[H]istory has been made at Sellafield after radioactive sludge was transferred from the world’s oldest nuclear storage pond for the first time.
Sludge is an unplanned by-product of the nuclear industry formed from decaying nuclear fuel, natural growing algae and other debris.
It has developed in the murky depths of the Pile Fuel Storage Pond during its 65 year lifespan and now needs removing so the facility can be safely decommissioned.
The first transfer of a 500-litre drum of the mud-like substance was completed last week, marking the culmination of years and planning and preparation.
Once transferred to an encapsulation plant, the sludge is grouted and processed into a storage state ready for final disposal in the UK’s geological disposal facility.
It will take several years to remove all of the sludge in the pond.
The project is being delivered 10 years ahead of schedule and for half of the predicted cost of £200 million. A 10-year project to dewater the pond will start in 2019, while sludge is still being removed.
The 100-metre long pond was originally used to store nuclear fuel used to make atomic weapons.
All of its bulk stocks of fuel have now been removed, leaving sludge as the biggest remaining radioactive hazard.
It is one of the four legacy ponds and silos at Sellafield which the Nuclear Decommissioning Authority’s has prioritised for clean-up.
Dorothy Gradden, head of legacy ponds for Sellafield Ltd, said: “There’s lots of hard work ahead to get all the sludge out, but this is another key moment for our decommissioning mission and another sign of visible progress.
“This is one of the first examples of a legacy facility producing a waste ready for a geological disposal facility – it’s a cradle-to-grave solution.
“With the start earlier this year of bulk fuel and sludge removal from our other legacy pond, we’re now firing on all cylinders in reducing the hazard and risk in these legacy facilities and making them safer places.”
Sludge accounts for one third of the pond’s remaining radioactive content, after 70 per cent was removed earlier this year with the completion of fuel exports.
The sludge removal process involves pumping the material into a purpose-built treatment plant next door, from where it is then transferred to the drum filling plant.
Once filled, drums are placed in nuclear transport flasks and transferred to the Waste Encapsulation Plant.
There, drums are grouted and processed into a storage state ready for final disposal in the UK’s geological disposal facility.
During this grouting process, the product in the drums is no longer ‘sludge’ and can be classed as ‘passively safe’.