Divider Plate Leak Inspections Using an Acoustic Tool ALIS

Abstract

Divider plate leakage in the primary head of steam generators may be a contributor to high Reactor Inlet Header Temperature (RIHT) which can have a negative effect on the operation of a plant. A method to provide quick information of divider plate leakage can be very useful in helping operators to make timely and cost effective repair and maintenance decisions. As part of a CANDU Owners Group (COG) funded program, a novel acoustic tool for performing inspections in empty steam generators during a shutdown has been developed and successfully demonstrated by Ontario Hydro Technologies (OHT). The basic principle of this technique utilizes sound transmission through the leakage paths of a divider plate assembly for creating a graphic image which reveals the locations and relative sizes of leaks. This is accomplished by injecting one side of the primary head with a series of airborne, ultrasonic sound bursts while scanning the divider plates from the opposite side and collecting transmitted sound pressure levels. Once a scan is completed the results are processed and displayed graphically as a color mapping of the entire divider plate assembly showing an image of the leakage locations and relative severity. The special transducers of the acoustic leak inspection system (ALIS) are installed through the manways of the steam generator at both sides of the primary head. These are clamped to the tube sheet and operated from a convenient remote location within the containment building. This process minimizes radiation exposure of the workers; as well, it reduces risk of contamination of the ALIS equipment. The current version of this tool performs the scans by remote manual control.