Background In September 2003, the United States and other nations endorsed IAEA’s Code of Conduct, which established basic principles and guidance to promote the safe and secure use of radioactive material. The Code of Conduct applies to category 1, 2, and 3 quantities of radioactive material—all of which are potentially dangerous to human health and could, if not properly controlled, cause permanent injuries or death to a person who handled or was otherwise in contact with them. IAEA’s system considers radioactive material dangerous when gathered in close proximity to people in sufficient quantity and for a sufficient time to cause direct human health effects. NRC, working with the Department of Energy, developed a list of 16 radionuclides of concern that, if gathered in category 1 or 2 quantities, pose the greatest risk of being used by terrorists to make an RDD. Of these 16 radionuclides of concern, 4 are most prevalent in the U.S. economy: americium-241, cobalt-60, cesium- 137, and iridium-192. Since the terrorist attacks in September 2001, concerns have grown that terrorists could obtain and use radioactive material and build an RDD. The risk of an RDD is determined by the function of three components: threat, vulnerability, and consequence. Threat is generally defined as entities or actions with the potential to cause harm—including terrorist attacks. According to NRC officials, there is a general credible threat of malevolent use of radioactive materials. The second component of RDD risk, vulnerability, includes physical features or operational attributes that render an asset open to exploitation, including gaps in security measures such as gates, locks, perimeter fences, and computer networks. Finally, the third component of RDD risk, consequence, includes the effects of terrorist attacks or natural disasters that result in losses to public health and safety and the economy. Taken together, the three components make up a “risk triplet,” which is shown in figure 1. The consequences of detonating an RDD would depend on the quantity and type of radioactive material used and the size and characteristics of the area in which the material was dispersed. An example of the consequence of an RDD occurred in 1987 when two people in Goiânia, Brazil, found an abandoned medical machine containing 1,400 curies of cesium-137. The individuals, who were unaware of the nature of the radioactive material, extracted it from the machine and distributed the material to several families, causing 20 people to be hospitalized and four deaths. The very high internal and external contamination was caused by the way they handled the cesium-137, including rubbing their skin with the material and eating with contaminated hands. In addition, 112,000 people in the surrounding area were monitored for exposure to radiation, of which 249 were found to be internally or externally contaminated. The accident also contaminated 85 houses and required the demolition of homes and other buildings, generating 3,500 cubic meters of radioactive waste. This example shows the range of consequences from the dispersal of radioactive material, from fatalities to socioeconomic effects. Potential consequences of an RDD are outlined in figure 2. Depending on the size and radioactivity of an RDD, the affected population could be evacuated and possibly relocated. EPA’s Protective Action Guide (PAG) presents radiation dose guidelines that are used by federal agencies to protect people from unhealthy levels of radiation. According to the PAG, evacuation is recommended when there is enough radiation to reach 5.0 rem over the first 4 days. The PAG also outlines actions that can be taken in response to projected radiation dose rates, including evacuation, shelter in place, relocation, and avoidance of drinking water or food supplies. The PAG does not consider a specific geographic area, such as a square kilometer, when recommending evacuation. Domestically, the Atomic Energy Act of 1954, as amended, gives NRC primary responsibility for regulating most domestic industrial, medical, and research uses of radioactive material to protect public health and safety, among other things. NRC is composed of five Commissioners (the Commission) appointed by the President and confirmed by the Senate for 5-year terms. One of the Commissioners is designated by the President to be the Chairman and official spokesperson of the Commission. According to NRC’s website, the Commission formulates policies, develops regulations governing nuclear reactor and nuclear and radioactive material safety, issues orders to licensees, and adjudicates legal matters. Issues before the Commission are decided by majority vote, and the Commission directs subsequent actions be implemented by NRC staff. NRC Periodically Assesses Risk When Establishing Security Requirements for Radioactive Material When establishing security requirements for radioactive material, since 2004, NRC has assessed the risks of such material based on the potential of that material to cause prompt fatalities and the deterministic health effects from its radiation; it has not used socioeconomic consequences as a basis for establishing regulations related to the security of radioactive material. Moreover, in response to the recommendations we made in 2016 that NRC should better track category 3 quantities of radioactive material, NRC staff assessed whether they should require additional security measures for category 3 radioactive material and determined that such material did not merit additional security measures. NRC Considers Prompt Fatalities and Deterministic Health Effects When Assessing the Risk of an RDD and Does Not Consider Socioeconomic Consequences Since 2004, NRC has assessed the risks of radioactive material based on the potential of that material to cause prompt fatalities and deterministic health effects from radiation. NRC on several occasions reassessed and repeatedly reaffirmed its use of the occurrence of prompt fatalities and deterministic health effects as its primary criteria for measuring the consequences of an RDD, including when developing its decision-making framework in 2004, reviewing its regulatory framework after the Fukushima nuclear disaster in 2011, and in its 2014 response to recommendations from the Radiation Source Protection and Security Task Force (the Task Force). NRC first considered prompt fatalities from radiation as criteria for measuring consequences in November 2004 when developing its decision-making framework for evaluating vulnerabilities for theft of radioactive material. Specifically, in 2004 NRC staff recommended that the Commission approve a decision-making framework that assessed risk based on prompt fatalities from radiation. In the Commission Paper, NRC staff stated that the framework would employ the consequence criteria of preventing prompt fatalities from radiation exposure, but they also recognized that including additional consequence criteria, such as land contamination, might be warranted. They also pointed out that DHS’s Risk Analysis and Management for Criteria Asset Protection framework used criteria including economic, environmental, and loss of output of production capability, among