Activity concentrations of environmental samples collected in Fukushima Prefecture immediately after the Fukushima nuclear accident

Indoor concentrations of radioactive aerosols from nuclear accidents

In previous studies, some of the important factors that affect the spread of radioactive aerosols into indoors were considered. The studies were based on a new CFD approach and provided good descriptions for the deposition of aerosol particles inside small spaces and the penetration of aerosols into buildings through wall cracks. In this article, an application of those studies is implemented, where all the graphical relations that are required to estimate the indoor concentrations of radioactive aerosols from nuclear accidents are provided. This includes the deposition velocities, deposition rate, and the penetration factor. Particular interest is in the Fukushima-Daiichi nuclear power plant accident that took place in Japan in 2011. The aerosols carrying the radioiodine iodine-131 and the radiocesium cesium-134 and cesium-137 are studied. Based on the model's assumptions, and assuming steady-state air concentrations, the radioactive aerosols' concentrations in indoor air are about 97% of the concentrations in outdoor air. The applications demonstrate the model to be convenient and practical.

Highly Sensitive Adsorption and Detection of Iodide in Aqueous Solution by a Post-Synthesized Zirconium-Organic Framework

Effective methods of detection and removal of iodide ions (I^-) from radioactive wastewater are urgently needed and developing them remains a great challenge. In this work, an Ag⁺ decorated stable nano-MOF UiO-66-(COOH)₂ was developed for the I^- to simultaneously capture and sense in aqueous solution. Due to the uncoordinated carboxylate groups on the UiO-66-(COOH)₂ framework, Ag⁺ was successfully incorporated into the MOF and enhanced the intrinsic fluorescence of MOF. After adding iodide ions, Ag⁺ would be produced, following the formation of AgI. As a result, Ag⁺@UiO-66-(COOH)₂ can be utilized for the removal of I^- in aqueous solution, even in the presence of other common ionic ions (NO₂^-, NO₃^-, F^-, SO₄^2-). The removal capacity as high as 235.5 mg/g was calculated by Langmuir model; moreover, the fluorescence of Ag⁺@UiO-66-(COOH)₂ gradually decreases with the deposition of AgI, which can be quantitatively depicted by a linear equation. The limit of detection toward I^- is calculated to be 0.58 ppm.

Strategy to combine two functional components: Efficient nano material development for iodine immobilization

The development of effective radioactive iodine adsorption materials from nuclear waste remains a significant challenge due to the drawbacks of the previous technologies such as complex synthesis process, high cost, and low stability. In this work, a Metal Oxidation-Carbon (MOC) composite material was designed and synthesized to solve this problem. The structure, composition, and physicochemical properties of this MOC were characterized to reveal its mesoporous material properties. Experiment results showed that this MOC material contain great physical and chemical adsorption efficiency towards iodine vapor, the adsorption capacity could up to 2647.54 mg/g. And the average desorption rate of 86.57% (in absolute ethanol) further proved its advanced recyclability. Moreover, this mesoporous material has great prospects in industrialization due to its simple one-step synthesis method, well-defined adsorption mechanism, and competitive application property.

Hydroxy-Functionalized Hypercrosslinked Polymers (HCPs) as Dual Phase Radioactive Iodine Scavengers: Synergy of Porosity and Functionality

Large-scale nuclear power plant production of iodine radionuclides (129 I, 131 I) pose huge threat in the events of nuclear disaster. Effective removal of radioiodine from nuclear waste is one of the most critical challenge because of the drawbacks of state-of-the-art adsorbents such as high cost, low uptake capacity and non-recyclability. Herein, two hydroxy-functionalized (-OH) hypercrosslinked polymers (HCPs), namely HCP-91 and HCP-92, have been synthesized and employed towards capture of iodine. High chemical stability along with synergistic harmony of high porosity and functionality of these materials makes them suitable candidates for capture of iodine from both vapor phase and water medium. Moreover, both the HCPs showed superior iodine removal performance from water in terms of fast kinetics and high removal efficiency (2.9 g g-1 and 2.49 g g-1 for HCP-91 and HCP-92 respectively). The role of functionality (-OH groups) and porosity has been established with the help of HCP-91, HCP-92 and non-functionalized biphenyl HCP for the efficient capture of I3 - ions from water. In addition, both HCPs exhibited excellent selectivity and recyclability towards triiodide ions, rendering the potential of these materials towards real-time applications. Lastly, Density functional theoretical studies revealed key insights and corroborate well with the experimental findings.

