Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 129

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Guidance for ${it in situ}$ gamma spectrometry intercomparison based on the information obtained through five intercomparisons during the Fukushima mapping project

Mikami, Satoshi; Ishikawa, Daisuke*; Matsuda, Hideo*; Hoshide, Yoshifumi*; Okuda, Naotoshi*; Sakamoto, Ryuichi*; Saito, Kimiaki

Journal of Environmental Radioactivity, 210, p.105938_1 - 105938_7, 2019/12

 Times Cited Count:0 Percentile:100(Environmental Sciences)

Five intercomparisons of in situ $$gamma$$ spectrometry by 6-7 participating teams have been conducted between December 2011 and August 2015 at sites in Fukushima prefecture which affected by the fallout of FDNPS accident occurred in March 2011. The evaluated deposition densities agreed within 5-6% in terms of coefficient of variation (CV) for radiocesium ($$^{134}$$Cs and $$^{137}$$Cs), by our best achievement, and the ratio of $$^{134}$$Cs/$$^{137}$$Cs in deposition density agreed within 1-2% in CV, through five intercomparisons. These results guarantee the accuracy of the measurements of the mapping project. Two different methods for intercomparison were conducted: (1) sequential measurements at an identical point; and (2) simultaneous measurements in a narrow area within 3 m radius. In a comparison between the two methods at a site, no significant difference was observed between the results. The standard protocols for the two different intercomparison methods were proposed based on our experience.

Journal Articles

Summary of temporal changes in air dose rates and radionuclide deposition densities in the 80 km zone over five years after the Fukushima Nuclear Power Plant accident

Saito, Kimiaki; Mikami, Satoshi; Ando, Masaki; Matsuda, Norihiro; Kinase, Sakae; Tsuda, Shuichi; Yoshida, Tadayoshi; Sato, Tetsuro*; Seki, Akiyuki; Yamamoto, Hideaki*; et al.

Journal of Environmental Radioactivity, 210, p.105878_1 - 105878_12, 2019/12

 Times Cited Count:5 Percentile:29.47(Environmental Sciences)

Journal Articles

The Deposition densities of radiocesium and the air dose rates in undisturbed fields around the Fukushima Dai-ichi nuclear power plant; Their temporal changes for five years after the accident

Mikami, Satoshi; Tanaka, Hiroyuki*; Matsuda, Hideo*; Sato, Shoji*; Hoshide, Yoshifumi*; Okuda, Naotoshi*; Suzuki, Takeo*; Sakamoto, Ryuichi*; Ando, Masaki; Saito, Kimiaki

Journal of Environmental Radioactivity, 210, p.105941_1 - 105941_12, 2019/12

 Times Cited Count:7 Percentile:17.5(Environmental Sciences)

The deposition densities of radiocesium and the air dose rates were repeatedly measured in a large number of undisturbed fields within the 80km zone that surrounds the Fukushima Dai-ichi Nuclear Power Plant site between 2011 and 2016, and features of their temporal changes were clarified. The average air dose rate excluding background radiation in this zone decreased to about 20% of the initial value during the period from June 2011 to August 2016, which was essentially a result of the radioactive decay of $$^{134}$$Cs with a half-life of 2.06y. The air dose rate reduction was faster than that expected from the decay of radiocesium by a factor of about two, with most of this reduction being attributed to the penetration of radiocesium into the soil. The average deposition densities of $$^{134}$$Cs and $$^{137}$$Cs in fields that were not decontaminated were found to have decreased nearly according to their expected radioactive decay, which indicated that the movement of radiocesium in the horizontal direction was relatively small. The effect of decontamination was apparently observed in the measurements of air dose rates and deposition densities. Nominally, the average air dose rates in the measurement locations were reduced by about 20% by decontamination and other human activities, of which accurate quantitative analysis is and continue to be a challenge.

Journal Articles

Reconstruction of a Fukushima accident-derived radiocesium fallout map for environmental transfer studies

Kato, Hiroaki*; Onda, Yuichi*; Gao, X.*; Sanada, Yukihisa; Saito, Kimiaki

Journal of Environmental Radioactivity, 210, p.105996_1 - 105996_12, 2019/12

 Times Cited Count:3 Percentile:38.8(Environmental Sciences)

Journal Articles

Sea water flow boiling heat transfer involving sea salt deposition; Role of deposited sea salt

Koizumi, Yasuo*; Uesawa, Shinichiro; Ono, Ayako; Shibata, Mitsuhiko; Yoshida, Hiroyuki

