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Journal Articles

Solidification and re-melting mechanisms of SUS-B$$_{4}$$C eutectic mixture

Sumita, Takehiro; Kitagaki, Toru; Takano, Masahide; Ikeda, Atsushi

Journal of Nuclear Materials, 543, p.152527_1 - 152527_15, 2021/01

Journal Articles

Distribution map of natural gamma-ray dose rates for studies of the additional exposure dose after the Fukushima Dai-ichi Nuclear Power Station accident

Sanada, Yukihisa; Yoshimura, Kazuya; Urabe, Yoshimi*; Iwai, Takeyuki*; Katengeza, E. W.*

Journal of Environmental Radioactivity, 223-224, p.106397_1 - 106397_9, 2020/11

Journal Articles

Measurements of the doses of eye lens for the workers of Fukushima Daiichi Nuclear Power Plant

Yokoyama, Sumi*; Ezaki, Iwao*; Tatsuzaki, Hideo*; Tachiki, Shuichi*; Hirao, Kazushige*; Aoki, Katsunori; Tanimura, Yoshihiko; Hoshi, Katsuya; Yoshitomi, Hiroshi; Tsujimura, Norio

Radiation Measurements, 138, p.106399_1 - 106399_5, 2020/11

Journal Articles

Reservoir sediments as a long-term source of dissolved radiocaesium in water system; a mass balance case study of an artificial reservoir in Fukushima, Japan

Funaki, Hironori; Sakuma, Kazuyuki; Nakanishi, Takahiro; Yoshimura, Kazuya; Katengeza, E. W.*

Science of the Total Environment, 743, p.140668_1 - 140668_9, 2020/11

Journal Articles

A Model intercomparison of atmospheric $$^{137}$$Cs concentrations from the Fukushima Daiichi Nuclear Power Plant accident, phase III; Simulation with an identical source term and meteorological field at 1-km resolution

Sato, Yosuke*; Sekiyama, Tsuyoshi*; Fang, S.*; Kajino, Mizuo*; Qu$'e$rel, A.*; Qu$'e$lo, D.*; Kondo, Hiroaki*; Terada, Hiroaki; Kadowaki, Masanao; Takigawa, Masayuki*; et al.

Atmospheric Environment; X (Internet), 7, p.100086_1 - 100086_12, 2020/10

The third model intercomparison project for investigating the atmospheric behavior of $$^{137}$$Cs emitted during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident (FDNPP-MIP) was conducted. A finer horizontal grid spacing (1 km) was used than in the previous FDNPP-MIP. Nine of the models used in the previous FDNPP-MIP were also used, and all models used identical source terms and meteorological fields. Our analyses indicated that most of the observed high atmospheric $$^{137}$$Cs concentrations were well simulated, and the good performance of some models improved the performance of the multi-model ensemble. The analyses also confirmed that the use of a finer grid resolution resulted in the meteorological field near FDNPP being better reproduced. The good representation of the wind field resulted in the reasonable simulation of the narrow distribution of high deposition amount to the northwest of FDNPP and the reduction of the overestimation over the area to the south of FDNPP. In contrast, the performance of the models in simulating plumes observed over the Nakadori area, the northern part of Gunma, and the Tokyo metropolitan area was slightly worse.

Journal Articles

Construction of virtual reality system for radiation working environment reproduced by gamma-ray imagers combined with SLAM technologies

Sato, Yuki; Minemoto, Kojiro*; Nemoto, Makoto*; Torii, Tatsuo

Nuclear Instruments and Methods in Physics Research A, 976, p.164286_1 - 164286_6, 2020/10

 Times Cited Count:0 Percentile:100(Instruments & Instrumentation)

Journal Articles

Development of side thruster system for ASV

Kato, Tetsu*; Kawamura, Yamato*; Tahara, Junichiro*; Baba, Shoichiro*; Sanada, Yukihisa

