The integrity of the waterproofing on a nuclear power plant is designed to the highest standards and is regularly inspected. On the rare occasions that there is a potential or suspected breach in the waterproofing, remedial action would be taken promptly to rectify this.
As part of planned maintenance, a protective coating manufactured by Flexcrete Technologies Limited, part of the AkzoNobel group of companies, has been used to refurbish a surface water drain chamber at Dungeness B. Cemprotec E942, a high-performance waterborne cementitious coating, was chosen due to its rapid curing nature and ability to allow a speedy return to service of the surface water drainage system. The system used on this project is expected to have a minimum service life of 20 years.
Dungeness B in Kent was the first advanced gas-cooled reactor (AGR) to begin construction in the UK on a commercial scale. Work began in 1965 and the reactor started generating electricity in 1983. Now owned and operated by EDF Energy, Dungeness B was initially due to be decommissioned in 2018, but following £150 million in extra investment, the station was granted a ten-year life extension in 2015 and is now expected to generate electricity until 2028. Approximately 550 people are employed by EDF Energy at Dungeness B, along with over 200 contract partners.
Surface water drain chamber project
The surface water drain chamber is one of eight that forms part of the surface water drainage system. It is also the authorised minor discharge route for waste condensate water being discharged from the station. Although the chamber, which is 2m deep and 1.5m square, was intact there were voids in the mortar and cracking around pipe penetrations. The defects had to be repaired to ensure environmental compliance was maintained. A protective lining was required that would tolerate the heat from the water being discharged.
CSC Services UK, a specialist repair and coatings contractor to the power and water industries, was appointed to carry out the application work. The Cemprotec E942 coating from Flexcrete was selected.
Prior to work commencing in December 2017, the drain was blocked and allowed to dry, and CSC Services installed an over-pumping system to isolate the chamber. The chamber was then lined with Cemprotec E942, which forms a hard, durable, waterborne cementitious coating that is resistant to water, chloride ions, oxygen and also aggressive chemicals.
A major advantage of Cemprotec E942 is that it can be applied to damp substrates with far lower levels of surface preparation than conventional coating systems. Its fast-curing nature was a distinct advantage for this project, as it allowed a rapid return to service of the surface water drainage system. The work required confined space access but that raised no concerns as the coating is water-based, and poses minimal risk during application. No hazardous solvents or heavy odours are released.
Cemprotec E942 can be used as a stand-alone anti- corrosion coating for ferrous metals, as well as waterproofing and protection of concrete where enhanced chemical and abrasion resistance are required. It is CE-Marked in accordance with the demands of the standard BS EN 1504 Part 2.
Speaking about the project, Alan Smith, project engineer from Dungeness B, said: “The work required confined space access and was subject to plant isolation which was delayed by one day…Despite the delay, the refurbishment was completed to a very high standard and within the programme.”
