Ballooning and rupture behavior of Zircaloy-4 cladding under transient-heating conditions

過渡加熱条件におけるジルカロイ-4被覆管の膨れ破裂挙動

成川 隆文 ; 天谷 政樹  

Narukawa, Takafumi; Amaya, Masaki

Phenomena of fuel fragmentation, relocation and dispersal have been observed in several experiments on very-high-burnup fuels under simulated loss-of-coolant-accident (LOCA) conditions using a test reactor. In order to improve the prediction of the phenomena, ballooning and rupture behaviors of cladding under simulated LOCA conditions were investigated by performing laboratory-scale experiments in which internally pressurized non-irradiated Zircaloy-4 (Zry-4) claddings were heated to burst. The maximum circumferential strains of the ballooned claddings were strongly dependent on burst temperature and the trends seemed to depend on the heating rate in the experiment. Values of the maximum circumferential strain were normalized by dividing them by engineering hoop stress at the time of rupture. A correlation between the normalized values and the burst temperatures suggests that the fraction of phase in Zry-4 affects the extent of the strain of cladding ballooning.