Other Dimensions of Radiological Terrorism
John F. Ahearne
Sigma Xi, The Scientific Research Society
An examination of possible threats to the United States and Russia begins with the conclusion that there are groups in the world who would like to destroy these countries or, at least, topple their governments. Russia has experienced a number of terrorist attacks such as the hostage taking in a Moscow theater, suicide bombers on airplanes, and the horrific siege of a school full of children. The United States has experienced the September 11, 2001, terrorist attacks.
A 2002 National Academies study, Making the Nation Safer: The Role of Science and Technology in Countering Terrorism,1 grouped nuclear and radiological threats into three categories:
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stolen state-owned nuclear weapons or weapons components, modified as necessary to permit terrorist use
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improvised nuclear devices (INDs) fabricated from stolen or diverted special nuclear material (SNM)—plutonium and, especially, highly enriched uranium (HEU)
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attacks on nuclear reactors or spent nuclear fuel or attacks involving radiological devices
For these categories, that report provided matrices of the threat, risk (probability and consequence), and policy issues, shown in Table 1.
Potential Consequences |
Probability of Occurrence |
Technical and Policy Changes |
Approaches to Mitigation |
Potentially catastrophic-massive loss of life and severe political and economic destruction possible |
Moderate over the next five years, with a high potential for surprise |
Theft or diversion may not require state assistance and may go undetected if theft occurs in Russia |
Improve indications and warnings capabilities |
|
|
Stolen or diverted weapons could be converted for terrorist use |
Improve security of Russian and Pakistani nuclear weapons at storage sites and borders |
|
|
HEU-based weapons smuggled into the United States could be difficult to detect and recover |
Accelerate deployment of sensor arrays at critical U.S. entry points and targets |
|
|
First responders may be killed or incapacitated by attack |
Develop and announce policies to deter use of weapons by terrorist states |
|
|
|
Improve attribution capabilities |
A recent book2 added radioactive sources to this list and described what the authors called the four faces of nuclear terrorism, as follows:
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the theft and detonation of an intact nuclear weapon
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the theft or purchase of fissile material leading to the fabrication and detonation of a crude nuclear weapon—an IND
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attacks against and sabotage of nuclear facilities, in particular nuclear power plants, causing the release of large amounts of radiation
Potential Consequences |
Probability of Occurrence |
Technical and Policy Changes |
Approaches to Mitigation |
Potentially catastrophic-massive loss of life and severe political and economic destruction possible |
Moderate over the next five years, with a high potential for surprise |
Theft or diversion may not require state assistance and may go undetected if theft occurs in Russia |
Improve indications and warnings capabilities |
|
|
Stolen or diverted weapons could be converted for terrorist use |
Improve security of Russian and Pakistani nuclear weapons at storage sites and borders |
|
|
HEU-based weapons smuggled into the United States could be difficult to detect and recover |
Accelerate deployment of sensor arrays at critical U.S. entry points and targets |
|
|
First responders may be killed or incapacitated by attack |
Develop and announce policies to deter use of weapons by terrorist states |
|
|
|
Improve attribution capabilities |
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the unauthorized acquisition of radioactive materials contributing to the fabrication and detonation of a radiological dispersion device (RDD)—a dirty bomb—or radiation emission device (RED)
The authors of this book wrote, “The United States has faced the threat of nuclear terrorism for many years, but this peril looms larger today than ever before.”3
Finally, at the Workshop on Terrorism in a High-Tech Society and Modern Methods for Prevention and Response in 2001, the following was presented from the Russian viewpoint:
TABLE 1-B Improved Nuclear Devices |
||
Threat Category |
Threat Description |
Threat Level |
Improvised nuclear devices |
Theft or diversion of SNM for fabrication of nuclear devices for use against U.S. targets or assets |
United States: Low—SNM is well protected |
|
|
Britain, China, France, India, Israel, Pakistan: Low—small amounts of materials are well protected |
|
|
Russia: High—large inventories of SNM are stored at many sites that apparently lack inventory control, and indigenous threats have increased |
