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

Stress corrosion cracking (SCC) in the welds of a pressurized DSC has been identified as a potential safety concern. The high tensile residual stress and microstructure sensitization in the welds and heat-affected zone (HAZ) of DSC may drive the initiation of pitting and/or the transition to SCC growth and a through-wall failure when exposed to an aggress chemical environment, such as the chloride-rich salts on outer canister surfaces. To minimize the potential of a through-wall SCC 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, X-wave Innovations, Inc. (XII) with support from TechOpp Consulting Inc. (TOC), proposes to develop an Ultrasonic Residual Stress Reliever (URSR) system. Our goal is to go beyond currently demonstrated SCC mitigation technologies, and provide a robust, efficient, cost effective SCC mitigation technology for DSCs. Our main objectives of the Phase I program are to prototype a URSR and demonstrate the feasibility of the proposed technique for relieving the tensile residual stress in welds and HAZ for mitigating SCC in DSCs. Based upon XII’s experience and success in this area, our Phase I efforts will be concentrated on the URSR system design and prototyping, which include the transducer design/development, integration of a URSR prototype and conducting experiments on weld specimens, and residual stress measurements. Proposed URSR system and technology will provide a highly efficient and repeatable residual stress relief to mitigate the SCC in SNF DSCs. This technology will help to reduce the overall cost associated with the inspection and maintenance of SS dry storage casks, which results in improved reliability and life extension by minimizing the catastrophic failure of the nuclear waste storages. This new technology can also find many applications for weld structures such as pressure vessels and pipelines..