Evaluation of Environmental Contamination and Estimated Radiation Doses for the Return to Residents’ Homes in Kawauchi Village,Fukushima Prefecture

To evaluate the environmental contamination and radiation exposure dose rates due to artificial radionuclides in Kawauchi Village, Fukushima Prefecture, the restricted area within a 30-km radius from the Fukushima Dai-ichi Nuclear Power Plant (FNPP), the concentrations of artificial radionuclides in soil samples, tree needles, and mushrooms were analyzed by gamma spectrometry. Nine months have passed since samples were collected on December 19 and 20, 2011, 9 months after the FNPP accident, and the prevalent dose-forming artificial radionuclides from all samples were ¹³⁴Cs and ¹³⁷Cs. The estimated external effective doses from soil samples were 0.42–7.2 µSv/h (3.7–63.0 mSv/y) within the 20-km radius from FNPP and 0.0011–0.38 µSv/h (0.010–3.3 mSv/y) within the 20–30 km radius from FNPP. The present study revealed that current levels are sufficiently decreasing in Kawauchi Village, especially in areas within the 20- to 30-km radius from FNPP. Thus, residents may return their homes with long-term follow-up of the environmental monitoring and countermeasures such as decontamination and restrictions of the intake of foods for reducing unnecessary exposure. The case of Kawauchi Village will be the first model for the return to residents’ homes after the FNPP accident.     

Measurement of Individual Doses of Radiation by Personal Dosimeter Is Important for the Return of Residents from Evacuation Order Areas after Nuclear Disaster

To confirm the availability of individual dose evaluation for the return of residents after the accident at the Fukushima Dai-ichi Nuclear Power Plant (FNPP), we evaluated individual doses of radiation as measured by personal dosimeters in residents who temporarily stayed in Evacuation Order Areas in Kawauchi village, which is partially located within a 20 km radius of the FNPP. We also compared individual doses with the external radiation doses estimated from the ambient dose rates and with doses estimated from the concentrations of radionuclides in the soil around each individual’s house. Individual doses were significantly correlated with the ambient doses in front of the entrances to the houses (r = 0.90, p<0.01), in the backyards (r = 0.41, p<0.01) and in the nearby fields (r = 0.80, p<0.01). The maximum cumulative ambient doses in the backyards and fields around the houses were 6.38 and 9.27 mSv/y, respectively. The maximum cumulative individual dose was 3.28 mSv/y, and the median and minimum doses were 1.35 and 0.71 mSv/y. The estimated external effective doses from concentrations of artificial radionuclides in soil samples ranged from 0.03 to 23.42 mSv/y. The individual doses were moderately correlated with external effective doses in the backyards (r = 0.38, p<0.01) and in the fields (r = 0.36, p<0.01); however, the individual doses were not significantly correlated with the external effective doses in front of the entrances (r = 0.01, p = 0.92). Our study confirmed that individual doses are low levels even in the evacuation order area in Kawauchi village, and external effective dose levels are certainly decreasing due to the decay of artificial radionuclides and the decontamination of contaminated soil. Long-term follow-up of individual doses as well as internal-exposure doses, environmental monitoring and reconstruction of infrastructure are needed so that residents may return to their hometowns after a nuclear disaster.     

Reconstruction of local fallout composition and gamma-ray exposure in a village contaminated by the first USSR nuclear test in the Semipalatinsk nuclear test site in Kazakhstan

