Damages formed in pure Cu irradiated by 14 MeV D-T neutrons at fusion neutron source facility (FNS) in JAERI

A 14 MeV D-T(fusion) neutron irradiation was earned out at fusion neutron source facility (INS) in Japan Atomic Energy Research. Institute (JAERI). Fluence range of 6.1x10(17) to 1.1x10(21) n/m(2) in the present FNS experiment was smaller than dig of the previous RTNS-II experiment in LLNL. This paper reports on damages observed by electron microscopy in Cu primarily and those in Au and Ag supplementally At a low fluence as 10(18) n/m(2), defects observed were single isolated dot defects in Cu, Au and Ag, and some was an isolated stacking fault tetrahedron in Cu. With increasing fluence, dot defects grew to complicate structure and formed groupings. In a dot group, interstitial clusters and vacancy clusters were observed together The present result was explained by the modeling that point defects in a nascent damage cascade move in crystal at 288 K and form their defect groupings. An effect of strain field on movements of small point defect clusters has an important role on the evolution of damage structure in neutron-irradiated metals.