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Ogasawara Katsuhiko - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of the Regionality of the Number of Tweets Related to the 2011 Fukushima Nuclear Power Station Disaster: Content Analysis
    'JMIR Publications Inc.', 2018
    Co-Authors: Aoki Tomohiro, Suzuki Teppei, Yagahara Ayako, 長谷川 慎, Tsuji Shintaro, Ogasawara Katsuhiko
    Abstract:

    Background: The Great East Japan Earthquake on March 11, 2011, triggered a huge tsunami, causing the Fukushima Daiichi nuclear disaster. Radioactive Substances were carried in all directions, along with the risks of Radioactive contamination. Mass media companies, such as television stations and news websites, extensively reported on radiological information related to the disaster. Upon digesting the available radiological information, many citizens turned to social media, such as Twitter and Facebook, to express their opinions and feelings. Thus, the Fukushima Daiichi nuclear disaster also changed the social media landscape in Japan. However, few studies have explored how the people in Japan who received information on radiation propagated the information.Objective: This study aimed to reveal how the number of tweets by citizens containing radiological information changed regionally on Twitter.Methods: The research used about 19 million tweets that included the terms “radiation,” “radioactivity,” and “Radioactive Substance” posted for 1 year after the Fukushima Daiichi nuclear disaster. Nearly 45,000 tweets were extracted based on their inclusion of geographic information (latitude and longitude). The number of monthly tweets in 4 districts (Fukushima Prefecture, prefectures around Fukushima Prefecture, within the Tokyo Electric Power Company area, and others) were analyzed.Results: The number of tweets containing the keywords per 100,000 people at the time of the casualty outbreak was 7.05 per month in Fukushima Prefecture, 2.07 per month in prefectures around Fukushima Prefecture, 5.23 per month in the area within Tokyo Electric Power Company, and 1.35 per month in others. The number of tweets per 100,000 people more than doubled in Fukushima Prefecture 2 months after the Fukushima Daiichi nuclear disaster, whereas the number decreased to around 0.7~0.8 tweets in other districts.Conclusions: The number of tweets per 100,000 people became half of that on March 2011 3 or 4 months after the Fukushima Daiichi Nuclear Plant disaster in 3 districts except district 1 (Fukushima Prefecture); the number became a half in Fukushima Prefecture half a year later

  • Relationships Among Tweets Related to Radiation: Visualization Using Co-Occurring Networks
    'JMIR Publications Inc.', 2018
    Co-Authors: Yagahara Ayako, Hanai Keiri, Hasegawa Shin, Ogasawara Katsuhiko
    Abstract:

    Background: After the Fukushima Daiichi nuclear accident on March 11, 2011, interest in, and fear of, radiation increased among citizens. When such accidents occur, appropriate risk communication must provided by the government. It is therefore necessary to understand the fears of citizens in the days after such accidents.\nObjective: This study aimed to identify the progression of people’s concerns, specifically fear, from a study of radiation-related tweets in the days after the Fukushima Daiichi nuclear accident.\nMethods: From approximately 1.5 million tweets in Japanese including any of the phrases “radiation” (放射線), “radioactivity” (放射能), and “Radioactive Substance” (放射性物質) sent March 11-17, 2011, we extracted tweets that expressed fear. We then performed a morphological analysis on the extracted tweets. Citizens’ fears were visualized by creating co-occurrence networks using co-occurrence degrees showing relationship strength. Moreover, we calculated the Jaccard coefficient, which is one of the co-occurrence indices for expressing the strength of the relationship between morphemes when creating networks.\nResults: From the visualization of the co-occurrence networks, we found high citizen interest in “nuclear power plant” on March 11 and 12, “health” on March 12 and 13, “medium” on March 13 and 14, and “economy” on March 15. On March 16 and 17, citizens’ interest changed to “lack of goods in the afflicted area.” In each co-occurrence network, trending topics, citizens’ fears, and opinions to the government were extracted.\nConclusions: This study used Twitter to understand changes in the concerns of Japanese citizens during the week after the Fukushima Daiichi nuclear accident, with a focus specifically on citizens’ fears. We found that immediately after the accident, the interest in the accident itself was high, and then interest shifted to concerns affecting life, such as health and economy, as the week progressed. Clarifying citizens’ fears and the dissemination of information through mass media and social media can add to improved risk communication in the future

Yasushi Nauchi - One of the best experts on this subject based on the ideXlab platform.

