Sunderland train station was evacuated after a train carrying two nuclear flasks to Sellafield broke down.
The train station has since re-opened to passengers
Smoke was seen coming from the train after an axle overheated, according to British Transport Police (BTP).
The station was closed on Wednesday afternoon but has now re-opened to passengers. Mainline and Metro services were hit but are now running again.
BTP said the nuclear load did not pose a danger and the station was evacuated because of fumes from the axle.
The train is operated by Direct Rail Services, a freight operating company created by British Nuclear Fuels Limited (BNFL).
A Direct Rail Services spokesman said that all used nuclear fuel was transported in heavily shielded, purpose built flasks.
Each is constructed from forged steel, more than 30cm thick, and typically weighs more than 50 tonnes.
The spokesman said: "The nuclear industry uses rail as the primary mode of transport.
"The in-built safety systems, that allow the network to operate, are ideally suited to the security requirements for moving these types of cargoes.
"The load remained secure and in no danger at any time. Operational procedures to safely move the train are now being activated."
Shortly afterwards, British Transport Police confirmed that the train left the station after engineers replaced some brakes.