• Title/Summary/Keyword: Fukushima Daiichi Nuclear Power Plant Accident

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Panel Session toward Improved Communication and Engagement with the Public after the Fukushima Daiichi Nuclear Power Plant Accident: Study Reports and Discussion with Specialists from Relevant Fields

  • Yoshida, Hiroko;Kuroda, Yujiro;Kono, Takahiko;Naito, Wataru;Sakoda, Akihiro
    • Journal of Radiation Protection and Research
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    • v.46 no.3
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    • pp.134-142
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    • 2021
  • Background: From 2018 to 2020, the Expert Study on Public Understanding after the Fukushima Daiichi Nuclear Power Plant Accident (the Expert Study Group) identified and analyzed activities designed to promote public understanding of science and radiation since the Fukushima accident, and held discussions on how to achieve public understanding in the situation where public confidence has been lost, and how experts should prepare for dealing with the public. This panel session was held at the 53rd meeting of the Japan Health Physics Society on June 30, 2020. Materials and Methods: First, three subgroup (SG) leaders reported their research methods and results. Then, two designated speakers, who participated as observers of the Expert Study Group, commented on the activities. Next, the five speakers held a panel discussion. Finally, the rapporteur summarized. Results and Discussion: SG leaders presented reports from researchers and practitioners in health physics and environmental risks who provided information after the Fukushima accident. During the discussion, experts in sociology and ethics discussed the issues, focusing on the overall goals of the three groups, local (personal) and mass communication, and ethical values. Many of the activities instituted by the experts after the accident were aimed at public understanding of science (that is, to provide knowledge to residents), but by taking into account interactions with residents and their ethical norms, the experts shifted to supporting the residents' decision-making through public engagement. The need to consider both content and channels is well known in the field of health communication, and overlaps with the above discussion. Conclusion: How to implement and promote the public engagement in society was discussed in both the floor and designated discussions. Cooperation between local communities and organizations that have already gained trust is also necessary in order to develop relationships with local residents in normal times, to establish an information transmission system, and to make it work effectively.

Radioactivity data analysis of 137Cs in marine sediments near severely damaged Chernobyl and Fukushima nuclear power plants

  • Song, Ji Hyoun;Kim, TaeJun;Yeon, Jei-Won
    • Nuclear Engineering and Technology
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    • v.52 no.2
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    • pp.366-372
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    • 2020
  • Using several accessible published data sets, we analyzed the temporal change of 137Cs radioactivity (per unit mass of sample) in marine sediments and investigated the effect of the water content of sediment on the 137Cs radioactivity, to understand the behavior of 137Cs present in marine environments. The 137Cs radioactivity in sediments decreased more slowly in the Baltic Sea (near the Chernobyl nuclear power plant) than in the ocean near the Fukushima Daiichi nuclear power plant (FDNPP). The 137Cs radioactivity in the sediment near the FDNPP tended to increase as the water content increased, and the water content decreased at certain sampling sites near the FDNPP for several years. Additionally, the decrease in the water content contributed to 51.2% of the average 137Cs radioactivity decrease rate for the same period. Thus, it may be necessary to monitor both the 137Cs radioactivity and the water content for marine sediments to track the 137Cs that was discharged from the sites of Chernobyl and Fukushima nuclear power plants where severe accidents occurred.

Thyroid Doses in Children from Radioiodine following the Accident at the Fukushima Daiichi Nuclear Power Plant

  • Kim, Eunjoo;Kurihara, Osamu
    • Journal of Radiation Protection and Research
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    • v.45 no.1
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    • pp.2-10
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    • 2020
  • Background: Huge amounts of radionuclides were released into the environment due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, which caused not only serious contamination on the ground, but also radiation exposure to the public. One problem that remains in performing the dose estimation is the difficulty of estimating the internal thyroid dose due to the intake of radioiodine (mainly, 131I) because of limitations to the human data available. Materials and Methods: The relevant papers were collected and reviewed by the authors. The results of thyroid dose estimates from different studies were tabulated for comparison. Results and Discussion: The thyroid dose estimates from the studies varied widely. The dose estimates by the United Nations Scientific Committee on the Effects of Atomic Radiation were higher than the others due to the ingestion dose being based on conservative assumptions. The dose estimates by Japanese experts were mostly below 20-30 mSv. The recent studies suggested that exposure on March 12, 2011 would be crucial for late evacuees from the areas near the FD-NPP because of the possible intake of short-lived radionuclides other than 131I. Further multilateral studies are vital to reduce uncertainties in the present dose estimations. Conclusion: The estimation of the thyroid doses to Fukushima residents still has many uncertainties. However, it is considered unlikely that the thyroid doses exceeded 50 mSv except in some extreme cases. Further multilateral studies are thus necessary to reduce the uncertainties in the present dose estimations.

