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Kubota Y.,Japan National Institute of Radiological Sciences | Takahashi H.,Tokyo Nuclear Services Co. | Watanabe Y.,Japan National Institute of Radiological Sciences | Fuma S.,Japan National Institute of Radiological Sciences | And 9 more authors.
Journal of Environmental Radioactivity | Year: 2015

The dose rates of radiation absorbed by wild rodents inhabiting a site severely contaminated by the Fukushima Dai-ichi Nuclear Power Plant accident were estimated. The large Japanese field mouse (Apodemus speciosus), also called the wood mouse, was the major rodent species captured in the sampling area, although other species of rodents, such as small field mice (Apodemus argenteus) and Japanese grass voles (Microtus montebelli), were also collected. The external exposure of rodents calculated from the activity concentrations of radiocesium (134Cs and 137Cs) in litter and soil samples using the ERICA (Environmental Risk from Ionizing Contaminants: Assessment and Management) tool under the assumption that radionuclides existed as the infinite plane isotropic source was almost the same as those measured directly with glass dosimeters embedded in rodent abdomens. Our findings suggest that the ERICA tool is useful for estimating external dose rates to small animals inhabiting forest floors; however, the estimated dose rates showed large standard deviations. This could be an indication of the inhomogeneous distribution of radionuclides in the sampled litter and soil. There was a 50-fold difference between minimum and maximum whole-body activity concentrations measured in rodents at the time of capture. The radionuclides retained in rodents after capture decreased exponentially over time. Regression equations indicated that the biological half-life of radiocesium after capture was 3.31d. At the time of capture, the lowest activity concentration was measured in the lung and was approximately half of the highest concentration measured in the mixture of muscle and bone. The average internal absorbed dose rate was markedly smaller than the average external dose rate (<10% of the total absorbed dose rate). The average total absorbed dose rate to wild rodents inhabiting the sampling area was estimated to be approximately 52 μGyh-1 (1.2 mGyd-1), even 3 years after the accident. This dose rate exceeds 0.1-1mGyd-1 derived consideration reference level for Reference rat proposed by the International Commission on Radiological Protection (ICRP). © 2015 Elsevier Ltd. Source


Fuma S.,Japan National Institute of Radiological Sciences | Kubota Y.,Japan National Institute of Radiological Sciences | Ihara S.,Hokkaido University of Education | Takahashi H.,Tokyo Nuclear Services Co. | And 4 more authors.
Journal of Environmental Radioactivity | Year: 2016

Analysis of radioactivity data obtained under the food monitoring campaign in Japan indicates that elevated 134Cs+137Cs activity concentrations in wild boar meat remained constant or slowly decreased in Fukushima and surrounding prefectures from 2011 to 2015. The activity concentrations in some samples are still over the regulatory limit of 100 Bq kg−1 fresh weight, even in 2015. Activity concentrations of 137Cs in muscle of wild boars we captured in 2011 were higher than those in kidney, liver, spleen, heart and lung. A food processing retention factor, Fr, was 0.5 or 0.6 for 137Cs when the wild boar meat was boiled, suggesting that a parboiling process is effective for reduction of radiocaesium intake from wild boar meat. © 2016 Elsevier Ltd Source


Ishii N.,Japan National Institute of Radiological Sciences | Koiso H.,Tokyo Nuclear Services Co. | Takeda H.,Japan National Institute of Radiological Sciences | Uchida S.,Japan National Institute of Radiological Sciences
Journal of Nuclear Science and Technology | Year: 2010

The partitioning ratios of 14C in solid, liquid, and gas phases were determined by batch sorption tests using 97 paddy soil samples. Each of the soil samples was suspended in deionized water containing [1, 2- 14C] sodium acetate and shake-incubated for 7 days. More than 65% of the spiked 14C was released into the air, approximately 30% was partitioned into the solid phase, and the 14C remaining in the liquid phase was only a few percent. These results suggested that if the 14C incorporated into acetate migrated from a TRU repository site to paddy fields, most of the 14C would be released into the air and the rest would be partitioned into the soil phase. It is likely that microorganisms in the soils are responsible for these partitioning ratios because about 97% of the spiked 14C remained in the liquid phase in the microorganism-depleted sample. © Atomic Energy Society of Japan. Source


