IMDB lists numerous filming locations for various scenes in Star Trek IV: The Voyage Home. Not explicitly listed are scenes set aboard the USS Enterprise (the aircraft carrier CVN 65). Of specific interest to me are the shots of Chekhov and Uhura at the nuclear reactor. In one shot there is a square-ish orange glass window, behind which are puffs of mist. That strikes me as a bit hokey, yet many of the aboard-ship scenes look plausibly like they were shot aboard a real naval vessel, especially what appears to be the hangar deck.
So... was the "reactor" real ship-board equipment, or a set on a sound stage? If real ship-board equipment, what was standing in for the reactor?