Comparison of Radioactivity Release and Contamination from the Fukushima and Chernobyl Nuclear Power Plant Accidents

Abstract

Although both the Fukushima Daiichi Nuclear Power Plant (FNPP) accident in 2011 and the Chernobyl NPP Unit 4 (CNPP) accident in 1986 are classified as Level 7, the worst nuclear incidence on the International Nuclear and Radiological Event Scale by the International Atomic Energy Agency, there are various differences between the two, including the accident process, released radionuclide composition, and meteorological and geological conditions. The amounts of iodine-131 (131I) and cesium-137 (137Cs) released into the atmosphere were about six times smaller after the FNPP accident compared to the CNPP accident. Cesium-137 is the most important radionuclide in considering long-term effects of nuclear accidents. According to Chernobyl laws in Ukraine, Belarus and Russia, depending on the level of 137Cs contamination, the contaminated territories were classified as alienation zone (>1480 kBq m−2), obligatory resettlement zone (555–1480 kBq m−2) and voluntarily resettlement zone (185–555 kBq m−2). The areas of the corresponding zones around FNPP were 272, 459 and 1405 km2, respectively, which were 11–15 times smaller compared to the CNPP accident. Meanwhile, the number of affected people around FNPP was only three to five times smaller compared to CNPP, reflecting the higher population density for the FNPP accient. Cumulative exposures for the 1st year 1 m above ground (normalized to the initial 137Cs deposition of 1 MBq m−2) were 63 mGy for the FNPP accident, while it was 500 mGy for the CNPP accident because more various radionuclides were emitted in case of the CNPP accident than the FNPP accident. Cumulative exposures at 30 years were evaluated to be 500 mGy and 970 mGy for the FNPP accident and the CNPP accident, respectively.