Experts at Sellafield have opened and repacked a 50-year-old plutonium can for the first time as part of a £1 billion programme.

The outer packaging in a small number of canisters had began to show signs of degradation so had to be repackaged.

The material was originally placed in an inner can which was wrapped in a plastic casing and then placed into an ‘overpack’ can.

Operators had to manoeuvre the package inside a sealed glovebox, to take the plastic-coated can out of the ‘overpack’, clean off as much plastic as possible and then reseal it in a modern and more robust outer can.

James Millington, head of special nuclear materials at Sellafield Ltd, said: "Our teams have practised and practised the techniques using mock-up gloveboxes, so I’m delighted to see that all the preparation has paid off.

"Safely getting the first package into the new outer can represents one of the most significant risk reduction milestones we’ve delivered in recent years."

Its completion of the first successful repackaging kicks off a five-year work programme.

In parallel, a new purpose-built repackaging plant is under construction which is scheduled to begin operations in the 2020s.

This will enhance the repackaging process by removing impurities in the plutonium which contribute to the degrading process.