Of the prototype commercial nuclear power plants that were built in the United States during the late 1950s and early 1960s, the most successful types used the light-water reactor system, either PWR or BWR. From the mid-1960s, larger units were ordered in the expectation of an ever-increasing commercial utilization of nuclear power, and by the early 1970s, nuclear plant orders were coming in at such a rapid pace that the unit sizes were increased so as to reduce the number of separate projects for which each vendor would have to provide trained staff. By the later years of the decade, however, the surfeit of orders in the United States had been followed by a large number of project cancellations, partly as a result of sharp reductions in estimates of how quickly the demand for electricity was expected to grow in the future. It began to appear that the new plants simply were not needed. Moreover, the cost of new nuclear plants had begun to escalate to the point where their economics became questionable. Finally, public fears of nuclear power, which had always been a factor, were brought to a head by the Three Mile Island accident of 1979. Following that event, not a single new reactor was approved in the United States until 2012, when the Nuclear Regulatory Commission approved the construction of two PWRs in Augusta, Georgia. By that time, a growing demand for electricity, as well as improvements in reactor designs and government incentives to install power plants that were not dependent on fossil fuels, had created the potential for a rebirth of nuclear power in the United States.

Numerous other countries around the world adopted nuclear power as a part of their energy strategy in the late 20th century. Most programs utilized light-water reactor technology of the BWR or PWR type. France, following the oil shocks of the 1970s, embraced nuclear power as a strategic energy source, to be pursued for reasons of national security as well as energy independence, and as such the country invested heavily in the technology rather than relying on U.S. designs. The PWR fleet developed by the French nuclear industry eventually succeeded in producing more than three-quarters of the country’s electric power. Toward the end of the century, several European reactor vendors, including France’s Areva and Germany’s Siemens, produced an advanced Generation III PWR design known as the European Pressurized Reactor or Evolutionary Power Reactor (EPR). The standard EPR design yielded approximately 1,650 megawatts of electric power; early in the 21st century, construction began on several units in Europe as well as in China.

Japan, a country that was particularly dependent on foreign imports for traditional fossil fuels, became an active member of the nuclear research community in the early 1960s; it began to harness nuclear power as a source of electricity soon after. Its first reactor to produce electricity was started in 1963, and its first commercial reactor, a gas-cooled British design, started operation in 1966. Following this initial construction, Japan switched to light-water reactors. By 2011, the year of the Fukushima accident, Japan had constructed more than 50 BWRs and PWRs for commercial power production and was generating almost one-third of its electricity from nuclear power plants. The first light-water reactors in Japan were American designs, but Japan went on to develop its own advanced BWRs and PWRs. Japan was also developing facilities to reprocess its own spent reactor fuel instead of transporting the fuel to plants in Europe. In the aftermath of the Fukushima accident, all reactors in Japan, as they shut down for maintenance, were not permitted to restart unless they were able to pass new safety and stress tests.

As part of its nuclear weapons program, China developed reactor and reprocessing technology in the 1950s and 1960s, at first with Soviet assistance but soon using its own considerable resources. (The first test of a Chinese atomic explosive device took place in 1964.) By the first decade of the 21st century, China had grown to become the world’s largest consumer of energy, and the country’s leaders had promulgated a strategic energy plan that included a doubling of nuclear power generation in the period 2005–20. Fourteen nuclear power plants were in operation and more than 25 under construction, and many more were being planned. The first commercial-scale nuclear power plant in China had started operation in 1994 at Daya Bay on the coast of Guangdong province, near Hong Kong. The Daya Bay reactors were PWRs of French design, and PWRs formed the basis of China’s growth into the 21st century—though CANDU reactors were also built, and both high-temperature gas-cooled reactors (HTGRs) and fast-neutron liquid-metal reactors (LMRs) were under consideration for the longer-term future. As a part of its strategic energy effort, China, like Japan, developed reprocessing technology in order to create a closed-loop nuclear fuel cycle.