EVALUATION OF PLANT OPERATIONAL STATES WITH THE CONSIDERATION OF LOOP STRUCTURES UNDER ACCIDENT CONDITIONS

  • MATSUOKA, TAKESHI
    • Nuclear Engineering and Technology
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    • v.47 no.2
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    • pp.157-164
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    • 2015
  • Nuclear power plants have logical loop structures in their system configuration. This paper explains the method to solve a loop structure in reliability analysis. As examples of loop structured systems, the reactor core isolation cooling system and high-pressure core injection system of a boiling water reactor are considered and analyzed under a station blackout accident condition. The analysis results show the important role of loop structures under severe accidents. For the evaluation of the safety of nuclear power plants, it is necessary to accurately evaluate a loop structure's reliability.

Clonal plant as experimental organisms - DNA mutation rate evaluation in the radiation contaminated area of Fukushima Daiichi NPP accident

  • KANEKO, Shingo
    • Proceedings of the Plant Resources Society of Korea Conference
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    • 2018.10a
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    • pp.25-25
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    • 2018
  • The Fukushima Daiichi Nuclear Power Plant accident in March 2011 caused severe radioactive contamination in the surrounding environment. Since the accident, much attention has been paid to the biological and genetic consequences of organism inhabiting the contaminated area. The effect of radiation exposure on genetic mutation rates is little known, especially for low doses and in situ conditions. Evaluating DNA mutation by low levels of radiation dose is difficult due to the rare mutation event and lack of sequence information before the accident. In this study, correlations with air dose levels and somatic DNA mutation rates were evaluated using Next Generation Sequencer for the clonal plant, Phyllostachys edulis. This bamboo is known to spread an identical clone throughout Japan, and it has the advantage that we can compare genetic mutation rate among identical clone growing different air dose levels. We collected 94 samples of P. edulis from 14 sites with air dose rates from $0.04{\sim}7.80{\mu}Gy/h$. Their clonal identity was confirmed by analysis using 24 microsatellite markers, and then, sequences among samples were compared by MIG sequence. The sequence data were obtained from 2,718 loci. About ~200,000 bp sequence (80 bp X 2,718 loci) were obtained for each sample, and this corresponds to about 0.01% of the genome sequence of P. edulis. In these sequences, 442 loci showed polymorphism patterns including recent origin mutation, old mutation, and sequence errors. The number of mutations per sample ranged from 0 to 13, and did not correlate with air dose levels. This result indicated that DNA mutations have not accumulated in P. edulis living in the air doses levels less than $10{\mu}Gy/h$. Our study also suggests that mutation rates can be assessed by selecting an appropriate experimental approach and analyzing with next generation sequencer.

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Mass Interception Fractions and Weathering Half-lives of Iodine-131 and Radiocesium in Leafy Vegetables Observed after the Fukushima Daiichi Nuclear Power Plant Accident

  • Tagami, Keiko;Uchida, Shigeo
    • Journal of Radiation Protection and Research
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    • v.46 no.4
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    • pp.178-183
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    • 2021
  • Background: This study was carried out to provide environmental transfer parameter values to estimate activity concentrations of these radionuclides in agricultural crops when direct contamination occurred. Materials and Methods: Mass interception fractions (FBs) and weathering half-lives (Tws) of 131I and radiocesium were calculated using openly available monitoring data obtained after the Fukushima Daiichi Nuclear Power Plant accident. FB is the ratio between the initial radioactivity concentration of a radionuclide retained by the edible part of the plant (Bq·kg-1 fresh weight [FW]) and the amount of deposited radionuclide in that area (Bq·m-2). Tw values can be calculated using activity concentrations of crops decreased with time after the initial contamination. Results and Discussion: Calculated FB and Tw values for 131I and radiocesium were mostly obtained for leafy vegetables. The analytical results showed that there was no difference of FBs between 131I and radiocesium by t-test; geometric mean values for leafy vegetables cultivated under outdoor conditions were 0.058 and 0.12 m2·kg-1 FW, respectively. Geometric mean Tw value of 131I in leafy vegetables grown under outdoor conditions was 8.6 days, and that of radiocesium was 6.6 days; there was no significant difference between Tw values of these radionuclides by Wilcoxon rank sum test. Conclusion: There was no difference between 131I and radiocesium for FBs and Tws. By using these factors, we would be able to carry out a rough estimation of the activity concentrations of 131I and radiocesium in the edible part of leafy crops when a nuclear accident occurred.

A Buoyant Combined Solar-Wave Power Generation and Its Application for Emergency Power Supply of Nuclear Power Plant (부유식 태양광-파력 복합발전 개념 및 원자력발전소 비상전원을 위한 응용)

  • Cha, Kyung-Ho;Kim, Jung-Taek
    • New & Renewable Energy
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    • v.7 no.4
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    • pp.37-41
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    • 2011
  • This paper presents a Combined solar-wave Power Generation (CPG) concept that the CPG unit is maintained as buoyant at the level of sea water and it is also supported by a submerged tunnel, with the aim of supplying emergency electric power during the station blackout events of nuclear power plants. The CPG concept has been motivated from the 2011 Fukushima-Daiichi Accidents due to the loss of both offsite AC power and emergency diesel power caused by natural hazards such as earthquake and tsunami. The CPG is conceptualized by applying different types and different sites for emergency power generation, in order to reduce common cause failures of emergency power suppliers due to natural hazards. Thus, the CPG can provide a new mean for supplying emergency electric power during station blackout events of nuclear power plants. For this application, the CPG requirements are described with a typical configuration at the ocean side of a submerged tunnel.

