Nuclear Reactor Flow Diffusion Element for Uniform Core Inlet Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In nuclear reactors, the heterogeneous distribution of heat transfer fluid flow rates at the inlet of the core causes hydraulic excitations, leading to vibrations and premature wear of fuel rods, affecting thermohydraulic and neutron behavior, and limiting the maximum allowed flow rate.
Innovation Solution
A flow diffusion element with a circular flat surface and tapered portion, featuring orifices of uniform diameter, is positioned to create a mixing zone free of obstacles, directing the fluid uniformly across the core inlet and reducing swirling structures, thereby optimizing flow distribution and mechanical constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heat transfer fluid is returned at the vessel bottom to circulate through the inner enclosure, then the cooling function of the core is achieved, but heterogeneous flow distribution is caused with strong overflow at the centre and underflow at the periphery
Solution Approach 1:
The invention divides the single return path into multiple paths by introducing a second inner enclosure with its own return path. The flow is segmented into two separate circulation loops: one through the first inner enclosure and another through the second inner enclosure. This segmentation allows independent control and optimization of flow distribution in each enclosure, eliminating the heterogeneous flow pattern caused by the single central return path.
Solution Approach 2:
The second inner enclosure acts as an intermediary structure between the vessel bottom and the core. It provides an alternative flow path that mediates the flow distribution issue by capturing fluid at the periphery and returning it through a dedicated path, thus preventing the direct central overflow that causes heterogeneous distribution.
2Manufacturing precision
If operating margins are used to limit flow rate, then flow rate heterogeneity is reduced, but the maximum allowed flow rate and thermohydraulic performance are limited
Solution Approach 1:
By segmenting the flow into two independent circulation paths, each path can be optimized for uniform flow distribution. This allows the system to operate at higher overall flow rates without suffering from the heterogeneous distribution problems of a single path, thus increasing productivity while maintaining flow uniformity.
Solution Approach 2:
The invention changes the flow path parameters by introducing a second enclosure with different geometric characteristics. This parameter change allows the system to achieve better flow distribution at higher flow rates, as each enclosure's return path is designed to handle specific flow characteristics, thereby increasing the maximum allowed flow rate.
3Manufacturing precision
If a flow calming structure is added at the inlet of the inner enclosure, then flow fluctuations are reduced, but the structure complexity increases and neutron instrumentation support capability is compromised
Solution Approach 1:
The second inner enclosure serves as an intermediary flow calming structure that naturally reduces flow fluctuations through its dedicated return path. Instead of adding complex calming structures to the first enclosure, the invention uses the second enclosure as a mediating element that smooths out flow variations before they reach the core inlet, thereby maintaining flow uniformity without increasing structure complexity.
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 solution ensures a more uniform fluid distribution, reduces mechanical stresses, extends the service life of reactor components, and increases the operational flow rate capacity of the core.
Implementation Method 1
A flow diffusion element configured to make uniform the flow entering into the enclosure (5), the diffusion element comprising a substantially circular flat surface portion (10), the flat portion (10) comprising a plurality of orifices (12)... the diffusion element (9) defining a mixing zone (13) free of any obstacle between said diffusion element (9) and the vessel bottom (4)
Data Source
AI summary
A nuclear reactor includes a vessel having an outer wall and vessel bottom, and an enclosure delimited by a cylindrical inner wall disposed inside the vessel such that the inner wall and outer wall define a circuit with an annular cross-section. A support element is located adjacent the bottom of the enclosure to hold control elements of the core. A flow diffusion element is positioned between the support element and the vessel bottom and has a circular flat surface portion including disc shaped orifices of the same diameter. The space between the flat portion and the vessel bottom forms an unobstructed mixing zone to allow uniform distribution of flow rates of fluid circulated through the enclosure.