Abstract: In order to provide a load environment for the reliability enhancement testing of half-size water-lubricated bearing in the reactor coolant pump, enhanced test principle based on water-lubricated bearing failure mode is researched, and an axial and radial magnetic loading system is developed. Three typical failure modes, including wear, lubrication and vibration, are selected, and their test programs are given to research reliability enhancement testing principle. The qualitative and quantitative relations between load and failure are analyzed. On the basis, the static and dynamic load requirements for the enhanced test of half-size water-lubricated bearing are proposed. A magnetic loading system including structure module and control module is built. The static and dynamic load structures of axial loading component are independent. The radial loading component uses an 8-pole scheme. And the control module supports two kinds of control strategy of open-loop and closed-loop. The performances of loading system are verified by the special experiments. The results show that, the wear loss of tile will increase from 1.0 to 1.2 times, and the start-stop times will reduce by 50% to 54% while the load increases 20% in samples. The axial load module can generate static load, impulse and sinusoidal excitation, and static load can be 100 kN when the gap is 2 mm and the current is 1.2 A. Static load，amplitude of impulse excitation and sinusoidal excitation generated by radial load components are 3.7 kN，500 N and 115 N respectively. The feasibility of magnetic loading technique introduced in reliability enhancement test is initially verified. Open-loop control strategy realized by the artificial adjustment of current is more effective for the multi-field coupling bearing test system with loading device.

Key words: failure mode, low viscosity lubricated bearings, magnetic loading, reactor coolant pump, reliability enhancement testing