[en] For many years the CEA and Intercontrole, a subsidiary, have been using an in-service inspection machine (MIS) equipped with focused transducers for in-service inspection of PWR pressure vessels. At the end of 1979, subcladding defects were discovered inside inlet and outlet nozzles on French pressure vessels. French regulations required the inspection of all the nuclear plant reactor nozzles. A device called MIT (Nozzle inspection machine) was developed for detection and characterization of this type of defect. This paper describes the NDT method and the corresponding equipment