Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Yamashita, Takayuki*; Koga, Norimitsu*; Kawasaki, Takuro; Morooka, Satoshi; Tomono, Shohei*; Umezawa, Osamu*; Harjo, S.
Materials Science & Engineering A, 819, p.141509_1 - 141509_10, 2021/07
Times Cited Count：21 Percentile：83.73(Nanoscience & Nanotechnology)Yamashita, Takayuki; Tomono, Shohei*; Morooka, Satoshi; Harjo, S.; Kawasaki, Takuro; Nameki, Tatsuya*; Koga, Norimitsu*; Umezawa, Osamu*
JPS Conference Proceedings (Internet), 33, p.011064_1 - 011064_6, 2021/03
Koga, Norimitsu*; Umezawa, Osamu*; Yamamoto, Masayuki*; Yamamoto, Takashi*; Yamashita, Takayuki; Morooka, Satoshi; Kawasaki, Takuro; Harjo, S.
Metallurgical and Materials Transactions A, 52(3), p.897 - 901, 2021/03
Times Cited Count：3 Percentile：25.78(Materials Science, Multidisciplinary)Yamashita, Takayuki; Morooka, Satoshi; Harjo, S.; Kawasaki, Takuro; Koga, Norimitsu*; Umezawa, Osamu*
Scripta Materialia, 177, p.6 - 10, 2020/03
Times Cited Count：31 Percentile：90.48(Nanoscience & Nanotechnology)Hiyama, Miyabi*; Shiga, Motoyuki; Koga, Nobuaki*; Sugino, Osamu*; Akiyama, Hidefumi*; Noguchi, Yoshifumi*
Physical Chemistry Chemical Physics, 19(15), p.10028 - 10035, 2017/04
Times Cited Count：7 Percentile：31.12(Chemistry, Physical)In this study, the effect of hydration on the absorption spectra of oxyluciferin anion isomers in an aqueous solution is investigated for elucidating the influence of characteristic hydration structures. Using a canonical ensemble of hydration structures obtained from first-principles molecular dynamics simulations, the instantaneous absorption spectra of keto-, enol-, and enolate-type aqueous oxyluciferin anions at room temperature are computed from a collection of QM/MM calculations using an explicit solvent. It is demonstrated that the calculations reproduce experimental results concerning spectral shifts and broadening, for which traditional methods based on quantum chemistry and the Franck-Condon approximation fail because of the molecular vibrations of oxyluciferin anions and dynamical fluctuations of their hydration structures.
Inagaki, Shigeru*; Kanki, Takashi*; Koga, J. K.; Ishihara, Osamu*
Purazuma, Kaku Yugo Gakkai-Shi, 88(9), p.534 - 536, 2012/09
Hata, Haruhi; Yokoyama, Kaoru; Tsunashima, Yasumichi; Ohashi, Yusuke; Koga, Osamu; Sugitsue, Noritake
JAEA-Research 2011-022, 35 Pages, 2011/09
JAEA-Research-2011-022.pdf:2.92MB
For disposal of Very low-level radioactive Waste (VLLW) from nuclear related facilities, one of important factors for safety assessment is the characteristics of elution. As for VLLW from the nuclear power plant, concrete pit and trench disposals have been performed and the evaluation methods for the characteristics have been established. On the other hand, as for the uranium waste, the concept on how to test the elution characteristics is not shown yet. Based on these circumstances, preliminary tests have been conducted to study elution characteristics of uranium waste. The results show that the important factors for the uranium elution are how uranium exists in waste. In addition, the elution characteristics also depend on the precipitation amount on the disposal site. Therefore, to assess the elution rate from uranium waste, these factors must be considered.
Tanaka, Masaru*; Gofuku, Akio*; Ishizaka, Kaoru*; Tokizawa, Takayuki; Sato, Kazuhiko; Koga, Osamu
JAEA-Research 2010-054, 76 Pages, 2011/02
JAEA-Research-2010-054.pdf:4.46MB
To obtain public understanding on the uranium mining sites reclamation at Ningyo-toge Environmental Engineering Center, it is necessary to conduct appropriate Risk Communication (RC). In this study, to discuss the appropriate Risk communication method on the uranium mining sites reclamation, making of explanatory material by university student, and questionnaire survey on the risk perception were conducted.
