Radial and axial development of boiling Two-Phase flowin A 5 × 5 Heated rod bundle under atmospheric pressure condition

The boiling two-phase flow in the fuel rod bundle of a boiling water reactor exhibits multidimensional and transient flow dynamics. Coolability of the fuel is the key to ensuring safety, particularly in the event of any accident that involves the coolant injection malfunctioning and the core becoming uncovered. This paper addresses boiling two-phase flow dynamics in a 5 £ 5 heated rod bundle under atmospheric pressure. The diameter of the heated rod is 10 mm, the rod pitch is 13 mm, and the heated length is 3.71 m. The radial power profile is the key experimental parameter: (i) uniform, (ii) center peak, (iii) side peak, and (iv) corner peak. The cross-sectional void-fraction distribution of a total of 132 points was acquired at more than 800 frames (cross sections) per second with a SubChannel Void Sensor (SCVS). The axial void-fraction distribution was also acquired with eight pairs of SCVS, which explain the radial and axial development of boiling two-phase flow in the rod bundle.