  • early construction and operation of the highly contaminated water treatment system in fukushima daiichi nuclear power station iv assessment of hydrogen behavior in stored cs adsorption vessel
    Journal of Nuclear Science and Technology, 2014
    Co-Authors: Masahiro Kondo, Takahiro Arai, Yoshihisa Nishi, Masahiro Furuya, Taizou Kanai, Ryo Morita, Yuta Uchiyama, Masaaki Satake, Kenetsu Shirakawa, Yasushi Nauchi
    Abstract:

    Hydrogen diffusion behavior in a cesium adsorption vessel is assessed. The vessel is used to remove Radioactive Substance from contaminated water, which is proceeded from Fukushima accident. Experiment and numerical calculation are conducted to clarify the characteristics of natural circulation in the vessel. The natural circulation arising from the temperature difference between inside and outside the vessel is confirmed. We develop an evaluation model to predict the natural circulation and its prediction agrees well with the results obtained by the experiment and the calculation. Using the model, we predict steady and transient behavior of hydrogen concentration. Results indicate that hydrogen concentration is kept lower than the flammability limit when the short vent pipe is open.

Masahiro Kondo - One of the best experts on this subject based on the ideXlab platform.

  • early construction and operation of the highly contaminated water treatment system in fukushima daiichi nuclear power station iv assessment of hydrogen behavior in stored cs adsorption vessel
    Journal of Nuclear Science and Technology, 2014
    Co-Authors: Masahiro Kondo, Takahiro Arai, Yoshihisa Nishi, Masahiro Furuya, Taizou Kanai, Ryo Morita, Yuta Uchiyama, Masaaki Satake, Kenetsu Shirakawa, Yasushi Nauchi
    Abstract:

    Hydrogen diffusion behavior in a cesium adsorption vessel is assessed. The vessel is used to remove Radioactive Substance from contaminated water, which is proceeded from Fukushima accident. Experiment and numerical calculation are conducted to clarify the characteristics of natural circulation in the vessel. The natural circulation arising from the temperature difference between inside and outside the vessel is confirmed. We develop an evaluation model to predict the natural circulation and its prediction agrees well with the results obtained by the experiment and the calculation. Using the model, we predict steady and transient behavior of hydrogen concentration. Results indicate that hydrogen concentration is kept lower than the flammability limit when the short vent pipe is open.

Kazunari Ishida - One of the best experts on this subject based on the ideXlab platform.

  • On a Field Investigation and Open Data Analysis to Identify Diffusion Sources of Radioactive Substance
    International Journal of Environmental Science and Development, 2013
    Co-Authors: Kazunari Ishida
    Abstract:

    After the Fukushima No. 1 nuclear power plant disaster due to the huge earthquake, spreading contamination is a serious fear for Japanese society. In this paper, a field investigation is described to understand the contamination in the west part of Japan, which is in a region approximately a thousand km from the east power plant. Based on the contamination origin found in the investigation, open data is analyzed to identify important factors for spreading Radioactive Substance in terms of relationship between air dose rate and weather conditions. Based on the analysis, a detection rule or algorithm for the contamination origin is summarized to develop a detection system for radiation warning. Air dose rate is observed on each public monitoring point. The nearest weather observation station for each public monitoring point concerning air dose rate is also identified to analyze the relationship between air dose rate and weather conditions. According to the analysis, rainfall is an effective trigger to drop Radioactive Substance, such as contaminated airborne particles, to the ground. However, long-term rainfall, e.g., over half of a day, also has an effect to clean the air and ground. The most serious factor is wind direction from spreading origins of the particles in terms of air dose rate. In addition, consistent wind from a spreading origin can bring the particles without rainfall. On the other hand, wind speed seems not to be a big factor of increase of air dose rate, although the speed could multiply the effect of wind consistency on a spike of the dose rate.

  • Detecting Contamination Sources of Radioactive Substance based on Open Data Analysis
    2013
    Co-Authors: Kazunari Ishida
    Abstract:

    One of the serious fears for Japanese society is contamination of Radioactive Substances due to the huge earthquake and subsequent Fukushima No. 1 nuclear power plant disaster. This paper proposes a detection method to identify contamination sources of Radioactive Substances in the air based on open data, which are composed of air dose rate, amount of rain, wind speed, and direction. To select an appropriate area for analyzing contamination sources with this method, a field investigation is conducted in the west part of Japan, which is in a region approximately one thousand km from the east power plant. Based on the possible contamination origin found in the investigation, open data are analyzed by the method in terms of relationship between air dose rate and weather conditions. Air dose rate is observed on each public monitoring point. The nearest weather observation station for each public monitoring point concerning air dose rate is also identified to analyze the relationship between air dose rate and weather conditions. This method focuses on all cases of continuous rainfall duration, because various sizes of spike concerning air dose rate on a public monitoring point are observed among the cases. Each spike starts when rainfall begins and the spike disappears when rainfall continues. This is because rainfall cleans up Radioactive particles in the atmosphere. The method confirms a statistically significant difference of increase rate of air dose rate between each pair among rainfall cases. It also identifies a range of direction from a monitoring point to diffusion sources based on significance tests of correlation coefficients.

