Where the radiation went

摘要

Most of the radiation emitted by Japans Fukushima Daiichi nuclear power plant after March's earthquake was blowr out to sea, but some was deposited at hot spots on land. Toshimasa Ohara and his colleagues at the National Institute for Environmental Studies in Tsukuba, Japan, simulated the transport and deposition of iodine-131 and caesium-137, two radioactive materials that were released in large quantities. They found that 13% of iodine-131 and 22% of caesium-137 fell on land. Surprisingly, the deposition created hot spots at which caesium-137 levels reached up to 20 kilobecquerels per square metre as far away as the northern part of the Kanto Plain, some 250 kilometres from the plant.