Small radiation hotspots have been detected in Tokyo, and radioactive strontium has been found in nearby Yokohama seven months into the nuclear crisis, stoking worries in the nation’s most populated areas far from the crippled Fukushima plant.
The Daiichi nuclear power plant, struck by a huge quake and tsunami in March, released radiation into the atmosphere that was carried by winds and deposited widely by rain and snow in eastern Japan.
Setagaya, a major residential area in Tokyo about 235km southwest of the plant, said this week it found a radioactive hotspot on a pavement near schools. The radiation there measured as much as 2.7 microsieverts per hour, higher than some areas in the evacuation zone near the plant.
Washing down the area with water did not help lower the radiation levels, Setagaya Mayor Nobuto Hosaka said but added the district had been advised it was safe for people to walk by.
The city of Funabashi in Chiba, near Tokyo, said today a citizens’ group had measured a radiation level of 5.8 microsieverts per hour at a park and it was now making checks.
Government data this week showed radiation levels in the 20 km radius evacuation zone around the Daiichi plant ranged from 0.5 to 64.8 microsieverts per hour. About 80,000 residents were forced to evacuate from this zone.
The unit microsievert quantifies the amount of radiation absorbed by human tissue.
In Yokohama, radioactive strontium-90, which can cause bone cancer and leukaemia, was detected in soil taken from an apartment rooftop, media reports said.
Strontium has been detected within an 80km zone around the Daiichi plant, but this is the first time it has been found in an area so far away, the reports said.