A duplex bearing is configured for use with a nuclear reactor control rod drive mechanism. The duplex includes an outer member and an inner member wherein each defines an interior surface and an exterior surface. The outer member interior surface defines a first and second outer raceway; and the inner member defines a first and second inner raceway. A first plurality of load-carrying rolling elements and a first plurality of spacer rolling elements are disposed in a first annular cavity defined between the first inner raceway and first outer raceway. A second plurality of load-carrying rolling elements and a second plurality of spacer rolling elements are disposed in a second annular cavity defined between the second inner raceway and the second outer raceway. The duplex bearing is configured to operate with sealed de-ionized water exhibiting a temperature in the range of up to about 1200° F. as a sole lubricant.