Public Safety against a dirty bomb

Wolfram König, President of Federal Office for the Safety of Nuclear Waste Management

Public Safety against a dirty bomb

Type the term "dirty bomb" into any Internet browser and you get a seven-figure hit rate: a neat example of the term’s common currency and, by extension, of the topicality of any discussion focusing on the dangers posed by such a device.

The International Atomic Energy Agency refers to dirty bombs as devices containing conventional explosives with an integral radioactive element or as devices featuring an additional radioactive component. Conventional explosives serve to ensure the wide-ranging dispersal of radioactive materials in the surrounding area. In the USA devices intended to release and disperse radioactivity are therefore referred to as Radioactive Dispersion Devices or RDD; the German equivalent is USBV-A. This abbreviation stands for "Unkonventionelle Spreng- und Brandvorrichtung", the "A" in this context means "atomic".

The potential threat of a dirty bomb

The use of a dirty bomb and comparable scenarios are currently regarded as the most likely form of deliberate misuse of radioactive material. Other scenarios such as the use of a nuclear weapon, improvised or otherwise, have on the other hand been conventionally regarded as far less likely. As concerns the likelihood of a dirty bomb scenario, I would say this:

1. Drawing on generally accessible sources, it can be assumed that terrorist organisations are considering using radioactive materials.
2. Radioactive materials are used widely around the world in the fields of medicine, technology and research.

Putting aside the probability of such a scenario, it remains necessary to analyse the potential threat posed by a dirty bomb. For its part the Federal Office for Radiation Protection has come to the conclusion that the radiological dangers of a dirty bomb are commonly overestimated. This is naturally in direct reference to the radiological dangers; the BfS is not called upon to assess any other associated risks directly.

The BfS bases its conclusion on estimates concerning the radiological aftermath of plausible attack scenarios. Let’s start by addressing the basics: Radioactive materials can impair health in a number of different ways. If an individual is directly exposed to radiation emitted by radioactive materials in the environment, this is known as direct radiation. If radioactive materials are absorbed by the body and begin "radiating immediately from within", this is known as incorporation, which in turn may occur in two different ways: by inhalation (intake via the respiratory tract) or by ingestion (intake via foodstuffs).

Three ways in which individuals may be affected

In the event of a dirty bomb explosion and the dispersion of the radionuclides used, those individuals in the area may be affected in three different ways.

1. The dispersed material is located in the environment and emits radiation, leading to individuals being exposed to direct radiation. Radiation intensity is dependent on the person’s proximity to the dispersed radioactive materials. Therefore, knowing whether the radioactive material is finely dispersed or evident in larger particles is crucial to any analysis.
2. Fine dispersal is also of relevance when considering inhalation, the second impact route of radioactive materials. If those responsible manage to disperse the materials so finely that the particles are respirable (i.e. are smaller than approximately 2 micrometers and can thus penetrate the lungs via the respiratory tract), additional radiation exposure from within is possible.
3. When it comes to terrorist attack scenarios, the third way – incorporation - in contrast to “general emergency response” situations, which describe accidents at nuclear facilities in Germany and elsewhere, plays a very minor role.

As far as terrorist attack scenarios are concerned, it may be assumed that it would be possible to evacuate those individuals in question swiftly from the rather restricted geographical area affected. Measures implemented by the civil protection agencies would thus be largely able to prevent foodstuffs from the affected area from being consumed.

"LASAIR" analysis

In LASAIR, a program system designed to simulate the dispersal and inhalation of radionuclides, the BfS has produced a computer program with the aim of estimating the atmospheric dispersal of radionuclides and the radiation dose that would affect humans as a result. The program is based on the Lagrange particle dispersion model.

Dose rate calculations are principally derived from the following parameters:

• quantity and type of radioactive material
• quantity and type of explosive used
• local weather conditions including subsequent development, plus
• orography, i.e. roughness and other terrain characteristics.

The BfS has made this program available to other government bodies. It even enables the evaluation of potential civil radiation exposure caused by direct radiation prior to any release, and in this case solely via inhalation, which makes sense.

Key parameters are the quantity and type of radioactive material used. When constructing a dirty bomb, potential operatives are most likely to use those radioactive materials found in technological or medical applications.

Securing nuclear facilities

The first move when initiating protection against the impact of such a weapon is naturally to ensure the physical protection of any radioactive materials on site, thereby ruling out any misuse. The BfS and the other nuclear licensing bodies monitor adherence to these requirements under the heading "Securing nuclear facilities" in accordance with a set of rules approved between federal and state ministries of the interior and of the environment.

