TOKYO (Reuters) - Exhausted engineers attached a power cable to the outside of Japan's tsunami-crippled nuclear station on Saturday in a race to prevent deadly radiation from an accident now rated at least as bad as America's Three Mile Island in 1979.
Further cabling inside was underway before an attempt to restart water pumps needed to cool overheated nuclear fuel rods at the six-reactor Fukushima plant in northeastern Japan, 240 km (150 miles) north of Tokyo.
Japan's unprecedented multiple crisis of earthquake, tsunami and radiation leak has unsettled world financial markets, prompted international reassessment of nuclear safety and given the Asian nation its sternest test since World War Two.
It has also stirred unhappy memories of Japan's past nuclear nightmare -- the U.S. atomic bombs dropped on Hiroshima and Nagasaki in 1945.
Working inside a 20 km (12 miles) evacuation zone at Fukushima, nearly 300 engineers were focused on trying to restore power at pumps in four of the reactors.
"TEPCO has connected the external transmission line with the receiving point of the plant and confirmed that electricity can be supplied," the plant's operator Tokyo Electric Power Co said in a statement.
Another 1,480 meters (5,000 feet) of cable are being laid inside the complex before engineers try to crank up the coolers at reactor No. 2, followed by 1, 3 and 4 this weekend, company officials added.
Should that work , it will be a turning point.
"If they can get those electric pumps on and they can start pushing that water successfully up the core, quite slowly so you don't cause any brittle failure, they should be able to get it under control in the next couple of days," said Laurence Williams, of Britain's University of Central Lancashire.
If not, there is an option of last resort under consideration to bury the sprawling 40-year-old plant in sand and concrete to prevent a catastrophic radiation release.
That method was used to seal huge leakages from the 1986 Chernobyl disaster.
Underlining authorities' desperation, fire engines sprayed water overnight in a crude tactic to cool reactor No. 3, considered the most critical because of its use of mixed oxides, or mox, containing both uranium and highly toxic plutonium.
Japan has raised the severity rating of the nuclear crisis from level 4 to level 5 on the seven-level INES international scale, putting it on a par with the Three Mile Island accident in 1979, although some experts say it is more serious.
Chernobyl, in Ukraine, was a 7 on that scale.
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