Study of the Unirradiated Weld Metal of the VVER-440 Reactor Vessel after 45 Years of Operation

Abstract—The results of studying the mechanical characteristics and chemical composition of metal specimens cut from an unirradiated weld joint of a VVER-440 reactor pressure vessel (RPV) after 45 years of operation are given. The calculated distribution of the ductile-to-brittle transition temperature over the thickness of the irradiated weld joint of the VVER-440 reactor pressure vessel (140 mm) is obtained accounting for the distribution of the initial properties, the content of phosphorus and copper, and the density of the fast neutron flux over the thickness of the joint. Since all the circular welds connecting the shells in the VVER-440 RPV are made using the same technology, the results of studying the unirradiated weld can be used to assess the distribution of properties in the irradiated weld. At the same time, it is assumed that the effect of thermal aging at a temperature of 270°C (operating temperature of a unirradiated weld) is insignificant and can be neglected.