Ofcom told us "this content is deeply disturbing".

The government said in January that the plant, when complete, would- currently stored at a secure facility at the site.

Sellafield said it aimed for the building, which was one of its "largest and most complex construction projects", to be in operation by 2029 until 2060.The UK has the world's largest stockpile of the hazardous material, which is a product of nuclear fuel reprocessing.It has been kept at the site and has been piling up for decades in a form that would allow it to be recycled into new nuclear fuel.

In January the government said it would put 140 tonnes of the hazardous material, currently stored at Sellafield in Cumbria, "beyond reach" making it ready for permanent disposal deep underground.But the GMB union previously said

Sellafield said the project would "play an essential role in managing the UK's plutonium stockpile".

The roof slab took 12 weeks to complete, with more than 2,700 cubic metres of concrete being poured and pumped to heights of up to 30m, a spokesman said.In September, thirteen volunteers and two staff from Butterfly Conservation carried out surveys at 20 sites, with recorded numbers more than doubling.

A short spell of dry, clement weather in June is thought to have played a part in the butterfly’s surge, along with site management.The charity’s Northern Ireland Conservation Manager Rose Cremin said the results were “a good sign” that work to protect habitats was delivering.

“Now we need the government to continue to reward farmers for farming with nature," she said.“We urge the government to put more money into agri-environment schemes aimed at not just maintaining but increasing the grassland habitat which can provide a home for marsh fritillary and a host of other species."