Japan eyes damage to spent nuclear fuel

Japanese authorities say high radiation
readings from one of the spent fuel pools at
the Fukushima Daiichi nuclear power plant
may be caused by radioactive debris from
outside rather than from damage to the fuel
rods inside.
A water sample taken from the pool that
houses the No. 4 reactor's old fuel rods
showed a higher-than-normal amount of
radioactive iodine-131, said Hidehiko
Nishiyama, the chief spokesman for the
Nuclear and Industrial Safety Agency. That's
an indication that the fuel rods may have
sustained some damage since the disaster,
but the cause was still under investigation, he
said.
The elevated radiation levels first reported
Wednesday were "not that high," Nishiyama
said. That suggesting the source may have
been radioactive debris blowing into the
pools from outside the badly damaged
building.
"If the fuel rod had some problems, the value
would go much higher," Nishiyama said.
The safety commission reported radioactivity
from iodine-131, the most commonly
measured reactor byproduct, at 84
millisieverts per hour on Wednesday -- a level
that would give plant workers their
maximum annual dose in about three hours.
Engineers have been struggling to stabilize
the crippled Fukushima Daiichi plant since
March 11, when the tsunami that followed
Japan's magnitude 9 earthquake knocked out
its cooling systems. The cores of of three of
the plant's six reactors were damaged by
overheating and resulting hydrogen
explosions in the early days of the disaster,
now classified as a top-scale nuclear accident.