Operations were being carried out in the residue recovery plant of the Prototype Fast Reactor Reprocessing Plant at Dounreay on the evening of 29 June 1993. Following the opening of a drum which contained centrifuge filter there was a small release of radioactive material, which was fully contained within the plant and easily cleaned up. The inital indications were that no significant doses had been received by workers. Subsequent tests for possible internal dose have shown that one worker received an intake of insoluable plutonium oxide which in current estimates is likely to exceed the legal dose limit. A final estimate of the dose received will not be available for some months because prolonged faecal and urine analysis is required.