Kawamura K.,Japan National Institute of Radiological Sciences | Naganawa M.,Japan National Institute of Radiological Sciences | Konno F.,Japan National Institute of Radiological Sciences | Yui J.,Japan National Institute of Radiological Sciences | And 12 more authors.
Nuclear Medicine and Biology | Year: 2010

Introduction: Imidazoline receptors (IRs) have been established as distinct receptors, and have been categorized into at least two subtypes (I1R and I2R). I2Rs are associated with depression, Alzheimer's disease, Huntington's disease and Parkinson's disease. A few positron emission tomography (PET) probes for I2Rs have been synthesized, but a selective PET probe has not been evaluated for the imaging of I2Rs by PET. We labeled a selective I2R ligand 2-(3-fluoro-4-tolyl)-4,5-dihydro-1H-imidazole (FTIMD) with 11C and performed the first imaging of I2Rs by PET using 2-(3-fluoro-[4-11C]tolyl)-4,5-dihydro-1H-imidazole ([11C]FTIMD). Methods: [11C]FTIMD was prepared by a palladium-promoted cross-coupling reaction of the tributylstannyl precursor and [11C]methyl iodide in the presence of tris(dibenzylideneacetone)dipalladium(0) and tri(o-tol)phosphine. Biodistribution was investigated in rats by tissue dissection. [11C]FTIMD metabolites were measured in brain tissues and plasma. Dynamic PET scans were acquired in rats, and the kinetic parameters estimated. Results: [11C]FTIMD was successfully synthesized with a suitable radioactivity for the injection. Co-injection with 0.1 mg/kg of cold FTIMD and BU224 induced a significant reduction in the brain-to-blood ratio 15 and 30 min after the injection. In metabolite analysis, unchanged [11C]FTIMD in the brain was high (98%) 30 min after the injection. In PET studies, high radioactivity levels were observed in regions with a high density of I2R. The radioactivity levels and VT values in the brain regions were prominently reduced by 1.0 mg/kg of BU224 pretreatment as compared with control. Conclusion: [11C]FTIMD showed specific binding to I2Rs in rat brains with a high density of I2R. © 2010 Elsevier Inc. Source


Takata H.,Japan National Institute of Radiological Sciences | Takata H.,Marine Ecology Research Institute | Aono T.,Japan National Institute of Radiological Sciences | Zheng J.,Japan National Institute of Radiological Sciences | And 3 more authors.
Analytical Methods | Year: 2013

A highly sensitive and simple analytical method is applied to the determination of Cs in estuarine and coastal waters. This analytical method combines adsorption of Cs on ammonium 12-molybdophosphate (AMP) and an ion exchange resin column, followed by subsequent ICPMS measurement. Significantly, the method requires a relatively small amount of sample volume (minimum volume: 20 mL) for the analysis by the selection of AMP with a low Cs impurity (0.02 ng-Cs mg-1-AMP). The method has a detection limit of 1.0 ng L -1 and a limit of quantification of 3.3 ng L-1 based on replicate analyses of purified water samples. A sample storage strategy is also investigated: no time dependent changes are found in the concentrations for acidified samples (pH 1.0-1.5) used immediately (storage: 0 day) to those stored for two months in a dark place at room temperature (4-20 °C) or in a freezer (ca. -20 °C). Respective Cs concentrations of 95.8 ± 0.9, 202.8 ± 3.6 and 197.0 ± 1.9 ng L-1 are obtained in estuarine water (SLEW-3), coastal seawater (CASS-4) and seawater (NASS-5) certified reference materials for heavy metals. In an application of the method to determination of Cs in estuarine and coastal regions of Japan, the obtained Cs concentrations vary from 11.2 to 306.4 ng L-1 at a salinity range of 0.1 to 33.6. This journal is © 2013 The Royal Society of Chemistry. Source

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