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Nagata, Hiroshi; Omori, Takazumi; Maeda, Eita; Otsuka, Kaoru; Nakano, Hiroko; Hanakawa, Hiroki; Ide, Hiroshi
JAEA-Review 2023-033, 40 Pages, 2024/01
JAEA-Review-2023-033.pdf:1.39MB
Japan Materials Testing Reactor (JMTR) was decided as a one of decommission facilities in April 2017. In order to submit the decommissioning plan to the Nuclear Regulation Authority, the type of accident assumed in the first stage of the decommissioning plan was selected, and the public exposure dose was evaluated. A fuel handling accident and a fire accident during storage of waste were selected as assumed accidents in the first stage of the decommissioning plan. An evaluation of the public exposure dose from the radioactive materials released into the atmosphere due to these accidents was estimated to be a maximum of 0.019 mSv (due to a fire accident during storage of waste). This estimated value was found to be sufficiently smaller than the judging criteria (5 mSv), and not to pose a significant risk of radiation exposure to the general public.
Togawa, Orihiko; Okura, Takehisa; Kimura, Masanori
JAEA-Review 2022-049, 76 Pages, 2023/01
JAEA-Review-2022-049.pdf:3.74MB
Before construction and after operation of nuclear facilities, environmental consequence assessments are conducted for normal operation and an emergency. These assessments mainly aim at confirming safety for the public around the facilities and producing relief for them. Environmental consequence assessments are carried out using observations/ measurements by environmental monitoring and/or model predictions by calculation models, sometimes using either of which and at other times using both them, according to the situations and necessities. First, this report investigates methods, roles, merits/demerits and relationship between observations/measurements and model predictions which are used for environmental consequence assessments of nuclear facilities, especially holding up a spent nuclear fuel reprocessing plant at Rokkasho, Aomori as an example. Next, it explains representative examples of utilization of data on observations/measurements and results on model predictions, and considers points of attention at using them. Finally, the report describes future direction, for example, improvements of observations/measurements and model predictions, and fusion of both them.
Homma, Toshimitsu; Tomita, Kenichi*; Hato, Shinji*
Nuclear Engineering and Technology, 37(3), p.245 - 258, 2005/06
This paper addresses two types of uncertainty: stochastic uncertainty and subjective uncertainty in probabilistic accident consequence assessments. The off-site consequence assessment code OSCAAR has been applied to uncertainty and sensitivity analyses on the individual risks of early fatality and latent cancer fatality in the population due to a severe accident. A new stratified meteorological sampling scheme was successfully implemented into the trajectory model for atmospheric dispersion and the statistical variability of the probability distributions of the consequence was examined. A total of 65 uncertain input parameters was considered and 128 runs of OSCAAR were performed in the parameter uncertainty analysis. The study provided the range of uncertainty for the expected values of individual risks of early and latent cancer fatality close to the site. In the sensitivity analyses, the correlation/regression measures were useful for identifying those input parameters whose uncertainty makes an important contribution to the overall uncertainty for the consequence.
Hidaka, Akihide; Kudo, Tamotsu; Ishikawa, Jun; Fuketa, Toyoshi
Journal of Nuclear Science and Technology, 42(5), p.451 - 461, 2005/05
Times Cited Count：6 Percentile：39.62(Nuclear Science & Technology)The radionuclide release from MOX under severe accident conditions was investigated in VEGA program to contribute to the technical bases for safety evaluation including PSA for LWR using MOX. The MOX specimens irradiated at ATR Fugen were heated up to 3123K in helium at 0.1 and 1.0MPa. The release of volatile FP was slightly enhanced below 2200K compared with that of UO
. The volatile FP release at elevated pressure was decreased as in the case with UO. The total fractional release of Cs reached almost 100% while almost no release of low-volatile FP even after the fuel melting. The release rate of plutonium above 2800K increased rapidly although the amount was small. Since the existing models cannot predict this increase, an empirical model was prepared based on the data. There is no large difference in FP inventories between UO and MOX, and the fractional releases from MOX can be mostly predicted by the model for UO. This suggests that the consequences of LWR using MOX are mostly equal to those using UO from a view point of risks.
Homma, Toshimitsu
Proceedings of 4th International MACCS Users Group Meeting, p.57 - 66, 2002/10
no abstracts in English
Liu, X.*; Tomita, Kenichi*; Homma, Toshimitsu
JAERI-Research 2002-004, 37 Pages, 2002/03
JAERI-Research-2002-004.pdf:2.14MB
One important step in Level 3 Probabilistic Safety Assessment is meteorological sequence sampling, on which the previous studies were mainly related to code systems using straight line plume model and more efforts are needed for trajectory puff model such as the OSCAAR code system. This report describes the development of a new meteorological sampling scheme for the OSCAAR code system that explicitly considers population distribution. A group of principles was set forth for the development of this new sampling scheme, including completeness, stratification, sample allocation, practicability and so on. The calculation results illustrate that although it is quite difficult to idealize stratification of meteorological sequences based on a few environmental parameters the new scheme do gather the most inverse conditions in a single subset of meteorological sequences. The size of this subset may be as small as a few dozens, so that the tail of a CCDF curve is possible to remain relatively static in different trials of the PCA code system.
Liu, X.; Homma, Toshimitsu
JAERI-Tech 2001-054, 49 Pages, 2001/08
JAERI-Tech-2001-054.pdf:1.54MB
no abstracts in English
Homma, Toshimitsu; Matsunaga, Takeshi
JAERI-Research 2000-059, 63 Pages, 2001/01
JAERI-Research-2000-059.pdf:2.36MB
no abstracts in English
Homma, Toshimitsu; Ishikawa, Jun; Tomita, Kenichi*; Muramatsu, Ken
JAERI-Research 2000-060, 80 Pages, 2000/12
JAERI-Research-2000-060.pdf:4.49MB
no abstracts in English
Homma, Toshimitsu; Inoue, Yoshihisa*; Tomita, Kenichi*
JAERI-Research 2000-049, 101 Pages, 2000/10
JAERI-Research-2000-049.pdf:3.03MB
no abstracts in English
Homma, Toshimitsu; Liu, X.; Tomita, Kenichi*
Proceedings of 5th International Conference on Probabilistic Safety Assessment and Management (PSAM-5), p.2753 - 2758, 2000/00
no abstracts in English
W.Nixon*; P.J.Cooper*; C.M.Bone*; S.Acharya*; U.Baeverstam*; J.Ehrhardt*; I.Hasemann*; Steinhauer, C.*; E.G.Diaz*; J.C.Glynn*; et al.
EUR-15109, 0, 338 Pages, 1994/00
no abstracts in English
Homma, Toshimitsu; Togawa, Orihiko
3rd Int. Symp. on Advanced Nuclear Energy Research; Global Environment and Nuclear Energy, 5 Pages, 1991/00
no abstracts in English
Ishigami, Tsutomu;
JAERI-M 89-112, 84 Pages, 1989/09
no abstracts in English
) reactions in binary organic systems containing bromine, IZ.ABEDINZADEH*; S.GRILLET*; J.STEVOVIC*; Tanaka, Kichizo; M.MILMAN*
Radiochimica Acta, 9(4), p.38 - 40, 1968/00
no abstracts in English
Tanaka, Kichizo; Stevovic, J.*; Milman, M.*
Journal of Inorganic and Nuclear Chemistry, 3, p.415 - 418, 1967/00
no abstracts in English
Yonomoto, Taisuke; Nakatsuka, Toru; Hirane, Nobuhiko; Tsumura, Takashi
no journal, ,
no abstracts in English
Homma, Toshimitsu
no journal, ,
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.