Sorption-desorption coefficients of uranium in contaminated soils collected around Fukushima Daiichi Nuclear Power Station

Various radionuclides including fission products and heavy nuclides were released into the environment during the Fukushima Daiichi Nuclear Power Station (FDNPS) accident. The dissolution followed by migration of deposited radionuclides of Cs, Sr and U on soils could take place to the local environment. Therefore, it is necessary to determine sorption-desorption coefficients of U in soil-water system around the FDNPS from a migration viewpoint. The determination of sorption coefficient K_d(S) as well as desorption coefficient K_d(D) for U has been carried out in the present study using a laboratory batch method. Stable U was used for sorption from simulated ground water onto contaminated soil samples collected from Okuma Town, Fukushima. Different soil parameters were measured to understand their effects on sorption and desorption processes. The obtained K_d(S) and K_d(D) values of U were compared with values of K_d(S) and K_d(D) of Cs and Sr and K_d(S)-U in known Fukushima accident contaminated soils reported in the literature for better understanding. It was observed that K_d(S)-U varied from 160 to 5100 L/kg, whereas K_d(D)-U ranged from 200 to 11000 L/kg. K_d(D) was higher than K_d(S) for U in these soils implying irreversibility of the sorption process. Pearson's correlation of K_d(S) values suggested that U sorption is affected by various soil parameters. However, desorption is decided by the nature of U species formed in sorption process and soil parameters like pH, presence of carbonates, Ca ions, clay minerals etc. to some extent. The comparison between K_d(S) and K_d(D) values for Cs, Sr and U revealed that unsorbed Sr could migrate farther than unsorbed Cs or U under the present experimental conditions. Both sorption and desorption studies are of great importance to understand migration of metal ions from contaminated sites to local uncontaminated areas.

Deposition of Fukushima nuclear power plant accident-derived radiocesium in the soils of Jeju Island, Korea, and evidence for long- and short-lived radionuclides in rainwater

In this study, we investigated the concentrations of Fukushima nuclear power plant accident (FNPPA)-derived radiocesium (¹³⁴Cs, ¹³⁷Cs) deposited in the topsoil of Jeju Island, Korea. We also evaluated the soil inventories of radionuclides and compared the concentrations deposited by rainwater and fallout. We present the first evidence of FNPPA-derived radionuclides directly entering the environment of Jeju Island. In the case of FNPPA-derived ¹³⁴Cs in soil, only a trace amount was identified in the surface layer (1 cm depth), whereas ¹³⁷Cs derived from past atmospheric deposition of nuclear testing were detected along with those derived from the nuclear power plant accident. The total measured radiocesium (¹³⁴Cs + ¹³⁷Cs) indicates that although the value obtained from soils was slightly lower, both values were within the same order of magnitude. Of the FNPPA-derived radiocesium deposited in the soil, the impact from April 2011 was the largest at most sampling sites indicating that the radioactive plume directly covered Jeju Island. Furthermore, a variety of long- and short-lived gamma-emitting radionuclides were detected in the rainwater samples collected on April 7, 2011. Among them, short-lived radionuclides such as ¹⁴⁰La, ^110mAg, ⁹⁵Nb, ¹²⁵Sb, ¹¹³Sn, ¹²⁹Te, ^129mTe, ¹³²Te, ¹³²I, and ¹³⁶Cs, were observed. The findings of this study provide evidence for the direct effects of FNPPA-derived radionuclides in Jeju Island. This is the first location in Korea and the first in the entire East Asian region, excluding Japan that is confirmed to have been directly affected FNPP accident.

