Energy29.12.2023

Final test for renewed Koeberg unit

Eskom said that Unit 1 at its Koeberg Nuclear Power Station will be undergoing its final test following the installation of new steam generators over the past year.

The full load rejection test to be carried out on Saturday, 30 December 2023, will “verify and demonstrate” the unit’s ability to supply its auxiliary load and return to steady state conditions following a sudden disconnection from the national grid.

Eskom explained that the South African Grid Code (SAGC) required that units be tested if modifications were made that could impact their capability to meet the SAGC requirements.

“As part of the steam generator replacement project, significant changes were made on numerous plant components, including control systems,” Eskom said.

“Therefore, in line with SAGC, the response of the unit to a full load rejection incident needs to be tested and verified.”

Eskom said it was confident the test would be a success as it had conducted various successful commissioning tests in the lead-up to this last hurdle.

“However, in the unlikely event of the test failing and resulting in a unit trip, the Koeberg team is ready to respond and will work towards safely returning the unit back to service as soon as possible,” Eskom said.

One of the new steam generators destined for Eskom’s Koeberg Power Station.

The power utility synchronised Unit 1 back onto the grid on 18 November 2023. It had been offline for a critical long-term refurbishment and refuelling project since December 2022.

Eskom originally planned to bring the unit back online by June 2023 but suffered multiple delays.

Following Unit 1’s return to the grid, Unit 2 was taken offline for its refurbishment on 11 December 2023.

Electricity minister Kgosientsho Ramokgopa said that Eskom had learnt from the mistakes and shortcomings relating to Unit 1, and he had asked the project team to keep to the timelines for Unit 2’s return.

In its near 40 years of commercial operation, Koeberg has been Eskom’s most reliable power plant, providing a peak capacity of about 1,940MW when both units are operational.

However, even if both Unit 1 and Unit 2’s refurbishments are a success, the plant will rarely be operating with both units at the same time over the next few years.

According to the National Nuclear Regulator, the units will each face a 200-day outage following the completion of Unit 2’s steam generator replacement.

These outages will take place for containment pressure testing aimed at ensuring that the concrete structures housing the units are secure.

These additional outages will occur regardless of whether Koeberg’s licence is de-coupled, another major hurdle in Eskom’s attempt to avoid having the power station exceed its permitted operating lifetime before the extension.