After the disintegration of the USSR in end of 1991, it became possible for foreign scientists to visit Kazakhstan, in order to investigate the radiological consequences of nuclear explosions that had been conducted at the Semipalatinsk nuclear test site (SNTS). Since the first visit in 1994, our group has been continuing expeditions for soil sampling at various areas around SNTS. The current level of local fallout at SNTS was studied through γ-spectrometry for ¹³⁷Cs as well as α-spectrometry for ^239,240Pu. Average values of soil inventory from wide areas around SNTS were 3,500 and 3,700 Bq m^?2 for ¹³⁷Cs and ^239,240Pu, respectively, as of January 1, 2000. The average level of ¹³⁷Cs is comparable to that in Japan due to global fallout, while the level of ^239,240Pu is several tens of times larger than that in Japan. Areas of strong contamination were found along the trajectories of radioactive fallout, information on which was declassified after the collapse of the USSR. Our recent efforts of soil sampling were concentrated on the area around the Dolon village heavily affected by the radioactive plume from the first USSR atomic bomb test in 1949 and located 110 km east from ground zero of the explosion. Using soil inventory data, retrospective dosimetry was attempted by reconstructing γ-ray exposure from fission product nuclides deposited on the ground. Adopting representative parameters for the initial ¹³⁷Cs deposition (13 kBq m^?2), the refractory/volatile deposition ratio (3.8) and the plume arrival time after explosion (2.5 h), an absorbed dose in air of 600 mGy was obtained for the 1-year cumulative dose in Dolon village, due to the first bomb test in 1949. Considering possible ranges of the parameters, 350 and 910 mGy were estimated for high and low cases of γ-ray dose in air, respectively. It was encouraging that the deduced value was consistent with other estimations using thermal luminescence and archived monitoring data. The present method can be applied to other settlements affected by local fallout from SNTS.     

Analysis of Plasma Protein Concentrations and Enzyme Activities in Cattle within the Ex-Evacuation Zone of the Fukushima Daiichi Nuclear Plant Accident

The effect of the Fukushima Daiichi Nuclear Power Plant (FNPP) accident on humans and the environment is a global concern. We performed biochemical analyses of plasma from 49 Japanese Black cattle that were euthanized in the ex-evacuation zone set within a 20-km radius of FNPP. Among radionuclides attributable to the FNPP accident, germanium gamma-ray spectrometry detected photopeaks only from ¹³⁴Cs and ¹³⁷Cs (radiocesium) commonly in the organs and in soil examined. Radioactivity concentration of radiocesium was the highest in skeletal muscles. Assuming that the animal body was composed of only skeletal muscles, the median of internal dose rate from radiocesium was 12.5 μGy/day (ranging from 1.6 to 33.9 μGy/day). The median of external dose rate calculating from the place the cattle were caught was 18.8 μGy/day (6.0–133.4 μGy/day). The median of internal and external (total) dose rate of the individual cattle was 26.9 μGy/day (9.1–155.1 μGy/day). Plasma levels of malondialdehyde and superoxide dismutase activity were positively and glutathione peroxidase activity was negatively correlated with internal dose rate. Plasma alanine transaminase activity and percent activity of lactate dehydrogenase (LDH)-2, LDH-3 and LDH-4 were positively and LDH-1 was negatively correlated with both internal and total dose rate. These suggest that chronic exposure to low-dose rate of ionizing radiation induces slight stress resulting in modified plasma protein and enzyme levels.     

Estimated Dietary Intake of Radionuclides and Health Risks for the Citizens of Fukushima City,Tokyo, and Osaka after the 2011 Nuclear Accident

The radionuclides released from the Fukushima Daiichi nuclear power plant in 2011 pose a health risk. In this study, we estimated the 1st-year average doses resulting from the intake of iodine 131 (¹³¹I) and cesium 134 and 137 (¹³⁴Cs and ¹³⁷Cs) in drinking water and food ingested by citizens of Fukushima City (∼50 km from the nuclear power plant; outside the evacuation zone), Tokyo (∼230 km), and Osaka (∼580 km) after the accident. For citizens in Fukushima City, we considered two scenarios: Case 1, citizens consumed vegetables bought from markets; Case 2, citizens consumed vegetables grown locally (conservative scenario). The estimated effective doses of ¹³⁴Cs and ¹³⁷Cs agreed well with those estimated through market basket and food-duplicate surveys. The average thyroid equivalent doses due to ingestion of ¹³¹I for adults were 840 µSv (Case 1) and 2700 µSv (Case 2) in Fukushima City, 370 µSv in Tokyo, and 16 µSv in Osaka. The average effective doses due to ¹³⁴Cs and ¹³⁷Cs were 19, 120, 6.1, and 1.9 µSv, respectively. The doses estimated in this study were much lower than values reported by the World Health Organization and the United Nations Scientific Committee on the Effects of Atomic Radiation, whose assessments lacked validation and full consideration of regional trade in foods, highlighting the importance of including regional trade. The 95th percentile effective doses were 2–3 times the average values. Lifetime attributable risks (LARs) of thyroid cancers due to ingestion were 2.3–39×10⁻⁶ (Case 1) and 10–98×10⁻⁶ (Case 2) in Fukushima City, 0.95–14×10⁻⁶ in Tokyo, and 0.11–1.3×10⁻⁶ in Osaka. The contributions of LARs of thyroid cancers due to ingestion were 7.5%–12% of all exposure (Case 1) and 12%–30% (Case 2) in Fukushima City.     

