Updated

As Japan crossed the one-week mark since the twin natural disasters spawned the nuclear crisis, the Japanese government conceded Friday it was slow to respond and welcomed ever-growing help from the United States in hopes of preventing a complete meltdown at the Fukushima Dai-ichi power plant.

The natural disasters claimed more than 7,200 lives, with many thousands more missing in an area struck first by a magnitude 9.0 quake and then an enormous wall of water that seemed to scrape the earth clean.

Rescues have been few, with the latest Saturday in the rubble of Kesennuma city, where a young man was pulled from a crushed house. He was too weak to talk and transferred immediately to a hospital, a military official said, declining to be named because he was not authorized to speak with reporters.

Emergency crews at the nuclear plant faced two continuing challenges: cooling the nuclear fuel in reactors where energy is generated and cooling the adjacent pools where thousands of used nuclear fuel rods are stored in water.

"In hindsight, we could have moved a little quicker in assessing the situation and coordinating all that information and provided it faster," Chief Cabinet Secretary Yukio Edano said Friday.

The plant operator was working steadily to rebuild the wiring of power lines to six reactors, and planned to finish circuitry to units 1, 2, 5 and 6 finished Saturday, said Hidehiko Nishiyama of the Nuclear and Industrial Safety Agency said. Workers planned to reconnect troubled Unit 3 on Sunday, he said.

However, much work remains to be done before operators can flip the switch to test crucial cooling systems at the plant.

"Most of the motors and switchboards were submerged by the tsunami and they cannot be used. A thorough examination must be carried out to determine if there is leakage of electricity and whether some switchboards remain usable," Nishiyama said at a briefing Saturday.

Even once the power is reconnected, it is not clear if the cooling systems will still work.
The storage pools need a constant source of cooling water. Even when removed from reactors, uranium rods are still extremely hot and must be cooled for months, possibly longer, to prevent them from heating up again and emitting radioactivity.

In the largely destroyed town of Hirota, 70-year-old Tetsuko Ito wept as she hugged an old friend she met at a refugee center. One of her sons was missing and another had been evacuated from his home near the Fukushima complex.

"Every day is terrifying. Is there going to be an explosion at the reactor? Is there going to be word my other son is dead?" she said.

If the situation gets worse in Fukushima, she said her evacuated son and his family will have to live at her already crowded house, which escaped the tsunami.

"It's strange when this destroyed area is a place someone would consider safe," she said.

Japan's government raised the accident classification for the nuclear crisis from Level 4 to Level 5 on a seven-level international scale. That put it on a par with the Three Mile Island accident in Pennsylvania in 1979, and signified its consequences went beyond the local area.

Edano also said Tokyo was asking Washington for additional help, a change from a few days ago, when Japanese officials disagreed with American assessments of the severity of the problem.

The Science Ministry said radiation levels about 19 miles northwest of the Fukushima Dai-ichi plant rose at one time Friday to 0.15 millisieverts per hour, about the amount absorbed in a chest X-ray. While levels fluctuate, radiation at most points at that distance from the facility have been far below that. The ministry did not have an explanation for the rise.

A U.S. military fire truck was among a fleet of Japanese vehicles that sprayed water into Unit 3, according to air force Chief of Staff Shigeru Iwasaki, sending tons of water arcing over the facility in an attempt to prevent nuclear fuel from overheating and emitting dangerous levels of radiation.

Additionally, the United States also conducted overflights of the reactor site, strapping sophisticated pods onto aircraft to measure radiation aloft. Two tests conducted Thursday gave readings that U.S. Deputy Energy Secretary Daniel B. Poneman said reinforced the U.S. recommendation that people stay 50 miles away from the Fukushima plant. Japan has ordered only a 12-mile evacuation zone around the plant.

American technical experts also are exchanging information with officials from the Tokyo Electric Power Co. which owns the plants, as well as with Japanese government agencies.

The tsunami knocked out power to cooling systems at the nuclear plant and its six reactors. In the week since, four have been hit by fires, explosions or partial meltdowns. The events have led to power shortages and factory closures, hurt global manufacturing and triggered a plunge in Japanese stock prices.

Most of Japan's auto industry is shut down. Factories from Louisiana to Thailand are low on Japanese-made parts. Idled plants are costing companies hundreds of millions of dollars. And U.S. car dealers may not get the cars they order this spring.

Prime Minister Naoto Kan vowed that the disasters would not defeat Japan.

"We will rebuild Japan from scratch," he said in a nationally televised address, comparing the work with the country's emergence as a global power from the wreckage of World War II.

While nuclear experts have been saying for days that Japan was underplaying the crisis' severity, Hidehiko Nishiyama of the nuclear safety agency said the rating was raised when officials realized that at least 3 percent of the fuel in three of the complex's reactors had been severely damaged.

That suggests those reactor cores have partially melted down and thrown radioactivity into the environment.

Low levels of radiation have been detected well beyond Tokyo, which is 140 miles south of the plant, but hazardous levels have been limited to the plant itself.

Police said more than 452,000 people made homeless by the quake and tsunami were staying in schools and other shelters, as supplies of fuel, medicine and other necessities ran short.