On a subzero December morning, the future of nuclear energy was lying on a plywood platform in a cinder-block building tucked inside a remote, heavily secured corner of the Idaho National Laboratory.

At least that’s how Yasir Arafat viewed the 12-foot-long system of stainless-steel pipes resting on its side next to him: as one of the first concrete steps toward deploying large numbers of small, cheap, safe and reliable reactors that could provide jobs, tax revenue and a stable foundation for the carbon pollution-free electricity sector that the United States government aims to create by 2035.