Nippon Kikai Gakkai Netsu Kogaku Konfarensu 2019 Koen Rombunshu (USB Flash Drive), 1 Pages, 2019/10

no abstracts in English

Journal Articles

Estimation of the release time of radio-tellurium during the Fukushima Daiichi Nuclear Power Plant accident and its relationship to individual plant events

Takahashi, Sentaro*; Kawashima, Shigeto*; Hidaka, Akihide; Tanaka, Sota*; Takahashi, Tomoyuki*

Nuclear Technology, 205(5), p.646 - 654, 2019/05

 Times Cited Count:2 Percentile:28.85(Nuclear Science & Technology)

Journal Articles

Development of evaluation method for aerosol particle deposition in a reactor building based on CFD

Horiguchi, Naoki; Miyahara, Naoya; Uesawa, Shinichiro; Yoshida, Hiroyuki; Osaka, Masahiko

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05

For source term evaluation from reactor buildings (RBs) in LWR severe accidents, we have launched to develop an evaluation method of FP aerosol particle deposition onto surfaces of internal structures in an RB based on computational fluid dynamics (CFD). This paper describes development of a CFD simulation tool as the base part of the evaluation method. A preliminary simulation for a representative RB under a representative flow condition was conducted to confirm the tool performance by roughly grasping the deposition behaviors of FP aerosol particle and decontamination factor (DF) in the RB. Calculation results showed that most of aerosol particles were deposited along with gas flow formed by the internal structures in the RB, demonstrating the advantageous feature of the present CFD tool. The DFs from 4 to 14 were obtained with increase of the particle diameters from 0.1 to 10 $$mu$$m as expected in terms of the particle movement equation.

Journal Articles

Model intercomparison of atmospheric $$^{137}$$Cs from the Fukushima Daiichi Nuclear Power Plant accident; Simulations based on identical input data

Sato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qu$'e$lo, D.*; et al.

Journal of Geophysical Research; Atmospheres, 123(20), p.11748 - 11765, 2018/10

 Times Cited Count:8 Percentile:32.79(Meteorology & Atmospheric Sciences)

A model intercomparison of the atmospheric dispersion of $$^{137}$$Cs emitted following the Fukushima Daiichi Nuclear Power Plant accident was conducted by 12 models to understand the behavior of $$^{137}$$Cs in the atmosphere. The same meteorological data, horizontal grid resolution, and an emission inventory were applied to all the models to focus on the model variability originating from the processes included in each model. The multi-model ensemble captured 40% of the observed $$^{137}$$Cs events, and the figure-of-merit in space for the total deposition of $$^{137}$$Cs exceeded 80. Our analyses indicated that the meteorological data were most critical for reproducing the $$^{137}$$Cs events. The results also revealed that the differences among the models were originated from the deposition and diffusion processes when the meteorological field was simulated well. However, the models with strong diffusion tended to overestimate the $$^{137}$$Cs concentrations.

Journal Articles

Study on Pu-burner high temperature gas-cooled reactor in Japan; Test and characterization for ZrC coating

Ueta, Shohei; Aihara, Jun; Mizuta, Naoki; Goto, Minoru; Fukaya, Yuji; Tachibana, Yukio; Okamoto, Koji*

Proceedings of 9th International Topical Meeting on High Temperature Reactor Technology (HTR 2018) (USB Flash Drive), 7 Pages, 2018/10

The security and safety fuel (3S-TRISO fuel) employs the coated fuel particle with a fuel kernel made of plutonium dioxide (PuO$$_{2}$$) and yttria stabilized zirconia (YSZ) as an inert matrix. Especially, a zirconium carbide (ZrC) coating is one of key technologies of the 3S-TRISO, which performs as an oxygen getter to reduce the fuel failure due to internal pressure during the irradiation. R&Ds on ZrC coating directly on the dummy CeO$$_{2}$$-YSZ kernel have been carried in the Japanese fiscal year 2017. As results of ZrC coating tests by the bromide chemical vapor deposition process, stoichiometric ZrC coatings with 3 - 18 microns of thicknesses were obtained with 0.1 kg of particle loading weight.

