Radiation Monitoring — BetaScintTM
Accurate measurements of radioactivity in soils contaminated with beta-emitters such as Strontium-90 (Sr-90) or Uranium-238 (U-238) are essential for many Department of Energy (DOE) site remediation programs. These crucial measurements determine if excavation and soil removal is necessary, where remediation efforts should be focused, and/or if a site has reached closure. Measuring soil contamination by standard EPA laboratory methods typically takes weeks, often delaying expensive operations such as excavation.
The BetaScintTM fiber-optic sensor is a much more rapid, less costly alternative, measuring Sr-90 or U-238 contamination in soil samples on site in about 20 minutes. The BetaScintTM sensor contains plastic fibers doped with fluorescent compounds. These one-millimeter-thick fibers light up (i.e., scintillate) when they contact highly energized beta particles produced by radionuclides. The intensity of the light is counted by photo-detectors to determine the beta radioactivity of the soil sample. When background counts are subtracted, the number of scintillations counted in a given time is proportional to the average beta radioactivity of the soil sample.
The BetaScintTM system does not create secondary wastes. The BetaScintTM surface/soil monitor can be placed directly on or above contaminated soil or surfaces to detect and quantify radiation associated with the decay of U-238 or Sr-90.
Limitations and Concerns
Five to ten percent of soil samples need to be sent to off-site laboratories for quality assurance/quality control. The BetaScintTM technology must be supplemented by technologies suitable for measuring other types of radioactive contamination if radionuclides other than Sr-90 or U-238 are known or suspected to be present in the material sampled.
High levels of Cesium 137 (Cs-137) in the soil may produce interference if its concentration exceeds that of Sr-90 by several orders of magnitude. When Cs and Sr levels are comparable and less than 100 pCi/g (i.e., typical soil remediation conditions), the Cs contribution to the sensor background is negligible.
Proper understanding and analysis of background radiation is always an issue.
As presently configured, the BetaScintTM sensor can only measure contamination from Sr-90 or U-238 in soil. Versions are being developed for beta detection in gas and groundwater.
Technology Development Status
This technology is commercially available.
Other Resources and Demonstrations
The technology has been used at the DOE Hanford Reservation by Bechtel Hanford, Inc., successfully deployed at the DOE Inhalation Toxicology Research Institute (Albuquerque, New Mexico), and demonstrated at the Fernald Environmental Management Project (Cincinnati, Ohio). ÒBetaScintTM Fiber-Optic Sensor for Detecting Strontium-90 and Uranium-238 in Soil,Ó (prepared for the DOE Office of Science and Technology, December 1998) covers an application of the sensor at the Laboratory for Energy-related Health Research (LEHR) at the University of California at Davis.
See http://www.itrcweb.org/Documents/RAD_4Web.pdf for a general description of real time monitoring of radiation.