[dwqjedyi] 2 nuclear control rooms

Each day, operators of a nuclear power plant report to one of two (or more) control rooms.  One control room is actually connected to the nuclear reactor(s); the other one interfaces with a simulation.  Each day, the operators do not know whether they are in simulation or reality.

The simulation one allows the operators to be frequently tested and drilled to handle events -- emergencies -- which occur infrequently in reality but would be catastrophic if handled poorly.