Pressure-Actuated Elastic Seals for Nuclear Reactor Flow Paths
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Solution Overview
Problem
In nuclear reactors, particularly in natural-circulation designs like ESBWR, there is a challenge in preventing leakage between flows of different pressures, which can disrupt the natural circulation drive, especially during loss of offsite power transients, as cooler downcomer flow can leak into hotter core flows, cooling or condensing the fluid and reducing the pressure gradient.
Innovation Solution
The use of elastic seals with various cross-sections such as C-shaped, E-shaped, or annular designs that take advantage of pressure differentials to enhance sealing between components like core plates, shrouds, and chimney structures, preventing fluid leakage and energy transfer between distinct flow paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If components are designed to be movable and removably joined for maintenance and operation, then ease of operation and maintenance are improved, but sealing between components becomes more difficult to maintain
Solution Approach 1:
The patent employs flexible seals including C-shaped, E-shaped, and annular cross-sections made of elastomeric or resilient materials that can deform to maintain sealing contact between movable components during operation and maintenance movements
Solution Approach 2:
The seal design incorporates expandable concavities that dynamically adjust to pressure differentials, allowing the seal to expand toward the higher pressure flow path to enhance sealing effectiveness while maintaining flexibility for component movement
2Ease of operation
If seals are designed to be simple and easy to install, then ease of operation is improved, but sealing effectiveness under pressure differentials may be insufficient
Solution Approach 1:
The seal design utilizes self-actuating expandable concavities that automatically respond to pressure differentials between flow paths, expanding toward the higher pressure side to enhance sealing without requiring external actuation or complex control mechanisms
Solution Approach 2:
The seal geometry incorporates variable cross-sections with expandable concavities that change their dimensional parameters in response to pressure differentials, allowing the seal to adapt its sealing surface area and contact pressure based on operating conditions
3Adaptability or versatility
If flow paths are separated by movable components, then adaptability for different operating modes is improved, but leakage between flows of different pressures can occur
Solution Approach 1:
The seal acts as an intermediary element between distinct flow paths, using pressure-differential-actuated expansion to actively prevent leakage while allowing the movable components to maintain their adaptability for different operating 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
These seals effectively isolate flows with different characteristics, reducing unwanted mixing and maintaining the natural pressure gradient, thus enhancing the reliability of natural circulation cooling in nuclear reactors.
Implementation Method 1
seal may include an expandable concavity that opens toward the flow with the higher pressure and is closed against other flows. The higher pressure may expand or drive the concavity and thus seal further in the direction of the components' joining
Implementation Method 2
Example seals can be any shape or size to enhance sealing between distinct components... elastic seals with a C-shaped or E-shaped cross-section
Data Source
AI summary
Seals are positioned between abutting nuclear reactor components. Example seals are held in position by gravity, grooves, retainers, direct joining, or other mating structures to seal the abutting components. Compression of example seals drives the seals against the joining components, preventing fluid passage therebetween. Example seals may include a cavity opening to a higher pressure fluid outside the joined components to drive expansion or sealing of the seal. Seals may have a C-shaped, E-shaped, O-ring, coiled, helical, or other cross-section to provide such a cavity. Example seals may be flexible materials compatible with radiation and heat encountered in a nuclear reactor. Seals may be continuous or sectional about the abutment of the components. An annular seal may extend continuously around a perimeter of removably joined core plates, supports, shrouds, and/or chimney heads and structures. Seals can be installed between and in the components at any time access is available to the components.