Yagahara Ayako - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of the Regionality of the Number of Tweets Related to the 2011 Fukushima Nuclear Power Station Disaster: Content Analysis
    'JMIR Publications Inc.', 2018
    Co-Authors: Aoki Tomohiro, Suzuki Teppei, Yagahara Ayako, 長谷川 慎, Tsuji Shintaro, Ogasawara Katsuhiko
    Abstract:

    Background: The Great East Japan Earthquake on March 11, 2011, triggered a huge tsunami, causing the Fukushima Daiichi nuclear disaster. Radioactive Substances were carried in all directions, along with the risks of Radioactive contamination. Mass media companies, such as television stations and news websites, extensively reported on radiological information related to the disaster. Upon digesting the available radiological information, many citizens turned to social media, such as Twitter and Facebook, to express their opinions and feelings. Thus, the Fukushima Daiichi nuclear disaster also changed the social media landscape in Japan. However, few studies have explored how the people in Japan who received information on radiation propagated the information.Objective: This study aimed to reveal how the number of tweets by citizens containing radiological information changed regionally on Twitter.Methods: The research used about 19 million tweets that included the terms “radiation,” “radioactivity,” and “Radioactive Substance” posted for 1 year after the Fukushima Daiichi nuclear disaster. Nearly 45,000 tweets were extracted based on their inclusion of geographic information (latitude and longitude). The number of monthly tweets in 4 districts (Fukushima Prefecture, prefectures around Fukushima Prefecture, within the Tokyo Electric Power Company area, and others) were analyzed.Results: The number of tweets containing the keywords per 100,000 people at the time of the casualty outbreak was 7.05 per month in Fukushima Prefecture, 2.07 per month in prefectures around Fukushima Prefecture, 5.23 per month in the area within Tokyo Electric Power Company, and 1.35 per month in others. The number of tweets per 100,000 people more than doubled in Fukushima Prefecture 2 months after the Fukushima Daiichi nuclear disaster, whereas the number decreased to around 0.7~0.8 tweets in other districts.Conclusions: The number of tweets per 100,000 people became half of that on March 2011 3 or 4 months after the Fukushima Daiichi Nuclear Plant disaster in 3 districts except district 1 (Fukushima Prefecture); the number became a half in Fukushima Prefecture half a year later

  • Relationships Among Tweets Related to Radiation: Visualization Using Co-Occurring Networks
    'JMIR Publications Inc.', 2018
    Co-Authors: Yagahara Ayako, Hanai Keiri, Hasegawa Shin, Ogasawara Katsuhiko
    Abstract:

    Background: After the Fukushima Daiichi nuclear accident on March 11, 2011, interest in, and fear of, radiation increased among citizens. When such accidents occur, appropriate risk communication must provided by the government. It is therefore necessary to understand the fears of citizens in the days after such accidents.\nObjective: This study aimed to identify the progression of people’s concerns, specifically fear, from a study of radiation-related tweets in the days after the Fukushima Daiichi nuclear accident.\nMethods: From approximately 1.5 million tweets in Japanese including any of the phrases “radiation” (放射線), “radioactivity” (放射能), and “Radioactive Substance” (放射性物質) sent March 11-17, 2011, we extracted tweets that expressed fear. We then performed a morphological analysis on the extracted tweets. Citizens’ fears were visualized by creating co-occurrence networks using co-occurrence degrees showing relationship strength. Moreover, we calculated the Jaccard coefficient, which is one of the co-occurrence indices for expressing the strength of the relationship between morphemes when creating networks.\nResults: From the visualization of the co-occurrence networks, we found high citizen interest in “nuclear power plant” on March 11 and 12, “health” on March 12 and 13, “medium” on March 13 and 14, and “economy” on March 15. On March 16 and 17, citizens’ interest changed to “lack of goods in the afflicted area.” In each co-occurrence network, trending topics, citizens’ fears, and opinions to the government were extracted.\nConclusions: This study used Twitter to understand changes in the concerns of Japanese citizens during the week after the Fukushima Daiichi nuclear accident, with a focus specifically on citizens’ fears. We found that immediately after the accident, the interest in the accident itself was high, and then interest shifted to concerns affecting life, such as health and economy, as the week progressed. Clarifying citizens’ fears and the dissemination of information through mass media and social media can add to improved risk communication in the future