HIGH security accompanied the transport of the first of a series of nuclear loads from Dounreay to the USA on Saturday.
Armed police escorted two lorries carrying heavily shielded containers of highly enriched uranium from the site to Wick John O'Groats Airport.
Roads around the airport were closed off as the convoy arrived at the airport where the highly radioactive cargo was loaded on to a US Air Force plane.
The plane left early in the afternoon with the bomb-grade material which is believed to be bound for the giant Savannah River site in South Carolina.
In return, a radioisotope which can help to diagnose certain types of cancer, will be returned to the UK
Around £8 million has been spent to upgrade the runway at the airport to accommodate the transatlantic flights.
The monthly movements to ship over the 700 kilogram stockpile of fuel from Dounreay follow talks between former UK Prime Minister David Cameron and US president Barack Obama earlier this year.