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 (Am₂O ₃). 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.