Accurate and precise determination of 90Sr at femtogram level in IAEA proficiency test using Thermal Ionization Mass Spectrometry

A novel method for the determination of ultra-trace level ⁹⁰Sr has been recently developed applying thermal ionization mass spectrometry (TIMS). The method includes the chemical separation of Zr (isobaric interference of ⁹⁰Zr) from the samples followed by determination of ⁹⁰Sr/⁸⁸Sr abundance  sensitivity (2.1 × 10⁻¹⁰). The analytical performance of this method was assessed in the IAEA-TEL 2017-3 worldwide open proficiency test. For ⁹⁰Sr determination, tap water and milk powder samples were distributed amongst the participant laboratories with reference values of 11.2 ± 0.3 Bq kg⁻¹ (2.2 ± 0.1 fg g⁻¹) and 99.9 ± 5.0 Bq kg⁻¹ (19.5 ± 1.0 fg g⁻¹), respectively. The stable Sr concentrations were 39.4 ± 0.9 ng g⁻¹ and 2.5 ± 0.1 µg g⁻¹ while the ⁹⁰Sr/⁸⁸Sr isotope ratios were 6.47 ± 0.17 × 10⁻⁸ and 9.04 ± 0.45 × 10⁻⁹ in the tap water and milk powder samples, respectively. For TIMS measurement, 50 mL water and 1 g milk powder samples were taken for analysis. This TIMS method demonstrated an impressive accuracy (relative bias of 4.2% and −2.1%, respectively) and precision (relative combined uncertainty of 4.1% and 7.6%, respectively) when compared with radiometric techniques. For the first time in the history of inorganic mass-spectrometry, ⁹⁰Sr analysis using a TIMS instrument is confirmed by an independent proficiency test.

EVALUATIONS OF INVENTORY AND ACTIVITY CONCENTRATION OF RADIOCESIUM IN SOIL AT A RESIDENTIAL HOUSE 3 YEARS AFTER THE FUKUSHIMA NUCLEAR ACCIDENT

Soil samples from the surface to a 5 cm depth were collected at a residential house in Koriyama City, Fukushima Prefecture using a scraper plate every three months from March 2014 to September 2014 to evaluate the vertical distribution profiles and inventories of 134Cs and 137Cs in soil. The vertical distribution profiles of radiocesium (134Cs and 137Cs) in soil showed that greater than 86% of the total radiocesium was absorbed in the upper 2 cm 3 years after the accident. Radiocesium in the surface layer seems to move to the lower layer over time. The migration of radiocesium in surface layer might be influenced by the ground surface runoff by rainfall. Radiocesium inventories in June increased significantly over the short period between March and June. In contrast, the radiocesium inventories in September did not increase significantly compared to the values in June. Radiocesium resuspension and deposition caused by decontamination work and meteorological events might be one possible reason for the increased radiocesium inventories observed in June.

COMPARISON OF BACTERIAL FLORA IN RIVER SEDIMENTS FROM FUKUSHIMA AND AOMORI PREFECTURES BY 16S RDNA SEQUENCE ANALYSIS

Monitoring of radioactive materials has been reported in rivers and soil in Fukushima post the Fukushima Daiichi Nuclear Power Plant accident in March 2011. However, there are few reports on the influence of this event on bacteria in forest soils and rivers. Therefore, through amplicon sequencing of 16S rDNA we compared the bacterial flora in river sediment soils from Fukushima prefecture and from an area not exposed to radioactive contamination, Aomori prefecture. The bacterial composition in the Aomori prefecture soil and Fukushima soil were found to be very similar at the phylum level. However, Fukushima soil had significantly fewer Bacteroidetes than the Aomori soil (p = 0.014), while the content of Firmicutes and Latescibacteria (WS3) was significantly higher (p = 0.001, 0.013 respectively). However, no increase in the content of radioactive-resistant bacteria was observed. In future studies, it is necessary to standardise the conditions for soil collection to assess its content of radioactive substances.

Measurement of uranium distribution coefficient and 235U/238U ratio in soils affected by Fukushima dai-ichi nuclear power plant accident

