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Before the Fukushima disaster unfolded in 2011, Japanese government and energy company officials were aware of the warning signs and risks of a potential crisis at the reactor site. They failed to use safety mechanisms or update regulations over time to address the vulnerabilities of the power plants. Because interest groups had led the public to believe the power plants were completely safe, the plants were run with little accountability. Following this disaster, Japan established a new nuclear regulatory commission and nuclear regulatory authority in and implemented new regulatory mechanisms. These efforts have been limited, however, and have shifted the issue from regulation to implementation. The enormous cost of meeting new safety protocols has created new barriers for restarting the power plants under updated regulations, but the energy demands of the country will remain. The tension between managing operational risks and meeting public energy needs will test the public and private sectors' ability to sufficiently revamp the nuclear industry and prevent crises in years to come. [ABSTRACT FROM AUTHOR]

Atomic energy has played an important role in international relations as a means of state power. From 1945 to 1959, Japan was significantly influenced by developments in atomic energy as a result of the Anglo-American "special relationship." During World War II, Britain and the United States cooperated to develop atomic weapons to use against Japan. In the ensuing Cold War era, the two countries advanced peaceful uses of atomic energy for Japan to counter the influence of the Soviet Union through psychological warfare. The U.S. Atomic Energy Peace Mission visited Japan in May 1955. However, the Japanese government altered its nuclear policy to solicit support from Britain because the United States was falling behind in atomic energy development. A British nuclear reactor was used as the first commercial nuclear power station, in 1959, whereby Britain earned parity with the United States in the context of nuclear power. [ABSTRACT FROM AUTHOR]

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]

The United States Nuclear Regulatory Commission issued requests for licensees to re-evaluate the seismic hazards at their sites after the accident at the Fukushima Daiichi Nuclear Power Plant in Japan on March 11 in 2011 and to identify and address any site-specific vulnerabilities associated with seismic hazards. The primary guidance for performing those evaluations is provided in the Electric Power Research Institute EPRI-1025287 report, which also provides guidance for evaluating spent fuel pool (SFP) integrity. In addition, the EPRI-3002009564 report also provides evaluation approaches regarding the effects of seismic ground motions on SFPs that supplement the guidance provided in EPRI-1025287. SFP integrity has become increasingly important for active and decommissioned nuclear power plants. According to EPRI-1025287, the SFP integrity evaluation emphasizes failure modes of the SFP that could result in "rapid drain-down." The definition of "rapid drain-down" is a failure that could lead to the uncovering of irradiated fuel stored in the SFP within 72 h of an earthquake. Possible failures can be classified into two categories: failures relevant to the SFP structure and failures relevant to non-structural elements. This paper aims to study the approaches of implementing seismic evaluation of an SFP structure. EPRI-3002009564 provides separate seismic evaluation approaches for plants with a ground motion response spectrum (GMRS) peak Sa ≤ 0. 8 g and for plants with a GMRS peak Sa > 0. 8 g. Structural dynamic analysis is also a common approach for implementing seismic evaluation if a detailed finite element model is available. In this paper, a sample SFP structure was evaluated using the two approaches, structural dynamic analysis and structural analysis criteria. The results indicate that shear failure controlled the failure mode of the SFP structure for both approaches. This shows that the two approaches drew the same conclusion regarding the failure mode. Furthermore, a smaller seismic margin was obtained using the structural analysis criteria, which means this evaluative approach is more conservative. [ABSTRACT FROM AUTHOR]

One of the lessons learned from the Fukushima Daiichi nuclear power plant (NPP) accident is strengthening the station blackout (SBO) mitigation capabilities by enhancing defense in depth for all existing and new NPPs. One of the possible remedies is diverse and flexible coping strategies (FLEX). The objective of this study is to address the benefits of FLEX in various accident scenarios in terms of both risk and cost. FLEX was originally devised against SBO accidents. In this research, we investigate the fundamental plant responses against accidents considering two fundamentally different cases: accidents that lead to high pressure on the primary side and accidents that lead to low pressure on the primary side. Several uncertainties are associated with the characteristics of the FLEX portable equipment. Specifically, the time for FLEX deployment may depend on several factors such as type of accident, point of injection, availability of safety systems, battery backup timings, and human actions. This study utilizes a dynamic risk assessment framework to analyze accident scenarios and suggests a novel importance measure, which is a cumulative distribution function–based importance metric that characterizes the influence of input distribution on complete output distribution. The importance of the existing and newly developed FLEX strategy based on risk significance is illustrated with examples. The suggested measure provides clear insight into how FLEX affects risk of the whole system and additional risk margins thanks to new safety systems. [ABSTRACT FROM AUTHOR]

The nuclear‐contaminated water in the seawater near the site of the Fukushima nuclear power plant (NPP) accident is being investigated for treating the radioactive material. One of the most important considerations in the treatment is the management of the vast aquatic area of the oceanic scale. There are two methods in the application of osmosis and filtration for the modeling. There is the molecule quantity by the water volume where the list of transition of quantities is shown, where it decreases to 10% from the reversed osmosis method and to 0.01% from the filtration method in 9 days. In the filtrations, the discharge variations in the sea are described as the maximum and minimum values within 100 square velocities. A design for the general radioactive contaminated seawater treatment facility is introduced. [ABSTRACT FROM AUTHOR]

