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- Title
Assessment of Effective Length of Microcracks in the Water and Steam Line under Cyclic Operation of the NPP Steam Generator.
- Authors
Elokhin, A. P.
- Abstract
An acute issue arises in relation to the operation of water-moderated water-cooled reactors (VVER), including KLT-40 type reactors, which are widely used nowadays on icebreakers and floating power units (FPU), which is the duration of safe operation of steam generators (SGs). The issue is related to the generation of microcracks in the water and steam line of the steam generator under normal power operation. 16N7 penetrates the steam line through those microcracks and its presence is evidence of an untight water and steam line of the SG secondary circuit. This effect, which was later called a "leak," was studied in a number of papers of the authors in relation to the conditions of cyclic operation of the water and steam mode of the SG. This paper focuses on the mathematical and physical analysis of the mechanisms causing the formation of microcracks in the SG steam line and occurring in the steam line area where steam and water pressures are balanced; and their effective length is assessed. The temperature distribution along the thickness of the steam pipeline in the steam and water transition part was calculated for the periodic water whipping of the area. It has been demonstrated that, depending on the time of the steam and water oscillation period, the radial temperature distribution along the tube thickness has a significant difference in the distribution under normal temperature on the outer surface of the tube. However, the maximum temperature difference is in the inner surface of the tube. The distribution of mechanical stresses arising in the tube metal is characterized by a linear dependence of stresses on temperature whose maximum value corresponds to the maximum temperature difference characteristic of the area of the inner surface of the tube. This allows us to conclude that the crack formation starts in the inner surface of the SG tube in the specified transitional area of the tube.
- Subjects
STEAM generators; WATER cooled reactors; NUCLEAR power plants; MICROCRACKS; STRAINS &; stresses (Mechanics); TEMPERATURE distribution; SURFACE area
- Publication
Physics of Atomic Nuclei, 2023, Vol 86, Issue 12, p2592
- ISSN
1063-7788
- Publication type
Article
- DOI
10.1134/S1063778823120025