Koeberg (Image: Eskom)
Work at unit 1 passed a significant milestone on 28 July, when the mechanical work on the steam generator replacement - the most significant part of the operation - was completed, the company said. This means it can now complete outage activities that could not be performed in parallel with the replacement of the steam generators. The reactor will then be reloaded with fuel and returned to service. Commissioning, including tests of the new steam generators, will take place while the unit is synchronised to the grid.
"Given all the outstanding activities, Koeberg unit 1 is planned to be commercially available on 3 November 2023," Eskom said. "Due to the deferment of the return of unit 1, the outage of unit 2 has been postponed to 7 November 2023 to ensure that there is no simultaneous shutdown of both Koeberg units and can confirm that resources are ready to start with the first activities of unit 2 outage."
The steam generators are the last of three major plant components that are being replaced at Koeberg to enable the state-owned utility to apply for a licence to operate South Africa's only nuclear power units for a further 20 years, to 2045. Both units' refuelling water storage tanks and reactor vessel closure heads have already been replaced in previous years. The new, more efficient, steam generators will also enable the plant to produce an additional 27 MWe, Eskom said.
Koeberg 1's maintenance outage began on 10 December 2022 and had originally been expected to last about six months. In May, Eskom said it envisaged the unit returning to service this September. The loss of unit 1's generating capacity - some 924 MWe (net) - alongside continuing issues, particularly at the Kusile coal-fired power plant, have contributed to severe constraints on South Africa's electricity system, where regular loadshedding has been in place over the South African winter months of June, July and August.
The deferral of Koeberg 1's return to service does not negatively impact Eskom's application with South Africa's National Nuclear Regulator to amend Koeberg's operating licence, Eskom said. "Furthermore, as part of a continual improvement process, Eskom is analysing the causes of the delays on unit 1 to ensure that they are not repeated during the upcoming steam generator replacement on unit 2," it added.
