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After the Fukushima nuclear accident in Japan, whether the structural safety of the nuclear power plant (NPP) can be guaranteed under an earthquake has been of wide concern. Automatic seismic trip systems (ASTS) have been deployed in NPPs. There are generally two units or more double units on the one NPP site, and the vibration energy of the structure can certainly affect its adjacent structures through the soil, and there is energy transfer and conversion between adjacent structures. At present, the distance between two reactors of NPPs of different reactor types is generally 100–200 m (this distance is referring to the distance between the centers of two reactors, which is slightly different for different reactor types). In the past, seismic instruments were used in the ASTS and the setting of shutdown threshold, so the impact of only one unit was considered in the structural analysis of NPPs, and the interaction of two reactors through site conditions was not considered. In addition, as the site conditions of NPPs become more and more complex, it is necessary to consider the impact of one reactor structure on another reactor structure through the soil on the same site under an earthquake. In order to analyze the influence of structure–soil–structure interaction (SSSI), a three-dimensional refined finite element model of NPPs is established in this paper. The soil–structure interaction (SSI) is considered by using viscoelastic boundary. The seismic responses of different positions of the raft foundation and NPP structure, under the conditions of considering SSI effect (one reactor) and SSSI effect (two reactors), are compared. The influence of SSSI effect on the seismic responses of the raft foundation and NPP structure is revealed. It is proposed that SSSI effect should be reasonably considered according to the site conditions for the structural analysis of NPPs for the NPP ASTS. [ABSTRACT FROM AUTHOR]

The concept and methodology of traditional Defense in Depth (DID) was challenged in the Fukushima nuclear accident. In order to fix the weakness of the traditional emergency strategies of nuclear power plants (NPPs) and to enhance the DID for nuclear safety, the U.S. Nuclear Energy Institute (NEI) put forward the concept of Diverse and Flexible Coping Strategies (FLEX) for the special purpose of beyond-design-basis external event (BDBEE) hazard mitigation and the corresponding FLEX support guidelines (FSG). The theory has been wildly spread and accepted by many countries that generate nuclear power. The research on the FLEX strategy is a new trend in nuclear engineering in the recent decade. It provides not only fixed on-site equipment/devices but also on- and off-site portable resources to strengthen the reliability of the nuclear safety system, especially for the disaster/hazards (similar to the Fukushima nuclear accident) triggered by BDBEEs. After a brief introduction of the FLEX strategy, four opportunities and ten challenges are summarized. Subsequently, in view of these challenges and technical difficulties, five suggestions for future work are recommended. [ABSTRACT FROM AUTHOR]

The damage caused by disasters is increasing worldwide, with hundreds of thousands of deaths due to the occurrence of complex large-scale disasters such as the 2010 Haiti earthquake and the 2004 Indian tsunami. South Korea has also experienced human casualties and damage to property caused by large-scale disasters in the past 10 years. Accordingly, a disaster-appropriate response measure is needed. Thus, we conducted this study to present a measure of utilizing spatial database and image information to improve the efficiency of disaster management that is operated based on the country's existing national disaster management system. We present an efficient disaster response measure that differs from the existing collection-, reporting-, and propagation-oriented operating methods of disaster information through the use of spatial database and image-based information that can be combined with mandatory information with regard to nuclear power plant accidents. Thus, this study contributes to deriving a system that could collect and provide information rapidly at the time of disaster by defining the attribute and spatial information required at the time of disaster during nuclear power plant accidents and by deriving available systems and providing institutions. [ABSTRACT FROM AUTHOR]

