Design work is to begin later this year on robotic machinery to work underwater, recovering hazardous waste at a defunct nuclear power complex.
The company leading the decommissioning of the Dounreay nuclear complex in Caithness said the operation would be one of most demanding tasks so far.
More than 1,500 tonnes of waste has been submerged at two water-filled underground sites for up to 50 years.
Called the Shaft and the Silo, the two are within the grounds of Dounreay.
Robotic machines have already been used in other clean-up jobs at Dounreay.
The Shaft runs to 65m below ground, while the Silo was described as being like a swimming pool with a concrete roof.
Both were used as dumps for radioactive material from experiments run at the complex.
Tests are also under way in Scotland, Germany and the USA to develop heavily-shielded plant that will sift and package the hazardous debris once it is brought 65m to the surface by the machines.
An x-ray system being tested in Germany and America will scan and identify each piece of waste.
Steve Efemey, project manager at Dounreay Site Restoration Limited (DSRL), said the first waste was expected to be brought to the surface in 2017.
A remotely-controlled pipe crawler, built at a cost of £100,000, has already been used at the site.