The invention: The first full-scale commercial nuclear power plant, which gave birth to the nuclear power industry.
The people behind the invention:
Enrico Fermi (1901-1954), an Italian American physicist who won the 1938 Nobel Prize in Physics Otto Hahn (1879-1968), a German physical chemist who won the 1944 Nobel Prize in Chemistry Lise Meitner (1878-1968), an Austrian Swedish physicist Hyman G. Rickover (1898-1986), a Polish American naval officer
Discovering Fission
Nuclear fission involves the splitting of an atomic nucleus, leading to the release of large amounts of energy. Nuclear fission was discovered in Germany in 1938 by Otto Hahn after he had bombarded uranium with neutrons and observed traces of radioactive barium. When Hahn’s former associate, Lise Meitner, heard of this, she realized that the neutrons may have split the uranium nuclei (each of which holds 92 protons) into two smaller nuclei to produce barium (56 protons) and krypton (36 protons). Meitner and her nephew, Otto Robert Frisch, were able to calculate the enormous energy that would be released in this type of reaction. They published their results early in 1939.
Nuclear fission was quickly verified in several laboratories, and the Danish physicist Niels Bohr soon demonstrated that the rare uranium 235 (U-235) isotope is much more likely to fission than the common uranium 238 (U-238) isotope, which makes up 99.3 percent of natural uranium. It was also recognized that fission would produce additional neutrons that could cause new fissions, producing even more neutrons and thus creating a self-sustaining chain reaction. In this process, the fissioning of one gram of U-235 would release about as much energy as the burning of three million tons of coal.
The first controlled chain reaction was demonstrated on December 2,1942, in a nuclear reactor at the University of Chicago, under the leadership of Enrico Fermi. He used a graphite moderator to slow the neutrons by collisions with carbon atoms. “Critical mass” was achieved when the mass of graphite and uranium assembled was large enough that the number of neutrons not escaping from the pile would be sufficient to sustain a U-235 chain reaction. Cadmium control rods could be inserted to absorb neutrons and slow the reaction.
It was also recognized that the U-238 in the reactor would absorb accelerated neutrons to produce the new element plutonium, which is also fissionable. During World War II (1939-1945), large reactors were built to “breed” plutonium, which was easier to separate than U-235. An experimental breeder reactor at Arco, Idaho, was the first to use the energy of nuclear fission to produce a small amount of electricity (about 100 watts) on December 20, 1951.
Nuclear Electricity
Power reactors designed to produce substantial amounts of electricity use the heat generated by fission to produce steam or hot gas to drive a turbine connected to an ordinary electric generator. The first power reactor design to be developed in the United States was the pressurized water reactor (PWR). In the PWR, water under high pressure is used both as the moderator and as the coolant. After circulating through the reactor core, the hot pressurized water flows through a heat exchanger to produce steam. Reactors moderated by “heavy water” (in which the hydrogen in the water is replaced with deuterium, which contains an extra neutron) can operate with natural uranium.
The pressurized water system was used in the first reactor to produce substantial amounts of power, the experimental Mark I reactor. It was started up on May 31, 1953, at the Idaho National Engineering Laboratory. The Mark I became the prototype for the reactor used in the first nuclear-powered submarine. Under the leadership of Hyman G. Rickover, who was head of the Division of Naval Reactors of the Atomic Energy Commission (AEC), West-inghouse Electric Corporation was engaged to build a PWR system to power the submarine USS Nautilus. It began sea trials in January of 1955 and ran for two years before refueling.
Cooling towers of a nuclear power plant. (PhotoDisc)
In the meantime, the first experimental nuclear power plant for generating electricity was completed in the Soviet Union in June of 1954, under the direction of the Soviet physicist Igor Kurchatov. It produced 5 megawatts of electric power. The first full-scale nuclear power plant was built in England under the direction of the British nuclear engineer Sir Christopher Hinton. It began producing about 90 megawatts of electric power in October, 1956.
On December 2,1957, on the fifteenth anniversary of the first controlled nuclear chain reaction, the Shippingport Atomic Power Station in Shippingport, Pennsylvania, became the first full-scale commercial nuclear power plant in the United States. It produced about 60 megawatts of electric power for the Duquesne Light Company until 1964, when its reactor core was replaced, increasing its power to 100 megawatts with a maximum capacity of 150 megawatts.
Consequences
The opening of the Shipping port Atomic Power Station marked the beginning of the nuclear power industry in the United States, with all of its glowing promise and eventual problems. It was predicted that electrical energy would become too cheap to meter. The AEC hoped to encourage the participation of industry, with government support limited to research and development. They encouraged a variety of reactor types in the hope of extending technical knowledge.
The Dresden Nuclear Power Station, completed by Commonwealth Edison in September, 1959, at Morris, Illinois, near Chicago, was the first full-scale privately financed nuclear power station in the United States. By 1973, forty-two plants were in operation producing 26,000 megawatts, fifty more were under construction, and about one hundred were on order. Industry officials predicted that 50 percent of the nation’s electric power would be nuclear by the end of the twentieth century.
The promise of nuclear energy has not been completely fulfilled. Growing concerns about safety and waste disposal have led to increased efforts to delay or block the construction of new plants. The cost of nuclear plants rose as legal delays and inflation pushed costs higher, so that many in the planning stages could no longer be competitive. The 1979 Three Mile Island accident in Pennsylvania and the much more serious 1986 Chernobyl accident in the Soviet Union increased concerns about the safety of nuclear power. Nevertheless, by 1986, more than one hundred nuclear power plants were operating in the United States, producing about 60,000 megawatts of power. More than three hundred reactors in twenty-five countries provide about 200,000 megawatts of electric power worldwide.
Many believe that, properly controlled, nuclear energy offers a clean-energy solution to the problem of environmental pollution.
See also Breeder reactor; Compressed-air-accumulating power plant; Fuel cell; Geothermal power; Nuclear reactor; Solar thermal engine; Tidal power plant.
