A Case Study Correlating Innovative Gamma Ray Scanning Detection Systems Data to Surface Soil Gamma Spectrometry Results - 13580

Conference · Mon Jul 01 00:00:00 EDT 2013

OSTI ID:22230965

Thompson, Shannon; Rodriguez, Rene; Billock, Paul ^[1]; Lit, Peter ^[2]

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1. HydroGeoLogic, Inc., 11107 Sunset Hills Road, Suite 400, Reston, VA 20190 (United States)
2. Nomad Science Group, 7738 Nautilus Shell Street, Las Vegas, NV 89139 (United States)

HydroGeoLogic (HGL), Inc. completed a United States Environmental Protection Agency (USEPA) study to characterize radiological contamination at a site near Canoga Park, California. The characterized area contained 470 acres including the site of a prototype commercial nuclear reactor and other nuclear design, testing, and support operations from the 1950's until 1988 [1]. The site history included radiological releases during operation followed by D and D activities. The characterization was conducted under an accelerated schedule and the results will support the project remediation. The project has a rigorous cleanup to background agenda and does not allow for comparison to risk-based guidelines. To target soil sample locations, multiple lines of evidence were evaluated including a gamma radiation survey, geophysical surveys, historical site assessment, aerial photographs, and former worker interviews. Due to the time since production and decay, the primary gamma emitting radionuclide remaining is cesium-137 (Cs-137). The gamma ray survey covered diverse, rugged terrain using custom designed sodium iodide thallium-activated (NaI(Tl)) scintillation detection systems. The survey goals included attaining 100% ground surface coverage and detecting gamma radiation as sensitively as possible. The effectiveness of innovative gamma ray detection systems was tested by correlating field Cs-137 static count ratios to Cs-137 laboratory gamma spectrometry results. As a case study, the area encompassing the former location of the first nuclear power station in the U. S. was scanned, and second by second global positioning system (GPS)-linked gamma spectral data were evaluated by examining total count rate and nuclide-specific regions of interest. To compensate for Compton scattering from higher energy naturally occurring radionuclides (U-238, Th-232 and their progeny, and K-40), count rate ratios of anthropogenic nuclide-specific regions of interest to the total count rate were calculated. From the scanning data, locations with observed Cs-137 ratios exceeding six standard deviations above the mean ratio were mapped in high resolution [2]. Field teams returned to those locations to collect static count measurements using the same detection systems. Soil surface samples were collected at 30 locations and analyzed for Cs-137. An exponential correlation was identified between Cs-137 concentrations in surface soil and field-scanned Cs-137 ratios. The data indicate field minimum detectable concentration (MDC) of Cs-137 at 0.02 Bq/g (0.5 pCi/g) or lower depending on contaminant distribution in soil. (authors)

• Research Organization: WM Symposia, 1628 E. Southern Avenue, Suite 9-332, Tempe, AZ 85282 (United States)
• OSTI ID: 22230965
• Report Number(s): INIS-US-13-WM-13580; TRN: US14V0722052050
• Resource Relation: Conference: WM2013: Waste Management Conference: International collaboration and continuous improvement, Phoenix, AZ (United States), 24-28 Feb 2013; Other Information: Country of input: France; 14 refs.
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
CESIUM 137
COMPTON EFFECT
CONCENTRATION RATIO
COUNTING RATES
GAMMA DETECTION
GAMMA SPECTROSCOPY
GLOBAL POSITIONING SYSTEM
NUCLEAR POWER PLANTS
PHOTOGRAPHY
POTASSIUM 40
PROGENY
REACTORS
RECOMMENDATIONS
RECREATIONAL AREAS
REMEDIAL ACTION
SODIUM IODIDES
SOILS
THORIUM 232
URANIUM 238