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Volume 66, Issue 3
Special Articles : Radiation and Analytical Chemistry – Five Years since the Fukushima Daiichi Nuclear Power Plant Accident –
Displaying 1-8 of 8 articles from this issue
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Reviews
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Yuichiro KUMAMOTO, Michio AOYAMA, Yasunori HAMAJIMA, Hisao NAGAI, Take ...Article type: Reviews
2017 Volume 66 Issue 3 Pages 137-148
Published: March 05, 2017
Released on J-STAGE: April 07, 2017
JOURNAL FREE ACCESSWe reviewed studies concerning the spreading of radiocesium derived from the accident of Fukushima Daiichi Nuclear Power Plant in March 2011 into the North Pacific Ocean by the end of 2014, including our latest observational data. In the north of Kuroshio Front, which is derived from eastward-flowing Kuroshio and its extension currents in the south of Japan, namely in the mixing and subarctic areas, radiocesium atmospheric-deposited and directly-discharged had been transported eastward from off Japan to Gulf of Alaska along the North Pacific Current in the mid-latitude region in the surface layer above about 200 m depth. Just south of the front, the northern area of the subtropical area, atmospheric-deposited radiocesium had been transported southward in the subsurface layer between 200 and 400 m depth, approximately, due to the southward subduction of the subtropical mode water in the winter season. These observational results indicate that the Fukushima-derived radiocesium had spread into the whole western North Pacific Ocean by the end of 2014.View full abstractDownload PDF (19744K)
Accounts
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Yukihisa SANADA, Azusa ISHIZAKI, Yukiyasu NISHIZAWA, Yoshimi URABEArticle type: Accounts
2017 Volume 66 Issue 3 Pages 149-162
Published: March 05, 2017
Released on J-STAGE: April 07, 2017
JOURNAL FREE ACCESSThe Great East Japan Earthquake that occurred on 11 March 2011 generated a series of large tsunami waves that caused serious damage to the Fukushima Dai-ichi Nuclear Power Station, following which a large amount of radioactive material was discharged from the nuclear power plant into the environment. Airborne radiation measurements using a manned helicopter were applied to measure the radiation distribution immediately after accident as technique to quickly measure the radiation distribution over a wide area. In Japan, this technique was researched and developed in the 1980s. However, this technique and system were not applied immediately after the accident because standardization of analysis was not established and the Japanese system became deteriorated. This technique is important for post-accident studies at a nuclear facility. We summarized the methods of the airborne radiation measurement using a manned helicopter. In addition, measurement results of the dose rate distribution at the Fukushima Dai-ichi Nuclear Power Station are given in this paper.View full abstractDownload PDF (2164K)
Research Papers
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Shuntaro KINNO, Hiroshi OKOCHI, Naoya KATSUMI, Hiroko OGATA, Jun KATAO ...Article type: Research Papers
2017 Volume 66 Issue 3 Pages 163-174
Published: March 05, 2017
Released on J-STAGE: April 07, 2017
JOURNAL FREE ACCESSRadio-Cs concentrations in fresh leaves/needles, litter, surface soil, and stream sand were continuously investigated in a deciduous broadleaf forest and cedar forest in Namie-town, Fukushima prefecture from June 2012 to June 2016, except for snow-cover periods. The result of a car-borne survey from Fukushima city to Minamitsushima showed that the air dose rate declined faster than the physical attenuation due to decontamination, outside of forests. Radio-Cs concentrations (137Cs + 134Cs) in litter and surface soil in broadleaf forest were constant at 52.0, 102 kBq kg-dry−1, respectively from 2014. In a cedar forest, however, the radio-Cs concentrations in fresh needles and litter declined from 2012 to 2015, probably because of washing and leaching by throughfall, and radio-Cs was