After the wave receded, two employee were missing, apparently washed away while working on unit No. 4. Two contractors were treated for leg fractures and two others were treated for slight injuries. A ninth worker was being treated for a stroke.
In the chaos of the early response, workers did not notice when the diesel pumps at No. 2 ran out of fuel, allowing water levels to fall and fuel to become exposed and overheat. When the Fukushima plant suffered its second hydrogen blast in three days the following Monday, Tokyo electric executives only notified the prime minister's office an hour later. Seven workers had been injured in the explosion along with four soldiers.
An enraged Prime Minister Naoto Kan pulled up to Tokyo Electric's headquarters the next morning before dawn. "What the hell is going on?" reporters outside the closed-door discussion reported hearing Kan demand angrily of senior executives.
Errors of judgment by workers in the hot zone and errors of calculation by plant managers hampered the emergency response a full week later as some 600 soldiers and workers struggled to contain the spread of radiation.
On Thursday, two workers at Fukushima were shuttled to the hospital to be treated for potential radiation burns after wading in water in the turbine building of reactor No. 3. The workers had ignored their radiation alarms thinking they were broken.
Then Tokyo electric officials pulled workers back from an effort to pump water out of the No. 2 reactor and reported that radiation readings were 10 million times normal. They later apologized, saying that reading was wrong. The actual reading was still 100,000 times normal, Tokyo Electric said.
The government's chief spokesman was withering in his assessment. "The radiation readings are an important part of a number of important steps we're taking to protect safety," Chief Cabinet Secretary Yukio Edano told reporters. "There is no excuse for getting them wrong."
VENTS AND GAUGES
Although U.S. nuclear plant operators were required to install "hardened" vent systems in the 1980s after the Three Mile Island incident, Japan's Nuclear Safety Commission rejected the need to require such systems in 1992, saying that should be left to the plant operators to decide.
A nuclear power plant's vent represents one of the last resorts for operators struggling to keep a reactor from pressure that could to blow the building that houses it apart and spread radiation, which is what happened at Chernobyl 25 years ago. A hardened vent in a U.S. plant is designed to behave like the barrel on a rifle, strong enough to withstand an explosive force from within.
The U.S. Nuclear Regulatory Commission concluded in the late 1980s that the General Electric designed Mark I reactors, like those used at Fukushima, required safety modifications.
The risks they flagged, and that Tokyo did not heed, would come back to haunt Japan in the Fukushima crisis.
First, U.S. researchers concluded that a loss of power at one of the nuclear plants would be one of the "dominant contributors" to the most severe accidents. Flooding of the reactor building would worsen the risks. The NRC also required U.S. plants to install "hard pipe" after concluding the sheet-metal ducts used in Japan could make things much worse.
"Venting via a sheet metal duct system could result in a reactor building hydrogen burn," researchers said in a report published in November 1988.
In the current crisis, the failure of the more vulnerable duct vents in Fukushima's No. 1 and No. 3 reactors may have contributed to the hydrogen explosions that blew the roof off the first and left the second a tangled hulk of steel beams in the first three days of the crisis.
The plant vents, which connect to the big smokestack-like towers, appear to have been damaged in the quake or the tsunami, one NISA official said.
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