Effect of neutron irradiation hardening of the base metal on the results of WWER-1000 reactor pressure vessel residual lifetime assessment

摘要

This paper discusses the assessment of the WWER-1000 reactor pressure vessel integrity and the analyses performed to protect the irradiated vessel against brittle failure. The paper focuses on studies assessing the effects of base metal hardening on fast fracture evaluation results. It is shown that the results depend significantly on the material model used (elastic or elastic plastic) as well as on the base metal mechanical properties (including or not the hardening produced by irradiation). Considering the change in tensile properties of the base material under irradiation may change the identification of the limiting combination of the pressurised thermal shock scenario, the limiting crack front point, and the crack aspect ratio. To demonstrate these effects, the results of the calculations performed for the South Ukrainian Nuclear Power Plant Unit 2 reactor pressure vessel residual lifetime are presented.