Condition Monitoring and Reliability Prediction of I&amp;C Cables for Use in Probabilistic Safety Assessment of NPPs

T V Santhosh,A K Ghosh,V Gopika,B G Fernandes,J Chattopadhyay

doi:10.1007/978-981-15-3643-4_37

Condition Monitoring and Reliability Prediction of I&C Cables for Use in Probabilistic Safety Assessment of NPPs

T V Santhosh, A K Ghosh + Show 3 more

https://doi.org/10.1007/978-981-15-3643-4_37

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AbstractElectrical cables are one of the most important components of instrumentation and control (I&C) systems in nuclear power plants (NPPs) for safe and reliable operation. The polymeric materials used for insulation and sheath in I&C cables are subjected to degradation due to deteriorative stressors present in NPPs. Although there are many remaining useful life estimations and condition monitoring (CM) techniques available in the literature, a well-established approach for incorporating the cable ageing into probabilistic safety assessment (PSA) is not available. In this paper, an integrated approach has been presented for determining the time-dependent reliability of I&C cables from the performance assessment techniques and Weibull distribution. The accelerated radiation and thermal ageing experiment have been carried out on low voltage I&C cable insulation materials and the performance degradation has been assessed by various CM approaches. The studies have been carried out to establish the correlation amongst various techniques such as oxidation induction time (OIT) or oxidation onset temperature (OOT) measurements using differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FTIR) and elongation-at-break (EAB) measurements. It was also evident from the positron annihilation lifetime spectroscopy (PALS) that a large variation in the size of free volume holes exists in the samples subjected to gamma radiation. Also, the micrographs from the scanning electron microscopy (SEM) support the performance degradation predicted from other techniques. The estimated time-dependent reliabilities are used in reliability analysis of safety and control systems of NPPs in order to account for the cable failures in PSA.KeywordsInsulation resistanceOxidation induction timeOxidation onset temperatureElongation-at-breakScanning electron microscopyFourier transform infrared spectroscopyPositron annihilation lifetime spectroscopyProbabilistic safety assessmentTime-dependent reliabilityNuclear power plants

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