French authorities ordered a train carrying reprocessed nuclear waste to Germany to stop near the border for 24 hours on Thursday to try to avoid more mass protests.

Riot police battled anti-nuclear protesters when the train began its journey in northern France on Wednesday and thousands more demonstrators were expected to try to block it once it crosses the border.

The train was halted at Remilly junction 50 kilometres (30 miles) from the border while nuclear company Areva, French rail firm SNCF and police decided which of three possible routes it can now take, a security source said.

A heavy police presence was deployed in and around the small town and on the tracks around the station, where a dozen buses full of riot police were on standby, an AFP reporter at the scene said.

German police were due to take over from their French counterparts once the train, carrying the last German nuclear waste to be reprocessed in France, resumes its 1,500-kilometre trip to Gorleben in eastern Germany.

Last November a similar convoy took 91 hours to arrive at its final destination -- a day longer than planned -- as it was dogged the length of the route by French and then German protesters.

Around 50,000 activists turned out in Germany to try to disrupt the train during that shipment, and protest organisers expect around 20,000 to demonstrate against the convoy this week.

Spooked by Japan's Fukushima disaster, Germany has decided to phase out its use of nuclear power, and thus bring to an end the controversial practice of sending radioactive waste overland to France for reprocessing.

Anti-nuclear activists want France to follow suit and shut its reactors, an idea firmly dismissed by President Nicolas Sarkozy.

The final shipment left a railway yard in the town of Valognes in Normandy, northwest France, more than an hour late Wednesday after police clashed with hundreds of activists, firing teargas and making 16 arrests.

The train travelled across France towards the German border overnight without further incident.

Six of those arrested were ordered Thursday to appear in court next year to face charges that included stealing soda from a police van, carrying weapons such as flick-knives, hatchets and tear gas, and trespassing on rail lines.

There has long been widespread public opposition in Germany to nuclear power, which environmentalists believe presents an unacceptable radioactive threat to public health and the environment.

In March, the Japanese nuclear plant at Fukushima Daiichi was hit by an earthquake and a tsunami, triggering a meltdown and massive radiation leak -- and increasing worldwide concerns over nuclear power.

Chancellor Angela Merkel's German government buckled under political pressure and agreed to halt its reactors by 2022, forcing energy suppliers to close profitable plants and levying a tax on the reactors' fuel.

In the meantime, Germany will no longer send nuclear waste for reprocessing in France, but will instead stockpile it until a way is found to make it safe.

Fukushima also increased concerns in France, where Sarkozy's government has vowed to stand by the industry, despite attacks by Greens.

France produces 75 percent of its electricity needs in nuclear plants -- a higher proportion than any other country -- and its electricity bills are around 25 percent cheaper than in its neighbours, a boon to industry.

The 11 wagons on the train halted Thursday hold the same amount of "highly radioactive" waste as the last one -- a year ago -- to leave the reprocessing plant at La Hague for Gorleben, according to pressure group Greenpeace.

German protesters are angry that Merkel's announced nuclear phase-out will take another decade, and that there is still no permanent storage site for the waste generated in the country's reactors.

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