Under actual reactor conditions, the mechanical characteristics of nuclear fuel are particularly affected by thermal expansion of the fuel pellets. The results of an experiment studying the vibration behavior of nuclear fuel under reactor conditions are presented. The experiment was conducted in an experimental reactor in a two-phase flow test loop simulating a Canada deuterium uranium (CANDU) reactor fuel channel. The effect of fuel power in particular was investigated. The natural frequency of the fuel elements increased by ∼50% at full power. The effect of the fuel channel parameters such as flow velocity, steam quality, and pressure were also investigated.