Artificial radionuclides in aquatic plants of the Yenisei River in the area affected by effluents of a Russian plutonium complex

The Yenisei River, one of the largest rivers in the world, is contaminated with artificial radionuclides released by one of the Russian nuclear plants, which produces weapons-grade plutonium and has been in operation for many years. The aim of the study that was conducted between 1997 and 2002 was to investigate accumulation of artificial radionuclides by aquatic plants of the Yenisei River. The aquatic plants sampled were: Potamogeton lucens (shining weed) and Fontinalis antipyretica (water moss). The -spectrometric analysis of the samples of aquatic plants for artificial radionuclides has revealed a wide spectrum of long-lived and short-lived radionuclides. Artificial radionuclides such as ⁵¹Cr, ⁵⁴Mn, ⁵⁸Co, ⁶⁰Co, ⁶⁵Zn, ¹³⁷Cs, and ¹⁵²Eu were found in aquatic plants collected both near the plutonium complex and 194 km downstream in the river. The radiochemical analysis of aquatic plants revealed strontium and isotopes of plutonium. Fontinalis antipyretica had very high concentration factors of the principal radionuclides: 14220, 3110 and 500 of ⁵¹Cr, ⁴⁶Sc and ²³⁹Np, respectively.     

Internal Radiation Exposure Dose in Iwaki City,Fukushima Prefecture after the Accident at Fukushima Dai-ichi Nuclear Power Plant

As a result of the accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) on 11 March 2011, a huge amount of radionuclides, including radiocesium, was released and spread over a wide area of eastern Japan. Although three years have passed since the accident, residents around the FNPP are anxious about internal radiation exposure due to radiocesium. In this study, we screened internal radiation exposure doses in Iwaki city of Fukushima prefecture, using a whole-body counter. The first screening was conducted from October 2012 to February 2013, and the second screening was conducted from May to November 2013. Study participants were employees of ALPINE and their families who underwent examination. A total of 2,839 participants (1,366 men and 1,473 women, 1–86 years old) underwent the first screening, and 2,092 (1,022 men and 1,070 women, 1–86 years old) underwent the second screening. The results showed that 99% of subjects registered below 300 Bq per body in the first screening, and all subjects registered below 300 Bq per body in the second screening. The committed effective dose ranged from 0.01–0.06 mSv in the first screening and 0.01–0.02 mSv in the second screening. Long-term follow-up studies are needed to avoid unnecessary chronic internal exposure and to reduce anxiety among the residents by communicating radiation health risks.     

Dose assessment for the Metlino and Muslyumovo populations who lived along the Techa river from 1949 to 1954

In the period from 1949 to 1956, liquid radioactive waste was routinely and accidentally discharged by the Mayak Production Association, Southern Urals, Russia, into the Techa river. Based on a novel approach, the contamination of the Techa river water, the bottom sediments and the adjacent flood plains was modelled, and internal and external doses were estimated for two villages located downstream of the site of liquid radioactive waste release. Altogether, 11 radionuclides that occurred in the liquid radioactive waste were included in the calculations. The results suggest significantly higher doses than previously assumed, with the major contribution in the year 1951. Radionuclides with half-lives of less than 1 year, such as ⁸⁹Sr, ¹³¹I, ⁹⁵Zr+⁹⁵Nb, ¹⁰³Ru+^103mRh, ¹⁴⁰Ba+¹⁴⁰La, and ¹⁴⁴Ce+¹⁴⁴Pr, represent the major sources and, in contrast, long-lived radionuclides, such as ⁹⁰Sr and ¹³⁷Cs that have so far been assumed to be most important, did not dominate the doses. For adults from the village Metlino, located 7 km downstream of the site of liquid radioactive waste discharge, the committed effective doses due to intake of radionuclides were calculated to be about 2.3 Sv, while the external doses were between about 1.2 Sv and 6.9 Sv. On the other hand, for adults from Muslyumovo, located 75 km downstream, the commited effective doses due to intake of radionuclides were calculated to be about 0.5 Sv, while the external doses were between 0.5 Sv and 2.0 Sv. The values for the skin doses to the Metlino and Muslyumovo populations were about 7.1 Sv and 1.3 Sv, respectively. It is concluded that the current dose estimates for the residents of the Techa river need, therefore, reevaluation.     

