Assessing the dose after a radiological dispersal device (RDD) attack using a military radiac instrument

Abstract

The detonation of a radiological dispersal device (RDD) may result in casualties receiving exposure of radioactive materials. Assessments of potentially contaminated personnel are necessary to determine the level of contamination received in order to prioritize and treat individuals. The use of improvised explosive devices (IEDs) and the number of orphan sources in deployed and combat areas such as Iraq, present an opportunity for terrorists to use an RDD against deployed ground forces. There is limited capability in Iraq to assess radiological casualties, as the process of obtaining and analyzing bioassays is time consuming and not readily available in country. Military units are equipped with AN/VDR-2 and AN/PDR-77 radiac detectors which are capable of detecting gamma radiation. Therefore, a study of the use of these radiac sets in assessing internal contamination was conducted. A model of the detector probe was created using the Los Alamos National Laboratory Monte Carlo N-Particle transport code, MCNP Version 5. This model was experimentally validated and used in conjunction with both reference male and reference female computational Medical Internal Radiation Dose (MIRD) phantoms to compute internal dose. The instrument model was evaluated at the following locations, the posterior upper right torso, the anterior upper right torso, the lateral upper left thigh and the anterior of the neck. Nuclides were distributed throughout the phantoms using the Oak Ridge National Laboratory Dose and Risk Calculation (DCAL) software for inhalation pathways. Based on the likelihood for use in RDDs and the capabilities of the instrument, Co-60, Cs-137 and Ir-192 were evaluated.