Positron annihilation lifetime study of JRQ and JPA irradiated and annealed reactor pressure vessel steels

The model reactor pressure vessel steels known as JRQ and JPA were manufactured in Japan for the IAEA neutron embrittlement research studies. These model alloys belong to the commercially used steel A533B-1 type and show relatively large changes in mechanical properties after relevant neutron irradiation. The neutron irradiation was performed by different neutron fluxes as well as different neutron fluences (up to about 150 × 1018 cm−2 (E > 0.5 MeV)). For a better understanding of the neutron embrittlement, the Positron Annihilation Lifetime Spectroscopy (PALS) technique was applied in 2014. PALS measurement of irradiated specimens was performed using three detectors set-up due to induced 60Co radioactivity of the studied specimens. We confirmed that the JPA steel, considered to be high-copper steel, is much more sensitive to defect creation due to neutron irradiation than the low-copper JRQ steel. •We used Positron Annihilation Spectroscopy to study western RPV steels.•We examine microstructural changes in the studied JRQ and JPA steels.•Specimens were irradiated and annealed in many levels.•We confirmed that copper has crucial effect to neutron-induced defect creation.•High-copper JPA steel was more sensitive to the creation of defects than JRQ.