[en] For the testing of nozzle areas in the bottom calotte of BWR pressure tanks as well as the cover of PWR pressure tanks, segmented ring-array probes were designed, produced as prototypes, electrically and acoustically measured and their capability to detect failures was experimentally tested. This probe was selected because it permits a three-dimensional control of the sound beam, which means that angle of squint and acoustic irradiation angle can be electronically varied independent from each other. Because the now available phased-array electronics has 24 channels, the tests started with a single ring, which is divided into 24 segments. The experiments showed, however, that despite the high amplification reserve of the probe, no sufficient failure detection was possible because of occurring dimensional data. Within the framework of re-development phase, the probe was modified: instead of a single ring, a double ring system was chosen, which is divided in 48 elements. The symmetry of the probe was used for the electrical connection of two individual oscillators. Thus, the sound beam can be electronically rotated; a change of the angle of squint is, for the present, only possible by mechanical movement. Experiments at the spherical bottom of the large container of the materials testing institute were carried out with this probe. The indications of most of the test reflectors, placed in the perforated zones, distinguished very clearly from the plating noise background and could be easily distinguished from the indications caused by the bore surfaces. A determination of the size of failures by detection of peak indications in form of sector-B images and compound-B images proved to be very problematic. (orig./HP)