other things. In January 2005, the Commission approved using prompt fatalities from radiation for measuring consequence. In its decision, the Commission also said that NRC staff should not independently develop criteria and standards for other consequences, such as land contamination and economic impacts. After the Fukushima nuclear disaster in 2011, NRC staff again considered broadening the criteria for assessing risk to include socioeconomic impacts. Specifically, in an August 2012 analysis presented to NRC commissioners in response to Fukushima that addressed whether NRC’s regulatory framework should be modified to consider economic consequences, NRC staff noted that NRC’s existing requirements have the effect of minimizing economic consequences by preventing or mitigating events that could lead to a radioactive release. The analysis prepared by NRC staff recommended improving guidance for estimating offsite economic costs based on up-to-date data. In March 2013, the Commission approved the staff’s recommendation to provide enhanced guidance but found that socioeconomic consequences should not be considered. at 2 rem for the first year. socioeconomic consequences to the Commission in January 2014, reiterating the staff’s view that Part 37 provides adequate security protection against a significant RDD. The NRC staff also concluded that the current protection and security framework and posture adequately protects against contamination and resulting economic consequences. NRC Assessed the Risk Associated with Category 3 Material and Determined That No Additional Security Measures Are Needed In 2016, NRC established the Category 3 Source Security and Accountability Working Group (the Working Group) in response to our 2016 recommendations to NRC to better track dangerous quantities of radioactive material. This group issued a report in 2017 assessing whether NRC should require additional security measures for category 3 material and determined that such material did not meet the threshold of prompt fatalities and deterministic health effects set by NRC, and therefore, did not require additional security measures. As part of its analysis, the Working Group stated that a category 2 quantity of a certain radioactive material would not be sufficient to achieve an RDD of consequence that would cause deterministic health effects. NRC officials also told us that there is not enough of this same radioactive material in the United States to create an RDD of consequence even if all of it was used in an RDD. The Working Group also concluded that there is no evidence of adversarial interest in acquiring category 3 quantities of material by theft, that security weaknesses at facilities that contain category 3 quantities of radioactive material had not increased since first evaluated by NRC, and the consequences of an RDD using category 3 material are not significant enough to require additional security measures. Based on the findings of the working group’s report, NRC staff recommended that the Commission not amend regulations to require license verification of category 3 radioactive material or impose security requirements to prevent the aggregating of category 3 material to a category 2 quantity. The report did recommend that the Commission approve the pursuit of rulemaking to require safety and security equipment be in place before granting a license for an unknown entity and clarify license verification methods for transfers involving quantities of radioactive material below the category 2 threshold. Experts Generally Agreed That NRC’s Assessment of Risk Does Not Include All Relevant Criteria for Establishing Security Requirements The experts we convened with assistance from the National Academies generally agreed that NRC’s assessment of risk does not include the all relevant criteria for establishing security requirements. The experts at our meeting generally agreed that prompt fatalities from radiation and deterministic health effects are not the only relevant criteria for determining the consequences of an RDD, which recent studies we reviewed support. These experts and studies generally agreed that socioeconomic effects and fatalities from subsequent evacuations are relevant criteria for assessing the consequences of an RDD. Experts Generally Agreed and Studies Support That Prompt Fatalities and Deterministic Health Effects Have Limited Value as Criteria The experts at our meeting generally agreed that using prompt fatalities and deterministic health effects from radiation as the basis for analyzing consequence have limited value to NRC as criteria for determining the consequences of an RDD, as they are unlikely to occur in the event of an RDD. Experts generally said at our meeting expressed the opinion that NRC is not focusing on all relevant criteria for assessing consequence. For example, one expert from the regulatory community said that prompt fatalities are an unlikely consequence of an RDD. Another expert affiliated with users of radioactive material noted that deterministic health effects from an RDD are limited. Finally, a security expert said that it would be difficult to kill large numbers of people with an RDD, and therefore prompt fatalities are not a good measure of consequence. Another expert pointed out that NRC’s current criteria would be unlikely to support regulating category 1 and 2 materials since an RDD with these materials is unlikely to cause prompt fatalities. He added that this creates a disconnect where category 3 material is ignored, but NRC regulates category 1 and 2 material even though category 1 and 2 materials do not meet NRC’s criteria of causing prompt fatalities and deterministic health effects. Recent studies from Sandia also show that prompt fatalities and deterministic health effects are unlikely to result from an RDD. Specifically, Sandia completed two studies in 2017 and 2018 that modeled an RDD blast and evaluated the potential consequences in New York City. The 2017 study modeled the potential consequences of a category 1 quantity of radioactive material detonated in an RDD and estimated that there would likely be no prompt fatalities from radiation. The 2018 study undertook the same analysis with a category 3 quantity of radioactive material and estimated that it would also produce no prompt fatalities from radiation. Experts Stated and Studies Support That Socioeconomic Effects and Fatalities Resulting From Evacuations Are Relevant Criteria for Determining the Consequences of an RDD The experts who participated in our meeting discussed what type of consequences should be considered and generally agreed that socioeconomic effects and fatalities from subsequent evacuations, rather than prompt fatalities and deterministic health effects, are relevant criteria for NRC to consider when assessing the consequences of an RDD, which recent studies we reviewed support. For example, one expert said that while deterministic health effects from an RDD are limited, socioeconomic impacts are significant. Another expert said that the main point of a terrorist detonating an RDD is to create economic effects, not deterministic health effects. This expert added that the dispersal of radioactive material would