Asymmetric Flow Inlets for Boiling Water Reactor Core Plates
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Solution Overview
Problem
In boiling water reactors, the complex geometry of circular flow inlets creates vortices, leading to pulsating mass flow and pressure fluctuations, resulting in cooling deficiencies and potential dry-out events in fuel assemblies due to varying pressure loss coefficients.
Innovation Solution
Modifying the flow inlets to a non-circular cross-sectional shape, such as a circular hole with recesses extending in a sideward direction, reduces vortex formation and mass flow fluctuations, ensuring a smoother and more uniform coolant flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If circular flow inlets are used in the transition piece, then the manufacturing is simple and geometry is symmetric, but vortices are created leading to pulsating mass flow and pressure fluctuations
Solution Approach 1:
The patent applies asymmetry by changing the flow inlet geometry from a symmetric circular shape to an asymmetric shape with a straight edge and curved edge. This asymmetric configuration disrupts the vortex formation that occurs with circular inlets, thereby eliminating pulsating mass flow and pressure fluctuations while maintaining manufacturing feasibility through standard cutting processes
2Device complexity
If circular flow inlets are used, then the geometry is simple, but mass flow fluctuates due to vortex formation at the orifice
Solution Approach 1:
The patent introduces geometric asymmetry into the flow inlet by providing a straight edge and a curved edge instead of a fully circular symmetric shape. This asymmetric design prevents the formation of stable vortices at the orifice, thereby stabilizing the mass flow through the passage into the fuel assembly while adding minimal complexity to the overall device structure
3Manufacturing precision
If circular orifices are used, then the pressure loss coefficient is constant in design, but it varies with time due to vortex fluctuations
Solution Approach 1:
The patent resolves the contradiction between manufacturing precision and reliability by designing an asymmetric flow inlet geometry that inherently prevents vortex formation. The straight edge and curved edge configuration ensures that the pressure loss coefficient remains stable over time during operation, while still allowing for precise manufacturing using conventional cutting methods
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 non-circular flow inlets significantly decrease mass flow and pressure fluctuations, reducing the likelihood of cooling deficiencies and dry-out issues, and can be implemented in existing reactors using an elongated tool to modify existing circular inlets.
Implementation Method 1
vortices are created due to the complex geometry outside the transition piece. These vortices fluctuate at the orifice of the flow inlet
Data Source
AI summary
A core plate assembly for a boiling water reactor, and a method of performing work thereon are disclosed. The core plate assembly comprises a core plate having through-going apertures, and a beam structure comprising parallel first beams and parallel second beams being perpendicular to the first beams. The beams enclose a plurality of rectangular areas each enclosing four of the through-going apertures. Control rod guide tubes are aligned with a respective one of the through-going apertures. A transition pieces is received in a respective one of the control rod guide tubes, and has four passages for communicating with a respective fuel assembly. Each passage permits a coolant flow into the respective fuel assembly. A flow inlet is provided for the coolant into each passage. At least one of the flow inlets has a cross-sectional shape deviating from a circular shape.