A radiation hotspot has been detected in Tokyo, reports said yesterday as researchers carry out stringent tests to map how far contamination has spread from the crippled Fukushima Dai-ichi nuclear power plant.
Japanese media said researchers found radiation levels of 3.35 microsieverts per hour along a street in the west of the capital — 220km from Fukushima — much higher than previously reported levels.
According to calculations based on the Japanese science ministry’s criteria, the equivalent annual dose in the hotspot would be 17.6 millisieverts, just below the 20 millisieverts per year threshold that requires evacuation.
The reading is also higher than levels measured recently at Iitate, an area in Fukushima Prefecture that has been evacuated.
The reading in Tokyo’s Setagaya ward was taken 1m above the ground near a hedge, national broadcaster NHK said, while other parts of the same sidewalk showed lower readings.
The reading came after ward authorities said on Wednesday that levels of 2.7 microsieverts per hour had been detected on Thursday last week, higher than levels of less than 0.1 microsieverts in other parts of Setagaya according to official data.
The higher readings come as more tests illustrate how far fallout from the Fukushima disaster have spread, with elevated levels of radioactive cesium recently found as far away as Yokohama, more than 241km from the plant.
Radiation fears are a daily fact of life in many parts of Japan following the earthquake and tsunami-sparked meltdowns at the plant, with reported cases of contaminated water, beef, vegetables, tea and seafood.
Variable winds, weather and topography result in an uneven spread of contamination, experts say, and radioactive elements tend to concentrate in places where dust and rainwater accumulate, such as drains and ditches.
Setagaya did not immediately confirm yesterday’s reading.
“We don’t know the cause [of the high radiation levels] yet. We are asking experts to find it urgently and decontaminate the area,” a spokeswoman said.
She added that the high readings have been shown only in a 2m long area and below 1.5m from the ground.
“We also plan to check sand in the ward’s 258 parks over one month from late October,” she said.
Radiation levels in the area have not fallen since the ward’s efforts to decontaminate it on Oct. 6 and authorities are instructing children to avoid the walkway as they go to school.
Setagaya Mayor Nobuto Hosaka told TBS: “I thought the reading must be a mistake when I first heard. We will push ahead with decontamination after confirming levels are high.”