Journal Articles

Altitudinal characteristics of atmospheric deposition of aerosols in mountainous regions; Lessons from the Fukushima Daiichi Nuclear Power Station accident

Sanada, Yukihisa; Katata, Genki*; Kaneyasu, Naoki*; Nakanishi, Chika*; Urabe, Yoshimi*; Nishizawa, Yukiyasu*

Science of the Total Environment, 618, p.881 - 890, 2018/03

 Times Cited Count:6 Percentile:42.63(Environmental Sciences)

Although the reconstruction of atmospheric deposition processes of radiocesium during the Fukushima Daiichi Nuclear Power Station (FDNPS) accident is essential, the whole picture of the deposition mechanism in complex topography has not been well understood yet. To understand atmospheric deposition processes of aerosols over the complex mountainous topography, we analyzed altitudinal characteristics of radiocesium released during the accident. At five selected mountainous areas in the eastern Japan, altitudinal characters of air dose rate observed by our high-resolution airborne surveys after the accident was analyzed based on the results of three typical (dry, wet, and cloud water) deposition obtained from the latest atmospheric dispersion.

Journal Articles

Hydrogen production tests by hydrogen iodide decomposition membrane reactor equipped with silica-based ceramics membrane

Myagmarjav, O.; Tanaka, Nobuyuki; Nomura, Mikihiro*; Kubo, Shinji

International Journal of Hydrogen Energy, 42(49), p.29091 - 29100, 2017/12

 Times Cited Count:10 Percentile:52.29(Chemistry, Physical)

The catalytic decomposition of hydrogen iodide in a membrane reactor using silica membranes derived from hexyltrimethoxysilane (HTMOS) was investigated for the production of hydrogen in the thermochemical water splitting iodine-sulfur process. The silica membranes were prepared by counter-diffusion chemical vapor deposition using porous alumina support tubes in both the absence and presence of a $$gamma$$-alumina layer. The silica membranes formed on $$gamma$$-alumina-coated $$alpha$$-alumina tubes displayed a higher H$$_{2}$$ permeance than that formed directly on an $$alpha$$-alumina tube. A silica membrane based on a 1.5 $$mu$$m-thick $$gamma$$-alumina layer fabricated under deposition conditions of 450$$^{circ}$$C, 1200 s, and a N$$_{2}$$ carrier gas velocity of 0.044 m s$$^{-1}$$ exhibited a high H$$_{2}$$ permeance of 9.4 $$times$$ 10$$^{-7}$$ mol Pa$$^{-1}$$ m$$^{-2}$$ s$$^{-1}$$ while maintaining an H$$_{2}$$/N$$_{2}$$ selectivity of over 80.0. The performance of a membrane reactor based on an HTMOS-derived silica membrane was evaluated at 400$$^{circ}$$C by measuring the HI conversion and H$$_{2}$$ flow rates. The conversion was approximately 0.48 when the HI flow rate was 9.7 mL min$$^{-1}$$.

Journal Articles

Role of soil-to-leaf tritium transfer in controlling leaf tritium dynamics; Comparison of experimental garden and tritium-transfer model results

Ota, Masakazu; Kwamena, N.-O. A.*; Mihok, S.*; Korolevych, V.*

Journal of Environmental Radioactivity, 178-179, p.212 - 231, 2017/11

 Times Cited Count:4 Percentile:68.6(Environmental Sciences)

Environmental transfer models assume that organically-bound tritium (OBT) is formed directly from tissue-free water tritium (TFWT) in environmental compartments. Nevertheless, studies in the literature have shown that measured OBT/TFWT ratios are variable. The importance of soil-to-leaf HTO transfer pathway in controlling the leaf tritium dynamics is not well understood. A model inter-comparison of two tritium transfer models (CTEM-CLASS-TT and SOLVEG-II) was carried out with measured environmental samples from an experimental garden plot set up next to a tritium-processing facility. The garden plot received one of three different irrigation treatments - no external irrigation, irrigation with low tritium water and irrigation with high tritium water. The contrast between the results obtained with the different irrigation treatments provided insights into the impact of soil-to-leaf HTO transfer on the leaf tritium dynamics. Concentrations of TFWT and OBT in the garden plots that were not irrigated or irrigated with low tritium water were variable, responding to the arrival of the HTO-plume from the tritium-processing facility. In contrast, for the plants irrigated with high tritium water, the TFWT concentration remained elevated due to a continuous source of high HTO in the soil. Calculated concentrations of OBT in the leaves showed an initial increase followed by quasi-equilibration with the TFWT concentration. In this quasi-equilibrium state, concentrations of OBT remained elevated and unchanged despite the arrivals of the plume. These results from the model inter-comparison demonstrate that soil-to-leaf HTO transfer significantly affects OBT/TFWT ratio in the leaf regardless of the atmospheric HTO concentration, only if there is elevated HTO concentrations in the soil. The results of this work indicate that assessment models should be refined to consider the importance of soil-to-leaf HTO transfer to ensure that dose estimates are accurate and conservative.

