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The medical situation during disasters often differs from that at usual times. Disasters can lead to significant mortality that can be difficult to monitor. The types of disaster-related deaths are largely unknown. In this study, we conducted a survey to categorize the disaster-related deaths caused by a radiation disaster. A total of 520 people living in Minamisoma City, Fukushima Prefecture, at the time of the Fukushima Daiichi Nuclear Power Plant accident, who were certified to have died due to disaster-related causes were surveyed. We divided the participants into those who were at home at the time of the earthquake and those who were in hospitals or facilities when the disaster struck and conducted a hierarchical cluster analysis of the two groups. Disaster-related deaths could be divided into seven groups for those who were at home at the time of the disaster and five groups for those who were in hospitals or facilities at the time of the disaster. Each group showed different characteristics, such as "the group with disabilities," "the group receiving care," and "the group with depression," and it became evident that not only uniform post-disaster support, but support tailored to the characteristics of each group is necessary. [ABSTRACT FROM AUTHOR]

Radiocesium released by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident still exists in the environment in two forms: adsorbed species on mineral particles in the soil and microparticles containing radiocesium mainly composed of silicate glass (CsMPs). CsMPs are dispersed not only around the FDNPP but also over a wide area of the Kanto region. The behavior and characteristics of CsMPs must be investigated to evaluate the impact of the FDNPP accident. Deposited particles including radiocesium were wiped from metal handrails on balconies and car hoods using tissue papers at six locations in the Kanto region (Tokai village, Ushiku City, Abiko City, Chiba City, Kawaguchi City, and Arakawa Ward) between March 15 and 21, 2011. CsMPs were isolated from the samples, and their characteristics were investigated. In total, 106 CsMPs derived from Unit 2 were successfully separated from 13 tissue paper samples. The radiation images of the two types of CsMPs discovered in Ushiku City demonstrate that CsMPs can easily become susceptible to fragmentation over time, even in the absence of weathering effects. [ABSTRACT FROM AUTHOR]

In order to improve the safety of operating nuclear power plants with RBMK-1000 reactors, work is underway for developing and substantiating the control actions of personnel under severe accident conditions for all possible initial states of the power unit, including shutdown for decommissioning. An accident is considered using the STEPAN‑T 3D program developed specifically for simulating an accident with the complete blackout of a RBMK reactor. The time dependence of the temperature in the core, metal structures, and OR scheme is given. Quantitative estimates of the hydrogen formation during an accident are shown. The possibility of re-criticality and release of radioactive substances occurring during the accident are discussed. Possible measures to mitigate the consequences of the accident are given. [ABSTRACT FROM AUTHOR]

There has been considerable debate about the formation mechanisms of Cs-bearing silicate glass microparticles (CsMPs) (Types A–E) released uniquely during the Fukushima Daiichi nuclear power station accident. The author proposed that these CsMPs were formed because the high-efficiency particulate air (HEPA) filters or the insulation materials in the reactor building melted and atomized during the hydrogen explosion. However, this hypothesis is complex because it includes the interdisciplinary issues between the thermohydraulics in the reactor and atmospheric dispersion. This paper describes the basis of the hypothesis, verification, future issues, and recommendations from the viewpoint of improving nuclear safety. [ABSTRACT FROM AUTHOR]

Reactor pressure vessel (RPV) is in the center of the nuclear containment building and houses nuclear fuel, there is a risk of a nuclear power plant radiation leakage accident in the event of an earthquake. It is important to determine stress intensities that evaluate structural integrity and also analyze the seismic response of RPV in order to prevent severe disasters. We propose a stress intensity regression model using a signal extraction method and machine learning in addition to the existing method. The combined way between the methods from finite element model enables us to predict the stress intensity immediately with only signal features and properties. It could be an additional verification tool to ensure safety of nuclear power plants. [ABSTRACT FROM AUTHOR]

