Fukushima Nuclear Power Plant Research Articles

Subtle effects of radiation on embryo development of the 3-spined stickleback

The Chernobyl and Fukushima nuclear power plant (NPP) accidents that occurred in 1986 and 2011 respectively have led to many years of chronic radiation exposure of wildlife. However, controversies remain on the dose threshold above which an impact on animal health occurs. Fish have been highly exposed immediately after both accidents in freshwater systems around Chernobyl and in freshwater and marine systems around Fukushima. The dose levels decreased during the years after the accidents, however, little is known about the effects of environmental low doses of radiation on fish health. The present laboratory study assesses the effects of an environmentally relevant dose range of radiation (0.1, 1 and 10 mGy/day) on early life stages of the 3-spined stickleback, Gasterosteus aculeatus.The cardiac physiology and developmental features (head width, diameter, area) of high exposed embryos (10 mGy/day) showed no significant change when compared to controls. Embryos exposed to the medium and high dose were slower to hatch than the controls (between 166 and 195 h post-fertilization). After 10 days of exposure (at 240 h post-fertilization), larvae exposed to the high dose displayed comparable growth to controls. High-throughput sequence analysis of transcriptional changes at this time point revealed no significant changes in gene regulation compared to controls regardless of exposure conditions. Our results suggest that exposure of fish embryos to environmental radiation elicits subtle delays in hatching times, but does not impair the overall growth and physiology, nor the gene expression patterns in the recently hatched larvae.

Application of multiple γ-ray detection to long-lived radioactive nuclide determination in environmental samples

ABSTRACT Gamma-gamma coincidence measurement utilized in γ-ray spectroscopy experiments is well known to be effective for the improvement of signal-to-noise ratio in a γ-ray spectrum. We study its applicability to the determination of long-lived radioactive nuclides in environmental samples. The γ-ray simulation code Geant 4.10.2 was used. A conventional and effective detector system comprising five Ge detectors was assumed. We took up 38 nuclides which need to be determined for the evaluation of fission product leakage at the nuclear accident in the Fukushima nuclear power plants in Japan. Among them 12 nuclides emit γ-rays and five nuclides of 60Co, 94Nb, 134Cs, 152Eu, and 154Eu can be the objectives of the multiple γ-ray detection methods. The simulation results indicate that the signal-to-noise ratio can be improved by a factor between 9.84 and 283, and the detection limit by a factor between 2.71 and 8.53 relative to the singles measurement, implying that the method can be well applied to the determination of the long-lived radioactive nuclides and will provide a quick and non-destructive analysis method.

Measurements of atmospheric Δ14CO2 along the R/V Xuelong cruise track from Zhongshan Station (Antarctica) to Shanghai

During January–March 2011, 29 atmospheric Δ14CO2 samples were measured along the R/V Xuelong cruise track from Zhongshan Station (69.37°S, 76.38°E; Antarctica) to Shanghai. The extent of fossil fuel contamination in the samples was evaluated by comparison with contemporary hemispheric-scale averages of Δ14CO2, together with transport analysis and consideration of the δ13CO2 levels in the samples. Generally, the Δ14CO2 levels along the route south to 40.67°S were lower than the hemispheric-scale average. Circumpolar deep water (CDW) upwelling, stratosphere–troposphere transport (STT), and regional transport associated with the Fukushima nuclear power plant (NPP) accident in Japan on 12 March 2011 were found to have influenced Δ14CO2 levels at the sampling sites. In comparison with the atmospheric Δ14CO2 level (45.7 ± 3.5‰ (1σ)) measured in the coastal region of East Antarctica, CDW upwelling caused reduction of ∼10‰ in Δ14CO2 in two cross sections: 62.0°–64.0°S along 74.0°E and 51.7°–54.0°S along 80.5°–84.0°E. Conversely, STT-enhanced Δ14CO2 was ∼7‰ (∼3‰) at Zhongshan (around 45.0°S). The linkage was supported by a certain Model-3/CMAQ simulation that indicated dispersion of radionuclides from the Fukushima NPP accident over the East Asian region, which explained the individual high Δ14CO2 (52‰) level on 29 March 2011 in Shanghai.

