The million-year questions

Author: John Monczunski

Since nuclear energy is a source of clean, virtually limitless power, many people see it as a key to solving the planet’s greenhouse gas problem. Unfortunately, it’s a solution with its own serious problem: radioactive waste. How do you safely store something that will remain toxic for a million years? To answer that challenge, a host of basic scientific questions must be answered first.

Of these, the question that interests Jeremy Fein most is what happens to waste uranium when it’s placed in the ground. What minerals will it change into? How soluble are these in water? The ND professor of civil engineering and geological sciences says these questions are key since radioactivity could spread with disastrous results if it leaches into groundwater.

As uranium decays, it changes into other elements over time, Fein explains, and so it is important to understand how it interacts chemically with the elements with which it comes in contact. “What we’re trying to do is isolate the reactions that might be important and reproduce them in the lab and then use modeling to predict what might happen in a real-world system,” he says.

Fein and his team are almost finished with their initial survey of the most likely mineral candidates which nuclear power waste uranium would transform into. Little has been known about the process. “When we started there were very few measurements of uranium minerals and solubilities,” he notes. “With this initial phase we now have a pretty good idea of the relative stabilities of the most likely uranium phases.”

Uranium phosphate minerals are among the most stable. Because they precipitate uranium out of solution and bind it up, they may be useful in cleaning up spills. Currently, Fein is studying how the presence of bacteria may erode that stability.

John Monczunski is an associate editor of this magazine.