Reactor vessel in-service inspection assembly and ultrasonic centering device

An improved reactor vessel in-service inspection assembly having an inspection transducer positioning arm wherein the improvement comprises means for locating the positioning arm at a pre-established location within a hollow portion of the reactor vessel cavity wherein the locating means includes:

• means affixed to the positioning arm for generating and simultaneously, radially, directing acoustic signals around the circumference of the hollow portion of the vessel cavity and receiving the signals reflected off of the cavity walls and redirected to the location from which the signals were originally, radially directed, at a position within the hollow portion wherein the generating and receiving means comprises an acoustic transducer and reflector wherein the reflector is constructed to radially direct the acoustic signals generated by the transducer to the walls of the hollow portion of the reactor vessel cavity and redirect the acoustic energy reflected off the cavity walls back to the reflector to the transducer;
• means for monitoring the received signals as a function of time;
• and
• means for positioning the arm in response to the monitored difference in time of reception of the received signals, at the pre-established location within the hollow portion of the reactor vessel cavity.