Fukushima Nuclear Accident Research Articles

Fukushima Daiichi Nuclear Power Station Accident and Monitoring Post Data —The Role of Monitoring Posts in the Early Stages of a Nuclear Power Plant Accident

Fukushima Daiichi Nuclear Power Station Accident and Monitoring Post Data —The Role of Monitoring Posts in the Early Stages of a Nuclear Power Plant Accident

Exploring the differences and influencing factors between top-down and opinion-reflective approaches regarding public acceptance of final disposal of soils removed after the Fukushima nuclear accident.

The final disposal of the soils removed from the area affected by the Fukushima nuclear accident will be carried out by 2045. This study investigated how acceptance of final disposal differed between top-down, opinion-aggregative, and opinion-reflective approaches to the decision outcome, and what factors influenced these differences. In 2022, a survey of 3000 randomly selected participants living outside Fukushima Prefecture was conducted using the postal method, with responses obtained from 871 consenting participants. The proportions of respondents who agreed to accept the final disposal were 22.6, 37.6 and 56.9% for the top-down, opinion-aggregative, and opinion-reflective approaches, respectively. The preferences for both opinion-aggregative and opinion-reflective approaches showed significant positive associations with interest in final disposal and social benefits, and significant negative associations with intergenerational expectations and age. This study highlights the importance of procedural fairness in determining final disposal sites, and identifies factors that contribute to greater acceptance through this process.

Behavior of radioactive cesium concentration for 13 years after FDNPP accident at Koriyama campus of Nihon University, Fukushima, Japan.

The concentration of the radioactive cesium (134Cs and 137Cs) in soils and in atmospheric fallouts has been measured at the Koriyama campus, Nihon University, after the Fukushima Dai-ichi Nuclear Power Plant accident for 13y, from October 2011 till September 2023 and now ongoing. The concentration of them decreased very rapidly due to decontamination activities and weathering effects, with an environmental half-life of 1.21 and 2.82y in soils, with those of 1.58 and 2.08y in atmospheric fallouts for 134Cs and 137Cs, respectively. The behavior of the decrease was not simple, due to particles raised from the surface soil in wooded areas that had not been thoroughly decontaminated or that had been accumulated due to the re-release of radioactive cesium by trees after decontaminated activity.

Non-returning factors from an interview survey of 16 residents of Katsurao village 12years after the Fukushima nuclear power plant accident.

People generally wish to return home after being evacuated due to disaster situations. Evacuation orders have now been lifted in the Fukushima region following the nuclear accident in 2011, and the Japanese government is promoting a return policy. However, many residents who wish to return home remain unable to and continue living in evacuation sites or other areas. Sixteen residents of Katsurao village were interviewed after evacuation orders were lifted in 2016 who have not yet returned. Concerns were cited regarding radiation, prolonged evacuation, health problems, buying a house in the evacuation area and schooling. The problems identified were primarily due to the rapid ageing and decline of the regional population, reflecting similar issues throughout Japan. In particular, health problems and intention to return were thought to be closely related. Over 10 y have passed since the evacuation, and many residents have experienced familial separation and divided living situations.

Should the current radiation protection paradigm and its recommendations be modified to make them more fit to protect the public in future nuclear emergencies?

The present radiation protection paradigm and its associated recommendations as developed by bodies such as the ICRP have performed very well over past decades both for those occupationally exposed to radiation and for the public in planned exposures. There is, however, growing evidence that the role played by this paradigm in the decision-making process to protect the public in nuclear emergencies in the past may have, unwittingly and unintentionally, caused more harm than good to some sections of the public. This seems to have been the case in the use of population evacuation as the principal protection response to the Chernobyl (1986) and Fukushima (2011) accidents. There is thus a need to develop improved guidelines or tools on how to apply radiation protection recommendations for the public compatible with the Principle of Justification in the event of any future major radiation emergencies. It can also be argued that the present radiation protection paradigm, with its emphasis primarily on the physical health detriments from radiation, should be more inclusive and needs to shift to a more holistic or total health approach than heretofore to include mental health effects associated with nuclear emergencies. For severe mental health effects, some of the consequences, such as suicide, can even be as or more severe than most physical detriments likely to be suffered by those affected.

