Experimental study on graphite dust deposition in straight pipes under simulated HTGR operating conditions

The high-temperature gas-cooled reactor (HTGR), especially in the pebble-bed design like China’s HTR-PM, offers key safety and efficiency benefits. However, radioactive graphite dust generated during long-term operation poses safety and maintenance challenges. This study experimentally investigates graphite dust deposition and resuspension in a straight pipeline under varying flow velocities, temperatures, and carrier gases (air and helium). Deposition was measured at upstream, midstream, and downstream locations. Results show that increasing flow velocity significantly reduces deposition, with a 97.6 % decrease at 6 m/s compared to 1.5 m/s and near elimination at 9 m/s. Axial deposition remained consistent, with most dust settling in the front and middle sections. Higher temperatures (25–300 °C) reduced deposition and improved uniformity. Helium, due to its higher viscosity and lower density, led to lower overall deposition than air. Resuspension tests revealed partial particle detachment at high wind speeds (up to 28  m/s), but complete resuspension was not achieved, likely due to strong adhesion forces such as electrostatic interactions. These results provide critical experimental data for CFD model validation and support the development of effective dust control strategies, contributing to safer and more efficient HTGR operation.