Buoyancy-Operated Depressurization Valve for Steam-Triggered Coolant Relief
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Solution Overview
Problem
Current passive depressurization systems in nuclear reactors, such as Accumulator Isolation Passive Valve (AIPV) and Automatic Safety Valve for Accumulator Depressurisation (ASVAD), are inadequate for isolating high-pressure, high-temperature water and may not function correctly during intact circuit fault transients, posing safety risks and requiring complex control systems, which increase costs.
Innovation Solution
A buoyancy-operated depressurization valve with a main chamber, pilot line, and blowdown line, featuring a secondary float valve that opens in the presence of steam, allowing the main valve to automatically depressurize the coolant system, independent of circuit pressure, ensuring safe operation during Loss of Coolant Accident (LOCA) events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive depressurization systems (AIPV or ASVAD) are used, then system simplicity is improved, but reliability deteriorates because they cannot function correctly during intact circuit fault transients
Solution Approach 1:
The patent replaces complex control systems (instrumentation, control logic, actuators) with a purely mechanical buoyancy-based actuation system. The float automatically rises with steam bubbles in the pilot line, mechanically opening the valve without any electronic or control system intervention. This maintains simplicity while dramatically improving reliability during transient conditions.
Solution Approach 2:
The depressurization valve system is self-actuating through buoyancy forces generated by steam bubbles in the pilot line. The float mechanism automatically detects the presence of steam and opens the valve without external control signals, power sources, or operator intervention. The system serves itself by using the physical phenomenon (steam bubble rise) directly to actuate the valve.
2Ease of manufacture
If conventional passive valves (AIPV or ASVAD) are used, then cost is reduced, but safety deteriorates due to inability to open during intact circuit fault transients
Solution Approach 1:
The patent exploits the phase transition of water to steam duringLOCA events. Steam bubbles rise through the pilot line, creating buoyancy forces that lift the float and open the valve. This phase transition serves as the triggering mechanism, allowing the valve to automatically respond to transient conditions without complex sensors or control systems, maintaining low cost while improving safety.
3Reliability
If control systems with instrumentation and actuators are used, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent eliminates instrumentation, control logic, and actuators by replacing them with a mechanical buoyancy-based float system. The physical rise of steam bubbles in the pilot line directly actuates the valve through the float mechanism, achieving reliable automatic operation without any complex control system components.
Solution Approach 2:
The valve system is completely self-actuating, using the natural buoyancy force of steam bubbles to open the valve. No external control signals, power sources, or complex actuation mechanisms are required. The system uses the physical phenomenon present in the process (steam generation during LOCA) to automatically perform the safety function.
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 valve automatically opens in the presence of steam, enhancing system safety by allowing efficient depressurization without relying on complex control systems, reducing the risk of spurious operations and maintaining safety even under transient conditions.
Implementation Method 1
A buoyancy operated depressurisation valve with a main chamber, pilot line, and blowdown line, featuring a secondary float valve that opens in the presence of steam
Data Source
Figure 1
Figure 2
AI summary
A depressurisation valve (100) for a coolant system; comprising a main chamber (105) having a main valve (101), a pilot line (104), and a blowdown line (106), having a secondary valve (107); the main valve being located to seal a coolant line of the coolant system. The main chamber being located downstream of the cooling system, the main chamber being filled with fluid from the coolant system via a pilot line, the pressure of fluid in the main chamber acts upon a piston head (102) of the main valve and causes the main valve to open or close dependent upon the fluid pressure in the main chamber. Fluid can escape from the main chamber via the blowdown line, which has a variable fluid pressure depending upon an operating state of the secondary valve, and wherein the secondary valve is opened automatically dependent upon the conditions within the coolant system.