Walter H. Zinn; Pioneer in Atomic Reactors

Walter H. Zinn, 93, a pioneer in nuclear physics and commercial development of atomic reactors who was the first director of the Argonne National Laboratory outside Chicago. Zinn was a member of the team led by Enrico Fermi that started the world’s first nuclear chain reaction at the University of Chicago in December 1942, and oversaw the construction of the nuclear reactor for what was code-named the Manhattan Project. After World War II, he became the first director of the Argonne lab, established by the Atomic Energy Commission to study and develop nuclear power. At Argonne, where he worked from 1946 to 1956, Zinn supervised production of the world’s first experimental breeder reactor, so named because it produced more nuclear fuel than it used by making fissionable plutonium out of the uranium-238 that lined the reactor. Nicknamed ZIP for “Zinn’s Infernal Pile,” in 1952 it became the first reactor to generate electricity. He focused the laboratory’s efforts on development of the breeder and later the boiling-water reactors because he saw their vast potential. The boiling-water reactor later became common in U.S. nuclear submarines and served as a prototype for General Electric power plants still operating in this country and Japan. A native of Kitchener, Canada, who earned a doctorate from Columbia University in 1934, Zinn became a consultant and worked in private industry after leaving Argonne. He received a special commendation from the Atomic Energy Commission in 1956, the Atoms for Peace Award in 1960 and the Enrico Fermi Award in 1969. On Feb. 14 in Clearwater, Fla.