UPDATE 1-Eskom's Koeberg plant unit shut after fault

* Koeberg’s second unit shuts due to technical fault

* Entire Koeberg plant offline as other unit on maintenance

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JOHANNESBURG, April 2 (Reuters) - South Africa’s power utility Eskom [ESCJ.UL] said on Thursday the second unit at its Koeberg nuclear power station had shut down automatically after a technical fault, and the company was investigating the cause.

Koeberg’s only other unit has been shut for scheduled maintenance since January, which means the facility’s total power capacity of 1,800 megawatts was out of service.

Each of the two units at Koeberg, Africa’s sole nuclear power generating facility, produce 900 MW.

“Unit 2 automatically shut down this afternoon due to an unspecified technical fault and we are still investigating the cause of that fault,” Eskom’s spokesman Tony Stott said.

He said it was unclear when the unit would be re-started.

Stott said the nuclear section of the unit was not affected by the fault and was in a safe condition, and the problem had taken place in the turbo generator section of the unit.

He said the company had sufficient backup of a total of about 2,000 MW from gas-fired power generators, and said there was no immediate concerns of a national power shortage.

Eskom said its other unit at Koeberg would undergo refuelling, maintenance and upgrading, a process expected to be completed in May 2009. (Reporting by James Macharia; editing by Sue Thomas)