Cytological examination of the thyroid in children and adolescents after the Fukushima Nuclear Power Plant accident: the Fukushima Health Management Survey.

The Fukushima Daiichi Nuclear Power Plant accident occurred on March 11 2011, following the Great East Japan Earthquake and tsunami. Radioactive materials, including I-131, were released into the environment after the accident. Shortly after, the prefectural government initiated the Fukushima Health Management Survey for monitoring the long-term health conditions of the residents of Fukushima Prefecture. In the survey, thyroid ultrasonography was scheduled for all people aged 18 years or younger who were living in Fukushima Prefecture at the time of disaster. The total number of examinees was approximately 370,000 in the Preliminary Baseline Survey (PBLS), and 380,000 in the first Full-scale Survey (FSS). First, thyroid ultrasonography was performed as the Primary Examination. When a thyroid nodule that meets the fine needle aspiration cytology (FNAC) guideline is detected, thyroid FNAC is performed. By the end of June 2017, the cytological specimens of 187 examinees had been interpreted as Malignant or Suspicious for Malignancy (SFM). In this article, the cytological results of whole categories are presented using the criteria of The Bethesda System for Reporting Thyroid Cytopathology. The total numbers of examinees with SFM or Malignant in PBLS and at the first FSS were 106 (62.0%) and 71 (38.0%), respectively. The data of the cytological results of SFM and Malignant were already reported. However, this is the first report of cytological data from categories other than SFM and Malignant. The results of the current study will contribute to future research into the thyroid conditions of children and adolescents.

Area Dose Response of Prevalent Childhood Thyroid Cancers after the Fukushima Nuclear Power Plant Accident

Background and Methods: After the Fukushima Nuclear Power Plant accident, thyroid ultrasound screening was carried out on all residents of ages≤18 years at the accident. In order to find the cause for thyroid cancer prevalence, area dose dependence of childhood thyroid cancer proportion in the first and second round screening (E-I, E-II), and in 6 years as a whole (E-I+II) was analyzed for external dose estimated by Fukushima Health Management Survey and effective dose estimated by UNSCEAR. The results were analyzed by the regression analysis of Microsoft Excel. Results: Thyroid cancer incidence within 4-6 years and prevalence in 6 years after the accident had tendency to increase with doses. In OM-model according to Ohira’s map, thyroid cancer prevalence in E-I+II after 6 years showed linear prevalence-effective dose response with positive coefficient 5.6 (CI=3.4-7.9) (cancer cases / 100,000 / mSv) in the 1.6–5 mSv range. In F-model according to official regional division, thyroid cancer proportion in E-II and E-I+II showed linear response to UNSCEAR effective dose with R2>0.86 and p<0.075. This correlation was higher than the correlation between external dose and effective dose with R2=0.71. Conclusion: The observed linear area dose relation in 6 years after exposure suggests highly probable association between childhood thyroid cancer in Fukushima and radiation exposure. UNSCEAR effective dose was found to give the best fit to linear regression line for E-II and E-I+II, irrespective of models. Linear dose response for reasonable area division can be a direct evidence for radiation related thyroid cancer because linear dose response cannot be observed in mass-screening for sporadic thyroid cancers.

Some Aspects of Practical Application of Regulatory Requirements Related to Operating and Seismic Load Combinations for Thermomechanical Equipment and Piping

