Source: Reuters via
Scientific American
Date: October 13, 2011
by: Yoko Kubota
A radiation hotspot has been detected in Tokyo seven
months into Japan's nuclear crisis, but local officials said on Thursday
high readings appeared to be coming from mystery bottles stored under a
house, not the tsunami-crippled Fukushima atomic plant.
TOKYO (Reuters) - A radiation hotspot
has been detected in Tokyo seven months into Japan's nuclear crisis,
but local officials said on Thursday high readings appeared to be coming
from mystery bottles stored under a house, not the tsunami-crippled
Fukushima atomic plant.
The Fukushima Daiichi
nuclear power
plant, struck by a devastating quake and tsunami in March, has released
radiation into the atmosphere that has been carried by winds, rain and
snow across eastern Japan.
Officials in Setagaya, a major
residential area in Tokyo about 235 km (150 miles) southwest of the
plant, said this week it found a radioactive hotspot on a sidewalk near
schools, prompting concerns in the country's most populated area far
from the damaged nuclear plant.
The radiation measured as much as
3.35 microsieverts per hour on Thursday, higher than some areas in the
evacuation zone near the Fukushima plant, the center of the world's
worst nuclear disaster since Chernobyl 25 years ago.
But the local government found several bottles under the floor of a nearby house emitting high levels of radiation.
"A measuring device, when pointed at
them, showed very high readings. Radiation levels were even exceeding
the upper limit for the device," Setagaya Mayor Nobuto Hosaka told a
news conference.
Officials from the Education Ministry are now looking into the matter, including the contents of the bottles.
Public broadcaster NHK said no one had been living in the house in question.
The city of Funabashi, near Tokyo,
said that a citizens' group had measured a radiation level of 5.8
microsieverts per hour at a park, but that the city's own survey showed
the highest reading at the park was a quarter of that level.
Radiation levels in the 20 km radius
evacuation zone around the Fukushima Daiichi plant ranged from 0.5 to
64.8 microsieverts per hour, government data showed this week.
About 80,000 residents have evacuated this zone. A microsievert quantifies the amount of radiation absorbed by human tissue.
In Yokohama, also near Tokyo, radioactive strontium-90, which can cause bone
cancer and leukemia, was detected in soil taken from an apartment rooftop, media reported.
Strontium has been detected within an
80 km zone around the Fukushima Daiichi plant, but this is the first
time it has been found in an area so far away, local media added.
Radiation exposure from natural sources in a year is about 2,400 microsieverts on average, the U.N. atomic watchdog says.
Japan's education ministry has set a
standard allowing up to 1 microsievert per hour of radiation in schools
while aiming to bring it down to about 0.11 microsievert per hour.
(Additional reporting by Kiyoshi Takenaka; Editing by Yoko Nishikawa and Nick Macfie)