atw - International Journal for Nuclear Power | 06.2021

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atw Vol. 66 (2021) | Issue 6 ı November 22 ENVIRONMENT AND SAFETY Practical Response to a Dirty Bomb James Conca Introduction The global community has recognized that a class of weapons known as radiation dispersal devices (RDDs), or dirty bombs, pose a grave threat to the United States and the European Union. Dirty bombs use conventional methods, such as a car bomb, to disperse radioactive materials in a populated economic district to cause great economic and social disruption disproportionate to their actual radiological effects and well beyond the physical destruction from their conventional bomb components. They take many forms, from containers of radioactive materials wrapped with conventional explosives, to aerosolized materials sprayed by conventional equipment, to manual dispersion of fine powders into the environment [1]. Also included are radiation-exposure devices (REDs), used to expose people to dangerous beams or particles of radiation. RDD attacks can produce general panic, immediate death and long-term increases in cancer incidence, longterm loss of property use, disruption of services, and costly remediation of property and facilities. The risk is more than just theo retical. Several credible designs and plans for a dirty bomb attack against the United States have been found in Al Qaeda records. About 20 years ago, two actual dirty bombs were deployed by Chechen separatists; one was foiled and the other failed. In the mid-2000s, 38 Alazan shoulder-fired missiles outfitted with 137 Cs dirty bomb warheads were for sale from a Moldovan arms dealer. Fortunately, few people will likely die from the radiological effects of a dirty bomb although tens to hundreds could die from the conventional blast. Unfortunately, with no precedence, we are struggling with generalizations | Fig. 1. Radiation dispersal devices (RDDs), or dirty bombs, are devices that disperse radioactive materials by any means possible. The most effective means of dispersal from a terrorist standpoint is the car bomb with several pounds of highly radioactive material that is easily dispersable, e.g., 137 CsCl powder in an Oklahoma-type ANFO car bomb. (Photo: Courtesy of Middle East Intelligence Bulletin) and how to prepare and respond to the first event. The following structures the problem and provides guidelines that are fluid and which should be formalized by the Department of Homeland Security (DHS) in conjunction with the Department of Energy (DOE, the Nuclear Regulatory Commission (NRC), the International Atomic Energy Agency (IAEA) and other cognizant agencies around the world. Rules of Thumb The challenge to training anyone outside the fields of radiation, radiochemistry and nuclear science is to provide enough information to be useful without creating confusion. First responders know all too well how dangerous it is to oversimplify. However, it is not possible to make all responders radiochemists or health physicists. So some simplifying concepts are in order: 1) the logistical difficulty in successfully carrying out a significant dirty bomb attack is roughly the same as that of the 9-11 attacks, 2) the most likely device will be a 137 CsCl car bomb and the level of response and danger to responders is of the order of a 20 alarm fire, 3) defining the hot zone is the most important first response and a simple alarming dosimeter is the most useful piece of equipment for a dirty bomb attack, 4) following protocols, it is difficult to obtain a significant radiation dose in the first hours of response to an attack without actually handling radioactive material, 5) the greater the dispersion, the greater the affected area, but the lower the dose, 6) the scene will be a war zone, not a superfund or environmental cleanup site, 7) it is possible to quickly triage most victims without significant harm to the responder, 8) persons with no significant physical injuries should not be significantly contaminated, 9) while not effective against g-radiation, the PPE of a firefighter (uniform, gloves, goggles and/or air purifying respirator) will provide complete protection against a- and b-radiation, and almost complete protection against ingestion and inhalation of radioactive material dispersed by the attack, including g-emitting radioactive material, and 10) removing clothing and washing with soap and water is effective at removing radioactive contamination. The greater the training and experience with radioactive materials, the better able the responder will be to evaluating the usefulness of such generalizations. Dirty Bomb Materials Radioactive materials are used in many fields in almost all countries around the world, particularly for research, medical, and industrial applications. Dozens of radiological source producers and suppliers are found on six continents, and about a billion sources exist worldwide although most, like household smoke detectors, have such low specific activities that they pose no threat. With the increase of radioisotope applications in nuclear medicine diagnostics, therapeutics, sterilization and the food irradiation, the radio logical source production and fabri cation industry is an emerging growth industry in several countries, parti cularly in areas with depressed eco nomies. The rise in the number of terrorist acts during the last ten years has raised concerns about these radiological sources being used in RDDs. Because the general public is so frightened about anything radioactive, panic must be anticipated even if there is no likely health threat from the radioactive component. The degenerate case of a phantom RDD, where no radioactive material is used but an implication or anonymous tip indicates there is, could still cause considerable panic with large economic consequences, particularly in this era of fake news. The serious radiological threats come from large RDDs containing Environment and Safety Practical Response to a Dirty Bomb ı James Conca
atw Vol. 66 (2021) | Issue 6 ı November | Fig. 2. The primary uses, specific isotope and activity levels of radiological source materials. Note that the largest sources use only 60 Co, 137 Cs or 90 Sr (Courtesy of Greg van Tuyle). thousands to hundreds of thousands of curies (Ci) of activity. These could cause significant and lasting health and contamination problems. Although many variables determine the effectiveness of an RDD attack, the key factor is the quantity and type of radiological source material that is dispersed. Although it has been difficult to quantify, globally there are about 10,000 sources that exceed 1000 Ci, and perhaps a thousand that exceed 100,000 Ci. Briefly, the differences in sources relate to their specific activity (the type and amount of radiation emitted), and its chemical form (whether it is a powder, and nonmetal solid or a metal). Gamma radiation (g) can penetrate great distances and, depending upon the energies, requires shielding of about 7 inches (18 cm) of lead (Pb) or about 3-feet (1 meter) of reinforced concrete. Beta radiation (b) can only penetrate a short distance and the personal protective gear of a firefighter can block much of the dose. Alpha radiation (a) is the least penetrating of all and can be stopped by a piece of paper or ordinary clothing. The most important pathway of accumulating dose from a or b sources is ingestion, or particularly inhalation, where the emitter is directly adjacent to tissue for long periods of time. For g sources, mere proximity is all that is required for significant doses. For RDD discussions, isotopes of Pu, Am and U are primarily a emitters, 60 Co and 137 Cs are g emitters, and 90 Sr is a b emitter. 60 Co usually occurs as a metal (either pellets or small rods), 137 Cs is as a powder, 90 Sr is as a ceramic titanate, and Pu, Am and U are various oxides, metals, salts and non-metal solids. Although the public generally thinks of Pu and enriched-U when hearing the word radioactive, these are not considered RDD materials of choice because they are primarily a emitters, are costly, cannot be obtained in large amounts, are welltracked and secured, and are more useful to terrorists in the production of actual nuclear weapons than in being wasted in an RDD. In this sense, 137 CsCl powder is much more effective as an RDD material. Although inclusion of any radioactivity, no matter how small, in a dirty bomb will cause disruption at some level, the real health and economic threat resides in large sources | Fig. 3. 137 CsCl powder, presently used in the irradiation industry, is the dirty bomb material of choice. 137 Cs is inexpensive (
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atw - International Journal for Nuclear Power | 06.2021

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