SOURCE: NRC Committee on Science and Technology for Countering Terrorism. 2002. Pp. 42–47 in Making the Nation Safer: The Role of Science and Technology in Countering Terrorism. Washington, D.C.: The National Academies Press. |
Potential Consequences |
Probability of Occurrence |
Technical and Policy Changes |
Approaches to Mitigation |
Potentially catastrophic-massive loss of life and severe political and economic destruction possible |
Moderate over the next five years, with a high potential for surprise |
Theft or diversion may not require state assistance and may go undetected |
Improve indications and warnings capabilities |
|
|
Crude HEU weapons could be fabricated without state assistance |
Consolidate SNM at Russian sites, improve inventory controls, and improve security at sites and borders |
|
|
HEU-based INDs smuggled into the United States could be difficult to detect and recover |
Accelerate blend-down of Russian HEU |
|
|
First responders may be killed or incapacitated by attack |
Accelerate the development and deployment of SNM sensor arrays at critical U.S. entry points and targets |
|
|
|
Improve capabilities for remote detection of HEU |
|
|
|
Develop and announce policies to deter use of INDs by terrorist states |
|
|
|
Improve attribution capabilities |
Terrorist acts using sources of radiation may be divided into three categories:
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the detonation of (or threat to detonate) either a nuclear explosive device stolen from storage arsenals or a homemade nuclear bomb device using highly enriched uranium or plutonium
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the theft of radioactive waste material and similar substances from nuclear facilities such as atomic power stations, research reactors, irradiated fuel processing plants, and storage facilities
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the detonation of an ordinary explosive device including radioactive isotopes as one of its components (60Co, 90Sr, 137Cs, 239Pu, and so forth), with the aim of subsequently dispersing them over significant areas; this category would also include the possible addition of radioactive substances to water systems4
NUCLEAR BOMBS
The National Commission on Terrorist Attacks Upon the United States wrote the following:
The greatest danger of another catastrophic attack in the United States will materialize if the world’s most dangerous terrorists acquire the world’s most dangerous weapons. [We note that] al Qaeda has tried to acquire or make nuclear weapons for at least ten years.5
The greatest concern is an actual nuclear bomb. A bomb is not necessarily a nuclear weapon, which implies a device designed to be used in warfare, mounted on an airplane, in a missile, or used in a torpedo or landmine. A nuclear bomb is a device than can result in a nuclear explosion. India exploded a “peaceful” device in May 1974. Of course, theft of a real weapon could be disastrous, if the thieves knew how to set it off. This is not particularly easy and may be impossible unless the thieves included insiders.
Whereas there is serious concern about radiological sources, especially for high dose-rate sources hidden in congested areas, use of a nuclear device would be catastrophic. This could be delivered using the current delivery system of choice—a truck bomb. Another delivery system would be on a ship berthed in a city’s harbor.
How could such a nuclear device be made? As stated by the NRC Committee on Upgrading Russian Capabilities to Secure Plutonium and Highly Enriched Uranium, “A major technical impediment confronting a nation or group bent on
developing nuclear weapons is the difficulty of obtaining the necessary directuse material. A minimum of a few kilograms of plutonium or several times that amount of highly enriched uranium (HEU) is required, with the quantity depending on the composition of the material, type of weapon, and sophistication of the design.”6
To make a nuclear device, one needs fissile material, either highly enriched uranium or plutonium (Pu). The amount for an explosion is related to the critical mass needed for the chain reaction that is the explosion. This “is about 10 kilograms for plutonium-239 and about 60 kilograms for uranium-235, when these materials are in the form of metal spheres at their normal density. In nuclear weapons, these values might be reduced by a factor of 4 if the force of a powerful explosive is sufficient to double the density of the plutonium by compression….”7
Although much less material is needed, plutonium devices are harder to make and plutonium is harder to obtain. It is not naturally occurring, but must be produced in neutron irradiation of uranium followed by chemical separation of the plutonium, that is, reprocessing of the irradiated uranium. This requirement makes it unlikely to be constructed by a subnational group. Also, once made, it is radioactive and therefore not easily hidden from inspections or surveillance.
