Identification of constitutive parameters for high temperature deformation of pressure tube of Indian PHWR considering multi-axial state of stress

In case of severe accidents like loss of coolant accident with failure of emergency core cooling system, the pressure tubes get heated quickly causing severe deformation. In this paper, an analytical solution technique has been used for calculating the radial deformation behaviour of pressure tubes. The analysis is carried out for different cases when the pressure tube is subjected to different values of internal pressure and heating rates. In the absence of specimen level creep test data of Indian pressure tube, data of Canadian pressure tube of similar material has been used. Due to observed differences between experimental and analytical values of radial deformation with time, the actual parameters have been calibrated from component level experiments using an optimization algorithm. Both uniaxial and bi-axial states of stress have been considered. Finite element method has also been used to calculate radial deformation of pressure tube and compared with experiment.