Assessment of Elevated Radionuclide Levels in Soils Associated with an Avian Colony in a High Arctic Environment

This article presents the results of an investigation into the occurrence of elevated levels of radionuclides in soils associated with a seabird colony in the Arctic. Soils and other materials were collected from a seabird colony (primarily composed of kittiwakes) in Kongsfjorden, located in the High Arctic archipelago of Svalbard. The samples were analyzed for a suite of gamma emitting natural and anthropogenic radionuclides, including ¹³⁷Cs and nuclides of the ²³⁸U and ²³²Th series, to establish the level of enrichment and the behavior of the radionuclides in the immediate area. The results indicate that soils near the colony exhibit enrichment factors of 8 for ¹³⁷Cs, 5 for ²³⁸U and 2 for ²²⁶Ra compared to the nuclide content of soils from the general area. The spatial patterns of the nuclides in the soil are consistent with enrichment of the soil via run-off draining from a large accumulation of fecal and nesting material that has developed at the base of the colony. ¹³⁷Cs ingress to the soil appears to have peaked at some point in the past as patterns of enrichment at the colony are different to those exhibited by ²³⁸U, which must be assumed to be a steady state contribution. The means of introduction of radionuclides to the colony remains unclear but the transfer of ¹³⁷Cs from the marine environment to the terrestrial environment via the food chain and deposition of feces is discussed.     

Concentration of Radiocesium in the Wild Japanese Monkey (Macaca fuscata) over the First 15 Months after the Fukushima Daiichi Nuclear Disaster

Following the massive earthquake that struck eastern Japan on March 11, 2011, a nuclear reactor core meltdown occurred at the Fukushima Daiichi Nuclear Power Plant, operated by Tokyo Electric Power Company, and was followed by the release of large amounts of radioactive materials. The objective of this study was to measure the concentration of radiocesium ¹³⁴Cs and ¹³⁷Cs in the muscle of Japanese monkeys (Macaca fuscata) inhabiting the forest area of Fukushima City and to determine the change in concentration over time as well as the relationship with the level of soil contamination. Cesium concentrations in the muscle of monkeys captured at locations with 100,000–300,000 Bq/m² were 6,000–25,000 Bq/kg in April 2011 and decreased over 3 months to around 1,000 Bq/kg. However, the concentration increased again to 2,000–3,000 Bq/kg in some animals during and after December 2011 before returning to 1,000 Bq/kg in April 2012, after which it remained relatively constant. This pattern of change in muscle radiocesium concentration was similar to that of the change in radiocesium concentration in atmospheric fallout. Moreover, the monkeys feed on winter buds and the cambium layer of tree bark potentially containing higher concentrations of radiocesium than that in the diet during the rest of the year. The muscle radiocesium concentration in the monkeys related significantly with the level of soil contamination at the capture locations.     

