National Geographic Emerging Explorer Leslie Dewan is helping to revolutionize the nuclear power industry by designing a safer, more efficient alternative to today’s reactors.Conventional nuclear reactors only use about 3 to 4 percent of uranium’s accessible energy. The energy left behind is what makes conventional nuclear waste—radioactive for hundreds of thousands of years—so dangerous. Extracting more of the available energy reduces the radioactive lifetime of the waste. To this end, Dewan is helping to develop techniques that extract 96 percent of the available energy.