Low-Temperature Reactor Irradiation Effects in Metals

The effects of structural and chemical defects on the low-temperature (30–50°K) annealing peak in low-temperature reactor-irradiated aluminum and copper were studied. From the fact that the density of reactor-induced defects did not affect the annealing kinetics, it was possible to conclude that the low-temperature annealing process was of the first order without a unique activation energy. The fact fact that both oversized and undersized atoms could suppress this annealing peak led to the conclusion that the radiation-induced defects were more complicated than simple point defects. The suggestion is made that a defect similar to a crowdion must be created by low-temperature neutron irradiation. This data also supports to some degree the viewpoint that a radiation-induced defect, possibly a crowdion, has sufficient knock-on energy to migrate several hundred atomic distances. The experiments also contain evidence which rule out all forms of vacancy-interstitial annihilation.