LA HAGUE, France -- Visiting the spent nuclear fuel reprocessing facility here is a bit like stepping into the script from a 1960s Star Trek show. When visitors peer through a 40-inch-thick, radiation-shielding plate of glass, they can see a ballet of industrial-strength robots handling old nuclear fuel assemblies. The facility is part of France's answer to the question pressing nuclear power plant owners in nearly every part of the world: What do you do with spent nuclear fuel?

YUCCA MOUNTAIN, Nev. -- From the top of this brown, loaf-shaped ridge about 90 miles northwest of Las Vegas, there is little sign that this place remains a major battleground in U.S. energy and climate policy. Twenty-five years of government work and at least $9 billion of taxpayers' money have been sunk into the ground here. It may seem odd that a president who says the nation needs nuclear power pulls back from this project and that a Democrat-led Congress whose leaders want to mobilize against global warming bleeds Yucca Mountain's budget to the point of immobility. But one law professor who has closely followed the project thinks much of this can be explained by the peculiar politics here, which he says is determined by state lines.

PIKETON, Ohio -- A group of U.S. engineers and technicians sat down one day in 2001 to figure out where the nation's future nuclear power plant fuel was going to come from. Their decision was to leap backward 30 years and re-engineer an idea perfected during the Cold War and then abandoned here in 1985. Now the first prototypes of that idea, an ultra-high-speed, 40-foot-high centrifuge called the "American centrifuge," are up and running.

One of the biggest question marks in the nation's energy and climate policy is the future of nuclear power. In the past, the United States has made a major commitment to it. The U.S. nuclear power industry is the world's largest. The nation's 104 operating plants produce 20 percent of its electricity, making them, by far, the largest source of electricity that does not result in greenhouse gas emissions. If a cap and a price are imposed on carbon dioxide emissions, these plants could be among the biggest economic winners in the vast economic shifts that would be created by greenhouse gas regulations. But the future of the industry may still hang precariously on decisions made by the Obama administration, in which multiple issues remain unsettled.