Development of a human reliability analysis (HRA) guide for qualitative analysis with emphasis on narratives and models for tasks in extreme conditions

  • Kirimoto, Yukihiro;Hirotsu, Yuko;Nonose, Kohei;Sasou, Kunihide
    • Nuclear Engineering and Technology
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    • v.53 no.2
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    • pp.376-385
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    • 2021
  • Probabilistic risk assessment (PRA) has improved its elemental technologies used for assessing external events since the Fukushima Daiichi Nuclear Power Station Accident in 2011. HRA needs to be improved for analyzing tasks performed under extreme conditions (e.g., different actors responding to external events or performing operations using portable mitigation equipment). To make these improvements, it is essential to understand plant-specific and scenario-specific conditions that affect human performance. The Nuclear Risk Research Center (NRRC) of the Central Research Institute of Electric Power Industry (CRIEPI) has developed an HRA guide that compiles qualitative analysis methods for collecting plant-specific and scenario-specific conditions that affect human performance into "narratives," reflecting the latest research trends, and models for analysis of tasks under extreme conditions.

Dose Estimation Model for Terminal Buds in Radioactively Contaminated Fir Trees

  • Kawaguchi, Isao;Kido, Hiroko;Watanabe, Yoshito
    • Journal of Radiation Protection and Research
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    • v.47 no.3
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    • pp.143-151
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    • 2022
  • Background: After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, biological alterations in the natural biota, including morphological changes of fir trees in forests surrounding the power plant, have been reported. Focusing on the terminal buds involved in the morphological formation of fir trees, this study developed a method for estimating the absorbed radiation dose rate using radionuclide distribution measurements from tree organs. Materials and Methods: A phantom composed of three-dimensional (3D) tree organs was constructed for the three upper whorls of the fir tree. A terminal bud was evaluated using Monte Carlo simulations for the absorbed dose rate of radionuclides in the tree organs of the whorls. Evaluation of the absorbed dose targeted 131I, 134Cs, and 137Cs, the main radionuclides subsequent to the FDNPP accident. The dose contribution from each tree organ was calculated separately using dose coefficients (DC), which express the ratio between the average activity concentration of a radionuclide in each tree organ and the dose rate at the terminal bud. Results and Discussion: The dose estimation indicated that the radionuclides in the terminal bud and bud scale contributed to the absorbed dose rate mainly by beta rays, whereas those in 1-year-old trunk/branches and leaves were contributed by gamma rays. However, the dose contribution from radionuclides in the lower trunk/branches and leaves was negligible. Conclusion: The fir tree model provides organ-specific DC values, which are satisfactory for the practical calculation of the absorbed dose rate of radiation from inside the tree. These calculations are based on the measurement of radionuclide concentrations in tree organs on the 1-year-old leader shoots of fir trees. With the addition of direct gamma ray measurements of the absorbed dose rate from the tree environment, the total absorbed dose rate was estimated in the terminal bud of fir trees in contaminated forests.

What Can Radiation Protection Experts Contribute to the Issue of the Treated Water Stored in the Damaged Fukushima Daiichi Nuclear Power Plant?

  • Yamaguchi, Ichiro
    • Journal of Radiation Protection and Research
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    • v.46 no.1
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    • pp.24-31
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    • 2021
  • Decommissioning efforts are underway at the reactor where the accident occurred, namely the damaged Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Plant (FDNPP). However, a large amount of groundwater flowing into the site has become contaminated with radioactive substances and is stored in tanks on site, which has hampered the decommissioning work. Although the inflow of groundwater has been greatly reduced through measures such as the construction of frost walls, approximately 170 ㎥ of water treated by the Advanced Liquid Processing System (ALPS) is being stored in tanks, each day. The tanks used to store this treated water are expected to become full by around the summer of 2022. It is not easy to get people to understand the efforts of all concerned parties, and providing clear information to these concerned parties is also a challenge. Questions have also been raised regarding whether other alternatives have been fully explored in the ALPS subcommittee. Some people have commented that the answers to the questions raised regarding the biological effects of tritium transmutation are inadequate. Some suspect that the answers are too detailed and incomprehensible, and that the respondents may be manipulating the public with some malicious intent. In any case, each possible plan presents both advantages and disadvantages, depending on the people who are involved. That makes it an ethical and vexing issue that can sway decisions, as perspectives change. While the environmental release plan is scientifically safe, it may represent a painful alternative. On the other hand, a more careful and imaginative approach to the idea of continued storage in tanks or other forms of storage may reveal some troublesome hidden disadvantages. Under these circumstances, experts must be prepared to answer people's questions in a comprehensive and robust manner.