MSR Gas Equalization Valves for Rapid Shutdown Drainage
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Solution Overview
Problem
Conventional molten salt reactor (MSR) designs face challenges in reliably depressurizing the reactor vessel during shutdown events, particularly due to unreliable freeze plugs and potential gas leaks, which can compromise safety and efficiency.
Innovation Solution
The system employs an inert gas system to maintain a pressurized volume between the reactor vessel and drain tank, using fail-open equilibrium control valves and a cross-connection to equalize pressure, and includes a compressor to manage inert gas flow, ensuring rapid depressurization and drainage of molten salt without relying on freeze plugs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If freeze plugs are used to isolate the reactor vessel from the drain tank, then the system can maintain isolation during normal operations, but the freeze plugs may undergo thermal cycling and fatigue leading to leaks and unreliable depressurization during shutdown events
Solution Approach 1:
The patent removes the freeze plug component entirely from the system. Instead of using a freeze plug to isolate the reactor vessel from the drain tank, the system uses a valve-controlled fluid communication path. This extraction of the problematic freeze plug component eliminates thermal cycling and fatigue issues while maintaining the necessary isolation function through the valve system.
Solution Approach 2:
The patent replaces the mechanical/thermal freeze plug system with a controlled valve system. Instead of relying on thermal cycling to freeze and melt salt to control isolation, the system uses valves that can be opened or closed to control fluid communication between the reactor vessel and drain tank, providing more reliable and controllable operation.
2Object-affected harmful factors
If inert gas is used to pressurize the drain tank, then the system can prevent radionuclide leaks, but the inert gas system adds complexity and requires additional control mechanisms
Solution Approach 1:
The inert gas system serves multiple functions: it pressurizes the drain tank to prevent radionuclide leaks, provides a protective atmosphere, and works in conjunction with the valve system to control fluid communication. By integrating the inert gas system with the overall depressurization and isolation mechanism, the patent reduces the need for separate specialized systems.
3Speed
If conventional drainage systems are used, then the system can drain the reactor vessel, but the drainage process is slow and may not achieve subcriticality in time during emergency shutdown events
Solution Approach 1:
The system pre-positions the drain tank below the reactor vessel and maintains the valve system ready for rapid opening. The inert gas pressurization is maintained in advance to ensure immediate depressurization capability. This preliminary preparation allows the system to achieve rapid drainage and subcriticality when a shutdown event occurs, meeting emergency response time requirements.
Solution Approach 2:
The patent uses pneumatic pressure from the inert gas system to accelerate the drainage process. By pressurizing the drain tank and controlling the fluid communication path with valves, the system creates a pressure differential that drives rapid molten salt flow from the reactor vessel to the drain tank, achieving much faster drainage than gravity alone would provide.
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 system enables rapid depressurization and drainage of the reactor, achieving subcriticality in under one minute, enhancing safety and efficiency by eliminating the need for freeze plugs and reducing drainage time by several orders of magnitude compared to conventional systems.
Implementation Method 1
an inert gas system fluidically coupled with the fuel salt system and configured to maintain a pressurized volume fluidically between the molten salt and a drain tank by circulating an inert gas
Implementation Method 2
an equalization system configured to equalize pressure between all head spaces of the molten salt reactor system including the reactor vessel and the drain tank in response to a shutdown event
Implementation Method 3
a first flow path with one or more fail-open equilibrium control valves in series with one another and each fluidically coupling the head space of the reactor vessel and the drain tank
Implementation Method 4
Typically, gravity is used to facilitate drainage, i.e., permitting the molten fuel salt composition to drain into a tank located beneath the reactor vessel
Data Source
AI summary
A molten salt reactor system includes a fuel salt system configured to circulate a molten salt through a reactor vessel. The molten salt reactor system further includes an inert gas system fluidically coupled with the fuel salt system and configured to maintain a pressurized volume in a head space of a drain tank by circulating an inert gas along a first inert gas flow path. The molten salt reactor system further includes an equalization system configured to equalize pressure between head spaces of the reactor vessel and the drain tank in response to a reactor shutdown event. The inert gas system is configured to cease maintenance of the pressurized volume in response to the reactor shutdown event.