Given the threat of radiological and nuclear terrorism, it is imperative to understand and evaluate the security risk of radioactive sources. In this context, risk assessment is a function of threat, vulnerability, and consequences. Currently, no broad risk index exists for radiological facilities, such as healthcare centers and universities. This study aims to develop and demonstrate a methodology to compute a potential facility risk index (PFRI) based on a probable loss event (LE) and loss magnitude (LM) resulting from a radiological dispersal device (RDD) attack. The threat component of the PFRI is devised as a utility function weighing the threat group attributes and RDD radioactive material preference. The principles of probabilistic risk assessment and pathway analysis are implemented to account for RDD radioactive material theft probabilities in different attack scenarios. Locational hazards and nuclear security culture are measured as a function of radiological facility vulnerability for LE. The LM of the attack, in the form of loss of life and economic damage, is then estimated to construct the PFRI. The methodology is applied to a hypothetical healthcare facility with a single radioactive material asset. For this example, the PFRI resulted in a value of 2.0 (on a scale of 1–10), showing low risk to the facility. The development of the PFRI provides a risk analysis tool that may be useful in making decisions for radiological security improvements.

Securing radioactive sources has become increasingly important given the rising threat of radiological terrorism. While radiation safety has long been established in most applicable industries, the importance of nuclear and radiological source security has lagged behind in nonnuclear material specific industries, such as academic institutions and medical facilities. To evaluate the attitudes and behaviors regarding nuclear security culture, an assessment of nuclear and radiological material practices was developed and conducted on 73 radioactive material users at a university. The survey portion of the assessment was comprised of a series of questions segregated into four categories: policy, enforcement, leadership, and behavior. Nuclear security awareness questions formed a subset of the questionnaire. Users were classified by their radioactive material experience and work classification: student, faculty, or other staff. Of the users surveyed, 9% were also interviewed face-to-face to further expand on their views of nuclear security culture. Results of the assessment showed that students from the work classification group as well as the cohort of radioactive material users with 2–5 y of experience possessed a greater degree of awareness towards nuclear security compared to faculty and other more experienced radioactive material users. Relative to students and faculty, other staff from the work classification group faced some difficulty judging the enforcement of policies, adequacy of inspection, and job performance review related to nuclear security. The response from all three groups emphasized the need to enhance threat-response preparedness and greater communication among stakeholders.

Radiological dispersal devices (RDD) pose a threat to the United States. Healthcare facilities housing high-risk radioactive materials and devices are potentially easy targets for unauthorized access and are vulnerable to malevolent acts of theft or sabotage. The three most attractive candidates for use in RDD considered in this study are: ⁶⁰Co (radiosurgery devices), ¹³⁷Cs (blood irradiators) and ¹⁹²Ir (brachytherapy high dose radiation device). The threat posed by RDDs has led to evaluating the security risk of radioactive materials and defending against attacks. The concepts of risk analysis used in conjunction with game theory lay the foundations of quantitative security risk management. This paper develops a two player non-cooperative one-shot simultaneous defender-attacker game. The defender (healthcare facility) chooses to defend one of the three high-risk radioactive material targets and the attacker (terrorists or adversaries) chooses to attack one of the three high-risk radioactive material targets. A risk-informed approach is used to model players’ payoffs or expected utilities for each choice of strategies. A game-theoretic model (RDD game) captures the strategic interaction between competing players who act rationally to maximize their expected utility. The evaluation of the RDD game results in a von Neuman max-min strategy solution being preferable to a mixed strategy Nash equilibrium solution. The von Neumann max-min strategy solution of the defender defending cobalt and the attacker attacking cesium is found to be the most prescriptive result, thus favoring the current efforts of phasing out cesium blood irradiators and replacing them with alternative technologies. The RDD game not only gives the defender strategic options to budget scarce security resources but also helps healthcare facilities make optimal choices under severe uncertainty about the terrorist threat.