result in low-level radiation scattered across an area, leading to socioeconomic consequences. A participating expert from the regulatory community said that it is difficult to quantify socioeconomic effects. Furthermore, the expert said that any model used to determine regulation by predicting consequence must be reproducible. The federal government has recently taken steps to better understand the socioeconomic costs associated with an RDD. For example, Sandia studies completed in 2017 and 2018 estimated socioeconomic costs for RDDs with category 1 and category 3 quantities of radioactive material. The 2017 study that modeled a category 1 quantity of radioactive material estimated that the socioeconomic impact on the national gross domestic product would be approximately $30 billion. The 2018 study, which substituted a category 3 quantity of radioactive material, estimated the socioeconomic impact on gross domestic product at $24 billion. One expert noted that the estimates may be understated. Specifically, the 2017 Sandia study took into account that the facades of some buildings in New York City could be replaced, which would aid cleanup and reduce socioeconomic costs. However, one expert who attended our meeting said that New York City may be a best-case example of an urban target because the city has solid response plans and modern buildings with facades that can be removed more easily than those in other cities. This expert said these factors likely lead to an optimistic calculation of socioeconomic consequence in the study, due to the preparation and resilience posture of New York City, creating a best-case scenario regarding cleanup that may not accurately quantify costs in other cities. In this expert’s view, the federal government may also be underestimating the economic consequences of an RDD by not accounting for the potential that local cleanup standards may be more stringent than the federal government standards assumed in the study. The expert said that locals will always want to clean up to a higher standard than federal government guidance recommends, largely due to a desire to protect economic assets such as trade, brand, and image. In addition to socioeconomic concerns, experts who attended our meeting generally noted that an assessment of the consequence of an RDD should consider fatalities resulting from the evacuation of homes and business. For example, one expert from our meeting said that there were few deaths from radiation during the incident at the Fukushima nuclear complex in 2011, but there were many deaths from the evacuation. Another expert agreed and said that there is evidence from Chernobyl and Fukushima linking health effects to evacuations and that, therefore, fatalities from evacuations should be included on the list of consequences from an RDD. A third expert said that panic cannot be underestimated in the event of an RDD, and the consequences of evacuation and relocation would exceed prompt fatalities and deterministic health effects. Finally, one expert said that many people outside of the evacuation area will also choose to relocate after an RDD rather than wait for direction from the government, which could increase the number of evacuees and lead to additional fatalities. The 2017 and 2018 Sandia studies support these concerns, estimating that these evacuations could cause hundreds to thousands of deaths and that fatalities during evacuations are similar for RDDs using category 1 and category 3 quantities of the same material. Specifically, the 2017 Sandia study examined the number of fatalities that occurred during the evacuation from the disaster at the Fukushima nuclear complex. Using that event as a baseline, the Sandia study estimated that approximately 1,500 people could die from the evacuation associated with the detonation of an RDD containing a category 1 quantity of radioactive material in New York City. The 2018 Sandia study of a detonation of an RDD containing a category 3 quantity of radioactive material estimated that approximately 800 people could die from the evacuation. NRC does not consider socioeconomic consequences or fatalities from evacuations when assessing the consequence of an RDD. Agency officials told us that, under the authority of the Atomic Energy Act, NRC staff has discretion to consider other criteria, including socioeconomic effects, if so directed by the Commission. However, NRC staff told us that they do not currently consider socioeconomic consequences as criteria because they have been specifically directed not to do so by the Commission. In discussions with agency officials, it is unclear why the Commission has directed the NRC staff not to consider other criteria for evaluating the impact of an RDD. NRC’s own guidance states that RDDs would cause few deaths from radiation but result in significant socioeconomic impacts. Specifically, NRC guidance issued in May 2014 states: “RDDs are considered weapons of mass disruption; few deaths would occur due to the radioactive nature of the event; 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.” NRC’s decision to not consider other criteria has limited its assessments of risk presented by the use of radioactive material in an RDD. By considering socioeconomic impacts and fatalities resulting from evacuations in its criteria, NRC would have better assurance that it was considering the more likely and more significant consequences of an RDD when establishing its security requirements for this material. NRC’s 2016 Report Does Not Fully Reflect the Risks of High-Risk Category 3 Material, Collocation of Americium-241, and Protection against Insider Threats In 2016, NRC evaluated the effectiveness of Part 37, as required by Public Law 113-235, and concluded that the rule is effective for ensuring category 1 and 2 radioactive materials are secure from theft or diversion. However, experts who attended our meeting stated, and recent studies support, that if category 3 quantities of radioactive materials were used in an RDD, the consequences could be comparable to a category 1 or 2 quantity of the same material, which are protected from theft by additional security measures. In addition, experts who participated in our meeting generally said that NRC’s current requirements permit collocation at the same facility of multiple category 3 quantities of americium-241 that in total reach or surpass the threshold for a category 2 quantity without the enhanced security required for category 1 and 2 materials. Furthermore, experts generally agreed that there are security weaknesses in the current trustworthiness and reliability process to protect against an insider threat. NRC’s 2016 Evaluation of Part 37 Determined That Current Security Requirements are Adequate for Category 1 and 2 Radioactive Materials In December 2016, NRC issued a report evaluating the effectiveness of Part 37, as required by Public Law 113-235. NRC’s evaluation included an analysis of events and inspection findings related to the security of category 1 and 2 materials, including an analysis of 189 violations issued to NRC State licensees from March 2014 through March 2016. The report found that almost all of the violations were related to conducting