The total annual effective dose has steadily decreased since the fallout of the Chernobyl Nuclear Power Plant. However, chronic internal exposure to 137Cs still persists and fluctuates in a complex and unpredictable manner. Recently, body contamination was found to primarily occur owing to the intake of forest foodstuffs that contain long-lived 137Cs. Forest foodstuffs may have up to 100 times higher concentration of cesium than does local milk and meat. The present study aimed to investigate the recent dietary habits of residents in the Zhytomyr region of Ukraine, and assess the effect of the intake of forest foodstuffs on the increase in internal radioactivity from 137Cs. We screened 1,612 participants, from July 2016 to February 2018 for internal radioactivity, using whole-body counter at Korosten Medical Center and surveyed their background and intake habits. We analyzed the association among food type, intake frequency, and internal exposure dose. The analysis revealed that nearly 90% of the participants regularly consumed one of the forest foodstuffs (mushrooms, berries, fish) or milk. Nearly 80% of the participants indicated that they consumed mushrooms or berries or both. Internal radioactivity was detected in 30% of the participants. The diet that included mushrooms exhibited the highest internal radioactivity. The lowest Bq/kg concentration was observed in the only-berry group, following the no-intake group. There was a significant correlation between the intake frequency and the magnitude of Bq/kg. Radioactivity detected in the mushroom-berry and only-mushroom group were 8.6 and 9.2 Bq/kg, respectively. The lowest and highest intake frequency showed a radioactivity of 2.4 and 7.5 Bq/kg, respectively. Radioactivity in the winter season was significantly higher than that in other seasons. In conclusion, our study revealed that internal radioactivity varies depending on the type of food, intake frequency, and season. [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]

This article focuses on the Akkuyu Nuclear Power Plant in Turkey. Its thesis is that its construction marks a turning point in the history, character, dynamics and risk profile of both Turkey and the Greater Middle East. The construction of the Plant reflects a number of emerging phenomena with unmistakable geopolitical implications. These encompass the nuclearization of Turkey, the nuclearization of the Greater Middle East and what appears to be an increasingly intimate Russo-Turkish bilateral relationship at odds with Turkey's membership of NATO. Against this background, the article pinpoints several causes for concern. Among these is the detachment of Turkey from a string of international conventions that seek to promote nuclear safety or to protect the sea, the wider environment, workers or other people. Other causes for concern include the absence in Turkey of a deep-rooted culture steeped in transparency, press freedom, whistleblowing and other potential facilitators of nuclear safety. The article ends with five sets of recommendations directed towards the Government of Turkey plus the Governments and inhabitants of other states in the Greater Middle East and the EU, two of whose member states, the Republic of Cyprus and Greece, are situated in relatively close proximity to the Plant. [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]

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]

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]

Radionuclide contamination in foods has been a public concern in Japan after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. To estimate time and regional trends of daily intake and annual committed effective dose of strontium-90 (90Sr) after the accident, we analysed Market basket samples using a low background 2π gas-flow counter. Samples were collected from six regions, once a year from 2013 to 2018. There appeared to be little variation in estimated daily intake and annual committed effective dose of 90Sr across the time periods and regions. The estimated maximum annual committed effective dose of 90Sr was 0.00076 mSv/year, a value sufficiently lower than the intervention exemption level, 1 mSv/year, in foods in Japan. There was no noticeable difference between the range of estimated daily intake of 90Sr in this study compared with daily intake measured before the FDNPP accident. These results suggested that no obvious increase in dietary intake of 90Sr was observed after the FDNPP accident, and that the effects on commercial foods from 90Sr due to the FDNPP accident were negligible. [ABSTRACT FROM AUTHOR]

Many people living around the Chernobyl Nuclear Power Plant (CNPP) have been exposed to 137Cs for several decades after the CNPP accident. Although half-life of 137Cs is about 30 years, some wild forest foodstuffs are contaminated by 137Cs even now. We pointed out in a previous report that low-dose internal radiation has been occasionally detected in people's body. Moreover, some doctors in local hospitals have claimed that internal exposure from contaminated foodstuffs may affect the digestive organs and possibly cause gastrointestinal (GI) diseases. Thus, we attempt to assess whether internal radiation exposure affects digestive organs or not, and the possible factors that influence digestive organs. Overall, 1,612 residents were assessed for internal 137Cs concentration using Whole-Body Counter and their digestive organs were screened with upper GI endoscopy from 2016–2018 in the Zhytomyr region, Ukraine. All participants answered to the questionnaire including their background, intake of wild forest foodstuff, intake frequency, smoking habits, and alcohol consumption. We checked the number of upper GI endoscopic diagnosis per person to assess the extent of damage to the upper digestive organs. Next, we statistically analyzed associations between this number and age, sex, level of internal exposure dose, alcohol consumption, wild forest foodstuff intake, and smoking. Consequently, we revealed that the number of GI diagnosis is significantly increased by factors such as sex, intake of wild forest foodstuff, and alcohol consumption. However, the average level of internal exposure of 137Cs and smoking did not relate to the number of GI diagnosis. Thus, the results of multiple regression revealed that alcohol consumption is independently related to the number of GI diagnosis that is most likely accompanied by the intake of wild forest foodstuff. In conclusion, the low-dose internal exposure may not affect the digestive organs of residents living around CNPP. [ABSTRACT FROM AUTHOR]

After the Great East Japan Earthquake and the aftermath of the Fukushima Nuclear Disaster, Yōko Tawada has written many works that touch the issues surrounding earthquakes and natural disasters - she raises salient questions through the power of literature. The novel The Last Children of Tokyo, which will be examined in this study, is a dystopian novel written by Yōko Tawada after her trip to the disaster zone of Fukushima. The novel presents a society which was impacted by ecological disasters and environmental problems - a life of drifting into dystopia, taking place in the capital city of Tokyo the center of Japan's industry and economy. Tawada's novel leads us to a confrontation with today's human questions; on environmental problems, the danger of nuclear radiation, and the relationship of nuclear power plants to civilization. In this regard, Tawada's text was analyzed through the concept of "deep ecology" that emerged in the field of ecocriticism. The term "deep ecology" was first used by the philosopher Arne Naess in his 1973 article titled, Deep Ecology Movement: Some Philosophical Aspects. Explaining the basic principles of deep ecology into eight items, Naess provides a defense for the richness and diversity of life forms and states that human and non-human beings are values in themselves. The Last Children of Tokyo, emphasizing the value of not only human but also non-human beings, defending the equality of all beings and depicting all beings as part of the web of life has shown that it is compatible with the basic principles of Naess's philosophy of deep ecology. [ABSTRACT FROM AUTHOR]

