Testing in sodium and qualification of the bearings used in inclined fuel transfer machine of prototype fast breeder reactor

Track roller type double row deep groove ball bearings made of SS-440C material are used in inclined fuel transfer machine (IFTM) of PFBR. The bearings are unlubricated, need to operate under sodium and subsequently in cover gas at 50°C. The number of rotations of the bearings during 40 years of the reactor operation is 1.15 million. This paper presents the experiment carried out to examine the performance of the bearings used in IFTM under simulated conditions as in reactor. The bearing was initially tested in air, argon and in sodium at 200°C. It is observed that the frictional torque value of the sodium wetted bearing in cover gas at 50°C is increasing due to solidified sodium sticking on the bearing. Wear in the bearing is significant after 1,065,000 rotations. This paper presents the scheme of testing of the bearing, details of the test facility, test results and discussion. The frequency of replacement of the bearings in IFTM of PFBR is established based on the experiment. This experiment gave better insight to use bearings for under sodium applications.