Electric Power Company Fukushima Daiichi Research Articles

No evidence of thyroid consequences in seven nuclear workers at the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant accident: 10-year follow-up results of thyroid status.

Seven emergency nuclear workers, who had internal exposure due to an intake of radionuclides, mainly I-131, during the emergency response operation in March 2011, after the accident at the Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Plant (FDNPP), visited the National Institute of Radiological Sciences (NIRS) outpatient clinic for medical evaluation. They were followed up after their first visit for 10 years. The estimated committed equivalent doses to the thyroid were distributed between 3.2 to 1.2 × 10Sv. This group thought to be received highest exposure at the accident. None of the workers had symptoms related to abnormal thyroid function. The examinations, including thyroid function tests and ultrasound, detected no abnormalities related to radiation exposure. However, there is a need for continuous monitoring of their thyroid status for longer periods in the future.

Analysis of Groundwater Flows under the Fukushima Daiichi Nuclear Power Plant Reactors Using Contaminated Water from 42 Subdrain Pits

We analyzed groundwater collected from 42 subdrain pits (wells) located around the reactor buildings of plant units #1 to #4 of the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant (F1-NPP) to understand the groundwater dynamics and water flows around F1-NPP. Since water samples collected from this small area exhibit very similar water quality, there are difficulties in understanding the flow dynamics of the groundwater using conventional chemical analyses. In this study, we clarified the groundwater flows using an altitude-modified principal component analysis (PCA) with a total of 798 data items (19 factors × 42 pits) in the chemical analyses. The PCA results showed that six specific pits deviated from the common values and that the others contained contributions from both the natural elements and radioactive nuclides. The groundwater flows under units #1–#4 into two flow lines originating from two main water sources were classified, and these lines merged around the bayside of unit #2 due to the lower groundwater head. This method proved suitable for elucidating the groundwater dynamics and water flows in this small area by the proposed altitude-modified PCA.

Radiocesium-bearing microparticles cause a large variation in 137Cs activity concentration in the aquatic insect Stenopsyche marmorata (Tricoptera: Stenopsychidae) in the Ota River, Fukushima, Japan.

After the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant accident in Japan, freshwater ecosystems near the site remained contaminated by radiocesium (RCs). Clarifying RCs concentrations in aquatic insects is crucial because fishes consume these insects that transfer RCs into freshwater ecosystems. As aquatic insects are usually measured for radioactivity in bulk samples of several tens of insects, variation in RCs concentration among individuals is not captured. In this study, we investigated the variability in 137Cs activity concentration in individual aquatic insects in detritivorous caddisfly (Stenopsyche marmorata) and carnivorous dobsonfly (Protohermes grandis) larvae from the Ota River, Fukushima. Caddisfly larvae showed sporadically higher radioactivity in 4 of the 46 caddisfly larvae, whereas no such outliers were observed in 45 dobsonfly larvae. Autoradiography and scanning electron microscopy analyses confirmed that these caddisfly larvae samples contained radiocesium-bearing microparticles (CsMPs), which are insoluble Cs-bearing silicate glass particles. CsMPs were also found in potential food sources of caddisfly larvae, such as periphyton and drifting particulate organic matter, indicating that larvae may ingest CsMPs along with food particles of similar size. Although CsMP distribution and uptake by organisms in freshwater ecosystems is relatively unknown, our study demonstrates that CsMPs can be taken up by aquatic insects.

Reorganization of advanced radiation emergency medicine systems in Japan after the Fukushima Nuclear Power Plant accident

The Japanese organizational system for radiation emergency medicine was reorganized and strengthened after the Great East Japan Earthquake and the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant accident on 11 March 2011. In prefectures with or near nuclear facilities (within a 30 km radius), “nuclear emergency core hospitals”, which have sufficient functions, staff, and facilities, were newly designated after the accident by the prefectural governments. “Nuclear emergency medical cooperative institutions” were also registered in the prefectures. At the national level, these hospitals are assisted by two types of national-level centers, namely “advanced radiation emergency medical support centers” and “nuclear emergency medical support centers”. Additionally, to coordinate these support centers, the NIRS-QST was designated as the “core advanced radiation emergency medical support center” by the Nuclear Regulation Authority in April 2019. The new NIRS-QST Core Center is striving to strengthen our educational and training courses, to improve the contents of educational and training materials, to develop common guidelines/manuals for biological and physical dose measurement and estimation, and cultivate human resources in the field of radiation emergency medicine in Japan.

Trend in Cancer Incidence and Mortality in Fukushima From 2008 Through 2015.