However, uncomfortably large amounts of plutonium from the reprocessing of spent fuel exist in several countries, such as Russia. Although this plutonium is not weapons grade but reactor grade, it is quite adequate to make a nuclear weapon. “[I]t would be quite possible for a potential proliferator to make a nuclear explosive from reactor-grade plutonium using a simple design that would be assured of having a yield in the range of one to a few kilotons, and more using an advanced design.”8
HEU weapons are easier to construct. The key factor is obtaining the fissionable material. HEU is made by reducing the amount of nonfissionable uranium in naturally occurring uranium. Enrichment technology is well known, although it is advanced technology. While it may be difficult to obtain HEU, the Pakistan nuclear designer A. Q. Khan apparently widely spread the knowledge and technology. It still is not easy for a nonnational group to obtain enrichment technology. However, there is another route to obtain HEU: steal or divert it from a research reactor, many of which are fueled with HEU. The United States and Russia, as well as many other countries, have such research reactors, which are a growing nonproliferation concern.9
In one of a series of articles on threats, a reporter for The Washington Post wrote, “Nuclear scientists tend to believe the most plausible route for terrorists would be to build a crude device using stolen uranium from the former Soviet Union. Counterterrorism officials think Bin Laden would prefer to buy a readymade weapon stolen in Russia or Pakistan and to obtain inside help in detonating it.”10
ACCESS TO SPECIAL NUCLEAR MATERIAL
In discussing the future threats to the United States, the National Commission on Terrorist Attacks Upon the United States wrote, “A complex international terrorist operation aimed at launching a catastrophic attack cannot be mounted by just anyone in any place. Such operations appear to require [among many factors] … access, in the case of certain weapons, to the special materials for a nuclear, chemical, radiological, or biological attack… ”11
Keeping HEU and plutonium out of the hands of terrorists is the most important action in protecting against use of nuclear devices by such groups. This requires protection of materials at the storage locations, tracking of materials when in transit, and an accounting system that enables authorities to verify amounts at locations. Both Russia and the United States have devoted efforts to improve the materials protection, control, and accounting (MPC&A) systems in Russia, with the United States having contributed hundreds of millions of dollars to upgrade security at locations where HEU and plutonium are stored.
There continue to be concerns about a black market for these materials, with periodic reports of small amounts being found by inspectors. In a 2003 workshop, a Russian official wrote, “A fundamental component in the creation of a state system for countering the illegal circulation of radioactive material is the development of devices for their detection, location, and identification and the provision of such instruments to the structural components of the system.”12
There are other very significant amounts of radioactive materials in the United States and Russia.13 Both countries have large quantities of spent nuclear
fuel, that is, fuel removed from reactors after useful fuel life. This spent nuclear fuel is highly radioactive and thus might be seen as a potential material to be used with conventional explosives to construct an improvised radiological device, or dirty bomb. The amounts of such material are vast, but the difficulties of using it are also large because of the intense radiation field associated with spent fuel. Similarly, liquid and, in some cases, solid radioactive wastes are also stored in large amounts in the United States and Russia. Waste is unlikely the material of choice for a device due to difficulty of access, radiation fields associated with the waste storage areas, and difficulty of using it in a device. However, such storage areas do present targets for explosive dispersal.
The U.S. Nuclear Regulatory Commission has increased the design basis threat against which U.S. nuclear power plant operators are required to defend. The Department of Energy (DOE) also has increased the design basis threat against which DOE nuclear laboratories and other nuclear facilities must defend.
CONCLUSIONS
In all these cases, including radiological sources and so-called dirty bombs, the words nuclear and radioactive can cause fear and, if stressed enough, panic. The fear associated with these words is hard to counter. It has been called radiophobia,14 and “it is generally agreed that the greatest consequences of an RDD are public fear and the potentially enormous cleanup costs along with the consequent economic losses.”15
The U.S. National Academies and the Russian Academy of Sciences have worked together for a half-century.16 There is no issue more important for these two institutions than to continue mutual efforts on nonproliferation, including efforts to reduce the threats of radiological terrorism.