Fukushima Daiichi Nuclear Power Plant (FDNPP) accident resulted radioactive contamination in soil due to deposition of mainly radiocesium as well as many long-lived radionuclides surrounding a large area around FDNPP. Depending upon environmental conditions, radionuclides in soil can be mobilized in aquatic systems. Therefore, the fate and transfer of these radionuclides in the soil water system is very important for radiation protection and dose assessment. In the present study, soil and water samples were collected from contaminated areas around FDNPP. Inductively coupled plasma mass spectrometry (ICP-MS) is used for total uranium concentration. Emphasis has been given on isotope ratio measurement of ²³⁵U/²³⁸U ratio using thermal ionization mass spectrometry (TIMS) that gives us the idea about its contamination during accident. For the migration behavior, its distribution coefficient (K_d) has been determined using laboratory batch method. Chemical characterization of soil with respect to different parameters has been carried out. The effect of these soil parameters on distribution coefficient of uranium has been studied in order to explain the radionuclide mobility in this particular area. The distribution coefficient values for uranium are found to vary from 30 to 36000 L/kg. A large variation in the distribution coefficient values shows the retention or mobility of uranium is highly dependent on soil characteristics in the particular area. This variation is explained with respect to soil pH, Fe, Mn, CaCO₃ and organic content. There is a very good correlation of uranium K_d obtained with Fe content. There is no enrichment of ²³⁵U has been noticed in the studied area.

Radiocesium and 40K distribution of river sediments and floodplain deposits in the Fukushima exclusion zone

In this study, radiocesium and ⁴⁰K analysis were accomplished for samples of riverbed sediments and floodplain deposits collected from five rivers in the vicinity (<20 km) of the damaged Fukushima Daiichi Nuclear Power Plant after seven years of the accident. Sediment particle size distribution and major oxide content were determined also for six selected samples to understand the retention and migration process of radiocesium in river environments. The radiocesium activity concentration varied from 103 ± 6 Bq·kg^-1 to 22,000 ± 500 Bq·kg^-1 in riverbed sediments and from 92 ± 5 Bq·kg^-1 to 117,000 ± 2000 Bq·kg^-1 in floodplain deposits. The ¹³⁴Cs/¹³⁷Cs ratio (decay corrected to 15 March 2011) was 1.02 in the both samples. Compared to monitoring results in 2011, it was proved that the radiocesium distribution pattern had been changed remarkably during seven years. The radiocesium was primarily attached to fine clay particles but its sorption on sand and coarse sand particles was also considerable. The sorption process of radiocesium was not affected by the presence of water and moreover, after seven years of the Fukushima accident, a significant radiocesium migration cannot be expected without particle migration. Consequently, radiocesium will remain for a long time in the river environments and its redistribution is mainly affected by the erosion process of the sediments. The average ⁴⁰K activity concentration of riverbed sediment and floodplain deposit samples was 640 ± 152 Bq·kg^-1 changing from 319 ± 18 Bq·kg^-1 to 916 ± 41 Bq·kg^-1. In the river estuary zones, significant activity concentration decrements were observed for both radionuclides. This suggests that seawater intrusion has a decreasing effect on both natural and artificial radionuclides via wash-out of particulate radiocesium and ⁴⁰K, and desorption of these radionuclides, but to reveal the detail of this process further investigations are required. The analysis of ⁴⁰K can help in a simple and easy way to reveal the mineral composition differences of sediment samples.

Cellulose Fibers Constructed Convenient Recyclable 3D Graphene-Formicary-like δ-Bi2O3 Aerogels for the Selective Capture of Iodide

Radioiodine is highly radioactive and acutely toxic, which can be a serious health threat, and requires effective control. To fully utilize an adsorbent and reduce the overall production cost, successive recycling applications become necessary. Here, 3D formicary-like δ-Bi₂O₃ (FL-δ-Bi₂O₃) aerogel adsorbents were synthesized using a one-pot hydrothermal method. In this hybrid structure, abundant flowerlike δ-Bi₂O₃ (MR-δ-Bi₂O₃) microspheres were inlaid into the interconnected ant nest channel, forming a 3D hierarchical structure, which is applied as an efficient adsorbent with easy recovery for radioiodine removal. Notably, the FL-δ-Bi₂O₃ aerogel adsorbent exhibited a very high uptake capacity of 2.04 mmol/g by forming an insoluble Bi₄I₂O₅ phase. Moreover, the FL-δ-Bi₂O₃ worked in a wide pH range of 4-10 and displayed fast uptake kinetics and excellent selectivity due to the 3D porous interconnected network and larger specific surface area. Importantly, the recycling process is easy, using only tweezers to directly move the 3D aerogel adsorbents from one reaction system to another. Therefore, the FL-δ-Bi₂O₃ aerogel may be a promising practical adsorbent for the selective capture of radioactive iodide.

