ANALYSIS: Japan Tepco struggles to save stricken Fukushima-1 nuke unit
Washington (Platts)--13Mar2011/827 am EDT/1227 GMT
Japan, the most disaster-ready nation in the world, is struggling to cope
from the massive 8.9-magnitude earthquake and the resulting tsunami that hit
it on Friday. One of the major outcomes of the quake is the radiation threat
from its largest power utility Tokyo Electric Power Company's Fukushima
Daiichi nuclear plant.
Tepco began injecting sea water into a reactor at the Fukushima Daiichi
nuclear power plant Saturday in an effort to maintain cooling of the unit,
which lost power after the tsunami.
Tepco reported Saturday higher-than-normal levels of radioactivity at the
site but did not provide numbers. Some people being evacuated from near the
plant have been confirmed to have been exposed to radiation above the
threshold considered low by Japan's Nuclear and Industrial Safety Agency.
Earlier, the International Atomic Energy Agency said radiation levels at
the plant, which rose earlier, had fallen.
The effort to use sea water at the coastal plant to cool the Fukushima
Daiichi reactor core was "an act of desperation," said Robert Alvarez, a
senior scholar at the Institute for Policy Studies in the US and a former
Department of Energy official. The effort may reflect a loss of water
circulation capacity at the site, Alvarez said in a conference call sponsored
by the anti-nuclear organization Nuclear Information and Resource Service.
Tepco said in an update on its website Saturday that injection of sea
water into the reactor core, followed by addition of boron, which is used to
reduce the rate of nuclear fission, began at 8:20 pm local time (1120 GMT)
local time. The effort was later halted because of concerns about another
possible tsunami brought on by an aftershock, Tepco said.
The utility said it shut all its seven operating power reactors at
Fukushima after the earthquake. The six-unit Fukushima Daiichi station lost
power, and emergency diesel generators that were designed as a backup failed
about an hour after the earthquake, possibly because of the tsunami.
The government ordered the evacuation of residents living within 20
kilometers (12.4 miles) of Fukushima Daiichi, widening the area from the
initial 3 km.
NISA has confirmed the presence of radioactive cesium-137 and iodine-131
in the vicinity of the plant, the IAEA said on its website.
The presence of cesium could be an indication of damage to the fuel in
the reactor, Alvarez said.
The explosion at the Fukushima plant affected the concrete building that
covers the top of the reactor's steel containment vessel, which remains
intact, the IAEA said.
The cause of the explosion is unclear, but could have been an
accumulation of hydrogen in the concrete building from the interaction of fuel
cladding materials and water, former US Nuclear Regulatory Commission member
Peter Bradford said during the NIRS call. That hydrogen could have been vented
into the containment vessel and then migrated to the building where it could
ignite when mixed with oxygen, he added.
The accident could significantly reduce public support for nuclear power
around the world, Bradford said.
The nuclear industry will examine the root causes of the accident and
seek to learn from it, Nuclear Energy Institute spokesman Tom Kauffman said
"The world nuclear industry will be paying close attention to this," he
said. Tepco and its workers have done "a heroic job" attempting to control the
reactor, he added.
Dale Klein, a former chairman of the NRC, said in an interview Saturday
that using seawater to flood Fukushima Daiichi's reactor core -- and
containment as a precautionary measure -- is part of the plant's emergency
planning process. "If you're near the end of your options, that's one of
them," he said.
Klein said such a procedure leads him to believe the condensate tank was
broken or empty or the pipes leading to it were broken because it would have
been used otherwise. The condensate tank is used to provide water to the
emergency core cooling system.
Klein, who chaired the NRC from July 2006 to May 2009, said future
operation of the reactor "would be an economic decision that Tepco would have
to make." But he expected the company to consider building a new one instead
as "it would be a major cleanup of contaminated components and water."
The 460-MW unit 1 at Fukushima Daiichi began commercial operation in 1971
and is the oldest and smallest of the Fukushima reactors. Klein said he would
characterize the quake impact on Fukushima-1 as "more like a Three Mile Island
[but] with a lot more knowledge."
Operators at the Japanese unit "knew early on what they had to do, they
just had trouble doing it," he said.
At the Three Mile Island-2 unit in Pennsylvania on March 28, 1979,
operators mistakenly turned off the emergency core cooling system, which had
automatically activated, because they believed the core was covered. The
accident, in which there was a partial core meltdown, is considered the worst
in US commercial nuclear power plant history but led to no deaths or injuries
to plant workers, according to the NRC.
The workers at Fukushima-1 set up emergency diesel generators to provide
backup power for the cooling system, but they apparently ran for only a short
time before being damaged by the tsunami, Klein said. Backup power could have
been provided by batteries but that typically lasts only a few hours, and
damage to the surrounding area appears to have cut off the option of bringing
in additional emergency diesel generators, he said.
"The earthquake had minimal impact; the tsunami had the impact," Klein
The problem in cooling Fukushima Daiichi was officially rated an accident
on the IAEA scale Saturday, with a rating of 4 on the International Nuclear
Events Scale, an accident with local consequences. Events can be rated from 1,
an anomaly, to 7, a major accident.
The explosion of a reactor at the Chernobyl nuclear plant in Ukraine in
1986 was a level 7 event; the partial meltdown of the core at Three Mile
Island-2 was rated 5, IAEA said.
Japanese authorities were reportedly planning to distribute potassium
iodide tablets to residents around the plant. In the event of a radiation
release from an accident, potassium iodide can protect the thyroid gland from
possible radiation damage by blocking the absorption of radioactive iodine.
The Fukushima Daiichi reactor is a boiling water reactor or BWR design
that has a large number of ways to get cooling water into the core, Ken
Bergeron, a physicist and former Sandia National Laboratory scientist, said on
the NIRS call. The design counts on steam-driven components that do not
require offsite power except for controls, he said.
"They have a lot of options and they're using them now," Bergeron said.
But the small metal containment vessel in which the reactor is located
does not present as much protection in case the core of fuel rods should melt,
Bergeron said. Unlike the containment at Three Mile Island-2, that of
Fukushima Daiichi might not survive a core melt, he added.
Nuclear reactors have various barriers -- including the containment
building, reactor vessel and fuel cladding -- aimed at preventing the release
of radioactivity in case of an accident or a terrorist attack.
The NRC is sending two BWR specialists to Japan as part of a delegation
of US Agency for International Development workers. NRC has some of the top
experts in BWRs and will assist Japan as much as possible, Chairman Gregory
Jaczko said Saturday in the statement.
--William Freebairn, email@example.com
--Tom Harrison, firstname.lastname@example.org
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