Application of Non-Destructive Testing to Assess Corrosion Damage in SAVY Containers

Stainless steel SAVY containers are widely used for long-term storage of nuclear materials. Recent surveillance activities completed have shown that these SAVY containers are prone to interior corrosion while in use due to a number of factors they encounter in the facility. There is a strong need to develop non-intrusive inspection techniques which can monitor these corrosion processes in-situ. Non-destructive testing (NDT) and procedures for assessing corrosion within SAVY containers are being developed to augment current destructive container monitoring procedures. An earlier trade study completed at Los Alamos National Laboratory (LANL) narrowed down the choices to ultrasonic testing (UT) and eddy current array technology (ECA). The two methods of NDT were validated for SAVY container surveillance through controlled corrosion experiments and simulated pit detection. The results have shown that UT and ECA testing complement each other and can be used to determine corrosion on the interior surface as well as pitting. In addition, ECA can also be used to determine cracks within the containers. The wall thickness measurements completed on baseline containers using UT were within 5.5% of those measured using a CMM (Contour Measurement Machine) and those measurements completed on corroded containers were within 6.3% of the CMM measurements. The smallest detectable pit depth on a SAVY container was accurately measured at 0.0762 mm (even though the detection limit of the technique is lower) and was repeatable. Building upon this work, an automated inspection system can generate color-coded contour plots of the interior of each container.