The Fukushima Daiichi Nuclear Power Plant accident, triggered by the Great East Japan Earthquake and the tsunami, has had a major impact on societies across the world. The subsequent focus on decommissioning efforts has attracted worldwide attention. It has been consistently asserted since the aftermath of the accident that the decommissioning of the Fukushima Daiichi Nuclear Power Plant will take approximately 30 to 40 years. The promotion of decommissioning work means that we will continue to face the problems with uncertainties in the work, as sometimes referred to as Unknown Unknowns. Typical elemental technologies required in remotely operated robotic systems for decommissioning include mobile mechanisms and their control, handling mechanisms and their control, information communication, operation interface (information presentation and command input), shielding (radiation resistance) and so on. Although many tasks using remotely operated robotic systems have been carried out with noteworthy results, there are lingering issues yet to be clarified. To ensure the safe and effective execution of various types of decommissioning tasks over a period of several decades, continuous research and development of each elemental technology are imperative, and these technologies must be integrated into a system appropriately to the assumed tasks. In addition, human resource development and the transfer of knowledge and experience are also important issues. From such viewpoint, this special issue is titled "Robotic, Mechatronic and Information Systems for Decommissioning." It contains papers and development reports on robotics, mechatronics, information processing, and information systems technologies relevant to decommissioning work. It also features recent activities of nuclear emergency response organizations. We hope this special issue will acquaint readers with the latest research and development results and organizational activities related to decommissioning. At the same time, we hope that we were able to provide readers interested in robots, mechatronics, and information technology with an opportunity to become aware of the issues and necessary perspectives related to decommissioning and nuclear disasters. Lastly, we would like to thank the editorial board of the Journal of Robotics and Mechatronics, the editorial team of Fuji Technology Press, and the reviewers for their support in the planning and publication of this special issue. Their dedicated efforts are deeply appreciated. [ABSTRACT FROM AUTHOR]

The unexpected accident at the Fukushima Daiichi Nuclear Power Station in Japan, which occurred on March 11th, 2011, after the Great East Japan Earthquake and tsunami struck the north-eastern coast of Japan, released radionuclides into the environment. Today, because of the amounts of radionuclides released and their relatively long half-life, the levels of radiocesium contaminating foodstuffs remain a significant food safety concern. Foodstuffs in Japan have been sampled and monitored for 134,137Cs since the accident. More than 2.5 million samples of foodstuffs have been examined with the results reported monthly during each Japanese fiscal year (FY, from April 1st to March 31st) from 2012 to 2021. A total of 5,695 samples of foodstuffs within the "general foodstuffs" category collected during this whole period and 13 foodstuffs within the "drinking water including soft drinks containing tea as a raw material" category sampled in FY 2012 were found to exceed the Japanese maximum permitted level (JML) set at 100 and 10 Bq/kg, respectively. No samples from the "milk and infant foodstuffs" category exceeded the JML (50 Bq/kg). The annual proportions of foodstuffs exceeding the JML in the "general foodstuffs" category varied between 0.37% and 2.57%, and were highest in FY 2012. The 134,137Cs concentration for more than 99% of the foodstuffs monitored and reported has been low and not exceeding the JML in recent years, except for those foodstuffs that are difficult to cultivate, feed or manage, such as wild mushrooms, plants, animals and fish. The monitoring data for foodstuffs show the current status of food safety risks from 134,137Cs contamination, particularly for cultured and aquaculture foodstuffs on the market in Japan. [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]

A fleet of thirteen in-service global container ships continuously measured the air dose rates over the North Pacific after the Fukushima Daiichi Nuclear Power Station (FDNPS) accident. The results showed that the elevated air dose rates over the Port of Tokyo and the FDNPS emissions are significantly correlated (log(emission fluxes) = 54.98 x (air dose rates) (R = 0.95, P-value<0.01), and they are also significantly correlated with the Tsukuba deposition fluxes (log(deposition fluxes) = 0.47 + 30.98 (air dose rates) (R = 0.91, P-value<0.01). These results demonstrate the direct impact of the FDNPS emissions on the depositions of radionuclides and the air dose rates over the Port of Tokyo. Over the North Pacific, the correlation equations are log(emission fluxes) = -2.72 + 202.36 x (air dose rates over the northwestern Pacific) (R = 0.40, P-value<0.01), and log(emission fluxes) = -0.55 + 80.19 x (air dose rates over the northeastern Pacific) (R = 0.29, P-value = 0.0424). These results indicate that the resuspension of the deposited radionuclides have become a dominant source in the transport of radionuclides across the North Pacific. Model simulations show underestimated air dose rates during the periods of 22-25 March 2011 and 27-30 March 2011 indicating the lack of mechanisms, such as the resuspension of radionuclides, in the model. [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]

Improper operation leading to an emergency shutdown in a nuclear power plant can result in significant energy loss and have a substantial impact on the economy. This study focuses on a sodium-cooled fast reactor (SFR) nuclear power plant, analyzing system characteristics under different accidents through feedwater system simulation and improving control system performance. The results show that the single module accident will affect the whole feedwater system, and the influence of faulty SG on the loop signal should be eliminated. The improved control system reduces sodium temperature fluctuation by 3%–41.5%, shortens adjustment time by 57.9%, and ensures standby pump activation within 10 s after the feedwater pump trips or when the system stabilizes. Although the feedforward of mass flowrate ratio can improve the response of the system to flow disturbance, it resists the temperature feedback. However, considering inlet temperature's impact on feedwater demand, this confrontation can be effectively avoided, and a good control effect can be maintained during accidents. • The third circle accident of sodium-cooled fast reactor is simulated. • An improved feedwater control system, based on energy balance, is proposed. • Recommendations for addressing different types of accidents in the third circuit are provided. • The performance of feedwater system under accident has been significantly improved. [ABSTRACT FROM AUTHOR]