More than a decade has passed since the Fukushima nuclear accident in 2011 and contamination around the nuclear power plant is primarily caused by 137Cs. One of the materials retaining radiocesium in the environment is radiocesium-bearing silicate glass microparticles (CsMPs), which have not been reported in previous nuclear accidents. Although the prediction of environmental fates of CsMPs is of interest because of their extremely high specific radioactivity, knowledge about their physicochemical properties is still limited. Here we show that the dissolution behavior of CsMPs is comparable to that of silica-rich glass and significantly depends on the surrounding environment. CsMP dissolution experiments were conducted in solutions with various solute components and pH levels at 60 °C. In neutral and basic solutions, the estimated dissolution rate was accelerated by alkali ions such as Na+, which is known to play a catalytic role for the dissolution of silica. In contrast, the dissolution in acid was slow even in the presence of alkali ions. The dissolution under acid conditions was possibly retarded by a thin amorphous silica layer formed on the CsMP surfaces. Such characteristics of the dissolution are consistent with that of silica-rich glass. To infer the dissolution behavior of CsMPs in the human body, the dissolution rate in Ringer's solution at 37 °C was estimated as 1.00 ± 0.37 μm/year. [ABSTRACT FROM AUTHOR]

This article analyzes methods and technologies for assessing the way of formation, composition, characteristics, and features of corium, i.e., a mixture of nuclear and structural materials of a nuclear reactor core, which formed as a result of an accident that is accompanied by partial or complete melting of the core. The analysis is based on data from studying the corium formed as a result of the accident at the Fukushima Daiichi nuclear power plant, which are in the public domain and are the result of the work of many scientific organizations around the world. The study of corium is a main problem in improving nuclear safety in the future and an objective in developing the successful procedure for eliminating the consequences of the accident at the Fukushima Daiichi nuclear power plant. Without a detailed analysis of the neutron physics, materials science, gravimetric, and other characteristics of the corium and without creation of a corium data set that combines these characteristics, it is impossible to create a full fledged model of the corium in the future and to organize an efficient and safe process for removing nuclear materials from the damaged units of the Fukushima Daiichi nuclear power plant. This study is aimed at combining the existing research results into a data set, which can later be used to simulate the corium using neutron physics codes. The set being created includes data, such as the size, density, and morphology of corium samples and their approximate nuclide composition. The created data set will allow one not only to perform tasks related to increasing the level of safety when accomplishing the procedure for eliminating the consequences of the accident at the Fukushima Daiichi nuclear power plant through simulation but also will serve as a basis for creating an international benchmark for simulating a mixture that contains nuclear materials (NMs). [ABSTRACT FROM AUTHOR]

In the course of the Fukushima nuclear accident, radionuclides were released in various forms, including so-called radiocesium-bearing microparticles (CsMP). So far, four types of CsMP were described: Type A is smaller in size (< 10 μm), Types B, C, and D are larger (> 100 μm). In this work, we present a novel type of CsMP (proclaimed Type E). Three particles of Type E were extracted from a contaminated blade of grass that was sampled 1.5 km from the Fukushima Daiichi nuclear power plant in late 2011. They were located using autoradiography, isolated using an optical microscope and micromanipulator, and characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy, and low-level gamma-ray spectrometry. Type E CsMPs are 10–20 μm in size and exhibit an unusually low and barely detectable 137Cs activity of only ≤ 10 mBq per particle. Their brittle and fragile character may indicate a high surface tension. [ABSTRACT FROM AUTHOR]

After the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP), much of the wild and edible mushrooms and plants in the surrounding areas were contaminated with radiocesium (137Cs). To elucidate their concentration characteristics, we analyzed 137Cs radioactivity data in edible forest products brought in for food inspection by the residents of Kawauchi Village, 12–30 km away from the FDNPP, from 2012 to 2019. A Bayesian model to estimate 137Cs concentration was constructed. Parameters of the normalized concentration of species (NCsp) for mushrooms were similar to those of the same species obtained in a previous study. Although NCsp values were highly varied among species, mycorrhizal mushrooms tended to have high NCsp values, followed by saprotrophic mushrooms, and wild edible plants values were low. Also, half of mycorrhizal mushroom species (8 of 16) showed an increasing trend in concentration with time; however, saprotrophic mushrooms and wild plants generally demonstrated a decreasing trend (22 of 24). The model considering the sub-village location information decreased the error of individual samples by 40% compared to the model not considering any location information, indicating that the detailed geo-information improved estimation accuracy. Our results indicate that the radioactivity data from samples collected by local residents can be used to accurately assess internal exposure to radiation due to self-consumption of contaminated wild mushrooms and plants. [ABSTRACT FROM AUTHOR]

