Compact Primary Heat Exchanger for Liquid-Metal Reactors
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Solution Overview
Problem
Existing liquid-metal-cooled nuclear reactors with helical-tube heat exchangers face issues with complex and costly production, fluid-induced vibrations, increased dimensions due to spaced tubes for reduced fluid velocity, impractical component replacement, and risk of catastrophic pressure wave damage from failed tubes.
Innovation Solution
A nuclear reactor design featuring spiral-shaped heat-exchange tubes with a compact, adjustable mechanical system for pre-compression and a controlled-failure safety system, allowing for closer tube spacing, reduced head losses, and safe fluid circulation with a telescopic connection duct for easy assembly and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If helical-tube heat exchangers are used to absorb thermal gradients, then thermal performance is improved, but production complexity and cost increase
Solution Approach 1:
The heat exchanger is divided into multiple straight tube segments arranged in bundles rather than using complex helical tubes. Each tube is a simple straight cylinder, making manufacturing straightforward while the bundled arrangement provides the necessary heat exchange surface area and thermal gradient management.
Solution Approach 2:
Instead of curving tubes into helical shapes to handle thermal expansion, the invention uses straight tubes with a different support structure that accommodates thermal gradients through the bundle configuration and support system, inverting the approach to solving the thermal management problem.
2Loss of energy
If tubes are spaced further apart to reduce fluid velocity and head losses, then fluid dynamic performance is improved, but heat exchanger volume increases
Solution Approach 1:
The invention arranges tubes in a three-dimensional bundled configuration with optimized spacing in multiple dimensions. The tubes are positioned at specific pitch distances in both radial and axial directions, creating an efficient space utilization that maintains low fluid velocity while minimizing overall volume through compact bundling.
Solution Approach 2:
The tube pitch and spacing parameters are optimized to specific values that balance fluid velocity reduction with compact volume. The tubes are spaced at distances that reduce head losses while the overall bundle dimensions are constrained through the support structure design, achieving a parameter optimization that resolves the contradiction.
3Ease of manufacture
If tube-bundle heat exchangers with vertical straight tubes are used, then manufacturing is simplified, but fluid-induced vibrations and supporting system complexity remain
Solution Approach 1:
The support structure is merged with the tube bundle itself, where the tubes are directly supported by a common support system at their lower ends. This integrated approach combines the tube holding function with the bundle structure, eliminating the need for separate complex supporting systems while still providing vibration resistance through the unified structure.
Solution Approach 2:
The support structure uses simple, inexpensive elements that can be easily replaced if needed. The supports are designed as basic structural components rather than complex engineered systems, making them cost-effective and simple to manufacture while still providing the necessary mechanical support and vibration resistance.
4Ease of operation
If extensive openings are made in the reactor roof for heat-exchange assemblies, then component installation is enabled, but roof strength is weakened
Solution Approach 1:
The heat exchanger assembly is segmented into modular components that can be installed through smaller openings in the reactor roof. Rather than requiring a single large opening, the modular design allows components to be brought in separately and assembled, reducing the size of roof openings needed and preserving roof structural integrity.
Solution Approach 2:
The assembly approach uses vertical installation through the roof opening, with components being lowered or raised through the opening in the vertical dimension. This dimensional approach allows for smaller opening sizes compared to horizontal installation, as the opening only needs to accommodate the cross-sectional area of the components rather than their full assembled footprint.
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 design achieves reduced volume, lower head losses, simplified and cost-effective construction, enhanced safety against pressure waves, and improved performance with reduced risk of reactor damage, enabling efficient heat transfer and safe operation.
Implementation Method 1
a compact, adjustable mechanical system for pre-compression
Implementation Method 2
where the heat produced in the core is transferred from a primary fluid (liquid metal) to a secondary fluid (water)
Implementation Method 3
The spiral shape of the tubes enables thermal expansion of the various components of the heat exchanger
Data Source
Figure 1
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AI summary
A nuclear reactor (1), in particular a liquid-metal-cooled reactor, is provided with at least one compact primary heat exchanger (11), in particular a steam generator, which has a plurality of heat-exchange tubes (27) having respective spiral portions (37) set in levels on top of one another to form an annular tube bundle (40) delimiting a substantially cylindrical internal central zone (17), which houses, at the bottom, a circulation pump (10) and is pre-arranged for supply from below with primary fluid (liquid metal), which then traverses the tube bundle radially.