Daiichi Nuclear Power Plant Accident Research Articles

Comparative analysis of gender and prefecture-based attitudes toward future parenthood following the Fukushima Daiichi Nuclear Power Plant accident

This study aimed to examine both concerns about future childbirth and childcare associated with radiation exposure among men and women in different prefectures. In December 2018, a cross-sectional, online questionnaire-based survey was conducted on 620 adults in the general population. The survey included 155 men and 155 women who lived in Fukushima Prefecture at the time of the Great East Japan Earthquake (March 11, 2011), and 155 men and 155 women who lived outside of Fukushima Prefecture. Regardless of gender and prefecture, the greater the perceived anxiety about radiation effects on a partner, the greater the perceived anxiety about future childbirth. In addition, those who did not want to have children were more anxious about rearing children in the future. Compared with women in other prefectures, men in Fukushima Prefecture were more knowledgeable about radiation, thought that radiation would have fewer health effects on their children, and were more confident about future childbearing. These findings suggest that for those who are anxious about future childbirth and childcare, it is important to create an environment where necessary information can be accessed regardless of gender or residence in an area affected by a nuclear accident.

Southward key pathways of radioactive materials from the Fukushima Daiichi Nuclear Power Plant

This study examines the interannual and seasonal variations in the distribution of radioactive materials released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in the surface layer of the Kuroshio Extension (KE). Focusing on the contrasting flow conditions in 2015 (southward) and 2021 (northward) – significant oscillatory phases of the KE’s mean flow axis – the research analyzes the impact of seasonal variations on particle transport pathways. The findings reveal distinct seasonal patterns: summer releases primarily follow the eastward KE movement, while winter releases exhibit a southward trajectory. The study further quantifies the transport timescales, demonstrating that particles can reach the Luzon Strait within 10 months, subsequently diverging northward along the Kuroshio and northwestward along the Kuroshio Branch Current, potentially entering the South China Sea within 13 months. This research contributes valuable insights into the seasonal dynamics governing the dispersion and transport of Fukushima-derived radioisotopes in the surface ocean, highlighting the crucial role of the KE in influencing their trajectories.

Resilient design in nuclear energy: Critical lessons from a cross-disciplinary analysis of the Fukushima Dai-ichi nuclear accident

This paper presents a multidisciplinary analysis of the Fukushima Dai-ichi Nuclear Power Plant accident. Along with the latest observations and simulation studies, we synthesize the time-series and event progressions during the accident across multiple disciplines, including in-plant physics and engineering systems, operators' actions, emergency responses, meteorology, radionuclide release and transport, land contamination, and health impacts. We identify three key factors that exacerbated the consequences of the accident: (1) the failure of Unit 2 containment venting, (2) the insufficient integration of radiation measurements and meteorology data in the evacuation strategy, and (3) the limited risk assessment and emergency preparedness. We conclude with new research and development directions to improve the resilience of nuclear energy systems and communities, including (1) meteorology-informed proactive venting, (2) machine learning-enabled adaptive evacuation zones, and (3) comprehensive risk-informed emergency planning while leveraging the experience from responses to other disasters.

Surface and subsurface dispersal of radioactive materials from Fukushima by subpolar gyre and intermediate waters in the North Pacific

Radioactive materials were released into the ocean following the Fukushima Daiichi Nuclear Power Plant accident in 2011. Six years after the accident, the radioactive material concentration was markedly increased in the Okhotsk Intermediate Water (OIW) of the Sea of Okhotsk. This material may have been subjected to southward subsurface dispersal by the North Pacific Intermediate Water (NPIW), which originates from the OIW. The spatiotemporal limitations of available methods have made it challenging to track the dispersal paths of radioactive materials in the North Pacific Subpolar region. Here, we performed a tracer experiment using a three-dimensional numerical model to determine the path of 137Cs from Fukushima to the Sea of Okhotsk via surface subpolar gyre currents and subsurface dispersion by OIW and NPIW. The results showed that the 137Cs concentration in the Sea of Okhotsk increased via the surface current and moved progressively southward via OIW six years after the accident and eastward via OIW and NPIW nine years after the accident, indicating that 137Cs transported by NPIW entered the subtropical region. Based on experiments, this temporal change was mainly caused by ocean currents. Thus, subsurface recirculation of radioactive material via the OIW and NPIW should be considered based on the predicted path and travel time of additional materials released from the power plant.

