Strain-rate dependent plasticity in thermo-mechanical transient analysis

The thermo-mechanical behavior of LWR fuel rods during reactor transients is generally governed by the strain-rate properties of the clad material. Relevant constitutive modeling requires extensive material experiments that simulate actual in-reactor thermal histories and environmental conditions. Unfortunately, however, the prevalent sources of available data are simple experiments involving internally heated pressurized tubes. The material data are generally presented in the form of average circumferential strain and nominal stress as functions of temperature and heating rates. Such data implicitly includes environmental and time history effects that are unique to the experiment and, hence, are difficult to generalize to actual in-reactor transients. (orig.)