The Department of Energy Office of Nuclear Energy (DOE-NE) and the National Nuclear Security Administration (NNSA) Office of Nonproliferation and International Security requested that the National Academy of Sciences (NAS) perform a study on improving the assessment of proliferation risk of nuclear fuel cycles for use by nonproliferation policy makers and decision makers. Both sponsors are considering how technical assessments of proliferation risk can more effectively contribute to
• improved programmatic decisions on research and development (R&D) of future nuclear fuel cycles including scientific engagement;
• better information for nonproliferation policy decisions, for example, on nuclear export and peaceful nuclear engagement; and
• clearer communication of those decisions to other U.S. government agencies, the public, and international partners.
The committee found that nonproliferation policy makers use a variety of data and information sources to guide their decisions. One type of technical assessment methodology, which the committee terms “predefined frameworks,” guides a subset of decisions by comparing future nuclear fuel cycles to existing ones. This methodology typically divides the nuclear fuel cycle into processing steps, assigns values to intrinsic (material- and fuel cycle-specific technical details) and extrinsic (safeguards, inspections, and facility operational details) proliferation barriers at each step, combines the results using weighting functions, and determines the overall proliferation resistance of fuel cycle options using a predefined approach. A more common type of technical assessment uses multidisciplinary teams of experts to address technical topics as they arise. These have been termed “case-by-case” assessments to differentiate them from predefined frameworks.
The committee evaluated several predefined framework methodologies and found benefits as well as shortcomings. Relative differences in intrinsic barriers among fuel cycles can be considered robust and enduring because the characteristics tend to be quantifiable (e.g., decay rates of the radionuclides within the proposed fuel). However, even the quantifiable values of intrinsic barriers are not purely objective because expert knowledge is required to assign limit and threshold values associated with many of the measures. The committee is aware of calls to improve future expert elicitation practices, but the proposed changes still fall short, for example, by relying on surveys to collect information. Further, the applications seen by the committee had shortcomings in assigning uncertainties and determining sensitivity to the information collected.
The analysis of intrinsic barriers can highlight points of low proliferation resistance within a proposed fuel cycle so that safeguards or other extrinsic barriers can be applied at those points to increase the overall proliferation resistance. However some extrinsic measures—such as facility layout, transportation paths, or the piping between critical processes—are not known until a facility has been designed, but are critical in determining the final level of proliferation resistance. All technical assessments are limited by details not yet known or defined.
The frameworks present a reasonable and consistent approach for organizing known technical information of complex nuclear fuel systems, but they have so far not highlighted previously unknown technical issues (determined by other technical analysis methods). Further, the existing frameworks assess proliferation resistance but not proliferation risk, which includes, among other things, an assessment of a host state’s proclivity to proliferate. Although there is a significant amount of work being performed on various approaches (e.g., probabilistic risk assessment, game theory, and political science) for modeling the intent of host states to proliferate, the committee did not see results that are compelling enough to recommend the use of these approaches for this application or to endorse the inclusion of this assessment into the predefined frameworks’ analysis at this time. Furthermore, the committee notes that although increased proliferation resistance can raise barriers to proliferation, a highly motivated host state will be able to overcome them.
The committee has identified the following applications as opportunities in which the current predefined frameworks can provide value and utility to policy makers if the shortcomings in their execution are addressed:
1) Comparing the proliferation resistance of fuel cycles and identifying locations to apply safeguards or material monitoring,
2) Educational applications (e.g. academic applications or new nuclear energy states), and
3) Enabling consistent communication with international partners or the public on nuclear energy decisions by providing analysis through the application of a predefined, internationally accepted and known methodology.
Nonetheless, the committee does not support a new or expanding R&D program in this area. Based on discussions with policymakers, the committee determined that the existing tools have limited utility to inform their nonproliferation decisions beyond what a case-by-case analysis would produce. Case-by-case analysis also uses expert knowledge and can suffer from the same challenges listed above regarding predefined frameworks. However, their use of expert opinion and knowledge is clear and understood by policymakers while predefined frameworks’ use of expert knowledge is less clear because it is often combined and presented as an integrated result.
The committee recommends that fuel cycle R&D decisions include proliferation resistance instead of proliferation risk as one factor among others (such as cost and safety) to guide those decisions. Technical assessments are limited by the availability of technical details associated with future nuclear fuel cycles. Therefore, the committee recommends that DOE-NE and NNSA jointly decide upon a set of high-level questions
comparing the proliferation resistance of proposed future fuel cycles to the current once-through fuel cycles. Assessments should be revisited at key milestones throughout the technologies’ development and eventual deployment as new and better information and data emerge.
Finally, the committee finds that the terms “proliferation risk” and “proliferation resistance” are frequently used interchangeably and incorrectly, which hampers communication at all levels (within the U.S. government, industry, the public and international partners). There is a distinct difference between these terms: “proliferation risk” includes host state and region-specific considerations while “proliferation resistance” is focused on the nuclear energy system’s intrinsic and extrinsic barriers. The U.S. government (e.g., DOE-NE and the NNSA) could improve communication by initiating efforts to define “proliferation risk” and lead by example with proper and consistent use of these terms.