The cooling towers of Cattenom, one of 56 reactors built in France's crash nuclear program after the 1973 oil shock.

Map the share of electricity each country generates from nuclear power and one result jumps out immediately: France, at roughly two-thirds, in a color class by itself. Its neighbors are scattered across the low end of the scale — Germany near zero, Italy at zero, Spain and Britain in the teens and twenties. Data: Our World in Data (CC BY). Nuclear reactors need uranium, capital and engineering talent, none of which France has in unusual abundance. What it has is a decision, made in a single week fifty years ago, that no other democracy was willing to make at the same speed or scale.

The decision was born of panic. In October 1973, Arab oil producers embargoed states seen as supporting Israel in the Yom Kippur War, and the price of oil quadrupled within months. For most Western economies this was a painful shock. For France it was closer to an emergency: the country imported roughly three-quarters of its energy, almost all of it oil, almost none of it produced at home. France had no North Sea fields like Britain, no Ruhr coal seams like Germany. What it did have, thanks to decades of investment in its Commissariat à l'énergie atomique, was one of the world's deepest pools of nuclear engineering expertise — built originally to power submarines and a nuclear deterrent, not homes.

On March 6, 1974, Prime Minister Pierre Messmer announced what the press immediately dubbed the Messmer Plan: France would build enough nuclear capacity to generate essentially all of its electricity from the atom, starting with a program of 44 reactors to be under construction within six years. It was decided in the Council of Ministers with almost no public debate or parliamentary vote — a fact that infuriated opponents then and still colors the program's reputation now. Roughly 4,000 French scientists signed a petition of protest. The government pressed ahead anyway, with the near-unanimous backing of the political establishment across the normal left-right divide; energy independence was one of the few subjects on which Gaullists and Communists could agree.

What followed was, by the standards of large infrastructure programs, a remarkable execution. Rather than let each utility pick its own design, as the United States and Britain did, France standardized on a single reactor type, licensed originally from the American firm Westinghouse and built by the French manufacturer Framatome. Building the same design over and over let crews climb a learning curve that other countries never got to climb, because they kept switching blueprints. Over the following fifteen years, France commissioned 56 reactors — an average of one new unit roughly every three months — and by the late 1980s had turned an oil-dependent importer into the world's most nuclear-reliant electricity producer and a net exporter of power to its neighbors.

The payoff shows up starkly in a second map: carbon intensity of electricity. In 2023, generating a kilowatt-hour of French electricity released about 56 grams of CO2. In Germany, which shut down its nuclear fleet after the 2011 Fukushima accident and leaned harder on coal and gas to fill the gap, the figure was around 371 grams — roughly six times dirtier, despite Germany's much larger investment in wind and solar. Nuclear and renewables both cut carbon; France's map simply shows what happens when a country bets almost everything on one of them, early, and sticks with the bet for half a century.

The bet has not been free of costs. France has struggled for decades to agree on where to permanently store its nuclear waste. Its aging fleet needs increasingly expensive maintenance — corrosion problems idled more than half the reactors at once in 2022, forcing France to import electricity for the first time in years. And the flagship of its next generation, the Flamanville EPR reactor, was approved in 2007 and finally entered commercial service in 2024, roughly six times over its original budget. Yet in February 2022, President Emmanuel Macron used a speech in Belfort — the town where Alstom once built French locomotives and turbines — to announce a revival: six new EPR2 reactors, with an option for eight more, explicitly framed as answering both climate targets and, weeks before Russia's invasion of Ukraine made the phrase inescapable, energy security.

The map of nuclear power, in other words, is not really a map of geology or geography at all. Uranium can be shipped from Kazakhstan or Niger to anywhere with a reactor and a port. It is a map of a handful of political decisions, made under pressure, that a few governments were willing to see through across decades and changes of government while others reversed course. France's colored-in two-thirds is the visible residue of one long-ago Tuesday in the Council of Ministers.

Sources: Our World in Data, "Share of Electricity from Nuclear Power"; World Nuclear Association, "Nuclear Power in France"; Gabrielle Hecht, The Radiance of France: Nuclear Power and National Identity after World War II; Encyclopaedia Britannica, "Messmer Plan" and "Nuclear power in France."

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