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New Advances in Damage Analysis and Lifetime Prediction of Electrical Cables in Nuclear Power Plants

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "B4: Nuclear Energy".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 11755

Special Issue Editors


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Guest Editor
LIMES–Department of Electrical, Electronic and Information Engineering–University of Bologna, 40136 Bologna, Italy
Interests: polymers; electrical insulation; nuclear low voltage cables
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
PIMM, Arts et Métiers Institute of Technology, CNRS, CNAM, HESAM University, 151 Boulevard de l’Hôpital, 75013 Paris, France
Interests: organic matrix composites; polymers; ageing and durability; kinetic analysis and modeling; embrittlement; lifetime prediction
Special Issues, Collections and Topics in MDPI journals

E-Mail Website
Guest Editor
LIMES, Department of Electrical, Electronic and Information Engineering, University of Bologna, Bologna, Italy
Interests: electrical technologies; nanomaterials; diagnosis of electrical apparatus; electrospinning
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Electrical cables are one of the most important pieces of equipment in terms of both abundance and role inside nuclear power plants (NPPs). It has been estimated that each NPP owns about 1500 km of cables, mainly used for delivering power, control, and measurement signals. Assessing the reliability of these cables is an extremely critical issue for the validation of the possible life extension of NPPs. As is already known, cable health status is strictly related to the condition of the primary insulation, usually made up of polymer-based compounds. In nuclear environments, these latter ones are typically subjected to both thermal and radiochemical aging, which significantly accelerates the degradation of the organic matrix.

This Special Issue aims to give an overview on the most recent advances in damage analysis and lifetime prediction of cables used in nuclear power plants. Selected contributions are invited to provide reviews and analyses of the main polymer degradation mechanisms and their effects on material reliability and properties at various scales (from physical–chemical to mechanical and electrical material behavior). Potential topics include but are not limited to:

  • Multiscale analyses of degradation and aging mechanisms inside electrical cables;
  • Lab-scale techniques for cable aging assessment;
  • Development of non-destructive testing techniques for monitoring the health of cables on site;
  • Lifetime prediction and reliability of cables under radiothermal stresses.

Dr. Simone Vincenzo Suraci
Prof. Dr. Davide Fabiani
Prof. Dr. Xavier Colin
Guest Editors

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Keywords

  • cables
  • nuclear cables
  • aging
  • aging modeling
  • low-voltage cables
  • I&C cables

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Published Papers (6 papers)

