Japan's nuclear regulator has
suggested wants raising the severity level of a radioactive water leak
discovered Monday at the tsunami-struck Fukushima-Daiichi plant from one
to three on a seven-point international scale, Japanese media have
reported.
The
new characterization of the leak would reclassify it from an “anomaly” to a
“serious incident” on the seven point International Nuclear Event Scale (INES)
maintained by the International Atomic Energy Agency (IAEA).
Plant
operator Tokyo Electric Power Co. (Tepco) said about 300 tons (some 300,000
liters) of contaminated water has leaked from one of hundreds of 1,000-ton
cylindrical steel tanks around the decimated plant, much of which has
apparently seeped into the ground, Asashi Shimbun reported.
The
utility is also checking for leaks at other tanks holding contaminated water at
the site.
Bellona
General Director and nuclear physicist Nils Bøhmer question whether Japanese
authorities shouldn’t consider moving the classification of the accident to a
Level 4, which would characterize it as “an accident with local consequences.”
“That
highly radioactive water is presumably seeping into the ground would imply that
this is somewhat more serious that the Level 3 Japanese officials are
suggesting,” said Bøhmer. “Fukushima is the never-ending story and it is just
getting worse and worse.”
Tepco
officials said they presume the leaky tank is located somewhere west of
Fukushima-Daiichi’s reactor No 4. Part of the water remains pooled within a
concrete barrier surrounding a group of 26 tanks, said the paper.
Some
one thousand tanks have been built to contain the water from the three
melted down reactors, as well as underground water that is contaminated
when it runs into reactor and turbine basements.
However,
350 of these tanks, holding 300,000 tonnes of water, are less durable than
others, with rubber seams. Japanese officials say they have no choice but to
keep building tanks to contain the contaminated water.
Tanks
sloshing with highly radioactive water in ad-hoc containment system
The
water in the tanks has a concentration of 80 million becquerels per litter,
which translates into 24 trillion becquerels for 300 tons, Asashi Shimbun
reported The water contains cesium, strontium, tritium and other radioactive
materials, although cesium concentrations have been reduced through treatment.
Jerry-built
coolant systems continue to keep the reactors and spent fuel ponds cool, but
the consequence has been that enormous volumes of contaminated water have to be
stored onsite at the destroyed nuclear power plant.
Tepco
said that because the leaking tank is assumed to be about 100 meters from the
coastline, the leak does not pose an immediate threat to the sea.
But
Hideka Morimoto, an NRA spokesman, stomped on that report from Tepco, telling
the Associated Press that contaminated water could reach the sea via a drain
gutter.
The
incidents have shaken confidence in the reliability of the tanks.
Tank
leaks nothing new
Four
other tanks of the same design have had similar leaks since last year. Earlier
this month, it was reported that 300 tons of low-level contaminated water a day
were escaping the territory of the
plant and sullying the waters of the Pacific.
The
most recent water incidents are viewed as the most serious since the initial
explosion and meltdown.
A
puddle of the contaminated water was emitting 100 millisieverts an hour of
radiation, Kyodo news agency said earlier this week.
Masayuki
Ono, general manager of Tepco, told Reuters news agency: “One hundred
millisieverts per hour is equivalent to the limit for accumulated exposure over
five years for nuclear workers; so it can be said that we found a radiation
level strong enough to give someone a five-year dose of radiation within one
hour.”
High
radioactivity levels slow work
This
severely complicates measures to stem the leak: The water is so radioactive
that teams working to stem the flow must constantly be rotated because of the
high exposure rates, and it is clear that most of the contaminated water has
already been absorbed into the ground.
“We
are extremely concerned,” Morimoto told reporters Wednesday. He urged Tepco to
quickly determine the cause of the leak and its possible effect on water
management plans.
Tepco
spokesman Masayuki Ono told AP that workers were pumping out the puddle and the
remaining water and will transfer it to other containers in a desperate effort
to prevent it from escaping into the sea ahead of heavy rain predicted later in
the day around Fukushima.
By
Tuesday afternoon they had captured only about 4 tons (4,000 liters), Ono said.
Third
revision in INES scale suggested
Japanese
officials first suggested the most recent tank leak be classified as a level
one incident on the INES scale. Suggestions by Japan’s newly constituted
Nuclear Regulatory Authority (NRA) represent the third time incidents
surrounding the Fukushima disaster, which began on March 11, 2011, have been
upwardly revised on the INES scale.
The
Fukushima incident was initially reported as a Level 5 “accident with wider
consequences” on INES – by Japanese authorities immediately following the
triple meltdown and reactor building explosions triggered by a total loss of
primary and back up cooling systems after an 11-meter tsunami hit the plant.
Within
days, that figure was upwardly revised by Japan to a Level 7 “major accident” –
the first Level 7 since Chernobyl.
Japanese
media has reported the upward revision of Monday’s radioactive water leak is a
provisional measure that must be confirmed by the IAEA – just as the initial
accident classifications were.
The
move to classify the leak was announced in a document posted only in Japanese on the NRA’s
website on Monday, the BBC reported. The move to reclassify the leak was
subsequently approved at a Wednesday meeting of the regulators.
The
Chinese Foreign Ministry said in a statement that it “hopes that the
Japanese side can earnestly take effective steps to put an end to the negative
impact of the after-effects of the Fukushima nuclear accident.”
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