NNSA and the National Aeronautics and Space Administration (NASA) joined forces to address a unique challenge: developing a power source able to support deep space travel and outlast existing fuel sources.
NNSA came through with the technical expertise required to achieve this goal.
“The relationship between NNSA and NASA is a ‘win-win’ partnership,” said Patrick Cahalane, NNSA’s Principal Deputy Associate Administrator for Safety, Infrastructure and Operations. “NASA gets a prototype demonstration for a kilowatt-range fission power source, and NNSA gets a benchmark-quality experiment that provides new nuclear data in support of our Nuclear Criticality Safety Program.”
The experiment, nicknamed KRUSTY (Kilowatt Reactor Using Stirling TechnologY), was part of NASA’s larger Kilopower project. KRUSTY was designed to test a prototype fission reactor coupled to a Stirling engine. Stirling technology is efficient, doesn’t require significant maintenance, and does not degrade in performance over time.
Scientists from NNSA’s Los Alamos National Laboratory (LANL) and Nevada National Security Site partnered with NASA to develop and test the KRUSTY design at the National Criticality Experiments Research Center (NCERC).
Researchers designed and performed initial testing of the KRUSTY reactor design using a surrogate, or non-fissile, reactor core and resistive heating elements. Experts from NNSA’s Y-12 National Security Complex manufactured the uranium reactor core, which was delivered to the NCERC in the fall of 2017.
Assembly of the KRUSTY experiment began shortly after the core arrived, bringing together the NNSA and NASA components, including the Stirling converters, shielding materials, sodium heat pipes, and a neutron reflector.
The uranium core is subcritical in air, but it becomes critical once surrounded by the neutron reflector, which means it maintains a self-sustaining reaction of splitting uranium atoms until the reflector is removed.
Experimenters at NCERC achieved the initial criticality in November 2017. Since then, a series of experiments followed that helped to characterize the assembly and obtain experimental benchmark data for use by the Nuclear Criticality Safety Program. These efforts culminated in a 28-hour continuous full-power demonstration in March.
The full-power run showed that it may be feasible for NASA to use small fission reactors for deep space exploration and manned missions to the moon and Mars. NASA shared the successful completion of the experiment during a press conference at the NASA Glenn Research Center earlier this month.
LANL is currently using the KRUSTY nuclear data to develop experimental benchmarks for a variety of applications, including nuclear criticality safety, emergency response, and nuclear nonproliferation.
Experts from Lawrence Livermore National Laboratory, Sandia National Laboratories, and other NNSA field offices and production sites also contributed to the completion of the design, safety analysis, fabrication, and final testing of the KRUSTY experiment.