by Julian Ryall
12 May 2011
One of the reactors
at the crippled Fukushima Daiichi power plant did suffer
a nuclear meltdown, Japanese officials admitted for the
first time today, describing a pool of molten fuel at
the bottom of the reactor's containment vessel.
Nuclear meltdown at
Workers pour concrete into a pit to stop contaminated water leaking
from the reactor building
Engineers from the Tokyo Electric
Power company (Tepco) entered the No.1 reactor at the end of
last week for the first time and saw the top five feet or so of the
core's 13ft-long fuel rods had been exposed to the air and melted
Previously, Tepco believed that the core of the reactor was
submerged in enough water to keep it stable and that only 55 per
cent of the core had been damaged.
Now the company is worried that the molten pool of radioactive fuel
may have burned a hole through the bottom of the containment vessel,
causing water to leak.
"We will have to revise our plans,"
said Junichi Matsumoto, a spokesman for Tepco. "We cannot deny
the possibility that a hole in the pressure vessel caused water
Tepco has not clarified what other
barriers there are to stop radioactive fuel leaking if the steel
containment vessel has been breached.
Greenpeace said the situation
could escalate rapidly if,
"the lava melts through the vessel".
However, an initial plan to flood the
entire reactor core with water to keep its temperature from rising
has now been abandoned because it might exacerbate the leak.
Tepco said there was enough water at the
bottom of the vessel to keep both the puddle of melted fuel and the
remaining fuel rods cool.
Meanwhile, Tepco said on Wednesday that it had sealed a leak of
radioactive water from the No.3 reactor after water was reportedly
discovered to be flowing into the ocean. A similar leak had
discharged radioactive water into the sea in April from the No.2
Greenpeace said significant amounts of radioactive material had been
released into the sea and that samples of seaweed taken from as far
as 40 miles of the Fukushima plant had been found to contain
radiation well above legal limits. Of the 22 samples tested, ten
were contaminated with five times the legal limit of iodine 131 and
20 times of
Seaweed is a huge part of the Japanese diet and the average
household almost 7lbs a year. Greenpeace's warning came as fishermen
prepared to start the harvest of this season's seaweed on May 20.
Inland from the plant, there has been a huge cull of the livestock
left inside the 18-mile mandatory exclusion zone with thousands of
cows, horses and pigs being destroyed and some 260,000 chickens from
the town of Minamisoma alone. The Environment ministry has
announced, however, that it will attempt to rescue the thousands of
pets that were left behind when residents were ordered to evacuate.
At least 5,800 dogs were owned by the
residents of the zone, although it is unclear how many remain alive,
two months after the earthquake struck.
Damage Worse Than Thought
by Joe Carroll and Michio Nakayama
May 12, 2011
To contact the reporters on this story: Michio Nakayama in Tokyo at
firstname.lastname@example.org; Joe Carroll in Chicago at email@example.com
To contact the editor responsible for this story: Amit Prakash at
May/12/ :07 GMT
Tepco Says Fuel Rods at Fukushima Reactor Are Fully Exposed
A worker measures the radiation dose inside the No. 1 reactor
at Tokyo Electric Power Co.'s Fukushima Dai-Ichi nuclear
plant, on May 5, 2011.
Source: Tokyo Electric Power Co. via
The No. 1 reactor at Tokyo Electric Power Co.'s Fukushima Dai-Ichi
nuclear power plant.
Source: Air Photo Service via Bloomberg
Tokyo Electric Power Co. said one of the reactor cores at its
stricken Fukushima Dai-Ichi nuclear plant is more seriously damaged
than previously thought, setting back the utility’s plan to resolve
Fuel rods in the core of the No. 1 reactor are fully exposed, with
the water level 1 meter (3.3 feet) below the base of the fuel
assembly, Junichi Matsumoto, a general manager at the utility known
as Tepco, told reporters at a briefing in Tokyo.
Melted fuel has
dropped to the bottom of the pressure vessel and is still being
cooled, Matsumoto said.
Japan is trying to contain the worst nuclear disaster since
Chernobyl after a quake and tsunami two months ago knocked out power
and cooling systems at the Fukushima station.
While authorities have
previously suspected a partial meltdown at unit 1, high radiation
levels had prevented workers from entering the building to check the
damage until last week.
“What this means is this is probably going to be a much more
difficult cleanup than they originally planned for,” said Paul
Padley, a particle physicist at Rice University in Houston. The
government and Tepco “have consistently appeared to be
underestimating the severity of the situation.”
There’s no danger of another explosion like the one that blew the
roof off the reactor in March, Matsumoto said at the briefing.
That’s because the lack of water means there’s nothing for the
zirconium-alloy cladding encasing the uranium to react with to
create high-pressure clouds of hydrogen, said Roger N. Blomquist,
principal nuclear engineer at the U.S. Energy Department’s Argonne
National Laboratory near Chicago.
Fuel rods are submerged in water to prevent overheating that would
crack the casing and release radiation, said Blomquist, who oversees
the nuclear section at Argonne, a federal research center managed by
the University of Chicago, birthplace of the atomic industry.
“This is what operators of nuclear reactors want to avoid,” he said
in a telephone interview.
Holes have been found in the base of the pressure vessel, and most
of the fuel has likely melted, Kyodo News reported yesterday, citing
the utility. It’s possible the fuel has leaked into the containment
vessel, which was damaged in the explosion, according to the report.
Flooding the chamber was one of the steps Tepco outlined in April to
bring the crisis under control.
“The plan needs to be revised,” Matsumoto said. “We can’t deny the
possibility that a hole in the pressure vessel caused water to
Tepco shares fell 8.8 percent to 479 yen in Tokyo yesterday. The
stock has declined 77 percent since March 11 when Japan’s worst
quake on record triggered a tsunami that left more than 24,000
No China Syndrome
The company doesn’t know how long the rods have been exposed, it
said in the briefing.
It’s likely they’ve been uncovered since the
first days of the disaster, Blomquist said.
The six-reactor complex, Japan’s third-largest by capacity, has been
spewing radiation since March 11 and the severity rating of the
accident was raised to the same as Chernobyl nearly one month ago.
The station is located about 220 kilometers (137 miles) north of
While the risk of explosions still exists if the rods aren’t kept
cool, there’s no likelihood of a catastrophic meltdown, with fuel
burning through the Earth’s crust, said Tony Roulstone, who directs
the University of Cambridge’s masters program in nuclear technology.
“China syndrome’s not a real risk because it would require too much
The U.S. Nuclear Regulatory Commission, which has officials in Japan
monitoring the crisis, hasn’t changed its advice of March 16, urging
U.S. citizens to stay 50 miles from the stricken plant, said Eliot
Brenner, an NRC spokesman.
Brenner declined to comment on the specific condition of the
Fukushima reactors. The agency is holding a public meeting to
discuss a safety review of U.S. reactors which was triggered by the
events in Japan.
Tepco has said it expects a sustained drop in radiation levels at
the entire plant by July, according to the plan announced on April
Following that, a cold shutdown of reactors No. 1, 2 and 3 may
take place as early as October, the utility said at the time.