The design and autmation allows it to only turn on when the reactor is needed and the energy of the fuel can be stored.
The reactor is only fueled when there is low steam in storage (<5k Steam average), no fuel is present and the reactor temp is below the threshold (600 C° default)
The automation connecting the Engines below the reactor only turn the engines on when the accumulators are below 30% and stops charging at 75%.
!!! It uses the ability to chose the inserter arm position from Bobs inserters. You can still use it in vanilla since the rotation seems to transition but it may ruffle some feathers on a pure vanilla server !!!
The deciders have descriptions if you want't to only use the automation parts.