Probabilistic Risk Assessment for Radiological Dispersal Devices


D. S. Haslip, L. S. Erhardt, C. L. Larsson, M. R. Desrosiers, D. Cole, E. J. Waller


Recent events have focused attention on radiological dispersal devices (RDDs) as potential terrorist weapons. However, there are many outstanding questions as to the feasibility of constructing and deploying an RDD, and to the effectiveness of such a weapon once it is deployed. As a result, emergency response plans and radioactive materials (RAM) security enhancements are driven by incomplete risk assessments (at best) or even conjecture and misinformation (at worst). Hence, there is a need for a well-researched, comprehensive risk assessment to address all aspects of RDD construction and use. We have developed a probabilistic risk assessment (PRA) model for the terrorist use of RDDs. The PRA is created using the fault- and event-tree analysis familiar to the nuclear industry. The PRA includes such critical and diverse elements as RAM acquisition, risks and difficulties in constructing a device, the feasibility and efficacy of various delivery mechanisms, and the consequences of RDD use. Interpretation of the PRA results diverge from classic PRA applications, since this analysis is designed to provide risk indicators, as opposed to failure probabilities. The PRA database is populated with information from a plethora of sources, including experimental trials we conducted on the efficacy of a variety of dispersion modalities. A software tool facilitates access to the PRA database. This tool allows intelligent searching and manipulation of the database. This would include, for example, identifying scenarios of highest concern under a set of user-specified restrictions (such as particular isotopes or dissemination modalities).


This abstract was presented at the 38th Annual Midyear Meeting, "Materials Control and Security: Risk Assessment, Handling, and Detection", Materials Control and Security Risk Assessments Session, 2/13/2005 - 2/16/2005, held in New Orleans, LA.

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