An investigation is under way after a train carrying radioactive waste was derailed in Devon on Monday.
The incident occurred at Devonport Dockyard in Plymouth.
A spokesman for DML, which runs the yard, said the locomotive was partially derailed, although the trailer carrying the waste module was not.
It said there was no safety risk and the Health and Safety Executive's Nuclear Installations Inspectorate had been informed.
At the time the train was probably travelling at only 2mph, the company added.
In a statement, DML said: "At no time was there any radiological or conventional safety hazard to anyone on our site or members of the public outside of the site.
"The incident will be the subject of a full independent regulatory investigation in addition to our own formal investigation."
The dockyard, which is located approximately two miles from Plymouth city centre, has two diesel locomotives for moving new and used submarine fuel.
Devonport is the UK's only refitting and defuelling site for nuclear submarines.
Elizabeth Knight, Plymouth spokeswoman for anti-nuclear submarine group Trident Ploughshares, said the accident highlighted the risks posed to people living and
working in the city.
She said: "Having this population so close to this kind of business is not compatible from a health and safety point of view.
"Maybe in this case we were in no danger, but it could have been otherwise very easily."