Transparency trial â Four radioactive incidents, one question: What do Koebergâs maintenance failures reveal?

This story has significance for readers across Africa and beyond.

The incidents â including failures in ventilation equipment during a planned maintenance outage â have renewed concerns among experts about operational discipline after Koebergâs delayed refurbishments.

The widely reported incidents unfolded while Koebergâs Unit 2 reactor was offline during the planned outage, which involved the testing of steam generators

Initial media reports earlier this week, citing the National Nuclear Regulator (NNR), referred to three incidents of elevated airborne radioactive contamination on 30 June, 2 July and 7 July.

However, Eskom chief nuclear officer Velaphi Ntuli said during a subsequent media briefing on Sunday that the events were not all cases of airborne contamination and had to be distinguished from one another.

The briefing was convened by Electricity and Energy Minister Kgosientsho Ramokgopa alongside Eskom, South Africaâs state-owned power utility.

The minister said they wanted to address public concerns triggered by reports of the incidents and especially ahead of the governmentâs scheduled expansion of nuclear power.

âFourâ, not three, incidents

Koeberg is Africaâs only nuclear power station.

It is situated just 25km north of Cape Town on the Western Capeâs West Coast.

According to Ntuli, a 30 June event started with an alarm on a workersâ electronic personal dosimeter. He said Eskom did not classify this as an airborne contamination event: workers were allowed to resume their activities when reportedly no significant problem was found.

Two subsequent incidents, on 2 and 7 July, were marked by increased levels of airborne radioactive material inside the containment building.

When addressing the press, Eskom disclosed a fourth occurrence for the sake of âtransparencyâ.

Contamination during steam-generator testing

Ntuli said that, although the containment building was opened during outages to allow planned maintenance work, it was placed under negative air pressure to prevent uncontrolled air escaping.

But an âeddy-current testingâ phase of steam generators had dislodged small quantities of radioactive corrosion products, including cobalt-58, which became airborne within the immediate work area.

This testing technique, Eskom stressed in its own post-briefing statement, was âa globally applied, non-destructive inspection techniqueâ.

Because the airborne cobalt was the sort of thing that was anticipated, Ntuli claimed, Eskom had placed a temporary enclosure, or âtentâ, around the relevant work area and used portable ventilation units to filter contaminated air.

However, the ventilation units suffered power-supply failures on two occasions.

When monitors then flagged airborne contamination, a âstandardâ procedure was followed. Work was stopped, workers were shuttled out and radiation-protection teams investigated before any other work would be allowed to resume, he noted.

About those ventilation failures

On 2 July, monitors detected a rising radiation trend. Next, Ntuli explained, a precautionary evacuation was ordered. As workers left the containment building, an alarm confirmed the presence of airborne contamination.

At the time, 51 workers were evacuated. About 245 workers who had been inside the building at some point that day underwent whole-body counting, a test used to detect internal radioactive contamination.

Ntuli said the 2 July incident was traced to a ventilation unit whose electrical cord had burnt out.

On 7 July, radiation-protection staff detected contamination leaking from the tent into the wider containment area and ordered another âpre-emptiveâ evacuation.

Ntuli put it delicately: âThere was a challenge with the power supply. It looks like that it had been displaced from the power socket.â

Fourteen workers were involved in the affected area. A further seven âvoluntarilyâ underwent whole-body counting.

On 16 July, monitors again detected an increase in airborne contamination during steam-generator testing. Work was stopped, no alarm was triggered.

âSo why are we seeing so much?â Ntuli asked during his Sunday slide presentation. âAfter a steam generator replacement outage, this is to be expected because of corrective material that accumulates...â

Ntuli said Eskom was still finalising the results of voluntary tests, and was investigating further details around the loss of power to the ventilation system.

Low worker doses

The âmaximumâ dose recorded during the incidents was 20 microsieverts.

Ntuli compared this to Koebergâs annual occupational exposure limit of 20,000 microsieverts for radiation workers.

He denied that negligence was a cause and also rejected any suggestions that potassium iodide tablets had been issued, which are intended to offer protection against radioactive iodine.

That is because reactor fuel had been removed from the containment building before maintenance was launched and was stored in the plantâs fuel building. The incidents, therefore, did not involve damaged fuel or a release of radioactive iodine.

Since the material detected during maintenance was associated with cobalt corrosion rather than iodine-131, the tablets would have provided no protection, he argued.

No release beyond the plant

The NNR and Eskom were at pains to point out that no radioactive material escaped into the environment and there was no danger to surrounding communities.