background investigations, controlling access to radioactive material, and physical security measures. The violations mainly occurred when licensees had not yet implemented Part 37 or failed to fully document how their security program complied with Part 37. The report noted that there were no Severity Level I or Severity Level II violations. The NRC report looked at the theft of six category 2 quantities of radioactive material since the introduction of the Increased Controls security requirements in 2003 and concluded that carelessness or human error, rather than any gaps in the requirements of Part 37, contributed to the thefts. As we reported in 2014, the thefts included industrial radiography cameras with category 2 quantities of iridium-192 sources stolen from radiography trucks parked outside a company facility, in hotel parking lots, and at a gas station. NRC concluded that in all the events, carelessness or human error contributed to the thefts and had the licensees followed existing regulatory requirements, the thefts could have been prevented. NRC’s 2016 report concluded that better outreach and communication would help improve compliance with Part 37. NRC’s report also documents NRC staff’s determination that the requirements in Part 37 are effective in preventing the theft or diversion of category 1 and 2 quantities of radioactive material. NRC determined that potential rule clarifications and guidance initiatives could help to enhance the clarity and effectiveness of the rule, ensure better understanding of security expectations, and allow for more complete and adequate implementation. NRC’s overall assessment is that Part 37 provides reasonable assurance for the security of category 1 and 2 quantities of radioactive material by protecting the material from theft or diversion. NRC’s 2016 Evaluation Did Not Consider the Security of Category 3 Material That Experts Consider High Risk In conducting its evaluation, NRC examined past security incidents and inspection reports, but its report did not review the security requirements for category 3, 4, or 5 quantities of radioactive material because NRC does not consider these categories to be a significant risk. NRC chose to define high-risk radioactive material as only category 1 and 2. NRC does not further elaborate why it took this approach. NRC’s reliance on prompt fatalities and deterministic health effects and its exclusion of socioeconomic consequences and deaths from evacuations as criteria for determining the consequences of an RDD, as discussed earlier, has resulted in security requirements that do not include all high- risk quantities of some radioactive materials. Experts who participated in our meeting generally agreed that some category 3 quantities of radioactive material should be considered high risk based on their potential consequences if used in an RDD. For example, one international expert pointed out that IAEA guidance includes security measures for category 3 quantities of material and expressed surprise that U.S. guidelines do not include additional security measures for category 3 quantities. Another expert suggested that NRC include category 3 quantities of radioactive material in the National Source Tracking System, which would allow for license verification during purchases. In this expert’s opinion, the main vulnerability for category 3 quantities of radioactive material is that they can be purchased with a license that has not been verified as legitimate by the NRC or an agreement state. The experts also generally said that some category 3 radioactive material should be considered high risk and should be subject to additional security measures. For example, one expert suggested that some types of category 3 radioactive material may need additional oversight. However, this expert said that NRC should consider a more nuanced approach to increasing the security for some, but not all, quantities of category 3 radioactive material. Another expert agreed and said that the ability to disperse material is a primary factor in determining if something is high risk. For this reason, this expert said, category 3 quantities of some types of radioactive material should be considered high risk, and there may be need for an additional category of materials that falls below category 2 but that includes the most dangerous high-risk materials in category 3 quantities. An expert who attended our meeting stated that certain radioactive materials pose a unique decontamination challenge because those materials bind to materials like asphalt and concrete, making decontamination difficult and expensive. One expert said that the consequences listed in the 2018 Sandia report were enough to justify requiring additional security measures for category 3 quantities of certain radioactive materials. As shown in table 1, the 2018 Sandia study found that a category 3 quantity of radioactive material could result in socioeconomic consequences and fatalities from evacuations similar to an RDD with a category 1 quantity of radioactive material. The experts also generally said that there could be long-term socioeconomic consequences unique to the risk posed by an RDD that used a category 3 quantity of radioactive material, and certain radioactive materials in smaller quantities should be considered high risk. As we described earlier, NRC reported in a 2017 Threat, Consequence, and Vulnerability Assessment that even if several hundred category 3 quantities of a certain radioactive material were used in an RDD, it would not create an RDD of consequence. In our discussions with NRC staff, they expanded on this point and stated that there may not be enough of this material in the United States to build an RDD of consequence. However, new research from Sandia found that a category 3 quantity of the same material could trigger an evacuation and result in significant socioeconomic consequences. According to an expert from the regulatory community, while the Commission has considered requiring additional security measures for category 3 quantities of material, NRC staff recommended against doing so because the costs of providing additional security would outweigh the benefits. For example, one expert who attended our meeting said that the choice is between the difference in costs of absolute security and adequate security, and the cost/benefit analysis does not support including category 3 quantities of radioactive materials in Part 37. The expert pointed out that there have been relatively few thefts of category 3 sources in the United States and suggested that providing additional security should be weighed against the low likelihood that the radioactive materials would be stolen. While there were differing views in our expert meeting between the regulatory community and other experts, the experts generally agreed, and the Sandia studies support, that the consequences of category 3 quantities of certain types of material could be significant. By requiring additional security measures for these high-risk quantities of category 3 material, and assessing whether other category 3 radioactive materials should also be safeguarded with additional security measures, NRC could have better assurance