Radioactive traces found on beach
The particles were found below the tide level during routine monitoring of the beach in late July.
A 100-yard stretch of the beach has been cordoned off and the Scottish Environment Protection Agency (Sepa) yard has launched an investigation.
NHS Grampian said the amount found poses a negligible risk to the public.
Although Sepa does not know where the material has come from, it is working with oil services firm Scotoil which cleans offshore radioactive equipment.
The company has a discharge pipe with an outlet close to where the material was found.
Scotoil said it has voluntarily shut the pipe down while investigations continued.