NNR spokesperson Gino Moonsamy told Daily Maverick the events were also not categorised as a nuclear emergency.

âThere was no safety impact on the public. It is an internal operational issue,â he said. âThe NNRâs regulatory investigation and verification process are active and currently ongoing.â

For his part, Ntuli remarked that the incidents were not reportable under Eskomâs procedures and argued that the plantâs radiation-protection systems had operated as intended.

âOur systems and safeguards that we put in place worked,â he said. Where a ventilation unit failed, the monitoring system detected the change in conditions.

âThe event was safely managed to international standards by Koebergâs highly trained teams, with no impact on nuclear safety, plant operations, maintenance activities or the planned scheduled outage completion date of November 2026,â Eskom said. âThe outage remains on schedule and Koeberg Unit 1 remains in full operation.â

âThat should never happenâ

Energy experts interviewed by Daily Maverick agreed that the incidents did not appear to have endangered the public.

They differed from Eskom, however, on whether the equipment failures should be regarded as routine operational occurrences or as part of a broader pattern of problems during Koebergâs refurbishment.

Energy analyst Chris Yelland said the contamination events appeared limited in severity, but were concerning.

âFrom what I can read, itâs not a very severe problem in the sense that it hasnât resulted in radiation outside of the containment building,â he said.

The analyst said the failure of ventilation equipment during planned maintenance warranted scrutiny.

âThat should never happen,â he said.

Proud of our Koeberg Nuclear teamâs swift, professional response to recent minor internal events - fully contained, no environmental release, no risk to the public.

— Mteto Nyati (@mteton) July 19, 2026

40+ years of safe operation, with both unitsâ licences extended to 2044/2045. This is what skilled people,⦠pic.twitter.com/wQJEDJyh1Z

Peter Becker, spokesperson for the anti-nuclear civil society organisation Koeberg Alert Alliance, said the events should be considered alongside previous operational errors during Koebergâs refurbishment.

âThere have been a long list of slip-ups during the refurbishment aimed at extending the planned life of the plant,â Becker said.

âOne would not expect a well-managed plant to have these incidents,â said Becker, who served as a non-executive director of the NNR from June 2021 until his removal by then Mineral Resources and Energy Minister Gwede Mantashe in February 2022.

Mantashe argued that Beckerâs public opposition to nuclear energy created a conflict of interest. In June 2024, the Supreme Court of Appeal ruled that his removal had been unlawful.

Becker linked the recent contamination events to workforce experience and capacity, particularly following the loss of skilled nuclear personnel to other countries.

Disagreement over the significance of the failures

Professor Hartmut Winkler, a physicist at the University of Johannesburg, said the new information supplied by Eskom showed that the incidents were not nuclear accidents and did not pose a catastrophic risk.

But repeated problems affecting the plantâs contamination-control measures were a legitimate worry.

âThis,â he said, echoing Yelland, âshould not have happened.â

Winkler said he wanted to see âa proper, official report of what happened and the full consequences. Eskom has to improve its communications.â

Calls for greater disclosure

Koeberg has operated since the mid-1980s.

After safety assessments and major refurbishment work, both reactors have received NNR approval to operate for a further 20 years beyond their original operating lives.

Unit 1 is licensed to operate until 2044; Unit 2 is set push ahead to 2045.

When both units are operating, Koeberg produces roughly 5% of South Africaâs electricity.

But Isabel Bosman-Burnett, a governance researcher at the South African Institute of International Affairs, observed that ânuclear power plants do not operate in a legal vacuum and are subject to very strict international and domestic safety and security requirementsâ.

âThe fact that the leak was detected by the safety systems in the containment building should contribute to reassurance that the plant remains safe and that systems function as intended.â

She defended South Africaâs ârobust nuclear regulatory framework and ecosystem of organisations that all work together to ensure the continued safe operation of Koeberg and the wider domestic nuclear industryâ.

Francesca de Gasparis, executive director of the South African Faith Communitiesâ Environment Institute, said the incidents reinforced the need for greater transparency.

The story of the first three incidents had broken on Thursday, 16 July. Eskom issued a statement on Sunday â and only disclosed the fourth incident after days of speculation in local and international media.

She argued that, while contamination was contained, it should be examined as a possible indicator of broader operational weaknesses.

âThe concerning thing is that we donât really know whatâs going on inside Unit 2,â she argued. DM

Reporting originally appeared via Daily Maverick. Read the full source for additional context.