[en] Due to the high combined stress caused by thermal and rotational loading, the highest stress in the hollow rotor forging of typical nuclear power steam turbine and generator units is in the region at or near the bore. Material discontinuities aligned along the axis of the rotor centerline, with depth in the radial plane of the rotor, have the highest probability of becoming flaws of concern to the integrity of the rotor. Due to the nature of the casting/forging process a great number of material discontinuities can be found near the rotor bore. During the ultrasonic examination of rotors with a large number of discontinuities, the engineer must determine if these discontinuities are ultrasonic reflectors caused by fabrication anomalies, reflectors that are probably fabrication discontinuities but in such close proximity that they may link up and form a defect of concern to future operation, or reflectors that have significant size and are real growing flaws, but may appear as separated indications. Until recently, plotting of ultrasonic data to determine the significance of closely spaced indications was time consuming and required special 3-D analysis methods to determine if indications were isolated or linked to form larger discontinuities. To overcome this problem, a software program, compatible with portable personal computers, was written to define a parameter necessary for determining if a group of indications detected from nondestructive ultrasonic testing of turbine and generator rotors could combine to form larger ones. The approach involved using a computer algorithm to model each indication as a three dimensional sphere with a diameter equal to the ultrasonic signal amplitude from an equivalent flat bottom hole reflector and setting a minimum gap distance between spheres necessary for a link up. The program was implemented following a commonly used data format accepted by industry recognized computer codes. The gap distance and link up parameters were developed empirically. In addition, these parameters can be optimized further by taking into account other factors such as metal composition, stress level and location with respect to the bore surface. Once the discontinuity is defined in three dimensions it can be used with a number of commercially available computer codes (SAFER, etc.) to determine remaining life of the rotor and the number of safe stop/start cycles until the next required inspection. (author)