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Journal Articles

Recent status of the pulsed spallation neutron source at J-PARC

Takada, Hiroshi; Haga, Katsuhiro

JPS Conference Proceedings (Internet), 28, p.081003_1 - 081003_7, 2020/02

At the Japan Proton Accelerator Research Complex (J-PARC), the pulsed spallation neutron source has been in operation with a redesigned mercury target vessel from October 2017 to July 2018, during which the operational beam power was restored to 500 kW and the operation with a 1-MW equivalent beam was demonstrated for one hour. The target vessel includes a gas-micro-bubbles injector and a 2-mm-wide narrow mercury flow channel at the front end as measures to suppress the cavitation damage. After the operating period, it was observed that the cavitation damage at the 3-mm-thick front end of the target vessel could be suppressed less than 17.5 $$mu$$m.

Journal Articles

Examination of $$^{131}$$I and $$^{137}$$Cs releases during late phase of Fukushima Daiichi NPP accident by using $$^{131}$$I/$$^{137}$$Cs ratio of source terms evaluated reversely by WSPEEDI code with environmental monitoring data

Hidaka, Akihide; Yokoyama, Hiroya

Journal of Nuclear Science and Technology, 54(8), p.819 - 829, 2017/08

AA2016-0500.pdf:0.44MB

 Times Cited Count:11 Percentile:80.67(Nuclear Science & Technology)

To clarify what happened during the Fukushima accident, the phenomena within RPV and the discussion of ties with the environmental monitoring are very important. However, the previous study has not necessarily advanced until the present that passed almost six years from the accident. The present study investigated $$^{131}$$I and $$^{137}$$Cs release behaviors during the late phase of the accident based on $$^{131}$$I/$$^{137}$$Cs ratio of the source terms that were recently evaluated backward by WSPEEDI code based on environmental monitoring data. The $$^{131}$$I release from the contaminated water in the basement of 1F2 and 1F3 reactor buildings was evaluated to be about 10% of $$^{131}$$I source term. The increase in $$^{137}$$Cs release from March 21 to 23 and from March 30 to 31 could be explained by the release of CsBO$$_{2}$$ which is formed as a result of chemical reactions of Cs with B$$_{4}$$C due to re-ascension of the core temperature caused by slight shortage of the core cooling water.

Journal Articles

Development of a long-range atmospheric transport model for nuclear emergency and its application to the Chernobyl nuclear accident

Terada, Hiroaki; Chino, Masamichi

Proceedings of 2nd International Conference on Radioactivity in the Environment, p.15 - 18, 2005/10

The previous version of Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI) has been composed of mass-consistent wind field model WSYNOP and particle dispersion model GEARN. Because WSYNOP has no capability to predict meteorological fields, its accuracy and resolution depends on meteorological input data, and it is impossible to treat physical processes realistically. To improve these problems, an atmospheric dynamic model MM5 is introduced and applied to the Chernobyl accident for the verification. Two calculation cases are conducted, CASE-1 a calculation for European region Domain-1, and CASE-2 a domain nesting calculation for Domain-1 and the region around Chernobyl Domain-2. The air concentration and surface deposition of $$^{137}$$Cs calculated by CASE-1 agree well with the measurements by statistical analysis and comparison for the horizontal distribution. In the result of CASE-2, the detailed distribution of surface $$^{137}$$Cs deposition around Chernobyl which was impossible to calculate in CASE-1 is predicted with high accuracy.

Journal Articles

Research activities for development of CTBT-related technologies in JAERI

Shinohara, Nobuo; Asano, Yoshie; Hirota, Naoki*; Hokida, Takanori; Inoue, Yoji; Kumata, Masahiro; Nakahara, Yoshinori*; Oda, Tetsuzo*; Uchikoshi, Takako*; Yamamoto, Yoichi

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 3 Pages, 2005/10

Research activities of JAERI related to the CTBT verification regime are presented in the International Conference. The subjects of this presentation are (1) an overview of the CTBT verification regime, (2) construction and operation of the radionuclide monitoring stations of Okinawa (RN37) and Takasaki (RN38) and the certified radionuclide laboratory (RL11), and (3) preparation of the National Data Center at Tokai (JAERI NDC) for radionuclide data. The RN38 station has been certified by the CTBTO/PrepCom and sending the measured data every day. The infrastructures and operational manuals for RN37 and RL11 are now preparing for their operations. The JAERI NDC has experimentally analyzed and evaluated the radionuclide data from all over the world through International Data Center (IDC). As an example of the JAERI NDC works, atmospheric dispersion backtracking system has been developing by using WSPEEDI (Worldwide Version of System for Prediction of Environmental Emergency Dose Information) code to estimate a source location of radionuclide release by nuclear explosion/accident.

