A video grab show a helicopter is dumping water on a stricken reactor in Japan to cool overheated fuel rods inside the core on March 17, 2011. [Photo/Xinhua]

The storage pools need a constant source of cooling water. Even when removed from reactors, the rods retain radioactivity and must be cooled for months, possibly longer, to prevent them from posing a threat of meltdown.

Japanese officials raised hopes of easing the crisis earlier Thursday, saying that they may be close to bringing power back to the plant and restoring the reactors' cooling systems.

The new power line would revive electric-powered pumps, allowing the company to control the rising temperatures and pressure that have led to at least partial meltdowns in three reactors. The company is also trying to repair its existing disabled power line.

Tokyo Electric Power spokesman Naoki Tsunoda said the new power line to the plant is almost finished and that officials plan to try it "as soon as possible," but he could not say exactly when.

Reflecting the state of alarm over the issue, Japan's 77-year-old emperor expressed deep concern in a rare unexpected television broadcast on Wednesday, saying "I hope things will not get worse."

He urged the Japanese to care for each other and not give up hope. Millions of lives were disrupted by the magnitude 9 earthquake and subsequent tsunami, which are believed to have killed more than 10,000 people.

Nearly a week after the disaster, police said more than 452,000 were staying in schools and other shelters, as supplies of fuel, medicine and other necessities ran short. Both victims and aid workers appealed for more help.

More than 4,300 people are officially listed as dead, but officials believe the toll will climb to well over 10,000.

"There is enough food, but no fuel or gasoline," said Yuko Niuma, 46, as she stood looking out over Ofunato harbor, where trawlers were flipped on their sides.

The threat of nuclear disaster only added to Japanese misery and frustration.

"The anxiety and anger being felt by people in Fukushima have reached a boiling point," the governor of Fukushima prefecture, Yuhei Sato, fumed in an interview with the Japanese television network NHK. He said evacuation preparations were inadequate, saying centers lacked enough hot meals and basic necessities.