Fuel Bundle Internal Mixer for Liquid Metal Cooled Reactors
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Solution Overview
Problem
Liquid metal cooled nuclear reactors, such as sodium cooled fast reactors, experience thermal striping due to the development of hot and cold spots in the sodium flow, leading to damaging thermal stresses in the primary vessel.
Innovation Solution
A fuel bundle design incorporating internal and external mixers with flow control members to direct and mix the liquid metal, reducing thermal gradients and striping by controlling the flow turbulence within and exiting the fuel bundle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid metal flows through the fuel bundle, then heat is removed from the fuel rods, but thermal striping occurs causing hot and cold spots that lead to thermal stresses
Solution Approach 1:
The patent introduces an internal mixer as an intermediary device within the liquid metal flow path. The mixer comprises flow control members that actively manipulate the sodium flow to break up thermal striping patterns and redistribute heat more uniformly across the fuel bundle exit, thereby reducing thermal stresses in the primary vessel
Solution Approach 2:
The flow control members change the flow parameters of the liquid metal by creating turbulence and mixing patterns. This transforms the laminar or stratified flow into a more uniform turbulent flow, altering the temperature distribution and reducing hot and cold spots
2Object-affected harmful factors
If flow control members are added to mix the liquid metal, then thermal striping is reduced, but the device complexity increases
Solution Approach 1:
The internal mixer is segmented into multiple flow control members arranged in a specific pattern. Each member independently influences the flow, and their collective arrangement creates the desired mixing effect without requiring a single complex structure
Solution Approach 2:
The flow control members utilize a porous or lattice structure that allows liquid metal to pass through while creating turbulence and mixing. This porous approach achieves effective flow control with simpler geometric forms rather than solid complex structures
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 mixer system effectively reduces thermal striping, minimizing thermal stresses on reactor components and extending equipment lifetime by ensuring uniform sodium flow and reducing turbulence.
Implementation Method 1
controlling the flow turbulence within and exiting the fuel bundle
Implementation Method 2
liquid metal flowing through the channel
Implementation Method 3
reducing thermal gradients and striping
Implementation Method 4
ensuring uniform sodium flow
Data Source
AI summary
In one embodiment, a fuel bundle for a liquid metal cooled reactor includes a channel, a nose assembly secured to a lower end of the channel, a plurality of fuel rods disposed within the channel, and an internal mixer disposed within the channel above the plurality of fuel rods. The internal mixer includes peripheral flow control members and interior flow control members. The peripheral flow control members are located near walls of the channel, and the interior flow control members are located towards a longitudinal center of the housing. At least one of the peripheral flow control members is configured to direct liquid metal flowing through the channel towards an interior of the channel, and at least one of the interior flow control members is configured to direct liquid metal flowing through the channel away from the interior of the channel.