Abstract
A severe accident occurred in March 2011 at the Fukushima Dai-ichi nuclear power plant (FDNPP) operated by the Tokyo Electric Power Company (TEPCO), causing serious environmental pollution over a wide range covering eastern Japan and the northwestern Pacific. This accident created a large mark in the atmospheric radionuclide chronological record at the Meteorological Research Institute (MRI). This paper reports the impacts from the FDNPP accident over approximately 3 years in Tsukuba, Ibaraki (approximately 170 km southwest from the accident site), as a typical example of the atmospheric pollution from the accident. The monthly atmospheric 90Sr and 137Cs depositional fluxes in March 2011 reached approximately 5 Bq/m2/month and 23 kBq/m2/month, respectively. They are 3–4 and 6–7 orders of magnitude higher, respectively, than before the accident. Sr-90 pollution was relatively insignificant compared to that of 137Cs. The 137Cs atmospheric concentration reached a maximum of 38 Bq/m3 during March 20–21, 2011. After that, the concentrations quickly decreased until fall 2011 when the decrease slowed. The pre-FDNPP accident 137Cs concentration levels were, at most, approximately 1 μBq/m3. The average level 3 years after the accident was approximately 12 μBq/m3 during 2014. The atmospheric data for the 3 years since the accident form a basis for considering temporal changes in the decreasing trends and re-suspension (secondary emission), supporting our understanding of radioCs’ atmospheric concentration and deposition. Information regarding our immediate monitoring, modeling, and data analysis approaches for pollution from the FDNPP accident is provided in the Appendices.
Highlights
The heat and blast at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident resulted in the leakage of a huge amount of anthropogenic radionuclides, near the levels of the Chernobyl accident in 1986, into the environment (IAEA 2006; Janžekovič and Križman 2011; Nuclear and Industrial Safety Agency (NISA) 2011), as seen on both the domestic and Northern Hemispheric scale (Hernández-Ceballos et al 2012; Masson et al 2011; Takemura et al 2011; Tanaka 2013)
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; Ministry of Education (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)
After April 2011, the sample size was reduced to two trays, each 1 m2, which we considered sufficient for the levels present after the FDNPP accident
Summary
The heat and blast at the FDNPP accident resulted in the leakage of a huge amount of anthropogenic radionuclides, near the levels of the Chernobyl accident in 1986, into the environment (IAEA 2006; Janžekovič and Križman 2011; NISA 2011), as seen on both the domestic and Northern Hemispheric scale (Hernández-Ceballos et al 2012; Masson et al 2011; Takemura et al 2011; Tanaka 2013). To evaluate their radioactive pollution levels, the aerosol components were radiochemically extracted from the HV filter sample to analyze the radioSr and assess the emission ratios of 137Cs, 89Sr, and 90Sr. We have conducted observational research on radionuclides in the environment for almost 60 years at the Meteorological Research Institute (MRI) in Japan, ever since the 1950s when the USA, Soviet Union, and others performed vigorous nuclear tests in the atmosphere. Other information about the accident, related to our immediate monitoring and modeling endeavors and data analysis approaches to short-lived γ-emitters and 89Sr, is summarized in the Appendices
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