Johannesburg - Power utility Eskom said on Wednesday it would shut one of two units at its 1 800 MW Koeberg nuclear plant for a month for repairs.
Eskom said it would seek to ensure sufficient generating capacity to meet demand for electricity, but appealed to consumers to conserve energy.
"Koeberg Unit 1 is experiencing higher than normal levels of radioactivity in its primary coolant circuit as a result of one or more defective fuel rods in the reactor," Eskom said. It added there was no safety risk to the public or its staff.
The unit would be shut on Sunday December 19, ahead of the holiday period when demand for power is expected to be lower than usual.
The summer period is, however, also Eskom's prime maintenance season, which could lead to supply being tight.
Eskom, which supplies the majority of South Africa's electricity, has been struggling to meet fast-rising demand and has warned that supply would remain tight until 2015, and especially over the next two years, until its two new power plants come on stream.