that its requirements are sufficient to help ensure all high-risk radioactive material is protected from theft and use in an RDD. NRC’s 2016 Report Does Not Fully Address Weaknesses in Part 37’s Regulation of the Collocation of Americium- 241 and How NRC Protects against an Insider Threat NRC’s 2016 report looked at the risks posed by the collocation of category 3 quantities of material and insider threats. NRC concluded that rule clarifications and additional guidance could help enhance clarity and effectives of the rule, but its report does not fully address how these risks should be managed. For example, experts who participated in our meeting generally agreed that weaknesses continue to exist in how Part 37 regulates the collocation of multiple category 3 quantities of americium-241 at a single facility. Specifically, NRC requirements permit collocation of multiple category 3 quantities of material that in total reach a category 1 or 2 quantity of material, without applying Part 37. Experts told us that well logging companies, which use americium-241 to inspect wells for oil and natural gas, are storing multiple category 3 quantities, each just below the threshold for category 2, of americium-241 at the same facility; thus, the total quantity does not trigger additional security requirements under Part 37. Figure 3 shows a well logging storage facility containing multiple category 3 quantities of americium-241. Experts at our meeting generally said that collocation of multiple quantities of category 3 americium-241 at well logging facilities creates specific security weaknesses that should be addressed. For example, one expert who attended our meeting from the regulatory community said that NRC has no formal definition for collocation, but Part 37 considers it acceptable to store multiple category 3 quantities of radioactive material in separate, locked containers that, together, add up to a category 2 quantity. Another expert pointed out that when NNSA evaluates threats to materials, it totals up the quantity of materials located at the same facility to determine the total amount of material at risk. A third expert noted that licensees are required to inventory category 3 quantities of material only twice per year. Furthermore, the experts pointed out that these types of facilities are not subject to stricter security requirements, and therefore, do not undertake trustworthiness and reliability evaluations for their employees with unescorted access to radioactive material. By requiring that all licensees implement additional security measures when they collocate multiple quantities of category 3 americium-241—that in total reach a category 1 or 2 quantity—at a single facility, NRC could have better assurance that the material is protected from theft and use in an RDD. Furthermore, experts who participated in our meeting generally agreed that there continue to be security weaknesses in the current trustworthiness and reliability process for securing radioactive material from theft and use in an RDD. For example, one expert from the licensee community who attended our meeting said that NRC’s Part 37 does not go far enough in ensuring the trustworthiness and reliability of individuals given unescorted access. Specifically, the expert said that, based on the Part 37 requirements, licensees make all trustworthiness and reliability determinations for granting unescorted access to employees, which leads to inconsistencies across licensees. The experts generally said that NRC should give licensees more guidance on acceptable criteria for granting unescorted access, which is consistent with recommendations included in past GAO reports. NRC is currently in the process of making revisions to its trustworthiness and reliability guidance. Experts who attended our meeting said that licensees face challenges in making trustworthiness and reliability determinations, including the fear of being sued if they deny employment to an individual with a criminal record, difficulty conducting background investigations for foreign nationals, and the potential for individuals to be radicalized more quickly than the current trustworthiness and reliability process protects against. One expert from the regulatory community who attended our meeting said that trustworthiness and reliability decisions are a “judgment call,” and when an applicant has a criminal record or has committed a felony, a company may not want to give them unescorted access to radioactive material. However, the expert added that denial of unescorted access without backup from NRC guidance may leave the company open to lawsuits. In addition, another expert who attended our meeting said institutions that often employ foreign nationals as researchers, such as hospitals, struggle with verifying limited background information for these individuals. Finally, an expert who attended our meeting said that perception of trustworthiness and reliability has recently changed, and there is now greater concern that people can be radicalized quickly, rendering background investigations insufficient to identify potential issues with an employee’s trustworthiness and reliability during their employment. The expert told the group that there is evidence that individuals can be radicalized in a matter of months. The expert said that current trustworthiness and reliability procedures should take into account that people’s beliefs can change rapidly. Conclusions Radioactive material is used in thousands of locations throughout the United States for medical, industrial, and research purposes. On several occasions over the past 20 years, NRC has examined and revised the security requirements for these materials in order to prevent terrorists from acquiring radioactive material and constructing an RDD, or “dirty bomb.” When assessing the risk posed by an RDD, NRC has repeatedly looked at different criteria for measuring consequences and chose to base its decisions primarily on preventing prompt fatalities and deterministic health effects from radiation. However, the experts who participated in our meeting generally agreed, and Sandia studies support, that socioeconomic effects and fatalities from subsequent evacuations are relevant criteria for assessing the consequences of an RDD. NRC’s decision to not consider other criteria to assess the consequence of an RDD has resulted in security requirements that do not address the full risks presented by the danger that category 3 quantities of some radioactive material could be used in an RDD to cause significant socioeconomic consequences comparable to what could be caused by category 2 or category 1 quantities of material. By considering socioeconomic impacts and fatalities resulting from evacuations in its criteria, NRC would have better assurance that it was considering more likely and more significant consequences of an RDD when establishing its security requirements for this material. Furthermore, Part 37 requires enhanced security measures for categories 1 and 2 quantities of radioactive material and does not require additional security for category 3, 4, and 5 quantities of material beyond existing safety requirements. Although NRC chose to limit its 2016 