Passive Shutdown Sealing Device for Reactor Coolant Pump
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Solution Overview
Problem
Conventional shutdown sealing devices for reactor coolant pump units in pressurized water nuclear reactors require auxiliary activation sources and may fail to effectively control primary coolant leakage during accidental situations like Station Black Out, necessitating a passive solution that activates without external triggers.
Innovation Solution
A passive shutdown sealing device with a split sealing ring, pistons, and temperature-dependent locking/unlocking means that automatically activates to stop leakage by using elastic means to position the sealing ring when temperature thresholds are exceeded, eliminating the need for auxiliary activation sources and allowing for customization based on reactor types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional shutdown sealing devices are used, then sealing function can be achieved, but auxiliary activation sources are required and device complexity increases
Solution Approach 1:
The shutdown sealing device utilizes the thermal energy already present in the system during accident conditions to activate the sealing function. The heat-sensitive material automatically melts when exposed to elevated temperatures, triggering the sealing action without requiring external power sources, control systems, or auxiliary activation mechanisms.
Solution Approach 2:
The patent replaces conventional mechanical or electrical activation systems with a thermally-driven passive mechanism. Instead of using motors, solenoids, or control valves requiring external energy, the invention employs heat-sensitive materials that undergo phase change or property modification in response to temperature, directly actuating the sealing elements through thermal-mechanical coupling.
2Device complexity
If passive activation is implemented, then auxiliary sources are eliminated, but activation reliability during accidental situations must be ensured
Solution Approach 1:
The invention exploits the fundamental physical parameter of temperature, which naturally changes during accident conditions. By selecting heat-sensitive materials with specific transition temperatures matched to expected accident thermal conditions, the device ensures automatic and reliable activation when needed, without requiring external sensing or control systems.
Solution Approach 2:
The patent employs materials that undergo phase transitions (such as melting, softening, or decomposition) at predetermined temperature thresholds. This phase change provides a clear, binary response that reliably triggers the sealing function when temperature exceeds the threshold, ensuring activation under accident conditions while maintaining simplicity.
3Adaptability or versatility
If the device is designed for broad applicability, then adaptability to different reactor types is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies different heat-sensitive materials with varying transition temperatures to different locations or aspects of the sealing device, allowing customization for specific reactor types or operating conditions. This enables the same basic device design to be adapted to different applications by selecting appropriate materials rather than redesigning the entire system.
Solution Approach 2:
The invention utilizes composite material systems combining heat-sensitive components with thermally stable structural materials. This allows the device to withstand high-temperature reactor environments while the heat-sensitive portion triggers activation at lower, predetermined temperatures, achieving both versatility and manufacturing precision.
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 device effectively stops primary coolant leakage without external activation, simplifies installation on existing reactor architectures, and can be adjusted for specific reactor requirements by modifying the auto-activation temperature, ensuring reliable operation during accidental conditions.
Implementation Method 1
locking/unlocking means designed to lock said at least one piston in its inactivated position when the temperature of said locking/unlocking means is below a temperature threshold, and to release said at least one piston when the temperature of said locking/unlocking means is above said temperature threshold
Implementation Method 2
elastic means designed to move said at least one piston when the latter is released, so as to position said sealing ring into its activated position
Data Source
AI summary
The present invention relates to a passive shutdown sealing device (20) for a reactor coolant pump unit comprising: a split sealing ring (23) having an inactivated position in which a leakage flow is permitted and an activated position in which said ring stops said leakage flow; at least one piston (22) designed to position said split sealing ring (23) in its activated position; locking/unlocking means (25) designed to lock said at least one piston (22) in its inactivated position when the temperature of said locking/unlocking means is below a temperature threshold and to release said at least one piston (22) when the temperature of said locking/unlocking means is above said temperature threshold; elastic means (24) designed to move said at least one piston (22) when said piston is released, so as to position said sealing ring (23) in its activated position.