accumulated in surface soil. In broadleaf forest, the buffer depth of radio-Cs in soil (1.26 cm) which indicates the extent of infiltration into deeper layers was greater than in the cedar forest (1.14 cm) in April 2013. However, the buffer depth in the cedar forest overtook that in the broadleaf forest in December, 2015 (1.5 cm in broadleaf forest and 2.6 cm in cedar forest). The radio-Cs values in the stream bottom sand were concentrated in smaller sand (over 2 mm, 3.04; 0.21-2.0 mm, 10.2; under 0.21 mm, 54.5 kBq kg-dry−1 in downstream near the broadleaf forest and over 2.0 mm, 2.67, 0.21-2.0 mm, 7.95; under 0.21 mm, 41.3 kBq kg-dry−1 in the upstream area near the cedar forest). It is concerned that a part of them causes the outflow of radio-Cs as suspended sand. The relative radio-Cs concentration ratio between smaller bottom sand and surface soil, which indicates the outflow of radio-Cs from forest via stream declined (2013: 0.54, 2016: 0.29 in downstream and 2013: 1.4, 2016: 0.31 in the upstream region). However, we found that floating male flowers of cedar containing high radio-Cs (23.8 kBq kg-dry−1) could be another transport media in the spring.View full abstractDownload PDF (2259K) -
Kotaro OCHI, Kengo FUJII, Kenta HAGIWARA, Atsushi OHBUCHI, Yuya KOIKEArticle type: Research Papers
2017 Volume 66 Issue 3 Pages 175-180
Published: March 05, 2017
Released on J-STAGE: April 07, 2017
JOURNAL FREE ACCESSFukushima-derived radiocesium (134Cs and 137Cs) was spread out all over the world after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. After this accident, radiocesium was detected in soil at the Koshinetsu and Kanto regions. In this study, the activity concentration and the chemical forms of radiocesium in soil were analyzed for predicting any long-term effect of radiocesium in soil at low-dose areas. It is revealed that the distribution of radiocesium depends on the kind of clay minerals in soil. During passing years after the FDNPP accident, the activity concentrations of radiocesium in soil were nearly constant because of the insoluble chemical form. It is suggested that radiocesium would be fixed to minerals in soil for a long time.View full abstractDownload PDF (829K) -
Makoto FURUKAWA, Makoto MATSUEDA, Yoshitaka TAKAGAIArticle type: Research Papers
2017 Volume 66 Issue 3 Pages 181-187
Published: March 05, 2017
Released on J-STAGE: April 07, 2017
JOURNAL FREE ACCESSOnline solid phase extraction ICP-MS is superior to simple ICP-MS in the enhancement of the target signal. However, the elution of the matrix material, which is pre-concentrated with target elements on the column, can lead to a decrease in the signal intensity of the target elements due to the introduction of large amounts of matrix material into the plasma. To overcome this problem, the internal standard-corrected signal integration method was developed. The proposed method was conducted in such a way that the chromatogram-like concentrated elution peak and the continuous stable internal standard peak can be simultaneously observed, and the ratio of the signal intensities was integrated during measurement time. In this study, the proposed method was applied to the analysis of radioactive strontium (90Sr). When the apparent recovery percentage in the actual quantification exhibited 87 % without the use of the presented method, the recovery increased to 103 % by using the presented method. In addition, the quantification with the proposed system exhibited good repeatability, ranging from 5.2 to 12.6 % for ultra-trace amounts of radioactive strontium {0.4–2.0 ppq (equal to 2–10 Bq L−1)}.View full abstractDownload PDF (1252K)
Notes
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Takuma HORITA, Shiho ASAI, Miki KONDA, Yukiko HANZAWA, Kyoichi SAITO, ...Article type: Notes
2017 Volume 66 Issue 3 Pages 189-193
Published: March 05, 2017
Released on J-STAGE: April 07, 2017
