Depressurisation Valve Circuit for Passive Reactor Coolant Isolation
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Solution Overview
Problem
Current safety systems in pressurized water reactors, such as the Squib Valve, rely on explosive charges and complex control systems, posing risks and increasing costs, and existing passive valves do not effectively isolate high-pressure, high-temperature coolant circuits during Loss of Coolant Accident (LOCA) events.
Innovation Solution
A passive depressurization valve with a main valve and secondary valve configuration, utilizing a piston and valve stem in a main chamber connected via a pilot line and blowdown line, where fluid pressure maintains the valve closed and opens it under extreme conditions, eliminating the need for explosive charges and allowing complete depressurization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If explosive charges are used to open the valve (Squib Valve), then the valve can be opened reliably, but the risk of spurious operation and radiological hazard increases
Solution Approach 1:
The patent replaces the explosive charge system with a purely mechanical spring-loaded valve mechanism. The spring provides the force to open the valve when pressure differential exceeds the spring force, eliminating explosive charges and their associated spurious operation risks while maintaining reliable valve opening functionality.
Solution Approach 2:
The valve system uses the existing pressure differential in the coolant circuit itself to drive the valve opening mechanism. The high-pressure coolant directly acts on the valve disc to overcome the spring force and open the valve, eliminating the need for external explosive charges or complex control systems.
2Ease of operation
If complex control systems are used to operate the valve, then the valve operation can be controlled, but the system complexity and cost increase
Solution Approach 1:
The valve automatically responds to pressure differential changes in the coolant circuit without requiring external control signals. The spring force and pressure differential directly control valve opening, eliminating complex control systems, sensors, and actuators while ensuring appropriate valve operation.
Solution Approach 2:
The patent extracts and removes the complex control system, instrumentation, and power supply requirements from the valve mechanism, retaining only the essential mechanical components (spring, valve disc, seat) needed for safe and reliable depressurization.
3Reliability
If the valve remains latched open to allow complete system depressurisation, then complete depressurisation is achieved, but the valve cannot isolate the line when pressure equalises
Solution Approach 1:
The valve is designed to dynamically respond to changing pressure conditions. The spring force allows the valve to open when pressure differential is high (enabling complete depressurization) and close when pressure equalizes (maintaining isolation capability), providing adaptability to different operational states without latching mechanisms.
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 solution ensures safe and reliable depressurization of the coolant circuit during LOCA events, reducing the risk of radiological hazards and operational costs by using stored energy and temperature/pressure-based mechanisms, providing a diverse and efficient safety mechanism.
Implementation Method 1
in use the pressure of the fluid in the main chamber maintains the main valve in a closed position
Implementation Method 2
The valve mechanism comprises a valve body, a main valve, a secondary valve, a piston, a valve stem and a compression spring
Implementation Method 3
fluid enters the main chamber via the pilot line, which has a lower fluid resistance than the blowdown line
Data Source
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AI summary
A depressurisation valve (100) for a cooling system comprising: a main chamber (107) having a main valve (101), a pilot line (104) having a secondary valve (109) and a blowdown line (108); the main valve being located to seal a path of the coolant system of the nuclear reactor. The main chamber is connected to the cooling circuit via the pilot line allowing coolant to enter the main chamber, and the blowdown line allows coolant to escape from the main chamber, the pilot line having a lower fluid resistance than the blowdown line. The pressure of coolant in the main chamber maintains the main valve in a closed position, and under elevated temperature and/or pressure conditions fluid is prevented from entering the main chamber via a closure of the secondary valve on the pilot line and reduce the pressure from the valve, moving it to its open position.