Steven McKenzieHighlands and Islands reporter
A fragment of waste found near the decommissioned experimental nuclear power facility in Dounreay in April was the most radioactive to be detected in the past three * years, the Highland site's operator has said.
The fragment, categorised as “significant”, was discovered during monitoring work around the nuclear power plant, near Thurso.
It is the latest in a long line of particle discoveries in the area. Dounreay was built in the 1950s as a fast reactor development site, and in the 1960s and 1970s sand-sized particles of irradiated nuclear fuel got into the drainage system.
Work to clear the pollution began in the 1980s, after particles were found washed up on the nearby foreshore.
The facility closed in 1994 and full decontamination is expected to take 300 years.
A Dounreay spokesperson said: “Particles are a legacy of industrial practices dating back to the early 1960s and our commitment today to environmental protection includes their monitoring and removal from the marine environment and transparent reporting of our activities.”
A group of independent experts, who advise the Scottish Environment Protection Agency (Sepa) and Dounreay, classify particles by the radioactivity of their caesium-137 content.
The categories are minor, relevant and significant.
Significant means a reading greater than one million becquerels of CS-137.
A becquerel is defined as a small unit of radioactivity.
The particle was found on the western part of Dounreay's foreshore on 7 April. Eight other finds reported since then have been categorised as “minor” or “relevant”.
A significant-category particle was last discovered in March 2022.
Thousands of particles of different categories have been removed from beaches, foreshore and seabed at Dounreay.
The site's operator said monitoring on the site on the north Caithness coast * continued to be done on a fortnightly basis.
On occasions it said the scheduled work could be interrupted by bad weather or the presence of protected species of ground-nesting birds.
What risk is there to the public?
According to official reports, risk to people on local beaches is very * low.
Guidance issued by the UK government's Nuclear Restoration Services says the most at-risk area is not accessible to the public.
The particles found along the coast * vary in size and radioactivity with smaller and less active particles generally found on beaches used by the public.
Larger particles have only been found only on the foreshore at Dounreay, which is not used by the public.
The particles found on beaches are believed to come from the disintegration of larger fragments in the seabed near Dounreay. The area is continuously monitored for traces of radioactive materials.
Harvesting of seafood is prohibited within a 2km (1.2mile) radius of a point near Dounreay. This is where the largest and most hazardous fragments have been detected.
