Riot police have used tear gas on hundreds of nuclear protesters in northern France trying to head off the departure of a train carrying recycled uranium to Germany.

Some 300 protesters clashed with police on Wednesday in fields in the village of Lieusaint, outside Valognes, site of the rail depot where the train loaded with the uranium treated by Areva was expected to depart.

It was not immediately clear if there were injuries from the clashes, and it was not known when the train was to begin its journey to the German town of Gorleben.

Some protesters waved banners reading "Stop This Radioactive Train."

State-run Areva treats spent nuclear fuel from other nations, to the ire of those who contend such shipments are too dangerous for rail, sea or road.