Around 1,500 cubic meters of radioactive sludge will be emptied from First Generation Magnox Storage Pond (FGMSP), which was constructed to store, cool and prepare used Magnox nuclear fuel for recycling into new fuel.

The sludge has to be carefully removed, while leaving the water in place to provide a radioactive shield for the stored nuclear fuel.

Sellafield First Generation Magnox Storage Pond head Martin Leafe said: "The pond is six metres deep and we’ve spent years devising an engineering solution to literally suck up the radioactive sludge from the bottom of the pond, which in places is over one metre deep.

"What makes the job more difficult is that the pond is very congested and full of large metal boxes containing nuclear fuel, so we need to work around these and ensure these remain fully submerged at all times.

"Just to make matters more difficult we have to drive the platform remotely from a control cabin to minimize the radiation dose to the workforce."

The removal of sludge from the pond will enable the remaining radioactive inventory to be progressively removed to reduce the inherent hazard posed by the facility.

Sellafield is using a pump to transfer the first sludge to a new £240m advanced sludge storage plant comprising three stainless steel buffer storage vessels.

"We transfer the sludge in batches to the new plant where it settles in one of the enormous buffer storage tanks and then the top layer of water is sent back to the pond. It will take several months of work to transfer enough sludge to fully test and commission the sludge plant and in parallel we’ll install the bulk sludge removal equipment," Leafe added.

Image: The very first radioactive sludge has been removed from one of the most hazardous nuclear plants in Europe. Photo: courtesy of Sellafield Ltd.