evaluation of Part 37 to only category 1 and 2 quantities of material, experts who participated in our meeting generally said that they consider certain category 3 quantities of radioactive material high risk based on their potential consequences if used in an RDD, and data from recent studies support this determination. By requiring additional security measures for these high-risk quantities of category 3 material, and assessing whether other category 3 radioactive materials should be safeguarded with additional security measures, NRC can have better assurance that its requirements are sufficient to help ensure all high-risk radioactive material are protected from theft and use in an RDD. In addition, NRC’s 2016 report looked at the risk posed by the collocation of category 3 quantities of material and concluded that rule clarifications and additional guidance could help enhance the clarity and effectiveness of the rule. However, the report does not fully address how this risk should be resolved. Current NRC security requirements permit the collocation of multiple category 3 quantities of material that in total reach a category 2 quantity of material or higher, without triggering additional security requirements under Part 37. By requiring that all licensees implement additional security measures when they collocate multiple quantities of category 3 americium-241—that in total reach a category 1 or 2 quantity—at a single facility, NRC could have better assurance that the material is protected from theft and use in an RDD. Recommendations for Executive Action We are making the following three recommendations to the Nuclear Regulatory Commission: The Chairman of NRC should direct NRC staff to consider socioeconomic consequences and fatalities from evacuations in the criteria for determining what security measures should be required for radioactive materials that could be used in an RDD. (Recommendation 1) The Chairman of NRC should require additional security measures for high-risk quantities of certain category 3 radioactive material, and assess whether other category 3 materials should also be safeguarded with additional security measures. (Recommendation 2) The Chairman of NRC should require all licensees to implement additional security measures when they have multiple quantities of category 3 americium-241 at a single facility that in total reach a category 1 or 2 quantity of material. (Recommendation 3) Agency Comments We provided a draft of this report to the Chairman of NRC, the Administrator of NNSA, the Secretary of the Department of Homeland Security, and the Attorney General of the United States. NRC provided written comments on the draft report, which are presented in appendix III. In addition, NRC provided technical comments, which we incorporated as appropriate. NNSA, DHS, and FBI did not provide written comments. NRC disagreed with two of our recommendations and neither agreed nor disagreed with an additional recommendation. Specifically, it disagreed with our recommendations that it (1) consider socioeconomic consequences and fatalities from evacuations when determining security measures for radioactive materials; and (2) require licensees to implement additional security measures when they have multiple quantities of category 3 americium-241 at a single facility that in total reach a category 1 or 2 quantity. NRC stated that it is considering an additional recommendation that it require additional security measures for high-risk quantities of category 3 materials. Regarding the first recommendation with which NRC disagreed, the agency stated that its current regulatory requirements provide for the safe and secure use of radioactive materials, and that we only focused on potential consequences of an RDD without consideration of the two other elements of risk—threat and vulnerability. We disagree. NRC agrees that a general threat exists, and this report, in combination with our previous reports, demonstrate that there are vulnerabilities in current NRC security requirements and that the potential consequences of misusing these materials could be significant. Furthermore, the report discusses new evidence related to the consequence of an RDD that NRC has not yet considered. For the second recommendation with which it disagreed, NRC stated that it has already considered the issue of aggregation of radioactive material and has taken or is in the process of taking actions to clarify relevant guidance and procedures. Again, we disagree. We acknowledge that NRC is taking action to better educate licensees on how to comply with requirements related to aggregation. However, these actions do not address the issue of licensees taking advantage of NRC’s security requirements which permit the storing of multiple category 3 quantities that are just below the threshold for category 2 at the same facility. Finally, for the NRC recommendation to consider additional security measures for high-risk quantities of category 3 materials, the agency said that it has been considering our recommendation in connection with its response to the recommendations in GAO-16-330. However, after we issued GAO-16-330, NRC staff subsequently recommended that the NRC Commission not implement the recommendations from that report. NRC stated that our report and recommendations lack important context in that we did not consider all aspects of risk—threat, vulnerability, and consequences. We disagree. First, as the report states, NRC agrees that a general threat exists for the theft and misuse of radiological materials. Second, the report also states that we have addressed vulnerability in several past GAO reports that provide examples of how the controls that NRC and others have put in place to prevent the theft or misuse of these materials are not always implemented correctly. In fact, we found gaps in these controls each time we reviewed the security of radioactive materials. These gaps in controls create vulnerabilities. Having discussed threat and vulnerability, this report adds important new information concerning the consequences of an RDD. In this regard, both the Sandia studies and the results from our National Academy of Sciences expert meeting show that prompt fatalities from radiation are unlikely to occur if an RDD is detonated, while the same event could result in tens of billions of dollars in economic damage and potentially hundreds to thousands of deaths from evacuations. NRC also stated that our evidence was insufficient for recommending regulatory and policy changes. Specifically, they said that the Sandia studies (1) were based on scenarios that were not probable, (2) did not credit existing protective measures to prevent an RDD, and (3) were not subjected to a formal review and endorsement process. In addition, they said that the views expressed by experts who attended our National Academy of Sciences meeting resulted in conclusions that were not fully supported. We disagree with these characterizations of the studies and our expert meeting. Specifically, the Sandia studies did not attempt to assess existing security measures for radioactive material or the probability or likelihood of an RDD. These Sandia studies examined the consequences