Determination of 90Sr in highly radioactive aqueous samples via conversion to a kinetically stable 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex followed by concentration–separation–fractionation based on capillary electrophoresis–liquid scintillation

BackgroundThe Fukushima Daiichi Nuclear Power Plant accident (2011) released large amounts of radioactive substances into the environment and generated highly radioactive debris. Post-accident countermeasures are currently in the phase of fuel debris removal, which requires the analysis of radioactive contaminants in the environment and fuel. The spectra of solely β-emitting nuclides, such as 90Sr, overlap; thus, an effective method for nuclide separation is desired. Since conventional methods for high-dose sample analysis pose substantial exposure risks and generate large amounts of secondary radioactive waste, faster procedures allowing for decreased radiation emission are highly desirable. ResultsIn this study, we developed a 90Sr2+ quantitation technique based on liquid scintillation counting (LSC)–coupled capillary transient isotachophoresis (ctITP), along with two-point detection and relying on the rapid concentration, separation, and fractionation of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-complexed 90Sr2+ in a single run. The applicability of our method for the analysis of real-world samples was verified by conducting addition-recovery experiments using a seawater reference material and radioactive liquid waste obtained from the radioactive waste treatment facility at the Japan Atomic Energy Agency. The recovery determined by LSC was 95–113%, indicating successful quantitative analysis. 90Sr recovery was determined to be 90.1% from a contaminated water sample obtained from the Fukushima Daiichi Nuclear Power Plant, which was analyzed using the standard addition of 90Sr. The sensitivity (detection limit = 0.016 Bq) of the proposed method on a radioactivity basis was equal to or higher than that of the conventional method using ion exchange-LSC (0.012–0.07 Bq). Significance and noveltyOur method allows for the handling of high-dose radioactive samples at the microliter level and is substantially faster than conventional ion exchange protocols, whereas ctITP has not been used for practical applications due to inaccurate collection and lack of a suitable chemical system. The concentration–separation–fractionation protocol in ctITP is successful due to the existence of a rare inert Sr2+ complex and precise fractionation. This study establishes a pathway toward safer and more practical analysis of radionuclides.

Special Issue on Robotic, Mechatronic and Information Systems for Decommissioning

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.

Transport of radioactive materials from terrestrial to marine environments in Fukushima over the past decade

Abstract While 20 % of radionuclides released from the Fukushima Daiichi Nuclear Power Plant accident had been deposited in the terrestrial environment, rivers remain the long-term source for 137Cs, primarily through particulate transfer, from terrestrial to marine ecosystems. In this study, we estimated the suspended 137Cs flux to the ocean at 11 sites in the coastal area between October 2012 and December 2020 to be 17 TBq, based on our long-term monitoring data of concentrations of suspended 137Cs and suspended solids. The cumulative loss of suspended 137Cs from each site to the ocean ranged from 0.1 % to 1.7 % of initial deposition throughout the observation period, depending on the effect of dam lakes and normalized river discharge. The higher loss is also thought to be the large outflow of runoff during the typhoon. The current level of the suspended 137Cs concentrations was lowered to 1/10–1/100 of those immediately after the accident. The average value of the decreasing trend for each site was approximated using the equation: y = a1 e −k 1 t + a2 e −k 2t. The rate constant k 1 is higher in areas with intensive land use, such as pastures, bare land, and water surfaces, and k 2 is lower in urban areas.

Dispersant-enhanced migration of radiocesium among soil size fractions: A novel strategy for volume reduction of radioactively contaminated soil

In the aftermath of the Fukushima Daiichi Nuclear Power Plant accident, a pioneering large-scale decontamination project was initiated, aiming to enable the return of evacuees. This project, the first of its kind in human history, involved the transportation of soils collected during decontamination to interim storage facilities. Before recycling or disposal, these soils undergo processes like volume reduction. However, there's a need for innovative methods to reduce volume effectively and treat secondary wastes more efficiently. The current study explores the impact of a dispersant, sodium hexametaphosphate (SHMP), on the behavior of radiocesium (r-Cs: 137Cs) dynamics in different size fractions of radioactively contaminated soils from Fukushima. The solid-phase speciation analysis of Fukushima soils validated that at least 50% of the 137Cs or other minerals are associated with difficult-to-extract soil phases. Nonetheless, the low 137Cs/133Cs ratio in corresponding soil phases implies a slower r-Cs fixation mechanism. The wet-sieving of r-Cs contaminated soil fraction, < 2 mm, with SHMP, resulted in different soil subfractions (2000–212, 212–53, and < 53 μm). Following SHMP treatment, dispersion of > 92% of 137Cs associated with < 212 μm soil size fractions was observed. The migration of 137Cs towards smaller soil size fractions can be attributed to either SHMP-induced cation exchange or the formation of polyvalent complexes involving SHMP and soil minerals. The condensation of 137Cs in < 212 μm, as induced by SHMP, enabled the subsequent reuse of the larger soil fraction (> 212 μm), which was less contaminated. This study provides a new perspective on the effects of dispersants and contributes to a better understanding of the complex interactions among organic carbon, 137Cs, monovalent and polyvalent cations, and soil functional groups concerning the volume reduction of soils contaminated with r-Cs.

