Eskom has released details of two airborne radioactivity events that temporarily halted steam generator inspections at Koeberg Unit 2 on July 2 and 7.
Microscopic oxide particles became airborne within an enclosed work area during the inspections, triggering the nuclear power station’s monitoring alarms. The area was secured and radiological assessments were completed before work resumed, Eskom said. No radioactive material was released into the environment and the Unit 2 outage schedule remains unaffected.
The events occurred while robotic probes were being moved through the steam generator tubes as part of eddy current testing. According to Eskom, the particles remained within the controlled work area inside the containment building.
“A very small quantity of microscopic oxide particles, commonly referred to in the nuclear industry as ‘crud’, became airborne within the enclosed work area,” Eskom said.
Eddy current testing is a non-destructive inspection technique used to measure the condition and wall thickness of steam generator tubes. The inspections are intended to detect wall thinning before it can affect the integrity of the barrier between the reactor coolant system and the secondary steam system.
Eskom said the work area is enclosed by physical containment barriers and maintained under negative pressure using high-efficiency particulate air-filtered ventilation. Constant air monitors continuously measure airborne radioactivity.
Monitoring equipment detected the increase in airborne activity and activated an alarm. Inspection work was stopped temporarily, the area was secured and the ventilation and filtration systems were allowed to remove the airborne particles. Radiological assessments were completed before work resumed, the utility said.
“All monitoring results confirmed that the transient remained confined within the controlled work area and that there was no release of radioactive material to the environment,” Eskom said.
The utility classified the events as Level 0, or no safety significance, on the International Nuclear and Radiological Event Scale.
Unit 2 has been offline for a scheduled maintenance outage since April. Its return to service remains scheduled for November while Unit 1 continues operating.
