Cage-less duplex bearing for nuclear reactor control rod drive
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Solution Overview
Problem
Standard duplex bearings used in control rod drive mechanisms for nuclear reactors face challenges with cage failure and limited operational life in high-temperature, de-ionized water environments, requiring improved stiffness and reliability without active lubrication.
Innovation Solution
A duplex bearing with a cage-less design featuring a one-piece outer and inner ring configuration, utilizing load-carrying and spacer rolling elements made from suitable materials like cobalt alloys, which are preloaded and operate effectively in elevated-temperature de-ionized water without external lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard duplex bearings with cages are used, then the bearing structure is complete and can carry loads, but the cage fails in high-temperature de-ionized water environments reducing reliability
Solution Approach 1:
The patent removes the cage component entirely from the bearing assembly. The cage-less design eliminates the part that fails in high-temperature de-ionized water environments, directly resolving the reliability issue while simplifying the overall bearing structure.
Solution Approach 2:
By eliminating the cage component, the patent removes a part with limited life in the harsh nuclear reactor environment. The design accepts simpler, more durable components that can withstand the operating conditions without requiring replacement of failed cage elements.
2Duration of action of stationary object
If conventional bearings are used, then the bearing provides basic support, but the operational life is limited in high-temperature environments
Solution Approach 1:
The patent employs composite material construction with cobalt alloy rolling elements and races, providing enhanced thermal stability and durability. This material selection enables the bearing to operate reliably at elevated temperatures typical of nuclear reactor environments, extending operational life beyond conventional bearings.
3Manufacturing precision
If standard bearing designs are used, then the bearing can be manufactured conventionally, but stiffness and accuracy are insufficient for precise control rod positioning
Solution Approach 1:
The patent divides the bearing into distinct functional segments: precision-machined cobalt alloy races and rolling elements for accuracy, and a simplified cage-less structure for ease of assembly. This segmentation allows each component to be optimized independently while maintaining overall manufacturability.
Data Source
AI summary
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.