Study of clad ballooning and rupture behavior of fuel pins of Indian PHWR under simulated LOCA condition

Highlights: • We study ballooning and rupture characteristic of Indian PHWR fuel cladding. • Burst pressure and temperature, circumferential and diametral strain and burst opening area were measured. • Two circumferential strain maxima at ∼790 °C and ∼1030 °C and a minimum at ∼880 °C were observed. • Burst opening area varies in the range 2–142 mm². • We establish a burst correlation (stress vs. temperature) in α, α + β and β phase regions. - Abstract: Deformation and rupture characteristics of Indian PHWR fuel pin under loss-of-coolant accident (LOCA) conditions were investigated to develop rupture database that will be used for the formulation and verification of mathematical modeling. Experiments were carried out on single fuel pins over a wide range of initial internal pressures (3–73.5 bar) and in the heating rate range of 7–12 °C/s under inert gas environment. The cladding surface temperature and internal pressure data were recorded on-line during the experiment and the cladding deformation and rupture measurements were made on the fuel pins after the test. Rupture characteristics were studied with the help of macroscopic examination of the rupture location. It was found that the phase transformation from α to α + β and α + β to β has a great influence on the material ductility. Two circumferential strain maxima and a minimum at the burst temperatures of ∼790 °C and ∼1030 °C and ∼880 °C respectively were observed. The burst data of this experiment have been utilized to develop the burst correlation for Zircaloy-4 cladding of PHWR fuel pins