Methods of non-destructive testing in the examination of WWER-440 reactor pressure vessel steels

Moessbauer spectroscopy and electron-positron annihilation were applied to the investigation of properties of the WWER-440 reactor pressure vessel steel. Changes in the basic parameters of spectra of pressure vessel material specimens during the use of the reactor for power generation were evaluated. Moessbauer spectra measured at room temperature confirmed changes in the material structure due to radiation stress, while spectra run after annealing the specimens in a vacuum documented recovery of the initial structure. The results of Moessbauer spectroscopy were consistent with electron-positron annihilation measurements using both time and correlation spectra. (author). 3 tabs., 4 figs., 16 refs