Proposed solution will prevent leak of radioactive materials at storage sites

Lucy Yu, an associate professor of mechanical engineering in the College of Engineering and Computing, is developing a technology that will repair and mitigate stress corrosion cracks in nuclear spent fuel storage containers. Her research will potentially reduce the safety hazards associated with nuclear spent fuel storage by preventing leaks of radioactive materials.

In October 2020, Yu received an $800,000 grant from the Department of Energy (DOE) through its Nuclear Energy University Program (NEUP). With co-principal investigator Yuh-Jin Chao, she is collaborating with Savannah River National Laboratory (SRNL) and the Electric Power Research Institute to develop an engineered composite patch that will absorb moisture, repair existing stress corrosion cracks in nuclear containers and prevent cracks from further growth.

Yu said, “The patch is like a Band-Aid put on top of a small cut on the human body. We design and develop such a patch made of laminated composite materials and will put it on the SCC in the storage structural component to prevent it from further growing.”

As there are over 3,000 canisters with spent nuclear fuel in dry storage across the United States, it is vital to have repair/remediation technologies in the event the canisters suffer from stress corrosion cracking. SRNL is proud to support the development of the composite patch.

- Thanh-Tam Truong, senior scientist at Savannah River National Laboratory

Yu explains that her work is designed to address the safety surrounding the storage of nuclear spent fuel. Stress corrosion cracks have been identified as a potential nuclear safety concern because of the possibility that through-wall penetration could breach the confinement/containment boundary of the canisters and release radioactive materials.

The stainless-steel canisters are a temporary storage solution for nuclear spent fuel while permanent repositories are built, but many canisters are used beyond their original planned usage time.

“The DOE is seeking a proactive solution for when and if cracks develop that will ensure the integrity of the storage. If an opening develops in a canister and fuel leaks, then a health hazard develops,” Yu said.

The risk is particularly great for canisters stored near coastal regions, as chloride-bearing salts in the atmosphere may deposit on the external surface of the canisters and exacerbate corrosion and deterioration. 

Thanh-Tam Truong, senior scientist at SRNL, said, “As there are over 3,000 canisters with spent nuclear fuel in dry storage across the United States, it is vital to have repair/remediation technologies in the event the canisters suffer from stress corrosion cracking. SRNL is proud to support the development of the composite patch and will perform irradiation tests on the patches.”

During the three-year study, Yu’s research team will develop test patches made of various laminated composite materials and perform experiments to see what materials, and what size and thickness, are most effective in mitigating crack growth. The desired result is a flexible composite patch equipped with corrosion inhibitors that will be bonded to the surface of fuel canisters to absorb moisture in the cracks, while reducing the residual stress to prevent the crack from growing throughout the wall of the cannister.

In order to monitor crack growth after the repair, a nondestructive evaluation inspection capability will be integrated into Yu’s proposed solution. This process will evaluate the bond quality for patch integrity and continue to monitor the crack growth and/or development.

The DOE is awarding more than $38.6 million through NEUP to support 57 university-led nuclear energy research and development projects in 24 states for the development of innovative technologies and solutions for civil nuclear capabilities.

Yuh-Jin Chao is a Distinguished Professor Emeritus of mechanical engineering in the College of Engineering and Computing. His research interests include theoretical and experimental studies on failure, fracture and fatigue of materials and structures; welding modeling for residual stress and distortion; impact mechanics for material characterization and failure criterion; biomechanics and nanomechanics; and the durability of PEM fuel cell systems.

Lingyu Yu is an associate professor of mechanical engineering in the College of Engineering and Computing. Her research interests include condition monitoring of the aircraft structures and systems, integrity monitoring of large composite structures, detecting and quantifying cracks in metal structures such as steel bridges and their subsequent propagation, and corrosion growth monitoring in piping structures.