Measurement of the Young modulus anisotropy of a reactor pressure vessel cladding

The dynamic elastic modulus for directions in the plane of the cladding of a reactor pressure vessel was found to have an unusual low value of 165 GPa. In order to examine this phenomenon further, a cantilever bend test method was developed which allowed measuring the modulus along any desired direction relative to the cladding. It was found that in the as-clad as well as in the clad-and-annealed condition the deviations of the modulus from the bulk modulus depend on the orientation. The modulus values range from 145 GPa perpendicular to the cladding plane to 219 GPa at an angle of 35° to the cladding plane. These deviations from the bulk value are explained by the texture resulting from the directional heat flow during solidification and by the presence of the δ phase.