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<DIV class=timestamp>May 17, 2011</DIV>
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<H1><NYT_HEADLINE type=" " version="1.0">In Japan Reactor Failings, Danger Signs
for the U.S.</NYT_HEADLINE></H1><NYT_BYLINE>
<H6 class=byline>By HIROKO TABUCHI, KEITH BRADSHER and MATTHEW L.
WALD</H6></NYT_BYLINE><NYT_TEXT>
<DIV id=articleBody><NYT_CORRECTION_TOP></NYT_CORRECTION_TOP>
<P>TOKYO — Emergency vents that American officials have said would prevent
devastating hydrogen explosions at nuclear plants in the United States were put
to the test in Japan — and failed to work, according to experts and officials
with the company that operates the crippled Fukushima Daiichi plant. </P>
<P>The failure of the vents calls into question the safety of similar nuclear
power plants in the United States and Japan. After the venting failed at the
Fukushima plant, the hydrogen gas fueled explosions that spewed radioactive
materials into the atmosphere, reaching levels about 10 percent of estimated
emissions at Chernobyl, according to Japan’s nuclear regulatory agency. </P>
<P>Venting was critical to relieving pressure that was building up inside
several reactors after the March 11 tsunami knocked out the plant’s crucial
cooling systems. Without flowing water to cool the reactors’ cores, they had
begun to dangerously overheat. </P>
<P>American officials had said early on that reactors in the United States would
be safe from such disasters because they were equipped with new, stronger
venting systems. But Tokyo Electric Power Company, which runs the plant, now
says that Fukushima Daiichi had installed the same vents years ago. </P>
<P>Government officials have also suggested that one of the primary causes of
the explosions was a several-hour delay in a decision to use the vents, as Tokyo
Electric managers agonized over whether to resort to emergency measures that
would allow a substantial amount of radioactive materials to escape into the
air. </P>
<P>But the release this week of company documents and interviews with experts
provides the most comprehensive evidence yet that mechanical failures and design
flaws in the venting system also contributed to delays. The documents paint a
picture of increasing desperation at the plant in the early hours of the
disaster, as workers who had finally gotten the go-ahead to vent realized that
the system would not respond to their commands. </P>
<P>While venting would have allowed some radioactive materials to escape,
analysts say that those releases would have been far smaller than those that
followed the explosions at three of the plant’s reactors, which blew open
containment buildings meant to serve as a first line of defense against
catastrophe. The blasts may also have been responsible for breaches in
containment vessels that have complicated efforts to cool the fuel rods and
contain radioactive leaks from the site. </P>
<P>One reason the venting system at the plant, which was built by General
Electric, did not work is that it relied on the same sources of electricity as
the rest of the plant: backup generators that were in basements at the plant and
vulnerable to tsunamis. But the earthquake may also have damaged the valves that
are part of the venting system, preventing them from working even when operators
tried to manually open them, Tokyo Electric officials said. </P>
<P>In either case, regulators in the United States and Japan will now need to
determine if such systems at similar plants designed by G.E. need to undergo
expensive and time-consuming retrofitting or redesign to allow them to function
even in severe accidents. </P>
<P>“Japan is going to teach us lessons,” said David Lochbaum at the Union of
Concerned Scientists. “If we’re in a situation where we can’t vent where we need
to, we need to fix that.” </P>
<P>Officials from General Electric did not comment on Tuesday. </P>
<P>The seriousness of the crisis at the Fukushima plant became evident within
hours of the quake and the tsunami that rushed over the plant’s sea wall. </P>
<P>Just 12 hours after the quake, the pressure inside Reactor No. 1 had reached
roughly twice the maximum pressure the unit had been designed to withstand,
raising fears that the vessels that house fuel rods would rupture, setting a
possible meltdown in motion. With the pressure high, pumping in additional
cooling water also was not possible. </P>
<P>The government became rattled enough that it ordered Tokyo Electric to begin
venting. But even then, Tokyo Electric’s executives continued to deliberate,
according to a person close to government efforts to bring the reactors under
control. The exchanges became so heated, the person said, that the company’s
nuclear chief, Vice President Sakae Muto, and the stricken plant’s director,
Masao Yoshida, engaged in a “shouting match” — a rarity in reserved Japan. </P>
<P>Mr. Yoshida wanted to vent as soon as possible, but Mr. Muto was skeptical
whether venting would work, the person said, requesting anonymity because he is
still an adviser to the government and is not permitted to comment publicly.
“There was hesitation, arguments and sheer confusion over what to do,” he said.
