Research and examination of seismic safety evaluation and function maintenance for important equipment in nuclear facilities

Furuya, Osamu*; Fujita, Satoshi*; Muta, Hitoshi*; Otori, Yasuki*; Itoi, Tatsuya*; Okamura, Shigeki*; Minagawa, Keisuke*; Nakamura, Izumi*; Fujimoto, Shigeru*; Otani, Akihito*; et al.

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 6 Pages, 2021/07

Since the Fukushima accident, with the higher safety requirements of nuclear facilities in Japan, suppliers, manufacturers and academic societies have been actively considering the reconstruction of the safety of nuclear facilities from various perspectives. The Nuclear Regulation Authority has formulated new regulatory standards and is in operation. The new regulatory standards are based on defense in depth, and have significantly raised the levels of natural hazards and have requested to strengthen the countermeasures from the perspective of preventing the simultaneous loss of safety functions due to common factors. Facilities for dealing with specific serious accidents are required to have robustness to ensure functions against earthquakes that exceed the design standards to a certain extent. In addition, since the probabilistic risk assessment (PRA) and the safety margin evaluation are performed to include the range beyond the design assumption in the safety improvement evaluation, it is very important to extent the special knowledge in the strength of important equipment for seismic safety. This paper summarizes the research and examination results of specialized knowledge on the concept of maintaining the functions of important seismic facilities and the damage index to be considered by severe earthquakes. In the other paper, the study on reliability of seismic capacity analysis for important equipment in nuclear facilities will be reported.

Radiation processes of impurities and hydrogen in detached divertor plasmas of JT-60U

Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Konoshima, Shigeru; Fujimoto, Kayoko; Kawashima, Hisato; Higashijima, Satoru

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

http://www-naweb.iaea.org/napc/physics/FEC/FEC2006/html/node246.htm#49158

Volume recombination of C and into C is observed for the first time in detached plasmas with MARFE. It is found that the recombination flux of C to C is comparable to the ionization flux of C to C, and that the recombination zone is above an X-point and beneath the ionization zone. This result suggests that this volume recombination predominantly produces C ions, which contribute 60-80 % to the total radiation power in the divertor plasma.

Dose equivalent rate and radiation monitoring results during power distribution measurements of HTTR

Takada, Eiji*; Fujimoto, Nozomu; Nojiri, Naoki; Umeta, Masayuki; Kokusen, Shigeru; Ashikagaya, Yoshinobu

JAERI-Data/Code 2002-009, 83 Pages, 2002/05

JAERI-Data-Code-2002-009.pdf:3.51MB

Dose equivalent rate around the fuel handling machine, the control rod handling machine, stand pipe compartment, maintenance pit were measured during gamma ray measurements from HTTR fuel, which was called as “power distribution measurements". The power distribution measurement was the first time to handle the fuel blocks irradiated in the core. Dose equivalent rate measurement aiming the check of shielding performance of components, the check of unexpected streaming path. The radiation monitoring during operation was carried out. As the results, there was no problem on shielding. The measured data at operation condition were also obtained. The data will be useful to expect operation circumstance in the future.

Control rod position and temperature coefficients in HTTR power-rise tests; Interim report

Fujimoto, Nozomu; Nojiri, Naoki; Takada, Eiji*; Saito, Kenji; Kobayashi, Shoichi; Sawahata, Hiroaki; Kokusen, Shigeru

JAERI-Tech 2000-091, 49 Pages, 2001/03

JAERI-Tech-2000-091.pdf:2.0MB

no abstracts in English

Dynamic behavior and base isolation effect of three dimensional base isolation test system for nuclear components

Tsutsumi, Hideaki*; Yamada, Hiroyuki; Ebisawa, Katsumi; Shibata, Katsuyuki; Fujimoto, Shigeru*

Doboku Gakkai Dai-2-Kai Menshin, Seishin Korokiumu Koen Rombunshu, p.75 - 82, 2000/11

no abstracts in English

Development of vibration analysis code for fast breeder reactor core structure (II)