BackgroundCancer incidence in Fukushima Prefecture, especially thyroid cancer, has been a public concern, since the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plants accident following the Great East Japan Earthquake on March 11, 2011; however, cancer incidence for Fukushima residents before and after the accident based on a population-based cancer registry (PBCR) has not been known worldwide.MethodsWe obtained the corrected-incidence data for invasive cancers newly diagnosed from 2008 through 2015 from the Fukushima Cancer Registry. We checked data quality indicators for PBCRs to confirm comparability. We calculated age-standardized annual incidence and mortality of cancer for all-site, thyroid, and leukemia by calendar year and sex, as we did for Tochigi Prefecture and all of Japan as references for comparison. We applied joinpoint trend analysis to test an apparent trend in incidence and mortality.ResultsThe corrected incidence data from the Fukushima Cancer Registry had sufficient quality comparable to other PBCRs. For the age-standardized annual incidence by sex and cancer type in Fukushima and Tochigi, we did not detect any joinpoint in trend with statistical significance. Cancer incidence gently increased from 2008 through 2015 nationwide. Incidence and mortality of cancer for Fukushima before the accident was very close to that for Tochigi.ConclusionsWe interpreted the incidence statistics of cancer for Fukushima residents from 2008 through 2015. Our results will provide fundamental statistics for subsequent researchers to assess the relationship between the disaster and cancer incidence among Fukushima residents in the long term.

Environmental and Economic Recovery Post-Fukushima Daiichi Nuclear Disaster: Isotope Characteristics and the Recovery of a Crippled Fisheries Industry

The 2011 Tohoku earthquake and subsequent tsunami had a catastrophic effect on the aquaculture industry of the North-East Japanese coast. Ten years on, this paper examines the environmental and economic impacts of this disaster within the context of the Fukushima nuclear meltdown. Following structural damage to the Tokyo Electric Power Company Fukushima Daiichi plant, fisheries and aquaculture industries were suspended, given the initially high radio caesium output into the coastal water column. Daily radiation testing began on all fisheries products, with tentative industry resuming within the Fukushima prefecture once radiation had dropped below the 50 Bq/kg, as stipulated by the Fukushima Fisheries Association. Routine testing continues biweekly (at least until March 2021). As of May 2016, 73 fish species were passed for consumption. The rapid functional recovery of the fisheries industry has been mediated by two factors, the sedimentation characteristics of the caesium isotopes and deposition of isotopes out to sea in an Easterly direction, given the interaction of oceanic currents. While the aquaculture industry may have recovered and food reduced to safe radiation levels, the disaster continues to exert a domestic and international economic impact given the stigma of Fukushima radiation.

Effects of 137Cs contamination after the TEPCO Fukushima Dai-ichi Nuclear Power Station accident on food and habitat of wild boar in Fukushima Prefecture

After the Tokyo Electric Power Company Fukushima Dai-ichi Nuclear Power Station accident, wild boar was found to have greater radiocesium (137Cs) activity concentrations in their bodies than other wild animals in Japan; however, the reason for this remains unknown. To understand the mechanism of 137Cs transfer from the environment to wild boar, and the factors that affect variation in 137Cs contamination in wild boar, we sampled muscle and stomach contents from wild boar captured in Fukushima Prefecture and analyzed the relationships among 137Cs concentrations in muscle tissue and in the stomach contents, 137Cs ground deposition at capture sites, and wild boar food habits. Significant positive relationships were observed among 137Cs activity concentrations in muscle and stomach contents, as well as 137Cs deposition density at capture sites. These results suggest that 137Cs is transferred from the environment to plant and animal materials consumed by wild boar, and then from these foods to the bodies of wild boar through digestion. However, no correlation was observed between 137Cs concentrations in stomach contents and the presence of any particular food item in stomachs of wild boar, including mushrooms. These findings suggest mushrooms and underground food items, which were found to affect 137Cs concentrations in wild animals in Europe, were not important contributors to high levels of 137Cs contamination in Japanese wild animals.

Trust-what Connects Science to Daily Life.

Seven years have passed since the Tokyo Electric Power Company Fukushima Dai-ichi nuclear power plant disaster in March 2011. The actions taken by the Japanese government, such as issuing evacuation orders and setting decontamination and food safety standards, created huge confusion in society that led to a breakdown of trust. The residents of Suetsugi, a small village located about 30 km south of the plant, sought to understand and overcome the effects of radiation by measuring contamination and personal dose, etc. In my work through Ethos in Fukushima (a nonprofit organization in Iwaki, Fukushima), I learned that trust-not just measuring radiation or acquiring more scientific knowledge-has been the critical factor for them to regain a sense of order in their lives. The level of radiation has decreased since 2011; however, the community still struggles with rebuilding the community.

