A chain reaction which provided sustained and controlled nuclear energy in Scotland was achieved for the first time 50 years ago.
The chain reaction occurred on an afternoon in 1957
The experiment at Dounreay put the site in Caithness at the cutting edge of nuclear technology at the time.
Half a century on, the plant is being decommissioned at a cost of £2.9bn.
The chain reaction occurred at 1300 BST on 13 August, 1957. Supernoah, the name of the building where it happened, has been demolished.
It is one of 99 facilities cleared from the 140 acre (56 hectare) site so far. Decommissioning is expected to be completed by 2033.
The event at Dounreay was the first time a chain reaction had taken place in Scotland and meant nuclear power could be sustained and controlled.
The area of Dounreay was farmland until 1954, when the government selected it as the location for the national centre for research and development of fast breeder reactors, a new type of atomic energy.
Opened in 1955, it operated for 40 years.
More recently, the mothballed plant has been dogged by the discoveries of rogue radioactive particles on nearby beaches linked to historic leaks at the complex.