Fukushima Fuel Rods May Have
Completely Melted
Fukushima Power Plant
EMF Protection Devices
Magnetic Field Detector
2 December 2011
Fuel rods inside one of the
reactors at the Fukushima Daiichi nuclear power plant may
have completely melted and bored most of the way through a
concrete floor, the reactor's last line of defence before
its steel outer casing, the plant's operator said.
Tokyo Electric Power (Tepco) said in a report that fuel
inside reactor No 1 appeared to have dropped through its
inner pressure vessel and into the outer containment vessel,
indicating that the accident was more severe than first
thought.
The revelation that the plant
may have narrowly averted a disastrous"China
syndrome" scenario
comes days after reports that the company had dismissed a
2008 warning that the plant was inadequately
prepared to resist a tsunami.
Tepco revised its view of the
damage inside the No 1 reactor – one of three that suffered
meltdown soon after the 11 March disaster – after running a
new simulation of the accident.
It would not comment on the
exact position of the molten fuel, or on how much of it is
exposed to water being pumped in to cool the reactor. More
than nine months into the crisis, workers are still unable
to gauge the damage directly because of dangerously high
levels of radiation inside the reactor building.
"Uncertainty involved in the
analysis is significant, due to the uncertain nature of the
original conditions and data used," Tepco said in a report.
It said the concrete "could have been penetrated", but added
that the fuel remained inside the reactor's outer casing.
Previously, the firm had said
that only some of the fuel had burned
through its inner pressure vessel and dropped into the
containment vessel.
"Almost no fuel remains at
its original position," Tepco said. The simulation shows
that the fuel may have penetrated the concrete floor by up
to 65cm, just 37cm from the reactor's outer steel wall.
Tepco said that about 60% of
the fuel in the two other reactors that experienced meltdown
had dropped onto the concrete base, but had caused less
damage.
After the tsunami, workers at
the site stopped injecting reactor No 1 with water for about
14 hours, resulting in more serious damage than sustained by
the two other reactors.
The company added, however,
that fuel in all three reactors was being kept stable by
cooling water, adding that the erosion had stopped.
It said the findings would
not affect plans to bring the reactors to a safe state,
known as cold shutdown, possibly by the middle of the month.
Japanese authorities may
announce cold shutdown on 16 December, the Yomiuri Shimbun
reported on Friday. That stage is reached when water used to
cool the fuel rods remains below boiling point, thereby
preventing the fuel from heating up again.
Stabilising the reactors is
just the first stage of the operation to resolve the crisis.
Tepco has said it won't be able to begin removing the fuel
for another 10 years. Decommissioning
the plant could take at least 30 years.
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