Intra-mediary expertise: Trans-science and expert understanding of the public.

What is the role of experts and their expertise in the context of trans-science, in which issues that are raised in scientific terms cannot be answered by science alone? This article examines the discourses and practices around safety of low-dose exposure to radiation in the ongoing aftermath of the Fukushima Daiichi Nuclear Power Plant accident in Japan in 2011. Following the nuclear fallout, scientific experts and STS scholars in Japan debated what forms of science communication were adequate to address the situation. Ethnographic research and textual analysis of their debates show a shift in emphasis on the role of experts from cultivating 'public understanding of science' for the sake of science and policy to an 'expert understanding of the public' for the sake of the public and its diverse everyday concerns. Two forms of expertise are emerging: 'co-expertise' and 'intra-mediary expertise'. Both are parts of a transition from a paternalistic form of expertise to one that acknowledges the need to engage the public to address issues of scientific uncertainty. However, co-expertise ultimately upholds the existing political structures that shape risk governance, while intra-mediary expertise engages those often excluded from current structures of accountability. Discussion of the potentials and limitations of emerging forms of expertise in Japan show that epistemic justice is not enough. Civic justice that acknowledges diverse publics and their needs must be upheld in the uncertain sphere between science, politics, and everyday life.

Evaluating thyroid cancer risks for nuclear workers related to the Fukushima Daiichi Nuclear Power Plant accident based on LNT theory is problematic.

Evaluating thyroid cancer risks for nuclear workers related to the Fukushima Daiichi Nuclear Power Plant accident based on LNT theory is problematic.

Categorization of disaster-related deaths in Minamisoma city after the Fukushima nuclear disaster using clustering analysis

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.

Post-Disaster Community Transition of Psychiatric Inpatients: Lessons from the Fukushima Nuclear Accident.

This study sought to explore factors related to community transition after the mandatory evacuation of psychiatric inpatients to other hospitals owing to the Fukushima Daiichi Nuclear Power Plant accident. A retrospective cohort design was adopted and 391 psychiatric patients were examined. Univariate and multivariate analyses were conducted to confirm the association between the achievement or non-achievement of discharge to community living and their backgrounds (age, gender, evacuation destination, psychiatric diagnoses, and physical complications). Multivariate analysis indicated that patients with psychiatric diagnoses of schizophrenia, schizotypal, and delusional disorders (International Statistical Classification of Diseases and Related Health Problems 10th revision, F20-29), and those with physical diagnoses of the circulatory (I00-95) and digestive (K00-93) systems showed a significant association with the non-attainment of community transition. From these results, we hypothesized that difficulties in the management of medication during and immediately after the extremely chaotic settings of evacuation could have negative effects on the community transitions. Furthermore, another possible concern was that individuals' persistent psychotic status before the accident had been carried over to the destination hospitals. Therefore, pre-disaster daily cooperation across hospitals and challenges for vulnerable psychiatric patients' future community lives are also essential.

Study on the relationship between the dispersal of wild boar (Sus scrofa) and the associated variability of Cesium-137 concentrations in its muscle Post-Fukushima Daiichi Nuclear Power Plant accident

