By metallography and scanning electron microscopy the effect of titanium carbonitride and silicon carbide on degradation of steel 08X18H10T was revealed on heat exchanging tubes (HET) of steam generators of powergenerating units of WWER-1000. The role of structural features of steam generators on nucleation and growth of operational defects of HET is shown.

С помощью металлографии и растровой электронной микроскопии установлено воздействие включений карбонитридов титана и карбида кремния на деградацию стали 08Х18Н10Т в теплообменных трубах (ТОТ) парогенераторов энергоблоков ВВЭР-1000. Показана также роль конструкционных особенностей парогенераторов в зарождении и росте эксплуатационных дефектов ТОТ.

The microstructure and mechanical properties of 10MnNi2MoV (high-quality) steel of the main circulation pipeline (MCP) of the WWER-1000 NPP after 200 thousand hours of operation were investigated. Metallographic methods, electron microscopy, mechanical static and impact tests were used. The obtained results are compared with those obtained for the metal samples of the MCP after 100 thousand hours of operation. The signs of metal aging are revealed. The probable cause of metal aging may be operational factors and processes occurring at the microstructural level. The example of MCP shows that small-scale metal cuttings are sufficiently informative in terms of controlling the structure and mechanical properties of metal in equipment and pipelines of NPP.

Defect formation into the heat exchangers of WWER-1000 steam generators at the South-Ukraine nuclear power plants (SU NPP) was considered using the data of multi-year eddy current control (ECC), taking into account the results of new metallographic investigations. The features of the defect distribution according to the control characteristics (amplitude of the signal, "lack of metal") are established. It has been shown that the damage germs formed in the metal can be non-metallic inclusions, which initiate the processes of local corrosion and corrosion fatigue. The analysis can be used to improve the regulations and plans for the next control at the NPP.

A comparative analysis is performed for Brinell hardness values obtained with the help of different testing equipment and procedures for determining the mechanical characteristics of steels from the results of hardness testing used in the nuclear power engineering, including the testing unit and procedure developed at the Pisarenko Institute of Problems of Strength of the National Academy of Sciences of Ukraine.

The paper presents the distribution of the strength characteristics of weld metal in heat-resistant steel 10GN2MFA over the thickness and height of the hot collector-to-nozzle welded joint in NPP steam generator determined by the instrumented indentation test method.

Mechanical properties of metal of pipelines of reactor and turbine separation of power units Sonth-Ukrainian NPP are certain after 100.000 hours of exploitation. Properties of metal concerned by direct methods on standard specimens, on cross-correlation dependences of basic descriptions with hardness, and also on microspecimens made from templets main circulation pipelines. Executed the comparative analysis of properties of exhausted metal with the initial state and requirements of normative documents. Microstructure research of exhausted metal was carried out, surface fractography of tension tested specimens and Charpy impact was studied by means of a raster microscope.