Stress identification in steam generator tubes from profile measurements Original Research Article

An identification method devoted to the determination of stresses in tubes, by means of profile measurements, available from on site non-destructive evaluations, is presented here. From the only furnished data (the radial displacement component w on the inner wall), the computation of the strain, and consequently the stresses in the elastic-plastic range, is made within the framework of the shell theory. For this purpose, we need to determine the associated curvature w″: this step is an ill-posed problem because of the lack of continuity with respect to the discrete data. This difficulty is overridden by means of an appropriate regularization procedure. The predictive ability of the method has been tested by comparison with direct simulations; we present an industrial application. This diagnosis tool has been applied successfully to PWR steam generator tubes (in the roll expansion transition zone) and vessel closure head penetrations.