Seasonal variation of Cesium-137 concentration in Asian black bear (Ursus thibetanus) and wild boar (Sus scrofa) in Fukushima Prefecture, Japan.

To elucidate and reduce the risk of radionuclide contamination in wildlife caused by the Tokyo Electric Power Company Fukushima Dai-ichi Nuclear Power Station accident, it is important to understand radionuclide variations in the wild animal population. Here, we used environmental monitoring data and muscle samples collected from Asian black bear (Ursus thibetanus) and wild boar (Sus scrofa) from May 2011 to March 2016 to examine seasonal variation in radiocesium (137Cs) concentrations in muscle tissues (hereafter, muscle 137Cs) of these important game species in Fukushima Prefecture. We measured muscle 137Cs of bears and wild boars killed by hunters or in animal control culls. First, using a linear mixed model (LMM), we tested for a positive relationship between muscle 137Cs and 137Cs in the soil at the site of capture (hereafter, soil 137Cs) estimated from a soil 137Cs deposition map produced by the Japan Atomic Energy Agency. In the LMM, muscle 137Cs was positively related to estimated soil 137Cs, which corroborates the results of previous studies. The LMM regression coefficients differed between the two species, with wild boar muscle 137Cs being higher than that of bears sampled at the same locations. We then employed a generalized additive mixed model (GAMM) to estimate seasonal variation in the muscle 137Cs of the target species. GAMM showed that muscle 137Cs varied seasonally and that this seasonal variation also differed between the two species. In bears, muscle 137Cs decreased from spring to early autumn, before increasing in winter. Wild boar muscle 137Cs remained low during spring and summer and was high during autumn and early spring. These patterns are likely influenced by differences in diet, habitat use, and physiology between these two species.

Tokyo Electric Power Company Fukushima Dai-ichi Nuclear Power Plant accident and public health

Tokyo Electric Power Company Fukushima Dai-ichi Nuclear Power Plant accident and public health

Potassium behavior and clay mineral composition in the soil with low effectiveness of potassium application

ABSTRACT Increasing exchangeable potassium (ExK) content in soil to an appropriate level is important to mitigate the transfer of radioactive cesium to crops. We focused on a buckwheat (Fagopyrum esculentum Moench) field with a low ExK content, despite the application of K, in Fukushima Prefecture, Japan (Field A), following the Tokyo Electric Power Company Fukushima Dai-ichi (No. 1) Nuclear Power Plant accident in March 2011. We examined the relationship between K concentration and clay mineral composition in the soil of Field A and compared the findings with another field in Fukushima Prefecture (Field B) to clarify whether K applied to the soil was leached or remaining fixed. Pot experiments showed that K concentration in water seepage from pots following irrigation was significantly lower in pots from Field A than in those from Field B. Soil ExK content after soybean cultivation was lower in soils of Field A than those of Field B. These results indicate that K applied to Field A was fixed in the soil. Analysis of clay mineral composition confirmed the distinctive vermiculitic nature of Field A soils. This clay mineralogy would be associated with the higher K fixation ability of Field A than Field B soils. This study demonstrated that K fixation in vermiculite was a factor preventing the increase in ExK content from K application to Field A.

Fukushima Health Management Survey and Related Issues.

After the Great East Japan Earthquake on March 11, 2011, the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant accident occurred. The Fukushima prefectural government decided to launch the Fukushima Health Management Survey; Fukushima Medical University was entrusted to design and implement the survey. The survey process and development is described from the standpoint of its background and aim. An overview of the basic survey and 4 detailed surveys is briefly provided. Issues related to the survey are discussed from the perspective of supporting the Fukushima residents.

THREE-YEAR RETENTION OF RADIOACTIVE CAESIUM IN THE BODY OF TEPCO WORKERS INVOLVED IN THE FUKUSHIMA DAIICHI NUCLEAR POWER STATION ACCIDENT.

Direct measurements of seven highly exposed workers at the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station accident have been performed continuously since June 2011. Caesium clearance in the monitored workers is in agreement with the biokinetic models proposed by the International Commission on Radiological Protection. After 500 d from the initial measurement, however, the caesium clearance slowed. It was thought to be unlikely that additional Cs intake had occurred after the initial intake, as activity in foods was kept low. And, the contribution from the detector over the chest was enhanced with time. This indicates that insoluble Cs particles were inhaled and a long metabolic rate showed.

