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Value: £0.4 million
In the mid 1960’s, six steel lined concrete tanks that held radioactively contaminated liquors reached the end of their useful life. The tanks were situated within a concrete bund at the Liquid Effluent Treatment Plant (LETP) on the UKAEA Harwell site. In accordance with decommissioning standards at the time, steel liners were removed and, under a burial authorisation, the concrete tanks were collapsed into the bund and a car park was built on top.
VHE, in joint venture with AEA Technology, won a contract to remediate the contaminated bund by excavating the contents and either removing the bund structure or de-contaminating and providing a weatherproof cover dependent on the results of a structural survey. Working within a 40m x 40m x 7m high containment, the site was characterized and the solid radioactive waste was removed. Liquid wastes were collected in a settling tank and transferred, after sampling, to the site low active effluent system.
A structural survey showed that total removal of the bund would jeopardise the stability of adjacent facilities. So, in close cooperation with UKAEA, an alternative end-point was developed. This involved decontamination of the bund by scrabbling, partial removal of the bund wall to form a new entrance, and installation of storm drains. This innovative approach avoided ongoing costs to maintain a weatherproof cover and re-instated the car park facility.
Careful disciplines applied to contamination control meant that the work was completed with no contamination spread, despite exceptional weather conditions. Industrial hazards were also present, including heavy excavation machinery in confined conditions and extensive use of high vibration scrabbling equipment. The project had an excellent safety record throughout, due to a good spirit of partnership between all parties.