Mechanical Behavior of PHWR Fuel Cladding Tested Under Simulated LOCA Condition

After Fukushima daiichi nuclear accident in March 2011, the post-loss-of-coolant accident (LOCA) fracture resistance of fuel cladding against various loads arising during long term core cooling, fuel handling and storage became a concern in the safety evaluation of reactor core. In this study, the residual bending moment and offset displacement were measured using four point bend tests of fuel cladding which experienced simulated LOCA tests to determine the resistance to fracturing of ballooned-burst-oxidised and quenched cladding. The obtained results suggested that the decrease in the maximum bending moment and offset displacement of the cladding were mainly influenced by its microstructure evolved during the testing i.e ductile prior β-Zr layer thickness, oxygen and hydrogen in it. It was observed that with increasing ratio of prior β-Zr to oxygen the maximum bending moment and offset displacement increased. Hydrogen played an indirect role on the cladding embrittlement. Due to increasing hydrogen concentration, the oxygen solubility in the prior β-Zr increased causing enhanced embrittlement of the clad at ambient temperature.