Kamide, Hideki; Miyakoshi, Hiroyuki; Watanabe, Osamu*; Eguchi, Yuzuru*; Koga, Tomonari*
Nihon Kikai Gakkai Rombunshu, B, 76(763), p.460 - 462, 2010/03
Fully natural circulation system is adopted in a decay heat removal system (DHRS) of the designs of Japan Sodium Cooled Fast Reactor (JSFR). Several investigations of experiments and simulation methods on this DHRS are performed. Water experiments are carried out for the primary heat transportation system including a reactor vessel and heat exchangers of DHRS using a 1/10 model. As for the DHRS loop, sodium experiments were carried out, especially for a heat exchanger installed in an Intermediate Heat Exchanger (IHX). Here, several results of the sodium experiments were described. Transient characteristics during the start up in the air system of the air cooler, secondary loop of DHRS, and the primary loop were examined by the sodium experiments. Smooth increase of natural circulation flow rates in all systems of air and sodium was confirmed. Verifications of numerical simulation methods are planned based on the water and sodium experiments in this investigation plan.
Kamide, Hideki; Miyakoshi, Hiroyuki; Watanabe, Osamu*; Eguchi, Yuzuru*; Koga, Tomonari*
Dai-14-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu, p.427 - 428, 2009/06
Fully natural circulation system is adopted in a decay heat removal system (DHRS) of the designs of Japan Sodium Cooled Fast Reactor (JSFR). Several investigations of experiments and simulation methods on this DHRS are performed. Water experiments were carried out for the primary heat transportation system including a reactor vessel and heat exchangers of DHRS using a 1/10 model. As for the DHRS loop, sodium experiments were carried out, especially for a heat exchanger installed in an Intermediate Heat Exchanger (IHX). Here, several results of the sodium experiments were described. Transient characteristics during the start up in the air system of the air cooler, secondary loop of DHRS, and the primary loop were examined by the sodium experiments. Smooth increase of natural circulation flow rates in all systems of air and sodium were confirmed. Verifications of numerical simulation methods are planned based on the water and sodium experiments in this investigation plan.
Ishizaka, Kaoru*; Tanaka, Masaru*; Suzuki, Kazuhiko*; Tokizawa, Takayuki; Sato, Kazuhiko; Koga, Osamu
JAEA-Research 2008-086, 64 Pages, 2008/12
JAEA-Research-2008-086.pdf:1.99MB
In this study, to discuss the appropriate Risk Communication (RC) method on the uranium mining sites reclamation, comparative investigation of RC cases which concern the siting of solid waste management facilities and nuclear facilities, and questionnaire survey on the risk perception of landfill were conducted. As a result of comparative investigation, information disclosure and supplement are important factor to obtain public trust on the siting plan and developer. As assumption of the public participation, it is necessary the safety assurance of the siting plan and regional development plan cover a long period. As a result of questionnaire survey, it was shown that the almost people worried about health and the environmental impact of radioactive waste; moreover, there are a lot of ratios of the peoples who felt a dangerous and scary sensuously.
Yabuta, Naohiro*; Kawai, Jun*; Hikawa, Tamae*; Tokizawa, Takayuki; Sato, Kazuhiko; Koga, Osamu
JAEA-Review 2008-015, 92 Pages, 2008/11
JAEA-Review-2008-015.pdf:11.88MB
On the closure of uranium mine site at Ningyo-Toge Environmental Engineering Center Japan Atomic Energy Agency, the action plans for risk communication with residence and local governments were developed and implemented. Under a practical program of the risk communication, an ethnographical research on Ningyo-Toge Environmental Engineering Center has been conducted by local high school students. The research was focused on several social groups such as engineers at the Center and residents around Ningyo-Toge and described their circumstances from the past to the present, since the discovery of the uranium outcrop 1955. In the second year of the program, the results of the research were presented at symposium and the students had opportunities to exchange their views with others from different high schools that held in similar programs. Through those activities, the importance of the program was rediscovered and some new issues were also identified.
Yabuta, Naohiro*; Kawai, Jun*; Hikawa, Tamae*; Tokizawa, Takayuki; Sato, Kazuhiko; Koga, Osamu
JAEA-Review 2008-014, 133 Pages, 2008/11
JAEA-Review-2008-014.pdf:11.04MB
On the closure of uranium mine site at Ningyo-Toge, the action plans for risk communication with residence and local governments were developed and implemented. Under a practical program of the risk communication, an ethnographical research on Ningyo-toge has been conducted by local high school students. The research was focused on several social groups such as engineers at the Center and residents around Ningyo-toge and described their circumstances from the past to the present. In addition, it should be noted that as a results, the research project led several effects listed below; (1) High school students understood significance of the uranium development projects implemented at Ningyo-toge, (2) Differences of standpoints between local residents and Ningyo-toge became clearer, (3) Foundation to communicate between local communities and Ningyo-toge was found out, (4) The educational program on an ethnographical research was conducted autonomously by local high school students.
