(Source)
http://scandanewz.blogspot.co.uk/2013/08/insight-in-fukushima-end-game-radiated.html
TOKYO (Reuters) - In the
weeks after the Fukushima nuclear plant was destroyed by a triple
meltdown in March 2011, the plant's owner turned to three of Japan's
largest construction companies for a quick fix to store radiated
water that was pooling in the disaster zone.
The result was a rush order
for steel tanks supplied by Taisei Corp, Shimizu Corp and Hazama Ando
that were relatively cheap and could be put together quickly,
according to the utility and three people involved in the project.
The tanks, which stand as
tall as a three-storey building, were shipped in pieces and bolted
together as makeshift repository for the cascade of water being
pumped through the reactors of Fukushima every day to keep fuel in
the melted cores from overheating.
The bolted tanks were sealed
with resin and designed to last until about 2016 - long enough to buy
time for Tokyo Electric Power, or Tepco, to work out a more permanent
solution. But at least one of the tanks has already failed, leaking
300 tons of highly radioactive water that may have seeped into a
drainage ditch and into the Pacific Ocean.
The discovery of the leak -
which Tepco said on Friday was the fifth from the same type of tank -
prompted Japan's first declaration of a nuclear incident since a 9.0
magnitude earthquake and tsunami triggered reactor meltdowns and
hydrogen explosions that spewed radiation around Fukushima in 2011.
It has also focused attention
on the uncomfortable end-game for the radiated water collecting at
Fukushima.
Some 330,000 tons of
contaminated water - enough to fill more than 130 Olympic swimming
pools - has been pumped into storage pits and above-ground tanks at
the crippled facility.
The sheer scale of the
build-up has prompted some experts and officials to warn that in
order to focus on containing the most toxic waste, less contaminated
water will have to be dumped into the sea.
"Think about it in
simple terms. If you don't release the water, there's nowhere to
store it. So we also think it may have to be released," said
Shinichi Nakayama, deputy director of the Nuclear Safety Research
Center at the Japan Atomic Energy Agency and a member of a regulatory
panel on Fukushima's problems.
Before the latest leak,
Toshimitsu Motegi, Japan's minister of trade and industry, and
Shunichi Tanaka, the top nuclear regulator, both indicated support
for releasing water with low levels of radiation from Fukushima. No
one has given any timeframe for such a move.
NOT BUILT TO LAST
Officials say the immediate
priority is to figure out why the bolted storage tank failed less
than two years since it was installed. They are also looking at
adjusting plans for the more than 400,000 tons of additional water
storage Tepco plans to build by 2016.
When Tepco commissioned the
first bolted tanks the advantage was the relative speed with which
contractors could finish the job just a few hundred meters from the
wrecked reactor building. "These could be quickly built,"
said Masayuki Ono, a manager at Topco's nuclear division.
Tepco spokeswoman Mayumi
Yoshida said a joint venture of Taisei, Shimzu and Hazama Ando won
the first contract to build storage tanks at Fukushima in April 2011.
She declined to say whether the contractors built the tank that began
to leak. Tepco has not identified the cause of the leak, and has
consistently declined to give details on the value of contracts it
has awarded or winning bidders, citing a need to protect "corporate
secrets". The Fukushima decommissioning is projected to cost at
least $11 billion and take at least 30 years to complete.
Taisei, which built the
structure around Japan's newest reactor at Tomari in Hokkaido in
2009, was heavily involved in the construction of the Fukushima
tanks, according to three people involved, who asked not to be named.
Workers and engineers at Fukushima have been put on an "emergency"
footing to work on the storage tanks this week, they said.
Shimizu, which also has
experience in building nuclear plants in Japan, had technology needed
to build the bolted tanks and brought in experts, one of the sources
said.
Taisei said it could not
comment on individual client projects. Shimizu and Hazama Ando
declined to comment.
There are 350 of the
bolted-style tanks in place at Fukushima, and another 710 welded
tanks, a more expensive design that takes longer to assemble. Nuclear
Regulation Authority Commissioner Toyoshi Fuketa said on Friday that
regulators also needed to examine the environmental risks posed by
any failures of those tanks, especially in cases where they have been
lined up directly on the ground rather than a concrete foundation.
Tepco plans to more than
double the current storage capacity by 2016, but doesn't have a plan
beyond that point. The math is daunting. The utility has to find
space for an additional 400 tons of radioactive water each day
because of the need to keep the reactors cool for the next seven
years.
CONTROVERSIAL
A radiation filtering machine
known as ALPS was supplied by Toshiba Corp to scrub the water clean
of most radioactive elements, including cesium and strontium. The
system, which remains in testing and under review by nuclear
regulators, would leave treated water with tritium, a radioactive
element typically discharged in the coolant water of reactors and
considered one of the least dangerous radioactive elements.
Japanese officials have
indicated support for releasing water containing tritium into the sea
to make room to store more dangerous radioactive materials. But that
seems certain to be controversial at a time when Japanese utilities
are applying to restart nuclear stations that have been idled and
Prime Minister Shinzo Abe is on a drive to sell nuclear technology to
countries like India and Vietnam.
The World Nuclear
Association, an international organization that promotes nuclear
power, endorses a limited discharge at Fukushima. "Tepco has
been prevented from discharging any treated water due to political
opposition," the organization said in response to questions from
Reuters. "Permitting sea release of treated water would
alleviate the much larger problem of a demand for massive volumes of
water storage."
Tepco's already shaky
credibility with regulators and the Japanese public has been further
damaged by recent events.
[...]
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