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Hidaka, Akihide
Journal of Nuclear Science and Technology, 56(9-10), p.831 - 841, 2019/09
Times Cited Count：12 Percentile：80.27(Nuclear Science & Technology)The insoluble Cs particles (Type A) were firstly observed in Tsukuba-city on the morning of March 15. The particles have been considered to be generated in RPV of Unit 2 by evaporation/condensation based on the measured 
Cs/
Cs ratio and the core temperatures of each unit. However, the Type A particles with smaller diameter than the Type B particles of Unit 1 origin, are covered by almost pure silicate glass and have a trace of the quenching. This indicates that the particles could have been generated due to the melting of the HEPA filter in SGTS by the fire of H
detonation at Unit 3, and atomization followed by quenching of the molten materials by air blast of the explosion. Although the particles were mostly dispersed to the sea because of the wind direction, some of them deposited onto the lower elevation of R/B at Unit 3, could have been subsequently re-suspended and released into the environment, by the steam flow in the R/B caused by restart of the Unit 3 core cooling water injection at 2:30 of March 15.
Tamaki, Hitoshi; Ishikawa, Jun; Sugiyama, Tomoyuki; Maruyama, Yu
Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.72 - 82, 2019/08
JAEA participated in the OECD/NEA BSAF2 project with our integrated severe accident analysis code, THALES2/KICHE, in order to analyze and discuss the accident progression and source term of the accident at the Fukushima Daiichi NPS. One of important characteristics of THALES2/KICHE code is that it has the capability of predicting iodine chemistry based on reaction kinetics in the aqueous phase. JAEA performed the three week analysis for the accident at unit 1 on the basis of the boundary conditions and assumptions proposed by the BSAF2 project and our own assumptions. In addition to the failure of the drywell, it was assumed in the present analysis that continuous leakage occurred through the containment venting line due to incomplete closing of valves in the line. The releases of fission products, especially for iodine and cesium, within three weeks after the earthquake were estimated to be approximately 6% and 1% of the initial inventory, respectively.
Tamaki, Hitoshi; Ishikawa, Jun; Sugiyama, Tomoyuki; Maruyama, Yu
Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.100 - 111, 2019/08
JAEA participated in the OECD/NEA BSAF2 project with our integrated severe accident analysis code, THALES2/KICHE, in order to analyze and discuss the accident progression and source term of the accident at the Fukushima Daiichi NPS. One of important characteristics of THALES2/KICHE code is that it has the capability of predicting iodine chemistry based on reaction kinetics in the aqueous phase. JAEA performed the three week analysis for the accident at unit 2 on the basis of the boundary conditions and assumptions proposed by the BSAF2 project and our own assumptions. One of focusing points in the BSAF2 project was the trend of measured data of reactor vessel from 20:00 March 14 to 02:00 March 15. An assumption was made that the lower part of the suppression chamber failed to form a water leakage path. The released iodine and cesium within three weeks after the earthquake were predicted to be approximately 3% and 0.1% of the initial inventory, respectively.
Hidaka, Akihide; Yokoyama, Hiroya
Proceedings of Symposium on Water Chemistry and Corrosion in Nuclear Power Plants in Asia 2017 (AWC 2017) (USB Flash Drive), p.29 - 42, 2017/09
no abstracts in English
I and Cs releases during late phase of Fukushima Daiichi NPP accident by using I/Cs ratio of source terms evaluated reversely by WSPEEDI code with environmental monitoring dataHidaka, Akihide; Yokoyama, Hiroya
Journal of Nuclear Science and Technology, 54(8), p.819 - 829, 2017/08
Times Cited Count：12 Percentile：75.51(Nuclear Science & Technology)To clarify what happened during the Fukushima accident, the phenomena within RPV and the discussion of ties with the environmental monitoring are very important. However, the previous study has not necessarily advanced until the present that passed almost six years from the accident. The present study investigated I and Cs release behaviors during the late phase of the accident based on I/Cs ratio of the source terms that were recently evaluated backward by WSPEEDI code based on environmental monitoring data. The I release from the contaminated water in the basement of 1F2 and 1F3 reactor buildings was evaluated to be about 10% of I source term. The increase in Cs release from March 21 to 23 and from March 30 to 31 could be explained by the release of CsBO which is formed as a result of chemical reactions of Cs with B
C due to re-ascension of the core temperature caused by slight shortage of the core cooling water.
Ishikawa, Jun; Muramatsu, Ken; Sakamoto, Toru*
JAERI-Research 2005-021, 133 Pages, 2005/09
JAERI-Research-2005-021.pdf:7.58MB
The THALES-2 code is an integrated severe accident analysis code in order to simulate the accident progression and transport of radioactive material for probabilistic safety assessment (PSA) of a nuclear power plant, a part of a level 3 PSA being performed at JAERI for a 1,100MWe BWR-5 with a Mark-II containment. Results and insights from the analyses were that (1) the calculated release fractions of CsI and CsOH to the environment were in the range of 0.01 to 0.1 for late containment overpressure failure cases, and the release fractions for the containment venting case were one order of magnitude smaller than that of over-pressure case and those for drywell spray recovery cases where no containment failure occurred were two orders of magnitude smaller than the containment venting cases, (2) the governing factors for source terms of Iodine and Cesium are different depending on whether the containment fails before core melt or not, (3) the containment venting, which is one of the accident management measures, can be expected to reduce source terms if suppression pool bypass is avoided.
Kobayashi, Kensuke; Ishigami, Tsutomu; ; ; *
Journal of Nuclear Science and Technology, 32(5), p.476 - 487, 1995/05
Times Cited Count：3 Percentile：36.75(Nuclear Science & Technology)no abstracts in English
Ishigami, Tsutomu; Kobayashi, Kensuke
Nihon Genshiryoku Gakkai-Shi, 35(6), p.549 - 560, 1993/06
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)no abstracts in English
Yamane, Yuichi; Abe, Hitoshi
no journal, ,
After the experience of the accident at the Fukushima Dai-ichi Nuclear Power Plants of Tokyo Electric Power Company (TEPCO),Japan's nuclear safety standard for reprocessing plant has been renewed and the standard now requires accident management measures and the assessment of their effectiveness to the severe accident such as criticality accident. This paper summarizes the issues for the best estimation in criticality accident consequence analysis and proposes a new method to estimate source term in criticality accident. Unique characters of criticality accident in nuclear fuel facilities, such as the production of short life nuclides, are described in association with the best estimation of public and worker's dose. In the light of those characters, this paper proposes a procedure to estimate source term in criticality accident by utilizing five-component equation described in DOE handbook.
Hidaka, Akihide
no journal, ,
