[en] In contrast to conventional approaches used for diagnostics (i.e. when inspection results are used as data for numerical calculative strength analysis) the specific feature of the new proposed approach consists in a fact that the approach is based on application of the 'inverse problem' principle. As regards to implementation of the proposed new approach, first of all a detailed numerical calculative finite-element model of the monitored equipment must be developed. Results of preliminary calculations allow to make reasonable selection of definite installation places and types of control sensors intended for more effective and precise work of the calculative model. As a rule, the control sensors are high-temperature strain gauges, temperature probes, pressure, acceleration and displacement sensors, as well as acoustic-emission and ultrasonic sensors used for monitoring of actual defectiveness kinetics in the zone of potential damaging. All the sensors work in the on-line mode during several years of operation, the optimal frequency of data records is selected, all recorded data after prompt processing are transferred to the finite-element calculative modulus for strength calculations of a monitored zone. Software for strength calculation must be based on an individual calculative code, since it should also work in the on-line mode. Comprehensible strength analysis in conjunction with obtained results of defectiveness kinetics monitoring allow not only to foresee the most unfavorable scenario resulting to damaging, but also to have a possibility for prompt analysis and elaboration of compensating measures allowing to reduce operational loadings. In the report the results of development and practical application of the new approach at NPPs and corresponding technology are presented. (author)