On Sunday 1 February 2015 Koeberg Unit 1 tripped due to an earth fault, which was triggered by a scaffold touching the neutral earthing bar above the restricted earth circuit. At 20:20 on Thursday, 5 February 2015, while the unit was being synchronized to the national grid, a breaker trip occurred resulting in a turbine trip.
This means that the South African power grid will go into the weekend without the 930MW that was expected to come on line from the unit today.
The system will continue to be under severe pressure over the weekend and next week, so the risk of load shedding remains high, especially tomorrow. There is a shortage of generation capacity due to units that are on planned and unplanned maintenance. The focus is on returning the units that are on unplanned maintenance back on line in order to increase available capacity next week. Eskom will also use the weekend to build up diesel stocks and dam water levels for the open cycle gas turbines (OCGTs) and pumped storage schemes respectively in order to ensure that these reserves are available during the week.
Eskom has decided to keep the Koeberg’s Unit 1 on shutdown to enable completion of a detailed investigation to determine the root cause of the trip. The reactor is being operated as per the safety specifications and there is no threat to plant, personnel, members of the public, and the environment.
At no stage during the incidents, was there any threat to the reactor or nuclear safety.
Koeberg Unit 1 is scheduled to enter into a refueling and maintenance outage on Monday, 9 February 2015 and is expected to return back to service at the end of May.
The scheduled shutdown of Koeberg Unit 1 is part of Eskom’s overall maintenance programme for its fleet of power stations. Every 16 to 18 months, each of the two units at Koeberg is shut down for refuelling, inspection and maintenance. The routine shutdowns are scheduled so as to avoid having both units out of service at the same time and to avoid the winter months in each year.
During these routine planned outages, one third of the used nuclear fuel is replaced with new fuel. Statutory inspections and maintenance is performed, and modifications, that will ensure that international safety standards continue to be met or that improve the plant performance, are implemented.
Koeberg Unit 2 is currently operating at 100% power and is contributing 930MW to the national grid.
We would like to thank all the customers who responded to our call and reduced their energy consumption, which helps reduce the severity of load shedding. We sincerely apologise for the inconvenience to affected customers.
We call on all South Africans to continue using electricity sparingly in order to limit the severity of load shedding. Businesses and households can make a difference by implementing saving measures in their processes and daily lives. Eskom implements load shedding as a last resort to protect the grid, shedding only what is required to balance demand and supply. We are implementing our maintenance plan to increase the reliability of our plant, which will in turn increase our operating reserves and stabilise the grid. Load shedding schedules are available at http://loadshedding.eskom.co.za