Spatial and temporal distributions of (134)Cs and (137)Cs derived from the TEPCO Fukushima Daiichi Nuclear Power Plant accident in the North Pacific Ocean by using optimal interpolation analysis.

Optimal interpolation (OI) analysis was used to investigate the oceanic distributions of (134)Cs and (137)Cs released from the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant (FNPP1) accident. From the end of March to early April 2011, extremely high activities were observed in the coastal surface seawater near the FNPP1. The high activities spread to a region near 165°E in the western North Pacific Ocean, with a latitudinal center of 40°N. Atmospheric deposition also caused high activities in the region between 180° and 130°W in the North Pacific Ocean. The inventory of FNPP1-released (134)Cs in the North Pacific Ocean was estimated to be 15.3 ± 2.6 PBq. About half of this activity (8.4 ± 2.6 PBq) was found in the coastal region near the FNPP1. After 6 April 2011, when major direct releases ceased, the FNPP1-released (134)Cs in the coastal region decreased exponentially with an apparent half-time of about 4.2 ± 0.5 days and declined to about 2 ± 0.4 PBq by the middle of May 2011. Taking into account that the (134)Cs/(137)Cs activity ratio was about 1 just after release and was extremely uniform during the first month after the accident, the amount of (137)Cs released by the FNPP1 accident increased the North Pacific inventory of (137)Cs due to bomb testing during the 1950s and early 1960s by 20%.

134Cs and 137Cs in the North Pacific Ocean derived from the March 2011 TEPCO Fukushima Dai-ichi Nuclear Power Plant accident, Japan. Part two: estimation of 134Cs and 137Cs inventories in the North Pacific Ocean

We estimated the inventories of radiocaesium released by the Tokyo Electric Power Company Fukushima Dai-ichi Nuclear Power Plant (FNPP1) accident to the North Pacific Ocean by using compiled data and model simulations. By comparing the observed inventories with model-simulated results, we obtained 12–15 PBq of 137Cs for the atmospheric deposition released by the FNPP1 accident in the North Pacific Ocean. Before the Fukushima accident, 137Cs activity in the North Pacific Ocean was about 69 PBq. Therefore, the 12–15 PBq of 137Cs newly added by atmospheric deposition together with the 3.5 ± 0.7 PBq added by direct discharge increased the total 137Cs inventory in the North Pacific Ocean by 22–27 %. We also estimated the total amount of 137Cs released to the atmosphere to be 15–20 PBq, and the total amount of 137Cs released to the environment to be 19–24 PBq, respectively. Observed 134Cs to 137Cs activity ratio at the time of accident was close to 1 and extremely uniform, therefore, the total amount of 134Cs deposition in the North Pacific Ocean, that of released to the atmosphere, that of direct discharge to the ocean and that of released to the environment were the same amounts as those of 137Cs.

Influence of the Fukushima Dai-ichi Nuclear Power Plant accident on environmental radioactivity in Aomori Prefecture.

Radioactive nuclides with a short half-life, such as (131)I and (134)Cs, were detected in environmental samples collected in Aomori Prefecture after the Tokyo Electric Power Company Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. In addition, the observed (137)Cs concentration was increased over the background level. The gaseous (131)I concentration in air observed in April was higher than that observed in March immediately after the accident. Using a backward trajectory analysis, the authors found that the air mass had passed the vicinity of the Fukushima Dai-ichi Nuclear Power Plant when the gaseous (131)I concentration in air was increasing. Maximum (131)I and radioactive Cs concentrations in daily fallout samples collected in Aomori city were observed on 28 April, when (131)I was also detected in air. (134)Cs and (137)Cs concentration ratios in pine needles and pasture grass were nearly equal to 1, which indicates that the source of these radionuclides was the nuclear power plant accident.

Radiation signatures in childhood thyroid cancers after the Chernobyl accident: possible roles of radiation in carcinogenesis.

After the Tokyo Electric Power Company Fukushima Daiichi nuclear power plant accident, cancer risk from low-dose radiation exposure has been deeply concerning. The linear no-threshold model is applied for the purpose of radiation protection, but it is a model based on the concept that ionizing radiation induces stochastic oncogenic alterations in the target cells. As the elucidation of the mechanism of radiation-induced carcinogenesis is indispensable to justify the concept, studies aimed at the determination of molecular changes associated with thyroid cancers among children who suffered effects from the Chernobyl nuclear accident will be overviewed. We intend to discuss whether any radiation signatures are associated with radiation-induced childhood thyroid cancers.

A review of the Fukushima nuclear reactor accident: radiation effects on the thyroid and strategies for prevention.

