Simulation of the fracture behavior of zircaloy-4 cladding under reactivity-initiated accident conditions with a damage mechanics model combined with fuel performance codes FEMAXI-7 and RANNS

Udagawa, Yutaka  ; Mihara, Takeshi  ; Sugiyama, Tomoyuki ; Suzuki, Motoe; Amaya, Masaki  

In order to investigate the detailed processes of pellet cladding mechanical interaction (PCMI) failure, a continuum damage mechanics model using FEM calculations was proposed to be applied to analyses of the RIA-simulated NSRR tests with unirradiated and pre-hydrided claddings. The simulation made reasonable prediction regarding with cladding fracture strain in hoop direction and reproduced the typical fracture behaviour under PCMI loading characterized by a ductile shear zone. The effect of a local temperature rise in the cladding inner region on the failure strain was found to be less than 5%. Failure strains predicted under a plane strain loading were smaller by 20-30% than those predicted under equi-biaxial tensions between the hoop and the axial directions.