Environmental radioactivity levels of the Fukushima Dai-ichi nuclear power plant and the Chernobyl nuclear power plant

To evaluate the environmental contamination and contributory external exposure immediately after the accident at the Fukushima Nuclear Power Plant (FNPP) and to evaluate the current environmental contamination and contributory external exposure at the Chernobyl Nuclear Power Plant (CNPP), the concentrations of artificial radionuclides in soil samples from each area were analyzed by gamma spectrometry. Six artificial radionuclides (iodine-131, cesium-134, cesium-137, tellurium-129m, niobium-95, and cesium-136) were detected in soil samples around FNPP, whereas cesium-137 was only detected in soil samples around CNPP and in Nagasaki. Calculated external effective doses from artificial radionuclide contamination in soil samples around FNPP were 3.7-5.7 micro-Sv/h in Fukushima city as of March 22, 2011, 0.11 micro-Sv/h in Iwaki city, and 0.18 micro-Sv/h in Ono town as of April 7, 2011. On the other hand, calculated external effective doses in soil samples around CNPP were 0.00023 micro-Sv/h in Gomel city and 0.00041 micro-Sv/h in Klincy city in January 2011. Moreover, the calculated external effective dose in soil was 0.00010 micro-Sv/h in Nagasaki city in August 2010. The present study revealed that artificial radionuclides derived from the accident were detected in soil samples around FNPP even though current levels are decreasing gradually. Also, the dose rates from external exposure around FNPP immediately after the accident, especially in Fukushima city, were higher than those around CNPP and in Nagasaki. Long-term environmental monitoring around FNPP, as well as evaluation of health effects in the population residing around these areas, contribute to radiation safety with a reduction in unnecessary exposure to the residents.