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Okuno, Hiroshi; Suyama, Kenya
Proceedings of 12th International Conference on Nuclear Criticality Safety (ICNC2023) (Internet), 8 Pages, 2023/10
The criticality accident that resulted in the evacuation of residents occurred on September 30, 1999, at JCO's nuclear fuel fabrication plant in Ibaraki prefecture, Japan. This paper presents the outline, technical issues and background of the accident and the situations that followed. The review of this accident was one of the hot issues in the last ICNC2003 organized in Tokai-mura. At the this turn of ICNC in Japan, we would like to revisit the accident to reaffirm and share the idea that the response and preparedness should be strengthened to protect people and the environment from nuclear disasters. The accident occurred in a factory of JCO during the informal and unusual process of preparing a uranium nitrate solution of medium-enriched (18.8 weight% 
U) uranium from U
O
using the precipitation tank of 45 cm in diameter, which exceeded the critical diameter (ca. 23 cm) of an infinite cylinder with a full thick water reflector. A 2.2-cm-thick water "jacket" surrounded and enclosed the tank, and the jacket was connected to the cooling tower beside the factory. The jacket not only functioned as the neutron reflector but also prevented the evaporation of the solution, and then the criticality continued for about 20 hours. Because JCO's plant had not anticipated the criticality accident, the response to the accident was confusing. During the accident, the JAERI and JNC, both the predecessors of the Japan Atomic Energy Agency (JAEA), acted to terminate the criticality and reduce the residents' exposure to radiation. After the accident, the JAERI and the National Institute of Radiological Sciences provided the telephone consultation at the village office of Tokai-mura. The JNC did the same things at the prefectural building of Ibaraki to advise the residents. The presentation may include issues of applying the Slide rule, identifying a nuclear criticality accident to occur, and responding to the emergency.
Oka, Kiyoshi
Kikai No Kenkyu, 57(6), p.641 - 649, 2005/06
no abstracts in English
Sakurai, Kiyoshi; Nojiri, Ichiro*
JAERI-Conf 2003-019, p.855 - 857, 2003/10
This paper provides overview of sub-criticality safety analysis seminar (July 2000-July 2003, JAERI, total 40 engineers from universities, research institutes and enterprises) for nuclear fuel cycle facility with the Monte Carlo method in Japan. MCNP-4C2 system (MS-DOS version) was installed in each note-type personal computer. Fundamental theory of reactor physics and Monte Carlo simulation including MCNP-4C manual was lectured. Effective neutron multiplication factor and neutron spectrum were calculated for JCO deposit tank, JNC uranium solution storage tank, JNC plutonium solution storage tank and JAERI TCA core. In the seminar, methodology of safety management for nuclear fuel cycle facility was discussed in order to prevent criticality accident.
-ray monitorTonoike, Kotaro; Nakamura, Takemi*; Yamane, Yuichi; Miyoshi, Yoshinori
Nuclear Technology, 143(3), p.364 - 372, 2003/09
Times Cited Count：2 Percentile：19(Nuclear Science & Technology)no abstracts in English
Endo, Akira; Yamaguchi, Yasuhiro; Sumita, Kenji*
Journal of Nuclear Science and Technology, 40(8), p.628 - 630, 2003/08
Times Cited Count：4 Percentile：31.64(Nuclear Science & Technology)no abstracts in English
Sakamoto, Yukio
JAERI-Research 2002-025, 34 Pages, 2002/11
JAERI-Research-2002-025.pdf:1.91MB
no abstracts in English
Umemoto, Michitaka; Ishigami, Tsutomu; Kobayashi, Kensuke
Chiiki Anzen Gakkai Rombunshu, 4, p.231 - 240, 2002/11
no abstracts in English
Watanabe, Shoichi; Miyoshi, Yoshinori; Yamane, Yuichi
JAERI-Tech 2002-043, 93 Pages, 2002/03
JAERI-Tech-2002-043.pdf:6.74MB
no abstracts in English
Uchida, Masaaki
IAEA Regional Workshop on Accident Management and Emergency Response for Research Reactors, 11 Pages, 2002/00
no abstracts in English
Tanaka, Shunichi
Journal of Radiation Research, 42(Suppl.), p.S1 - S9, 2002/00
A criticality accident occured on September 30,1999, in a conversion facity at the JCO tokai site. The accident continued for about 19 hours before the criticality could be stopped, during which time neutrons and gamma-rays were emitted continuously due to fission reactions. The total number of fission reactions was 2.5x10
. The accident gave radiation dose to 3 employees and fatal dose to 2 of them. The individual dose was estimated for 234 resident, 169 JCO employees and 260 emergency personnel, of which the maximum dose was 48 mSv.
Tamaki, Hitoshi; Watanabe, Norio*; Muramatsu, Ken
Proceedings of the 2001 Topical Meeting on Practical Implementation of Nuclear Criticality Safety (CD-ROM), 10 Pages, 2001/11
no abstracts in English
Uchiyama, Gunzo; Watanabe, Kazuo; Miyauchi, Masakatsu; Togashi, Yoshihiro; Nakahara, Yoshinori; Fukaya, Hiroyuki; Inagawa, Jun; Suzuki, Daisuke; Sonoda, Takashi; Kono, Nobuaki; et al.
Journal of Radiation Research, 42(Suppl.), p.S11 - S16, 2001/10
no abstracts in English
Sakamoto, Yukio
KEK Proceedings 2001-14, p.236 - 242, 2001/06
no abstracts in English
Shinohara, Nobuo; Kono, Nobuaki; Suyama, Kenya; Inagawa, Jun; Nakahara, Yoshinori; Kurosawa, Setsumi; Watanabe, Kazuo; Usuda, Shigekazu; Oshima, Masumi; Katsuta, Hiroji; et al.
Radiochimica Acta, 89(3), p.135 - 138, 2001/05
Times Cited Count：2 Percentile：19.66(Chemistry, Inorganic & Nuclear)no abstracts in English
Project Planning Division
JAERI-Tech 2001-008, 32 Pages, 2001/03
JAERI-Tech-2001-008.pdf:5.49MB
no abstracts in English
Watanabe, Shoichi; Miyoshi, Yoshinori
JAERI-Data/Code 2001-008, 62 Pages, 2001/03
JAERI-Data-Code-2001-008.pdf:17.38MB
no abstracts in English
Yamamoto, Toshihiro; Nakamura, Takemi*; Miyoshi, Yoshinori
JAERI-Data/Code 2001-001, 30 Pages, 2001/02
JAERI-Data-Code-2001-001.pdf:1.53MB
no abstracts in English
Tanabe, Fumiya; Yamaguchi, Yukichi
Nihon Genshiryoku Gakkai-Shi, 43(1), p.48 - 51, 2001/01
Times Cited Count：5 Percentile：38.97(Nuclear Science & Technology)no abstracts in English
Tanabe, Fumiya; Yamaguchi, Yukichi
Nihon Genshiryoku Gakkai-Shi, 43(1), p.52 - 55, 2001/01
Times Cited Count：1 Percentile：12.01(Nuclear Science & Technology)no abstracts in English
Yamamoto, Katsumune
Proceedings of 15th Sino-Japanese Seminar on Nuclear Safety, p.267 - 278, 2000/12
no abstracts in English
