Photo: Koeberg is South Africa's only nuclear power plant (Credit: Pipodesign, Philipp P Egli CC BY 3.0)Unit 2 of South Africa’s Koeberg nuclear plant was closed down on 17 January for refuelling and modernisation. The work is part of plans to extend its operation for 20 years. The two 920MWe pressurised water reactors (PWRs) at Koeberg, which supply some 5% of the South Africa’s electricity, were built by Framatome, with unit 1 starting commercial operation in 1984 and unit 2 in 1985.  

Power utility Eskon said unit 2 had operated without interruption for 450 and that the outage is expected to last for five months. This will be the 25th refuelling outage of unit 2 since commissioning and will see the replacement of the unit’s three steam generators. During this outage the reactor pressure vessel head, which houses the nuclear fuel while the station is in operation, will also be replaced.

An outage of Koeberg 1, of a similar duration, will follow later in the year during which its steam generators will also be replaced. Its reactor pressure vessel head was replaced several years ago. Unit 1 was closed down for several months in January 2021 after an increasing leak rate was observed on one of its steam generators. Eskom used the outage to also undertake routine maintenance and refuelling, which was originally scheduled to start in February.

“The Koeberg outages are planned at times of the year when the impact on the overall electricity supply is minimised as far as possible,” Eskom said. “The extended unavailability of the units due to the planned long outages does mean the electricity supply system may be under additional strain during the coming year.”

Riedewaan Bakardien, Eskom’s Chief Nuclear Officer, noted: “This is going to be a long, but needed outage – the first of its kind for Koeberg. Our staff are prepared and committed to make history by ensuring success of this project. Nuclear safety is the paramount factor. We will progress the outage work diligently, making sure nuclear safety and safety of plant, personnel and public is top of mind.”

Koeberg Nuclear Power Station recently completed a key industry periodic nuclear safety review, and the station was confirmed by independent industry reviewers to be performing strongly in terms of safety and reliability. The National Nuclear Regulator (NNR) also routinely performs crucial regulatory reviews and monitoring aimed at ensuring that the station remains safe and meets all regulatory requirements.

“Replacing the steam generators is a precautionary safety measure. For the past five years Eskom and the NNR have been working on its application for extending Koeberg’s operating life,” Eskom said. “The replacement of the reactor pressure vessel head and steam generators has been identified by Eskom as a requirement for life extension. The successful replacement of these components is therefore an important element of the Safety Submission being prepared for submittal to the National Nuclear Regulator in mid-2022, in support of Koeberg’s operation for 20 additional years.”

In 2014, Eskom signed a ZAR4.4 billion ($285 million) contract with Areva — now Orano — to design, manufacture and install the replacement steam generators, each 20 metres long and weighing about 380 tonnes. They were made in China under subcontract by Shanghai Electric Power Equipment Company. 

Photo: Koeberg is South Africa's only nuclear power plant (Credit: Pipodesign, Philipp P Egli CC BY 3.0)