Educational Activity for the Radiation Emergency System in the Northern Part of Japan: Meeting Report on "The 3rd Educational Symposium on Radiation and Health (ESRAH) by Young Scientists in 2016"

In the northern part of Japan, close cooperation is essential in preparing for any possible emergency response to radiation accidents because several facilities, such as the Low-Level Radioactive Waste Disposal Facility, the MOX Fuel Fabrication Plant and the Vitrified Waste Storage Center, exist in Rokkasho Village (Aomori Prefecture). After the accident at Fukushima Daiichi Nuclear Power Plant in 2011, special attention should be given to the relationship between radiation and human health, as well as establishing a system for managing with a radiation emergency. In the area of Hokkaido and Aomori prefectures in Japan, since 2008 an exchange meeting between Hokkaido University and Hirosaki University has been held every year to have opportunities to discuss radiation effects on human health and to collect the latest news on monitoring environmental radiation. This meeting was elevated to an international meeting in 2014 titled "Educational Symposium on Radiation and Health (ESRAH) by Young Scientists". The 3rd ESRAH meeting took place in 2016, with the theme "Investigating Radiation Impact on the Environmental and Health". Here we report the meeting findings on the continuing educational efforts after the Fukushima incident, what was accomplished in terms of building a community educational approaches, and future goals.

Observation of radioactive iodine ((131)I, (129)I) in cropland soil after the Fukushima nuclear accident

During the early stages of the Fukushima nuclear accident, the temporal variations of (131)I deposited on the ground and of (131)I accumulated in cropland soil were monitored at a fixed location in Japan. Moreover, concentrations of long-lived radioactive iodine ((129)I) in atmospheric deposits and soil were measured to examine the feasibility of retrospectively reconstructing (131)I levels from the levels of accident-derived (129)I. The exceptionally high levels of (131)I in deposits and soil were attributed to rainfall-related deposition of radionuclides. In the crop field studied, the losses of deposited (131)I and (129)I due to volatilization were small. The atomic ratio (129)I/(131)I in the topsoil corresponded to the same ratio in deposits. The (131)I concentrations measured in the topsoil were very consistent with the (131)I concentrations reconstructed from the (129)I concentrations in the soil.

A comparison of the dose from natural radionuclides and artificial radionuclides after the Fukushima nuclear accident

Due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the evacuees from Namie Town still cannot reside in the town, and some continue to live in temporary housing units. In this study, the radon activity concentrations were measured at temporary housing facilities, apartments and detached houses in Fukushima Prefecture in order to estimate the annual internal exposure dose of residents. A passive radon-thoron monitor (using a CR-39) and a pulse-type ionization chamber were used to evaluate the radon activity concentration. The average radon activity concentrations at temporary housing units, including a medical clinic, apartments and detached houses, were 5, 7 and 9 Bq m(-3), respectively. Assuming the residents lived in these facilities for one year, the average annual effective doses due to indoor radon in each housing type were evaluated as 0.18, 0.22 and 0.29 mSv, respectively. The average effective doses to all residents in Fukushima Prefecture due to natural and artificial sources were estimated using the results of the indoor radon measurements and published data. The average effective dose due to natural sources for the evacuees from Namie Town was estimated to be 1.9 mSv. In comparison, for the first year after the FDNPP accident, the average effective dose for the evacuees due to artificial sources from the accident was 5.0 mSv. Although residents' internal and external exposures due to natural radionuclides cannot be avoided, it might be possible to lower external exposure due to the artificial radionuclides by changing some behaviors of residents.

Carbon, cesium and iodine isotopes in Japanese cedar leaves from Iwaki, Fukushima

Japanese cedar leaves from Iwaki, Fukushima were analyzed for carbon, cesium and iodine isotopic compositions before and after the 2011 nuclear accident. The Δ14C values reflect ambient atmospheric 14C concentrations during the year the leaves were sampled/defoliated, and also previous year(s). The elevated 129I and 134,137Cs concentrations are attributed to direct exposure to the radioactive fallout for the pre-fallout-expended leaves and to internal translocation from older parts of the tree for post-fallout-expended leaves. 134Cs/137Cs and 129I/137Cs activity ratios suggest insignificant isotopic and elemental fractionation during translocation. However, fractionation between radioiodine and radiocesium is significant during transportation from the source.