Sasaki, Yoichi*; Fujimoto, Shigeru*; Goda, Katsuhiko*; Sasaki, Tsuneo*

PNC TJ201 80-20VOL2, 70 Pages, 1980/02

PNC-TJ201-80-20VOL2.pdf:1.17MB

no abstracts in English

Radiation processes of impurities in detached divertor plasmas of JT-60U

Nakano, Tomohide; Asakura, Nobuyuki; Shimizu, Katsuhiro; Konoshima, Shigeru; Fujimoto, Kayoko; Kawashima, Hisato; Higashijima, Satoru

no journal, , 

WeThe intensity ratios of 9 C IV lines from the C IV emission peak were analyzed with a collisional-radiative model. From the analysis, it was found that the lowly-excited levels () were predominantly populated by the excitation from the ground state of by an electron impact with an electron temperature of 10 eV and an electron density of , while the highly-excited levels () by the volume recombination of and an electron with an electron temperature of 3 eV. With these parameters and the absolute intensity of C IV () and C IV () lines, the radiation power due to the excitation and the recombination process were determined to be, respectively, 40% and 0.5% of the total radiation power measured by a bolometer. Further, it was found that the recombination flux was comparable to the ionization flux.

Reliability enhancement of seismic risk assessment of NPP as risk management fundamentals, 1; Program plan and objectives

Muramatsu, Ken*; Takada, Tsuyoshi*; Itoi, Tatsuya*; Nishida, Akemi; Uchiyama, Tomoaki*; Furuya, Osamu*; Fujimoto, Shigeru*; Hirano, Mitsumasa*; Muta, Hitoshi*

no journal, , 

In this research project, study on probabilistic models and treatment of epistemic uncertainty, study on quantification of epistemic uncertainty on fragility assessment and verification of usefulness of proposed method are performed for reliability enhancement of seismic risk assessment. In this report, program plan and objectives are shown as part 1.

Study on next generation seismic PRA methodology, 1; Program plan and proposal of new mathematical framework

Muramatsu, Ken*; Takada, Tsuyoshi*; Nishida, Akemi; Uchiyama, Tomoaki*; Muta, Hitoshi*; Furuya, Osamu*; Fujimoto, Shigeru*; Itoi, Tatsuya*

no journal, , 

This is the first of a series of papers on a study on next generation seismic probabilistic safety assessment methodology being conducted by the authors as a three-year project "Reliability Enhancement of Seismic Risk Assessment of Nuclear Power Plants as Risk Management Fundamentals", which was started in 2012 and is funded by the Ministry of Education, Culture, Sports, Science & Technology (MEXT) of Japan. This paper gives an overview of the program plan and a proposal of new mathematical framework of S-PRA. We developed a computer code based on SECOM2-DQFM developed by JAEA. The proposed mathematical framework will be built-in it in order to make it possible to estimate the accident sequence occurrence probability and its uncertainty.

Reliability enhancement of seismic risk assessment of NPP as risk management fundamentals, 13; Evaluation of piping and components

Furuya, Osamu*; Fujimoto, Shigeru*; Muramatsu, Ken*; Muta, Hitoshi*; Nishida, Akemi

no journal, , 

This project, focusing on uncertainty assessment framework and utilization of expertise, and finally developing relevant computer codes to improve reliability of seismic probabilistic risk assessment (SPRA) and to promote its further use of the SPRA, develops methodology for quantification of uncertainty associated with final results from SPRA in the framework of risk management of NPP facilities. The following scopes are set. (1) Development of framework of probabilistic models for uncertainty quantification and Computer codes, (2) Aggregation of expert opinion on structure/equipment fragility estimation and development of implementation guidance on epistemic uncertainty (modeling uncertainty), (3) Study on applicability of SPRA to model plant. In this report, epistemic uncertainty of the equipment and piping responses on the same floor is estimated by analytical point of view.