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Research

16 pages, 8370 KiB  
Article
Implementation of Non-Destructive Condition Monitoring Techniques on Low-Voltage Nuclear Cables: II. Thermal Aging of EPR/CSPE Cables
by Ehtasham Mustafa, Ramy S. A. Afia, Aamir Nawaz, Oumaima Nouini and Zoltán Ádám Tamus
Energies 2022, 15(9), 3231; https://doi.org/10.3390/en15093231 - 28 Apr 2022
Cited by 7 | Viewed by 1666
Abstract
Determining the aging state of low-voltage nuclear power plant cables using a nondestructive and reliable condition monitoring technique is highly desirable as the cables experience multiple aging stresses during the service period. This paper deals with the implementation and investigation of such nondestructive [...] Read more.
Determining the aging state of low-voltage nuclear power plant cables using a nondestructive and reliable condition monitoring technique is highly desirable as the cables experience multiple aging stresses during the service period. This paper deals with the implementation and investigation of such nondestructive techniques, which can detect the overall aging state of low-voltage instrumentation and control (I&C) cables, which are subjected to accelerated thermal aging. The dielectric spectroscopy, extended voltage response, and polarization–depolarization current as nondestructive electrical aging techniques were used for the investigation purpose, while the elongation at break was also adopted as a mechanical measurement and for comparison. Prominent variations in the electrical parameters for the insulation and jacket were observed, whereas the elongation at break for both materials also decreased under thermal aging. Based on the electrical techniques, aging markers were selected that showed a strong correlation with the aging and elongation at break, proving the ability of the adopted electrical methods as a nondestructive condition monitoring technique. Full article
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13 pages, 2366 KiB  
Article
Radio-Oxidation of Electric Cabled Models: Ageing Evaluation at the Atomic Scale
by Muriel Ferry and Frederic Miserque
Energies 2022, 15(5), 1631; https://doi.org/10.3390/en15051631 - 22 Feb 2022
Cited by 3 | Viewed by 1431
Abstract
The functionality of electric cables, being the safety components of plants, has to be ensured. In nuclear power plants, when they are in the reactor building, these cables can suffer γ irradiation even in normal operating conditions. Their ageing behaviour needs to be [...] Read more.
The functionality of electric cables, being the safety components of plants, has to be ensured. In nuclear power plants, when they are in the reactor building, these cables can suffer γ irradiation even in normal operating conditions. Their ageing behaviour needs to be well understood to be able to determine a precise end-of-life criterion. As polymers are the most radiosensitive material of the cables, this paper focuses on the ageing of this kind of material and, more specifically, on the ageing of silane-crosslinked polyethylenes (XLPEs). XLPEs are now one of the most employed polymers to manufacture cables. We performed irradiation under oxidative conditions of several model silane-crosslinked polyethylenes with different additives and filler: at three different doses (0, 67, 220 and 374 kGy) for one dose rate (78 Gy·h−1) and at one dose (67 kGy) for three dose rates (8.5, 78 and 400 Gy·h−1). Modifications in the organic materials were followed by X-ray photoelectron spectroscopy. This analytical technique allows following the evolution of the different chemical products formed under irradiation. A better understanding at the atomic scale of the effect of additives on the degradation of polymers is proposed as a function of the ageing conditions. Full article
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15 pages, 3889 KiB  
Article
Dielectric Spectroscopy as a Condition Monitoring Technique for Low-Voltage Cables: Onsite Aging Assessment and Sensitivity Analyses
by Simone Vincenzo Suraci, Chuanyang Li and Davide Fabiani
Energies 2022, 15(4), 1509; https://doi.org/10.3390/en15041509 - 17 Feb 2022
Cited by 7 | Viewed by 2068
Abstract
This work presents the development, validation, and sensitivity analyses of a portable device capable of performing high-frequency dielectric spectroscopy tests on site. After a brief introduction on the operation principle and the description of the impact of frequency on dielectric spectroscopy, the article [...] Read more.
This work presents the development, validation, and sensitivity analyses of a portable device capable of performing high-frequency dielectric spectroscopy tests on site. After a brief introduction on the operation principle and the description of the impact of frequency on dielectric spectroscopy, the article presents the results of tests on reference samples confirming good agreement with expected values. The frequency region in which the device operates, 1–200 kHz, was chosen because of its correlation with oxidative species of polymeric compound. The sensitivity analyses were performed measuring the dielectric response of low voltage cables with different aged lengths. The outcome of these tests is twofold. On the one hand, they confirm the suitability of the technique for aging evaluation, and, on the other hand, they allow the assessment of the minimum aged length (damage ratio) which causes appreciable variations on the obtained dielectric spectrum. This quantity was found to be ~35% of the total cable length. Full article
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10 pages, 1796 KiB  
Article
Influence of Optic Cable Construction Parts on Recovery Process after Gamma Irradiation
by Zuzana Šaršounová, Vít Plaček, Václav Prajzler, Kateřina Masopustová and Petr Havránek
Energies 2022, 15(2), 599; https://doi.org/10.3390/en15020599 - 14 Jan 2022
