A major concern about the global expansion of nuclear power is the potential spread of nuclear fuel cycle technology (particularly uranium enrichment and spent fuel processing) that could be used for nuclear weapons. Despite 30 years of effort to limit access to uranium enrichment, several undeterred states pursued clandestine nuclear programs, the A.Q. Khan black market network's sales to Iran and North Korea representing the most egregious examples. However, concern over the spread of enrichment and reprocessing technologies may be offset by support for nuclear power as a cleaner and more secure alternative to fossil fuels. This book explores the history of reactor and fuel cycle technologies development with a focus on the policy implications of expanding global access to nuclear power and U.S. uranium reserve estimates.