The Tricastin Nuclear Power Plant run by Areva and EDF located in four different communes | Philippe Desmazes/AFP via Getty Images The next French president’s nuclear problem Candidates face tough decisions on the country’s nuclear energy future.

France's next president is in for a big nuclear headache.

He or she will have to figure out how to either extend the life of or shut down 58 reactors fast approaching retirement age and keep the country's energy supply flowing at the same time.

All the options risk being complicated and costly — financially and politically — and require savvy planning to encourage France’s dominant electricity company EDF to shift away from an energy source that has long been the core of its business.

The top candidates going into the April 23-May 7 election have widely varying nuclear energy policies, from a far-left push to get rid of it entirely to a far-right call to hang on to the country’s biggest energy source and a decades-old source of pride in the country's industrial prowess. Center-left front-runner Emmanuel Macron falls somewhere in the middle: He wants to carry on with the existing policy, which aims to shrink the share of nuclear energy in France’s mix from 75 percent to 50 percent.

“These things are being discussed as if they were a matter of opinion, and they are not,” said Mycle Schneider, a Paris-based energy policy adviser. “The financial stress has become so harsh that it is virtually impossible to imagine maintaining a nuclear fleet of 58 reactors. They cannot afford to maintain the status quo, so consecutive shutdowns will be forced upon decisionmakers.”

“Nuclear is not a right or a left issue. It is a long-time industry that needs consensus” — Valerie Faudon, delegate general of the French nuclear industry group SFEN

Despite the industry's financial problems, navigating the politics of nuclear power can be dangerous in a very close election campaign. A 2016 poll by the French public opinion institute Ifop found that 53 percent of people are against a nuclear phase-out. Right-leaning voters are generally pro-nuclear, while left-leaning ones support a phase-out — which keeps candidates from shifting positions.

EDF and France's nuclear technology company Areva have experienced huge financial strain in recent years as European power prices dropped and new nuclear plants under construction in France and Finland ran into significant cost overruns and delays. As a result, the French government pushed EDF to take over Areva and approved €3 billion in support before EDF committed to building a new nuclear plant in the U.K. last year. The costs and problems around these projects, however, have raised doubts about the future of Areva's European Pressurized Reactor technology after the British plant.

Nuclear battle lines

French divisions over nuclear were on display this month in a battle over the closure of France’s oldest nuclear power plant, the 39-year-old Fessenheim.

Ségolène Royal, the energy and environment minister, issued a decree to close the plant — fulfilling one of outgoing President François Hollande’s electoral promises. The decision was largely symbolic because Fessenheim will have to be closed by the time EDF starts operating its new Flamanville nuclear plant in Normandy, likely in 2019. Royal wanted the closure this year, but EDF resisted and decided to wait until Flamanville is ready.

Royal’s push brought nuclear power to the forefront of the presidential campaign.

“This is an ideological decision taken under pressure from the Greens,” said Marine Le Pen, the far-right National Front candidate, who vowed to repeal Royal's decree. Le Pen says ending nuclear energy would be tantamount to France “shooting itself in the foot” — a message that aligns with her views on protectionism and patriotism.

As for the rest of the presidential field, Socialist Benoît Hamon and far-left candidate Jean-Luc Mélenchon want to do away with nuclear energy quickly. Conservative François Fillon, from Les Republicains, is pro-nuclear and wants to maintain the current energy mix.

While Macron backs progressively reducing the share of nuclear to 50 percent, he has also made it clear he doesn't intend to go further. “Nuclear in France has a future” and will be here “for decades,” he said during a prime-time political show earlier this month.

The nuclear industry broadly argues that France and Europe need its emissions-free fuel to meet their climate goals at a reasonable cost. The sector has been wary of getting too involved in the political debate.

“Nuclear is not a right or a left issue. It is a long-time industry that needs consensus,” said Valerie Faudon, delegate general of the French nuclear industry group SFEN. “We feel we deserve better than a discussion over one plant’s closing.”

A tricky transition

Even sticking with the French energy transition law adopted in 2015 poses challenges for the next president, which aims to reduce the share of nuclear energy in France to 50 percent by 2025, from 75 percent now, and boost renewables to 32 percent of the mix by 2030.

The Fessenheim uproar showed that the French government is relying on EDF’s goodwill to implement its vision for energy transition.

The law doesn't lay out clear incentives for EDF to shift away from nuclear, Schneider said. Its target for renewables is also too low to make up for less nuclear, analysts said in a report by S&P Global Platts published this month.

Whatever the campaign rhetoric, France's next president will have to take into account an unpleasant truth: Any option is going to cost a lot of money.

Decommissioning nuclear power plants is complicated, long and expensive work, but so is building new reactors or upgrading old ones. A quick nuclear phase-out would cost €217 billion, according to the French liberal think tank Institut Montaigne. The Mélenchon and Hamon campaigns responded by pointing to a Court of Auditors estimate that it would cost €100 billion to keep existing reactors running.

Macron balanced between the two extremes during his recent TV appearance: “Nobody knows the total cost for nuclear energy,” he said. “I was minister for industry and I could not tell you.”