Reactor No 3 was restarted at 5:30 am (0330 gmt) after almost five months of repairs, and was gradually increasing output, said a spokeswoman for the plant requesting anonymity. She wouldn't say when the reactor was expected to reach full power

Officials at Chernobyl insist that Reactor No 3 is safe and free of any potential Y2K bugs.

Western governments and environmental groups have long urged the Ukrainian Government to close the plant, but the Ukrainian Government says it needs US $ 1.2 billion from the West to finish construction of two new reactors to replace the output that will be lost by closing Chernobyl.

The European Bank for Reconstruction and Development (EBRD), which has played a leading role in the discussions on financing, was supposed to make a loan decision in September. But it has taken no action, and other potentiallenders are expected to wait for the EBRD before they commit any money.

Chernobyl's Reactor No 4 exploded in April in 1986, spewing radiation over much of Europe. The reactor has been encased in a steel-and-concrete sarcophagus, and two others have were permanently shut down later.

Meanwhile, workers have begun repairs on the sarcophagus, which was hastily constructed after the accident to prevent additional radiation leaks. The workers will strengthen the sarcophagus' concrete beams, working through December from both inside and outside the huge structure.