Long-Term Investigation (1968–2023) of 137Cs in Apples

Due to the consequences of nuclear and/or radiological accidents in the past (Chernobyl, Fukushima, etc.), and potential future events of that kind, the constant monitoring of environmental radioactivity is important. There are different pathways of the transfer of radionuclides from environment to humans (ingestion, inhalation and external). Food ingestion greatly contributes to the total effective dose; hence, it is of great importance to investigate exposure to radionuclides through food. This paper presents the results of a long-term investigation of 137Cs activity concentration in apples in northwestern Croatia for the period 1968–2023. The highest 137Cs activity concentration in apples was measured in 1986, decreasing exponentially ever since. The Fukushima-Daiichi accident in 2011 did not cause a significant increase in 137Cs activity concentration, although the presence of the consequent fallout was detected via the appearance of 134Cs in some parts of the environment. The observed residence time for 137Cs in apples was estimated to be 4.5 and 3.9 years for the pre-Chernobyl and post-Chernobyl periods, respectively. The correlation between 137Cs in fallout and apples is very good, the correlation coefficients being 0.99, which indicates that fallout is the main source of contamination. The estimated effective dose received by adult members of the Croatian public due to intake of radiocaesium from apples over the overall observed period is 6.4 µSv. Therefore, the consumption of apples was not a critical pathway for the transfer of radiocaesium to humans.

Robotics in Disaster Management: AI-Driven Rescue, Aerial Mapping, and Emerging IoT Applications for Effective Response

This review paper explores the growing role of robotics in disaster management, focusing on the integration of artificial intelligence (AI), Internet of Things (IoT) applications, and advanced simulation environments. Highlighting lessons from events like the Fukushima nuclear disaster and Wenchuan earthquake, it examines the deployment of aerial, ground, and underwater robots in tasks such as data collection, search and rescue, and hazard monitoring. AIoT frameworks enable these robotic systems to classify objects and make decisions on-site, supporting timely and efficient responses in hazardous conditions. Virtual platforms like the DARPA Virtual Robotics Challenge, using simulators such as Gazebo and CloudSim, facilitate realistic testing of robotic capabilities in disaster scenarios, advancing operational readiness through virtual training. This review synthesizes recent progress in AI-driven disaster robotics, identifies challenges, and discusses potential improvements for future applications.

Seismic fragility analysis of nuclear containment structure with Bayesian cloud analysis framework

Nuclear containment structure plays a critical role in safe operation of nuclear power plants. Seismic safety of nuclear power plant structures has become a hot issue in nuclear engineering community following Fukushima nuclear accident. Seismic fragility analysis, as a key element in probabilistic safety assessment of nuclear power plants, is widely used in nuclear power plant structures. This study presents an innovative method for seismic fragility analysis of engineering structures. The proposed methodology combines conventional Cloud analysis method and Bayesian framework. The accuracy and efficiency of the proposed methodology were demonstrated by a single-degree-of-freedom system, heavy computational efforts but high accuracy seismic fragility analysis method was adopted for comparison. Seismic fragility analysis of a typical prestressed concrete nuclear containment structure was analyzed using the proposed method. Results indicated that method proposed in this study can improve the accuracy of seismic fragility analysis. Furthermore, with the enhance of performance level, the increasing ratios for median seismic capacity of the nuclear containment structure was decreasing.

Assessment of individual external exposure doses based on environmental radiation in areas affected by the Fukushima Daiichi Nuclear Power Station accident

Assessing individual external exposure doses from ambient dose equivalents is valuable for predictive and retrospective purposes when personal dosimeters are impractical. This study developed a model to assess individual external exposure doses from ambient dose equivalents, considering daily life patterns (location and time spent in various places), and evaluated parameters associated with individual external exposure doses, such as the reduction effects of radiation due to buildings and vehicles. The model parameters were evaluated using the robust datasets of environmental radiation measured in areas affected by the Fukushima Daiichi Nuclear Power Station (FDNPS) accident. The effective dose estimated by the model was compared to 106 daily personal dose equivalents measured using personal dosimeters in the residents’ living environments near the FDNPS. The estimated effective dose well consists with the measured personal dose equivalents, particularly when considering natural radiation in indoor dose estimation. This model is adequate for radiation protection, enabling the predictive and retrospective estimation of individual external exposure doses using environmental radiation monitoring data.

