주증기계통 오리피스 후단 소구경 배관의 감육 및 누설 발생
Cause Analysis for the Wall Thinning and Leakage of a Small Bore Piping Downstream of an Orifice
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참고문헌
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초록
A number of components installed in the secondary system of nuclear power plants are exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), Cavitation, Flashing, and LDIE (Liquid Droplet Impingement Erosion). Those aging mechanisms can lead to thinning of the components. In April 2013,one (1) inch small bore piping branched from the main steam line experienced leakage resulting from wall thinning in a 1,000 MWe Korean PWR nuclear power plant. During the normal operation, extracted steam from the main steam line goes to condenser through the small bore piping. The leak occurred in the downstream of an orifice. A control valve with vertical flow path was placed on in front of the orifice. This paper deals with UT (Ultrasonic Test) thickness data, SEM images, and numerical simulation results in order to analyze the extent of damage and the cause of leakage in the small bore piping. As a result, it is concluded that the main cause of the small bore pipe wall thinning is liquid droplet impingement erosion. Moreover,it is observed that the leak occurred at the reattachment point of the vortex flow in the downstream side of the orifice.
Abstract
A number of components installed in the secondary system of nuclear power plants are exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), Cavitation, Flashing, and LDIE (Liquid Droplet Impingement Erosion). Those aging mechanisms can lead to thinning of the components. In April 2013,one (1) inch small bore piping branched from the main steam line experienced leakage resulting from wall thinning in a 1,000 MWe Korean PWR nuclear power plant. During the normal operation, extracted steam from the main steam line goes to condenser through the small bore piping. The leak occurred in the downstream of an orifice. A control valve with vertical flow path was placed on in front of the orifice. This paper deals with UT (Ultrasonic Test) thickness data, SEM images, and numerical simulation results in order to analyze the extent of damage and the cause of leakage in the small bore piping. As a result, it is concluded that the main cause of the small bore pipe wall thinning is liquid droplet impingement erosion. Moreover,it is observed that the leak occurred at the reattachment point of the vortex flow in the downstream side of the orifice.
참고문헌 (7)
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- R. Morita, "Development of a Wall Thinning Rate Model for Liquid Droplet Impingement Erosion", ASME, PVP2012-78443, ~ (2012)
- J. H. Brunton, "Erosion of Solid Surfaces by the Impact of Liquid Drops, Erosion–Treatise on Materials Science and Technology, 16" (1979), Academic Press