JOURNAL FREE ACCESSA Sr adsorption fiber was prepared for rapid analysis of 90Sr content in the fiber using radiation-induced emulsion graft polymerization and subsequent chemical modification. A polyethylene fiber with a diameter of 13 μm was first immersed in a methanol solution of an epoxy-group-containing vinyl monomer, glycidyl methacrylate (GMA), and polyoxyethylene sorbitol ester (Tween20) as a surfactant for the graft-polymerization of GMA. Octadecylamine was then bound to a polymer chain extending from the fiber surface, providing hydrophobicity to the polymer chain. Dicyclohexano-18-crown-6 (DCH18C6) was finaly impregnated onto the polymer chain via a hydrophobic interaction between the octadecyl moiety of the polymer chain and the cyclohexyl moiety of DCH18C6. The fiber surface structure, characterized by DCH18C6 molecules loosely entangled with polymer chains, allowed for the rapid adsorption of Sr ions at an adsorption rate of approximately 100-times higher than that of a commercially available Sr-selective resin (Sr Resin®).View full abstractDownload PDF (865K) -
Kyuma SUZUKI, Shun WATANABE, Yumi ONOZEKI (YUASA), Hajime ARAI, Hideki ...Article type: Notes
2017 Volume 66 Issue 3 Pages 195-200
Published: March 05, 2017
Released on J-STAGE: April 07, 2017
JOURNAL FREE ACCESSThe accident of the Fukushima Dai-ichi Nuclear Power Plant in March, 2011, released large amounts of radiocesium into the atmosphere, and contaminated the environment of Gunma Prefecture in eastern Japan. In particular, 640 Bq kg–1-wet of radiocesium concentration was found in wakasagi (Hypomesus nipponensis) in Lake Onuma on Mt. Akagi in August, 2011. Thus, to elucidate the body-size effect in weight-dependent and dynamics of radiocesium in the ecosystem of Lake Onuma, we determined the age of wakasagi, the body-weight class of the radiocesium concentration in wakasagi and the effective ecological half-life (Teff) of radiocesium in wakasagi 0+ from 2012 to 2016. The body-size effect was found for the 137Cs concentration of wakasagi fished from 2012 to 2015, i.e., the concentration of 137Cs increased with the increase in its body weight. On the other hand, no body size effect was found in 2016. This result may be caused by the following two factors: the 137Cs concentration of the lake water reached a steady state after May 2014; wakasagi is a small plankton-feeding fish, while it is known that larger piscivorous fishes show the strong body size effect. Teff of the 137Cs concentration in wakasagi 0+ consists of two components, fast- and slow-term ones, and the decay rate of the 137Cs concentration in wakasagi 0+ was greatly reduced. As stated above, the radiocesium contamination in Lake Onuma has still been lasting; we are thus continuing our monitoring studies.View full abstractDownload PDF (750K)
Analytical Reports
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Naoto HAGURA, Haruaki MATSUURA, Takafumi UCHIYAMA, Yukiko OKADAArticle type: Analytical Reports
2017 Volume 66 Issue 3 Pages 201-204
Published: March 05, 2017
Released on J-STAGE: April 07, 2017
JOURNAL FREE ACCESSPassed five and a half years from the Great East Japan Earthquake, a large number of research papers on the distribution of radioactive material have been published. In this work, based on the monitoring value of the air-dose rate and the radioactive cesium concentration in Tokyo City University Atomic Energy Research Laboratory, we focused on the temporal change of these values and indicated the attenuation of the dose rate. According to the long-term monitoring results, before the Fukushima NPP accident the average of air-dose rate, which is the background level of the laboratory, was 0.034 μSv h–1. In Aug. 2013, the measured data was close to the background value. On the other hand, the concentration of radioactive cesium (Cs-137) decreased drastically until Sep. 2011, and after that the attenuation speed had been quite slow. We focused on the slow pace of the attenuation region, and indicated the correlation coefficient between the air-dose rate and the Cs-137 concentration of airborne particulate matter. As a result, we considered that the magnitude of the correlation coefficients might be related to the existence form of Cs-137.View full abstractDownload PDF (763K)
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