Irradiation Damage Structure in VVER-440 Steels after Irradiation at Different Temperatures and Post-Irradiation Annealing

摘要

Neutron irradiation of VVER-440-type reactor pressure vessel steel 15Kh2MFA at lower temperature causes an increase of the content of point defects in the iron lattice. The ratio between the magnetic and nuclear scattering of these point defects shows that not noly vacancies are formed but also the number of foreign atoms in solution is increased. Additionally, small precipitates grow. These precipitates are smaller and have a weaker thermal stability than the precipitates grown in this steel after neutron irradiation at service temperature. In some cases the number of precipitates which can be found in the unirradiated state decreases significantly by irradiation at 60deg C. Annealing at 475deg C/1h provokes coarsening of the precipitates and re-dissolution of the precipitates formed by irradiation at lower temperature.