Strontium-90 activity concentration in soil samples from the exclusion zone of the Fukushima daiichi nuclear power plant

The radioactive fission product ⁹⁰Sr has a long biological half-life (˜18 y) in the human body. Due to its chemical similarity to calcium it accumulates in bones and irradiates the bone marrow, causing its high radio-toxicity. Assessing ⁹⁰Sr is therefore extremely important in case of a nuclear disaster. In this work 16 soil samples were collected from the exclusion zone (<30 km) of the earthquake-damaged Fukushima Daiichi nuclear power plant, to measure ⁹⁰Sr activity concentration using liquid scintillation counting. ¹³⁷Cs activity concentration was also measured with gamma-spectroscopy in order to investigate correlation with ⁹⁰Sr. The ⁹⁰Sr activity concentrations ranged from 3.0 ± 0.3 to 23.3 ± 1.5 Bq kg⁻¹ while the ¹³⁷Cs from 0.7 ± 0.1 to 110.8 ± 0.3 kBq kg⁻¹. The fact that radioactive contamination originated from the Fukushima nuclear accident was obvious due to the presence of ¹³⁴Cs. However, ⁹⁰Sr contamination was not confirmed in all samples although detectable amounts of ⁹⁰Sr can be expected in Japanese soils, as a background, stemming from global fallout due to the atmospheric nuclear weapon tests. Correlation analysis between ⁹⁰Sr and ¹³⁷Cs activity concentrations provides a potentially powerful tool to discriminate background ⁹⁰Sr level from its Fukushima contribution.

Radioprotective effect of hesperetin against γ-irradiation-induced DNA damage and immune dysfunction in murine splenocytes

This study was conducted to evaluate the preventive effect of hesperetin against radiation-induced DNA damage and immune dysfunction in murine splenocytes. Isolated splenocytes from BALB/c mice were treated with hesperetin (20, 100, and 500 µM), and then irradiated at a dose of 2 and 4 Gy of γ-irradiation. Exposure to ?-radiation resulted in DNA damage and a reduction of cell viability as well as an elevation of the levels of proinflammatory cytokines, intracellular ROS (reactive oxygen species), and NO (nitric oxide). Hesperetin significantly enhanced the cell viability of the splenocytes compared with the irradiated group. In addition, hesperetin was found to be highly effective in preventing DNA damage as identified by comet and DNA ladder assays. Hesperetin also effectively inhibited proinflammatory cytokines, intracellular ROS, and NO in irradiated splenocytes. In conclusion, hesperetin was shown to be radioprotective against irradiation-induced DNA damage and immune dysfunction in murine splenocytes.

MnO2 nanomaterials for flexible supercapacitors: performance enhancement via intrinsic and extrinsic modification

Increasing power and energy demands for next-generation portable and flexible electronics have raised critical requirements (flexibility, stretch-ability, environmental friendliness, lightweight, etc.) for the energy storage devices. Flexible supercapacitors (SCs), as one of the most promising next-generation energy storage devices, have stimulated intensive interest owing to their outstanding features including small size, low weight, ease of handling, excellent reliability, and high power density. Manganese oxide (MnO₂), has attracted much interest in the development of flexible SCs with high electrochemical performance. Yet, the poor electronic and ionic transport in MnO₂ electrodes still limits its promotion in practical applications. This review aims to describe the recent progress in the application of MnO₂ materials in the development of flexible SCs and summarizes the intrinsic modification of MnO₂via crystallinity, crystal structure, and oxygen vacancy introduction and the extrinsic modification of MnO₂via non-three-dimensional (3D) and 3D flexible conductive scaffolds for high performance flexible SCs. Moreover, we also discuss briefly on the current challenges, future directions, and opportunities for the development of high-performance MnO₂ based flexible SCs.

Novel method for estimation of the indoor-to-outdoor airborne radioactivity ratio following the Fukushima Daiichi Nuclear Power Plant accident

The accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in Japan resulted in significant releases of fission products. While substantial data exist concerning outdoor air radioactivity following the accident, the resulting indoor radioactivity remains pure speculation without a proper method for estimating the ratio of the indoor to outdoor airborne radioactivity, termed the airborne sheltering factor (ASF). Lacking a meaningful value of the ASF, it is difficult to assess the inhalation doses to residents and evacuees even when outdoor radionuclide concentrations are available. A simple model was developed and the key parameters needed to estimate the ASF were obtained through data fitting of selected indoor and outdoor airborne radioactivity measurement data obtained following the accident at a single location. Using the new model with values of the air exchange rate, interior air volume, and the inner surface area of the dwellings, the ASF can be estimated for a variety of dwelling types. Assessment of the inhalation dose to individuals readily follows from the value of the ASF, the person's indoor occupancy factor, and the measured outdoor radioactivity concentration.