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011, the wild boar (Sus scrofa) population within the Fukushima Evacuation Zone (FEZ) increased substantially in size and distribution. This growing population and their potential dispersal from the FEZ, where they are exposed to high levels of radionuclides, into the surrounding landscape underscores the need to better understand boar movement patterns in order to establish policies for managing shipping restrictions for boar meat and develop management strategies. In this study, we quantified the genetic population structure of boar in and around Fukushima prefecture using sequence data of the mitochondrial DNA control region and MIG-seq analysis using 348 boar samples to clarify boar dispersal patterns. Among boar samples, seven Asian haplotypes and one European haplotype were detected. The European haplotype originated from hybridization between domestic pigs and native boar in the evacuation zone after the accident and was detected in 15 samples across a broad geographic area. Our MIG-seq analysis revealed genetic structure of boar was significantly different between boar inhabiting the eastern (including FEZ. i.e., East clade) and western (i.e., West clade) regions in Fukushima prefecture. In addition, we investigated the relationships between boar dispersal and Cesium (Cs)-137 activity concentrations in boar muscle using MIG-seq genetic data in Nihonmatsu city, located in the central-northern region of Fukushima. High Cs-137 activity concentrations, exceeding 1000 Bq/kg, in boar muscle had a significantly high probability of belonging to the East clade within localized regions. Thus, our results provide evidence of the spatial scale of dispersal of individuals or offspring of boar from the FEZ. Results of this research also indicate that dispersal of individuals between areas with different Cs-137 contamination levels is one of the biggest factors contributing to variation in Cs-137 activity concentration in boar muscle within localized regions.

Prolonged impact of the Fukushima Nuclear Power Plant Accident on health and society

Prolonged impact of the Fukushima Nuclear Power Plant Accident on health and society Naomi Ito, Research Assistant at the Fukushima Medical University, tells us how the 2011 Fukushima Daiichi Nuclear Power Plant Accident impacted and continues to impact local residents. The health effects on local residents following a nuclear power plant accident are diverse, not only because of radiation exposure but also because of changes in lifestyle and social environment. It has also been indicated that various environmental changes that could emerge during the restoration process may affect residents in various ways over a long time. On March 11, 2011, the Great East Japan Earthquake struck Japan with a magnitude of 9.0. Within an hour, a tsunami hit the shore. Three reactors at the Fukushima Daiichi Nuclear Power Plant (FDNPP, operated by Tokyo Electric Power Company) lost power. The reactors could not be cooled, and core meltdowns occurred, which resulted in an explosion due to hydrogen being generated at high temperatures. As a result, radioactive materials were released and scattered northwest from the power plant.

Continuing Steady Challenges Involved in the Lifting of Evacuation Orders after the Fukushima Daiichi Nuclear Power Plant Accident.

Steady efforts for recovery and reconstruction after the accident at the Fukushima Daiichi Nuclear Power Plant have been underway for 12.5 y. The present study reports on the world's first-ever efforts for a gradual and safe return to areas contaminated with radiation fallout and reconstruction support by providing an overview of the actual situation regarding the strategy for return, especially with the transition after the lifting of the evacuation order by the Japanese government. A stage-by-stage progression of the evacuation order and lifting strategy is summarized chronologically in the following three phases: the Emergency Phase in 2011, the Reconstruction Phase from 2013 to 2020, and the Challenging Phase for Lifting All the Evacuation Zones from 2023. Through the lifting strategy of the government, the number of evacuees decreased significantly, especially during the Reconstruction Phase, from 152,113 in May 2013 to 37,826 in May 2020. It is crucial to strengthen support for reconstruction and convey an unbiased and accurate understanding of Fukushima Prefecture by developing a concrete strategy for community development and increasing the size of the exchange population.

Disaster-related deaths with alcohol-related diseases after the Fukushima Daiichi nuclear power plant accident: case series.

The health of patients with mental disorders, such as alcohol-related diseases, often deteriorates after disasters. However, the causes of death among those with alcohol-related diseases during and after radiation disasters remain unclear. To minimize and prevent alcohol-related deaths in future radiation disasters, we analyzed and summarized six cases of alcohol-related deaths in Minamisoma City, a municipality near the Fukushima Daiichi nuclear power plant. Patients were generally treated for alcohol-related diseases. In one case, the patient was forced to evacuate because of hospital closure, and his condition worsened as he was repeatedly admitted and discharged from the hospital. In another case, the patient's depression worsened after he returned home because of increased medication and drinking for insomnia and loss of appetite. The overall findings revealed that, in many cases, evacuation caused diseases to deteriorate in the chronic phase, which eventually resulted in death sometime after the disaster. To mitigate loss of life, alcohol-related diseases must be addressed during the chronic phases of future large-scale disasters, including nuclear disasters.

Health and productivity management initiatives to promote worker health and improve the workplace environment at the Fukushima Daiichi nuclear power plant.

