Control Rod Drive Outer Tube Sealing Design
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Solution Overview
Problem
Conventional control rod drive mechanisms for boiling water reactors require frequent maintenance of O-rings, necessitating the removal of the spool piece from the outer tube, which prolongs maintenance time due to the need for bolt disconnection and gap confirmation for airtightness verification.
Innovation Solution
The control rod drive mechanism features an outer tube with a smaller outside diameter than the spool piece, eliminating the need for O-rings between the outer and spool piece surfaces, thus allowing for reduced maintenance time by avoiding the removal of the spool piece for O-ring maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If O-rings are installed between the outer tube and spool piece for sealing, then airtightness is ensured, but maintenance time increases due to frequent O-ring replacement requirements
Solution Approach 1:
The invention removes the O-ring sealing components from the system by designing a direct metal-to-metal contact interface between the outer tube and spool piece. This extraction of the sealing element eliminates the need for O-ring replacement while maintaining airtightness through the interference fit and flange connection structure.
Solution Approach 2:
The invention replaces the mechanical O-ring sealing system with a mechanical interference fit system. The outer tube's outer diameter is designed to be slightly larger than the spool piece's inner diameter, creating a press-fit connection that provides both structural support and sealing function without requiring elastomeric components.
2Ease of repair
If the spool piece is removed from the outer tube for O-ring maintenance, then O-rings can be replaced, but the complexity of the maintenance procedure increases due to bolt disconnection and gap confirmation requirements
Solution Approach 1:
The invention extracts the O-ring sealing components entirely from the system, eliminating the maintenance task of O-ring replacement. The direct metal-to-metal contact interface requires no periodic sealing component replacement, simplifying the maintenance procedure to basic inspection only.
3Reliability
If multiple O-rings are used for sealing between flanges, then airtightness is improved, but the number of potential leakage points increases
Solution Approach 1:
The invention removes all O-ring sealing elements from the system, eliminating potential leakage points associated with elastomeric seals. The metal-to-metal contact interface between the outer tube and spool piece, secured by flange and bolt connection, provides a more reliable sealing solution with fewer potential failure modes.
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 shortens the maintenance time for the control rod drive mechanism by eliminating the need for O-ring replacement and bolt disconnection, enhancing operational efficiency and reducing potential cooling water leakage points.
Implementation Method 1
an inner magnet coupling disposed in the spool piece, a ball screw which is rotated by the inner magnet coupling... an outer magnet coupling which is disposed outside the spool piece, is connected to a rotary shaft of the motor, and is disposed opposite to the inner magnet coupling across the spool piece
Data Source
AI summary
A control rod drive mechanism includes an outer tube and a guide tube which is arranged in the outer tube and is held by the outer tube. Furthermore, the control rod drive mechanism includes a spool piece with an inner magnet coupling and a rotary shaft connected to the inner magnet coupling arranged internally. The lower end portion of the outer tube is supported by the spool piece in the spool piece. The outside diameter of the outer tube, through the length of the outer tube, is smaller than the inside diameter of the spool piece and the outer tube, in the radial direction of the outer tube, is not projected outside the inner surface of the spool piece. Therefore, the installation places of the O-rings which are a seal member are reduced and the time required for maintenance of the control rod drive mechanism can be shortened.