One of the "biggest clean up challenges in the world" has begun at the Dounreay nuclear complex in Caithness.
Up to 400 boreholes are being drilled
Up to 400 boreholes are being drilled around the site's waste shaft in the biggest step so far towards its eventual clean out.
The project will prevent large volumes of ground water flowing into the shaft during waste retrieval and becoming contaminated.
The work also aims to reduce the risk of leakage.
The work has started as managers at Dounreay reassured the public that there is no cause for concern after the most radioactive particle to date was found on nearby Sandside Beach.
It is the fourth to be discovered in three days bringing the total to 81.