Interactions between processed high-level radioactive waste and stainless-steel containers could undermine long-term safe geologic disposal of the material, researchers at Ohio State University said in a study published this week.
“The corrosion that is accelerated by the interface interaction between dissimilar materials could profoundly impact the service life of the nuclear waste packages, which, therefore, should be carefully considered when evaluating the performance of waste forms and their packages,” according to the abstract for the Jan. 27 article in the journal Nuclear Materials. “Moreover, compatible barriers should be selected to further optimize the performance of the geological repository system.”
The research team focused on changes in chemistry of defense waste generated by nuclear weapons production, the university stated in a press release.
The Department of Energy is responsible for 11,655 metric tons of defense high-level radioactive waste from production of plutonium and other nuclear-weapon materials, along with 2,195 metric tons of defense spent nuclear fuel, the Government Accountability Office said in 2017. It also holds a small amount of commercial high-level waste and spent nuclear fuel, totaling 379 metric tons.
These materials are held in five states, primarily at the Hanford Site in Washington state, Savannah River Site in South Carolina, and Idaho National Laboratory. The Energy Department is conducting, or preparing for, large-scale programs to convert the waste into a form that is safe for permanent disposal.
Trouble could develop in such a disposal operation, both in the United States and other nations dealing with high-level waste, the Ohio State researchers determined.
The waste would be merged with other materials to create a glass or ceramic form, with the resulting material then placed in steel vessels for geologic disposal. However, the interaction between glass and ceramics and stainless steel within an aqueous environment can produce accelerated corrosion of the materials that hold the waste, the study says.
This was demonstrated through testing in which glass and ceramic materials, shaped into the forms in which nuclear waste is encapsulated, were pressed against stainless steel and then placed in solutions for as many as 30 days. The conditions simulated those that would be found in the U.S. geologic repository planned for Yucca Mountain, Nev., the university said.
“In the real-life scenario, the glass or ceramic waste forms would be in close contact with stainless steel canisters,” lead author Xiaolei Guo, deputy director of the university’s Center for Performance and Design of Nuclear Waste Forms and Containers, said in the release. “Under specific conditions, the corrosion of stainless steel will go crazy It creates a super-aggressive environment that can corrode surrounding materials.”
Under contract to the Energy Department, Bechtel National is building a plant to vitrify some portion of the 56 million gallons of radioactive waste stored in underground tanks at Hanford, a former plutonium production complex. The Defense Waste Processing Facility is already converting Savannah River’s high-level sludge waste into glass.
The Energy Department does not yet have a permanent disposal facility for the processed waste. Its 2008 application to the Nuclear Regulatory Commission to build and operate the facility under Yucca Mountain has been moribund for a decade after the Obama administration defunded the proceeding. The Trump administration has tried in three budget cycles to persuade Congress to appropriate funds to restart licensing, but has struck out. There are unconfirmed rumors that the White House does not intend to request appropriations for the upcoming 2021 federal fiscal year.
The Energy Department’s Office of Science provided funding for the Ohio State research. The office did not comment by deadline Friday to a request for comment on the findings.