Scotland's first operational nuclear reactor is to be demolished.
The Dounreay Materials Test Reactor (DMTR) achieved criticality, a nuclear term referring to the balance of neutrons in the system, in 1958.
The site at Dounreay, near Thurso, was built using 600 tonnes of steel. It was shut down in 1969.
Large parts of the DMTR site have already been demolished as part of wider work to decommission the Dounreay nuclear power site.
The control room desk and panels for the reactor were moved to Caithness Horizons, a museum in Thurso, in 2015.
A contractor has been sought for the work of demolishing the reactor.
Notice of the contract has been released on 60 years since the first criticality was achieved in Scotland.
A system known as a rig and named the Zero Energy Thermal reactor installed at Dounreay in 1956 went critical for the first time on 13 August 1957.
This was the first artificially made criticality in Scotland.
Bill Lambie, DMTR project manager, said: "This month we celebrate the 60th anniversary of the first criticality in Scotland, which took place in a temporary test rig.
"That was an immense achievement, and we are now poised to demolish its successor and the oldest reactor on site, DMTR.
"The removal of DMTR from the skyline will be a significant step for Dounreay, and will be a real and visible sign of the decommissioning progress being made."