Radiation Expert Says Outcome Of Nuke Crisis
Hard To Predict, Warns Of Further Dangers
Fukushima Power Plant
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(Mainichi Japan) September 9, 2011
As a radiation metrology and nuclear safety expert at
Kyoto University's Research Reactor Institute, Hiroaki Koide
has been critical of how the government and Tokyo Electric
Power Co. (TEPCO) have handled the nuclear disaster at the
Fukushima No. 1 nuclear plant. Below, he shares what he
thinks may happen in the coming weeks, months and years.
The nuclear disaster is ongoing. Immediately after the
crisis first began to unfold, I thought that we'd see a
definitive outcome within a week. However, with radioactive
materials yet to be contained, we've remained in the
unsettling state of not knowing how things are going to turn
out.
Without accurate information about what's happening
inside the reactors, there's a need to consider various
scenarios. At present, I believe that there is a possibility
that massive amounts of radioactive materials will be
released into the environment again.
At the No. 1 reactor, there's a chance that melted fuel
has burned through the bottom of the pressure vessel, the
containment vessel and the floor of the reactor building,
and has sunk into the ground. From there, radioactive
materials may be seeping into the ocean and groundwater.
The use of water to cool down the reactors immediately
after the crisis first began resulted in 110,000 cubic
meters of radiation-tainted water. Some of that water is
probably leaking through the cracks in the concrete reactor
buildings produced by the March 11 quake. Contaminated water
was found flowing through cracks near an intake canal, but I
think that's just the tip of the iceberg. I believe that
contaminated water is still leaking underground, where we
can't see it. Because of this, I believe immediate action
must be taken to build underground water barriers that would
close off the nuclear power plant to the outside world and
prevent radioactive materials from spreading. The important
thing is to stop any further diffusion of radioactive
materials.
The government and plant operator TEPCO are trumpeting
the operation of the circulation cooling system, as if it
marks a successful resolution to the disaster. However,
radiation continues to leak from the reactors. The longer
the circulation cooling system keeps running, the more
radioactive waste it will accumulate. It isn't really
leading us in the direction we need to go.
It's doubtful that there's even a need to keep pouring
water into the No.1 reactor, where nuclear fuel is suspected
to have burned through the pressure vessel. Meanwhile, it is
necessary to keep cooling the No. 2 and 3 reactors, which
are believed to still contain some fuel, but the cooling
system itself is unstable. If the fuel were to become
overheated again and melt, coming into contact with water
and trigger a steam explosion, more radioactive materials
will be released.
TEPCO says it is aiming to bring the No. 1, 2 and 3
reactors to cold shutdown by January 2012. Cold shutdown,
however, entails bringing the temperature of sound nuclear
fuel in pressure vessels below 100 degrees Celsius. It would
be one thing to aim for this in April, when the government
had yet to confirm that a meltdown had indeed taken place.
But what is the point of "aiming for cold shutdown" now,
when we know that fuel is no longer sound?
In the days ahead, the storage of enormous quantities of
radiation-contaminated waste, including tainted mud
resulting from the decontamination process, will become a
major problem. Because the responsibility for spreading
nuclear materials into the environment lies with TEPCO, it
makes sense to bring all the radioactive waste to TEPCO
headquarters in Tokyo.
Since that's not possible, the waste should be taken to
the grounds of the nuclear power plant. If the plant is not
large enough to accommodate all the waste, then a location
close to the plant will also have to be designated as a
nuclear graveyard. However, no one should take advantage of
the chaos and force Fukushima to host interim radioactive
waste repositories for spent fuel from other nuclear power
plants.
Recovering the melted nuclear fuel is another huge
challenge. I can't even imagine how that could be done. When
the Three Mile Island accident took place in 1972, the
melted nuclear fuel had stayed within the pressure vessel,
making defueling possible. With Fukushima, however, there is
a possibility that nuclear fuel has fallen into the ground,
in which case it will take 10 or 20 years to recover it. We
are now head to head with a situation that mankind has never
faced before.
http://mdn.mainichi.jp/perspectives/news/20110909p2a00m0na016000c.html
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