Securing U.S. Radioactive Sources

Although the U.S. government has stepped up efforts to prevent acts of radiological terrorism, significant gaps in security remain to be filled.

The catastrophic attacks of September 11, 2001, and the anthrax mailings that took place shortly thereafter highlighted the nation’s vulnerability to unconventional forms of terrorism. One type of threat that has recently received close attention from policymakers and the news media is the potential for attacks with radiological dispersal devices (RDDs). Such weapons, which include so-called dirty bombs, are designed to spread radioactive contamination, causing panic and disruption over a wide area. The number and diversity of radioactive sources pose a serious security challenge, and the United States has yet to take all the necessary steps to strengthen controls to match the heightened terrorist threat.

Most people are aware of the danger of radioactive material associated with nuclear power, but the potential sources of material for an RDD include a large class of commercial radioactive sources used in medicine, industry, and scientific research. Of the millions of sources in use worldwide, only a small fraction, if maliciously employed in an RDD, are powerful enough to cause serious harm to human health. Yet this fraction still includes tens of thousands of sources of the type and quantity useful for a potent RDD. (See the end for information on the types of potentially high-risk sources within the United States.)

Although an RDD uses radioactive materials, even a very powerful RDD would cause far less damage than a nuclear weapon. The difference between a dirty bomb and a nuclear bomb is, as Graham Allison of Harvard University so eloquently put it, “the difference between a lightning bug and lightning.” Unlike a nuclear weapon, an RDD would likely cause few deaths from the direct effects of exposure to ionizing radiation. Nevertheless, many people could develop cancer over years or decades. And the costs of decontamination and, if necessary, rebuilding could soar into the billions of dollars, especially if an RDD attack occurred in a high-value urban setting. Moreover, terrorists detonating RDDs would try to sow panic by preying on people’s fears of radioactivity.

Although there have been no actual RDD detonations, two case studies involving radioactive sources point to the psychological, social, and economic damage that could result from an RDD. First, in 1987 in Goiania, Brazil, scavengers stole a powerful radioactive source (containing about 1,375 curies of radioactivity) from an abandoned medical clinic. Not realizing what it was, they broke the source open. Four people died, more than 100,000 others had to be monitored for contamination, and cleanup costs amounted to tens of millions of dollars. The second case study concerns the U.S. steel industry. Radioactive sources that found their way into scrap yards have accidentally been melted in steel mills 21 times, most recently in July 2001. Those contamination incidents have cost the steel industry an estimated quarter billion dollars. In response, the industry has installed radiation detectors in scrap yards, as well as at the entrances of and throughout mills. Such “defense in depth” appears to have reduced the frequency of incidents.

The sources that fall outside regulatory controls are not limited to those that show up in scrap yards. In the United States, a radioactive source is lost, stolen, or missing about once a day. Although most of those “orphan” sources are relatively weak, they could still cause panic and disruption if detonated in an RDD.

Federal agencies are now reviewing and revising their programs and policies to improve the security of radioactive sources against theft, diversion, and use in radiological terrorism. It is a challenging assignment: Regulatory responsibilities were fragmented enough before the new Department of Homeland Security was added to the mix. This is an appropriate time to review the origins of security practices and past problems with the security of radioactive sources in order to gain insights into whether current efforts to improve security are soundly based and properly directed. It is also essential to examine whether the United States has a well-developed, coordinated national plan for managing the risks of radiological terrorism.

Even before the terrorist attack of September 11, 2001, the Nuclear Regulatory Commission (NRC) had begun action to tighten controls on general-licensed radioactive sources, in particular those used in manufacturing and other settings, because disused sources were sometimes being found mixed with scrap metal. After September 11, the NRC requested that licensees undertake more stringent interim security measures. Although the details of the measures are sensitive information not intended to be published openly, we know that these security improvements were meant to increase security mainly at locations containing very highly radioactive material. The enhanced security entails, among other efforts, restricting access to radioactive material and coordinating the security efforts of licensees with local and federal law enforcement. The NRC’s security plans use as a starting point the results of a joint Department of Energy and NRC study identifying radioactive sources in the highest risk categories based on potential health effects resulting from radiation exposure. As we will explain, to realize maximum effectiveness the plans should incorporate a multifaceted approach that also includes cooperation and shared responsibility among government agencies, suppliers, and licensees.