Bipolarization of Risk Perception about the Health Effects of Radiation in Residents after the Accident at Fukushima Nuclear Power Plant

The late health effects of low-dose rate radiation exposure are still a serious public concern in the Fukushima area even four years after the accident at Fukushima Daiichi Nuclear Power Plant (FNPP). To clarify the factors associated with residents’ risk perception of radiation exposure and consequent health effects, we conducted a survey among residents of Kawauchi village in May and June 2014, which is located within 30 km of FNPP. 85 of 285 residents (29.8%) answered that acute radiation syndrome might develop in residents after the accident, 154 (54.0%) residents responded that they had anxieties about the health effects of radiation on children, and 140 (49.1%) residents indicated that they had anxieties about the health effects of radiation on offspring. Furthermore, 107 (37.5%) residents answered that they had concerns about health effects that would appear in the general population simply by living in an environment with a 0.23 μSv per hour ambient dose for one year, 149 (52.2%) residents reported that they were reluctant to eat locally produced foods, and 164 (57.5%) residents believed that adverse health effects would occur in the general population by eating 100 Bq per kg of mushrooms every day for one year. The present study shows that a marked bipolarization of the risk perception about the health effects of radiation among residents could have a major impact on social well-being after the accident at FNPP.     

Global searches for microalgae and aquatic plants that can eliminate radioactive cesium, iodine and strontium from the radio-polluted aquatic environment: a bioremediation strategy

The Fukushima 1 Nuclear Power Plant accident in March 2011 released an enormously high level of radionuclides into the environment, a total estimation of 6.3 × 10¹⁷ Bq represented by mainly radioactive Cs, Sr, and I. Because these radionuclides are biophilic, an urgent risk has arisen due to biological intake and subsequent food web contamination in the ecosystem. Thus, urgent elimination of radionuclides from the environment is necessary to prevent substantial radiopollution of organisms. In this study, we selected microalgae and aquatic plants that can efficiently eliminate these radionuclides from the environment. The ability of aquatic plants and algae was assessed by determining the elimination rate of radioactive Cs, Sr and I from culture medium and the accumulation capacity of radionuclides into single cells or whole bodies. Among 188 strains examined from microalgae, aquatic plants and unidentified algal species, we identified six, three and eight strains that can accumulate high levels of radioactive Cs, Sr and I from the medium, respectively. Notably, a novel eustigmatophycean unicellular algal strain, nak 9, showed the highest ability to eliminate radioactive Cs from the medium by cellular accumulation. Our results provide an important strategy for decreasing radiopollution in Fukushima area.     

Estimation of soil-to-plant transfer factors of radiocesium in 99 wild plant species grown in arable lands 1 year after the Fukushima 1 Nuclear Power Plant accident

One year after the deposition of radionuclides from the Fukushima 1 Nuclear Power Plant (A formal name is Fukushima Daiichi Nuclear Power Station) in March 2011, radiocesium (¹³⁴Cs, ¹³⁷Cs) concentrations ([Cs]) were comprehensively investigated in the wild plants of 99 species most of which were annual or summer green perennial herbs and started to grow from April 2012 at the heavily contaminated fields of paddy (three study sites) and upland (one study site) in Fukushima Prefecture. The survey was conducted three times (April, July and October) in the year. In each site, soils (soil cores of 5-cm depth) and plants (aerial shoots) were collected for determination of [Cs] on a dry weight basis, and then the transfer factor (TF) of radiocesium from soil to plant ([Cs]_plant/[Cs]_soil) was estimated in each species. The [Cs] values of both soils and plants largely varied. However, some species exhibited relatively high TF values (more than 0.4) (e.g., Athyrium yokoscense, Dryopteris tokyoensis, and Cyperus brevifolius), while others exhibited almost negligible values (less than 0.01) (e.g., Salix miyabeana, Humulus scandens, and Elymus tsukushiensis). In addition, judging from the 11 species grown in both paddy and upland fields, TF values were generally higher in the paddy fields. The estimation of phytoextraction efficiency of soil radiocesium by weed communities in the paddy fields suggests that the weed community is not a practical candidate for phytoremediation technique.     

