Radiation Monitoring —
BetaScintTM
Description
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.
Applicability
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.
Web Links
http://www.osti.gov/bridge/servlets/purl/354883-CE2isg/webviewable/
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.