About Electrical and Mechanical Behaviour of Low-Voltage I&C Cables Used in Nuclear Power Plants

About Electrical and Mechanical Behaviour of Low-Voltage I&C Cables Used in Nuclear Power Plants

Simone V. SuraciDavide Fabiani Stefano Bulzaga 

Department of Electrical Engineering, University of Bologna, Bologna 40126, Italy

Corresponding Author Email: 
simone.suraci@unibo.it
Page: 
79-82
|
DOI: 
https://doi.org/10.18280/mmc_c.790303
Received: 
10 April 2018
| |
Accepted: 
14 May 2018
| | Citation

OPEN ACCESS

Abstract: 

This 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.

Keywords: 

low-voltage control cables, post-irradiation effect, degradation of polymers, nuclear power plants

1. Introduction
2. Experimental Setup
3. Experimental Results
4. Discussion
5. Conclusions
Acknowledgment

The research has been carried out thanks to the specimens provided within the FP7 EU project ADVANCE. The authors are grateful to Vit Placek of UJV Řež (Czech Republic) for specimen aging, Luca Verardi and Chiara Gualandi for helping with tests.

  References

[1] International Atomic Energy Agency. (2004). Management of life cycle and ageing at nuclear power plants - Improved I&C maintenance.

[2] International Atomic Energy Agency. (2012). Assessing and managing cable aging in nuclear power plants.

[3] Laboratories S. (2005). Nuclear energy plant optimization (NEPO) - Final report on aging and condition monitoring of low-voltage cable materials.

[4] Verardi L. (2014). Aging of nuclear power plant cables: in search of non-destructive diagnostic quantities. PhD Thesis, University of Bologna. 

[5] Verardi L, Fabiani D, Montanari GC. (2014). Correlation of electrical and mechanical properties in accelerated aging of LV nuclear power plant cables. IEEE ICHVE Poznan, Poland.

[6] Linde E, Verardi L, Fabiani D, Gedde UW. (2015). Dielectric spectroscopy as a condition monitoring technique for cable insulation based on crosslinked polyethylene. Polymer Testing.

[7] Wise J, Gillen KT, Clough RL. (1997). Quantitative model for the time development of diffusion-limited oxidation profiles. Polymer 38(8): 1929-1944.

[8] Suljovrujic E. (2013). Post-irradiation effects in polyethylenes irradiated under various atmospheres, Radiation Physics and Chemistry.

[9] IEC/IEEE 62582-3. (2012). Nuclear power plants – Instrumentation and control important to safety - Electrical equipment condition monitoring methods Part 3: Elongation at break.

[10] Nakamura S, Murabayashi F, Iida K, Sawa G, Ieda M. (1987). Degradation of dielectric properties of polyethylene by combined -irradiation and thermal stresses. IEEE Transactions on Electrical Insulation 22(6): 715-720.

[11] Fu M, Chen G, Dissado LA, Fothergill JC, Zou C. (2007). The effect of gamma irradiation on space charge behaviour and dielectric spectroscopy of low-density polyethylene. IEEE Conference Winchester, UK.