Fukushima Nuclear Power Plant Research Articles

Advances on identification and animated simulations of radioactivity risk levels after Fukushima Nuclear Power Plant accident (with a data bank): A Critical Review

This review study has been based on two main foundations as advances on the attainment of the risk radioactive fallouts levels, and the applications of methods for risk assessment to actual data and visual results, which are based on a 3-year study. A risk analysis model is developed with the animated simulations including the isotope distribution based on soil activity data, 131I measured at 19 stations after the Fukushima accident. Probability distribution functions of the risk levels are obtained in addition to the probability of occurrence (risk) and the probability of non-occurrence (reliability) of the activity risks concerning 131I. The results are used for prediction of 60-day radioactive fallout subsequence and animated (.mp4) through simulations.

Dose calculations in aircrafts after Fukushima nuclear power plant accident – Preliminary study for aviation operations

There is little information to decision support in air traffic management in case of nuclear releases into the atmosphere. In this paper, the dose estimation due to both, external exposure (i.e. cloud immersion, deposition inside and outside the aircraft), and due to internal exposure (i.e, inhalation of radionuclides inside the aircraft) to passengers and crew is calculated for a worst-case emergency scenario. The doses are calculated for different radionuclides and activities. Calculations are mainly considered according to International Commission on Radiological Protection (ICRP) recommendations and Monte Carlo simulations. In addition, a discussion on potential detectors installed inside the aircraft for monitoring the aerosol concentration and the ambient dose equivalent rate, H*(10), for during-flight monitoring and early warning is provided together with the evaluation of a response of a generic detector. The results show that the probability that a catastrophic nuclear accident would produce significant radiological doses to the passengers and crew of an aircraft is very low. In the worst-case scenarios studied, the maximum estimated effective dose was about 1 mSv during take-off or landing operations, which is the recommended yearly threshold for the public. However, in order to follow the ALARA (As Low As Reasonably Achievable) criteria and to avoid aircraft contamination, the installation of radiological detectors is considered. This would, on one hand help the pilot or corresponding decision maker to decide about the potential change of the route and, on the other, allow for gathering of 4D data for future studies.

Sensitivity analysis of in-vessel accident progression behavior in Fukushima Daiichi Nuclear Power Plant Unit 3

The Great East Japan earthquake and the subsequent tsunami which occurred on March 11th 2011 put the operating Units 1–3 at Fukushima Daiichi Nuclear Power Plant (NPP) in severe accident conditions resulting from loss of offsite power and AC power. It is believed that the Station Blackout (SBO) and loss of heat sink led to core meltdown in all Units 1–3. Despite past research efforts on the severe accident progression in Fukushima NPP Units 1–3, there are still knowledge gaps and uncertainties existing in understanding of the severe accident scenarios and consequences.Hence, this study aims at identifying the modeling uncertainties and addressing the sensitivity parameters in Fukushima NPP Unit 3. A more detailed Control Volume (CV) division model of the reactor core region has been developed to better simulate the thermal-hydraulic behavior of liquid water and steam, which is considered to be crucial in simulating the core uncovery and degradation process. The boundary conditions such as the water injection rates by the Reactor Core Isolation Cooling (RCIC) system, the High Pressure Core Injection (HPCI) system and Alternative Water Injection (AWI) to the reactor core were determined based on the available reactor water level and pressure measurement data. The current study suggested that the local vapor heatup behavior could influence the core melting and relocation behavior, which can lead to different core degradation scenarios. With the current modeling assumptions in MELCOR, the best estimate conditions for RPV pressure history of Unit 3 suggested that 6 SRVs could have remained open when the major core slumping took place at ca. 45:20 h (ca. 12:00, March 13) with 50 to 80 tons of water inventory in the lower plenum. The current analysis also suggested that the efficiency of the AWI to the reactor core could have been only 15% as of reported by TEPCO with the current modeling conditions if debris dryout was assumed to have occurred at around ca. 54.0 h (20:40 h, March 13th). As for lower head failure, there is still large uncertainty in predicting lower head failure time with Larson-Miller creep rupture model in the current MELCOR modeling.