of an RDD and represent the most recent research on RDD consequences from an independent and reliable source. In addition, NRC’s claim that the Sandia studies were conducted without a formal review and endorsement process is misleading. Specifically, according to NNSA officials, Sandia and NNSA officials met with officials from NRC, DHS, and EPA, among others, to discuss and gather input on the assumptions to be used in the 2017 Sandia study. During this meeting, according to NNSA officials, NRC staff provided input on key assumptions and subsequently provided data to help support the Sandia study. In addition, NNSA and Sandia briefed their interagency partners, including NRC, about the findings in the study before publishing and received generally positive feedback on their results. Furthermore, we partnered with the National Academies to identify and select a broad range of experts in the field of radioactive material security, including federal agency and agreement state officials; academics; representatives of nonprofit organizations, licensees, and industry; international regulators; and national laboratory specialists. For additional information on how we developed, held, and analyzed data from our National Academy of Sciences expert meeting, please refer to appendix 2. NRC’s comments also state that GAO does not account for the work of the 2014 Radiation Source Protection and Security Task Force (the Task Force), which considered economic consequences related to an RDD. However, as noted in our report, NRC’s response to the Task Force’s recommendations said that NRC staff would need additional direction from the Commission to consider examining alternative consequences. In addition, in 2014, NRC staff recommended that NRC not consider changing the policy to include consideration of socioeconomic consequences to the Commission, reiterating the staff’s view that Part 37 provides adequate security protection against a significant RDD. Today, NRC staff still does not have direction from the Commission to consider socioeconomic effects when setting security requirements. We think that needs to change in order for NRC to conduct a complete analysis of the consequences of an RDD. Finally, NRC stated that a significant gap related to the security of category 3 sources has not been identified. We disagree. As noted in the report, requirements for the security of category 3 quantities of radioactive materials are significantly less stringent than those required for category 1 and 2 quantities of material. Nevertheless, our report shows that the use of category 3 quantities of certain radioactive materials in an RDD may have comparable socioeconomic consequences. Furthermore, previous GAO reports have repeatedly shown that gaps exist related to the security of category 3 and higher radioactive material. We are sending copies of this report to the appropriate congressional committees, the Chairman of the U.S. Nuclear Regulatory Commission, the Secretary of Energy, the Secretary of Homeland Security, the Administrator of the Environmental Protection Agency, and the Attorney General of the United States, and other interested parties. In addition, the report is available at no charge on the GAO website at http://www.gao.gov. If you or your staff have any questions about this report, please contact me at (202) 512-3841 or trimbled@gao.gov. Contact points for our offices of Congressional Relations and Public Affairs are on the last page of this report. GAO staff who made key contributions to this report are listed in appendix IV. Appendix I: List of Experts Appendix II: Scope and Methodology We focused our review primarily on the Nuclear Regulatory Commission (NRC) because it is the principal federal agency with responsibility for licensing the commercial use of and regulating the security of radioactive materials in the United States. Additionally, Public Law 113-235 specifically directs us to review NRC’s security requirements for radioactive material. We also interviewed officials at various agencies that play a role in radioactive material security, including the National Nuclear Security Administration (NNSA), the Department of Homeland Security (DHS), the Environmental Protection Agency (EPA), and the Federal Bureau of Investigation (FBI). We interviewed officials at NNSA because NNSA’s Office of Radiological Security provides upgrades and enhancements to NRC licensees and removes and disposes of disused radioactive material. We also spoke to DHS officials because DHS is the primary federal agency for implementing domestic nuclear detection efforts for a managed and coordinated response to radioactive and nuclear threats. Additionally, we interviewed officials at EPA, because the agency developed the Protective Action Guide (PAG) manual, which contains radiation dose guidelines that would trigger public safety measures. Finally, we interviewed the FBI, which offered us information on the potential threat related to radioactive material security. In addition to federal agencies, we were contacted by and spoke to a working group that represents the commercial radioactive source industry and received a briefing from a company, which is also a member of the working group that utilizes large panoramic irradiators. We received a series of risk briefings from federal agencies to collect information on current risks related to radioactive material security. NRC officials provided us with information about how the agency evaluates risks associated with radioactive material, including the threat, vulnerability, and consequence of an adversary acquiring and using radioactive material in a radioactive dispersal device (RDD). DHS officials provided us with a risk briefing on current threats to radioactive material and potential consequences of an RDD attack. Specifically, those officials briefed us on historical terrorist interest in using radioactive materials in attacks. NNSA officials and Sandia National Laboratory experts in radioactive security and consequence modeling briefed us on potential economic consequences from an RDD, which they based on an economic impact study completed by Sandia in 2018. Finally, FBI officials gave us a threat briefing focused on current radioactive material security threats, including interest by adversaries in conducting an RDD attack. These briefings were held at a classified level. In order to fulfill the Public Law 113-235 requirement to work with an independent group of experts, we partnered with the National Academies of Sciences to convene a group of experts on radioactive material security on July 26 and 27, 2018. We determined that this method offered the best means of gathering a balanced group of leading experts in the field of radioactive security to discuss issues in a moderated setting. In addition, this method allowed us to implement a structured and systematic approach when gathering evidence. Specifically, our methodology for the meeting included selecting a broad range of experts to participate in the meeting, administering a written questionnaire to the experts before the meeting, designing specific scenarios used during the moderated discussion, and performing a thematic analysis upon completion