New state-of-the-art regulatory document has been developed and implemented in Ukraine to present requirements for seismic hazard assessment of nuclear power plant (NPP) sites and seismic resistance of nuclear power units taking into account lessons learnt from the accident at Fukushima-1 NPP. One of the new important regulatory requirements in this document is the extension of the list of mandatory load combinations, which should be considered in assessing seismic resistance of unit components.
 Advantages and disadvantages of the algorithm proposed by the operating organization to determine the necessity to consider some load combinations in assessing the seismic resistance of pipelines and thermomechanical equipment based on previously performed seismic strength calculations have been analyzed in the paper. The pipelines as well as the thermomechanical equipment of Zaporizhzhya NPP Unit 3, for which seismic strength evaluation was calculated, have been considered.
 The results of expert seismic calculations of YP13S02 valve of ZNPP-1 and ZNPP-3 have been provided. The paper presents the comparative analysis of the floor response spectra for the lower, middle and high elevations of ZNPP-3 containment with the corresponding floor response spectra of other Ukrainian NPPs and conclusions.
 The possibility for disseminating results obtained by the operating organization for ZNPP-3 to other units of the Ukrainian NPPs has been analyzed.

Longitudinal associations of radiation risk perceptions and mental health among non-evacuee residents of Fukushima prefecture seven years after the nuclear power plant disaster.

We aimed to explore the effects of prolonged radiation risk perceptions on mental health after the Fukushima nuclear power plant accident occurred in 2011. We investigated the longitudinal associations of radiation risk perceptions five years after the accident with psychological distress and posttraumatic stress symptoms two years later among non-evacuee community residents of Fukushima prefecture. A two-wave questionnaire survey was administered for 4,900 randomly sampled residents in 49 municipalities of Fukushima prefecture excluding the evacuation area designated by the Japanese government. Radiation risk perceptions were assessed with a seven-item scale. Psychological distress and posttraumatic stress symptoms were measured by the K6 and the six-item abbreviated version of the Posttraumatic Stress Disorder Checklist-Specific version, respectively. We investigated the associations of radiation risk perceptions in the first survey conducted in 2016 with psychological distress and posttraumatic stress symptoms in the follow-up survey conducted in 2017–18, controlling for the baseline level of distress or symptoms using multivariate logistic regression analyses. Valid responses were obtained from 1,148 residents (23.4%). Higher risk perceptions of radiation exposure in the first survey predicted later posttraumatic stress symptoms but not psychological distress after controlling for baseline symptoms or distress. High risk perceptions of radiation exposure after nuclear power plant accidents can lead to posttraumatic stress symptoms.

DOSE ESTIMATION FOR CONTAMINATED SOIL STORAGE IN LIVING ENVIRONMENT.

After the Fukushima Nuclear Power Plant accident, most of radiocesium-contaminated soil generated from decontamination activities outside Fukushima prefecture has been stored at decontamination sites such as schools, parks and residential lands (storage at sites) according to the Decontamination Guidelines. However, additional exposure due to the present storage has not been evaluated. Moreover, entering storage sites, which is not restricted for storage at sites, was not considered in safety assessment conducted in the guidelines. To continue the storage and confirm the effectiveness, understanding of present possible exposures is important. In this study, we evaluated exposure doses for residents and users of storage sites based on the present situation. As a result, annual doses due to residence were 10-2 to 10-3mSvy-1 and doses due to annual entries were of the order of 10-3mSvy-1. Hence, we confirmed that the exposure due to present storage outside Fukushima is significantly <1mSvy-1.

NEED OF A NEXT GENERATION SEVERE ACCIDENT CODE

Two international severe accident benchmark problems have been performed recently by using several existing parametric severe accident codes: The Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Plant (BSAF) and the Benchmark of the In-Vessel Melt Retention (IVMR) Analysis of a VVER-1000 Nuclear Power Plant (NPP). The BSAF project was organized by the Nuclear Power Engineering Center (NUPEC) of the Institute of Applied Energy (IAE) in Japan for the three Boiling Water Reactors (BWRs) of the Fukushima NPP. The IVMR Project was organized by the Joint Research Center (JRC) of the European Commission (EC) in Holland (Europe) for a Pressurized Water Reactor (PWR). The obtained results of both projects have shown very large discrepancies between the used severe accident codes for both reactor types BWR and PWR. Consequently, the results for a real plant analysis by these integral codes, may not be correct after the beginning of core melt. Discrepancies of results of ex-vessel phenomena in the containment between the codes are in general larger. Therefore, there is a strong need for a reliable new generation mechanistic severe accident code which can simulate severe accident scenarios from an initiating event till containment failure with better accuracy not only for existing light water reactors but also for new generation IV reactor types. SAMPSON mechanistic ex-vessel modules coupled with SCDAPSIM and a new thermal-hydraulic module ASYST-ISA with particularly newly developed options for the reactor coolant system (RCS) and material properties applicable to new reactor deigns, is proposed as a best etimate new generation severe accident code for several reasons which are described in this paper.Keywords: Severe accident, SAMPSON, SCDAPSIM, ASYST-ISA, Steam explosion, Hydrogen detonation

