Electricity utility Eskom reported on Monday that Koeberg Unit 1 would be taken offline for repairs one month ahead of scheduled maintenance after an increasing leak rate was detected from one of the unit’s three steam generators.

Eskom said in a statement that the leak rate was “well within the safety limits” and posed “no risk to plant, personnel, or the environment”. It also described the decision to take the unit offline as a conservative one.

“During this period the unit will also undergo its routine maintenance and refuelling, which was originally scheduled to start during February. The unit is expected to return to service during May 2021.”

Eskom also confirmed with Engineering News that it had decided that the first three new steam generators delivered in September for installation at Unit 1 during a planned outage between February and June, would instead be installed at Unit 2 during its next refuelling and routine maintenance outage scheduled for between January and May 2022.

The installation of the six new steam generators is a core part of a larger R20-billion programme to extend Koeberg’s operational life by 20 years to 2045.

The steam generator is a tubular heat exchanger which mechanically dries the steam produced during the nuclear power generation process.

The replacement of the six steam generators at units 1 and 2 has already been delayed from the original completion date of late 2019, owing to serious manufacturing problems as reported by energy expert Chris Yelland last year.

Framatome, of France, is the main contractor, but the steam generators were manufactured primarily in China, with additional components sourced in various countries in Asia, Europe and US.

Eskom reports that installation will be conducted through a consortium of Framatome and a local company.

The other major components of the life-extension plan include:

• a refuelling water storage tank replacement project, which was completed in 2019;
• the Unit 2 reactor pressure vessel head replacement, for which manufacturing is scheduled to be completed in 2021 and the installation of which is planned for 2022;
• the replacement of feed-train components on the conventional power plant, which is conducted during maintenance outages; and
• the ongoing Koeberg safety aspects of long-term operation (SALTO) assessment.

The SALTO assessment is designed to provide the equipment ageing management “argument” to enable the Koeberg plant to operate beyond the original 40 years life span to at least 60 years.

This safety case will be presented to the National Nuclear Regulator mid-2022 to enable approval of the Koeberg plant to enter into long-term operation from mid-2024.

Eskom said Koeberg Unit 2, which returned to service late last year following its twenty-fourth refuelling outage, continued to operate and generate at full power on January 4.

Nevertheless, the shutting of Unit 1 removed 930 MW of capacity at a time when much of Eskom’s coal fleet was unavailable, owing either to the summer maintenance peak or to unplanned breakdowns.

"Eskom has repeatedly told the public that the risk of load-shedding remains high until the reliability maintenance has been completed in the later part of this year," spokesperson Sikonathi Mantshansha said in response to an Engineering News enquiry about the outlook for the system following the shutdown of Unit 1.

"We have 7 641 MW of capacity in planned maintenance, with unplanned outages of 11 381 MW.

"As we have always done, should there be a need to make any announcement about load-shedding, Eskom will do so timeously," he added.