Workers at the Berkeley nuclear site in Gloucestershire have begun removing historic radioactive waste from underground vaults using plant designed, built and installed by Cavendish Nuclear.

It’s a major breakthrough for the Nuclear Decommissioning Authority and site licence company Magnox after a number of previous attempts at developing a retrieval system were unsuccessful.

The world’s first commercial nuclear power station on the shores of the River Severn provided enough electricity to power a city the size of nearby Bristol until it closed down in 1989.

The twin reactors have been decommissioned successfully and are now in “safestore” but developing a plant to clear out its waste storage area proved more challenging.

Some 620 tonnes of metallic fuel element debris and 6665 containers - some of which are sludge cans – accumulated in underground vaults during operations at the site.

In 2010, Cavendish Nuclear won a contract to design a plant capable of recovering the waste and getting it into a condition safe for interim storage pending deep geological disposal.

This lead to a second contract in late 2012 to manufacture, test, install and commission the successful design.

Modules were manufactured by a number of different sub-contractors and assembled for testing at the Cavendish Nuclear site at Whetstone in Leicestershire.

From there, each unit was transported by road to the site in Gloucestershire where Cavendish Nuclear engineers worked closely with Magnox staff on their installation and commissioning.

The big breakthrough came this summer when the plant started successful waste retrieval operations.

"Although we originally anticipated that all the material would be intermediate-level waste (ILW), a campaign of innovative retrieval techniques and segregation enabled some of it to be disposed of as low-level waste and very low-level waste, diverting over 50 tonnes away from the site's interim storage facility and saving millions of pounds," said Paul Oswald, Berkeley site head of projects.

For Cavendish Nuclear, the £40m project demonstrates its ability to solve some of the most complex engineering tasks faced by the nuclear clean-up industry.

“We’re delighted that Cavendish Nuclear has been able to provide Magnox with a trusted solution to a problem that had thwarted others for the previous 20 years,” said Paul Smith, director of UK projects at Cavendish Nuclear.

Clearance of the waste vaults is critical for Berkeley's entry into 'care and maintenance'. This is when the units will be placed in long-term passive storage to allow time for residual radioactive materials to decay before final site clearance work begins in 2074.