An overview of the dialogue meetings initiated by ICRP in Japan after the Fukushima accident

In its recommendations for the protection of people living in long-term contaminated territories after a nuclear accident, the International Commission on Radiological Protection (ICRP) emphasizes the effectiveness of directly involving the affected population and local professionals in the management of the situation, and the responsibility of authorities at both national and local levels to create the conditions and provide the means favouring the involvement and empowerment of the population. In this perspective, ICRP initiated in the fall 2011 a dialogue between representatives of the Fukushima Prefecture, local professionals, local communities and representatives of Belarusian, Norwegian and French organisations to find ways to respond to the challenges of the long-term rehabilitation of the living conditions in the territories affected by the Fukushima nuclear power plant. After a first series of twelve “ICRP Dialogue” meetings between 2011 and 2015 closed by an international workshop, a group of local stakeholders took over and organized a new series of eight “Fukushima Dialogue” meetings between 2016 and 2018. The article gives an overview of the dialogue meetings initiated by ICRP in Japan after the Fukushima nuclear accident.

Current Status and Future Developments in Nuclear-Power Industry of the World

It is well known that electrical-power generation plays the key role in advances in industry, agriculture, technology, and standard of living. Also, strong power industry with diverse energy sources is very important for a country's independence. In general, electrical energy can be mainly generated from: (1) nonrenewable energy sources (75.5% of the total electricity generation) such as coal (38.3%), natural gas (23.1%), oil (3.7%), and nuclear (10.4%); and (2) renewable energy sources (24.5%) such as hydro, biomass, wind, geothermal, solar, and marine power. Today, the main sources for electrical-energy generation are: (1) thermal power (61.4%)—primarily using coal and secondarily using natural gas; (2) “large” hydro-electric plants (16.6%); and (3) nuclear power (10.4%). The balance of the energy sources (11.6%) is from using oil, biomass, wind, geothermal, and solar, and has visible impact just in a few countries. This paper presents the current status of electricity generation in the world, various sources of industrial electricity generation and role of nuclear power with a comparison of nuclear-energy systems to other energy systems. A comparison of the latest data on electricity generation with those several years old shows that world usage of coal, gas, nuclear, and oil has decreased by 1–2%, but usage of renewables has increased by 1% for hydro and 2% for other renewable sources. Unfortunately, within last years, electricity generation with nuclear power has decreased from 14% before the Fukushima Nuclear Power Plant (NPP) severe accident in March 2011 to about 10%. Therefore, it is important to evaluate current status of nuclear-power industry and to make projections on near (5–10 yr) and far away (10–25 yr and beyond) future trends.

Research on High Efficiency and Optimization of Compact Wind Power Generation System applying "Mahalanobis-Taguchi-System"

Abstract: While global reinforcement of countermeasures against global warming is required, Japan depends on overseas imports for over 95% of energy consumption. From the resource production site to the domestic final consumption, it is important to continuously build a stable energy supply system. With the accident at TEPCO Fukushima nuclear power plant occurred on March 11, 2011, the expectation for renewable energy is rapidly rising. Among them, the eyes to wind power generation are changing in particular. At the end of 2012, the amount of wind power generation equipment installed worldwide corresponds to 280 nuclear power plants. National Institute of Technology Tsuruoka College introduced a fully independent power supply system by wind power as a part of human resource development project for engineers. In this research, we were able to extract the task by analyzing the power generation characteristics applying Mahalanobis-Taguchi-System (MTS), diagnosing the cause and optimizing power generation efficiency.

