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Tachi, Yukio
Kagaku To Kyoiku, 71(10), p.420 - 423, 2023/10
no abstracts in English
Umino, Yoshinori; Kato, Keisuke; Tanigawa, Masafumi; Kobayashi, Daisuke; Obu, Tomoyuki; Kimura, Yuichi*; Nemoto, Ryo*; Tajiri, Kazuma*
Nihon Hozen Gakkai Dai-19-Kai Gakujutsu Koenkai Yoshishu, p.33 - 36, 2023/08
In the basic laboratory of the Plutonium Conversion Development Facility in Tokai Reprocessing Plant, tests had been conducted to obtain effective data for manufacturing mixed plutonium and uranium oxide powder by irradiating a mixture of plutonium and uranium solution with microwaves. The test has already been completed, and we are currently dismantling and removing equipment. In this paper, techniques related to equipment renewal, dismantling and removal works inside the glove-box are discussed.
Takahashi, Shigeo*; Sakurai, Daisuke*; Nagao, Fumiya; Kurikami, Hiroshi; Sanada, Yukihisa
Shimyureshon, 42(2), p.68 - 75, 2023/06
This paper introduces a case in which scientific knowledge on understanding the deposition process of radionuclides and evaluating the dose rate reduction due to decontamination work was obtained through visual analysis based on data on the spatio-temporal distribution of air dose rates accumulated through radiation monitoring after the accident. We will discuss the prospects for future efforts to effectively obtain important knowledge that will assist in the planning of policies for reconstruction from the nuclear power plant accident in the future.
Suzuki, Gen*; Ishikawa, Tetsuo*; Oba, Takashi*; Hasegawa, Arifumi*; Nagai, Haruyasu; Miyatake, Hirokazu*; Yoshizawa, Nobuaki*
Journal of Radiation Research (Internet), 63(6), p.796 - 804, 2022/11
Times Cited Count：2 Percentile：27.14(Biology)To elucidate the association between radiation dose and thyroid cancer after the 2011 Fukushima Daiichi Nuclear Power Station (FDNPS) accident, it is essential to estimate individual thyroid equivalent doses (TEDs) to children. In a previous study, we reported a methodology for reconstructing TEDs from inhalation based on individual behavioural survey sheets combined with a spatiotemporal radionuclides database constructed by an atmospheric transport, diffusion, and deposition model (ATDM). In the present study, we further refined our methodology and estimated the combined TEDs from inhalation and ingestion among children in 16 municipalities around the nuclear power station utilizing 3,256 individual whereabouts questionnaire survey sheets. Distributions of estimated TEDs were similar to estimates based on direct thyroid measurements in 1080 children in Iwaki City, Kawamata Town, Iitate Village, and Minamisoma City. Mean TEDs in 1-year-old children ranged from 1.3 mSv in Date City to 14.9 mSv in Odaka Ward in Minamisoma City, and the 95th percentiles varied from 2.3 mSv in Date City to 28.8 mSv in Namie Town. In the future, this methodology can be useful for a case-control study of thyroid cancer after the FDNPS accident.
Tamai, Hiroshi
Nihon Genshiryoku Gakkai-Shi ATOMO
, 64(8), p.465 - 467, 2022/08
Though nuclear safety and nuclear security share the same goal of protecting the public and the environment from the harmful effects of ionizing radiation, their response actions may have differences, especially during transport, where protection could be vulnerable. The interface between them is a major issue. In December 2021, with the aim of complementarily strengthening nuclear safety and nuclear security in the transportation of radioactive materials IAEA published a related technical report and held an international conference. The outline of the technical report and the international conference is introduced.
Hokama, Tomonori; Fujita, Hiroki; Nakano, Masanao; Iimoto, Takeshi*
Radiation Protection Dosimetry, 196(3-4), p.136 - 140, 2021/11
Times Cited Count：0 Percentile：0.01(Environmental Sciences)During the early phase of a nuclear accident, major radioactive materials are released into the environment, necessitating the prompt deployment of various protective actions to avoid or reduce radiation exposure. To implement these actions, the levels of radioactivity in the environment should be determined. However, the radioactivity concentrations of artificial alpha-particle-emitting radionuclides such as plutonium are difficult to measure in airborne samples, because they are interfered with natural radionuclides such as uranium decay products. Therefore, chemical separation is required to measure the concentrations. This study presents a new emergency monitoring system for airborne samples, which performs multiple-pulse time-interval analysis (MTA) without chemical separation. The system is used in conjunction with an alpha/beta-particle survey meter and adopted an analysis method focusing on the detected time interval of each particle. Its features are that a short time to output measurement result, easy handling and nondestructive. The estimated detection limit of the system was 9.5
10
Bq m
. The MTA-based monitoring system could be useful in situations requiring prompt measurement and screening of samples.
