Imagine if bricks or other common building materials could act as cameras that can show their location and distribution of radioactive materials that once were in their locality. A team of researchers from North Carolina State University has developed a technique that turned that idea into a reality.
The team was able to recover a historical snapshot using optically stimulated luminescence. Radioactive elements, including weapons-grade plutonium, affected certain minerals in the materials, allowing them to retrieve the image.
The concept is that building materials can pick up residual gamma radiation signatures by acting as a 3D camera. How can the material act as a camera? Some minerals such as feldspar or quartz, react to gamma rays by trapping electrons in their crystalline matrix. When these electrons are stimulated, they shift from their prison and release light. This light can then be measured on a photomultiplier, enabling scientists to build up a picture of any radioactive source that might have been in the zone.
Robert Hayes, an Assoc. Prof of nuclear engineering at NC State explained:
“Our new work effectively shows that we could take an array of bricks and turn them into a gamma-ray camera, characterizing the location and distribution of a radiation source. Although this time, we did not use bricks, instead, relying on commercial dosimeters. Also, the radiation source we imaged this time was 10 lb of weapons-grade plutonium. In this most recent study, we were able to rather accurately predict not only the location of the weapons-grade plutonium but even the radius of the source, just with passive dosimeters.”
He explained that even though they used commercial dosimeters, their findings show that they could do the same using bricks. The silicates in bricks such as feldspars, zircons, and quartz are individual dosimeters; that’s why they could use it. Hayes notes that although it’s a tedious process to remove those grains from the brick for measurements, they’ve done it several times.
Hayes said:
“For the goals of this new research, it wasn’t necessary to use brick – we’ve already shown we can do that. This was simply a question of determining how much information we could glean from this approach. And the answer is that we could learn a lot – about the size and shape of the radiation source, as well as the nature of the radioactive material itself.”
In April, the North Carolina team published their research in Radiation Measurements.
