1

Background and Study Task

Radioactive sources are used in a variety of essential and beneficial medical, research, sterilization, and other commercial applications. These applications include cancer therapy, irradiation of blood for transplant patients and of laboratory animals for research, sterilization of medical devices, irradiation to reduce the transmission of foodborne illnesses and protect domestic crops from invasive species, nondestructive testing of structures and industrial equipment, exploration of geological formations to find oil and gas deposits, and instrument calibration. Radioactive sources used in these applications are stored in university, medical, research, government, commercial, and other facilities that are accessed and used by qualified personnel. If these sources are mishandled, particularly with malicious intent in a radiological dispersal device (RDD), they could cause significant damage and injury. Although immediate fatalities and deterministic effects due to radiation from an RDD are unlikely, the societal consequences could be severe because of the required cleanup and loss of access to the affected areas. The economic damage from area denial and rebuilding could also be large, possibly amounting to billions of dollars.

An RDD has not been deployed in the United States or elsewhere.¹ However, domestic and international terrorist attacks and several attempts to traffic radioactive materials or to use radioactive sources for malicious purposes highlight the need to prepare for an RDD. Worldwide, about 3,700 unauthorized activities and events involving nuclear and radioactive material were reported from 1992 to 2019,² including incidents of trafficking and malicious use (see, e.g., Elfrink, 2017; Malone and Smith, 2016; Schreuer and Rubin, 2016).

The responsibility for securing nuclear and radioactive materials rests with the licensees who possess these materials. Although adequate security measures can reduce the risks posed by radioactive sources, the most direct approach to risk reduction is elimination of radioisotope use and its replacement with technologies that do not pose such risks but can adequately perform the intended function of the radioactive sources. Hospitals, research centers, and governments have increasingly recognized the safety and security risks and liabilities associated with possession of radioactive sources and in some cases are voluntarily removing and replacing them with alternative technologies.

This chapter provides background information on the study request and the current radiation source categorization system and discusses implementation of the recommendations of the 2008 National Academies of Sciences, Engineering, and Medicine (the National Academies) report (NRC, 2008) on the same topic.

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¹ Stephen Musolino, Brookhaven National Laboratory, presentation to the committee on November 20, 2020.

² Jose Garcia Sainz, International Atomic Energy Agency, presentation to the committee on June 10, 2020.

1.1 STUDY REQUEST

The Office of Radiological Security (ORS) within the Department of Energy’s (DOE’s) National Nuclear Security Administration (NNSA) expanded the focus of its efforts from encouraging voluntary physical protection measures of radiation sources to include promoting alternative technologies. ORS is charged to “work with government, law enforcement, and businesses across the globe to protect radioactive sources used for medical, research, and commercial purposes; remove and dispose of disused radioactive sources; and reduce the global reliance on high activity radioactive sources through the promotion of viable nonradioisotopic alternative technologies.”³

ORS requested that the National Academies review and assess developments in radioactive source applications and feasible alternative technologies for replacing the radioactive sources currently used in those applications. The goal of this study is to provide technical information and independent insights that can support existing and future activities of ORS aiming to reduce the current use of high-risk radiological materials in these applications and promote alternative technologies. ORS delegated management of the study to Sandia National Laboratories (referred to as Sandia in this report). Sandia supports the ORS mission by installing security systems at sites that use high-activity radiological sources in the United States and internationally, and by encouraging users to replace high-activity radioactive sources with alternative (nonradioisotopic) technologies.

The sources discussed in this report are primarily sealed radioactive sources, typically radioactive material double-encapsulated in stainless steel containers prior to use in devices. The capsule prevents the radioactive material from being released under normal operations or most accidental conditions. Sealed radioactive sources usually have the appearance of a small, regular piece of metal (see Figure 1.1). In most applications, a sealed radioactive source is installed in a device that is designed either to allow the source to move safely in and out of the radiation shield where it is stored or to allow a beam of radiation to be released from the shielded source. Some radiological devices use multiple sources. Sealed sources, when intact, typically present a risk from external radiation exposure only. However, if the sources are breached or leak, they can also cause internal exposure through inhalation or ingestion.

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³ Office of Radiological Security, National Nuclear Security Administration, https://www.energy.gov/nnsa/office-radiological-security-ors.

