Experimental study of interfacial area transport in air-water two phase flow in a scaled 8 × 8 BWR rod bundle

► Facility scaled from 'typical' BWR fuel bundle. ► New data for local flow quantities in an 8 × 8 rod bundle. ► Data includes axial development of flow parameters. ► Data shows interfacial area concentration higher than in pipes and strong effect of length scales. ► Spacer grid effects require further study.