On the basis of the experience of long-term operation of nuclear power plants with RBMK (high-power channel reactors) and water-cooled water-moderated reactors, we analyze the events of failures of pipelines made of Kh18N10T steel. It is shown that the main mechanism of failures of welded joints in pipelines made of this type of steel is intercrystalline corrosion cracking. As the causes of the appearance of defects of this sort, one can mention the joint action of high levels of stresses, significant amounts of oxygen in the heat carrier, and sensitization of steel in the heat-affected zone of welded joints in pipelines. We propose compensating measures aimed at decreasing the negative effect of intercrystalline corrosion cracking in the process of operation.Introduction. The experience of operation of power-generating equipment at nuclear power plants in Russia and other countries shows that some elements of this equipment (for the most part, welded joints made of austenitic stainless steels) fail during the designed service life. According to the world statistics, up to 41% of the general number of these failures are caused by the action of the heat carrier. Among the most dangerous events of this sort, we can mention the failures of pipelines of the first contour. The common feature of all failures of pipelines made of 18-8 type steel is the formation of intergranular cracks either in the heat-affected zones (HAZ) of welded joints whose metal is sensitized in the process of welding or in elements made of metals subjected to sensitizing thermal treatment in the process of manufacturing. In the practice of operation of foreign nuclear power plants (USA, Germany, and Japan), this problem is of primary importance. At the same time, in Russia, it is customary to use 08Kh18N10T stabilized austenitic steel as a material of power-generating equipment. This type of steel is characterized by high stability in high-temperature oxygen-containing aqueous media. Nevertheless, numerous cases of crack initiation were detected in pipelines of stainless steel at different nuclear power plants equipped with RBMK (high-pow er channel reactors) after more than 50,000 h of operation.1. Defects in Pipelines. The problem of corrosion cracking of welded joints made of austenitic stainless steels appeared in the late 1960s. Defects in the form of cracks were first detected in the HAZ of welded joints of pipelines (∅ 6-8 inches) at two nuclear power plants in the USA (Dresden-1 and Oyster Greek-1). The phenomenon of corrosion cracking was recorded in the pipelines of the first contour made of AISI-304 and AISI-316 stainless steels both in boiling-water reactors (BWR) and pressurized-water reactors (PWR). Later, the problem of corrosion cracking at nuclear power plants in the USA became much more serious. Thus, 64 events of cracking were recorded in 1975. Moreover, in 1982 and1985, the number of events of this sort exceeded 400 and 800, respectively [1, 2]. Defects occurred mainly in pipelines of small diameters (< 25.4 cm). Although ...
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