WASHINGTON, D.C. -- Energy Secretary Steven Chu said on Friday that roughly 70 percent of the core of one reactor at the crippled Fukushima nuclear plant in Japan had suffered severe damage.
His assessment of the damage to Reactor No. 1 was the most specific yet from a U.S. official on how close the plant came to a full meltdown after it was hit by a severe earthquake and massive tsunami on March 11.
Japanese officials have spoken of a "partial meltdown" at some of the stricken reactors. But they have been less than specific, especially on the question of how close No. 1 came to a full meltdown.
Chu, a Nobel laureate in physics, suggested that the worst moments of the crisis appeared to be receding, saying that the best information the United States had received from Japanese authorities indicated that water was once again covering the cores of the stricken reactors and that pools of spent fuel atop the reactor buildings were "now under control."
In addition to the severe damage at Reactor No. 1, the Energy Department said that Reactor No. 2 had suffered a 33 percent meltdown. Chu cautioned that the figures were "more of a calculation" because radiation levels inside the plant had been too high for workers to get inside.
He called the nuclear crisis "a cascade of events" that led to multiple failures of backup systems. He told reporters at a breakfast that while officials were reviewing the accident to see if U.S. nuclear plants needed significant changes, he did not want to rush into changes. "First and foremost, we are trying to make sure that fuller damage is not done," he said.
Questioned about the long-term effects of Japan's effort to "feed and bleed" the reactors -- pouring in cooling water, then releasing it as steam into the atmosphere -- he said there was an effort under way to "minimize the release" of radioactivity into the air.
"They're trying to reach a steady state," he said, in which cooling could take place with minimal radioactive releases.
Meanwhile, Japan and the United States combined efforts on Friday in a final search for thousands of people still missing after the earthquake and tsunami. The three-day effort will be the last big sweep before officials in Tokyo shift their focus to a daunting national reconstruction effort.
In the largest rescue mission ever carried out in Japan, 18,000 Japanese searchers have been joined by 7,000 U.S. sailors and Marines in an operation using 120 helicopters and reconnaissance aircraft and 65 ships to scour a coastal area from the northern tip of Iwate Prefecture to the southern end of Fukushima Prefecture.
The National Policy Agency still lists 16,464 as missing and the number of dead at 11,620.
