The foundational treaty of the global nuclear order, the Nuclear Non-Proliferation Treaty (NPT), does not define what constitutes a nuclear weapon and therefore what activities, technologies, and materials should be regarded as evidence that a state is seeking to acquire nuclear weapons. This lack of definition exacerbates the nonproliferation challenge of distinguishing between legitimate nuclear activities (be they peaceful or military applications such as naval propulsion) and illegitimate ones (namely, those oriented toward nuclear weapons). This challenge, in turn, exacerbates the difficulty of promoting the peaceful spread of nuclear energy while preventing weapons proliferation. This grant provides continued support to an initiative by the Carnegie Endowment for International Peace to build an international, science-based, de-politicized consensus around how to distinguish legitimate from illegitimate nuclear activity as defined by the NPT. Funds will support preparation for an international meeting of stakeholders in Beijing in 2014, finalization of technical documentation, the identification of use-cases and potential applications of the new identification regime, and outreach and communication efforts aimed at garnering broad international support.