The Coolant kindof keeps the Reactor at the same temperature at all times, so the sensor doesn’t really make much sense there at all.
And the only explosion condition is running out of Coolant.
Also since when are Reactors ignited?? If anything you need to turn them off before inserting the Rods, unless you wanna plunge Rods into the Reactor by hand while it is technically running.
This is all a mostly Gameplay focused thing, using Absorber Rods will lead to twice the Energy Output for Neutrons that hit the Absorber.