Article

2011 Fukushima Dai-ichi nuclear power plant accident: Summary of regional radioactive deposition monitoring results

Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyodaku, Tokyo 102-8554, Japan.
Journal of Environmental Radioactivity (Impact Factor: 2.48). 11/2011; 111:13-7. DOI: 10.1016/j.jenvrad.2011.09.003
Source: PubMed

ABSTRACT

After the Great East Japan Earthquake and resulting Tsunami on March 11, 2011, serious accident of the Fukushima Dai-ichi Nuclear Power Plant has been occurred. Huge amounts of radionuclides were released in atmosphere and ocean. Japanese prefectural governments have carried out environmental radioactivity monitoring; external dose rate, radioactivity measurements in environmental samples and others. Since March 18, 2011, daily and monthly deposition samples were collected in 45 stations covering Japanese Islands and radionuclides in the deposition samples were determined. We summarize radioactive deposition data reported by Japanese Government and study the depositional behaviors of the Fukushima-derived radionuclides. The results revealed that Fukushima-derived radioactive cloud dominantly affected in the central and eastern part of Honshu-Island, although it affected all of Japanese land area and also western North Pacific. The temporal change of the Fukushima-derived (137)Cs revealed that the apparent atmospheric residence time of the Fukushima-derived (137)Cs in sites within 300 km from the Fukushima Dai-ichi NPPis about 10 d.

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Available from: Katsumi Hirose
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    • "Following the accident of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), large areas were contaminated by radioactive atmospheric fallouts onto soils, forests and villages of the region (NERH, 2011). The most contaminated soils (where initial 137 Cs contamination exceeded 100 kBq/m 2 ) cover an area of 3000 km 2 , situated below a plume extending some 50 km north-west of the FDNPP (MEXT, 2011; Chino et al., 2011; Hirose, 2012; Hisamatsu, 2012; Chartin et al., 2013) and are drained by several coastal rivers. Consequently, waters and solid particles transferred from the contaminated soils to the rivers by erosion and runoff represent durable vectors for the contamination of the water resource which is extremely precious in this region. "
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    ABSTRACT: To investigate riverine transfers from contaminated soils of the Fukushima Prefecture in Japan to the marine environment, suspended sediments, filtered water, sediments and detrital organic macro debris deposited onto river beds were collected in November 2013 within small coastal rivers during conditions of low flow rates and low turbidity. River waters were directly filtered on the field and high efficiency well-type Ge detectors were used to analyse radiocaesium concentrations in very small quantities of suspended particles and filtered water (a few mg to a few g). For such base-flow conditions, our results show that the watersheds studied present similar hydro-sedimentary behaviours at their outlets and that the exports of dissolved and particulate radiocaesium are comparable. Moreover, the contribution of these rivers to the instantaneous export of radiocaesium to the ocean is similar to that of the Abukuma River. Our preliminary results indicate that, in the estuaries, radiocaesium concentrations in suspended sediments would be reduced by more than 80%, while radiocaesium concentration in filtered waters would be maintained. Significant correlations between radiocaesium concentrations and radiocaesium inventories in the soils of the catchments indicate that there was at that time little intra and inter-watershed variability in the transfer processes of radiocaesium from lands to rivers at this regional scale. The apparent liquidesolid partition coefficient (K D) values acquired for the lowest loads/finest particles complement the values acquired by using sediment traps and highlight the strong capacity of the smallest particles to transfer radiocaesium. Finally, but not least, our observations suggest that there could be a significant transfer of highly contaminated detrital biomass from forest litter to the downstream rivers in a rather conservative way.
    Full-text · Article · Nov 2016 · Journal of Environmental Radioactivity
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    • "In case of a Fukushima-like nuclear severe accident, soils contamination will likely result from the washout of radionuclides by precipitations. This was confirmed by measurements of soils cesium contamination in the first days following the Fukushima accident which have shown higher activities downwind of the radioactive plumes after snow and rainfall events (Katsumi, 2012). The monitoring of cesium deposits is particularly important because contamination measurements of Cs-137 after the Chernobyl accident revealed that this radionuclide may remain adsorbed on the surface of the soils for decades making their use impossible (Giani and Helmers, 1997). "
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    ABSTRACT: Latest investigation completed at IRSN has revealed the substantial influence of flow morphology around the drops, in atmospheric washout of fine aerosol particles by precipitations, in complement to classical mechanisms. Moreover, several authors have claimed that rain drops during stormy rainfall carry millions of elementary electric charges which could increase by couple orders of magnitude the collection efficiency as a consequence of electrostatic forces. In non-thunderstorm clouds, model calculations indicate that the image charge effect resulting from aerosol charging can significantly affect their washout, even by uncharged raindrops.However, investigations on the influence of electric charges on aerosol washout (or collection efficiency) by simulated raindrops are very fragmented and contradictory.In this article, we report results of self-charged water drop generated by hypodermic needle over charge values comparable to those reported in the literature during stormy rainfall. We also controllably charged aerosol particles by corona discharge and evaluate how it affects their collection efficiency. Electric charges on drops and aerosols are precisely monitored by high resolution electrometers. Our preliminary results tend to accredit the impact of electric charges in collection efficiency.
    Full-text · Article · Dec 2015 · Annals of Nuclear Energy
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    • "Many authors have attempted to determine the environmental impacts of the FDNPP accident, which have gradually come to light (e.g., Aoyama et al. 2012, 2013; Hirose 2012; Kusakabe et al. 2013; Masson et al. 2011; Masumoto et al. 2012; MEXT 2011a ; MEXT and USDOE 2011; Povinec et al. 2013a, b; Tsumune et al. 2013; Yamamoto et al. 2012; Yoshida and Kanda 2012; Yoshida and Takahashi 2012). We still need to study the following issues from an atmospheric science point of view (Igarashi 2009): (1) primary source terms including emissions inventory and temporal changes (e.g., Chino et al. 2011; Katata et al. 2012, b, 2014; Maki et al. 2013; Stohl et al. 2012; Terada et al. 2012; Winiarek et al. 2012), (2) transport and diffusion (e.g., Masson et al. 2011; Morino et al. 2011; Sekiyama et al. 2015; Stohl et al. 2012; Takemura et al. 2011; Tanaka 2013; Terada et al. 2012), and (3) dry and wet removal (e.g., Adachi et al. 2013; Hirose et al. 1993; Kristiansen et al. 2012), which governed radioactive surface contamination during the early phase of the accident. In addition, the physical and chemical properties of the radioactive materials (e.g., Adachi et al. 2013; Kaneyasu et al. 2012) are important factors that influence the second and third subjects to be investigated. "

    Full-text · Dataset · Dec 2015
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