Proceedings of the 30th (2020) International Ocean and Polar Engineering Conference (ISOPE 2020) (USB Flash Drive), p.1255 - 1260, 2020/10

Journal Articles

Development and validation of the eutectic reaction model in JUPITER code

Chai, P.; Yamashita, Susumu; Yoshida, Hiroyuki

Annals of Nuclear Energy, 145, p.107606_1 - 107606_13, 2020/09

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

The eutectic reaction model in JUPITER code was validated against two series of experimental tests that performed by JAEA. An experiment that aimed to evaluate the eutectic reaction between Zircaloy and Stainless steel, was simulated by JUPITER code to validate its reliability on predicting the binary eutectic reaction phenomenon. A comparison of the simulation and experimental results demonstrates good agreement on the increase rate of the solution depth at various temperature environments. Another series of tests which aimed to predict the eutectic reaction between the control rod blade and channel box in BWR, were simulated by JUPITER code to test its applicability on predicting the eutectic reaction between multiple mixture components. Although the deviation could not be completely eliminated, the reaction performance in the experiment was reasonably reproduced. As a result, it could be concluded that JUPITER code is feasible to predict the eutectic reaction behavior in nuclear severe accident.

Journal Articles

Radiocesium distribution in the sediments of the Odaka River estuary, Fukushima, Japan

Hagiwara, Hiroki; Nakanishi, Takahiro; Konishi, Hiromi*; Tsuruta, Tadahiko; Misono, Toshiharu; Fujiwara, Kenso; Kitamura, Akihiro

Journal of Environmental Radioactivity, 220-221, p.106294_1 - 106294_9, 2020/09

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

Journal Articles

Investigation of high-temperature chemical interaction of calcium silicate insulation and cesium hydroxide

Rizaal, M.; Nakajima, Kunihisa; Saito, Takumi*; Osaka, Masahiko; Okamoto, Koji*

Journal of Nuclear Science and Technology, 57(9), p.1062 - 1073, 2020/09

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

The interaction of cesium hydroxide and a calcium silicate insulation material was experimentally investigated at high temperature conditions. A thermogravimetry equipped with differential thermal analysis was used to analyze thermal events in the samples of mixed calcium silicate and cesium hydroxide under Ar-5%H$$_{2}$$ and Ar-4%H$$_{2}$$-20%H$$_{2}$$0 with maximum temperature of 1100$$^{circ}$$C. Prior being mixed with cesium hydroxide, a part of calcium silicate was pretreated at high temperature to evaluate the effect of possible structural changes of this material due to a preceding thermal history and also the sake of thermodynamic evaluation to those available ones. Based upon the initial condition (preliminary heat treatment) of calcium silicate, it was found that if the original material consisted of xonotlite (Ca$$_{6}$$Si$$_{6}$$0$$_{17}$$(0H)$$_{2}$$), the endothermic reaction with cesium hydroxide occurred over the temperature range 575-730$$^{circ}$$C meanwhile if the crystal phase of original material was changed to wollastonite (CaSi0$$_{3}$$), the interaction occurred over temperature range 700-1100$$^{circ}$$C. Furthermore, the X-ray diffraction analyses have indicated on both type of pretreated calsils that regardless of Ar-5%H$$_{2}$$ and Ar-4%H$$_{2}$$-20%H$$_{2}$$0 atmosphere, cesium aluminum silicate, CsAlSi0$$_{4}$$ was formed with aluminum in the samples as an impurity or adduct.