Kato, Tetsu*; Kawamura, Yamato*; Tahara, Junichiro*; Baba, Shoichiro*; Sanada, Yukihisa; Fujii, Shun*
International Journal of Offshore and Polar Engineering, 31(3), p.316 - 324, 2021/09
Times Cited Count：2 Percentile：20.79(Engineering, Civil)The development of a side thruster system (vehicle (ASV)) that can maintain the direction of travel on the autonomous surface will be explained. Currently, we are working on a mud radioactivity survey in collaboration with Japan Agency for Marine-Earth Science and Technology, Japan Atomic Energy Agency, and Tokyo University of Marine Science and Technology. Deposited at the mouth of Fukushima Prefecture, Japan, the main purpose is to collect unmanned mud using ASV. The Mad Collection has developed a side thruster system and implemented it in ASV. We have confirmed the operation of the ASV with the joystick by using the thruster system for operating the ASV by one person using the joystick.
Plutonium Fuel Development Center
JAEA-Review 2021-007, 61 Pages, 2021/06
JAEA-Review-2021-007.pdf:7.56MB
The contamination incident in an operation room (Room No. A-103) of Plutonium Fuel Fabrication Facility (PFFF) in Japan Atomic Energy Agency (JAEA), Nuclear Fuel Cycle Engineering Laboratory occurred on January 30, 2019 during replacement of the double plastic bags which enclose a storage container containing nuclear material. At this time, some of nuclear materials spread all over the room. Nine workers in the room were contaminated with plutonium, but internal exposure of them was not confirmed. In order to restore the Room No. A-103 of PFFF, the Restoration Activity Team organized in JAEA carried out the decontamination work after the investigation of the contamination level in the room. The team had decontaminated the surface of walls, ceiling, gloveboxes and other instruments. Suitable decontamination methods were selected depending on the contamination distribution and installation state of the instruments. In addition to the manual wiping using wet wipes, the exfoliation method using a microfiber mop was applied for narrowed areas. As a result, the loose alpha-contamination level throughout the room fell below the detection limit. On other hand, the fixed alpha-contaminations were confined by painting after the decontamination. This report shown detail restoration activities for this time incident. This information is useful for making a manual on restoration activities and performing practice for the largescale contamination incident. We hope this report will be used for other facilities handled alpha-radioactive materials such as plutonium.
Hidaka, Akihide; Himi, Masashi*; Addad, Y.*
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
no abstracts in English
Sato, Yuki; Torii, Tatsuo
Isotope News, (757), p.44 - 47, 2018/06
no abstracts in English
Hidaka, Akihide
Enerugi Rebyu, 35(9), p.20 - 24, 2015/09
Operation of nuclear power plant causes accumulation of radionuclides in fuel rods as a result of nuclear fission of uranium and plutonium. During severe accidents, large amount of radionuclides are released from fuel and transport in the reactor coolant system and/or the containment. When the containment fails or its confinement function is lost, radionuclides could be released into the environment. Meanwhile, radionuclides can be removed by condensation onto wall, natural deposition such as gravitational settling, the engineered safety features (ESF) such as containment spray and so on. After various processes described above, the species, amounts and timing of radionuclide released into the environment is called source terms. The behavior of radionuclide can be described mechanistically by condensation or evaporation of gaseous radionuclide, deposition, growth and removal of aerosol by ESF. Present paper summarizes the radionuclide behavior during severe accidents.
