Ultrasonic simulation tools have been developed and integrated in the multi-techniques plateform CIVA developed by the french Atomic Energy Commission (CEA), in order to conceive and to predict performances of different inspection techniques. The models rely on semi-analytical kernels and numerical integration, so as to take account of realistic configurations in terms of component (of arbitrary geometry and materials), probes (monolithic or phased arrays), and flaws (calibration reflectors or more complex shapes), with computation times allowing parametrical studies. These simulation modules allow both to predict the ultrasonic field radiated by the probe, and its interaction with a flaw inside the component, so that the inspection performances for a given flaw using according to a given technique, are fully determined. This paper presents some applications carried out in collaboration with the the french Institute for Radioprotection and Nuclear Safety (IRSN). The validity range of the models and their potential applications are presented, along with experimental validations over realistic inspection configurations.