Most climate and energy scenarios created by international organizations and researchers include a considerable expansion of nuclear energy. In the IPCC Sixth Assessment Report, for example, nuclear energy increases from a current 3,000 terawatt hours on average to over 6,000 terawatt hours in 2050 and to over 12,000 terawatt hours in 2100. This doubling and quadrupling of nuclear energy production by 2050 and 2100 is contradictory to the technical and economic realities: At no point have newly built nuclear energy plants ever been competitive, nor will they become so in the foreseeable future. This contradiction, referred to here as the nuclear energy scenario paradox, can be explained by a series of politico- economic, institutional, and geopolitical factors. In particular, the close relationship between the military and commercial uses of nuclear energy as well as the interest of the nuclear industry and its organizations in self-preservation play a role. The assumptions and model logic of the scenarios must be critically scrutinized. There is the risk that considerable public and private funds will be invested in developing technologies for the commercial use of nuclear energy despite the fact that other technologies are expected to offer a significantly better cost-performance ratio with fewer economic, technical, and military risks. In light of the urgency of climate change mitigation, continuing to channel personnel and financial resources into nuclear energy is problematic.