Kobayashi, Yasuhiko
Shokuhin No Anzen To Anshin; Koza 1, p.52 - 69, 2015/02
no abstracts in English
Hidaka, Akihide*; Kudo, Tamotsu; Kida, Mitsuko; Fuketa, Toyoshi
JAERI-Research 2005-001, 67 Pages, 2005/02
JAERI-Research-2005-001.pdf:3.38MB
In the VEGA program to investigate radionuclides release from irradiated fuel during severe accidents, the analyses are being performed with VICTORIA2.0 code for comprehensive understanding of radionuclides release and transport phenomena. The VEGA-1 and -3 tests were analyzed in the present study. The correlation for Cs diffusion coefficient in fuel grain obtained from VEGA-1 was applied to the release analysis of VEGA-3. The calculated release of Cs agreed well with the measurement. The correlation was applied to subsequent Cs transport and deposition analyses. The calculation underpredicted the total mass of Cs deposited onto the test apparatuses because nucleation of aerosol and its growth were underestimated due to the consideration of aerosol nucleation originated only from released FP in VICTORIA2.0. A sensitivity analysis with aerosol seeds for heterogeneous nucleation showed a reasonable agreement with the measured Cs distribution. It turned out that additional aerosol seeds besides the released FP be considered when the VICTORIA2.0 code is applied to the VEGA test analyses.
Kanazawa, Toru*; Hidaka, Akihide; Kudo, Tamotsu; Nakamura, Takehiko*; Fuketa, Toyoshi
JAERI-Tech 2004-050, 53 Pages, 2004/06
JAERI-Tech-2004-050.pdf:4.35MB
As a part of release evaluation in VEGA program, the mass balances of released and deposited FP onto the test apparatus are estimated from gamma ray measurement for acid solution leached from the apparatus, but short-life or radionuclides without emitting 
rays and very small quantity of elements cannot be quantified. Therefore, a microanalysis by ICP-AES is planed for acid solution leached from apparatuses. Since Cs have strong ray spectrum, they have to be removed from solution in advance to avoid contamination of ICP system and to decrease exposure to ray. The method for Cs separation using inorganic ion exchanger, AMP was applied to the test solutions. The results showed that more than 99.9% of Cs could be removed from test solution, and once removed Sb by AMP was recovered by using a complexing agent such as citric acid. The ICP-AES analysis showed that amount of U, Sr and Zr were successfully quantified. The release and deposition will be quantified through ICP-AES analysis for acid solutions from which Cs is separated by AMP or other precipitation method.
Hidaka, Akihide
Nihon Genshiryoku Gakkai-Shi, 45(8), p.493 - 496, 2003/08
In order to investigate the radionuclides release from irradiated fuel under severe accident conditions of LWR, VEGA experimental facility that realizes the highest temperature and pressure conditions was designed and constructed at JAERI. The effect of ambient pressure on radionuclides release was uniquely quantified by using this facility. A model that explains the observed pressure effect was also proposed based on the experimental results. For this effort, the atomic energy society of Japan gave us the preeminent monograph award in FY 2002. This paper describes my encounter with the research awarded this time, fascination of this research, hard-worked points, future plans and so on.
fuel in helium atmosphere under elevated pressure of 1.0MPa at temperature up to 2,773KHidaka, Akihide; Kudo, Tamotsu; Nakamura, Takehiko; Uetsuka, Hiroshi
Journal of Nuclear Science and Technology, 39(7), p.759 - 770, 2002/07
Times Cited Count：6 Percentile：39.54(Nuclear Science & Technology)no abstracts in English
Amano, Hikaru; Takahashi, Tomoyuki*
Genshiryoku eye, 48(6), p.69 - 73, 2002/06
no abstracts in English
Ashikagaya, Yoshinobu; Nakazawa, Takashi; Yoshino, Toshiaki; Yasu, Katsuji
JAERI-Tech 2001-092, 76 Pages, 2002/01
JAERI-Tech-2001-092.pdf:11.72MB
no abstracts in English
Matsuzuru, Hideo
Nihon Gakujutsu Kaigi Kohaishita Seikatsu Kankyo No Sentan Gijutsu Ni Yoru Kaifuku Kenkyu Renrakukai Iinkai Shimpojiumu "Hoshasei Busshitsu Ni Yoru Kankyo Osen No Yobo Ni Mukete", p.53 - 62, 2002/00
no abstracts in English
Hidaka, Akihide; Nakamura, Takehiko; Kudo, Tamotsu; Uetsuka, Hiroshi
JAERI-Research 2001-055, 48 Pages, 2001/12
JAERI-Research-2001-055.pdf:3.9MB
no abstracts in English
