The temperature dependence of the damage microstructures in neutron-irradiated vanadium

Vanadium and vanadium with boron carbide additions (V-B4C) were irradiated to approx.=1 dpa at controlled temperatures ranging from 455 to 925 K. The V-B4C alloy was enriched in 10B, which produced approx.=3900 at. ppm helium. In the vanadium specimens, the dislocation mictrostructures varied from clusters of small dislocation loops (455 to 625 K) to larger, homogeneously distributed loops at higher temperatures. The V-B4C specimens contained only tangled dislocation segments. Cavities were observed in all specimens. The cavity concentration decreased and the average diameter increased with increasing irradiation temperature. At 725 K, the maximum swelling was observed in both the vanadium (0.1%) and V-B4C (1.4%). At comparable temperatures the cavities in the V-B4C specimens were smaller and more numerous than those in the vanadium specimens. Helium bubbles were found on the grain boundaries in all of the V-B4C specimens. (orig./RK)