EDF (Electricite de France, France's state nuclear operator) took three reactors fully offline on Sunday 12 July, shutting Chooz on the Meuse, Golfech on the Garonne and Bugey on the Rhone on cooling-water discharge limits 1. Eight further reactors ran at reduced power. EDF had won a Rhone-temperature exemption for Bugey from the economy ministry on Saturday 11 July, valid to 20 July, with the government judging grid security worth the environmental breach 2.
EDF's plants on the Rhone, Garonne and Meuse draw river water to cool their condensers and must throttle output when the returned water would push downstream temperatures past regulatory ceilings. Reactor hardware sat available; the rivers, not the turbines, forced the cut. That distinction is why the government can relax the constraint by decree, as it did for Bugey, and why the summer France-Germany trade now carries a policy-discretion component on top of a weather one.
The curtailment inverted the topic's defining trade. French day-ahead power cleared roughly €7/MWh above Germany on Sunday 12 July, reversing the €18-26/MWh France-cheaper spread of 5 July 3. With reactors off, gas-fired plant moved up the merit order to set the French marginal price, so the nuclear-long-France, carbon-short-Germany relative-value play briefly ran the other way. That play had reset France cheaper by €17.29 barely a fortnight earlier . EDF had flagged fresh heat-curtailment risk at Chooz only three days earlier, on 9 July , and the risk duly materialised.
By Monday 13 July the spread had settled back to about €3/MWh with France cheaper again, still far inside the early-July gap 4. The reversal carries a clock: Bugey's exemption expires 20 July, and one market report puts Chooz-2 back on 25 July 5. Treat the daily averages as approximate, drawn from hourly prints on Fraunhofer ISE's energy-charts feed; the sign flip itself is robust.
