Um... Source?
An EMP is devastating to fine electronics, but I don't see how it could be devastating to anything mechanical ─ which the cooling process at nuclear power plants is. As the matter of fact, you could easily expose a 1970s-era automobile to an EMP, and the only thing that would be fried would be its radio. In a modern car however, the only things that would still work would be the power windows, the horn and the windscreen wipers. And maybe the lights too. But the engine management system and (if it is an automatic) the gear-shifting logic would be toast.