Journal Articles

Factors affecting the effectiveness of sheltering in reducing internal exposure

Hirouchi, Jun; Takahara, Shogo; Komagamine, Hiroshi*; Watanabe, Masatoshi*; Munakata, Masahiro

Proceedings of Asian Symposium on Risk Assessment and Management 2017 (ASRAM 2017) (USB Flash Drive), 11 Pages, 2017/11

no abstracts in English

Journal Articles

Identification of penetration path and deposition distribution of radionuclides in houses by experiments and numerical model

Hirouchi, Jun; Takahara, Shogo; Iijima, Masashi; Watanabe, Masatoshi; Munakata, Masahiro

Radiation Physics and Chemistry, 140, p.127 - 131, 2017/11

BB2016-0282.pdf:0.38MB

 Times Cited Count:0 Percentile:100(Chemistry, Physical)

Journal Articles

Saturated pool nucleate boiling on heat transfer surface with deposited sea salts

Uesawa, Shinichiro; Koizumi, Yasuo; Shibata, Mitsuhiko; Yoshida, Hiroyuki

Journal of Nuclear Engineering and Radiation Science, 3(4), p.041002_1 - 041002_13, 2017/10

Journal Articles

Challenges for enhancing Fukushima environmental resilience, 2; Features of radionuclide release and deposition with accident progress

Saito, Kimiaki; Nagai, Haruyasu; Kinase, Sakae; Takemiya, Hiroshi

Nippon Genshiryoku Gakkai-Shi, 59(6), p.40 - 44, 2017/06

no abstracts in English

Journal Articles

Improvement in quantitative performance of underwater laser-induced breakdown spectroscopy based on the understanding of laser ablation phenomena

Matsumoto, Ayumu

Reza Kako Gakkai-Shi, 23(3), p.222 - 231, 2016/10

no abstracts in English

Journal Articles

Utilization of $$^{134}$$Cs/$$^{137}$$Cs in the environment to identify the reactor units that caused atmospheric releases during the Fukushima Daiichi accident

Chino, Masamichi; Terada, Hiroaki; Nagai, Haruyasu; Katata, Genki; Mikami, Satoshi; Torii, Tatsuo; Saito, Kimiaki; Nishizawa, Yukiyasu

Scientific Reports (Internet), 6, p.31376_1 - 31376_14, 2016/08

 Times Cited Count:22 Percentile:3.08(Multidisciplinary Sciences)

Journal Articles

Measurements and evaluations of air dose rates around Fukushima, 5; Characteristics of air dose rate distribution in the environment around the Fukushima Nuclear Power Plant site

Mikami, Satoshi; Matsuda, Norihiro; Ando, Masaki; Kinase, Sakae; Kitano, Mitsuaki; Kawase, Keiichi; Matsumoto, Shinichiro; Yamamoto, Hideaki; Saito, Kimiaki

Radioisotopes, 64(9), p.589 - 607, 2015/09

This article presents the features of regional distributions and temporal changes in air dose rate and radionuclide deposition densities in Fukushima on the basis of analyses on large-scale environmental monitoring results using diverse methods. The continuity of decontamination effects is discussed according to repeated monitoring data after the decontamination model project. Further, some examples are shown on the projection of air dose rates together with the ecological half lives for different land uses.

Journal Articles

Thermal properties of redeposition layers in the JT-60U divertor region

Ishimoto, Yuki; Goto, Yoshitaka*; Arai, Takashi; Masaki, Kei; Miya, Naoyuki; Oyama, Naoyuki; Asakura, Nobuyuki

Journal of Nuclear Materials, 350(3), p.301 - 309, 2006/05

 Times Cited Count:20 Percentile:17.23(Materials Science, Multidisciplinary)

Thermal properties of the redeposition layer on the inner plate of the W-shaped divertor of JT-60U have been measured with laser flash method for the first time so as to estimate transient heat loads onto the divertor. Measurement of a redeposition layer sample of more than 200 m thick showed following results: (1) the bulk density of the redeposition layer is about half of that of carbon fiber composite material; (2) the specific heat of the layer is roughly equal to that of the isotropic graphite; (3) the thermal conductivity of the redeposition layer is two orders of magnitude smaller than that of the carbon fiber composite. The difference between the divertor heat loads and the loss of the plasma stored energy becomes smaller taking account of thermal properties of the redeposition layer on the inner divertor, whereas estimated heat loads due to the ELMs is still larger than the loss. This is probably caused by the poloidal distribution of the thermal properties and heat flux asymmetry inherent in the device.

129 (Records 1-20 displayed on this page)