원자력 발전소 감마선 환경에서의 EPDM 열화거동 평가

Abstract

This study evaluates the degradation behavior of ethylene propylene diene rubber (EPDM) under gamma irradiation in normal operating conditions and design basis accident conditions of nuclear power plants (NPPs). Polymeric materials used in nuclear power plants, such as cables and sealing materials, are known to be vulnerable to degradation when exposed to environmental factors such as radiation for normal operation and accident periods. The degradation of these polymeric materials can affect the functionality of safety-related equipment and components, resulting in an effect on the safety of NPPs. EPDM is used in safety-related equipment, such as insulation and jackets for cables, and the assessment of its radiation-induced degradation is imperative. To evaluate the degradation behavior of EPDM, gamma irradiation was performed at a total integrated dose (TID) of 200, 400, 800, 1200, 1600, and 2000 kGy with a dose rate of 9 kGy/hr in atmospheric air. EPDM was evaluated through hardness tests, thermogravimetric analysis (TGA), Fourier transformed infrared (FT-IR) spectroscopy, and element analysis (EA) to evaluate the materials properties under gamma irradiation. As the gamma irradiation dose increased, a hardening phenomenon was observed, characterized by an increase in hardness. The evaporation of additive such as oil was accelerated by gamma irradiation, resulting in to increasing of weight loss. The FT-IR spectrum analysis revealed the scission of EPDM polymer chains and the evaporation of additives, suggesting insights into the molecular degradation mechanism