Micro-mechanical evaluations of adhesion properties for Cr-coated accident tolerant fuel cladding

The development of accident tolerant fuel (ATF) cladding has been encouraged to satisfy increased nuclear safety demands under accident conditions since Fukushima accident. Coating techniques using oxidation-resistant materials, such as Cr and Al, on existing Zr-alloy claddings have been widely applied as short-term solutions. However, coating delamination due to poor adhesion may reduce its benefits, such as low waterside corrosion/oxidation rates and fretting resistance, which necessitates accurate evaluation of coating adhesion suitability. In this study, micro-mechanical tests, micro-cantilever bending test and surface and interfacial cutting analysis system test, were conducted to qualitatively and quantitatively evaluate adhesion properties on a coated ATF cladding. In situ scanning electron microscopy-based micro-cantilever bending tests were performed using a pico-indenter equipped with a diamond flat tip. We present the results for magnetron-sputtered Cr-coated ATF claddings in detail. Micro-cantilever tests on the Cr-Zr interface revealed that deformation and failure primarily occurred in the Zr substrate, rather than at the interface. And the Cr-coated cladding showed highly adherent mechanical bonds, as evidenced by the interfacial strength and elastic modulus. SAICAS tests confirmed that peeling of the coating layer occurred only when the applied force exceeded the cutting force of the coating layer. The experimental results suggest that the Cr-coated cladding exhibited a sufficiently adherent mechanical bond to prevent delamination of the coating.

FLEXPART version 11: improved accuracy, efficiency, and flexibility

Abstract. Numerical methods and simulation codes are essential for the advancement of our understanding of complex atmospheric processes. As technology and computer hardware continue to evolve, the development of sophisticated code is vital for accurate and efficient simulations. In this paper, we present the recent advancements made in the FLEXible PARTicle dispersion model (FLEXPART), a Lagrangian particle dispersion model, which has been used in a wide range of atmospheric transport studies over the past 3 decades, extending from tracing radionuclides from the Fukushima nuclear disaster, to inverse modelling of greenhouse gases, and to the study of atmospheric moisture cycles. This version of FLEXPART includes notable improvements in accuracy and computational efficiency. (1) By leveraging the native vertical coordinates of European Centre for Medium Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) instead of interpolating to terrain-following coordinates, we achieved an improvement in trajectory accuracy, leading to a ∼8 %–10 % reduction in conservation errors for quasi-conservative quantities like potential vorticity. (2) The shape of aerosol particles is now accounted for in the gravitational settling and dry-deposition calculation, increasing the simulation accuracy for non-spherical aerosol particles such as microplastic fibres. (3) Wet deposition has been improved by the introduction of a new below-cloud scheme, by a new cloud identification scheme, and by improving the interpolation of precipitation. (4) Functionality from a separate version of FLEXPART, the FLEXPART CTM (chemical transport model), is implemented, which includes linear chemical reactions. Additionally, the incorporation of Open Multi-Processing parallelisation makes the model better suited for handling large input data. Furthermore, we introduced novel methods for the input and output of particle properties and distributions. Users now have the option to run FLEXPART with more flexible particle input data, providing greater adaptability for specific research scenarios (e.g. effective backward simulations corresponding to satellite retrievals). Finally, a new user manual (https://flexpart.img.univie.ac.at/docs/, last access: 11 September 2024) and restructuring of the source code into modules will serve as a basis for further development.

