Dr. Richard Brow, Curators’ Professor of ceramic engineering at Missouri University of Science and Technology, is working to find a way to make certain nuclear wastes easier to consolidate in borosilicate glass, reducing the waste’s environmental footprint and lowering costs for storage.
The work is funded by an Office of Nuclear Energy grant for $210,747 per year for up to three years.
Stored in steel drums and buried in mountainsides, nuclear waste can remain radioactive for tens or hundreds of thousands of years. Reducing the space needed to store the waste, Brow says, saves time and money and will reduce the overall environmental impact.
Brow is working to find a way to make the waste vitrify — or, turn into glass — that is more efficient than current and historical methods. Using surrogates for radioactive isotopes, Brow will melt the borosilicate glass and surrogates, looking for the sweet spot where phase separation and crystallization processes capture the most waste in the smallest volume of a chemically stable glass.
Phase separation occurs when a single liquid (melt) separates into two liquids, and it can happen when the borosilicate glass is cooled under the right conditions. Borosilicate glass is similar to what Pyrex labware is made of.
“When this phase-separated melt cools, we end up with two different glasses intermixed. An example of immiscible liquids is oil and water,” Brow says.
Upon further cooling, the phase separated regions can crystallize into phases that concentrate dangerous isotopes. If the waste composition is designed correctly, then these crystals can be surrounded by a chemically stable glass for long-term storage.
Brow will use techniques developed in part by researchers in the Peaslee Steel Manufacturing Research Center at S&T. He’ll study metallurgical slags to describe the processes in which homogeneous melts phase separate and then crystallize on cooling.
“To understand how fast these processes occur, we will quench the melts — probably from 1,450 degrees, Celsius — at different rates to freeze in different microstructures, ranging from phase-separated droplets, known as fast quench, to fully crystallized phases, or slow quench,” he says.
It’s all to get to the point where the borosilicate glass concentrates the radioactive components into micro-phases within the glass. And when that happens, the benefits will be substantial.
“We could possibly double our waste loading,” Brow says.