The challenge of nuclear waste - another factor that has held back new construction in the U.S., since no one can agree where to put it - is also at the heart of another atomic start-up. TerraPower is experimenting with a traveling-wave reactor design, which would largely eliminate the need for uranium enrichment. (Traveling wave refers to the fact that fission occurs bit by bit in the reactor core, as if a wave of energy were slowly spreading through it, rather than in the entire core all at once as in standard fission.) In conventional reactors, composition of the isotope uranium-235 has to be increased in the fuel before it becomes fissile. TerraPower's reactor design could use the depleted uranium found in nuclear waste, burning it for decades without refueling. That revolutionary potential is what attracted Bill Gates, who is one of TerraPower's main funders. "We think we could have a prototype by the early 2020s and become the commercial reactor of choice by the 2030s," says John Gilleland, TerraPower's CEO.

David Fuller's view These are promising developments and new nuclear projects offer the best and most practical long-term solutions to our energy problems.