Integral PWR Central Riser Flow Distribution
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Solution Overview
Problem
The operational efficiency of pressurized water reactors (PWRs) is hindered by flow resistance and non-uniform coolant distribution in the downcomer annulus, which affects temperature uniformity and overall performance.
Innovation Solution
A radially expanding upper orifice in the central riser merges into an annular divider plate, creating separate upper and lower plenums, with a low-profile annular weir in the lower plenum to diffuse flow and reduce jetting effects, and reactor coolant pumps supported by a pump support plate that forms part of the pressure boundary, enhancing flow uniformity and reducing pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If primary coolant flow is reversed through the downcomer annulus using conventional designs, then steam generation is enabled, but flow resistance increases substantially
Solution Approach 1:
The downcomer annulus is segmented into multiple flow paths using radial flow distributors and circumferential flow distributors. These distributors divide the single large flow path into many smaller parallel paths, reducing flow resistance while maintaining the necessary steam generation capability. The segmentation allows coolant to flow through multiple channels simultaneously, lowering the resistance in each individual path.
Solution Approach 2:
The invention introduces radial and circumferential flow distribution dimensions to the traditional axial flow path. By adding radial flow distributors that create radial flow patterns and circumferential flow distributors that create circumferential flow patterns, the system utilizes multiple spatial dimensions for flow distribution, reducing flow resistance while maintaining steam generation efficiency.
2Productivity
If conventional central riser designs are used, then coolant flow is maintained, but temperature uniformity in the downcomer annulus is poor
Solution Approach 1:
The invention implements local quality by providing differentiated flow distribution in different radial and circumferential positions. Radial flow distributors are positioned at specific radial locations, and circumferential flow distributors are positioned at specific circumferential locations. Each distributor is optimized for its specific position, creating locally optimized flow patterns that ensure uniform temperature distribution throughout the downcomer annulus while maintaining overall coolant flow productivity.
3Temperature
If flow distribution is improved using distributors, then temperature uniformity increases, but device complexity increases
Solution Approach 1:
The invention merges the functions of radial flow distribution and circumferential flow distribution into an integrated system. The radial flow distributors and circumferential flow distributors are combined to work together synergistically, creating a unified flow distribution system that achieves superior temperature uniformity. The merging of these two distribution functions allows the system to achieve better temperature uniformity than either function could achieve independently, while the combined system is more compact and manageable.
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 design significantly reduces flow turbulence and pressure drop, promotes radial and circumferential flow uniformity, and minimizes jetting effects, thereby improving the operational efficiency and temperature uniformity of the PWR system.
Implementation Method 1
facilitates diffusion and lateral flow of primary coolant water exiting the upper orifice of the central riser
Implementation Method 2
a low-profile annular weir in the lower plenum to diffuse flow and reduce jetting effects
Implementation Method 3
electromechanical reactor coolant pumps
Implementation Method 4
This is a natural convection flow circuit that can, in principle, be driven by heat injection from the reactor core and cooling of the primary coolant
Data Source
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AI summary
A pressurized water reactor (PWR) comprises: a nuclear core comprising a fissile material; a cylindrical pressure vessel having a vertically oriented cylinder axis and containing the nuclear core immersed in primary coolant water; and a hollow cylindrical central riser disposed concentrically with and inside the cylindrical pressure vessel. A downcomer annulus is defined between the hollow cylindrical central riser and the cylindrical pressure vessel. The hollow cylindrical central riser has a radially expanding upper orifice that merges into an annular divider plate that separates an upper plenum above the annular divider plate from a lower plenum below the annular divider plate. The upper plenum is in fluid communication with the radially expanding upper orifice and the lower plenum is in fluid communication with the downcomer annulus. A weir may extend away from a bottom wall of the lower plenum into the lower plenum.