Britain’s most hazardous nuclear building has moved a step closer to being decommissioned.

Work has begun to install the second of three emptying machines at Sellafield’s Magnox Swarf Storage Silo.

The first piece of the 350-tonne machine – a transfer tunnel – was lifted into the building last month.

The silo contains an estimated 60,000 items of intermediate level nuclear waste in 22 chambers.

It was built in the 1960s, with no plan made at the time for how it would be emptied.

Engineers have been working for decades to design, build, and install three machines to do the job.

One is fully built, the second is now under construction, and a third will follow.

Waste retrievals are scheduled to start later this year.

By 2024, Sellafield Ltd expects all three machines to be up and running.

Retrievals are set to be completed by 2045.

Decommissioning the building has been identified as one of the Nuclear Decommissioning Authority’s priority programmes.

Chris Halliwell, head of the Magnox Swarf Storage Silo for Sellafield Ltd, said: “This is another milestone on the journey to tackling our biggest challenge.

“It’s a statement of our intent to press on with the job as quickly and safely as we can.”

The machine will move over the top of the building’s 16 metre deep chambers on rails.

Once in place over a chamber, it will lock on and tooling will reach in to pull up the waste inside.

The material will be placed in boxes and dispatched out of the building via the transfer tunnel.

The boxes will then be transferred to a new modern storage building on the Sellafield site.

The exact contents of the silo are unknown because record keeping at the time was patchy.

However, the bulk of its inventory is radioactive scrap metal and contaminated engineering debris.

In March last year, a £250m Silos Maintenance Facility was unveiled at Sellafield to house and maintain the machinery that will get the waste out of the Magnox Swarf Storage Silo.

It will also be used to house and maintain machinery used in emptying waste from the site's Pile Fuel Cladding Silo.