1,721,347 research outputs found
Changes in Physical-Chemical and Electrical Properties of Cross-Linked-Polyethylene-Insulated Cable Subjected to Radio-Thermal Aging and Simulation of Loss-of-Coolant Accident (LOCA)
No full textThis article investigates how aging treatments and simulated accident conditions affect the electrical and chemical integrity of low-voltage instrumentation and control cables in nuclear power plants
Post-irradiation effect investigation on low-voltage XLPE cables through dielectric spectroscopy
No full textElectrical aging markers for EPR-based low-voltage cable insulation wiring of nuclear power plants
No full textThis paper presents results of electrical property measurements on EPR-based insulations of low-voltage power cables used in nuclear power plants. The specimens underwent accelerated aging through the simultaneous application of high temperature and gamma-radiation. Mechanical properties and the dielectric response at different frequencies were investigated. Results showed significant variation of the electrical and mechanical properties of aged cables at low frequencies, i.e. lower than 10−2 Hz. In particular, the real and imaginary parts of permittivity increase with aging time, accumulated dose and stress levels applied showing good correlation with elongation at break, which decreases as a function of extent of insulation aging
About electrical and mechanical behaviour of low-voltage I&C cables used in nuclear power plants
Full text linkThis paper focuses on the electrical and mechanical properties of irradiated and thermally-stressed NPP cables used for instrumentation and control (I&C). These cables show some noteworthy changes after few years of uncontrolled environment conditions due to a phenomenon called post-irradiation effect. Strong post-irradiation effects, e.g. reduction of mechanical properties, raise of crosslinking and oxidation grade, were found on XLPE cable insulation years after irradiation. These degradation mechanisms can be correlated with electrical measurements in which imaginary permittivity values raise, in particular at low-frequencies where interfacial phenomena take place. This behavior can be linked to the increase of interfacial area between amorphous and crystalline region of polymer, supporting the evidence that post-irradiation effects can lead to polymer crosslinking during a storage period even at room temperature
Post-irradiation effect analysis on XLPE-insulated LV cables used in nuclear power plants
Full text linkThis paper investigates aging of low voltage cables used in nuclear power plants by the means of the dielectric spectroscopy technique. Aging has been performed on XLPE cables through high temperature and different dose rates in order to evaluate the electrical response under different aging conditions. Test have been carried out immediately after aging and years after the radiation source has been turned off. Significant changes in dielectric response have been observed due to postirradiation effects, suggesting that degradation continues even after the aging source has been removed
Electrical Analyses of Gamma Radiation-Induced Aging on EPDM-Based Insulation Systems
Full text linkThis paper deals with the investigation of the insulating
properties of EPDM materials subjected to radiation aging with two
non-destructive techniques: electrical (dielectric spectroscopy) and
chemical (FTIR). Flat samples of EPDM were subjected to
accelerated aging at 860 Gy/h for 664 h with four withdrawals at
room temperature. The dielectric spectroscopy results indicate that
the tan δ at 100 kHz coherently follows the aging evolution of the
materials and it is suggested to be a suitable aging marker. The
spectra of FTIR results suggest that EPDM undergoes chain scission
and oxidation after radiation ageing. These results confirm the
suitability of the electrical nondestructive technique for aging
evaluation
Nanodielectrics: examples of preparation and microstructure
No full textWhen investigating the dielectric properties of nanodielectrics the synthesis and processing of the material are often neglected. It seems intuitive to think that the physical properties of the constituent parts of an insulation material directly lead to the physical properties of a composite material. However, as has been shown in literature, nanodielectrics are more than just the sum of their parts [1]. Compounding of dielectric nanocomposites is a complex endeavor and it seems that nanodielectrics can only unleash their full potential when the filler material is distributed evenly throughout the host material. This article gives an overview of common preparation methods and discusses the influence of the preparation method on the microstructure
Aging assessment of insulating materials through broadband dielectric measurements: the appropriate frequency choice
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