Long-term external radiation exposure of inhabitants in the western Bryansk region of Russia as a consequence of the Chernobyl accident

The western Bryansk region in south-western Russia was highly contaminated with ¹³⁷Cs and ¹³⁴Cs due to the Chernobyl accident in 1986. In 1990, a joint Nordic-Russian project was initiated in order to make measurements and estimates of the absorbed doses to selected groups of inhabitants in this area. The participating individuals were living in small villages with contamination levels between 0.9 and 2.7 MBq m^–2. Only some villages had been decontaminated. Both schoolchildren and adults participated in the study and the number of persons was between 100 and 130 each year, residing in 5 villages. Every year in September–October, from 1990 to 1998, we performed individual measurements of external absorbed doses, assessed with thermoluminescent (TL) dosemeters (LiF). The mean effective dose per year from external irradiation due to the Chernobyl accident of the inhabitants in the villages ranged between 0.8 and 2.9 mSv during the study period and decreased with an apparent half-time of 3.7–8.2 years, depending on village and group. The highest individual doses within one village were, on average higher by a factor of 3 than the mean value for that village. Under the conservative assumption of a decrease rate in the external effective dose of 2% per year after 1998, individuals in the most highly exposed village are assumed to receive a life-time effective dose of about 75 mSv (between 1986 and 2056) from external exposure to caesium radionuclides. The mean value for the villages under study was estimated to be around 65 mSv using the assumed rate of decrease. Received: 20 December 2000 / Accepted: 1 October 2001     

Radionuclide concentrations in the diet of residents in a high level natural radiation area in Iran

Concentrations of ¹³⁷Cs and ²²⁶Ra in the diet (foodstuffs and drinking water) of adult inhabitants in the high-level natural radiation area (HLNRA) of Ramsar, Iran have been determined. The annual intake of foodstuffs was estimated on the basis of their average annual consumption. Food samples collected from local markets were analyzed by means of a gamma spectrometer. The estimated annual dietary intakes of ¹³⁷Cs and ²²⁶Ra were 130Bq and 245Bq, respectively. The concentrations of natural radionuclides in food and drinking water of the residents are higher than the world average, and are correlated with the high concentration of these radionuclides in soil and water. Calculations were also made to determine the potential dose to an individual consuming such diets.     

Transfer of radionuclides to ants, mosses and lichens in semi-natural ecosystems

There is a scarcity of data on transfer of both natural and anthropogenic radionuclides to detritivorous invertebrates for use in the assessment of radiation exposure. Although mosses and lichens have been extensively used in biomonitoring programs, the data on transfer of radionuclides to these species are limited, particularly for natural radionuclides. To enhance the available data, activity concentrations of ¹³⁷Cs, ²²⁶Ra and ²²⁸Ra were measured in ants, mosses and lichens and corresponding undisturbed soil collected from semi-natural ecosystems in Serbia and Montenegro and biota/soil concentration ratios (CR) calculated. Since the majority of internal dose to biota is expected to come from ⁴⁰K, the activity concentrations of this radionuclide were also determined. The mean CR values for ¹³⁷Cs, ²²⁶Ra and ²²⁸Ra in ants analyzed in this study were found to be 0.02, 0.06 and 0.02, respectively. The mean CR values of radionuclides in mosses were found to be 2.84 for ¹³⁷Cs, 0.19 for ²²⁶Ra and 0.16 for ²²⁸Ra, while those in lichens were found to be 1.08 for ¹³⁷Cs, 0.15 for ²²⁶Ra and 0.13 for ²²⁸Ra. The CR values obtained in this study were compared with default CR values used in the ERICA Tool database and also with those reported in other studies.     

Measurement of resuspended aerosol in the Chernobyl area

Size distribution measurements of particulate radionuclides were performed at two sites in the Chernobyl 30-km exclusion zone using several cascade impactors. The results obtained in the period September 1986 till June 1993 were discussed with regard to the general assumption of a log-normal activity size distribution in inhalation dose assessment. At Zapolie (a site 14 km from the Chernobyl reactor) a bimodal distribution was observed in 91% of all measured distributions. In most cases the medians were about 4 µm and in the range 20–30 µm. According to soil granulometric data this finding was explained by superimposing two processes: local resuspension and advective transport of radioactive aerosol from highly contaminated territories. The mean air concentration showed an increasing proportion of inhalable particles over the years since the accident. In 1993 the inhalable fraction was about 48% of the total concentration. At Pripyat, a site situated within a highly contaminated area, unimodal types of size distributions were predominant with the median diameters in the range 5–10 µm for ¹³⁷Cs. For the three nuclides ¹³⁷Cs, ¹⁴⁴Ce and ¹⁰⁶Ru, very similar types of distribution were observed. Apparently, the radioactive aerosol was of fuel origin. During a forest fire at a distance of 17 km, the majority of the radioactivity was associated with submicrometer particles with median diameters in the range 0.28–0.50 µm.     

