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Journal Articles

External exposure dose estimation by electron spin resonance technique for wild Japanese macaque captured in Fukushima Prefecture

Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Mitsuyasu, Yusuke*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; Osaka, Ken*; et al.

Radiation Measurements, 134, p.106315_1 - 106315_4, 2020/06

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

The relationship between the CO$$_{2}$$ radical intensity and the absorbed dose (dose response curve) of tooth enamel of Japanese macaque was observed by electron spin resonance and the detection limit of our system was estimated to be 33.5 mGy, which is comparable to the detection limit for human molar teeth. Using the dose response curve, external exposure dose for seven wild Japanese macaques captured in Fukushima prefecture were examined. The results suggest that the external exposure dose for the wild Japanese macaques were ranged between 45 mGy to 300 mGy.

Journal Articles

The 20th Workshop on Environmental Radioactivity

Koarai, Kazuma

Hosha Kagaku, (40), p.26 - 27, 2019/09

Report about "The 20th Workshop on Environmental Radioactivity" was submitted in ${it hoshakagaku}$. There were 195 participants in the workshop. They actively discussed environmental radioactivity and pollution after the Fukushima-Daiichi Nuclear Power Plant. Presentation awards were given to 4 persons.

Journal Articles

Studies on incorporation of $$^{90}$$Sr and $$^{137}$$Cs in hard tissues of cattle and monkey in the Fukushima environment

Koarai, Kazuma

Hosha Kagaku, (40), p.34 - 36, 2019/09

Abstract of doctor thesis was submitted to "Hoshakagaku", which is Japanese article. I described main theme of the thesis. The hard tissues of the animals incorporated $$^{90}$$ at the development stage and bone methabolism of the tissues. On the other hand, $$^{137}$$Cs was incorporated not only the development stage but also after the stage. Strontium-90 and cesium-137 in the cattle teeth reflected the pollution after the Fukushima-Daiichi Nuclear Power Plant accident. The thesis showed $$^{90}$$ and $$^{137}$$Cs in the hard tissues would an important indicator of the environmental pollution.

Oral presentation

Trial of rapid measurement for $$^{90}$$Sr in animal bone by ICP-MS

Koarai, Kazuma; Matsueda, Makoto; Yanagisawa, Kayo*; Fujiwara, Kenso; Kitamura, Akihiro

no journal, , 

Strontium-90 and $$^{90}$$Y, its daughter nuclide, adverse effects on the bone marrow. Monitring of $$^{90}$$Sr have been required after the Fukushima-Daiichi Nuclear Power Plant. However, radioactivity measurement method requires a complicated separation and a time-consuming $$beta$$-ray measurement. ICP-MS system has been applied to $$^{90}$$Sr contamination survey of soil and water samples. We applied the ICP-MS system for the bones for the first time. In this study, reference bone was used as measurement samples. After sample preparation, $$^{90}$$Sr was determined using ICP-MS system with cascade separation steps based on on-line column separation and oxygen reaction. Strontium-90 in the bones was successfully separated from Ca, Ba, Y, Zr, Fe, and Ge, which interfered in ICP-MS measurement, in the separation steps. We found that the ICP-MS system could be applied to the rapid measurement of $$^{90}$$Sr in the bones.

Oral presentation

Examination of solid phase extraction of $$^{90}$$Sr in bones for ICP-MS analysis

Koarai, Kazuma; Matsueda, Makoto; Yanagisawa, Kayo*; Fujiwara, Kenso; Kitamura, Akihiro

no journal, , 

Strontium-90 ($$^{90}$$Sr) is one of an artificial radionuclide after the Fukushima-Daiichi Nuclear Power Plant accident. The ICP-MS system for $$^{90}$$Sr have been developed. The ICP-MS system could apply to measurement of $$^{90}$$Sr in soils and water. In this study, solid phase extraction method of $$^{90}$$Sr was optimized the ICP-MS system for bones. After MW digestion, fish bone was dissolved in 2.6 M nitric acid. Sr resin was used for solid phase extraction of $$^{90}$$Sr in a flow-injection system. Sr and interference elements were determined with ICP-MS. Chemical yield of Sr was over 90% in the solid phase extraction system. Interference elements were removed in the extraction. The extraction method could applied to the ICP-MS system for $$^{90}$$Sr. The method required only 30 minutes. The ICP-MS system would be rapid method for $$^{90}$$Sr measurement in bones.

