Depleted Uranium Discrimination Using Spectral Ratios from Data-Starved Spectra - 18619

Conference · Sun Jul 01 04:00:00 EDT 2018

OSTI ID:22977868

Unz, Ronald; Phillips, Kate ^[1]; Larson, Steve; Waggoner, Charles ^[2]

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1. Institute for Clean Energy Technology, Mississippi State University (United States)
2. Environmental Laboratory, U.S. Army Engineer Research and Development Center (United States)

The Institute for Clean Energy Technology (ICET) has developed mobile surveying platforms for the retrieval of fired depleted uranium (DU) munitions. ICET surveying platforms are fitted with differential global positioning system (GPS), scintillation detectors, and central processing units (CPUs). The surveying technology has historically been used to assist facilities where DU contamination is a concern to locate, retrieve, and remediate DU-contaminated areas. Residence times over DU sources for mobile systems normally do not produce enough data to use gamma ray spectroscopy to verify the source type. Discussed is a potential method used to discriminate DU signatures in data-starved gamma ray spectral data collected during field surveys. Laboratory tests have shown that data-starved gamma ray spectra for zero-valence, oxide, and uranium ores can be distinguished from each other and from background by spectral ratioing. Zero-valence DU and DU oxide gamma ray signatures differ due to the attenuation of low-energy gammas emitted from U-238 daughters. DU signatures can be differentiated from naturally occurring uranium spectra due to the presence of daughters below U-234, primarily bismuth (Bi)-214, in the uranium decay series. Three primary regions of interest (ROI) within the analyzed test spectra are used to roughly characterize the shape of each test spectrum and compare them to background. The three ROIs are focused around the gamma-emitting daughters of U-238: thorium (Th)-234, protactinium (Pa)-234 metastable (m), and Bi-214. One of the three regions is considered the base region. This region is used to estimate what the counts in the other two regions should be by multiplying the counts in the ROIs by a ratio of background counts from an area previously found to be impacted. Using this spectral ratioing technique, a non-zero difference in spectral ratio values indicates a shift in the test spectra away from background. Calculating ratios between the base region and the other two regions allows for a graphical representation of the data in a two-dimensional spectral ratioing space, which is used to differentiate between the types of uranium sources previously mentioned. Surveying processes that are based on gross counts from scintillation counters can result in a large number of false positives as a result of shifting background signals or the presence of naturally occurring uranium. Application of the spectral ratioing technique can further assist in site characterization by analyzing all of the data-starved survey spectra to identify false positives or the need for additional data collection. Accurate surveys of DU testing and training ranges reduces the costs associated with range clean-up by discriminating clean areas from those requiring remediation. (authors)

• Research Organization: WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
• OSTI ID: 22977868
• Report Number(s): INIS-US--20-WM-18619
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
AMMUNITION
BISMUTH 214
CONTAMINATION
DEPLETED URANIUM
GAMMA RADIATION
GAMMA SOURCES
GAMMA SPECTROSCOPY
GLOBAL POSITIONING SYSTEM
OXIDES
PROTACTINIUM 234
SCINTILLATION COUNTERS
SITE CHARACTERIZATION
THORIUM 234
URANIUM 238
URANIUM ORES