Seismic nonlinear interaction and uplifting effects between the nuclear island building and soil

Since the Fukushima nuclear accident, seismic design requirements have increased, necessitating a more refined evaluation of base uplift for weakly anchored nuclear island buildings. The elevated cooling water over 3000 t is a distinguishing feature of third-generation reactor buildings (RBs). To assess potential safety-adverse coupling effects, seismic wave propagation process through viscoelastic soils, discontinuous interfaces, and sloshing water was analysed. To facilitate nonlinear systematic simulation and parametric study, the traditional soil-structure interaction direct methods are improved and programmed on: thickness-independent viscous-spring elements for stable static-dynamic boundary transitions; seismic forces separated from the artificial boundary for flexible mesh planning; elevated water simulated with gravity stacking and hydrodynamic action. A nuclear island region encompassing water-cooled RBs and underlying soil cushion layer was investigated as a typical scenario to reveal rules using the proposed high-precision simulation platform. Non-negligible structural risks and correlations between multiple factors were quantitatively elucidated according to simulation findings. A time-lagged increase in the base overturning moment may occur because of water oscillations. As the water level increases to 85 %, the uplift height increases, adversely affecting the in-structure response spectra. Earthquake-induced intense uplift may lead to an increase in hydrodynamic pressure along the inner wall. The research results support the practical assessment of buildings with water cooling facilities located in soft composite sites with high seismic intensities.

State-of-art review of beyond design basis evaluation approach of a generic nuclear power plant in the UK

Abstract The Fukushima accident prompted rapid development in the appreciation and codification of BDB methodology into regulatory guidance and this is still continuing, especially at IAEA, which has recently and is due to publish several new standards documents directly relevant to BDB analysis. The objective of this paper is to provide a state-of-art review on how BDB evaluations are undertaken in the UK nuclear industry. Then, using the work undertaken for the Generic Design Assessment (GDA) in the UK for UK HPR1000, this paper proposed a more systematic approach for “cliff-edge” evaluation based on a generic nuclear power plant design currently being developed in the UK.

Study on dynamic post-buckling stability of fast reactor vessels subjected to vertical vibration

Abstract As a lesson learned from the Fukushima nuclear accident, the importance of accident mitigation for Beyond Design Basis Events (BDBEs) is recognized. Excessive earthquake is a typical BDBE. During such events, the Fast Reactor Vessel (FRV) is vulnerable to buckling. The safety goal of FRV under excessive earthquake is to achieve a stable post-buckling state. Our previous study on bending buckling confirmed a global response stability under horizontal vibration. As a parallel study, this paper focuses on axial compression buckling under vertical vibration. Shaking table experiments using thin-walled cylindrical models (R/t=260) are carried out. Similar methodology is applied to investigate the buckling and post-buckling behavior. It is found that axial compression buckling shares an extensive similarity with bending buckling in both buckling mode and post-buckling behavior. Similar global response stability is confirmed due to phase-inverse phenomenon. After buckling, buckling failure becomes stable and does not progress further even when an intense input amplitude is continuously applied. The vibrational load acts as a displacement-controlled load in the out-of-phase domain such that immediate collapse is prevented. Most input energy is dissipated in hysteresis loops rather than being carried by the mass. These mechanisms are independent of input waveform and can be applied to an arbitrary seismic input. In addition, a conservative limit displacement for global response stability is identified. Moreover, the effect of the input frequency ratio, the initial geometrical imperfection and the gravitational force on the post-buckling behavior are clarified.

Multiple relocation cases in disaster-related deaths after the Fukushima nuclear accident

IntroductionRelocation after a disaster often has negative health effects on vulnerable people, particularly older adults. However, little is known about the number of repeated evacuations and relocations after disasters among those experienced disaster-related deaths. This case series aimed to summarize the secondary problems and mortality risks in patients involved in relocation after disasters.MethodsWe analyzed and summarized the data on 520 disaster-related deaths in Minamisoma City, a municipality near the Fukushima Daiichi Nuclear Power Plant, focusing on the number of relocations. Herein, we describe the cases of three individuals over 80 years old, who died after eight or more relocations, which were certified as disaster-related deaths.ResultsWe discuss following three cases, which are (1) a female patient in her 90s who had a stroke and was completely disabled, (2) a female patient in her 80s whose cancer was detected later due to her failing to see her family doctor, and (3) a male patient in his 80s whose regular postoperative treatment was disrupted following cancer recurrence.DiscussionOur findings indicate that evacuation led to the worsening of chronic diseases and eventually to post-disaster death. Prolonged wide-area evacuation and repeated relocation likely interrupted the continuum of care and led to the failure of adequate care provision. To reduce the loss of human life, it is necessary to review the number of wide-area evacuations and relocations over the medium to long term after large-scale disasters, including nuclear disasters, which may occur in the future. Simultaneously, it is important to establish a medical system at the evacuation site so that disaster victims can continue to receive medical care even after evacuation or relocation.

