Radioisotopes for Peace

A nuclear bone scan showing radioisotopes (enhanced red-orange) at the site of a compression fracture.

A nuclear bone scan showing radioisotopes (enhanced red-orange) at the site of a compression fracture.

In 1942 President Roosevelt ordered the U.S. Army Corps of Engineers to coordinate nuclear weapons research. The enterprise that came to be known as the Manhattan Project involved national laboratories throughout the country. One of those facilities, Clinton Laboratories, found an unlikely home in East Tennessee.

In 1942 President Roosevelt ordered the U.S. Army Corps of Engineers to coordinate nuclear weapons research. The enterprise that came to be known as the Manhattan Project involved national laboratories throughout the country. One of those facilities, Clinton Laboratories, found an unlikely home in East Tennessee.

East Tennessee did not seem a propitious spot for a war-related facility: the region had few scientists and no sophisticated laboratory equipment. But it had cheap, abundant electricity thanks to the Tennessee Valley Authority, which had been electrifying the region since 1933. The area's relative isolation also proved ideal for top-secret research.

Construction began on 1 February 1943, and on 4 November the world's first operational nuclear reactor went critical. Known as the Clinton pile, or the graphite reactor, it was designed to bombard uranium-238 with neutrons to produce plutonium for developing a nuclear weapon. Eventually other facilities built on the pilot work done at Clinton Laboratories to produce the plutonium used in the atomic bomb dropped on Nagasaki.

When World War II ended, so apparently did the mission of the Manhattan Project and its associated facilities. At first it was unclear what purpose Clinton Laboratories would serve during peacetime, but researchers soon identified a tool for medicine: radioisotopes. On 2 August 1946, Eugene Wigner, the director of Clinton Laboratories, presented a small container of carbon-14 to the director of the Barnard Free Skin and Cancer Hospital of St. Louis for research in cancer studies. These were the first carbon-14 isotopes to be produced for use outside the Manhattan Project, and Wigner's presentation marked the beginning of peacetime use of atomic energy.

Clinton Laboratories, which became Oak Ridge National Laboratory (ORNL) in 1948, made more than 1,000 shipments of radioisotopes, mostly of iodine-131, phosphorus-32, and carbon-14, in the first year of production; by 1950 the number of shipments neared 20,000. After the graphite reactor closed in 1963, production shifted to the Oak Ridge research reactor, which produced radioisotopes until 1987. Today most radioisotopes are made outside the United States, but ORNL continues to produce specialty isotopes at its high-flux isotope reactor.

Radioisotopes are used in agricultural research, industrial controls, and even household smoke detectors. But their applications in nuclear medicine are probably the best known. When radioisotopes are injected into the body, the radiation emitted reveals disorders in the thyroid, heart, liver, other organs, and bones. In some cases radiation is then used to treat diseased organs or to shrink or eliminate tumors.

ORNL was the site of production for one of the Manhattan Project's most important scientific by-products. Over the years radioisotopes of carbon, cesium, cobalt, and other elements have been used in cancer therapy. Other isotopes, notably technetium-99, have a multitude of diagnostic imaging uses. Annually more than 10 million nuclear medicine procedures are performed and over 100 million nuclear- medicine tests are conducted on Americans. Perhaps as many as 100 types of radioisotopes are used in diagnosis or therapy. Although it was conceived for weapons research, ORNL achieved far greater heights by first making radioisotopes available for scientific research that has advanced the health and safety of individuals throughout the world.

Judah Ginsberg is manager of the National Historic Chemical Landmarks Program at the American Chemical Society.