A suspected radioactive particle, found on a beach near Dounreay nuclear power station, has been taken for analysis.
The Dounreay nuclear plant is being decommissioned
The particle was detected on Dunnet Beach, about 14 miles east of the Caithness plant, by workers carrying out monitoring of the area.
It is the second radioactive item found on the beach in less than a month.
More than 50 pieces of reprocessed reactor fuel have been found on the public beach at Sandside to the west of the site over the past two decades.
The Scottish Environment Protection Agency (Sepa) first indications show that the particle on Dunnet beach is a fragment of reactor fuel.
The particle appears to have broken up on collection.
The activity of the find appears to be comparable to that of some of the lower level finds at Sandside Bay, however further analysis is being undertaken.
Dounreay spokesman Colin Punler said all precautions to protect the public will be taken.
"We started monitoring there at the end of January and periodically during February," he said.
"We have now monitored about one fifth of the surface area of the beach.
"To date we have found one particle, today, and a stone with contamination on 2 March."
Mr Punler said that previous particles found at Sandside beach had contained a "low-level" of radioactivity.
He said that public health authorities had come to the conclusion that there was no justification for the closure of the beach.
The particles are specks of irradiated fuel which are similar in size to a grain of sand.
They are the result of former operations at the nuclear plant, which is being decommissioned, during the 1960s and 1970s.
Sandside Beach is normally monitored on about 12 days each month using a combination of vehicle-mounted and hand-held detection systems.
The UK Atomic Energy Authority is required under authorisation from Sepa to routinely monitor Sandside Bay, the Dounreay Foreshore, Crosskirk, Brims Ness, Scrabster and Thurso Beaches.
A study into the health effects of contamination from particles has been commissioned by Sepa. This report will be published later this year.