of the meeting. To describe how NRC assesses risk when establishing security requirements for high-risk radioactive materials and how it chose to primarily consider prompt fatalities as criteria for measuring consequences of an RDD, we reviewed NRC documents addressing how NRC evaluates an RDD, NRC’s study evaluating the effectiveness of Part 37 in response to Public Law 113-235, and NRC’s analysis of the risks posed by high-risk radioactive materials. Specifically, we reviewed NRC Commission Papers and NRC responses to actions taken by the Radiation Source Protection and Security Task Force. We also conducted interviews with agency officials at NRC, NNSA, DHS, EPA, and FBI, as well as academics, agreement state officials, and security managers from industry about the risks associated with different categories of radioactive materials and how NRC regulates these materials. We selected interviewees based on their expertise, but the results of these interviews are not generalizable. To examine the extent to which radioactive security experts agreed that NRC’s assessment of risk includes all relevant criteria for establishing security requirements, we partnered with the National Academies to identify and select a broad range of experts in the field of radioactive material security, including federal agency and agreement state officials; academics; representatives of nonprofit organizations, licensees, and industry; international regulators; and national laboratory specialists. In choosing the group of 18 experts, we specifically chose individuals with a diversity of backgrounds on topics. This ensured a balanced range of opinions and specific expertise on given topics but did not represent a generalizable sample of experts on a specific topic. For example, some individuals had specific expertise in certain topics and could provide a more insightful perspective than others in the group. In advance of the meeting, we developed a written questionnaire to obtain the experts’ views on the key threats, vulnerabilities and consequences of materials regulated under Part 37 and those not regulated under Part 37. We administered the questionnaire to the experts via email and obtained completed questionnaires from all of them. We analyzed their responses to focus the topics we discussed during our two-day meeting. During the meeting, we introduced the threat of malevolent use of radioactive material, and we asked the experts to focus their discussion the potential consequences of an RDD, the vulnerabilities of radiological materials under current security requirements and whether current security requirements were sufficient given these consequences and vulnerabilities. We asked them to discuss the reasons to account for the consequence in the regulation of radioactive material, the reasons not to account for the consequence, and whether the consequence should be accounted for. In addition, we asked the experts the reasons various radionuclides should be considered high risk, the reasons these radionuclides should not be considered high risk, and on balance, whether these radionuclides should be considered high risk. Our meeting agenda and moderator guide also included detailed scenarios designed to probe issues related to radioactive security and provide clear parameters within which the experts could make observations. In particular, we presented the experts with four scenarios of differing quantities of radioactive material used for particular medical and industrial purposes and stored under particular circumstances. The four scenarios presented different types of radioactive materials stored under particular circumstances. For these scenarios, we asked experts about the primary vulnerabilities of these materials in terms of access, monitoring and detection and response, and given the consequences and vulnerabilities, whether the Part 37 security requirements were sufficient. We based these scenarios on situations we observed during our prior work on the security of radioactive material. For each of these scenarios, we asked experts to assess two key elements of the risk triplet—vulnerability to being used and consequences if used. For example, we included a presentation on threat associated with radioactive materials. Additionally, for each scenario we moderated discussions on scenarios focused on vulnerabilities of category 1 and category 3 radioactive materials or scenarios focused on the consequences of category 1 and category 3 RDDs. Furthermore, a GAO methodologist and a National Academies of Sciences official guided discussions, following the structured moderator guide to ensure the discussions addressed all topics. The moderators ensured that experts from all sides had the opportunity to voice their opinions, but time constraints and the nature of an expert meeting may have limited some experts from contributing. Because of this structure, we had no expectation of reaching outright consensus on any specific topic. After the expert meeting, we conducted a structured and systematic thematic analysis of the information gathered to better understand the potential vulnerabilities of radioactive materials to theft and the consequences of an RDD using various radioactive materials. We also worked with GAO methodologists to sort the content in the meeting transcript, identify themes from the sorted information for additional analysis, and evaluate the credibility of expert statements. GAO internally reviewed our analysis for completeness and accuracy and it was found to be sufficient for our purposes. The meeting transcript write-up allowed us to focus on strengths and weaknesses in current security requirements, how the federal government evaluates the consequences of an RDD, what materials should be considered high risk, and whether additional security measures are necessary for these materials. Experts did not speak on every topic, did not have the same level of expertise on every topic, and the meeting format was not designed to quantify experts’ comments. Therefore, we do not report the number of the 18 experts who agreed or disagreed with various statements. Instead, through our thematic analysis, we determined that during the expert meeting experts generally made two types of statements on topics with varying degrees of agreement or corroboration, which we refer to as either “strong evidence” or “evidence of varying viewpoints.” GAO, Government Auditing Standards, 2018 Revision, GAO-18-568G (Washington, D.C.: July 2018). According to government auditing standards, testimonial evidence obtained from an individual who is not biased and has direct knowledge about the area is generally more reliable than testimonial evidence obtained from an individual who is biased or has indirect or partial knowledge about the area. Appendix III: Comments from the Nuclear Regulatory Commission Appendix IV: GAO Contact and Staff Acknowledgments GAO Contact Staff Acknowledgments In addition to the individual named above, Ned Woodward (Assistant Director), Jeffrey Barron (Analyst in Charge), Kevin Bray, Mark Braza, Kendall Childers, Tara Congdon, Gabrielle Matuzsan, Amanda Miller, Danny Royer, and Kiki Theodoropoulos made key contributions to this report.