Japan rushes against time to avert nuclear plant meltdown

TOKYO, March 17 (Reuters):  Japanese military helicopters dumped water on an overheating nuclear plant on Thursday while the United States expressed growing alarm about leaking radiation and said it was sending aircraft to help Americans leave the country.
Engineers tried to run power from the main grid to start water pumps needed to cool two reactors and spent fuel rods considered to pose the biggest risk of spewing radioactivity into the atmosphere as the capital faced possible widespread powercuts.
While Japanese officials scrambled with a patchwork of fixes, the top U.S. nuclear regulator warned that the cooling pool for spent fuel rods at reactor No.4 may have run dry and another was leaking.
Gregory Jaczko, head of the Nuclear Regulatory Commission, told a parliamentary hearing that radiation levels around the cooling pool were extremely high, posing deadly risks for workers still toiling in the wreckage of the earthquake-shattered power plant.
"It would be very difficult for emergency workers to get near the reactors. The doses they could experience would potentially be lethal doses in a very short period of time," he said in Washington.
Japan's nuclear agency said it could not confirm if water was covering the fuel rods. The plant operator said it believed the reactor spent-fuel pool still had water as of Wednesday, and made clear its priority was the spent-fuel pool at the No.3 reactor. On Thursday morning alone, military helicopters dumped around 30 tonnes of water, all aimed at this reactor.
Inside the complex, torn apart by four explosions since a 9.0-magnitude earthquake and tsunami hit last Friday, workers in protective suits and using makeshift lighting tried to monitor what was going on inside the six reactors. They have been working in short shifts to minimize radiation exposure.
U.S. officials took pains not to criticize the Japanese government, which has shown signs of being overwhelmed by the crisis, but Washington's actions indicated a divide with its close ally about the perilousness of the situation.
"The worst-case scenario doesn't bear mentioning and the best-case scenario keeps getting worse," Perpetual Investments said in a note on the crisis.
Japan said the United States would fly a high-altitude drone over the stricken complex to gauge the situation, and had offered to send nuclear experts.
A State Department official said flights would be laid on for Americans to leave, and family of embassy staff had been authorized to leave if they wanted.
Health experts said panic over radiation leaks from the Daiichi plant, around 240 km (150 miles) north of Tokyo, was diverting attention from other life-threatening risks facing survivors of last Friday's earthquake and tsunami, such as cold, heavy snow in parts and access to fresh water.
The latest images from the nuclear plant showed severe damage to some of the buildings after the four explosions. Two of the buildings were a mangled mix of steel and concrete.
Sebastian Pflugbeil, president of the private German-based Society for Radiation Protection, said Japan's efforts to pull the Fukushima plant back from the brink signaled "the beginning of the catastrophic phase".
"Maybe we have to pray," he said, adding that a wind blowing any nuclear fallout east into the Pacific would limit any damage for Japan's 127 million people in case of a meltdown or other releases, for instance from spent fuel storage pools.
Low and harmless concentrations of radioactive particles were heading from Japan toward the United States, Lars-Erik De Geer, research director at the Swedish Defense Research Institute, a government agency, said, citing data from a network of international monitoring stations.
An unexpected, large-scale power outage was possible in Tokyo and surrounding areas at night if power demand exceeded that of the morning, Japan's trade minister said as a beautiful sunset bathed the city in purple, Mount Fuji in stark relief on the horizon. The earthquake and tsunami cut electricity supplies.
In a possible sign of panic, one bank, Mizuho, said all its automatic teller machines in the country crashed twice during the day after excessive transactions at some branches.