New delays at South Africa’s nuclear power station add to load shedding woes

 ·17 May 2023

Eskom plans to shut down unit 1 of the Koeberg Nuclear Power plant for another 200 days next year, says energy expert Chris Yelland, EE Business Intelligence – and this will likely add to the group’s inability to keep South Africa supplied with power.

Koeberg nuclear power station is currently offline for maintenance, refuelling and refurbishment in preparation for a 20-year life extension. The process has already been delayed, with the unit only expected to come back online in August.

However, Yellend noted that there is already another shutdown of the unit planned for 24 July 2024 – three days after its current 40-year operating licence for the station expires on 21 July 2024.

Eskom is now in a race against time to meet stringent requirements for extending the nuclear power station’s operating licence before July next year, when the National Nuclear Regulator (NNR) will have to decide whether Koeberg is able to safely operate for another 20 years.

“Each of the two units at Koeberg – Unit 1 and Unit 2 – has a rated capacity of 970 MW. The further outage of Unit 1 will therefore remove about 900 MW from the grid for another 200 days,” he said.

This is equivalent to nearly one stage of load shedding at a time when the electricity supply in South Africa is already severely constrained, said Yelland.

The latest planned shutdown, announced in an Eskom briefing on 9 May, means that Unit 1 will not be operating from 24 July 2024 until mid-February 2025, and suggests that the continued operation of Unit 1 after the deadline will be delayed, said the energy expert.

During the briefing by the power company, Eskom said that the NNR-approved licence is needed to allow fuel to be re-introduced to the nuclear reactor.

Koeberg Unit 1 has been offline for maintenance and other life-extension work since December 2022.

Yelland said that it is not immediately clear why Eskom and/or the NNR would require another 200-day shutdown.

Eskom told EE Business Intelligence that the extended delay was a result of a test that needed to be performed on the nuclear plant relating to leaking. The company plans to conduct a routine 10-yearly containment integrated leak rate test, said Yelland

It has been previously indicated to EE Business Intelligence that corrosion of steel reinforcing (rebar) under coastal conditions is resulting in cracks in the concrete of the nuclear reactor containment silos and that this requires ongoing maintenance and repair work, said Yelland.

Perhaps it is this work, and the associated inspections and testing, that is required during further outages before the reactors can resume long-term operation for another 20 years.

The details and timing of a similar further outage 227 for Koeberg Unit 2 have not been clarified by Eskom yet, said the energy expert.

Extending the life of Koeberg was initially given a rough budget of R20 billion in 2010. Eskom now insists that the actual cost – 13 years later – is R22 billion.

Yelland said that the total capital cost of the Koeberg life extension project is particularly murky and will likely never be known publicly.

“This is because many of the capital costs, such as the replacement of the reactor head on Unit 1, and several other plant replacements and refurbishments, have been treated by Eskom as normal routine maintenance and expensed,” said Yelland.

He added that these costs are insignificant when the cost to the South African economy as a result of Koeberg being out for about 28 months is taken into account.

“Based on an estimated cost of unserved energy of R30 per kWh, the cost of not having 900 MW of continuous power from Koeberg when needed by the productive economy for 28 months is conservatively estimated at some R500 billion,” said Yelland.


The Koeberg life-extension project, which aimed to extend the lifespan of the power plant, has faced mismanagement and delays since its start in 2008.

Eskom originally identified three critical components that needed replacement: steam generators, refuelling water storage tanks, and reactor pressure vessel heads.

The process of bringing those back to operational capacity was set back when the steam generator replacement contract was halted in 2012 and only restarted in 2014.

According to Yelland, legal disputes further delayed the project, and due to manufacturing defects, the steam generator replacement was rescheduled multiple times.

The steam generators had to be remanufactured in China after unsuccessful attempts in France. Despite challenges, the refuelling water storage tanks and reactor pressure vessel heads have been replaced, and the replacement of the steam generators on Unit 1 is currently underway, said the energy expert.

The steam generators on Unit 2 are scheduled to be replaced starting in late 2023, with completion expected in April 2024, he added.

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