“…Besides power, the effect of other parameters, such as flow velocity and steam quality in two-phase flow, was also studied, but the excitation mechanism was not clearly explained. Smith and Derken (1998) measured the overall unsteady forces acting on a CANDU 6 inlet bundle. The investigation indicated that the bundle vibration mode was a mixture of rolling and bending motion, and the most concerned frequencies were those less than 30 Hz and characterized by almost rigid-body motion, including a low frequency motion as the bundle rocking from side to side in the pressure tube.…”