Pool-Type Reactor Coolant Risers and Diodes for Passive Backflow Control
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Solution Overview
Problem
Pool-type nuclear reactors face challenges with coolant backflow during shutdown periods, leading to increased core temperature and potential safety risks due to the loss of positive pressure, which existing systems attempt to mitigate with backup power sources that increase complexity and cost.
Innovation Solution
Implementing coolant risers and one-way flow structures, such as fluidic diodes and check-valves, to maintain forward coolant flow and prevent reverse flow, ensuring passive operation without external power sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backup power sources are used to maintain coolant flow during shutdown, then reactor safety is improved, but device complexity and cost increase
Solution Approach 1:
The system uses passive gravity-driven flow and one-way fluidic diodes that require no external power or control systems. The coolant naturally flows from the hot pool through the core to the cold pool using gravity, and the fluidic diodes automatically prevent reverse flow without requiring backup power sources, making the system self-regulating during shutdown conditions
Solution Approach 2:
The patent replaces active mechanical pump systems with passive gravity-driven flow and replaces electronic control systems with passive one-way fluidic diodes. This substitution eliminates the need for backup power sources while maintaining safety, as the gravity-driven flow and fluidic diodes provide reliable coolant circulation and reverse flow prevention without external power
2Object-generated harmful factors
If coolant risers and one-way flow structures are implemented, then coolant backflow is reduced, but device complexity increases
Solution Approach 1:
The patent uses passive hydraulic principles through gravity-driven coolant flow from the hot pool through the core to the cold pool. One-way fluidic diodes utilize hydraulic pressure differentials to automatically prevent reverse flow without mechanical moving parts, reducing complexity while effectively eliminating coolant backflow during shutdown conditions
Solution Approach 2:
The coolant system is segmented into distinct zones (hot pool, core, cold pool, riser) with one-way fluidic diodes positioned at specific locations to control flow direction. This segmentation allows targeted prevention of backflow at critical interfaces without requiring complex systems throughout the entire coolant loop
3Device complexity
If gravity-driven coolant flow is used, then system simplicity is improved, but flow control precision deteriorates
Solution Approach 1:
One-way fluidic diodes serve as passive intermediaries that automatically regulate flow direction between the coolant riser and core inlet. These diodes allow forward flow during normal operation while blocking reverse flow during shutdown, providing flow control precision without requiring complex active control systems or external power
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 effectively reduces coolant backflow by up to 90%, providing safe and reliable reactor shutdowns with reduced complexity and cost, eliminating the need for redundant power sources and enhancing reactor safety.
Implementation Method 1
the riser's elevation will have a greater gravity pressure head of coolant compared to coolant flowing into the inlet, such that the coolant will flow under gravity alone into the reactor
Implementation Method 2
The one-way flow structures include fluidic diodes and check-valves that prevent nearly all reverse flow
Data Source
AI summary
Systems limit backflow through a nuclear reactor cores from a hot pool to a cold pool. Example systems include coolant risers and/or one-way flow structures before a coolant inlet for the reactor. The coolant riser provides coolant that will flow under gravity alone into the reactor despite hot pool pressure head. Fluidic diodes and/or check-valves prevent nearly all reverse flow. Such structures may be positioned with the flow limiter before the riser in the normal direction of coolant flow into the inlet. Such structures may be positioned anywhere they can functionally provide coast down cooling and prevent reverse flow, including as a pump annulus or pool. For a sodium-cooled fast reactor, the riser and fluidic diode may provide sufficient volume to cool the reactor with forward coolant flow for an entire reactor coast down period, when the reactor is shut down and generating only decay heat.