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Reactor internals are subjected to three principal operation effects: neutron and gamma irradiation, static and dynamic mechanical stresses and coolant chemistry. In this study, we investigate the effect of these mechanisms on WWER 440 reactor vessel internals and present lifetime analysis, in order to extend the operational lifetime of reactor vessel internals. [ABSTRACT FROM AUTHOR]

Mechanical properties of WWER-440 RPV weld joints have been studied with account of different states of the material: baseline (unirradiated), irradiated up to the average fast neutron fluence of $\backslash 6.5\; cdot\; 10^19$ n/$\backslash cm^2$, irradiated and eventually annealed, re-irradiated with the accumulated fast neutron fluence $\backslash 1.3\; cdot\; 10^20$ n/$\backslash cm^2$. Tensile, impact fracture, and fracture toughness tests were performed for each state of the material with the use of Charpy specimens (standard, reconstituted, and pre-cracked). [ABSTRACT FROM AUTHOR]