Thu 24 Jul 2008, 15:36 GMT

JOHANNESBURG (Reuters) - South Africa's state power utility Eskom, struggling to meet domestic demand, said on Thursday it saw an increased risk of power load-shedding in the next few weeks while a unit at its nuclear plant was out for repairs.

Eskom said on Tuesday it had shut down one of two electricity generating units at its Koeberg nuclear power station after a technical fault.

"Any loss of generating capacity places strain on the national grid. During the next few weeks while the unit at Koeberg is out for repairs the risk of load shedding is increased," Eskom said in a statement on Thursday.

It said due to the stringent safety requirements of the shutting down procedure, repairs and the restarting procedure would take about three weeks to complete.

Eskom it had also also had technical failures on generating units at its Majuba and Duvha power stations on Wednesday.

The Majuba unit had come back on stream on Thursday morning while the unit at Duvha was expected back by the weekend.

Eskom, which produces about 95 percent of South Africa's electricity, started rationing power through a process called load-shedding in January when the national power supply system virtually collapsed and millions were plunged into darkness.

Eskom suspended the programme in May, citing increased electricity savings from municipalities.

But South Africa's mines, including the world's biggest platinum and key gold operations -- which were shut down for five days in January -- are still operating with between 90 and 95 percent of their electricity requirements.

On Thursday the utility said the inadequate reserve margin between available generation and demand will continue until the benefits of an ongoing expansion programme become available or consumers reduced demand for electricity throughout the country.