ABSTRACT Horizontal nuclear proliferation presents what is sometimes referred to as the “Nth country problem,” or identifying which state could be next to acquire nuclear weapons. Nuclear fuel cycle technologies can contribute to both nuclear power generation and weapons development. Consequently, observers often view civilian nuclear programs with suspicion even as research on nuclear latency and the technological inputs of proliferation has added nuance to these discussions. To contribute to this debate, I put forth a simple theoretical proposition: En route to developing a civilian nuclear infrastructure and mastering the fuel cycle, states pass through a proliferation “danger zone.” States with fuel cycle capabilities below a certain threshold will likely be unable to proliferate. States that pass through the “danger zone” without proliferating will be unlikely to do so in the future. I support this proposition by introducing preliminary analysis from the Nuclear Fuel Cycle (NFC) Index, a new heuristic tool to complement political assessments of the connection between civilian nuclear energy development and nuclear weapons proliferation. I conclude with policy implications for contemporary Iran, Saudi Arabia, Japan, and South Korea. Taken together, this article calls for increased policymaker interaction with historical cases and more sophisticated academic engagement with the nuclear fuel cycle.

中文翻译：

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核燃料循环与扩散“危险区”

摘要横向核扩散提出了有时被称为“第N个国家的问题”，或确定了哪个国家可能紧挨着获得核武器。核燃料循环技术可以促进核能发电和武器开发。因此，即使对核潜伏期的研究和核扩散的技术投入为这些讨论增添了细微差别，观察员也常常对民用核计划持怀疑态度。为了促进这场辩论，我提出了一个简单的理论命题：在发展民用核基础设施和掌握燃料循环的过程中，各州都穿过了扩散的“危险区”。燃料循环能力低于某个阈值的国家可能将无法扩散。没有扩散通过“危险区”的国家今后将不太可能这样做。我通过引入核燃料循环指数（NFC）的初步分析来支持这一主张，NFC指数是一种新的启发式工具，可以补充对民用核能发展与核武器扩散之间联系的政治评估。我以对当代伊朗，沙特阿拉伯，日本和韩国的政策影响作总结。两者合计，要求政策制定者与历史案例进行更多的互动，并在核燃料循环方面进行更复杂的学术交流。一种新的启发式工具，可补充对民用核能发展与核武器扩散之间联系的政治评估。我以对当代伊朗，沙特阿拉伯，日本和韩国的政策影响作总结。两者合计，要求政策制定者与历史案例进行更多的互动，并在核燃料循环方面进行更复杂的学术交流。一种新的启发式工具，可补充对民用核能发展与核武器扩散之间联系的政治评估。我以对当代伊朗，沙特阿拉伯，日本和韩国的政策影响作总结。两者合计，要求政策制定者与历史案例进行更多的互动，并在核燃料循环方面进行更复杂的学术交流。