Tungsten is a very strong material that maintains its form and shape, even when exposed to extremely hot conditions. These characteristics make it a good candidate for space exploration and travel. The CSNR staff uses a Spark Plasma Sintering (SPS) furnace to fabricate tungsten into specific shapes much faster and at lower temperatures than previous methods. With the SPS furnace, researchers can create a dense metal matrix to encapsulate radioisotopes to prevent the loss of gaseous fission products and release of radiation in accident scenarios. Tungsten-encapsulated material is an excellent candidate for radioisotope power sources and fuel for fission reactors.
Radioisotope Thermo-Photovoltaic (RTPV) Power Sources
Radioisotopic Thermoelectric Generators (RTGs) have powered scientific instruments in space since the 1960s. The Mars Science Laboratory mission currently underway utilizes multi-mission RTGs that can operate in space or in a planet’s atmosphere.
These systems rely on thermocouples to convert heat to electricity, a highly inefficient process (only about 6 percent of the thermal energy is converted into electricity). Because of this inefficiency, the power supplies are a significant portion of the platform mass.
CSNR is developing a new, robust encapsulation of plutonium dioxide that contains five times the power density of the RTG heat source and can be resized (0.5w to 500w) so power levels match mission requirements. By converting the light emitted by a hot surface using photovoltaic cells, high efficiency, no moving part, low mass power sources can be created.
These characteristics would enable the system to reach higher temperatures and improve conversion efficiency.
Coating the surface of the shell--or the emitter--to alter the light emitted from the surface toward visible wavelengths also could improve the efficiency of the PV cells.
Together, these design changes could potentially help an RTG achieve 25 percent conversion efficiency.