A fluid catalytic cracking reactor including a vessel, a chamber housed within the vessel, and a plurality of cyclones housed within the vessel, but externally of the chamber. The plurality of cyclones are arranged in a plurality of cyclone clusters, where each of the cyclone clusters includes a grouping of at least two cyclones that share common outlet piping for communication with the chamber. Alternatively, a fluid catalytic cracking reactor including a vessel, a chamber housed within the vessel, and a plurality of catalytic separation devices housed within the vessel, but externally of the chamber. The catalytic separation devices are in communication with the chamber via outlet piping. Preferably, the catalytic separation devices of the reactor are also in communication with a plenum via separator gas outlet piping, and optionally at least one of the catalytic separation devices feeds an outlet vapor stream into at least two different separator gas outlet piping members.