Stabilizer for Steam Generator Tube Rupture Prevention
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Solution Overview
Problem
Steam generator tubes in pressurized water reactors are prone to rupture, especially when worn out, leading to potential damage to surrounding tubes due to oscillations, and existing sealing methods do not adequately address the risk of rupture and subsequent instability.
Innovation Solution
A lengthy stabilizer extending from a tube section within the tube sheet to a section above it, providing support without sealing, allows for pressure balance and minimizes mechanical stress through a clamping mechanism designed for small forces, using a cylindrical body with varying diameters for insertion and expansion, and a radial bore for fluid passage, made integrally from alloys like Inconel 690 TT to avoid welding and ensure high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing plug is inserted to close a damaged steam generator tube, then the flow of primary reactor coolant is diverted to other tubes, but the closed tube may still rupture and oscillate causing damage to surrounding tubes
Solution Approach 1:
A stabilizer is introduced as an intermediary element between the sealing plug and the tube rupture risk. The stabilizer has a first section that clamps onto the tube inside the tube sheet and a second section that extends above the tube sheet to physically restrain the tube, preventing oscillations that could damage surrounding tubes while allowing the sealing plug to maintain the coolant seal.
Solution Approach 2:
The stabilizer is divided into two functional sections: a first section within the tube sheet that provides clamping and anchoring, and a second section extending above the tube sheet that provides the stabilizing restraint. This segmentation allows each section to be optimized for its specific function while working together to solve the overall stability problem.
2Reliability
If a stabilizer is inserted to prevent tube oscillations, then surrounding tubes are protected from damage, but the stabilizer must be securely clamped which could create mechanical stresses
Solution Approach 1:
The stabilizer applies clamping force locally at the first section within the tube sheet rather than distributing force throughout the entire tube structure. This localized clamping approach provides effective stabilization while concentrating mechanical stresses in a controlled region that can be designed to accommodate them without compromising the overall tube sheet integrity.
3Stability of the object's composition
If the stabilizer clamps tightly to provide stability, then the tube is securely held, but high clamping forces create mechanical stresses on the steam generator tube and tube sheet
Solution Approach 1:
The stabilizer applies just enough clamping force through its first section to achieve adequate stabilization and prevent tube oscillations, rather than applying maximum possible clamping force. This partial action approach provides sufficient stability to protect surrounding tubes while avoiding excessive mechanical stresses that could damage the steam generator tube or tube sheet.
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
The stabilizer effectively minimizes the risk of rupture and oscillations, reduces mechanical stress, and allows for easy installation and maintenance by providing stability and pressure balance while avoiding the need for high-force clamping, thus protecting surrounding tubes and maintaining dimensional accuracy.
Implementation Method 1
a radial bore reaches through the wall from the cavity to a circular gap between the body and the steam generator tube wall, forming a fluid passage for achieving the pressure balance mentioned above
Implementation Method 2
The stabilizer is fixed to the steam generator tube by roll expansion of a section of the wall around the cavity
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a steam generator (6) for a pressurized water reactor, comprising a tube sheet (34), a steam space (36) adjoining the tube sheet (34), and a number of steam generator tubes (4) being designed to carry a primary re- actor coolant during normal operation, wherein each steam generator tube (4) comprises a first tube section being fixed in the tube sheet (34) and a second tube section protruding into the steam space (36), and wherein at least one of the steam generator tubes (4) is closed by a sealing plug (40) inserted into the first tube section. In order to minimize the risk of rupture of the such-closed steam generator tube (4) in a manner which is easy to produce, to install, and to maintain, the invention suggest a separate stabilizer (2) inserted into said closed steam generator tube (4) adjacent to or above the sealing plug (40), the stabilizer (2) comprising a lengthy body (8) with a clamping section (30) fixed inside the first tube section and a sup- porting section (26) resting against the second tube section, wherein the stabilizer (2) is designed to permit a fluid flow through and/or around its body (8).