Experimental study and modelling of the phase transformation of Zircaloy-4 alloy under high thermal transients

Abstract

Dilatometry tests were performed to study the phase transformation kinetic of nuclear fuel claddings made of Zircaloy-4 upon fast heating rates (up to 2000 • C/s). These tests highlighted that from equilibrium to 500 • C/s the temperature at which the transformation starts shifts towards higher temperatures with increasing heating rates. Above 500 • C/s, no impact of the heating rate was observed. The temperature at which the transformation ends remains close to 960 • C with no clear dependence on heating rate. Metallurgical analyses were carried out and were in agreement with the results obtained by dilatometry. A phase transition model was identified from equilibrium to 2000 • C/s.

Solid state phase transformation kinetics in Zr-base alloys

“…More recent investigations of phase transformation kinetics include Nguyen et al’s 22 , 23 in-situ synchrotron X-ray diffraction (SXRD) measurements of cold-worked (CW) Zircaloy-4L subjected to heating rates in the range of 10 to 100 K/s, and electrical resistivity measurements of CW Zircaloy-4L and RX Zircaloy-4L at 100 K/s 22 , 24 , supporting their SXRD measurements. In a new study, Jailin et al 25 using dilatometric technique measured the phase transformation kinetics of SRA Zircaloy-4L subjected to very high heating rates, i.e. from 50 to 2000 K/s.…”

Thermo-mechanical behavior of Zircaloy-4 claddings under simulated post-DNB conditions

“…The equilibrium data can be found in [4]. The 1200 • C/s curve was obtained by a stress-free dilatometry experiment performed at an imposed heating rate of 1200 • C/s on a GLEEBLE-3500 device [31]. The 230 phase fraction accuracy is estimated to be 5% of the phase fraction between 10 and 90% of β content.…”

FEMU based identification of the creep behavior of Zircaloy-4 claddings under simulated RIA thermo-mechanical conditions

“…From this, it follows that it is sometimes necessary to work directly on structural samples, in order to take into account the effects of geometry and fabrication process of the specimen on its thermomechanical behavior. On another hand, the loading conditions example, the heating rate may affect the phase transformation of the material [2,3,4] and thus may affect its mechanical properties [3,5,6]. Therefore, the identification of a constitutive model must be done in conditions as close as possible to real life conditions in order to avoid extrapolations that may lead to 30 uncontrolled discrepancies.…”

“…The ballooning deformation and the temperature at the sample surface were measured by stereo-correlation and near infrared thermography, respectively. The sample, made of Zircaloy-4 alloy, shows a (α → β) phase 50 transformation at high temperature from around 800 to 1000 °C [3, 9,10,4]. This transformation, studied and modeled in [4] from equilibrium to 2000 °C/s, shows a strong dependence to the heating rate.…”