Volume 25: Accelerated Energy Innovations and Emerging Technologies

In-Core Printed Circuit Heat Exchange in Molten Salt Reactors Kraig Farrar, Mark Kimber



Printed circuit heat exchange has been found beneficial in various chemical applications to allow for high rates of reaction per unit volume of reactor space. This is especially true where large amounts of heat exchange are necessary to provide either energy input to the reaction or remove heat produced from an exothermic reaction. Given that fission is a highly exothermic chemical reaction, the same concept may be applied to a fluid phase fission reaction like in a molten salt reactor. Calculations performed both with the NTU-efficiency method as well as in RELAP5-3D suggest an order of magnitude increase in power density is possible relative to a base case thermal spectrum, graphite moderated, molten salt reactor core. Along with the benefit of increased power density, other benefits are identified: elimination of hot leg/cold leg corrosion and deposition mechanisms, nearly flat axial temperature profile, having a maximum axial temperature gradient of 6.5 °C or less in the core at full power, elimination of the primary heat exchanger from the fuel loop, since primary heat exchange occurs in-core; minimal reduction in delayed neutron fraction due to a lower ex-core salt fraction, and facilitation of chemical separations of radionuclides due to smaller fuel salt volume and higher radionuclide concentration. Increasing the rate of heat transfer in the core with a novel heat exchange design drastically improves the output of a small footprint reactor, allowing for the benefits of small modular manufacturing while exceeding the thermal and electrical output of traditional large scale nuclear construction projects on a volumetric basis.


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