Radiological urban threat due to special protective actions from security forces

The neutralization of suspicious objects by a conventional explosion in public places seems to be an option often considered by security forces. A radiological dispersive device (RDD) uses a radioactive material coupled to an amount of conventional explosive in order to contaminate an area. Extremist groups may take advantage of such protocol by leaving the radioactive material in public places to provoke suspicion, thus leading to the neutralization by an explosion, which in turn creates a RDD event. This work aims to discuss the influence of such a protocol in the radiological threat by means of computational simulation. The total maximum effective dose equivalent (TEDE Max), the Pasquill–Gifford atmospheric stability classes (PG classes), and the potentially affected population size were evaluated. The results consider two radionuclides Cs-137 and Sr-90. The findings allow us to infer that TEDE Max and surface contamination are strongly dependent on the PG classes. In addition, the affected population size depends on the plume size, which seems to be independent of the radionuclide, but not of the PG classes. Therefore, PG classes play a key role in the radiological threat. The findings may be of value to support decisions when facing an event.