Oral presentation

Evaluation and correction of Sr-90 value in bones quantified by online solid phase ICP-MS

Matsueda, Makoto; Koarai, Kazuma; Yanagisawa, Kayo*; Fujiwara, Kenso; Kitamura, Akihiro

no journal, , 

Sr-90 accumulates in hard tissues such as bones and teeth in the case of uptake into the human or animal bodies. Therefore, the analysis of these hard tissues from the viewpoint of exposure evaluation has required, but the conventional radioactivity analysis requires a period of about one month, it is difficult to process a large number of samples. From this thing, we tried to apply application of the online solid phase extraction/ICP-MS method which can be measured quickly compared to radioactivity analysis. This method has mainly been utilizing as the analysis of Sr-90 contained in the water samples such as rainwater, and it has already equipped the correction functions corresponding to the shift of recovery rate at the Sr resin and the sensitivity shift in ICP-MS. However, hard tissues contain a large amount of matrix. Therefore, we investigated whether the isobaric interference, stable Sr, and other high matrix influence to Sr-90 values and attempted to correct the values.

Oral presentation

External dose estimation of Japanese macaque and Procyon lotor using electron spin resonance spectroscopy

Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Ono, Takumi*; Tamaki, Hiroaki*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; et al.

no journal, , 

Releases of the radioactive materials from the Fukushima Daiichi Nuclear Power Plant accident result in an ionization exposure to people and animals, the precise dosimetry is required. To estimate the external dose due to the accident, we utilize electron spin resonance (ESR) spectroscopy which is a powerful tool for the dosimetry of external dose. The detection limit of this technique was 146 mGy, so that we have to improve the detection limit for the precise dosimetry. In this work, we developed a novel enamel-dentine separation technique and improved the detection limit down to 43 mGy, and estimated the external dose for Japanese macaque and Procyon lotor collected in Fukushima prefecture.

Oral presentation

Incorporation record of radionuclides in teeth and otoliths

Koarai, Kazuma; Matsueda, Makoto; Fujiwara, Kenso; Ono, Takumi*; Kino, Yasushi*; Oka, Toshitaka; Okutsu, Kenichi*; Takahashi, Atsushi*; Suzuki, Toshihiko*; Shimizu, Yoshinaka*; et al.

no journal, , 

We have investigated incorporation of $$^{90}$$Sr and $$^{137}$$Cs in teeth of cattle and otoliths of fish. Specific activity of $$^{90}$$Sr in the dentin tissue was higher than that in the enamel tissue. The result shows change of $$^{90}$$Sr incorporation in cattle even within a tooth. Concentrations of stable Sr and Cs were 94 ppm and 3 ppb. Distributions of stable Sr and Cs were uniform in the otolith of fish. If distribution of $$^{90}$$Sr and $$^{137}$$Cs in the otolith was measured, change of $$^{90}$$Sr and $$^{137}$$Cs incorporation into the fish would be found. These findings suggest that distribution patterns of $$^{90}$$Sr and $$^{137}$$Cs in the environment could be estimated from distribution of the radionuclides in the tooth and otolith.

Oral presentation

Rapid and simple concentration method for radionuclide analysis of environmental samples

Matsueda, Makoto; Koarai, Kazuma; Fujiwara, Kenso; Kitamura, Akihiro

no journal, , 

Radionuclide analysis of environmental water requires large amount of samples to be concentrated, because generally the radionuclide level is very low. In order to achieve rapid and simple concentration method, we applied homogeneous liquid-liquid extraction for sample enrichment. This method extracts the desired solute existing in the homogeneous solution into the water-immiscible phase by time and pH dependent phase separations. Since the method forms large surface area of the interface between the solvent and the desired solute, we only need small amount of extraction solvents to migrate desired solute into the formed phase. In this study, we tried two kind of phase separation phenomenon. (1) pH dependent extraction. (2) Ionic liquid extraction.

