Clyde Valley Drilling staff working in Dounreay in Caithness

Workers from Clyde Valley Drilling (CVD) used a new technique called a dry wire saw to cut out a drain.

Traditional concrete drilling methods require water to keep the drill cool and for removing dust.

However, this posed a risk of radioactive waste escaping into the ground or the environment.

To prevent contaminated dust particles from leaking into the atmosphere, CVD designed a modular containment system to enclose the cutting area.

Workers nicknamed the protective suits they had to wear inside the module their Cybermen costumes after the Dr Who characters.

Owen Barrett, managing director of Glasgow-based CVD, said: "This was the first piece of nuclear decommissioning work to be completed in the UK involving a dry wire saw.

Fast reactor

"The equipment worked perfectly and the early finish is a credit to this and the commitment and enthusiasm of the staff who worked on the project.

"I understand they became quite attached to their Dr Who-style Cybermen suits."

The United Kingdom Atomic Energy Authority, which runs the 140-acre site, expects the decommissioning of Dounreay to take 30 years.

The clean-up includes dealing with liquid metal coolants from Dounreay's fast reactor and prototype fast reactor.