Design and application of an engineered composite patch toward crack damage mitigation on stainless steel plates

Abstract

High level nuclear spent fuel canisters have been designed and used for nuclear waste storage since the 1950’s. Stress corrosion cracking (SCC) has shown to occur under certain corrosive chemical conditions when the residual stress was not relived in a welded plate. Typical SCC would eventually cause catastrophic failure of structures. In the case of spent nuclear canisters, the radioactive materials may leak through the cracks if they penetrate the tank wall. Early detection of SCC is crucial, followed with appropriate mitigation methods. Various mitigation methods have been funded and explored for the nuclear facilities. Among them, engineered composite patch repairing technique that was originally developed and adopted for aerospace aluminum structures has been proposed as one of the solutions. We first explored the fundamentals of composite patches for crack repairing through literature study, followed with the development of a complete procedure from composite material selection, adhesive selection, to surface preprocessing. To understand the effect of the patch performance for crack repairing, tensile test with stainless steel coupon samples will be performed. A Lamb wave based noncontact evaluation was performed beforehand to identify the precrack length in the coupon samples and to guide the dimension design of the patch. After that, the surface processing of both the composite patch and the steel plate as well as the patch installation techniques were explored. Finally, samples with and without the mitigation composite patches will be tested under tensile loading in order to understand the benefits of composite patches and meanwhile to identify potential improvements.