The abnormal abrasion of graphite pad surface on thrust bearing occurred during operation of the primary coolant pump(PCP)in Tianwan Nuclear Power Plant was analyzed

on the basis of the work principle and wear mechanism of the water lubrication bearing.It pointed out that the major reasons include:1)over large axial load of friction pairs during startup and shutdown of the PCP;2)obvious cavitation corrosion on the graphite pad surface

caused by agreat amount of bubbles being compressed and condensing at high pressures during fluid flowing in the PCP.Thus

several suggestions were put forward:1)using electromagnet for a long time to reduce the axial load of the PCP from 450 kN to about 200 kN

and this method is during the experimental stage;2)closing the PCP water tank and pressurizing the PCP water tank by saline system to improve the hydrostatic head of graphite pad cooling circuit.After the second method was adopted

the PCP ran normal and abnormal shutdown problems of the unit resulted by parameter over standard have never happened.