TOKYO - (AP) - One week after an earthquake and tsunami spawned anuclear crisis, the Japanese government conceded it was slow torespond to the disaster and welcomed ever-growing help from theUnited States in hopes of preventing a complete meltdown at theFukushima Dai-ichi power plant.

The entire world was on alert, watching for any evidence ofdangerous spikes in radioactivity spreading from the six-reactorfacility, or that damage to the Japanese economy might send rippleeffects around the globe.

As day broke in northeastern Japan on Saturday, steam rose fromUnit 3, an unwelcome development if not a new one that signaledcontinuing problems. Emergency crews faced two continuingchallenges at the plant: cooling the nuclear fuel in reactors whereenergy is generated and cooling the adjacent pools where thousandsof used nuclear fuel rods are stored in water.

Crucial to the effort to regain control over the plant is layinga new power line to the complex, allowing operators to restorecooling systems. Tokyo Electric said it has brought the cable tothe plant and was expected Saturday to try to connect it to thefacility's Unit 2; the utility has already missed a Thursdaydeadline to do that.

Power company official Teruaki Kobayashi warned that expertswill have to check for anything volatile to avoid an explosion whenthe electricity is turned on. "There may be sparks, so I can'tdeny the risk," he said.

Even once the power is reconnected, it is not clear if thecooling systems will still work.

The storage pools need a constant source of cooling water. Evenwhen removed from reactors, uranium rods are still extremely hotand must be cooled for months, possibly longer, to prevent themfrom heating up again and emitting radioactivity.

The government raised the accident classification for thenuclear crisis from Level 4 to Level 5 on a seven-levelinternational scale. That put it on a par with the Three MileIsland accident in Harrisburg, Pa., in 1979, and signified itsconsequences went beyond the local area.

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

The Science Ministry said radiation levels about 30 kilometers(19 miles) northwest of the Fukushima Dai-ichi plant rose at onetime Friday to 0.15 millisieverts per hour, about the amountabsorbed in a chest X-ray. While levels fluctuate, radiation atmost points at that distance from the facility have been far belowthat. The ministry did not have an explanation for the rise.

A U.S. military fire truck was among a fleet of Japanesevehicles that sprayed water into Unit 3, according to air forceChief of Staff Shigeru Iwasaki, sending tons of water arcing overthe facility in an attempt to prevent nuclear fuel from overheatingand emitting dangerous levels of radiation.

Additionally, the United States also conducted overflights ofthe reactor site, strapping sophisticated pods onto aircraft tomeasure radiation aloft. Two tests conducted Thursday gave readingsthat U.S. Deputy Energy Secretary Daniel B. Poneman said reinforcedthe U.S. recommendation that people stay 50 miles (80 kilometers)away from the Fukushima plant.

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

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