Nuclear Reactor Pump Shaft Profile for Uniform Flow
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Solution Overview
Problem
Existing pump/heat exchanger assemblies in nuclear reactors face issues with primary flow distribution, resulting in axial velocity drops and overpressure differences across the heat exchanger, due to radial tube bundle feed configurations.
Innovation Solution
The pump/heat exchanger assembly features an impeller shaft with an optimized axial profile, where the shaft diameter increases from the bottom to the top, matching the cross-sectional area of the feed duct to the height of the tube bundle, ensuring uniform fluid flow and mechanical stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a radial tube bundle feed configuration is used in a compact pump/heat exchanger assembly, then the assembly achieves extreme compactness, but the axial velocity of the primary fluid drops from bottom to top in the heat exchanger feed area, causing overpressure in the upper part
Solution Approach 1:
The shaft cross-sectional area is varied locally along its axial length, with the area increasing from bottom to top to match the decreasing flow velocity. This local geometric adaptation ensures uniform flow distribution throughout the heat exchanger tube bundle while maintaining the compact radial feed configuration.
Solution Approach 2:
The shaft's geometric parameter (cross-sectional area) is changed along its length to compensate for the axial velocity drop. By increasing the shaft area from bottom to top, the flow area is maintained constant, thereby maintaining uniform velocity and pressure distribution in the heat exchanger.
2Stress or pressure
If the shaft cross-sectional area is increased from bottom to top to match flow distribution, then uniform fluid flow is achieved, but the shaft requires higher mechanical stiffness
Solution Approach 1:
The shaft employs a curved or tapered profile rather than a straight cylindrical form. This curved geometry naturally provides both the required cross-sectional area variation for uniform flow and inherent structural stiffness to support the mechanical loads in the pump assembly.
3Reliability
If floating bearings are eliminated in high-density fluid environments, then mechanical inertia is increased for smoother transition between circulation modes, but the shaft requires higher mechanical stiffness
Solution Approach 1:
The shaft is constructed from materials or material composites that provide both the necessary mechanical stiffness to eliminate floating bearings and the appropriate density to maintain high mechanical inertia for smooth transitions between forced and natural circulation modes.
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 maintains constant or adjusted axial velocity, ensuring uniform flow distribution and eliminating the need for floating bearings, while providing high mechanical inertia for smooth transition between forced and natural circulation, even in reactors with high-density primary fluids like lead.
Implementation Method 1
the shaft of the impeller has an optimized axial profile so as to overcome the above-mentioned drawbacks of the known art... maintains constant or adjusted axial velocity, ensuring uniform flow distribution
Implementation Method 2
providing high mechanical inertia for smooth transition between forced and natural circulation
Implementation Method 3
a pump/heat exchanger assembly comprising a pump for circulating the primary cooling fluid of the reactor
Data Source
AI summary
One or more embodiments of the present invention relate to a pump/heat exchanger assembly of a nuclear reactor, in particular a liquid metal cooled nuclear reactor, the pump being characterized in that the shaft for driving the impeller is inserted in an shell inside the heat exchanger and has a smaller cross section at the bottom part of the tube bundle of the heat exchanger and a cross section that gradually increases up to a widest cross section at the top part of the tube bundle of the heat exchanger. The resulting axial profile of the impeller's shaft is, at the same time, designed to uniformly distribute the flow of the primary fluid inside the tube bundle of the heat exchanger and to provide high mechanical inertia to the pump.