E-Gen plants have human supervision 24/7. To “not show up to work in the morning” would not make sense unless the crew on-shift purposely left their posts.
I would think that if you are looking at a Galt-like situation, the employees would safely shut it down prior to leaving.
No, the situation is people will not be at the plant period. There won't be an orderly shutdown they just are not there for whatever reason.
Can a nuke plant shutdown safely under automation? And IIRC those rods can't be shutoff they still are hot and water is used to keep them from overheating if the water goes then the problems start. (At least that is how I understand it.) So even if the plant shuts of generation there is still the problem of the rods. I am guessing eventually the water dissipates without human supervision.
Scenario: “everybody out! Now! Vertical or horizontal, you choose!”
For fiction, situations can be invented as needed.