The Paks nuclear plant has operated for 42 years. It has never fully shut down, not for politics, not for the end of communism, not for the reorganisation of the Hungarian grid around it. This week it stopped completely, because the Danube ran too low to cool it. [1]
A nuclear reactor is, at its least glamorous, a device for boiling water, and the steam it makes has to be condensed back into water by something colder. At Paks, that something is the Danube. When the river drops far enough, there is no longer enough cool water to take the heat away safely, and the plant has to come off. The record low this summer took it below that line. [1]
What leaves the grid with it: nearly half of Hungary's electricity, roughly 2,000 megawatts, starting Monday. [1]
The European Commission is prepared to convene an emergency meeting of the Electricity Coordination Group, the body that exists precisely for a member state suddenly missing a large block of generation. [1] Hungary will import, and it will import during a European heatwave, when everyone else's demand is also high and their own thermal plants are facing the same rivers.
The part worth holding onto is that nothing failed. No component broke, no operator erred, no regulator intervened. The plant is fine. The river is not, and a plant whose cooling depends on a river is only as available as the river is.
Every thermal generator on the continent has this dependency, nuclear and coal and gas alike, and it is the piece of energy planning that gets discussed least because for four decades at Paks it simply never mattered. This week it mattered enough to take half a country's power off the board.
