Japan is considering a novel approach to stem the spread of radioactive water at the crippled Fukushima Daiichi nuclear plant: installing a subterranean ring of ice.
Japan
is
considering a novel approach to stem the spread of radioactive water at the
crippled Fukushima Daiichi nuclear plant: installing a subterranean ring of
ice.
The project, being touted by Japanese officials from the chief government
spokesman to the minister overseeing the plant's private operator, is risky
because it could cost hundreds of millions of dollars and hasn't been tried on
such a large scale and over such a lengthy period before. Indeed, some experts
view it as a stopgap measure.
But the government, which said recently it would take the lead from the plant's
operator, Tokyo Electric Power Co. (9501.TO), after Japan's nuclear regulator
last week declared a 79,000-gallon leak "a serious incident," is
leaning towards the ice plan as the best and fastest chance at keeping
groundwater from becoming contaminated.
The government has ordered a study on the proposal to be completed by year's
end.
The push to move ahead with the project despite its uncertainty underscores
Japan's scramble--29 months after Fukushima Daiichi melted down following an
earthquake and tsunami in one of the world's worst nuclear accidents--to
prevent potentially dangerous amounts of radioactive contamination from
spreading through water beyond the plant.
Signaling growing concern,
Fukushima
prefecture's fisheries cooperatives on Wednesday said their members have
suspended plans to restart fishing in the waters near the plant, until it is
clear they aren't contaminated.
Furthermore, during the past few days, some regulatory officials have
questioned whether last week's leak at a site outside the proposed ice ring
could mean groundwater is already contaminated over a larger area than
initially thought.
So far, the amounts of radioactive water that have leaked out to the sea don't
pose much risk to human health, experts say.
Still, some of the Japanese experts on a closed government-appointed panel who
have met to hammer out a water-containment strategy in recent weeks are
considering using the ice wall as a defense against the spread of contaminated
water over the three or four decades that experts believe it will take to clean
up Fukushima Daiichi.
Others see it as a temporary measure while other more conventional barriers are
erected from steel or concrete, say people with knowledge of the panel's
discussions.
In another scenario, the plant's reactors and surrounding areas may have to be
guarded by layers of defenses including the ice walls, some on the panel say,
according to the people with knowledge of discussions.
In any case, the government this month pledged people and money for the
ice-wall project, which could cost several tens of billions of yen to build and
nearly Y1 billion ($10 million) a year to maintain, according to an estimate
from another government panel.
The project entails circulating super-cool liquid through a line of pipes
inserted into the ground every yard or so. The pipes freeze the soil and
groundwater around them, which solidifies into a solid wall of ice that blocks
all movement of water.
Experts say an ice barrier could be advantageous at Fukushima Daiichi, where
Tokyo Electric Power, known as Tepco, is struggling to keep an estimated 1,000
metric tons of groundwater that flows through the site daily towards the sea
from getting contaminated by contact with the damaged reactors and other
radioactive spots.
An ice wall around the reactors could completely shut groundwater out of the
most heavily contaminated areas, and it is faster to build than other
traditional sunken barriers, said Atsunao Marui, head of the groundwater
research group at
Japan
's
National Institute of Advanced Industrial Science and Technology, and a panel
member.
Kajima Corp. (1812.TO), the giant Japanese contractor that proposed the ice
wall, estimated total construction time would be under two years, versus two or
more years for other barrier types.
Meantime, Tepco is applying and preparing measures, including pumps, sea walls
and removal and storage of 400 tons of contaminated water a day.
But experts also point out drawbacks to the plan. The wall needs a constant
supply of electricity to keep frozen--an expensive proposition, especially in
Japan
,
where the closure of most of the nation's nuclear plants following the
Fukushima Daiichi accident means power is largely supplied by costly, imported
fossil fuels.
"Ground freezing is usually looked at last because of the cost," said
Joseph Sopko, director of ground freezing at New Jersey-based geotechnical
contractor Moretrench America Corp.
More troubling for the experts panel is that ground freezing hasn't been done
on such a scale before. Kajima's proposal calls for a nearly mile-long ring of
1,540 pipes, passing near spots where high levels of radiation have been
measured.
Companies are also concerned that their small pool of expert engineers could be
devastated if they are accidentally exposed to high levels of radiation, said
one person close to discussions on the ice-wall experts panel.
A handful of big ice-wall projects have been planned, but never realized,
including one at a gold mine in
Canada
that
was abandoned when gold prices fell and the cost become prohibitive, and
another at a nuclear cleanup site in
Washington
state
that turned out to be too dry to work well, Mr. Sopko said.
Only a few Japanese companies specialize in ground freezing, largely for tunnel
and other underground construction. One has already bowed out, saying the
Fukushima Daiichi project is beyond its technical expertise. Another, the
subsidiary of Kajima, has largely handled jobs that are a fraction of the size
and are maintained for a year or two, according to a list of projects on its
website.
Part of the goal of the feasibility study being conducted now is to see if the
ice wall can be built and maintained with a non-specialist engineering staff,
the person said.
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