The globalisation of terrorism is addressed by programmes such as the "Global Initiative to Combat Nuclear Terrorism", in which a number of states have undertaken to co-operate in future when it comes to protecting civilian nuclear facilities. This is how we can make an active contribution within Germany and other countries. It will, however, do nothing to prevent contraband in radioactive materials.

The use of radioactive materials in industry and medicine

Which radioactive materials are used in medicine and technology that could potentially be misused as radiation sources for dirty bombs? To provide an insight into the scope of their technical application outside nuclear facilities, I include a couple of examples:

• Iridium-192 is by far the most commonly used radionuclide in material testing. It is particularly suited to tests on iron components between 1 and 7 cm thick and posesses a very high specific activity, thus allowing the quantity of the radiation source used to be kept to a minimum.
• The second most commonly applied material is cobalt-60, which is generally used for larger gauge iron components – between 5 and 15 cm. Specific activities commonly used these days range from around 7 to 15 terabecquerel per gram.
• Silo level sensors generally work with gamma sources (cobalt-60 and caesium-137) with an activity of up to 1 gigabecquerel. Measurements are based on the density-dependent absorption of ionised radiation.
• The radionuclides krypton-85, strontium-90 and promethium-147 are generally used as beta emitters and cobalt-60 and caesium-137 as gamma emitters when measuring thickness and density. Activity ranges from between approximately 370 megabecquerel to 370 gigabecquerel.
• Equipment using beta radiation is found in the paper, textiles, rubber and plastic industries, whereas gamma radiation devices are used in the timber, foam and steel industries to measure thickness, and in the food and chemical industries for measuring density.
• As regards medical applications, it is once again cobalt-60 and caesium-137 that present the greatest potential for misuse.

Evacuation the exception

On this basis, it is possible to estimate the radiological consequences for the civil population were such a source to be used to create a dirty bomb. As a result, the following emerges: Even in the event of larger quantities of caesium-13, the dose rates for the population would be so low in the immediate vicinity, i.e. outside direct detonation range, that special radiation protection measures, such as staying indoors or even evacuation, would not be necessary.

It would be different in the case of an attack using plutonium-239, which is known to possess much greater radiotoxicity than all other nuclides under consideration. In such an instance, scenarios are conceivable in which emergency protection measures would be required in the immediate vicinity and within a radius of several kilometres from the detonation site, since it would not be possible to rule out effective dose values in the region of 100 mSv for individuals residing in the area. Plutonium-239, however, is neither used in industrial or medical applications; it is a product of nuclear facilities, and its misuse therefore depends on achieving access to extremely high-security sites.

Civil protection parameters: the effective dose

100 mSv is the effective dose also used as the parameter by civil protection agencies to determine when population evacuation following a nuclear accident is necessary. This value owes its radiation-hygienic justification to the fact that, if exceeded, direct and acute detriment to health can not be ruled out.

To sum up, this means: Even in the immediate vicinity of the detonation site, dirty bombs using radioactive materials found in industrial and medical contexts would accordingly pose no radiological risk to the majority of civilians. The potential radiological threat of a dirty bomb is limited.

Civilian fears – a risk not be underestimated

The explosion of a dirty bomb, however, would likely lead to great anxiety among the population and – owing to ignorance concerning the actual danger and the association with atomic explosions – to overreaction. Measures aimed at countering this threat are therefore especially important.

To the general public, the radiation emitted by a dirty bomb is an unknown quantity. The potential population reaction mechanisms are well-known. An association with the known consequences of radiation exposure produces psychosocial effects, such as insecurity (authoritarianism, aggression), excessive strain (distress, panic), fear and uncontrolled reactions (hysteria, hyperactivity and overloading communication lines).

Comprehensive prevention strategy crucial

The association with nuclear weapons in particular, with the devastating aftermath that followed the atomic bombing of Hiroshima and Nagasaki, with the latent danger during the Cold War, combined with the feeling of personal powerlessness when it comes to perceiving the danger – humans have no means of sensing this type of radiation – means we face some unique challenges.

The credibility of government bodies and with it their ability to act, can suffer in such situations. Informing the public about the actual threat, preventative measures and – hopefully never necessary – coping with the aftermath, are therefore the logical additional components of any comprehensive prevention strategy.