Koga, Osamu; Nagara, Shuichi; Sato, Kazuhiko; Tokizawa, Takayuki
JNC TN6410 2005-001, 38 Pages, 2005/03
JNC-TN6410-2005-001.pdf:1.33MB
Mesh models are formed to carry out simulations of the groundwater flow and the solute transport at around former Yotsugi Open-Pit Mine and Yotsugi Mill Tailings Dam. Also, hydraulic field survey and literature survey are carried out to set boundary conditions and property values for the simulations.Mesh models are formed for Yotsugi Open-Pit Mine, Yotsugi Mill Tailings Dam and the wide area so that boundary conditions could be given to the model for Yotsugi Mill tailings Dam. These three models are confirmed to perform properly for analyses.Hydraulic field survey is carried out in the wide area to estimate the groundwater distribution and to understand the top hydraulic head boundary of the model. As result, groundwater level at the ridge used as a boundary of the model is set to be twenty meters depth.Values of effective diffusion coefficient, specific storage and absolute density are set to be used for the simulation of the solute transport by the literature survey.
Saito, Kimiaki; Sato, Kaoru; Kinase, Sakae; Noguchi, Hiroshi; Funabiki, Jun*; Takagi, Shunji*; Sato, Osamu*; Emoto, Yutaka*; Koga, Sukehiko*
Proceedings of Monte Carlo 2005 Topical Meeting (CD-ROM), 14 Pages, 2005/00
The voxel phantoms for Japanese male and female adults developed from CT data have been utilized for radiation protection purposes. User codes based on the EGS4 Monte Carlo program have been constructed to calculate external and internal exposures for photons and electrons. The calculated doses were compared with those using stylized MIRD type and other phantoms. The difference for external dose is not simply explained by the difference in body size, but the positions of organs were found to be an important factor to determine the doses. In internal exposure, the positional relations among organs drastically affect the specific absorption fractions, if the source and target organs are different. The simple approximation which has been used by ICRP to evaluate the dose at the boundary of two different media was found to give S values being too conservative. These calculated data shows the usefulness of realistic voxel phantoms combined with the Monte Carlo calculations.
Koga, Osamu; Nagara, Shuichi; Matsumura, Toshihiro; Takeuchi, Akira*; Takeda, Shinji; Yamamoto, Masahiro*; Sato, Kazuhiko
JNC TN6440 2004-003, 66 Pages, 2004/03
JNC-TN6440-2004-003.pdf:1.95MB
To analyze high precision in groundwater flow and radionuclide transport around Yotsugi open-pit mining place site and around Yotsugi mill tailing yard, besides the topic in past analysis is extracted, following it did examination of the corresponding method and arrangement of physical properties value.
Nagara, Shuichi; Yamamoto, Masahiro*; Koga, Osamu; Takeuchi, Akira; Matsumura, Toshihiro; Takeda, Shinji; Sato, Kazuhiko
JNC TN6420 2004-001, 75 Pages, 2004/03
JNC-TN6420-2004-001.pdf:2.93MB
The radon concentration in groundwater summarized around the Yotsugi open-pit site has been measured from 2002 to 2003 and examined radon observation system built in 2001. Moreover, the maintenance actual result of the radon observation system was summarized.
Sato, Kazuhiko; Koga, Osamu; Tokizawa, Takayuki
no journal, ,
For the purpose of safety analysis on reclamation of uranium mine and site release after decommissioning of uranium utilizing facilities at Ningyo-toge Environmental Engineering Center, realistic selection of partition coefficients from published data has been carried out based on groundwater chemistry. It is concluded as follows; (1) Values of selected partition coefficients on uranium, thorium, lead, polonium, protactinium and actinium were larger compare to conservative values applied for the preliminary study in the reclamation plan of uranium mine site at Ningyo-toge, whereas values on radium were smaller. (2) Radionuclide fluxes estimated for Yotsugi mill tailings site with those coefficients would be smaller than that of conservative settings due to potential existence of clay and iron-bearing minerals. However, (3) it is necessary to consider validation with certain real data and application of modeling such as surface complex model to make them more reliable.
Sato, Kazuhiko; Koga, Osamu; Tokizawa, Takayuki; Iimoto, Takeshi*; Kosako, Toshiso*
no journal, ,
Koga, Osamu; Sato, Kazuhiko; Tokizawa, Takayuki; Tanaka, Masaru*; Ishizaka, Kaoru*
no journal, ,
In Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency, to understand the consciousness of residents of related matters of the radiation and the waste disposal, it investigates about the resident in Okayama prefecture in cooperation with Okayama University, as part of informational sharing activity for the reclamation project. The research that information sending to others is continuously done based on the cooperation of Okayama University students and the local high school students, and it reports on the situation.