Radionuclides from the reactor accident Fukushima Daiichi nuclear power plant were observed in the airborne aerosols at CTBT International Monitoring System (IMS) stations (MRP43, CMP13) in Africa. The maximum activity concentrations in the air measured in Mauritania were 186.44 10−6 Bq.m−3, 264.16 10−6 Bq.m−3 and 1269.94 10−6 Bq.m−3 for 134Cs, 137Cs and 131I respectively, and in Cameroon 16.42 10−6 Bq.m−3, 25.53 10−6 and 37.58 10−6 Bq.m−3 respectively for 134Cs, 137Cs and 131I. The activity ratio of 134Cs/137Cs is almost constant throughout the period of time relevant to this study due to their long half-lives of 30.2 years for 137Cs and 2.06 years for 134Cs. Whereas the 131I/137Cs activity ratio varies in time according to the radioactive decay with a half-live of 8.06 days for 131I and different removal rates of both radionuclides from the atmosphere during transport. The EMAC atmospheric chemistry-general circulation was used to simulate the emission and transport of the isotope 137Cs and map the deposition of the 137Cs deposition over Africa. • IMS stations in Africa (MRP43, CMP13) detected first 131I, caesium isotopes appearing with a delay of 6 days in Cameroon and 4 days for 134Cs in Mauritania. • The highest activity concentrations of fission products were found in Mauritania. • The EMAC atmospheric chemistry-general circulation was used to simulate the emission and transport of the isotope 137Cs and map the deposition of the 137Cs deposition over Africa. [ABSTRACT FROM AUTHOR]

Since 2018, the use of AP1000 nuclear technology has been growing due to its advantages in terms of nuclear safety and security. Knowing that the occurrence rate of the serious nuclear reactor accidents has increased due to the natural disasters that the world has encountered in recent decades, such as earthquakes, floods, tsunamis, etc., we propose to carry out an impact study and analyze the consequences of these accidents, with the aim of avoiding exposure of the public and workers to ionizing radiation. This work is divided into two sections: firstly, calculate the source term by using the ORIGEN-JR depletion code, and compare the obtained results with those published in the document AP1000 Design Control. The obtained results are in agreement with the literature. Secondly, starting from the results of the source term calculation, we have evaluated the atmospheric dispersion using health HotSpot code. The Total Effective Doses (TED) is estimated over two meteorological periods: the first period, from April to August, and the second one, from September to March. The simulation results showed that the TED was higher, around 27 Sv at 0.6 km from the source during the April–August period. However, for the second period, the TED is about 8 Sv at 2 km from the source. Generally, the TED of all radionuclide groups exceeds the IAEA annual regulatory limits, which are one millisievert per year (1 mSv/year) for public exposure and twenty millisieverts per year (20 mSv/year) for occupational exposure of workers. Therefore, the probability of risks to workers, the public, and the environment rises. There are generic criteria for acute doses, according to which preventive actions must be taken in all circumstances in order to minimize the serious effects of radionuclides on the population. • Computing the source term of eight radionuclide groups using the ORIGEN JR code for an AP1000 reactor. • Predicting the early atmospheric dispersion of radionuclides using the HotSpot code in the event of a hypothetical accident. • Compare the obtained results of the source term with those published in the document AP1000 Design Control. • The TED, GD, Different pathways of exposure and CEDE for some human body organs are estimated. • The results provide important information for severe accident management and safety assessment. [ABSTRACT FROM AUTHOR]

• Assessment of the acute and chronic exposure situations in a hypothetical accident of long term station black out at the proposed Buyende nuclear site in Uganda. • Total effective dose equivalents and thyroid dose at the exclusion are boundary and emergency protection zone were within the regulatory limits. Uganda's energy policy of 2023 and Vision 2040 plans to address the country's electricity shortage by introducing nuclear power of 24,000 MW capacity by 2040. The pioneer nuclear power plants with a generation capacity of 8,400 MW will be built in Buyende District. This study focused on assessing the radiological consequences of potential nuclear accident on any of the four technologies of APR1400, VVER1200, HPR1000, and APR1000. Evaluation of acute and chronic radiation effects from a long-term station blackout accident using RASCAL and GENII codes identified the order of minimum health risks to the public as APR100, HPR1000, VVER1200, and APR1400 if single units are constructed. The total effective dose equivalents and thyroid doses at the exclusion area boundary and emergency protection zone were within the regulatory limits of 250 mSv and 3,000 mSv, respectively for all the reactor technologies. [ABSTRACT FROM AUTHOR]

Large-scale decontamination work has been carried out in the aftermath of the Fukushima Daiichi nuclear power station accident in Japan in 2011. The soil that was removed and the wastes that were generated during the decontamination will be finally disposed of outside Fukushima Prefecture by 2045. To ensure successful and socially acceptable implementation of this final disposal process, it is essential to have a good understanding of what is considered important by the public. We used a choice-based conjoint analysis in the form of a web-based questionnaire to examine the relative importance of several factors in the choice of the final disposal sites of the removed soil and incinerated ash of the wastes. The questionnaires covered four attributes and 12 levels, namely the distance between the disposal site and a person's residential area, procedural fairness (decision process), distributive fairness (direct mitigation of inequity through multiple siting locations), and the volume and radioactivity of the substances to be disposed. Responses were received from 4000 people nationwide, excluding Fukushima residents. The results showed that the respondents gave high importance to choosing sites that were far from residential areas and to the two types of fairness, especially distributive fairness. The respondents showed no preference for the volume and radioactivity. This indicates that the public cares about the fairness of the siting for the final disposal sites and feels uncomfortable with plans for a final disposal site located close to them. Distributive fairness is necessary to pursue consensus in addition to procedural fairness. [ABSTRACT FROM AUTHOR]