This study uses the previous National Academies report (NRC, 2008; see Section 1.4 for a summary of the key recommendations of that report) as a baseline to assess developments in use of radioactive sources and alternative technologies. However, this study has an expanded scope that includes both domestic and international developments in radioactive source applications. Furthermore, while the previous National Academies study was restricted to review of high-activity (Category 1 and Category 2) sources, this study also reviews moderate-activity (Category 3) sources. The complete Statement of Task for the study is shown in Sidebar 1.1. The recent estimate is that approximately 80,000 Category 1 and Category 2 sources are in the United States. There is no current estimate of the number of Category 3 sources. Around 2008, the U.S. Nuclear Regulatory Commission (U.S. NRC) performed a one-time data collection and estimated the number of Category 3 sources in the United States to be approximately 5,200.⁴

This study was carried out by the Committee on Radioactive Sources: Applications and Alternative Technologies (referred to as “the committee” in this report), which was appointed by the president of the National Academy of Sciences. Brief biographies of the committee members and staff involved in this study are provided in Appendix A. The committee consists of experts in disciplines relevant to the study request and includes users, developers, and implementers of radioactive sources and alternative technologies in medical, research, sterilization, and other industrial applications. The committee also includes experts in safety and security of radioactive sources and economic analyses. Two committee members also served on the committee that conducted the 2008 National Academies study on the same topic.

The committee collected the information needed to write its report from January 2020 to March 2021. During that period, the committee received briefings from national and international subject-matter experts, including federal and state representatives, national laboratory experts, industry and small-business representatives, and representatives from trade associations. Presentations provided to the committee are posted on the National Academies website.⁵ Staff from several International Atomic Energy Agency (IAEA) sections collectively provided several hours of briefings on the agency’s activities related to radioactive sources and alternative technologies for all

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⁴ Letter from George Smith, U.S. Nuclear Regulatory Commission, to Ourania Kosti, National Academies, February 5, 2021.

⁵ See https://www.nationalacademies.org/our-work/radioactive-sources-applications-and-alternative-technologies.

applications examined in this report. Appendix B provides the list of presentations the committee received during its information-gathering meetings. The committee also received written comments, both solicited and unsolicited, from government agencies, industry associations, and technical experts. These comments were helpful in informing the committee about perspectives related to the study and for uncovering useful data sources and documents.

Because of the COVID-19 pandemic and associated travel restrictions and canceling of large events, all of the committee’s meetings, except the first one in January 2020, took place remotely. The committee, with support from the National Academies staff, quickly adjusted to virtual interactions to address its Statement of Task and produce this report. Although the committee did not have the benefit of interpersonal dynamics among members or with outside experts, a positive outcome of the virtual interactions was accessibility to a number of national and international experts who might not have been available for in-person meetings.

The committee emphasizes the following points related to its approach to responding to the Statement of Task:

1. It agrees with the recommendation of the 2008 National Academies report on elimination of cesium-137 in the form of cesium chloride from commercial applications (see Section 1.4.2 of this report). Cesium chloride’s dispersibility and presence in medical and research centers across the United States and elsewhere make it of particular concern.
2. Point (1) notwithstanding, it does not make technical value judgments related to the magnitude of risks associated with different radioactive sources or radioisotopes, and it does not attempt to prioritize replacement of certain sources or radioisotopes over others. This is because the committee did not access information related to dispersibility and other properties of the radioisotopes discussed in this report or information on security of the facilities where these sources are stored.
3. It does not take the position that any possession of Category 1, 2, and 3 radioactive sources poses an unacceptable risk to society or that the end state needs to be complete elimination of Category 1, 2, and 3 sources. The committee understands that any decision regarding replacement of these sources with alternatives involves balancing risks and benefits by the organizations that possess them.
4. References to specific technologies and in some cases to specific commercial products and manufacturers do not necessarily constitute or imply their endorsement by the committee.

1.2 THE RADIOACTIVE SOURCE CATEGORIZATION SYSTEM

The IAEA is the leading international organization for intergovernmental scientific and technical cooperation in the nuclear and radiological field. In 2004, the IAEA published the Code of Conduct on the Safety and Security of Radioactive Sources (IAEA, 2004). This document marked the beginning of a global trend toward the increased control of, accountability for, and security of radioactive sources. Since then, the IAEA has produced documents with guidance and standards on safety and security of radioactive sources and their applications. Although the IAEA seeks consensus in developing standards, these standards are not legally binding on Member States, but rather serve as guidance for best practices that can be adopted by governments and regulatory bodies.

