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Okumura, Keisuke
Fission Product Behavior under Severe Accident, p.116 - 121, 2021/05
no abstracts in English
Okumura, Keisuke; Riyana, E. S.; Sato, Wakaei*; Maeda, Hirobumi*; Katakura, Junichi*; Kamada, So*; Joyce, M. J.*; Lennox, B.*
Progress in Nuclear Science and Technology (Internet), 6, p.108 - 112, 2019/01
In order to establish the prediction method of the dose rate distribution in the primary containment vessel (PCV) of the Fukushima Daiichi Nuclear Power Station, a series of calculations were carried out in the following way; (1) burnup calculation to obtain fuel composition at the time of accident, (2) activation calculation for the structural materials including impurities, (3) estimation of Cs contamination in PCV based on the result of severe accident analysis by IRID, (4) decay calculation of radioactive nuclides, (5) photon transport calculation to obtain dose rate distribution. After that, Cs concentration around the dry-well of 1F was modified to be consistent with locally measured dose rates in the PCV-investigation by IRID.
(Al,Ga)
O
scintillator Compton camera mounted on an unmanned helicopterShikaze, Yoshiaki; Nishizawa, Yukiyasu; Sanada, Yukihisa; Torii, Tatsuo; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; et al.
Journal of Nuclear Science and Technology, 53(12), p.1907 - 1918, 2016/12
Times Cited Count：37 Percentile：96.48(Nuclear Science & Technology)The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 4
4 to 88 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m 60 m and 65 m 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the 
-ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10
).
Nagaoka, Toshi; Moriuchi, Shigeru; Sakamoto, Ryuichi; Saito, Kimiaki; Tsutsumi, Masahiro
Hoken Butsuri, 30, p.9 - 14, 1995/00
no abstracts in English
Nagaoka, Toshi
Radioisotopes, 41(1), p.57 - 58, 1992/00
no abstracts in English
Nagaoka, Toshi; Sakamoto, Ryuichi; Tsutsumi, Masahiro; Saito, Kimiaki; Moriuchi, Shigeru
Nihon Genshiryoku Gakkai-Shi, 32(5), p.507 - 513, 1990/05
Times Cited Count：1 Percentile：19.6(Nuclear Science & Technology)no abstracts in English
; ; ; ; *; *
JAERI-M 9517, 42 Pages, 1981/06
no abstracts in English
; Yoshida, Kenzo; ; Araki, Kunio
Radiation Physics and Chemistry, 11, p.327 - 334, 1978/00
no abstracts in English
Nakajima, Hayato; ; ; *; *; ; ; Takehisa, Masaaki; Machi, Sueo
JAERI-M 5485, 21 Pages, 1973/12
no abstracts in English
;
Oyo Butsuri, 36(10), p.782 - 788, 1967/00
no abstracts in English
Okumura, Keisuke; Kojima, Kensuke; Hagura, Hiroyuki*; Ito, Takashi*; Miyoshi, Katsumasa*
no journal, ,
In order to contribute to the removal of fuel debris from Fukushima Daiichi Nuclear Power Station (1F), an efficient estimation method of the dose rate distribution in the primary containment vessel of 1F, by using photon transport calculations with a Monte Carlo calculation code and information on the radiation sources obtained from computations for fuel burnup, activation of structural materials, severe accident analysis, etc.
Okumura, Keisuke; Sato, Wakaei; Maeda, Hirobumi; Wakaida, Ikuo; Washiya, Tadahiro; Katakura, Junichi*
no journal, ,
In order to develop the evaluation technology of the most probable radiation source and dose rate distributions in the primary containment vessel (PCV), we evaluated the radiation source distribution based on the results of fuel burn-up calculation, activation calculation of structural materials and severe accident analysis. Then, we built a three-dimensional PCV model for the particle transport Monte Carlo calculation code PHITS. From the PHITS calculation, we obtained the response function of the dose rate distribution due to each unit radiation source.
Katakura, Junichi*; Okumura, Keisuke; Kim, K.*; Joyce, M. J.*; Lennox, B.*
no journal, ,
To contribute to the decommissioning acceleration of the Fukushima Daiichi Nuclear Power Station, the following two key technology developments have been carried out in cooperation with UK research organization. One is "the development of the evaluation technology of dose rate distribution" which is aiming to evaluate the most probable dose rate distribution by combination of the actual measurement value and the theoretical calculation. Another is "the technology development to search for the submerged fuel debris" by using sonar, small detector, underwater robot. In this presentation, we report on the research objectives and the overall plan.
Oda, Yoshihiro; Dohi, Terumi; Kanaizuka, Seiichi*; Iijima, Kazuki
no journal, ,
We make a research to understand the detailed distribution of radioactive caesium deposition on mountain forests around Fukushima Dai-ichi Nuclear Power Plant. By the research data, we analysed the relations between dose rate and landform by using geographical information system.
Dohi, Terumi; Fujiwara, Kenso; Kikuchi, Naoyuki; Hagiwara, Hiroki; Iijima, Kazuki
no journal, ,
no abstracts in English
-ray dose rates on the upper core structure of Joyo by the optical fiberYamamoto, Takahiro; Ito, Chikara; Maeda, Shigetaka; Ito, Hideaki; Sekine, Takashi
no journal, ,
In the experimental fast reactor Joyo, replacement of upper core structure (UCS) was conducted in 2014. Since the UCS replacement was not anticipated in the original design, the UCS surface dose rate was evaluated for the equipment design using QAD code considering the in-vessel dose rate measurement results. In order to confirm the accuracy of the evaluation, measurement of the surface ray distribution of cask, which included the old-UCS, was conducted using a plastic scintillating optical fiber (PSF) detector. With comparing the measured ray distribution with the calculated ray distribution, it was confirmed that the C/E was approximately 1
1.5.
Riyana, E. S.; Okumura, Keisuke
no journal, ,
A technology to predict the most probable dose rate distribution in the primary containment vessel (PCV) of the Fukushima Daiichi Nuclear Power Station (1F) have been developed by combined use of sophisticated theoretical calculation and local measurement results. It was applied to the Unit-1 of 1F.
Okumura, Keisuke; Riyana, E. S.; Sato, Wakaei*; Maeda, Hirobumi*; Katakura, Junichi*
no journal, ,
Based on the results of fuel burn-up calculations and activation calculations for structural materials and on those of severe accident progression analyses and internal investigations by IRID, we predicted a three-dimensional dose rate distribution in the containment vessel of Unit 1 at the Fukushima Daiichi Nuclear Power Station.
Okumura, Keisuke
no journal, ,
As a part of human resource development for the decommissioning of the Fukushima Daiichi Nuclear Power Station(1F), I will give a lecture on the following contents to researchers who mainly specialize in reactor physics; (1) Activities of Collaborative Laboratories for Advanced Decommissioning Science (CLADS), (2) Activation calculation method for decommissioning of nuclear reactor, (3) Development of the method to predict dose rate distribution in 1F plant, (4) Simulation of the germanium detector, (5) Development of Non-Destructive Assay (NDA) technology for nuclear material accountancy of fuel debris canister by Monte Carlo simulation.