Life cycle of radioactive sources

Developing a systematic plan requires understanding the stages of a source’s life cycle and the security measures in place at each stage. The first stage is the production of the radioisotopes that power radioactive sources. Such radioisotopes are made either in nuclear reactors or in particle accelerators. Reactor-produced radioisotopes present a greater security risk because they typically have longer half-lives and are generated in larger quantities. Government-required security standards are typically in place at the reactor sites, but the United States is not a leading producer of commercial radioisotopes at reactors.

The next stage involves placing radioisotopes into radioactive sources and manufacturing the equipment that will contain the sources. Major U.S. equipment manufacturers import most of their radioisotopes from foreign reactors. These companies are believed to protect their materials using the same industrial security measures that are applied to other high-value goods. After September 11, the NRC advised manufacturers to step up security. Sources are shipped to hospitals, universities, food irradiation facilities, oil well drilling sites, industrial radiography facilities, and other venues. Security practices vary according to the type of facility and activity. Food irradiation plants, which employ highly radioactive materials, probably have tighter security than hospitals, for example.

Security is of particular concern in the oil industry, which often transports radioactive sources across borders. Recently, a high-risk radioactive source was stolen from a major oil company in Nigeria. Of the more than 22,000 portable radioactive gauges in use, about 50 are reported stolen each year, according to the NRC. To prevent such thefts, the NRC announced in July 2003 that it is considering a new rule that would require portable gauges to be secured with at least two independent physical controls whenever they are left unattended.

Some radioactive sources pass through yet another phase if they are shipped overseas. Current U.S. regulations allow the import and export (except to the embargoed countries of Cuba, Iran, Iraq, Libya, North Korea, and Sudan) of most high-risk radioactive sources under a general license, meaning that the government is not required to conduct a detailed review of the credentials of the sender and recipient. The NRC is reportedly considering a proposed rule change to remedy this problem and has already instituted interim security measures. In March, during Operation Liberty Shield, licensees were requested to give the NRC at least 10 days’ notice of any shipment of highly radioactive sources. The commission is also working closely with U.S. Customs to develop a source-tracking database. Monitoring began in earnest in April, and preliminary data suggest that a few hundred shipments of highly radioactive sources enter or leave the United States every year.

A major vulnerability of the process for licensing radioactive sources is its susceptibility to fraud.

A radioactive source eventually becomes ineffective as its potency declines, but the “disused” source might still contain potent amounts of radioactivity. Ideally, users would dispose of or recycle such sources quickly, but because disposal is expensive and proper facilities are few, users often hold on to their sources. The risk of loss, theft, or seizure by terrorists goes up accordingly. Not all source manufacturers provide disposal or recycling services, so the government also must provide safe and secure disposal sites. As we explain below, the current disposal system in the United States is in dire need of repair.

Other issues attend the shipment of sources between stages of their life cycle. The U.S. Department of Transportation (DOT) regulates shipments within the United States, adjusting security measures according to the size of the shipment. Labeling and packaging requirements provide for the protection of transportation workers and bystanders both in routine transit and under accident conditions. DOT sets packaging specifications for small quantities of radioactive material, and the NRC is responsible for large quantities. Although the security measures for large, highly radioactive shipments are reportedly stringent, both industry and parts of the government have resisted implementing improved security efforts such as background checks of drivers and adequate arming of guards.

Alternative technologies

The International Commission on Radiological Protection and the congressionally chartered National Council on Radiation Protection and Measurements (NCRP) hold as a pillar of radiation protection the principle of justification. This principle calls for evaluating the risks and benefits of using a radioactive source for a particular application. Users are supposed to opt for a nonradioactive alternative if there is one that provides comparable benefit and less risk, including the risk associated with waste management.

The NRC has taken the position that advocating alternative technologies is not part of its mission. The commission’s reasons, which have not been explained, might be that it believes it is only in the business of regulating the radioactive sources that licensees choose to use, not the business of overseeing licensees’ decisions to use them. Nonetheless, it can be argued that the NRC’s charge from Congress—to protect public health, safety, and property as well as provide for the common defense and security—is sufficient to require the commission to adopt the principle of justification and, at least in principle, to encourage the consideration of alternative technologies. This is not to suggest that the NRC should second-guess licensees’ decisions to use radioactive sources, simply that the commission should ensure that licensees are making informed decisions that take into account justification and technological alternatives. Applying the principle of justification would reduce the number of radioactive sources in use and thus cut the risk of an RDD event occurring. The National Academy of Sciences, the International Atomic Energy Agency (IAEA), the NCRP, and the Health Physics Society have all recommended that users consider alternative technologies.

