The Clustering of Cu Atoms in Neutron Irradiated Reactor Pressure Vessel Steels Studied by Positron Annihilation
Defect studies of neutron-irradiated Cr-Mo-V (VVER-440) type reactor pressure vessel steels were performed in the present work. The steels were irradiated in the nuclear power plant reactor under the conditions of a regular operation. Characterization of the irradiation induced defects was performed by two complementary techniques of positron annihilation spectroscopy: (i) positron lifetime spectroscopy was used for identification of defects and determination of defect densities, (ii) coincidence Doppler broadening was employed for investigation of Cu atom aggregates. Long range diffusion of Cu atoms is assisted by the irradiation induced vacancies. The solute Cu atoms form small clusters in the irradiated steels. Subsequent isochronal annealing of the irradiated steel leads to vacancy assisted clustering of Cu atoms and formation of small precipitates. The Cu clusters exhibit maximum diameter at 400oC. Above this temperature the clusters dissolve again in the matrix.
Andreas Öchsner and Graeme E. Murch
J. Čížek et al., "The Clustering of Cu Atoms in Neutron Irradiated Reactor Pressure Vessel Steels Studied by Positron Annihilation", Defect and Diffusion Forum, Vols. 273-276, pp. 81-86, 2008