ADVANCE

Ageing Diagnostics and Prognostics of low-voltage I&C cables

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 Obiettivo del progetto (Objective)

'The assessment of the condition of low-voltage instrumentation, control, and power cables in nuclear power plants is of increasing importance as plants age and lifetime extensions are envisaged. Furthermore as new reactors are being constructed and many other are planned for the near future, the initial cables choice and the use of effective in-situ condition monitoring (CM) techniques to follow cable condition indicators from the beginning, can result to be very valuable at a later time for an effective cable lifetime management. The overall objective of the proposed project is to adapt, optimise and assess electrical CM techniques for nuclear cables that would allow utilities to assess in-situ the current cable degradation condition and, together with the establishment of appropriate acceptance criteria, to verify its qualified state over its entire length and to estimate its residual lifetime. To this extent, the project will consist in studying with accelerated ageing tests a representative selection of cables already installed in European Nuclear Power Plants (NPPs) in order to evaluate the ability of electrical CM techniques to detect local and global cable ageing. The results will be compared and correlated to those obtained with more conventional CM techniques for validation and residual life estimation. These tests will be supported by the study of the impact of cable polymers ageing on the electrical properties. These studies will allow not only to guide the adaptation and the optimisation of existing CM techniques, but also to interpret the results of the electrical measurements, to extend the validity of the results to other similar cables and to adapt the future cable design and formulations to electrical CM techniques. This investigation on innovative cables for future plants could open the way to a new generation of “intelligent” cables with improved diagnostic capability.'

Introduzione (Teaser)

Low-voltage cables at nuclear power plants (NPPs) are critical to plant function both during normal operating conditions and during accident response. Using electrical condition monitoring (CM) systems for cables will enhance safety in case of extension of plant lifetime.

Descrizione progetto (Article)

In situ CM of low-voltage cables is becoming increasingly important as existing power plants age. In addition, degradation mechanisms and profiles will be important in planning lifetime extensions to existing plants as well as in selecting cable materials and configurations for new plants.

Although cables are an integral component of NPPs, the small number of European experts is spread throughout industry, utilities providers, research centres and universities. Scientists from many of these came together to study a representative set of cables in European NPPs and assess the performance of electrical CM techniques to characterize the ageing of cables in comparison with more conventional ones.

EU funding of the project 'Ageing diagnostics and prognostics of low-voltage I&C cables' (http://www.advance-fp7.eu/ (ADVANCE)) facilitated this programme, including studies and tests. It also supported a rigorous programme of mobility, education and training of young scientists.

Having selected six different cable types from an inventory of European NPPs, the team conducted two types of experiments. Short cables were aged and used to develop multi-stress models under various ageing conditions. Long cables were subjected to ageing tests tracked by various CM techniques.

Data suggest that dielectric spectroscopy is the most promising of the electrical CM techniques investigated. Further, the team concluded that the reflectometry techniques are best suited at the moment to local defect evolution rather than global ageing. Further experiments were proposed to improve measurement techniques and analysis. In parallel, the team developed a new cable design to facilitate online CM of NPP cables.

The ADVANCE project made an important contribution to the safety of existing and future NPPs through assessment of electrical CM techniques for low-voltage safety-related electrical cables. Criteria correlating physical, chemical and electrical properties to electrical condition will aid in predicting degradation and remaining service life. Extending the lifetime of NPPs is a priority of the global nuclear industry.