Plutonium from the Sellafield site in the UK must be recycled into new nuclear fuel instead of immobilised and stored in a planned deep geological disposal facility, one of the country’s largest trades unions has said.

GMB Union said the Sellafield site, in northwest England, has one of the world’s largest stockpiles of plutonium.

In January the government said it would “immobilise” 140 tonnes of plutonium stored at Sellafield, putting it beyond reach and further mitigating the long-term safety and security risks associated with it more efficiently.