Cape Town - Eskom's Koeberg nuclear power plant outside Cape Town will return to full service on Sunday after a fault exacerbated load-shedding this week, the power utility said on Thursday.
Unit 1 at South Africa's only nuclear power plant was taken offline by operators on Tuesday after its cooling capability was compromised by a faulty pump.
The pump was not able to reduce heat because a drum filter was clogged by marine life, Eskom said.
"The circulating cooling water system pump that tripped was due to low level in the suction pit as a result of the drum filter that was clogged by an acute ingress of marine life (jellyfish and fish)."
It added that normally Koeberg units can withstand the impact of one cooling water system pump failing, provided that operators reduce power to below 60 percent and ensure that the temperature of various secondary components stabilise.
In this case, however, the temperature could not be stabilised because a heat exchanger had reduced functionality and had been due for maintenance in the coming week.
"The excess marine life and debris has been cleared off the drum filter and it is back in service. The level in the suction pit has sufficiently recovered and the circulating water system pump has been put back in service and no anomalies have been noted. Upon inspection, it was found that the pump had not been damaged as initially feared," Eskom said.
The necessary technical assessments and approvals have now been obtained to safely return Unit 1 to service. At this stage, Eskom was expected to do so on Sunday.
The power utility said Stage 4 loadshedding was expected to continue until Friday evening, and that reduced levels of staged blackouts would be implemented over the weekend.
It said it was currently using emergency generation reserves to supplement electricity supply.
In total the national grid was experiencing a shortage of supply of more than 17 500 megawatt.