One U.S. industry that is adopting alternative technologies is steel, itself no stranger to the risks and costs of radioactive contamination. Steel mills use nuclear gauges to monitor the level of molten steel in continuous casters. If molten steel breaks through the casting system and strikes a gauge, the gauge housing and even the source could melt, causing contamination. Accordingly, mill operators are replacing nuclear gauges on continuous casters with eddy current and thermal systems, even though they are more expensive. The tradeoff—the cost of alternative technology versus the cost of contamination—makes the new systems a smart choice.

Some of the national laboratories are performing R&D to replace the most dangerous radioactive sources (those containing very dispersible radioactive compounds) with sources that pose less of a security hazard. Unfortunately, technology developed at the national labs is not readily available to the marketplace. At an IAEA conference on the radioactive source industry in April 2003, major source producers reportedly expressed interest in forming public-private partnerships to bring these alternative technologies to market. In the United States, such partnerships are sorely needed.

Licensing fraud

A major vulnerability of the process for licensing radioactive sources is its susceptibility to fraud. The first noteworthy U.S. case became public in 1996, when Stuart Lee Adelman pled guilty to fraudulently obtaining radioactive material and was sentenced to a five-year prison term. Adelman, also known as Stuart von Adelman, posed as a visiting professor at the University of Rochester and, illicitly using university resources, obtained licensed materials from suppliers. That was not his first such crime. In 1992, he was arrested in Toronto on a U.S. fugitive warrant and was found to have illegally obtained radioactive material and stashed it in a public storage locker.

Although no definite evidence points to terrorism in the Adelman case, an assistant U.S. District Attorney remarked that the radioactive material found in Canada may have been part of a scam to obtain money from terrorists. Adelman, who reportedly possessed a graduate degree in nuclear physics, had been employed by a state licensing agency and had worked as a radiation safety officer at two universities, illustrating the alarming potential for insider crime.

Thousands of high-risk disused radioactive sources throughout the United States have no clear disposal pathway and could therefore fall into the hands of terrorists.

Fraudulent licenses might also be used to import radioactive sources into the United States. In May 2003, Argentina’s nuclear regulatory agency red-flagged a request from a party in Texas for a teletherapy-sized shipment of radioactive cobalt. That quantity could provide enough radioactivity for a potent RDD. When the “license” presented to the supplier proved to be nothing more than a dental x-ray registration certificate, a concerned Argentine official contacted the Texas radiation control program. The FBI is investigating to determine whether the incident was a serious attempt to fraudulently import radioactive material, a hoax, or a test of the regulatory system.

Such incidents teach many lessons. First, fraud is not hypothetical; it is happening. Second, creation of a master list on the Web of regulatory authorities worldwide would facilitate communication among officials (in the Argentine case, the official had to search the Internet to find the relevant agency in Texas). The IAEA could host such a list. Third, regulatory agencies should exchange information about possible fraud and do so expeditiously. In the United States, information needs to flow more freely between the NRC, the Agreement States (33 U.S. states that regulate certain radioactive materials under NRC agreements), and other federal agencies. Internationally, such communication could be encouraged by the IAEA. Finally, suppliers should routinely verify requests for the purchase of large quantities of radioactive material.


One of the most worrisome unresolved problems concerning the safety and security of radioactive sources in the United States is providing for adequate end-of-life cycle management. In principle, users can return their disused sources to manufacturers, transfer them to other users, store them, or ship them to government disposal sites. However, none of those methods is foolproof.

The option to return radioactive sources to the manufacturer is an acceptable disposal method to list on an application for a license, but manufacturers can and do go out of business. That has happened in the case of some teletherapy sources, which usually contain cobalt-60 in kilocurie quantities and hence meet NRC criteria for high security concerns. Owners of General Electric or Westinghouse teletherapy machines cannot return sources to the manufacturer, because neither company makes the machines any longer.

