Thermomechanical Behavior and Modeling Between 350°C and 400°C of Zircaloy-4 Cladding Tubes From an Unirradiated State to High Fluence (0 to 85⋅10[sup 24] nm[sup −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 parr, a viscoplastic model is proposed to simulate, for different isotherms, 350 degreesC < 100.10(24) nm(-2) (E > 1 MeV). The model, identified for tests conducted at 350 degreesC, has been validated from tests made at 380 degreesC and 400 degreesC. 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 (congruent to 45.10(24) nm(-2) (E > 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].