Diagnostics of Chlorine Induced Stress Corrosion Cracking Using Laser Ultrasonics

The stainless steel canister inside a dry cask storage system (DCSS) is at risk for chlorine-induced stress corrosion cracking (SCC), especially near welds and at storage sites exposed to high humidity. It is highly desirable to have a viable technique for in-situ nondestructive evaluation of SCC and to correlate the crack characteristics with models for crack initiation and growth. Statement of how this problem is being addressed. We propose to perform nondestructive evaluation of realistic test samples using laser ultrasonics testing. Our test results will be referenced to models of corrosion development. Our laser-based inspection technique requires no wiring or electronic circuits within the interior of the cask. The measurement head is fiber-delivered and contains only optical components that can be designed to resist radiation damage. What is to be done in Phase I? The major technical goal in Phase I is to demonstrate the feasibility of measuring the length and depth of individual stress corrosion cracks in realistic test samples. Additional tasks will relate crack properties to corrosion models and will develop a strategy for overcoming technical and integration challenges associated with implementing our technique in dry cask storage systems. Commercial Applications and Other Benefits: The safe storage of spent fuel is of great importance for the nuclear power industry and is a priority for insuring public safety. Our approach will be a significant advance in insuring the integrity of stored nuclear fuel containers. Our technique can also be adapted for the inspection of piping and other components used for nuclear power generation. Key Words: laser ultrasonics, stress corrosion cracks, dry cask storage systems