This paper's theme "Creative Robot Contest for Decommissioning (hereinafter, this Creative Robot Contest)" may be called a contest that would never have been planned in the absence of the Great East Japan Earthquake on March 11, 2011 and the core meltdown accident at Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Company. When it was decided to decommission the nuclear reactors, their decommissioning was immediately put in hand, which, however, met with a high barrier of high radiation doses unconquerable even by the modern science and technologies. In order to advance the stagnating decommissioning work and in hopes of some creative breakthrough ideas from KOSEN students, this Robot Contest, first held in 2016, has been held by KOSEN teams who have shown their willingness to participate in it as a venue useful to address any difficulties they will face in the real world or as teaching material for them to consider social problems. This Robot Contest, sponsored by the Japan Atomic Energy Agency and the Council of Technical Colleges for Human Resource Development for Decommissioning, is planned and managed by the Executive Committee of Creative Robot Contest for Decommissioning (hereinafter, the Executive Committee) with its secretariat at National Institute of Technology, Fukushima College (hereinafter, Fukushima KOSEN) in Fukushima Prefecture where Fukushima Daiichi Nuclear Power Plant is located. In this paper, teachers at Osaka Metropolitan University College of Technology (hereinafter, Osaka Metropolitan University KOSEN) and at Nara National College of Technology, Nara College (hereinafter, Nara KOSEN), whose respective teams have participated in this Robot Contest every year from the first one, and teachers at Fukushima KOSEN who organize and manage the executive committee describe their own views on this Robot Contest based on their viewpoints as KOSEN educators. In the first half, this paper reviews this Robot Contest and outlines the robots of Osaka Metropolitan University KOSEN which participated in it in FY2016 and FY2017 and of Nara KOSEN which did in FY2016. In the latter half, this paper describes the views of the KOSEN teachers who educate engineers in the framework of robot contests from the viewpoints of the teachers who have instructed the teams of Osaka Metropolitan University KOSEN and Nara KOSEN who have participated in this Robot Contest up to the sixth one and who have held this Robot Contest. [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]

Objective: This study continues former studies on perinatal mortality in Japan after the Fukushima Daiichi nuclear power plant (FDNPP) accident in March 2011. An increased study region is chosen, and the study period is extended to 2019. Methods: Japanese monthly perinatal mortality data are provided on a prefecture level by the Japanese government. The study region consists of 12 prefectures around the FDNPP; the rest of Japan is used as the control region. A combined non-linear regression of perinatal mortality rates in the study- and control regions is conducted. The regression model allows for a common asymptotic lower limit of perinatal mortality, seasonal variations, and periodic peaks in 2012–2019 in the study region. To determine the dependency of the effect on distance from the FDNPP, the study region is divided into four core prefectures and eight prefectures surrounding the core prefectures. Results: Perinatal mortality rates in the study region show a significant 6.4% (95% CI: 1.8%, 13.4%) overall increase in 2012–2019 relative to the trend in preceding years with no attenuation during 2012–19. The increase translates to 590 (165, 1226) excess perinatal deaths (p = 0.016). It is characterized by annual peaks with maxima in April. A 13.6% increase is determined in the four core prefectures and a 4.3% increase in eight prefectures surrounding the core prefectures. Before 2012, there is a peak around April 2011 and a decline in October 2011; another significant peak is detected in November 2012. In the 4 core prefectures, large increases are found in the first quarter of 2018 (+70%) and in May 2019 (+130%). Conclusion: This study finds periodic peaks in perinatal mortality in spring 2012–2019 in 12 prefectures of Japan surrounding the FDNPP. In light of massive increases in 2018 and 2019 in the four core prefectures, continued investigation of perinatal mortality in contaminated regions of Japan is recommended. [ABSTRACT FROM AUTHOR]

In order to further clarify the fire safety evaluation of nuclear grade activated carbon, thermal analysis combined with pore structure and phase analysis was adopted for coal-based activated carbon and coconut shell activated carbon used in nuclear power plants. On the basis of establishing the relative fire safety evaluation model by using four important parameters: activation energy (E), maximum mass loss rate (DTG p), maximum mass loss rate temperature (T p) and rapid reaction percentage (A 12), the O/C ratio and enthalpy (H) were further introduced into the evaluation model to calculate the relative fire safety factor (RFSF). The results show that O/C ratio and enthalpy have greater influence on the fire safety of activated carbon than porosity characteristics. The RFSF values of coal-based and coconut shell activated carbon are 1.33 and 1.08, indicating that fire safety is higher than that of impregnated coconut shell activated carbon. • A relatively perfect fire safety evaluation model of nuclear grade activated carbon was successfully established. • The O/C ratio and enthalpy have greater influence on the fire safety of activated carbon than porosity characteristics. • RFSF of CBAC and CSAC are 1.33 and 1.08, indicating that fire safety is higher than that of ICSAC. • The introduction of O/C ratio and enthalpy will further improve the evaluation model of relative fire risk. [ABSTRACT FROM AUTHOR]

Regulators around the world have devised practical methods for evaluating the safety of nuclear power plants (NPPs) and increasing public awareness of plant safety. One essential approach is the regulatory safety-related inspection, which plays a crucial role in confirming the safety of power plants to prevent and mitigate accidents. In recent years, many developed countries have adopted a risk-informed methodology, which, similar to the conventional deterministic approach, prioritizes various aspects of regulatory inspection which relies on PSA insights for decision-making, rather than being rooted in a deterministic approach. In the United Arab Emirates, where three nuclear units are in operation, the regulatory inspection focuses on reducing the likelihood of incidents through a defense-in-depth (DiD) concept and the insights gained from risk analysis. To strengthen accident prevention oversight, both deterministic and probabilistic approaches are utilized, including probabilistic risk assessments (PRA) aimed at identifying safety improvements. This study aims to develop a preliminary safety inspection methodology using AIMS-PSA as an analysis tool. It involves constructing event trees and fault trees to understand how to secure the success path of Loss of Coolant Accidents (LOCAs) transients, block potential failure paths, and assess their impact on Core Damage Frequency (CDF) by analyzing the generated cut sets. This study will offer quantifiable insights into key risk factors, improving our capacity to anticipate and prevent accidents, maintain high reliability, and conduct effective risk assessments for the continued operability of safety systems. While previous investigations have explored nuclear accident frequencies, often with limitations, this research aims to provide a more comprehensive perspective on nuclear power plant safety, addressing a wide range of accident scenarios and their implications. • Regulatory safety inspections are crucial for verifying nuclear power plant safety. • The UAE's focus on minimizing incident probability using a defense-in-depth approach. • AIMS-PSA is used to analyze LOCA transient success and failure paths. • The study identifies core contributors to risk and aids in accident anticipation. • The methodology enhances safety, reliability, and long-term accident mitigation. [ABSTRACT FROM AUTHOR]

