Automatic security systems at the Khmelnitsky nuclear power plant first cut off the reactor from the power grid Sunday only hours after it was launched, an official with Ukraine's governmental commission for atomic energy said.

The reactor was reconnected to the grid three hours later, but had to be totally shut down later because of a failure in the cooling system caused by a power breakdown, the official added.

It was restarted Monday, only to be stopped again Tuesday, officially to test its shut-down system and cooling units.

It is scheduled to be relaunched Thursday.

A plant spokesman contacted by AFP declined to comment, stressing that there had been no rise in radioactivity levels in and around the plant.

The K2 Russian-type water reactor, which has a capacity of 1,000 megawatts, came on stream on Sunday, at a ceremony attended by Ukrainian president Leonid Kuchma.

In a separate case, Ukrainian authorities on Wednesday gave the go-ahead to the controversial launch of a new nuclear reactor at the Rivne nuclear power plant on the country's western border with Poland, despite European protests and safety concerns.

Nuclear plants produce half of Ukraine's energy, which is otherwise forced to rely on supplies from Russia and its own decrepit and dangerous coal mining industry.

In 1986 one of the reactors at Chernobyl in Ukraine blew up in the world's worst nuclear accident, contaminating a large part of Europe.

Since the disaster, an estimated 25,000 people from all over the former Soviet Union who came to clean up after the accident have lost their lives.

WAR.WIRE