The brains behind this smart sensor are plastic fibers doped with fluorescent compounds. These one-millimeter-thick fibers scintillate, or light up, when they contact highly energized beta particles produced by radionuclides. "As the beta particles travel through the fibers, the fibers glow. We look at the intensity of that light to quantify the activity level of strontium-90 and uranium in the surface of the soil," Schilk says.
But how does BetaScint know whether it is sensing strontium-90 and uranium or some other radioactive contaminant? Schilk says the secret is in how far the beta particles penetrate the sensor's fiber ribbons. "The more energetic the particle is, the more ribbons it penetrates. The sensor can discriminate between the high-energy beta particles of strontium-90 and uranium and the low-energy particles of lesser interest," Schilk says. "Then we measure the intensity of the light that the fiber layers scintillate simultaneously to determine how much of the contaminant is in the soil.
The light is translated into electrical current which is transmitted to a portable computer where the data is read and stored by the sensor operator.
Although BetaScintīs work is complex, its simple design and lightweight materials make it easy to carry into the field. This portability gives BetaScint a significant advantage over other soil characterization methods. Currently, contaminated soil samples are sent to an off-site laboratory, where a full suite of radiochemical analysis are completed. "This can take 60 - 90 days and cost between $3,000 and $4,000 per sample," Schilk says. "We can take BetaScint out in the field, lay it on the ground and within seconds, have an indication of the soilīs radioactivity level."
