Nested Thermal Exchange Pipe for Boiling Water Reactor Decay Heat Removal
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Solution Overview
Problem
Existing passive containment cooling systems for boiling water reactors face challenges in efficiently managing decay heat without forced flow or electric power, particularly during depressurization scenarios where steam condensation and gas accumulation can lead to over-pressurization risks.
Innovation Solution
A passive containment cooling system utilizing thermal exchange pipes with an outer and inner pipe configuration, where the inner pipe extends through an opening in the outer pipe, allowing for natural convection and gravity-driven water circulation between the primary containment vessel and the reactor cavity pool, eliminating the need for valves and pumps, and incorporating a spring support for thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive containment cooling system uses natural convection without forced flow mechanisms, then system reliability is improved by eliminating pumps and valves, but heat removal efficiency deteriorates due to limited heat transfer capability
Solution Approach 1:
The patent employs a nested pipe configuration where an inner pipe is positioned inside an outer pipe, creating multiple flow paths for natural convection. This nested structure increases the effective heat transfer surface area while maintaining passive operation, allowing improved heat removal efficiency without introducing active pumping mechanisms.
Solution Approach 2:
The patent transitions from single-pipe to multi-pipe configuration, adding spatial dimensions to the heat transfer pathway. By arranging pipes in a nested configuration with different diameters and positions, the system creates multiple parallel convection currents, effectively increasing heat removal capacity while preserving passive safety features.
2Strength
If thermal exchange pipe is rigid to maintain structural integrity, then strength is improved, but thermal expansion during operation causes stress and potential damage
Solution Approach 1:
The patent explicitly incorporates thermal expansion joints into the pipe system design. These joints allow the pipes to expand and contract freely in response to temperature changes during reactor operation, absorbing thermal stress without compromising the structural integrity of the containment system or causing damage to connected components.
3Device complexity
If pipe configuration is simplified to reduce complexity, then device complexity is reduced, but adaptability to thermal expansion and operational variations deteriorates
Solution Approach 1:
The patent incorporates thermal expansion joints into the pipe system design. These joints allow the pipes to expand and contract freely in response to temperature changes during reactor operation, absorbing thermal stress without compromising the structural integrity of the containment system or causing damage to connected components.
Solution Approach 2:
The patent introduces flexible elements and expansion joints that enable the pipe system to dynamically adapt to thermal conditions. Rather than using a completely rigid fixed structure, the system incorporates controlled flexibility at specific points, allowing movement and expansion while maintaining overall structural stability and connection integrity.
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 configuration enables effective decay heat removal through natural circulation, preventing over-pressurization and ensuring continuous cooling without relying on forced mechanisms, thus enhancing safety and operational reliability during accident scenarios.
Implementation Method 1
Nuclear plants with passive-safety features may remove this decay heat by natural convection, conduction and/or radiant heat transfer unassisted by forced flow or electric power.
Implementation Method 2
Nuclear plants with passive-safety features may remove this decay heat by natural convection, conduction and/or radiant heat transfer unassisted by forced flow or electric power.
Implementation Method 3
incorporating a spring support for thermal expansion
Data Source
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AI summary
A boiling water reactor includes a reactor building, a reactor cavity pool, a primary containment vessel, and a passive containment cooling system. The reactor building includes a top wall defining a penetration therein, a bottom wall, and at least one side wall, which define a chamber. At least a portion of the primary containment vessel is in the chamber. The passive containment cooling system includes a thermal exchange pipe including an outer pipe and an inner pipe. The outer pipe has a first outer pipe end and a second outer pipe end. The first outer pipe end is closed and in the primary containment vessel. The second outer pipe end is open and extends into the reactor cavity pool. The inner pipe has a first inner pipe end and a second inner pipe end, which are open. The second inner pipe end extends out of the outer pipe and into the reactor cavity pool.