The interest to build a nuclear power plant in West Nusa Tenggara Province has caused a concern related to the seismic hazard. One of the challenges was that the existing low-resolution national seismic hazard map did not cover the entire islands of West Nusa Tenggara Province. In this paper, preliminary probabilistic seismic hazard analysis of West Nusa Tenggara was performed to complement the existing national seismic hazard map for West Nusa Tenggara. The analysis was carried out using OQ software based on the seismotectonic model and GMPE developed by PUSGEN. Similar seismotectonic model and seismic event trees were implemented using a finer grid spacing of 500–1000 m. The seismotectonic model included active shallow crustal, subduction interface, and background sources with a total number of 50 seismogenic sources and was calculated using 108 GMPE paths. Two hazard levels were considered, each representing 1% and 2% POE in a 100-year return period. A comparison to the existing national seismic hazard map on the PGA level has been presented in this study and yielded a 13–25% difference in the ground acceleration value. Spectral hazard maps representing the shorter period (0.2 s) showed a maximum ground acceleration value of more than 2 g, especially in the northern part of Sumbawa Island. Beyond the longer spectral period (1 s), ground acceleration gradually decreases to the level below the PGA level. [ABSTRACT FROM AUTHOR]

We have measured artificial radionuclides, such as 90Sr and 137Cs, in atmospheric depositions since 1957 in Japan. We observed the variations in 90Sr and 137Cs, which were emitted from atmospheric nuclear tests and nuclear power plant accidents, due to their diffusion, deposition, and resuspension. In March 2011, the Fukushima Daiichi Nuclear Power Plant accident occurred in Japan, and significant increases in 90Sr and 137Cs were detected at our main site in Tsukuba, Ibaraki. Our continual observations revealed that the 137Cs monthly deposition rate in 2018 declined to ~ 1/8100 of the peak level, but it remained more than ~ 400 times higher than that before the accident. Chemical analysis suggested that dust particles were the major carriers of 90Sr and 137Cs during the resuspension period at our main site. Presently, the effective half-life for 137Cs deposition due to radioactive decay and other environmental factors is 4.7 years. The estimation suggests that approximately 42 years from 2011 are required to reduce the atmospheric 137Cs deposition to a state similar to that before the accident. The current 90Sr deposition, on the other hand, shows the preaccident seasonal variation, and it has returned to the same radioactive level as that before the accident. [ABSTRACT FROM AUTHOR]

The present study aimed to clarify the psychological status of 766 former residents of Tomioka Town, Fukushima Prefecture, and their intent to return (ITR) 8 years after the disaster at Fukushima Daiichi Nuclear Power Plant. We investigated their ITR home and their perception of the risk of health effects from radiation exposure. We also evaluated rates of post-traumatic stress disorder (PTSD) using a PTSD checklist (PCL-S) and of psychological stress using the patient health questionnaire-9 (PHQ-9). Among the residents, 102 (13%) had returned home (group 1), 214 (28%) were unsure about returning (group 2), and 450 (59%) had decided not to return (group 3). Concern about exposing the next generation to radiation was significantly more prevalent in groups 2 and 3 than in group 1. The frequency of positive PCL-S and PHQ-9 responses was higher in group 2 than in groups 1 and 3. Factors that were independently associated with returning to Tomioka were positive PCL-S (OR, 4.3) and PHQ-9 (OR, 2.2) scores, concerns about consuming locally sourced food, and living with children, and were more prevalent in group 2 than group 1 (reference). Group 2 was more anxious about radiation exposure and health effects, and had higher rates of psychological stress and PTSD. Providing support to such residents through careful risk communication will be required to recover this community after the nuclear disaster. [ABSTRACT FROM AUTHOR]

Vertical profiles of radiocesium (134Cs and 137Cs) were measured in the western subarctic area of the North Pacific in 2017. The highest concentration of 134Cs, which was derived from the accident of the Fukushima Dai-ichi Nuclear Power Plant in 2011, was 0.14 Bq m−3 (or 1.19 Bq m−3 after the decay correction to the accident date). Although the vertical inventory of 134Cs decreased between 2014 and 2017, the inventory in 2017 was larger than that expected. That was probably arose from the return of some portion of the high-concentration water mass along with the anticlockwise subarctic gyre current. [ABSTRACT FROM AUTHOR]