This is a summary of the nuclear accident at the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Stations (FDNPS) on 11 March 2011 to be used as a review of the radiation effects to the thyroid and strategies of prevention. The amount of radioiodine released to the environment following the Fukushima accident was 120 Peta Becquerel, which is approximately one-tenth of that in the Chernobyl accident. Residents near the FDNPS were evacuated within a few days and foodstuffs were controlled within 1 or 2 weeks. Therefore, thyroid radiation doses were less than 100 mSv (intervention levels for stable iodine administration) in the majority of children, including less than 1 year olds, living in the evacuation areas. Because the incidence of childhood thyroid cancer increased in those residing near the site following the Chernobyl accident, thyroid screening of all children (0-18 years old) in the Fukushima Prefecture was started. To date, screening of more than 280 000 children has resulted in the diagnosis of thyroid cancer in 90 children (approximate incidence, 313 per million). Thus, although the dose of radiation was much lower, the incidence of thyroid cancer appears to be much higher than that following the Chernobyl accident. A comparison of the thyroidal consequences following the Fukushima and Chernobyl nuclear reactor accidents is discussed. We also summarize the recent increased incidence in thyroid cancer in the Fukushima area following the accident in relation to increased thyroid ultrasound screening and the use of advanced ultrasound techniques. http://links.lww.com/COE/A8.

Radioactive caesium concentrations in pigs fed brown rice contaminated by the Tokyo Electric Power Company Fukushima Daiichi nuclear power plant

This experiment was conducted to determine radioactive caesium levels in the tissues of pigs fed brown rice contaminated by the fallout from the Tokyo Electric Power Company Fukushima Daiichi nuclear power plant accident that occurred after the Great East Japan Earthquake of March 2011. We prepared a control diet mainly consisting of imported corn and a test diet including brown rice (700g/kg diet) grown in Fukushima Prefecture during 2011. The radioactive caesium concentrations in the control diet were below the limits of detection. Concentrations of 134Cs and 137Cs in the test diet were 15.0Bq/kg and 20.0Bq/kg, respectively. Twelve barrows, Duroc×(Large White×Landrace), aged 8 weeks were assigned to each diet for 3 weeks after which samples of longissimus dorsi muscle, liver, and digestive tract (from stomach to ileum) were then taken. Radioactive caesium levels in control group tissues were close to the limits of detection or less, while 134Cs and 137Cs were detected in the tissues taken from the test group (134Cs: muscle 13.3Bq/kg, liver 11.7Bq/kg, digestive tract 10.3Bq/kg; 137Cs: muscle 18.5Bq/kg, liver 15.3Bq/kg, digestive tract 13.7Bq/kg). The results clearly demonstrate oral uptake and retention of radioactive ceasium in pigs fed on a fallout-contaminated diet.

Spatiotemporal Characteristics of Internal Radiation Exposure In Evacuees and First Responders after the Radiological Accident in Fukushima

After the Tokyo Electric Power Company Fukushima Daiichi nuclear power plant accident on March 11, 2011, the reconstruction of early internal radiation doses in residents of Fukushima plays a major role in evaluating their future heath risk, including thyroid cancer by internal radioiodine. Internal radioactivity was measured using a whole body counter (WBC) at the Nagasaki University Medical School to evaluate the health risks of residents and short term visitors in Fukushima. Measurable (131)I, (134)Cs and (137)Cs were detected altogether in 49 out of 196 people who were in Fukushima prefecture at any time during March 11 and April 20, 2011. In 49 people, the 90 percentile of the thyroid equivalent dose by (131)I and the committed effective dose (total effective dose over a lifetime) by the sum of (134)Cs and (137)Cs was 3 mSv and 0.06 mSv, respectively. The radionuclide intakes in early evacuees who left Fukushima before March 16 were more than five times as high as in the responders who moved to Fukushima later. The intake ratio of (131)I/(137)Cs of the earlier evacuees was approximately three. The spatial analysis of 16 evacuees to the south indicated a reduction of internal radioactivity depending on the distance from the nuclear power plant. Among them, high internal (131)I radioactivity in 6 people in a particular evacuation route could be explained by the arrival of a radioactive cloud with a high airborne (131)I/(137)Cs ratio to the environment, as predicted by atmospheric dispersion simulations. Overall, the actual internal radioactivity assessed by a WBC examination comparatively agreed with the predicted airborne radioactivity. These results suggest that the accurate estimation of internal doses in the first week after the radiological accident is critical for the dose reconstruction. The evaluation of internal doses of residents based on their evacuation routes and the advanced estimation of airborne radioactivity from the atmospheric dispersion model should continue to be assessed.