High Power and High Temperature Heat Pipes for Small and Modular Reactors

It is desired and beneficial that Small Modular Reactors (SMR) be reduced size and footprint as well as simpler in installation, more cost effective, reliable and safe. Heat pipe cooled SMRs use hundreds of heat pipes/thermosyphons to transfer the heat from the reactor to the conversion system. The number of these heat pipes is dictated by how much heat a pipe can transport (within the geometrical constraints imposed by the fuel) as well as the level of redundancy imposed by the policies and regulations characteristic to the application. These heat pipes are typically limited in the thermal power that they can transport by the flooding limit which results from the impact of vapor flow onto the adversely returning liquid (condensate). Advanced Cooling Technologies is proposing the development of a wick structure that would eliminate the flooding limit and, consequently bust the performance of a heat pipe (thermosyphon) 2-4 times. The benefits of this thermosyphon improvement consist in less heat pipes required per reactor resulting in a reduced size and footprint, simpler configuration and assembly, less materials, more cost effective as well as higher redundancy and safety level. Advanced Cooling Technologies, Inc. (ACT), in collaboration with Idaho National Laboratory (INL), will develop the advanced wick during a Phase I and II program where in Phase I the feasibility of the proposed concept will be demonstrated while in Phase II the technology will advance to full scale prototypes testable in relevant environment including irradiation. In parallel, a robust mathematical model will de developed that will predict performance and simulate behavior in both transient (including startup) and steady state modes of operation. The resulted mathematical model will be adapted in such a way that it will have the potential of extending the capabilities of Sockeye (the heat pipe code currently being written in the MOOSE framework). The incorporation of this specific sub-model will be performed by the MOOSE staff. ACT will develop a high-performance wick for thermosyphons. Based on the new wick configuration a mathematical model will be developed for heat pipe performance prediction and behavior simulation. Four reduced scale prototypes will be developed in Phase I, two of them using water and two using sodium for wick verification and model validation. A full-scale prototype sodium prototype will be developed as well at the end of Phase I. The proposed concept will significantly improve the performance of any thermosyphon in any application it may be used. Particularly, DOE is interested in further compacting the Heat Pipe Cooled Small Modular Reactors and Microreactors by decreasing the number of thermosyphons. Distribute Energy Generation based on microreactors would also benefit. Space applications where planetary surface fission power (like NASA’s Kilopower program) is needed represent another beneficiary.