Since the Fukushima Daiichi nuclear power plant (FDNPP) accident in 2011, measures have been taken to address occupational health risks, such as heat illness and infectious diseases, and ensure fitness for duty with the Tokyo Electric Power Company and its contractors. However, with the decommissioning operations set to span several decades and an aging workforce, there arose a need for proactive occupational health strategies that not only addressed these risks but also promoted employee health and created a comfortable work environment. With the Japanese government's promotion of health and productivity management (HPM) for corporations, an HPM-based initiative was launched at the FDNPP in 2019. We designed an HPM questionnaire tailored to the unique conditions at the FDNPP for contractors in 2019. Subsequently, we adjusted the questionnaire annually in light of evolving societal contexts and insights derived from contractors' feedback. This initiative also involved the annual recognition of outstanding contractors. These efforts have led to a steady increase in the number of contractors participating in the HPM survey, with respondents' scores continually improving. We also emphasized dissemination of HPM practices from contractors to their subcontractors due to the complex subcontracting structure at FDNPP, and our results showed that more contractors have been extending these efforts to their subcontractors. Our findings suggest that individual contractors are steadily enhancing their HPM efforts. We are committed to continually offering support to advance HPM throughout the FDNPP.

Impact of Changes in Lifestyle and Psychological Factors on the Incidence of Metabolic Syndrome after the Great East Japan Earthquake: Follow-up of the Fukushima Health Management Survey.

The Fukushima Daiichi Nuclear Power Plant accident caused lifestyle changes and psychological distress in residents living near the plant. This study clarified the associations between changes in residents' lifestyles and psychological factors with the onset of metabolic syndrome (METs) after the accident. This longitudinal study included 10,373 residents who underwent the Comprehensive Health Check and Mental Health and Lifestyle Survey in Fiscal Year (FY) 2013. Follow-up surveys were conducted between FY 2014 and FY 2017. Lifestyle changes and the METs incidence were evaluated using a logistic regression model. METs developed in 14.0% of subjects. In addition to metabolic factors, such as the body mass index, hypertension, dyslipidemia, and diabetes mellitus, there were differences in physical activity, fast walking, eating fast, eating habits before bedtime, skipping breakfast, current smoking, and alcohol intake between subjects with and without new-onset METs. Eating fast, current smoking, and drinking alcohol were positively associated with new-onset METs, whereas starting physical activity and fast walking were inversely associated with new-onset METs. Disaster-related lifestyle changes, such as eating fast, starting to smoke, and continued alcohol intake, were risk factors for new-onset METs after the Fukushima Daiichi Nuclear Power Plant accident.

2023 Fukushima Medical University International Symposium on the Fukushima Health Management Survey, "Thinking Together about Health, Life, and our Future in Fukushima".

In response to the release of radioactive materials and evacuation of residents after the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant accident, caused by the Great East Japan Earthquake, the Fukushima Health Management Survey (FHMS) began in June of 2011. This survey aims to provide long-term follow-up of the physical and mental health of Fukushima residents and to maintain and improve their health for the future. Every year since 2019, Fukushima Medical University (FMU) has organized the FHMS International Symposium to share survey results with people in Fukushima Prefecture and beyond. The fifth annual symposium convened at FMU's Ekimae Campus on Saturday, 4 March 2023, with the theme, "Thinking Together about Health, Life and our Future in Fukushima."

Effectiveness of an Intervention Program to Enhance the Self-Confidence of Kindergarten Teachers Dealing with Radiation-Related Health Concerns from Parents of Young Children: A Quasi-Experimental Study.

This study examined the effectiveness of an intervention program to enhance the self-confidence of kindergarten teachers who address radiation-related health concerns among parents following the Fukushima Daiichi Nuclear Power Plant accident in March 2011, wherein radiation anxiety among mothers with young children was high. Kindergarten teachers are expected to address the concerns of these parents. Participants from 2 private kindergartens in Fukushima City were assigned to either the intervention group (n = 10), which received an intervention program comprising lectures, group discussions, and presentations, or the control group (n = 16), which received only written materials used in the intervention program. Changes in the measured scores post-intervention were calculated, and the mean values were compared between both groups using the Student's t-test. The primary outcome was self-confidence, and the difference-in-differences approach was used to assess the effectiveness of the intervention program. The study found a more significant difference between pre- and post-intervention self-confidence in the intervention group compared to the control group (P < 0.01). The intervention program effectively enhanced the self-confidence of kindergarten teachers in dealing with radiation-related health concerns of parents with young children.