Investigation on Hydrogen Embrittlement and Failure Characteristics of Zr-4 Cladding Based on the GTN Method

Based on the classical Gursone-Tvergaarde-Needleman (GTN) method, a theoretical model was developed and applied to predict the mechanical behavior and fracture characteristics of hydrogenated zirconium cladding. With full consideration of the influence of hydrogen on plastic stain and void volume in materials, the damage parameters in the classical GTN model were modified. Through benchmarking with experimental data, it was proved that the hydrogen embrittlement phenomenon in zirconium materials can be properly simulated by the modified GTN model proposed in this study. By integrating this modified model into ABAQUS software, numerical simulation of a cladding tensile test was further conducted at different temperature, hydrogen concentration and oxidation conditions. Influence of hydrogen embrittlement on the mechanical properties and fracture characteristics of zirconium cladding was analyzed. The results suggest that the effect of hydrogenation on the cladding mechanical performance varies in magnitude at different temperatures, because hydrogen exists in different forms and also varies significantly at different temperatures. At a relatively low temperature, a considerable amount of hydrogen is presented in the form of precipitates, which is more likely to cause hydrogen embrittlement failure. In addition, the numerical simulation of a cladding tube burst test was carried out under a loss of coolant accident. It was concluded that the influence of hydrogen embrittlement on the burst stress and burst strain was still considerable, despite of the rather high temperature at the burst position.