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Idaho National Laboratory and the Universities Space Research Association created the Center for Space Nuclear Research (CSNR) in 2005 to foster collaboration with university scientists. CSNR scientists and engineers research and develop advanced space nuclear systems, including power systems, nuclear thermal propulsion, and radioisotopic generators. The CSNR is located at the Center for Advanced Energy Studies (CAES) building in Idaho Falls, Idaho.
Nuclear Thermal Propulsion
The United States first explored the use of nuclear power in space in the 1950s. Between 1955 and 1972, the U.S. built and tested more than 20 nuclear-propelled rocket engines in the Rover/NERVA program.
Researchers are revisiting the concept, which is viewed as one of the most promising technologies for powering a manned mission to Mars.
 Idaho National Laboratory
CSNR researchers are developing a tungsten-based fuel for use in a nuclear thermal rocket that shares many of the benefits of the graphite fuels developed in the NERVA program -- a lot of energy in a small mass. But unlike graphite fuels, CSNR's tungsten fuel emits a clean, nonradioactive exhaust, a major environmental concern associated with the NERVA project.
The nuclear thermal rocket (NTR) is a "game changing" technology that could be developed, tested, and deployed in the next few decades.
Developing an NTR requires fuel to be fabricated and characterized, a full-scale, surrogate-loaded tungsten fuel element to be demonstrated, and the microstructure and material behavior to be quantified.

Tungsten Encapsulation


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.