The company expects to move its work platform – the 60-metre barge LM Constructor – into position early in May.
It will deploy a remotely-operated vehicle capable of detecting and retrieving fragments buried in the seabed 30 metres below the surface.
The aim of the clean-up is to recover fragments that are high in radioactivity and present a significant hazard to public health.
Last year, the system detected and retrieved 74 such fragments, as well as 355 less hazardous fragments.
The fragments buried in the seabed near Dounreay are believed to be the source of smaller particles that are washed up on nearby beaches.
The scope of this year’s work has been agreed with the Particles Recovery Advisory Group, a body of independent experts set up to guide DSRL and the Scottish Environment Protection Agency.
The fragments came from the historical reprocessing of nuclear fuel at Dounreay. It is believed they entered the effluent discharge system that was connected to the reprocessing plants.