Still, for nearly a decade, with no new plants, nukes' 20 percent share of U.S. electricity production has held steady, keeping pace as overall electricity output has risen 15 percent. In the 1970s and 80s unscheduled shutdowns for repairs or other problems limited U.S. plants to less than 65 percent of their potential output. Today, with experience and improved operating practices, output exceeds 90 percent.

So is it time to embrace the atom again? There's a "nuclear renaissance" buzz emitting from engineers who design and operate reactors, think-tank academics who worry about long-range energy and environmental strategies, utility company executives, top members of the Bush Administration, and members of Congress. Proponents say atomic energy is a proven technology for a 21st-century civilization desperate to swear off fossil fuels and not to go broke doing it. Nuclear fission emits none of the greenhouse gases that are warming the climate. The Nuclear Energy Institute estimates that without nuclear power playing its current role in the generation of electricity, the U.S. would spew 29 percent—190 million metric tons—more carbon than it does now.

Scratch a nuclear engineer these days, and you'll likely find, under the buttoned-down exterior, a raving green activist. Even among the ranks of environmentalists who a decade ago could barely tolerate the mention of nukes, the possibility is getting an occasional thumbs-up. Climate change, for many, trumps any fear of nuclear energy. Its overwhelming advantage is that it's atmospherically clean, writes Stewart Brand, founder of the 1970s Whole Earth Catalog.

Yet, Brand points out: "Nuclear certainly has problems—accidents, waste storage, high construction costs, and the possible use of nuclear fuel for weapons." Most experts agree that such problems are no small drawback to forging ahead with new nukes. So despite shifting attitudes, atomic allergy has eased only slightly if at all among the bulk of prominent environmental leaders. Analysts also point to other problems, such as unresolved waste questions and limited public input on the whole issue of nuclear power. The current strategy, predicts Gus Speth, co-founder of the Natural Resources Defense Council and Dean of Forestry and Environmental Studies at Yale University, will just replay the battles of the 1970s.

Other nations are watching the U.S., but not waiting. France gets 78 percent of its electricity from nuclear power and is considering replacing its older plants with new ones. And the industry is expected to burgeon in Asia in the next quarter century. China, on top of its headlong rush to build coal-burning plants, also has ambitious plans for new reactors: It can get 6,600 mega­watts of power now from nine reactors. It's aiming for 40,000 megawatts.