A polyolefin production system, comprising a polymerization reactor (such as a polyethylene loop slurry reactor) and a fractionation system that receives reactor effluent processed in a diluent/monomer recovery system for recycle to the reactor and to suppliers. A conduit diverts a portion of a reflux flow comprising monomer, such as ethylene, from within the fractionation system to the polymerization reactor, providing for less venting of monomer, such as ethylene, to the supplier. Accordingly, monomer yield is advantageously increased, as the monomer returned to the reactor displaces monomer feedstock to the reactor. The reflux flow may originate from a condensed overhead lights from a diluent recycle column disposed in the fractionation subsystem. The diluent recycle column may receive a stream comprising diluent and monomer as feed from the diluent/monomer recovery subsystem, and may receive the non-diverted portion of the reflux flow as reflux.