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TitleAerial mobile radiation survey following detonation of a radiological dispersal device
AuthorSinclair, L E; Fortin, R; Buckle, J L; Coyle, M J; Van Brabant, R A; Harvey, B; Seywerd, H C J; McCurdy, M W
SourceHealth Physics vol. 110, issue 5, 2016 p. 458-470,
Alt SeriesEarth Sciences Sector, Contribution Series 20150258
PublisherHealth Physics Society
Mediapaper; on-line; digital
File formatpdf
ProgramCanadian Hazard Information Service, Canadian Hazard Information Service
AbstractA 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 140La 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 140La 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.
Summary(Plain Language Summary, not published)
The results indicate that not all of the radioactivity of a dirty bomb is deposited locally. This has importance for emergency management. It means that if a radioactive source is known to have been stolen, and only 30% of it has been detected after a bomb explosion, the bad guys are not necessarily still in possession of 70% of the stolen material. Also, experimental validation of dirty bomb models leads to greater confidence in their predictions, also for different configurations from those of the experiment.