Plutonium believed to be from the Fukushima No. 1 nuclear plant has been detected at 10 locations in four municipalities in Fukushima Prefecture, the science ministry said.
The highest reading was 11 becquerels of plutonium-238 per square meter, detected in the town of Namie, the ministry said Tuesday. That is about 1.4 times higher than the level that originated from fallout from nuclear weapons tests abroad.
The other municipalities are the town of Okuma, the village of Iitate and the city of Minamisoma.
The ministry said there was no health hazard, given the small quantities involved.
The findings were from a survey in which samples were taken at 62 locations within 100 km of the stricken plant. No plutonium was found in samples from areas 45 km or farther from the plant, the ministry said.
The ministry released similar investigation results last September that covered an area 80 km from the plant. This time, the ministry expanded the area to 100 km.
In the latest survey, plutonium-238 was detected in 10 of 62 locations. The farthest point was in Iitate, some 32 km from the plant.
Students file petition
A group of 18 Japanese and Brazilian high school students on Tuesday presented the secretariat of the U.N. Conference on Disarmament in Geneva with nearly 155,000 signatures they collected from across the globe that seek the abolition of nuclear weapons.
It is the 15th time that high school students selected by a civic organization in Nagasaki have visited the U.N. office in Switzerland since 1998. This year, the number of signatures the group collected was a record high, amounting to around double the average figure in the past, according to the delegation.
The group included five students from Hiroshima and Nagasaki, as well as three from Iwate and Fukushima prefectures, which were severely hit by the March 2011 quake and tsunami and are still affected by the nuclear disaster, and two youths from Brazil.
Each member of the group called for the elimination of nuclear weapons in English speeches at the U.N. European headquarters in Geneva, which houses the secretariat of the disarmament conference.
The students were set to fly to Japan on Thursday after conducting a signature-collection campaign in Berne, the Swiss capital.