Estimation of external dose by car-borne survey in Kerala, India

A car-borne survey was carried out in Kerala, India to estimate external dose. Measurements were made with a 3-in × 3-in NaI(Tl) scintillation spectrometer from September 23 to 27, 2013. The routes were selected from 12 Panchayats in Karunagappally Taluk which were classified into high level, mid-level and low level high background radiation (HBR) areas. A heterogeneous distribution of air kerma rates was seen in the dose rate distribution map. The maximum air kerma rate, 2.1 μGy/h, was observed on a beach sand surface. ²³²Th activity concentration for the beach sand was higher than that for soil and grass surfaces, and the range of activity concentration was estimated to be 0.7–2.3 kBq/kg. The contribution of ²³²Th to air kerma rate was over 70% at the measurement points with values larger than 0.34 μGy/h. The maximum value of the annual effective dose in Karunagappally Taluk was observed around coastal areas, and it was estimated to be 13 mSv/y. More than 30% of all the annual effective doses obtained in this survey exceeded 1 mSv/y.

Selective capture of iodide from solutions by microrosette-like δ-Bi₂O₃

Radioactive iodine isotopes that are produced in nuclear power plants and used in medical research institutes could be a serious threat to the health of many people if accidentally released to the environment because the thyroid gland can absorb and concentrate them from a liquid. For this reason, uptake of iodide anions was investigated on microrosette-like δ-Bi2O3 (MR-δ-Bi2O3). The MR-δ-Bi2O3 adsorbent showed a very high uptake capacity of 1.44 mmol g(-1) by forming insoluble Bi4I2O5 phase. The MR-δ-Bi2O3 also displayed fast uptake kinetics and could be easily separated from a liquid after use because of its novel morphology. In addition, the adsorbent showed excellent selectivity for I(-) anions in the presence of large concentrations of competitive anions such as Cl(-) and CO3(2-), and could work in a wide pH range of 4-11. This study led to a new and highly efficient Bi-based adsorbent for iodide capture from solutions.

Comprehensive data on ionising radiation from Fukushima Daiichi nuclear power plant in the town of Miharu, Fukushima Prefecture: The Misho Project

Data related to radioactivity released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on 15 March 2011 gathered by residents of Miharu, Fukushima Prefecture, and by Tohoku University are presented. These data sets consist of (1) the earliest radiation monitoring by a Geiger counter in the town, (2) ratios of radioactivity between (132)Te and (137)Cs for a wide area between Fukushima and Tokyo, (3) radiation measurement of soil samples collected from 18 school grounds, and (4) external radiation exposure of 1400 students using OSL badges. By combining and analysing these various data sets, a curve for the cumulative total external exposure as a function of time, with 16 : 00 h on 15 March 2011 being time zero, is obtained. The average cumulative external dosage is estimated to be 10 mSv (σ = 4.2 mSv) over 10 years. In addition, the initiative that the residents of Miharu took in response to the FDNPP accident, which became known as The Misho Project (MP), is documented; in particular, the time at which the municipality instructed the immediate ingestion of iodine tablets by those under the age of 40, 13 : 00 h on 15 March 2011, is assessed.

Radiation dose reduction efficiency of buildings after the accident at the Fukushima Daiichi Nuclear Power Station

