Metal matrix composite fuel for space radioisotope energy sources

Radioisotope fuels produce heat that can be used for spacecraft thermal control or converted to electricity. They must retain integrity in the event of destruction or atmospheric entry of the parent spacecraft. Addition of a metal matrix to the actinide oxide could yield a more robust fuel form. Neodymium (III) oxide (Nd2O3) – niobium metal matrix composites were produced using Spark Plasma Sintering; Nd2O3 is a non-radioactive surrogate for americium (III) oxide (Am2O3). Two compositions, 70 and 50 wt% Nd2O3, were mechanically tested under equibiaxial (ring-on-ring) flexure according to ASTM C1499. The addition of the niobium matrix increased the mean flexural strength by a factor of about 2 compared to typical ceramic nuclear fuels, and significantly increased the Weibull modulus to over 20. These improved mechanical properties could result in reduced fuel dispersion in severe accidents and improved safety of space radioisotope power systems.

► Neodymium (III) oxide Nd2O3 – niobium composites created via Spark Plasma Sintering.
► Nd is a surrogate for Am-241 fuel for European Space radioisotope power systems.
► Composites mechanically tested under equibiaxial flexure per ASTM C1499.
► Fifty weight percent Nb increased mean flexural strength × 2 versus typical ceramic nuclear fuels.
► Could reduce fuel dispersion in severe accidents: may improve launch safety case.