In South Africa, Eskom’s nuclear power plant Koeberg recently underwent pressure testing of its pressurised water reactors. This is in line with international law stipulating nuclear containment buildings must be pressure tested every ten years.
To facilitate this assignment the state-owned Eskom contracted compressor and generator hire company Rand-Air, who had previously supplied oil-free compressors for the containment integrated leak rate test in 2005.
Andre Hopley, projects lead technician at Rand-Air stated: “The purpose of the pressure testing of the containment building at Koeberg was to ensure that there was no leakage which could be harmful to the surrounding environment and public.”
The pressure testing process
Hopley explained: “Using ten PTS916 Rand-Air units running through desiccant dryers, dry oil-free air was pumped into the containment building. Both the inner and the outer sector of the building were surveyed before, during and after the test.”
He continued: “Water particles have a big influence on pressure testing and the end result. We were required to match 18 degrees Celsius in temperature of the air going into containment. We found that using heat exchangers and chillers reduce the pressure testing time by a few hours allowing us to control the air pressure distribution. The requirement for the pressure testing was minus 20 degree dew point and we managed to achieve minus 40.”
Stability during the testing is strategic
Hopley concluded: “The pressure test took between seven to eight hours. It took two and a half hours to reach a pressure of one bar. The procedure stops for eight hours when it reaches one bar, this is key in ensuring that everything is stable enough to continue to four bar. The process requires the go ahead from two parties namely Électricité de France (EDF) and Eskom. It is critical to monitor the progression thoroughly [as] damage to the equipment inside the building could be detrimental.”
Koeberg’s on-going planned maintenance
Unit 1, which has been on a planned maintenance and refuelling programme since February this year, came back online on 2 June. This was a big outage for Koeberg and probably the biggest maintenance scope of work ever undertaken at the station, reflecting the typical approach for a plant at this stage of its life.
The scheduled shutdown of Unit 1 was part of the overall maintenance programme Eskom has undertaken for its fleet of power stations. Every 16 to 18 months, each of the two units at Koeberg is shut down for refueling, inspection and maintenance.
The routine shutdowns are scheduled to avoid having both units out of service at the same time and to avoid the winter months each year.