• Anaerobic wet fermentations were conducted for treating genuine radioactive grass. • Alkaline-heat and ultrasonic methodologies were used to pre-treat the grass. • Alkaline-heat-treated grass showed an optimal anaerobic conversion efficiency. • Pre-treatments and wet fermentations barely leached Rad-Cs from grass. • Soil with high cesium affinity mixed with grass limited the Rad-Cs leaching. Persistent concerns regarding environmental hazards arise from the difficulty in disposing of radioactive plant-based wastes originating from the nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) in Japan in 2011. In this study, three anaerobic digestion (AD) strategies were proposed: Sole anaerobic wet fermentation, and wet fermentations with either alkaline-heat or ultrasonic pre-treatment, which were employed for long-term anaerobic treatment of a genuine radioactive grass stemming from the FNPP accident. The objectives of this work are to investigate the effects of pre-treatments on biomass conversion efficiency and to gain insight into the leaching behavior of radiocaesium (Rad-Cs) within AD processes. Experimental results indicate that by introducing alkaline-heat and ultrasonic pre-treatments to AD systems, the removal efficiencies of total solids (TS) from the raw grass increased by 60.8 % and 42.5 %, respectively, compared to sole wet fermentation. Pre-treatments have been shown to enhance the stability of AD systems, both in terms of enhancing methane production and mitigating pH fluctuations triggered by the accumulation of organic acids. Remarkably, even though the Rad-Cs leaching rate was highest when the AD system was fed with the alkaline-heat pre-treated grass, it remained unsatisfactory at only 5.77 %. We inadvertently isolated a soil-like component from the raw grass, and analyzed both its proportion in the raw grass and the radioactivity intensity. The results indicate that although the soil constituted only 9.51 % TS of the raw grass, it accounted for a significant 81.35 % of the total radioactivity. The soil, which has a pronounced affinity for ionic Cs, being mixed into the raw grass, was identified as the primary factor limiting the leaching efficiency of Rad-Cs throughout both the pre-treatment and wet fermentation phases. [Display omitted] [ABSTRACT FROM AUTHOR]

Following the accident at the Fukushima Dai-ichi Nuclear Power Station, radiocaesium concentrations were specifically elevated in rockfish species compared to other fish species. To clarify the likely reasons, a caesium metabolic rate in the Japanese rockfish Sebastes cheni was derived by an aquarium experiment of live fish collected from the area off Fukushima. Stable caesium and 137Cs concentration in prey organisms, stomach contents and muscle of rockfish were measured and the bioavailable fraction in prey organisms was evaluated. Using derived transfer parameters, 137Cs radioactivity levels in S. cheni and prey organisms were simulated by a model, and verified by the measured radioactivity concentrations of biota in coastal waters south of the Fukushima Dai-ichi Nuclear Power Station. As a result, slow caesium metabolism in S. cheni was confirmed with the biological half-life (Tb 1/2) of 190 d. The determining factor for the initial 137Cs radioactivity levels in S. cheni , was the maximum radioactivity levels in surrounding seawater which was constrained by the sedentary nature of rockfish. Controlling factors of depuration rate of 137Cs levels in S. cheni were slow caesium metabolism, enhanced 137Cs radioactivity level of prey organisms, and survival of older contaminated individuals due to a long life-span. During the study period 2017–2021, 137Cs radioactivity concentrations in seawater decreased close to the level measured before 2010, whereas those in prey organisms and rockfish in southern Fukushima waters were still above the levels that existed before 2010. An additional source for enhancing 137Cs radioactivity in rockfish and biota of the food chain was indicated by the greater 137Cs/133Cs atom ratios in rockfish compared to those in the surrounding seawater, however it was considered to be radiologically insignificant in relation to seafood safety limits. • Very slow radiocaesium excretion confirmed in rockfish. • Depuration in rockfish was delayed by 137Cs transfer from prey. • 137Cs excretion in contaminated old fish completed after 10 years. • 137Cs transfer among rockfish and adjacent ecosystems reached equilibrium after 2019. [ABSTRACT FROM AUTHOR]

After the Fukushima nuclear meltdown, the Angela Merkel government in Germany officially announced its decision to permanently shut down all of its seventeen nuclear reactors. In closer proximity to Fukushima, the Lee Myung-bak government in South Korea expanded its nuclear energy program with specific plans to construct more nuclear reactors in various locations and pursued more export opportunities. It was only in 2017 that the South Korean government, under President Moon Jae-in, announced a gradual phase-out of nuclear power plants in South Korea. What explains the contrasting paths of the German and South Korean nuclear energy programs in the immediate aftermath of the Fukushima nuclear disaster? Why did the same external shock prompt sudden policy reversal in Germany while it took six more years for South Korea to turn its course? While existing studies are helpful in accounting for the rise of particular energy policies, they are insufficient for explaining the causes and specific timing of major policy reversals in the face of external crises. Building upon the literature on political opportunity structures, this article argues that the emergence of new political opportunities and the shift in political framing with respect to nuclear energy caused nuclear phase-out in both countries. A closer look at the two national cases offers an opportunity to delineate the domestic political process of nuclear energy policymaking and evaluate the role of exogenous shocks, such as a major nuclear disaster, in shifting political opportunity structure and reshaping the perceptions of energy security and political risks. [ABSTRACT FROM AUTHOR]

This article argues that the history of nuclear energy can and should be analyzed as a history of water. Taking inspiration from David Edgerton's The Shock of the Old and recent efforts to merge the history of technology with environmental history, here the focus shifts from nuclear reactors to the "conventional" parts of nuclear power plants. This brings to the fore that a range of hydraulic technologies with long prehistories—pumps, pipes, valves, dams, dikes, and so on—have been crucially important for nuclear safety. The "atomic age" is fundamentally a hydraulic age and should be seen in relation to experiences gathered by past hydraulic civilizations. [ABSTRACT FROM AUTHOR]

