Positron Annihilation Studies of Reactor Pressure Vessel Steels Treated by Hydrogen Ion Implantation

V. Slugena, S. Peckoa, S. Sojaka, W. Eggerb, M. Saroa, M. Petriskaa aInstitute of Nuclear and Physical Engineering, Slovak University of Technology, Ilkovičova 3, 81219 Bratislava, Slovakia bUniversity of Bundeswehr, Werner Heisenberg Weg 39, Munich, Germany

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Long term operation of nuclear reactors is one of the most discussed challenges in nuclear power engineering. Radiation degradation of nuclear materials limits the operational lifetime of all nuclear installations or at least decreases its safety margin. This paper is focused on experimental simulation and evaluation of materials via hydrogen ion implantation and on comparison with our previous results obtained from neutron-irradiated samples. In our case, German reactor pressure vessel (RPV) steels, originally from CARINA/CARISMA program, were studied by positron annihilation lifetime spectroscopy (PALS) and the pulsed low energy positron system (PLEPS) with the aim to study microstructural changes in RPV steels after high level of irradiation. Unique specimens were irradiated by neutrons in the German experimental reactor VAK (Versuchsatomkraftwerk Kahl) in the 1980s and these results were compared with the results from a high level of hydrogen nuclei implantation. Defects with sizes of about 1-2 vacancies with relatively small contributions (with intensity on the level of 20-40%) were observed in all ``as-received'' steels. An increase in the sizes of the induced defects (2-3 vacancies) due to neutron damage was observed in the irradiated specimens. On the other hand, the size and intensity of defects reached extremely high values due to displacement damage caused by implantation of hydrogen ions in a very narrow damaged region. This fact can be a limiting factor in the operation of new fission or fusion nuclear facilities.

DOI:10.12693/APhysPolA.137.238 topics: Radiation damage, neutron embrittlement, ion implantation, positron annihilation, reactor pressure vessel steels\\vs*{8pt}