Operating wear of pipelines of the second circulation loop of WWER-1000 power units

Досліджено характер експлуатаційних ушкоджень трубопроводів теплообмінного устаткування другого контуру енергоблока ВВЕР-1000. Встановлено, що у ряді випадків труби зі сталі 20 (Ø32×4 мм) схильні до інтенсивного ерозійно-корозійного зношування, причиною чого можуть бути турбулентні потоки теплоносія, що виникають на згинах трубопроводів і виступах зварних з’єднань. Розглянуто також ушкодження трубопроводу зі сталі 20 (Ø325×13 мм). У трубопроводі зі сталі 08Х18Н10Т (Ø25×2 мм) ушкодження мають вигляд наскрізних зімкнених тріщин невеликої протяжності. Ушкодження носять локальний характер і за усіма ознаками зумовлені корозійним розтріскуванням під напруженням.Corrosion damage in the pipe system of the second circulation loop is one of the problems of long-term operation of NPP with WWER-1000 power units. Subject of the research were flat spiral pipe elements (SFPE) made of steel 20, 32×4 mm, used in high-pressure heater; pipe-line 325×13 was made of steel 20 and pipe elements of heat exchangers 25×2 mm were made of corrosion-resistant steel of austenitic class 08Cr18Ni10Ti. The performed investigations have testified that SFPE pipes (32×4mm) in the medium of the second circulation loop are subjected to the intense erosive-corrosive wear. The reason of this phenomenon is the turbulent flows of heat-transfer agent caused by the wrong groove weld connecting SFPE and tailpress. Formation of through crack was revealed on the pipeline 325×13 mm made of steel 20 without substantial erosion of the metal. Cracking has occurred on the area of tap for 90o in front of controller. Impact tests of longitudinal and transverse specimens testified the presence of anisotropy of mechanical properties of the metal. Metallographic examination revealed the presence of fibrous structure. Os the whole mechanical and metallographic properties of steel meet the specification. The reason of the crack formation was likely to be the combination of factors: overspecified operation loads and presence of corrosive component. Erosion wear of the metal was not revealed in the pipeline 25×2 mm produced of steel 08Cr18Ni10Ti. In this case the operating damages are like through closed cracks of small extent. Damages are local and are caused by the corrosion cracking under stress

PECULARITIES OF MECHANICAL PROPERTIES OF HIGH-PURITY, IODIDE AND HAFNIUM GFE-1 IN TEMPERATURE RANGE 20-900°C

Here is given the results of investigation of mechanical properties of high-purity hafnium, iodide hafnium and hafnium GFE-1 at temperature range 20-900°C. Taken results are testifying about considerable influence of methods of receiving hafnium, its purity and mechanical-thermal processing on mechanical properties. The characteristic abnormalities of mechanical properties in the temperature range 20-900°C for different purity hafnium are discussed