A Generation IV International Forum (GIF) Working Group has developed a methodology with which to evaluate the proliferation resistance and physical protection (PR&PP) robustness of nuclear energy systems. For such nuclear systems, there is a need to evaluate designs that are not fully developed, technology issues from fuels to fuel cycles that are not yet determined, and safeguards, security, and other measures that are not yet decided. To that end, this paper proposes use of formal expert elicitation in conjunction with the PR&PP methodology. This combination would provide a systematic and transparent qualitative analysis of proliferation resistance and physical protection and also would contribute to the development of credible input for quantitative analyses. The outcome would be valuable for internal planning purposes for nuclear designers, safeguards experts, and technical and policy stakeholders involved in the development of Generation IV nuclear energy systems.