Safe operations of nuclear power plants (NPP's), their lifetime extension beyond 40 years as well as new designs require better knowledge on material and equipment ageing. Electrical cables located inside as well as outside the containment building are critical components due to their amount and highly complicated replacement. These cables have to maintain required electrical and mechanical properties during their entire life not only during normal operation but also during accidents. Managing the ageing of installed cable requires new approaches on testing and condition monitoring techniques with proven capabilities. Estimating the actual cable condition and assessing its residual life time require a good ageing model and appropriate end-point criteria. The paper summarizes the research effort and main gaps in the area of NPP cables for reliable life time prediction. The main activities are focused on following topics: - Assess the actual cable condition at NPP. - Define appropriate end-point criteria. - Find a reliable ageing model for life time prediction. - Perform reliable qualification. - Simulate design basis events and design extension conditions (includes severe accidents). - Investigate the influence of polymer additives on cable ageing. All these issues are complicated by the fact, that cable insulation material is not a pure polymer. It always contains a lot of other additives, like stabilizer, filler, fire retardants, pigments, etc. Any small variation of their concentration or manufacturing process may influence the ageing very much. Moreover, typical problems for old cables are variations between polymer batches which result in variation of properties along the cable. All these facts make the study of the cable ageing and assessment of the residual cable life time at NPP quite difficu especially if you are mostly not allowed to remove samples for laboratory testing.
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