Even before the Nautilus was finished, nuclear power plants were about to come into their own. On December 20, 1951, near the town of Arco, Idaho, engineers from Argonne National Laboratory started up a reactor that was connected to a steam turbine generator. When the chain reaction reached criticality, the heat of the nuclear fuel turned water into steam, which drove the generator and cranked out 440 volts, enough electricity to power four lightbulbs. It was the first time a nuclear reaction had created usable power. A few years later Arco became the world's first community to get its entire power supply from a nuclear reactor when the town's power grid was temporarily connected to the reactor's turbines.

Arco had been an experiment, but by 1957 a commercially viable nuclear power plant was operating in the western Pennsylvania town of Shippingport. It was one of the first practical manifestations of President Eisenhower's Atoms for Peace Program, established in 1953 specifically to promote commercial applications of atomic energy. Nuclear power plants of various designs were soon supplying significant percentages of energy needs throughout the developed world. There was certainly no question about the advantages. One ton of nuclear fuel produces the energy equivalent of 2 million to 3 million tons of fossil fuel. Looked at another way, 1 kilogram of coal generates 3 kilowatt-hours of electricity; 1 kilogram of oil generates 4 kilowatt-hours; and 1 kilogram of uranium generates up to 7 million kilowatt-hours. Also, unlike coal- and oil-burning plants, nuclear plants release no air pollutants or the greenhouse gases that contribute to global warming. Currently, some 400 nuclear plants provide electricity around the world, including 20 percent of energy in the United States, 80 percent in France, and more than 50 percent in Japan.

But the nuclear chain reaction still carries inherent dangers, which were made frighteningly apparent during the reactor accidents at Pennsylvania's Three Mile Island plant in 1979 and Ukraine's Chernobyl plant in 1986. In each case, radiation was released into the atmosphere, a small amount at Three Mile Island but a tragically large amount at Chernobyl. Human error played a significant role in both events, but Chernobyl also revealed the need to improve safeguards in future reactor designs.

Although public sentiment in the United States turned against nuclear power for a number of years after the Three Mile Island accident, the international growth of nuclear power continued virtually unabated, with an additional 350 nuclear plants built worldwide in the past 2 decades—almost doubling the previous total. A strong incentive for continuing to improve nuclear technology is the fact that it may offer a solution to global warming and reduce the free release of emissions such as sulfur oxides and nitrous oxides as well as trace metals. In addition, engineers in other countries and the United States have continued to refine reactor designs to improve safety. Most recently, designs have been proposed for reactors that are physically incapable of going supercritical and causing a catastrophic meltdown of the reactor's radioactive core, and such designs are ready to be moved beyond the drawing board. Nations with nuclear power plants continue to wrestle with the problem of disposing of nuclear waste—spent nuclear fuel and fission products—which can remain radioactively lethal for thousands, and even tens of thousands, of years. In the United States, most power plants store their own nuclear waste onsite in huge pools of water, while the longer-term option of a national repository, deep within the bedrock of Yucca Mountain in Nevada, continues to be debated. Other countries reprocess waste, extracting every last particle of fissionable fuel. And plans are also afoot to convert nuclear material from obsolete weapons—particularly those of the former Soviet Union—into usable nuclear fuel. Even though no new nuclear plants have been ordered in the United States since 1977, most existing facilities have requested extensions of their operating licenses—in part because of the many advantages of nuclear power over other forms of energy.

Still, developments in nuclear technology remain controversial. A case in point is the irradiation of food, approved by the Food and Drug Administration in 1986 but only slowly gaining public acceptance. Irradiation involves subjecting foods to high doses of radiation, which kills harmful bacteria on spices, fruits, and vegetables and in raw meats, preventing foodborne illnesses and dramatically reducing spoilage. No residual radiation remains in the food, but—despite laboratory evidence to the contrary—critics have expressed concerns that the process may cause other chemical changes that could give rise to toxic or carcinogenic substances. Nevertheless, as its benefits become more and more obvious, irradiaton has come into wider use.

In 1970 many nations signed a nuclear nonproliferation treaty in an effort to limit the spread of nuclear weapons. That issue remains front and center in the news, even as engineers keep working to make peaceful uses of nuclear power safer. It may well be that harnessing the tremendous power of the atom will continue to be a story of both swords and plowshares.