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Sludge retrieval is big step in cleaning up historic legacy
An important programme in helping to clean up legacy waste, the floc retrieval project has recovered and encapsulated over 1,000 cubic metres of historic waste in the form of sludges in the past three years.
The sludge storage tanks were built back in the 1950s but have been disused since the early 1990s. Some of these were used to allow active floc to settle and collect.
The tanks are showing their age, and so the floc retrieval process was developed to enable the clay-like settled floc to be re-suspended as a liquid, and pumped to the Enhanced Actinide Removal Plant (EARP) for treatment.
Ian MacPherson, head of LAEMG manufacturing explained: “We have used novel technology – not used anywhere else in the world – involving a high flow re-circulation system to re-suspend the settled floc. “The contents of the most-active 1950s tank were safely suspended and transferred to a modern buffer tank during 2005. “Over 1,000m3 of this suspended floc has now been processed in batches in the EARP, and all of those batches have been made into solid concrete waste in steel drums which are safe and stable waste ready for ultimate disposal.
“When we emptied the first tank the radioactive inventory within the 1950s tanks complex was immediately reduced by 50%. “This achievement has been an important step in cleaning up Sellafield’s historic legacy. “This has also proved the technology and enables us to carry on emptying the remaining five tanks.
“Engineering work is currently on-going ready to suspend the floc in the next tank for transfer early in 2009.” Preparations for this programme of work included the erection of a large building over the whole of the tank complex which was an engineering feat in itself – the whole structure was assembled adjacent to the complex and slid into place in sections.
