EXPERTS have discovered the most significant radioactive particle yet on a public beach two miles west of Dounreay.

Dounreay clean-up contractor DSRL has informed the Scottish Environment Protection Agency of additional tests being carried out on a particle recovered during routine monitoring of a beach near the redundant nuclear site.

The particle was detected at the water's edge at Sandside, where more than 200 particles have been found in the last 15 years. Provisional checks carried out on the beach indicated the particle had a higher than normal beta dose rate.

A spokesman for DSRL said it was the first time a particle classed as significant – the highest classification in terms of radioactivity – had been found on the beach, although many had been found on the seabed and foreshore at Dounreay as well as on the site itself.

Any particle with radioactivity above one million Becquerel (Bq) units is classed as significant.

Initial tests estimated an isotope called Strontium-90 in the particle had radioactivity of between one and two million Bq. What was also unusual was that normally the radioactivity in Caesium and Strontium would match but on this occasion the Caesium reading was only 1000Bq.

A spokesman for DSRL said: "The chemistry of the particle is puzzling the experts at the moment. Further tests are also being done to establish the potential hazard to health."

Stan Blackley, chief executive of Friends of the Earth Scotland, said: "The more we look at this site, the more and worse we seem to find. We are now several hundred particles down the line and still they keep coming and getting hotter and hotter."