Quote: "I am sceptical that a usb stick or internet connection would be anywhere near a computer controlling a nuclear reactor."
Yeah, probably no chance of a computer like that even being designed to access the internet. What would concern me is the ancillary systems, like fire detection, cooling, and valve control equipment that would run alongside. For instance there might be a coolant pump connected to a control PC, which could well have internet access to allow remote monitoring and maintenance. We had a major fire at work (wiped out a silicon wafer fab) because a temperature sensor connected to a PC failed - god only knows what a trained engineer 'could' do through remote maintenance on these systems.

Health, Ammo, and bacon and eggs!
