A new procedure to calculate the constitutive equation of nuclear fuel cladding from ring compression tests

Abstract The geometry of the nuclear fuel cladding (thin-walled tube) makes it difficult to obtain its hoop mechanical properties. A new procedure is devised to obtain the constitutive equation of nuclear fuel cladding along the hoop direction from ring compression tests. The method combines experimental results, finite element simulations and an original iterative algorithm to adjust the experimental data. The process is successfully applied to unirradiated pre-hydrided ZIRLO nuclear fuel cladding, tested at three temperatures (20, 135 and 300 °C) with hydrogen contents (0, 150, 250, 500, 1200 and 2000 ppm). The stress-strain curves were obtained for each configuration with an excellent agreement between the numerical results (based on back calculation of the obtained constitutive equation) and the experimental data. The stress-strain curves calculated show that the mechanical properties do not depend strongly on hydrogen concentration, only a small ductility decrease with the hydrogen concentration was observed. The cladding shows a light strain hardening which is similar for the samples tested at 20 and 135 °C and does not depend on the hydrogen concentration. However, at 300 °C, the samples with the highest hydrogen concentrations (1200 and 2000 ppm) present a behavior that is close to an elastic-perfectly plastic material.