The time variation of dose rate artificially increased by the Fukushima nuclear crisis

Abstract

A car-borne survey for dose rate in air was carried out in March and April 2011 along an expressway passing northwest of the Fukushima Dai-ichi Nuclear Power Station which released radionuclides starting after the Great East Japan Earthquake on March 11, 2011, and in an area closer to the Fukushima NPS which is known to have been strongly affected. Dose rates along the expressway, i.e. relatively far from the power station were higher after than before March 11, in some places by several orders of magnitude, implying that there were some additional releases from Fukushima NPS. The maximum dose rate in air within the high level contamination area was 36 μGy h−1, and the estimated maximum cumulative external dose for evacuees who came from Namie Town to evacuation sites (e.g. Fukushima, Koriyama and Nihonmatsu Cities) was 68 mSv. The evacuation is justified from the viewpoint of radiation protection.

Low dose ionizing radiation produces too few reactive oxygen species to directly affect antioxidant concentrations in cells

“…We calculated the direct effects of radiolysis on antioxidant concentrations at a total (external þ internal) radiation dose rate of 417 mGy h 21 low LET radiation, representative of the highest doses to organisms in the Chernobyl zone (see electronic supplementary material) and also relevant to current contamination densities and dose rates at Fukushima [14]. No significant changes in antioxidant concentrations or cellular redox potential were calculated.…”

Radiation dose rates now and in the future for residents neighboring restricted areas of the Fukushima Daiichi Nuclear Power Plant

“…In the early stages of radiation exposure following the FDNPP accident, short-lived radionuclides such as 132 Te and 133 Xe were observed (9,10) and were noted as a major source of external exposure. The outdoor external dose rate within 80 km of the FDNPP decreased by 11% from June to November 2011 (i.e., less than 1 y after the accident) owing to the physical decay of 134 Cs (half-life of 2.07 y) and weathering (11); however, radiation exposure from deposited 137 Cs (half-life of 30.2 y) (i.e., groundshine) will persist long term.…”

Investigation of Absorbed Dose Rate in Air by a Car-borne Survey in Namie Town, Fukushima Prefecture

“…The values obtained in the car-borne survey indicate the radiation dose along paved roads, which are covered by asphalt. According to previous reports, 3,20) the observation of lower dose rates over sealed surfaces can be explained by easier removal of deposited radionuclides from them. Contamination in the air can be eliminated away more easily by rain and is also diluted by resuspension from wind, which is easier along sealed surface by concrete/asphalt rather than unsealed surface such as forested areas where contamination adheres to soil particles and plants.…”

“…Thus, car-borne surveys of radiation doses in the environment have been conducted by many research groups. 3, 6, 11~13) HOSODA et al 3) reported that the highest dose rate of 36 Gy h -1 was measured in Namie Town on April 11 th , 2011. Furthermore, a similarly high value of more than 30 Gy h -1 was measured in Akougi, Namie Town on April 18 th -21 st , 2011.…”

“…1,6) In addition, the highest dose rates were reported in Iitate Village and Namie Town, located at the northwest of the FDNPP. 3,7) Following the release of the artificial radionuclides to nearby residences, the public and many scientists were concerned about the radiation contamination in food and water sources. In particular, concerns were raised regarding long-lived radionuclides such as 137 Cs (T 1/2 : 30.05 y) and 134 Cs (T 1/2 : 2.04 y) which can accumulate in the organs if they are introduced into the body.…”