I don't know how much power they need to run the coolant pumps, but hopefully they're flying in every generator they can find . . .
The nuclear power standby cooling units I saw were 20 cylinder EMD locomotive diesels, probably >4000 HP back in the day (1984). They were set to start on a electrical power outage, and were started with airmotors, and were heated so everything was at operating temp. They would spin up in 10 seconds and be at full power with load applied. They would power a 3000 GPS pump. Yes that is Gallons per Second.