News & Media
Improving nuclear waste storage models by studying the chemistry of material interactions
WastePD EFRC research on the glass-steel interface was published in Nature Materials
New research unravels the chemistry of how materials in the waste packages used for the disposal of high-level radioactive waste interact in deep geologic repository environments. Having a better understanding of the interactions between materials under various conditions provides more information to make waste storage performance models more robust.
“Many performance models use conservative approaches such as assuming that the steel canister walls don’t even exist or that they dissolve very fast. This study provides the opportunity to better incorporate the canister barrier in the models,” said Joseph Ryan, a PNNL materials scientist and coauthor on the paper, “Self-accelerated corrosion of nuclear waste forms at material interfaces,” published in Nature Materials.
The United States is converting highly radioactive nuclear waste, also known as high-level waste, into glass. The molten glass is poured into steel canisters for long-term storage and ultimate disposal in a geologic repository. The goal is to design waste storage and disposal systems that would remain safe for hundreds of thousands of years to come, even if they are exposed to water. Because of the extensive time span of waste storage, researchers turn to cutting-edge science to project what will happen during that time period. The data is used to inform extensive safety analyses—helping make sure the system is engineered to be compatible with the natural system so that waste remains separate from the environment.
“We can’t just do a test on a material and say, ‘That material corroded this much in 30 days and extrapolate that to a million years.’ It doesn’t work that way,” Ryan said. “At the most basic level, we try to understand the underlying chemistry of corrosion. Then, we feed that information into computer models to calculate the expected release over time.”
In this study, led by the WastePD Energy Frontier Research Center based at Ohio State University, researchers unpacked the chemistry that occurs when two materials are close together, focusing on glass-steel along with ceramic-steel interactions. This chemical situation could occur when water has percolated into the repository and has breached the steel canister, exposing the glass-steel interface to water.
When water finally breaches the waste package container, it will fill the microscopic space that forms between the solid glass and the steel canister. Chemical reactions that happen in localized and tiny microenvironments such as these can be quite different than those happening in a more open setting. In this case, this localized area can have a different chemistry than the surrounding solution, causing more corrosion than would be expected.
The researchers tested their theory in the laboratory. They pressed glass and steel together in salty liquid and kept it at 90° C (194° F) for a month. At the end of the experiment, they found differences in the width of thin layers that indicated higher corrosion between the glass-steel couple interface than in a control sample.
Why it matters: This research allows scientists to improve models that project how a disposal canister could perform in a deep geologic environment. Having a better understanding of the interactions between materials under various conditions provides more information to make the models more robust. Currently, some models project what happens to waste under the assumption that the steel canister walls do not exist. Operating under this pretext can result in higher projections of waste degradation than would likely occur when taking a conservative approach. But better understanding the chemistry of how the solid waste and the steel canister interact allows a scientifically based understanding of how the canisters behave and interact with the glass to be included in performance assessment models.
Summary: High-level waste is immobilized as glass in stainless steel canisters. On cooling, a confined crevice space forms at the stainless steel-glass interface. If the disposal canister is breached and if water can enter the steel-glass interface, it could result in anodic dissolution of the stainless steel, generating metal cations, which hydrolyze to form protons and strongly increase the local acidity. This acidic environment may locally enhance the corrosion of both the stainless steel and the glass, which leads to the release of cations from the glass. Further, the coupled corrosion may trigger the precipitation of additional secondary phases that may impact subsequent canister corrosion or nuclear glass durability.
What’s Next: While this study sheds light on the chemical interactions that occur at the stainless steel-glass interface, there are more interactions to explore. Ultimately, a better understanding of different chemical mechanisms will improve the overall performance model.
Sponsors: This work was supported as part of the Center for Performance and Design of Nuclear Waste Forms and Containers, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under Award no. DESC0016584.
Research Team: Xiaolei Guo, Gerald S. Frankel, Gopal Viswanathan, Tianshu Li (Ohio State University); Stéphane Gin (CEA, France); Penghui Lei, Tiankai Yao, Jie Lian (Rensselaer Polytechnic Institute); Hongshen Liu, Dien Ngo, Seong H. Kim (Pennsylvania State University); Daniel K. Schreiber, John D. Vienna, Joseph V. Ryan (PNNL); Jincheng Du (University of North Texas)
Improving Solar Forecasting
The development of an enhanced version of WRF-Solar
By improving the Weather Research and Forecasting (WRF)-Solar model, this project aims to reduce forecast errors of Global Horizontal Irradiance (GHI) and Direct Normal Irradiance (DNI) by 25%, yield better forecasts of irradiance ramps, improve estimates of sub-grid scale variability, and more accurately estimate forecast uncertainty. This enables solar power system operators to know how much solar power will be generated over the coming hours and days, ensuring economic and reliable delivery of renewable energy to American households and businesses.
