimoto, Maki; Tai, R.; et al.

Japanese Journal of Applied Physics, Part 1, 43(5A), p.2519 - 2522, 2004/05

https://doi.org/10.1143/JJAP.43.2519

We conducted high-precision measurements of the wavelength of the nickel-like silver X-ray laser in order to compare it with a theoretical wavelength. The reasons for using this laser are as follows: First, this laser line is in the wavelength region of Mo/Si multi-layer mirrors; therefore, this laser line is important for applications. Second, the strongamplification of this laser line has been obtained in our previous work, and the higher order line in the spectra obtained by our spectrometer can be used. Third, since silver is arelatively low-z material (z = 47), this wavelength is a ideal benchmark of atomic structural codes such as the Multiconfiguration Dirac-Fock (MCDF) code. The wavelength of the nickel-like silver X-ray laser was determined to be 13.887 nm. The comparison with MCDF codes shows that the present experimental result can work as a good benchmark of the accuracy of the codes.

Deep level transient spectroscopy study of electron-irradiated CuInSe thin films

Okada, Hiroshi*; Fujita, Naoki*; Lee, H.-S.*; Wakahara, Akihiro*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi

Journal of Electronic Materials, 32(9), p.L5 - L8, 2003/09

https://doi.org/10.1007/s11664-003-0234-8

no abstracts in English

Dosimetry for 3-45 MeV/u ion beams using thin film dosimeters

Kojima, Takuji; Sunaga, Hiromi; Takizawa, Haruki; Hanaya, Hiroaki; Tachibana, Hiroyuki*

JAERI-Review 2002-035, TIARA Annual Report 2001, p.123 - 124, 2002/11

Thin film dosimeters of about 10-200 mm in thickness, which were well -characterized for Co -rays or 2-MeV electrons, have been applied to dosimetry for ion beams. For development of dosimetry covering the dose range of 0.005 to 200 kGy with high precision within 5%, the linear energy transfer (LET) characteristics of thin films were studied involving development of precise fluence measurement. Dose mapping technique was also developed achieving high spatial resolution values of about 1m and 10m for lateral and depth directions respectively. The outline of the recent development is summarized in this paper.

Numerical simulation of radiative effects in the laser-produced plasma

Utsumi, Takayuki*; Sasaki, Akira; Kunugi, Tomoaki*; Fujii, Sadao*; Akamatsu, Mikio*

Proceedings of 4th International Conference on Supercomputing in Nuclear Applications (SNA 2000) (CD-ROM), 10 Pages, 2000/09

no abstracts in English

Fundamental experiments on accumulation behavior of molten fuel in a pressure vessel lower head

Shibamoto, Yasuteru; Nakamura, Hideo; Anoda, Yoshinari; Kukita, Yutaka*

JAERI-Tech 99-042, 41 Pages, 1999/05

JAERI-Tech-99-042.pdf:3.36MB

no abstracts in English