SEDL / STP / STP1366-EB / STP12399S

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

Grosse, M
Research scientists, Forschungszentrum Rossendorf Inc., Dresden,

Böhmert, J
Leader, Forschungszentrum Rossendorf Inc., Dresden,

Pages: 20    Published: Jan 2000

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Abstract

Neutron irradiation of the 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 only 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 60°C. Annealing at 475°C/1h provokes coarsening of the precipitates and re-dissolution of the precipitates formed by irradiation at lower temperature.