Re-entrant Fuel Channel for Balanced Radial Power Distribution
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Solution Overview
Problem
The Canadian SCWR design faces challenges in achieving balanced radial power distribution and optimal reactivity coefficients due to uneven power distribution between inner and outer fuel rings, leading to underutilization of fuel elements and adverse effects on performance.
Innovation Solution
The introduction of a fuel bundle with a central coolant tube and encapsulated insulator, along with adjustments in fuel pin sizes and number, creates a re-entrant flow configuration and balanced radial power distribution, optimizing coolant void reactivity and exit burnup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional fuel bundle arrangement is used, then fuel elements are simpler to manufacture, but radial power distribution becomes unbalanced
Solution Approach 1:
The patent applies local quality by differentiating fuel element properties across radial positions. Fuel elements in the inner ring have different characteristics (e.g., enrichment, geometry) compared to those in the outer ring, allowing each region to contribute optimally to achieving balanced radial power distribution while maintaining manufacturing feasibility through standardized production methods for each type.
Solution Approach 2:
The patent introduces asymmetry in the fuel bundle configuration by arranging fuel elements in distinct inner and outer rings with different properties. This asymmetric arrangement compensates for the natural radial power distribution imbalance in pressurized tube reactors, creating a more uniform overall power profile across the reactor core.
2Productivity
If inner and outer fuel rings have different power levels, then fuel utilization improves, but coolant void reactivity increases
Solution Approach 1:
The patent employs parameter changes by carefully adjusting fuel enrichment, geometry, and arrangement in the inner and outer rings to optimize the power distribution. These parameter adjustments achieve improved fuel utilization while simultaneously controlling coolant void reactivity within acceptable limits for safe reactor operation.
3Device complexity
If conventional coolant flow arrangement is used, then system complexity is reduced, but power distribution uniformity deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the fuel bundle into inner and outer rings with distinct characteristics. This segmentation allows independent optimization of each ring's power contribution, enabling balanced radial power distribution while maintaining a relatively simple overall coolant flow system architecture.
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 configuration results in improved fuel utilization, reduced coolant void reactivity, increased exit burnup, and balanced radial power distribution, enhancing the overall performance and safety of the nuclear reactor.
Implementation Method 1
the inner conduit including a central flow passage for receiving a flow of the coolant in an opposite direction
Implementation Method 2
a fuel bundle positioned within the fuel bundle chamber, the fuel bundle comprising a plurality of fuel elements
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A fuel assembly for a nuclear reactor, comprising a fuel channel assembly (12) comprising an outer conduit (16), an inner conduit (14) received within the outer conduit (16) and defining an annular fuel bundle chamber (18) therebetween for receiving a flow of coolant in one direction, the inner conduit (14) comprising a central flow passage (20) for receiving a flow of the coolant in an opposite direction; and a fuel bundle (10) positioned within the fuel bundle chamber (18), the fuel bundle (10) comprising a plurality of fuel elements (28a, b), wherein at least one of the following conditions is satisfied: (i) a first ratio of a cross sectional area of the coolant in the fuel bundle chamber (18) and the central flow passage (20) to a cross sectional area of the fuel elements (28a, b) is between approximately 2.6 and 7.5; and (ii) a second ratio of a cross sectional area of the coolant in the central flow passage (20) to a cross sectional area of the coolant in the fuel bundle chamber (18) is between approximately 0.8 and 1.3.