Koeberg Unit 1 Return Delayed Until August 2025, Eskom Confirms No Increased Loadshedding Risk

July 15, 2025

Koeberg Unit 1 Maintenance Extended, No Increased Loadshedding Risk

Eskom has extended the planned maintenance for Koeberg Nuclear Power Station's Unit 1, pushing its return to service from July to the end of August 2025. Despite the delay, the power utility maintains this will not increase the risk of loadshedding during the winter period.

The extension comes after routine inspections detected defects in four tubes across two of the unit's newly installed steam generators, requiring additional maintenance work before the unit can safely return to operation.

What Caused the Delay?

During scheduled eddy current inspections — a non-destructive testing method that detects flaws in metal components — maintenance teams identified defects in four tubes among several thousand inspected in the newly installed steam generators.

Eskom reports that an automated repair process has already been completed on these tubes, with international specialists working alongside local experts to maintain safety and quality standards.

Importantly, the unit has successfully passed its mandatory 10-year Integrated Leak Rate Test (ILRT), confirming the structural integrity and leak-tightness of the reactor containment building after being pressurized over a 72-hour testing period.

Winter Electricity Supply Remains Stable

According to Eskom, the extended maintenance period for Koeberg Unit 1 will not affect the Winter Outlook released on May 5, which remains valid through August 31, 2025.

The winter plan does not depend on Koeberg Unit 1's return and indicates:

• No loadshedding if unplanned outages stay below 13,000MW
• Maximum of 21 days of loadshedding (capped at Stage 2) if unplanned outages reach 15,000MW

Significantly, no loadshedding has been implemented since May 15, 2025, with only 26 hours recorded since the beginning of the financial year on April 1.

Generation Improvements Bolster Grid Stability

While Koeberg Unit 1 undergoes maintenance, Eskom has achieved several generation milestones in 2025 that have added 1,600MW to the national grid:

• Kusile Unit 6 (800MW) was synchronized to the grid on March 23, 2025, with commercial operation expected by September
• Kusile Units 1, 2, and 3 (2,400MW total) were reconnected to the repaired west stack between February and May 2025, now operating with their flue gas desulphurisation (FGD) systems
• Medupi Unit 4 (800MW) returned to service on July 6, 2025, after being offline since August 2021

Koeberg Unit 2 continues to operate at full capacity, contributing up to 946MW with an impressive year-to-date Energy Availability Factor (EAF) of 99.38% as of June 2025.

Outlook: What This Means for South Africans

The national power system appears to be in a relatively stable position compared to previous years, with Eskom reporting a month-to-date EAF of 62% — significantly better than the sub-50% levels seen during the height of the 2023 crisis.

While the delay in returning Koeberg Unit 1 represents a setback in Eskom's maintenance schedule, the utility's improved generation capacity elsewhere in the fleet has created enough headroom to absorb this extension without triggering additional loadshedding.

However, the power system remains vulnerable to unexpected breakdowns, particularly during winter when demand typically rises. Prudent energy usage continues to be recommended as winter progresses.

Key Terms Explained

Eddy Current Inspection: A non-destructive testing method that uses electromagnetic induction to detect flaws in conductive materials without damaging them — like an MRI scan for metal components.

Integrated Leak Rate Test (ILRT): A mandatory safety test conducted every 10 years where a nuclear reactor's containment building is pressurized to ensure it can effectively prevent radioactive material from escaping in case of an accident.

Flue Gas Desulphurisation (FGD): An environmental control system that removes sulphur dioxide from exhaust gases before they're released into the atmosphere, reducing harmful emissions from coal power plants.

Energy Availability Factor (EAF): A percentage measuring how much of a power station's maximum generating capacity is available for use. A higher EAF means more reliable electricity production — Eskom targets 70% EAF for a stable grid.

Baseload Power: Electricity that consistently supplies the minimum level of demand on the power grid. Nuclear plants like Koeberg provide reliable baseload power that runs 24/7, unlike intermittent renewable sources.

1MW: Enough electricity to power approximately 650 average South African homes. Koeberg's total capacity of 1,860MW can therefore power around 1.2 million homes when both units are operational.