Nuclear Fuel Assembly Bottom Nozzle Pressure Drop Reduction
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Solution Overview
Problem
The pressure drop across the bottom nozzle of nuclear fuel assemblies in nuclear reactors is significant, leading to uneven coolant flow and potential temperature imbalances among fuel assemblies, which can limit power output and increase the risk of debris damage to fuel rod cladding.
Innovation Solution
The design of the bottom nozzle features 'egg-crate' protrusions on both sides of the flow plate, gradually changing the lateral flow area to minimize pressure drop, with funnel-like appendages on the upstream side reducing entry losses and increasing area on the downstream side to reduce exit losses, and additional flow holes aligned with fuel rods for enhanced coolant flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional bottom nozzle design with simple holes is used, then manufacturing is simple, but pressure drop is high causing uneven coolant flow
Solution Approach 1:
The patent applies curvature by designing funnel-like appendages with curved surfaces that gradually expand from the horizontal plate. These curved structures guide coolant flow smoothly, reducing turbulence and pressure drop while maintaining manufacturing feasibility through standard forming processes.
Solution Approach 2:
The invention transitions from simple two-dimensional holes in the horizontal plate to three-dimensional funnel-like structures with appendages extending vertically. This dimensional enhancement creates gradual flow expansion and contraction zones that reduce pressure drop while maintaining reasonable manufacturing complexity.
2Productivity
If bottom nozzle with large openings is used, then coolant flow is enhanced, but debris can damage fuel rod cladding
Solution Approach 1:
The patent applies local quality by creating different flow characteristics in different regions. The funnel-like appendages provide localized flow guidance and expansion zones at specific locations, allowing large overall openings for high flow rate while creating local debris-trapping zones where flow velocity is reduced and debris can be captured.
Solution Approach 2:
The funnel-like appendages act as intermediary structures between the large openings and the fuel rods. These appendages create intermediate flow zones that can capture debris before it reaches the fuel rod cladding, mediating between the need for large openings and the need to protect fuel rods.
3Reliability
If bottom nozzle with flow control features is added, then pressure drop is reduced, but device complexity increases
Solution Approach 1:
The funnel-like appendages serve multiple functions simultaneously: they guide coolant flow to reduce pressure drop, create debris-trapping zones, and provide structural support. This multi-functionality reduces the need for separate components, thereby limiting the increase in overall device complexity while achieving pressure drop reduction.
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
This design reduces pressure drop across the fuel assemblies, promoting balanced coolant flow and heat transfer, while preventing debris from damaging the fuel rods, thereby enhancing reactor performance and power output.
Implementation Method 1
The pressure drop across the bottom nozzle of nuclear fuel assemblies in nuclear reactors is significant
Implementation Method 2
gradually changing the lateral flow area to minimize pressure drop, with funnel-like appendages on the upstream side reducing entry losses and increasing area on the downstream side to reduce exit losses
Implementation Method 3
promoting balanced coolant flow and heat transfer, while preventing debris from damaging the fuel rods
Data Source
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AI summary
A nuclear fuel assembly having a bottom nozzle with protrusions that extend from the upstream and downstream side of a horizontally supported perforated flow plate. The protrusions have a funnel-like shape that gradually decreases the lateral flow area on the upstream side of the perforated flow plate and gradually increases the lateral flow area on the downstream side of the perforated plate. The protrusions on the downstream side are preferably recessed to accommodate the ends of the fuel rods.