Seabed particles found off Dounreay were 'health risk'
Tests have suggested 38 out of 351 radioactive particles recovered from the seabed off Dounreay posed a significant health risk.
The fragments of irradiated nuclear fuel were flushed into the sea through the Caithness power plant's liquid discharge pipe in the 1970s.
A contractor has been cleaning the particles from the seabed.
Dounreay Site Restoration Limited said 2,300 particles have now been recovered from the seabed and beaches.
The clean up operation began several years ago, but the latest 351 were retrieved from the sea in the past nine weeks.
The company said provisional testing had indicated 38 of the finds were large enough to be a significant risk to human health.
Meanwhile, equipment has arrived at the nuclear site for the storage of fuel that powered its fast reactor.
The kit includes a huge box called a flask and designed to hold the highly radioactive material once it has been removed from the Dounreay Fast Reactor.
DFR was the world's first fast reactor 50 years ago and supplied electricity to the national grid.
Dounreay is being demolished in a decommission project running to £2.6bn.