Flow Barrier Structure for Reactor Pressure Vessel Mixing
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Solution Overview
Problem
Conventional natural circulation reactor pressure vessel assemblies experience incomplete mixing between the separator downcomer flow and sub-cooled feedwater, leading to temperature variations in the reactor core, which can affect the fuel rods and their supports.
Innovation Solution
A reactor pressure vessel assembly with a flow barrier structure, typically made of stainless steel, is introduced to force mixing between the sub-cooled feedwater and the downcomer fluid from the steam separators by positioning it vertically over the chimney and below the steam separators, redirecting the downcomer flow to enhance mixing before it enters the reactor core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the downcomer flow is allowed to flow directly into the reactor core without obstruction, then the flow path is simple and device complexity is low, but incomplete mixing between downcomer flow and sub-cooled feedwater occurs, causing temperature variations that affect reactor core stability
Solution Approach 1:
The flow barrier structure segments the downcomer flow path by introducing vertical barriers that divide the flow into multiple channels. This segmentation forces the downcomer flow to mix with sub-cooled feedwater in a controlled manner, improving temperature uniformity in the reactor core without requiring complex external mixing devices
Solution Approach 2:
The flow barrier structure acts as an intermediary element between the downcomer flow and the reactor core. It mediates the mixing process by providing a physical structure that redirects and combines flows, achieving temperature uniformity without direct complex interaction between the flow sources
2Stability of the object's composition
If a flow barrier structure is introduced to force mixing between downcomer flow and sub-cooled feedwater, then mixing efficiency and temperature uniformity improve, but the device complexity and structural requirements increase
Solution Approach 1:
The flow barrier structure implements local quality changes by positioning specific barrier elements at strategic locations within the downcomer region. These localized barriers create targeted mixing zones where downcomer flow and sub-cooled feedwater interact, achieving improved temperature uniformity without requiring complex structures throughout the entire system
Solution Approach 2:
The flow barrier structure introduces vertical dimensionality to the mixing process by extending barriers in the vertical direction. This dimensional approach forces multi-directional flow interaction and enhances mixing efficiency without requiring complex horizontal or radial structural arrangements
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 flow barrier structure effectively redirects the downcomer flow, allowing for improved mixing with the sub-cooled feedwater, reducing temperature variations and ensuring more uniform conditions for the fuel rods within the reactor core.
Implementation Method 1
The flow barrier structure is configured to force mixing between the sub-cooled feedwater and the downcomer flow from the steam separators
Data Source
AI summary
A reactor pressure vessel assembly may include a housing surrounding a reactor core, steam separators, and a chimney. Inner surfaces of the chimney and reactor core define a conduit for transporting a two phase flow stream from the reactor core through the chimney to the steam separators. The housing defines an opening. An inner surface of the housing and outer surfaces of the chimney and reactor core define an annulus in fluid communication with the opening and conduit. A feedwater sparger in the housing is connected to the at least one opening and configured to deliver a sub-cooled feedwater into the annulus. A flow barrier structure between the chimney and the steam separators may force mixing between the sub-cooled feedwater and a downcomer fluid from the steam separators. An outer steam separator may be vertically over a portion of the flow barrier structure in a plan view.