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

We summarized temporal changes in air dose rates and radionuclide deposition densities over five years in the 80 km zone based on large-scale environmental monitoring data obtained continuously after the Fukushima Nuclear Power Plant (NPP) accident, including those already reported in the present and previous special issues. After the accident, multiple radionuclides deposited on the ground were detected over a wide area; radiocesium was found to be predominantly important from the viewpoint of long-term exposure. The relatively short physical half-life of 134Cs (2.06 y) has led to considerable reductions in air dose rates. The reduction in air dose rates owing to the radioactive decay of radiocesium was more than 60% over five years. Furthermore, the air dose rates in environments associated with human lives decreased at a considerably faster rate than expected for radioactive decay. The average air dose rate originating from the radiocesium deposited in the 80 km zone was lower than that predicted from radioactive decay by a factor of 2–3 at five years after the accident. Vertical penetration of radiocesium into the ground contributed greatly to the reduction in air dose rate because of an increase in the shielding of gamma rays; the estimated average reduction in air dose rate was approximately 25% with penetration compared to that without penetration. The average air dose rate measured in undisturbed fields in the 80 km zone was estimated to be reduced owing to decontamination by approximately 20% compared to that without decontamination. The average deposition density of radiocesium in undisturbed fields has decreased owing to radioactive decay, indicating that the migration of radiocesium in the horizontal direction has generally been slow. Nevertheless, in human living environments, horizontal radiocesium movement is considered to contribute significantly to the reduction in air dose rate. The contribution of horizontal radiocesium movement to the decrease in air dose rate was estimated to vary by up to 30% on average. Massive amounts of environmental data were used in extended analyses, such as the development of a predictive model or integrated air dose rate maps according to different measurement results, which facilitated clearer characterization of the contamination conditions. Ecological half-lives were evaluated in several studies by using a bi-exponential model. Short-term ecological half-lives were shorter than one year in most cases, while long-term ecological half-lives were different across the studies. Even though the general tendency of decrease in air dose rates and deposition densities in the 80 km zone were elucidated as summarized above, their trend was found to vary significantly according to location. Therefore, site-specific analysis is an important task in the future.

Radioactive <sup>35</sup>S emitted from the Fukushima Nuclear Power Plant and its re-suspension from the contaminated area

Radioactive <sup>35</sup>S emitted from the Fukushima Nuclear Power Plant and its re-suspension from the contaminated area

Proposal for Improvement of Professional Engineer System from the Analysis of the Cause of Accident at Fukushima Nuclear Power Plant

Proposal for Improvement of Professional Engineer System from the Analysis of the Cause of Accident at Fukushima Nuclear Power Plant

Longitudinal Factors Associated With Increased Alcohol and Tobacco Use in Fukushima Nuclear Power Plant Workers 32 Months After the Nuclear Disaster: The Fukushima News Project Study.

The aim of this study was to predict increased alcohol and tobacco use in Fukushima nuclear power plant (NPP) workers 3 years after a nuclear disaster. Surveys were conducted in two postdisaster waves (Wave 1: 2 to 3 months; Wave 2: 32 months). Adjusted risk ratio (aRR) was computed to assess the covariates of increased alcohol and tobacco use in Wave 2. Increased alcohol use was associated with age of 29 years or less [aRR (95% confidence interval (95% CI): 1.26 (1.01 to 1.57)], major property loss [1.25 (95% CI 1.02 to 1.55)], and high posttraumatic stress responses (PTSRs) [1.34 (95% CI 1.08 to 1.67)] in Wave 1. Increased tobacco use was associated with age of 29 years or less [1.46 (95% CI 1.12 to 1.90)] and high PTSR [1.62 (95% CI 1.25 to 2.10)] in Wave 1 (P < 0.05). The workers' increased alcohol and tobacco use were predicted by major property loss (alcohol), age of 29 years or less, and high PTSR (alcohol/tobacco) in Wave 1.

