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Sellafield achieves liquid waste removal milestone

20 February 2015

The removal of two million litres of liquid radioactive waste from silos used to store swarf waste from Magnox fuel reprocessing at the UK's Sellafield site marks a significant  hazard reduction milestone, according to Sellafield Ltd. The company said the removal of the liquid has "halved the radioactive content of some of its historic liquid nuclear waste, significantly reducing the potential hazard.

Magnox Swarf Storage Silo - Image: Sellafield Ltd
Magnox Swarf Storage Silo - Image: Sellafield Ltd

The Magnox Swarf Storage Silo (MSSS – pictured) project was built to accommodate the swarf waste produced by the decanning of Magnox fuel prior to reprocessing. The swarf was stored underwater, and the first facility of six silos began operations in 1964. By 1983 a total of 22 silos had been built, but by the early 1990s wet storage of Magnox swarf was superseded by dry storage.

The Magnox Encapsulation Plant was built to receive dry Magnox swarf, encapsulate it in cement and seal it in stainless steel drums. The MSSS is now being decommissioned, but all the waste stored in the silos, including the water in which the swarf is submerged, must be removed before the building can be demolished.

“Engineers designed a system to purge the water by pumping it out of the store, and then use a clever chemical process to remove the radioactivity from it, with fresh water replacing it in the store, making the plant safer and the job of receiving the swarf easier,” the company said in a news release.

In less than five years since the programme to remove liquid effluent from the silo started, two million litres has been pumped out.

Head of MSSS, Chris Halliwell, explained: “Back in the day, the MSSS literally helped keep the lights on by supporting Magnox electricity generation, however it’s now been retired from active service. The radioactivity we’ve removed and treated arose from several hundred tonnes of uranium fuel which during its lifecycle would have generated enough electricity to power over eleven million homes for a year.

“It was never built with decommissioning in mind and safely removing the liquid and solid nuclear wastes requires some ingenious engineering. We have now successfully removed liquid waste containing 10,000 terabequerels of radioactivity from the store – which equates to locking away roughly the same amount of nuclear waste discharged to sea in the Japanese Fukushima accident. Completion of this liquor transfer from the MSSS is an important step towards emptying the silos, processing the waste and safely decommissioning this legacy plant.”

The next stage will be to remove the solid waste inventory from the facility, process it and encapsulate it for safe long term storage. Three silo emptying plants are being built, the first of which will be brought to the Sellafield in a few months time. This will undergo testing before being available for solid waste retrievals in 2017.

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