Heat Pipe Cooling for Nuclear Reactor Control Rod Drive Mechanisms
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Solution Overview
Problem
Control Rod Drive Mechanisms (CRDMs) in nuclear reactors face cooling challenges, particularly in evacuated containment vessels where convective heat transfer is ineffective, leading to potential failures due to leaks or blockages in water cooling systems, which can trigger reactor shutdowns.
Innovation Solution
A cooling system utilizing heat pipes to transfer heat from electrical motors to finned heat exchangers, enabling effective heat transfer through radiation in vacuum environments without the need for external power or fluid transfer, simplifying the design and reducing the risk of failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If water cooling systems with hoses are used to cool CRDM electrical motors, then cooling effectiveness is improved, but system complexity and failure risk increase due to leaks or blockages
Solution Approach 1:
The patent removes the complex water hose cooling system from the CRDM assembly, extracting only the essential cooling function. The heat pipe integration directly into the motor structure eliminates external hoses, pumps, and valves, thereby reducing system complexity while maintaining cooling effectiveness.
Solution Approach 2:
The cooling function is merged with the motor structure itself by integrating heat pipes directly into the motor housing. This combination eliminates the need for separate cooling system components and their associated complexity, while the heat pipe's phase change mechanism ensures effective heat removal.
2Temperature
If water cooling systems are used in evacuated containment vessels, then cooling capability is maintained, but reliability decreases due to potential leaks or blockages
Solution Approach 1:
The heat pipe cooling system is self-contained and requires no external water supply, pumps, or control systems. It automatically transfers heat from the motor to the containment vessel wall through phase change, eliminating components that could leak or block, thereby significantly improving reliability in evacuated environments.
Solution Approach 2:
The active mechanical water pumping and circulating system is replaced with a passive heat pipe system that uses phase change physics. This substitution eliminates mechanical failures, leaks, and blockages associated with water hoses and pumps, providing reliable cooling without moving parts or external fluid transfer.
3Device complexity
If forced air cooling is used instead of water cooling, then system simplicity is improved, but cooling adequacy deteriorates in vacuum environments
Solution Approach 1:
The patent replaces air convection cooling (which requires atmospheric pressure) with heat pipe-based conduction and radiation cooling. The heat pipe transfers heat through phase change and conduction to the containment wall, which then radiates heat in the vacuum environment, providing adequate cooling without relying on air convection.
4Temperature
If complex water hose arrangements are installed, then cooling effectiveness is improved, but ease of maintenance deteriorates due to difficulty in removing hoses during refueling
Solution Approach 1:
The cooling function is merged into the motor structure itself through integrated heat pipes. This eliminates external hoses that would need to be disconnected and reconnected during refueling operations, making maintenance straightforward while preserving cooling effectiveness through the permanent heat pipe integration.
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 heat pipe cooling system enhances heat transfer efficiency, prevents CRDM failures, and avoids unnecessary reactor shutdowns by maintaining effective cooling in vacuum environments, simplifying the CRDM and containment vessel designs.
Implementation Method 1
A simplified cooling system uses heat pipes to cool electrical motors in Control Rod Drive Mechanisms (CRDM) while operating in an evacuated containment vessel (CNV)
Implementation Method 2
The heat pipes may transfer heat from CRDM electrical coils to finned heat exchangers located above the CRDM electrical coils increasing the ability to transfer heat through radiation through the vacuum to the surrounding CNV vessel walls
Data Source
AI summary
A representative cooling system for a nuclear reactor control rod drive mechanism (CRDM) includes an evaporation section located within or next to the CRDM and a condensation section fluidly coupled to the evaporation section. The cooling system includes a set of heat fins coupled to drive coils in the CRDM and heat pipes that extend through the drive coils and heat fins. A fluid evaporates while in the evaporation section of the heat pipes from heat generated by the CRDM and moves out of the evaporation section into the condensation section in the heat fins. The fluid cools and condensates while in the condensation section, recirculating back into the evaporation section. This passive natural circulation cooling system reduces or eliminates the number of water hoses, piping, and other water pumping equipment typically used for cooling a CRDM thereby increasing nuclear reactor reliability and simplifying nuclear reactor operation and maintenance.