WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- The Radioanalytical Laboratory at the United States Air Force School of Aerospace Medicine here has revolutionized the way samples are dissolved to test for radioactive materials: by using automated fusion.

The fusion technique is used to dissolve tough samples, usually soil containing refractory materials, where the material hampers scientists’ ability to separate and measure non-volatile radioactive materials that might be present, such as actinides (uranium, plutonium) and strontium.

When compared to the standard technique of dissolving a sample in a heated acid solution, the fusion technique has many advantages.

“First, the fusion technique is much faster,” said Dr. Aurelie Soreefan, the lab’s technical director. “It takes only 5 minutes to achieve total dissolution of a sample for testing, rather than the days or even weeks it takes using acid digestion methods.

“Even more importantly, it’s safer,” Soreefan continued. “The fusion technique requires much less acid. There are no fumes that might be harmful to workers, and there is much less waste. Finally, this technique is much more accurate -- our test results have been correct every time with this technique. Total dissolution of the sample allows us to capture all analytes of interest to our lab, even the minor elements. And because the process is automated, the results are more consistent and reproducible.”

The fusion technique requires a sample size of less than one gram. A sample is stirred into a crucible with a special salt, and then a propane-fired burner heats the sample up to about 1000 degrees Celsius, melting the salt, which in turn dissolves the sample. After a fixed time on the burner, the molten salt and sample are dumped into a small container of swirling acid. That solution is then ready for chemical separation and testing. The process is entirely automated, and a self-contained, bench-top unit can process three samples simultaneously.

The Radioanalytical Laboratory at USAFSAM -- part of the Air Force Research Laboratory’s 711th Human Performance Wing -- serves as the sole radioanalytical lab for the Air Force, supporting nearly 180 bases.

“Few other laboratories have the automated fusion capabilities we do,” explained Soreefan. “Right now we process about 50 samples each year. We just implemented the fusion technique in 2014, after collaborative work with Professor Dominic Larivière’s group at Laval University, Canada, and much of the work we do is to test our proficiency. The number of samples we process is steadily rising.

“This innovative, safe and fast technique is so helpful to us,” she continued. “In the case of a crisis, for example, we could have as many as 500 samples at once. We need to be prepared to respond to commanders quickly.”