Tackling one of the most extreme environments on Earth: Nuclear waste
The complicated chemistry of legacy nuclear waste presents a challenge in environmental management. The presence of radioactive ions induces chemical changes that range from faster than the blink of an eye to decades in the making.
Since 2016, researchers led by Pacific Northwest National Laboratory (PNNL) have been persistent in tracking and analyzing the chemical phenomena that occur in the extreme environments found in legacy nuclear waste. Together with two other national laboratories and five universities, the Ion Dynamics in Radioactive Environments and Materials (IDREAM) Energy Frontier Research Center (EFRC) will now continue its crucial mission with four additional years of funding.
In this next four-year chapter, IDREAM researchers will focus their fundamental science efforts on how radiation has driven the complex chemistry—or more specifically, the solution to speciation and precipitation—in the Cold War-era radioactive waste stored at the Hanford Site in Washington State.
The next decade of waste cleanup at Hanford will focus on completing the necessary infrastructure and facilities for retrieving, treating, and immobilizing solid waste from underground storage tanks. This transition from treatment of liquid waste to the removal of solid tank waste requires a scientific understanding of how radiation changes the composition of tank waste—for example, chemically transforming from a liquid to a gel, resulting in clogged pipes. Such an understanding is essential to effective remediation and to plan future waste retrieval and treatment.
Much of the team's work to date has centered on aluminum, an important component in legacy tank waste because of the dissolved aluminum cladding that surrounded the nuclear fuel rods—results that also could apply to aluminum extraction from industrial waste.
"Since 2016, IDREAM has leveraged our effective team and novel experimental and computational capabilities to establish a track record of major accomplishments," said Carolyn Pearce, IDREAM's director.
"In one example, we revealed how ion hydration interactions and clusters control behavior in highly concentrated solutions. This understanding can allow us to tune the solution conditions to enable safer legacy waste processing."
Connecting fundamental science to radioactive waste
The 56 million gallons of waste that have been stored in 177 underground tanks represent one of the most challenging environmental cleanups in the United States and the world. The significant amounts of radiation and actively decaying materials result in an ever-changing elemental mixture.
Most chemical models and theories are based on a system in equilibrium, where things reach a standard steady state. Legacy tank waste is one of the most chemically far-from-equilibrium environments accessible on Earth.
In these ultraconcentrated environments, radiation effects multiply and ripple out from atom to atom. These interfacial processes start at ultrafast timescales that are essentially instantaneous. The IDREAM team has experience working with these incredibly fast processes—they were able to take an "atomic freeze-frame" of water. The research relies on attosecond X-ray pulses, which can only be produced at a handful of facilities around the globe.
The ultrafast experiments can show what happens to electrons immediately after a target is hit with X-rays. These initial changes influence the rest of the system's reactivity, especially as new ion networks form and evolve over time. Understanding the first steps helps set the stage for exploring longer timescales.
This next phase in IDREAM's evolution will connect the ultrafast atomic processes they previously studied to the formation of larger solids, which can occur slowly enough to be observed by the human eye. These timescales are generally studied independently because each requires different expertise and tools.
The IDREAM team will explore what happens once the ion networks are established in liquid waste. At this point, a cascade of reactions begins. What happens next ultimately controls the composition of the tank waste.
In the next stage, compounds begin to group together and form solids. This takes the longest time, but is critically relevant to waste processing. These solids are the materials that require treatment and can clog up pipes or form challenging-to-break crusts on top of waste.
By bridging these broad timescales, IDREAM will continue to develop the fundamental science needed to better understand how to safely and effectively treat legacy tank waste.
Enhancing collaboration with new partners
Collaboration has been core to the success of IDREAM.
The partnerships serve a valuable purpose, bringing specialized expertise together and building a network of scientists across the United States. The ambitious work of IDREAM requires tools that range from models of atomic motion to beamlines at a synchrotron. The challenge of understanding tank waste requires an EFRC approach because no single group or organization has the necessary breadth to tackle the massive scope.
"IDREAM brings together researchers with the necessary skills to understand the fundamental radiation chemistry of extremely complex systems across timescales," said Jay LaVerne, IDREAM's deputy director and a professor at the University of Notre Dame.
"Equally important is our role in developing the new energy workforce. IDREAM exposes students to a multidisciplinary team of exceptional computational and experimental scientists with access to the specialized facilities in the national laboratories."
For example, Hunter College of the City University of New York joined IDREAM in September 2024, bringing expertise in using radiochemistry probes. This new collaboration directly ties into IDREAM's focus on understanding radiation-induced changes to the fundamental properties of various waste-relevant atoms.
"IDREAM is the only team equipped to identify the underlying radiation-induced changes controlling the stability of solutions and solids relevant to sludge mobilization, retrieval, and treatment," said Pearce.
IDREAM collaborations are about more than the science. The IDREAM Early Career Network encourages connections among early-career scientists, including graduate students. It offers opportunities for newly minted researchers to develop their careers by collaborating on manuscripts, presenting at conferences, taking leadership roles, receiving mentorship from senior staff at different institutions, and even partnering on creative science communications like poetry.
"Our new partnership with Hunter/CUNY—a minority-serving institution—will provide a pipeline of students through a new radiation chemistry course, developed alongside DOE Basic Energy Sciences' Radiation Chemistry Core Program principal investigators," said Pearce. "These students will help us meet an emerging need for the next generation of radiation chemistry researchers."
The IDREAM partner institutions are Pacific Northwest National Laboratory, Argonne National Laboratory, Oak Ridge National Laboratory, Georgia Institute of Technology, Hunter College of the City University of New York, the University of Notre Dame, the University of Utah, and the University of Washington.
Provided by Pacific Northwest National Laboratory