Perforated Flow Skirt for Uniform Reactor Coolant Distribution
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Solution Overview
Problem
In water-cooled nuclear reactors, non-uniform coolant flow and pressure across reactor core coolant inlet openings lead to uneven cooling of fuel assemblies, potentially causing derating and vortex formation in the lower plenum, which disrupts coolant flow and pressure distribution.
Innovation Solution
A perforated cylindrical flow skirt is installed in the lower reactor vessel plenum, featuring multiple holes and attachment legs that direct coolant flow uniformly across the lower core support plate, suppressing vortices and ensuring consistent pressure and flow distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coolant is pumped into the annular downcomer and circulates downward into the lower plenum, then cooling of the reactor core is achieved, but non-uniform coolant flow and pressure distribution occurs across the core inlet openings
Solution Approach 1:
The lower plenum is segmented into multiple flow paths using a perforated baffle structure. The baffle divides the plenum into an upper region and lower region, with coolant flowing through multiple openings in the baffle to reach different core inlet openings. This segmentation ensures uniform flow distribution across all inlet openings by creating multiple parallel flow paths.
Solution Approach 2:
The perforated baffle acts as an intermediary component between the downcomer and the core inlet openings. It mediates the coolant flow by distributing the coolant from the downcomer through multiple openings to various core inlet openings, ensuring uniform flow and pressure distribution across the core.
2Ease of operation
If instrumentation conduits are present in the lower plenum, then core monitoring instrumentation can be connected, but vortex formation is suppressed less effectively
Solution Approach 1:
The baffle structure segments the plenum space and creates multiple flow paths that prevent vortex formation. The perforated openings in the baffle create a distributed flow pattern that eliminates large-scale vortex formation while still allowing instrumentation conduits to be routed through the baffle for core monitoring.
Solution Approach 2:
The baffle serves as an intermediary structure that simultaneously achieves two functions: it distributes coolant uniformly across core inlet openings and it suppresses vortex formation in the plenum. The perforated design allows instrumentation conduits to pass through while maintaining flow distribution and vortex suppression.
3Temperature
If the lower plenum is designed to circulate coolant evenly, then uniform cooling is achieved, but the structure becomes more complex
Solution Approach 1:
The baffle structure provides a simple yet effective segmentation of the plenum into upper and lower regions. The perforated openings in the baffle create multiple flow paths without requiring complex piping or valve systems, achieving uniform flow distribution with minimal structural complexity.
Solution Approach 2:
The baffle is a relatively simple intermediary component that achieves uniform coolant distribution through its perforated design. It provides flow distribution and vortex suppression functions without requiring complex mechanisms, maintaining structural simplicity while achieving the desired cooling uniformity.
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 ensures uniform coolant distribution and pressure across all reactor core coolant inlet openings, preventing derating and vortex formation, thereby maintaining efficient and even cooling of fuel assemblies.
Implementation Method 1
A cylinder having a vertical wall with a plurality of holes extending therethrough is supported from a plurality of locations around the lower head with the upper edge of the cylinder proximate the lower core support plate so that the majority of coolant flow entering the reactor pressure vessel and down the annulus between the cylindrical reactor pressure vessel walls and the core barrel passes through the holes in the vertical wall of the cylinder on route to the core inlet holes in the lower core support plate
Data Source
AI summary
A pressurized water reactor vessel having a flow skirt formed from a perforated cylinder structure supported in the lower reactor vessel head at the outlet of the downcomer annulus, that channels the coolant flow through flow holes in the wall of the cylinder structure. The flow skirt is supported at a plurality of circumferentially spaced locations on the lower reactor vessel head that are not equally spaced or vertically aligned with the core barrel attachment points, and the flow skirt employs a unique arrangement of hole patterns that assure a substantially balanced pressure and flow of the coolant over the entire underside of the lower core support plate.