The U.S. Department of Energy (DOE) this week announced a new series of cost-sharing grants to promote the development of small-scale, factory-made nuclear reactors, an emerging energy source that Obama administration officials say could help replace the coal-fired plants expected to cease operations in the coming decades. The administration, which has allocated $452 million for the program, hopes to spur the production and licensing of as many as 50 so-called modular reactors annually by 2040, said Rebecca Smith-Kevern, director of light water reactor technology at the DOE’s Office of Nuclear Energy. DOE officials say these modular reactors, which would be about one-third the size of typical nuclear power plants, also include scalable designs that will provide safety and economic benefits. “We have a vision of having a whole fleet of [modular reactors] produced in factories,” Smith-Kavern said at a conference. “We envision the U.S. government to be the first users.” Citing a 2011 paper, she said plants could cost $3 billion to $5 billion apiece.