Sellafield Ltd has says a ‘significant milestone’ has been reached after two million litres of liquid nuclear waste was pumped out of the Magnox Swarf Storage Silo (MSSS), one of the oldest nuclear waste stores in the world.

The MSSS received magnox fuel cladding or swarf, which is almost 100% magnesium, from the First Generation Magnox Storage Pond and the Fuel Handling Plant along with a range of other items of intermediate level waste until 1991. The swarf was transported in purpose built flasks and tipped into the 22 silo compartments, where it was stored underwater. At the time there was no real plan in place for how the swarf would be removed and repackaged in the future.

Since the inception of the Nuclear Decommissioning Authority (NDA) in 2004, focus has been on decommissioning the store as quickly as is safely possible. For that to happen, all the waste stored in the silo, including the water in which the swarf is submerged, needs to be removed so that the building can be demolished.

Engineers designed a system to purge the water by pumping it out of the store, and then use a 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.

Since the programme started less than five years ago, over two million litres of liquid effluent have been pumped out of the MSSS.
"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," said head of MSSS, Chris Halliwell.
"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 site in a few months time. This will undergo testing before being available for solid waste retrievals in 2017.

Photo: Magnox Swarf Storage Facility (MSSS)