RADIOACTIVE sludge from a Sellafield storage pond has been packaged into a modern store for the first time.

This material has been removed from the oldest pond of its kind in the world and is being held for safe long-term disposal.

It has been transferred from the pond to a new encapsulation plant, where it is grouted and processed into a storage state ready for final disposal in the UK’s geological disposal facility.

Sludge is an unplanned by-product of the nuclear industry, formed from decaying nuclear fuel, natural growing algae and other debris.

The mud-like substance developed over the course of 65 years inside the Pile Fuel Storage Pond at Sellafield.

It is now being removed so the facility can be safely decommissioned.

Planning and preparation for this has taken several year and this is the start of efforts to remove all of the sludge in the pond.

Encapsulation is a process that used to enclose the substance into a new state which is ready for storage.

The sludge arrives directly from the pile fuel storage pond in a 500L (110 gallons) drum which it is to be stored in, cement is added and is then mixed up using a stirrer in the drum.

Once the mixture is cured and a cement cap has been added, the drum can be lidded and transferred remotely to a modern storage plant where it will remain until it is sent to a long term facility.

The project is being delivered 10 years ahead of schedule at a cost of £100m, half of the predicted cost.

A 10-year project to dewater the pond will start in 2019, while sludge is still being removed.

The 100-metre (328 ft)long pond was originally used to store nuclear fuel, which was then used to make atomic weapons.

Speaking about the success, Eric Bowe, head of encapsulation plants said: “This is a great achievement for us; it is the first drum of historic sludge to be encapsulated and stored ready for long term storage.

“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.”

Sellafield's reactors first became active in 1956.