Oral presentation

Sample preparation procedure for the estimation of external exposure dose of wild animals using elecron spin resonance spectroscopy

Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Mitsuyasu, Yusuke*; Ono, Takumi*; Tamaki, Hiroaki*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

no journal, , 

Release of the radioactive materials from Fukushima Daiichi Nuclear Power Plant accident results in a long-term low dose rate ionization exposure to wild animals. The biological effects of the wild animal do not show a clear correlation with the external dose, which is estimated from the external dose rate of the captured point of the animal, a precise external dose estimation using ESR and tooth enamel is required instead of using the external dose rate. In this work, we attempted to estimate the external dose of wild Japanese macaque and Procyon lotor captured in the high dose rate area.

Oral presentation

External exposure dose of Japanese macaque captured in Fukushima prefecture

Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Mitsuyasu, Yusuke*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; Osaka, Ken*; et al.

no journal, , 

Due to the Fukushima Daiichi Nuclear Power Plant accident, the exposure dose estimation for human is examined by the whole body counter or by the Fukushima Health Management Survey, however, the precise estimated dose cannot obtained by such methods. We applied electron spin resonance (ESR) dosimetry for the external dose estimation using tooth enamel of human/animal. As we reported last year, we improved the detection limit of ESR dosimetry down to 43 mGy. We used this improved ESR dosimetry system and attempted to estimate the external dose of wild Japanese macaque capture in Fukushima prefecture, however, the metal component which may obstruct the ESR measurement was observed, so that we cannot estimate the external dose. In this work, we investigated how to remove such metal components, obtain the clear ESR spectrum, and estimate the external dose.

Oral presentation

System validation of ICP-MS measurement for determination of $$^{90}$$Sr in hard tissues of animals

Koarai, Kazuma; Matsueda, Makoto; Aoki, Jo; Yanagisawa, Kayo*; Fujiwara, Kenso; Terashima, Motoki; Kitamura, Akihiro; Abe, Hironobu

no journal, , 

Strontium-90 and $$^{90}$$Y, its daughter nuclide, adverse effects on the bone marrow. Monitoring of $$^{90}$$Sr in the bones have been required after the Fukushima-Daiichi Nuclear Power Plant accident. However, conventional radioactivity measurement method for $$^{90}$$Sr requires a complicated separation of $$^{90}$$Y and a time-consuming measurement. ICP-MS system has been applied to $$^{90}$$Sr concentration survey of water, soil, and edible part of fish. We applied the ICP-MS system for the bones. We determined $$^{90}$$Sr in the hard tissues of animals that collected in the Fukushima prefecture. Limit of detection in the measurement was 19 Bq/kg.

Oral presentation

Strontium-90 measurement in trace amount of hard tissues for distribution analysis

Koarai, Kazuma; Matsueda, Makoto; Aoki, Jo; Yanagisawa, Kayo*; Fujiwara, Kenso; Terashima, Motoki; Kino, Yasushi*; Oka, Toshitaka; Okutsu, Kenichi*; Yamashita, Takuma*; et al.

no journal, , 

We demonstrated a method of $$^{90}$$Sr measurement in small pieces of hard tissues with radioactivity measurement or ICP-MS measurement. Interference elements of the measurements were removed by chemical separation. We could determine $$^{90}$$Sr in 0.1 g of hard tissues by radioactivity measurement method and ICP-MS method. Limit of detection of the ICP-MS method was lower than that of the radioactivity measurement. The ICP-MS method is adequate method for distribution analysis of $$^{90}$$Sr in the hard tissues.

Oral presentation

Sample preparation procedure for ESR dosimetry using teeth of wild animal

Oka, Toshitaka; Mitsuyasu, Yusuke*; Takahashi, Atsushi*; Koarai, Kazuma; Kino, Yasushi*; Sekine, Tsutomu*; Okutsu, Kenichi*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

no journal, , 

Releases of the radioactive materials from the Fukushima Daiichi Nuclear Power Plant accident result in a low dose exposure to wild animals. The external dose of wild animals is commonly estimated by the external dose rate of the captured point, but the estimated exposure dose has huge uncertainties because the size of the habitat and/or the movement of the wild animals are not included in the estimation. To estimate the external dose precisely, we utilize electron spin resonance (ESR) dosimetry. In this work, we investigated the sample preparation procedure of wild animals. The ESR spectrum of enamel of racoon captured in Namie-town, Fukushima has a broad ESR signal due to metal components. The linear relationship between the Co$$_{2}$$ intensity and the absorbed dose that we can apply ESR dosimetry for racoon teeth. Using this relationship, the external exposure dose was estimated.

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