Clinicopathological Findings of 220 Pediatric, Adolescent, and Young Adult Patients with Thyroid Cancer in Fukushima Medical University Hospital.

Background: Thyroid ultrasound examinations (TUEs), conducted as part of the Fukushima Health Management Survey (FHMS), were initiated to monitor the health status of residents after the Fukushima Daiichi Nuclear Power Plant accident owing to concerns regarding the increased incidence of thyroid cancer among children, as observed after the Chernobyl Nuclear Power Plant accident. This study reported the clinicopathological characteristics of patients with thyroid cancer diagnosed through the FHMS and treated at the Fukushima Medical University Hospital. Methods: Data regarding the clinicopathological characteristics of patients with thyroid cancer were collected and evaluated in this descriptive study. Results: Among the 263 patients diagnosed with thyroid cancer as of September 2021, 220 patients with cytologically diagnosed thyroid cancer were treated as referrals from the FHMS. The median (interquartile range) age at the time of diagnosis was 18.6 (16.2-20.3) years. The median maximum tumor diameter was 13.0 (10.4-18.0) mm. To reduce surgical invasiveness, 199 patients (90.1%) underwent unilateral lobectomy. Pathological findings were suggestive of papillary thyroid carcinomas (PTC) in 216 (98.2%) patients; among them, 205 patients had PTC of the classical type. In addition, 216 (98.2%) patients had stage I disease. Cancer cell extension in the sternothyroid muscle or perithyroidal soft tissues and microscopic lymphovascular invasion were observed in 112 (50.9%) and 123 (55.9%) patients, respectively. No differences were observed between the two age groups (<18.6 years and ≥18.6 years) in terms of the clinical or pathological characteristics of thyroid cancer: risk classification (p = 0.69) and American Thyroid Association pediatric risk level (p = 0.24). Compared with those from previous reports, few surgical complications were observed. Conclusions: Patients with thyroid cancer diagnosed with TUEs underwent safe and minimally invasive operations, and careful postoperative follow-up was provided. The pathological findings of the detected thyroid cancers indicated that the majority were classical papillary carcinomas, and approximately half of the patients had extrathyroidal or lymphovascular invasion. No differences were observed between the two age groups in terms of the clinical or pathological characteristics of thyroid cancer.

Development of a three-dimensional variational data assimilation system for 137Cs based on WRF-Chem model and applied to the Fukushima nuclear accident

Abstract Nuclear explosions and accidents release large amounts of radionuclides that harm human health and the environment. Accurate forecasting of nuclide pollutants and assessment of the ramifications of nuclear incidents are necessary for the emergency response and disaster assessment of nuclide pollution. In this study, we developed a three-dimensional variational (3Dvar) system to assimilate 137Cs based on the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) model. The distribution of 137Cs after the Fukushima nuclear accident in Japan on 15 March 2011 was analysed. The 137Cs background field at 06:00 UTC was assimilated using a 3Dvar system and surface observational data to optimise the 137Cs analysis field. Compared with the background field, the root mean square error (RMSE) and mean bias in the 137Cs analysis field decreased by 98% and 94%, respectively. The average fraction of predictions within factors of 2 (FAC2), 5 (FAC5), and 10 (FAC10) increased from 0.67, 0.72, and 0.72 to 0.90, 1.00, and 1.00, respectively. This substantial enhancement indicated the effectiveness of the 3DVar system in mitigating the uncertainty associated with the background field. Two 12 h forecast experiments were conducted to gauge the advancement in 137Cs forecasting facilitated by data assimilation (DA). The control experiment was conducted without DA, whereas the assimilation experiment was conducted with DA. Compared with the control experiment, the average FAC2, FAC5, and FAC10 in the assimilation experiment increased by 28%, 30%, and 29%, respectively. The average RMSE decreased by 33%. The mean bias and correlation coefficient increased by 41% and 36%, respectively. These results indicated that the 3Dvar method improves the forecast accuracy of 137Cs concentration.