Radionuclides in siberian Thymallus from radiation-contaminated area in the middle stream of the Yenisei River

Concentration of artificial radionuclides in bodies of arctic grayling from the radioactively contaminated zone of the Yenisei River in the vicinity of the Mining-and-Chemical Combine of Rosatom was investigated in 2007-2010. Gamma-spectrometric analysis revealed artificial radionuclides in all the organs and tissues of fish. The isotope composition was the most diverse (60Co, 65Zn, 85Sr, 99Mo, 106Ru, 137Cs, 144Ce) in internal organs of grayling. The activity of radionuclides increased in internal organs including liver and kidney and in the content of digestive tract of grayling during winter and spring, which coincided with the change in the feeding spectrum of grayling. The trophic transfer factor of radionuclides from zoobenthos (Philolimnogammarus spp.) to whole bodies and muscles of grayling was over 1 (1.8-2.4) only for natural radionuclide 40K. The trophic transfer of artificial radionuclides (60Co, 65Zn, 137Cs) to muscles and bodies of grayling was one-two orders of magnitude less effective.     

Removal Efficiency of Radioactive Cesium and Iodine Ions by a Flow-Type Apparatus Designed for Electrochemically Reduced Water Production

The Fukushima Daiichi Nuclear Power Plant accident on March 11, 2011 attracted people’s attention, with anxiety over possible radiation hazards. Immediate and long-term concerns are around protection from external and internal exposure by the liberated radionuclides. In particular, residents living in the affected regions are most concerned about ingesting contaminated foodstuffs, including drinking water. Efficient removal of radionuclides from rainwater and drinking water has been reported using several pot-type filtration devices. A currently used flow-type test apparatus is expected to simultaneously provide radionuclide elimination prior to ingestion and protection from internal exposure by accidental ingestion of radionuclides through the use of a micro-carbon carboxymethyl cartridge unit and an electrochemically reduced water production unit, respectively. However, the removability of radionuclides from contaminated tap water has not been tested to date. Thus, the current research was undertaken to assess the capability of the apparatus to remove radionuclides from artificially contaminated tap water. The results presented here demonstrate that the apparatus can reduce radioactivity levels to below the detection limit in applied tap water containing either 300 Bq/kg of ¹³⁷Cs or 150 Bq/kg of ¹²⁵I. The apparatus had a removal efficiency of over 90% for all concentration ranges of radio–cesium and –iodine tested. The results showing efficient radionuclide removability, together with previous studies on molecular hydrogen and platinum nanoparticles as reactive oxygen species scavengers, strongly suggest that the test apparatus has the potential to offer maximum safety against radionuclide-contaminated foodstuffs, including drinking water.     

Measurement of absorbed doses from X-ray baggage examinations to tooth enamel by means of ESR and glass dosimetry

The contribution of radiation from X-ray baggage scans at airports on dose formation in tooth samples was investigated by electron spin resonance (ESR) dosimetry and by glass dosimetry. This was considered important, because tooth samples from population around the Semipalatinsk Nuclear Test Site (SNTS), Kazakhstan, had been transported in the past to Hiroshima University for retrospective dose assessment of these residents. Enamel samples and glass dosimeters were therefore examined at check-in time at Kansai airport (Osaka, Japan), Dubai airport (Dubai, United Arab Emirates) and Domodedovo airport (Moscow, Russia). These airports are on the route from Kazakhstan to Japan. Three different potential locations of the samples were investigated: in pocket (without X-ray scans), in a small bag (with four X-ray scans) and in large luggage (with two X-ray scans). The doses obtained by glass and ESR dosimetry methods were cross-compared. As expected, doses from X-ray examinations measured by glass dosimetry were in the μGy range, well below the ESR detection limit and also below the doses measured in enamel samples from residents of the SNTS.