A torque-based method for the study of roller bearing degradation under poor lubrication conditions in a lead-bismuth environment

The bearing is a critical and complex component of the in-vessel fuel manipulator in the future MYRRHA nuclear research reactor. All components are fully submerged in the LBE (lead-bismuth eutectic) primary coolant. LBE poses various challenges to bearing operation however. In addition to material attacks, it is a poor lubricant. The effects on the bearing are examined with extensive screening tests in LBE. The most widely implemented bearing monitoring sensor, the accelerometer, is not sufficiently reliable in this hostile environment. This paper outlines a torque-based method for remote monitoring radially-loaded deep-groove ball bearings in LBE. Challenges to existing torque models posed by inadequate lubrication are discussed. The parameters of the bearing torque most representative of the bearing condition are identified in both the time and frequency domains. These are correlated with the micro-analyses of selected test cases towards the validation of a diagnosis method for bearing degradation in LBE.