Atomic plants. Why? I guess because it doesn't stop.
https://www.theregister.co.uk/2013/06/19/nuke_plants_to_keep...
http://www.mapps.l-3com.com/candu-plant-control-systems.html
https://www.theregister.co.uk/2013/06/19/nuke_plants_to_keep...
http://www.mapps.l-3com.com/candu-plant-control-systems.html
I have never worked with this system, but I have heard great things about its scalability and availability.