[dreamcompiler]

> But the "grid power" needed to run the reactor's control systems, etc., can almost surely be generated by the reactor itself while it's online, right?

In theory, yes. But in practice, most nuclear power plants are required by law to trip offline if their local grid goes down or even experiences a minor disturbance [0]. Nuclear power plants always have onsite diesel generators to run pumps, operate control rods, and shut down the reactor if needed.

Nuclear plants are notoriously finicky about offsite power quality because they take a long time to ramp up and down and the consequences of e.g. losing cooling are potentially disastrous.

[0] http://large.stanford.edu/courses/2016/ph241/yang2/docs/bick...