History of Energy in the United States: 1635-2000
	Nuclear Energy
	Of all the major forms of energy now in use, only nuclear power has truly modern roots. The central insight--that the controlled fission of heavy elements could release enormous energies--came to British physicist Ernest Rutherford in 1904. Research during the 1930s convinced scientists that such a controlled chain reaction was possible, and Enrico Fermi's group first achieved one in December 1942 at the University of Chicago, in a crude graphite-moderated reactor built on a vacant squash court.
	World War II postponed further progress toward commercial nuclear electric power, but the theoretical foundation had been established and several factors encouraged nuclear power's development when peace returned. It was believed that fuel costs would be negligible and therefore that nuclear power would be relatively inexpensive. In addition, both the United States and Western Europe became net importers of crude oil in the early 1950s and nuclear power was seen as critical to avoiding energy dependence. Geopolitics appear to have played a role as well; President Dwight Eisenhower's Atoms for Peace program was intended in part to divert fissionable materials from bombs to peaceful uses such as civilian nuclear power.
	In 1951 an experimental reactor sponsored by the U.S. Atomic Energy Commission generated the first electricity from nuclear power. The British completed the first operable commercial reactor, at Calder Hall, in 1956. The U.S. Shippingport unit, a design based on power plants used in nuclear submarines, followed a year later. In cooperation with the U.S. electric utility industry, reactor manufacturers then built several demonstration plants and made commitments to build additional plants at fixed prices. This commitment helped launch commercial nuclear power in the United States.
	The success of the demonstration plants and the growing awareness of U.S. dependency on imported crude oil led to a wave of enthusiasm for nuclear electric power that sent orders for reactor units soaring between 1966 and 1974 (Figure 28). The number of operable units increased in turn, as ordered units were constructed, tested, licensed for full power operation, and connected to the electricity grid (Figure 29). However, the curve of operable units lagged behind the curve of ordered units somewhat because of the long construction times required for the large, complex plants. The total number of U.S. operable reactor units peaked in 1990 at 112.
	Figure 28. Nuclear Generation Unit Orders and Permits
	Figure 29. Number of Operable Units
	Orders for new units fell off sharply after 1974. Of the total of 259 units ordered to date, none was ordered after 1978. Although safety concerns, especially after the accident at Three Mile Island in 1979, reinforced a growing wariness of nuclear power, the chief reason for its declining momentum in the United States was economic. The promise of nuclear electric power had been that it would, in the now-famous phrase, make energy "too cheap to meter." In reality, nuclear power plants have always been costly to build and, for several reasons, became radically more costly between the mid-1960s and the mid-1970s. Utilities began building large plants before much experience had been gained with small ones. Expected economies of scale did not materialize. Many units were forced to undertake costly design changes and equipment retrofits, partially as a result of the Three Mile Island accident. Meanwhile, nuclear power plants have also had to compete with conventional coal- or natural gas-fired plants with declining operating costs.
	These trends disillusioned many utilities and investors. Interest in further orders subsided and many ordered units were canceled before they were built. By the end of 2000, 124 units had been canceled, 48 percent of all ordered units (Figure 30).
	Figure 30. Unit Cancellations and Shutdowns
	The average capacity factor of U.S. nuclear units--the ratio of the electricity they actually produced in a given year to the electricity they could have produced if run at continuous full power--has improved steadily over the years, and reached 88 percent in 2000. However, as operable nuclear power plants have aged, some have become uneconomic to operate or have otherwise reached the end of their useful lives. By the end of 2000, 28 once-operable units had been shut down permanently. The joint effect of shutdowns and lack of new units coming on line is that the number of U.S. operable units has fallen off since 1990 to 104. In its Annual Energy Outlook 2001, EIA projects that 27 percent of the nuclear generating capacity that existed at the end of 1999 will be retired by 2020. No new plants are expected to be built during the period.