The IAEA published a safety guide for categorization of radioactive sources in 2005 (IAEA, 2005). The guide, which aims to provide a risk-based ranking of radioactive sources in terms of their potential to cause harm to human health, is based on the categorization system reported in the IAEA-TECDOC-1344 (IAEA, 2003a) that is referenced in the Statement of Task. The potential of a source to cause harm to human health is quantified in terms of a D value, defined as the radionuclide specific activity above which a radioactive source with activity A is considered dangerous because it has significant potential to cause severe deterministic effects if not managed safely and securely.

The categorization system set out in the safety guide has five categories, with Category 1 sources being the most hazardous and Category 5 sources the least hazardous. Table 1.1 lists the activity (A/D) ratios and examples of practices for each of the five categories in the categorization system. A hazardous source is one that could give rise to an exposure sufficient to cause a severe deterministic effect if not managed safely and securely. A Category 1 quantity of a given radionuclide, the most dangerous, is defined as an amount 1,000 times or more (i.e., A/D > 1,000) than the amount needed to cause permanent human injury. For comparison, a Category 3 quantity of

a given radionuclide is defined as an amount equal or 10 times less (i.e., 10 > A/D > 1) than the amount needed to cause permanent human injury. The IAEA safety guide also discusses aggregation of sources and suggests a “sum of fractions” approach if multiple sources or multiple radionuclides are stored in the same location. The U.S. NRC and other regulatory bodies internationally have adopted the IAEA categorization system in their radioactive source regulatory framework. The U.S. NRC uses the activity ratio to determine what category a discrete source would fall into, and the sum of fractions to determine the category that aggregated quantities of radioactive materials would fall into. The U.S. NRC does not ascribe source categories based on device type or practice.

The IAEA categorization system does not consider two important factors that are relevant to this committee’s work: (a) stochastic effects, such as future cancer development, that could be induced by being in proximity to the radioactive sources if not managed safely and securely; and (b) socioeconomic consequences of radiological incidents that involve these radioactive sources.

For factor (a), the IAEA takes the view that, because the risk of stochastic effects increases with exposure, higher category sources will in general present a higher risk of stochastic effects. That is, the IAEA system indi-

TABLE 1.1 Radioactive Source Categories

^a As described by the U.S. NRC, https://www.nrc.gov/reading-rm/basic-ref/glossary/category-of-radioactive-sources.html.

^b 1 TBq = 27 Ci.

^c High-dose-rate brachytherapy sources are typically Category 2 sources according to the IAEA categorization system, but in the United States they are Category 3 sources and are regulated as such by the U.S. NRC.

SOURCE: Adopted and modified from IAEA, 2004.

rectly accounts for stochastic effects only to the likely small number of individuals who, if exposed to the radiation sources, would also suffer from deterministic effects. However, it does not account for stochastic effects to those individuals who did not suffer deterministic effects because they were not in close proximity to the source but might be exposed to levels of radiation below the threshold for deterministic effects.

For factor (b), the IAEA does not generally consider socioeconomic consequences in its categorization system, because no methodology for quantifying and comparing these effects was available at the time the system was created. Since the IAEA report was issued, the U.S. government has taken steps to better understand the socioeconomic costs associated with an RDD and has estimated billions of dollars in damage when modeling the effects of an RDD involving a Category 1 or a Category 3 source (see Section 2.7). In addition, real-life experience from the Fukushima Daiichi nuclear power plant accident and other radiological incidents has demonstrated that radiation releases and radiation exposures to populations far below the levels that can cause deterministic effects can have serious and long-term socioeconomic consequences (see Sections 2.3.2 and 2.3.4).

IAEA representatives who briefed the committee stated that there is no current plan to reevaluate the agency’s radioactive source categorization system.⁶

1.3 COMMON RADIOISOTOPES IN RADIOACTIVE SOURCES

The U.S. government developed a list of 16 radionuclides⁷ of greatest concern for use in an RDD. Of these 16 radioisotopes, the 5 most common account for 99 percent of all sealed Category 1 and Category 2 sources in the United States. These five are cobalt-60, cesium-137, iridium-192, americium-241, and selenium-75. The main characteristics of these radioisotopes are summarized in the following sections and in Table 1.2.