An application of PCR-RFLP species identification assay for environmental DNA detection.

Recent advancement of environmental DNA (eDNA) methods for surveying species in aquatic ecosystems has been used for various organisms and contributed to monitoring and conservation of species and environments. Amphibians are one of the promising taxa which could be monitored efficiently by applying quantitative PCR (qPCR) or next generation sequencing to eDNA. However, the cost of eDNA detection using these approaches can be quite high and requires instruments that are not usually installed in ecology laboratories. For aiding researchers in starting eDNA studies of amphibians, especially those not specialized in molecular biology, we developed a cost efficient protocol using PCR-RFLP method. We attempted to detect eDNA of three Japanese Rana species (Rana japonica, Rana ornativentris, and Rana tagoi tagoi) in various spatial scales including an area close to the Fukushima nuclear power plant where the environment is recovering after the disaster in 2011. Our PCR-RFLP protocol was successful in detecting Rana species in static water in both laboratory and field; however, it could not detect Rana species in non-static water samples from the field. Even a more sensitive detection method (standard qPCR) was unable to detect frogs in all non-static water samples. We speculate that our new protocol is effective for frogs living in lentic habitats, but not for lotic habitats which may still require the gold standard of field observation for detection approach.

Factors relating to anxiety among medical teams dispatched to the Fukushima nuclear power plant disaster

At the time of the accident at Tokyo Electric Power Company's Fukushima Dai-ichi Nuclear Power Plant, medical teams and radiation experts were solicited from all over Japan by the Japanese government to go to Fukushima Prefecture. While several reports on the incident and its management have been published, there have been no reports on the causes of anxiety felt by the volunteers or problems foreseen by organizations that declined to send volunteers. To identify the factors contributing to the anxiety levels of the dispatched personnel and to understand the difficulties faced while dispatching volunteers to the affected area, two different questionnaires were sent out to the recruited volunteers and recruiting organizations. Among the professionals sent to Fukushima Prefecture, we found that previous knowledge of radiation emergency or disaster medicine was inversely proportional to their anxiety levels (p < 0.001). Factors giving rise to apprehension depended on the professional's occupation (p = 0.042). Possessing and sharing radiological information among team members helped alleviate anxiety once the professionals entered the hazardous area. It is thus desirable to establish systematic plans with guidelines for proactive education and training for each kind of professional and policies regarding the dispatch of volunteered professionals to alleviate anxiety levels prior to dispatch.

Spatial modelling of Cs-137 and Sr-90 fallout after the Fukushima Nuclear Power Plant accident

Determination of radionuclides transport characteristics is among the most significant research topics, which require extensive multidisciplinary works. The spatial modeling methods are suggested to determine the effects of radioactive fallout. The spatial analysis has a history of approximately 250 years based on micro-scales, but today it has extended to macroscopic systems. After Fukushima accident, radioactive fallout in water and bottom sediment samples are collected from the deepest tectonic freshwater lake in Turkey, Hazar Lake, and Point Cumulative SemiVariogram and Triple Diagram models are employed for depiction their features.

