Predictions of Pulse-Echo Ultrasonic Signals From Inner Wall Cracks in BWR Nozzles

A. Minachi

R.B. Thompson

Volume: 14A Page Numbers: 139-146

Abstract:

To inspect BWR nozzles in nuclear power plants, ultraound is often used. These nozzles, which connect the piping to the pressure vessel of nuclear reactors, are inspected periodically for detection of cracks appearing around the inner wall of the nozzles. The curvature of these components can greatly influence the waves propagating through them. Thus, any beam model which predicts the propagation of ultrasonic waves through the exterior surfaces must consider their curvatures. An approximate Gaussian beam model has already been developed to simulate the propagation through curved surfaces. In its initial form, this model could only be used for propagation through curved interfaces with incident angles in the local plane of the symmetry of the interface. (By local plane of symmetry, we mean the symmetry of a Taylor series representation of the surfaces in a local coordinate system centered about the point of entry of the central ray.) However, the probe orientations used in practical inspections do not necessarily satisfy these constraints. Last year, we reported on the development of a model which predicts the propagation of Gaussian beam with incident angles out of this plane of local symmetry. Also, the effect of the curvature on the amplitude and phase of the Gaussian beam was discussed. This year we will report on the further development of the model and its use to predict of a pulse-echo response from an embedded crack, observed through such surfaces.--This work is supported by the Electric Power Research Institute.

References:

1. A. Minachi and R. B. Thompson. "Propagation of Gaussian Beam Through a Curved Interface for Planes of Incidence not Containing a Principle Radius of Curvature." Review of Progress in Ouantitative Nondestructive Evaluation, Vol. 13,1993.

2. J. W. Goodman. Introduction to Fourier Optics. New York: McGraw-Hill, 1968.

3. B. A. Auld. "General Electromechanical Reciprocity Relations Applied to the Calculation of Elastic Wave Scatering Coefficients." Wave Motion. Vol. 1 (1979):3-10.