Cobalt-60 is used mainly in medical device sterilization (99 percent of applications)⁸ but also in research, cancer therapy, and industrial radiography. There are approximately 72,000 Category 1 and Category 2 cobalt-60 sources in the United States, accounting for approximately 90 percent of all Category 1 and Category 2 sources in the United States. In these sources, cobalt-60 is used in the form of a solid, nonsoluble, nondispersible metal or metal alloy with a half-life of 5.27 years. Cobalt-60 decay produces two gamma rays with energies of 1.17 and 1.33 mega-electron volts (MeV). Cobalt-60 is produced as a byproduct in nuclear reactors by neutron activation of cobalt-59. Cobalt-60 is currently produced in 21 reactors in Argentina, Canada, China, India, and Russia. Concerns about cobalt-60 supply were heightened in 2014 following the announcement of the termination of the REVISS joint venture between a Russian state-owned enterprise and a British company that resulted in an almost immediate reduction in the global cobalt-60 supply. At roughly the same time (in 2016), the Argentinian Embalse reactor was shut down for refurbishment, removing additional cobalt-60 from the global supply. According to a recent estimate, supply of cobalt-60 is below the amount needed to meet demand for sterilization applications by approximately 5 percent (Nordion, 2021).

Cesium-137 is used mainly in self-shielded irradiators (cesium irradiators) for blood irradiation and research applications, as well as in well logging. There are approximately 3,200 Category 1 and Category 2 cesium-137 sources in the United States, accounting for approximately 4 percent of all Category 1 and Category 2 sources. Cesium-137 in irradiators and calibration devices is in the form of a compressed cesium chloride powder, which is soluble in water and can be dispersed relatively easily. In well logging devices and gauges, cesium-137 is in a ceramic or glass form and thus not readily dispersible or soluble. The half-life of cesium-137 is 30.17 years and its primary gamma-ray emission is at 0.662 MeV (or 662 kilo-electron volts [keV]). Cesium-137 is produced by nuclear fission of uranium at a yield of about 6 percent of all fission products. Until recently, separated radioactive cesium sold internationally was produced only by the Production Association Mayak (PA Mayak) in the Chelyabinsk region of Russia. In 2015, India’s Bhabha Atomic Research Centre (BARC) announced that it has begun production of cesium-137 for use in blood irradiators and has considered use of this radionuclide in other applications such as brachytherapy, food irradiation, and sterilization of medical devices. India was the first country to

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⁶ Ronald Pacheco, IAEA, presentation to the committee on June 10, 2020.

⁷ See https://www.nrc.gov/docs/ML0531/ML053130250.pdf.

⁸ Ian Downie, Nordion, presentation to the committee on October 13, 2020.

TABLE 1.2 Summary of Most Common Radionuclides Contained in Category 1, 2, and 3 Radioactive Sources in the United States

^a Based on number of devices.

^b The elemental form of selenium-75 is only supplied from Russia and is not commercially available or approved for transport in the United States.

SOURCE: Adopted and modified from NRC, 2008.

report use of vitrified cesium in pencil-shaped form (BARC, 2017). Future availability of cesium-137 in the form of cesium chloride is uncertain because a number of countries aim to eliminate risks associated with this form.

Iridium-192 is used in industrial nondestructive testing (NDT) to image the interior structure of metal castings, welds, and manufactured components. It is also used in cancer therapy to treat localized tumors. Medical iridium-192 is used in the form of discs or capsules. There are approximately 4,000 Category 1 and Category 2 iridium-192 sources used in NDT, accounting for approximately 5 percent of all Category 1 and Category 2 sources in the United States. Iridium-192 sources used in medical applications are Category 3 sources. The half-life of iridium is 73.83 days, and the gamma-ray emissions range from 0.110 to 1.378 MeV with the average iridium-192 gamma-ray emission at 0.375 MeV (or 375 keV). Iridium-192 is produced in a nuclear reactor by neutron irradiation of stable iridium-191. Iridium-192 for industrial radiography is manufactured in reactors in Europe, Russia, and South Africa.

Americium-241 is mixed with beryllium to create a neutron source for borehole (well) logging to infer subsurface rock porosity, density, and composition. Approximately 200 Category 2 americium-241 sources are licensed for use in the United States, accounting for less than 1 percent of total licensed Category 1 and Category 2 sources in the United States. The americium used in these sources is in the form of highly compressed pellets of a blend of americium oxide and beryllium metal powder. Americium-241 is primarily an alpha emitter, and the most prevalent alpha-particle emission peaks at 5.486 MeV (about 85 percent of decays). Alpha interactions with beryllium nuclei in americium-beryllium sources result in a neutron energy spectrum from thermal energies to about 10 MeV with peaks at approximately 3 MeV and 5 MeV. The primary americium-241 gamma-ray emission (about 36 percent of decays) is at 59.5 keV. Americium has a half-life of 432.2 years. Americium-241 is produced in a nuclear reactor by successive neutron capture from uranium-238 and by the decay of plutonium-241 contained in decommissioned nuclear weapons,⁹ which decays by beta emission with a half-life of 14.35 years to americium-241. Americium-241 is supplied globally by PA Mayak. In March 2020, following a 16-year hiatus, the DOE Isotopes Program announced the restart of routine production and availability of americium-241 in the United States.

