Raj et al. describe the promise of nuclear energy as a sustainable, affordable, and carbon-free source available this century on a scale that can help meet the world's growing need for energy and help slow the pace of global climate change. However, the factor of millions gain in energy release from nuclear fssion compared to all conventional energy sources that tap the energy of electrons (Figure 1) has also been used to create explosives of unprecedented lethality and, hence, poses a serious challenge to the expansion of nuclear energy worldwide. Although the end of the cold war has eliminated the threat of annihilating humanity, the likelihood of a devastating nuclear attack has increased as more nations, subnational groups, and terrorists seek to acquire nuclear weapons.