This contribution provides an overview of the SINAPS@ French research project and its main achievements. SINAPS@ stands for "Earthquake and Nuclear Facility: Improving and Sustaining Safety", and it has gathered the broad research community together to propose an innovative seismic safety analysis for nuclear facilities. This five-year project was funded by the French government after the 2011 Japanese Tohoku large earthquake and associated tsunami that caused a major accident at the Fukushima Daïchi nuclear power plant. Soon after this disaster, the international community involved in nuclear safety questioned the current methodologies used to define and to account for seismic loadings for nuclear facilities during the design and periodic assessment review phases. Within this framework, worldwide nuclear authorities asked nuclear licensees to perform 'stress tests' to estimate the capacity of their existing facilities for sustaining extreme seismic motions. As an introduction, the French nuclear regulatory framework is presented here, to emphasize the key issues and the scientific challenges. An analysis of the current French practices and the need to better assess the seismic margin of nuclear facilities contributed to the shaping of the scientific roadmap of SINAPS@. SINAPS@ was aimed at conducting a continuous analysis of completeness and gaps in databases (for all data types, including geology, seismology, site characterization, materials), of reliability or deficiency of models available to describe physical phenomena (i.e., prediction of seismic motion, site effects, soil and structure interactions, linear and nonlinear wave propagation, material constitutive laws in the nonlinear domain for structural analysis), and of the relevance or weakness of methodologies used for seismic safety assessment. This critical analysis that confronts the methods (either deterministic or probabilistic) and the available data in terms of the international state of the art systematically addresses the uncertainty issues. We present the key results achieved in SINAPS@ at each step of the full seismic analysis, with a focus on uncertainty identification, quantification, and propagation. The main lessons learned from SINAPS@ are highlighted. SINAPS@ promotes an innovative integrated approach that is consistent with Guidelines #22, as recently published by the French Nuclear Safety Authority (Guidelines ASN #22 2017), and opens the perspectives to improve current French practice. [ABSTRACT FROM AUTHOR]

Concentrations of Cs measured in water collected from seven rivers under base-flow conditions in eastern Fukushima Prefecture in 2014 were combined with previously reported data for the same sampling points from 2012 to 2013. Dissolved Cs concentrations at the sampling points were strongly correlated with the Cs inventories of the corresponding catchment areas. The ratios of the dissolved Cs concentrations to the Cs inventories have declined exponentially since the 2011 Fukushima nuclear power plant accident with an effective decreasing coefficient of 0.40 y (effective half-time of 1.7 y), within the range reported in European rivers following the Chernobyl accident. [ABSTRACT FROM AUTHOR]

For estimation of residents' exposure dose after a nuclear accident, the reduction factor, which is the ratio of the indoor dose to the outdoor dose is essential, as most individuals spend a large portion of their time indoors. After the Fukushima nuclear accident, we evaluated the median reduction factor with an interquartile range of 0.43 (0.34-0.53) based on 522 survey results for 69 detached wooden houses in two evacuation zones, Iitate village and Odaka district. The results indicated no statistically significant difference in the median reduction factor to the representative value of 0.4 given in the International Atomic Energy Agency (IAEA)-TECDOC-225 and 1162. However, with regard to the representative range of the reduction factor, we recommend the wider range of 0.2 to 0.7 or at least 0.2 to 0.6, which covered 87.7% and 80.7% of the data, respectively, rather than 0.2 to 0.5 given in the IAEA document, which covered only 66.5% of the data. We found that the location of the room within the house and area topography, and the use of cement roof tiles had the greatest influence on the reduction factor. [ABSTRACT FROM AUTHOR]

The Fukushima nuclear accident released radioactive materials into the environment over the entire Northern Hemisphere in March 2011, and the Japanese government is spending large amounts of money to clean up the contaminated residential areas and agricultural fields. However, we still do not know the exact physical and chemical properties of the radioactive materials. This study directly observed spherical Cs-bearing particles emitted during a relatively early stage (March 14-15) of the accident. In contrast to the Cs-bearing radioactive materials that are currently assumed, these particles are larger, contain Fe, Zn, and Cs, and are water insoluble. Our simulation indicates that the spherical Cs-bearing particles mainly fell onto the ground by dry deposition. The finding of the spherical Cs particles will be a key to understand the processes of the accident and to accurately evaluate the health impacts and the residence time in the environment. [ABSTRACT FROM AUTHOR]