In the United States, the use of teletherapy units has declined as accelerators, which generate cancer-treating radiation without using a radioactive source, have replaced them. Some units have been abandoned or are in the possession of clinics that have gone bankrupt. In other cases, former users have exported their sources to countries that still use the technology. Many of the recipient countries are in the developing world, which taps into this secondhand market. As the IAEA has emphasized, more than half of the world’s nations, including most of the developing world, have inadequate regulatory controls. Thus, the secondhand market could pose increasing security risks.

Thousands of high-risk disused radioactive sources throughout the United States have no clear disposal pathway and could therefore fall into the hands of terrorists. Only three disposal sites for low-level waste—a classification that includes most disused radioactive sources—operate in the United States. These sites are located in Barnwell, South Carolina; Hanford, Washington; and Clive, Utah. The Clive disposal site can accept waste from all states, but it handles only the lowest-level waste. The other two sites are available only to certain states. Starting in 2008, when restrictions on access to the Barnwell site take effect, most states will have no disposal site for the bulk of their low-level radioactive waste. Unwanted radioactive materials will accumulate at hospitals, universities, and other facilities where they are vulnerable to loss, theft, or seizure by terrorists. Even when a disposal site is available, disused sources are often kept at relatively unsecured facilities for long periods because of high disposal costs. An estimated half million radioactive sources in the United States belong to this category, but only a small fraction of these sources could fuel potent RDDs.

Why does the country face this problem? In 1986, Congress passed the Low Level Radioactive Waste Policy Amendments Act, which placed responsibility for most low-level waste disposal on the states and gave the federal government responsibility for disposal of the higher-level waste. But because of strong resistance to siting low-level disposal facilities on states’ land, fewer commercial disposal sites are operating today than when Congress enacted the legislation. Another problem is that after 17 years, the federal government has yet to provide a permanent repository for the higher-activity waste. Indeed, it has only begun to make progress toward securing some of this radioactive material in temporary storage.

Although the federal effort got off to a slow start, the Off-Site Source Recovery (OSR) Project of the U. S. Department of Energy (DOE) has in recent years rounded up more than 7,000 disused sources, most of them radioactive enough to pose a security concern. Thousands more sources that remain to be secured are now registered on the OSR database. Despite the project’s relative success, a recent U.S. General Accounting Office audit found that the OSR suffers from a lack of DOE management support and that the project has not identified a pathway toward final disposal of the higher-activity waste. The project also faces an impending funding shortage: The supplemental support issued by Congress in October 2002 is slated to run out next year.

The United States lacks a comprehensive functioning national program for managing the radioactive waste generated from disused sources. As a step toward a solution, regional repositories could be established to securely store unwanted sources until their final disposal. Existing secure federal sites could be used for interim storage as a way to cut through the roadblocks that have stalled the states from siting disposal facilities. In parallel, the federal government can move toward a decision on final disposal. The states still have a crucial role to play by pressing the federal government to use its resources to correct the problem. New legislation must establish clear requirements for DOE to set up, without delay, safe and secure federal regional storage facilities for unwanted radioactive sources.

Managing the risks

Clearly, other measures are needed to close the gaps in the security of radioactive sources. The priority that the NRC assigns to the security requirements for different radioactive sources should take into account the kind of damage they would inflict if they were used in an RDD. The commission’s current priority system is based on preventing radiation injuries and deaths, which, in the case of a terrorist act using an RDD, are likely to be limited. The major consequences of an RDD would be psychosocial and economic, and the NRC’s system for prioritizing sources does not reflect that.

Although psychosocial effects can be difficult to quantify, there is an ample body of data on the economic effects. The cost for contaminated steel mills to shut down and clean up and dispose of radioactive waste averaged $12 million per event. Most of the sources that caused that damage would not have met NRC criteria for high priority. But radioactive sources that are less likely to cause radiation injuries or deaths are still quite capable of causing significant economic damage. The U.S. priority system for radioactive sources needs to be refined to account for such consequences.

Of course, the responsibility for improving radioactive source security does not fall solely on the U.S. government. Suppliers, users, and the states have a fundamental interest in closing gaps and, equally important, can contribute ideas to improve safety and security. Fostering partnerships that facilitate information exchange and cooperation among federal agencies, state regulators, suppliers, and states would do much to reduce the risk of radioactive sources going astray. Indeed, given the number and diversity of radioactive sources, cooperation and shared responsibility are the only way to achieve the highest level of security.