Transparent information essential

Taking the knowledge we have accrued in the field of general emergency protection, the BfS has also commissioned research into methods of conveying information to the public in the case of terrorist threats. These issues are currently being addressed by a project with the admittedly rather cumbersome title of "Public relations and measures concerning extraordinary (bearing no relation to nuclear facilities) nuclear accident prevention in the case of new types of threat: information provision and handling in the face of nuclear terrorism".

An interim report was issued in August 2006. This clearly indicates that the public discussion concerning the dangers of nuclear power is a major factor in this context, because it affects the ability to communicate of those involved (politicians, government bodies and individuals).

As well as developing strategies for PR work in the aftermath of such an event, preventative information is also regarded as a priority. Through such means, government bodies must earn the trust of the population, trust that will be crucial should an attack occur - if the feared consequences arising from the public’s reaction to the event are to remain as limited as the radiological aftermath.

German security authorities well-prepared

In operational terms, Germany’s security authorities, including the BfS, are well-prepared to defend the population against any attack using a dirty bomb. Preventing the illegal purchase and the misuse of such sources is of prime importance. Compared with safeguards in other European countries, the measures already implemented within the relevant sectors in Germany are of a high standard.

European initiatives to align the different standards used by the various member states are underway. In addition, Germany’s federal and state security authorities have taken steps to reduce the probability and potential aftermath of what currently remains a hypothetical event still further.

Central federal support group

Two preventative measures have already been mentioned: the securing of nuclear facilities and the informing of the general public, preferably prior to such an event, of the extent of such a threat.

The Federal Office for Radiation Protection has recently established yet another important preventative measure – a register of highly radioactive sources, the so-called HRQ register. This is used to record every radioactive source exceeding a certain (isotope-dependent) activity, making it possible to ascertain the whereabouts of said material at any time. This register may be accessed by the German security authorities.

Focal element: police work

Police work nevertheless remains the focal element in the fight against nuclear crime. This is the responsibility of the individual federal states. The local police force receive support in this area - known as "Defence Against Nuclear Hazards" - from the relevant state radiation protection office. The federation offers additional backup in the form of the "Central Federal Support Group for Serious Cases of Nuclear Hazard Defence", or ZUB for short. Of course any serious indication of a terrorist attack being planned for a target in Germany involving the use of radioactive materials is regarded as a serious case.

At the ZUB the Federal Bureau of Investigation, the federal police force and the Federal Office for Radiation Protection co-operate together. In a state of perpetual readiness, the ZUB is able to spring into action at any time. Its responsibilities include the detection of radioactive materials, the identification of nuclides and their activity (i.e. their magnitude), estimating potential radiological consequences, and last but not least using police measures to avert the threat effectively. Of crucial importance to the ZUB is that the concepts of common action developed for the scenarios under consideration are continually updated and practised by means of ongoing training.

Keeping pace with developments

Should such prevention measures fail, not only the forensic experts but also the federal and state emergency and civil protection services would be called upon to take action. Another crucial aspect would be a comprehensive, tried and tested, crisis information policy that takes the concerns of both the population and the emergency task force – with the emphasis on the latter – into account.

The Federal Office for Radiation Protection is responsible in such instances for advising federal decision-makers on health-related radiological issues and radiation protection measures. The organisation also keeps its operatives in a state of readiness for such an attack. This allows it for instance to offer call-off support for decontamination programmes.

Conclusion

As far as the limited radiological consequences of a dirty bomb scenario, as described at the outset, are concerned, we in Germany are sufficiently well-prepared. Unfortunately, the ongoing adaptation of international terrorism to the defence measures taken by individual countries means that our strategies constantly require updating – for instance when it comes to measuring technology or logistics. And this will continue to be a drain on resources in future.

In conclusion therefore, it should be noted that:

Estimates concerning the radiological aftermath of a dirty bomb scenario reveal that one would only expect to find alarmingly high dose values in those individuals in immediate proximity to the detonation site.

For the majority of the population, the subjective perception of the health risks produced by a dirty bomb attack would exceed the actual risk of radiation exposure and could therefore lead to comparably a high rate of secondary consequences.

Averting the threat of a dirty bomb attack requires action from the government: operative measures to avert such threats, operative measures to cope with such attacks, the preventative dissemination of information to allow the population to properly assess the risks associated with such an event, and comprehensive communications in the event of a crisis.