* Vote on whether to quickly end nuclear power production
* "Yes" vote would lead to more imports of German fossil fuels
* Swiss utilities say would sue
* Supporters of quick exit say nuclear power unsafe
By Vera Eckert and John Miller
ZURICH/FRANKFURT, Nov 24 (Reuters) - Switzerland votes in a referendum on Sunday on whether to make a speedy withdrawal from atomic energy production, a move that would reduce nuclear risks but raise reliance on fossil fuels from Germany or imported nuclear power from France.
The opposition Swiss Greens and Social Democrats have pushed for a vote since the 2011 Fukushima disaster in Japan, but the government and industry oppose a quick exit, saying Switzerland would be unable to replace power supplies with renewable energy.
Recent surveys from the gfs.bern polling institute show the "Yes" and "No" camps in the referendum are neck and neck.
Switzerland prides itself on the fact that two thirds of its power is hydroelectric, from reservoirs in the Alps, but it also counts on nuclear energy for a third of its power output.
Anti-nuclear groups are pushing for it to follow neighbouring Germany, which shut 40 percent of its nuclear reactors after Fukushima and will close the rest by 2022.
Swiss reactors Muehleberg and Beznau I and II would be closed next year, followed by Goesgen in 2024 and Leibstadt in 2029.
That would leave insufficient time to develop solar and wind alternatives, the government says. Nor would Switzerland be nuclear free, due to a long-term nuclear energy supply relationship with France which relies on atomic power stations for three quarters of its electricity.
"The Swiss would relinquish some of their autonomy in power and they would have to get used to the idea of getting more coal- and gas-fired power from cheaper Germany," said Philipp Goetz, a senior consultant at Berlin-based Energy Brainpool.
Reliance on nuclear energy is being debated across Europe: while Germany is getting out, France is shoring up its industry and Britain recently signed a deal to build its first nuclear plant in decades.
Advertising by the "No" campaign in the referendum asks the Swiss if they really want "dirty power" from Germany. Supporters of the "Yes" vote for a quick exit say Switzerland's nuclear fleet is ageing -- Beznau I, launched in 1969, is the world's oldest operating nuclear plant -- and is too close to urban areas.
"Safety of the people is a matter of highest importance," said Regula Rytz, a co-president of the "Alliance for an orderly Atomic Exit" and a Green Party lawmaker.
The government wants to phase out nuclear power eventually, but energy minister Doris Leuthard has raised the prospect of blackouts if a referendum vote accelerates the process.
"In our view, it would be a disorderly exit," Leuthard said last month. "Suddenly, we will have endangered the energy supply for 1.6 million households."
Swiss power network operator Swissgrid has also said it is unlikely to be ready by 2017 to accommodate the shutdown.
"Our grid infrastructure cannot be quickly modified to handle the changes," the private company said in a statement.
Poyry Management Consulting Switzerland has calculated that the impact on prices for consumers would be small as imports would be relatively inexpensive because of a German capacity surplus.
Germany's move to shut down its nuclear reactors has public backing, but Berlin faces billions of euros' worth of lawsuits as dispossessed operators try to reclaim losses.
Should the Swiss initiative succeed, the nation's utilities have likewise suggested they would pursue more than 7 billion Swiss francs ($6.89 billion) in "economic damages" from having to shut their plants before the end of their lifespan.
Swiss utilities argue the best option, at least for now, is to keep nuclear stations running as long as possible, to recoup their investments and stock up on decommissioning and storage reserves amid a transition to different sources of power.
Alpiq, which owns slices of Goesgen and Leibstadt, has branded a voluntary early shutdown "economically unacceptable."
"Regardless of how the vote goes, exiting nuclear power will cost billions of dollars," an Alpiq spokesman said in an email. "For Alpiq, under the present conditions, continuing to operate the plants is the one option that will cause least damage." ($1 = 1.0162 Swiss francs)
Editing by Susan Fenton