Journal Articles

Observation of morphological abnormalities in silkworm pupae after feeding $$^{137}$$CsCl-supplemented diet to evaluate the effects of low dose-rate exposure

Tanaka, Sota; Kinouchi, Tadatoshi*; Fujii, Tsuguru*; Imanaka, Tetsuji*; Takahashi, Tomoyuki*; Fukutani, Satoshi*; Maki, Daisuke*; Notomi, Akihiro*; Takahashi, Sentaro*

Scientific Reports (Internet), 10, p.16055_1 - 16055_7, 2020/09

Since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, morphological abnormalities of the lepidopteran insects have been reported. However, it is unclear whether the abnormalities were caused directly by radiation because they did not study on absorbed dose and dose-effect relationship. In this study, we conducted an internal exposure experiment on silkworm using $$^{137}$$CsCl-supplemented artificial diet and estimated the absorbed dose to evaluate the morphological abnormalities in silkworm. The ratio of wing to whole body of pupae was compared between the $$^{137}$$CsCl-exposured and control groups and no significant differences were observed between the groups. This result suggest that morphological abnormalities in lepidopterans are unlikely due to direct radiation effects from $$^{137}$$Cs contamination after the FDNPP accident.

Journal Articles

Effect of seawater components on corrosion rate of steel in air/solution alternating condition

Otani, Kyohei; Tsukada, Takashi; Ueno, Fumiyoshi; Kato, Chiaki

Zairyo To Kankyo, 69(9), p.246 - 252, 2020/09

The purpose of this study was to investigate the effect of artificial sea water concentration on the corrosion rate of carbon steel under air/solution alternating condition, and to clarify the corrosion mechanism of carbon steel that changes with artificial seawater concentration. Mass measurements showed that the corrosion rate of carbon steel in the alternating condition accelerates with increasing concentration in the concentration region between deionized water to 200 times diluted artificial seawater (ASW), and the corrosion rate decreases with increasing concentration in the concentration region between 20 times diluted ASW to undiluted ASW. It can be considered that the reason why the carbon steel corrosion was suppressed in highly concentrated artificial seawater would Mg ions and Ca ions in the artificial seawater precipitate and cover on the surface due to the increase in pH near the surface by oxygen reduction reaction.

Journal Articles

Seven-year temporal variation of caesium-137 discharge inventory from the port of Fukushima Daiichi Nuclear Power Plant; Continuous monthly estimation of caesium-137 discharge in the period from April 2011 to June 2018

Machida, Masahiko; Yamada, Susumu; Iwata, Ayako; Otosaka, Shigeyoshi; Kobayashi, Takuya; Watanabe, Masahisa; Funasaka, Hideyuki; Morita, Takami*

Journal of Nuclear Science and Technology, 57(8), p.939 - 950, 2020/08

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

After direct discharges of highly contaminated water of the Fukushima Daiichi Nuclear Power Plant (1F) from April to May 2011, Kanda suggested that relatively small amounts of run-off of radionuclides from the 1F port into the Fukushima coastal region subsequently continued by his estimation method. However, the estimation period was limited to up to September 2012. Therefore, this paper estimates the discharge inventory up to June 2018. In the missing period, the Japanese government and Tokyo Electric Power Company Holdings have continued efforts to stop the discharge, and consequently, the radionuclide concentration in seawater inside the 1F port has gradually diminished. We show the monthly discharge inventory of $$^{137}$$Cs up to June 2018 by two methods, i.e., Kanda method partially improved by the authors and a more sophisticated method using Voronoi tessellation reflecting the increase in the number of monitoring points inside the 1 F port. The results show that the former always yields overestimated results compared with the latter, but the ratio of the former to the latter is less than one order of magnitude. Using these results, we evaluate the impact of the discharge inventory from the 1F port into the coastal area and radiation dose upon fish ingestion.

Journal Articles

A Cubic CeBr$$_{3}$$ gamma-ray spectrometer suitable for the decommissioning of the Fukushima Daiichi Nuclear Power Station

Kaburagi, Masaaki; Shimazoe, Kenji*; Otaka, Yutaka*; Uenomachi, Mizuki*; Kamada, Kei*; Kim, K. J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*; et al.