Even after 7 years of the nuclear accident that occurred in 2011 at the Fukushima Dai-ichi nuclear power plant (F1NPP), high levels of 137Cs have been detected in ambient aerosols from some polluted areas of Fukushima. Higher levels of radionuclides were often observed in the atmosphere during and after rain events. We presume that biological processes such as fungal activity associated with higher relative humidity may be involved with a possible emission of radioactivity to the atmosphere, which was originally emitted from the F1NPP accident and was deposited over the ground, forest, soil, etc. Here, we report, for the first time, relationships of 137Cs and organic tracers of fungal spores (i.e., arabitol, mannitol and trehalose) in the aerosol samples collected from Fukushima, Japan. Although we found twice-higher concentrations of 137Cs at nighttime than at daytime, fungal spore tracers did not show a consistent trend to 137Cs, that is, organic tracers at nighttime were similar with those at daytime or were even higher in daytime. This study has not clearly demonstrated that fungal spores are the important source of high levels of 137Cs at nighttime. The current unclear relationship is probably associated with the sampling strategy (four consecutive days with a sampling on/off program for day/nighttime samples) taken in this campaign, which may have caused a complicated meteorological situation. [ABSTRACT FROM AUTHOR]

In this paper, methane hydrate R&D in Japan was examined in the context of Japan's evolving energy policies. Methane hydrates have been studied extensively in Japanese national R&D programs since 1993, with the goal of utilizing them as an energy resource. Currently, the Research Consortium for Methane Hydrate Resources in Japan (MH 21) is in the third phase of a project that began in early 2002. Based on publicly available reports and other publications, and presentations made at the ten International Workshops for Methane Hydrate Research and Development, we have attempted to provide a timeline and a succinct summary of the major technical accomplishments of MH 21 during project Phases 1, 2, and 3. [ABSTRACT FROM AUTHOR]

The author reflects on the consequences of the usage of nuclear power plants in generating electricity mentioning the incident in Fukushima, Japan. He is critical to the action taken by Tokyo Electric Power Company (TEPCO), and regarded it as equitable and was under given conditions. Moreover, he points out lessons learned from the disaster, which deals with the risks of nuclear technology, accurate selection in nuclear plants' location, and updates on cost assessment for nuclear stations.

We conducted single-model initial-perturbed ensemble simulations to quantify uncertainty in aerosol dispersion modeling, focusing on a point-source radioactive aerosol emitted from the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011. The ensembles of the meteorological variables were prepared using a data assimilation system that consisted of a non-hydrostatic weather-forecast model with a 3-km horizontal resolution and a four-dimensional local ensemble transform Kalman filter (4D-LETKF) with 20 ensemble members. The emission of radioactive aerosol was not perturbed. The weather and aerosol simulations were validated with in-situ measurements at Hitachi and Tokai, respectively, approximately 100 km south of the FDNPP. The ensemble simulations provided probabilistic information and multiple case scenarios for the radioactive aerosol plumes. Some of the ensemble members successfully reproduced the arrival time and intensity of the radioactive aerosol plumes, even when the deterministic simulation failed to reproduce them. We found that a small ensemble spread of wind speed produced large uncertainties in aerosol concentrations. [ABSTRACT FROM AUTHOR]

Nuclear power remains one of the most accessible choices in addressing environmental and social concerns due to the continuously increasing energy needs around the world. While it remains an excellent source of energy due to its low price and low level of emissions, potential accidents remain a serious problem. An example of such is the most recent accident in the Fukushima Daiichi Nuclear Power Plant (2011), which reminded the world of the potential risks of nuclear energy and the consequences of which continue to have a lasting effect. There is no nuclear power plant in Serbia, but there are about 15 nuclear power stations scattered within its neighboring countries. Therefore, the Serbian Government decided to study how the Serbian public perceives the risks related to the potential construction of nuclear power stations in the country, nuclear energy in general, and its possible benefits and risks. The objective of this paper is to present the results of this assessment along with a literature overview on the (environmental) risk of nuclear power. A pilot study consisted of a series of 270 randomized face-to-face interviews that took place in the public square of Belgrade in March 2019. Logistic regression was used to examine the cumulative effects of the different risk factors. The results showed that the majority of the respondents are skeptical and do not support the construction of nuclear power stations in Serbia. Furthermore, this research identified several additional important correlations that have a significant impact on the public perception of risk. [ABSTRACT FROM AUTHOR]

