A map released by the Education, Culture, Sports, Science and Technology Ministry on Friday shows plutonium was found in soil samples taken from a total of six locations in Futabamachi, Namiemachi and Iitatemura, Fukushima Prefecture.
The map is based on a survey conducted by the ministry to determine how much soil around the power plant contains plutonium and strontium, which is also a hazardous radioactive substance.
The survey was conducted in June and July by sampling soil at 100 locations around the plant. The ministry compared the data obtained from the survey with data obtained in surveys conducted from fiscal 1999 to fiscal 2008 to measure the residual effects of radioactive fallout on Japan from nuclear atmospheric tests conducted during the Cold War.
A preliminary ministry calculation shows that the level of plutonium contamination in Namiemachi will remain at 0.027 millisieverts for about 50 years. The other five spots were contaminated with 0.55 to 2.3 becquerels of plutonium.
The farthest spot from the plant where plutonium was detected was in Iitatemura, about 45 kilometers from the plant.
Meanwhile, strontium-89 and strontium-90, both believed to have been released from the power plant, were detected at 45 spots.
The maximum quantity of strontium-90, whose half-life of about 29 years is much longer than the approximately 50-day half-life of strontium-89, was 5,700 becquerels per square meter detected in Futabamachi. This is six times that of the maximum quantity of 950 becquerels found before the Fukushima plant accident.