C-Shaped Flexure Seal Ring for Nuclear Reactor Cavity
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Solution Overview
Problem
Existing nuclear reactor containment designs with narrow thermal expansion gaps fail to provide a reliable, leak-proof seal during refueling operations while accommodating vessel movement and ensuring adequate cooling air flow, as they lack the necessary structural strength and flexibility to withstand thermal expansion and potential impacts.
Innovation Solution
An annular stainless steel ring with a rigid cantilevered support and C-shaped flexure members is affixed between the reactor vessel flange and the containment wall, allowing for vertical and lateral movement, and incorporating hatch openings to maintain air flow without compromising structural integrity or water tightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a permanent seal ring is installed to provide a water-tight seal during refueling, then reliability of sealing is improved, but the ability to accommodate thermal expansion and vessel movement is reduced
Solution Approach 1:
The patent employs a flexible gasket seal ring made of elastomeric material that can deform to accommodate thermal expansion and vessel movement while maintaining a water-tight seal. The gasket's flexibility allows it to conform to changes in the gap between the reactor vessel and containment wall, resolving the contradiction between seal reliability and adaptability to movement.
Solution Approach 2:
The seal ring design incorporates dynamic characteristics by allowing the gasket to flex and deform in response to changing conditions during reactor operation and refueling. The elastomeric material provides inherent damping and adaptability, enabling the seal to maintain effectiveness despite lateral and vertical translation of the reactor vessel.
2Strength
If the seal ring is made rigid to withstand heavy blows from falling objects, then structural integrity is improved, but flexibility to accommodate vessel movement is reduced
Solution Approach 1:
The patent uses a composite structure combining a rigid support framework with a flexible elastomeric gasket. The rigid portion provides strength to withstand heavy blows from falling fuel assemblies, while the elastomeric gasket maintains flexibility to accommodate thermal expansion and vessel movement. This composite approach resolves the contradiction between strength and flexibility.
Solution Approach 2:
The seal ring is segmented into distinct functional zones: a rigid structural component for impact resistance and a flexible gasket portion for sealing and movement accommodation. This segmentation allows each part to optimize its specific function without compromising the other.
3Ease of operation
If the seal ring structure is simplified for ease of installation, then ease of operation is improved, but the ability to provide multiple functions (sealing, cooling air flow, impact resistance) is reduced
Solution Approach 1:
The seal ring is designed as a universal component that simultaneously performs multiple functions: providing a water-tight seal during refueling, allowing cooling air flow through integrated openings, and withstanding impact from falling objects. The elastomeric gasket and rigid support structure work together to achieve these diverse functions in a single integrated component, resolving the contradiction between simplicity and multi-functionality.
Solution Approach 2:
The patent merges the sealing function, structural support function, and impact resistance function into a single integrated seal ring assembly. The elastomeric gasket and rigid support are combined in one component that can be installed as a single unit, simplifying installation while maintaining multiple critical functions.
4Adaptability or versatility
If the seal ring is designed for narrow expansion gaps, then adaptability to different plant configurations is improved, but structural strength to retain large water volume is reduced
Solution Approach 1:
The elastomeric gasket provides flexible sealing capability that adapts to narrow expansion gaps while maintaining water retention. The material's elasticity allows it to conform to the tighter clearance in narrow gap plants without sacrificing the ability to hold back the large volume of refueling water, resolving the contradiction between adaptability and strength.
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 solution provides a reliable, water-tight seal during refueling, accommodates thermal expansion, and ensures sufficient cooling air flow in nuclear reactors with narrow expansion gaps, enhancing operational efficiency and safety.
Implementation Method 1
A distal portion of the rigid cantilevered annular support has one end of a generally C-shaped flexure member attached thereto. Another end of the C-shaped flexure member is anchored to the other of the floor of the refueling canal or the refueling ledge.
Data Source
AI summary
A permanent cavity seal ring that replaces the function of the temporary cavity seal ring typically used in narrow thermal expansion gap pressurized water reactors, to seal the gap between the reactor cavity well and the reactor during refueling. The permanent seal ring uses a C-shaped flexure that is shielded by a rigid cantilevered support arm from any accidentally dropped equipment from above in the refueling canal. The construction accommodates the thermal expansion of the reactor vessel while permitting the reactor cavity cooling air to exit the annulus between the vessel and the reactor cavity wall during plant operation, without a significant increase in pressure drop.