Selenium-75, like iridium-192, is used to conduct NDT. It is much less common than iridium-192 in the United States but is widely used elsewhere (CISA, 2019). Selenium-75 used in these sources is in the form of a cylindrical or quasi-spherical pellet. Selenium-75 sources emit gamma rays with an average energy of 215 to 230 keV. (The precise energy of emissions depends on the focal spot size.) There are two primary gamma rays at 136 keV and 265 keV (each about 60 percent of decays) and a useful energy range spanning 97 to 401 keV. Selenium-75 has a half-life of 119.8 days. It is produced in a nuclear reactor by neutron irradiation of stable isotopically enriched selenium-74 in Russian, U.S., and European reactors. Selenium-75 sources manufactured in the United States typically use a metal alloy of selenium and vanadium.

Details of the applications of these radionuclides and available alternative technologies are discussed in Chapters 4 to 6.

1.4 IMPACT OF THE 2008 NATIONAL ACADEMIES REPORT

The study that resulted in the 2008 National Academies report (NRC, 2008) was conducted at the request of Congress under Section 651 of the Energy Policy Act of 2005 (often referred to as EPAct). As part of the Act, the U.S. Congress directed the U.S. NRC to take several actions including funding a National Academies study to evaluate the uses of high-risk (Category 1 and Category 2) sources that could be replaced with an equivalent process or one that would pose a lower risk if an accident or attack occurs. The Act also established a Task Force on Radiation Source Protection and Security (the Task Force), whose role is to provide recommendations to the U.S. president and Congress relating to the security of radioactive sources. EPAct designated the chairperson of the U.S. NRC, or designee, as chair of the Task Force that would consist of members of 14 federal agencies, the Conference of Radiation Control Program Directors (CRCPD), and the Organization of Agreement States. To date, the Task Force has issued four reports, the latest in 2018 (U.S. NRC, 2018). Relevant to this committee’s work is that the Task Force recommends that the U.S. government enhance support of research and development of alternative technologies to replace the use of high-risk radioactive sources and establish a government-incentivized program for replacement of high-risk devices with effective alternatives (U.S. NRC, 2018).¹⁰

When the 2008 National Academies report was released, the U.S. NRC estimated that there were approximately 54,000 civilian Category 1 and Category 2 sources in the United States (NRC, 2008). Data on Category 1 and Category 2 sources were recorded in an interim database, from 2004 to 2008, the precursor to the National Source Tracking System (see Section 2.4). The interim database was designed to collect a one-time inventory of devices and the sources containing the materials. Reporting to the interim database was voluntary. As noted in a previous section, today there are approximately 80,000 Category 1 and Category 2 sources.¹¹

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⁹ Decommissioning of weapons was part of the 1993 Strategic Arms Reduction Treaty (START 2) between the United States and Russia.

¹⁰ The 2018 Task Force report indicates that one member from the Organization of Agreement States was represented as a non-voting member; CRCPD was not represented.

¹¹ Letter from George Smith, U.S. NRC, to Ourania Kosti, National Academies, February 5, 2021.

The radiological security community considers the 2008 National Academies report as a landmark report¹² for identifying the need to

• Reconsider ranking of radiation sources based on their hazard to include their potential to cause economic and social disruption; and
• Replace cesium-137 used in the form of cesium chloride.

These recommendations, and progress with implementing them, are discussed in the following sections.

1.4.1 Proposed Change to Ranking of Source Hazards

The 2008 National Academies report highlighted that the U.S. NRC ranks the hazards of radioactive sources primarily based on the potential for deterministic health effects (death or severe bodily harm due to radiation) and does not consider the potential of a source to contaminate large land areas resulting in area denial if these sources are not used safely and securely. The 2008 report committee made the following recommendation to address that issue:

The U.S. NRC has historically reevaluated the consideration of offsite property damage from radiological releases within its regulatory framework, including the consideration of socioeconomic impacts from unintended release of radiation to the environment (U.S. NRC, 1997, 1998, 1999, 2000, 2001). In general, these reevaluations did not lead to changes in the U.S. NRC’s regulatory framework. The agency continues to use immediate fatalities and deterministic health effects as its primary criteria for measuring the consequences of a radiological release.

