Removal of Koeberg steam generators gets under way

The replacement of the steam generators at unit 1 had originally been planned to take place between February and June 2021, with those of unit 2 scheduled for replacement between January and May 2022. However, this has been delayed due to concerns about the tight supply of electricity while the units are offline.

The first steam generator has now been removed from the containment building of unit 1 - which entered a refuelling and maintenance outage on 10 December last year - and placed in the storage building that was built to house the steam generators, owner Eskom announced on 21 March.

"This is a significant accomplishment for the Koeberg team, the contractor and the numerous local and international subcontractors involved in the project," the company said. "It is a great relief to have reached this milestone as the steam generator replacement project has experienced numerous false starts in previous outages and some unexpected challenges during the execution in the current outage to get to this point in the project."

The steam generator being manoeuvred into the storage building (Image: Eskom)

Eskom noted that once all three steam generators have been removed and the new ones installed, it still needs to complete the maintenance activities scheduled for the outage, commission all the systems, refuel the reactor and return the unit to service.

The company had earlier said the unit was expected to remain out of service until June 2023.

"Due to the delays that have already been experienced, the original return to service date for the unit is no longer achievable," Eskom noted. "Although every effort is being made to reduce the impact, we are currently running a few weeks late. The generation production plan is being optimised to minimise as far as possible the impact of the projected delay on the system."

Koeberg 2 will then undergo a similar outage for refuelling, maintenance and steam generator replacement starting in "the later part of this year". This is expected to last 180-200 days.

In 2014, Eskom signed a ZAR4.4 billion (USD240 million) contract with Areva - now Framatome - to design, manufacture and install the replacement steam generators, which each weigh over 320 tonnes and are 22 metres long. They have been made in China under subcontract by Shanghai Electric Power Equipment Company.

The work being done at Koeberg is part of activities to enable the plant to operate for another 20 years beyond its current licence, which expires in 2024-2025. The formal application to extend the operating licence was submitted to South Africa's National Nuclear Regulator in 2021, and Eskom submitted the safety case for long-term operation in support of the application in July 2022. The regulator has two years to conclude the review and provide an outcome, but no safety concerns have been identified that would preclude long term operation, and the company anticipates receiving the licence to operate beyond 2024.

"In accordance with the safety analysis that was performed and submitted to the National Nuclear Regulator in support of the application to extend the plant life by 20 years, the steam generators are the last large component replacements that are needed to ensure Koeberg can operate safely for the requested additional period of operation," Eskom said. "Thus, Eskom sees this milestone as an important step on the path to safely extending the life of Koeberg."

The twin 930 MWe (net) pressurised water reactors at Koeberg were built by Framatome, with unit 1 beginning commercial operation in 1984 and unit 2 the following year. They generate about 5% of the country's electricity.