</P>
<P>The executives did not give the order to begin venting until Saturday — more
than 17 hours after the tsunami struck and 6 hours after the government order to
vent. </P>
<P>As workers scrambled to comply with their new directive, they faced a
cascading series of complications. </P>
<P>The venting system is designed to be operated from the control room, but
operators’ attempts to turn it on failed, most likely because the power to open
critical valves was out. The valves are designed so they can also be opened
manually, but by that time, workers found radiation levels near the venting
system at Reactor No. 1 were already too high to approach, according to Tokyo
Electric’s records. </P>
<P>At Reactor No. 2, workers tried to manually open the safety valves, but
pressure did not fall inside the reactor, making it unclear whether venting was
successful, the records show. At Reactor No. 3, workers tried seven times to
manually open the valve, but it kept closing, the records say. </P>
<P>The results of the failed venting were disastrous. </P>
<P>Reactor No. 1 exploded first, on Saturday, the day after the earthquake.
Reactor No. 3 came next, on Monday. And No. 2 exploded early Tuesday morning.
</P>
<P>With each explosion, radioactive materials surged into the air, forcing the
evacuation of tens of thousands of earthquake survivors living near the plant,
contaminating crops and sending a faint plume of radioactive isotopes as far as
the United States within days. Aerial photos of the reactor buildings showed No.
1 and 3 had been blown apart and another was seriously damaged. </P>
<P>As the troubles mounted, Tokyo Electric and government officials conducted a
series of news conferences that began to suggest the scope of the damage. The
blasts, they said, probably caused breaches in containment vessels that are
among the final layers of protection against meltdowns and even larger releases
of radioactive materials. </P>
<P>Tokyo Electric in recent days has acknowledged that damage at the plant was
worse than previously thought, with fuel rods most likely melting completely at
Reactors 1, 2 and 3 in the early hours of the crisis, raising the danger of more
catastrophic releases of radioactive materials. The company also said new
evidence seemed to confirm that at Reactor No. 1, the pressure vessel, the last
layer of protection, was broken and leaking radioactive water. </P>
<P>The improved venting system at the Fukushima plant was first mandated for use
in the United States in the late 1980s as part of a “safety enhancement program”
for boiling-water reactors that used the Mark I containment system, which had
been designed by General Electric in the 1960s. Between 1998 and 2001, Tokyo
Electric followed suit at Fukushima Daiichi, where five of six reactors use the
Mark I design. </P>
<P>The company said that was the case this week, after a review of Japanese
regulatory filings made in 2002 showed that the vents had been installed. </P>
<P>The fortified venting system addressed concerns that the existing systems
were not strong enough to channel pent-up pressure inside the reactors in an
emergency. Pressure would be expected to rise along with temperature, damaging
the zirconium cladding on the fuel rods at the reactor core and allowing them to
react chemically with water to produce zirconium oxide and hydrogen gas. </P>
<P>The new vents were designed to send steam and gas directly from the reactor’s
primary containment, which houses the reactor vessel, racing past the usual
filters and gas treatment systems that would normally slow releases of gas and
eliminate most radioactive materials. </P>
<P>But the emergency vents were fitted with numerous safeguards, some of which
require electricity to work, rendering them useless when all power is lost at a
nuclear plant, experts say. </P>
<P>The most important of those safeguards are the valves, operated from a switch
under lock and key in the control room, that must be opened for the vents to
work. When a key is inserted into the keyboard in the nuclear reactor’s control
room and turned, the valves are supposed to open, letting gases rush out of the
reactor building. </P>
<P>Tokyo Electric has said the valves did not work at Fukushima Daiichi after
the power failed. </P>
<P>That would suggest that operators of similar plants in the United States and
Japan could protect reactors by moving generators to higher floors if the
equipment is currently in places that could be affected by tsunamis or flooding
from rivers. </P>
<P>But a redesign of the venting system itself might also be necessary. </P>
<P>The design is the result of conflicting schools of thought among United
States nuclear officials, said Michael Friedlander, a former senior operator at
several American nuclear power plants. </P>
<P>Mr. Friedlander said, referring to the Nuclear Regulatory Commission: “You
have the N.R.C. containment isolation guys who want containment closed, always,
under every conceivable accident scenario, and then you’ve got the reactor
safety guys who need containment to be vented under severe accident scenarios.
It is a very controversial system.” </P><NYT_AUTHOR_ID>
<DIV class=authorIdentification>
<P>Hiroko Tabuchi reported from Tokyo, Keith Bradsher from Hong Kong, and
Matthew L. Wald from
Washington.</P></DIV></NYT_AUTHOR_ID><NYT_CORRECTION_BOTTOM>
<DIV
class=articleCorrection></DIV></NYT_CORRECTION_BOTTOM><NYT_UPDATE_BOTTOM></NYT_UPDATE_BOTTOM></DIV></NYT_TEXT></FONT></DIV><FONT
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