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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.
이태현(Taehyun Lee),윤재영(Jae Young Yoon),류경하(KyungHa Ryu),박종원(Jong Won Park) 한국신뢰성학회 2018 신뢰성응용연구 Vol.18 No.3
Purpose: Probabilistic safety analysis was performed to enhance the safety and reliability of nuclear power plants because traditional deterministic approach has limitations in predicting the risk of failure by crack growth. The study introduces a probabilistic approach to establish a basis for probabilistic safety assessment of passive components. Methods: For probabilistic modeling of fatigue crack growth rate (FCGR), various FCGR tests were performed either under constant load amplitude or constant ΔK conditions by using heat treated X-750 at low temperature with adequate cathodic polarization. Bayesian inference was employed to update uncertainties of the FCGR model using additional information obtained from constant ΔK tests. Results: Four steps of Bayesian parameter updating were performed using constant ΔK test results. The standard deviation of the final posterior distribution was decreased by a factor of 10 comparing with that of the prior distribution. Conclusion: The method for developing a probabilistic crack growth model has been designed and demonstrated, in the paper. Alloy X-750 has been used for corrosion fatigue crack growth experiments and modeling. The uncertainties of parameters in the FCGR model were successfully reduced using the Bayesian inference whenever the updating was performed.
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.