In Washington, Nuclear Regulatory Commission Chairman Gregory Jaczko said at a congressional hearing that all of the water had evaporated from the spent-fuel pool at the No. 4 reactor. Japanese officials contended Thursday that military spotters had confirmed from the air that there was still water in the pool.
Acting on Jaczko's advice, the White House made its recommendation that U.S. citizens keep 50 miles or more away.
Jaczko told lawmakers that the 50-mile evacuation radius was based largely on concerns about the spent-fuel pool, which is believed to be seriously damaged and responsible for "very significant radiation levels likely around the site." The pool, which contains an estimated 125 tons of uranium fuel pellets, is not enclosed in a containment vessel, and if the pellets start burning, radiation will escape directly into the environment.
If the backup efforts to cool the reactors were to fail, "it would be very difficult for the emergency workers to get near the reactors. The doses they could experience would potentially be lethal doses in a very short period of time," Jaczko said. "That is a very significant development."
The nuclear crisis is vastly complicating quake relief efforts as well as search-and-rescue operations, including those involving the American military. U.S. forces in Japan were also observing a 50-mile no-go zone around the damaged plant. Pentagon spokesman Col. Dave Lapan described the prohibition as a precaution and said exceptions could be made with authorization.
Inside the crippled plant, emergency workers, wearing protective gear and doing short shifts to limit their radiation exposure, have been pumping seawater into the reactors to try to cool them. The work is hard and perilous and, among many Japanese, the workers have taken on the status of folk heroes.
"They're our last line of defense, and they are in there trying to control the situation … a really, really dangerous situation," said Kazuo Enomoto, who grows vegetables outside Tokyo.
Authorities have raised the maximum radiation dose allowed for the workers in an effort to avoid having to abruptly order them to abandon their posts, as happened Wednesday. About 180 workers were back at the site Thursday.
Since the magnitude 9 quake and the massive tsunami it spawned, damage and malfunctions at the Daiichi plant have spiraled rapidly. The situation at times has seemed to be spinning out of control. Many Japanese do not have confidence in their government either to solve the crisis or to be forthcoming about the danger to public health.
"I want to know that this nuclear situation is safe, and that it's solved quickly," said Toshiko Sugiyama, a 37-year-old businessman living near the affected area. Public alarm has grown by the day, spurred by the government's release of often-contradictory and vague information.
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