[en] With the long term operation of nuclear power plants, decisions to replace or repair should be optimized from an economical, human resource and safety point of view. In that frame, the operation requires a continuous inspection and testing of systems in order to detect degradations and failures at an early stage. Nevertheless, in spite of the fact that such assiduous vigilance ensures safety, it is not optimized in terms of man power and maintenance costs. Preventive strategies show the same types of drawbacks. On top of that, these maintenance procedures rely on process measurements which accuracy, availability and reliability cannot always be ensured. The present paper introduces a new approach to the maintenance management of ageing installations and suggests a method that overcomes the actual drawbacks. The Reconciliation and Validation of data (DVR) is an advanced and innovative technology that relies on process data statistics, thermodynamic and on-site process knowledge. Benefits of real-time applications are also presented. (author)