NISA says that damage at the Fukushima nuclear power plant has resulted in the release of a massive amount of radioactive substances, which are a risk to human health and the environment over a wide area. It says the radiation dosage levels accumulated over a 25-day period at some locations in Fukushima Prefecture exceed the maximum permissible dosage for a full year. Data was collected at 53 locations, as a distance of up to 60 km from the Daiichi power plant, from March 12 through April 5th. At Namie Town, about 24 km northwest of the plant, over this period an accumulated dosage of 34 mSv of radiation was recorded. Prorated to a year, NISA says that this would mean 314 mSv per year, more than 3 times the maximum permissible aggregate dosage of 100 mSv per year for a nuclear power industry worker.
As a result the Japanese government has expanded the evacuation zone around the Fukushima Daiichi nuclear power plant to include areas where there is a risk of more than 20 mSv annual dosage. The expanded evacuation zone includes Namie Town, Iitate Village, parts of Minami Soma City.and other villages.