Nondestructive flaw characterization has keen research interests throughout industry. The nuclear industry is no exception. Identifying the size, shape, orientation, type and position of material flaws in nuclear reactor pressure vessels has a top priority. Under a contract with the Electric Power Research Institute of Palo Alto, California, Battelle-Northwest is developing a demonstration model of a sequentially pulsed phased linear array system for ultrasonic inspection of reactor vessels. This program employs the linear array in both pulse echo and holographic modes and provides near real time images of the weld zone volume. The objectives of the program are to develop a rapid and accurate means for sizing subsurface defects in heavy section steel members. This article outlines the first six months effort on the two year program.