During the serious accident at the Fukushima-1 NPP (Japan), the cores of the Nos. 2 and 3 units were cooled for a long period of time by safety systems which were not designed for operation under prolonged power loss. The serviceability of BWR-4 high-head makeup systems and the reasons for their failure are analyzed. It is shown that taking dc losses in the No. 2 unit into account the makeup system remained serviceable in the unanticipated regime. The shutdown of the makeup systems in both units could have been due to the maximum backpressure being reached at the turbine outlets or by cavitation in the turbopumps. It is shown that it is important to make a realistic assessment of the depletion time of the storage batteries in the No. 3 unit. [ABSTRACT FROM AUTHOR]

Aerosol radionuclides (I, Cs, Cs) and gaseous radioactive xenon (Xe) were monitored at Xi'an, China following the accident at the Fukushima nuclear power plant in March 2011. The additional annual effective dose attributable to the Fukushima emissions was much lower than the public annual effective dose from natural radiation, according to Chinese national standards. The monitoring results were compared with data from other countries as well as with the radionuclide concentrations observed in Xi'an after the Chernobyl nuclear accident in 1986. Possible transport pathways of the released radionuclides from Fukushima to Xi'an were investigated. The occurrence of an anticyclone in the Pacific Ocean region and the extended period over which the radionuclides were released made the determination transport pathways complex, but divergence in the plume and easterly flow evidently brought the initial suite of radionuclides to Xi'an. [ABSTRACT FROM AUTHOR]

Even in the face of the March 2011 accident at the Fukushima nuclear power plant in Japan, nuclear power is being promoted in the U.S. as a necessary response to global climate change. Conducted prior to the Fukushima accident, the present study used a nation-wide telephone survey of 2751 U.S. residents to assess the factors that influence whether a person has become more open to nuclear power because of global climate change rather than supportive or opposed to nuclear power. Results showed that belief that climate change is a risk and is human-caused, belief that nuclear energy contributes to climate change, environmental support, cultural worldviews, and selected socio-demographics consistently predicted openness to nuclear power because of climate change. Implications of the current results and avenues for additional research on this topic are discussed. [ABSTRACT FROM AUTHOR]

The work done by the Technical Crisis Center at the Institute of Problems in the Safe Development of Nuclear Energy of the Russian Academy of Sciences on providing scientific-technical support to the National Control Center for Crisis Situations of the Russian Ministry of Emergency Situations and Crisis Situation Center at Rosatom during the first few days and subsequent period after the accident at the Fukushima-1 NPP in Japan in March 2011 is described. The results of computer calculations of possible development of the situation in the power-generating units of the damaged NPP, predictions of the dynamics of the change of the radiation conditions near and at large distances from the NPP, right up to the Far East territory of our country as well estimates of the irradiation dose to the population are presented. [ABSTRACT FROM AUTHOR]

The irradiation dose rate in March-May 2011 is evaluated for marine biota in the coastal zone near the destroyed Fukushima reactor and in the open sea. It is shown that for representative marine organisms (fish and mollusks) the irradiation dose rate did not exceed the safe level 0.4 mGy/h (10 mGy/day). In the open sea, 30 km from the nuclear power plant, the irradiation of marine biota is much lower than in the coastal zone near the nuclear power plant. A comparative evaluation is made of the irradiation dose rate for water organisms in the exclusion zones of the Eastern-Urals track of radioactivity and the Chernobyl and Fukushima nuclear power plants. [ABSTRACT FROM AUTHOR]

The article discusses the status of contamination in the radioactive aerosols associated with the cases of nuclear accidents that occurred at Chernobyl Nuclear Power Plant (NPP) and Fukushima-1 NPP. It talks about accumulation of radionuclide on the additional filter as the main cause of accident at Chernobyl NPP. It explores that the content of radioactive aerosols products in the case of Fukushima-1 NPP did not exceed the standard concentration of radionuclide in air.

The author reflect on the safety requirements in nuclear power plants in France. The author states that upgrading nuclear safety regulation is being opposed by some nuclear industries. The author cites the Fukushima nuclear power plant accident occurred in Japan in March 2011 as well as the report from the Nuclear Safety Authority regarding the sweeping of safety regulations.

The author reflects on the continued use of nuclear power despite the Fukushima Dai-ichi nuclear power plant accident in Japan on March 2011. The author mentions that Tokyo Electric Power Co. estimated that the radiation leaks can be reduced in 3 months. The author cites that nuclear power can be a means of making up the energy budget now and in the coming years.