When the rivers ran warm: how France's nuclear fleet broke in 2022

Twenty-One Point Seven Gigawatts

On Sunday 28 August 2022, the French transmission operator RTE recorded available nuclear capacity of 21.7 gigawatts. The installed fleet behind that number is 56 reactors and a little over 61 gigawatts: the largest nuclear machine in Europe, the second largest in the world, the plant park that had made France the continent's structural power exporter for four decades. On that Sunday, nearly 65% of it was offline. Two days earlier, on Friday 26 August, the French year-ahead baseload contract (Cal-23, the price of a flat megawatt delivered through every hour of 2023) had traded above €1,100 per megawatt-hour. The German equivalent touched €995 the same day. A product that had spent most of the previous decade between €35 and €50 was pricing a French winter at more than twenty times its historical norm.

By the end of the year the annual accounts confirmed what the August screen had been screaming. EDF's French nuclear fleet produced 279 TWh in 2022, its lowest output in some three decades and roughly a quarter below the 360.7 TWh of 2021. Average fleet availability for the year was 54%, against a 2015–2019 average of 73%. Hydro, hit by the same drought that was warming the rivers, delivered 49.6 TWh, a fifth below its recent average. And France, the country whose exports had underwritten Belgian, Italian, Swiss and British winters since the Mitterrand era, ended the year as a net importer of 16.5 TWh of electricity. It was the first net-importing year since 1980.

Two separate failures produced that outcome, and they are worth keeping separate in your head even though they compounded in the market as one. The first was regulatory and environmental: French reactors are legally forbidden from warming their rivers beyond set temperatures, and in the hottest, driest European summer in decades, the rivers arrived at the power stations already warm. The second was metallurgical: in December 2021, EDF confirmed that a weld in the safety pipework of its newest reactor family was cracking through a mechanism nobody had predicted there, and the only responsible answer was to shut reactors down and cut the pipes open. This editorial is about both: the physics, the law, the market carnage, and what a power analyst should actually watch the next time the rivers run warm. Which, as we shall see, was last month.