Compact Plate Heat Exchanger Layout for Smaller Nuclear Reactors
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Solution Overview
Problem
Existing heat exchangers in nuclear reactors are large and limit design flexibility, necessitate substantial space, and increase complexity and cost due to high neutronic activity and the use of sodium as a secondary coolant, especially in sodium-cooled fast reactors.
Innovation Solution
A compact plate heat exchanger with separate fluid pathways for primary and secondary coolants, optionally including a third fluid pathway for leak detection, fission product capture, or oxidation layer formation, allowing for flexible placement and reduced size within the reactor vessel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional heat exchanger is used to transfer thermal energy from primary to secondary coolant, then thermal energy transfer is achieved, but the heat exchanger occupies substantial space within the reactor vessel and increases overall reactor size
Solution Approach 1:
The heat exchanger is segmented into multiple separate heat transfer modules arranged in series. Each module contains discrete heat transfer surfaces and flow channels, allowing the total heat transfer area to be distributed across multiple compact units rather than requiring a single large volume component.
Solution Approach 2:
The heat exchanger modules are nested within the reactor vessel's existing structural space, utilizing vertical arrangement and integration with the reactor core support structure. The modules are positioned to fit within available void spaces without requiring additional horizontal footprint.
2Temperature
If the heat exchanger is positioned near the reactor core to receive thermal energy, then heat transfer efficiency is improved, but the heat exchanger is exposed to high neutronic activity requiring additional shielding
Solution Approach 1:
A sodium intermediary loop is introduced between the reactor core and the heat exchanger. The primary sodium coolant transfers heat to an intermediate sodium loop, which then transfers heat to the secondary coolant in the heat exchanger. This intermediary sodium loop acts as a radiation shield, absorbing neutron flux and protecting the heat exchanger components from high neutronic activity while maintaining thermal energy transfer.
3Temperature
If sodium is used as the secondary coolant to maintain thermal conductivity, then heat transfer performance is maintained, but the heat exchanger size increases when using coolants with lower thermal conductivity
Solution Approach 1:
The heat exchanger design incorporates adjustable flow rate parameters and temperature differential optimization to compensate for lower thermal conductivity of alternative coolants. By increasing the flow rate and optimizing the temperature gradient across the heat transfer surfaces, the system maintains effective heat transfer performance without requiring proportionally larger heat transfer area when using coolants like molten salt instead of sodium.
4Length of stationary object
If the reactor vessel height is reduced to decrease overall reactor size, then containment structure size is reduced, but heat exchanger placement options are limited
Solution Approach 1:
The heat exchanger modules are arranged in a vertical stacking configuration, transitioning from horizontal placement to vertical arrangement. This dimensional change allows multiple heat transfer modules to be stacked within the reduced vessel height, maintaining total heat transfer area while adapting to the constrained vertical space. The modular design enables flexible stacking arrangements to optimize space utilization.
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 compact design reduces the overall size of the reactor vessel, enhances coolant flexibility, and minimizes shielding requirements while effectively managing thermal stresses and tritium penetration.
Implementation Method 1
a plate heat exchanger for transferring thermal energy from a first fluid to a second fluid
Implementation Method 2
the third fluid may be used to create an oxidation layer within the third fluid pathway
Data Source
AI summary
A nuclear reactor includes a heat exchanger that transfers thermal energy from a primary reactor coolant to a secondary coolant. The heat exchanger is a compact plate heat exchanger and more than one heat exchanger may be spaced about the reactor vessel. A plurality of heat exchangers may be spaced vertically, radially, and/or circumferentially about the reactor vessel. A first heat exchanger may be in fluid communication with a second heat exchanger. Two or more heat exchangers may share a thermal load and therefore share thermal stresses. The heat exchanger may have a third fluid flow path and a third fluid. The third fluid may be used to remove fission products, be used for leak detection, create an oxidation layer to inhibit migration of activation products, and/or provide additional heat transfer.