Aerial Mobile Radiation Survey Following Detonation of a Radiological Dispersal Device

Abstract

A series of experiments was conducted in 2012 at the Defence Research and Development Canada's Suffield Research Centre in Alberta, Canada, during which three radiological dispersal devices were detonated. The detonations released radioactive (140)La into the air, which was then carried by winds and detectable over distances of up to 2 km. The Nuclear Emergency Response group of Natural Resources Canada conducted airborne radiometric surveys shortly following the explosions to map the pattern of radioactivity deposited on the ground. The survey instrument suite was based on large volume NaI(Tl) scintillation gamma radiation detectors, which were situated in a basket mounted exterior to the helicopter and oriented end-to-end to maximize the sensitivity. A standard geophysical data treatment was used to subtract backgrounds and to correct the data to produce counts due to (140)La at the nominal altitude. Sensitivity conversion factors obtained from Monte Carlo simulations were then applied to express the measurements in terms of surface activity concentration in kBq m(-2). Integrated over the survey area, the results indicate that only 20 to 25% of the bomb's original inventory of radioactive material is deposited within a 1.5-km radius of ground zero. These results can be accommodated with a simple model for the RDD behavior and atmospheric dispersion.

Deposition Measurements From the Full-Scale Radiological Dispersal Device Field Trials

“…These plots are most accurate when using a technique like in situ gamma measurements that intrinsically average over a wide area, as witnessed by the good agreement between the RadEye PRD array measurements and the airborne measurements reported by Sinclair et al (2016). For these trials, measurements showed that 15-30% of the original source was deposited within 450 m from ground zero.…”

“…Again, the data for shot 3 are suspect due to the path of the plume. Another comparison between these deposition plots and those reported by Sinclair et al (2016) from helicopter survey data. Their helicopter survey cumulative deposition plots show deposition (up to~450 m from ground zero) consistent with a deposition velocity, v d = 35 mm s −1 for shot 1 and v d = 20 mm s −1 for shot 2.…”

“…The in situ gamma measurements provide the gamma dose-rate due to the ground shine produced by the deposited radioactive contamination. These measurements are complementary and can be used for cross-comparison with other data sets, such as the helicopter-based aerial radiation surveys (Sinclair et al 2016), as well as for comparison with dispersion models (Lebel et al 2016a;Purves and Parkes 2016;Neuscamman and Yu 2016).…”

“…5. The indicated plume centerlines were based upon aerial measurements of ground deposition(Sinclair et al 2016).…”

Introduction to the Special Issue on Experiments Involving the Outdoor Energetic Release of Radioactive Materials

“…Measurements of the deposition are presented in three papers. Erhardt et al (2016) present deposition measurements taken using handheld and fixed-point, in situ, beta and gamma detectors, Sinclair et al (2016) present aerial survey measurements of the deposition, and Berg et al (2016) present laboratory analysis of measurements using passive deposition filters. Comparison of dispersion model results to the FSRDD Field Trial measurements and analysis of model performance are presented in four papers.…”