Nuclear Reactor Vessel Annular Seal for Leak Prevention
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Solution Overview
Problem
Leaks occur in nuclear reactor vessels due to micro-chips of metal or other particles on the seal surfaces during tightening operations, caused by friction and migration of debris through gaps, which complicates maintenance and increases shutdown time.
Innovation Solution
An annular seal with self-holding metal tabs and a flexible ring design is placed between the vessel flange and lid, preventing particle migration by locking onto the vertical wall of the shoulder, ensuring secure confinement during closure operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If studs are tightened during closing operations, then the vessel cover is securely fixed, but micro-chips and particles are generated on seal surfaces causing leaks
Solution Approach 1:
A protective cover is introduced as an intermediary element between the studs and the seal surfaces. This cover prevents direct contact between the tightening operation and the seals, thereby preventing micro-chip generation while still allowing the studs to perform their fixing function. The protective cover acts as a barrier that mediates the interaction between the tightening mechanism and the sensitive seal surfaces.
Solution Approach 2:
The protective cover is installed on the seal surfaces before the tightening operation begins. This preliminary protective measure ensures that when the studs are tightened, the seal surfaces are already protected from chip generation. The protection is applied in advance of the harmful action, preventing the problem rather than addressing it afterward.
2Ease of operation
If temporary inflatable seal is removed before stud screwing, then access is provided for tightening operations, but particles can migrate to seal face causing leaks
Solution Approach 1:
The protective cover serves as an intermediary that remains in place during the tightening operation. It allows the studs to be screwed and tightened while simultaneously preventing particles from migrating to the seal face. The cover mediates between the need for access during tightening and the need to protect the seal surfaces from contamination.
Solution Approach 2:
The protective cover is installed on the seal surfaces before the tightening operation and remains in place throughout the process. This preliminary protective measure ensures that even though the temporary inflatable seal has been removed for access, the seal surfaces remain protected from particle migration during the entire tightening operation.
3Strength
If welding is performed after lid fitting, then the annular seal is securely attached, but micro-particles can travel to joint surface and require additional maintenance operations
Solution Approach 1:
The protective cover is installed on the seal surfaces before the welding operation. This preliminary protective measure ensures that when welding is performed to attach the annular seal, micro-particles generated during welding cannot travel to the joint surface. The protection is in place before the harmful welding process begins.
Solution Approach 2:
The protective cover acts as an intermediary barrier between the welding operation and the joint surface. It allows the welding to proceed for secure seal attachment while simultaneously preventing welding debris and micro-particles from contaminating the joint surface, thereby eliminating the need for additional maintenance operations to remove such particles.
4Strength
If multiple studs are used to fix the cover, then secure fixation is achieved, but dismantling and refitting requires unscrewing all studs increasing shutdown time
Solution Approach 1:
The protective cover is introduced as a separate, removable element that can be independently installed and removed without affecting the studs themselves. This extraction of the protective function from the fixation system allows the studs to remain in place while the protective cover is swapped during maintenance operations, significantly reducing shutdown time.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The method consists of placing around the shoulder (20) of the cover (1a) an annular seal (40) formed by a metal strip (41) held on the vertical wall of the shoulder by self-holding members (50) attached to said strip, putting the cover (1a) carrying the annular seal (40) in place above the tank by positioning it at a determined height, carrying out a cleanliness check of the sealing surface (10), lowering and placing the cover (1a) on the tank so that the lateral end edges (41a, 41b) of the strip (41) come into contact with a horizontal wall (17, 18), respectively of the cover (1a) and of the tank flange (1b) and fixing this cover (1a) on the tank flange (1b).