Application of Non-Destructive Condition Monitoring Techniques on Irradiated Low Voltage Unshielded Nuclear Power Cables

Abstract

In this paper, the effect of radiation stress on the overall degradation of jacket and insulation of low voltage unshielded power cable used in nuclear power plants is discussed. The XLPE insulated and CSPE jacketed cable samples were exposed to a total dose of 400 kGy γ-irradiation with 0.5 kGy/h dose-rate. Dielectric spectroscopy; complex permittivity, and extended voltage response; namely slopes of decay and return voltages were used to study the effect of the irradiation on the cable with an aim to establish the application of these techniques for a non-destructive condition monitoring of the unshielded cables. Shore D hardness was also used to investigate the mechanical characteristic of the cable. It was observed that the radiation stress affected the electrical and mechanical properties of the cable polymeric components i.e. insulation and jacket. The imaginary part of permittivity at low frequency; 100 Hz, the slope of return voltage, and hardness showed a significant increase with absorbed dose showing the effect of irradiation on the jacket and insulating material, as well. A strong correlation was observed between the imaginary part of permittivity at 100 Hz, slopes of return voltage, and hardness. The results show the dielectric measurement techniques are potential non-destructive condition monitoring methods for the unshielded low voltage nuclear power plant power cables for on-site diagnosis.

Electrical and Mechanical Condition Assessment of Low Voltage Unshielded Nuclear Power Cables Under Simultaneous Thermal and Mechanical Stresses: Application of Non-Destructive Test Techniques

“…The VR technique is successfully applied for condition monitoring of PVC insulated NPP cables [40]. This research was focused on the advanced version of the VR method called Extended Voltage Response (EVR) [26], [39].…”

“…Also, dielectric response has been introduced as a reliable and applicable NDCM technique to assess various insulation systems including EPR, XLPE, and CSPE materials, as well [21]. In [26], the dielectric spectroscopy measurement combined with Shore D hardness was a very auspicious tool in the detection of radiation ageing. Other test techniques were mentioned by the International Atomic Energy Agency (IAEA) report [27].…”

Aging Mechanisms and Non-Destructive Aging Indicators of XLPE/CSPE Unshielded LV Nuclear Power Cables Subjected to Simultaneous Radiation-Mechanical Aging

“…The predominant cable types used in the NPPs are LV power cables and I&C cables since a typical NPP may compose about 1500 km of LV cables [5,8]. NPP LV cables are exposed to harsh conditions during their operation, and they are exposed to different stresses, as illustrated in Figure 1 [9,10]. However, recent studies suggest that heavy metal perovskite materials that absorb high-energy rays can be used to absorb potential hazards [11,12].…”

“…However, the EaB test is naturally destructive, and it requires samples removal; thus, it is not practical for on-site testing [2,5,10,26]. Therefore, non-destructive electrical-based condition monitoring techniques have been the focus of scientific interest, such as dielectric spectroscopy, return voltage measurement, and the polarization-depolarization current method [8][9][10]14,15,19,20,[26][27][28][29][30]. These techniques have been successfully adapted to various insulation systems [2,5,26,30].…”

“…However, the EaB measurement is a commonly used method to determine the degradation of polymers [ 24 , 25 ]. However, the EaB test is naturally destructive, and it requires samples removal; thus, it is not practical for on-site testing [ 2 , 5 , 10 , 26 ]. Therefore, non-destructive electrical-based condition monitoring techniques have been the focus of scientific interest, such as dielectric spectroscopy, return voltage measurement, and the polarization-depolarization current method [ 8 , 9 , 10 , 14 , 15 , 19 , 20 , 26 , 27 , 28 , 29 , 30 ].…”