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News Analysis
Japan May Declare Control of Reactors,
Over Serious Doubts
Tepco Via Jiji Press/Agence France-Presse — Getty Images
Workers sprayed water in March to cool the spent nuclear fuel in a reactor building at the
Fukushima Daiichi nuclear plant.
By MARTIN FACKLER
Published: December 14, 2011
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TOKYO — Nine months after the devastating earthquake and tsunami knocked out cooling
systems at the Fukushima Daiichi nuclear plant, causing a meltdown at three units, the Tokyo
government is expected to declare soon that it has finally regained control of the plant’s
overheating reactors.
Related
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Times Topic: Japan — Earthquake, Tsunami and Nuclear Crisis (2011)
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Reuters
Leakage from an evaporation condensation apparatus inside the Fukushima Daiichi nuclear
power plant.
But even before it has been made, the announcement is facing serious doubts from experts.
On Friday, a disaster-response task force headed by Prime Minister Yoshihiko Noda will vote on
whether to announce that the plant’s three damaged reactors have been put into the equivalent of
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a “cold shutdown,” a technical term normally used to describe intact reactors with fuel cores that
are in a safe and stable condition. Experts say that if it does announce a shutdown, as many
expect, it will simply reflect the government’s effort to fulfill a pledge to restore the plant’s
cooling system by year’s end and, according to some experts, not the true situation.
If the task force declares a cold shutdown, the next step will be moving the spent fuel rods innearby cooling pools to more secure storage, and eventually opening the reactors themselves.
However, many experts fear that the government is declaring victory only to appease growing
public anger over the accident, and that it may deflect attention from remaining threats to the
reactors’ safety. One of those — a large aftershock to the magnitude 9 earthquake on March 11,
which could knock out the jury-rigged new cooling system that the plant’s operator hastily built
after the accident — is considered a strong possibility by many seismologists.
They also said the term cold shutdown might give an exaggerated impression of stability to
severely damaged reactors with fuel cores that have not only melted down, but melted throughthe inner containment vessels and bored into the floor of their concrete outer containment
structures.
“The government wants to reassure the people that everything is under control, and do this by the
end of this year,” said Kazuhiko Kudo, a professor of nuclear engineering at Kyushu University.
“But what I want to know is, are they really ready to say this?”
Perhaps to give itself some wiggle room, the government is expected to use vague terminology,
announcing that the three damaged reactors are in a “state of cold shutdown.” Experts say that in
real terms, this will amount to a claim that the reactors’ temperatures can now be kept safely
below the boiling point of water, and that their melted cores are no longer at risk of resuming the
atomic chain reaction that could allow them to again heat up uncontrollably.
And indeed, experts credit the operator, the Tokyo Electric Power Company, or Tepco, with
making progress in regaining control of the damaged reactors. They say the plant’s makeshift
new cooling system, built with the help of American, French and Japanese companies, has
managed to cool the reactors’ cores, including the molten fuel attached to the outer containment
vessels.
Experts also say a new shedlike structure built over the heavily damaged Unit 1 reactor building
has helped cap the plant’s radiation leaks into the atmosphere. The building was one of threereactor buildings destroyed in hydrogen explosions in March that scattered dangerous particles
over a wide swath of northeastern Japan.
Still, experts say the term is usually reserved for healthy reactors, to indicate that they are safe
enough that their containment vessels can be opened up and their fuel rods taken out. But they
warn it may take far longer than even the government’s projected three years to begin cleaning
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up the melted fuel in Fukushima Daiichi’s damaged reactors. This has led some experts to say
that proclaiming a cold shutdown may actually be deceptive, suggesting the Fukushima plant is
closer to getting cleaned up than it actually is.
“Claiming a cold shutdown does not have much meaning for damaged reactors like those at
Fukushima Daiichi,” said Noboru Nakao, a nuclear engineering consultant at InternationalAccess Corporation.
In fact, experts point out, damaged fuel cores have yet to be removed from plants that suffered
meltdowns decades ago. In the case of Chernobyl, Soviet officials simply entombed the damaged
reactor in a concrete sarcophagus after the explosion there in 1986. Some experts said talk of a
cold shutdown deflected attention from the more pressing problem of further releases of
radioactive contamination into the environment. In particular, they said there was still a danger to
the nearby Pacific Ocean from the 90,000 tons of contaminated water that sit in the basements of
the shattered reactor buildings, or are stored in fields of silver tanks on the plant’s grounds.
“At this point, I would be more worried about the contamination than what’s happening inside
the reactor s,” said Murray E. Jennex, an expert on nuclear containment at San Diego State
University.
Mr. Jennex said he believed the government’s claim that the reactors themselves were now
stable, and particularly that the resumption of the heat-producing chain reaction called fission
was no longer possible. While the discovery last month of the chemical xenon, a byproduct of
fission, in one of Fukushima Daiichi’s reactors briefly raised alarms that a chain reaction had
restarted, Mr. Jennex said enough of the radioactive fuel had decayed since the accident in
March to make that unlikely.
Other experts disagreed. Kyushu University’s Mr. Kudo said that the restart of fission, a
phenomenon known as recriticality, could not be ruled out until the reactors could be opened,
allowing for an examination of the melted fuel. But he and other experts said their biggest fear
was that another earthquake or tsunami could knock out Tepco’s makeshift cooling system. They
noted that it was not built to earthquake safety standards, and relied on water purifiers and other
vulnerable equipment connected to the reactors by more than a mile and a half of rubber hoses.
“All it would take is one more earthquake or tsunami to set Fukushima Daiichi back to square
one,” Mr. Kudo said. “Can we really call this precarious situation a cold shutdown?”