[en] Alloy nitrides (U, Zr), (U, Ce), and (U, Y) were prepared and exposed to vacuum at temperatures to 17000C and compared with pure UN. Weight loss data and physical observations showed that the alloy samples were more stable than UN. In weight loss, (U, Zr)N was 3 times as stable as UN at 16000C for 100 h at 0.000002 torr (0.000266n/sq.m.). (U.S.)