Following the 2011 Fukushima Daiichi nuclear power plant accident, the U.S. NRC analyzed its processes to consider economic consequences arising from offsite property damage caused by radiological contamination events. The analysis did not specifically consider radiological incidents such as an RDD. The U.S. NRC staff concluded that the existing regulatory framework has the effect of minimizing economic consequences by preventing or mitigating events that could lead to a radioactive release. The U.S. NRC staff also recommended improving guidance for estimating offsite economic costs based on up-to-date data (U.S. NRC, 2012a). The Commission approved the staff’s recommendation to provide improved guidance but found that socioeconomic consequences should not be considered in the regulatory framework as equivalent to adequate protection of public health and safety (U.S. NRC, 2013).

At about the same time (in 2010), the Task Force for Radiation Source Protection and Security identified the need for the federal government to reevaluate protection and mitigation strategies against the definitions of a significant radiological exposure device (RED) and an RDD and to consider consequences beyond immediate fatalities from radiation and deterministic health effects (U.S. NRC, 2012a,b). In 2012, the U.S. NRC staff reported that considering socioeconomic consequences and contamination would constitute a significant change in the underpinning assumptions used to determine the consequence of an RDD (U.S. NRC, 2012b) and that it would need additional direction from the Commission to consider examining alternative consequences. The U.S. NRC staff also concluded that the current security framework adequately protects against contamination and its resulting economic consequences. Interestingly, U.S. NRC guidance recognizes that “few deaths would occur due to the radioactive nature of the event [RDD]; however, significant social and socioeconomic impacts could result from public panic, decontamination costs, and the denial of access to infrastructure and property for extended periods of time” (U.S. NRC, 2014a).

Experts at a Government Accountability Office (GAO) meeting convened with support from the National Academies generally agreed that using immediate fatalities and deterministic health effects from radiation has

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¹² The report had a broad reach. As of February 2021 it has been downloaded from the National Academies Press website more than 5,600 times in 126 countries.

limited value to the U.S. NRC as criteria for determining the consequences of an RDD. Instead, these experts viewed socioeconomic effects and fatalities resulting from evacuation as more relevant criteria for determining the holistic consequences of an RDD (GAO, 2019).

1.4.2 Proposed Elimination of Cesium-137 from Commercial Applications

The 2008 National Academies report identified cesium-137 in cesium chloride form as the radioisotope of most concern, because an RDD that intentionally spreads cesium-137 in that form would have the most devastating consequences. Other potentially dangerous isotopes are solid metals dispersed as fragments that could be picked up from the ground or extracted from buildings after detonation. However, cesium-137, when chemically combined with chlorine to form cesium chloride, is a highly dispersible powder. Buildings exposed to cesium chloride might have to be demolished and the debris removed and buried if these structures cannot be adequately decontaminated in situ. A cesium chloride RDD would likely deny access to the contaminated area for years.

When the 2008 report was issued, approximately 550 licensees in the United States possessed about 1,100 self-contained cesium chloride irradiators, which contain at a minimum Category 2 quantities of radioactivity. The report concluded that for most applications, radioactive cesium chloride could be replaced by either less hazardous forms of radioactive cesium, radioactive cobalt, or nonradionuclide alternatives. At that time, x-ray irradiators were commercially available as substitutes for applications that did not require the gamma rays with the specific energies emitted by cesium-137 and cobalt-60, but they were less reliable and expensive. In addition, feasibility of using x-ray systems at facilities that required high throughput was also a question.

The 2008 report committee made this recommendation concerning cesium chloride:

Licensing of radioactive sources is the responsibility of the U.S. NRC and the Agreement States (see Section 2.4.1). Around the time that the National Academies report was released and partly in response to recommendations made in the report, the U.S. NRC undertook several activities to determine the best path for control of radioactive sources, particularly cesium-137 sources. These activities included investigating the potential of alternative forms of cesium, from a production standpoint as well as evaluating the potential risk reduction that these alternative forms could provide. The result of that effort was the Policy Statement of the U.S. NRC on the Protection of Cesium-137 Chloride Sources (U.S. NRC, 2011). The policy statement highlighted that “licensees have the primary responsibility to securely manage and to protect sources in their possession from misuse, theft, and radiological sabotage” and that sources will be adequately protected by licensees following the requirements of the U.S. NRC and Agreement States. Nonetheless, the policy statement noted that “design improvements could be made that further mitigate or minimize the radiological consequences” (U.S. NRC, 2011). Neither the U.S. NRC nor the Agreement States have discontinued licensing of cesium-137 chloride sources. Since 2015, 16 licenses either were granted or amended to add discrete sources of cesium-137 at or above Category 2 levels for irradiation of blood, research applications, or dose calibration.¹³

