The first generation Magnox storage pond (FGMSP) – which dates back to the 1950s and was constructed to store, cool and prepare used Magnox nuclear fuel for recycling – urgently needs to be emptied of 1,500m3 of radioactive sludge.
"We're making history at Sellafield by transferring the first sludge using a tried and tested pump to a £240 million storage plant containing three stainless steel buffer storage vessels, each the same volume as seven double decker buses," says head of FGMSP Martin Leafe.
"Working with both Westinghouse and Energy Solutions, the technology already in use at European reactor stations has been adapted for our needs and rigorously tested in a full-scale test facility at Forth Engineering here in West Cumbria," he adds.
Leafe explains that the sludge is similar in consistency to sand and has to be carefully removed, leaving the water in place to provide a radioactive shield for the stored nuclear fuel.
Its retrieval from the pond will enable the remaining radioactive inventory to be progressively removed.
The pond holds 14,000m3 of contaminated water, beneath which is Magnox spent nuclear fuel, miscellaneous nuclear wastes and skips all covered in the radioactive sludge.
The pond has thick reinforced concrete walls, but was built with no roof and is open to the elements – hence the accumulating sludge.
"The pond is six metres deep and we've spent years devising an engineering solution to suck up the radioactive sludge from the bottom of the pond," states Leafe.
"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 they remain fully submerged," he continues.
"And just to make matters more difficult we have to drive the platform remotely from a control cabin to minimise the radiation dose to the workforce."