Sellafield (formerly known as Windscale) is a nuclear processing and former electricity generating site, close to the village of Seascale on the coast of the Irish Sea in Cumbria, England.
Facilities at the site include the THORP nuclear fuel reprocessing plant and the Magnox nuclear fuel reprocessing plant. It is also the site of the remains of Calder Hall, the world’s first commercial nuclear power station, now being decommissioned, as well as some other older nuclear facilities
The BBC understands the men were taking photographs and are all believed to be Bangladeshi.
Four houses in east London were raided by counter-terror detectives as part of the investigation.
Scotland Yard said a small container was removed at one of the addresses.
The container is being examined. Explosives officers attended as a precaution, although the container is now not thought to have had explosives or hazardous material in it.
The arrests were made within hours of the news breaking that Osama Bin Laden had been killed in Pakistan, and members of the public have been warned to remain vigilant amid fears of reprisals from groups sympathetic to al-Qaeda.
In a statement, Greater Manchester Police (GMP) said: “At this stage we are not aware of any connection to recent events in Pakistan.”
The Thermal Oxide Reprocessing Plant, or THORP, is a nuclear fuel reprocessing plant at Sellafield in Cumbria, England. THORP is owned by the Nuclear Decommissioning Authority and operated by Sellafield Ltd (which is the site licensee company). Spent nuclear fuel from nuclear reactors is reprocessed to separate the 96% uranium and the 1% plutonium, which can be reused in mixed oxide fuel, from the 3% radioactive wastes, which are treated and stored at the plant. The uranium is then made available for customers to be manufactured into new fuel.