Fourteen years after receiving its permit, the nation’s first new nuclear reactors in decades just fired up in Georgia. Massive, traditional nuclear reactors like this have faced so many cost overruns and construction delays that the investment market for them all but vanished. Despite a handful of recent technical breakthroughs in fusion power, its promise of virtually limitless power remains just a promise. But could a new wave of small, modular fission reactors bring new carbon-free power onto the market faster and cheaper (and safer?) than traditional nukes in time to help the world decarbonize?