Radiation damage in nuclear structural materials - Past, present and future challenges

Abstract

Positron annihilation spectroscopy (PAS) had been used at the Slovak University of Technology for almost 20 years for various studies of radiation effects in nuclear grade structural materials [1-4]. In the early years, the studies were often focused radiation-induced precipitation of impurities in reactor pressure vessel (RPV) steels for the second generation of nuclear fission reactors, mostly VVER type [5]. These studies were motivated by the search for an optimal heat treatment for the recovery of the material's mechanical properties. Next generation of reactor pressure vessel (RPV) steels with improved chemical composition turned the aim of the research to increased displacement damage and the experimental simulation high neutron fluencies by utilizing ion implantations [6]. Thermonuclear fusion and spallation target technologies introduced even more severe radiation conditions with high production rates of gaseous transmutation products such as hydrogen and helium. Recent research activities of the Institute of Nuclear and Physical Engineering (INPE) are focused on distinct effects of flux, temperature and oxide dispersions on the behavior of nuclear materials exposed in harsh radiation conditions [7,8]. This contribution reviews experimental PAS studies of various grades of nuclear structural steels investigated by authors during last years. The new results are compared to those from the earlier studies in order to distinguish between various processes involved in the formation of the microstructure of irradiated materials. Future challenges in the understanding and characterization of advanced structural materials for nuclear applications are also outlined.