Sewing Wedding Dresses for Interspecies Marriage: Tomoko Kōnoike’s Reimagining of Animal Bridegroom Tales after the Tōhoku Earthquake

Japanese artist Tomoko Kōnoike’s (1960- ) work underwent a radical transformation after the earthquake and tsunami in northeastern Japan (Tōhoku) on March 11, 2011, which also caused the Fukushima nuclear power plant accident, making it the most devastating case of a combined natural and man-made disaster in Japan. For those living in Japan, this triple disaster has posed a fundamental question regarding human beings’ relationship with nature, urging them to rethink radically the ways in which social, cultural, and economic activities have been organized and conducted at the expense of the natural environment and its nonhuman inhabitants. One of the most distinctive changes in Kōnoike’s work is to do with the representation of animals and human–animal hybrids, motifs that have been central to her work from the earliest stage. The most prominent is the motif of the wolf-girl hybrid that she has reworked in various media and that has been interpreted as a symbolic figure that transcends binary oppositions. The cultural anthropologist Shin’ichi Nakazawa, for example, claims that the wolf in Kōnoike’s early work Knifer Life (fig. 1; 2000–01) functions as the “hole” in mythological thinking that “howl[s] from the realm of the dead in the direction of our world” and “calls over the distance with a power that comes from outside the human realm” (Nakazawa 109). As I have discussed elsewhere, the wolf-girl hybrid also evokes the story of Little Red Riding Hood, suggesting the merging of the two characters conceived as antagonistic in traditional fairy tales (Murai 2015).

Calculation of Evaporation From Fukushima Nuclear Power Plant Spent Fuel Pools

Prediction of evaporation rates from spent fuel pools of nuclear power plants in normal and postaccident conditions is of great importance for the design of safety systems. A severe accident in 2011 Fukushima nuclear power plant caused failure of cooling systems of its spent fuel pools. The postaccident evaporation from the spent fuel pools of Fukushima units 2 and 4 is compared to a model based on analogy between heat and mass transfer which has been validated with a wide range of data from many water pools including a spent fuel pool. Calculations are done with two published estimates of fuel decay heat, one 25% lower than the other. The model predictions are close to the evaporation using the lower estimate of decay heat. Other relevant test data are also analyzed and found in good agreement with the model.

DNA damage induction during localized chronic exposure to an insoluble radioactive microparticle

Insoluble radioactive microparticles emitted by the incident at the Fukushima nuclear power plant have drawn keen interests from the viewpoint of radiation protection. Cs-bearing particles have been assumed to adhere in the long term to trachea after aspirated into respiratory system, leading to heterogeneous dose distribution within healthy tissue around the particles. However, the biological effects posed by an insoluble radioactive particle remain unclear. Here, we show cumulative DNA damage in normal human lung cells proximal and distal to the particle (β-ray and γ-ray-dominant areas, respectively) under localized chronic exposure in comparison with uniform exposure. We put a Cs-bearing particle into a microcapillary tip and placed it onto a glass-base dish containing fibroblast or epithelial cells cultured in vitro. A Monte Carlo simulation with PHITS code provides the radial distribution of absorbed dose-rate around the particle, and subsequently we observed a significant change in nuclear γ-H2AX foci after 24 h or 48 h exposure to the particle. The nuclear foci in the cells distal to the particle increased even under low-dose-rate exposure compared with uniform exposure to 137Cs γ-rays, which was suppressed by a treatment with a scavenger of reactive oxygen species. In contrast, such focus formation was less manifested in the exposed cells proximal to the particle compared with uniform exposure. These data suggest that the localized exposure to a Cs-bearing particle leads to not only disadvantage to distal cells but also advantage to proximal cells. This study is the first to provide quantitative evaluation for the spatial distribution of DNA double strand breaks after the heterogeneous chronic exposure to a Cs-bearing particle in comparison with uniform Cs exposure.

