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Ryu, Kyungha,Lee, Taehyun,Baek, Dong-cheon,Park, Jong-won Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.4
The accelerated corrosion by Flow Accelerated Corrosion (FAC) has caused unexpected rupture of piping, hindering the safety of nuclear power plants (NPPs) and sometimes causing personal injury. For the safety, it may be necessary to select some pipes in terms of condition monitoring and to measure the change in thickness of pipes in real time. Direct current potential drop (DCPD) method has advantages in on-line monitoring of pipe wall thinning. However, it has a disadvantage in that it is difficult to quantify thinning due to various thinning shapes and thus there is a limitation in application. The machine learning approach has advantages in that it can be easily applied because the machine can learn the signals of various thinning shapes and can identify the thinning using these. In this paper, finite element analysis (FEA) was performed by applying direct current to a carbon steel pipe and measuring the potential drop. The fundamental machine learning was carried out and the piping thinning model was developed. In this process, the features of DCPD to thinning were proposed.
송인영(Inyoung Song),이태현(Taehyun Lee),류경하(Kyungha Ryu),김지현(Ji Hyun Kim) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
Polymeric materials are widely used in several equipment of nuclear power plants (NPPs), such as seal in valve and cable, etc. However, these polymeric materials are relatively vulnerable in radiation from normal operation condition and accident environment of NPP. Therefore, in this study, gamma irradiation tests using 60CO source were performed to investigate the degradation behavior of EPDM, FKM, and NBR. Mechanical and thermal degradation caused by gamma irradiation were measured by shore A hardness, tensile test, and thermogravimetric analysis (TGA). And molecular structure analysis was conducted through Fourier transformed infrared (FT-IR) spectroscopy. FT-IR analysis results showed that C=O and C-O bonds were increased with increasing of gamma radiation dose. Because of unstable molecular structure generated by reaction between free radicals and scissioned molecular and oxidized chemical bonds, polymeric materials were hardened and decrease of thermal stability as increasing gamma radiation dose.
원자력발전소 중대사고 환경에서의 고분자소재의 열화거동 평가
송인영(Inyoung Song),이태현(Taehyun Lee),류경하(Kyungha Ryu),김상교(Sangkyo Kim),김지현(Ji Hyun Kim) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
In this study, the effects of heat and radiation on degradation behavior of fluoroelastomer were investigated. Irradiation and thermal degradation under normal operating condition and severe accident environment were simulated by sequential test. To evaluate the degradation behavior, measurement of mechanical properties, fourier transformed infrared (FT-IR) analysis and thermogravimetric analysis were performed. The hardness of fluoroelastomer increased significantly after the irradiation under severe accident environment than heat. And FT-IR analysis shows that C-O and C=O increased after the irradiation. The free radical generated by break of the molecules due to radiation react with oxygen in the air and form crosslinks with other molecules, resulting in hardening.