The process of an aerosol rainout in wet deposition induces large uncertainties among atmospheric aerosol simulations, especially for particles in the fine mode. In this study, we performed an intercomparison study of four different rainout schemes on the model (the nonhydrostatic icosahedral atmospheric model or NICAM) to simulate particulate Cs-137 in the emission scenario of the March 2011 accident at the Fukushima Dai-ichi Nuclear Power Plant. The schemes include global climate models (GCMs) approach with a simple tuning parameter to determine the scavenging coefficient, and another optimized for cloud resolving models (CRMs) to account for prognostic precipitation and realistic vertical transport. The third approach was the conventional method under the assumption of a pseudo-first-order approximation based on the surface precipitation flux. The fourth approach was involved in offline chemical transport models (CTMs) with a simplified parametric analysis approach to clouds and precipitation flux. In most experiments, statistical metrics of the Cs-137 concentrations using in-situ measurements were calculated to be within ±30 % (bias), 0.6 - 0.9 (correlation), 67 - 112 Bq m-3 (uncertainty), and < 40 % (precision within a factor of 10). The CRM-type method yielded the best results but required a lower limit of tuning parameters to compensate for the results. Both the GCM-type and the conventional methods were also useful by setting proper tuning parameters. The CTM-type yielded better correlation and lower uncertainty but larger negative bias. These analyses suggest the overestimation of the conversion rate from cloud droplets into raindrops by the NICAM. However, this cannot be resolved by simply interchanging cloud microphysics schemes. It was found that the sensitivity of the rainout scheme has a stronger influence on the Cs-137 concentration than the different treatments of cloud microphysics. Thus, to replicate the observed Cs-137 distribution, it is essential to have a better meteorological field as well as a proper rainout scheme. [ABSTRACT FROM AUTHOR]

On 16 March 2021, the Teach311 + COVID-19 Collective () hosted a virtual roundtable discussion entitled "Sources of Disaster: New Epistemic Perspectives in Post-3.11 Japan." The event brought together scholars and students researching the history and anthropology of Japan to explore how the earthquake, tsunami, and nuclear power plant disaster of 11 March 2011 (3.11) changed our ways of knowing the world. The roundtable focused on the idea of the "source" to get at these epistemic shifts in lived experience and practical knowledge as well as historiography, and to investigate ideas that range from what we can know about acceptable risk and safety to notions of home and belonging. "Source" is a way to think about origins, but also the materials—texts, media, or testimony—that we collect and analyze to give rise to new or better knowledge. Building upon previous Teach311 activities that explored the roots of 3.11 and genba, participants in this roundtable expanded upon the significance and meanings of the notion of a "source" relative to the politics of epistemology in their research and studies in order to examine what reconstruction means in history when it is conducted alongside recovery. [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]

Emergency response planning associated with written procedures play a key role in the process safety to ensure that accident can be properly managed. Although the extensive use of digital techniques have significantly reduced the accident risk by early warnings and operation guidance, the Fukushima nuclear disaster reminds us that the unexpected events may still exceed existing system capability to indicate appropriate responding measures. A novel digitalized approach is hence required for planning decision support. This article presents a joint utilizing of two modeling and analysis methodologies, which are complementary to each other to provide comprehensive insights for decision-making in the accident emergency response. Multilevel Flow Modeling (MFM) is applied to develop an intelligent reasoning system, which can harness plant's qualitative functional knowledge to search available equipments and corresponding action sequences potentially being able to manage the accident. Go-Flow is a success-oriented reliability analysis method specially suitable for quantitative risk assessment in the situations involving configuration changes. The underlying configuration of each MFM-driven emergency response measure will update the understanding of goal achievement and modify the Go-Flow chart, by which plan's effectiveness of risk reduction can be evaluated. Moreover, Go-Flow is also used to conduct the risk matrix assessment for identifying critical components, which can provide a reference for effective assignment of resources in the long-term accident management. This work is expected to strengthen operator's ability of emergency response planning from perspective of both measure development and optimization. An accident scenario similar to what occurred in the Fukushima Daiichi nuclear power plant has been used to demonstrate the application of the propose approach. [ABSTRACT FROM AUTHOR]

An enormous amount of environmental monitoring data has been acquired by various organisations for the evaluation and implementation of countermeasures to mitigate the effects of the accident at the Fukushima Daiichi Nuclear Power Plant. However, it is difficult to collate, compare, and analyse this data because it was published in different formats at different sites according to the respective objectives of the publishing organisations. Moreover, these organisations have been accumulating data in large volumes for over nine years after the accident. We established procedures to collect this data, convert them into a unified format, classify them according to categories, and make the data accessible on a web-based database system. The database contains environmental monitoring data on air dose rates, ground deposition densities, and concentrations in various environmental samples such as soil, water, and food. This data is being provided not only in numerical format for quantitative analysis but also as distribution maps and time-series graphs for visual understanding. The database system enabled us to spatially and temporally compare large volumes of monitoring data. By using the database functions, characteristics of some representative data in the database was clarified. [ABSTRACT FROM AUTHOR]

Using two horizontal resolutions (3 km and 250 m), this study examined the performance of Eulerian models in simulating dispersion fields at two coastal monitoring stations in the vicinity of a pollutant source (3.2 km and 17.5 km distant) under the situation of the Fukushima 2011 nuclear accident. A 250-m grid simulation was newly conducted for the examination and was able to reproduce the wind and concentration fields in detail over complex terrain. The 3-km grid model could not reproduce the details of the winds and plumes around the Fukushima Daiichi Nuclear Power Plant but occasionally yielded a higher performance with a lower undetected error rate compared with the 250-m grid model due to the large numerical diffusion of the former. A disadvantage of Eulerian dispersion models is expected to be the artificial numerical diffusion in the advection process near emission sources. The artificial numerical diffusion increases the false alarm ratio (number of strikeouts while swinging) but fortunately decreases the undetected error rate (number of strikeouts while looking). This characteristic is appropriate for environmental emergency response (EER) systems. Furthermore, the 250-m grid model result was improved by a plume augmentation (i.e., max pooling) process, which enlarged the plume widths and masked short time lags and small plume drifts. Plume augmentation was advantageous to the high-resolution model for improving statistical scores, which is beneficial for EER systems. [ABSTRACT FROM AUTHOR]

