According to Ned Beach, the TRITON needed two reactors because of her size and the relatively low power output of the water-cooled reactor, mark 1. She was a biiiiiig boat (although Beach said he hated the tiny conning tower!). Also, not sure how much turbo-electric power was needed to light up that friggen massive radar she was built with inside that huge sail. CVA(N) 65 needed 8 friggen nuke steam kettles when built! Not sure, but I think she was refitted with fewer, but newer, plants.
PF