German nuclear plant infected with computer viruses, operator says (2016)
If a virus can cause  accident that releases radiation, it&#x27;s not a computer safety problem, it&#x27;s a failure in  nuclear plant automation design.<p>Modern nuclear plant&#x27;s usually have analog monitoring and safety system&#x27;s parallel to digitized control in critical parts like  neutron flux measurement and calibration, fuel loading monitoring, control rod position indicator, control rod actuators, .... Any error caused by virus attempting sabotage the plant should result shutdown.<p>You can divide the system into 1) process automation 2) limiting systems and 3) Protection systems.<p>Process automation can be fully digitized and computerized. If it fails or computer virus attempts to sabotage the system, it should not cause critical conditions because limiting systems have diversified digital and analog control systems that limit given parameters. If that fails independent protections systems trigger shutdown if those same parameters are exceeded.<p>Another way to divide the safety is four principles:<p>1) parallel principle: parallel subsystems<p>2) separation principle: parallel subsystems are placed so that  simultaneous damage to all of them is very unlikely.<p>3) diversity principle: same function is implemented with different operating principles. The same valve can be operated using electric motor, compressed air, or manually.<p>4) safe-state principle: system failing falls back to the safe state