The total cost of decommissioning will be about £800m
Work is getting under way on removing more than 38,000 spent uranium fuel rods from a former nuclear plant in southern Scotland.
It is the latest step in the £800m decommissioning process at the Chapelcross site near Annan.
It is five years since it ceased energy production and almost two years since its cooling towers were demolished.
The fuel will be extracted over the next three years and taken by road to Sellafield in Cumbria for reprocessing.
A total of 269 loads will leave Chapelcross between the beginning of March and the end of 2011.
Defuelling and operations manager Tim Dunham said it was the most significant part of the decommissioning operation.
The radioactive fuel rods will be taken to the nearby Sellafield plant
"The demolition of the cooling towers was spectacular but it was simply a civil operation," he said.
"This is a significant nuclear operation that we are about to start now and we will remove the vast majority of the hazard from the Chapelcross site."
Site director David Wilson said it represented a major milestone in a long and costly decommissioning process.
"We've got to take the station to a care and maintenance phase by about 2023," he said.
"That programme of work is about £800m."
He said the site had been gearing up for defuelling for some time and it was an "immense relief" to the workforce to get the operation under way.
The Chapelcross nuclear plant was built in 1959 and ceased generation in 2004.
In 2007, its landmark cooling towers were demolished and last year formal permission was received to start the lengthy process of defuelling its four reactors.