Proceedings of the conference

Kuleshova E.A. Zhurko D.A Erak A.D. Bubyakin S.A. Kiselev A.S.

Study of local normal stress values for cylindrical specimens with circular notch of VVER-type reactor pressure vessels tested for uniaxial static tension in different states

Reactor pressure vessel (RPV) is an irreplaceble part of a nuclear power plant (NPP) and substantially limites the lifetime of the entire power unit. Reactor pressure vessel is known to be exposed to elevated temperature and ionizing irradiation (in the reactor core area) during operation, which leads to degradation of mechanical properties of the RPV material, in particular resulting in cohesive strength reduction of grain boundaries that eventually leads to the most dangerous kind of destruction - brittle intergranular fracture. To assess the influence of operational factors (this paper considers the influence of high temperature) on the brittle fracture we propose to use local normal stress value at the boundary of the brittle fracture origin - the "leader". Non-metallic inclusions and structural boundaries of the material are detected to be brittle fracture origins.

This paper presents experimental data on uniaxial static tension of cylindrical specimens of VVER-type RPV steel with a circular notch in highly embrittled and annealed states. Fractographic study of fracture surfaces of investigated specimens is performed. The local characteristics of the "leaders" are determined in different states. The influence of long-term exposure to high temperature on the change of brittle fracture origin type is revealed.

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