In 2014, following the recommendation by the 2008 National Academies report to provide incentives for decommissioning existing cesium-137 sources, the U.S. government piloted the Cesium Irradiator Replacement Project (CIRP). This project, administered by NNSA, aims to work with domestic users to facilitate the voluntary replacement of cesium chloride blood and research irradiators with x-ray devices on a cost-share basis (typically 50 percent) (see Sidebar 1.2 for a description of CIRP and Figure 1.2 for an image of a source removal opera-

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¹³ Margaret Cervera, U.S. NRC, presentation to the committee on June 11, 2020.

tion). Additional financial incentives of CIRP include the disposal of the cesium irradiator by NNSA. In addition to cesium irradiators, which were the focus of the 2008 National Academies report recommendation, CIRP also includes removal and disposal of cobalt-60 blood and research irradiators. Cobalt-60 sources do not carry concerns similar to those for cesium-137 sources because the source is solid and therefore not easily dispersible.

ORS also supports cesium irradiator replacements internationally. Sandia representatives noted that the international aspect of the program is more complicated due to different in-country rules and regulations; ambiguous lines of authority regarding licensing and regulation of alternative technologies; infrastructure constraints; and challenges with international contracting, among other factors.¹⁴

Regarding export of cesium chloride sources, the 2010 Task Force Report recommended,

The U.S. NRC’s policy statement is consistent with this recommendation (U.S. NRC, 2011). Since 2015, there have been 23 exports of cesium chloride. One of them was related to export of a cesium chloride irradiator in 2015; the remainder were either returns of cesium chloride irradiators or other industrial devices that use cesium chloride to a manufacturer.¹⁵

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¹⁴ Michael Itamura and Jodi Lieberman, Sandia, presentation to the committee on April 29, 2020.

¹⁵ Margaret Cervera, U.S. NRC, presentation to the committee on September 9, 2020.

1.5 RELEVANT WORK BY OTHERS

The committee had the benefit of reviewing several reports and of building on the work of multiple organizations that have examined safety and security issues related to radioactive sources and the progress and challenges of adopting alternative technologies for different applications.

GAO has been instrumental in identifying vulnerabilities of the regulatory system in the United States related to radioactive sources, for example, in the use of radioactive materials in medical (GAO, 2012) and industrial facilities (GAO, 2014), in acquiring Category 3 licenses (GAO, 2016), and in verification of licenses (GAO, 2018). GAO also convened a meeting of experts with support from the National Academies to examine whether the U.S. NRC’s assessment of risk includes all relevant criteria (GAO, 2019). At the time of this writing, following the fiscal year 2020 Senate Energy and Water Development Appropriations Bill (U.S. Congress, Senate, 2020), GAO was undertaking another review focusing on federal activities relating to alternative nonradioisotopic technologies. The review is expected to be released in fall 2021.

The Department of Homeland Security (DHS) Alternative Technology Working Group issued a report in 2019 that describes the status of the development and adoption of alternative technologies to high-risk radioactive sources used in industrial, medical, and research applications (CISA, 2019). That report details the efficacy, life-cycle costs, and applications of these alternative technologies and potential barriers to adoption.

The National Science and Technology Council Interagency Working Group on Alternatives to High-Activity Radioactive Sources (known as GARS) released a best practices guide for federal agencies. The guide provides measures that federal agencies can consider for facilitating the transition to alternative technologies in their long-term strategic planning (NSTC, 2016).

The James Martin Center for Nonproliferation Studies (CNS) issued a paper in 2014 and recommended that the United States lead a global effort to phase out the use of cesium chloride blood irradiators (Pomper et al., 2014) and later proposed a road map for replacing high-risk radioactive sources (Moore and Pomper, 2015). CNS has also partnered with the International Cancer Experts Corps to advance ideas to address the growing need for cancer treatment, especially in low- and middle-income countries, while ramping up the adoption of alternative technologies such as linear accelerators (Coleman et al., 2017). In addition, since 2013, CNS has maintained the only publicly available database (sponsored and hosted by NTI) on global incidents of nuclear and radiological materials outside of regulatory control (see Section 2.5.3).

