One of Japan's Damaged
Reactors Has High Radiation, Little Water, Renewing
Stability Concerns
Japan Nuclear
Reactor
EMF Computer Protection
Magnetic Field Detector
March 28, 2012
TOKYO - One of Japan's crippled nuclear reactors still has
fatally high radiation levels and much less water to cool it
than officials had estimated, according to an internal
examination that renews doubts about the plant's stability.
A tool equipped with a tiny video camera, a
thermometer, a dosimeter and a water gauge was used to
assess damage inside the No. 2 reactor's containment chamber
for the second time since the tsunami swept into the
Fukushima Dai-ichi plant a year ago.
The data collected Tuesday showed the damage
from the disaster is so severe, the plant operator will have
to develop special equipment and technology to tolerate the
harsh environment and decommission the plant, a process
expected to last decades.
The other two reactors that had meltdowns could
be in even worse shape. The No. 2 reactor is the only one
officials have been able to closely examine so far.
Tuesday's examination with an industrial
endoscope detected radiation levels up to 10 times the
fatal dose inside the chamber. Plant officials previously
said more than half of the melted fuel has breached the core
and dropped to the floor of the primary containment vessel,
some of it splashing against the wall or the floor.
Particles from melted fuel have probably sent
radiation levels up to a dangerously high 70 sieverts per
hour inside the container, said Junichi Matsumoto, spokesman
for Tokyo Electric Power Co. The figure far exceeds the
highest level previously detected, 10 sieverts per hour,
which was detected around an exhaust duct shared by No. 1
and 2 units last year.
"It's extremely high," he said, adding that an
endoscope would last only 14 hours in those conditions. "We
have to develop equipment that can tolerate high radiation"
when locating and removing melted fuel during the
decommissioning.
The probe also found that the containment vessel
— a beaker-shaped container enclosing the core — had cooling
water up to only 60 centimetres (2 feet) from the bottom,
far below the 10 metres (yards) estimated when the
government declared the plant stable in December. The plant
is continuing to pump water into the reactor.
Video footage taken by the probe showed the
water inside was clear but contained dark yellow sediments,
believed to be fragments of rust, paint that had been peeled
off or dust.
A probe done in January failed to find the water
surface and provided only images showing steam, unidentified
parts and rusty metal surfaces scarred by exposure to
radiation, heat and humidity. Finding the water level was
important to help locate damaged areas where radioactive
water is escaping.
Matsumoto said that the actual water level
inside the chamber was way off the estimate, which had used
data that turned out to be unreliable. But the results don't
affect the plant's "cold shutdown status" because the water
temperature was about 50 degrees Celsius (122 Fahrenheit),
indicating the melted fuel is cooled.
Three Dai-ichi reactors had meltdowns, but the
No. 2 reactor is the only one that has been examined because
radiation levels inside the reactor building are relatively
low and its container is designed with a convenient slot to
send in the endoscope.
The exact conditions of the other two reactors,
where hydrogen explosions damaged their buildings, are still
unknown. Simulations have indicated that more fuel inside
No. 1 has breached the core than the other two, but
radiation at No. 3 remains the highest.
The high radiation levels inside the No. 2
reactor's chamber mean it's inaccessible to the workers, but
parts of the reactor building are accessible for a few
minutes at a time — with the workers wearing full
protection.
Last year's massive earthquake and a tsunami set
off the worst nuclear accident since Chornobyl, sending
three reactor cores to melt and causing massive radiation
leaks. The government said in December that the reactors are
safely cooled and the plant has stabilized, while experts
have questioned its vulnerability.
During a recent visit by a group of journalists
including The Associated Press, the head of the plant said
it remains vulnerable to strong aftershocks and tsunami, and
that containing contaminated water and radiation is a
challenge. Radioactive water had leaked into the ocean
several times already.
Workers found a fresh leak of 120 tons from a
water treatment unit this week from one of its hoses, with
estimated 80 litres (20 gallons) escaping into the ocean,
Matsumoto said. Officials are still investigating its
impact.
Fukushima's accident has instilled public distrust and
concerns about nuclear safety, making it difficult for the
government to start up reactors even after regular safety
checks. All but one of Japan's 54 reactors are now offline,
with the last one scheduled to stop in early May.
http://www.emfnews.org/store |