Radioactivity data analysis of 137Cs in marine sediments near severely damaged Chernobyl and Fukushima nuclear power plants

Abstract Using several accessible published data sets, we analyzed the temporal change of 137Cs radioactivity (per unit mass of sample) in marine sediments and investigated the effect of the water content of sediment on the 137Cs radioactivity, to understand the behavior of 137Cs present in marine environments. The 137Cs radioactivity in sediments decreased more slowly in the Baltic Sea (near the Chernobyl nuclear power plant) than in the ocean near the Fukushima Daiichi nuclear power plant (FDNPP). The 137Cs radioactivity in the sediment near the FDNPP tended to increase as the water content increased, and the water content decreased at certain sampling sites near the FDNPP for several years. Additionally, the decrease in the water content contributed to 51.2% of the average 137Cs radioactivity decrease rate for the same period. Thus, it may be necessary to monitor both the 137Cs radioactivity and the water content for marine sediments to track the 137Cs that was discharged from the sites of Chernobyl and Fukushima nuclear power plants where severe accidents occurred.

Internal exposure risk due to radiocesium and the consuming behaviour of local foodstuffs among pregnant women in Minamisoma City near the Fukushima nuclear power plant: a retrospective observational study

ObjectivesThis study aimed to evaluate the internal cesium (Cs) level among pregnant women in Minamisoma City (the area straddling the evacuation zones) over a 5-year period after Japan’s 2011 Fukushima...

Anthropogenic traces in bottom sediments of Chukchi Sea

This paper presents results of a high-resolution study of bottom sediments from the central and northern parts of the Chukchi Sea. Magnetic susceptibility and grain size distribution within the sediments indicate calm depositional conditions of mainly lithogenic material. The biogenic material is dominated by SiO2bio (up to 15%) and to a much lesser extent by Corg (up to 2%) and Ntot (up to 0.25%). The distinct increase of organic material within the uppermost parts of the cores causes a decrease of magnetic susceptibilty and reflects an increase of biological productivity of the Chukchi Sea, triggered by global warming of the climate.Fallout activity peaks of 137Cs, measured in the core taken in the central area of the Chukchi Sea, are assumed to represent the fall-out of the accidents of the Chernobyl nuclear power plant in 1986 and of the Fukushima nuclear power plant in 2011. The two fallout peaks of 137Cs in the sediments of the northern area correspond to the maximum of the atmospheric tests of nuclear weapons in 1963 and to the accident at Chernobyl nuclear power plant in 1986. Rates of recent sedimentation, dated by 137Cs fall-out peaks and by additional measurements of 210Pb are estimated to be 2–2.7 mm a−1 in the central part and 0.9–1.3 mm a−1 in the northern part of the Chukchi Sea.

A Numerical Investigation on Gaseous Stratification Break-Up Phenomenon of Air Fountain Experiment by Code_Saturne

Since the Fukushima nuclear power plant accident, the nuclear safety experts devote a number of efforts to explore the potential risk of hydrogen detonation and measures for the mitigation of hydrogen safety during a severe accident in the nuclear power plant. A series of experiments have been performed to investigate the behavior of hydrogen distribution during a severe accident in the nuclear power plant. This study aims to investigate the gaseous stratification break-up phenomenon in the presence of a vertical gas fountain on the top of containment using Code_Saturne. The computed results not only analyze the flow field of the gas and the density distribution in the containment, but also measure the adequacy of Code_Saturne concerning the multi-component gas flow calculation.

Social Support During Emergency Work and Subsequent Serious Psychological Distress: A Cross-Sectional Study Among Emergency Workers who Responded to the Fukushima Daiichi Nuclear Power Plant Accident.

To examine the association between social support for emergency workers and levels of subsequent psychological distress, focusing on workers who responded to the Fukushima Nuclear Power Plant accident. Male emergency workers (N = 1405) completed self-administered questionnaires, measuring social support during emergency work, subsequent serious psychological stress, occupational and demographic characteristics, and some confounders. Multiple logistic regression analyses were performed. Supervisor support was significantly associated with lower psychological distress, particularly for workers present at the site for over 31 days. For workers present for 10 days or less, coworker support was marginally significant. Social support is an important resource for reducing the risk of subsequent serious psychological distress among emergency workers. The associations of social support with psychological distress can differ depending on work duration and the providers of the support.