Radioactive Sources in the United States

Because the United States lacks a comprehensive national inventory of radioactive sources, their exact number is unknown. In 1998, Joel O. Lubenau and James G. Yusko estimated that some 2 million U.S. devices contained licensed radioactive sources. Some devices, such as radiography cameras and teletherapy units, contain a single source; others, such as large irradiators for sterilization and food preservation, some medical devices, and certain nuclear gauges, contain multiple sources. About a quarter of the devices, including those containing the largest sources, are used under a specific license, the rest under a general license. The absence of a national inventory also hinders reporting the number of radioactive devices or sources by category of use. The following table lists many of the more common practices using larger radioactive sources. The data are derived from IAEA-TECDOC-1344.

Practice Typical Radioisotopes Typical Radioactivity Amounts (Curies)
Radioisotope thermoelectric generators Strontium-90 20,000
  Plutonium-238 280
Sterilization & food irradiators Cobalt-60 4,000,000
  Cesium-137 3,000,000
Self-contained & blood irradiators Cobalt-60 2,400—25,000
  Cesium-137 7,000—15,000
Single-beam teletherapy Cobalt-60 4,000
  Cesium-137 500
Multibeam teletherapy Cobalt-60 7,000
Industrial radiography Cobalt-60 60
  Iridium-192 100
Calibration Cobalt-60 20
  Cesium-137 60
  Americium-241 10
High and medium dose rate brachytherapy Cobalt-60 10
  Cesium-137 3
  Iridium-192 6
Well logging Cesium-137 2
  Americium-241/beryllium 20
  Californium-252 0.03
Level and& conveyor gauges Cobalt-60 5
  Cesium-137 3—5


Recommended Reading

  • Committee on Science and Technology for Countering Terrorism, National Research Council, “Nuclear and Radiological Threats,” chapter 2 in Making the Nation Safer: The Role of Science and Technology in Countering Terrorism (Washington, D.C.: National Academy Press, 2002) (available at ).
  • DOE/NRC Interagency Working Group on Radiological Dispersal Devices, Radiological Dispersal Devices: An Initial Study to Identify Radioactive Materials of Greatest Concern and Approaches to Their Tracking, Tagging, and Disposition, Report to the Nuclear Regulatory Commission and the Secretary of Energy, May 2003.
  • Charles D. Ferguson, Tahseen Kazi, and Judith Perera, Commercial Radioactive Sources: Surveying the Security Risks, Occasional Paper No. 11 (Center for Nonproliferation Studies, January 2003) (available at ).
  • Charles D. Ferguson, “Reducing the Threat of RDDs,” IAEA Bulletin, 45, no. 1 (2003) (available at ).
  • General Accounting Office, Nuclear Nonproliferation: DOE Action Needed to Ensure Continued Recovery of Unwanted Sealed Radioactive Sources (Washington, D.C.: GAO-03-483, April 2003).
  • Health Physics Society, “State and Federal Action is Needed for Better Control of Orphan Sources” (HPS Position Statement, April 2002) (available at
  • International Atomic Energy Agency, Categorization of Radioactive Sources, (IAEA-TECDOC-1344, June 2003, Vienna, Austria).
  • Michael A. Levi and Henry C. Kelly, “Weapons of Mass Disruption,” Scientific American (November 2002).
  • Joel O. Lubenau and Daniel J. Strom, “Safety and Security of Radiation Sources in the Aftermath of 11 September 2001,” Health Physics 88, no. 2 (August 2002): pp. 155-164.
  • Joel O. Lubenau and James G. Yusko, “Radioactive Material in Recycled Metals—An Update,” Health Physics 74, no. 3 (March 1998): pp. 293-299.
  • National Council on Radiation Protection and Measurements, Management of Terrorist Events Involving Radioactive Material (NCRP Report No. 138, October 2001).
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Cite this Article

Ferguson, Charles D., and Joel O. Lubenau. “Securing U.S. Radioactive Sources.” Issues in Science and Technology 20, no. 1 (Fall 2003).

Vol. XX, No. 1, Fall 2003