Fundamental study on the filtered containment venting system for decommissioning of the Fukushima Nuclear Power Plant

Fundamental study on the filtered containment venting system for decommissioning of the Fukushima Nuclear Power Plant

Dose dependence of pediatric thyroid cancer prevalence in the 6 years after the Fukushima nuclear power plant accident

Background: After the Fukushima nuclear accident in March 2011, Fukushima Prefecture initiated thyroid ultrasound screening as part of the Fukushima Health Management Survey (FHMS). Regional differences in external radiation dose were often reported not associated with thyroid cancer prevalence in the firstround screening E-I (2011-2013). The association between childhood thyroid cancer and radiation exposure in the 6 years after the accident is studied by analyzing the results of the first and second-round examinations E-I+II (2011-2015). Methods: Dose dependence of thyroid cancer proportion in E-I and E-II for all residents aged ≤18 years at the accident was analyzed for FHMS external dose and UNSCEAR effective dose by regression analysis using Microsoft Excel. Two divisions of Fukushima prefecture, O-model in the order of decreasing external dose and S-model according to the initial screening schedule, were adopted. Results: In O-model, thyroid cancer proportion per 100,000 in E-II and in E-I+II were found to increase linearly to FHMS external dose in 0.2–1.4 mSv range and UNSCEAR effective dose in 1.6–5 mSv range. Thyroid cancer proportion in E-II and E-I+II was observed to increase linearly to effective dose in Smodel. Conclusion: The observed linear prevalence–dose relation after 6 years from the accident and incidencedose relation during 4-6 years after exposure suggest a possible association between pediatric thyroid cancer and radiation exposure. Regional differences were not obvious in E-I presumably because of the short interval from exposure to screening in high-dose areas. High prevalence of thyroid cancer cannot be attributed only to mass screening effect that does not depend on radiation dose and elapsed time from exposure.

Impact of repeated dose of stable iodine in an in utero rat model using a metabolomic approach

The Fukushima nuclear power plant blast resulted in the release of 131Iodine for several weeks. This unexpected issue challenged the iodin doctrine [1], in which the counter-measure is to provide a unique iodine tablet to saturate thyroid during the radioactive contamination not expected to last more than several hours. A new doctrine must be implemented to take into account such case of extended exposure based on repeated iodine administration with adapted dosage. But repeated administration of iodine can block the thyroid [2] and few scientific evidences regarding repeated iodine administration (and its potential undesirable effect) are at our disposal [3]. Moreover, unborn and young children are at high risk during a nuclear incident: it is currently recognized that one of the risks of exposure to radioactive iodine is the development of thyroid cancer, especially when exposure occurred during childhood [4]. Their protection is a main priority. Our goal was to evaluate the potential undesirable effects of such repeated iodine administration in the offspring using an untargeted metabolomic approach on a rat reproductive model.

Factors affecting &lt;sup&gt;137&lt;/sup&gt;Cs concentration in wild plants and soils of different land use in Iitate village after the Fukushima nuclear power plant accident

Factors affecting &lt;sup&gt;137&lt;/sup&gt;Cs concentration in wild plants and soils of different land use in Iitate village after the Fukushima nuclear power plant accident

The reasons of people keep the exterior of farmland in the Fukushima nuclear power plant disaster area

The reasons of people keep the exterior of farmland in the Fukushima nuclear power plant disaster area

Role of filamentous fungi in migration of radioactive cesium in the Fukushima forest soil environment.

The fate of radioactive Cs deposited after the Fukushima nuclear power plant accident and its associated radiological impacts are largely dependent on its mobility from surface soils to forest ecosystems. We measured the accumulation of radioactive Cs in the fruit bodies of wild fungi in a forest at Iitate, Fukushima, Japan. The transfer factors (TFs) of radioactive Cs from soil to the fruit bodies of wild fungi were between 10-2 and 102, a range similar to that reported for the fruit bodies collected in Europe after the Chernobyl accident and in parts of Japan contaminated by the nuclear bomb test fallout. Comparison of the TFs of wild mushroom and those of fungal hyphae of 704 stock strains grown on agar medium containing nutrients and 137Cs showed that the TFs of wild mushroom were lower. The TF was less than 0.1 after the addition of the minerals zeolite, vermiculite, phlogopite, smectite, or illite of 1.0% weight to the agar medium. These results indicate that the presence of minerals decreases Cs uptake by fungi grown on the agar medium, and filamentous fungi still accumulate radioactive Cs even when minerals are present in the medium.

