December is a big month in the history of nuclear energy. From the first self-sustaining chain reaction to a pivotal breakthrough in nuclear fusion, some of the biggest events that laid the foundation for the nuclear energy sector all happened in the final month of the year.
Here are the seven monumental moments that helped nuclear energy become one of the largest, most reliable sources of carbon-free electricity in the world.
Discovery of nuclear fission (1938)
In December 1938, chemists Otto Hahn and Fritz Strassman in Berlin noticed something unusual when they bombarded uranium atoms with neutrons. The experiment produced traces of barium, a much lighter element, which couldn’t be explained by scientific theory at the time. Physicists Lise Meitner and Otto Frisch unraveled the mystery: the nucleus of the atom had split in two, a process they called “nuclear fission.” Hahn later went on to win a Nobel Prize for the discovery.
The first self-sustaining nuclear fission chain reaction (1942)
A team of scientists and engineers led by Enrico Fermi made atomic history on December 2, 1942, when the world’s first nuclear reactor went critical. It happened in a squash court under the University of Chicago’s Stagg Field when Fermi ordered physicist George Weil to remove the final control rod by hand from Chicago Pile-1's graphite blocks to achieve the first-ever controlled, self-sustaining nuclear fission chain reaction. The achievement laid the foundation for decades of progress in nuclear energy, science, and medicine, including the early development of naval and nuclear reactors.
The first electricity generated by a nuclear power plant (1951)
On December 20, 1951, the Experimental Breeder Reactor-1 (EBR-I) became the first power plant to produce usable electricity through atomic fission. At first, it generated enough electricity to light up four 200-watt lightbulbs. By the next day, it powered the entire building. EBR-I was a liquid metal-cooled fast reactor designed to demonstrate that it could create more fuel than it consumed. It operated as a test reactor until 1964 and is now a museum and historic landmark — take a virtual tour, or stop by for a visit if you’re ever in the area!
Eisenhower’s “Atoms for Peace” speech (1953)
President Dwight D. Eisenhower delivered his famous address on December 8, 1953, before the United Nations, beseeching the assembled leaders of the world to heed the dangers of proliferation of atomic weapons. He proposed new international collaboration to use the power of the atom for peaceful — rather than destructive — purposes. The speech helped galvanize the creation of a commercial nuclear energy industry and led to the formation of the International Atomic Energy Agency in 1957.
Experimental Boiling Water Reactor achieves criticality (1956)
The Experimental Boiling Water Reactor was the first-ever prototype for a boiling water reactor power plant. It was designed and built by Argonne National Laboratory in Illinois and went critical on December 1, 1956. EBWR was the first reactor that used the heat of the reactor to boil water, which was directly used to turn a turbine and generate electricity. It generated power for the lab’s physical plant in 1966 and shut down the following year — providing crucial data that informed the designs of many commercial boiling water reactor power plants operating today.
Shippingport Atomic Power Station goes critical (1957)
Fifteen years to the day after the historic achievement at Chicago Pile-1, the Shippingport Atomic Power Station near Pittsburgh, Pennsylvania reached criticality on December 2, 1957. Shippingport was the world’s first full-scale nuclear power plant. The pressurized water reactor delivered its first electricity to the Pittsburgh-area grid on December 18 and provided invaluable data for nuclear plants that followed. The Atomic Energy Commission later converted the plant into a light-water breeder reactor to test the viability of using thorium and uranium-233 to breed more fuel than was consumed by the plant while it produced power.
Fusion ignition at Lawrence Livermore National Laboratory (2022)
Finally, while most of the milestones on this list concern advances in nuclear fission, nuclear fusion holds tremendous potential as a source of plentiful, carbon-free energy. On December 5, 2022, scientists at Lawrence Livermore National Laboratory in California became the first to demonstrate fusion ignition — a reaction that produced more energy than was used to start the process. The breakthrough, which brings us one step closer to harnessing the power of the sun, has been called “one of the most impressive scientific feats of the 21st century.”
Together, these milestones helped make nuclear energy a leading source of clean energy worldwide. Nuclear energy is a key contributor in our efforts to combat the climate crisis and generates nearly half the emissions-free electricity in the United States alone.
Learn more about the big strides nuclear energy has made in our blog: 5 Fast Facts About Nuclear Energy.