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1 W S R C - M Portable Radiation Detector and Mapping System (U) / by K. J. Hofstetter Westinghouse Savannah River Company. Savannah River Site Aiken, South Carolina D. W. Hays R. F. Edde. m w n? r i OF,THISDOCUMENT IS UNLIMITED A document prepared for ANS ANNUAL MEETINGANS TRANSACTIONAS at San Francisco from 10/29/9511/02/95. DOE Contract No. DE-AC09-89SR18035 This paper was prepared in connection with work done under the above contract number with the U. -. Department of Energy. By acceptance of this paper, the publisher and/or recipient acknowledges the U. S. Government's right to retain a nonexclusive, royalty-free license in and to any copyright covering this paper, along with the right to reproduce and to authorize others to reproduce all or part of the copyrightedpaper.

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4 Portable Radiation Detector and Mapping System K. J. Hofstetter, D. W. Hayes, and R. F. Eakle Westinghouse Savannah River Company Savannah River Technology Center Aiken, SC Introduction A portable radiation detector and mapping system (RADMAPS) has been developed to detect, locate and plot nuclear radiation intensities on commercially available digital maps and other images. The field unit records gamma-ray spectra or neutron signals together with positions from a Global Positioning System (GPS) on flash memory cards. The recorded information is then transferred to a lap-top computer for spectral data analyses and then georegistered graphically on maps, photographs, etc. RADMAPS integrates several existing technologies to produce a preprogrammable field unit uniquely suited for each survey, as required. The system presently records spectra from a NaI(T1) gamma-ray detector or an enriched Li-6 doped glass neutron scintillator. Standard Geographic Information System s o h a r e installed in a lap-top, complete with CD-ROM supporting digitally imaged maps, permits the characterization of nuclear material in the field when the presence of such material is not otherwise documented. This paper gives the results of a typical site survey of the Savannah River Site (SRS) using RADMAPS. Description As a field test of the prototype RADMAPS Unit, a gamma-ray radiation survey was conducted of the area surrounding a decommissioned test reactor at SRS. The survey instrument was a 2.5 cm x 2.5 cm NaI(T1) detector connected to an analog-to-digital converter which recorded integrated count rates every second. The surveys were conducted from a vehicle equipped with a portable GPS which recorded positions every second. These two data sets were merged by time after the survey and the results plotted on a site facility map using standard GIs georegistering techniques. The areas of high count rates (maximum dose rate NN 6 psv/hr at 7 meters) were then highlighted to locate the area responsible for the elevated readings. See Figure 1. To further demonstrate the GIs

5 capability, the data were overlayed on USGS digital maps and aerial photographs which confirmed the location. The hand-held RADMAPS unit then recorded gamma-ray spectra in the area using a 5 cm x 5 cm NaI(T1) detector. Results The gamma-ray spectra indicated the presence of Pa-234m, a daughter of U-238, suggesting the presence of large quantities of U-238 in the building. The building was a temporary storage area for approximately 2000 drums of depleted uranium. Spectra taken with a portable high resolution HPGe detector confirmed the presence of depleted uranium. These spectra complemented the earlier scintillation spectrometry measurements. Simplified simulation codes have been written to interpret scintillation spectra with the laptop computer. Standard codes have also been installed to include matrix and absorber effects in the resulting spectra. During the movement of the drums of depleted uraniu to the final storage location, integrated count rates were recorded with the small NaI(T1) detector at a remote (25 meter) location during one day s typical operation. The drums were removed from the building using a fork lift, placed in a secondary container overpack, and then loaded onto a flat bed truck for transportation to the permanent storage facility. During a typical %-hour period, the count rates changed by a factor of two confirming that the movement of material can be monitored using the remote radiation detector and data acquisition system. The small detector and data acquisition system was later placed by the side of the road and monitored the gamma-ray count rates during periods of normal vehicular traffic. The trucks loaded with depleted uranium (10 drums each) were easily detected using this system. In both experiments, the system was left unattended for extended periods and the data downloaded to the lap-top computer for analysis. Summary RADMAPS is an effective tool for detecting, locating, and characterizing nuclear material in the field. The ability to provide rapid evaluation of field data should be valuable to field personnel involved in NPT verification, on-site and off-site regional inspectors, safeguards surveillance, decontamination and decommissioning, and nuclear weapons dismantlement. This work is supported in part by the US DOE in accordance with subcontract DE-AC09-89SR18035.

6 0 4 X Background 0 Background.- Figure 1. Radiation survey data plotted on a USGS digital map. The presence of above background radiation levels is noted in the northeast part of the survey.