Radiometric data collected from an uncrewed airborne system and handheld meters at the Grand Junction Regional Airport radiometric calibration facility, 2023-2024

Radiometric data were collected at the Grand Junction Regional Airport radiometric calibration facility in March 2023 and August 2024. The facility consists of five ~9 by ~12 m (30 x 40 feet) concrete pads, each 18 in thick. Each pad provides sources of radioelements that are spatially homogeneous (see Ward, 1978). Three pads are dedicated K, Th, and U pads, each of which contains high levels of their radioelement namesake. There is also a “mixed pad,” which contains moderate amounts of all three radioelements, and a background pad, which contains low levels of each radioelement. In March 2023, handheld measurements were acquired over all five pads using three different NaI handheld gamma spectrometers, a GF Instruments Gamma Surveyor and two GF Instruments Gamma Varios. These data were collected to assess the precision and accuracy of each hand held meter. In August 2024, a small uncrewed airborne system (sUAS) equipped with a lightweight CsI radiometric sensor, the Medusa MS-350, was flown over the calibration pads at varying heights to observe the radiometric signal decay with height and to determine decay coefficients that can be applied to other radiometric surveys. We performed "hover" tests over the K, Th, U, and Mixed pads, where measurements were taken at 1m, 2m, 4m, 6m, 8m, 10m, 12m, 14m, 16m, and 20m above each pad for a duration of 1 minute at each height.

Reference:
Ward, Dan L., 1978, Construction of Calibration Pads Facility Walker Field, Grand Junction, Colorado: U.S. Department of Energy Report GJBX-237(78), 61 p., https://www.energy.gov/lm/articles/construction-calibration-pads-facility-walker-field-grand-junction-colorado.