Four types of high purity W were irradiated with 2MeV electrons to 5dpa using a high-voltage electron microscope, and defect structural evolutions were examined as a function of the irradiation temperature and the concentration of impurity atoms. Three samples were made by sintering W powders with purities of 5N-, 4N- and 3N5-purity, and one was made from chemical vapor deposited 6N-purity W. The formation of interstitial-type dislocation loops was observed above room temperature by electron irradiation. In sintered W, the number density of loops increased with increasing density of impurity atoms. The density of loops in the chemical vapor deposited W was relatively high; in spite of its purity. In the latter, heterogeneous formation of loops was observed above 573K. Loops were aligned on layers, and no loops were formed between the layers. All 4 types of specimen exhibited a change in slope of the temperature dependence of the loop number-density at about 500K; which was caused by impurity atoms.

Defect Structural Evolution in High Purity Tungsten Irradiated with Electrons using High Voltage Electron Microscope. S.Fukuzumi, T.Yoshiie, Y.Satoh, Q.Xu, H.Mori, M.Kawai: Journal of Nuclear Materials, 2005, 343[1-3], 308-12