Dirty bombs: have the risks to the UK increased?

I am frequently asked to assess the risk of a 'dirty bomb' being used for terrorist purposes in the UK. Until now, my response has been that the likelihood of being struck by lightning is greater than that of being hit by a dirty bomb attack. However, I have recently begun to question this reply.

The likelihood of any type of weapon being used is dependent on the capability to produce it, the willingness of an individual or group to use it and the existence of a viable target. If these criteria are satisfied, then there is a high probability of the weapon being used. I believe that a gradual shift in these criteria has increased the probability of a dirty bomb being used on UK soil.

Assessing capabilities

The term 'dirty bomb' refers to a device designed to disperse radioactive material. Examples include attacks on nuclear facilities that produce, store, or use hazardous radioactive materials, including spent nuclear fuel or nuclear material in transit; or the detonation of a conventional explosive surrounded by a radioactive substance, such as those used in research laboratories or hospitals. Conventional explosives, whether improvised, industrial or military, are the staple of modern terrorists.

There have been continued international efforts to increase the physical protection of fissile material and nuclear weapons. For example, in 2005 the UN General Assembly adopted the International Convention for the Suppression of Acts of Nuclear Terrorism, requiring the domestic criminalisation of acts of nuclear terrorism, together with the commitment of the signatories to international co-operation in the prevention, investigation and prosecution of acts of nuclear terrorism. Although beset with many obstacles, including the hindrance of international co-operation due to concerns over the corrosion of sovereignty, legal liability and budgetary constraints, progress has been made in achieving security. However, most commentators agree that medical and laboratory sources, including waste, remain vulnerable.

The size and extent of the international market for radioactive sources is at the root of the security problem. Sources are used in many fields, including nuclear and energy, metallurgy, geology, mining, ecology, metrology, chemistry, oil and gas, medicine and agriculture. The main focus of regulation in this area has been the protection of workers and the public from the misuse of and accidents involving such materials. Security has concentrated on petty theft and accidental loss rather than the threat from organised criminal activity.

However, the International Atomic Energy Agency's 2005 report on nuclear trafficking shows a significant increase in illicit radioactive material. This could be a temporary rise or it could signal the start of a trend. However, these figures do not in themselves create cause for alarm. It could turn out that the sources most attractive to smugglers out to make money quickly are not those best suited for the construction of a dirty bomb. Most sources of radioactive material in commercial use are not suitable for bombs. They have too little activity or too short a half-life. Large sources are difficult to weaponise due to the risk of lethal doses to the constructors before deployment.

Nevertheless, these figures do indicate that radioactive material is increasingly being found on the black market. This increases the likelihood of such materials becoming available to those wishing to make dirty bombs.

Willingness to use a dirty bomb

Early studies on political extremism, as reviewed in 1990 by David Knoke in Political Networks: The Structural Perspective, are dominated by psychological explanations. Extremism of ideology is assumed to be a result of marginalisation, alienation or poverty. Extremism of action is assumed to be due to intolerable psychological stress. However, empirical evidence of recent collective actions shows that extremists are generally of high socio-economic status, indicating that extremism of ideology and action are both often rational choices.

The same rational choice has been seen to be true of extreme terrorist actions, such as suicide bombings. Studies such as The Strategic Logic of Suicide Terrorism by Robert A Pape argue that most suicide attacks have occurred in organised, coherent campaigns aimed at democracies, indicating a degree of strategic rationality rather than fanaticism or irrationality.

For would-be terrorists to make a rational choice on whether to take a particular course of action, they would need to understand the potential consequences of that action. However, despite the concerns about security of supply mentioned above, there have been only two documented incidences where ionizing radiation has been used for terrorist purposes. In 1996, rebels from Chechnya planted, but did not detonate, a radiological dispersion device in Moscow's Izmailovo Park. The bomb consisted of dynamite and caesium-137 removed from cancer treatment equipment. Reporters were tipped off about its location and it was defused. In 1998, the head of the Russian-backed Chechen Security Service, Ibragim Khultygov, announced that a Security Service team had found a container filled with radioactive materials and attached to an explosive mine hidden near a railway line. The bomb was safely defused.

Given the scant historical evidence of the effect of such weapons, the decision to use one would rest largely on the terrorists' perception of the effect. Academic sources of information on which to base such perceptions are also scant and obscure. Therefore, terrorists' perceptions of the effects of such weapons might be drawn largely from the depiction of apocalyptic catastrophes in popular fiction and films.

Effects of an attack

However, not every dirty bomb is capable of causing a catastrophe. An attack would have four main effects:

  • injury or damage due to the conventional explosive element of the dirty bomb
  • injury due to contaminated dust inhalation
  • injury or disruption due to contaminated deposited material
  • injury and disruption due to contaminated food and water supplies.

Consequences could also include public panic, even if casualties are low, and the potential for widespread abandonment and demolition. The effects of a dirty bomb would most likely be disruptive rather than destructive.

Although the motivations and aims of those wishing to harm the UK and its interests are wide and varied, the objectives of acts of political terrorism generally fall into five broad categories:

  • capturing attention
  • obtaining acknowledgement of existence
  • securing recognition of a cause
  • establishing authority
  • governance.

With a few notable exceptions, the nature of the act of terrorism perpetrated is generally more closely related to these objectives than to the motivation of the individual terrorist. Therefore, to determine the likelihood of the use of a dirty bomb, it is necessary to establish what the major objective of political terrorism in the UK is.

Events such as the attack on the UK's mass transport system on 7 July 2005 are characterised by their objective to cause mass indiscriminate fatalities. This would indicate that capturing attention is the main objective. Such attacks tend to be perpetrated without warning, breach social norms in terms of methods and targeting, use unsophisticated methods and aim for indiscriminate mass killing.

However, the objective appears to be transitioning from one of capturing attention to one of obtaining acknowledgement of existence. Events designed to obtain acknowledgement of existence are frequently designed to sow seeds of doubt about the governing body. Signatures of this type of act include attacks on critical infrastructure and the use of disruptive rather than destructive weapons.


Whether or not a dirty bomb will be used will ultimately be the result of a dynamic and complex interplay between political, social, technological and economic factors.

However, with radioactive sources increasingly available on the black market and terrorists turning their focus to disruptive rather than destructive attacks, the odds may have tipped in favour of the possibility of a dirty bomb being used in the UK sometime in the future.

Dr Sandra Bell is director of the Department for Homeland Security and Resilience at the Royal United Services Institute for Defence and Security Studies.


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