After the Fukushima disaster, the authors analyzed all past core-melt accidents and estimated a failure rate of 1 per 3704 reactor years. This rate indicates that more than one such accident could occur somewhere in the world within the next decade. The authors also analyzed the role that learning from past accidents can play over time. This analysis showed few or no learning effects occurring, depending on the database used. Because the International Atomic Energy Agency (IAEA) has no publicly available list of nuclear accidents, the authors used data compiled by the Guardian newspaper and the energy researcher Benjamin Sovacool. The results suggest that there are likely to be more severe nuclear accidents than have been expected and support Charles Perrow's "normal accidents" theory that nuclear power reactors cannot be operated without major accidents. However, a more detailed analysis of nuclear accident probabilities needs more transparency from the IAEA. Public support for nuclear power cannot currently be based on full knowledge simply because important information is not available. [ABSTRACT FROM AUTHOR]

Summary: The Extensive Damage Mitigation Guideline (EDMG), which was developed by the U.S. Nuclear Energy Institute (NEI) owing to the motivation of 911 terrorist attacks and not allowed to spread before the Fukushima nuclear accident, was publicly available after Fukushima nuclear accident and paid attention to worldwide. Many countries have adopted the U.S. EDMG methodology and developed their strategies (some are not called EDMG but have similar functions), planning to introduce it into the emergency plans of their domestic nuclear power plants (NPPs). Based on the defense‐in‐depth (DID) concept of nuclear safety, the experience of the Fukushima nuclear accident, and the state‐of‐the‐art of EDMGs research, this paper will give a comprehensive review of EDMG. To illustrate the reason for the introduction of EDMG into the traditional NPP procedures/guidelines, the review work started from the perspective of DID in nuclear safety and the reason for the Fukushima nuclear accident from the viewpoint of DID, which showed the weaknesses of DID implementation strategy ‐ underestimation of the damage during a beyond‐design‐basis external event (BDBEE). EDMG is crucial complementary for the old framework of procedures/guidelines to enhance the concept of DID. The research progress of EDMG in different countries has been reviewed and a rough comparison has been made among them according to the present state‐of‐the‐art from literature. The methodology of EDMG is summarized as follows: (a) Loss of Large Area (LOLA) ‐ the originally designed scenario for EDMG; (b) elements of EDMG ‐ the summarized contents for EDMG implementation; (c) classification of EDMG ‐ initial response EDMGs and Technical Support Center (TSC) response EDMGs; (d) implementation of EDMG‐introduction of three phases of EDMG implementation step by step. Furthermore, three typical methods to integrate EDMG into the traditional procedures/guidelines are reviewed. Finally, this paper gives some concluding remarks for EDMG‐related critical issues and recommended future work, which may be challenges for the development and application of EDMG and useful for the related researchers. Novelty Statement: The studies of the extensive damage mitigation guideline (EDMG), its methodology, and the progress in different countries have been reviewed.Three typical methods to integrate EDMG into the traditional procedures/guidelines are summarized and reviewed.Concluding remarks for EDMG‐related critical issues and recommended future work are summarized. [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]

At approximately 6:24 AM CET on the morning of 22 March 2020, a 5.3 Mw or 5.5 ML earthquake hit Zagreb, Croatia, with an epicentre 7 kilometres north of the city centre. Over 1900 buildings are reported to have been made uninhabitable by earthquake damage. While the earthquake was felt also in the neighbouring Slovenia, the nuclear power plant Krško – which is situated in Slovenia, but roughly 50 kilometres north-west of Zagreb – remained unaffected. However, the event triggered the question of applicability of the existing international nuclear liability conventions to cases of nuclear incidents, occurring as a consequence of a natural disaster. This article aims to analyse various nuclear liability regimes, established under existing international conventions, with respect to those nuclear damages occurring as a consequence of an earthquake. Attention is paid to the question of which subject is to be held liable under these various liability regimes and what would be the nature of such liability. Further, the article addresses the question of how the states concerned could strengthen the existing liability regime in such circumstances, in particular with respect to the region of Central Europe. [ABSTRACT FROM AUTHOR]

Switzerland has long met a good portion of its energy needs by using nuclear power. But in the wake of the accident at Fukushima, the country will have to turn elsewhere—while still remaining true to its history of self-sufficiency and energy independence. This effort is made more complicated by fears that one of its traditional energy sources, hydropower, may no longer be as reliable as in the past. But with a combination of energy conservation, greater efficiencies, alternative energy sources, the “smart grid,” and the introduction of new technologies currently on the drawing board, the country may readily be able to replace the energy lost by the closing of its existing nuclear power plants. And the loss of the snowpack and glaciers (due to climate change) may not be as dire for Switzerland’s hydropower as first anticipated. [ABSTRACT FROM AUTHOR]

In response to a station blackout accident similar to the Fukushima nuclear accident, China's Generation III nuclear power HPR1000 designed and developed a passive residual heat removal system connected to the secondary side of the steam generator. Based on the two-phase natural circulation principle, the system is designed to bring out long-term core residual heat after an accident to ensure that the reactor is in a safe state. The steady-state characteristic test and transient start and run test of the PRS were carried out on the integrated experiment bench named ESPRIT. The experiment results show that the PRS can establish natural circulation and discharge residual heat of the first loop. China's Fuqing no. 5 nuclear power plant completed the installation of the PRS in September 2019 and carried out commissioning work in October. This debugging is the first real-world debugging of the new design. This paper introduces the design process of the PRS debugging scheme. [ABSTRACT FROM AUTHOR]