A 50-year clean-up operation is under way

The three-year trial is part a �4bn clean-up of the Caithness plant, which is expected to take about 50 years to complete.

Willow has already been grown in other countries to help remove contamination, including radioactivity, from soil.

Dounreay's operators, the UK Atomic Energy Authority (UKAEA), are conducting trials with three different species.

A spokesman said that 36 cuttings were being cultivated in 12 pots, half in low level contaminated soil and the rest in clean soil.

There is a long history of plants being used for in-situ remediation of soil and groundwater through contaminant removal Doug McAlister Dounreay

The trial has just completed its first season of the three-year growing period and leaves from the trees are being sent to the lab for analysis by UKAEA scientists.

They will look at the growth rates and take-up of radioactivity and examine where any traces concentrate in the plants.

Doug McAlister, of Dounreay's environmental programmes department, said: "There is a long history of plants being used for in-situ remediation of soil and groundwater through contaminant removal, containment or degradation."

Cost hopes

It is hoped that if the willows manage to soak up radioactivity the costly and time-consuming process of excavating contaminated ground for decontamination will be reduced.

The phytoremediation system has been in operation in the US and the French have also conducted trials using mushrooms.

If successful the scheme will be used to remove historical contamination from the site, mainly related to seepage from a drainage system.

The trees will eventually be disposed of as a form of radioactive waste.