Charles Demarest has literally immersed himself in nuclear energy. For almost a decade, Demarest served as an electrician on nuclear submarines, operating, repairing and maintaining their power plants. This firsthand experience has convinced him that nuclear power is a viable, low-carbon bridge technology to renewable sources like wind and solar—if the nuclear power industry can address long-term storage concerns. Demarest has taken on that challenge.
"If we can develop a better system for storing nuclear waste for long periods of time, I feel I would be doing my part to advance nuclear power in the United States and reduce our reliance on fossil fuels ~ Chuck Demarest"
As a graduate student in the Material Science and Engineering Department, he is working with Professor John Scully to develop a new generation of canisters for storing krypton-85, a radioactive gas produced during the reprocessing of nuclear fuel. Their research is funded by the U.S. Department of Energy. “If we can develop a better system for storing nuclear waste for long periods of time, I feel I would be doing my part to advance nuclear power in the United States and reduce our reliance on fossil fuels,” Demarest says.
From Scully’s point of view, Demarest’s background as a nontraditional student made him the ideal student for the project. It was only after his stint in the Navy that he completed his undergraduate degree in engineering science at UVA, majoring in material science. “Having a graduate student of Chuck’s caliber with the depth of experience in nuclear power that he possesses was a great opportunity for us,” Scully says. “He has demonstrated great promise.” The National Science Foundation (NSF) echoes Scully’s assessment. It awarded Demarest a prestigious Graduate Research Fellowship, which provides three years of financial support within a five-year fellowship period. In 2018, the NSF selected just 2,000 fellows from a field of 12,000 applicants.
Among radioactive materials, krypton-85 is relatively short-lived. In slightly more than 10 years, half of any given quantity of krypton-85 will decay into the nonradioactive metal rubidium. After a hundred years, the fraction of krypton-85 remaining is so minute that it no longer poses a safety risk. Unfortunately, the carbon-steel canisters used to store krypton-85 in the United States are corroding at a much faster rate. Scully, Demarest and a team that includes Professor Sean Agnew and researchers from the Pacific Northwest National Laboratory are charged with understanding the dynamic mix of factors that are producing corrosion inside these cannisters in order to be able to predict corrosion rates. This information could be used to suggest a replacement system.
The prime suspect is the resulting rubidium. A liquid at the elevated temperatures inside the canisters, rubidium is highly reactive, but there is no consensus among researchers about whether it affects the corrosion resistance of steel. But rubidium is not the only possible culprit. Within the canister, the krypton-85 gas is encapsulated in particles of zeolite, a highly porous, highly adsorbent substance. The process of creating the zeolite can leave chlorides, which will also contribute to the corrosion. In addition the atmosphere within the canister is likely to have oxygen, hydrogen and water vapor—and all the electrochemical reactions these materials might promote—alone and in combination—must be understood in the presence of ongoing radioactive decay. This decay may also degrade the corrosion performance of the steel. Once the research team develops a clear picture of the process of corrosion, it will suggest a better canister material from among newer alloys known for improved corrosion resistance. Ultimately, Demarest hopes that fundamental insights into the corrosion that is occurring inside krypton-85 canisters can be applied to containment systems used for other, more long-lasting forms of nuclear waste.
“We are hoping to find a holistic solution that can be more broadly applied,” Demarest says. “Such a solution could go a long way in making nuclear power more acceptable.”