Cruciform Absorber Tube with Rounded Corners for BWR Control Rods
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Solution Overview
Problem
Conventional control rods in nuclear reactors face challenges in manufacturing cost and structural integrity due to acute corners and interstitial regions, which affect their ability to withstand internal pressure and conform to fuel channel geometries.
Innovation Solution
The design features a cruciform-shaped control rod with elongated members having cylindrical inner capsules for neutron absorption, an outer surface with flat, planar sides between rounded corners, and a cruciform tie rod for bracing, allowing for flexible conformation and reduced manufacturing complexity by eliminating interstitial regions and using welding technologies like laser or electron beam welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional control rods with acute corners and interstitial regions are used, then manufacturing is simpler, but structural integrity and ability to withstand internal pressure deteriorates
Solution Approach 1:
The patent applies curvature by replacing acute corners with rounded corners on the absorber tubes. This spherical/curved geometry eliminates stress concentration points that would otherwise exist at sharp corners, thereby improving structural integrity and pressure resistance. The rounded corners allow stress to distribute more evenly throughout the tube structure, preventing premature failure while maintaining manufacturability through standard forming processes.
2Adaptability or versatility
If conventional control rods with interstitial regions are used, then manufacturing is simpler, but conformance to fuel channel geometries deteriorates
Solution Approach 1:
The rounded corner design allows the control rod assembly to better conform to the curved surfaces of fuel channel geometries. The curved transitions at corners enable smoother fitting into the fuel channel interstices, improving adaptability without requiring additional complex structural elements or adjustment mechanisms.
3Reliability
If conventional control rods with acute corners are used, then manufacturing cost is lower, but welding quality and structural reliability deteriorate
Solution Approach 1:
Rounded corners eliminate sharp edges that would create stress concentration points and potential defect sites in welds. The curved geometry provides more uniform stress distribution across weld joints, improving welding quality and structural reliability. This design change enhances the integrity of welded connections between absorber tubes and support structures without significantly increasing manufacturing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances structural integrity by withstanding higher internal pressure, reduces manufacturing costs, and improves conformance to fuel channel geometries, ensuring effective neutron absorption and stability during seismic events.
Implementation Method 1
Each elongated member may include a cylindrical inner capsule configured to contain neutron absorbing material therein
Data Source
AI summary
In a control rod having a plurality of elongated members for absorbing neutrons within a nuclear reactor to control a nuclear reaction, each elongated member may include a cylindrical inner capsule configured to contain neutron absorbing material therein. The elongated member may also include an absorber tube enclosing the cylindrical inner capsule, the absorber tube having an outer surface configured with a plurality of generally flat, planar sides between adjacent rounded corners.