Use of passive alpha detectors to screen for uranium contamination in a field at Fernald, Ohio Page: 4 of 10
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rhe technology has already been commercialized for the monitoring of environmental radon. Millions of
detectors of the ATD type have been sold both to individual homeowners and to federal agencies
mandated to screen their facilities for radon. The ATD technology has passed the stringent test criteria,
blind testing, and quality assurance procedures set under EPA's Radon Measurement Proficiency
To adapt this technology to other needs, the track-registering plastic element of the radon monitor
can be laid directly on or in an alpha-contaminated soil or soil sample. After the plastic is chemically
etched and optically scanned, both the surface alpha activity and a spatial map of the contaminant
distribution may be determined. Several technical issues are being addressed to improve the performance
of the ATD as applied to environmental restoration (ER) and decontamination and decommissioning
(D&D) needs. The commercially available application of ATDs to airborne alpha activity measurements
produces chips with damage tracks that are randomly distributed. The currently used optical scanning
systems have been optimized for randomly distributed tracks. Future applications will yield chips with
clusters of tracks due to the presence of macroscopic radioactive particles in some cases. Techniques are
being developed to detect and evaluate track clusters. Most available devices for holding the chips during
exposure were developed for the indoor environment, which is highly controlled. Future applications will
call for ATDs to be left outside and exposed to extremes of temperature, humidity, and wind. Protocols
and device holders are being developed to mitigate adverse effects of moisture condensation, abrasion,
and 222Rn decay products in soil gas.
Preliminary experiments indicate great potential for ultimate success in the application of ATDs to
ER and D&D projects. Pilot measurements have already demonstrated that ATDs can:
" Quantify contamination at 100 dpm/100 cm2after an hour's exposure,
" Provide a permanent record of the alpha radiation field,
" Show whether the contamination is homogeneously or inhomogeneously distributed,
" Identify the presence of "hot" microparticles such as PuO,,
" Be cut to a size and shape to fit into any location, such as inside a crack, and
" Be deployed on interior or outdoor surfaces, on or under the surface of soil, or under
The above results have been published.
EICs provide another inexpensive measurement technique that is very easy to implement.
Kotrappa and coworkers34 have described the application of EICs to the measurement of indoor alpha
activity. The underlying principle of the measurement is that ionizing particles that pass through the air in
the sensitive volume of the EIC create electron showers that are attracted to the positively charged face
of the electret. neutralizing the charge. The rate at which the charge is neutralized is proportional to the
energy deposited in the air. The technology has already been commercialized for the monitoring of
environmental radon. Hundreds of thousands of detectors of the EIC type have been sold both to
individual homeowners and to governmental agencies (principally school systems) mandated to screen
their facilities for radon. The EIC technology has passed the stringent test criteria, blind testing, and
quality assurance procedures set under EPA's Radon Measurement Proficiency Program.
To adapt this technology to ER and D&D needs in the field site personnel can use inexpensive
(-750) hand-held voltmeters to record EIC voltages before and after deployment. Before this
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Dudney, C. S.; Meyer, K. E.; Gammage, R. B.; Wheeler, R. V.; Salasky, M. & Kotrappa, P. Use of passive alpha detectors to screen for uranium contamination in a field at Fernald, Ohio, article, June 1995; Tennessee. (digital.library.unt.edu/ark:/67531/metadc741879/m1/4/: accessed November 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.