The IAEA has issued dozens of reports that are directly relevant to this committee’s work. These reports span various topics related to radioactive sources including safety and security (IAEA, 2004, 2005, 2008a, 2011, 2014a,b, 2016, 2019d), feasibility of adopting alternative technologies (IAEA, 2012a, 2014a, 2019b,c; van Marcke, 2019), building capabilities in medical facilities for radiation therapy and other treatments (IAEA, 2008c,d, 2014c, 2015a,b,d), transportation of radioactive sources (IAEA, 2008b, 2018c), import and export controls (IAEA, 2012b), and management and disposal of disused sources (IAEA, 2013b, 2018a,d; Yusuf, 2020). The IAEA also maintains databases with information relevant to the committee’s task including the Incident and Trafficking Database (see Section 2.5.1), a directory of radiotherapy centers (see Section 4.3.1), and a directory of facilities using the sterile insect technique (see Section 5.4). Finally, the IAEA supports both collaborative research activities and technology transfer activities across developed and developing countries through the Coordinated Research Projects and the Technical Cooperation Programme. The Technical Cooperation Programme assists Member States by building capacity and partnerships, sharing knowledge, supporting networking, and facilitating procurement. The IAEA also receives extra-budgetary funding from donor countries to provide direct assistance such as Category 1 and Category 2 source removals.

NTI is broadly recognized as a resource and tool for tracking progress on global nuclear security by publishing the NTI Index, which assesses nuclear security conditions in 175 countries and Taiwan. In the context of radiological security, NTI has been instrumental in creating network models to raise awareness on risks and liabilities related to radioactive sources and facilitate dialogues between leadership of ORS, state and city representatives, regulators, operational decision makers, manufacturers, and users (NTI, 2017, 2018a,b). Recently, NTI published the first radiological index to evaluate national policies and commitments taken globally to prevent the theft of radioactive materials (NTI, 2020).

The World Institute for Nuclear Security (WINS) has issued several reports related to the security of radioactive sources and to the safe disposal of these sources (WINS, 2019a,b, 2020a,b). Through roundtables and other convening activities, WINS has informed stakeholders about alternatives to radioactive sources, has provided a framework to help decision makers about the appropriateness of considering alternatives, and has laid out a process to help organizations decide whether to adopt an alternative technology (WINS, 2018a,b).

The International Irradiation Association (IIA) and the International Source Suppliers and Producers Association raise awareness about the radiological security risks, the changing regulatory environments, and the full lifetime costs of using radioactive sources. The IIA has published white papers comparing different irradiation modalities (IIA, 2017). Reports released by these associations are typically only available to members.

1.6 REPORT ROAD MAP

This report is organized into six chapters that address the Statement of Task (see Sidebar 1.1) in its entirety:

• Chapter 1 (this chapter) provides background on the study request and describes the study task.
• Chapter 2 provides a broad overview of current uses of radioactive sources and discusses factors that affect safety and security risks associated with these sources, the roles and responsibilities within the government and other organizations to reduce these risks, and the efforts to track and dispose of radioactive sources at the end of life.
• Chapter 3 describes the primary alternative technologies considered in this report and institutional considerations that affect decisions related to adoption of these alternatives. This chapter also includes a section that summarizes progress in adopting alternative technologies for the different applications examined in this report.
• Chapter 4 assesses options for alternatives to radioactive sources used in medical and research applications.
• Chapter 5 assesses options for alternatives to radioactive sources used in sterilization.
• Chapter 6 assesses options for alternatives to radioactive sources used in industrial applications.

The appendixes provide short biographies of the committee and staff (Appendix A), descriptions of the information-gathering meetings for the study (Appendix B), a list of the most common acronyms and abbreviations (Appendix C), a glossary (Appendix D) that has been adopted from the previous National Academies report on the same topic (NRC, 2008), background information on the economic feasibility of adopting alternative technologies (Appendix E), and background on sterilization using radiation with different modalities (Appendix F).

The committee expects that the main audience of this technical report will be readers with some prior knowledge of the general issues related to radioactive sources and therefore will have some basic understanding of radiation principles and measures. Readers who lack certain background knowledge are encouraged to review reports and other material that provide such context. For example, the committee recommends Appendix B of the 2008 National Academies report (NRC, 2008).