Misuse of radioactive material in connection with an unconventional explosive device ("dirty bomb")

The dirty bomb scenario is of prime concern in recent international efforts to secure highly radioactive sources against terrorist abuse and use in weapons of mass destruction. Dirty bombs are devices which make use of conventional explosives to disperse radioactive material.

The International Atomic Energy Agency (IAEA) defines a dirty bomb as a device constructed from conventional explosives and radioactive material, the detonation of which would result in the dispersion of the radioactive material contained in the bomb into the environment.

In the USA the term "radiological dispersion device ( RDD)" is used. The German equivalent is "USBV-A". The use of a "dirty bomb" and comparable scenarios are considered possible misuses of radioactive materials.

Potential radiological danger

The potential radiological danger caused by a "dirty bomb" is generally over-estimated. Even for a high-activity caesium-137 source, the dose rates for the public very close to the point of release (i.e. very close to the centre of the explosion) would be so low, that extra radiation protection measures (e.g. staying inside or evacuation) would not be necessary.

The situation is different if plutonium-239 is used in a dirty bomb, as it has a much higher radiotoxicity compared to all other radionuclides considered. Scenarios are possible in which emergency management measures would be necessary up to a few kilometres away from the point of release, as effective dose rates of 100 mSv for members of the public could not be ruled out. An effective dose of 100 mSv is the decision value which is also used for the evacuation of the public during emergeny or disaster management of a nuclear accident resulting in a release of radioactive material.

Psychological effects

Aside from the objective assessment of the radiological danger, associations with the known effects of radiation and its possible health effects, which are long-held among the population, can cause psychological effects, such as; uncertainty (authoritarianism, aggression), feeling over-whelmed (distress), anxiety and excessive responses (hysteria, hyper-activity and over-communication).

The causes of the psychological consequences mentioned above are, in particular; the association with nuclear weapons, the devastating results of the nuclear weapons deployment in Hiroshima and Nagasaki, the latent threat during the cold war, and the feeling of helplessness regarding the detection - humans have no way to sense radiation - and the control of these dangers.

Communication measures

Based on the level of knowledge gained in general emergency preparedness and response, the BfS has commissioned additional investigations into methods of informing the public on the topic of terror threats. Currently, these questions are being investigated in the research project "Public communication and measures for nuclear emergency management not arising from technical nuclear facilities in connection with new forms of threat: Precautionary information and information management in the event of nuclear terrorism".

The initial results (see report below, pp. 72 to 74) show, that the public discussion on the risks of nuclear energy are also an important factor in this regard, as it influences the ability of those affected (state and citizen) to communicate. Along with the development of strategies for public relations after an event, precautionary information for the public before an event is of high importance.