The A2W designation stands for: This nuclear reactor was used in the world's first nuclear-powered aircraft carrier, the USS Enterprise (CVN-65).
Both reactors would have been on-line to simultaneously provide maximum ship speed and plane launching capability.
Much of the reactor power control during steady-state operation comes as a result of the coolant water's negative temperature coefficient.
The hot water from the reactors is sent, via large pipes, into heat exchangers called steam generators.
The expended steam from the main engine and other auxiliaries enters condensers to be cooled into liquid water and recycled to the feed system.