The effect of azimuthal temperature distribution on the ballooning and rupture behavior of Zircaloy-4 cladding tube under transient-heating conditions

For the purpose of investigating the effect of azimuthal temperature distribution on the ballooning and rupture behavior of Zircaloy-4 (Zry-4) cladding tube, laboratory-scale experiments on non-irradiated Zry-4 cladding tube specimens were performed under transient-heating conditions which simulate loss-of-coolant accident (LOCA) conditions by using an external heating method, and the data obtained were compared to those from a previous study, where an internal heating method was used. The maximum circumferential strains of the cladding tube specimens were firstly divided by the engineering hoop stress. The divided maximum circumferential strains, ks, of the previous study, which used the internal heating method, were then corrected based on the azimuthal temperature difference (ATD) in the cladding tube specimen. The ks for the external heating method which was used in this study agreed fairly well with the corrected ks obtained in the previous study which employed the internal heating method in the burst temperature range below ～1200 K. Also, the area of rupture opening tended to increase with increasing of the value which is defined as the engineering hoop stress multiplied by the maximum circumferential strain. From the results obtained in this study, it was suggested that the maximum circumferential strain and the size of rupture opening of a cladding tube under LOCA-simulated conditions can be estimated mainly by using the engineering hoop stress, the maximum circumferential strain, and ATD in the cladding tube specimen, irrespective of heating methods.