The compatibility of SAP 930 with uranium dioxide and uranium monocarbide was investigated in the temperature range 450–600° C. The results indicate that a severe reaction occurs between SAP 930 and UO2 within 8000 hours at 600° C, a slight reaction at 600° C for 1000 hours and after 11 900 hours at 525° C, and no reaction in 14 300 hours at 450° C. Of the three grades of UC tested (hot pressed, arc cast, cold pressed and sintered) the slightly substoichiometric, hot-pressed UC is judged to be least compatible with SAP 930, reaction occurring after 7300 hours at 450° C. No reaction was observed between SAP 930 and the other carbides at this temperature. All SAP−UC combinations are incompatible at 600° C for as little as 100 hours of heat treatment. Tests designed to study the effect of a diffusion barrier on the SAP−UC reaction have shown that anodized SAP 930 and the three uranium carbides are fully compatible at 450 and 525° C for at least 14 300 hours. Mechanical breakdown of the barrier within 8000 hours, however, limits the application of anodized SAP 930 at 600° C. X-ray diffraction analyses of the reaction products formed in each material combination tested show that the primary constituent is the intermetallic compound UAl3. A second phase, visible at the SAP/reaction-product interface, has been identified as UAl4 on the basis of its observed anisotropy and its position in the reaction zone.