The operator of a nuclear plant in Caithness has been fined £140,000 for illegally dumping waste.
Fragments of fuel were allowed to enter Dounreay's effluent pipe
Just hours later a suspected rogue radioactive particle potentially linked to the incidents at Dounreay was found washed up on a nearby beach.
The UK Atomic Energy Authority (UKAEA) pleaded guilty to four charges under the Radioactive Substances Act at Wick Sheriff Court earlier this month.
They related to activities at Dounreay between 1963 and 1984.
The UKAEA said a "suspect particle" was found by its monitoring team at Sandside Beach at 1400 GMT on Thursday - less than five hours after the authority was handed down its fine.
A spokesman said it would be 24 hours before experts complete their analysis of the fragment, which was registering radioactivity.
It was believed to be the 85th particle to be found at Sandside.
Geoffrey Minter, who owns the beach, said the UKAEA had "rightly been punished" for practices of more than 20 years ago.
Sheriff Andrew Berry had deferred sentence until Thursday after hearing from the fiscal and UKAEA's solicitor.
UKAEA's court appearance followed a report to the procurator fiscal by the Scottish Environment Protection Agency (Sepa).
The company admitted illegally dumping solid nuclear waste in a landfill site at Dounreay and three charges of allowing fragments of irradiated nuclear fuel to enter the plant's liquid effluent discharge pipe into the Pentland Firth.
UKAEA's director of safety, Dr John Crofts, said: "We accept that mistakes were made and regret those mistakes.
"We too share the view that this is an unacceptable legacy of the Dounreay experiment."
He added: "Our priority has been and will continue to be to minimise the risk to people and the environment."
Eleanor Scott, Green MSP for Highlands and Islands, said the case highlighted the dangers of nuclear power.
She added: "There must be no new nuclear power stations in Scotland.
"Dounreay is now being managed well, but the surrounding communities and the environment will keep paying for these errors for many years to come."