This new system builds on the first version of the WRF-Solar model developed by the National Center for Atmospheric Research (NCAR).
Anticipated improvements in Version 2 include the following:
- New representation of boundary-layer clouds (both shallow cumuli and the breakup of stratocumulus) including the impact of entrainment
- Improved treatment of cloud microphysics, and impacts of aerosol (including absorbing aerosol)
- New parameterizations to account for the sub-grid temporal variability of solar irradiance during periods with broken clouds
- Detailed analysis to better quantify model uncertainty and improved calibration of WRF-Solar v2 using Uncertainty Quantification (UQ) techniques
Millennial Nuclear Caucus 2019
Presented by the U.S. Department of Energy's Office of Nuclear Energy and Pacific Northwest National Laboratory.
The Millennial Nuclear Caucus being held April 4, 2019, at Pacific Northwest National Laboratory is part of a series of events hosted by the U.S. Department of Energy, Office of Nuclear Energy (DOE-NE) to bring together the next generation of leaders in nuclear innovation. The event features discussion on the path forward for the nuclear industry and the role innovative technology will play. Participants represent the full spectrum of the nuclear field, including young leaders supporting the existing fleet, those designing small modular and advanced reactors, and those advocating for a thriving nuclear future.
DOE-NE encourages all young people interested in nuclear energy, advanced science and technology solutions, or the future of clean energy to attend and join in the conversation. We all have a stake in the future of nuclear.
Attendance is free, but registration is required. If you can’t join us in person, please join the conversation on social media using #NuclearVisionary. See you April 4!
Wasteform Development Laboratory
The Wasteform Development Laboratory—formerly known as the "glass lab"—is in the Applied Process Engineering Laboratory.
PNNL’s Wasteform Development Lab (previously known as the “glass lab”) is key to the nation’s quest for the safe, long-term storage of nuclear waste.
Specifically, our researchers are looking to isolate actinides and radionuclides generated during energy production (including past plutonium production at the Hanford site), used nuclear fuel recycling, and legacy waste from other remediation sites.
PNNL helped pioneer nuclear waste vitrification efforts in the 1960s—we developed the technology for the ceramic joule-heated slurry-fed melters used at the West Valley and Savannah River sites.
We have since expanded our research capabilities to include glass, glass-ceramic, grout, metal, and metal-ceramic wasteforms that will withstand corrosion over geologic time. We also are working to increase the throughput capability of the waste treatment plants. For example, our researchers are expanding our understanding of how the waste—which is dissolved in the glass—transitions through the glass feed to the final pour.
Research in the Wasteform Development Laboratory is primarily conducted by PNNL’s Radiological Materials technical group in support of DOE’s Office of Environmental Management (EM) and Office of Nuclear Energy (NE), and in partnership with DOE contractors.
Based inside the Applied Process Engineering Laboratory, the Wasteform Development Lab offers a broad range of capabilities, including:
• Interfacial Sciences and Rheology
Marine and Coastal Research Laboratory
The Marine and Coastal Research Laboratory (MCRL), which was previously known as the Marine Sciences Laboratory, is the U.S. Department of Energy’s only marine research facility. MCRL, located at PNNL-Sequim, is uniquely positioned for marine-based research that is focused on helping the nation achieve sustainable energy, a sustaining environment, and coastal security.
Sequim Bay links a small, but relatively undisturbed, watershed to the Strait of Juan de Fuca in the Puget Sound. This allows for:
- direct studies of environmental impacts on marine species
- a potential study area for energy deployment
- use of seawater in adjacent lab facilities
- testing of innovative marine sensors
- rapid access to diverse marine environments.
Nearly 15,000 square feet of research laboratories are connected to the bay via a supply system that delivers 200 gallons of seawater per minute and returns it to the bay after treatment. MCRL's unique location is also within one of the cleanest airsheds in the world, providing an ultratrace background for work in measurement and signature sciences.
To defend coastal regions, MCRL researchers engineer new approaches to address the greatest challenges in detecting and responding to national and global threats. Programs focus on developing efficient and effective ways to translate data acquired from environmental media—air, water, sediment, and biota—into information that can be acted upon.
MCRL research is supported by more than 80 staff members with expertise in biotechnology, biogeochemistry, ecosystems science, toxicology, and Earth systems modeling. A dive team is also on staff to support in-water research and testing. Projects at MCRL span algal biofuels, biofouling and biocorrosion, climate change and ocean acidification, environmental monitoring, quantification of transport and effects of chemicals in marine environments, and coastal risk and hazard prediction and analysis.