Annealing behaviour of reactor pressure-vessel steels studied by positron-annihilation spectroscopy, Mossbauer spectroscopy and transmission electron microscopy

The annealing behaviour of commonly used reactor pressure-vessel steels was studied using positron-annihilation spectroscopy (PAS) (lifetime and Doppler broadening techniques), transmission Mossbauer spectroscopy (MS), integral low-energy electron MS (ILEEMS) and transmission electron microscopy (TEM). The results of these methods applied to different types of steels are discussed. Some significant differences in the experimental results are observed between the Russian (3 types) and Western Europe (5 types) steels and between individual specimens within these two groups. All specimens were annealed in vacuum and studied after this thermal treatment. It was confirmed that the heat affected zone (HAZ) is the most sensitive region for thermal and neutron irradiation-induced embrittlement in the reactor. Positron-annihilation lifetime measurements on HAZ specimens annealed at successively higher temperatures show the drastic increase in the vacancy-type defect formation between 525 degrees C and 600 degrees C. Therefore these specimens were selected for further detailed studies by TEM. (C) 1999 Elsevier Science B.V. All rights reserved.