Journal Articles

Improvement of Worldwide Version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI), 1; New combination of models, atmospheric dynamic model MM5 and particle random walk model GEARN-new

Terada, Hiroaki; Furuno, Akiko; Chino, Masamichi

Journal of Nuclear Science and Technology, 41(5), p.632 - 640, 2004/05

 Times Cited Count:21 Percentile:77.71(Nuclear Science & Technology)

The new version of WSPEEDI (Worldwide version of System for Prediction of Environmental Emergency Dose Information) is developed by introducing the combination of models, the atmospheric dynamic model MM5 and the Lagrangian particle dispersion model GEARN-new to improve the prediction capability. One of the improvements by the new system is that Environmental contaminations in multi domains are predicted simultaneously, and the other is that more precise physical processes are considered by using predicted meteorological conditions with high resolution in time and space. The performance of the system is evaluated for the test calculations of hypothetical nuclear accident in the East Asia region and the Chernobyl accident. The results of test calculation in East Asia seem to be reasonable and the calculated surface air concentrations of $$^{137}$$Cs from Chernobyl show good agreement with measurements.

Journal Articles

Development of SPEEDI-MP and its application to a hypothetical accident of a nuclear submarine in the Japan Sea

Kobayashi, Takuya; Nagai, Haruyasu; Chino, Masamichi; Togawa, Orihiko

Proceedings of International Symposium on Radioecology and Environmental Dosimetry, p.500 - 504, 2003/00

The possibility of radionuclide release to the environment is on the increase due to a growth of nuclear facilities in Asia, military problems, nuclear terrorism, etc. The released radionuclides circulate among the atmospheric, oceanic and terrestrial environment, influencing human and natural environment through complex processes. In order to reduce the damage from these pollutants, it is necessary to estimate their migration behavior in detail. A software system SPEEDI-MP (SPEEDI Multi-model Package) is under development to resolve such environmental problems by simulating the 'inclusive and successive' behavior of pollutants in the atmospheric, oceanic and terrestrial environment. As code verification, the system has been applied to a hypothetical accident of a nuclear submarine if it sinks in an offshore region around Japan. The predicted results are examined, and the applicability and validity of the system are discussed.

JAEA Reports

Pumping characteristics of roots blower pumps for light element gases

Hiroki, Seiji; Abe, Tetsuya; Tanzawa, Sadamitsu; Nakamura, Junichi*; Obayashi, Tetsuro*

JAERI-Tech 2002-056, 11 Pages, 2002/07

JAERI-Tech-2002-056.pdf:0.79MB

no abstracts in English

Journal Articles

Analysis of states of the X ray laser medium

Utsumi, Takayuki*; Sasaki, Akira

Oyo Suri Gakkai Heisei-12-Nendo Nenkai Hobunshu, 2 Pages, 2000/00

no abstracts in English

Journal Articles

Cryogenic system for CS test facility

Kato, Takashi; ; Kawano, Katsumi; Hiyama, Tadao; *; *; *; Otsu, K.*; Matsui, Kunihiro; Tsuji, Hiroshi

NIFS-PROC-28, 0, p.33 - 36, 1996/09

no abstracts in English

JAEA Reports

Vector-parralel processing of Car-Parrinello method

*

JAERI-Data/Code 96-007, 40 Pages, 1996/03

JAERI-Data-Code-96-007.pdf:1.36MB

no abstracts in English

Journal Articles

High-frame-rate video visualization of simulated lower head behavior during TMI accident using neutron radioscopy

Nakamura, Hideo; Shibamoto, Yasuteru; Anoda, Yoshinari; Kukita, Yutaka; Mishima, Kaichiro*; Hibiki, Takashi*

Fifth World Conf. on Neutron Radiography, 0, p.665 - 672, 1996/00

no abstracts in English

JAEA Reports

Numerical Studies on JT-60 Divertor Plasma Characteristics

Yoshida, H.; ;

JAERI-M 86-008, 54 Pages, 1986/02

JAERI-M-86-008.pdf:1.33MB

no abstracts in English

JAEA Reports

SPEEDI:System for Prediction of Environmental Emergency Dose Information

; ; ; ; Hidaka, Akihide; ; ; ; ; ; et al.

JAERI-M 84-050, 80 Pages, 1984/03

JAERI-M-84-050.pdf:2.3MB

no abstracts in English

JAEA Reports

Oral presentation

Effect of wall boundary on growing and collapsing behaviors of cavitation bubble

Kawamura, Shunsuke; Naoe, Takashi; Tanaka, Nobuatsu*; Futakawa, Masatoshi

no journal, , 

A mercury target for spallation neutron source has been in operation at the J-PARC. When the high-intense proton beams hits the mercury to produce spallation neutrons, pressure waves are generated due to the abrupt heat deposition of mercury. Mercury enclosure vessel made of stainless steel with a thin wall thickness of 3 mm is severely damaged by pressure wave-induced cavitation erosion. Recently a double-walled structure with narrow gap channel at the front part of the vessel has been developed to mitigate the cavitation damage. In this study, we observed experimentally the growth and collapse behavior of cavitation bubbles in the narrow channel by using a technique of spark discharge in water and a high-speed video camera. Furthermore, the effects of flow velocity and gap width on collapsing pressure were investigated with focusing on the ratio of the projection radius to the gap width. The relationship between the narrow gap and the collapsing pressure will be discussed.

17 (Records 1-17 displayed on this page)
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