Cited by 3 | Viewed by 1625
Abstract
Fibre optic cables are widely used as communication cables in Instrumentation and Control (I&C) systems. In the case of nuclear power plants (NPPs), using optic cables in mild environments outside of containment areas are very common. However, at present, there is a need [...] Read more.
Fibre optic cables are widely used as communication cables in Instrumentation and Control (I&C) systems. In the case of nuclear power plants (NPPs), using optic cables in mild environments outside of containment areas are very common. However, at present, there is a need for fibre optic cables to be used in containment areas, i.e., with radiation. An optical fibre consists of a highly transparent core that possesses a higher refractive index than the surrounding transparent cladding, which possesses a lower refractive index. Most optical fibres are manufactured from glass (silica with required dopants) which is created at high temperatures from the reaction between gasses. The glass used in optical fibres is sensitive; it becomes dark during exposure to radiation, which compromises the optic functions. That is why there has been a slow infiltration of optic cable in NPP containment areas. Radiation resistant optic fibres have been developed. Although these fibres are called “radiation resistant,” they go through a darkening process (absorbance increase) as well, but not as quickly. Immediately after the irradiation has stopped, a recovery process starts in the glass structure. During this period, optical losses of the glass improve, but not to the original level as before the irradiation. During the testing of optic cables for the installation in nuclear power plant containment areas, we observed an unusual recovery process. In the beginning, a healing effect was observed. However, after a few days of recovery, the healing process stopped, and the trend changed again as a worsening of the optical properties was observed. This paper describes experiments which explain the reasons for such an unexpected behaviour. Full article
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15 pages, 4596 KiB  
Article
Degradation of Soft Epoxy Resin for Cable Penetrations Induced by Simulated Severe Accidents
by Yoshimichi Ohki, Hiroyuki Ishii and Naoshi Hirai
Energies 2021, 14(21), 6932; https://doi.org/10.3390/en14216932 - 21 Oct 2021
Cited by 18 | Viewed by 1782
Abstract
To obtain the knowledge that contributes to the safer operation of nuclear power plants and their prompt recovery and termination in the event of an accident, soft epoxy resins with rubber-based additives—used as insulators and airtight sealants in electrical penetrations in nuclear power [...] Read more.
To obtain the knowledge that contributes to the safer operation of nuclear power plants and their prompt recovery and termination in the event of an accident, soft epoxy resins with rubber-based additives—used as insulators and airtight sealants in electrical penetrations in nuclear power plants—were aged under several simulated severe accident environments with different conditions of heat, gamma rays, and exposure to superheated steam containing no oxygen. Then, changes in structural, dynamic mechanical, mechanical, and dielectric properties were examined. It has been found that this resin becomes hard as a result of cross-linking if aged by irradiation with gamma rays. Since the cross-linking slows down the molecular motions, the glass transition temperature increases, whereas the dielectric permittivity and the dielectric loss factor decrease unless the steam penetrates the sample. Although the sample melts and disappears if directly exposed to superheated steam at 171 °C or 200 °C, the irradiation with gamma rays conducted prior to the steam exposure can mitigate the hydrolysis induced by the steam. Although the soft epoxy resin shows drastic changes in various properties, its properties after the aging approach or exceed the corresponding ones of the non-degraded ordinary hard epoxy resin. Therefore, it seems that using soft epoxy resin according to its purposes would not be a problem. Full article
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16 pages, 5077 KiB  
Article
Implementation of Non-Destructive Electrical Condition Monitoring Techniques on Low-Voltage Nuclear Cables: I. Irradiation Aging of EPR/CSPE Cables
by Ehtasham Mustafa, Ramy S. A. Afia, Oumaima Nouini and Zoltán Ádám Tamus
Energies 2021, 14(16), 5139; https://doi.org/10.3390/en14165139 - 20 Aug 2021
Cited by 15 | Viewed by 2330
Abstract
In a nuclear power plant environment, low-voltage cables experience different stresses during their service life which challenge their integrity. A non-destructive and reliable condition monitoring technique is desired to determine the state of these low-voltage cables during service and for the life extension [...] Read more.
In a nuclear power plant environment, low-voltage cables experience different stresses during their service life which challenge their integrity. A non-destructive and reliable condition monitoring technique is desired to determine the state of these low-voltage cables during service and for the life extension of nuclear power plants. Hence, in this research work, an EPR/CSPE-based low-voltage cable was exposed to γ-rays for five different absorbed doses. The overall behavior of the cable under stress was characterized by frequency and time domain electrical measurements (capacitance, tan δ, and Extended Voltage Response) and a mechanical measurement (elongation at break). Significant variations in the electrical parameters were observed, as was a decline in the elongation at break values. A strong correlation between the measurement methods was observed, showing the ability of the electrical methods to be adopted as a non-destructive condition monitoring technique. Full article
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