A quick parameter configuration tool for SCHISM’s ocean transport simulation of radioactive materials

Abstract A quick tool capable of processing output files generated by the SCHISM particle tracking module has been developed to handle complex data processing procedures and conduct parameter sensitivity testing. This tool performs calculations, considering the influence of half-lives and partition coefficients, for the conversion of activity concentrations, plots particle diffusion trajectories, conducts statistical analyses of regional particle amounts, and presents activity concentration within the defined area. Using the IAEA MODARIA program as an example, this study investigates the transport of radioactive 137Cs in the ocean following the Fukushima accident on March 11, 2011. A three-year diffusion simulation was conducted by incorporating data such as ocean currents, wind fields, and tides. The calculated results demonstrate a high level of consistency with measurements, and the calculated results in the low activity concentration fall within the variability range reported in the literature.

Enhanced cesium removal from wastewater using a potassium hexacyanoferrate/gelatin aerogel composite

In the wake of the 2011 Fukushima nuclear disaster, the presence of radioactive cesium (137Cs) in nuclear wastewater has posed a critical and enduring health risk. Addressing this challenge, we have synthesized a gelatin aerogel, denoted as KCuFC/GA, immobilized with potassium cupric ferrocyanide (KCuFC) through an in situ approach, aiming for the efficient extraction of 137Cs from aqueous environments. This novel aerogel's rich porous structure enhances the accessibility of adsorption sites, thereby significantly promoting the capture of Cs+. The adsorption of cesium onto KCuFC/GA was investigated under various experimental conditions, including initial solution pH, contact time, initial cesium concentration, and the presence of coexisting ions (K+, Na+, Ca2+, Mg2+, Sr2+). The results indicated that the adsorption performance was largely independent of pH, achieving a high cesium removal rate of 93.4 % within the first 5 minutes. The cesium adsorption data were well-described by the Langmuir adsorption model, indicating a maximum adsorption capacity of 222.22 mg·L−1. Furthermore, in the presence of various competing ions, KCuFC/GA has demonstrated unparalleled selectivity for Cs+, with a partition coefficient (Kd) of 2.49 × 105 mL·g−1, and has sustained its adsorptive properties across five cycles of use. Through systematic investigation, including X-ray photoelectron spectroscopy (XPS) analysis, we have elucidated the adsorption mechanism, highlighting the pivotal role of ion exchange between lattice K+ and Cs+. The straightforward fabrication process and the aerogel's robust cesium removal capabilities from complex solutions indicate that KCuFC/GA is a promising candidate for real-world applications in the treatment of radioactive wastewater.

Prevalence, incidence, and recovery of metabolic syndrome after the fukushima nuclear power plant disaster: A 10-year longitudinal study

After the 2011 Fukushima nuclear power plant accident, the prevalence of metabolic syndrome sharply increased in municipalities near the nuclear power plant, where a massive evacuation of community residents occurred (the evacuation area). However, after the initial increase, the rate of increase in metabolic syndrome in the evacuation area was slower than that in the surrounding area (non-evacuation area). In this study, we compared the incidence of and recovery from metabolic syndrome as well as its prevalence between evacuation and non-evacuation areas during the 10 years after the accident to explore whether the slower increase in metabolic syndrome after the initial increase in the evacuation area stemmed from suppressed incidence or from fast recovery. We analyzed specific health check-up data of community residents aged 40–74 in Fukushima Prefecture from fiscal year (FY) 2012 to FY 2021 (N = 710,201). To explore the prevalence of metabolic syndrome, we examined the associations of time, residential area, and their interaction with metabolic syndrome using mixed-model repeated measures. We used data from those without metabolic syndrome in FY 2012 to investigate the incidence. We similarly examined the associations of time, residential area, and their interaction with metabolic syndrome using FY 2013 to FY 2021 data. To explore recovery, we used the data of those with metabolic syndrome in FY 2012 and repeated the same procedure. The rate of increase in the prevalence and incidence of metabolic syndrome was slower in the evacuation area than in the non-evacuation area. On the other hand, as for the recovery, the time trend of metabolic syndrome did not differ between the two areas. The slower increase in metabolic syndrome in the evacuation area was partly explained by the slower incidence in the evacuation area but not by recovery.