Abrasion behavior of graphite pebble in lifting pipe of pebble-bed HTR

The present work explored the abrasion behavior of graphite pebble in the lifting pipe by measuring the abrasion rate at different lifting velocities. The abrasion rate of the graphite pebble in helium was found much higher than those in air and nitrogen. This gas environment effect could be explained by either tribology behavior or dynamic behavior. Friction testing excluded the possibility of tribology reason. The dynamic behavior of the graphite pebble was captured by analysis of the audio waveforms during pneumatic lift. The analysis results revealed unique dynamic behavior of the graphite pebble in helium. Oscillation and consequently intensive collisions occur during pneumatic lift, causing significant abrasion of the graphite pebble. This study provides an excellent explanation for the abrasion behavior of graphite pebbles in the lifting pipe of the pebble-bed HTR.