Experiment on flow-induced vibration of fuel rod in HTTR

This study was performed in order to investigate flow-induced vibration characteristics of a fuel rod in HTTR (High Temperature engineering Test Reactor). The fuel rod used this experiment is a graphite fuel rod which simulated a specification of the HTTR's fuel rod. The experiment carried out up to Re = 31,000 using air at room temperature and pressure. Air flowed toward downstream in an annular passage consisted of the fuel rod and the graphite channel. Vibration amplitudes and frequencies of the fuel rod were measured by two noncontact displacement sensors fixed on a side wall of the graphite channel. The following conclusions were drived: (1) The fuel rod amplitudes increase with a increase of the flow rate and with a decrease of the fuel rod weight. (2) The fuel rod amplitudes are obtained by δ/De = 2.22 × 10^-10Re^1.43 (9,000 ≤ Re ≤ 31,000), where δ is the vibration amplitude, De the hydraulic diameter and Re Reynolds number. (3) The fuel rod frequencies shift from lower natural frequency to higher as the flow rate increases. (author)