Oxygen can be extracted from lunar soil by hydrogen reduction: the lunar regolith is heated using a solar concentrator to approximately 1050°C and exposed to hydrogen gas. Water is formed from the reaction and the oxygen is recovered by electrolysis of the water. To minimize mass, it is desirable for the solar concentrator to supply heat to more than one reactor. In a dual reactor system, one reactor is at 1050°C extracting oxygen. The second reactor, filled with fresh, cold regolith, uses the majority of the solar power to heat the regolith up to the extraction temperature. After one hour, the roles of the reactors switch, and the fraction of power supplied to each reactor must be switched. A method has been developed using Pressure Controlled Heat Pipes (PCHPs) to shuttle the solar power from one reactor to the other. The final system will use sodium as the working fluid, with a Haynes 230 envelope material. This paper reports on the design and testing of two lower temperature Monel/water systems that have been used to verify the performance and control scheme for the overall design.