Experimental study on local interfacial parameters in upward air-water bubbly flow in a vertical 6 × 6 rod bundle

•A database of local two-phase flow parameters in a vertical 6 × 6 rod bundle is presented.•Radial core- and wall-peaking profiles of local void fraction and IAC are observed.•Bubbles prevailing in each cross section keep a similar size.•Bubbles rise in a core-peaking velocity profile with a slight motion toward channel box.•Area-averaged values of local void fraction and IAC are compared with selected models.