Abstract
Low-voltage cable systems in nuclear power plants are key components that have a crucial role in the safe operation of nuclear facilities. Thus, the aging management of cable systems is of utmost importance as they cannot easily or economically be replaced or upgraded. Therefore, there is a continuous need to develop reliable non-destructive condition monitoring techniques, mostly based on the measurement of the dielectric properties of cable insulation. This paper introduces the changing of dielectric and mechanical properties of XLPE insulated and CSPE jacketed unshielded low-voltage nuclear power plant power cable in case of simultaneous mechanical and radiation aging. The cable samples were bent and exposed to 400 kGy gamma irradiation with a 0.5 kGy/hr dose rate. Dielectric response (real and imaginary permittivity) in the 0.1 Hz−1 kHz frequency range, extended voltage response (EVR), and the Shore D hardness test techniques were measured to track aging. The electrical and mechanical parameters have increased monotonically with aging, except the imaginary permittivity, which increased only at frequencies higher than 10 Hz. Furthermore, different quantities were deducted based on the frequency and permittivity data. The electrical parameters and deducted quantities correlation with aging and mechanical parameters were investigated. Since the deducted quantities and the electrical parameters are strongly correlated with absorbed dose and mechanical properties, the electrical measurements can be applied as a non-destructive aging indicator for XLPE/CSPE unshielded low-voltage nuclear power cables.
Highlights
Most of the current fleet of nuclear power plants (NPPs) have reached the end or working beyond their initial qualification license to operate for 40 years [1,2]
For the safe and reliable operation of an NPP, it is essential to demonstrate that all the plant safety-related elements can fulfill their intended functions under both the normal operation and postulated events such as loss of coolant accident (LOCA) [4,5]
The voltage response (VR) technique was presented by Endre Németh in the 1960s [33]
Summary
Most of the current fleet of nuclear power plants (NPPs) have reached the end or working beyond their initial qualification license to operate for 40 years [1,2]. The majority of the NPPs have been granted a license renewal to operate for an additional period of 20 years [3]. Regulators and plant operators are considering extending the operating license to 80 years [1]. For the safe and reliable operation of an NPP, it is essential to demonstrate that all the plant safety-related elements can fulfill their intended functions under both the normal operation and postulated events such as loss of coolant accident (LOCA) [4,5]. Age-related degradation of NPP components has received more attention from regulators. Intensive research work has been done at the national and international level involving governmental, industrial, and academic research laboratories [1,6,7]
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