On the Categorization of Radiological Terrorism Threats

Abstract

Purpose: To develop approaches to categorizing (ranking) radiological terrorism (RT) threats on the basis of expert assessment of the possibility (likelihood) of the implementation of certain RT scenarios and assessment of their medical and hygienic consequences. 
 Results: Five categories of RT threats are highlighted. The first (most hazardous) threat category includes situations related to the use of radioactivity dispersing devices (RDD), including the “dirty bomb”. It is shown that the creation of a potential threat of radiation exposure to people at the thresholds of deterministic effects may require the activity of radionuclides in RDD in the range of several hundred TBq. The second category of threats includes scenarios of RT related to the placement of high dose rate radionuclide sources in areas of permanent location or mass gathering of people. The third category of threats includes situations when radionuclide sources maliciously place (enclose) into technological equipment and processes, which leads to radioactive contamination of the environment, industrial and socially significant facilities (water treatment plants, warehouses of food and raw materials), manufactured products. It is shown that in the case of the implementation of such RT scenarios, the dose criteria that require protective measures for the public are unlikely to be achieved. The fourth category of threats includes the physical impact on radioactive materials in the nuclear reactors, fuel element storage pools, and radioactive waste storage facilities. The fifth category of threats includes scenarios of RT related to the use of improvised nuclear devices or nuclear weapons by terrorists. 
 Conclusion: Threats of categories I–III, given the combination of the possibility of implementing RT scenarios and the scale of medical and hygienic consequences, are estimated as relatively high. Threats of category IV and V due to the extremely low probability of their implementation have the lowest rating, despite the great and even catastrophic nature of the consequences.