[Alas Babylon!]

The nuclear power reactors are not off, they're just not supplying power to the grid. In other words, the reactors are still up; loss of electricity elswhere shouldn't affect them. So they may spin down the generators, but the reactors should be ok.

[ThirdMate]

How do they "spin down the generators" and keep up steam from the reactors? That energy (high pressure steam) has to go somewhere. All the reports and common sense tells me you got to shut off that heat source if you have no load on the turbines.
But I am a deck officer, not an engineer.