Segmented ECC Duct Thermal Stress Management
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Solution Overview
Problem
Current emergency core cooling systems in pressurized light-water nuclear reactors face challenges such as water level reversal, structural weakness against cross-flow and thermal stress, and excessive backflow loads, which can lead to core overheating and safety issues during accidents.
Innovation Solution
A longitudinally divided emergency core cooling duct with side supports and a U-shaped cross section, designed to disperse thermal stress and resist strong cross-flows, featuring gaps or overlaps between ducts to accommodate thermal expansion and contraction, and an outlet guide to manage backflow, ensuring structural stability and effective water injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a long cooling duct is used to extend toward the lower side of the downcomer, then the emergency core cooling water can be effectively injected, but the structural strength against thermal stress and cross-flow weakens
Solution Approach 1:
The cooling duct is divided into multiple segments along its length, with expansion joints positioned at regular intervals. Each segment can independently expand or contract, distributing the thermal stress across multiple smaller structures rather than one long continuous duct. This segmentation maintains the overall length needed for effective cooling injection while preventing excessive stress concentration.
Solution Approach 2:
The expansion joints introduce flexibility to the duct system, allowing it to change its physical parameters (length, shape) in response to thermal conditions. The joints enable the duct to expand when hot and contract when cool, accommodating thermal cycles without exceeding structural strength limits.
2Ease of manufacture
If the cooling duct is made as a single long pipe, then the installation is simple, but the thermal expansion and contraction causes structural weakness
Solution Approach 1:
The duct is constructed as an assembly of discrete segments connected by expansion joints, which can be manufactured and tested separately before final assembly. This modular approach maintains manufacturing simplicity while enabling the structure to accommodate thermal changes through the articulated joints between segments.
Solution Approach 2:
The expansion joints transform the rigid, static duct into a dynamic structure that can adapt its configuration in response to thermal conditions. The joints allow controlled movement and deformation, enabling the duct to maintain structural integrity during thermal cycling while preserving overall system functionality.
3Reliability
If the cooling duct extends deeply into the downcomer, then the cooling effectiveness improves, but the backflow load increases
Solution Approach 1:
The segmented duct structure with expansion joints creates multiple connection points to the downcomer along its length. This distribution of injection points allows the system to achieve effective cooling coverage while reducing the concentration of backflow forces at a single location, as the backflow is distributed across multiple joint connections.
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 enhances structural stability and prevents water level reversal, effectively manages thermal stress and backflow, ensuring reliable emergency core cooling and improved safety by dispersing thermal stress and reducing flow-induced vibrations.
Implementation Method 1
the longitudinally-divided ducts move and slide relative to one another as the longitudinally-divided ducts expand or contract due to heat
Implementation Method 2
emergency core cooling water is injected from a high-pressure safety injection pump or a safety injection tank, to a downcomer
Data Source
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AI summary
The present invention relates to a longitudinally divided emergency core cooling (ECC) duct (130) in order to efficiently inject safety water to core of a pressurized light-water nuclear reactor. The ECC duct includes side supports (135) for preventing the flow-induced vibration in the annular downcomer (102), and has structural stability while thermally expanding and contracting. A longitudinally divided ECC duct for emergency core cooling water injection of a nuclear reactor is provided on the periphery of a core barrel (110) of a nuclear reactor, includes an emergency core cooling water inlet (133) facing a direct vessel injection nozzle (121), and extends in a longitudinal direction of the core barrel. The longitudinally divided ECC duct is divided into a plurality of longitudinally-divided ducts in the longitudinal direction of the longitudinally divided ECC duct.