Site Characterization Using the Global Positioning Radiometric Scanner System
K. C. Wright, F .L. Webber, C. M. Hiaring
At the Idaho National Engineering and Environmental Laboratory's Auxiliary Reactor Area, an investigation was conducted to determine the distribution and concentration of Cs-137 in soil. Cs-137 was selected as the indicator radionuclide in this area because it is known to be widespread and readily detected by field screening instruments. The area was surveyed using two different types of in situ detectors: a Global Positioning Radiometric Scanner (GPRS) and a portable Germanium spectrometer (Ge-spectrometer). The GPRS is mounted on a four-wheel drive vehicle and used two plastic scintillation detectors mounted 1-m aboveground, allowing a view of approximately 7-m diameter. The radiological data and geographical coordinates are recorded on an onboard computer. The GPRS collects real-time data and updates the file every two seconds, allowing numerous data points to be recorded in a short timeframe. The Ge-spectrometer measurements were collected in areas inaccessible to the GPRS and at a selected set of calibration points. Calibrations were developed by the INEEL Radiation Physics Products organization and utilized for both systems. A mathematical relationship (conversion factor) was established for Cs-137, and then the data was presented to the appropriate regulators for use in a Remedial Investigation/Feasibility Study to determine the extent of cleanup effort required. The data collection methods have enhanced the capability to produce maps, which provide a better definition of the areas considered for remediation. In addition, the in situ method significantly reduced the number of analytical samples required and more clearly defined the aerial extent of radionuclide contamination.
This abstract was presented at the 33rd Annual Midyear Meeting, "Instrumentation, Measurements, and Electronic Dosimetry", Site Characterization Session, 1/30/2000 - 2/2/2000, held in Virginia Beach, VA.