Thermomechanical Behavior and Modeling Between 350°C and 400°C of Zircaloy-4 Cladding Tubes From an Unirradiated State to High Fluence (0 to $85s˙1024 nm−2,$$E>1 MeV)$

This paper first describes the effect of neutron irradiation on the thermomechanical behavior of stress-relieved Zircaloy-4 fuel tubes that have been analyzed after exposure to five different fluences ranging from nonirradiated material to high burnup. In the second part, a viscoplastic model is proposed to simulate, for different isotherms, $350°C<T<400°C,$ out-of-flux anisotropic mechanical behavior of the cladding tubes over the fluence range $0<ϕ<100s˙1024 nm−2E>1 MeV.$ The model, identified for tests conducted at 350°C, has been validated from tests made at 380°C and 400°C. The model is capable of simulating strain hardening under internal pressure followed by a stress relaxation period, the loading producing an interaction between the pellet and cladding. Introduction of a state variable characterizing the damage caused by a bombardment with neutrons into the model has allowed us to simulate the irradiation-induced hardening and creep rate decrease, as well as the saturation noticed after two cycles of irradiation $≅45s˙1024 nm−2E>1 MeV$ in a pressurized water reactor (PWR). Finally, the numerical simulations show the model is able to reproduce the totality of the thermomechanical experiments. [S0094-4289(00)00202-4]