Engineering news
Sellafield has extended its use of remotely-operated vehicles for the removal of radioactive sludge from the bottom of a historic storage pond.
The company has attached an eductor, a powerful jet pump that creates a negative pressure differential, to the mini submarines to lift the sludge from the bottom of the 7m-deep First Generation Magnox Storage Pond (FGMSP).
During the trial radioactive sludge to a depth of 30cm was successfully removed from a small area of the pond. Video footage showed the grey sludge being pulled up through a hose leaving the yellow uranium clearly visible, said Sellafield.
Further trials are being carried out to capture and temporarily store the sludge before it is turned into a consistency suitable to start pumping to a new sludge packaging plant, built next door to the pond, at the end of 2014. The plant contains three stainless steel buffer storage vessels to contain the sludge. In future the tanks will be emptied and the sludge processed into a form suitable for final disposal.
Martin Leafe, head of FGMSP, said: “We have taken technology used in hazardous deep sea conditions and applied it at Sellafield. The mini submarines can explore, survey and carry out remote operations at the bottom of the pond, while the workers remain safe and dry outside the pond.
“We are building up our knowledge of the radioactive sludge characteristics to help develop equipment for bulk sludge retrievals, which will have to cope with sludge up to 1m deep in places. The greater our understanding of the sludge the more opportunities we will have to accelerate decommissioning of this priority project.
“Significant savings will be made using mini submarines rather than designing and building complex bespoke equipment which was our original plan. We now have the ability to clear space in this hugely congested storage pond to help with the recovery of nuclear fuel, contaminated waste and radioactive sludge as part of our work to empty this legacy facility.”
It is estimated that up to 1,500m3 of radioactive sludge, made up of algae, corrosion products and wind-blown material, remains in the 60-year-old pond.