Active magnetic bearings for sodium pump

Centrifugal Pumps are used in the primary and secondary heat transport systems of fast reactors for pumping liquid sodium. Lubrication oil leakage from the conventional bearings used in these pumps is a potential threat to cause reactivity changes which could result in extended reactor shut down. Actively controlled magnetic bearings which do not require lubrication is an excellent alternative to conventional bearings in overcoming these problems. The present work deals with the development of “Thrust and Radial Active” magnetic bearings for a small centrifugal sodium pump of 50 m3/h capacity, which controls both the axial and radial movements of rotor. The developed active magnetic bearing takes a thrust load of around 100kg, and a nominal radial load for the existing vertically-configured shaft system of the centrifugal pump. Performance of the active magnetic bearings has been tested successfully by running the pump up to the full operating speed of 2900 rpm and the measured vibration levels were well within the allowable limits of ISO 14839.