The experience obtained from the in-service inspection of reactor pressure vessels (RPV) of Spanish nuclear power plants and the participation in several international programs, such as PISC, has shown the need for a performance demonstration, not only for the ultrasonic inspection techniques of RPV, but also for other ISI non-destructive techniques as in the case of eddy current inspection of steam generator tubing. Section XI of the ASME Code, which is applied in Spain for ISI, has incorporated recently the Appendix VIII for performance demonstration of ultrasonic inspection techniques. As a direct consequence of this, a Spanish project for performance demonstration of ultrasonic inspection techniques has been launched recently, which includes the manufacturing of full-scale mock-ups of nozzle to vessel welds, reactor vessel welds, wrought austenitic piping welds and ferritic piping welds of PWR and BWR nuclear power plants from different suppliers. This considerable technical effort will let the different Spanish organizations which are part of the project to participate and colaborate with similar international projects and in particular with a European initiative for performance demonstration.