An industrial ultrasonic inspection system is capable of scanning for discontinuities in relatively thick solid objects such as solid core steel alloy turbine shafts. A phased array probe located on the turbine shaft periphery transmits ultrasonic pulses in a sector-shaped scanning field within the shaft that includes the inner 50% core volume that is of special interest in non-destructive evaluation and inspection. Staggered pulse firing alone or in combination with variable pulse repetition frequency (PRF) may be utilized in order to balance image quality with inspection speed. Discontinuities are identified by analysis of reflected echo waveform energy. Discontinuity size and position within the inspected object is correlated with an equivalent reflector size (ERS) by the Distance-Gain-Size (DGS) method.