A large amount of radionuclides was released from the Fukushima Dai-ichi Nuclear Power Station (FDNPS) following the damage caused by the tsunami due to the Great East Japan Earthquake on 11 March 2011. Although many radionuclides in various environmental samples around the FDNPS have been measured, 3H in the terrestrial environment has not yet been reported. We present here the first survey results of 3H concentrations in plant samples collected around the FDNPS in 2011 from shortly after the accident. The free-water 3H concentrations in herbaceous plant shoots and evergreen tree leaves were considerably higher than the previous background concentration, and diminished with distance from the FDNPS. Although reconstruction of atmospheric 3H concentrations after the accident is difficult, a rough estimate of the radiation dose due to 3H inhalation about 20 km from the FDNPS is on the order of a few microsieverts (μSv).

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