The restoration of power to the stricken plant, 140 miles north of Tokyo, had
led to hopes that the threat of a meltdown and major radiation leak was
past.
But scientists say they are not out of the woods yet and they still face some
of the most difficult and dangerous tasks.
They include manually draining hundreds of gallons of radioactive water from
the plant and "bleeding" radioactive gas from the pumps and piping
of the emergency cooling systems.
Technicians are also increasingly concerned about salt build-up inside the
reactors caused by evaporated seawater.
Crusts forming around fuel rods could block cooling water from getting to the
radioactive fuel and cause them to start heating up again.
Hundreds of thousands of pounds of salt crystals are thought to have been
deposited around the plant and if it is too thick will need to be manually
chipped away.
Work making the plant safe also requires a technician to reach a dozen valves,
sometimes using a ladder – with a great risk of radiation exposure.
The treacherous nature of the tasks was underlined yesterday when three
workers were taken to hospital with radiation burns, caused by wading
through water as they laid cables.
Public alarm about the crisis increased earlier after officials announced that
levels of radioactive iodine had been detected in Tokyo’s tap water.
Despite levels having subsided yesterday the fear is that more radiation is
being released than has been first understood.
There were no fresh incidents of smoke or steam at the plant but four of the
plant's reactors are still considered volatile, although on the way to
stability.
"It's still a bit early to make an exact time prognosis, but my guess is
in a couple of weeks the reactors will be cool enough to say the crisis is
over," said Peter Hosemann, a nuclear expert at the University of
California.
"It will still be important to supply sufficient cooling to the reactors
and the spent fuel pools for a longer period of time. But as long as this is
ensured and we don't see any additional large amount of radioactivity
released, I am confident the situation is under control."
Tokyo's 13 million residents were told not to give tap water to babies under
one year old after contamination hit twice the safety level this week. But
it dropped back to allowable amounts.
Radiation above safety levels has also been found in milk and vegetables from
Fukushima and press reports said radioactive caesium 1.8 times higher than
the standard level was found in a leafy vegetable grown in a Tokyo research
facility.
Singapore said it had found radioactive contaminants in four samples of
vegetables from Japan.
Earlier, it and Australia joined the United States and Hong Kong in
restricting food and milk imports from the zone, while Canada became the
latest of many nations to tighten screening after the world's worst nuclear
crisis since Chernobyl.
A shipping industry official, meanwhile, said some merchant vessels may be
avoiding Tokyo port due to concern that crew members may be exposed to
radiation.
Radiation particles have been found as far away as Iceland, and although Japan
insists levels are not dangerous to adults, it is the nation's most testing
time since world War Two.
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