Remote Inspection of a High Level Radioactive Waste Storage Tank for Cracking, Thinning, and Pitting

Abstract

Several of the high level radioactive waste storage tanks at the Savannah River Site (SRS) have been in service nearly 50 years. Periodic visual and ultrasonic (UT) nondestructive examinations (NDE) have been performed on the tanks to monitor the effects of service. These inspections revealed that several of the older tanks had suffered cracking as detected by through-wall visual indications. A new UT in-service inspection program has been recently established to provide for detection and characterization of cracking, thinning, or pitting of the sidewalls of the waste tanks. The program specifies examination of regions of the tank that would be most susceptible to corrosion attack, and to characterize the flaws and demonstrate acceptance to protect against potential leakage and instability. This paper summarizes the implementation of the program and inspection results for a tank that has been in service for over 40 years. No indications of reportable wall loss or pitting were detected. All thickness readings were above minimum design thickness. Several small indications of thinning were detected. The crack detection and sizing examinations detected five previously undetected indications, four of which were only partially through wall. The lengths of cracks that were examined are slightly longer than expected, but well below instability lengths.