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Surveillance of defects under cyclic loads by acoustic emission, UT and potential drop techniques. German HDR-program

: Brinette, R.; Deuster, G.

Italian Society for Nondestructive Testing Monitoring Diagnostics:
International Conference on Monitoring Surveillance and Predictive Maintenance of Plants and Structures. Proceedings
International Conference on Monitoring Surveillance and Predictive Maintenance of Plants and Structures <1989, Taormina>
Fraunhofer IZFP ()
Fehlernachweis; HDR; interpretation; Reaktordruckbehälter; Riß; Rißfeld; SAFT; Schallemission; stationäre Potentialsonde; Stutzenkante; Thermoschock

During cyclic thermal and mechanical loading NDT-techniques were applied in the cylindric pressure vessel wall. For the thermal shock test on nozzles and in the cylindric wall small initiating cracks could be indicated with the acoustic emission analysis in the cladding. It was possible to differentiate between crack growth and crack surface friction noise. The analysis of the temporal signal behaviour of AE-indications can be interpreted as corrosion dependent crack growth on the basis of fracture mechanical calculations. For online quantification of crack growth at some cracks stationary potential drop probes were applied. A resolution of crack growth of about 0,5 mm could be reached. The scattering of the measuring values is caused by temperature turbulences. In off-line-models the defect with the LSAFT procedure were analyzed. Also small defects in crack fields could be detected. Problems for the reconstruction are caused by shadowing effects and reflecting satellites in the defect area. The HDR safety program will be continued until 1991 with a third phase where the following focal points will be investigated: - containment behaviour under accident conditions, - longtime damage and surveillance of the components in operation, - behaviour of damaged components under accident conditions, - large burning of real components.