Analysis on Researchers’ Practical Activities for Radiation Risk Reduction and Risk Communication after the Fukushima Nuclear Power Plant accident

Analysis on Researchers’ Practical Activities for Radiation Risk Reduction and Risk Communication after the Fukushima Nuclear Power Plant accident

Protective Effects of Taurine on the Radiation Exposure Induced Cellular Damages in the Mouse Intestine.

There has been a growing interest in radiation effects as a result of the Fukushima nuclear power plant accident in 2011. Exposure to ionizing radiation causes oxidizing events to different organs such as the bone marrow, intestine, and kidney, which can result in radiation-induced injuries. Taurine (2-aminoethanesulfonic acid) is a sulfur-containing amino acid possessing several important physiological functions, including membrane stabilization, anti-oxidative activity, anti-inflammatory effects and modulation of intracellular calcium levels. Taurine appears to be an attractive candidate for use as a radioprotector and as a radiation mitigator, but its protection mechanism against radiation-induced cell damage is still unclear until now. In this review we describe some of the mechanisms explaining the radioprotective/mitigating effects of taurine on radiation-induced cellular damage and our recent findings on this subject.

Radiological safety assessment for incident-free transportation of radioactive decontamination waste after the Fukushima nuclear power plant accident

Radioactive decontamination waste generated by remediation following the Fukushima nuclear power plant accident was recently transported from its temporary storage sites to interim storage facilities as a pilot test. A transportation plan for the radioactive decontamination waste will be developed based on this pilot transportation experience and radiological safety assessment of pilot transportation. The objective of this study was to assess radiation doses to the public and crew workers released during incident-free pilot transportation. External dose rates around a transportation vehicle were calculated by using the Monte Carlo N-Particle code. Collective doses and maximally exposed individual doses to the public and effective doses to crew workers were calculated by using INTERTRAN. Two transportation routes, Asakawa-machi to Okuma-machi and Iwaki-shi to Okuma-machi, were considered. The maximum radioactivity concentration in the decontamination waste was calculated to be 660 kBqkg?1 which meets the value laid down by the guidelines of Japan's Ministry of the Environment. The collective doses to the public per shipment were 1.9 10?3 person-mSv for the Asakawa route and 2.2 10?4 person-mSv for the Iwaki route. Maximally exposed individual doses to the public were 9.6 10?7 mSv for the Asakawa route and 2.7 10?5 mSv for the Iwaki route. The total effective doses to crew workers were 0.27 mSv for the Asakawa route assuming five shipments per worker and 1.07 mSv for the Iwaki route assuming 45 shipments per worker. The radiation dose levels to the public and workers evaluated in this study were much lower than the annual dose limits for the general public and radiation workers. These study results can be used to develop transportation plans and guidelines for decontamination waste transportation.

137Cs transfer from canopies onto forest floors at Mount Tsukuba in the four years following the Fukushima nuclear accident

This study investigated the transport of 137Cs within a forest ecosystem by examining temporal changes in the inventory and determining the major pathways of transfer following significant atmospheric deposition. A forested area of eastern Japan was monitored for four years immediately after the Fukushima nuclear power plant accident in March 2011 that released a large amount of radionuclides. The long physical half-life of 137Cs means that contamination can persist for decades, so it is vital to understand the mechanisms underlying the 137Cs dynamics in ecosystems. We sampled litterfall, throughfall, and soil, mainly from a cedar stand, over a four-year period, and analyzed the 137Cs concentrations of each sample to determine the transfer rate and total inventory. After validating our methodology through a comparison with results from an earlier study, we determined the temporal changes in the 137Cs distribution and in the major transfer pathway. Results showed that most 137Cs intercepted by canopies was transferred rapidly over the first nine months, and that the major pathway was not litterfall but throughfall. The ecological half-life of the 137Cs stocked in the canopy was calculated for both the early and later stages of contamination. Although the former is consistent with previous results, the latter ecological half-life is somewhat longer, probably because of dependence on the meteorological and tree physiological conditions at the site. This study presents valuable new data on the post-Fukushima 137Cs contamination, enhancing our understanding of the associated dynamics in forest ecosystems.