  Widely present in the primary circuit of Nuclear Power Plants (NPP),
Dissimilar Metal Welds (DMW) are inspected using Ultrasonic nondestructive
Testing (UT) techniques to ensure the integrity of the structure and detect
defects such as Stress Corrosion Cracking (SCC).In a previous collaborative
research, CRIEPI and CEA have worked on the understanding of the propagation of
ultrasonic waves in complex materials. Indeed, the ultrasonic propagation can
be disturbed due to the anisotropic and inhomogeneous properties of the medium
and the interpretation of inspection results can then be difficult. An
analytical model, based on a dynamic ray theory, developed by CEA-LIST and
implemented in the CIVA software had been used to predict the ultrasonic
propagation in a DMW. The model evaluates the ray trajectories, the travel-time
and the computation of the amplitude along the ray tube in a medium described
thanks to a continuously varying description of its physical properties. In
this study, the weld had been described by an analytical law of the
crystallographic orientation. The simulated results of the detection of
calibrated notches located in the buttering and the weld had been compared with
experimental data and had shown a good agreement.The new collaborative program
presented in this paper aims at detecting a real SCC defect located close to
the root of the DMW. Thus, simulations have been performed for a DMW described
with an analytical law and a smooth cartography of the crystallographic
orientation. Furthermore, advanced ultrasonic testing methods have been used to
inspect the specimen and detect the real SCC defect. Experimental and simulated
results of the mock-up inspection have been compared.