This study explores the root causes of the Fukushima Daiichi disaster and discusses how the complexity and tight coupling in large-scale systems should be reduced under emergencies such as station blackout (SBO) to prevent future disasters. First, on the basis of a summary of the published literature on the Fukushima Daiichi disaster, we found that the direct causes (i.e., malfunctions and problems) included overlooking the loss of coolant and the nuclear reactor's failure to cool down. Second, we verified that two characteristics proposed in "normal accident" theory—high complexity and tight coupling—underlay each of the direct causes. These two characteristics were found to have made emergency management more challenging. We discuss how such disasters in large-scale systems with high complexity and tight coupling could be prevented through an organizational and managerial approach that can remove asymmetry of authority and information and foster a climate of openly discussing critical safety issues in nuclear power plants. [ABSTRACT FROM AUTHOR]

Utilizing the data of a large nationwide household survey conducted in 2014, we investigate public preferences on nuclear power in Japan after the Fukushima nuclear accident and the role of four sets of factors: (1) household/individual socioeconomic characteristics, (2) psychological status, (3) geographical aspects, and (4) Fukushima accident-related experiences. The preferred energy mix, according to the averaged responses from the survey, includes 0.59 for renewables, 0.29 for fossil fuels, and 0.12 for nuclear—much more skewed towards the renewables than the actual national share of renewables of less than 0.2. Male, older, unmarried, less educated, high-income people, and government party supporters have a preference towards a higher share of nuclear power, except if they live near nuclear power plants. The experience of blackout and aversion to nuclear power during the Great East Japan Earthquake of 2011 lowers the share of nuclear power in the preferred mix. [ABSTRACT FROM AUTHOR]

The Fukushima nuclear accident in March 2011 caused the massive release of anthropogenic radioactive materials from the Fukushima Dai-ichi Nuclear Power Plant to its surrounding environment. Its biological effects have been studied using the pale grass blue butterfly, Zizeeria maha (Lepidoptera: Lycaenidae), but the overwintering states of this butterfly remain elusive. Here, we conducted a series of field surveys in March 2018, March 2019, and April 2019 in Fukushima and its vicinity to clarify the overwintering states of this butterfly at the time of the Fukushima nuclear accident. We discovered overwintering individuals in situ associated with the host plant Oxalis corniculata under natural straw mulch as first-instar to fourth-instar larvae in March 2018 and 2019. No other developmental stages were found. The body length and width were reasonably correlated with the accumulated temperature. On the basis of a linear regression equation between body size and accumulated temperature, together with other data, we deduced that the pale grass blue butterfly occurred as fourth-instar larvae in Fukushima and its vicinity at the time of the accident. This study paves the way for subsequent dosimetric analyses that determine the radiation doses absorbed by the butterfly after the accident. [ABSTRACT FROM AUTHOR]

Probabilistic safety assessment (PSA) of nuclear facilities on external multi-hazards has become a major issue after the Fukushima accident in 2011. However, the existing external hazard PSA methodology is for single hazard events and cannot cover the impact of multi-hazards. Therefore, this study proposes a methodology for quantifying multi-hazard risks for nuclear energy plants. Specifically, we developed an efficient multi-hazard PSA methodology based on the probability distribution-based Boolean algebraic approach and sampling-based method, which are currently single-hazard PSA methodologies. The limitations of the probability distribution-based Boolean algebraic approach not being able to handle partial dependencies between the components are solved through this sampling-based method. In addition, we devised an algorithm that was more efficient than the existing algorithm for improving the limits of the current sampling-based method, as it required a significant computational time. The proposed methodology was applied from simple examples to single- and multi-hazard PSA examples of actual nuclear power plants. The results showed that the proposed methodology was verified in terms of accuracy and efficiency perspectives. Regarding the sampling-based method, it was confirmed that the proposed algorithm yielded fragility and risk results that have similar degrees of accuracy, even though it extracted a smaller number of samples than the existing algorithm. [ABSTRACT FROM AUTHOR]