The U.S. Department of Energy (DOE) is spending $230 million this fiscal year to start building two new prototype nuclear reactors over the next seven years as part of an Advanced Reactor Demonstration Program. Both will be built in equal partnership with an industrial firm and could receive up to $4 billion in funding from the DOE. Commercial nuclear generators supply 20 percent of U.S. electrical power and 50 percent of our carbon-free energy. The inventory comprises 96 reactors, down from 113 in the early 1990s. More reactors are slated to close, and the nuclear industry’s share of the electricity supply is expected to fall, yet engineers continue to develop designs for reactors they say will be safer and more efficient. Proponents of nuclear power doubt the program will spur construction of new commercial reactors as long as natural gas and renewable energy remain relatively cheap. Robert Rosner, a physicist at the University of Chicago, says, “New builds can’t compete with renewables.”