A project aimed at moving nuclear material from Scotland to England has highlighted the importance of the UK's rail freight infrastructure.

Leaders at the Nuclear Decommissioning Authority (NDA) confirmed that 90 shipments of breeder material have been made under armed escort from Dounreay in Caithness to Sellafield in Cumbria, BBC Highlands & Islands reports.

The uranium is being transported 400 miles at a cost of £60 million, which is said to be cheaper than developing the Scottish site so it is capable of processing it.

NDA chiefs also suggested that other material - known as "exotics" - could be moved between the two sites over a six-year period starting in 2014 or 2015.

"Our priority throughout has been to move this material in a way that protects the public and the environment from harm at all times," Alex Anderson, deputy project director for fuels and waste at Dounreay, was quoted as saying.

The NDA announced last week it was going ahead with the next phase of the National Nuclear Archive Project, which will see records and archive material from other nuclear sites stored at a purpose-built facility in Wick.