Ultrasonic Residual Stress Reliever System for Mitigation of Stress Corrosion Cracking in Spent Nuclear Fuel Dry-Storage Canister WeldsDegradation

Chlorideinduced stress corrosion cracking CISCC in the welds of a pressurized SNFDSC has been identified as a potential safety concern. The high tensile residual stress and microstructure sensitization in the welds and heataffected zone HAZ of SNFDSC may drive the initiation of pitting and/or the transition to CISCC growth and a throughwall failure when exposed to an aggressive chemical environment. To minimize the potential of a throughwall CISCC failure, it is necessary to develop mitigation technologies to relieve the tensile stress concentration in welds and HAZ of DSCs. To address this critical need, Xwave Innovations, Inc. XII is developing an Ultrasonic Residual Stress Reliever URSR technology. Our goal is to go beyond currently demonstrated CISCC mitigation technologies, and provide a robust, effective, efficient, and lowcost CISCC mitigation technology for SNFDSCs. In Phase I, we successfully developed a URSR prototype and experimentally demonstrated the feasibility of URSR technology for residual stress relief in SNFDSC welds. Our main objectives of the Phase II program are to develop a fullyfunctional URSR prototype and demonstrate its abilities for relieving the tensile residual stress in welds and HAZ of SNFDSCs. Based upon XII’s experience and success in this area, our Phase II efforts will be concentrated on the refinement of URSR system design and development, which include the FEA simulation/prediction module, transducer assembly design/development, URSR prototype integration, systematic testing and evaluation of prototype performance with weld specimens from actual SNFDSCs, and verification through destructive and nondestructive residual stress measurements. Proposed URSR system and technology will provide a highly efficient and repeatable residual stress relief to mitigate the CISCC in SNFDSCs. This technology will benefit the reduction of overall cost associated with the inspection and maintenance of SS dry storage canisters, which results in improved reliability and life extension by minimizing the catastrophic failure of the nuclear waste storages. This new technology can also find broad applications for weld structures such as pressure vessels and pipelines.