Heat Transport and Power Conversion of the Kilopower Reactor Test

The Kilopower reactors have been designed to provide a steady-state thermal power range between 4 and 40 kW and to convert the heat generated to an electrical output of 1 to 10 kW(electric), providing an overall system efficiency of 25%. This range of thermal and electrical power has been derived from two basic designs: the small 1-kW(electric) design and the larger 10- kW(electric) electric design intended to support science and human exploration missions for surface and in-space power. The Kilowatt Reactor Using Stirling TechnologY (KRUSTY) experiment was built using the 1-kW(electric) Kilopower design to make the test affordable by using existing infrastructure and to complete it in a 3-year timeframe. The data from the smaller, lower-mass system could be extended to the larger 10-kW(electric) system, knowing that the materials and neutronic design are similar. Each of these designs use the same fuel, heat transport systems, and power conversion systems at the appropriate scale to produce the desired electrical output power for mission use. The heat transport system uses multiple heat pipes that operate passively and do not require any electrical pumps or other parasitic loads to cool the reactor core. This type of reactor cooling provides several layers of redundancy and makes it ideal for coupling a self-regulating reactor to a variable-output power conversion system. The power converters accept the reactor heat that has been delivered by the heat pipes and create the needed electrical power through their thermodynamic Stirling cycle and linear alternator. This paper provides details about the sodium heat pipes used in the experiment, the Stirling power converters that create the electricity, and the overall power system that make up the 1-kW(electric) Kilopower reactor.