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Fiber-optic sensor sheds light on radioactive contaminants

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March 17, 1995 Share This!

RICHLAND, Wash. — A new sensor developed at the U.S. Department of Energy's Pacific Northwest Laboratory can detect immediately two of the most prevalent contaminants left over from nuclear power generation and weapons development.

The BetaScint sensor relies on tiny fiber-optic strands to detect radioactive byproducts of uranium-238 and strontium-90 and has been tested successfully at DOE cleanup sites in Washington and Ohio.

"The BetaScint sensor provides immediate, inexpensive results in the field," said Dr. Alan Schilk, who leads the PNL development team. "It's lightweight and portable, which gives it an advantage over current soil characterization methods."

Generally, contaminated soil samples are sent to an off-site laboratory, where a full range of radiochemical analyses are done. This normally can take many weeks and cost hundreds to thousands of dollars per sample. "We can take the sensor out in the field, lay it on the ground and within moments have an indication of the soil's radioactivity level," Schilk said.

The brains behind this sensor are plastic fibers mixed with fluorescent compounds. These half-millimeter-thick and one-millimeter-thick fibers scintillate, or light up, when they contact highly energized beta particles produced by radionuclide decay. "As the beta particles travel through the fibers, the fibers glow. We look at the intensity of that light to quantify the level of strontium and uranium in the surface of the soil," said Schilk. The light is translated into electrical current, which is transmitted to a portable computer where the data is read and stored.

The BetaScint sensor is at work in a variety of areas. Westinghouse Hanford Company received an earlier version to detect strontium at DOE's Hanford Site in southeastern Washington. Newer models will be used at Hanford, both in the field and in mobile laboratories, to assist in the cleanup of abandoned waste areas contaminated with Sr-90. The sensor was demonstrated successfully at the Fernald nuclear processing facility in Cincinnati, Ohio, to map uranium contamination in surface soils. The sensor also was mounted on a conveyor belt at Fernald to verify that soil stripped of uranium was clean enough to return to the environment. A BetaScint sensor is under construction for the International Atomic Energy Agency. The agency is responsible for investigating potential nuclear proliferation throughout the world and is interested in using the sensor to monitor nuclear processing activities in countries such as Iraq and North Korea. "We can use it to detect strontium and uranium in the soil downwind of nuclear processing plants to determine if they are operating," said Schilk.

The sensor is scheduled to be demonstrated this spring at DOE sites in Albuquerque, N.M., and Aiken, S.C. The sensor will be used for characterization and detection of Sr-90. And, Ukrainian and Russian scientists have expressed an interest in the possibility of using the sensor to detect contaminants in and around the Chernobyl region.

Inventors envision a number of future applications for the BetaScint sensor, including a robotic version that could be used in the decontamination of retired facilities. A remotely operated sensor could be sent into confined spaces or decrepit structures to detect contamination, thereby avoiding the need to endanger workers.

The BetaScint sensor's development was funded though DOE's Office of Technology Development's Characterization, Monitoring and Sensors Cross Cutting program, as a way to support environmental cleanup operations.

A patent has been granted for the BetaScint sensor. It should be issued in early 1995.

PNL is looking for industrial partners interested in licensing the BetaScint sensor.

Tags: Energy, Environment, Operations, Nuclear Power, Facilities

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