Nuclear Instruments and Methods in Physics Research A, 971, p.164118_1 - 164118_8, 2020/08

 Times Cited Count:0 Percentile:100(Instruments & Instrumentation)

Journal Articles

Project IPAD; A Database to catalogue the analysis of Fukushima Daiichi accident fragmental release material

Martin, P.*; Alhaddad, O.*; Verbelen, Y.*; Satou, Yukihiko; Igarashi, Yasuhito*; Scott, T. B.*

Scientific Data (Internet), 7, p.282_1 - 282_8, 2020/08

 Times Cited Count:0

Journal Articles

The Ecological half-life of radiocesium in surficial bottom sediments of five ponds in Fukushima based on ${it in situ}$ measurements with Plastic Scintillation Fibers

Katengeza, E. W.*; Sanada, Yukihisa; Yoshimura, Kazuya; Ochi, Kotaro; Iimoto, Takeshi*

Environmental Science; Processes & Impacts, 22(7), p.1566 - 1576, 2020/07

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

Journal Articles

Low temperature heat capacity of Cs$$_{2}$$Si$$_{4}$$O$$_{9}$$

Suzuki, Eriko; Nakajima, Kunihisa; Osaka, Masahiko; Oishi, Yuji*; Muta, Hiroaki*; Kurosaki, Ken*

Journal of Nuclear Science and Technology, 57(7), p.852 - 857, 2020/07

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

The low temperature heat capacity of Cs$$_{2}$$Si$$_{4}$$O$$_{9}$$, which is one of the cesium chemisorbed compounds onto stainless steel during severe accident of the light water nuclear reactor, was experimentally determined for the first time in the temperature range of 1.9 - 302 K. The experimentally determined heat capacity, $$C_{p}$$$$^{o}$$ (298.15K), and the standard entropy, $$S^{o}$$ (298.15K), were 249.4 $$pm$$ 1.1 J K$$^{-1}$$ mol$$^{-1}$$ and 322.1 $$pm$$ 1.3 J K$$^{-1}$$ mol$$^{-1}$$, respectively. The standard Gibbs energy of formation of Cs$$_{2}$$Si$$_{4}$$O$$_{9}$$ at high temperatures, $$Delta$$$$_{f}$$$$G^{o}$$($$T$$), were reevaluated by using the presently obtained $$S^{o}$$ (298.15K) and the previously reported experimental results of the standard enthalpy of formation, $$Delta$$$$_{f}$$$$H^{o}$$ (298.15K), and the standard enthalpy increments at high temperatures, $$H^{o}$$($$T$$)-$$H^{o}$$ (298.15K).

Journal Articles

Retracted article; Visualization and integration of images of radioactive substances as point cloud data in 3-D environment models

Sato, Yuki; Torii, Tatsuo

Nuclear Technology, 206(7), p.v - xvi, 2020/07

 Times Cited Count:1 Percentile:19.53(Nuclear Science & Technology)

Journal Articles

Statement of retraction; Visualization and integration of images of radioactive substances as point cloud data in 3-D environment models

Sato, Yuki; Torii, Tatsuo

Nuclear Technology, 206(7), P. 1095, 2020/07

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Journal Articles

Key factors controlling radiocesium sorption and fixation in river sediments around the Fukushima Daiichi Nuclear Power Plant, 1; Insights from sediment properties and radiocesium distributions

Tachi, Yukio; Sato, Tomofumi*; Akagi, Yosuke*; Kawamura, Makoto*; Nakane, Hideji*; Terashima, Motoki; Fujiwara, Kenso; Iijima, Kazuki

Science of the Total Environment, 724, p.138098_1 - 138098_11, 2020/07

 Times Cited Count:1 Percentile:100(Environmental Sciences)

To understand and predict radiocesium transport behaviors in the environment, highly contaminated sediments from Ukedo and Odaka rivers around the Fukushima Daiichi Nuclear Power Plant were investigated systematically focusing on key factors controlling radiocesium sorption and fixation, including particle size, clay mineralogy and organic matter.

1166 (Records 1-20 displayed on this page)