Numerous radionuclides were released from the Fukushima Daiichi Nuclear Power Station (F1-NPS) in Japan following the magnitude 9.0 earthquake and tsunami on March 11, 2011. Local residents have been eager to calculate their individual radiation exposure. Thus, absorbed dose rates in the indoor and outdoor air at evacuation sites in the Fukushima Prefecture were measured using a gamma-ray measuring devices, and individual radiation exposure was calculated by assessing the radiation dose reduction efficiency (defined as the ratio of absorbed dose rate in the indoor air to the absorbed dose rate in the outdoor air) of wood, aluminum, and reinforced concrete buildings. Between March 2011 and July 2011, dose reduction efficiencies of wood, aluminum, and reinforced concrete buildings were 0.55±0.04, 0.15±0.02, and 0.19±0.04, respectively. The reduction efficiency of wood structures was 1.4 times higher than that reported by the International Atomic Energy Agency. The efficiency of reinforced concrete was similar to previously reported values, whereas that of aluminum structures has not been previously reported. Dose reduction efficiency increased in proportion to the distance from F1-NPS at 8 of the 18 evacuation sites. Time variations did not reflect dose reduction efficiencies at evacuation sites although absorbed dose rates in the outdoor air decreased. These data suggest that dose reduction efficiency depends on structure types, levels of contamination, and evacuee behaviors at evacuation sites.

The biological impacts of ingested radioactive materials on the pale grass blue butterfly

A massive amount of radioactive materials has been released into the environment by the Fukushima Dai-ichi Nuclear Power Plant accident, but its biological impacts have rarely been examined. Here, we have quantitatively evaluated the relationship between the dose of ingested radioactive cesium and mortality and abnormality rates using the pale grass blue butterfly, Zizeeria maha. When larvae from Okinawa, which is likely the least polluted locality in Japan, were fed leaves collected from polluted localities, mortality and abnormality rates increased sharply at low doses in response to the ingested cesium dose. This dose-response relationship was best fitted by power function models, which indicated that the half lethal and abnormal doses were 1.9 and 0.76 Bq per larva, corresponding to 54,000 and 22,000 Bq per kilogram body weight, respectively. Both the retention of radioactive cesium in a pupa relative to the ingested dose throughout the larval stage and the accumulation of radioactive cesium in a pupa relative to the activity concentration in a diet were highest at the lowest level of cesium ingested. We conclude that the risk of ingesting a polluted diet is realistic, at least for this butterfly, and likely for certain other organisms living in the polluted area.

Simultaneous sampling of indoor and outdoor airborne radioactivity after the Fukushima Daiichi nuclear power plant accident

Several studies have estimated inhalation doses for the public because of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Most of them were based on measurement of radioactivity in outdoor air and included the assumption that people stayed outdoors all day. Although this assumption gives a conservative estimate, it is not realistic. The "air decontamination factor" (ratio of indoor to outdoor air radionuclide concentrations) was estimated from simultaneous sampling of radioactivity in both inside and outside air of one building. The building was a workplace and located at the National Institute of Radiological Sciences (NIRS) in Chiba Prefecture, Japan. Aerosol-associated radioactive materials in air were collected onto filters, and the filters were analyzed by γ spectrometry at NIRS. The filter sampling was started on March 15, 2011 and was continued for more than 1 year. Several radionuclides, such as (131)I, (134)Cs, and (137)Cs were found by measuring the filters with a germanium detector. The air decontamination factor was around 0.64 for particulate (131)I and 0.58 for (137)Cs. These values could give implications for the ratio of indoor to outdoor radionuclide concentrations after the FDNPP accident for a similar type of building.

Estimation of internal exposure of the thyroid to (131)I on the basis of (134)Cs accumulated in the body among evacuees of the Fukushima Daiichi Nuclear Power Station accident

Namie Town was heavily contaminated by the Fukushima Daiichi Nuclear Power Station accident. The thyroid equivalent dose for residents who lived in Namie was estimated using results of whole body counting examinations which were carried out by the Japan Atomic Energy Agency a few months after the nuclear accident. Photon peaks of (131)I and (134)Cs were previously measured by the authors using a NaI(Tl) scintillation spectrometer and that information was used to estimate the (131)I/(134)Cs activity ratio of total intake in the present study. The maximum values of (131)I/(134)Cs activity ratio corresponding to thyroid uptake factors of 0.3, 0.1 and 0.03 were evaluated to be 0.9, 2.6 and 8.7, respectively. The maximum value of the (131)I/(134)Cs activity ratio was used to obtain the most conservative thyroid equivalent dose estimation. The maximum internal exposure of the thyroid to (131)I on the basis of (134)Cs accumulated in the body measured by the whole body counter was estimated to be 18mSv. This value was much smaller than 50mSv that the International Atomic Energy Agency recommends as the dose at which exposed persons should take stable iodine tablets.